Phononic thermal transport properties of C3N nanotubes.

Reverse nonequilibrium molecular dynamics (RNEMD) is employed to study the phononic thermal transport properties of C3N nanotubes. We study the effect of nanotube length and diameter on the thermal conductivity and investigate the phonon transport transition from ballistic to diffusive regime in C3N nanotubes. It is found that the thermal conductivity of C3N nanotubes is significantly lower than those of carbon nanotubes across the entire ballistic-diffusive range. In addition, significantly lower ballistic to diffusive transition length (72-80 nm) is observed in C3N nanotubes compared to carbon nanotubes. The inspection of phonon dispersion curves shows that carbon nanotubes have stiffer acoustic modes than C3N nanotubes which results in lower group velocities for C3N nanotubes. Due to the presence of nitrogen atoms, the phonon mean free paths and relaxation times of C3N nanotubes are shorter than those of the carbon nanotubes. The combined effect of lower group velocities and relaxation times leads to the lower thermal conductivity of C3N nanotubes.

An Atomistic Study of the Stress Corrosion Cracking in Graphene.

Using molecular dynamics (MD) simulations, we study the mechanism of stress corrosion cracking in graphene. Two sets of modelings are conducted. In the first one, large graphene sheets with cracks in the armchair and zigzag directions are exposed to oxygen molecules. The crack growth as a result of chemical reactions between carbon radicals and oxygen molecules at different mechanical tensile stress levels is studied. In the second set of simulations, MD simulations are combined with the density functional-based tight bonding method to enhance the accuracy. This set of modelings focuses on a smaller zone in the vicinity of the crack tip. The impact of initial crack orientation on corrosion is studied by investigating corrosion of cracks in both armchair and zigzag directions. We investigate the subcritical crack propagation occurring as a result of the combined effects of both mechanical loading and chemical reactions. Our results show that cracks in graphene can grow due to chemical reactions with the environmental molecules. The MD modelings also predict that reaction of carbon atoms with oxygen molecules might lead to a stress relaxation at the crack tip, hence preventing further crack propagation. The results show that subcritical crack growth can happen by two mechanisms, which include the failure of C-C bonds or by removing the carbon atoms from graphene sheets in the form of CO or CO2 molecules.

Predicting Corrosion Damage in the Human Body Using Artificial Intelligence: In Vitro Progress and Future Applications.

Artificial intelligence (AI) is used in the clinic to improve patient care. While the successes illustrate AI's impact, few studies have led to improved clinical outcomes. In this review, we focus on how AI models implemented in nonorthopedic fields of corrosion science may apply to the study of orthopedic alloys. We first define and introduce fundamental AI concepts and models, as well as physiologically relevant corrosion damage modes. We then systematically review the corrosion/AI literature. Finally, we identify several AI models that may be implemented to study fretting, crevice, and pitting corrosion of titanium and cobalt chrome alloys.

Platelet accumulation after laser angioplasty--a scintigraphic assessment.

Indium 111-labeled platelet scintigraphy was performed to evaluate platelet deposition in response to different levels of Nd:YAG laser/thermal energy. A dose-related increase in platelet deposition was observed. In clinical studies after laser-assisted balloon angioplasty, intense platelet deposition was observed in 2 patients who subsequently developed clinical arterial thrombosis. The pathogenesis of reocclusion appears, however, to be more complicated and ill understood. The authors suggest further extensive studies incorporating several parameters in the evaluation of the pathogenic factors involved in reocclusion after laser angioplasty. Such studies should also consider the role of arterial injury produced by the balloon catheter after laser-assisted balloon angioplasty.

Inflammatory fibrous histiocytoma of the posterior mediastinum.

A case of malignant fibrous histiocytoma (MFH) of inflammatory type from posterior mediastinum which is a rare site is reported here. Its clinico-pathological features are discussed.

Common iliac artery aneurysm presenting as acute sciatic nerve compression.

