Several competing models, although correctly dealing with the conformation of each individual peptide chain, gave way to the triple-helical " Madras " model, which provided an essentially correct model of the molecule's quaternary structure although this model still required some refinement .< ref > The packing structure of collagen has not been defined to the same degree outside of the fibrillar collagen types, although it has been long known to be hexagonal or quasi-hexagonal.

Several types of military bridging vehicles have existed through the years.

Several types of chocolate can be distinguished.

Figure 8: Several types of diodes.

Several laboratory scale techniques for distillation exist ( see also distillation types ).

Several thousand patients have been treated with various types of tumours.

Several grappling styles like Judo, Shoot wrestling, Catch wrestling, Brazilian jiu-jitsu, Sambo and several types of wrestling including Freestyle and Greco-Roman have gained global popularity.

Several types are existent in Qing dynasty and used in dishes of stewing hams ( 火腿炖肘子 ), and vegetables, or for a wide variety of soup and important soup stocks.

Several types of FDA approved vacuum therapy devices are available with a doctor's prescription.

Several types of wild greens, known collectively as chwinamul ( such as Aster scaber ), are a popular dish, and other wild vegetables such as bracken fern shoots ( gosari ) or Korean bellflower root ( doraji ) are also harvested and eaten in season.

Several different types of light sources exist, each having different properties that affect their appropriateness for certain tasks, particularly efficiency and spectral power distribution.

Several types of molecules are particularly important during morphogenesis.

Several types of cell adhesion molecules are known and one major class of these molecules are cadherins.

Several types of " mania " such as kleptomania and pyromania are related more closely to obsessive-compulsive disorder than to bipolar disorder, depending on the severity of these disorders.

Several types of plasmid addiction systems ( toxin / antitoxin, metabolism-based, ORT systems ) were described in the literature and used in biotechnical ( fermentation ) or biomedical ( vaccine therapy ) applications.

Several cell types may be present in the epidermis.

Several types of RNA can downregulate gene expression by being complementary to a part of an mRNA or a gene's DNA.

Several types of visual prosthesis are in development or trials in humans, and one device has been approved for sale in the European market.

Several types of random samples are simple random samples, systematic samples, stratified random samples, and cluster random samples.

Several types of mushroom ( het ) also feature in Thai cuisine such as straw mushrooms ( het fang ) and white jelly fungus ( het hu nu khao ).

) Several types of naval " torpedo " were developed and deployed, most often by the Confederates, who faced a severe disadvantage in more traditional warfare methods.

Several types of fish can detect ultrasound.

Several types of pumps may be used in sequence or in parallel.

Several types have technological importance, for example, in liquid crystal displays.

Several brain imaging techniques, such as EEG and fMRI, have been used for physical measures of brain activity in these studies.

Several speculative and yet untested hypotheses suggest that endogenous DMT is produced in the human brain and is involved in certain psychological and neurological states.

Several clinical and experimental data have implicated the failure of blood – brain barrier ( BBB ) function in triggering chronic or acute seizures, some studies implicate the interactions between a common blood protein — albumin and astrocytes.

Several brain structures other than the amygdala have also been observed to be activated when individuals are presented with fearful vs. neutral faces, namely the occipitocerebellar regions including the fusiform gyrus and the inferior parietal / superior temporal gyri.

Several conditions can cause facial paralysis, e. g., brain tumor, stroke, and Lyme disease.

Several neuropathological studies on postmortem brain samples argued for an SNpc alteration evidenced by neuromelanin hypopigmentation, reduction in the structure area, and even controversial, signs of apoptosis.

Several adaptations combine to protect the woodpecker's brain from the substantial pounding that the pecking behaviour causes: it has a relatively thick skull with relatively spongy bone to cushion the brain ; there is very little cerebrospinal fluid in its small subarachnoid space ; the bird contracts mandibular muscles just before impact, thus transmitting the impact past the brain and allowing its whole body to help absorb the shock ; its relatively small brain is less prone to concussion than other animals '.

Several areas of the human brain are not on the brain side of the BBB.

Several clinical and experimental data have implicated the failure of blood – brain barrier function in triggering chronic or acute seizures.

Several contradictory predictions have been made about when a whole human brain can be emulated ; some of the predicted dates have already passed.

Several neurological conditions such as Alzheimer's disease, various types of brain injury, Klüver-Bucy syndrome, Kleine-Levin syndrome, and many more neuro-degenerative diseases can cause hypersexual behavior.

Several areas in the brain, and especially the nucleus paragigantocellularis, have been identified to be involved in ejaculatory control.

Several published studies in the medical literature on psychoneuroendocrinology have examined the hypothesis that prenatal exposure to estrogens ( including DES ) may cause significant developmental impact on sexual differentiation of the brain, and on subsequent behavioral and gender identity development in exposed males and females.

Several studies have demonstrated correlations between race and brain size, with varying results.

Several mutations of genes involving the melanocortins ( used in brain signaling associated with appetite ) and their receptors have also been identified as causing obesity in a larger portion of the population than leptin mutations.

Several decades earlier, refugees from Earth fled to join a pre-existing human colony on Mars to escape the domination of One True, a massively parallel / cellular automata program that runs on the interconnected brains of most of the human beings on Earth ; the program in the individual human brain is called Resuna, probably a contraction from the Latin for One Thing.

Several functional subunits ( like vocal muscles and brain areals ) are needed to produce the echolocating system.

Several different regions of the brain govern the act of writing.

: Several studies have used the fMRI paradigm to observe brain states brought about by adjustments of paralinguistic information.