Impurity effect on weak anti-localization in the topological insulator Bi2Te3

We study weak anti-localization (WAL) effect in topological insulator Bi2Te3 thin films at low temperatures. Two-dimensional WAL effect associated with surface carriers is revealed in the tilted magnetic field dependence of magneto-conductance. Our data demonstrates that the observed WAL is robust against deposition of non-magnetic Au impurities on the surface of the thin films. But it is quenched by deposition of magnetic Fe impurities which destroy the pi Berry's phase of the topological surface states. The magneto-conductance data of a 5 nm Bi2Te3 film suggests that a crossover from symplectic to unitary classes is observed with the deposition of Fe impurities.Comment: 4 pages, 3 figures. Corresponding author email address: [email protected]

Functional analysis reveals G/U pairs critical for replication and trafficking of an infectious non-coding viroid RNA

While G/U pairs are present in many RNAs, the lack of molecular studies to characterize the roles of multiple G/U pairs within a single RNA limits our understanding of their biological significance. From known RNA 3D structures, we observed that the probability a G/U will form a Watson-Crick (WC) base pair depends on sequence context. We analyzed 17 G/U pairs in the 359-nucleotide genome of Potato spindle tuber viroid (PSTVd), a circular non-coding RNA that replicates and spreads systemically in host plants. Most putative G/U base pairs were experimentally supported by selective 2\u27-hydroxyl acylation analyzed by primer extension (SHAPE). Deep sequencing PSTVd genomes from plants inoculated with a cloned master sequence revealed naturally occurring variants, and showed that G/U pairs are maintained to the same extent as canonical WC base pairs. Comprehensive mutational analysis demonstrated that nearly all G/U pairs are critical for replication and/or systemic spread. Two selected G/U pairs were found to be required for PSTVd entry into, but not for exit from, the host vascular system. This study identifies critical roles for G/U pairs in the survival of an infectious RNA, and increases understanding of structure-based regulation of replication and trafficking of pathogen and cellular RNAs

Furanodiene alters mitochondrial function in doxorubicin-resistant MCF-7 human breast cancer cells in an AMPK-dependent manner

Furanodiene is a bioactive sesquiterpene isolated from the spice-producing Curcuma wenyujin plant (Y. H. Chen and C. Ling) (C. wenyujin), which is a commonly prescribed herb used in clinical cancer therapy by modern practitioners of traditional Chinese medicine. Previously, we have shown that furanodiene inhibits breast cancer cell growth both in vitro and in vivo, however, the mechanism for this effect is not yet known. In this study, therefore, we asked (1) whether cultured breast cancer cells made resistant to the chemotherapeutic agent doxorubicin (DOX) via serial selection protocols are susceptible to furanodiene\u27s anticancer effect, and (2) whether AMP-activated protein kinase (AMPK), which is a regulator of cellular energy homeostasis in eukaryotic cells, participates in this effect. We show here (1) that doxorubicin-resistant MCF-7 (MCF-7/DOXR) cells treated with furanodiene exhibit altered mitochondrial function and reduced levels of ATP, resulting in apoptotic cell death, and (2) that AMPK is central to this effect. In these cells, furanodiene (as opposed to doxorubicin) noticeably affects the phosphorylation of AMPK and AMPK pathway intermediates, ACLY and GSK-3β, suggesting that furanodiene reduces mitochondrial function and cellular ATP levels by way of AMPK activation. Finally, we find that the cell permeable agent and AMPK inhibitor compound C (CC), abolishes furanodiene-induced anticancer activity in these MCF-7/DOXR cells, with regard to cell growth inhibition and AMPK activation; in contrast, AICAR (5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside, acadesine), an AMPK activator, augments furanodiene-induced anticancer activity. Furthermore, specific knockdown of AMPK in MCF-7/DOXR cells protects these cells from furanodiene-induced cell death. Taken together, these findings suggest that AMPK and its pathway intermediates are promising therapeutic targets for treating chemoresistant breast cancer, and that furanodiene may be an important chemical agent incorporated in next-generation chemotherapy protocols

