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Breast Implant

Breast implant

A breast implant is a prosthesis used in cosmetic surgery to enlarge the size of a woman's breasts (known as breast augmentation) or to reconstruct the breast (for example, after a mastectomy, or during male-to-female sex reassignment surgery). There are four types of breast implant:
- Saline-filled, which have a silicone shell filled with sterile saline liquid. These implants are currently the only type available in the United States, but future regulation may make more available.
- Silicone gel-filled, which have a silicone shell filled with silicone gel. In the 60 countries where silicone implants are available, they are used in approximately 90% of implant operations. The implantation of silicone gel-filled breast implants is currently illegal in the US.
- String implant, a third, much less common type of implant, is a method of achieving extreme breast sizes, initially developed by Dr. Gerald W. Johnson, M.D.P.A., using polypropylene (PPP). String implants are unique in that they cause the breast to continue expanding after surgery, and are preferred by those women who choose to have the largest breasts possible, including many adult entertainers.
- Tissue engineered implant, a new form of implant currently in development. The principle is that cells are taken from the patient themselves, which are then combined with an appropriate scaffold material to produce a Tissue Engineered Breast Implant. The advantage of this method is that there is no risk of leakage or rupture, and the size can remain stable for the lifetime of the patient, a contrast from the silicone or saline filled implants which typically reduce by in the region of 40%. Further coverage may be found within the related links.

History

adult entertainer
Breast implants have been used at least since 1865 to augment the size of women's breasts. The earliest known implant occurred in Germany in which fat from a benign tumor was removed from a woman's back and implanted in her breast. In following years the medical community experimented with implants of various materials, most commonly paraffin. The first use of silicone as breast-implant material may have been by Japanese prostitutes in the period immediately following World War II, who would directly inject silicone into their breasts. Houston plastic surgeons Thomas Cronin and Frank Gerow developed the first silicone breast prosthesis with the Dow Corning Corporation in 1961 and the first woman was implanted in 1962. The implant was made of a silicone rubber envelope or sac filled with a thick, viscous silicone gel. Since then developments have focused on making the implants last longer, feel better and excite less fibrous tissue in the capsule around the device. A capsule tends to make the implant feel hard, look distorted and unnatural and may cause pain. Bacteria, leaking silicone and time are the main factors in capsule formation. Saline implants can also form capsule. Capsule rates have fallen with newer textured implants, thicker shells which leak less, and thicker 'cohesive' gels.

Risks and controversy

In the United States, implants made from silicone gel were restricted by the Food and Drug Administration because of growing concerns about the safety of such implants. More than one million women had availed themselves of the implants at the time of the ban, and the subsequent litigation led manufacturers to agree to a settlement of USD$4.25 billion. The degree of risk associated with silicone-gel breast implants is still a matter of debate within the scientific community. Currently silicone implants are available in the US only in the setting of controlled trials but they are widely used in the rest of the world where health authorities have not accepted that they pose an unacceptable threat. Food and Drug Administration Food and Drug Administration The health hazards of breast implants have been debated greatly in recent years. Some people believe that breast implants cause such illnesses as autoimmune disease, although both the AMA and FDA have found there to be no evidence of this. [http://www.fda.gov/cdrh/breastimplants/extracapstudy.html]. However, documented problems with breast implants include asymmetry, visibility, palpability, rupture, deflation, infection, scarring and hardening of the implants or 'capsule'. [http://www.fda.gov/cdrh/breastimplants/breast_implant_risks_brochure.html] It is noteworthy that implants, especially silicone implants, can impede radiography-based mammograms. Silicone contains silicon, a heavier element than is normally present in breast tissue. These silicon atoms will absorb X-ray photons more effectively than normal breast tissue. Assuming that the soft x-ray photons used for mamography (Mo-K) interact by the photoelectron effect then a typical silicone (O-Si(CH3)2-)n will be 4.2 times as able to absorb the X-rays than soft tissue. A paper on the subject was written by A.A. Beisang III, R.A. Geise and R.A. Ersek, Plastic and reconstructive surgery, 1991 (May), page 885. [http://personique.com/published_papers/Radiolucent%20Prosthetic%20Gel.pdf] Since the breast is commonly an erogenous zone, particularly for those with small breasts, breast augmentation can have the effect of reducing sexual pleasure by reducing sensitivity. According to the American Society of Plastic Surgeons, breast augmentation is the most commonly performed cosmetic surgical procedure on women in the United States. In 2002, 236,888 women in the U.S. underwent breast augmentation. [http://www.plasticsurgery.org/public_education/2002-Top-5-Female-Cosmetic-Procedures.cfm] According to the National Institute for Women, one in four silicone implant recipients must undergo surgery, within 5 years, to correct implant problems. As well as medical concerns, breast implants have been the subject of social controversy. Among some women they are seen as empowering and an exercise of control over the body; others see them as voluntary subjugation of the body to men's desires and a step backwards for women's empowerment. Some have compared breast implants to Chinese foot binding and female circumcision. Despite this, the social acceptability of breast implants seems to be increasing in most Western countries, although there remains a gulf between their portrayal in the media and in everyday life.

See also


- breast reconstruction
- breast reduction
- breast fetishism
- body modification
- List of celebrities with breast implants

External links


- [http://www.implantinfo.com Information site in support of breast implants]
- [http://www.siliconeholocaust.org Information site opposing breast implants, detailing complications]
- [http://www.fda.gov/cdrh/breastimplants/ U.S. Food and Drug Administration]
- [http://www.pbs.org/wgbh/pages/frontline/implants/cron.html Chronology of silicone breast implants]
- [http://www.paulkienitz.net/no-implants.html Opinion: "48 Reasons Not to Get Breast Implants]
- [http://tissue.medicalengineer.co.uk/Natural+Breast+Implants.php Tissue Engineered breast implants] Category:Plastic surgery Category:Gender transitioning

Cosmetic surgery

Plastic surgery is a general term for operative manual and instrumental treatment which is performed for functional or aesthetic reasons. The word "plastic" derives from the Greek plastikos meaning to mould or to shape; its use here is not connected with modern plastics. The principal areas of plastic surgery include two broad fields.
- Reconstructive surgery, including microsurgery, focuses on undoing or masking the destructive effects of trauma, surgery or disease. Reconstructive surgery may include closing defects with flaps—that is, by moving tissue from other parts of the body.
- Cosmetic (or aesthetic) surgery is most often performed in order to change features the patient finds unflattering. In many cases, however, there are medical reasons (for example, breast reduction when orthopedic problems are present).

History

The history of cosmetic surgery spans back to the ancient world. The Romans were able to perform simple techniques such as repairing damaged ears. Physicians in ancient India including the great Indian surgeon Susrutha were utilizing skin grafts for reconstructive work as early as 800 B.C and performed nose reconstruction, using a portion of the forehead, during periods where amputation of the nose was a punishment for certain crimes. In mid-15th century Europe, Heinrich von Pfolspeundt described a process "to make a new nose for one who lacks it entirely, and the dogs have devoured it" by removing skin from the back of the arm and suturing it in place. However, because of the dangers associated with surgery in any form, especially that involving the head or face, it was not until the 19th and 20th centuries that such surgeries became commonplace. The U.S.'s first plastic surgeon was Dr. John Peter Mettauer. He performed the first cleft palate operation in 1827 with instruments that he designed himself.

