Persius/hicric huggingface dataset:
Sit-up (exercise)
The sit-up is a strength training exercise commonly performed with the aim of strengthening the  abdominal muscles  and hip flexors. This begins with lying with the back on the floor, typically with the knees bent in an attempt to reduce stress on the back muscles and spine, and then elevating both the upper and lower spine from the floor until everything superior to the buttocks is not touching the ground. SomeTemplate:Who? now consider it dangerous and relatively ineffective, replacing it with the crunch in many training programs as an abdominal exercise.

# Criticism
Although still common in military training, martial arts, and mass taught exercise classes, the conventional sit-up is sometimes considered dangerous by modern experts, and has largely been replaced by the crunch, for the following reasons:

## Risks to vertebral column
Full sit-ups involve the hip flexors, as well as abdominal muscles. This can cause the back to arch, with the risk of spinal damage. This is a particular risk for individuals with weak abdominal muscles, but also for individuals who train aggressively, exhausting their abdominal muscles in a training session. Even if these risks are avoided, the leverage exerted by the hip flexors risks compression of the lumbar intervertebral discs. Most branches of the US armed forces have ceased using sit-ups in training because of the problems resulting from these factors, which can include direct back damage and referred pain or numbness due to pinching of the spinal cord.
According to the National Institute of Occupational Safety and Health,
a straight leg sit-up generates approximately 3500 newtons (790 lbf) of force on the spine, and a bent-knee sit-up 3350 newtons (750 lbf), both levels above the 3300 newtons (740 lbf) that correlates highly with lower back injury. 

## Hip flexor involvement
Modern research suggests that the abdominal muscles are responsible for only the first 30 of lift in a sit upeffectively the part of the motion where the shoulders only leave the ground. The hip flexors are responsible thereafter. This diversion of effort from the abdominals reduces the effectiveness of training for purposes of abdominal isolation and makes the sit-up a test of combined spinal and hip flexion rather than spinal flexion alone.

# Abdominal muscular hypertrophy
Strength exercises such as sit-ups and push-ups do not cause the spot reduction of fat. Gaining a 'six pack' requires both abdominal hypertrophy training and fat loss over the abdomenwhich can only be done by losing fat from the body as a whole.
Snowball sampling
In social science research, snowball sampling is a technique for developing a research sample where existing study subjects recruit future subjects from among their acquaintances. Thus the sample group appears to grow like a rolling snowball. As the sample builds up you gain enough data to use for your data. This sampling technique is often used in hidden populations which are difficult for researchers to access; example populations would be drug users or commercial prostitutes.
Because sample members are not selected from a sampling frame, snowball samples are subject to numerous biases.  For example, people who have many friends are more likely to be recruited into the sample.
It was widely believed that it was impossible to make unbiased estimates from snowball samples, but a variation of snowball sampling called respondent-driven sampling has been shown to allow researchers to make asymptotically unbiased estimates from snowball samples under certain conditions.  Respondent-driven sampling also allows researchers to make estimates about the social network connecting the hidden population.
Sodium dichromate
Sodium dichromate is the chemical compound with the formula Na2Cr2O7.  Usually, however, the salt is handled as its dihydrate Na2Cr2O72H2O. Its chemistry, appearance, and behaviour are very similar to those of the more widely encountered potassium dichromate.  This chemical is around twenty times more soluble in water than the potassium salt (49 g/L at 0 C) and its equivalent weight is also lower, which is often desirable.

# Applications in organic chemistry
This compound oxidizes benzylic and allylic C-H bonds to carbonyl derivatives. For example, 2,4,6-trinitrotoluene is oxidized to the corresponding carboxylic acid..  Similarly,  2,3-dimethylnaphthalene is oxidized by Na2Cr2O7 to 2,3-naphthalenedicarboxylic acid (m.p. 239241 C).

