Exciton effect in new generation of carbon nanotubes: graphdiyne nanotubes.

Graphdiyne-based nanotubes (GDNTs) are a novel type of carbon nanotubes. While conventional carbon nanotubes (CNTs) are generated by rolling graphene sheets, GDNTs are generated by rolling sheets that are similar to graphene but where the edges are elongated by the introduction of additional acetylene bonds between vertices (C6 aromatic rings). Such nanotubes are predicted to have many useful practical applications, but a thorough understanding of the relationship between their structure and their physical properties is still missing. We present a theoretical study of the electronic and optical properties of GDNTs. The structural, electronic, and optical properties of GDNTs with different diameters (i.e., 2-10 additional acetylene bonds) have been studied systematically by using density function theory (DFT) and self-consistent charge density functional tight-binding (SCC-DFTB) and by solving the Bethe-Salpeter equation (BSE), with and without considering the electron-hole interactions. The results indicate that the GDNTs are semiconductors with the direct band gap in close range, which is beneficial for photoelectronic devices and applications. Moreover, the absorption spectra of the GDNTs with different edge structures, (armchair, and zigzag) revealed little differences between the optical spectra of armchair and zigzag GDNTs, which could mean that fine separation between those structures (a process that is likely difficult and expensive in practice) will not be necessary. Importantly, the nanotubes were highly stable based on their cohesive energies, and their exciton binding energies were as large as about ~ 1 eV. From a methodological point of view, SCC-DFTB was found to be in agreement with more elaborate DFT calculations for most systems. Graphical abstract.

Nelaton catheter assisted versus standard nasogastric tube insertion: a randomized, clinical trial.

It is sometimes difficult to insert a nasogastric tube in an anaesthetized patient. We evaluated the benefit of reinforcing the distal portion of the nasogastric tube with a Nelaton catheter: 8 and 10 French Nelaton catheters were inserted into 16 and 18 French nasogastric tubes respectively through the first proximal holes of tubes up to their tips. The patients anaesthetized were randomly allocated into either the control or the Nelaton groups, and nasogastric tube was inserted as deeply as the catheter length, then the catheter was withdrawn and the tube was inserted farther to reach the stomach. Eighty patients (40 in each group) were included in this study. The success rate of nasogastric tube insertion was 90% in the Nelaton group and 57% in the control group (P = 0.001). The mean insertion time was 80 (SD 43) and 92 (SD 35) seconds in the Nelaton and the control groups respectively.

Service evaluation to establish the sensitivity, specificity and additional value of broad-range 16S rDNA PCR for the diagnosis of infective endocarditis from resected endocardial material in patients from eight UK and Ireland hospitals.

Infective endocarditis (IE) can be diagnosed in the clinical microbiology laboratory by culturing explanted heart valve material. We present a service evaluation that examines the sensitivity and specificity of a broad-range 16S rDNA polymerase chain reaction (PCR) assay for the detection of the causative microbe in culture-proven and culture-negative cases of IE. A clinical case-note review was performed for 151 patients, from eight UK and Ireland hospitals, whose endocardial specimens were referred to the Microbiology Laboratory at Great Ormond Street Hospital (GOSH) for broad-range 16S rDNA PCR over a 12-year period. PCR detects the causative microbe in 35/47 cases of culture-proven IE and provides an aetiological agent in 43/69 cases of culture-negative IE. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the 16S rDNA PCR assay were calculated for this series of selected samples using the clinical diagnosis of IE as the reference standard. The values obtained are as follows: sensitivity = 67 %, specificity = 91 %, PPV = 96 % and NPV = 46 %. A wide range of organisms are detected by PCR, with Streptococcus spp. detected most frequently and a relatively large number of cases of Bartonella spp. and Tropheryma whipplei IE. PCR testing of explanted heart valves is recommended in addition to culture techniques to increase diagnostic yield. The data describing the aetiological agents in a large UK and Ireland series of culture-negative IE will allow future development of the diagnostic algorithm to include real-time PCR assays targeted at specific organisms.

Nelaton catheter assisted versus standard nasogastric tube insertion: a randomized, clinical trial

It is sometimes difficult to insert a nasogastric tube in an anaesthetized patient. We evaluated the benefit of reinforcing the distal portion of the nasogastric tube with a Nelaton catheter: 8 and 10 French Nelaton catheters were inserted into 16 and 18 French nasogastric tubes respectively through the first proximal holes of tubes up to their tips. The patients anaesthetized were randomly allocated into either the control or the Nelaton groups, and nasogastric tube was inserted as deeply as the catheter length, then the catheter was withdrawn and the tube was inserted farther to reach the stomach. Eighty patients [40 in each group] were included in this study. The success rate of nasogastric tube insertion was 90% in the Nelaton group and 57% in the control group [P = 0.001]. The mean insertion time was 80 [SD 43] and 92 [SD 35] seconds in the Nelaton and the control groups respectively

Molecular dynamics simulation study of association in trifluoroethanol/water mixtures.