Study on Evolvement Complexity in an Artificial Stock Market

An artificial stock market is established based on multi-agent . Each agent has a limit memory of the history of stock price, and will choose an action according to his memory and trading strategy. The trading strategy of each agent evolves ceaselessly as a result of self-teaching mechanism. Simulation results exhibit that large events are frequent in the fluctuation of the stock price generated by the present model when compared with a normal process, and the price returns distribution is L\'{e}vy distribution in the central part followed by an approximately exponential truncation. In addition, by defining a variable to gauge the "evolvement complexity" of this system, we have found a phase cross-over from simple-phase to complex-phase along with the increase of the number of individuals, which may be a ubiquitous phenomenon in multifarious real-life systems.Comment: 4 pages and 4 figure

Widespread Sequence Variations in VAMP1 across Vertebrates Suggest a Potential Selective Pressure from Botulinum Neurotoxins

Botulinum neurotoxins (BoNT/A-G), the most potent toxins known, act by cleaving three SNARE proteins required for synaptic vesicle exocytosis. Previous studies on BoNTs have generally utilized the major SNARE homologues expressed in brain (VAMP2, syntaxin 1, and SNAP-25). However, BoNTs target peripheral motor neurons and cause death by paralyzing respiratory muscles such as the diaphragm. Here we report that VAMP1, but not VAMP2, is the SNARE homologue predominantly expressed in adult rodent diaphragm motor nerve terminals and in differentiated human motor neurons. In contrast to the highly conserved VAMP2, BoNT-resistant variations in VAMP1 are widespread across vertebrates. In particular, we identified a polymorphism at position 48 of VAMP1 in rats, which renders VAMP1 either resistant (I48) or sensitive (M48) to BoNT/D. Taking advantage of this finding, we showed that rat diaphragms with I48 in VAMP1 are insensitive to BoNT/D compared to rat diaphragms with M48 in VAMP1. This unique intra-species comparison establishes VAMP1 as a physiological toxin target in diaphragm motor nerve terminals, and demonstrates that the resistance of VAMP1 to BoNTs can underlie the insensitivity of a species to members of BoNTs. Consistently, human VAMP1 contains I48, which may explain why humans are insensitive to BoNT/D. Finally, we report that residue 48 of VAMP1 varies frequently between M and I across seventeen closely related primate species, suggesting a potential selective pressure from members of BoNTs for resistance in vertebrates

Cardiac CT perfusion imaging of pericoronary adipose tissue (PCAT) highlights potential confounds in coronary CTA

Features of pericoronary adipose tissue (PCAT) assessed from coronary computed tomography angiography (CCTA) are associated with inflammation and cardiovascular risk. As PCAT is vascularly connected with coronary vasculature, the presence of iodine is a potential confounding factor on PCAT HU and textures that has not been adequately investigated. Use dynamic cardiac CT perfusion (CCTP) to inform contrast determinants of PCAT assessment. From CCTP, we analyzed HU dynamics of territory-specific PCAT, myocardium, and other adipose depots in patients with coronary artery disease. HU, blood flow, and radiomics were assessed over time. Changes from peak aorta time, Pa, chosen to model the time of CCTA, were obtained. HU in PCAT increased more than in other adipose depots. The estimated blood flow in PCAT was ~23% of that in the contiguous myocardium. Comparing PCAT distal and proximal to a significant stenosis, we found less enhancement and longer time-to-peak distally. Two-second offsets [before, after] Pa resulted in [ 4-HU, 3-HU] differences in PCAT. Due to changes in HU, the apparent PCAT volume reduced ~15% from the first scan (P1) to Pa using a conventional fat window. Comparing radiomic features over time, 78% of features changed >10% relative to P1. CCTP elucidates blood flow in PCAT and enables analysis of PCAT features over time. PCAT assessments (HU, apparent volume, and radiomics) are sensitive to acquisition timing and the presence of obstructive stenosis, which may confound the interpretation of PCAT in CCTA images. Data normalization may be in order.Comment: 13 pages, 8 figure

