Absence Of Constriction Research Articles

Prevalence of Taurodontism in Contemporary and Historical Populations from Radom: A Biometric Analysis of Radiological Data.

Taurodontism is a morphological anomaly of multirooted molars characterized by apical displacement of the pulp chamber, shortened roots, and the absence of constriction at the dentoenamel junction. It can negatively impact the outcome of dental treatment plans. This study aimed to compare the prevalence of taurodontism among contemporary and historical populations from Radom, Poland. Five hundred eighty-two panoramic radiographs of contemporary patients and 600 radiographs of historical individuals were analyzed using the Shifman and Chanannel index. Group differences were determined with Pearson's chi-square tests according to sex, site, tooth group, and historical period. The study also evaluated the degree of severity of taurodontism in relation to dental groups, gender, and the periods from which contemporary patients as well as historical individuals originated. In the contemporary population, taurodontism was observed in 34% of individuals. In the historical data, the highest prevalence of taurodontism (31%) was observed among individuals from the 18th and 19th centuries, while earlier periods exhibited considerably lower prevalence rates. Across contemporary and historical populations, the maxillary molars were the most commonly affected teeth. Hypotaurodontism was the most prevalent form of taurodontism. The prevalence of taurodontism has gradually increased from the 11th century to the current day. The results of the research are of great importance for the clinician in terms of planning comprehensive dental treatment.

A Jurassic Tibetan theropod tooth reveals dental convergency and its implication for identifying fragmentary fossils

<p><b>The Tibetan Plateau is among the least explored areas in terms of dinosaur paleontology in the world. Here, we report a dromaeosaurid-like tooth from the Middle Jurassic Dongdaqiao Formation at the eastern part of the plateau. The tooth exhibits dromaeosaurid dental features such as the absence of constriction at the cervix, a relatively small crown-to-base ratio, a strongly recurved apex, and it lacks large transverse and marginal undulations. Parsimonious phylogenetic analyses using both dentition-based and complete morphological matrices support a dromaeosaurid affinity for this tooth and place this Tibetan theropod as the sister taxon to</b> <i><b>Velociraptor</b></i><b>. However, Bayesian tip dating analyses based on the velociraptorine affinity of the Tibetan tooth place the majority of the diversifications of early-diverging Paravian within �C or earlier than �C the Middle Jurassic, which conflicts with the paravian fossil record. Furthermore, our discriminant analysis based on morphometric data places the Tibetan theropod within Metriacanthosauridae. These results may suggest that the broad resemblance between the Tibetan specimen and velociraptorine teeth is due to convergent evolution. Based on our results, other dromaeosaurid-like teeth reported from the Middle and Late Jurassic deposits throughout Eurasia could potentially be from non-dromaeosaurids. This study suggests the presence of an early diverged theropod lineage with a wide geographical distribution and potentially a dromaeosaurid-like dietary niche. This study also highlights the importance of using multiple lines of data to identify fragmentary fossils.</b></p>

Impact of Inert Crowders on Host-Guest Recognition Process.

Biological environments typically contain high concentrations (300-400 mg/mL) of different macromolecules at volume fractions as large as 30%-40%. Biomolecular recognition processes, a ubiquitous biological phenomena, occurring in such crowded heterogeneous media would differ significantly compared to the dilute buffer solutions. Here we quantify the potential impact of inert crowders on prototypical host-guest recognition process by explicit-solvent molecular dynamics (MD) simulations in atomic resolution. We demonstrate that the crowders, when smaller in size, would facilitate the binding process of the guest molecule by decreasing the free energy barrier for binding via excluded volume effect and desolvation of the host receptor. However, the extent of crowder-induced stabilization of a host-guest complex is found to be significantly higher when the guest molecule is sterically constricted to approach the host along a centrosymmetric direction, compared to its unrestricted, freely diffusive movement. A kinetic analysis of the recognition process reveals that the origin of a relatively stronger crowder impact during constricted movement of guest molecule lies in the relatively enhanced residence time of the guest inside the host by crowders. Together, our results suggest that the extent of impact of crowding on recognition processes would be contingent upon the presence or absence of constriction on ligand movement.

Morphological diversity of benthic cyanobacterial assemblages in meltwater ponds along environmental gradients in the McMurdo Sound region, Antarctica.

