In-silico-mining of small sequence repeats in hydrogenase maturation subunits of E. coli,clostridium, and Rhodobacter

Presently, the world is facing energy crisis so there is a strong need of in silico mining and analysis of potential bacteria leading to renewable energy generation i.e. bio hydrogen production using bio-wastes as substrate. Hydrogenase (Hyd), a key enzyme mediates hydrogen evolution, is supported with multiple maturation proteins like HypA, HypB, HypC, HypD, HypE, HypF, HycE, and Formate dehydrogenase in hydrogen-producing bacteria. Simple sequence repeats (SSRs) are the large source of genetic markers and it contains tandemly repeated short units of 1–6 bp. It is the first time to find out the SSRs (Simple Sequence Repeats) in the hydrogenase maturation protein supported genes (hypABCDEF), hycE and formate dehydrogenase (fdhF), as well as the organization of these gene(s) supported operon, depending on its presence in different hydrogen-producing bacteria i.e. in E. coli, Clostridium and Rhodobacter. Four operons i.e. eco-b2726 (hypABCDE), eco-b2713 (hypF), eco-b2724 (hycE) and eco-b4079 (fdhF) in E. coli; 4 operons i.e. CBO0432 (hypA), cbo-CBO0431 (hypB), cbo-CBO1837 (hypED), and cbo-CBO1837 (hydA) in Clostridium; and 2 operons i.e. rsp- RSP_0503 (hypABCDE) and rsp- RSP_0491 (hypF) in Rhodobacter were used in the current study. In this paper, we have performed an intensive investigation to find out the SSRs in all the above subunits, and it was concluded that dinucleotides were the most frequent repeat class followed by trinucleotides, tetranucleotides, pentanucleotides, and hexanucleotides. A total of 467, 332, and 387 small repeats were detected in entire maturation protein-assisted genes of E. coli, Clostridium, and Rhodobacter respectively. The length of the screened repeats was short owing to the small length of the maturation protein supported genes and none of the long length SSRs was identified in this whole study. It has been concluded that the heptamer (GCCGATC)₂ in fdhF of E. coli, as well as the hexamer (GGGAGT)₂ in hypA of Clostridium, may serve as an ideal marker. We have employed SSRIT (Simple Sequence Repeat Identification Tool) software for isolation of the SSRs. The resulted SSR markers may facilitate in the genetic identification of different potential unknown hydrogen-producing bacteria in a short time.     

Analysis of device performance and thin-film properties of thermally damaged organic light-emitting diodes

This paper reports the variation in the optical and geometrical properties of individual organic layers to be used for thermally damaged top-emission organic light-emitting diodes (TEOLEDs). The copper deposited on the back of TEOLEDs is employed as a thermal facilitator, and a certain thermal damage occurs to the organic layers and devices. The phosphorescent host material 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) is rapidly damaged to a significant extent owing to the low glass transition temperature (T_g), which also changes its optical and geometrical surface properties. Although the optical properties of the hole transport layer, N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) were changed slightly, the surface morphology was changed significantly. Despite having a higher T_g, the exciton blocking layer, tris(4-carbazoyl-9-ylphenyl)amine (TCTA), shows notable variations in optical properties and surface morphology due to heat exposure. Surprisingly, the electroluminescence spectra and micro-cavity are affected by increasing temperature without any considerable changes in device performance. Hence, this study reveals that besides T_g, the surface morphologies and thicknesses of the organic layers are also important factors in the annealing process and play a vital role in causing thermal damage to TEOLEDs.     

Engineering bimetallic PtX (X=Sn,Cu) immobilized on graphene as efficient catalysts: Boosted charge migration and hydrogen evolution

In this work, bimetallic PtX (X = Sn, Cu) decorated graphene nanohybrids (PtX/G) were developed, which showed enhanced photocatalytic hydrogen evolution performance than that of Pt/G in Eosin Y sensitized H₂ production system. The presence of Sn or Cu in PtX/G nanohybrids can remarkably improve the photogenerated charge separation efficiency and contribute to promoting the reduction of protons to molecular hydrogen in comparison to with noble metal Pt. Meanwhile, graphene acted as a more suitable electronic support to accelerate the migration of electrons from sensitizer to catalysts, owing to its higher electron mobility and larger surface area than other supports (such as carbon sphere, Al₂O₃ and SiO₂). The optimal H₂ evolution rate PtSn/G and PtCu/G was about 2.2 and 2.0 times higher than that of Pt/G. The apparent quantum efficiency (AQE) of PtSn/G and PtCu/G reached up to 12.46% and 11.06% under visible light irradiation (λ ≥ 420 nm), respectively.     