Development of a LAMP assay for detection of Leishmania infantum infection in dogs using conjunctival swab samples

Background: Leishmania infantum infections in dogs play a crucial role in the transmission of pathogens causing visceral leishmaniasis to humans in the Gansu province, northwest China. To be able to control zoonotic transmission of the parasite to humans, a non-invasive loop-mediated isothermal amplification (LAMP) assay to specifically detect L. infantum infections in dogs was developed. Methods: The primers used in the LAMP assay were designed to target kinetoplast DNA minicircle sequences of the L. infantum isolate MCAN/CN/90/SC and tested using DNA isolated from promastigotes of different Leishmania species. The LAMP assay was evaluated with conjunctional swab samples obtained from 111 and 33 dogs living in an endemic and a non-endemic region of zoonotic visceral leishmaniasis in the Gansu province, respectively. The LAMP assay was also compared with conventional PCR, ELISA and microscopy using conjunctional swab, serum and bone marrow samples from the dogs, respectively. Results: The LAMP assay detected 1 fg of L. infantum DNA purified from cultured promastigotes which was 10-fold more sensitive than a conventional PCR test using Leishmania genus-specific primers. No cross reaction was observed with DNA isolated from promastigotes of L. donovani, L. major, L. tropica, and L. braziliensis, and the L. infantum reference strain MHOM/TN/80/IPT1. The L. infantum-positive rates obtained for field-collected samples were 61.3%, 58.6%, 40.5% and 10.8% by LAMP, PCR, ELISA and microscopy, respectively. As only one out of the 33 samples from control dogs from the non-endemic region of zoonotic visceral leishmaniasis was positive by the LAMP assay and the PCR test, the observed true negative rate (specificity) was 97% for both methods. Conclusion: This study has shown that the non-invasive, conjunctional swab-based LAMP assay developed was more sensitive in the detection of leishmaniasis in dogs than PCR, ELISA and microscopy. The findings indicate that the LAMP assay is a sensitive and specific method for the field surveillance of domestic dogs, particularly of asymptomatic canines, in ZVL-endemic areas in western China

Strain-induced enhancement of TcT_c in infinite-layer Pr0.8_{0.8}Sr0.2_{0.2}NiO2_2 films

The mechanism of unconventional superconductivity in correlated materials remains a great challenge in condensed matter physics. The recent discovery of superconductivity in infinite-layer nickelates, as analog to high-Tc cuprates, has opened a new route to tackle this challenge. By growing 8 nm Pr0.8Sr0.2NiO2 films on the (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate, we successfully raise the transition temperature Tc from 9 K in the widely studied SrTiO3-substrated nickelates into 15 K. By combining x-ray absorption spectroscopy with the first-principles and many-body simulations, we find a positive correlation between Tc and the pre-edge peak intensity, which can be attributed to the hybridization between Ni and O orbitals induced by the strain. Our result suggests that structural engineering can further enhance unconventional superconductivity, and the charge-transfer property plays a crucial role in the pairing strength.Comment: 8 pages, 4 figure

A gauge-mediated supersymmetry breaking model with an extra singlet Higgs field

We study in some detail the next-to-minimal supersymmetric standard model with gauge mediation of supersymmetry breaking. We find that it is feasible to spontaneously generate values of the Higgs mass parameters $\mu$ and $B_\mu$ consistent with radiative electroweak symmetry breaking. The model has a phenomenologically viable particle spectrum. Messenger sneutrinos with mass in the range 6 to 25 TeV can serve as cold dark matter. It is also possible to evade the cosmological domain wall problem in this scenario.Comment: revised version to appear in PR