Reconstructive surgery

Reconstructive surgical techniques were developed rapidly in the period after the First World War when patients with survivable but disfiguring injuries required new approaches. The English military hospitals of the period trained surgeons from the world over in these new techniques. These surgeons then returned to the Americas, the Pacific and to Europe to propagate their advances. The main advances were with flap surgery—moving tissue from one location to another with an intact blood supply. Ultimately, plastic surgeons have championed the use of microsurgical techniques to transfer remote tissue. They have for the past several decades been able to connect blood vessels that may be as small as 1-2mm in diameter to reperfuse the transferred tissue, thereby allowing coverage of a soft tissue defect when no local tissue is available. Common cases of reconstructive surgery are breast reconstruction for women who have had a mastectomy, facial- and contracture surgery for burn victims, closing skin- or mucosa defects after removal of tumors in the head and neck region. Sex reassignment surgery for transsexual people is another example of reconstructive surgery. Foreskin restoration for men who have undergone circumcision is sometimes performed using reconstructive surgery. There is a definite gray area between reconstructive and cosmetic surgery. For instance a "bat ear" correction is not considered cosmetic surgery, even though having prominent ears is not a debilitating or dangerous condition.

Cosmetic surgery

Cosmetic surgery is a very popular avenue for personal enhancement, as demonstrated by the 11.9 million cosmetic procedures performed in the U.S. alone in 2004. Although some may harbor a dim view of cosmetic surgery, seeing it as frivolous, the upsurge in number of procedures performed annually shows that cosmetic surgery has become acceptable to the mainstream American household. However, it should be noted that elective procedures involve risk like any operation, and should therefore not be undertaken lightly. Within the US, critics of plastic surgery have noted that it is legal for any doctor (regardless of speciality) to perform plastic surgery; a practice which may lead to a suboptimal result. It is vital to check a physician's credentials, looking for those MDs who are actually board certified by the American Board of Plastic Surgery. Because cosmetic surgery is seen as lucrative, many other specialties have tried to make themselves sound more official and qualified by making up associations or "medical boards", even though their training does not encompass all aspects of reconstructive and cosmetic/aesthetic surgery of plastic surgeons. However, there is only one governing board of American physicians (the American Board of Medical Specialties ) which only recognizes the American Board of Plastic Surgery and not these other "boards". Other "boards" such as "facial plastic surgery" or "American Cosmetic Surgery" are not officially recognized by the American Board of Medical Specialties. In fact, the term "facial plastic surgery" is particularly deceptive, as it implies there is a "general plastic surgery" field, which of course does not exist. Plastic surgeons who are board-certified by the American Board of Plastic Surgery can of course perform and excel in surgery of the face. Just because a non-plastic surgeon claims they have "training" in "facial plastic surgery" does not necessarily mean they can better perform reconstructive and aesthetic procedures of the face. The most prevalent aesthetic/cometic procedures are listed below. Most of these types of surgery are more commonly known by their "common names." These are also listed when pertinent.
- Abdominoplasty (or "tummy tuck"): reshaping and firming of the abdomen
- Blepharoplasty (or "eyelid surgery"): Reshaping of the eyelids or the application of permanent eyeliner, including Asian blepharoplasty
- Augmentation Mammaplasty (or "breast enlargement" or "boob job"): Augmentation of the breasts
- Muscle sculpting: Removal of the fat layer that is on top of chosen muscle to reveal a more appealing look after surgery (ie: six pack abs revealed through muscle sculpting)
- Chemical peel: Removal of acne scars and sagging skin—not technically surgery and can be performed by a cosmetologist
- Mastopexy (or "breast lift"): Raising of sagging breasts
- Rhinoplasty (or "nose job"): Reshaping of the nose
- Non-surgical Nose Job: A new method of reshaping of the nose without surgery. This non-invasive procedure, developed by Dr. Alexander Rivkin, uses injectable fillers to reshape the nose and hide imperfections.
- Otoplasty (or ear surgery): Reshaping of the ear
- Rhytidectomy (or "face lift"): Removal of wrinkles and signs of aging from the face
- Suction-Assisted Lipectomy (or liposuction): Removal of fat from the body
- Circumcision: Removal of the foreskin of the penis, esp. without any diagnosis
- Chin augmentation: Augmentation of the chin with an implant (e.g. silicone) or by sliding genioplasty of the jawbone.
- Cheek augmentation
- Collagen injections
- Mesotherapy : An alternative to liposuction where fluids are injected to break down and disolve the fat. This is considered the non-invasive method to fat tissue removal. In addition, there is increasing concern about cosmetic surgeries not done in the United States, especially liposuctions performed at the Dominican Republic: while liposuction in the Dominican Republic is considerably cheaper, six women were reported in 2004 to have returned to the United States from the Dominican Republic with an infection after having liposuctions there, and, in 2001, a Puerto Rican woman died, in a very widely publicized case by Puerto Rican newspapers.

Related disciplines

Plastic surgery is a broad field, and may be subdivided further. Plastic surgery training and approval by the American Board of Plastic Surgery includes mastery of the following as well:
- Craniofacial surgery mostly revolves around the treatment of pediatric congenital anomalies, such as cleft lip and palate, craniosynostosis, and other disturbances in facial growth and development. Because these children have multiple issues, they are often taken care of in an interdisciplinary approach which include oral surgeons, otolaryngologists, speech therapists, occupational therapists, geneticists.
- Hand surgery is a field that has some overlap with general surgeons and orthopedic surgeons. Plastic surgeons receive full training in hand surgery, with some trainees deciding even to do an additional full-year hand fellowship afterwards (this fellowship can also be pursued by general surgeons and orthopedic surgeons). However, hand surgery is particularly suited to plastic surgeons, as when there is hand traumatically amputated that requires a "replant" operation, plastic surgeons are trained to reconstruct all aspects to save the hand: blood vessels, nerves, tendons, muscle, bone. Many hand operations (such as reconstruction of injuries, replantations, rheumatoid surgery and surgery of congenital defects) are performed by plastic surgeons.
- Maxillofacial surgery (surgery involving the jaw) is an important aspect of plastic surgery. This field is shared by both the plastic surgeons and the oral surgeons, with each field contributing each other in order to benefit this area of the body.

Addiction to cosmetic surgery

Some people appear to become addicted to cosmetic surgery, possibly because of body dysmorphic disorder. Sufficient amounts of repeated cosmetic surgery can lead to irreversible damage to the normal body structure. However, due to the high cost of repeated cosmetic surgery, this disorder is generally one limited to the wealthy.

See also


- Body modification
- Botox
- Dr. 90210
- Extreme Makeover
- Genital modification and mutilation
- Nip/Tuck

External links


- [http://www.plasticsurgery.org/ American Society of Plastic Surgeons]
- [http://www.surgery.org The American Society for Aesthetic Plastic Surgery] Plastic surgery Category:Human appearance ja:形成外科

Breast

breasts]] The term breast, also known by the Latin mamma in anatomy, refers to the upper ventral region of an animal's torso, particularly that of mammals, including human beings. In addition, the breasts are parts of a female mammal's body which contain the organs that secrete milk used to feed infants. This article focuses on human female breasts, but it should be noted that male humans also have breasts (although usually less prominant) and are born with the main milk ducts intact. While the mammary glands that produce milk are present in the male, they normally remain undeveloped. In some situations male breast development does occur, a condition called gynecomastia. Milk production can also occur in both men and women as a rare adverse effect of some medicinal drugs (such as some antipsychotic medication). Both sexes have a large concentration of blood vessels and nerves in their nipples.

