Study of the weak annihilation contributions in charmless Bs→VVB_s\to VV decays

In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless $B_s\to VV$ (where $V$ stands for a light vector meson) decays, we perform the $\chi^2$-analyses for the end-point parameters within the QCD factorization framework, under the constraints from the measured $\bar B_{s}\to$$\rho^0\phi$, $\phi K^{*0}$, $\phi \phi$ and $K^{*0}\bar K^{*0}$ decays. The fitted results indicate that the end-point parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless $B\to PP$ and $PV$ (where $P$ stands for a light pseudo-scalar meson) decays observed in the previous work. Moreover, the abnormal polarization fractions $f_{L,\bot}(\bar B_{s}\to K^{*0}\bar K^{*0})=(20.1\pm7.0)\%\,,(58.4\pm8.5)\%$ measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of $\bar B_{s}\to\phi K^{*0}$ decay exhibits a tension between the data and theoretical result, which dominates the contributions to $\chi_{\rm min}^2$ in the fits. Using the fitted end-point parameters, we update the theoretical results for the charmless $B_s\to VV$ decays, which will be further tested by the LHCb and Belle-II experiments in the near future.Comment: 31 pages, 4 figures, 6 table

High cycle fatigue and ratcheting interaction of laser powder bed fusion stainless steel 316L:Fracture behaviour and stress-based modelling

Variations in the physical and mechanical properties of parts made by laser power bed fusion (L-PBF) could be affected by the choice of processing or post-processing strategies. This work examined the influence of build orientation and post-processing treatments (annealing or hot isostatic pressing) on the fatigue and fracture behaviours of L-PBF stainless steel 316L in the high cycle fatigue region, i.e. 104 – 106 cycles. Experimental results show that both factors introduce significant changes in the plastic deformation properties, which affect fatigue strength via the mechanism of fatigue-ratcheting interaction. Cyclic plasticity is characterised by hardening, which promotes mean stress insensitivity and improved fatigue resistance. Fatigue activities, involving the initiation of crack at defects and microstructural heterogeneities, are of greater relevance to the longer life region where the global deformation mode is elastic. As the simultaneous actions of ratcheting and fatigue generate complex nonlinear interactions between the alternating stress amplitude and mean stress, the fatigue properties could not be effectively predicted using traditional stress-based models. A modification to the Goodman relation was proposed to account for the added effects of cyclic plasticity and was demonstrated to produce good agreement with experimental results for both cyclic hardening and softening materials.EDB (Economic Devt. Board, S’pore)Accepted versio

Codon optimization, constitutive expression and antimicrobial characterization of hen egg white lysozyme (HEWL) in Pichia pastoris

Fusarium oxysporum (F. oxysporum) and Verticillium dahlia (V. dahlia) causes severe cotton disease in China and other cotton-producing countries. Hen egg white lysozyme (HEWL) has antimicrobial properties. In this study, a codon-optimized HEWL gene was synthesized and cloned into the yeast expression vector, pPIC9K, under the control of the Pichia pastoris (P. pastoris) glyceraldehyde-3-phosphate dehydrogenase promoter (pGAP). Results showed that codon-optimized HEWL (oHEWL) was constitutively expressed. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicated that the molecular weight of recombinant HEWL (roHEWL) was 14 kDa which corresponds to the standard HEWL. The expression of the roHEWL reached to 54 mg/L. Activity of the roHEWL was 1680 U/mL. The optimum pH for roHEWL was from 6.0 to 7.0, and the optimum temperature was 55°C. In vitro antimicrobial activity assay revealed that roHEWL can lyse cell walls of the gram positive bacteria, Micrococcus lysodeikticus (M. lysodeikticus). In vivo studies showed that it inhibits plant fungi, F. oxysporum and V. dahlia. roHEWL anti-fungal properties might be useful for future genetically engineered cotton plant resistance against pathogenic fungal disease.Keywords: Hen egg white lysozyme (HEWL), antimicrobial activity, glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter, codon optimization, constitutive expressio

Selective malaria antibody screening among eligible blood donors in Jiangsu, China

The risk of transfusion-transmitted malaria is a major concern in many countries. This study investigated the prevalence of malaria antibodies and parasitemia in eligible blood donors in Jiangsu, in Eastern China. Malaria antibodies were detected in 2.13% of the 704 plasma samples studied. We found that the prevalence of malaria antibodies was not significantly correlated with gender, occupation and frequency of donation, but it increased with age. No Plasmodium was observed in red blood cells and no Plasmodium DNA was detected in any of the antibody-positive samples. The prevalence of malaria antibodies was not higher than expected in Eastern China

