Theoretical polarization dependence of the two-phonon double-resonant Raman spectra of graphene

The experimental Raman spectra of graphene exhibit a few intense two-phonon bands, which are enhanced through double-resonant scattering processes. Though there are many theoretical papers on this topic, none of them predicts the spectra within a single model. Here, we present results for the two-phonon Raman spectra of graphene calculated by means of the quantum perturbation theory. The electron and phonon dispersions, electronic lifetime, electron-photon and electron-phonon matrix elements, are all obtained within a density-functional-theory-based non-orthogonal tight-binding model. We study systematically the overtone and combination two-phonon Raman bands, and, in particular, the energy and polarization dependence of their Raman shift and intensity. We find that the ratio of the integrated intensities for parallel and cross polarized light for all two-phonon bands is between 0.33 and 0.42. Our results are in good agreement with the available experimental data

Photoluminescence of the incompressible Laughlin liquid: Excitons, charged excitons, and fractionally charged excitons

The photoluminescence (PL) of a two-dimensional electron gas (2DEG) in a high magnetic field is studied as a function of the filling factor and the separation d between the electron layer and the valence hole. Depending on the magnitude of d relative to the magnetic length lambda, two distinct regimes in the response of the 2DEG to the valence hole occur, with different elementary emission processes contributing to the PL spectrum. At d<lambda ("strong coupling" regime), the hole binds one or two electrons to form an exciton (X) or one of three possible charged exciton (X-) states, a spin-singlet or one of two spin-triplets. At d>lambda ("weak coupling" regime), the hole decouples or binds one or two Laughlin quasielectrons to form fractionally charged excitons (FCX's). The binding energies as well as the emission energies and intensities of all X- and FCX states are calculated.Comment: 9 pages, 6 figures, sumbitted to physica status solidi (b

Indian Monsoon Depression: Climatology and Variability

The monsoon climate is traditionally characterized by large amount of seasonal rainfall and reversal of wind direction (e.g., Krishnamurti 1979). Most importantly this rainfall is the major source of fresh water to various human activities such as agriculture. The Indian subcontinent resides at the core of the Southeast Asian summer monsoon system with the monsoon trough extended from northern India across Indochina to the Western Tropical Pacific (WTP). Large fraction of annual rainfall occurs during the summer monsoon season, i.e., June – August1, with two distinct maxima. One is located over the Bay of Bengal with rainfall extending northwestward into eastern and central India, and the other along the west coast of India where the lower level moist wind meets the Western Ghat Mountains (Saha and Bavardeckar 1976). The rest of the Indian subcontinent receives relatively less rainfall.https://digitalcommons.usu.edu/modern_climatology/1001/thumbnail.jp

An Activating Mutation in sos-1 Identifies Its Dbl Domain as a Critical Inhibitor of the Epidermal Growth Factor Receptor Pathway during Caenorhabditis elegans Vulval Development

Proper regulation of receptor tyrosine kinase (RTK)-Ras-mitogen-activated protein kinase (MAPK) signaling pathways is critical for normal development and the prevention of cancer. SOS is a dual-function guanine nucleotide exchange factor (GEF) that catalyzes exchange on Ras and Rac. Although the physiologic role of SOS and its CDC25 domain in RTK-mediated Ras activation is well established, the in vivo function of its Dbl Rac GEF domain is less clear. We have identified a novel gain-of-function missense mutation in the Dbl domain of Caenorhabditis elegans SOS-1 that promotes epidermal growth factor receptor (EGFR) signaling in vivo. Our data indicate that a major developmental function of the Dbl domain is to inhibit EGF-dependent MAPK activation. The amount of inhibition conferred by the Dbl domain is equal to that of established trans-acting inhibitors of the EGFR pathway, including c-Cbl and RasGAP, and more than that of MAPK phosphatase. In conjunction with molecular modeling, our data suggest that the C. elegans mutation, as well as an equivalent mutation in human SOS1, activates the MAPK pathway by disrupting an autoinhibitory function of the Dbl domain on Ras activation. Our work suggests that functionally similar point mutations in humans could directly contribute to disease

High Fidelity Tape Transfer Printing Based On Chemically Induced Adhesive Strength Modulation

Transfer printing, a two-step process (i.e. picking up and printing) for heterogeneous integration, has been widely exploited for the fabrication of functional electronics system. To ensure a reliable process, strong adhesion for picking up and weak or no adhesion for printing are required. However, it is challenging to meet the requirements of switchable stamp adhesion. Here we introduce a simple, high fidelity process, namely tape transfer printing(TTP), enabled by chemically induced dramatic modulation in tape adhesive strength. We describe the working mechanism of the adhesion modulation that governs this process and demonstrate the method by high fidelity tape transfer printing several types of materials and devices, including Si pellets arrays, photodetector arrays, and electromyography (EMG) sensors, from their preparation substrates to various alien substrates. High fidelity tape transfer printing of components onto curvilinear surfaces is also illustrated

Adenoviruses Expressing PDX-1, BETA2/NeuroD and MafA Induces the Transdifferentiation of Porcine Neonatal Pancreas Cell Clusters and Adult Pig Pancreatic Cells into Beta-Cells