# Safety
Like all hexavalent chromium compounds, sodium dichromate is considered hazardous. It is also a known carcinogen.
Sodium dithionate
For the sterilizing agent, see sodium metabisulfite.  For the reducing agent, see sodium dithionite.
Sodium dithionate Na2S2O6 is an important compound for inorganic chemistry. It is also known under names disodium dithionate, sodium hyposulfate, and sodium metabisulfate.
Can be produced by following reactions:
2 NaHSO3 + MnO2  Na2S2O6 + Mn(OH)2
3 Cl2 + Na2S2O35H2O + 6 NaOH  Na2S2O6 + 6 NaCl + 8 H2O
The dithionate ion represents sulfur that is oxidized relative to elemental sulfur, but not totally oxidized. Sulfur can be reduced to sulfide or totally oxidized to sulfate, with numerous intermediate oxidation states in inorganic moieties, as well as organosulfur compounds. Example inorganic ions include sulfite and thiosulfate.
Sodium dithionate is a very stable compound which is not oxidized by permanganate, dichromate or bromine. It can be oxidized to sulfate under strongly oxidizing conditions: these include boiling for one hour with 5 M sulfuric acid with an excess of potassium dichromate, or treating with an excess of hydrogen peroxide then boiling with concentrated hydrochloric acid. The Gibbs free energy change for the oxidation is about 300 kJ/mol.
It should not be confused with sodium dithionITE, Na2S2O4, which is a very different compound, and is a powerful reducing agent with many uses in chemistry and biochemistry. Confusion between dithionate and dithionite is commonly encountered, even in manufacturers' catalogues!
Sodium metabisulfate is also encountered occasionally as a food preservative, especially in combination with sulfur dioxide in sweet, moist foods such as those containing coconut-flavored interiors.
Sodium dithionite
Sodium dithionite (aka sodium hydrosulfite or sodium hydrosulphite) is a white crystalline powder with a weak sulfurous odor. Although it is stable under most conditions, it will decompose in hot water and in acid solutions.  It can be obtained by the following reaction:

# Applications

## Industry
This compound is a water-soluble salt, and can be used as a reducing agent in aqueous solutions. It is used as such in some industrial dying processes, where an otherwise water-insoluble dye can be reduced into a water-soluble alkali metal salt. The reduction properties of sodium dithionite also eliminate excess dye, residual oxide, and unintended pigments, thereby improving overall colour quality. It can also be used as a bleach, in, for instance, paper pulp, cotton, wool, and kaolin clay.
This chemical can also be used for water treatment, gas purification, cleaning, and stripping. It can also be used in industrial processes as a sulfonating agent or a sodium ion source. In addition to the textile industry, this compound is used in industries concerned with leather, foods, polymers, photography, and many others. Its wide use is attributable to its low toxicity LD 50 at 5 gm/kg, and hence its wide range of applications.

## Biological sciences
Sodium dithionite is often used in physiology experiments as a means of lowering solutions' redox potential (Eo' ~ 420 mV at pH 7).  Potassium ferricyanide is usually used as an oxidizing chemical in such experiments (Eo' ~ 436 mV at pH 7). In addition, sodium dithionite is often used in soil chemistry experiments to determine the amount of iron that is not incorporated in primary silicate minerals. Hence, iron extracted by sodium dithionite is also referred to as "free iron."  The strong affinity of the dithionite ion for bi- and trivalent metal cations (M2+, M3+) allows it to enhance the solubility of iron, and therefore dithionite is a useful chelating agent. When you heat the reaction, rainbow colors emerge due to the high transition states of energy.
Sodium propionate

# Overview
Sodium propanoate or sodium propionate is the sodium salt of propionic acid which has the chemical formula Na(C2H5COO). This white crystalline solid is deliquescent in moist air.

# Reactions
It is produced by the reaction of propionic acid and sodium carbonate or sodium hydroxide.

# Uses
It is used as a food preservative and is represented by the food labeling E number E281 in Europe; it is used primarily as a mold inhibitor in bakery products. It is approved for use as a food additive in the EU, USA and Australia and New Zealand (where it is listed by its INS number 281).

