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The 1984 Summer Olympics in Los Angeles was the first time that massage therapy was televised as it was being performed on the athletes. And then, during the 1996 Summer Olympics in Atlanta massage therapy was finally offered as a core medical service to the US Olympic Team. Massage has been employed by businesses and organizations such as the U.S. Department of Justice, Boeing and Reebok. Athletes such as Michael Jordan and LeBron James have personal massage therapists that at times even travel with them.
Types and methods
Acupressure
Acupressure [from Latin acus "needle" (see acuity) + pressure (n.)] is a technique similar in principle to acupuncture. It is based on the concept of life energy which flows through "meridians" in the body. In treatment, physical pressure is applied to acupuncture points with the aim of clearing blockages in those meridians. Pressure may be applied by fingers, palm, elbow, toes or with various devices.
Some medical studies have suggested that acupressure may be effective at helping manage nausea and vomiting, for helping lower back pain, tension headaches, stomach ache, among other things, although such studies have been found to have a high likelihood of bias.
Ashiatsu
In ashiatsu, the practitioner uses their feet to deliver treatment. The name comes from the Japanese, ashi for foot and atsu for pressure. This technique typically uses the heel, sesamoid, arch, and/or whole plantar surface of foot, and offers large compression, tension and shear forces with less pressure than an elbow and is ideal for large muscles, such as in thigh, or for long-duration upper trapezius compressions. Other manual therapy techniques using the feet to provide treatment include Keralite, Barefoot Lomilomi, and Chavutti Thirumal.
Ayurvedic massage
Ayurvedic massage is known as Abhyangam in Sanskrit. According to the Ayurvedic Classics Abhyangam is an important dincharya (Daily Regimen) that is needed for maintaining a healthy lifestyle. The massage technique used during Ayurvedic Massage aims to stimulate the lymphatic system. Practitioners claim that the benefits of regular Ayurvedic massage include pain relief, reduction of fatigue, improved immune system and improved longevity.
Burmese massage | Massage | Wikipedia | 486 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
"Known in Myanmar as Yoe Yar Nhake Nal Chin, meaning 'traditional massage', Burmese massage has its ancient origins from Thai, Chinese and Indian medicine. Currently, Burmese massage also includes the use of local natural ingredients such as Thanaka which helps to promote smooth skin and prevents sunburn."
Burmese massage is a full body massage technique that starts from head to toes, drawing on acupuncture, reflexology and kneading. Signature massage strokes include acupressure using the elbows, quick gentle knocking of acupressure points, and slow kneading of tight muscles. The massage aims to improve blood circulation and quality of sleep, while at the same time help to promote better skin quality.
Biomechanical stimulation (BMS) massage
Biomechanical stimulation (BMS) is a term generally used for localised biomechanical oscillation methods, whereby local muscle groups are stimulated directly or via the associated tendons by means of special hand held mechanical vibration devices. Biomechanical oscillation therapy and training is offered in a variety of areas such as competitive sports, fitness, rehabilitation, medicine, prevention, beauty and used to improve performance of the muscles and to improve coordination and balance. It is often used in myofascial trigger point therapy to invoke reciprocal inhibition within the musculoskeletal system. Beneficial effects from this type of stimulation have been found to exist.
Biodynamic massage
Biodynamic massage was created by Gerda Boyesen as part of Biodynamic Psychotherapy. It uses a combination of hands-on work and "energy work" and also uses a stethoscope to hear the peristalsis.
Craniosacral therapy
Craniosacral therapy (CST) is a pseudoscience that aims to improve fluid movement and cranial bone motion by applying light touch to the skull, face, spine, and pelvis.
Erotic massage
A type of massage that is done in an erotic way via the use of massage techniques by a person on another person's erogenous zones to achieve or enhance their sexual excitation or arousal and to achieve orgasm.
It was also once used for medical purposes as well as for the treatment of "female hysteria" and "womb disease".
Nuru massage is a Japanese form of erotic massage.
Hammam ("Turkish bath") massage | Massage | Wikipedia | 492 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
In the traditional Hammam, massage involves not just vigorous muscle kneading, but also joint cracking, "not so much a tender working of the flesh as a pummeling, a cracking of joints, a twisting of limbs..." An 18th-century traveler reported:
Lomilomi and indigenous massage of Oceania
Lomilomi is the traditional massage of Hawaii. As an indigenous practice, it varies by island and by family. The word lomilomi also is used for massage in Samoa and East Futuna. In Samoa, it is also known as lolomi and milimili. In East Futuna, it is also called milimili, fakasolosolo, amoamo, lusilusi, kinikini, fai’ua. The Māori call it romiromi and mirimiri. In Tonga massage is fotofota, tolotolo, and amoamo. In Tahiti it is rumirumi. On Nanumea in Tuvalu, massage is known as popo, pressure application is kukumi, and heat application is tutu. Massage has also been documented in Tikopia in the Solomon Islands, in Rarotonga, in Pukapuka and in Western Samoa.
Lymphatic drainage
Manual lymphatic drainage is a technique used to gently work and stimulate the lymphatic system, to assist in reduction of localized swelling. The lymphatic system is a network of slow moving vessels in the body that carries cellular waste toward the liver, to be filtered and removed. Lymph also carries lymphocytes and other immune system agents. Manual lymphatic drainage claims to improve waste removal and immune function.
Medical massage
Medical massage is a controversial term in the massage profession. Many use it to describe a specific technique. Others use it to describe a general category of massage and many methods such as deep tissue massage, myofascial release and trigger-point therapy, as well as osteopathic techniques, cranial-sacral techniques and many more can be used to work with various medical conditions. | Massage | Wikipedia | 436 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Massage used in the medical field includes decongestive therapy used for lymphedema which can be used in conjunction with the treatment of breast cancer. Light massage is also used in pain management and palliative care. Carotid sinus massage is used to diagnose carotid sinus syncope and is sometimes useful for differentiating supraventricular tachycardia (SVT) from ventricular tachycardia. It, like the valsalva maneuver, is a therapy for SVT. However, it is less effective than management of SVT with medications.
A 2004 systematic review found single applications of massage therapy "reduced state anxiety, blood pressure, and heart rate but not negative mood, immediate assessment of pain, and cortisol level," while "multiple applications reduced delayed assessment of pain," and found improvements in anxiety and depression similar to effects of psychotherapy. A subsequent systematic review published in 2008 found that there is little evidence supporting the use of massage therapy for depression in high quality studies from randomized controlled trials.
Myofascial release
Myofascial release refers to the manual massage technique that claims to release adhered fascia and muscles with the goal of eliminating pain, increasing range of motion and equilibrioception. Myofascial release usually involves applying shear compression or tension in various directions, cross fiber friction or by skin rolling.
Reflexology
Reflexology, also known as "zone therapy", is an alternative medicine involving application of pressure to the feet and hands with specific thumb, finger, and hand techniques without the use of oil or lotion. It is based on a pseudoscientific belief in a system of zones and reflex areas that purportedly reflect an image of the body on the feet and hands, with the premise that such work effects a physical change to the body.
Shiatsu
Shiatsu (指圧) (shi meaning finger and atsu meaning pressure) is a form of Japanese bodywork based on concepts in traditional Chinese medicine such as qi meridians. It consists of finger, palm pressure, stretches, and other massage techniques. There is no convincing data available to suggest that shiatsu is an effective treatment for any medical condition.
Sports massage | Massage | Wikipedia | 453 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Sports massage is the use of specific massage therapy techniques in an athletic context to improve recovery time, enhance performance and reduce the risk of injury. This is accomplished using techniques that stimulate the flow of blood and lymph to and from muscles. Sports massage is often delivered before or after physical activity depending on the subject's needs, preferences and goals.
Structural Integration
Structural Integration's aim is to unwind the strain patterns in the body's myofascial system, restoring it to its natural balance, alignment, length and ease. This is accomplished by hands-on manipulation, coupled with movement re-education. There are about 15 schools of Structural Integration as recognized by the International Association of Structural Integration, including the Dr. Ida Rolf Institute (with the brand Rolfing), Hellerwork, Guild for Structural Integration, Aston Patterning, Soma, and Kinesis Myofascial Integration.
Swedish massage
The most widely recognized and commonly used category of massage is Swedish massage. The Swedish massage techniques vary from light to vigorous. Swedish massage uses five styles of strokes. The five basic strokes are effleurage (sliding or gliding), petrissage (kneading), tapotement (rhythmic tapping), friction (cross fiber or with the fibers) and vibration/shaking.
The development of Swedish massage is often inaccurately credited to Per Henrik Ling, though the Dutch practitioner Johann Georg Mezger applied the French terms to name the basic strokes. The term "Swedish massage" is actually only recognized in English- and Dutch-speaking countries, and in Hungary and Israel. Elsewhere the style is referred to as "classic massage".
Clinical studies have found that Swedish massage can reduce chronic pain, fatigue, joint stiffness and improve function in patients with osteoarthritis of the knee.
Thai massage
Known in Thailand as Nuat phaen boran, meaning "ancient/traditional massage", traditional Thai massage is generally based on a combination of Indian and Chinese traditions of medicine.
Thai massage combines both physical and energetic aspects. It is a deep, full-body massage progressing from the feet up, and focusing on sen or energy lines throughout the body, with the aim of clearing blockages in these lines, and thus stimulating the flow of blood and lymph throughout the body. It draws on yoga, acupressure and reflexology. | Massage | Wikipedia | 478 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Thai massage is a popular massage therapy that is used for the management of conditions such as musculoskeletal pain and fatigue. Thai massage involves a number of stretching movements that improve body flexibility, joint movement and also improve blood circulation throughout the body. In one study scientists found that Thai massage showed comparable efficacy as the painkiller ibuprofen in the reduction of joint pain caused by osteoarthritis (OA) of the knee.
Traditional Chinese massage
Massage of Chinese Medicine is known as An Mo (按摩) (pressing and rubbing) or Qigong Massage and is the foundation of Japan's Anma. Categories include Pu Tong An Mo (普通按摩) (general massage), Tui Na An Mo (推拿按摩) (pushing and grasping massage), Dian Xue An Mo (cavity pressing massage), and Qi An Mo (氣按摩 ) (energy massage). Tui na (推拿) focuses on pushing, stretching, and kneading muscles, and Zhi Ya(指壓) focuses on pinching and pressing at acupressure points. Technique such as friction and vibration are used as well.
Trigger point therapy
Sometimes confused with pressure point massage, this involves deactivating trigger points that may cause local pain or refer pain and other sensations, such as headaches, in other parts of the body. Manual pressure, vibration, injection, or other treatment is applied to these points to relieve myofascial pain. Trigger points were first discovered and mapped by Janet G. Travell (President Kennedy's physician) and David Simons. Trigger points have been photomicrographed and measured electrically and in 2007 a paper was presented showing images of Trigger Points using MRI. These points relate to dysfunction in the myoneural junction, also called neuromuscular junction (NMJ), in muscle, and therefore this technique is different from reflexology acupressure and pressure point massage.
Tui na
Tui na is a Chinese manual therapy technique that includes many different types of strokes, aimed to improve the flow of chi through the meridians.
Watsu | Massage | Wikipedia | 436 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Watsu, developed by Harold Dull at Harbin Hot Springs, California, is a type of aquatic bodywork performed in near-body-temperature water, and characterized by continuous support by the practitioner and gentle movement, including rocking, stretching of limbs, and massage. The technique combines hydrotherapy floating and immersion with shiatsu and other massage techniques. Watsu is used as a form of aquatic therapy for deep relaxation and other therapeutic intent. Related forms include Waterdance, Healing Dance, and Jahara technique.
Facilities, equipment, and supplies
Massage tables and chairs
Specialized massage tables and chairs are used to position recipients during massages. A typical commercial massage table has an easily cleaned, heavily padded surface, and horseshoe-shaped head support that allows the client to breathe easily while lying face down and can be stationary or portable, while home versions are often lighter weight or designed to fold away easily. An orthopedic pillow or bolster can be used to correct body positioning.
Ergonomic chairs serve a similar function as a massage table. Chairs may be either stationary or portable models. Massage chairs are easier to transport than massage tables, and recipients do not need to disrobe to receive a chair massage. Due to these two factors, chair massage is often performed in settings such as corporate offices, outdoor festivals, shopping malls, and other public locations.
Warm-water therapy pools
Temperature-controlled warm-water therapy pools are used to perform aquatic bodywork. For example, Watsu requires a warm-water therapy pool that is approximately chest-deep (depending on the height of the therapist) and temperature-controlled to about 35 °C (95 °F).
Dry-water massage tables
A dry-water massage table uses jets of water to perform the massage of the patient's muscles. These tables differ from a Vichy shower in that the client usually stays dry. Two common types are one in which the client lies on a waterbed-like mattress which contains warm water and jets of water and air bubbles and one in which the client lies on a foam pad and is covered by a plastic sheet and is then sprayed by jets of warm water, similar to a Vichy shower. The first type is sometimes seen available for use in shopping centers for a small fee. | Massage | Wikipedia | 451 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Vichy showers
A Vichy shower is a form of hydrotherapy that uses a series of shower nozzles that spray large quantities of water over the client while they lie in a shallow wet bed, similar to a massage table, but with drainage for the water. The nozzles may usually be adjusted for height, direction, and temperature to suit the patient's needs.
Cremes, lotions, gels, and oils
Many different types of massage cremes, lotions, gels, and oils are used to lubricate and moisturize the skin and reduce the friction between skin (hands of technician and client).
Massage tools
These instruments or devices are sometimes used during massages. Some tools are for use by individuals, others by the therapist.
Tools used by massage therapists
Instrument-assisted soft-tissue massage can deploy stainless-steel devices to manipulate tissue in a way that augments hands-on work.
A body rock is a serpentine-shaped tool, usually carved out of stone. It is used to amplify the therapist' strength and focus pressure on certain areas. It can be used directly on the skin with a lubricant such as oil or corn starch or directly over clothing.
Bamboo and rosewood tools are also commonly used. They originate from practices in southeast Asia, Thailand, Cambodia, and Burma. Some of them may be heated, oiled, or wrapped in cloth.
Cupping massage is often carried out using plastic cups and a manual hand-pump to create the vacuum. The vacuum draws the soft tissue perpendicular to the skin, providing a tensile force, which can be left in one site or moved along the tissue during the massage.
Tools used by both individuals and massagers
Hand-held battery-operated massaging and vibrating instruments are available, including devices for massaging the scalp following a haircut.
Vibrating massage pads come in a range of sizes, some with the option of heating.
Vibrating massage chairs can provide an alternative for therapy at home.
There is a widespread market in erotic massage instruments, including electric dildos and vibrators such as the massage wand. | Massage | Wikipedia | 428 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Medical and therapeutic use
The main professionals that provide therapeutic massage are massage therapists, athletic trainers, physical therapists, and practitioners of many traditional Chinese and other eastern medicines. Massage practitioners work in a variety of medical settings and may travel to private residences or businesses. Contraindications to massage include deep vein thrombosis, bleeding disorders, taking blood thinners such as warfarin, damaged blood vessels, or weakened bones from cancer, osteoporosis, fractures, and fever.
Beneficial effects
Peer-reviewed medical research has shown that the benefits of massage include pain relief, reduced trait anxiety and depression, temporarily reduced blood pressure, heart rate, and state of anxiety. Additional testing has shown an immediate increase in, and expedited recovery periods for, muscle performance. Theories behind what massage might do include: enhanced skeletal muscle regrowth and remodeling, blocking nociception (gate control theory), activating the parasympathetic nervous system (which may stimulate the release of endorphins and serotonin, preventing fibrosis or scar tissue), increasing the flow of lymph, and improving sleep.
Infant massage has been found to hold therapeutic benefits for premature infants and their parents. Premature infants are susceptible to low birth weight and decreased immune function; massage has been found to counter these effects, causing weight increase, reduced pain, and increased immune function. Administering infant massage also reduces stress and increased oxytocin in parental figures regardless of gender, and overall improves emotional attachment with their child.
Massage research is hindered from reaching the gold standard of scientific inquiry, which includes placebo-controlled and double blind clinical trials. Developing a "sham" manual therapy for massage would be difficult since even light touch massage could have effects on a subject. It would also be difficult to find a subject that would not notice that they were getting less of a massage, and it would be impossible to blind the therapist. Massage research can employ randomized controlled trials, which are published in peer reviewed medical journals. This type of study could increase the credibility of the profession because it displays that purported therapeutic effects are reproducible.
Single-dose effects | Massage | Wikipedia | 440 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Pain relief: Relief from pain due to musculoskeletal injuries and other causes is cited as a major benefit of massage. A 2015 Cochrane Review concluded that there is very little evidence that massage is an effective treatment for lower back pain. A meta-analysis conducted by scientists at the University of Illinois Urbana-Champaign failed to find a statistically significant reduction in pain immediately following treatment. Weak evidence suggests that massage may improve pain in the short term for people with acute, sub-acute, and chronic lower back pain.
State anxiety: Massage has been shown to reduce state anxiety, a transient measure of anxiety in a given situation.
Blood pressure and heart rate: Massage has been shown to temporarily reduce blood pressure and heart rate.
Multiple-dose effects
Pain relief: Massage may reduce pain experienced in the days or weeks after treatment.
Trait anxiety: Massage has been shown to reduce trait anxiety; a person's general susceptibility to anxiety.
Depression: Massage has been shown to reduce sub-clinical depression.
Neuromuscular effects
Massage has been shown to reduce neuromuscular excitability by measuring changes in the Hoffman's reflex (H-reflex) amplitude. A decrease in peak-to-peak H-reflex amplitude suggests a decrease in motoneuron excitability. Others explain, "H-reflex is considered to be the electrical analogue of the stretch reflex... and the reduction" is due to a decrease in spinal reflex excitability. Field (2007) confirms that the inhibitory effects are due to deep tissue receptors and not superficial cutaneous receptors, as there was no decrease in H-reflex when looking at light fingertip pressure massage. It has been noted that "the receptors activated during massage are specific to the muscle being massaged," as other muscles did not produce a decrease in H-reflex amplitude.
Global regulation and practice
Because the art and science of massage is a globally diverse phenomenon, different legal jurisdictions sometimes recognize and license individuals with titles, while other areas do not. Examples are:
Registered Massage Therapist (RMT) in Canada and New Zealand
Certified Massage Therapist (CMT) in New Zealand
Licensed Massage Practitioner (LMP)
Licensed Massage Therapist (LMT)
Licensed Massage and Bodywork Therapist (LMBT) in North Carolina
Therapeutic Massage Therapist (TMT) in South Africa
In some jurisdictions, practicing without a license is a crime. One such jurisdiction is Washington state, where any health professionals practicing without a license can be issued a fine and charged with a misdemeanor offense. | Massage | Wikipedia | 512 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Canada
In regulated provinces massage therapists are known as Registered Massage Therapists, in Canada six provinces regulate massage therapy: British Columbia, Ontario, Newfoundland and Labrador, Prince Edward Island, Saskatchewan, and New Brunswick. Registered Massage Therapy in British Columbia is regulated by the College of Massage Therapists of British Columbia (CMTBC). Regulated provinces have, since 2012, established inter-jurisdiction competency standards. Quebec is not provincially regulated. Massage therapists may obtain a certification with one of the various associations operating. There is the Professional Association of Specialized Massage Therapists of Quebec, also named Mon Réseau Plus, which represents 6,300 massage therapists (including ortho therapist, natural therapists, and others), the Quebec Federation of massage therapists (FMQ), and the Association québécoise des thérapeutes naturals; however, none of these are regulated by provincial law.
Canadian educational institutions undergo a formal accreditation process through the Canadian Massage Therapy Council for Accreditation (CMTCA).
China
Most types of massage, with the exception of some traditional Chinese medicine, are not regulated in China. Although illegal in China, some of the smaller massage parlors are sometimes linked to the sex industry and the government has taken a number of measures in recent times to curb this. In a nationwide crackdown known as the yellow sweep ("Yellow" in Mandarin Chinese refers to sexual activities or pornographic content), limitations on the design and operation of massage parlors have been placed, going so far as requiring identification from customers who visit massage establishments late at night and logging their visits with the local police.
