Graphene to graphite; a layer by layer experimental measurements and density function theory calculations of electric conductivity

ABSTRACT

We measured the electric conductivity of large (25?×?50?mm) graphene films as a function of number of layers in the range of 1–20 layers. We also calculated the energy gap for such samples using density function theory. Our results showed a conductivity slightly above that of ITO for monolayer graphene and an exponential decrease as the number of graphene layers increased. Both experimental and simulation results showed a convergence of graphene into graphite at as little as 18–20 layers.     

Green micellar stability-indicating high-performance liquid chromatography method for determination of rupatadine fumarate in the presence of its main impurity desloratadine: Oxidative degradation kinetics study

A green micellar stability-indicating high-performance liquid chromatography method was developed for rupatadine fumarate determination in existence with its main impurity desloratadine. Separation was attained using Hypersil ODS column (150 × 4.6 mm, 5 μm), the micellar mobile phase consisted of 0.13 M sodium dodecyl sulfate, 0.1 M disodium hydrogen phosphate adjusted by phosphoric acid to pH 2.8 and 10% n-butanol. The column was maintained at 45^◦C and detection was carried out at 267 nm. A linear response was achieved over the range of 2–160 μg/ml for rupatadine and 0.4–8 μg/ml for desloratadine. The method was applied for rupatadine determination in alergoliber tablets and alergoliber syrup without the interference of methyl paraben and propyl paraben present as main excipients. Rupatadine fumarate revealed pronounced susceptibility to oxidation; further study of oxidative degradation kinetics was carried out. Rupatadine was found to follow pseudo-first-order kinetics when exposed to 10% H₂O₂ at 60 and 80°C and the activation energy was found to be 15.69 Kcal/mol. At a lower temperature (40°C), degradation kinetics regression was best fitted as a polynomial quadratic relationship, thus rupatadine oxidation at a lower temperature tends to adopt a second-order kinetics rate. Oxidative degradation product structure was revealed using infrared and found to be rupatadine N-oxide at all temperature values.     

(−)‐Englerin A is a Potent and Selective Activator of TRPC4 and TRPC5 Calcium Channels

Current therapies for common types of cancer such as renal cell cancer are often ineffective and unspecific, and novel pharmacological targets and approaches are in high demand. Here we show the unexpected possibility for the rapid and selective killing of renal cancer cells through activation of calcium‐permeable nonselective transient receptor potential canonical (TRPC) calcium channels by the sesquiterpene (?)‐englerin A. This compound was found to be a highly efficient, fast‐acting, potent, selective, and direct stimulator of TRPC4 and TRPC5 channels. TRPC4/5 activation through a high‐affinity extracellular (?)‐englerin A binding site may open up novel opportunities for drug discovery aimed at renal cancer.     

Stable Encapsulated Air Nanobubbles in Water

The dispersion into water of nanocapsules bearing a highly hydrophobic fluorinated internal lining yielded encapsulated air nanobubbles. These bubbles, like their micrometer‐sized counterparts (microbubbles), effectively reflected ultrasound. More importantly, the nanobubbles survived under ultrasonication 100‐times longer than a commercial microbubble sample that is currently in clinical use. We justify this unprecedented stability theoretically. These nanobubbles, owing to their small size and potential ability to permeate the capillary networks of tissues, may expand the applications of microbubbles in diagnostic ultrasonography and find new applications in ultrasound‐regulated drug delivery.     

Enhancement of β-Glucan Biological Activity Using a Modified Acid-Base Extraction Method from Saccharomyces cerevisiae

Beta glucan (β-glucan) has promising bioactive properties. Consequently, the use of β-glucan as a food additive is favored with the dual-purpose potential of increasing the fiber content of food products and enhancing their health properties. Our aim was to evaluate the biological activity of β-glucan (antimicrobial, antitoxic, immunostimulatory, and anticancer) extracted from Saccharomyces cerevisiae using a modified acid-base extraction method. The results demonstrated that a modified acid-base extraction method gives a higher biological efficacy of β-glucan than in the water extraction method. Using 0.5 mg dry weight of acid-base extracted β-glucan (AB extracted) not only succeeded in removing 100% of aflatoxins, but also had a promising antimicrobial activity against multidrug-resistant bacteria, fungi, and yeast, with minimum inhibitory concentrations (MIC) of 0.39 and 0.19 mg/mL in the case of resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, respectively. In addition, AB extract exhibited a positive immunomodulatory effect, mediated through the high induction of TNFα, IL-6, IFN-γ, and IL-2. Moreover, AB extract showed a greater anticancer effect against A549, MDA-MB-232, and HepG-2 cells compared to WI-38 cells, at high concentrations. By studying the cell death mechanism using flow-cytometry, AB extract was shown to induce apoptotic cell death at higher concentrations, as in the case of MDA-MB-231 and HePG-2 cells. In conclusion, the use of a modified AB for β-glucan from Saccharomyces cerevisiae exerted a promising antimicrobial, immunomodulatory efficacy, and anti-cancer potential. Future research should focus on evaluating β-glucan in various biological systems and elucidating the underlying mechanism of action.     

Mechanisms of Microscopic Displacement During Enhanced Oil Recovery in Mixed-Wet Rocks Revealed Using Direct Numerical Simulation

Transport in Porous Media - We demonstrate how to use numerical simulation models directly on micro-CT images to understand the impact of several enhanced oil recovery (EOR) methods on microscopic...