Causality in Quantiles and Dynamic Stock Return-Volume Relations

This paper investigates the causal relations between stock return and volume based on quantile regressions. We first define Granger non-causality in all quantiles and propose testing non-causality by a sup-Wald test. Such a test is consistent against any deviation from non-causality in distribution, as opposed to the existing tests that check only noncausality in certain moment. This test is readily extended to test non-causality in different quantile ranges, and the testing results enable us to identify the quantile range for which causality is relevant. In the empirical studies of 3 major stock market indices, we find that, while the conventional test suggests no causality in mean, there are strong evidences that lagged volume Granger causes return in all but some middle quantiles. In particular, the causal effects have opposite signs at lower and upper quantiles and are stronger at more extreme quantiles. These relations form (symmetric) V shapes across quantiles. They also show that the dispersion of the return distribution increases with volume so that volume has a positive effect on return volatility. It is also shown that the quantile causal effects of lagged return on volume are mainly negative.Granger non-causality in quantiles, quantile causal effect, quantile regression, return-volume relation, sup-Wald test

Study of sponge gourd ascorbate peroxidase and winter squash superoxide dismutase under respective flooding and chilling stresses

AbstractThe objectives of this work were to study the responses of ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and physiological parameters of bitter melon (BM), sponge gourd (SG), and winter squash (WS) under waterlogged and low temperature conditions. The BM and SG plants were subjected to 0–72h flooding treatments. Moreover, BM and WS plants were exposed to chilling at 12/7°C (day/night) for 0–72h. The results show that different genotypes responded differently to environmental stress according to their various antioxidant enzymes and physiological parameters. The activity of APX in roots and leaves of SG plants significantly higher than that of BM plants during continuous flooding. Significant increases in SOD activity in leaves of WS plants were also observed throughout the entire chilling duration compared to BM plants. On the basis of our observations, we conclude that increased APX and SOD activities provide SG and WS plants with increased waterlogging and chilling stress tolerance, respectively. Both APX and SOD activities can be used for selecting BM lines with the best tolerances to water logging and chilling stresses

Less Invasive Mitral Valve Surgery via Right Minithoracotomy

Background/PurposeCurrent trends in cardiac surgical intervention are moving toward less invasiveness, with smaller wound or sternum-sparing, less pump time or off-pump, and beating rather than arrested heart. Data on the efficacy and safety of these newer less invasive techniques, as well as their cosmetic results, are limited. This study analyzed the results of a sternum-sparing mitral valve operation.MethodsThirty patients with mitral valve diseases, including 20 who underwent mitral valve repair and 10 mitral valve replacement, were enrolled. Cardiopulmonary bypass was established via femoral cannu-lation, and blood cardioplegic arrest was induced by using a percutaneous, transthoracic cross-clamp. The main surgical wound was made over the lateral border of the right breast. Two additional small wounds were required for the transthoracic aortic clamp and the mitral retractor.ResultsThere was no operative mortality, and all patients had an uneventful recovery. Two patients underwent redo mitral surgery. Nine associated procedures were performed including tricuspid valve annulo-plasty in six patients, tricuspid valve replacement in two patients and atrial septal defect repair in one patient. The length of the main wound was between 5.8 and 7.8 cm (mean, 7.1 cm). The mean cardiopul-monary bypass time and cross-clamp time were 91.1 and 43.7 minutes, respectively. Although the length of stay was not significantly reduced compared with traditional median sternotomy, all patients had satisfactory results with good cosmesis.ConclusionSternum-sparing mitral valve surgery appears to be a safe and effective alternative to conventional mitral valve surgery; it is less invasive and provides superior cosmetic results for patients

Studying antibiotic–membrane interactions via X-ray diffraction and fluorescence microscopy

AbstractAntibiotic drug resistance is a serious issue for the treatment of bacterial infection. Understanding the resistance to antibiotics is a key issue for developing new drugs. We used penicillin and sulbactam as model antibiotics to study their interaction with model membranes. Cholesterol was used to target the membrane for comparison with the well-known insertion model. Lamellar X-ray diffraction (LXD) was used to determine membrane thickness using successive drug-to-lipid molar ratios. The aspiration method for a single giant unilamellar vesicle (GUV) was used to monitor the kinetic binding process of antibiotic–membrane interactions in an aqueous solution. Both penicillin and sulbactam are found positioned outside the model membrane, while cholesterol inserts perpendicularly into the hydrophobic region of the membrane in aqueous solution. This result provides structural insights for understanding the antibiotic–membrane interaction and the mechanism of antibiotics