France
France requires three years of study and two final exams in order to apply for a license. | Massage | Wikipedia | 344 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Germany
In Germany, massage is regulated by the government on a federal and national level. Only someone who has completed 3,200 hours of training (theoretical and practical) can use the professional title "Masseur und Medizinischer Bademeister" 'Masseur and Medical Spa Therapist'. This person can prolong his training depending on the length of professional experience to a Physiotherapist (1 year to 18 months additional training). The Masseur is trained in Classical Massage, Myofascial Massage, Exercise, and Movement Therapy. During the training, they will study anatomy, physiology, pathology, gynecology, podiatry, psychiatry, psychology, surgery, dermiatry, and orthopedics. They are trained in Electrotherapy and Hydrotherapy. Hydrotherapy includes Kneipp, Wraps, underwater massage, therapeutic washing, Sauna, and Steambath. A small part of their training will include special forms of massage which are decided by the local college, for example, foot reflex zone massage, Thai Massage, etc. Finally, a graduate is allowed to treat patients under the direction of a doctor. Graduates are regulated by the professional body which regulates Physiotherapists. This includes restrictions on advertising and the oath of confidentiality to clients.
India
In India, massage therapy is licensed by The Department of Ayurveda, Yoga & Naturopathy, Unani, Siddha, and Homoeopathy (AYUSH) under the Ministry of Health and Family Welfare (India) in March 1995. Massage therapy is based on Ayurveda, the ancient medicinal system that evolved around 600 BC. In ayurveda, massage is part of a set of holistic medicinal practices, contrary to the independent massage system popular in some other systems. In Siddha, Tamil traditional medicine from south India, massage is termed as "Thokkanam" and is classified into nine types, each for a specific variety of diseases.
Japan
In Japan, shiatsu is regulated but oil massage and Thai massage are not. Prostitution in Japan is not heavily policed, and prostitutes posing as massage therapists in "fashion health" shops and "pink salons" are fairly common in the larger cities. | Massage | Wikipedia | 453 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Myanmar
In Myanmar, massage is unregulated. However, it is necessary to apply for a spa license with the government to operate a massage parlor in major cities such as Yangon. Blind and visually impaired people can become masseurs, but they are not issued licenses. There are a few professional spa training schools in Myanmar but these training centers are not accredited by the government.
Mexico
In Mexico massage therapists, called sobadores, combine massage using oil or lotion with a form of acupuncture and faith. Sobadores are used to relieve digestive system problems as well as knee and back pain. Many of these therapists work out of the back of a truck, with just a curtain for privacy. By learning additional holistic healer's skills in addition to massage, the practitioner may become a curandero.
In some jurisdictions, prostitution in Mexico is legal, and prostitutes are allowed to sell sexual massages. These businesses are often confined to a specific area of the city, such as the Zona Norte in Tijuana.
New Zealand
In New Zealand, massage is unregulated. There are two levels of registration with Massage New Zealand, the professional body for massage therapists within New Zealand, although neither of these levels are government recognized. Registration at the certified massage therapist level denotes competency in the practice of relaxation massage. Registration at the remedial massage therapist denotes competency in the practice of remedial or orthopedic massage. Both levels of registration are defined by agreed minimum competencies and minimum hours.
South Africa
In South Africa, massage is regulated, but enforcement is poor. The minimum legal requirement to be able to practice as a professional massage therapist is a two-year diploma in therapeutic massage and registration with the Allied Health Professions Council of SA (AHPCSA). The qualification includes 240 credits, about 80 case studies, and about 100 hours of community service.
South Korea
In South Korea, only blind and visually impaired people can become licensed masseurs.
Thailand
In Thailand, Thai massage is officially listed as one of the branches of traditional Thai medicine, recognized and regulated by the government. It is considered to be a medical discipline in its own right and is used for the treatment of a wide variety of ailments and conditions. Massage schools, centers, therapists, and practitioners are increasingly regulated by the Ministries of Education and Public Health in Thailand. | Massage | Wikipedia | 484 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
United Kingdom
To practice commercial massage or massage therapy in the UK, an ITEC or VTCT certificate must be obtained through training which includes Beauty and Spa Therapy, Hairdressing, Complementary Therapies, Sports & Fitness Training and Customer Service.
Therapists with appropriate paperwork and insurance may join the Complementary and Natural Healthcare Council (CNHC), a voluntary, government regulated, professional register. Its key aim is to protect the public.
In addition, there are many professional bodies that have a required minimum standard of education and hold relevant insurance policies including the Federation of Holistic Therapists (FHT), the Complementary Therapists Association (CThA), and the Complementary Health Professionals (CHP). In contrast to the CNHC these bodies exist to support therapists rather than clients.
United States
According to research done by the American Massage Therapy Association, as of 2012 in the United States, there are between 280,000 and 320,000 massage therapists and massage school students. As of 2022, there are an estimated 872 state-approved massage training programs operating in the U.S. Most states have licensing requirements that must be met before a practitioner can use the title "massage therapist", and some states and municipalities require a license to practice any form of massage. If a state does not have any massage laws then a practitioner need not apply for a license with the state. Training programs in the US are typically 500 hours to 1000 hours in total training time and can award a certificate, diploma, or degree depending on the particular school. Study will often include anatomy and physiology, kinesiology, massage techniques, first aid and CPR, business, ethical and legal issues, and hands-on practice along with continuing education requirements if regulated. The Commission on Massage Therapy Accreditation (COMTA) is one of the organizations that works with massage schools in the U.S. and there are almost 300 schools that are accredited through this agency. | Massage | Wikipedia | 391 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
Forty-seven states, Puerto Rico, and the District of Columbia currently offer some type of credential to professionals in the massage and bodywork field—usually licensure, certification or registration. Forty-five states require some type of licensing for massage therapists. There are two nationally recognized tests gain a massage therapy license, as well as state-specific exams. In the US, 38 states accept the now defunct National Certification Board for Therapeutic Massage and Bodywork's (NCBTMB) certification program as a basis for granting licenses either by rule or statute. The NCBTMB formerly offered the designation Nationally Certified in Therapeutic Massage and Bodywork (NCTMB) but now only offers its certificate program, Board Certification in Therapeutic Massage and Bodywork (BCTMB) which does not qualify for licensure. Forty-three states, as well as Puerto Rico and the District of Columbia, accept the Massage & Bodywork Licensing Examination (MBLEx), administered by the Federation of State Massage Therapy Boards (FSMTB). Between 10% and 20% of towns or counties independently regulate the profession. These local regulations can range from prohibition on opposite sex massage, fingerprinting and venereal checks from a doctor, to prohibition on house calls because of concern regarding sale of sexual services.
In the US, licensure is the highest level of regulation and this restricts anyone without a license from practicing massage therapy or calling themselves by that protected title. Certification allows only those who meet certain educational criteria to use the protected title and registration only requires a listing of therapists who apply and meet an educational requirement. In the US, most certifications are locally based. A massage therapist may be certified, but not licensed. Licensing requirements vary per state, and often require additional criteria be met in addition to attending an accredited massage therapy school and passing a required state-specified exam. Only Kansas, Minnesota, and Wyoming, California and Vermont do not require a license or a certification at the state level. Some states allow license reciprocity, where licensed massage therapists who relocate can relatively easily obtain a license in their new state.
In New York State in 2024, a man was arrested and charged with three counts of third-degree Sexual Abuse and three counts of Forcible Touching, as well as New York State Education Department Law violations, for providing massage therapy services without a New York State license to do so. | Massage | Wikipedia | 489 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
In 1997 there were an estimated 114 million visits to massage therapists in the US. Massage therapy is the most used type of alternative medicine in hospitals in the United States. Between July 2010 and July 2011 roughly 38 million adult Americans (18 percent) had a massage at least once. People state that they use massage because they believe that it relieves pain from musculoskeletal injuries and other causes of pain, reduces stress and enhances relaxation, rehabilitates sports injuries, decreases feelings of anxiety and depression, and increases general well-being.
In a poll of 25–35-year-olds, 79% said they would like their health insurance plan to cover massage. In 2006 Duke University Health System opened up a center to integrate medical disciplines with CAM disciplines such as massage therapy and acupuncture. There were 15,500 spas in the United States in 2007, with about two-thirds of the visitors being women.
The number of visits rose from 91 million in 1999 to 136 million in 2003, generating a revenue that equals $11 billion. Job outlook for massage therapists was also projected to grow at 20% between 2010 and 2020 by the Bureau of Labor Statistics, faster than the average. | Massage | Wikipedia | 245 | 43945 | https://en.wikipedia.org/wiki/Massage | Biology and health sciences | Treatments | Health |
A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric combination of extracellular polysaccharides, proteins, lipids and DNA. Because they have a three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
Biofilms may form on living (biotic) or non-living (abiotic) surfaces and can be common in natural, industrial, and hospital settings. They may constitute a microbiome or be a portion of it. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single cells that may float or swim in a liquid medium. Biofilms can form on the teeth of most animals as dental plaque, where they may cause tooth decay and gum disease.
Microbes form a biofilm in response to a number of different factors, which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or in some cases, by exposure of planktonic cells to sub-inhibitory concentrations of antibiotics. A cell that switches to the biofilm mode of growth undergoes a phenotypic shift in behavior in which large suites of genes are differentially regulated.
A biofilm may also be considered a hydrogel, which is a complex polymer that contains many times its dry weight in water. Biofilms are not just bacterial slime layers but biological systems; the bacteria organize themselves into a coordinated functional community. Biofilms can attach to a surface such as a tooth or rock, and may include a single species or a diverse group of microorganisms. Subpopulations of cells within the biofilm differentiate to perform various activities for motility, matrix production, and sporulation, supporting the overall success of the biofilm. The biofilm bacteria can share nutrients and are sheltered from harmful factors in the environment, such as desiccation, antibiotics, and a host body's immune system. A biofilm usually begins to form when a free-swimming, planktonic bacterium attaches to a surface.
Origin and formation | Biofilm | Wikipedia | 496 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Origin of biofilms
Biofilms are thought to have arisen during primitive Earth as a defense mechanism for prokaryotes, as the conditions at that time were too harsh for their survival. They can be found very early in Earth's fossil records (about 3.25 billion years ago) as both Archaea and Bacteria, and commonly protect prokaryotic cells by providing them with homeostasis, encouraging the development of complex interactions between the cells in the biofilm.
Formation of biofilms
The formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. The first colonist bacteria of a biofilm may adhere to the surface initially by the weak van der Waals forces and hydrophobic effects. If the colonists are not immediately separated from the surface, they can anchor themselves more permanently using cell adhesion structures such as pili. A unique group of Archaea that inhabit anoxic groundwater have similar structures called hami. Each hamus is a long tube with three hook attachments that are used to attach to each other or to a surface, enabling a community to develop. Hyperthermophilic archaeon Pyrobaculum calidifontis produce bundling pili which are homologous to the bacterial TasA filaments, a major component of the extracellular matrix in bacterial biofilms, which contribute to biofilm stability. TasA homologs are encoded by many other archaea, suggesting mechanistic similarities and evolutionary connection between bacterial and archaeal biofilms.
Hydrophobicity can also affect the ability of bacteria to form biofilms. Bacteria with increased hydrophobicity have reduced repulsion between the substratum and the bacterium. Some bacteria species are not able to attach to a surface on their own successfully due to their limited motility but are instead able to anchor themselves to the matrix or directly to other, earlier bacteria colonists. Non-motile bacteria cannot recognize surfaces or aggregate together as easily as motile bacteria. | Biofilm | Wikipedia | 412 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
During surface colonization bacteria cells are able to communicate using quorum sensing (QS) products such as N-acyl homoserine lactone (AHL). Once colonization has begun, the biofilm grows by a combination of cell division and recruitment. Polysaccharide matrices typically enclose bacterial biofilms. The matrix exopolysaccharides can trap QS autoinducers within the biofilm to prevent predator detection and ensure bacterial survival. In addition to the polysaccharides, these matrices may also contain material from the surrounding environment, including but not limited to minerals, soil particles, and blood components, such as erythrocytes and fibrin. The final stage of biofilm formation is known as development, and is the stage in which the biofilm is established and may only change in shape and size.
The development of a biofilm may allow for an aggregate cell colony to be increasingly tolerant or resistant to antibiotics. Cell-cell communication or quorum sensing has been shown to be involved in the formation of biofilm in several bacterial species.
Development
Biofilms are the product of a microbial developmental process. The process is summarized by five major stages of biofilm development, as shown in the diagram below:
Dispersal
Dispersal of cells from the biofilm colony is an essential stage of the biofilm life cycle. Dispersal enables biofilms to spread and colonize new surfaces. Enzymes that degrade the biofilm extracellular matrix, such as dispersin B and deoxyribonuclease, may contribute to biofilm dispersal. Enzymes that degrade the biofilm matrix may be useful as anti-biofilm agents. Evidence has shown that a fatty acid messenger, cis-2-decenoic acid, is capable of inducing dispersion and inhibiting growth of biofilm colonies. Secreted by Pseudomonas aeruginosa, this compound induces cyclo heteromorphic cells in several species of bacteria and the yeast Candida albicans.
Nitric oxide has also been shown to trigger the dispersal of biofilms of several bacteria species at sub-toxic concentrations. Nitric oxide has potential as a treatment for patients that have chronic infections caused by biofilms. | Biofilm | Wikipedia | 456 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
It was generally assumed that cells dispersed from biofilms immediately go into the planktonic growth phase. However, studies have shown that the physiology of dispersed cells from Pseudomonas aeruginosa biofilms is highly different from that of planktonic and biofilm cells. Hence, the dispersal process is a unique stage during the transition from biofilm to planktonic lifestyle in bacteria. Dispersed cells are found to be highly virulent against macrophages and Caenorhabditis elegans, but highly sensitive towards iron stress, as compared with planktonic cells.
Furthermore, Pseudomonas aeruginosa biofilms undergo distinct spatiotemporal dynamics during biofilm dispersal or disassembly, with contrasting consequences in recolonization and disease dissemination. Biofilm dispersal induced bacteria to activate dispersal genes to actively depart from biofilms as single cells at consistent velocities but could not recolonize fresh surfaces. In contrast, biofilm disassembly by degradation of a biofilm exopolysaccharide released immotile aggregates at high initial velocities, enabling the bacteria to recolonize fresh surfaces and cause infections in the hosts efficiently. Hence, biofilm dispersal is more complex than previously thought, where bacterial populations adopting distinct behavior after biofilm departure may be the key to survival of bacterial species and dissemination of diseases.
Properties
Biofilms are usually found on solid substrates submerged in or exposed to an aqueous solution, although they can form as floating mats on liquid surfaces and also on the surface of leaves, particularly in high humidity climates. Given sufficient resources for growth, a biofilm will quickly grow to be macroscopic (visible to the naked eye). Biofilms can contain many different types of microorganism, e.g. bacteria, archaea, protozoa, fungi and algae; each group performs specialized metabolic functions. However, some organisms will form single-species films under certain conditions. The social structure (cooperation/competition) within a biofilm depends highly on the different species present.
Extracellular matrix | Biofilm | Wikipedia | 429 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
The EPS matrix consists of exopolysaccharides, proteins and nucleic acids. A large proportion of the EPS is more or less strongly hydrated, however, hydrophobic EPS also occur; one example is cellulose which is produced by a range of microorganisms. This matrix encases the cells within it and facilitates communication among them through biochemical signals as well as gene exchange. The EPS matrix also traps extracellular enzymes and keeps them in close proximity to the cells. Thus, the matrix represents an external digestion system and allows for stable synergistic microconsortia of different species. Some biofilms have been found to contain water channels that help distribute nutrients and signalling molecules. This matrix is strong enough that under certain conditions, biofilms can become fossilized (stromatolites).
Bacteria living in a biofilm usually have significantly different properties from free-floating bacteria of the same species, as the dense and protected environment of the film allows them to cooperate and interact in various ways. One benefit of this environment is increased resistance to detergents and antibiotics, as the dense extracellular matrix and the outer layer of cells protect the interior of the community. In some cases antibiotic resistance can be increased up to 5,000 times. Lateral gene transfer is often facilitated within bacterial and archaeal biofilms and can leads to a more stable biofilm structure. Extracellular DNA is a major structural component of many different microbial biofilms. Enzymatic degradation of extracellular DNA can weaken the biofilm structure and release microbial cells from the surface.
However, biofilms are not always less susceptible to antibiotics. For instance, the biofilm form of Pseudomonas aeruginosa has no greater resistance to antimicrobials than do stationary-phase planktonic cells, although when the biofilm is compared to logarithmic-phase planktonic cells, the biofilm does have greater resistance to antimicrobials. This resistance to antibiotics in both stationary-phase cells and biofilms may be due to the presence of persister cells.
Habitats | Biofilm | Wikipedia | 433 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Biofilms are ubiquitous in organic life. Nearly every species of microorganism have mechanisms by which they can adhere to surfaces and to each other. Biofilms will form on virtually every non-shedding surface in non-sterile aqueous or humid environments. Biofilms can grow in the most extreme environments: from, for example, the extremely hot, briny waters of hot springs ranging from very acidic to very alkaline, to frozen glaciers.
Biofilms can be found on rocks and pebbles at the bottoms of most streams or rivers and often form on the surfaces of stagnant pools of water. Biofilms are important components of food chains in rivers and streams and are grazed by the aquatic invertebrates upon which many fish feed. Biofilms are found on the surface of and inside plants. They can either contribute to crop disease or, as in the case of nitrogen-fixing rhizobia on root nodules, exist symbiotically with the plant. Examples of crop diseases related to biofilms include citrus canker, Pierce's disease of grapes, and bacterial spot of plants such as peppers and tomatoes.
Percolating filters
Percolating filters in sewage treatment works are highly effective removers of pollutants from settled sewage liquor. They work by trickling the liquid over a bed of hard material which is designed to have a very large surface area. A complex biofilm develops on the surface of the medium which absorbs, adsorbs and metabolises the pollutants. The biofilm grows rapidly and when it becomes too thick to retain its grip on the media it washes off and is replaced by newly grown film. The washed off ("sloughed" off) film is settled out of the liquid stream to leave a highly purified effluent. | Biofilm | Wikipedia | 370 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Slow sand filter
Slow sand filters are used in water purification for treating raw water to produce a potable product. They work through the formation of a biofilm called the hypogeal layer or Schmutzdecke in the top few millimetres of the fine sand layer. The Schmutzdecke is formed in the first 10–20 days of operation and consists of bacteria, fungi, protozoa, rotifera and a range of aquatic insect larvae. As an epigeal biofilm ages, more algae tend to develop and larger aquatic organisms may be present including some bryozoa, snails and annelid worms. The surface biofilm is the layer that provides the effective purification in potable water treatment, the underlying sand providing the support medium for this biological treatment layer. As water passes through the hypogeal layer, particles of foreign matter are trapped in the mucilaginous matrix and soluble organic material is adsorbed. The contaminants are metabolised by the bacteria, fungi and protozoa. The water produced from an exemplary slow sand filter is of excellent quality with 90–99% bacterial cell count reduction. | Biofilm | Wikipedia | 235 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Rhizosphere
Plant-beneficial microbes can be categorized as plant growth-promoting rhizobacteria. These plant growth-promoters colonize the roots of plants, and provide a wide range of beneficial functions for their host including nitrogen fixation, pathogen suppression, anti-fungal properties, and the breakdown of organic materials. One of these functions is the defense against pathogenic, soil-borne bacteria and fungi by way of induced systemic resistance (ISR) or induced systemic responses triggered by pathogenic microbes (pathogen-induced systemic acquired resistance). Plant exudates act as chemical signals for host specific bacteria to colonize. Rhizobacteria colonization steps include attractions, recognition, adherence, colonization, and growth. Bacteria that have been shown to be beneficial and form biofilms include Bacillus, Pseudomonas, and Azospirillum. Biofilms in the rhizosphere often result in pathogen or plant induced systemic resistances. Molecular properties on the surface of the bacterium cause an immune response in the plant host. These microbe associated molecules interact with receptors on the surface of plant cells, and activate a biochemical response that is thought to include several different genes at a number of loci. Several other signaling molecules have been linked to both induced systemic responses and pathogen-induced systemic responses, such as jasmonic acid and ethylene. Cell envelope components such as bacterial flagella and lipopolysaccharides, which are recognized by plant cells as components of pathogens. Certain iron metabolites produced by Pseudomonas have also been shown to create an induced systemic response. This function of the biofilm helps plants build stronger resistance to pathogens. | Biofilm | Wikipedia | 349 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Plants that have been colonized by PGPR forming a biofilm have gained systemic resistances and are primed for defense against pathogens. This means that the genes necessary for the production of proteins that work towards defending the plant against pathogens have been expressed, and the plant has a "stockpile" of compounds to release to fight off pathogens. A primed defense system is much faster in responding to pathogen induced infection, and may be able to deflect pathogens before they are able to establish themselves. Plants increase the production of lignin, reinforcing cell walls and making it difficult for pathogens to penetrate into the cell, while also cutting off nutrients to already infected cells, effectively halting the invasion. They produce antimicrobial compounds such as phytoalexins, chitinases, and proteinase inhibitors, which prevent the growth of pathogens. These functions of disease suppression and pathogen resistance ultimately lead to an increase in agricultural production and a decrease in the use of chemical pesticides, herbicides, and fungicides because there is a reduced amount of crop loss due to disease. Induced systemic resistance and pathogen-induced systemic acquired resistance are both potential functions of biofilms in the rhizosphere, and should be taken into consideration when applied to new age agricultural practices because of their effect on disease suppression without the use of dangerous chemicals.
