Investigation of factors in improving Agrobacterium-mediated gene transfer in Ruellia tuberosa L. and evaluation of α-glucosidase inhibitory activity in established hairy roots

Ruellia tuberosa (family Acanthaceae) is widely known in traditional medicine in Asian countries for the treatment of diabetes and other diseases. Its roots were demonstrated to possess a hypoglycemic ability in diabetic animal models. In this study, an original induced procedure was investigated to establish hairy root (HR) from R. tuberosa. With the aim of increasing the transformation rate, some induced factors (acetosyringone (AS) dosage, type of explant, age, infection time, bacterial density, co-cultivation duration) were individually examined. As a result, an improved procedure was implemented: ten-day-old in vitro cotyledon explants were injured and then immersed in the bacterial suspension (OD600 nm = 0.4) added 200 µM AS during 10 min. The infected explants were co-cultivated for 4 days in the Murashige & Skoog (MS) medium before transferring to the medium containing cefotaxime for bacterial elimination. After thirty days of culture, the improved procedure revealed a synergistic effect by enhancing the rooting rate and number of secondary roots per explant up to 4.4- and 8.0-fold, respectively, in comparison with the original procedure. The R. tuberosa HR was then cultured in liquid MS medium and achieved the highest biomass production at the late exponential growth phase (3rd week). Its ethanol extract was also higher 2.0-fold in α-glucosidase inhibitory activity than that of the natural root. In conclusion, the α-glucosidase inhibitory activity of HR inducing by the improved procedure may offer an effective and reliable substitute for the utilization of this herbal plant

Distinct binding interactions of α5β1-integrin and proteoglycans with fibronectin

Dynamic single molecule force spectroscopy was performed to monitor the unbinding of fibronectin with the proteoglycans syndecan-4 and decorin, and to compare this with the unbinding characteristics of α5β1-integrin. A single energy barrier was sufficient to describe the unbinding of both syndecan-4 and decorin from fibronectin, while two barriers were observed for the dissociation of α5β1-integrin from fibronectin. The outer (high affinity) barrier in the interactions of fibronectin with α5β1-integrin and syndecan-4 are characterized by larger barrier heights and widths, and slower dissociation rates than those of the inner (low affinity) barrier in the interactions of fibronectin with α5β1-integrin and decorin. These results indicate that syndecan-4 and (ultimately) α5β1-integrin have the ability to withstand deformation in their interactions with fibronectin, while the decorin-fibronectin interaction is considerably more brittle

Phenomenology of the superconducting state in Sr2RuO4

The symmetry of the superconducting phase of Sr2RuO4 is identified as the odd-parity pairing state d(k)=\hat{z}(k_x \pm i k_y) based on recent experiments. The experimental evidence for the so-called orbital dependent superconductivity leads to a single-band description of superconductivity based on spin fluctuation mechanism. It is shown that the state \hat{z}(k_x \pm i k_y) can be stabilized by the spin fluctuation feedback mechanism analogous to the A-phase in 3He and by spin-orbit coupling effects.Comment: 7 pages, 1 figure, to be published in Proc. of the conference "Anomalous Complex Superconductors" (Crete, 1998

Modified Norris–Landzberg Model and Optimum Design of Temperature Cycling ALT

Accelerated life testing (ALT) is an effective way to assess the lifetime of a product. Due to the complex nature of its testing profile, it is difficult to carry out temperature cycling ALT. This paper establishes a modified Norris–Landzberg model as acceleration model, and proposes the optimum design method of temperature cycling ALT. First, the FEA method is used to study the influence of temperature cycling profile parameters on the thermal fatigue life of 63Sn–37Pb solder joints. Then, a modified Norris–Landzberg model is proposed by introducing ramp time and dwell time with an added weight value. Finally, the temperature cycling ALT is regarded as a special multi-stress ALT to study its optimum design method. The uniform design theory is used to determine the combined mode. The optimum model is established with the objective of minimizing the asymptotic variance of the estimation of median lifetime under normal use conditions, and the simulation example shows the workability of the proposed method

The effect of the annealing temperature on the local distortion of La0.67_{0.67}Ca0.33_{0.33}MnO3_3 thin films

