745 research outputs found
Evaluation of Deformable Boundary Condition Using Finite Element Method and Impact Test for Steel Tubes
Stainless steel pipelines are crucial components to transportation and storage in the oil and gas industry. However, the rise of random attacks and vandalism on these pipes for their valuable transport has led to more security and protection for incoming surface impacts. These surface impacts can lead to large global deformations of the pipe and place the pipe under strain, causing the eventual failure of the pipeline. Therefore, understanding how these surface impact loads affect the pipes is vital to improving the pipes’ security and protection. In this study, experimental test and finite element analysis (FEA) have been carried out on EN3B stainless steel specimens to study the impact behaviour. Low velocity impact tests at 9 m/s with 16 kg dome impactor was used to simulate for high momentum impact for localised failure. FEA models of clamped and deformable boundaries were modelled to study the effect of the boundaries on the pipes impact behaviour on its impact resistance, using experimental and FEA approach. Comparison of experimental and FE simulation shows good correlation to the deformable boundaries in order to validate the robustness of the FE model to be implemented in pipe models with complex anisotropic structure
2-Amino-4-methylpyridinium trifluoroacetate: a monoclinic polymorph
The title salt, C6H9N2
+·C2F3O2
−, is a monoclinic polymorph of a previously reported structure [Hemamalini & Fun (2010). Acta Cryst. E66, o781–o782]. In the crystal structure, the cations and anions are linked by two different types of N—H⋯O hydrogen bonds, forming cation–anion pairs. These pairs are hydrogen bonded to neighbouring pairs via another N—H⋯O hydrogen bonds involving an H atom of the NH2 group and one of the O atoms of the COO− group into a chain extended along the b axis
Design and applicability of DNA arrays and DNA barcodes in biodiversity monitoring
<p>Abstract</p> <p>Background</p> <p>The rapid and accurate identification of species is a critical component of large-scale biodiversity monitoring programs. DNA arrays (micro and macro) and DNA barcodes are two molecular approaches that have recently garnered much attention. Here, we compare these two platforms for identification of an important group, the mammals.</p> <p>Results</p> <p>Our analyses, based on the two commonly used mitochondrial genes cytochrome <it>c </it>oxidase I (the standard DNA barcode for animal species) and cytochrome b (a common species-level marker), suggest that both arrays and barcodes are capable of discriminating mammalian species with high accuracy. We used three different datasets of mammalian species, comprising different sampling strategies. For DNA arrays we designed three probes for each species to address intraspecific variation. As for DNA barcoding, our analyses show that both cytochrome <it>c </it>oxidase I and cytochrome b genes, and even smaller fragments of them (mini-barcodes) can successfully discriminate species in a wide variety of specimens.</p> <p>Conclusion</p> <p>This study showed that DNA arrays and DNA barcodes are valuable molecular methods for biodiversity monitoring programs. Both approaches were capable of discriminating among mammalian species in our test assemblages. However, because designing DNA arrays require advance knowledge of target sequences, the use of this approach could be limited in large scale monitoring programs where unknown haplotypes might be encountered. DNA barcodes, by contrast, are sequencing-based and therefore could provide more flexibility in large-scale studies.</p
About Gravitomagnetism
The gravitomagnetic field is the force exerted by a moving body on the basis
of the intriguing interplay between geometry and dynamics which is the analog
to the magnetic field of a moving charged body in electromagnetism. The
existence of such a field has been demonstrated based on special relativity
approach and also by special relativity plus the gravitational time dilation
for two different cases, a moving infinite line and a uniformly moving point
mass, respectively. We treat these two approaches when the applied cases are
switched while appropriate key points are employed. Thus, we demonstrate that
the strength of the resulted gravitomagnetic field in the latter approach is
twice the former. Then, we also discuss the full linearized general relativity
and show that it should give the same strength for gravitomagnetic field as the
latter approach. Hence, through an exact analogy with the electrodynamic
equations, we present an argument in order to indicate the best definition
amongst those considered in this issue in the literature. Finally, we
investigate the gravitomagnetic effects and consequences of different
definitions on the geodesic equation including the second order approximation
terms.Comment: 16 pages, a few amendments have been performed and a new section has
been adde
1,1′-(Ethane-1,2-diyl)dipyridinium dichromate(VI)
In the cation of the title salt, (C12H14N2)[Cr2O7], the two pyridinium moieties are in an anti orientation with respect to one another. The dihedral angle between the pyridine rings is 6.3 (2)°. The N—C—C—N torsion angle is 177.5 (2)°. In the dianion, the CrVI ions are in a slightly distorted tetrahedral coordination environment and the bond angles at the independent CrVI ions are in the ranges 105.93 (10)–110.60 (11) and 107.35 (11)–111.07 (12)°. The Cr—O—Cr angle is 127.96 (12)°. The crystal used was an inversion twin with refined components of 0.510 (19) and 0.490 (19)
Mechanobiology of Antimicrobial Resistant Escherichia coli and Listeria innocua
A majority of antibiotic-resistant bacterial infections in the United States are associated with biofilms. Nanoscale biophysical measures are increasingly revealing that adhesive and viscoelastic properties of bacteria play essential roles across multiple stages of biofilm development. Atomic Force Microscopy (AFM) applied to strains with variation in antimicrobial resistance enables new opportunities for investigating the function of adhesive forces (stickiness) in biofilm formation. AFM force spectroscopy analysis of a field strain of Listeria innocua and the strain Escherichia coli K-12 MG1655 revealed differing adhesive forces between antimicrobial resistant and nonresistant strains. Significant increases in stickiness were found at the nanonewton level for strains of Listeria innocua and Escherichia coli in association with benzalkonium chloride and silver nanoparticle resistance respectively. This advancement in the usage of AFM provides for a fast and reliable avenue for analyzing antimicrobial resistant cells and the molecular dynamics of biofilm formation as a protective mechanism
N,N′-Di-tert-butyl-N′′-(2,6-difluorobenzoyl)phosphoric triamide
In the title compound, C15H24F2N3O2P, the phosphoryl and carbonyl groups adopt anti positions relative to each other. The P atom is in a tetrahedral coordination environment and the environment of each N atom is essentially planar. In the crystal, adjacent molecules are linked via N—H⋯O=P and N—H⋯O=C hydrogen bonds into an extended chain parallel to the a axis. The crystal studied was a non-merohedral twin with a minor twin component of 36.4 (1)%
Spontaneous Regeneration of the Mandible after Hemimandibulectomy: Report of a Case
Mandibular defects may result from many conditions such as trauma, inflammatory diseases and tumors. There are rare cases reported in the literature that have demonstrated spontaneous bone regeneration after resection of the mandible. Several factors such as age, preservation of the periosteum and genetics seem to influence spontaneous bone regeneration capacity in individuals. Evaluation of these factors may lead to a better understanding of the mechanism of spontaneous bone regeneration and also help to create new methods for bone reconstruction. The purpose of this article was to describe the spontaneous regeneration of the hemi-mandible with a well shaped condyle and coronoid after resecting a mandibular pathologic lesion in a young man
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