Aneurysms of the iliac arteries usually remain silent, but when they rupture the consequences can be dramatic. They produce few clinical signs suggestive of their presence. However, such aneurysms have been found to be the cause of non-vascular clinical situations. Often they present with features of compression on adjacent viscera. We present a case in which a large common iliac artery aneurysm was found to be causing symptoms of acute sciatic nerve compression.

Arterial reconstruction for upper limb ischaemia: an alternative technique.

Reconstructive arterial surgery for upper limb ischaemia has been performed since the early 1950s. The commonest site of occlusion is in the subclavian artery for which the widely preferred surgical reconstruction is the carotid-subclavian bypass graft. We present a series of eight cases of subclavian artery occlusion for which direct subclavian to carotid anastomosis was performed yielding results comparable with carotid-subclavian bypass.

Detection of arterial thrombosis after laser angioplasty by platelet scintigraphy.

Indium-111-labelled platelet scintigraphy was performed in two patients after laser-assisted balloon angioplasty. Both patients demonstrated a significant 'hot spot' at the angioplasty site 24 h after successful recanalisation with laser and balloon. Clinically apparent thrombosis of the recanalised arteries occurred 5 and 6 days after angioplasty in both patients. Laser-assisted balloon angioplasty leads to significant platelet deposition over recanalised segments of the artery, which may result in arterial thrombosis, as evident from the reports presented. Indium-111-labelled platelet scintigraphy emphasises the extent of trauma caused by laser and balloon angioplasty to the arterial wall.

Characterization and differential expression of human vascular smooth muscle myosin light chain 2 isoform in nonmuscle cells.

The 20-kDa regulatory myosin light chain (MLC), also known as MLC-2, plays an important role in the regulation of both smooth muscle and nonmuscle cell contractile activity. Phosphorylation of MLC-2 by the enzyme MLC kinase increases the actin-activated myosin ATPase activity and thereby regulates the contractile activity. We have isolated and characterized an MLC-2 cDNA corresponding to the human vascular smooth muscle MLC-2 isoform from a cDNA library derived from umbilical artery RNA. The translation of the in vitro synthesized mRNA, corresponding to the cDNA insert, in a rabbit reticulocyte lysate results in the synthesis of a 20,000-dalton protein that is immunoreactive with antibodies raised against purified chicken gizzard MLC-2. The derived amino acid sequence of the putative human smooth muscle MLC-2 shows only three amino acid differences when compared to chicken gizzard MLC-2. However, comparison with the human cardiac isoform reveals only 48% homology. Blot hybridizations and S1 nuclease analysis indicate that the human smooth muscle MLC-2 isoform is expressed restrictively in smooth muscle tissues such as colon and uterus and in some, but not all, nonmuscle cell lines. Previously reported MLC-2 cDNA from rat aortic smooth muscle cells in culture is ubiquitously expressed in all muscle and nonmuscle cells, and it was suggested that both smooth muscle and nonmuscle MLC-2 proteins are identical and are probably encoded by the same gene. In contrast, the human smooth muscle MLC-2 cDNA that we have characterized from an intact smooth muscle tissue is not expressed in skeletal and cardiac muscles and also in a number of nonmuscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of the human smooth muscle alpha-actin gene. Analysis of a cDNA and 5' upstream region.

The structures of a cDNA and the 5' upstream region of the human smooth muscle alpha-actin gene have been characterized. Transcriptional start sites and the non-coding first exon were mapped by primer extension analysis and by comparing cDNA and genomic sequences. The deduced human smooth muscle alpha-actin protein sequence is identical to the corresponding bovine protein sequence, and thus confirms that the previously determined human genomic sequence contained a mutation at codon 312. Human smooth muscle cells express only a single, 1.4-kilobase smooth muscle alpha-actin transcript. 5' Noncoding sequences that have the greatest similarity to the chicken gene are located in five noncontiguous segments, extending from approximately 250 base pairs upstream of the cap site through the first exon. Conserved sequences encompass a region required for expression and tissue-specific regulation of chicken smooth muscle alpha-actin and therefore are probably also important for expression of the human gene.