# See Also
- Propionic acid, E 280
- Calcium propionate, E 282
- Potassium propionate, E 283
Sodium superoxide
Sodium superoxide is a yellow solid with the chemical formula NaO2.
NaO2 is formed when sodium is burned in oxygen at elevated temperature and pressure.
NaO2 is hydrolyzed by water to form sodium hydroxide plus oxygen.
Sommelet reaction
The Sommelet reaction is an organic reaction in which a benzyl halide is converted to an aldehyde by action of hexamine and water .
A conceptually related reaction is the Duff reaction (halide replaced by an arene).
In the Krohnke aldehyde synthesis  the oxidizing reagent is is a combination of pyridine and p-nitrosodimethylaniline.
Sound power level
Sound power level or acoustic power level is a logarithmic measure of the sound power in comparison to a specified reference level.
The measure of a ratio of two sound powers is  
L_\mathrm{W}=10\, \log_{10}\left(\frac{W_1}{W_0}\right)\ \mathrm{dB}
where W1 and W0 are the powers.
The sound power level is given the symbol Lw or SWL and is measured in "dBW", which stands for decibel with the suffix for watts.  Decibels are dimensionless.
SPL stands for sound pressure level, and is not the same thing. If an amount of sound power at a particular frequency produces a particular sound pressure level x, the same amount of power at half the frequency will produce twice the pressure level.
If W0 is the standard reference sound power, where
W_0=10^{-12}\ \mathrm{W}
(W = watt), then instead of "dB", dB SWL is used. (SWL = sound power level).

# Table: Sound power level and sound power of some sound sources
The Trumpet and excavator both have the same sound power of 0.3 watts, but may be judged psychoacoustically to be different levels. As noise is unwanted sound the trumpet can be perceived to be acceptable when listened to as music but at the same sound power level may be perceived to be noisy if one is trying to sleep.
One of the advantages of expressing the noise level of a source in terms of its power level is that one does not have to note any distance from the source.

## SWL in audio equipment
Most audio manufacturers use SWL to describe the efficiency of their speakers.  The most common means is measuring the sound power level from the speaker with the measuring device placed directly in front of and one meter away from the source.  Then a particular sound (usually white noise or pink noise) is played through the source at a particular intensity so that the source is consuming one watt of power. The SWL is then measured and the product labeled, something like "SWL: 93 dB 1 W/1 m". This measurement can also be represented as a strict efficiency ratio of audio output (sound power) to electrical input (electrical power), but this is far less common. This method of rating speakers using SWL is often deceiving because most speakers produce very different SWLs at different frequencies of sound, often varying as much as 10 dB throughout the speaker's usable frequency range (it generally varies less in higher quality speakers). The SWL quoted by the manufacturer is often an average over a particular range.
de:Schallleistungspegel
Spectrin, alpha 1
Spectrin alpha chain, erythrocyte is a protein that in humans is encoded by the SPTA1 gene.
Spectrin is an actin crosslinking and molecular scaffold protein that links the plasma membrane to the actin cytoskeleton, and functions in the determination of cell shape, arrangement of transmembrane proteins, and organization of organelles. It is a tetramer made up of alpha-beta dimers linked in a head-to-head arrangement. This gene is one member of a family of alpha-spectrin genes. The encoded protein is primarily composed of 22 spectrin repeats which are involved in dimer formation. It forms weaker tetramer interactions than non-erythrocytic alpha spectrin, which may increase the plasma membrane elasticity and deformability of red blood cells. Mutations in this gene result in a variety of hereditary red blood cell disorders, including elliptocytosis type 2, pyropoikilocytosis, and spherocytic hemolytic anemia.

# Interactions
Spectrin, alpha 1 has been shown to interact with Abl gene.
Spinotectal tract

# Overview
The spinotectal tract (spinotectal fasciculus) is supposed to arise in the dorsal column and terminate in the inferior and superior colliculi.
It is situated ventral to the lateral spinothalamic fasciculus, but its fibers are more or less intermingled with it.
It is also known as the spino-quadrigeminal system of Mott.
In the brain-stem the fibers run lateral from the inferior olive, ventro-lateral from the superior olive, then ventro-medial from the spinal tract of the trigeminal; the fibers come to lie in the medial portion of the lateral lemniscus.
Stasis dermatitis
Synonyms and keywords: Congestion eczema, gravitational dermatitis, gravitational eczema, stasis eczema, varicose eczema.

