At small strains elastin confers stiffness to the tissue and stores most of the strain energy. The collagen fibers are comparatively inextensible and are usually loose (wavy,crimped). With increasing tissue deformation the collagen is gradually stretched in the direction of deformation. When taut, these fibers produce a strong growth in tissue stiffness. The composite behavior is analogous to a nylon stocking, whose rubber band does the role of elastin as the nylon does the role of collagen. In soft tissues the collagen limits the deformation and protects the tissues from injury.

Soft tissues have the potential to undergo big defformations and still come back to the initial configuration when unloaded. The stress-strain curve is nonlinear, as can be seen in Figure 1. The soft tissues are also viscoelastic, incompressible and usually anisotropic. Some viscoelastic properties observable in soft tissues are: relaxation, creep and hysteresis .

Pseudoelasticity

Even though soft tissues have viscoelastic properties, i.e. stress as function of strain rate, it can be approximated by a hyperelastic model after precondition to a load pattern. After some cycles of loading and unloading the material, the mechanical response becomes independent of strain rate.

:mathbf{S}=mathbf{S}(mathbf{E},dot{mathb) quadrightarrowquad mathbf{S}=mathbf{S}(mathbf{E})

Despite the independence of strain rate, preconditioned soft tissues still present hysteresis, so the mechanical response can be modeled as hyperelastic with different material constants at loading and unloading (see Figure 1). By this method the elasticity theory is used to model an inelastic material. Fung has called this model as pseudoelastic to point out that the material is not truly elastic .

Residual stress

In physiological state soft tissues usually present residual stress that is released may be released when the tissue is excised. Physiologists and histologists must be aware of this fact to avoid mistakes when analyzing excised tissues. This retraction usually causes a visual artifact .

Fung-elastic material

Fung developed a constitutive equation for preconditioned soft tissues which is

:W = frac{1}{2}left[q + cleft( e^Q -1 right) right]

with

:q=a_{ijkl}E_{ij}E_{kl} qquad Q=b_{ijkl}E_{ij}E_{kl}

quadratic forms of Green-Lagrange strains E_{ij} and a_{ijkl}, b_{ijkl} and c material constants . w is the strain energy function per volume unit, which is the mechanical strain energy for a given temperature.

Adapted from the Wikipedia article Soft tissue, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

No related posts.

Most current research on SPPS has examined is application to create thermal barrier coatings (TBCs). These complex ceramic/metallic material systems are used to protect components in hot sections of gas turbine and diesel engines. The SPPS process lends itself particularly well to the creation of these TBCs. Studies report the generation of coatings demonstrating superior durability and mechanical properties. Superior durability is imparted by the creation of controlled through thickness vertical cracks. These cracks only slightly increase coating conductivity while allowing for strain relief of stress generated by the CTE mismatch between the coating and the substrate during cyclic heating. The generation of these through thickness cracks was systematically explored and found to be caused by the depositing a controlled portion of unpryolized material in the coating.. Superior mechanical properties such as bond strength and in-plane toughness result from the nanometer sized microstructure that are created by the SPPS process.

Other studies have shown that engineered coatings can reduce thermal conductivity to some of the lowest reported values for TBCs.. These low thermal conductivities were achieved through the generation of an alternating high-porosity, low-porosity microstructure or the synthesis of a low conductivity precursor composition with rare earth dopants.

Adapted from the Wikipedia article Solution precursor plasma spray, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

No related posts.

Probability and statistics

See also glossary of probability and statistics

*Probability theory (MSC 60) : The mathematical theory of random phenomena. Probability theory studies random variables and events, which are mathematical abstractions of non-deterministic events or measured quantities. See also :Category:probability theory, and the list of probability topics.

**Stochastic processes (MSC 60G/H) : An extension of probability theory that studies collections of random variables, such as time series or spatial processes. See also List of stochastic processes topics, and :Category:Stochastic processes.

*Statistics (MSC 62): The science of making effective use of numerical data from experiments or from populations of individuals. Statistics includes not only the collection, analysis and interpretation of such data, but also the planning of the collection of data, in terms of the design of surveys and experiments. See also the list of statistical topics and :Category:Statistics.