Promoter Polymorphism G-6A, which Modulates Angiotensinogen Gene Expression, Is Associated with Non-Familial Sick Sinus Syndrome

Background: It is well known that familial sick sinus syndrome (SSS) is caused by functional alterations of ion channels and gap junction. Limited information is available on the mechanism of age-related non-familial SSS. Although evidence shows a close link between arrhythmia and the renin-angiotensin system (RAS), it remains to be determined whether the RAS is involved in the pathogenesis of non-familial SSS. Methods: In this study, 113 patients with documented non-familial SSS and 125 controls were screened for angiotensinogen (AGT) and gap junction protein-connexin 40 (Cx40) promoter polymorphisms by gene sequencing, followed by an association study. A luciferase assay was used to determine the transcriptional activity of the promoter polymorphism. The interaction between nuclear factors and the promoter polymorphism was characterized by an electrophoretic mobility shift assay (EMSA). Results: Association study showed the Cx40 -44/+71 polymorphisms are not associated with non-familial SSS; however, it indicated that four polymorphic sites at positions -6, -20, -152, and -217 in the AGT promoter are linked to non-familial SSS. Compared to controls, SSS patients had a lower frequency of the G-6A AA genotype (OR 2.88, 95% CI 1.58–5.22, P = 0.001) and a higher frequency of the G allele at -6 position (OR 2.65, 95% CI 1.54–4.57, P = 0.0003). EMSA and luciferase assays confirmed that nucleotide G at position -6 modulates the binding affinity with nuclear factors and yields a lower transcriptional activity than nucleotide A (P,0.01). Conclusion: G-6A polymorphism, which modulates the transcriptional activity of the AGT promoter, may contribute to nonfamilial SSS susceptibility

An Intelligent Optimization System of Micro Electroforming Process for the Mesh Filter

This research integrates the Taguchi method, analysis of variables (ANOVA), back-propagation neural networks (BPNN), and hybrid PSO-GA to develop an intelligent optimization system of micro electroforming process for the mesh filter. From the outset of discussions with engineers in terms of past related literature survey of the micro electroforming process, the quality characteristics of product and control variables can be well ascertained, then transforming the problem of multiple quality characteristics into a single quality characteristic via the Taguchi method and ANOVA. However, the optimal parameter settings (solution) through the Taguchi experimental planning is still belong to a discrete optimal solution which is impossible to meet the process stability and quality goals. Therefore, this study first identifies the initial weight of BPNN，using hybrid PSO-GA with multilayer perceptron (MLP)，in order to improve training efficiency and precision of BPNN. Furthermore, the study constructs the signal-to-noise (S/N) ratios (BPNNS/N) and quality predictors (BPNNQ) based on hybrid PSO-GA and BPNN with the experimental data. The optimal parameter settings are obtained through a combination of BPNNS/N and BPNNQ with modified PSO-GA. Finally, confirmation experiments are performed to assess the effectiveness of the proposed system. The results show that the proposed system can create the best performance, and the optimal parameters not only enhance the stability in the micro electro forming process but also effectively improve the product quality

Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus), Prevents Platelet Activation in Human Platelets

Xanthohumol is the principal prenylated flavonoid in the hop plant (Humulus lupulus L.). Xanthohumol was found to be a very potent cancer chemopreventive agent through regulation of diverse mechanisms. However, no data are available concerning the effects of xanthohumol on platelet activation. The aim of this paper was to examine the antiplatelet effect of xanthohumol in washed human platelets. In the present paper, xanthohumol exhibited more-potent activity in inhibiting platelet aggregation stimulated by collagen. Xanthohumol inhibited platelet activation accompanied by relative [Ca2+]i mobilization, thromboxane A2 formation, hydroxyl radical (OH●) formation, and phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), and Akt phosphorylation. Neither SQ22536, an inhibitor of adenylate cyclase, nor ODQ, an inhibitor of guanylate cyclase, reversed the xanthohumol-mediated inhibitory effect on platelet aggregation. Furthermore, xanthohumol did not significantly increase nitrate formation in platelets. This study demonstrates for the first time that xanthohumol possesses potent antiplatelet activity which may initially inhibit the PI3-kinase/Akt, p38 MAPK, and PLCγ2-PKC cascades, followed by inhibition of the thromboxane A2 formation, thereby leading to inhibition of [Ca2+]i and finally inhibition of platelet aggregation. Therefore, this novel role of xanthohumol may represent a high therapeutic potential for treatment or prevention of cardiovascular diseases