Mn $K$-edge fluorescence data are presented for thin film samples (3000~\AA) of Colossal Magnetoresistive (CMR) La$_{0.67}$Ca$_{0.33}$MnO$_3$: as-deposited, and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in terms of three contributions: static, phonon, and an extra, temperature-dependent, polaron term. The polaron distortion is very small for the as-deposited sample and increases with the annealing temperature. In contrast, the static distortion in the samples decreases with the annealing temperature. Although the local structure of the as-deposited sample shows very little temperature dependence, the change in resistivity with temperature is the largest of these three thin film samples. The as-deposited sample also has the highest magnetoresistance (MR), which indicates some other mechanism may also contribute to the transport properties of CMR samples. We also discuss the relationship between local distortion and the magnetization of the sample.Comment: 11 pages of Preprint format, 8 figures in one tar fil

Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4

The transverse and longitudinal in-plane magnetoresistances in the normal state of superconducting Sr2RuO4 single crystals have been measured. At low temperatures, both of them were found to be positive with a linear magnetic-field dependence above a threshold field, a result not expected from electronic band theory. We argue that such behavior is a manifestation of a novel coherent state characterized by a spin pseudo gap in the quasi-particle excitation spectrum in Sr2RuO4.Comment: 4 pages + 5 figure

Phonon-assisted resonant tunneling of electrons in graphene–boron nitride transistors

We observe a series of sharp resonant features in the differential conductance of graphene-hexagonal boron nitride-graphene tunnel transistors over a wide range of bias voltages between 10 and 200 mV. We attribute them to electron tunneling assisted by the emission of phonons of well-defined energy. The bias voltages at which they occur are insensitive to the applied gate voltage and hence independent of the carrier densities in the graphene electrodes, so plasmonic effects can be ruled out. The phonon energies corresponding to the resonances are compared with the lattice dispersion curves of graphene–boron nitride heterostructures and are close to peaks in the single phonon density of states

Security and Privacy Issues in Wireless Mesh Networks: A Survey

This book chapter identifies various security threats in wireless mesh network (WMN). Keeping in mind the critical requirement of security and user privacy in WMNs, this chapter provides a comprehensive overview of various possible attacks on different layers of the communication protocol stack for WMNs and their corresponding defense mechanisms. First, it identifies the security vulnerabilities in the physical, link, network, transport, application layers. Furthermore, various possible attacks on the key management protocols, user authentication and access control protocols, and user privacy preservation protocols are presented. After enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. Comparative analyses are also presented on the security schemes with regards to the cryptographic schemes used, key management strategies deployed, use of any trusted third party, computation and communication overhead involved etc. The chapter then presents a brief discussion on various trust management approaches for WMNs since trust and reputation-based schemes are increasingly becoming popular for enforcing security in wireless networks. A number of open problems in security and privacy issues for WMNs are subsequently discussed before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the author's previous submission in arXiv submission: arXiv:1102.1226. There are some text overlaps with the previous submissio

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

B^0-\bar{B}^0 mixing and B \to X_s \gamma decay in the third type 2HDM: effects of NLO QCD contributions

In this paper, we calculated the next-to-leading order (NLO) new physics contributions to the mass splitting \dmd and the branching ratio \brbxsga induced by the charged Higgs loop diagrams in the third type of two-Higgs-doublet models (model III) and draw the constraints on the free parameters of model III. For the model III under consideration, we found that (a) an upper limit |\ltt|\leq 1.7 is obtained from the precision data of \dmd=0.502 \pm 0.007 ps^{-1}, while |\ltt| \approx 0.5 is favored phenomenologicaly; (b) for $B \to X_s \gamma$ decay, the NLO QCD contributions tend to cancel the LO new physics contributions; (c) a light charged Higgs boson with a mass around or even less than 200 GeV is still allowed at NLO level by the measured branching ratio \brbxsga: numerically, 188 \leq \mh \leq 215 GeV for (|\ltt|,|\lbb|)=(0.5,18); (d) the NLO QCD contributions tend to cancel the LO contributions effectively, the lower limit on \mh is consequently decreased by about 200 GeV; (e) the allowed region of \mh will be shifted toward heavy mass end for a non-zero relative phase $\theta$ between the Yukawa couplings \ltt and \lbb. The numerical results for the conventional model II are also presented for the sake of a comparison.Comment: 42 pages, 18 eps figures, Revtex, new references adde