Anatomy of the female breast

nipple The breasts are covered by skin; each breast has one nipple surrounded by the areola. The areola is colored from pink to dark brown, hairless, and has several sebaceous glands. The larger mammary glands within the breast produce the milk; they consist of several lobules, and each breast has some 10-20 lactiferous ducts that drain milk from the lobules to the nipple, where each duct has its own opening. Most of the breast is adipose tissue (fat) and connective tissue (known as Cooper's ligaments). The breasts sit over the pectoralis major muscle and usually extend from the level of the 2nd rib to the level of the 6th rib anteriorly. The superior lateral quadrant of the breast extends diagonally upwards in an 'axillary tail'. A thin layer of mammary tissue extends from the clavicle above to the seventh or eighth ribs below and from the midline to the edge of the latissimus dorsi posteriorly. The arterial blood supply to the breasts is derived from the internal thoracic artery (previously referred to as the internal mammary artery), lateral thoracic artery, thoracoacromial artery, and posterior intercostal arteries. The venous drainage of the breast is mainly to the axillary vein, but there is some drainage to the internal thoracic vein. The breast is innervated by the anterior and lateral cutaneous branches of the 4th through 6th intercostal nerves. The nipple is supplied by the T4 dermatome.

Lymphatic drainage

About 75% of lymph from the breast travels to the ipsilateral (same side) axillary lymph nodes. The rest travels to parasternal nodes, to the other breast, or abdominal lymph nodes. The axillary nodes include the pectoral, subscapular, and humeral groups of lymph nodes. These drain to the central axillary lymph nodes, then to the apical axillary lymph nodes. The lymphatic drainage of the breasts is particularly relevant to oncology, since cancer cells can break away from a tumour (breast cancer being a common cancer), and spread to other parts of the body through the lymph system by a process known as metastasis.

Function

The function of the mammary glands in female breasts is to nurture the young by producing milk, which emanates from the nipples during lactation. However, zoologists point out that no female mammal other than the human has breasts of comparable size when not lactating, and this suggests that the external form of the breasts is connected to factors other than lactation alone. The mammary glands that secrete the milk from the breasts actually make up a relatively small fraction of the overall breast tissue. It is commonly assumed by biologists that the real evolutionary purpose of women having breasts is to attract the male of the species; that, in other words, breasts are a sexually dimorphic, or secondary sex characteristics. Some biologists (notably Desmond Morris) believe that the shape of female breasts evolved as a frontal counterpart to that of the buttocks, the reason being that whilst other primates mate in the typical piggy-back position, humans are more likely to successfully copulate mating face on. A secondary sexual characteristic on a woman's chest would have encouraged this in more primitive incarnations of the human race, and a face on encounter would have helped found a relationship between partners beyond merely a sexual one. Others believe that the human breast evolved in order to prevent infants from suffocating while feeding[http://www.breastfeeding.com/reading_room/breasts_shaped_babies.html]. Since human infants do not have a protruding jaw like our ancestors and the other primates, the infant's nose might be blocked by a flat female chest while feeding. According to this theory, as the human jaw became recessed, so the breasts became larger to compensate.

Size, shape and composition

Most of the human female breast is actually adipose tissue (fat) and connective tissue, rather than the mammary glands. There is naturally a great variety in the size and shape of breasts in women (and men), with size being affected by various factors including genetics. The primary anatomical support for the breasts is thought to be provided by the Cooper's ligaments, with additional support from the skin covering the breasts themselves, and it is this support which determines the shape of the breasts. The breasts naturally sag through ageing, as the ligaments become elongated. This process may be accelerated by high impact exercises, and a brassiere may reduce this effect by providing external support, although the health benefits of wearing of a brassiere are not universally accepted. Sagging breasts (ptosis) are considered undesirable by some, and some older women seek cosmetic surgery to raise their busts. As breasts are mostly composed of adipose tissue, their size can change over time if the woman gains or loses weight. It is also typical for them to grow in size during pregnancy and whilst breastfeeding, mainly due to hypertrophy of the mammary gland in response to the hormone prolactin. The size of a woman's breasts usually fluctuates during the menstrual cycle, particularly with premenstrual water retention. An increase in breast size is also a common side effect of use of the contraceptive pill. There is no relationship between breast size and ability to breastfeed, and it is a common misconception that human female breasts are shaped the way they are so that they can feed babies by producing milk, their shape is thought to have evolved due to sexual attraction, as described above. The size of a woman's breasts is typically expressed as a "bra size". According to the results of the "Size UK" survey [http://www.sizeuk.org/], the average bra size in the UK has increased from a 34B in the 1950s to a 36C today, and the average size for U.S. women is a 34B as of 2005 by the CDC. Women with exceptionally large breasts may experience back pain, whilst in some Western societies there is a belief amongst some that small breasts make a woman less sexually attractive. Some women suffer from insecurity about their breasts, and in some cultures a number of women who are unhappy with their size seek surgery either to artificially reduce or enlarge their breasts. The American Society for Aesthetic Plastic Surgery found that 334,052 breast augmentation procedures were performed in 2004 [http://www.cosmeticplasticsurgerystatistics.com/statistics.html#2004-HIGHLIGHTS]. Some women in developed countries undergo breast reconstruction after mastectomy for breast cancer, a result of the high value placed on symmetry of the female human form in those cultures, and because women often identify their femininity and sense of self with their breasts. It is typical for a woman's breasts to be unequal in size (statistically it is slightly more common for the left breast to be the larger), particularly whilst the breasts are developing during puberty. In some rare cases, one breast may be greatly larger or smaller than the other, or fail to develop entirely.

Development

The development of a woman's breasts, during puberty, is caused by sex hormones, chiefly estrogen. This hormone has been demonstrated to cause the development of woman-like, enlarged breasts in men, a condition called gynecomastia, and is sometimes used deliberately for this effect in male-to-female sex reassignment surgery. A number of medical conditions are known to cause abnormal development of the breasts during puberty. Virginal breast hypertrophy is a condition which involves excessive growth of the breasts during puberty, and in some cases the continued growth beyond the usual pubescent age. Breast hypoplasia is a condition where one or both breasts fail to develop during puberty.

Terminology

:For slang terms for the breasts, see WikiSaurus:breasts — the WikiSaurus list of synonyms and slang words for breasts in many languages. A brassiere (from French, lit: arm-holder) or bra is an item of women's underwear consisting of two cups that totally or partially cover the breasts for support and modesty. Being topless is the state of having bare breasts. For more on modesty regarding breasts, see Nudity.