Mammalian gut
Studies in 2003 discovered that the immune system supports biofilm development in the large intestine. This was supported mainly with the fact that the two most abundantly produced molecules by the immune system also support biofilm production and are associated with the biofilms developed in the gut. This is especially important because the appendix holds a mass amount of these bacterial biofilms. This discovery helps to distinguish the possible function of the appendix and the idea that the appendix can help reinoculate the gut with good gut flora. However, modified or disrupted states of biofilms in the gut have been connected to diseases such as inflammatory bowel disease and colorectal cancer. | Biofilm | Wikipedia | 415 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Human environment
In the human environment, biofilms can grow in showers very easily since they provide a moist and warm environment for them to thrive. Mold biofilms on ceilings may form due to roof leaks. They can form inside water and sewage pipes and cause clogging and corrosion. On floors and counters, they can make sanitation difficult in food preparation areas. In soil, they can cause bioclogging. In cooling- or heating-water systems, they are known to reduce heat transfer. Biofilms in marine engineering systems, such as pipelines of the offshore oil and gas industry, can lead to substantial corrosion problems. Corrosion is mainly due to abiotic factors; however, at least 20% of corrosion is caused by microorganisms that are attached to the metal subsurface (i.e., microbially influenced corrosion).
Ship fouling
Bacterial adhesion to boat hulls serves as the foundation for biofouling of seagoing vessels. Once a film of bacteria forms, it is easier for other marine organisms such as barnacles to attach. Such fouling can reduce maximum vessel speed by up to 20%, prolonging voyages and consuming fuel. Time in dry dock for refitting and repainting reduces the productivity of shipping assets, and the useful life of ships is also reduced due to corrosion and mechanical removal (scraping) of marine organisms from ships' hulls.
Stromatolites
Stromatolites are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by microbial biofilms, especially of cyanobacteria. Stromatolites include some of the most ancient records of life on Earth, and are still forming today.
Dental plaque
Within the human body, biofilms are present on the teeth as dental plaque, where they may cause tooth decay and gum disease. These biofilms can either be in an uncalcified state that can be removed by dental instruments, or a calcified state which is more difficult to remove. Removal techniques can also include antimicrobials. | Biofilm | Wikipedia | 433 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Dental plaque is an oral biofilm that adheres to the teeth and consists of many species of both bacteria and fungi (such as Streptococcus mutans and Candida albicans), embedded in salivary polymers and microbial extracellular products. The accumulation of microorganisms subjects the teeth and gingival tissues to high concentrations of bacterial metabolites which results in dental disease. Biofilm on the surface of teeth is frequently subject to oxidative stress and acid stress. Dietary carbohydrates can cause a dramatic decrease in pH in oral biofilms to values of 4 and below (acid stress). A pH of 4 at body temperature of 37 °C causes depurination of DNA, leaving apurinic (AP) sites in DNA, especially loss of guanine.
Dental plaque biofilm can result in dental caries if it is allowed to develop over time. An ecologic shift away from balanced populations within the dental biofilm is driven by certain (cariogenic) microbiological populations beginning to dominate when the environment favors them. The shift to an acidogenic, aciduric, and cariogenic microbiological population develops and is maintained by frequent consumption of fermentable dietary carbohydrate. The resulting activity shift in the biofilm (and resulting acid production within the biofilm, at the tooth surface) is associated with an imbalance of demineralization over remineralization, leading to net mineral loss within dental hard tissues (enamel and then dentin), the symptom being a carious lesion, or cavity. By preventing the dental plaque biofilm from maturing or by returning it back to a non-cariogenic state, dental caries can be prevented and arrested. This can be achieved through the behavioral step of reducing the supply of fermentable carbohydrates (i.e. sugar intake) and frequent removal of the biofilm (i.e., toothbrushing).
Intercellular communication | Biofilm | Wikipedia | 413 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
A peptide pheromone quorum sensing signaling system in S. mutans includes the competence stimulating peptide (CSP) that controls genetic competence. Genetic competence is the ability of a cell to take up DNA released by another cell. Competence can lead to genetic transformation, a form of sexual interaction, favored under conditions of high cell density and/or stress where there is maximal opportunity for interaction between the competent cell and the DNA released from nearby donor cells. This system is optimally expressed when S. mutans cells reside in an actively growing biofilm. Biofilm grown S. mutans cells are genetically transformed at a rate 10- to 600-fold higher than S. mutans growing as free-floating planktonic cells suspended in liquid.
When the biofilm, containing S. mutans and related oral streptococci, is subjected to acid stress, the competence regulon is induced, leading to resistance to being killed by acid. As pointed out by Michod et al., transformation in bacterial pathogens likely provides for effective and efficient recombinational repair of DNA damages. It appears that S. mutans can survive the frequent acid stress in oral biofilms, in part, through the recombinational repair provided by competence and transformation.
Predator-prey interactions
Predator-prey interactions between biofilms and bacterivores, such as the soil-dwelling nematode Caenorhabditis elegans, had been extensively studied. Via the production of sticky matrix and formation of aggregates, Yersinia pestis biofilms can prevent feeding by obstructing the mouth of C. elegans. Moreover, Pseudomonas aeruginosa biofilms can impede the slithering motility of C. elegans, termed as 'quagmire phenotype', resulting in trapping of C. elegans within the biofilms and preventing the exploration of nematodes to feed on susceptible biofilms. This significantly reduced the ability of predator to feed and reproduce, thereby promoting the survival of biofilms. Pseudomonas aeruginosa biofilms can also mask their chemical signatures, where they reduced the diffusion of quorum sensing molecules into the environment and prevented the detection of C. elegans. | Biofilm | Wikipedia | 475 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Taxonomic diversity
Many different bacteria form biofilms, including gram-positive (e.g. Bacillus spp, Listeria monocytogenes, Staphylococcus spp, and lactic acid bacteria, including Lactobacillus plantarum and Lactococcus lactis) and gram-negative species (e.g. Escherichia coli, or Pseudomonas aeruginosa). Cyanobacteria also form biofilms in aquatic environments.
Biofilms are formed by bacteria that colonize plants, e.g. Pseudomonas putida, Pseudomonas fluorescens, and related pseudomonads which are common plant-associated bacteria found on leaves, roots, and in the soil, and the majority of their natural isolates form biofilms. Several nitrogen-fixing symbionts of legumes such as Rhizobium leguminosarum and Sinorhizobium meliloti form biofilms on legume roots and other inert surfaces.
Along with bacteria, biofilms are also generated by archaea and by a range of eukaryotic organisms, including fungi e.g. Cryptococcus laurentii and microalgae. Among microalgae, one of the main progenitors of biofilms are diatoms, which colonise both fresh and marine environments worldwide.
For other species in disease-associated biofilms and biofilms arising from eukaryotes, see below. | Biofilm | Wikipedia | 311 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Infectious diseases
Biofilms have been found to be involved in a wide variety of microbial infections in the body, by one estimate 80% of all infections. Infectious processes in which biofilms have been implicated include common problems such as bacterial vaginosis, urinary tract infections, catheter infections, middle-ear infections, formation of dental plaque, gingivitis, coating contact lenses, and less common but more lethal processes such as endocarditis, infections in cystic fibrosis, and infections of permanent indwelling devices such as joint prostheses, heart valves, and intervertebral disc. The first visual evidence of a biofilm was recorded after spine surgery. It was found that in the absence of clinical presentation of infection, impregnated bacteria could form a biofilm around an implant, and this biofilm can remain undetected via contemporary diagnostic methods, including swabbing. Implant biofilm is frequently present in "aseptic" pseudarthrosis cases. Furthermore, it has been noted that bacterial biofilms may impair cutaneous wound healing and reduce topical antibacterial efficiency in healing or treating infected skin wounds. The diversity of P. aeruginosa cells within a biofilm is thought to make it harder to treat the infected lungs of people with cystic fibrosis. Early detection of biofilms in wounds is crucial to successful chronic wound management. Although many techniques have developed to identify planktonic bacteria in viable wounds, few have been able to quickly and accurately identify bacterial biofilms. Future studies are needed to find means of identifying and monitoring biofilm colonization at the bedside to permit timely initiation of treatment.
It has been shown that biofilms are present on the removed tissue of 80% of patients undergoing surgery for chronic sinusitis. The patients with biofilms were shown to have been denuded of cilia and goblet cells, unlike the controls without biofilms who had normal cilia and goblet cell morphology. Biofilms were also found on samples from two of 10 healthy controls mentioned. The species of bacteria from intraoperative cultures did not correspond to the bacteria species in the biofilm on the respective patient's tissue. In other words, the cultures were negative though the bacteria were present. New staining techniques are being developed to differentiate bacterial cells growing in living animals, e.g. from tissues with allergy-inflammations. | Biofilm | Wikipedia | 500 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Research has shown that sub-therapeutic levels of β-lactam antibiotics induce biofilm formation in Staphylococcus aureus. This sub-therapeutic level of antibiotic may result from the use of antibiotics as growth promoters in agriculture, or during the normal course of antibiotic therapy. The biofilm formation induced by low-level methicillin was inhibited by DNase, suggesting that the sub-therapeutic levels of antibiotic also induce extracellular DNA release. Moreover, from an evolutionary point of view, the creation of the tragedy of the commons in pathogenic microbes may provide advanced therapeutic ways for chronic infections caused by biofilms via genetically engineered invasive cheaters who can invade wild-types 'cooperators' of pathogenic bacteria until cooperator populations go to extinction or overall population 'cooperators and cheaters ' go to extinction.
Pseudomonas aeruginosa
P. aeruginosa represents a commonly used biofilm model organism since it is involved in different types of biofilm-associated chronic infections. Examples of such infections include chronic wounds, chronic otitis media, chronic prostatitis and chronic lung infections in cystic fibrosis (CF) patients. About 80% of CF patients have chronic lung infection, caused mainly by P. aeruginosa growing in a non-surface attached biofilms surround by PMN. The infection remains present despite aggressive antibiotic therapy and is a common cause of death in CF patients due to constant inflammatory damage to the lungs. In patients with CF, one therapy for treating early biofilm development is to employ DNase to structurally weaken the biofilm.
Biofilm formation of P. aeruginosa, along with other bacteria, is found in 90% of chronic wound infections, which leads to poor healing and high cost of treatment estimated at more than US$25 billion every year in the United States. In order to minimize the P. aeruginosa infection, host epithelial cells secrete antimicrobial peptides, such as lactoferrin, to prevent the formation of the biofilms. | Biofilm | Wikipedia | 423 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Streptococcus pneumoniae
Streptococcus pneumoniae is the main cause of community-acquired pneumonia and meningitis in children and the elderly, and of sepsis in HIV-infected persons. When S. pneumoniae grows in biofilms, genes are specifically expressed that respond to oxidative stress and induce competence. Formation of a biofilm depends on competence stimulating peptide (CSP). CSP also functions as a quorum-sensing peptide. It not only induces biofilm formation, but also increases virulence in pneumonia and meningitis.
It has been proposed that competence development and biofilm formation is an adaptation of S. pneumoniae to survive the defenses of the host. In particular, the host's polymorphonuclear leukocytes produce an oxidative burst to defend against the invading bacteria, and this response can kill bacteria by damaging their DNA. Competent S. pneumoniae in a biofilm have the survival advantage that they can more easily take up transforming DNA from nearby cells in the biofilm to use for recombinational repair of oxidative damages in their DNA. Competent S. pneumoniae can also secrete an enzyme (murein hydrolase) that destroys non-competent cells (fratricide) causing DNA to be released into the surrounding medium for potential use by the competent cells.
The insect antimicrobial peptide cecropin A can destroy planktonic and sessile biofilm-forming uropathogenic E. coli cells, either alone or when combined with the antibiotic nalidixic acid, synergistically clearing infection in vivo (in the insect host Galleria mellonella) without off-target cytotoxicity. The multi-target mechanism of action involves outer membrane permeabilization followed by biofilm disruption triggered by the inhibition of efflux pump activity and interactions with extracellular and intracellular nucleic acids. | Biofilm | Wikipedia | 396 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Escherichia coli
Escherichia coli biofilms are responsible for many intestinal infectious diseases. The Extraintestinal group of E. coli (ExPEC) is the dominant bacterial group that attacks the urinary system, which leads to urinary tract infections. The biofilm formation of these pathogenic E. coli is hard to eradicate due to the complexity of its aggregation structure, and it has a significant contribution to developing aggressive medical complications, increase in hospitalization rate, and cost of treatment. The development of E. coli biofilm is a common leading cause of urinary tract infections (UTI) in hospitals through its contribution to developing medical device-associated infections. Catheter-associated urinary tract infections (CAUTI) represent the most common hospital-acquired infection due to the formation of the pathogenic E. coli biofilm inside the catheters.
Staphylococcus aureus
Staphylococcus aureus pathogen can attack skin and lungs, leading to skin infection and pneumonia. Moreover, the biofilm infections network of S. aureus plays a critical role in preventing immune cells, such as macrophages from eliminating and destroying bacterial cells. Furthermore, biofilm formation by bacteria, such as S. aureus, not only develops resistance against antibiotic medication but also develop internal resistance toward antimicrobial peptides (AMPs), leading to preventing the inhibition of the pathogen and maintaining its survival.
Serratia marcescens
Serratia marcescens is a fairly common opportunistic pathogen that can form biofilms on various surfaces, including medical devices such as catheters and implants, as well as natural environments like soil and water. The formation of biofilms by S. marcescens is a serious concern because of its ability to adhere to and colonize surfaces, protecting itself from host immune responses and antimicrobial agents. This strength makes infections caused by S. marcescens challenging to treat, specifically in hospitals where the bacterium can cause severe, and specific, infections.
Research suggests that biofilm formation by S. marcescens is a process controlled by both nutrient cues and the quorum-sensing system. Quorum sensing influences the bacterium's ability to adhere to surfaces and establish mature biofilms, whereas the availability of specific nutrients can enhance or inhibit biofilm development. | Biofilm | Wikipedia | 481 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
S. marcescens creates biofilms that ultimately develop into a highly porous, thread-like structure composed of chains of cells, filaments, and cell clusters. Research has shown that S. marcescens biofilms exhibit complex structural organization, including the formation of microcolonies and channels that facilitate nutrient and waste exchange. The production of extracellular polymeric substances (EPS) is a key factor in biofilm development, contributing to the bacterium's adhesion and resistance to antimicrobial agents. In addition to its role in healthcare-associated infections, S. marcescens biofilms have been implicated in the deterioration of industrial equipment and processes. For example, biofilm growth in cooling towers can lead to biofouling and reduced efficiency.
Efforts to control and prevent biofilm formation by S. marcescens involve the use of antimicrobial coatings on medical devices, the development of targeted biofilm disruptors, and improved sterilization protocols. Further research into the molecular mechanisms governing S. marcescens biofilm formation and persistence is crucial for developing effective strategies to combat its associated risks. The use of indole compounds has been studied to be used as protection against biofilm formation.
Uses and impact
In medicine
It is suggested that around two-thirds of bacterial infections in humans involve biofilms. Infections associated with the biofilm growth usually are challenging to eradicate. This is mostly due to the fact that mature biofilms display antimicrobial tolerance, and immune response evasions. Biofilms often form on the inert surfaces of implanted devices such as catheters, prosthetic cardiac valves and intrauterine devices. Some of the most difficult infections to treat are those associated with the use of medical devices.
The rapidly expanding worldwide industry for biomedical devices and tissue engineering related products is already at $180 billion per year, yet this industry continues to suffer from microbial colonization. No matter the sophistication, microbial infections can develop on all medical devices and tissue engineering constructs. 60-70% of hospital-acquired infections are associated with the implantation of a biomedical device. This leads to 2 million cases annually in the U.S., costing the healthcare system over $5 billion in additional healthcare expenses. | Biofilm | Wikipedia | 464 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
The level of antibiotic resistance in a biofilm is much greater than that of non-biofilm bacteria, and can be as much as 5,000 times greater. The extracellular matrix of biofilm is considered one of the leading factors that can reduce the penetration of antibiotics into a biofilm structure and contributes to antibiotic resistance. Further, it has been demonstrated that the evolution of resistance to antibiotics may be affected by the biofilm lifestyle. Bacteriophage therapy can disperse the biofilm generated by antibiotic-resistant bacteria.
It has been shown that the introduction of a small current of electricity to the liquid surrounding a biofilm, together with small amounts of antibiotic can reduce the level of antibiotic resistance to levels of non-biofilm bacteria. This is termed the bioelectric effect. The application of a small DC current on its own can cause a biofilm to detach from its surface. A study showed that the type of current used made no difference to the bioelectric effect.
In industry
Biofilms can also be harnessed for constructive purposes. For example, many sewage treatment plants include a secondary treatment stage in which waste water passes over biofilms grown on filters, which extract and digest organic compounds. In such biofilms, bacteria are mainly responsible for removal of organic matter (BOD), while protozoa and rotifers are mainly responsible for removal of suspended solids (SS), including pathogens and other microorganisms. Slow sand filters rely on biofilm development in the same way to filter surface water from lake, spring or river sources for drinking purposes. What is regarded as clean water is effectively a waste material to these microcellular organisms. Biofilms can help eliminate petroleum oil from contaminated oceans or marine systems. The oil is eliminated by the hydrocarbon-degrading activities of communities of hydrocarbonoclastic bacteria (HCB).
Biofilms are used in microbial fuel cells (MFCs) to generate electricity from a variety of starting materials, including complex organic waste and renewable biomass.
Biofilms are also relevant for the improvement of metal dissolution in bioleaching industry, and aggregation of microplastics pollutants for convenient removal from the environment. | Biofilm | Wikipedia | 452 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Food industry
Biofilms have become problematic in several food industries due to the ability to form on plants and during industrial processes. Bacteria can survive long periods of time in water, animal manure, and soil, causing biofilm formation on plants or in the processing equipment. The buildup of biofilms can affect the heat flow across a surface and increase surface corrosion and frictional resistance of fluids. These can lead to a loss of energy in a system and overall loss of products. Along with economic problems, biofilm formation on food poses a health risk to consumers due to the ability to make the food more resistant to disinfectants As a result, from 1996 to 2010 the Centers for Disease Control and Prevention estimated 48 million foodborne illnesses per year. Biofilms have been connected to about 80% of bacterial infections in the United States.