# Overview
Stasis dermatitis (also known as "Congestion eczema," "Gravitational dermatitis," "Gravitational eczema," "Stasis eczema," and "Varicose eczema") refers to the skin changes that occur in the leg as a result of "stasis" or blood pooling from insufficient venous return; the alternative name of varicose eczema comes from a common cause of this being varicose veins.
Insufficient venous return results in increased pressure in the capillaries with the result that both fluid and cells may "leak" out of the capillaries. This results in red cells breaking down, with iron containing hemosiderin possibly contributing to the pathology of this entity.

# Symptoms
- The skin appears thin, brown and tissue-like, with possible skin lesions (macule or patches), red spots, superficial skin irritation and/or darkening and/or thickening of the skin at the ankles or legs
- The skin may be weakened and may ulcerate in areas
- Legs, ankles, or other areas may become swollen
- Open sores, ulcers
- Itching and/or leg pains
- Sometimes pain may persist from swollen tissues and may feel like "stabbing" or "needle pricks"
The cracks and poor skin-condition of this disorder predisposes for the entry of bacterial infection causing spreading cellulitis infection in the leg. If the skin condition deteriorates further and breaks down, a venous ulcer (also known as a stasis ulcer) may form.

## Gallery

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# Treatment
Treatment may consist of topical applications of steroid based creams and the use of compression stockings to help force the underlying buildup of fluids back out of the lower leg or intermittent pneumatic compression pumps.
Stauffer syndrome

# Overview
Stauffer syndrome is a constellation of signs and symptoms of liver dysfunction that arise due to presence of renal cell carcinoma, and, more rarely, in connection with other malignant neoplasms. It is named for Dr. Maurice Stauffer, a gastroenterologist at the Mayo Clinic in Rochester, MN. The hepatic abnormalities are not due to tumor infiltration of the liver or intrinsic liver disease; they instead reflect the presence of a paraneoplastic syndrome.
Stauffer syndrome causes abnormal liver function tests, especially those that reflect the presence of cholestasis, i.e. abnormal bile flow.  The symptoms and signs resolve if the renal cell carcinoma (or another associated tumor) is successfully ablated.

# Eponym
Maurice H. Stauffer, M.D., a gastroenterologist at the Mayo Clinic in Rochester, MN, first characterized this syndrome in 1961, with the original name of "nephrogenic hepatomegaly."
Stellate ganglion
The stellate ganglion (or cervicothoracic ganglion) is a ganglion formed by the fusion of inferior cervical ganglion and the first paravertebral ganglion.
The clinical significance of these ganglion is that they may be cut in order to decrease the symptoms exhibited by Raynaud's phenomenon and hyperhydrosis (extreme sweating) of the hands.
Injection of local anesthetics near the stellate ganglion can sometimes mitigate the symptoms of sympathetically mediated pain such as complex regional pain syndrome type I (reflex sympathetic dystrophy).  Complications associated with a stellate ganglion block include Horner's syndrome, intra-arterial or intravenous injection, difficulty swallowing, vocal cord paralysis, epidural spread of local anaesthetic and pneumothorax.
Blunt needling of the stellate ganglion with acupuncture needle is used in Traditional Chinese Medicine to decrease sympathetically mediated symptoms as well.

# Location
Stellate ganglion is located at the level of C7 (7th cervical vertebrae), anterior to the transverse process of C7, posterior to the neck of the first rib, and just below the subclavian artery.
Stendhal syndrome

# Overview
Stendhal Syndrome or Stendhal's Syndrome is a psychosomatic illness that causes rapid heartbeat, dizziness, confusion and even  hallucinations when an individual is exposed to art, usually when the art is particularly 'beautiful' or a large amount of art is in a single place. The term can also be used to describe a similar reaction to a surfeit of choice in other circumstances, e.g. when confronted with immense beauty in the natural world.
It is named after the famous 19th century French author Stendhal (pseudonym of Henri-Marie Beyle), who described his experience with the phenomenon during his 1817 visit to Florence, Italy in his book Naples and Florence: A Journey from Milan to Reggio.
Although there are many descriptions of people becoming dizzy and fainting while taking in Florentine art, especially at the Uffizi, dating from the early 19th century on, the syndrome was only named in 1979, when it was described by Italian psychiatrist Graziella Magherini, who observed and described more than 100 similar cases among tourists and visitors in Florence.  The syndrome was first diagnosed in 1982.
The term is often used when describing the reactions of audiences to music of the Romantic period.