Cultural status

Nudity Historically, breasts were regarded as fertility symbols, due to their association with life-giving milk. Ancient statues of goddesses—so-called Venus figurines—often emphasised the breasts, as in the example of the Venus of Willendorf. In historic times, goddesses such as Ishtar were shown with multiple breasts, alluding to their role as goddesses of childbirth. Breasts are considered as secondary sex characteristics, and are sexually sensitive in many cases. Bare female breasts can elicit heightened sexual desires from men and women. Since they are associated with sex, in many cultures bare breasts are considered indecent, and they are not commonly displayed in public, in contrast to male chests. Other cultures accept the baring of breasts as acceptable, and in some countries women have never been forbidden to bare their chests. Opinions on the exposure of breasts is often dependent on the place and context, and in some Western societies, exposure of breasts on a beach may be considered acceptable, although in town centres, for example, it is usually considered indecent. In some cases, their display may be interepreted as indecent or sexual, even when they are being used for their primary purpose of nursing offspring. This has led, in several cases, to women being arrested for indecent exposure for breastfeeding their children in public. Women in some areas and cultures are approaching the issue of breast exposure as one of sexual equality, since men (and pre-pubescent children) may bare their chests, but women are forbidden. In the United States, the Topfree equality movement seeks to redress this imbalance; this movement has won a decision in 1992 in a New York Court of Appeals which seems to substantially support their assertions. A similar movement succeeded in most parts of Canada in the 1990s. In some cultures, breasts must always remain covered for religious reasons, for example, some Islamic cultures forbid exposure of any part of the female body. In addition to the above references, see also modesty, nudism and exhibitionism.

Disorders of the breasts

Infections and inflammations

exhibitionism
- Mastitis
  - bacterial mastitis
  - mastitis from milk engorgement
  - mastitis of mumps
  - subareolar mastitis
- Other infections
  - chronic intramammary abscess
  - chronic subareolar abscess
  - tuberculosis of the breast
  - syphilis of the breast
  - retromammary abscess
  - actinomycosis of the breast
- Inflammations
  - Mondor's disease
  - duct ectasia/periductal masbreastis
  - Breast engorgement

Benign breast disease


- Congenital disorders
  - inverted nipple
  - supernumerary nipples/supernumerary breasts
- Aberrations of normal development and involution
  - fibroadenomatosis
  - cyclical nodularity
  - cysts
  - fibroadenoma - benign tumor
- Duct ectasia/Periductal masbreastis
  - nipple discharge
  - abscesses
  - mammary fistula
- Epithelial hyperplasia
-
- Pregnancy-related
  - galactocoele
  - puerperal abscess

Malignant breast disease


- breast cancer (mammary carcinoma)
- carcinoma in situ
- Paget's disease of the nipple, also known as Paget's disease of the breast

See also


- breastfeeding
- breast fetishism
- breast implant
- breast reconstruction
- gynecomastia
- intimate parts
- topfree equality
- mammary intercourse
- puberty

External links


- [http://www.puberty101.com/p_stages_breasts.shtml Stages of breast development, from Puberty101]
- [http://www.veresch.com/fun/boobs.php Real or Fake?] — online quiz to spot breasts with implants
- [http://www.007b.com/ 007 Breasts] — a website promoting the view that breasts should not be considered sexual Category:Integumentary system Category:Secondary sexual characteristics Category:Reproductive system ja:乳房 simple:Breast th:เต้านม

Mastectomy

In medicine, mastectomy is the medical term for the surgical removal of one or both breasts, partially or completely. Mastectomy is usually done to combat breast cancer; in some cases, women believed to be at high risk of breast cancer have the operation prophylactically, that is, to prevent cancer rather than treat it. In contrast, in a lumpectomy, a lump of tissue rather than the whole breast is removed. Traditionally, in the case of breast cancer, the whole breast was removed. Often the mastectomy was performed during the same operation in which the biopsy was taken that confirmed the diagnosis. Nowadays the decision to do the mastectomy is usually based on the earlier performed biopsy. Also there is a trend to a more conservative approach to breast cancer. This has become possible due to improvements in radiotherapy and adjuvant treatment (e.g. chemotherapy or hormonal therapy). In developed countries, only a minority of cancers is still treated by mastectomy.

Types


- Simple mastectomy (or "total mastectomy") [http://www.breastcancer.org/simple_mastectomy.html illustration]
- Modified radical mastectomy [http://www.breastcancer.org/modified_radical_mastectomy.html illustration]
- Radical mastectomy (or "Halsted mastectomy") -- rarely done today [http://www.breastcancer.org/radical_mastectomy.html illustration]
- Skin-sparing mastectomy [http://www.breastcancer.org/skin_sparing_mastectomy.html illustration]
- Subcutaneous mastectomy PMID 11712794

See also


- Breast
- Breast cancer
- Breast reconstruction
- Sex reassignment surgery female-to-male

External links


- [http://mrbra.com/mastectomy.ivnu Types of Mastectomy]
- [http://news.bbc.co.uk/2/hi/health/3727554.stm Mastectomy study] Category:Surgical removal procedures

Silicone

Silicones, or polysiloxanes, are inorganic polymers consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. Certain organic side groups can be used to link two or more of these -Si-O- backbones together. By varying the -Si-O- chain lengths, side groups, and crosslinking, silicones can be synthesized into a wide variety of materials. They can vary in consistency from liquid to gel to rubber to hard plastic. The most common type is linear polydimethylsiloxane or PDMS. The second largest group of silicone materials is based on silicone resins, which are formed by branched and cage-like oligosiloxanes.

Properties

Silicones are odorless, colorless, water resistant, chemical resistant, oxidation resistant, stable at high temperature, and do not conduct electricity. They have many uses, such as lubricants, adhesives, sealants, gaskets, breast implants, pressure compensating diaphragms for drip irrigation emitters, sex toys, dishware, and Silly Putty. Due to their thermal stability and relatively high melting and boiling points, silicones are often used where organic polymers are not applicable. Their unreactivity generally makes them non-toxic (see below). An enormous controversy developed during the 1990s around allegations that the silicones in breast implants were responsible for several diseases. Health concerns included pain, deformity and the less obviously related connective tissue disorders (eg. scleroderma, arthritis) and chronic fatigue syndrome. Leakage of silicone from implants could be demonstrated easily but proof of its safety or otherwise was lacking. The Dow Corning corporation declared bankruptcy and settled several class actions globally; later, good evidence emerged clearing silicone of causing connective tissue disease. Silicone implants have been removed from the market in some countries (notably the US) because of the silicone controversy but are extensively used elsewhere. Simethicone, a silicone-based anti-foaming agent, has remained available as an over-the-counter substance and food additive.

Chemical terminology

food additive Silicone is often mistaken colloquially for elemental silicon, because of the similarity in pronunciation and spelling, but they are entirely different. For example, in the Shakira song "Objection (Tango)", the lyrics "next to her cheap silicon I look minimal" should be "next to her cheap silicone I look minimal." The word "silicone" is derived from ketone, and is technically not the correct term for the polymers this article describes. A true silicone group has a double bond between oxygen and silicon (see figure), like a ketone group with Si in place of C (the same terminology is used for compounds such as silane, which is an analogue of methane). Polysiloxanes are called "silicone" due to an early mistaken assumption about their structure, but it has since been shown that they contain no silicone groups at all. For an idea of what a genuine polysilicone molecule would look like, see polyketone.