Benthic cyanobacterial assemblages from ponds distributed along inland-coastal gradients in the McMurdo Sound region were studied during the 2011/12 Antarctic summer season. Twenty-five ponds were sampled in four distinct geographic locations, including the Lower and Upper Wright Valleys, Ross Island and the McMurdo Ice Shelf. For morphological identification, benthic mat samples were thawed and a subsample was directly observed by light microscopy. Remaining sample material was stored in 50 ml sterile polycarbonate bottles containing the mineral nutrient medium MLA for future studies, maintained at a temperature of 21°C. Ten morphological criteria were used to describe the morphotypes (trichome shape, number of trichomes in sheath, presence or absence of terminal attenuation of trichome, calyptra on mature apical cell, shape of apical cell, presence or absence of constrictions at transverse walls, granules, branching, range in width of trichomes and range of cell length) with reference to available identification literature. All morphospecies were documented using photomicrography. In total, 29 morphospecies were described, four assigned to the order Chroococcales, three to Nostocales and 22 to Oscillatoriales. The four geographic locations had similar taxonomic richness, sharing many morphospecies. However, each also contained distinct floristic elements that were rare or absent from the others.

Swirl number and nozzle confinement effects in a flat-vane axial swirler

This paper presents the results of a parametric experimental study of free swirling flow at the exit of a flat-vane axial swirler. A total of 16 data sets were acquired by combining four swirler vane angles (22°, 29°, 50.5°, and 58.3°) and four exit nozzles of different diameters (30, 40, 52, and 76 mm). Sophisticated pressure probes consisting of precise microphones and a two-component LDV system were used to investigate the effect of these geometrical parameters on swirling flow regimes characterized by the swirl number. Particular attention was paid to the precessing vortex core (PVC) phenomenon observed at the exit of the swirler nozzle. It has been shown that by varying the vane angle and the diameter of the exit nozzle, it is possible to independently control the swirl number value and the occurrence of a PVC. A distinct correlation has been found between the PVC-induced pressure pulsations detected by acoustic probes and the tangential velocity fluctuations measured by LDV. The use of microphones provides a quick way to measure the frequency response of swirl flow in a wide range of geometries and flow configurations. The PVC effect does not occur at low subcritical values of the integral swirl number (S < 0.5) and in the case of strong swirl flow (Sg = 0.9 and 1.2) in the absence of constriction by the nozzle (De/D0 = 1). The disappearance of the PVC effect for strong swirl flow without constriction is due to the extreme displacement of the flow to the nozzle walls. The absence of a PVC in the flow was inferred not only from measurements of the frequency response of the flow over a wide range of Re numbers, but also from the absence of specific markers in velocity RMS distributions. Measurement results are used to derive an empirical correlation of the integral swirl number and the Strouhal number with a modified geometric swirl number. This allows a generalization of the frequency characteristics of swirling flows with a PVC for flat-vane axial swirlers, which are widely used in engineering.

Investigation on arc plasma, droplet, and molten pool behaviours in compulsively constricted WAAM

In order to study the special constriction effect and physical process features during compulsively constricted WAAM (CC-WAAM), the dynamic behaviours of arc, droplets, and molten pool were visually investigated. Possible interactions inside the narrow space were discussed to explain the mechanism of the compulsive constriction on ejected plasma and droplets. Based on the captured images, the strong radiative emission indicates that the ejected plasma was at high temperature at least 6000 K. As the current increases higher-temperature plasma jets were expected, which would lead to a larger plasma volume in the absence of constriction. The relationship between current and droplet diameters was preliminarily established to enable prediction of the droplet size. An important feature of small-size droplets (as low as 0.89 mm) offered CC-WAAM a great potential to improve the precision of the additive manufacturing layers, although the minimum width of the deposited layer is much larger than the droplet diameter due to liquid spreading and accumulation. The droplets were found to have a slight impact on the molten pool behaviours, which produces stable molten pool shapes. Under the wide-range parameters, the deposited layers showed good appearances, which indicates the good adaptability of this novel technology.

Two new species of free-living nematodes genera Microlaimus de Man, 1880 and Aponema Jensen, 1978 (Nematoda: Microlaimidae) from the Black Sea.

Two new species of the family Microlaimidae Micoletzky, 1922 are described and illustrated from the Black Sea. Aponema pontica sp. n. is morphologically closest to A.torosum in the shape of the body and spicules, size of amphids, but differs in having small and triangular cardia, absence of constriction in head region, shape of gubernaculum apophyses, rounded and weakly sclerotised lumen of pharyngeal bulb and longer spicules. Microlaimus paraglobiceps sp. n. morphologically resembles M.globiceps de Man, 1880 in the shape of the body, structure of the male sexual organs and presence of precloacal pore, but the main difference is a shorter body, cuticle finely annulated all over the body and absence of sexual dimorphism in the size of amphideal fovea.