Triphenylamine-cored star-shape compounds as non-fullerene acceptor for high-efficiency organic solar cells: Tuning the optoelectronic properties by S/Se-annulated perylene diimide

Three novel star-shaped S/Se-annulated perylene diimide (PDI) small molecule acceptors with triphenylamine as the core, namely TPA-PDI, TPA-PDI-S and TPA-PDI-Se, were designed and synthesized. Using the wideband-gap polymer PDBT-T1 as the donor and Se-annulated perylene diimide (TPA-PDI-Se) as the acceptor, power conversion efficiencies (PCE) of up to 6.10% was achieved, which is 38% higher than the reference of TPA-PDI without heteroatom annulation. Impressively, the S/Se-annulated perylene diimides as acceptors showed high open-circuit voltage (V_OC) of 1.00 V. The high efficiency for TPA-PDI-Se can be attributed to complementary absorption spectra with the donor material, relatively high-lying LUMO level, balanced carrier transport and favorable morphologies. To the best of our knowledge, this PCE of 6.10% is among the highest values based on star-shaped non-fullerene acceptors so far.     

MoS2–Co3S4 hollow polyhedrons derived from ZIF-67 towards hydrogen evolution reaction and hydrodesulfurization

Co–Mo–S based catalysts have promising applications in both hydrogen evolution reaction (HER) and hydrodesulfurization (HDS). Herein, MoS₂–Co₃S₄ hollow polyhedrons have been successfully synthesized by the vulcanization of Mo doped ZIF-67. MoS₂–Co₃S₄ hollow polyhedrons show the superior HER and HDS catalytic activities to pure MoS₂, Co₃S₄ and MoS₂–Co₃S₄ nanoparticles prepared by the traditional coprecipitation methods, owing to the both morphology effect and synergistic effect between Co₃S₄ and MoS₂. DFT calculation studied the activation energies needed by MoS₂ and Co–Mo–S for HER and HDS, respectively. The required activation energies for C–S bond fracture and H₂ generation on Co–Mo–S structure are both obviously lower than that of MoS₂ structure. Our work reported a new method to synthesize Co–Mo–S catalysts with large surface area and numerous active sites, and further experimentally and theoretically proved Co–Mo–S structure had better catalytic activities for both HER and HDS.     

SeRWA: A secure routing protocol against wormhole attacks in sensor networks

A wormhole attack is particularly harmful against routing in sensor networks where an attacker receives packets at one location in the network, tunnels and then replays them at another remote location in the network. A wormhole attack can be easily launched by an attacker without compromising any sensor nodes. Since most of the routing protocols do not have mechanisms to defend the network against wormhole attacks, the route request can be tunneled to the target area by the attacker through wormholes. Thus, the sensor nodes in the target area build the route through the attacker. Later, the attacker can tamper the data, messages, or selectively forward data messages to disrupt the functions of the sensor network. Researchers have used some special hardware such as the directional antenna and the precise synchronized clock to defend the sensor network against wormhole attacks during the neighbor discovery process. In this paper, we propose a Secure Routing protocol against wormhole attacks in sensor networks (SeRWA). SeRWA protocol avoids using any special hardware such as the directional antenna and the precise synchronized clock to detect a wormhole. Moreover, it provides a real secure route against the wormhole attack. Simulation results show that SeRWA protocol only has very small false positives for wormhole detection during the neighbor discovery process (less than 10%). The average energy usage at each node for SeRWA protocol during the neighbor discovery and route discovery is below 25 mJ, which is much lower than the available energy (15 kJ) at each node. The cost analysis shows that SeRWA protocol only needs small memory usage at each node (below 14 kB if each node has 20 neighbors), which is suitable for the sensor network.     

Heteroepitaxial growth of Cu2O films on Nb-SrTiO3 substrates and their photovoltaic properties

In this paper, p-type Cu₂O thin films have been epitaxially grown on n-type semiconducting (001) oriented Nb-SrTiO₃ (NSTO) substrates with different Nb doping concentration by pulsed laser deposition technique. X-ray diffraction and high resolution transmission electron microscopy reveal a cube-on-cube epitaxial relationship between Cu₂O and NSTO. It is found that the deposition temperature, the thickness of Cu₂O films and the Nb doping concentration of NSTO substrates have critical impact on the photovoltaic (PV) properties of the Cu₂O/NSTO heterojunction devices. A maximum PV performance is observed in ITO/Cu₂O/NSTO device when the deposition temperature, film thickness and Nb doping concentration of NSTO are 550 °C, 76 nm, and 0.7 wt% NSTO, respectively. The optimized PV output corresponds to the open circuit voltage, short-circuit current density, fill factor and photovoltaic conversion efficiency about 0.45 V, 1.1 mA/cm², 46% and 0.23%,respectively. This work offers an insight into the strategy for developing and designing novel optoelectronics of NSTO-based oxide heterostructures.     

一种基于代理移动IPv6绑定更新的安全策略

随着移动IPv6技术的不断发展, 对网络的安全性提出了更高的要求。针对代理移动IPv6绑定更新过程当中的安全问题, 结合返回路径可达过程协议和不对称加密技术, 改进了返回路径可达过程协议, 提出一种基于自动密钥认证的返回路由可达过程绑定更新安全机制。分析了方案的安全性, 该方案能有效防止攻击者伪造、篡改绑定更新消息, 杜绝移动主机受到拒绝服务攻击等问题, 提高了通信主机绑定更新过程的安全性。