In produce, microorganisms attach to the surfaces and biofilms develop internally. During the washing process, biofilms resist sanitization and allow bacteria to spread across the produce, especially via kitchen utensils. This problem is also found in ready-to-eat foods, because the foods go through limited cleaning procedures before consumption Due to the perishability of dairy products and limitations in cleaning procedures, resulting in the buildup of bacteria, dairy is susceptible to biofilm formation and contamination. The bacteria can spoil the products more readily and contaminated products pose a health risk to consumers. One species of bacteria that can be found in various industries and is a major cause of foodborne disease is Salmonella. Large amounts of Salmonella contamination can be found in the poultry processing industry as about 50% of Salmonella strains can produce biofilms on poultry farms. Salmonella increases the risk of foodborne illnesses when the poultry products are not cleaned and cooked correctly. Salmonella is also found in the seafood industry where biofilms form from seafood borne pathogens on the seafood itself as well as in water. Shrimp products are commonly affected by Salmonella because of unhygienic processing and handling techniques The preparation practices of shrimp and other seafood products can allow for bacteria buildup on the products. | Biofilm | Wikipedia | 431 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
New forms of cleaning procedures are being tested to reduce biofilm formation in these processes which will lead to safer and more productive food processing industries. These new forms of cleaning procedures also have a profound effect on the environment, often releasing toxic gases into the groundwater reservoirs. As a response to the aggressive methods employed in controlling biofilm formation, there are a number of novel technologies and chemicals under investigation that can prevent either the proliferation or adhesion of biofilm-secreting microbes. Latest proposed biomolecules presenting marked anti-biofilm activity include a range of metabolites such as bacterial rhamnolipids and even plant- and animal-derived alkaloids.
In aquaculture
In shellfish and algal aquaculture, biofouling microbial species tend to block nets and cages and ultimately outcompete the farmed species for space and food. Bacterial biofilms start the colonization process by creating microenvironments that are more favorable for biofouling species. In the marine environment, biofilms could reduce the hydrodynamic efficiency of ships and propellers, lead to pipeline blockage and sensor malfunction, and increase the weight of appliances deployed in seawater. Numerous studies have shown that biofilm can be a reservoir for potentially pathogenic bacteria in freshwater aquaculture. Moreover, biofilms are important in establishing infections on the fish. As mentioned previously, biofilms can be difficult to eliminate even when antibiotics or chemicals are used in high doses. The role that biofilm plays as reservoirs of bacterial fish pathogens has not been explored in detail but it certainly deserves to be studied.
Eukaryotic
Along with bacteria, biofilms are often initiated and produced by eukaryotic microbes. The biofilms produced by eukaryotes is usually occupied by bacteria and other eukaryotes alike, however the surface is cultivated and EPS is secreted initially by the eukaryote. Both fungi and microalgae are known to form biofilms in such a way. Biofilms of fungal origin are important aspects of human infection and fungal pathogenicity, as the fungal infection is more resistant to antifungals.
In the environment, fungal biofilms are an area of ongoing research. One key area of research is fungal biofilms on plants. For example, in the soil, plant associated fungi including mycorrhiza have been shown to decompose organic matter and protect plants from bacterial pathogens. | Biofilm | Wikipedia | 505 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Biofilms in aquatic environments are often founded by diatoms. The exact purpose of these biofilms is unknown, however there is evidence that the EPS produced by diatoms facilitates both cold and salinity stress. These eukaryotes interact with a diverse range of other organisms within a region known as the phycosphere, but importantly are the bacteria associated with diatoms, as it has been shown that although diatoms excrete EPS, they only do so when interacting with certain bacteria species. | Biofilm | Wikipedia | 108 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Horizontal gene transfer
Horizontal gene transfer is the lateral transfer of genetic material between cellular organisms. It happens frequently in prokaryotes, and less frequently in eukaryotes. In bacteria, horizontal gene transfer can occur through transformation (uptake of free floating DNA in the environment), transduction (virus mediated DNA uptake), or conjugation (transfer of DNA between pili structures of two adjacent bacteria). Recent studies have also uncovered other mechanisms, such as membrane vesicle transmission or gene transfer agents. Biofilms promote horizontal gene transfer in a variety of ways.Bacterial conjugation has been shown to accelerate biofilm formation in difficult environment due to the robust connections established by the conjugative pili. These connections can often foster cross-species transfer events due to the diverse heterogeneity of many biofilms. Additionally, biofilms are structurally confined by a polysaccharide matrix, providing the close spatial requirements for conjugation. Transformation is also frequently observed in biofilms. Bacterial autolysis is a key mechanism in biofilm structural regulation, providing an abundant source of competent DNA primed for transformative uptake. In some instances, inter-biofilm quorum sensing can enhance the competence of free floating eDNA, further promoting transformation. Stx gene transfer through bacteriophage carriers has been witnessed within biofilms, which suggests that biofilms are also a suitable environment for transduction. Membrane vesicles HGT occurs when released membrane vesicles (containing genetic information) fuse with a recipient bacteria, and release genetic material into the bacteria's cytoplasm. Recent research has revealed that membrane vesicle HGT can promote single-strain biofilm formation, yet the role membrane vesicle HGT plays in the formation of multistrain biofilms is still unknown. GTAs, or gene transfer agents, are phage-like particles produced by the host bacteria and contain random DNA fragments from the host bacteria genome. HGT within biofilms can confer antibiotic resistance or increased pathogenicity across the biofilms' population, promoting biofilm homeostasis. | Biofilm | Wikipedia | 439 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Examples
Conjugative plasmids may encode biofilm-associated proteins, such as PtgA, PrgB, or PrgC which promote cell adhesion (required for early biofilm formation). Genes encoding type III fimbriae are found in pOLA52 (Klebsiella pneumoniae plasmid) which promote conjugative-pilus-dependent biofilm formation.
Transformation commonly occurs within biofilms. A phenomenon called fratricide can be seen among streptococcal species in which cell-wall degrading enzymes are released, lysing neighboring bacteria and releasing their DNA. This DNA can then be taken up by the surviving bacteria (transformation). Competence stimulating peptides may play an important role in biofilm formation among S. pneumoniae and S. mutans as well. Among V. cholerae, the competence pilus itself promotes cell aggregation through pilus-pilus interactions at the beginning of biofilm formation.
Phage invasion may play a role in biofilm life cycles, lysing bacteria and releasing their eDNA, which strengthens biofilm structures and can be taken up by neighboring bacteria in transformation. Biofilm destruction caused by the E. coli phage Rac and the P. aeruginosa prophage Pf4 causes detachment of cells from the biofilm. Detachment is a biofilm phenomenon which requires more study, but is hypothesized to proliferate the bacterial species that comprise the biofilm.
Membrane vesicle HGT has been witnessed occurring in marine environments, among Neisseria gonorrhoeae, Pseudomonas aeruginosa, Helicobacter pylori, and among many other bacterial species. Even though membrane vesicle HGT has been shown as a contributing factor in biofilm formation, research is still required to prove that membrane vesicle mediated HGT occurs within biofilms. Membrane vesicle HGT has also been shown to modulate phage-bacteria interactions in Bacillus subtilis SPP1 phage-resistant cells (lacking the SPP1 receptor protein). Upon exposure to vesicles containing receptors, transduction of pBT163 (a cat-encoding plasmid) occurs, resulting in the expression of the SPP1 receptor protein, opening the receptive bacteria to future phage infection. | Biofilm | Wikipedia | 486 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Recent research has shown that the archaeal species H. volcanii has some biofilm phenotypes similar to bacterial biofilms such as differentiation and HGT, which required cell-cell contact and involved formation of cytosolic bridges and cellular fusion events.
Cultivation devices
There is a wide variety of biofilm cultivation devices to mimic natural or industrial environments. Although it is important to consider that the particular experimental platform for biofilm research determines what kind of biofilm is cultivated and the data that can be extracted. These devices can be grouped into the following:
microtiter plate (MTP) systems and MBEC Assay® [formerly the Calgary Biofilm Device (CBD)]
BioFilm Ring Test (BRT) or clinical Biofilm Ring Test (cBRT)
Robbins Device or modified Robbins Device (such as the MPMR-10PMMA or the Bio-inLine Biofilm Reactor)
Drip Flow Biofilm Reactor®
rotary devices (such as the CDC Biofilm Reactor®, the Rotating Disk Reactor, the Biofilm Annular Reactor, the Industrial Surfaces Biofilm Reactor, or the Constant Depth Film Fermenter)
flow chambers or flow cells (such as the Coupon Evaluation Flow Cell, Transmission Flow Cell, and Capillary Flow Cell from BioSurface Technologies)
microfluidic approaches, such as 3D-bacterial "biofilm-dispersal-then-recolonization" (BDR) microfluidic model | Biofilm | Wikipedia | 295 | 43946 | https://en.wikipedia.org/wiki/Biofilm | Biology and health sciences | Basic anatomy | Biology |
Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. As a branch of astronomy, star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function. Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations.
History
The first stars were believed to be formed approximately 12-13 billion years ago following the Big Bang. Over intervals of time, stars have fused helium to form a series of chemical elements.
Stellar nurseries
Interstellar clouds
Spiral galaxies like the Milky Way contain stars, stellar remnants, and a diffuse interstellar medium (ISM) of gas and dust. The interstellar medium consists of 104 to 106 particles per cm3, and is typically composed of roughly 70% hydrogen, 28% helium, and 1.5% heavier elements by mass. The trace amounts of heavier elements were and are produced within stars via stellar nucleosynthesis and ejected as the stars pass beyond the end of their main sequence lifetime. Higher density regions of the interstellar medium form clouds, or diffuse nebulae, where star formation takes place. In contrast to spiral galaxies, elliptical galaxies lose the cold component of its interstellar medium within roughly a billion years, which hinders the galaxy from forming diffuse nebulae except through mergers with other galaxies.
In the dense nebulae where stars are produced, much of the hydrogen is in the molecular (H2) form, so these nebulae are called molecular clouds. The Herschel Space Observatory has revealed that filaments, or elongated dense gas structures, are truly ubiquitous in molecular clouds and central to the star formation process. They fragment into gravitationally bound cores, most of which will evolve into stars. Continuous accretion of gas, geometrical bending, and magnetic fields may control the detailed manner in which the filaments are fragmented. Observations of supercritical filaments have revealed quasi-periodic chains of dense cores with spacing comparable to the filament inner width, and embedded protostars with outflows. | Star formation | Wikipedia | 512 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
Observations indicate that the coldest clouds tend to form low-mass stars, which are first observed via the infrared light they emit inside the clouds, and then as visible light when the clouds dissipate. Giant molecular clouds, which are generally warmer, produce stars of all masses. These giant molecular clouds have typical densities of 100 particles per cm3, diameters of , masses of up to 6 million solar masses (), or six million times the mass of Earth's sun. The average interior temperature is .
About half the total mass of the Milky Way's galactic ISM is found in molecular clouds and the galaxy includes an estimated 6,000 molecular clouds, each with more than . The nebula nearest to the Sun where massive stars are being formed is the Orion Nebula, away. However, lower mass star formation is occurring about 400–450 light-years distant in the ρ Ophiuchi cloud complex.
A more compact site of star formation is the opaque clouds of dense gas and dust known as Bok globules, so named after the astronomer Bart Bok. These can form in association with collapsing molecular clouds or possibly independently. The Bok globules are typically up to a light-year across and contain a few solar masses. They can be observed as dark clouds silhouetted against bright emission nebulae or background stars. Over half the known Bok globules have been found to contain newly forming stars.
Cloud collapse
An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force. Mathematically this is expressed using the virial theorem, which states that, to maintain equilibrium, the gravitational potential energy must equal twice the internal thermal energy. If a cloud is massive enough that the gas pressure is insufficient to support it, the cloud will undergo gravitational collapse. The mass above which a cloud will undergo such collapse is called the Jeans mass. The Jeans mass depends on the temperature and density of the cloud, but is typically thousands to tens of thousands of solar masses. During cloud collapse dozens to tens of thousands of stars form more or less simultaneously which is observable in so-called embedded clusters. The end product of a core collapse is an open cluster of stars. | Star formation | Wikipedia | 465 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
In triggered star formation, one of several events might occur to compress a molecular cloud and initiate its gravitational collapse. Molecular clouds may collide with each other, or a nearby supernova explosion can be a trigger, sending shocked matter into the cloud at very high speeds. (The resulting new stars may themselves soon produce supernovae, producing self-propagating star formation.) Alternatively, galactic collisions can trigger massive starbursts of star formation as the gas clouds in each galaxy are compressed and agitated by tidal forces. The latter mechanism may be responsible for the formation of globular clusters.
A supermassive black hole at the core of a galaxy may serve to regulate the rate of star formation in a galactic nucleus. A black hole that is accreting infalling matter can become active, emitting a strong wind through a collimated relativistic jet. This can limit further star formation. Massive black holes ejecting radio-frequency-emitting particles at near-light speed can also block the formation of new stars in aging galaxies. However, the radio emissions around the jets may also trigger star formation. Likewise, a weaker jet may trigger star formation when it collides with a cloud.
As it collapses, a molecular cloud breaks into smaller and smaller pieces in a hierarchical manner, until the fragments reach stellar mass. In each of these fragments, the collapsing gas radiates away the energy gained by the release of gravitational potential energy. As the density increases, the fragments become opaque and are thus less efficient at radiating away their energy. This raises the temperature of the cloud and inhibits further fragmentation. The fragments now condense into rotating spheres of gas that serve as stellar embryos.
Complicating this picture of a collapsing cloud are the effects of turbulence, macroscopic flows, rotation, magnetic fields and the cloud geometry. Both rotation and magnetic fields can hinder the collapse of a cloud. Turbulence is instrumental in causing fragmentation of the cloud, and on the smallest scales it promotes collapse.
Protostar
A protostellar cloud will continue to collapse as long as the gravitational binding energy can be eliminated. This excess energy is primarily lost through radiation. However, the collapsing cloud will eventually become opaque to its own radiation, and the energy must be removed through some other means. The dust within the cloud becomes heated to temperatures of , and these particles radiate at wavelengths in the far infrared where the cloud is transparent. Thus the dust mediates the further collapse of the cloud. | Star formation | Wikipedia | 505 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
During the collapse, the density of the cloud increases towards the center and thus the middle region becomes optically opaque first. This occurs when the density is about . A core region, called the first hydrostatic core, forms where the collapse is essentially halted. It continues to increase in temperature as determined by the virial theorem. The gas falling toward this opaque region collides with it and creates shock waves that further heat the core.
When the core temperature reaches about , the thermal energy dissociates the H2 molecules. This is followed by the ionization of the hydrogen and helium atoms. These processes absorb the energy of the contraction, allowing it to continue on timescales comparable to the period of collapse at free fall velocities. After the density of infalling material has reached about 10−8 g / cm3, that material is sufficiently transparent to allow energy radiated by the protostar to escape. The combination of convection within the protostar and radiation from its exterior allow the star to contract further. This continues until the gas is hot enough for the internal pressure to support the protostar against further gravitational collapse—a state called hydrostatic equilibrium. When this accretion phase is nearly complete, the resulting object is known as a protostar.
Accretion of material onto the protostar continues partially from the newly formed circumstellar disc. When the density and temperature are high enough, deuterium fusion begins, and the outward pressure of the resultant radiation slows (but does not stop) the collapse. Material comprising the cloud continues to "rain" onto the protostar. In this stage bipolar jets are produced called Herbig–Haro objects. This is probably the means by which excess angular momentum of the infalling material is expelled, allowing the star to continue to form. | Star formation | Wikipedia | 367 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
When the surrounding gas and dust envelope disperses and accretion process stops, the star is considered a pre-main-sequence star (PMS star). The energy source of these objects is (gravitational contraction)Kelvin–Helmholtz mechanism, as opposed to hydrogen burning in main sequence stars. The PMS star follows a Hayashi track on the Hertzsprung–Russell (H–R) diagram. The contraction will proceed until the Hayashi limit is reached, and thereafter contraction will continue on a Kelvin–Helmholtz timescale with the temperature remaining stable. Stars with less than thereafter join the main sequence. For more massive PMS stars, at the end of the Hayashi track they will slowly collapse in near hydrostatic equilibrium, following the Henyey track.
Finally, hydrogen begins to fuse in the core of the star, and the rest of the enveloping material is cleared away. This ends the protostellar phase and begins the star's main sequence phase on the H–R diagram.
The stages of the process are well defined in stars with masses around or less. In high mass stars, the length of the star formation process is comparable to the other timescales of their evolution, much shorter, and the process is not so well defined. The later evolution of stars is studied in stellar evolution.
Observations
Key elements of star formation are only available by observing in wavelengths other than the optical. The protostellar stage of stellar existence is almost invariably hidden away deep inside dense clouds of gas and dust left over from the GMC. Often, these star-forming cocoons known as Bok globules, can be seen in silhouette against bright emission from surrounding gas. Early stages of a star's life can be seen in infrared light, which penetrates the dust more easily than visible light.
Observations from the Wide-field Infrared Survey Explorer (WISE) have thus been especially important for unveiling numerous galactic protostars and their parent star clusters. Examples of such embedded star clusters are FSR 1184, FSR 1190, Camargo 14, Camargo 74, Majaess 64, and Majaess 98. | Star formation | Wikipedia | 442 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
The structure of the molecular cloud and the effects of the protostar can be observed in near-IR extinction maps (where the number of stars are counted per unit area and compared to a nearby zero extinction area of sky), continuum dust emission and rotational transitions of CO and other molecules; these last two are observed in the millimeter and submillimeter range. The radiation from the protostar and early star has to be observed in infrared astronomy wavelengths, as the extinction caused by the rest of the cloud in which the star is forming is usually too big to allow us to observe it in the visual part of the spectrum. This presents considerable difficulties as the Earth's atmosphere is almost entirely opaque from 20μm to 850μm, with narrow windows at 200μm and 450μm. Even outside this range, atmospheric subtraction techniques must be used.
X-ray observations have proven useful for studying young stars, since X-ray emission from these objects is about 100–100,000 times stronger than X-ray emission from main-sequence stars. The earliest detections of X-rays from T Tauri stars were made by the Einstein X-ray Observatory. For low-mass stars X-rays are generated by the heating of the stellar corona through magnetic reconnection, while for high-mass O and early B-type stars X-rays are generated through supersonic shocks in the stellar winds. Photons in the soft X-ray energy range covered by the Chandra X-ray Observatory and XMM-Newton may penetrate the interstellar medium with only moderate absorption due to gas, making the X-ray a useful wavelength for seeing the stellar populations within molecular clouds. X-ray emission as evidence of stellar youth makes this band particularly useful for performing censuses of stars in star-forming regions, given that not all young stars have infrared excesses. X-ray observations have provided near-complete censuses of all stellar-mass objects in the Orion Nebula Cluster and Taurus Molecular Cloud.
The formation of individual stars can only be directly observed in the Milky Way Galaxy, but in distant galaxies star formation has been detected through its unique spectral signature.
Initial research indicates star-forming clumps start as giant, dense areas in turbulent gas-rich matter in young galaxies, live about 500 million years, and may migrate to the center of a galaxy, creating the central bulge of a galaxy. | Star formation | Wikipedia | 484 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
On February 21, 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs) in the universe. According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have been formed shortly after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets.
In February 2018, astronomers reported, for the first time, a signal of the reionization epoch, an indirect detection of light from the earliest stars formed - about 180 million years after the Big Bang.
An article published on October 22, 2019, reported on the detection of 3MM-1, a massive star-forming galaxy about 12.5 billion light-years away that is obscured by clouds of dust. At a mass of about 1010.8 solar masses, it showed a star formation rate about 100 times as high as in the Milky Way.
Notable pathfinder objects
MWC 349 was first discovered in 1978, and is estimated to be only 1,000 years old.
VLA 1623 – The first exemplar Class 0 protostar, a type of embedded protostar that has yet to accrete the majority of its mass. Found in 1993, is possibly younger than 10,000 years.
L1014 – An extremely faint embedded object representative of a new class of sources that are only now being detected with the newest telescopes. Their status is still undetermined, they could be the youngest low-mass Class 0 protostars yet seen or even very low-mass evolved objects (like brown dwarfs or even rogue planets).