BackgroundA limitation in the number of insulin-producing pancreatic beta-cells is a special feature of diabetes. The identification of alternative sources for the induction of insulin-producing surrogate beta-cells is a matter of profound importance. PDX-1/VP16, BETA2/NeuroD, and MafA overexpression have been shown to influence the differentiation and proliferation of pancreatic stem cells. However, few studies have been conducted using adult animal pancreatic stem cells.MethodsAdult pig pancreatic cells were prepared from the non-endocrine fraction of adult pig pancreata. Porcine neonatal pancreas cell clusters (NPCCs) were prepared from neonatal pigs aged 1-2 days. The dispersed pancreatic cells were infected with PDX-1/VP16, BETA2/NeuroD, and MafA adenoviruses. After infection, these cells were transplanted under the kidney capsules of normoglycemic nude mice.ResultsThe adenovirus-mediated overexpression of PDX-1, BETA2/NeuroD and MafA induced insulin gene expression in NPCCs, but not in adult pig pancreatic cells. Immunocytochemistry revealed that the number of insulin-positive cells in NPCCs and adult pig pancreatic cells was approximately 2.6- and 1.1-fold greater than those in the green fluorescent protein control group, respectively. At four weeks after transplantation, the relative volume of insulin-positive cells in the grafts increased in the NPCCs, but not in the adult porcine pancreatic cells.ConclusionThese data indicate that PDX-1, BETA2/NeuroD, and MafA facilitate the beta-cell differentiation of NPCCs, but not adult pig pancreatic cells. Therefore PDX-1, BETA2/NeuroD, and MafA-induced NPCCs can be considered good sources for the induction of pancreatic beta-cells, and may also have some utility in the treatment of diabetes

Herd Behaviors in the Stock and Foreign Exchange Markets

The herd behaviors of returns for the won-dollar exchange rate and the KOSPI are analyzed in Korean financial markets. It is shown that the probability distribution $P(R)$ of price returns $R$ for three values of the herding parameter tends to a power-law behavior $P(R) \simeq R^{-\beta}$ with the exponents $\beta=2.2$(the won-dollar exchange rate) and 2.4(the KOSPI). The financial crashes are found to occur at $h >2.33$ when the relative increase in the probability distribution of exteremely high price returns is observed. Especially, the distribution of normalized returns shows a crossover to a Gaussian distribution for the time step $\Delta t=252$. Our results will be also compared to the other well-known analyses.Comment: 4 pages, 5 figure

Co-translational protein targeting facilitates centrosomal recruitment of PCNT during centrosome maturation in vertebrates.

As microtubule-organizing centers of animal cells, centrosomes guide the formation of the bipolar spindle that segregates chromosomes during mitosis. At mitosis onset, centrosomes maximize microtubule-organizing activity by rapidly expanding the pericentriolar material (PCM). This process is in part driven by the large PCM protein pericentrin (PCNT), as its level increases at the PCM and helps recruit additional PCM components. However, the mechanism underlying the timely centrosomal enrichment of PCNT remains unclear. Here, we show that PCNT is delivered co-translationally to centrosomes during early mitosis by cytoplasmic dynein, as evidenced by centrosomal enrichment of PCNT mRNA, its translation near centrosomes, and requirement of intact polysomes for PCNT mRNA localization. Additionally, the microtubule minus-end regulator, ASPM, is also targeted co-translationally to mitotic spindle poles. Together, these findings suggest that co-translational targeting of cytoplasmic proteins to specific subcellular destinations may be a generalized protein targeting mechanism

Paradigm model of online learning experience during COVID-19 crisis in higher education

The study presents qualitative research on university students' online learning experience process at the higher education level. It used a grounded theory through semi-structured in-depth interviews with 25 university students for framing and structuring the paradigm model of university students' online learning experiences. A paradigm model illustrating this developmental process is presented, which includes the casual and contextual conditions that caused and evolved the central phenomenon for their online learning, the strategies used by the students to overcome external/internal disturbances in continuing their learning process, the conditions that helped/hindered those strategies, and the consequences. Finally, the following meaning units were discovered through the preceding paradigm model. The students started learning with a negative impression of unfamiliar learning methods such as online learning, but over time, they improved their self-management abilities and gained a broader understanding of self-discipline. In the midst of this, competence in digital literacy according to generational differences was also discovered as one of the factors affecting learning, forming a virtual community, and increasing personal learning through online interaction. Finally, the implications of the overall learning ecology for the future role of online learning were also considered. Based on this analysis of students' online learning experiences, the direction for online learning was suggested

Inhomogeneous Degradation of Polymer Electrolyte Membrane in PEM Fuel Cells

Membrane durability is one of the technical barriers for the commercialization of polymer electrolyte membrane (PEM) fuel cells. Membrane embrittlement (a form of mechanical weakening) can lead to the frequently observed “sudden death” behavior of PEM fuel cells. It is the objective of this study to explore the fundamental mechanisms of the mechanical weakening of perfluorosulfonic acid (PFSA) based electrolyte membranes during the accelerated degradation test