Semileptonic decays of BcB_c meson to S-wave charmonium states in the perturbative QCD approach

Inspired by the recent measurement of the ratio of $B_c$ branching fractions to $J/\psi \pi^+$ and $J/\psi \mu^+\nu_{\mu}$ final states at the LHCb detector, we study the semileptonic decays of $B_c$ meson to the S-wave ground and radially excited 2S and 3S charmonium states with the perturbative QCD approach. After evaluating the form factors for the transitions $B_c\rightarrow P,V$, where $P$ and $V$ denote pseudoscalar and vector S-wave charmonia, respectively, we calculate the branching ratios for all these semileptonic decays. The theoretical uncertainty of hadronic input parameters are reduced by utilizing the light-cone wave function for $B_c$ meson. It is found that the predicted branching ratios range from $10^{-6}$ up to $10^{-2}$ and could be measured by the future LHCb experiment. Our prediction for the ratio of branching fractions $\frac{\mathcal {BR}(B_c^+\rightarrow J/\Psi \pi^+)}{\mathcal {BR}(B_c^+\rightarrow J/\Psi \mu^+\nu_{\mu})}$ is in good agreement with the data. For $B_c\rightarrow V l \nu_l$ decays, the relative contributions of the longitudinal and transverse polarization are discussed in different momentum transfer squared regions. These predictions will be tested on the ongoing and forthcoming experiments.Comment: 12 pages, 3 figures, 5 table

Current rectification by asymmetric molecules: An ab initio study

We study current rectification effect in an asymmetric molecule HOOC-C$_6$H$_4$-(CH$_2$)$_n$ sandwiched between two Aluminum electrodes using an {\sl ab initio} nonequilibrium Green function method. The conductance of the system decreases exponentially with the increasing number $n$ of CH$_2$. The phenomenon of current rectification is observed such that a very small current appears at negative bias and a sharp negative differential resistance at a critical positive bias when $n\ge 2$. The rectification effect arises from the asymmetric structure of the molecule and the molecule-electrode couplings. A significant rectification ratio of $\sim$38 can be achieved when $n=5$.Comment: to appear in J. Chem. Phy

Construction of a Fish-like Robot Based on High Performance Graphene/PVDF Bimorph Actuation Materials.

Smart actuators have many potential applications in various areas, so the development of novel actuation materials, with facile fabricating methods and excellent performances, are still urgent needs. In this work, a novel electromechanical bimorph actuator constituted by a graphene layer and a PVDF layer, is fabricated through a simple yet versatile solution approach. The bimorph actuator can deflect toward the graphene side under electrical stimulus, due to the differences in coefficient of thermal expansion between the two layers and the converse piezoelectric effect and electrostrictive property of the PVDF layer. Under low voltage stimulus, the actuator (length: 20 mm, width: 3 mm) can generate large actuation motion with a maximum deflection of about 14.0 mm within 0.262 s and produce high actuation stress (more than 312.7 MPa/g). The bimorph actuator also can display reversible swing behavior with long cycle life under high frequencies. on this basis, a fish-like robot that can swim at the speed of 5.02 mm/s is designed and demonstrated. The designed graphene-PVDF bimorph actuator exhibits the overall novel performance compared with many other electromechanical avtuators, and may contribute to the practical actuation applications of graphene-based materials at a macro scale

Effects of relative orientation of the molecules on electron transport in molecular devices

Effects of relative orientation of the molecules on electron transport in molecular devices are studied by non-equilibrium Green's function method based on density functional theory. In particular, two molecular devices, with the planer Au$_{7}$ and Ag$_{3}$ clusters sandwiched between the Al(100) electrodes are studied. In each device, two typical configurations with the clusters parallel and vertical to the electrodes are considered. It is found that the relative orientation affects the transport properties of these two devices completely differently. In the Al(100)-Au$_7$-Al(100) device, the conductance and the current of the parallel configuration are much larger than those in the vertical configuration, while in the Al(100)-Ag$_{3}$-Al(100) device, an opposite conclusion is obtained

Assessment of diagnostic value of age for meridional amblyopia with Logistic regression and receiver operating characteristic curve

AIM: To assess the diagnostic value of age for meridional amblyopia by Logistic regression and receiver operating characteristic(ROC)curve.<p>METHODS: A total of 1 005 children(1 910 eyes)with unknown ocular abnormalities other than with-the-rule astigmatism(aged 4-8 years)were recruited. Astigmatism >or =1.00D and sphere < or = 3.00D were present in one or both eyes. The difference of sphere between both eyes was less 1.50D. The difference of astigmatism between both eyes was less 1.00D. All astigmatism was calculated by the absolute value. By analyzing age, sex, astigmatism type, diopter of cylinder and diopter of sphere with Logistic regression, two mathematical models were established. Then the diagnostic efficacy of the model was assessed using the ROC curve.<p>RESULTS: The model 1 included 4 parameters(sex, astigmatism type, diopter of cylinder and diopter of sphere). The model 2 included 5 parameters(the 4 parameters of the model 1 adding age). Using Logistic regression, the diopter of cylinder had an influence on the diagnosis of meridional amblyopia in two models. In model 2, age was another influencing factor on the diagnosis of meridional amblyopia. The model 1 area under ROC curve(AUC)was 0.64, and the model 2 was 0.74. The area of model 2 was greater than the model 1. There was statistical difference in the AUC of two models(<i>P</i><0.05).<p>CONCLUSION: Age might be an influential factor on the diagnosis of meridional amblyopia using Logistic regression and ROC curve

Milk fat globule membrane protein promotes C2C12 cell proliferation through the PI3K/Akt signaling pathway

Milk fat globule membrane (MFGM) protein is known to have several health benefits, including an anti-sarcopenia effect; however, its mechanism is unclear. The aim of this study was to investigate the potential mechanism of action of the MFGM protein. The MFGM protein was extracted and separated into 4 fractions, and Fraction 2 (57 % of total MFGM) demonstrated the greatest effect on C2C12 cell proliferation. Milk fat globule-EGF factor 8 (MFG-E8) accounted for 82.35 % of the MFGM protein. The effects of whole Fraction 2 (100 μg/mL, 200 μg/mL and 300 μg/mL) on cell proliferation and morphology were measured. Using qRT-PCR or a Western blot assay, several regulatory factors, e.g., PI3K P85α, p-pI3K p85α (Tyr 508), Akt, p-Akt (Ser 473), mTOR and p-mTOR (Ser 2448), were measured in cells incubated with 200 μg/mL of Fraction 2 with or without wortmannin. The results demonstrated that Fraction 2 induced C2C12 cell proliferation in a dose-dependent manner, upregulated the mRNA expression of mTOR and p70S6K, and activated PI3K, Akt, mTOR and P70S6K phosphorylation; however, Fraction 2 inhibited FOXO3a and 4E-BP. The results demonstrate that the MFGM protein, predominantly MFG-E8, promotes cell proliferation through the PI3K/Akt/mTOR signaling pathway. This study elucidated the molecular mechanism of the MFGM protein, primarily MFG-E8, in promoting C2C12 cell proliferation via the PI3K/Akt/mTOR/P70S6K signal pathway