GCIRS 8* – The youngest known main sequence star in the Galactic Center region, discovered in August 2006. It is estimated to be 3.5 million years old.
Low mass and high mass star formation
Stars of different masses are thought to form by slightly different mechanisms. The theory of low-mass star formation, which is well-supported by observation, suggests that low-mass stars form by the gravitational collapse of rotating density enhancements within molecular clouds. As described above, the collapse of a rotating cloud of gas and dust leads to the formation of an accretion disk through which matter is channeled onto a central protostar. For stars with masses higher than about , however, the mechanism of star formation is not well understood. | Star formation | Wikipedia | 492 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
Massive stars emit copious quantities of radiation which pushes against infalling material. In the past, it was thought that this radiation pressure might be substantial enough to halt accretion onto the massive protostar and prevent the formation of stars with masses more than a few tens of solar masses. Recent theoretical work has shown that the production of a jet and outflow clears a cavity through which much of the radiation from a massive protostar can escape without hindering accretion through the disk and onto the protostar. Present thinking is that massive stars may therefore be able to form by a mechanism similar to that by which low mass stars form.
There is mounting evidence that at least some massive protostars are indeed surrounded by accretion disks. Disk accretion in high-mass protostars, similar to their low-mass counterparts, is expected to exhibit bursts of episodic accretion as a result of a gravitationally instability leading to clumpy and in-continuous accretion rates. Recent evidence of accretion bursts in high-mass protostars has indeed been confirmed observationally. Several other theories of massive star formation remain to be tested observationally. Of these, perhaps the most prominent is the theory of competitive accretion, which suggests that massive protostars are "seeded" by low-mass protostars which compete with other protostars to draw in matter from the entire parent molecular cloud, instead of simply from a small local region.
Another theory of massive star formation suggests that massive stars may form by the coalescence of two or more stars of lower mass.
Filamentary nature of star formation
Recent studies have emphasized the role of filamentary structures in molecular clouds as the initial conditions for star formation. Findings from the Herschel Space Observatory highlight the ubiquitous nature of these filaments in the cold interstellar medium (ISM). The spatial relationship between cores and filaments indicates that the majority of prestellar cores are located within 0.1 pc of supercritical filaments. This supports the hypothesis that filamentary structures act as pathways for the accumulation of gas and dust, leading to core formation. | Star formation | Wikipedia | 441 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
Both the core mass function (CMF) and filament line mass function (FLMF) observed in the California GMC follow power-law distributions at the high-mass end, consistent with the Salpeter initial mass function (IMF). Current results strongly support the existence of a connection between the FLMF and the CMF/IMF, demonstrating that this connection holds at the level of an individual cloud, specifically the California GMC. The FLMF presented is a distribution of local line masses for a complete, homogeneous sample of filaments within the same cloud. It is the local line mass of a filament that defines its ability to fragment at a particular location along its spine, not the average line mass of the filament. This connection is more direct and provides tighter constraints on the origin of the CMF/IMF. | Star formation | Wikipedia | 177 | 43948 | https://en.wikipedia.org/wiki/Star%20formation | Physical sciences | Stellar astronomy | null |
Laboratory glassware is a variety of equipment used in scientific work, traditionally made of glass. Glass may be blown, bent, cut, molded, or formed into many sizes and shapes. It is commonly used in chemistry, biology, and analytical laboratories. Many laboratories have training programs to demonstrate how glassware is used and to alert first–time users to the safety hazards involved with using glassware.
History
Ancient era
The history of glassware dates back to the Phoenicians who fused obsidian together in campfires making the first glassware. Glassware evolved as other ancient civilizations including the Syrians, Egyptians, and Romans refined the art of glassmaking. Mary the Jewess, an alchemist in Alexandria during the 1st century AD, is credited for the creation of some of the first glassware for chemical such as the kerotakis which was used for the collection of fumes from a heated material. Despite these creations, glassware for chemical uses was still limited during this time because of the low thermal stability necessary for experimentation and therefore was primarily made using copper or ceramic materials.
Early modern era
Glassware improved once again during the 14th-16th century, with the skill and knowledge of glass makers in Venice. During this time, the Venetians gathered knowledge about glassmaking from the East with information coming from Syria and the Byzantine Empire. Along with knowledge about glassmaking, glassmakers in Venice also received higher quality raw materials from the East such as imported plant ash which contained higher soda content compared to plant ash from other areas. This combination of better raw materials and information from the East led to the production of clearer and higher thermal and chemical durability leading towards the shift to the use of glassware in laboratories. | Laboratory glassware | Wikipedia | 344 | 43958 | https://en.wikipedia.org/wiki/Laboratory%20glassware | Physical sciences | Research methods | Basics and measurement |
Modern era
Many glasses that were produced in bulk in the 1830s would quickly become unclear and dirty because of the low quality glass being used.
During the 19th century, more chemists began to recognize the importance of glassware due to its transparency, and the ability to control the conditions of experiments. Jöns Jacob Berzelius, who invented the test tube, and Michael Faraday both contributed to the rise of chemical glassblowing. Faraday published Chemical Manipulation in 1827 which detailed the process for creating many types of small tube glassware and some experimental techniques for tube chemistry. Berzelius wrote a similar textbook titled Chemical Operations and Apparatus which provided a variety of chemical glassblowing techniques. The rise of this chemical glassblowing widened the availability of chemical experimentation and led to a shift towards the dominant use of glassware in laboratories. With the emergence of glassware in laboratories, the need for organization and standards arose. The Prussian Society for the Advancement of Industry was one of the earliest organizations to support the collaborative improvement of the quality of glass used.
Following the development of borosilicate glass by Otto Schott in the late 19th century, most laboratory glassware was manufactured in Germany up until the start of World War I. Before World War I, glass producers in the United States had difficulty competing with German laboratory glassware manufacturers because laboratory glassware was classified as educational material and was not subject to an import tax. During World War I, the supply of laboratory glassware to the United States was cut off.
In 1915 Corning Glassworks developed their own borosilicate glass, introduced under the name Pyrex. This was a boon to the war effort in the United States. Though many laboratories turned back to imports after the war ended, research into better glassware flourished. Glassware became more resistant to thermal shock while maintaining chemical inertness.
During the 1920s efforts to standardise the dimensions of laboratory glassware began, particularly for ground glass joints, with some manufacturer specific standardisation beginning to occur around this time. Commercial standards began development around 1930, allowing the compatibility of joints between different manufacturers for the first time, along with other features. This quickly led to the high degree of standardisation and modularity seen in modern glassware. | Laboratory glassware | Wikipedia | 453 | 43958 | https://en.wikipedia.org/wiki/Laboratory%20glassware | Physical sciences | Research methods | Basics and measurement |
Laboratory glassware selection
Laboratory glassware is typically selected by a person in charge of a particular laboratory analysis to match the needs of a given task. The task may require a piece of glassware made with a specific type of glass. The task may be readily performed using low cost, mass-produced glassware, or it may require a specialized piece created by a glass blower. The task may require controlling the flow of fluid. The task may have distinctive quality assurance requirements.
Type of glass
Laboratory glassware may be made from several types of glass, each with different capabilities and used for different purposes. Borosilicate glass is a type of transparent glass that is composed of boron oxide and silica, its main feature is a low coefficient of thermal expansion making it more resistant to thermal shock than most other glasses. Quartz glass can withstand very high temperatures and is transparent in certain parts of the electromagnetic spectrum. Darkened brown or amber (actinic) glass can block ultraviolet and infrared radiation. Heavy-wall glass can withstand pressurized applications. Fritted glass is finely porous glass through which gas or liquid may pass. Coated glassware is specially treated to reduce the occurrence of breakage or failure. Silanized (siliconized) glassware is specially treated to prevent organic samples from sticking to the glass.
Scientific glass blowing
Scientific glass blowing, which is practiced in some larger laboratories, is a specialized field of glassblowing. Scientific glassblowing involves precisely controlling the shape and dimension of glass, repairing expensive or difficult-to-replace glassware, and fusing together various glass parts. Many parts are available fused to a length of glass tubing to create highly specialized piece of laboratory glassware.
Controlling fluid flow
When using glassware it is often necessary to control the flow of fluid. It is commonly stopped with a stopper. Fluid may be transported between connected pieces of glassware. Types of interconnecting components include glass tubing, T-connectors, Y-connectors, and glass adapters. For a leak-tight connection a ground glass joint is used (possibly reinforced using a clamping method such as a Keck clips). Another way to connect glassware is with a hose barb and flexible tubing. Fluid flow can be switched selectively using a valve, of which a stopcock is a common type fused to the glassware. Valves made entirely of glass may be used to restrict fluid flows. Fluid, or any material which flows, can be directed into a narrow opening using a funnel. | Laboratory glassware | Wikipedia | 512 | 43958 | https://en.wikipedia.org/wiki/Laboratory%20glassware | Physical sciences | Research methods | Basics and measurement |
Quality assurance
Metrology
Laboratory glassware can be used for high precision volumetric measurements. With high precision measurements, such as those made in a testing laboratory, the metrological grade of the glassware becomes important. The metrological grade then can be determined by both the confidence interval around the nominal value of measurement marks and the traceability of the calibration to an NIST standard. Periodically it may be necessary to check the calibration of the laboratory glassware.
Dissolved silica
Laboratory glassware is composed of silica, which is considered insoluble in most substances, with a few exceptions such as hydrofluoric acid or strong alkali hydroxides. Though insoluble, a minute quantity of silica will dissolve in neutral water, which may affect high precision, low threshold measurements of silica in water.
Cleaning
Cleaning laboratory glassware is a frequent necessity and may be done using multiple methods depending on the nature of the contamination and the purity requirements of its use. Glassware can be soaked in a detergent solution to remove grease and loosen most contaminations, these contaminations are then scrubbed with a brush or scouring pad to remove particles which cannot be rinsed. Sturdy glassware may be able to withstand sonication as an alternative to scrubbing. Solvents are used to remove organic residues that soap cannot remove, and inorganic residues that do not dissolve in water can often be dissolved with a dilute acid. When cleaning is finished it is common practice to rinse glassware multiple times, often finally with deionised water, before suspending it upside down on drying racks. Specialised dishwashers can be used to automate these cleaning methods.
Resistant residues may require more powerful cleaning methods. Base baths are commonly used for organic residues, although the strong alkaline conditions do slowly dissolve the glass itself, and concentrated hydrochloric acid is common for removing inorganic residues. Even more severe methods exist, such as acidic peroxide (piranha solution), aqua regia, and chromic acid, but these are considered somewhat of a last resort due to the hazards of using them, and their use by students is restricted in many institutions.
For certain sensitive experiments glassware may require specialised procedures and ultra-pure water or solvents to dissolve trace quantities of specific contaminations known to interfere with an experiment.
Examples
There are many different kinds of laboratory glassware items: | Laboratory glassware | Wikipedia | 485 | 43958 | https://en.wikipedia.org/wiki/Laboratory%20glassware | Physical sciences | Research methods | Basics and measurement |
Examples of glassware containers include:
Beakers are simple cylindrical shaped containers used to hold reagents or samples.
Flasks are narrow-necked glass containers, typically conical or spherical, used in a laboratory to hold reagents or samples. Examples flasks include the Erlenmeyer flask, Florence flask, and Schlenk flask.
Reagent bottles are containers with narrow openings generally used to store reagents or samples. Small bottles are called vials.
Jars are cylindrical containers with wide openings that may be sealed. Bell jars are used to contain vacuums.
Test tubes are used by chemists to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays
Desiccators of glass construction are used to dry materials or keep material dry.
Glass evaporating dishes, such as watch glasses, are primarily used as an evaporating surface (though they may be used to cover a beaker.)
The Petri dish is a flat dish filled with a nutritious gelatin that allows for microorganisms to quickly grow, its named after its inventor Julius Petri in the 1880s.
Microscope slides are thin strips used to hold items under a microscope.
Examples of glassware used for measurements include:
Graduated cylinders are thin and tall cylindrical containers used for volumetric measurements.
Volumetric flasks are for measuring a specific volume of fluid.
Burettes are similar to graduated cylinders but have a valve at the end used to disperse precise amounts of liquid reagents often for titrations.
Glass pipettes are used to transfer precise quantities of fluids.
Glass Ebulliometers are used to accurately measure the boiling point of liquids.
Other examples of glassware includes:
Stirring rods are glass rods used to mix chemicals.
Condensers are used to condense vapors by cooling them down and turning them into liquids.
Glass retorts are used for distillation by heating, they have a bulb with a long curved spout.
Drying pistols are used to free samples from traces of water, or other volatile impurities. | Laboratory glassware | Wikipedia | 431 | 43958 | https://en.wikipedia.org/wiki/Laboratory%20glassware | Physical sciences | Research methods | Basics and measurement |
A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber. It is one of the measurement devices used in the study of thermodynamics, chemistry, and biochemistry.
To find the enthalpy change per mole of a substance A in a reaction between two substances A and B, the substances are separately added to a calorimeter and the initial and final temperatures (before the reaction has started and after it has finished) are noted. Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction.
where is the amount of heat according to the change in temperature measured in joules and is the heat capacity of the calorimeter which is a value associated with each individual apparatus in units of energy per temperature (joules/kelvin).
History
In 1761 Joseph Black introduced the idea of latent heat which led to the creation of the first ice calorimeters. In 1780, Antoine Lavoisier used the heat released by the respiration of a guinea pig to melt snow surrounding his apparatus, showing that respiratory gas exchange is a form of combustion, similar to the burning of a candle. Lavoisier named this apparatus 'calorimeter', based on both Greek and Latin roots. One of the first ice calorimeters was used in the winter of 1782–83 by Lavoisier and Pierre-Simon Laplace. It relied on the heat required for the melting of ice to measure the heat released in various chemical reactions.
Adiabatic calorimeters
An adiabatic calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fueling the reaction. | Calorimeter | Wikipedia | 477 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
No adiabatic calorimeter is fully adiabatic - some heat will be lost by the sample to the sample holder. A mathematical correction factor, known as the phi-factor, can be used to adjust the calorimetric result to account for these heat losses. The phi-factor is the ratio of the thermal mass of the sample and sample holder to the thermal mass of the sample alone.
Reaction calorimeters
A reaction calorimeter is a calorimeter in which a chemical reaction is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heat flow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:
Heat flow calorimeter
The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition, fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although it is very less accurate.
Heat balance calorimeter
The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.
Power compensation
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.
Constant flux
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.
Bomb calorimeters | Calorimeter | Wikipedia | 417 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The change in temperature of the water allows for calculating calorie content of the fuel.
In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at ) and containing a weighed mass of a sample (typically 1–1.5 g) and a small fixed amount of water (to saturate the internal atmosphere, thus ensuring that all water produced is liquid, and removing the need to include enthalpy of vaporization in calculations), is submerged under a known volume of water (ca. 2000 ml) before the charge is electrically ignited. The bomb, with the known mass of the sample and oxygen, form a closed system — no gases escape during the reaction. The weighed reactant put inside the steel container is then ignited. Energy is released by the combustion and heat flow from this crosses the stainless steel wall, thus raising the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured with a thermometer. This reading, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts), is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.
At its core, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar or insulating container (to prevent heat flow from the calorimeter to its surroundings) and an ignition circuit connected to the bomb. By using stainless steel for the bomb, the reaction will occur with no volume change observed. | Calorimeter | Wikipedia | 489 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
Since there is no heat exchange between the calorimeter and surroundings (Q = 0) (adiabatic), no work is performed (W = 0)
Thus, the total internal energy change
Also, total internal energy change
(constant volume )
where is heat capacity of the bomb
Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated. The value of can be estimated by
and can be measured;
In the laboratory, is determined by running a compound with known heat of combustion value:
Common compounds are benzoic acid () or p-methyl benzoic acid ().
Temperature () is recorded every minute and
A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion: 981.2cal/g.
In order to calibrate the bomb, a small amount (~ 1g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned
The combustion of sample (benzoic acid) inside the bomb
Once value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by
Combustion of non-flammables
The higher pressure and concentration of in the bomb system can render combustible some compounds that are not normally flammable. Some substances do not combust completely, making the calculations harder as the remaining mass has to be taken into consideration, making the possible error considerably larger and compromising the data.
When working with compounds that are not as flammable (that might not combust completely) one solution would be to mix the compound with some flammable compounds with a known heat of combustion and make a pallet with the mixture. Once the of the bomb is known, the heat of combustion of the flammable compound (), of the wire () and the masses ( and ), and the temperature change (ΔT), the heat of combustion of the less flammable compound () can be calculated with:
CLFC = Cv ΔT − CFC mFC − CW mW | Calorimeter | Wikipedia | 455 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
Calvet-type calorimeters
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94% ± 1% of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.
The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called Joule effect or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials. The main advantages of this type of calibration are as follows:
It is an absolute calibration.
The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
It can be applied to any experimental vessel volume.
It is a very accurate calibration.
An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).
Adiabatic and Isoperibol calorimeters
Sometimes referred to as constant-pressure calorimeters, adiabatic calorimeters measure the change in enthalpy of a reaction occurring in solution during which the no heat exchange with the surroundings is allowed (adiabatic) and the atmospheric pressure remains constant. | Calorimeter | Wikipedia | 430 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
An example is a coffee-cup calorimeter, which is constructed from two nested Styrofoam cups, providing insulation from the surroundings, and a lid with two holes, allowing insertion of a thermometer and a stirring rod. The inner cup holds a known amount of a solvent, usually water, that absorbs the heat from the reaction. When the reaction occurs, the outer cup provides insulation. Then
where
, Specific heat at constant pressure
, Enthalpy of solution
, Change in temperature
, mass of solvent
, molecular mass of solvent
The measurement of heat using a simple calorimeter, like the coffee cup calorimeter, is an example of constant-pressure calorimetry, since the pressure (atmospheric pressure) remains constant during the process. Constant-pressure calorimetry is used in determining the changes in enthalpy occurring in solution. Under these conditions the change in enthalpy equals the heat.
Commercial calorimeters operate in a similar way. The semi-adiabatic (isoperibol) calorimeters measure temperature changes up to 10°C and account for heat loss through the walls of the reaction vessel to the environment, hence, semi-adiabatic. The reaction vessel is a dewar flask which is immersed in a constant temperature bath. This provides a constant heat leak rate that can be corrected through the software. The heat capacity of the reactants (and the vessel) are measured by introducing a known amount of heat using a heater element (voltage and current) and measuring the temperature change.
Adiabatic calorimeters most commonly used in materials science research to study reactions that occur at a constant pressure and volume. They are particularly useful for determining the heat capacity of substances, measuring the enthalpy changes of chemical reactions, and studying the thermodynamic properties of materials.
Differential scanning calorimeter
In a differential scanning calorimeter (DSC), heat flow into a sample—usually contained in a small aluminium capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan. | Calorimeter | Wikipedia | 433 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
In a heat flux DSC, both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.
Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its heat capacity Cp. The difference in flow dq/dt induces a small temperature difference ΔT across the slab. This temperature difference is measured using a thermocouple. The heat capacity can in principle be determined from this signal:
Note that this formula (equivalent to Newton's law of heat flow) is analogous to, and much older than, Ohm's law of electric flow:
.
When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.
From the integral of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.
Differential scanning calorimetry is a workhorse technique in many fields, particularly in polymer characterization.
A modulated temperature differential scanning calorimeter (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.
This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that respond to a changing heating rate (reversing) and that don't respond to the changing heating rate (non-reversing). It allows for the optimization of both sensitivity and resolution in a single test by allowing for a slow average heating rate (optimizing resolution) and a fast changing heating rate (optimizing sensitivity). | Calorimeter | Wikipedia | 416 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
A DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often gold, or gold-plated steel), and which will be able to withstand pressure (typically up to 100 bar). The presence of an exothermic event can then be used to assess the stability of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2–3 °C per min) due to much heavier crucible, and unknown activation energy, it is necessary to deduct about 75–100 °C from the initial start of the observed exotherm to suggest a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from ambient at a rate of 3 °C increment per half hour.