Fatigue and Fracture Behaviour of Laser Powder Bed Fusion Stainless Steel 316L: Influence of Processing Parameters

The laser powder bed fusion (L-PBF) process involves a large number of processing parameters. Extending the intricate relationship between processing and structure to mechanical performance is essential for structural L-PBF materials. The high cycle fatigue properties of L-PBF parts are very sensitive to process-induced porosities which promote premature failure through the crack initiation mechanisms. Results from this work show that for stainless steel 316L, porosity does not impinge on the high cycle fatigue properties when processing is kept within a ±30% tolerance band. In this ‘optimum’ processing region, crack initiation takes place due to defects at the solidification microstructure level. Beyond the ‘optimum’ processing region, over-melting and under-melting can lead to porosity-driven cracking and inferior fatigue resistance. In addition, regardless of the processing condition, fatigue resistance was found to follow a direct linear relationship with ductility and tensile strength in the low and high stress fatigue regimes respectively.Economic Development Board (EDB)Accepted versionThis work was supported by the Singapore Economic Development Board (EDB) Industrial Postgraduate Programme (IPP)

Animal personality can modulate sexual conflict over offspring provisioning

Sexual conflict over parental investment is widespread among species with biparental care. Studies have indicated that a high degree of behavioural similarity between the two parents can increase offspring survival; however, it remains unclear how sexual conflict over parental care is resolved. In this study, we examined whether similarity of personality traits between the two parents plays an important role in affecting the provisioning behaviour of each sex in a wild population of the chestnut thrush, Turdus rubrocanus. First, as expected, the mating pairs with more similar personality traits had higher provisioning rates than those pairs with dissimilar traits. Moreover, we found that the similarity of personality traits can modulate the sexual conflict over provisioning in this species, as both parents with more similar partners had relatively higher and less divergent provisioning rates. A partner removal experiment revealed how the sole female or male parent responded when the level of conflict over care increased (the removed partner does not provide any care). The majority of males always reduced their provisioning investment, while females’ decisions depended on the degree of similarity with their partners. Females compensated by provisioning more frequently in pairs of similar personality traits (i.e. accepting a high level of conflict), but reduced their provisioning investment in extremely dissimilar pairs. Our results promote a better understanding of the resolution of sexual conflict over provisioning and highlight the evolutionary significance of mating with similar partners based on certain personality traits

Stimulation of cannabinoid receptor 2 (CB(2)) suppresses microglial activation

BACKGROUND: Activated microglial cells have been implicated in a number of neurodegenerative disorders, including Alzheimer's disease (AD), multiple sclerosis (MS), and HIV dementia. It is well known that inflammatory mediators such as nitric oxide (NO), cytokines, and chemokines play an important role in microglial cell-associated neuron cell damage. Our previous studies have shown that CD40 signaling is involved in pathological activation of microglial cells. Many data reveal that cannabinoids mediate suppression of inflammation in vitro and in vivo through stimulation of cannabinoid receptor 2 (CB(2)). METHODS: In this study, we investigated the effects of a cannabinoid agonist on CD40 expression and function by cultured microglial cells activated by IFN-γ using RT-PCR, Western immunoblotting, flow cytometry, and anti-CB(2 )small interfering RNA (siRNA) analyses. Furthermore, we examined if the stimulation of CB(2 )could modulate the capacity of microglial cells to phagocytise Aβ(1–42 )peptide using a phagocytosis assay. RESULTS: We found that the selective stimulation of cannabinoid receptor CB(2 )by JWH-015 suppressed IFN-γ-induced CD40 expression. In addition, this CB(2 )agonist markedly inhibited IFN-γ-induced phosphorylation of JAK/STAT1. Further, this stimulation was also able to suppress microglial TNF-α and nitric oxide production induced either by IFN-γ or Aβ peptide challenge in the presence of CD40 ligation. Finally, we showed that CB(2 )activation by JWH-015 markedly attenuated CD40-mediated inhibition of microglial phagocytosis of Aβ(1–42 )peptide. Taken together, these results provide mechanistic insight into beneficial effects provided by cannabinoid receptor CB(2 )modulation in neurodegenerative diseases, particularly AD