External links


- [http://www.elmhurst.edu/~chm/vchembook/404silicone.html Silicone Polymers] (Virtual Chembook, Elmhurst College)
- [http://www.silicones-science.com/ Science of Silicone Polymers] (Silicone Science On-line, Centre Européen des Silicones - CES)
- [http://www.dowcorning.com/content/sitech/sitechbasics/default.asp Silicon Chemistry] (Silicon Chemistry Basics, Dow Corning)
- [http://www.fda.gov/fdac/features/995_implants.html FDA: A Status Report on Breast Implant Safety] (U.S. Food & Drug Administration)
- [http://books.nap.edu/catalog/9602.html Safety of Silicone Breast Implants] (Publication by Editors, Committee on the Safety of Silicone Breast Implants, Institute of Medicine (viewable online))
- [http://www.stockwell.com/pages/materials.php Silicone and Elastomerics materials] - Stockwell Elastomerics Category:Polymers Category:Lubricants ko:실리콘

Saline (medicine)

In medicine saline is a solution of sodium chloride in sterile water, used commonly for intravenous infusion, cleaning contact lenses, and nasal irrigation or jala neti. Sodium chloride (NaCl) is ordinary salt. Saline solutions are available in various concentrations for different purposes. Normal saline is the solution of 0.9% w/v of NaCl. It contains 154 meq/l of Na and Cl and has about the same degree of osmolality as blood (referred to as isotonic), about 300 mosm/l. Normal saline (NS) is therefore used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed severe dehydration. Normal saline is typically the first fluid used when dehydration is severe enough to threaten the adequacy of blood circulation and is the safest fluid to give quickly in large volumes. Other concentrations of saline are frequently used for other purposes, such as supplying extra water to a dehydrated patient or supplying the daily water and salt needs ("maintenance" needs) of a patient who is unable to take them by mouth. Because infusing a solution of low osmolality can cause problems, intravenous solutions with reduced saline concentrations typically have dextrose (glucose) added to maintain a safe osmolality while providing less sodium chloride. As the molecular weight of dextrose is greater, this has the same osmolality as normal saline but contributes less sodium to the circulation. Because dextrose monohydrate (MW 198 in contrast to MW 180 for glucose) is the commercial form of dextrose used in these preparations, 5% dextrose actually contains only 4.5 g/dl of glucose. Concentrations commonly used include #Half-normal saline (0.45% NaCl), often with "D5" (5% dextrose), contains 77 meq/l of Na and Cl and 4.5 g/l glucose. #Quarter-normal saline (0.22% NaCl) has 39 meq/l of Na and Cl and always contains 5% dextrose for osmolality reasons. #Dextrose (glucose) 4% in 0.18% saline is used sometimes for maintenance replacement. The amount of normal saline infused depends largely on the needs of the patient (e.g. ongoing diarrhoea or heart failure) but is typically between 1.5 and 3 litres a day for an adult.

See also


- Intravenous therapy
- Lactated Ringer's solution Category:Medical treatments

United States

:For alternative meanings, see the disambiguation page for US, USA, United States, or American. The United States of America is a federal democratic republic situated primarily in central North America. It comprises 50 states and one federal district, and has several territories. It is also referred to, with varying formality, as the United States, the U.S., the U.S.A., the States, or simply and most commonly, America. The official founding date of the United States is July 4, 1776, when the Second Continental Congress—representing thirteen British colonies—adopted the Declaration of Independence. However, the structure of the government was profoundly changed in 1788, when the states replaced the Articles of Confederation with the United States Constitution. The date on which each of the fifty states adopted the Constitution is typically regarded as the date that state "entered the Union" (became part of the United States). Since the mid-20th century, following World War II, the United States has emerged as a dominant global influence in economic, political, military, scientific, technological, and cultural affairs.

Geography and climate

The United States shares land borders with Canada (to the north) and Mexico (to the south), and territorial water boundaries with Canada, Russia, the Bahamas, and numerous smaller nations. It is otherwise bounded by the Pacific Ocean and the Bering Sea, in the west; the Arctic Ocean, in the northernmost areas; and the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, in the eastern and southeastern areas. Forty-eight of the states are in the single region between Canada and Mexico; this group is referred to, with varying precision and formality, as the continental or contiguous United States, sometimes abbreviated CONUS, and as the Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada. The archipelago of Hawaii is in the Pacific Ocean. The capital city, Washington, District of Columbia is a federal district located on land donated by the state of Maryland. (Virginia also donated land, but it was returned in 1847.) The United States also has overseas territories with varying levels of independence and organization. When inland water is included in the total area, only Russia and Canada are larger than the United States; if inland water is excluded, China ranks third and the U.S. ranks fourth. The United States' total area is 3,718,711 square miles (9,631,418 km²), of which land makes up 3,537,438 square miles (9,161,923 km²) and water makes up 181,273 square miles (469,495 km²). The United States' landscape is one of the most varied among those of the world's nations: among its many features are temperate forestland and rolling hills, on the east coast; mangrove, in Florida; the Great Plains, in the center of the country; the Mississippi–Missouri river system; the Great Lakes, four of the five of which are shared with Canada; the Rocky Mountains, west of the Great Plains; deserts and temperate coastal zones, west of the Rocky Mountains; and temperate rain forests, in the Pacific northwest. Alaska's tundra, and the volcanic, tropical islands of Hawaii add to the geographic diversity. Hawaii The climate varies along with the landscape, from tropical in Hawaii and southern Florida to tundra in Alaska and atop some of the highest mountains. Most of the North and East experience a temperate continental climate, with warm summers and cold winters. Most of the South experiences a subtropical humid climate with mild winters and long, hot, humid summers. Rainfall decreases markedly from the humid forests of the Eastern Great Plains to the semi-arid shortgrass prairies on the high plains abutting the Rocky Mountains. Arid deserts, including the Mojave, extend through the lowlands and valleys of the southwest, from westernmost Texas to California and northward throughout much of Nevada. Some parts of California have a Mediterranean climate. Rainforests line the windward mountains of the Pacific Northwest from Oregon to Alaska.