Computational sciences

;Numerical analysis, (MSC 65): Many problems in mathematics cannot in general be solved exactly. Numerical analysis studies study of iterative methods and algorithms for approximately solving problems to a specified error bound. Includes numerical differentiation, numerical integration and numerical methods; c.f. scientific computing. See also List of numerical analysis topics

*68: Computer science

Physical sciences

;Mechanics: Addresses what happens when a real physical object is subjected to forces. This divides naturally into the study of rigid solids, deformable solids, and fluids, detailed below.

;Particle mechanics (MSC 70): In mathematics, a particle is a point-like, perfectly rigid, solid object. Particle mechanics deals with the results of subjecting particles to forces. It includes celestial mechanics — the study of the motion of celestial objects.

;Mechanics of deformable solids (MSC 74) : Most real-world objects are not point-like nor perfectly rigid. More importantly, objects change shape when subjected to forces. This subject has a very strong overlap with continuum mechanics, which is concerned with continuous matter. It deals with such notions as stress, strain and elasticity. See also continuum mechanics.

;Fluid mechanics (MSC 76): Fluids in this sense includes not just liquids, but flowing gases, and even solids under certain situations. (For example, dry sand can behave like a fluid). It includes such notions as viscosity, turbulent flow and laminar flow (its opposite). See also fluid dynamics.

*78: Optics, electromagnetic theory

*80: Classical thermodynamics, heat transfer

*81: Quantum theory, including quantum optics

*82: Statistical mechanics, structure of matter

*83: Relativity and gravitational theory, including relativistic mechanics

*85: Astronomy and astrophysics

*86: Geophysics

Other mathematical sciences

*90: Operations research, mathematical programming

**Operations research (OR), also known as operational research, provides optimal or near-optimal solutions to complex problems. OR uses mathematical modeling, statistical analysis, and mathematical optimization.

**Mathematical programming (or optimization) minimizes (or maximizes) a real-valued function over a domain that is often specified by constraints on the variables. Mathematical programming studies these problems and develops iterative methods and algorithms for their solution.

*91: Game theory and mathematical social sciences (economics, sociology and psychology).

*92: Biology (see also mathematical biology) and other natural sciences

*93: Systems theory; control, including optimal control

*94: Information and communication, circuits

*97: Mathematics education

Category:Mathematics

Category:Subdivisions of mathematics

bn:গণিতের ক্ষেত্রসমূহ

de:Teilgebiete der Mathematik

es:Áreas de las matemáticas

is:Greinar stærðfræðinnar

ta:கணிதப் பிரிவுகளின் உறவுகள்

th:สาขาของคณิตศาสตร์
Adapted from the Wikipedia article Areas of mathematics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

No related posts.

The most common causes of myalgia are overuse, injury or stress. However, myalgia can also be caused by diseases, disorders, medications, as a response to vaccination It is also a sign of acute rejection after heart transplant surgery.

The most common causes are:

* Injury or trauma including sprains and strains

* Overuse: using a muscle too much, too soon, too often

* Tension or stress

Muscle pain may also be due to:

* Certain drugs, including:

** ACE inhibitors for lowering blood pressure

** Cocaine

** Statins for lowering cholesterol

* Dermatomyositis

* Electrolyte imbalances like too little potassium or calcium

* Fibromyalgia

* Infections, including:

** Influenza (the flu)

** Lyme disease

** Malaria

** Dengue Fever

** Muscle abscess

** Polio

** Rocky Mountain spotted fever

** Trichinosis (roundworm)

* Lupus

* Polymyalgia rheumatica

* Polymyositis

* Rhabdomyolysis

Overuse

Overuse of a muscle is using it too much, too soon and/or too often. Examples are:

*Repetitive strain injury.

Injury

The most common causes of myalgia by injury are: sprains and strain.