Mixtures of Trifluoroethanol (TFE) and water with different proportions are studied using molecular dynamics simulations. The radial and spatial distribution functions, as well as the size distribution of TFE clusters are obtained from the trajectories. The variation of radial and spatial distribution functions with composition show that the addition of TFE enhances the water structure, but the hydrogen bonds between TFE molecules are broken as TFE is diluted with water. The TFE-rich solutions have stronger TFE-water hydrogen bonds. The clustering of TFE molecules in low concentration region is attributed to the hydrophobic interactions between CF(3) groups. The distribution of cluster sizes in solution supports these conclusions.

The role of VEGF and a functional link between VEGF and p27Kip1 in acute myeloid leukemia.

Alterations in the expression and signalling pathways of vascular endothelial growth factor (VEGF) have been linked to the clinical features and pathogenesis of hematologic malignancies. In this study, we showed that VEGF protein expression was statistically significantly higher in the leukemic blasts than in the normal hematopoietic counterparts. A statistically significant correlation between expression of VEGF and p27(Kip1) was observed in bone marrows from 42 patients with acute myeloid leukemia (P<0.001). We further demonstrated that forced VEGF overexpression or autocrine VEGF stimulation of VEGFR-2 triggers proliferation and migration/invasion of U-937 leukemic cells, thereby inducing a more invasive tumor phenotype. U-937 cells overexpressing VEGF were resistant to all-trans-retinoic acid-(ATRA) or camptothecin-induced apoptosis. Finally, we showed that increased p27(Kip1) expression enhanced the ability of VEGF and VEGFR-2 to promote the migration of U-937 cells. Taken together, our results suggest that elevated level of VEGF may contribute to the adverse patient outcome by promoting cell growth, survival and migration of leukemic cells and by reducing the sensitivity of leukemic cells to therapeutic agents-induced apoptosis.

The correlation of RNase A enzymatic activity with the changes in the distance between Nepsilon2-His12 and N delta1-His119 upon addition of stabilizing and destabilizing salts.

The effect of stabilizing and destabilizing salts on the catalytic behavior of ribonuclease A (RNase A) was investigated at pH 7.5 and 25 degrees C, using spectrophotometric, viscometric and molecular dynamic methods. The changes in the distance between N(epsilon2) of His(12) and N(delta1) of His(119) at the catalytic center of RNase A upon the addition of sodium sulfate, sodium hydrogen sulfate and sodium thiocyanate were evaluated by molecular dynamic methods. The compactness and expansion in terms of Stokes radius of RNase A upon the addition of sulfate ions as kosmotropic salts, and thiocyanate ion as a chaotropic salt, were estimated by viscometric measurements. Enzyme activity was measured using cytidine 2', 3'-cyclic monophosphate as a substrate. The results from the measurements of distances between N(epsilon2) of His(12) and N(delta1) of His(119) and Stokes radius suggest (i) that the presence of sulfate ions decreases the distance between the catalytic His residues and increases the globular compactness, and (ii) that there is an expansion of the enzyme surface as well as elongation of the catalytic center in the presence of thiocyanate ion. These findings are in agreement with activity measurements.

Comparison of mirtazapine and fluoxetine in the treatment of major depressive disorder: a double-blind, randomized trial.

BACKGROUND: Depression is an international public health problem. The aim of this study was to compare the efficacy and tolerability of mirtazapine and fluoxetine treatment in a sample population consisting of Iranian patients suffering major depressive disorder. METHODS: Thirty-six inpatients and outpatients with a diagnosis of major depressive disorder (Diagnostic and Statistical Manual of Mental Disorders-IV) and a score > or = 18 on the 17-item Hamilton Rating Scale for Depression (HAM-D-17) were randomly assigned to 6 weeks of treatment with mirtazapine (30 mg/day) or fluoxetine (20 mg/day). Efficacy was assessed by HAM-D-17. Information about adverse events was obtained by questioning of participants and/or their examination. Assessments were performed at weeks 0, 1, 2, 3, 4 and 6. RESULTS: Sixteen of mirtazapine-treated patients and fifteen of fluoxetine-treated patients completed the 6-week study period. Both treatment groups were well matched at baseline with respect to demographic and disease characteristics. Both drugs showed a significant improvement over the 6 weeks of treatment (P < 0.001). There was no statistically significant difference between the mean +/- SEM HAM-D scores of two groups at weeks 1, 2, 3, 4, and at the end point. There were no significant differences between two groups in terms of response to treatment (> or = 50% decrease from baseline in HAM-D-17 total score) and remission (HAM-D-17 score of < or = 7). None of the differences in reported adverse events was statistically significant. CONCLUSION: In this study, mirtazapine and fluoxetine were equally effective and well tolerated after 6 weeks of treatment in patients with major depressive disorder.