History

American history started with the migration of people from Asia across the Bering land bridge approximately 12,000 years ago following large animals that they hunted into the Americas. These Native Americans left evidence of their presence in petroglyphs, burial mounds, and other artifacts. It is estimated that 2-9 million people lived in the territory now occupied by the U.S. before European contact, and the subsequent introduction of foreign diseases such as small pox that greatly diminished the native populations. Some advanced societies were the Anasazi of the southwest, who inhabited Chaco Canyon, and the Woodland Indians, who built Cahokia, located near present-day St Louis, a city with a population of 40,000 at its peak in AD 1200. Vikings first visited North America around 1000, but did not settle permanently. Following the discovery voyages of Christopher Columbus around 1492, other Europeans began to explore and settle there. During the 1500s and 1600s, the Spanish settled parts of the present-day Southwest and Florida, founding St. Augustine, Florida in 1565 and Santa Fe (in what is now New Mexico) in 1607. The first successful English settlement was at Jamestown, Virginia, also in 1607. Within the next two decades, several Dutch settlements, including New Amsterdam (the predecessor to New York City), were established in what are now the states of New York and New Jersey. In 1637, Sweden established a colony at Fort Christina (in what is now Delaware), but lost the settlement to the Dutch in 1655. This was followed by extensive British settlement of the east coast. The British colonists remained relatively undisturbed by their home country until after the French and Indian War, when France ceded Canada and the Great Lakes region to Britain. Britain then imposed taxes on the 13 colonies, widely regarded by the colonists as unfair because they were denied representation in the British Parliament. Tensions between Britain and the colonists increased, and the thirteen colonies eventually rebelled against British rule. British Parliament, George Washington (1789-1797).]] In 1776, the 13 colonies split from Great Britain and formed the United States, the world's first constitutional and democratic federal republic, after their Declaration of Independence of that year, and the Revolutionary War (1775 to 1783). The original political structure was a confederation in 1777, ratified in 1781 as the Articles of Confederation. After long debate, this was supplanted by the Constitution in 1789, forming a more centralized federal government. Prior to all these was the Albany Congress in 1754, in which a union was first seriously proposed. From early colonial times, there was a shortage of labor, which encouraged unfree labor, particularly indentured servitude and slavery. In the mid-19th century, a major division occurred in the United States over the issue of states' rights and the expansion of slavery. The northern states had become opposed to slavery, while the southern states saw it as necessary for the continued success of southern agriculture and wanted it expanded to the territories. Several federal laws were passed in an attempt to settle the dispute, including the Missouri Compromise and the Compromise of 1850. The dispute reached a crisis in 1861, when seven southern states seceded1 from the Union and formed the Confederate States of America, leading to the Civil War. Soon after the war began, four more southern states seceded. During the war, Abraham Lincoln issued the Emancipation Proclamation, mandating the freedom of all slaves in states in rebellion, though full emancipation did not take place until after the end of the war in 1865, the dissolution of the Confederacy, and the Thirteenth Amendment took effect. The Civil War effectively ended the question of a state's right to secede, and is widely accepted as a major turning point after which the federal government became more powerful than state governments. Thirteenth Amendment). The title of the painting, from a 1726 poem by Bishop Berkeley, was a phrase often quoted in the era of Manifest Destiny, expressing a widely held belief that civilization had steadily moved westward throughout history. [http://americanart.si.edu/t2go/1lw/1931.6.1.html (more)] ]] During the 19th century, many new states were added to the original 13 as the nation expanded across the continent. Manifest Destiny was a philosophy that encouraged westward expansion in the United States. As the population of the Eastern states grew and as a steady increase of immigrants entered the country, settlers moved steadily westward across North America. In the process, the U.S. displaced most American Indian nations. This displacement of American Indians continues to be a matter of contention in the U.S. with many tribes attempting to assert their original claims to various lands. In some areas American Indian populations were reduced by foreign diseases contracted through contact with European settlers, and US settlers acquired those emptied lands. In other instances American Indians were removed from their traditional lands by force. Though some would say the U.S. was not a colonial power until the Spanish-American War when it acquired Puerto Rico, Guam and the Philippines, the dominion exercised over land in North America the United States claimed is essentially colonial. The Philippines became independent in 1946. During this period, the nation also became an industrial power. This continued into the 20th century, which has been termed "the American Century" because of the nation's overriding influence on the world. The US became a center for innovation and technological development; major technologies that America either developed or was greatly involved in improving include the telephone, television, computer, the Internet, nuclear weapons, nuclear power, aviation, and aeronautics. In addition to the Civil War, another major traumatic experience for the nation was the Great Depression (1929 to 1939). The nation has also taken part in several major foreign wars, including World War I and World War II (in both of which the US later joined the Allies). During the Cold War, the US was a major player in the Korean War and Vietnam War, and, along with the Soviet Union, was considered one of the world's two "superpowers". With the collapse of the Soviet Union, the US emerged as the world's leading economic and military power. Beginning in the 1990s, the United States became very involved in police actions and peacekeeping, including actions in Kosovo, Haiti, Somalia and Liberia, and the first Persian Gulf War driving Iraq out of Kuwait. After attacks on the World Trade Center and the Pentagon on September 11, 2001, the United States and other allied nations found themselves involved in what has come to be called the "War on Terrorism," which has primarily encompassed military actions in both Afghanistan and Iraq.

Government

Iraq of the United States.]]

Republic and suffrage

The United States is an example of a constitutional republic, with a government composed of and operating through a set of limited powers imposed by its design and enumerated in the United States Constitution. Specifically, the nation operates as a presidential democracy. There are three levels of government: federal, state, and local. Officials of each of these levels are either elected by eligible voters via secret ballot or appointed by other elected officials. Americans enjoy almost universal suffrage from the age of 18 regardless of race, sex, or wealth. There are some limits, however: felons are disenfranchised and in some states former felons are likewise. Furthermore, the national representation of territories and the federal district of Washington, DC in Congress is limited: residents of the District of Columbia are subject to federal laws and federal taxes but their only Congressional representative is a non-voting delegate.

Federal government

The federal government is the national government, comprising the Legislative Branch (led by Congress), the Executive Branch (led by the President), and the Judicial Branch (led by the Supreme Court). These three branches were designed to apply checks and balances on each other. The Constitution limits the powers of the federal government to defense, foreign affairs, the issuing and management of currency, the management of trade and relations between the states, and the protection of human rights. In addition to these explicitly stated powers, the federal government—with the assistance of the Supreme Court—has gradually extended these powers into such areas as welfare and education, on the basis of the "necessary and proper" clause of the Constitution.

The Congress

necessary and proper The Congress of the United States is the legislative branch of the federal government of the United States. It is bicameral, comprising the House of Representatives and the Senate. The House of Representatives consists of 435 members, each of whom represents a congressional district and serves for a two-year term. House seats are apportioned among the states by population; in contrast, each state has two Senators, regardless of population. There are a total of 100 senators, who serve six-year terms. The powers of Congress are limited to those enumerated in the Constitution; all other powers are reserved to the states and the people. The Constitution also includes the necessary-and-proper clause, which grants Congress the power to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers."

The President

necessary-and-proper clause At the top level of the executive branch is the President of the United States. The President and Vice-President are elected as 'running mates' for four-year terms by the Electoral College, for which each state, as well as the District of Columbia, is allocated a number of seats based on its representation (or ostensible representation, in the case of D. C.) in both houses of Congress (see U.S. Electoral College). The relationship between the President and the Congress reflects that between the English monarchy and parliament at the time of the framing of the United States Constitution. Congress can legislate to constrain the President's executive power, even with respect to his or her command of the armed forces; however, this power is used only very rarely—a notable example was the constraint placed on President Richard Nixon's strategy of bombing Cambodia during the Vietnam War. The President cannot directly propose legislation, and must rely on supporters in Congress to promote his or her legislative agenda. The President's signature is required to turn congressional bills into law; in this respect, the President has the power—only occasionally used—to veto congressional legislation. Congress can override a presidential veto with a two-thirds majority vote in both houses. The ultimate power of Congress over the President is that of impeachment or removal of the elected President through a House vote, a Senate trial, and a Senate vote. The threat of using this power has had major political ramifications in the cases of Presidents Andrew Johnson, Richard Nixon, and Bill Clinton. The President makes around 2,000 executive appointments, including members of the Cabinet and ambassadors, which must be approved by the Senate; the President can also issue executive orders and pardons, and has other Constitutional duties, among them the requirement to give a State of the Union address to Congress once a year. Although the President's constitutional role may appear to be constrained, in practice, the office carries enormous prestige that typically eclipses the power of Congress: the Presidency has justifiably been referred to as 'the most powerful office in the world'. The Vice President is first in the line of succession, and is the President of the Senate ex officio, with the ability to cast a tie-breaking vote. The members of the President's Cabinet are responsible for administering the various departments of state, including the Department of Defense, the Justice Department, and the State Department. These departments and department heads have considerable regulatory and political power, and it is they who are responsible for executing federal laws and regulations. George W. Bush is the 43rd President, currently serving his second term.