Isothermal titration calorimeter
In an isothermal titration calorimeter, the heat of reaction is used to follow a titration experiment. This permits determination of the midpoint (stoichiometry) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)
The technique is gaining in importance particularly in the field of biochemistry, because it facilitates determination of substrate binding to enzymes. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.
Continuous Reaction Calorimeter
The Continuous Reaction Calorimeter is especially suitable to obtain thermodynamic information for a scale-up of continuous processes in tubular reactors. This is useful because the released heat can strongly depend on the reaction control, especially for non-selective reactions. With the Continuous Reaction Calorimeter an axial temperature profile along the tube reactor can be recorded and the specific heat of reaction can be determined by means of heat balances and segmental dynamic parameters. The system must consist of a tubular reactor, dosing systems, preheaters, temperature sensors and flow meters. | Calorimeter | Wikipedia | 429 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
In traditional heat flow calorimeters, one reactant is added continuously in small amounts, similar to a semi-batch process, in order to obtain a complete conversion of the reaction. In contrast to the tubular reactor, this leads to longer residence times, different substance concentrations and flatter temperature profiles. Thus, the selectivity of not well-defined reactions can be affected. This can lead to the formation of by-products or consecutive products which alter the measured heat of reaction, since other bonds are formed. The amount of by-product or secondary product can be found by calculating the yield of the desired product.
If the heat of reaction measured in the HFC (Heat flow calorimetry) and PFR calorimeter differ, most probably some side reactions have occurred. They could for example be caused by different temperatures and residence times. The totally measured Qr is composed of partially overlapped reaction enthalpies (ΔHr) of main and side reactions, depending on their degrees of conversion (U).
Calorimetry in Geothermal Reactors
Calorimeters can be used to measure the efficiency of geothermal energy conversion processes. Through measuring the heat input and output of the process, engineers can determine how effective the plant is at converting geothermal energy into usable electricity or other forms of energy.
Calorimeters can also monitor the quality of the steam extracted from the geothermal resource. By analyzing the heat content of the steam, engineers can ensure that the resource meets the required specifications for efficient energy production. | Calorimeter | Wikipedia | 306 | 43970 | https://en.wikipedia.org/wiki/Calorimeter | Technology | Measuring instruments | null |
In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas mixture is the sum of the partial pressures of the gases in the mixture (Dalton's Law).
The partial pressure of a gas is a measure of thermodynamic activity of the gas's molecules. Gases dissolve, diffuse, and react according to their partial pressures but not according to their concentrations in gas mixtures or liquids. This general property of gases is also true in chemical reactions of gases in biology. For example, the necessary amount of oxygen for human respiration, and the amount that is toxic, is set by the partial pressure of oxygen alone. This is true across a very wide range of different concentrations of oxygen present in various inhaled breathing gases or dissolved in blood; consequently, mixture ratios, like that of breathable 20% oxygen and 80% Nitrogen, are determined by volume instead of by weight or mass. Furthermore, the partial pressures of oxygen and carbon dioxide are important parameters in tests of arterial blood gases. That said, these pressures can also be measured in, for example, cerebrospinal fluid.
Symbol
The symbol for pressure is usually or which may use a subscript to identify the pressure, and gas species are also referred to by subscript. When combined, these subscripts are applied recursively.
Examples:
or = pressure at time 1
or = partial pressure of hydrogen
or or PaO2 = arterial partial pressure of oxygen
or or PvO2 = venous partial pressure of oxygen
Dalton's law of partial pressures
Dalton's law expresses the fact that the total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the individual gases in the mixture. This equality arises from the fact that in an ideal gas, the molecules are so far apart that they do not interact with each other. Most actual real-world gases come very close to this ideal. For example, given an ideal gas mixture of nitrogen (N2), hydrogen (H2) and ammonia (NH3):
where:
= total pressure of the gas mixture
= partial pressure of nitrogen (N2)
= partial pressure of hydrogen (H2)
= partial pressure of ammonia (NH3) | Partial pressure | Wikipedia | 480 | 43972 | https://en.wikipedia.org/wiki/Partial%20pressure | Physical sciences | Thermodynamics | Physics |
Ideal gas mixtures
Ideally the ratio of partial pressures equals the ratio of the number of molecules. That is, the mole fraction of an individual gas component in an ideal gas mixture can be expressed in terms of the component's partial pressure or the moles of the component:
and the partial pressure of an individual gas component in an ideal gas can be obtained using this expression:
The mole fraction of a gas component in a gas mixture is equal to the volumetric fraction of that component in a gas mixture.
The ratio of partial pressures relies on the following isotherm relation:
VX is the partial volume of any individual gas component (X)
Vtot is the total volume of the gas mixture
pX is the partial pressure of gas X
ptot is the total pressure of the gas mixture
nX is the amount of substance of gas (X)
ntot is the total amount of substance in gas mixture
Partial volume (Amagat's law of additive volume)
The partial volume of a particular gas in a mixture is the volume of one component of the gas mixture. It is useful in gas mixtures, e.g. air, to focus on one particular gas component, e.g. oxygen.
It can be approximated both from partial pressure and molar fraction:
VX is the partial volume of an individual gas component X in the mixture
Vtot is the total volume of the gas mixture
pX is the partial pressure of gas X
ptot is the total pressure of the gas mixture
nX is the amount of substance of gas X
ntot is the total amount of substance in the gas mixture
Vapor pressure
Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid's tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquid's atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point.
The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point of the liquid.
The vapor pressure chart displayed has graphs of the vapor pressures versus temperatures for a variety of liquids. As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points. | Partial pressure | Wikipedia | 487 | 43972 | https://en.wikipedia.org/wiki/Partial%20pressure | Physical sciences | Thermodynamics | Physics |
For example, at any given temperature, methyl chloride has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point (−24.2 °C), which is where the vapor pressure curve of methyl chloride (the blue line) intersects the horizontal pressure line of one atmosphere (atm) of absolute vapor pressure. At higher altitudes, the atmospheric pressure is less than that at sea level, so boiling points of liquids are reduced. At the top of Mount Everest, the atmospheric pressure is approximately 0.333 atm, so by using the graph, the boiling point of diethyl ether would be approximately 7.5 °C versus 34.6 °C at sea level (1 atm).
Equilibrium constants of reactions involving gas mixtures
It is possible to work out the equilibrium constant for a chemical reaction involving a mixture of gases given the partial pressure of each gas and the overall reaction formula. For a reversible reaction involving gas reactants and gas products, such as:
{\mathit{a}A} + {\mathit{b}B} <=> {\mathit{c}C} + {\mathit{d}D}
the equilibrium constant of the reaction would be:
For reversible reactions, changes in the total pressure, temperature or reactant concentrations will shift the equilibrium so as to favor either the right or left side of the reaction in accordance with Le Chatelier's Principle. However, the reaction kinetics may either oppose or enhance the equilibrium shift. In some cases, the reaction kinetics may be the overriding factor to consider.
Henry's law and the solubility of gases
Gases will dissolve in liquids to an extent that is determined by the equilibrium between the undissolved gas and the gas that has dissolved in the liquid (called the solvent). The equilibrium constant for that equilibrium is:
where:
= the equilibrium constant for the solvation process
= partial pressure of gas in equilibrium with a solution containing some of the gas
= the concentration of gas in the liquid solution
The form of the equilibrium constant shows that the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution. This statement is known as Henry's law and the equilibrium constant is quite often referred to as the Henry's law constant.
Henry's law is sometimes written as: | Partial pressure | Wikipedia | 484 | 43972 | https://en.wikipedia.org/wiki/Partial%20pressure | Physical sciences | Thermodynamics | Physics |
where is also referred to as the Henry's law constant. As can be seen by comparing equations () and () above, is the reciprocal of . Since both may be referred to as the Henry's law constant, readers of the technical literature must be quite careful to note which version of the Henry's law equation is being used.
Henry's law is an approximation that only applies for dilute, ideal solutions and for solutions where the liquid solvent does not react chemically with the gas being dissolved.
In diving breathing gases
In underwater diving the physiological effects of individual component gases of breathing gases are a function of partial pressure.
Using diving terms, partial pressure is calculated as:
partial pressure = (total absolute pressure) × (volume fraction of gas component)
For the component gas "i":
pi = P × Fi
For example, at underwater, the total absolute pressure is (i.e., 1 bar of atmospheric pressure + 5 bar of water pressure) and the partial pressures of the main components of air, oxygen 21% by volume and nitrogen approximately 79% by volume are:
pN2 = 6 bar × 0.79 = 4.7 bar absolute
pO2 = 6 bar × 0.21 = 1.3 bar absolute
The minimum safe lower limit for the partial pressures of oxygen in a breathing gas mixture for diving is absolute. Hypoxia and sudden unconsciousness can become a problem with an oxygen partial pressure of less than 0.16 bar absolute. Oxygen toxicity, involving convulsions, becomes a problem when oxygen partial pressure is too high. The NOAA Diving Manual recommends a maximum single exposure of 45 minutes at 1.6 bar absolute, of 120 minutes at 1.5 bar absolute, of 150 minutes at 1.4 bar absolute, of 180 minutes at 1.3 bar absolute and of 210 minutes at 1.2 bar absolute. Oxygen toxicity becomes a risk when these oxygen partial pressures and exposures are exceeded. The partial pressure of oxygen also determines the maximum operating depth of a gas mixture.
Narcosis is a problem when breathing gases at high pressure. Typically, the maximum total partial pressure of narcotic gases used when planning for technical diving may be around 4.5 bar absolute, based on an equivalent narcotic depth of . | Partial pressure | Wikipedia | 461 | 43972 | https://en.wikipedia.org/wiki/Partial%20pressure | Physical sciences | Thermodynamics | Physics |
The effect of a toxic contaminant such as carbon monoxide in breathing gas is also related to the partial pressure when breathed. A mixture which may be relatively safe at the surface could be dangerously toxic at the maximum depth of a dive, or a tolerable level of carbon dioxide in the breathing loop of a diving rebreather may become intolerable within seconds during descent when the partial pressure rapidly increases, and could lead to panic or incapacitation of the diver.
In medicine
The partial pressures of particularly oxygen () and carbon dioxide () are important parameters in tests of arterial blood gases, but can also be measured in, for example, cerebrospinal fluid. | Partial pressure | Wikipedia | 140 | 43972 | https://en.wikipedia.org/wiki/Partial%20pressure | Physical sciences | Thermodynamics | Physics |
Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing, but it is not limited to these applications. The word derives from the Latin for lead, plumbum, as the first effective pipes used in the Roman era were lead pipes.
In the developed world, plumbing infrastructure is critical to public health and sanitation.
Boilermakers and pipefitters are not plumbers although they work with piping as part of their trade and their work can include some plumbing.
History
Plumbing originated during ancient civilizations, as they developed public baths and needed to provide potable water and wastewater removal for larger numbers of people.
The Mesopotamians introduced the world to clay sewer pipes around 4000 BCE, with the earliest examples found in the Temple of Bel at Nippur and at Eshnunna, used to remove wastewater from sites, and capture rainwater, in wells. The city of Uruk contains the oldest known examples of brick constructed Latrines, constructed atop interconnecting fired clay sewer pipes, . Clay pipes were later used in the Hittite city of Hattusa. They had easily detachable and replaceable segments, and allowed for cleaning.
Standardized earthen plumbing pipes with broad flanges making use of asphalt for preventing leakages appeared in the urban settlements of the Indus Valley civilization by 2700 BC.
Copper piping appeared in Egypt by 2400 BCE, with the Pyramid of Sahure and adjoining temple complex at Abusir, found to be connected by a copper waste pipe.
The word "plumber" dates from the Roman Empire. The Latin for lead is . Roman roofs used lead in conduits and drain pipes and some were also covered with lead. Lead was also used for piping and for making baths. | Plumbing | Wikipedia | 395 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Plumbing reached its early apex in ancient Rome, which saw the introduction of expansive systems of aqueducts, tile wastewater removal, and widespread use of lead pipes. The Romans used lead pipe inscriptions to prevent water theft. With the Fall of Rome both water supply and sanitation stagnated—or regressed—for well over 1,000 years. Improvement was very slow, with little effective progress made until the growth of modern densely populated cities in the 1800s. During this period, public health authorities began pressing for better waste disposal systems to be installed, to prevent or control epidemics of disease. Earlier, the waste disposal system had consisted of collecting waste and dumping it on the ground or into a river. Eventually the development of separate, underground water and sewage systems eliminated open sewage ditches and cesspools.
In post-classical Kilwa the wealthy enjoyed indoor plumbing in their stone homes.
Most large cities today pipe solid wastes to sewage treatment plants in order to separate and partially purify the water, before emptying into streams or other bodies of water. For potable water use, galvanized iron piping was commonplace in the United States from the late 1800s until around 1960. After that period, copper piping took over, first soft copper with flared fittings, then with rigid copper tubing using soldered fittings.
The use of lead for potable water declined sharply after World War II because of increased awareness of the dangers of lead poisoning. At this time, copper piping was introduced as a better and safer alternative to lead pipes.
Systems
The major categories of plumbing systems or subsystems are:
potable cold and hot tap water supply
plumbing drainage venting
sewage systems and septic systems with or without hot water heat recycling and graywater recovery and treatment systems
Rainwater, surface, and subsurface water drainage
fuel gas piping
hydronics, i.e. heating and cooling systems using water to transport thermal energy, as in district heating systems, like for example the New York City steam system.
Water pipes
A water pipe is a pipe or tube, frequently made of plastic or metal, that carries pressurized and treated fresh water to a building (as part of a municipal water system), as well as inside the building.
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Lead was the favoured material for water pipes for many centuries because its malleability made it practical to work into the desired shape. Such use was so common that the word "plumbing" derives from plumbum, the Latin word for lead. This was a source of lead-related health problems in the years before the health hazards of ingesting lead were fully understood; among these were stillbirths and high rates of infant mortality. Lead water pipes were still widely used in the early 20th century and remain in many households. Lead-tin alloy solder was commonly used to join copper pipes, but modern practice uses tin-antimony alloy solder instead in order to eliminate lead hazards.
Despite the Romans' common use of lead pipes, their aqueducts rarely poisoned people. Unlike other parts of the world where lead pipes cause poisoning, the Roman water had so much calcium in it that a layer of plaque prevented the water contacting the lead itself. What often causes confusion is the large amount of evidence of widespread lead poisoning, particularly amongst those who would have had easy access to piped water, an unfortunate result of lead being used in cookware and as an additive to processed food and drink (for example as a preservative in wine). Roman lead pipe inscriptions provided information on the owner to prevent water theft.
Wooden pipes were used in London and elsewhere during the 16th and 17th centuries. The pipes were hollowed-out logs which were tapered at the end with a small hole in which the water would pass through. The multiple pipes were then sealed together with hot animal fat. Wooden pipes were used in Philadelphia, Boston, and Montreal in the 1800s. Built-up wooden tubes were widely used in the US during the 20th century. These pipes (used in place of corrugated iron or reinforced concrete pipes) were made of sections cut from short lengths of wood. Locking of adjacent rings with hardwood dowel pins produced a flexible structure. About 100,000 feet of these wooden pipes were installed during WW2 in drainage culverts, storm sewers and conduits, under highways and at army camps, naval stations, airfields and ordnance plants.
Cast iron and ductile iron pipe was long a lower-cost alternative to copper before the advent of durable plastic materials but special non-conductive fittings must be used where transitions are to be made to other metallic pipes (except for terminal fittings) in order to avoid corrosion owing to electrochemical reactions between dissimilar metals (see galvanic cell). | Plumbing | Wikipedia | 509 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Bronze fittings and short pipe segments are commonly used in combination with various materials.
Difference between pipes and tubes
The difference between pipes and tubes is a matter of sizing. For instance, PVC pipe for plumbing applications and galvanized steel pipe are measured in iron pipe size (IPS). Copper tube, CPVC, PeX and other tubing is measured nominally, basically an average diameter. These sizing schemes allow for universal adaptation of transitional fittings. For instance, 1/2" PeX tubing is the same size as 1/2" copper tubing. 1/2" PVC on the other hand is not the same size as 1/2" tubing, and therefore requires either a threaded male or female adapter to connect them. When used in agricultural irrigation, the singular form "pipe" is often used as a plural.
Pipe is available in rigid joints, which come in various lengths depending on the material. Tubing, in particular copper, comes in rigid hard tempered joints or soft tempered (annealed) rolls. PeX and CPVC tubing also comes in rigid joints or flexible rolls. The temper of the copper, whether it is a rigid joint or flexible roll, does not affect the sizing.
The thicknesses of the water pipe and tube walls can vary. Because piping and tubing are commodities, having a greater wall thickness implies higher initial cost. Thicker walled pipe generally implies greater durability and higher pressure tolerances. Pipe wall thickness is denoted by various schedules or for large bore polyethylene pipe in the UK by the Standard Dimension Ratio (SDR), defined as the ratio of the pipe diameter to its wall thickness. Pipe wall thickness increases with schedule, and is available in schedules 20, 40, 80, and higher in special cases. The schedule is largely determined by the operating pressure of the system, with higher pressures commanding greater thickness. Copper tubing is available in four wall thicknesses: type DWV (thinnest wall; only allowed as drain pipe per UPC), type 'M' (thin; typically only allowed as drain pipe by IPC code), type 'L' (thicker, standard duty for water lines and water service), and type 'K' (thickest, typically used underground between the main and the meter). | Plumbing | Wikipedia | 475 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Wall thickness does not affect pipe or tubing size. 1/2" L copper has the same outer diameter as 1/2" K or M copper. The same applies to pipe schedules. As a result, a slight increase in pressure losses is realized due to a decrease in flowpath as wall thickness is increased. In other words, 1 foot of 1/2" L copper has slightly less volume than 1 foot of 1/2 M copper.
Materials
Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead, bamboo, wood, or stone. Hollowed wooden logs wrapped in steel banding were used for plumbing pipes, particularly water mains. Logs were used for water distribution in England close to 500 years ago. US cities began using hollowed logs in the late 1700s through the 1800s. Today, most plumbing supply pipe is made out of steel, copper, and plastic; most waste (also known as "soil") out of steel, copper, plastic, and cast iron.
The straight sections of plumbing systems are called "pipes" or "tubes". A pipe is typically formed via casting or welding, whereas a tube is made through extrusion. Pipe normally has thicker walls and may be threaded or welded, while tubing is thinner-walled and requires special joining techniques such as brazing, compression fitting, crimping, or for plastics, solvent welding. These joining techniques are discussed in more detail in the piping and plumbing fittings article.
Steel
Galvanized steel potable water supply and distribution pipes are commonly found with nominal pipe sizes from to . It is rarely used today for new construction residential plumbing. Steel pipe has National Pipe Thread (NPT) standard tapered male threads, which connect with female tapered threads on elbows, tees, couplers, valves, and other fittings. Galvanized steel (often known simply as "galv" or "iron" in the plumbing trade) is relatively expensive, and difficult to work with due to weight and requirement of a pipe threader. It remains in common use for repair of existing "galv" systems and to satisfy building code non-combustibility requirements typically found in hotels, apartment buildings and other commercial applications. It is also extremely durable and resistant to mechanical abuse. Black lacquered steel pipe is the most widely used pipe material for fire sprinklers and natural gas. | Plumbing | Wikipedia | 495 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Most typical single family home systems will not require supply piping larger than due to expense as well as steel piping's tendency to become obstructed from internal rusting and mineral deposits forming on the inside of the pipe over time once the internal galvanizing zinc coating has degraded. In potable water distribution service, galvanized steel pipe has a service life of about 30 to 50 years, although it is not uncommon for it to be less in geographic areas with corrosive water contaminants.
Copper
Copper pipe and tubing was widely used for domestic water systems in the latter half of the twentieth century. Demand for copper products has fallen due to the dramatic increase in the price of copper, resulting in increased demand for alternative products including PEX and stainless steel.