# Pop culture instances
An extreme, fictionalized variation of Stendhal syndrome figures in the plot of the 2003 novel Diary by American author Chuck Palahniuk. The syndrome was also mentioned in the episode "Longing" from season one of the Showtime series The L Word, character Bette Porter, played by Jennifer Beals, experiences Stendhal Syndrome when she witnesses the photograph, "The Last Time I and You" by fictional photographer Carla Marie Freed.
The Stendhal Syndrome is a 1996 Italian thriller, written and directed by Dario Argento and starring his daughter Asia Argento. Detective Anna Manni (Asia Argento) travels to Rome on the trail of a serial rapist / killer (Thomas Kretschmann), ending up as his victim due to her sensibility to art and being struck by the Stendhal Syndrome.
Stendhal Syndrome is an album by Rusty Eye. This title is an homage to film director Dario Argento and to the illness itself; a result to multiple variations in sound, style and speed that cause a bizarre confusion of the senses i.e. the Stendhal syndrome.
Steroid sulfatase
Steroid sulfatase (STS), or steryl-sulfatase (EC 3.1.6.2), formerly known as arylsulfatase C, is a sulfatase enzyme involved in the metabolism of steroids. It is encoded by the STS gene.

# Reactions
This enzyme catalyses the following chemical reaction
Also acts on some related steryl sulfates.

# Function
The protein encoded by this gene catalyzes the conversion of sulfated steroid precursors to the free steroid. This includes DHEA sulfate, estrone sulfate, pregnenolone sulfate, and cholesterol sulfate, all to their unconjugated forms (DHEA, estrone, pregnenolone, and cholesterol, respectively). The encoded protein is found in the endoplasmic reticulum, where it is present as a homodimer.

# Clinical significance
A congenital deficiency in the enzyme is associated with X-linked ichthyosis, a scaly-skin disease affecting roughly 1 in every 2,000 to 6,000 males. The excessive skin scaling or hyperkeratosis is caused by a lack of breakdown and thus accumulation of cholesterol sulfate, a steroid that stabilizes cell membranes and adds cohesion, in the outer layers of the skin.
Steroid sulfates like DHEA sulfate and estrone sulfate serve as large biologically inert reservoirs for conversion into androgens and estrogens, respectively, and hence are of significance for androgen- and estrogen-dependent conditions like prostate cancer, breast cancer, endometriosis, and others.

# Inhibitors
Inhibitors of STS include irosustat, estrone sulfamate (EMATE), estradiol sulfamate (E2MATE), and danazol.

# Names
Steryl-sulfatase is also known as arylsulfatase, steroid sulfatase, sterol sulfatase, dehydroepiandrosterone sulfate sulfatase, arylsulfatase C, steroid 3-sulfatase, steroid sulfate sulfohydrolase, dehydroepiandrosterone sulfatase, pregnenolone sulfatase, phenolic steroid sulfatase, 3-beta-hydroxysteroid sulfate sulfatase, as well as by its systematic name steryl-sulfate sulfohydrolase.
Striae of Retzius

# Overview
The Striae of Retzius are incremental growth lines seen in enamel and are results of enamel's development.  When viewed microscopically in cross-section, they appear as concentric rings.  In a longitudinal section, they appear as a series of dark bands.  The presence of the dark lines is similar to the annual rings on a tree.
Darker lines in the striae of Retzius result from systemic disturbances in the human body.  For example, a fever can cause some lines to appear darker than those surrounding it. The neonatal line is the darkest band which represents the disrupted enamel formation after the stress of being born.
The formation of the striae of Retzius result from a constriction of Tomes' processes in conjunction with an increasing process of interrod enamel development.
Sublingual artery

# Course
The Sublingual Artery arises at the anterior margin of the Hyoglossus, and runs forward between the Genioglossus and Mylohyoideus to the sublingual gland.
It supplies the gland and gives branches to the Mylohyoideus and neighboring muscles, and to the mucous membrane of the mouth and gums.
One branch runs behind the alveolar process of the mandible in the substance of the gum to anastomose with a similar artery from the other side; another pierces the Mylohyoideus and anastomoses with the submental branch of the external maxillary artery.