The Courts

George W. Bush The highest court is the Supreme Court, which consists of nine justices. The court deals with federal and constitutional matters, and can declare legislation made at any level of the government as unconstitutional, nullifying the law and creating precedent for future law and decisions. Below the Supreme Court are the courts of appeals, and below them in turn are the district courts, which are the general trial courts for federal law. Separate from, but not entirely independent of, this federal court system are the individual court systems of each state, each dealing with its own laws and having its own judicial rules and procedures. A case may be appealed from a state court to a federal court only if there is a federal question; the supreme court of each state is the final authority on the interpretation of that state's laws and constitution.

State and local governments

supreme court of each state. Note that Alaska and Hawaii are shown at different scales, and that the Aleutian Islands and the uninhabited Northwestern Hawaiian Islands are omitted from this map.]] The state governments have the greatest influence over people's daily lives. Each state has its own written constitution and has different laws. There are sometimes great differences in law and procedure between the different states, concerning issues such as property, crime, health, and education. The highest elected official of each state is the Governor. Each state also has an elected legislature (bicameral in every state except Nebraska), whose members represent the different parts of the state. Of note is the New Hampshire legislature, which is the third-largest legislative body in the English-speaking world, and has one representative for every 3,000 people. Each state maintains its own judiciary, with the lowest level typically being county courts, and culminating in each state supreme court, though sometimes named differently. In some states, supreme and lower court justices are elected by the people; in others, they are appointed, as they are in the federal system. The institutions that are responsible for local government are typically town, city, or county boards, making laws that affect their particular area. These laws concern issues such as traffic, the sale of alcohol, and keeping animals. The highest elected official of a town or city is usually the mayor. In New England, towns operate directly democratically, and in some states, such as Rhode Island and Connecticut, counties have little or no power, existing only as geographic distinctions. In other areas, county governments have more power, such as to collect taxes and maintain law enforcement agencies.

Political divisions

With the Declaration of Independence, the thirteen colonies proclaimed themselves to be nation states modeled after the European states of the time. Although considered as sovereigns initially, under the Articles of Confederation of 1781 they entered into a "Perpetual Union" and created a fully sovereign federal state, delegating certain powers to the national Congress, including the right to engage in diplomatic relations and to levy war, while each retaining their individual sovereignty, freedom and independence. But the national government proved too ineffective, so the administrative structure of the government was vastly reorganized with the United States Constitution of 1789. Under this new union, the continued status of the individual states as sovereign nation states fell into dispute in 1861, as several states attempted to secede from the union; in response, then-President Abraham Lincoln claimed that such secession was illegal, and the result was the American Civil War. Since the Union victory in 1865, the independent status of the individual states has not been broached again by any state, and the status of each state within the union has been deemed by mainstream officials and academics to be settled as being subordinate to the union as a whole. In subsequent years, the number of states grew steadily due to western expansion, the purchase of lands by the national government from other nation states, and the subdivision of existing states, resulting in the current total of 50. The states are generally divided into smaller administrative regions, including counties, cities and townships. The United States–Canadian border is the longest undefended political boundary in the world. The U.S. is divided into three distinct sections:
- the "continental United States," also known as "the Lower 48" and more accurately termed the conterminous, coterminous or contiguous United States
- Alaska, which is physically connected only to Canada
- the archipelago of Hawaii, in the central Pacific Ocean. The United States also holds several other territories, districts, and possessions, notably the federal district of the District of Columbia, which is the nation's capital, and several overseas insular areas, the most significant of which are American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Palmyra Atoll is the United States' only incorporated territory; it is unorganized and uninhabited. The United States Navy has held a base at a portion of Guantanamo Bay, Cuba, since 1898. The United States government possesses a lease to this land, which only mutual agreement or United States abandonment of the area can terminate. The present Cuban government of Fidel Castro disputes this arrangement, claiming Cuba was not truly sovereign at the time of the signing. The United States argues this point moot because Cuba apparently ratified the lease post-revolution, and with full sovereignty, when it cashed one rent check in accordance with the disputed treaty.

Foreign relations and military

sovereign] The immense military and economic dominance of the United States has made foreign relations an especially important topic in its politics, with considerable concern about the image of the United States throughout the world. Reactions towards the United States by other nationalities are often strong, ranging from uninhibited admiration and mimicking of all things American to anti-Americanism. US foreign policy has swung about several times over the course of its history between the poles of strict isolationism and imperialism and everywhere in between. Three of the nation's four military branches are administered by the Department of Defense: the Army, the Navy (including the Marine Corps), and the Air Force. The Coast Guard falls under the jurisdiction of the Department of Homeland Security in peacetime, but is placed under the Department of the Navy in time of war. The combined United States armed forces consist of 1.4 million active duty personnel, along with several hundred thousand each in the Reserves and the National Guard. Military conscription ended in 1973. The United States Armed forces are considered to be the most powerful military (of any sort) on Earth and their force projection capabilities are unrivaled by any other nation. The 2005 defense budget amounted to $401.7 billion, which is an increase of 4% over 2004 and of 35% since 2001. Over 50% of that number is spent in research & development. (For comparison, in 2004 the European Union (considered as the second-largest military force) had a combined total of 1.6 million troops, and a defense budget of €160 billion, with less than 10% of that being spent on R&D.)

Largest cities

The United States has dozens of major cities, including 11 of the 55 global cities of all types — with three "alpha" global cities: New York City, Los Angeles, and Chicago. The figures expressed below are for populations within city limits. A different ranking is evident when considering U.S. metro area populations, although the top three would be unchanged. Note that some cities not listed (such as Atlanta, Boston, Las Vegas, Miami, Nashville, New Orleans, Seattle, and Washington, D.C.) are still considered important on the basis of other factors and issues, including culture, economics, heritage, and politics. The twenty largest cities, based on the United States Census Bureau's 2004 estimates, are as follows:

Economy

The United States has the largest single-country economy in the world, with a per-capita gross domestic product of $40,100. In this market-oriented economy, private individuals and business firms make most of the decisions, and the federal and state governments buy needed goods and services predominantly in the private marketplace. gross domestic product The largest industry of the U.S. is now service, which employs roughly three quarters of the U.S. work force. The United States has many natural resources, including oil and gas, metals, and such minerals as gold, soda ash, and zinc. In agriculture, the U.S. is a top producer of, among other crops, corn, soy beans, and wheat; the United States is a net exporter of food. The U.S. manufacturing sector produces goods such as, cars, airplanes, steel, and electronics, among many others. Economic activity varies greatly from one part of the country to another, with many industries being largely dependent on a certain city or region; New York City is the center of the American financial, publishing, broadcasting, and advertising industries; Silicon Valley is the country’s primary location for high-technology companies, while Los Angeles is the most important center for film production. The Midwest is known for its reliance on manufacturing and heavy industry, with Detroit, Michigan, serving as the center of the American automotive industry; the Great Plains are known as the "breadbasket" of America for their tremendous agricultural output; the intermountain region serves as a mining hub and natural gas resource; the Pacific Northwest for fish and timber, while Texas is largely associated with the oil industry; the Southeast is a major hub for both medical research and the textiles industry. Several countries continue to link their currency to the dollar or even use it as a currency (such as Ecuador), although this practice has subsided since the collapse of the Bretton Woods system. Many markets are also quoted in dollars, such as those of oil and gold. The dollar is also the predominant reserve currency in the world, and more than half of global reserves are in dollars. The largest trading partner of the United States is Canada (19%), followed by China (12%), Mexico (11%), and Japan (8%). More than 50% of total trade is with these four countries. In 2003, the United States was ranked as the third most visited tourist destination in the world; its 40,400,000 visitors ranked behind France's 75,000,000 and Spain's 52,500,000. Labor unions have existed since the 19th century, and grew large and powerful from the 1930s to the 1950s. See Labor history of the United States. Since 1970 they have shrunk in the private sector and now cover fewer than 8% of the workers. However union membership has grown rapidly in the public sector, especially among teachers, nurses, police, postal workers, and municipal clerks. There have been few strikes in recent years. The United States' imports exceed exports by 80%, leading to an annual trade deficit of $700,000,000,000, or 6% of gross domestic product. It is the largest debtor nation in the world, with total gross foreign debt of over $13,000,000,000,000 (2005 estimate); and it absorbs more than 50% of global savings annually. Since the 1980s, the U.S. has increased the use of neoliberal economic policies that reduce government intervention and reduce the size of the welfare state, backing away from the more interventionist Keynsian economic policies that had been in favor since the Great Depression. As a result, the United States provides fewer government-delivered social welfare services than most industrialized nations, choosing instead to keep its tax burden lower and relying more heavily on the free market and private charities. Sixteen states and the District of Columbia have minimum wages higher than the national level ($5.15 per-hour), including the highest, Washington State at $7.35. Twenty-six states are the same as the federal level; two--Ohio and Kansas--are below; and six do not have state laws. America's wealth is relatively highly concentrated. The average C.E.O. earns 500 times the typical amount a worker grosses, this is up from 25 times in the late 1970s. In terms of wealth the top 1% of Americans own 40% of all assets and 50.1% of the country's income goes to the top twenty percent of households. Average wages for the majority of employees have been largely stagnating since the 1970s. America's poverty line defined as a family of four earning less than $19,157 is at 12.7% of the general population. Approximately one out of every five children in the United States grows up below the official poverty line. Among racial groups; African Americans have the lowest median income while Asians had the highest. Regionally, the southern states had the lowest median incomes while the West Coast and New England had the highest. The current Federal Reserve Chairman Alan Greenspan remarked that the U.S.’s growing income inequality since the 1970s is, "not the type of thing which a democratic society - a capitalist democratic society - can really accept without addressing."[http://www.csmonitor.com/2005/0614/p01s03-usec.html?s=itm] However, Greenspan also noted, "...you can look at the system and say it's got a lot of problems to it, and sure it does. It always has. But you can't get around the fact that this is the most extraordinarily successful economy in history."

Transportation

Alan Greenspan ]] Because the United States is a relatively young nation, most of the development of U.S. cities has taken place since the invention of the automobile. To link its vast territory, the United States built a network of high-capacity, high-speed highways, of which the most important element is the Interstate Highway system, commissioned in the 1950s by President Dwight D. Eisenhower and modeled after the German Autobahn. The United States also has a transcontinental rail system, which is used for moving freight across the lower forty-eight states. Passenger rail service is provided by Amtrak, which serves forty-six of the lower forty-eight states. Many cities in the United States have extensive mass-transit systems. New York City operates one of the world's largest and most heavily used subway systems. The regional rail and bus networks that extend into Long Island, New Jersey, Upstate New York, and Connecticut are among the most heavily used in the world. Air travel is often preferred for destinations over 300 miles (500 kilometers) away. In terms of passengers, seventeen of the world's thirty busiest airports in 2004 were in the U.S., including the world's busiest, Hartsfield-Jackson Atlanta International Airport; in terms of cargo, in the same year, twelve of the world's thirty busiest airports were in the U.S., including the world's busiest, Memphis International Airport. There are several major seaports in the United States; the three busiest are the Port of Los Angeles, California; the Port of Long Beach, California; and the Port of New York and New Jersey. Others include Houston, Texas; Charleston, South Carolina; Savannah, Georgia; Miami, Florida; Portland, Oregon; San Francisco, California; Boston, Massachusetts; Philadelphia, Pennsylvania; and Seattle, Washington; plus, outside the contiguous forty-eight states, Anchorage, Alaska, and Honolulu, Hawaii.

Society

Demographics

Hawaii The mean center of the U.S. population continues to drift farther west and south. The fastest growing region is the western United States followed by the southern portion. According to Census 2000, the states that saw the greatest increases from 1990 were: Nevada (66.3%), Arizona (40%), Colorado (30.6%), Utah (29.6%), Idaho (28.5%), Georgia (26.4%), Florida (23.5%), Texas (22.8%), North Carolina (21.4%), and Washington (21.1%). [http://www.census.gov/population/cen2000/phc-t2/tab03.pdf]

Ethnicity and race

:Main article: Racial demographics of the United States The United States is a very racially diverse country. According to the 2000 census, it has 31 ethnic groups with at least one million members each, and numerous others represented in smaller amounts. The majority of Americans descend from white European immigrants who arrived at the establishment of the first colonies (most after Reconstruction). This majority--69.1% in 2000--decreases each year, and is expected to become a plurality within a few decades. The most frequently stated European ancestries are German (15.2%), Irish (10.8%), English (8.7%), Italian (5.6%) and Scandinavian (3.7%). Many immigrants also hail from Slavic countries such as Poland and Russia. Other significant immigrant populations came from eastern and southern Europe and French Canada. Russia Hispanics from Mexico and South and Central America are the largest minority group in the country, comprising 12.5% of the population (2000 census). People of Mexican descent made up 7.3% of the population in the 2000 census, and this proportion is expected to increase significantly in the coming decades. About 12.3% (2000 census) of the American people are African Americans (Blacks). African Americans are spread throughout the country, but their presence is largest in the South. Asian Americans--including Native Hawaiians and Pacific Islanders--are a third significant minority (3.7% of the population in 2000). Most Asian Americans are concentrated on the West Coast and Hawaii. The largest groups are immigrants or descendants of emigrants from the Philippines, China, India, Vietnam, South Korea, and Japan. Indigenous peoples in the United States, such as American Indians and Inuit, make up 0.9% of the population (2000 census). About 35% live on Indian reservations.

Religion

Polls estimate that just under 80 percent of Americans are Christians of various denominations. The other 20 percent comprises other religions such as Hinduism, Judaism, Islam, and Buddhism, other various faiths, and those without a specific religion. The United States is noteworthy among developed nations for its relatively high level of religiosity. According to a 2004 Gallup poll, about 44% of Americans attend a religious service at least once a week. However, this rate is not uniform across the country; attendance is more common in the Bible Belt—composed largely of Southern and Midwestern states—than in the Northeast and West Coast. In the Southern states, Baptists are the largest group, followed by Methodists; Roman Catholics are dominant in the Northeast and in large parts of the Midwest due to their being settled by descendants of Catholic immigrants from Europe (such as Germany, Ireland, Italy, and Poland) or other parts of North America (mainly Quebec and Puerto Rico). The rest of the country for the most part has a complex mixture of various Christian groups.

Education

West Coast's home at Monticello and the University of Virginia (library building shown above, and designed by Jefferson), the only collegiate campus on the list. Both sites are located in Charlottesville, Virginia.]] In the United States, education is a state, not federal, responsibility, and the laws and standards vary considerably. However, the federal government, through the Department of Education, is involved with funding of some programs and exerts some influence through its ability to control funding. In most states, all students must attend mandatory schooling starting with kindergarten, which children normally enter at age 5, and following through 12th grade, which is normally completed at age 18

Silicone

Silicones, or polysiloxanes, are inorganic polymers consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. C