Plastic | Plumbing | Wikipedia | 159 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Plastic pipe is in wide use for domestic water supply and drain-waste-vent (DWV) pipe. Principal types include:
Polyvinyl chloride (PVC) was produced experimentally in the 19th century but did not become practical to manufacture until 1926, when Waldo Semon of BF Goodrich Co. developed a method to plasticize PVC, making it easier to process. PVC pipe began to be manufactured in the 1940s and was in wide use for Drain-Waste-Vent piping during the reconstruction of Germany and Japan following WWII. In the 1950s, plastics manufacturers in Western Europe and Japan began producing acrylonitrile butadiene styrene (ABS) pipe. The method for producing cross-linked polyethylene (PEX) was also developed in the 1950s. Plastic supply pipes have become increasingly common, with a variety of materials and fittings employed.
PVC/CPVC – rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC stands for polyvinyl chloride, and it has become a common replacement for metal piping. PVC should be used only for cold water, or for venting. CPVC can be used for hot and cold potable water supply. Connections are made with primers and solvent cements as required by code.
PP – The material is used primarily in housewares, food packaging, and clinical equipment, but since the early 1970s has seen increasing use worldwide for both domestic hot and cold water. PP pipes are heat fused, being unsuitable for the use of glues, solvents, or mechanical fittings. PP pipe is often used in green building projects.
PBT – flexible (usually gray or black) plastic pipe which is attached to barbed fittings and secured in place with a copper crimp ring. The primary manufacturer of PBT tubing and fittings was driven into bankruptcy by a class-action lawsuit over failures of this system. However, PB and PBT tubing has since returned to the market and codes, typically first for "exposed locations" such as risers.
PEX – cross-linked polyethylene system with mechanically joined fittings employing barbs, and crimped steel or copper rings.
Polytanks – plastic polyethylene cisterns, underground water tanks, above ground water tanks, are usually made of linear polyethylene suitable as a potable water storage tank, provided in white, black or green. | Plumbing | Wikipedia | 510 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Aqua – known as PEX-Al-PEX, for its PEX/aluminum sandwich, consisting of aluminum pipe sandwiched between layers of PEX, and connected with modified brass compression fittings. In 2005, many of these fittings were recalled. | Plumbing | Wikipedia | 52 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Present-day water-supply systems use a network of high-pressure pumps, and pipes in buildings are now made of copper, brass, plastic (particularly cross-linked polyethylene called PEX, which is estimated to be used in 60% of single-family homes), or other nontoxic material. Due to its toxicity, most cities moved away from lead water-supply piping by the 1920s in the United States, although lead pipes were approved by national plumbing codes into the 1980s, and lead was used in plumbing solder for drinking water until it was banned in 1986. Drain and vent lines are made of plastic, steel, cast iron, or lead.
Gallery
Components
In addition to lengths of pipe or tubing, pipe fittings such as valves, elbows, tees, and unions. are used in plumbing systems. Pipe and fittings are held in place with pipe hangers and strapping.
Plumbing fixtures are exchangeable devices that use water and can be connected to a building's plumbing system. They are considered to be "fixtures", in that they are semi-permanent parts of buildings, not usually owned or maintained separately. Plumbing fixtures are seen by and designed for the end-users. Some examples of fixtures include water closets (also known as toilets), urinals, bidets, showers, bathtubs, utility and kitchen sinks, drinking fountains, ice makers, humidifiers, air washers, fountains, and eye wash stations.
Sealants
Threaded pipe joints are sealed with thread seal tape or pipe dope. Many plumbing fixtures are sealed to their mounting surfaces with plumber's putty.
Equipment and tools
Plumbing equipment includes devices often behind walls or in utility spaces which are not seen by the general public. It includes water meters, pumps, expansion tanks, back flow preventers, water filters, UV sterilization lights, water softeners, water heaters, heat exchangers, gauges, and control systems.
There are many tools a plumber needs to do a good plumbing job. While many simple plumbing tasks can be completed with a few common hand held tools, other more complex jobs require specialised tools, designed specifically to make the job easier. | Plumbing | Wikipedia | 448 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Specialized plumbing tools include pipe wrenches, flaring pliers, pipe vise, pipe bending machine, pipe cutter, dies, and joining tools such as soldering torches and crimp tools. New tools have been developed to help plumbers fix problems more efficiently. For example, plumbers use video cameras for inspections of hidden leaks or other problems; they also use hydro jets, and high pressure hydraulic pumps connected to steel cables for trench-less sewer line replacement.
Flooding from excessive rain or clogged sewers may require specialized equipment, such as a heavy duty pumper truck designed to vacuum raw sewage.
Problems
Bacteria have been shown to live in "premises plumbing systems". The latter refers to the "pipes and fixtures within a building that transport water to taps after it is delivered by the utility". Community water systems have been known for centuries to spread waterborne diseases like typhoid and cholera. However, "opportunistic premises plumbing pathogens" have been recognized only more recently: Legionella pneumophila, discovered in 1976, Mycobacterium avium, and Pseudomonas aeruginosa are the most commonly tracked bacteria, which people with depressed immunity can inhale or ingest and may become infected with.
Some of the locations where these opportunistic pathogens can grow include faucets, shower heads, water heaters and along pipe walls. Reasons that favor their growth are "high surface-to-volume ratio, intermittent stagnation, low disinfectant residual, and warming cycles". A high surface-to-volume ratio, i.e. a relatively large surface area allows the bacteria to form a biofilm, which protects them from disinfection.
Regulation
Much of the plumbing work in populated areas is regulated by government or quasi-government agencies due to the direct impact on the public's health, safety, and welfare. Plumbing installation and repair work on residences and other buildings generally must be done according to plumbing and building codes to protect the inhabitants of the buildings and to ensure safe, quality construction to future buyers. If permits are required for work, plumbing contractors typically secure them from the authorities on behalf of home or building owners.
Australia
In Australia, the national governing body for plumbing regulation is the Australian Building Codes Board. They are responsible for the creation of the National Construction Code (NCC), Volume 3 of which, the Plumbing Regulations 2008 and the Plumbing Code of Australia, pertains to plumbing. | Plumbing | Wikipedia | 504 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Each Government at the state level has their own Authority and regulations in place for licensing plumbers. They are also responsible for the interpretation, administration and enforcement of the regulations outlined in the NCC. These Authorities are usually established for the sole purpose of regulating plumbing activities in their respective states/territories. However, several state level regulation acts are quite outdated, with some still operating on local policies introduced more than a decade ago. This has led to an increase in plumbing regulatory issues not covered under current policy, and as such, many policies are currently being updated to cover these more modern issues. The updates include changed to the minimum experience and training requirements for licensing, additional work standards for new and more specific kinds of plumbing, as well as adopting the Plumbing Code of Australia into state regulations in an effort to standardise plumbing regulations across the country.
Norway
In Norway, new domestic plumbing installed since 1997 has had to satisfy the requirement that it should be easily accessible for replacement after installation. This has led to the development of the pipe-in-pipe system as a de facto requirement for domestic plumbing.
United Kingdom
In the United Kingdom the professional body is the Chartered Institute of Plumbing and Heating Engineering (educational charity status) and it is true that the trade still remains virtually ungoverned; there are no systems in place to monitor or control the activities of unqualified plumbers or those home owners who choose to undertake installation and maintenance works themselves, despite the health and safety issues which arise from such works when they are undertaken incorrectly; see Health Aspects of Plumbing (HAP) published jointly by the World Health Organization (WHO) and the World Plumbing Council (WPC). WPC has subsequently appointed a representative to the World Health Organization to take forward various projects related to Health Aspects of Plumbing.
United States
In the United States, plumbing codes and licensing are generally controlled by state and local governments. At the national level, the Environmental Protection Agency has set guidelines about what constitutes lead-free plumbing fittings and pipes, in order to comply with the Safe Drinking Water Act. | Plumbing | Wikipedia | 412 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
Some widely used Standards in the United States are:
ASME A112.6.3 – Floor and Trench Drains
ASME A112.6.4 – Roof, Deck, and Balcony Drains
ASME A112.18.1/CSA B125.1 – Plumbing Supply Fittings
ASME A112.19.1/CSA B45.2 – Enameled Cast Iron and Enameled Steel Plumbing Fixtures
ASME A112.19.2/CSA B45.1 – Ceramic Plumbing Fixtures
Canada
In Canada, plumbing is a regulated trade requiring specific technical training and certification. Standards and regulations for plumbing are overseen at the provincial and territorial level, each having its distinct governing body:
Governing Bodies: Each province or territory possesses its regulatory authority overseeing the licensing and regulation of plumbers. For instance, in Ontario, the Ontario College of Trades handles the certification and regulation of tradespeople, whereas in British Columbia, the Industry Training Authority (ITA) undertakes this function.
Certification: To achieve certified plumber status in Canada, individuals typically complete an apprenticeship program encompassing both classroom instruction and hands-on experience. Upon completion, candidates undergo an examination for their certification.
Building Codes: Plumbing installations and repairs must adhere to building codes specified by individual provinces or territories. The National Building Code of Canada acts as a model code, with provinces and territories having the discretion to adopt or modify to their specific needs.
Safety and Health: Given its direct correlation with health and sanitation, plumbing work is of paramount importance in Canada. Regulations ensure uncontaminated drinking water and proper wastewater treatment, underscoring the vital role of certified plumbers for public health.
Environmental Considerations: Reflecting Canada's commitment to environmental conservation, there is an increasing emphasis on sustainable plumbing practices. Regulations advocate water conservation and the deployment of eco-friendly materials.
Standards: The Canadian Standards Association (CSA) determines standards for diverse plumbing products, ensuring their safety, quality, and efficiency. Items such as faucets and toilets frequently come with a CSA certification, indicating adherence to required standards. | Plumbing | Wikipedia | 412 | 43982 | https://en.wikipedia.org/wiki/Plumbing | Technology | Food, water and health | null |
A candle is an ignitable wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a fragrance. A candle can also provide heat or a method of keeping time. Candles have been used for over two millennia around the world, and were a significant form of indoor lighting until the invention of other types of light sources. Although electric light has largely made candle use nonessential for illumination, candles are still commonly used for functional, symbolic and aesthetic purposes and in specific cultural and religious settings.
Early candles may be made of beeswax, but these candles were expensive and their use was limited to the elite and the churches. Tallow was a cheaper but a less aesthetically pleasing alternative. A variety of different materials have been developed in the modern era for making candles, including paraffin wax, which together with efficient production techniques, made candles affordable for the masses. Various devices can be used to hold candles, such as candlesticks, or candelabras, chandeliers, lanterns and sconces. A person who makes candles is traditionally known as a chandler.
The combustion of the candle proceeds in self-sustaining manner. As the wick of candle is lit, the heat melts and ignites a small amount of solid fuel (the wax), which vaporizes and combines with oxygen in the air to form a flame. The flame then melts the top of the mass of solid fuel, which moves upward through the wick via capillary action to be continually burnt, thereby maintaining a constant flame. The candle shortens as the solid fuel is consumed, so does the wick. Wicks of pre-19th century candles required regular trimming with scissors or "snuffers" to promote steady burning and prevent smoking. In modern candles, the wick is constructed so that it curves over as it burns, and the end of the wick gets trimmed by itself through incineration by fire.
Etymology
The word candle comes from Middle English , from Old English and from Anglo-Norman , both from Latin , from 'to shine'.
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Prior to the invention of candles, ancient people used open fire, torches, splinters of resinous wood, and lamps to provide artificial illumination at night. Primitive oil lamps in which a lit wick rested in a pool of oil or fat were used from the Paleolithic period, and pottery and stone lamps from the Neolithic period have been found. Because candle making requires a reliable supply of animal or vegetable fats, it is certain that candles could not have developed before the early Bronze Age; however, it is unclear when and where candles were first used. Objects that could be candlesticks have been found in Babylonian and middle Minoan cultures, as well in the tomb of Tutankhamun. The "candles" used in these early periods would not have resembled the current forms; more likely they were made of plant materials dipped in animal fat.
Early evidence of candle use may be found in Italy, where depiction of a candlestick exists in an Etruscan tomb at Orvieto, and the earliest excavated Etruscan candlestick dates from the 7th century BC. Candles may have evolved from taper with wick of oakum and other plant fibre soaked in fat, pitch or oil and burned in lamps or pots. Candles of antiquity were made from various forms of natural fat, tallow, and wax, and Romans made true dipped candles from tallow and beeswax. Beeswax candles were expensive and their use was limited to the wealthy, instead oil lamps were the more commonly used lighting devices in Roman times. Ancient Greece used torches and oil lamps, and likely adopted candle use in a later period from Rome. Early record in China suggests that candle was used in the Qin dynasty before 200 BC. These early Chinese candles may have been made from whale fat.
In Christianity, candles gained significance in their decorative, symbolic and ceremonial uses in churches. Wax candles, or candela cerea recorded at the end of the 3rd century, were documented as Easter candles in Spain and Italy in the fourth century, the Christian festival Candlemas was named after it, and Pope Sergius I instituted the procession of lighted candles. Papal bulls decreed that tallow be excluded for use in altar candles, and a high beeswax content is necessary for candles of the high altar. | Candle | Wikipedia | 460 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
In medieval Europe, candles were initially used primarily in Christian churches. Its use spread later to the households of the wealthy as a luxury item. In northern Europe, rushlight made of greased rushes were commonly used especially in England, but tallow candles were used during the Middle Ages, with a mention of tallow candles in English appearing in 1154. Beeswax was widely used in church ceremonies, and compared to animal-based tallow, it burns cleanly without smoky flame, and does not release an unpleasant smell like tallow. Beeswax candles were expensive, and relatively few people could afford to burn them in their homes in medieval Europe.
The candles were produced using a number of methods: dipping the wick in molten fat or wax, rolling the candle by hand around a wick, or pouring fat or wax onto a wick to build up the candle. In the 14th century Sieur de Brez introduced the technique of using a mould, but real improvement for the efficient production of candles with mould was only achieved in the 19th century. Wax and tallow candles were made in monasteries in the medieval period, and in rural households, tallow candles may be made at home. By the 13th century, candle making had become a guild craft in England and France, with a French guild documented as early as 1061. The candle makers (chandlers) went from house to house making candles from the kitchen fats saved for that purpose, or made and sold their own candles from small candle shops.
By the 16th century, beeswax candles were appearing as luxury household items among the wealthy. Candles were widely used in the 17th and 18th centuries, and a party in Dresden was said to have been lit by 14,000 candles in 1779. | Candle | Wikipedia | 356 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
In the Middle East, during the Abbasid and Fatimid Caliphates, beeswax was the dominant material used for candle making. Beeswax was often imported from long distances; for example, candle makers from Egypt used beeswax from Tunis. As in Europe, these candles were expensive and limited to the elite, and most commoners used oil lamps instead. According to legend, the practice of using lamps and candles in mosque started with Tamim al-Dari who lit a lamp he brought from Syria in the Prophet's Mosque in Medina. The Umayyad caliph Al-Walid II was known to have used candles in the court in Damascus, while the Abbasid caliph al-Mutawakkil was said to have spent 1.2 million silver dirhams annually on candles for his royal palaces.
In early modern Syria, candles were in high demand by all socioeconomic classes because they were customarily lit during marriage ceremonies. There were candle makers' guilds in the Safavid capital of Isfahan during the 1500s and 1600s. However, candle makers had a relatively low social position in Safavid Iran, comparable to barbers, bathhouse workers, fortune tellers, bricklayers, and porters.
In the 18th and 19th centuries, spermaceti, a waxy substance produced by the sperm whale, was used to produce a superior candle that burned longer, brighter and gave off no offensive smell. Later in the 18th century, colza oil and rapeseed oil came into use as much cheaper substitutes.
Modern era
A number of improvements were made to candle in the 19th century. In older candles, the wick of a burning candle was not in direct contact with air, so it charred instead of being burnt. The charred wick inhibited further burning and produced black smoke, so the wick needed to be constantly trimmed or "snuffed". In 1825, a French man M. Cambacérès introduced the plaited wick soaked with mineral salts, which when burnt, curled towards the outer edge of the flame and become incinerated by it, thereby trimming itself. These are referred to as "self-trimming" or "self-consuming" wicks. In 1823, Michel Eugène Chevreul and Joseph Louis Gay-Lussac separate out stearin in animal fats, and obtained a patent in 1825 to produce candles that are harder and can burn brighter. | Candle | Wikipedia | 500 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
The manufacture of candles became an industrialized mass market in the mid 19th century. In 1834, Joseph Morgan, a pewterer from Manchester, England, patented a machine that revolutionised candle making. It allowed for continuous production of molded candles by using a cylinder with a moveable piston to eject candles as they solidified. This more efficient mechanized production produced about 1,500 candles per hour. This allowed candles to be an affordable commodity for the masses.
In the mid-1850s, James Young succeeded in distilling paraffin wax from coal and oil shales at Bathgate in West Lothian and developed a commercially viable method of production. Paraffin could be used to make inexpensive candles of high quality. It was a bluish-white wax, which burned cleanly and left no unpleasant odor, unlike tallow candles. By the end of the 19th century, candles were made from paraffin wax and stearic acid.
By the late 19th century, Price's Candles, based in London, was the largest candle manufacturer in the world. Founded by William Wilson in 1830, the company pioneered the implementation of the technique of steam distillation, and was thus able to manufacture candles from a wide range of raw materials, including skin fat, bone fat, fish oil and industrial greases.
Despite advances in candle making, the candle industry declined rapidly upon the introduction of superior methods of lighting, including kerosene and lamps and the 1879 invention of the incandescent light bulb. From this point on, candles came to be marketed as more of a decorative item.
Use
Before the invention of electric lighting, candles and oil lamps were commonly used for illumination. In areas without electricity, they are still used routinely. Until the 20th century, candles were more common in northern Europe. In southern Europe and the Mediterranean, oil lamps predominated.
In the developed world today, candles are used mainly for their aesthetic value and scent, particularly to set a soft, warm, or romantic ambiance, for emergency lighting during electrical power failures. Candles, however, are still commonly used in religious and ceremonial contexts. Examples include votive candles, Paschal candles and yahrzeit candles. In the days leading to Christmas, some people burn a candle a set amount to represent each day, as marked on the candle. The type of candle used in this way is called the Advent candle, although this term is also used to refer to a candle that are used in an Advent wreath. | Candle | Wikipedia | 500 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
Symbolic use of candles has extended from the religious to the secular, for example, a candlelight vigil may be held in remembrance for a person, for a cause or an event, or as a form of political action or protest. In a social setting, candles are commonly used on birthday cakes.
In the 21st century, there has been a huge spike in sales of scented candles in recent years. The COVID-19 pandemic and the ensuing lockdowns led to a dramatic increase in the sales of scented candles, diffusers and room sprays.
Other uses
With the fairly consistent and measurable burning of a candle, a common use of candles was to tell the time. The candle designed for this purpose might have time measurements, usually in hours, marked along the wax. The Song dynasty in China (960–1279) used candle clocks.
By the 18th century, candle clocks were being made with weights set into the sides of the candle. As the candle melted, the weights fell off and made a noise as they fell into a bowl.
Components
Wax
For most of recorded history candles were made from tallow (rendered from beef or mutton-fat) or beeswax. From the mid-1800s, they were also made from spermaceti, a waxy substance derived from the Sperm whale, which in turn spurred demand for the substance. Candles were also made from stearin (initially manufactured from animal fats but now produced almost exclusively from palm waxes). Today, most candles are made from paraffin wax, a byproduct of petroleum refining.
Candles can also be made from microcrystalline wax, beeswax (a byproduct of honey collection), gel (a mixture of polymer and mineral oil), or some plant waxes (generally palm, carnauba, bayberry, or soybean wax).
The size of the flame and corresponding rate of burning is controlled largely by the candle wick. The kind of wax also affects the burn rate, with beeswax and coconut wax burning longer than paraffin or soy wax.
Production methods utilize extrusion moulding. More traditional production methods entail melting the solid fuel by the controlled application of heat. The liquid is then poured into a mould, or a wick is repeatedly immersed in the liquid to create a dipped tapered candle. Often fragrance oils, essential oils or aniline-based dye is added.