Autoimmune

Multiple sclerosis, Myalgic Encephalomyelitis, Myositis, Lupus erythematosus, Familial Mediterranean fever, Polyarteritis nodosa, Devic’s disease, Morphea

Metabolic defect

Carnitine palmitoyltransferase II deficiency, Conn’s syndrome, Adrenal insufficiency, Hyperthyroidism

Other

Chronic fatigue syndrome, Ehlers Danlos Syndrome, Hypokalemia, Exercise intolerance, Mastocytosis, Peripheral neuropathy, Eosinophilia myalgia syndrome, Fibromyalgia, Barcoo Fever, Herpes, Delayed onset muscle soreness, AIDS, HIV, Tumor-induced osteomalacia, Post Orgasmic Illness Syndrome

Medications

Acrylamide, colesevelam, darbepoetin, darunavir, ezetimibe, ibandronate sodium, imiquimod, interferons, isotretinoin, procainamide, quinupristin/dalfopristin, statins, sumatriptan, tasigna, tiotropium, vardenafil, zolmitriptan, zocor.

Withdrawal syndromes

Sudden cessation of opioids, barbiturates, benzodiazepines, or alcohol can induce myalgia.

Adapted from the Wikipedia article Myalgia, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

No related posts.

The term ”stress” had none of its contemporary connotations before the 1950s. It is a form of the Middle English ”destresse”, derived via Old French from the Latin ”stringere”, to draw tight.

It had long been in use in physics to refer to the internal distribution of a force exerted on a material body, resulting in strain. In the 1920s and 1930s, the term was occasionally being used in psychological circles to refer to a mental strain or unwelcome happening, and by advocates of holistic medicine to refer to a harmful environmental agent that could cause illness. Walter Cannon used it in 1934 to refer to external factors that disrupted what he called homeostasis.

The novel usage arose out of Seyle’s 1930s experiments. He started to use the term to refer not just to the agent but to the state of the organism as it responded and adapted to the environment. His theories of a universal non-specific stress response attracted great interest and contention in academic physiology and he undertook extensive research programmes and publication efforts.

However, while the work attracted continued support from advocates of psychosomatic medicine, many in experimental physiology concluded that his concepts were too vague and unmeasurable. During the 1950s Selye turned away from the laboratory to promote his concept through popular books and lecture tours. He wrote for both non-academic physicians and, in an international bestseller titled “Stress of Life”, for the general public.

A broad biopsychosocial concept of stress and adaptation offered the promise of helping everyone achieve health and happiness by successfully responding to changing global challenges and the problems of modern civilization. He coined the term “eustress” for positive stress, by contrast to distress.

He argued that all people have a natural urge and need to work for their own benefit, a message that found favor with industrialists and governments. He also coined the term “stressor” to refer to the causative event or stimulus, as opposed to the resulting state of stress.

From the late 1960s academic psychologists started to adopt Selye’s concept; they sought to quantify “life stress” by scoring “significant life events”, and a large amount of research was undertaken to examine links between stress and disease of all kinds. By the late 1970s stress had become the medical area of greatest concern to the general population, and more basic research was called for to better address the issue.

There was renewed laboratory research into the neuroendocrine, molecular and immunological bases of stress, conceived as a useful heuristic not necessarily tied to Selye’s original hypotheses. By the 1990s, “stress” had become an integral part of modern scientific understanding in all areas of physiology and human functioning, and one of the great metaphors of Western life. Focus grew on stress in certain settings, such as workplace stress. Stress management techniques were developed.

Its psychological uses are frequently metaphorical rather than literal, used as a catch-all for perceived difficulties in life. It also became a euphemism, a way of referring to problems and eliciting sympathy without being explicitly confessional, just “stressed out”.

It covers a huge range of phenomena from mild irritation to the kind of severe problems that might result in a real breakdown of health. In popular usage almost any event or situation between these extremes could be described as stressful.

The most extreme events and reactions may elicit the diagnosis of Posttraumatic stress disorder (PTSD), an anxiety disorder that can develop after exposure to one or more terrifying events that threatened or caused grave physical harm. PTSD is a severe and ongoing emotional reaction to an extreme psychological trauma; as such, it is often associated with soldiers, police officers, and other emergency personnel.

This stressor may involve viewing someone’s actual death, a threat to the patient’s or someone else’s life, serious physical injury, or threat to physical or psychological integrity, overwhelming usual psychological defenses coping. In some cases it can also be from profound psychological and emotional trauma, apart from any actual physical harm. Often, however, the two are combined.

The US military became a key center of stress research, attempting to understand and reduce combat neurosis and psychiatric casualties.

Adapted from the Wikipedia article Stress (biology), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

No related posts.