Numerical investigation on the effect of sudden contraction on flow behavior in a 90-degree bend

Here we investigate fluid flow in 90-degree bends with and without orifice-like constrictions. The results of flow in non-constricted bends were compared with experimental results for similar Reynolds numbers and found to be in good agreement. Calculations were then carried out for various Reynolds numbers in the laminar and turbulent regimes. In addition, constrictions up to a 60% blockage were incorporated. The present study shows that the Reynolds number and the presence of an orifice-like constriction affects the velocity profile and the pressure distribution. The results indicate that if a sudden contraction is encountered, the peak velocity is larger and the flow is more predisposed to the outer wall than it otherwise would be. In addition, a sudden contraction increases the pressure loss compared to the constant-area bend and it affects the pressure distribution throughout the entire bend. This paper provides a means to predict pressure losses (similar to minor loss coefficients) in rounded bends in the presence or absence of constrictions. Such information is important to practicing engineers for designing fluid-flow conveyance systems. The behavior of the fluid is shown to be connected to the constriction and is also affected by the Reynolds number.

Friction at the BAR Leads to Membrane Breakup

A long-standing question in cell biology is how endocytic vesicles and tubules detach from the plasma membrane in the absence of constriction by dynamin. In this issue of Cell, Simunovic etal. describe an elegant biophysical model in which friction between lipids and BAR-domain proteinsdrives the scission of elongating membrane tubules.

Microdictyon (Chlorophyta, Anadyomenaceae) do Estado da Bahia, Brasil

A morpho-taxonomic study of the genus Microdictyon from the littoral of Bahia, Brazil, is presented. The material studied was obtained by dredging in the infralittoral of the Municipality of Canavieiras, as well as from analysis of material collected along the Bahia coast and deposited in the herbaria SPF and RFA. The genus is characterized by a flat thallus, astipitate, monostromatic, composed of open, reticulate laminae formed by apical cell-coalition. Three species were identified, M. boergesenii, M. pseudohapteron and M. umbilicatum, which were defined based on the type of adhesion pads at the tip of cells, presence or absence of constrictions and differences in branching pattern. Microdictyon pseudohapteron presents crenulated adhesion pads on the tip of cells whereas M. boergesenii and M. umbilicatum present apical annulated adhesion, the latter two differing by branching patterns and the presence or absence of constriction. Descriptions, illustrations and comparison with related taxa are provided.

Numerical study of flow in a constricted curved annulus: An application to flow in a catheterised artery

The flow of an incompressible Newtonian fluid in a curved annulus with a local constriction at the outer wall is investigated numerically. The three-dimensional nonlinear elliptic partial differential equations governing the flow are simplified by use of small curvature and mild constriction approximations. The simplified equations of motion, which are locally two-dimensional elliptic in nature at each cross-section, are solved numerically by means of the finite-difference method described by Collins and Dennis [Quart. Jour. Mech. Appl. Math. 28 (1975) 133–156]. Although the results are restricted to small curvature and mild constriction, these are valid for all Dean numbers D in the entire laminar flow regime. The numerical results show that, for higher values of radii ratio k, the pressure gradient, pressure drop, and frictional resistance increase considerably and they vary markedly across the constricted length. These results are used to estimate the increase in frictional resistance in an artery when a catheter is inserted into it. In the absence of constriction (δ1=0) and depending on the value of k ranging from 0⋅1 to 0⋅7, the frictional resistance increases by a factor ranging from 1⋅32 to 23⋅91 for D=500 and 1⋅20 to 16⋅56 for D=2000. But, in the presence of constriction (δ1 = 0⋅1) with the same range for k, the increase in frictional resistance is by a factor ranging from 1⋅34 to 42⋅32 for D=500 and 1⋅18 to 29⋅5 for D=2000. In a straight annulus, the increased factor ranges from 1⋅74 to 32⋅61 for δ1=0 and 1⋅78 to 58⋅27 for δ1 = 0⋅1 (for all Dean numbers D).

Candida albicans hyphal formation and virulence: is there a clearly defined role?

Over the past two decades, the increasing number of immunocompromised individuals has resulted in an epidemic of diseases caused by opportunistic fungal pathogens. Of particular interest is candidiasis, a disease caused by members of the Candida genus. These microorganisms are the leading cause of life-threatening fungal disease and rank fourth among all bloodstream and urinary tract nosocomial infections in the USA (Ref. [ 1 Jarvis W.R. Martone W.J. J. Antimicrob. Chemother. 1992; 29: 19-24 Crossref PubMed Scopus (495) Google Scholar ]). The prevalent cause of candidiasis is Candida albicans, which usually resides as a normal commensal on human mucosal surfaces. This species is polymorphic, as it can exist as a simple yeast form or undergo morphogenesis and produce filaments in the form of pseudohyphae and/or hyphae. Pseudohyphae are formed by chains of elongated buds (blastoconidia) and are characterized by constrictions at cell–cell junctions. Hyphae develop as a result of germination of blastoconidia and are characterized by the presence of parallel walls at the point of germ tube emergence, the development of true cross walls or septa, and the absence of constrictions. All forms are usually present in clinical lesions, which has led to considerable speculation and experimentation on the virulence role of hyphae in the pathogenesis of candidiasis[ 2 Cutler J.E. Annu. Rev. Microbiol. 1991; 45: 187-218 Crossref PubMed Scopus (543) Google Scholar ].

