Bimodal Phonon Scattering in Graphene Grain Boundaries.

Graphene has served as the model 2D system for over a decade, and the effects of grain boundaries (GBs) on its electrical and mechanical properties are very well investigated. However, no direct measurement of the correlation between thermal transport and graphene GBs has been reported. Here, we report a simultaneous comparison of thermal transport in supported single crystalline graphene to thermal transport across an individual graphene GB. Our experiments show that thermal conductance (per unit area) through an isolated GB can be up to an order of magnitude lower than the theoretically anticipated values. Our measurements are supported by Boltzmann transport modeling which uncovers a new bimodal phonon scattering phenomenon initiated by the GB structure. In this novel scattering mechanism, boundary roughness scattering dominates the phonon transport in low-mismatch GBs, while for higher mismatch angles there is an additional resistance caused by the formation of a disordered region at the GB. Nonequilibrium molecular dynamics simulations verify that the amount of disorder in the GB region is the determining factor in impeding thermal transport across GBs.

The effect of different direct antivirals on hepatic steatosis in nondiabetic and naïve hepatitis C-infected Egyptian patients.

Background: Hepatitis C is associated with metabolic effects and fatty liver disease. The effect of different direct antivirals on the liver steatosis, and the metabolic profile, still needs to be established. The aim of this study is to determine the effect of achieving the sustained virological response after 12 weeks (SVR-12 weeks) with different combinations of direct antiviral drugs, on the hepatic steatosis, and fibrosis presented by laboratory and transient elastography parameters. Our study population is nondiabetic, chronically infected HCV Egyptian patients and naïve to any form of HCV treatment. Methods: This cohort study was carried on 100 nondiabetic HCV treatment-naïve patients attending the Hepatology Clinic, in the Gastroenterology and Hepatology Department, Ain Shams University, and Kobry El Koba Military Hospital. The patients were divided into four groups according to their treatment regimens as follows: group A: 25 patients who received sofosbuvir (400 mg) and daclatasvir (60 mg) daily for 12 weeks; group B: 25 patients who received sofosbuvir (400 mg) and ledipasvir (90 mg) daily for 12 weeks; group C: 25 patients who received ombitasvir (12.5 mg), paritaprevir (75 mg), and ritonavir (50 mg) daily for 12 weeks; and group D: 25 patients who received sofosbuvir (400 mg) and simeprevir (150 mg) daily for 12 weeks. All patients were subjected to the following investigations: HCV quantitative PCR before and after 12 weeks of treatment, clinical and laboratory metabolic evaluation including alfa-fetoprotein level, thyroid profile assessment, ferritin level, pelvi-abdominal ultrasound, and FibroScan examination. Results: All patients achieved SVR after 12 weeks. FibroScan median decreased (P < 0.001) from 19.29 ± 6.97 kPa at baseline to 14.15 ± 6.48 kPa at SVR12. NAFLD score median increased from 1.88 (1.49-2.22) at baseline to 2.01 (1.61-2.33) after 12 weeks of treatment. The highest level of NAFLD score was in group C, and the lowest was in group B. The BMI mean decreased from 28.31 ± 1.53 at baseline to 28.07 ± 1.52 at SVR12. HbA1C level mean decreased from 5.73 ± 0.23 at baseline to 5.40 ± 0.24 at SVR12. In addition, liver enzymes, cholesterol, triglycerides, APRI score (AST-platelet ratio index), and HBA1C decreased after 12-week treatment with a statistically significant difference, while the mean LDL increased after 12 weeks of treatment. Conclusions: DAAs affect the metabolic profile of the treated patients. There is a noticed improvement in the FibroScan, NAFLD score, and lipid profile after achieving the SVR-12 weeks. However, LDL is increased after viral cure, mostly due to viral-host molecular interaction.

Risk of thrombolytic therapy for acute ischemic stroke in patients with current malignancy.