Wick | Candle | Wikipedia | 500 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
A candle wick works by capillary action, drawing ("wicking") the melted wax or fuel up to the flame. When the liquid fuel reaches the flame, it vaporizes and combusts. The candle wick influences how the candle burns. Important characteristics of the wick include diameter, stiffness, fire resistance, and tethering.
A candle wick is a piece of string or cord that holds the flame of a candle. Commercial wicks are made from braided cotton. The wick's capillarity determines the rate at which the melted hydrocarbon is conveyed to the flame. If the capillarity is too great, the molten wax streams down the side of the candle. Wicks are often infused with a variety of chemicals to modify their burning characteristics. For example, it is usually desirable that the wick not glow after the flame is extinguished. Typical agents are ammonium nitrate and ammonium sulfate.
Characteristics
Light
Based on measurements of a taper-type, paraffin wax candle, a modern candle typically burns at a steady rate of about 0.1 g/min, releasing heat at roughly 80 W. The light produced is about 13 lumens, for a luminous efficacy of about 0.16 lumens per watt (luminous efficacy of a source) – almost a hundred times lower than an incandescent light bulb. If a 1 candela source emitted uniformly in all directions, the total radiant flux would be only about 18.40 mW.
The luminous intensity of a typical candle is approximately one candela. The SI unit, candela, was in fact based on an older unit called the candlepower, which represented the luminous intensity emitted by a candle made to particular specifications (a "standard candle"). The modern unit is defined in a more precise and repeatable way, but was chosen such that a candle's luminous intensity is still about one candela.
Temperature | Candle | Wikipedia | 395 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
The hottest part of a candle flame is just above the very dull blue part to one side of the flame, at the base. At this point, the flame is about . However, this part of the flame is very small and releases little heat energy. The blue color is due to chemiluminescence, while the visible yellow color is due to radiative emission from hot soot particles. The soot is formed through a series of complex chemical reactions, leading from the fuel molecule through molecular growth, until multi-carbon ring compounds are formed. The thermal structure of a flame is complex, hundreds of degrees over very short distances leading to extremely steep temperature gradients. On average, the flame temperature is about . The color temperature is approximately 1,000 K.
Combustion
For a candle to burn, a heat source (commonly a naked flame from a match or lighter) is used to light the candle's wick, which melts and vaporizes a small amount of fuel (the wax). Once vaporized, the fuel combines with oxygen in the atmosphere to ignite and form a constant flame. This flame provides sufficient heat to keep the candle burning via a self-sustaining chain of events: the heat of the flame melts the top of the mass of solid fuel; the liquefied fuel then moves upward through the wick via capillary action; the liquefied fuel finally vaporizes to burn within the candle's flame.
As the fuel (wax) is melted and burned, the candle becomes shorter. The end of the plaited wick bends and get consumed in the flame. The incineration of the wick limits the length of the exposed portion of the wick, thus maintaining a constant burning temperature and rate of fuel consumption. Pre-19th century wicks required regular trimming with scissors (or a specialized wick trimmer), usually to about one-quarter inch (~0.7 cm), to promote steady burning and to prevent it from releasing black smoke. Special candle scissors called "snuffers" were produced for this purpose in the 20th century and were often combined with an extinguisher. In modern candles, the wick is made in such a way that it curves over as it burns, which ensures that the end of the wick gets incinerated by fire, thereby trimming itself.
Candle flame | Candle | Wikipedia | 483 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
A candle flame is formed because wax vaporizes on burning. A candle flame is widely recognized as having between three and five regions or "zones":
Zone I – this is the non-luminous, lowest, and coolest part of the candle flame. It is located around the base of the wick where there is insufficient oxygen for fuel to burn. Temperatures are around .
Zone II – this is the blue zone, which surrounds the base of the flame. Here the supply of oxygen is plentiful, and the fuel burns clean and blue. It is heat from this zone which causes the wax to melt. Temperatures are around .
Zone III – the dark zone is a region directly above the wick containing unburnt wax. Pyrolysis takes place here. Temperature is around .
Zone IV – the middle or luminous zone is yellow/white and is located above the dark zone. It is the brightest zone, but not the hottest. It is an oxygen-depleted zone with insufficient oxygen to burn all of the wax vapor rising from below it, resulting in only partial combustion. The zone also contains unburnt carbon particles. Temperature is around .
Zone V – The non-luminous outer zone or veil surrounds Zone IV. Here, the flame is at its hottest, at around , and complete combustion occurs. It is light blue in color, though most of it is invisible.
The main determinant of the height of a candle flame is the diameter of the wick. This is evidenced in tealights where the wick is very thin and the flame is very small. Candles whose main purpose is illumination use a much thicker wick.
History of study
One of Michael Faraday's significant works was The Chemical History of a Candle, where he gives an in-depth analysis of the evolutionary development, workings and science of candles.
Hazards
According to the National Fire Protection Association, candles are a leading source of residential fires in the United States with almost 10% of civilian injuries and 6% of fatalities from fire attributed to candles.
A candle flame that is longer than its laminar smoke point will emit soot. Proper wick trimming will reduce soot emissions from most candles. | Candle | Wikipedia | 442 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
The liquid wax is hot and can cause skin burns, but the amount and temperature are generally rather limited and the burns are seldom serious. The best way to avoid getting burned from splashed wax is to use a candle snuffer instead of blowing on the flame. A candle snuffer is usually a small metal cup on the end of a long handle. Placing the snuffer over the flame cuts off the oxygen supply. Snuffers were common in the home when candles were the main source of lighting before electric lights were available. Ornate snuffers, often combined with a taper for lighting, are still found in those churches which regularly use large candles.
Glass candle-holders are sometimes cracked by thermal shock from the candle flame, particularly when the candle burns down to the end. When burning candles in glass holders or jars, users should avoid lighting candles with chipped or cracked containers, and stop use once a half-inch or less of wax remains.
A former worry regarding the safety of candles was that a lead core was used in the wicks to keep them upright in container candles. Without a stiff core, the wicks of a container candle could sag and drown in the deep wax pool. Concerns rose that the lead in these wicks would vaporize during the burning process, releasing lead vapors – a known health and developmental hazard. Lead core wicks have not been common since the 1970s. Today, most metal-cored wicks use zinc or a zinc alloy, which has become the industry standard. Wicks made from specially treated paper and cotton are also available.
Candles emit volatile organic compounds into the environment, which releases carbon into the air. The combustion process of lighting a candle includes the release of light, heat, carbon dioxide and water vapor, to fuel the flame. Candle use can be unsafe if fragrances are inhaled at high doses Non-toxic candles have been created as an alternative to prevent these volatile organic compounds from being released into the environment. Candle companies such as "The Plant Project" have created candles that are more environmentally sustainable and better for lung health. These alternatives include non-toxic wax blends, safe fragrances and eco-friendly packaging. Safer candles include candles made from coconut, soy, vegetable, and beeswax.
Users who seek the aesthetics of a candle sometimes install an electric flameless candle to avoid the hazards. | Candle | Wikipedia | 480 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
Regulation
International markets have developed a range of standards and regulations to ensure compliance, while maintaining and improving safety, including:
Europe: GPSD, EN 15493, EN 15494, EN 15426, EN 14059, REACH, RAL-GZ 041 Candles (Germany), French Decree 91-1175
United States: ASTM F2058, ASTM F2179, ASTM F2417, ASTM F2601, ASTM F2326 (all are federal and applies in all 50 states), California Proposition 65 (California only), CONEG (New England and New York states only)
China: QB/T 2119 Basic Candle, QB/T 2902 Art Candle, QB/T 2903 Jar Candle, GB/T 22256 Jelly Candle
Accessories
Candle holders
Decorative candleholders, especially those shaped as a pedestal, are called candlesticks; if multiple candle tapers are held, the term candelabra is also used. The root form of chandelier is from the word for candle, but now often refers to an electric fixture. The word chandelier is used to describe a hanging fixture designed to hold multiple lights. Other forms of candle holders include the wall-mounted sconces, lanterns, and girandoles.
Many candle holders use a friction-tight socket to keep the candle upright. In this case, a candle that is slightly too wide will not fit in the holder, and a candle that is slightly too narrow will wobble. Candles that are too big can be trimmed to fit with a knife; candles that are too small can be fitted with aluminium foil. Traditionally, the candle and candle holders were made in the same place, so they were appropriately sized, but international trade has combined the modern candle with existing holders, which makes the ill-fitting candle more common. This friction-tight socket is only needed for the federals and the tapers. | Candle | Wikipedia | 393 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
For tea light candles, there is a variety of candle holders, including small glass holders and elaborate multi-candle stands. The same is true for votives. Wall sconces are available for tea light and votive candles. For pillar-type candles, the assortment of candle holders is broad. A fireproof plate, such as a glass plate or small mirror, can be a candle holder for a pillar-style candle. A pedestal of any kind, with the appropriate-sized fireproof top, is another option. A large glass bowl with a large flat bottom and tall mostly vertical curved sides is called a hurricane. The pillar-style candle is placed at the bottom center of the hurricane. A hurricane on a pedestal is sometimes sold as a unit.
A bobèche is a drip-catching ring, which may also be affixed to a candle holder, or used independently of one. Bobèches can range from ornate metal or glass to simple plastic, cardboard, or wax paper. Use of paper or plastic bobèches is common at events where candles are distributed to a crowd or audience, such as Christmas carolers or people at other concerts or festivals.
Candle snuffers
Candle snuffers are instruments used to extinguish burning candles by smothering the flame with a small metal cup that is suspended from a long handle, and thus depriving it of oxygen. An older meaning refers to a scissor-like tool used to trim the wick of a candle. With skill, this could be done without extinguishing the flame. The instrument now known as a candle snuffer was formerly called an "extinguisher" or "douter".
Candle followers
These are glass or metal tubes with an internal stricture partway along, which sit around the top of a lit candle. As the candle burns, the wax melts and the follower holds the melted wax in, whilst the stricture rests on the topmost solid portion of wax. Candle followers are often deliberately heavy or weighted to ensure they move down as the candle burns lower, maintaining a seal and preventing wax escape. The purpose of a candle follower is threefold:
To contain the melted wax, making the candle more efficient, avoiding mess, and producing a more even burn.
As a decoration, either due to the ornate nature of the device, or (in the case of a glass follower) through light dispersion or colouration.
If necessary, to shield the flame from wind. | Candle | Wikipedia | 507 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
Candle followers are often found in churches on altar candles.
Gallery | Candle | Wikipedia | 12 | 44017 | https://en.wikipedia.org/wiki/Candle | Technology | Energy and fuel | null |
In mathematics, a permutation of a set can mean one of two different things:
an arrangement of its members in a sequence or linear order, or
the act or process of changing the linear order of an ordered set.
An example of the first meaning is the six permutations (orderings) of the set {1, 2, 3}: written as tuples, they are (1, 2, 3), (1, 3, 2), (2, 1, 3), (2, 3, 1), (3, 1, 2), and (3, 2, 1). Anagrams of a word whose letters are all different are also permutations: the letters are already ordered in the original word, and the anagram reorders them. The study of permutations of finite sets is an important topic in combinatorics and group theory.
Permutations are used in almost every branch of mathematics and in many other fields of science. In computer science, they are used for analyzing sorting algorithms; in quantum physics, for describing states of particles; and in biology, for describing RNA sequences.
The number of permutations of distinct objects is factorial, usually written as , which means the product of all positive integers less than or equal to .
According to the second meaning, a permutation of a set is defined as a bijection from to itself. That is, it is a function from to for which every element occurs exactly once as an image value. Such a function is equivalent to the rearrangement of the elements of in which each element i is replaced by the corresponding . For example, the permutation (3, 1, 2) is described by the function defined as
.
The collection of all permutations of a set form a group called the symmetric group of the set. The group operation is the composition of functions (performing one rearrangement after the other), which results in another function (rearrangement). The properties of permutations do not depend on the nature of the elements being permuted, only on their number, so one often considers the standard set .
In elementary combinatorics, the -permutations, or partial permutations, are the ordered arrangements of distinct elements selected from a set. When is equal to the size of the set, these are the permutations in the previous sense. | Permutation | Wikipedia | 493 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
History
Permutation-like objects called hexagrams were used in China in the I Ching (Pinyin: Yi Jing) as early as 1000 BC.
In Greece, Plutarch wrote that Xenocrates of Chalcedon (396–314 BC) discovered the number of different syllables possible in the Greek language. This would have been the first attempt on record to solve a difficult problem in permutations and combinations.
Al-Khalil (717–786), an Arab mathematician and cryptographer, wrote the Book of Cryptographic Messages. It contains the first use of permutations and combinations, to list all possible Arabic words with and without vowels.
The rule to determine the number of permutations of n objects was known in Indian culture around 1150 AD. The Lilavati by the Indian mathematician Bhāskara II contains a passage that translates as follows:
The product of multiplication of the arithmetical series beginning and increasing by unity and continued to the number of places, will be the variations of number with specific figures.
In 1677, Fabian Stedman described factorials when explaining the number of permutations of bells in change ringing. Starting from two bells: "first, two must be admitted to be varied in two ways", which he illustrates by showing 1 2 and 2 1. He then explains that with three bells there are "three times two figures to be produced out of three" which again is illustrated. His explanation involves "cast away 3, and 1.2 will remain; cast away 2, and 1.3 will remain; cast away 1, and 2.3 will remain". He then moves on to four bells and repeats the casting away argument showing that there will be four different sets of three. Effectively, this is a recursive process. He continues with five bells using the "casting away" method and tabulates the resulting 120 combinations. At this point he gives up and remarks:
Now the nature of these methods is such, that the changes on one number comprehends the changes on all lesser numbers, ... insomuch that a compleat Peal of changes on one number seemeth to be formed by uniting of the compleat Peals on all lesser numbers into one entire body;
Stedman widens the consideration of permutations; he goes on to consider the number of permutations of the letters of the alphabet and of horses from a stable of 20. | Permutation | Wikipedia | 497 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
A first case in which seemingly unrelated mathematical questions were studied with the help of permutations occurred around 1770, when Joseph Louis Lagrange, in the study of polynomial equations, observed that properties of the permutations of the roots of an equation are related to the possibilities to solve it. This line of work ultimately resulted, through the work of Évariste Galois, in Galois theory, which gives a complete description of what is possible and impossible with respect to solving polynomial equations (in one unknown) by radicals. In modern mathematics, there are many similar situations in which understanding a problem requires studying certain permutations related to it.
The study of permutations as substitutions on n elements led to the notion of group as algebraic structure, through the works of Cauchy (1815 memoir).
Permutations played an important role in the cryptanalysis of the Enigma machine, a cipher device used by Nazi Germany during World War II. In particular, one important property of permutations, namely, that two permutations are conjugate exactly when they have the same cycle type, was used by cryptologist Marian Rejewski to break the German Enigma cipher in turn of years 1932-1933.
Definition
In mathematics texts it is customary to denote permutations using lowercase Greek letters. Commonly, either or are used.
A permutation can be defined as a bijection (an invertible mapping, a one-to-one and onto function) from a set to itself: The identity permutation is defined by for all elements , and can be denoted by the number , by , or by a single 1-cycle (x).
The set of all permutations of a set with n elements forms the symmetric group , where the group operation is composition of functions. Thus for two permutations and in the group , their product is defined by: Composition is usually written without a dot or other sign. In general, composition of two permutations is not commutative: | Permutation | Wikipedia | 409 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
As a bijection from a set to itself, a permutation is a function that performs a rearrangement of a set, termed an active permutation or substitution. An older viewpoint sees a permutation as an ordered arrangement or list of all the elements of S, called a passive permutation. According to this definition, all permutations in are passive. This meaning is subtly distinct from how passive (i.e. alias) is used in Active and passive transformation and elsewhere, which would consider all permutations open to passive interpretation (regardless of whether they are in one-line notation, two-line notation, etc.).
A permutation can be decomposed into one or more disjoint cycles which are the orbits of the cyclic group acting on the set S. A cycle is found by repeatedly applying the permutation to an element: , where we assume . A cycle consisting of k elements is called a k-cycle. (See below.)
A fixed point of a permutation is an element x which is taken to itself, that is , forming a 1-cycle . A permutation with no fixed points is called a derangement. A permutation exchanging two elements (a single 2-cycle) and leaving the others fixed is called a transposition.
Notations
Several notations are widely used to represent permutations conveniently. Cycle notation is a popular choice, as it is compact and shows the permutation's structure clearly. This article will use cycle notation unless otherwise specified.
Two-line notation
Cauchy's two-line notation lists the elements of S in the first row, and the image of each element below it in the second row. For example, the permutation of S = {1, 2, 3, 4, 5, 6} given by the functioncan be written as
The elements of S may appear in any order in the first row, so this permutation could also be written:
One-line notation
If there is a "natural" order for the elements of S, say , then one uses this for the first row of the two-line notation: | Permutation | Wikipedia | 446 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
Under this assumption, one may omit the first row and write the permutation in one-line notation as
,
that is, as an ordered arrangement of the elements of S. Care must be taken to distinguish one-line notation from the cycle notation described below: a common usage is to omit parentheses or other enclosing marks for one-line notation, while using parentheses for cycle notation. The one-line notation is also called the word representation.
The example above would then be: (It is typical to use commas to separate these entries only if some have two or more digits.)
This compact form is common in elementary combinatorics and computer science. It is especially useful in applications where the permutations are to be compared as larger or smaller using lexicographic order.
Cycle notation
Cycle notation describes the effect of repeatedly applying the permutation on the elements of the set S, with an orbit being called a cycle. The permutation is written as a list of cycles; since distinct cycles involve disjoint sets of elements, this is referred to as "decomposition into disjoint cycles".
To write down the permutation in cycle notation, one proceeds as follows:
Write an opening bracket followed by an arbitrary element x of :
Trace the orbit of x, writing down the values under successive applications of :
Repeat until the value returns to x, and close the parenthesis without repeating x:
Continue with an element y of S which was not yet written, and repeat the above process:
Repeat until all elements of S are written in cycles.
Also, it is common to omit 1-cycles, since these can be inferred: for any element x in S not appearing in any cycle, one implicitly assumes . | Permutation | Wikipedia | 357 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
Following the convention of omitting 1-cycles, one may interpret an individual cycle as a permutation which fixes all the elements not in the cycle (a cyclic permutation having only one cycle of length greater than 1). Then the list of disjoint cycles can be seen as the composition of these cyclic permutations. For example, the one-line permutation can be written in cycle notation as:This may be seen as the composition of cyclic permutations: While permutations in general do not commute, disjoint cycles do; for example:Also, each cycle can be rewritten from a different starting point; for example,Thus one may write the disjoint cycles of a given permutation in many different ways.
A convenient feature of cycle notation is that inverting the permutation is given by reversing the order of the elements in each cycle. For example,
Canonical cycle notation
In some combinatorial contexts it is useful to fix a certain order for the elements in the cycles and of the (disjoint) cycles themselves. Miklós Bóna calls the following ordering choices the canonical cycle notation:
in each cycle the largest element is listed first
the cycles are sorted in increasing order of their first element, not omitting 1-cycles
For example, is a permutation of in canonical cycle notation.
Richard Stanley calls this the "standard representation" of a permutation, and Martin Aigner uses "standard form". Sergey Kitaev also uses the "standard form" terminology, but reverses both choices; that is, each cycle lists its minimal element first, and the cycles are sorted in decreasing order of their minimal elements.
Composition of permutations
There are two ways to denote the composition of two permutations. In the most common notation, is the function that maps any element x to . The rightmost permutation is applied to the argument first,
because the argument is written to the right of the function.
A different rule for multiplying permutations comes from writing the argument to the left of the function, so that the leftmost permutation acts first.
In this notation, the permutation is often written as an exponent, so σ acting on x is written xσ; then the product is defined by . This article uses the first definition, where the rightmost permutation is applied first. | Permutation | Wikipedia | 499 | 44027 | https://en.wikipedia.org/wiki/Permutation | Mathematics | Discrete mathematics | null |
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