Hypotensive action of parathyroid hormone in chicken.

In a recent series of studies, the hypotensive action of parathyroid hormone (PTH) was demonstrated in several vertebrate species. In mammals, the mechanism of this direct action on specific vascular beds was studied. An increase in intracellular cyclic AMP and an inhibition of entry of extracellular calcium into the vascular tissue was correlated with the vasorelaxing action of PTH. In the present report, PTH was found to relax chicken mesenteric vessels in vitro in the presence or absence of constriction with concentrated potassium chloride (KCl). PTH produced dose-related inhibition of the chicken vessel constricted with 10, 20, 40, or 60 mM KCl. Extracellular calcium-dependent constriction of the chicken mesenteric artery was also decreased by PTH. An inhibitory effect was also observed with D600, a known calcium-entry inhibitor, in the above in vitro test systems. The low affinity lanthanum-resistant pool of calcium, which supposedly reflects the rate of calcium entry into cells, was also decreased by PTH in the control or KCl-stimulated chicken mesenteric artery. These data suggest that PTH may produce vasorelaxation in chicken mesenteric artery by inhibition of calcium entry into cells. This vessel from the chicken seems to have a high turnover rate of calcium and may be a good model for studying the effects of substances on calcium entry in vascular smooth muscle.

Polypoid epithelial malignancies of the esophagus.

Polypoid epithelial malignancies of the esophagus are rare tumors. One hundred fifty cases of epithelial malignancy of the esophagus accessioned to the Registry of Radiologic Pathology at the Armed Forces Institute of Pathology were reviewed with respect to morphologic and pathologic characteristics. Only large intraluminal polypoid epithelial masses were analyzed. Criteria used to select cases were: (1) size greater than 4 cm, (2) expansion of the esophageal lumen by the bulky tumor, and (3) absence of constriction or wall infiltration. Twenty-two lesions met these criteria (15 spindle cell carcinomas, two carcinosarcomas, three squamous cell carcinomas, and two oat cell carcinomas). When an esophageal neoplasm is polypoid and bulky, creates a "cupola" effect, has scalloped edges, expands the lumen of the esophagus, and is pedunculated, one must consider spindle cell carcinoma as the primary diagnosis.

CULTURALLY INDUCED VARIATION IN FOUR MORPHOLOGICALLY DIVERSE BLUEGREEN ALGAE

Characters used in taxonomic placement at levels from family to species appeared, disappeared, or varied widely, while others remained constant, in cultures of four disparate species of blue‐green algae (Cyanophyta) under varying conditions of culture. Species of Anabaena and Gloeocapsa displayed fairly stable characteristics. Species of Calothrix and Lyngbya exhibited much greater variability, especially in twisting of filaments, presence or absence of constrictions at the cross walls, abundance of heterocysts, pseudovacuoles, fragmentation of filaments, and change of color. Color change was associated with abrupt pH shift in Lyngbya and could be reversed by adding nitrate. In the putatively nitrogen‐fixing Anabaena, similar change in color with age was not associated with sharp pH shift, nor could it be reversed with nitrate. In general, growth on agar in turbulent conditions and with decreased CO2–O2 exchange was less than that obtainable under other conditions, and media with acid pH were partially or totally inhibitory to growth.

Culturally Induced Variation in Four Morphologically Diverse Bluegreen Algae

Characters used in taxonomic placement at levels from family to species appeared, disappeared, or varied widely, while others remained constant, in cultures of four disparate species of blue-green algae (Cyanophyta) under varying conditions of culture. Species of Anabaena and Gloeocapsa displayed fairly stable characteristics. Species of Calothrix and Lyngbya exhibited much greater variability, especially in twisting of filaments, presence or absence of constrictions at the cross walls, abundance of heterocysts, pseudovacuoles, fragmentation of filaments, and change of color. Color change was associated with abrupt pH shift in Lyngbya and could be reversed by adding nitrate. In the putatively nitrogen-fixing Anabaena, similar change in color with age was not associated with sharp pH shift, nor could it be reversed with nitrate. In general, growth on agar in turbulent conditions and with decreased CO2–O2 exchange was less than that obtainable under other conditions, and media with acid pH were partially or totally inhibitory to growth.