There are numerous qualitative chemical tests, for example, the acid test for gold and the Kastle-Meyer test for the presence of blood.

Cooking can also occur through chemical reactions without the presence of heat, most notably as in Ceviche, a traditional South American dish where fish is cooked with the acids in lemon or lime juice.

The study was the first nationwide analysis measuring the presence of the chemical in U. S. water systems.

In the 1880s, Wilhelm Ostwald at Leipzig University started a systematic investigation into reactions that were catalyzed by the presence of acids and bases, and found that chemical reactions occur at finite rates and that these rates can be used to determine the strengths of acids and bases.

They share many similarities with the higher plants, including the presence of asymmetrical flagellated cells, the breakdown of the nuclear envelope at mitosis, and the presence of phytochromes, flavonoids, and the chemical precursors to the cuticle.

Conversely, factors that favor plate columns are: presence of solids in feed, high liquid rates, large column diameters, complex columns, columns with wide feed composition variation, columns with a chemical reaction, absorption columns, columns limited by foundation weight tolerance, low liquid rate, large turn-down ratio and those processes subject to process surges.

* Chemical diffusion occurs in a presence of concentration ( or chemical potential ) gradient and it results in net transport of mass.

* In chemical nomenclature, the prefix " hydroxy -" shows the presence of a hydroxyl functional group (- OH )

In glasses ( solids that exist in a vitreous disordered state ), atoms may also be held together by chemical bonds without presence of any definable molecule, but also without any of the regularity of repeating units that characterises crystals.

These works postulated the presence of chemical signals and physico-chemical processes such as diffusion, activation, and deactivation in cellular and organismic growth.

There are significant differences in the survival of archaeological material depending on whether a site is wet or dry, on the nature of the chemical environment, on the presence of biological organisms and on the dynamic forces present.

Little is known about the element but limited chemical experiments have shown that it forms a stable divalent ion in solution as well as the predicted trivalent ion that is associated with its presence as one of the actinides.

The presence of such a gap suggested communication via chemical messengers traversing the synaptic cleft, and in 1921 German pharmacologist Otto Loewi ( 1873 – 1961 ) confirmed that neurons can communicate by releasing chemicals.

It is not affected by external factors such as temperature, pressure, chemical environment, or presence of a magnetic or electric field.

The presence of a certain chemical element in such an absorption spectrum primarily indicates that the temperature conditions are suitable for a certain excitation of this element.

The presence of such a TE provides a straightforward means of identifying the mutant allele, relative to chemical mutagenesis methods.

No firm evidence of the presence of water, organic matter or other chemical compounds on their surfaces has been obtained.

These secondary peaks, not to be confused with high energy satellites which are discussed later, arise from the presence of the same element in multiple different chemical states on a surface ( i. e. Adsorbate layers ) or from relaxation transitions involving valence band electrons of the substrate.

The presence of satellites can distort the true Auger peak and / or small peak shift information due to chemical bonding at the surface.

As a gas is heated, electrons begin to leave the atoms, resulting in the presence of free electrons, which are not bound to nuclei, and ions, which are chemical species that contain unequal number of electrons and protons, and therefore possess an electrical charge.

A number of factors can influence its efficacy, including chemical composition of the stone, presence of anomalous renal anatomy and the specific location of the stone within the kidney, presence of hydronephrosis, body mass index, and distance of the stone from the surface of the skin.

This is triggered by the presence of a chemical produced by the females, bonellin.

In the presence of a temperature gradient this results in a nonuniform magnetic body force, which leads to fluid movement.

In the presence of a gravitational gradient, the calibration and data reduction process is numerically unstable.

Symptoms are not closely related to the presence or severity of an outflow tract gradient.

Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature-hydrothermal gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks.

An illusory contour is a perceived contour without the presence of a physical gradient.

* Thermoelectric generators ( TEGs ) consist of the junction of two dissimilar materials and the presence of a thermal gradient.

Determining the optimal parameters in a model of this type is not trivial, and local numerical optimization methods such as gradient descent can be sensitive to initialization because of the presence of local minima of the training criterion.

Since a liquid with a high surface tension pulls more strongly on the surrounding liquid than one with a low surface tension, the presence of a gradient in surface tension will naturally cause the liquid to flow away from regions of low surface tension.

In the presence of a Riemannian metric or a symplectic form, to every smooth function is associated a vector field ( the gradient or Hamiltonian vector field ).

The presence of a food supply gradient adds bias to the random walk and hence the phrase biased random walk.

For example, in the presence of H < sub > 2 </ sub > O < sub > 2 </ sub > formed by the eosinophil, and either chloride or bromide ions, eosinophil peroxidase provides a potent mechanism by which eosinophils kill multicellular parasites ( such as, for example, the nematode worms involved in filariasis ); and also certain bacteria ( such as tuberculosis bacteria ).

Commonly, this term is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions.

An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, is not considered a disease ; by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease.

Interferons ( IFNs ) are proteins made and released by host cells in response to the presence of pathogens such as viruses, bacteria, parasites or tumor cells.

For example, a food sample might be analyzed on three different nutrient mediums designed to indicate the presence of " total " bacteria ( conditions where many, but not all, bacteria grow ), molds ( conditions where the growth of bacteria is prevented by, e. g., antibiotics ) and coliform bacteria ( these indicate a sewage contamination ).

Many bacteria cease production of the enzyme in the presence of oxygen.

The protein content of peroxisomes varies across species, but the presence of proteins common to many species has been used to suggest an endosymbiotic origin ; that is, peroxisomes evolved from bacteria that invaded larger cells as parasites, and very gradually evolved a symbiotic relationship.

In January 2006, researchers from the University of Athens analyzed teeth recovered from a mass grave underneath the city, and confirmed the presence of bacteria responsible for typhoid.

The presence of 20S proteasomes in bacteria may result from lateral gene transfer, while the diversification of subunits among eukaryotes is ascribed to multiple gene duplication events.

Thus, presence of high levels of peptidoglycan is the primary determinant of the characterisation of bacteria as gram-positive.

In 1880, the presence of Rhizobium bacteria in the roots of legumes and their use of catalysts explained the increase of nitrogen in soils so cultivated.

In some arthropods, sex is determined by infection, as when bacteria of the genus Wolbachia alter their sexuality ; some species consist entirely of ZZ individuals, with sex determined by the presence of Wolbachia.

The ability to transform daidzein into S-equol is based on the presence of certain intestinal bacteria.

The presence of melanin in the archaea and bacteria kingdoms is an issue of ongoing debate among researchers in the field.

The medical industry also uses the blood of horseshoe crabs as a test for the presence of contaminant bacteria.

The presence of bacteria in the colon produces an ‘ organ ’ of intense, mainly reductive, metabolic activity, whereas the liver is oxidative.

Tooth decay is caused by certain types of acid-producing bacteria which cause the most damage in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose.

In the presence of oxygen ( aerobic ), some bacteria may directly oxidize iron to iron oxides and hydroxides, other bacteria oxidize sulfur and produce sulfuric acid causing biogenic sulfide corrosion.

According to Gold and the Soviet geologists who originated the abiogenic theory, bacteria feeding on the oil accounts for the presence of biological debris in hydrocarbon fuels, obviating the need to resort to a biogenic theory for the origin of the latter.