Little is known about the risk of thrombolysis in patients with malignancy, because these patients have been excluded from most clinical trials. We reviewed our acute ischemic stroke (AIS) database for clinical outcomes and complications in patients with current malignancy (CM) who received thrombolytic therapy. Consecutive AIS patients receiving thrombolysis between January 2003 and December 2006 were retrospectively abstracted in accordance with the American Stroke Association's Get With the Guidelines-Stroke definitions and charts were reviewed for history of malignancy. Patients with brain metastases did not receive tissue plasminogen activator (tPA). Stepwise logistic regression was used to identify independent predictors of in-hospital mortality. Of 308 AIS patients treated with thrombolytic therapy, 210 (68%) received intravenous (IV) tPA only, 41 (13%) received IV tPA plus intra-arterial therapy (IAT), and 57 (18%) received IAT only. Eighteen patients (5.8%) had a CM, and 26 patients (8.4%) had a remote history of malignancy. Patients with CM had a higher in-hospital mortality (38.9% vs 19.7 %; P=.05) and were more likely to have died due to worsening medical comorbidity (71.4% vs 9.6%; P < .001). The rate of symptomatic intracranial hemorrhage (ICH) was similar in the 2 groups (5.6% vs 2.7%; P=.47). In multivariate analysis, the only independent predictors of mortality were National Institutes of Health Stroke Scale score, history of hypertension, and smoking. CM was not independently associated with increased in-hospital mortality following thrombolysis. Mortality was attributable largely to medical comorbidities, not to symptomatic ICH. Our data suggest that thrombolysis may be a reasonable option for patients with malignancy who have acceptable medical comorbidities and performance status. Further research is warranted.

Quaternized N-substituted carboxymethyl chitosan derivatives as antimicrobial agents.

Introduction of quaternary ammonium moieties into N-substituted carboxymethyl chitosan (N-substituted CMCh) derivatives enhances their biological activity. Several derivatives of CMCh having a variety of N-aryl substituents bearing either electron-donating or electron withdrawing groups have been synthesized by the reaction between amino group of CMCh with various aromatic aldehydes under acidic conditions, followed by reduction of the produced Schiff base derivatives with sodium cyanoborohydride. Each of the reduced derivatives was further quaternized using N-(3-chloro-2-hydroxy-propyl)trimethylammonium chloride (Quat-188). The resulting quaternized materials were characterized by FTIR and (1)H NMR spectroscopy. Their antibacterial activities against Streptococcus pneumoniae (S. pneumonia, RCMB 010010), Bacillis subtilis (B. subtilis, RCMB 010067), as Gram positive bacteria and against Escherichia coli (E. coli, RCMB 010052) as Gram negative bacteria and their antifungal activities against Aspergillus fumigatus (A. fumigates, RCMB 02568), Geotricum candidum (G. candidum, RCMB 05097), and Candida albicans (C. albicans, RCMB 05031) were examined using agar disk diffusion method. The results indicated that all the quaternized derivatives showed better antimicrobial activities than that of CMCh. These derivatives are highly potent against Gram positive bacteria compared to Gram negative bacteria. This is illustrated for example as the values of minimum inhibitory concentration (MIC) of Q4NO2-BzCMCh against B. subtilis and S. pneumonia were 6.25 and 12.5 µg/mL, respectively corresponded to 20.0 µg/mL against E. coli. The antimicrobial activity of quaternized N-aryl CMCh derivatives affected by not only the nature of the microorganisms but also by the nature, position and number of the substituent groups on the phenyl ring. Thus while the derivatives with groups of electron withdrawing nature show higher inhibition zone diameter and lower MIC values relative to that of those having electron-donating nature, the non-substituted derivative lies between these two extremes. Antibacterial activities of Q4NO2-BzCMCh, Q3Cl-BzCMCh and Q3Br-BzCMCh against E. coli are nearly equivalent to that of the standard drug Gentamycin. Q3Br-BzCMCh emerged almost equivalent antibacterial activity to Ampicillin against S. pneumonia.