Chao Lv

A Nonaqueous Lyotropic Liquid Crystal Fabricated by a Polyoxyethylene Amphiphile in Protic Ionic Liquid

The aggregation behaviors of oleyl polyoxyethylene (10) ether, Brij 97, in room temperature ionic liquids, ethylammonium nitrate (EAN), pyrrolidinium nitrate ([Pyrr][NO(3)]), ethylammonium butyrate (EAB), 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF(6)]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]), have been investigated. Only in the Brij 97/EAN binary system is the hexagonal liquid crystalline phase formed, and its ordering is found to decrease with increasing temperature. The lattice spacing values measured from the small-angle X-ray scattering (SAXS) shrink with reduction of ionic liquid content at room temperature. The general rules for aggregate formation in these ionic liquids are discussed and compared with that in water. A degraded ability to produce the ordered self-assembly of Brij 97 from H(2)O to EAN to [Bmim][PF(6)], [Bmim][BF(4)], [Pyrr][NO(3)], and EAB is found and analyzed based on the molecular packing and Gordon parameters and also hydrogen-bonding or solvophobic interactions. Steady-shear rheological measurements combined with the frequency sweep data indicate the highly viscoelastic nature of this liquid crystalline phase.

Isolation and Asymmetric Total Synthesis of Perforanoid A

A novel limonoid, perforanoid A, was isolated, and an asymmetric total synthesis was achieved in 10 steps. The key steps are chiral tertiary aminonaphthol mediated enantioselective alkenylation of an aldehyde to an allylic alcohol, Pd-catalyzed coupling of the allylic alcohol with vinyl ether to form the γ-lactone ring, and cyclopentenone ring formation through a Rh-catalyzed Pauson-Khand reaction. Preliminary studies show that perforanoid A is cytotoxic towards HEL, K562, and CB3 tumor cell lines.

Cytosporone B, an Inhibitor of the Type III Secretion System of Salmonella enterica Serovar Typhimurium

ABSTRACT Bacterial virulence factors have been increasingly regarded as attractive targets for development of novel antibacterial agents. Virulence inhibitors are less likely to generate bacterial resistance, which makes them superior to traditional antibiotics that target bacterial viability. Salmonella enterica serovar Typhimurium, an important food-borne human pathogen, has type III secretion system (T3SS) as its major virulence factor. T3SS secretes effector proteins to facilitate invasion into host cells. In this study, we identified several analogs of cytosporone B (Csn-B) that strongly block the secretion of Salmonella pathogenicity island 1 (SPI-1)-associated effector proteins, without affecting the secretion of flagellar protein FliC in vitro. Csn-B and two other derivatives exhibited a strong inhibitory effect on SPI-1-mediated invasion to HeLa cells, while no significant toxicity to bacteria was observed. Nucleoid proteins Hha and H-NS bind to the promoters of SPI-1 regulator genes hilD, hilC, and rtsA to repress their expression and consequently regulate the expression of SPI-1 apparatus and effector genes. We found that Csn-B upregulated the transcription of hha and hns, implying that Csn-B probably affected the secretion of effectors through the Hha–H-NS regulatory pathway. In summary, this study presented an effective SPI-1 inhibitor, Csn-B, which may have potential in drug development against antibiotic-resistant Salmonella.

Chemiluminescence determination of metoclopramide

ABSTRACT A chemiluminescence (CL) system for metoclopramide combined with a flow-injection system is presented in this paper. It is based on CL produced by the oxidation of metoclopramide by permanganate. It was found that formaldehyde could highly enhance the CL intensity. The method permits the determination of metoclopramide over a concentration range of 0.06–60 µg/mL with the detection limit (signal/noise) of 0.03 µg/mL. The relative standard deviation (RSD) for 2 µg/mL metoclopramide standard solution was 1.6% (n = 11). The method has been applied successfully to the determination of metoclopramide in tablets and injections.

UA-MAC: An Underwater Acoustic Channel Access Method for Dense Mobile Underwater Sensor Networks

The long propagation delay and low data rate characteristics of acoustic communication attach many challenges to underwater wireless sensor networks. In this paper, a TDMA based underwater acoustic channel access method (UA-MAC) is proposed mainly to improve channel utilization in dense mobile underwater wireless sensor networks (MUWSN). In UA-MAC, the time slot of each node accessing to the acoustic channel is assigned according to a preverified template, which aims to minimize amount of slots so as to decrease the end-to-end delay. In addition, a piggyback based protocol is implemented to synchronize and schedule the network. The simulation results show that UA-MAC is much superior to common TDMA in throughput, channel utilization, and end-to-end delay especially in dense scenario. Based on the low-power low-cost underwater acoustic nodes we developed, the experiments were carried out to validate the proposed UA-MAC.

Thermo-sensitive amphiphilic supramolecular assembly based on cyclodextrin inclusion

The ionic self-assembled organic microrods are obtained through complexing two functional molecules, sodium deoxycholate and 1-adamantanamine hydro-chloride. Meanwhile, the amphiphilicity of the complex could be changed by a supramolecular approach with cyclodextrin (CD) inclusion to obtain a thermo-sensitive system. The microrod morphology and structure are characterized by optical microscopy, scanning electron microscopy, single crystal analysis and X-ray powder diffraction. The mechanism of thermo-sensitivity induced by beta-CD inclusion complex is discussed in view of dynamic balance between the host beta-CDs and guest molecules. Experimental results indicate the feasibility of single crystal culture in ionic self-assembly and potential application of CDs in thermo-sensitive supramolecular systems.

Research on Middleware of Automatic Finding and Integration of Deep Web Query Interface

In this paper, the Deep Web technologies are analyzed and discussed, and a middleware of finding and integrating Deep Web query interface automatically is proposed. This middleware extracts the attributes of query interfaces and judges them whether interfaces of Web databases by computing the similarity between them; it can also cluster query interfaces and construct an integrated query interface. This middleware provides a practical tool for finding query interface automatically and constructing integrated query interfaces.

A symbol timing recovery algorithm of M-PSK signals for burst modem applications with small packet size

Feedforward symbol timing recovery techniques are particularly important for initial acquisition in burst modems. However, these techniques either have large calculation burden or sensitive to frequency offsets. In this paper, we proposed an efficient symbol timing recovery algorithm of MPSK signals named OMQ (Ordered Maximum power using Quadratic approximation partially) algorithm which is based on the Quadratic Approximation (QA) algorithm. We used ordered statistic sorting method to reduce the computational complexity further, meanwhile maximum mean power principle was used to decrease frequency offset sensitivity. The proposed algorithm adopts estimation-down sampling structure which is suitable for small packet size transmission. The results show that, while comparing with the QA algorithm, the computational complexity is reduced by 75% at most when 8 samples per symbol are used. The proposed algorithm shows better performance in terms of the jitter variance and sensitivity to frequency offsets.