Bacillus sp. CDB3 possesses a novel eight-gene ars cluster (ars1, arsRYCDATorf7orf8) with some unusual features in regard to expression regulation. This study demonstrated that the cluster is a single operon but can also produce a short three-gene arsRYC transcript. A hairpin structure formed by internal inverted repeats between arsC and arsD was shown to diminish the expression of the full ope...

A model is proposed that accounts for regulation of the histidine operon by a mechanism involving alternative configuration of mRNA secondary structure (the alternative stem model). New evidence for the model includes sequence data on three regulatory mutations. The first (hisO1242) is a mutation that deletes sequences needed to form the attenuator mRNA stem and causes constitutive operon expre...

BACKGROUND Current efforts to develop HIV vaccines that seek to stimulate immune responses have been disappointing, underscoring the inability of natural immune responses to control HIV-1 infection. Here we tested an alternative strategy to induce anti-HIV immune responses by inhibiting a host's natural immune inhibitor. METHODS AND FINDINGS We used small interfering RNA (siRNA) to inhibit su...

[1] Ground-penetrating radar (GPR) has the potential to image the Martian subsurface to give geological context to drilling targets, investigate stratigraphy, and locate subsurface water. GPR depth of penetration depends strongly on the electromagnetic (EM) properties (complex dielectric permittivity, complex magnetic permeability, and DC resistivity) of the subsurface. These EM properties in t...

The severe vibration of a screw compressor outlet piping system caused the fatigue failure of some thermowells and the unscheduled shut down of the system. The main reasons of the abnormal vibration in the outlet piping system were investigated by developing an acoustic model to simulate the gas pulsation and establishing two finite element models to conduct the mechanical vibration analyses. T...

In this paper, measurement and calibration of a high-sensitivity microwave power sensor through an attenuator is performed using direct comparison transfer technique. To provide reliable results, a mathematical model previously derived using signal flow graphs together with non-touching loop rule analysis for the measurement estimate (i.e., calibration factor) and its uncertainty evaluation is ...

A scheme based on polarization modulators to generate Sub-Terahertz (Sub-THz) wave signal with frequency 32-tupling is proposed. The system consists of two subsystems in cascade, and each subsystem 4 paralleled modulators. In this scheme, by properly controlling subsystems, an optical carrier ±16th-order sidebands achieved. Next, adjusting the attenuator phase shifter, can be canceled. Finally,...

This paper describes two Si micromachined structures for sensing beta-particles. The basic device (the micro-detector) includes a square silicon cathode surrounded by a concentric anode, and is formed by stacks of glass and Si wafers. Incident beta-particles ionize the gas encapsulated between the electrodes, resulting in an avalanche current pulse or ‘count’. It is shown experimentally that de...

BACKGROUND L-tryptophan is an aromatic amino acid widely used in the food, chemical and pharmaceutical industries. In Escherichia coli, L-tryptophan is synthesized from phosphoenolpyruvate and erythrose 4-phosphate by enzymes in the shikimate pathway and L-tryptophan branch pathway, while L-serine and phosphoribosylpyrophosphate are also involved in L-tryptophan synthesis. In order to construct...

Based on micromagnetic simulations, we report on a novel magnetic helix in a soft magnetic film that is sandwiched between and exchange-coupled to two hard magnetic layers with different anisotropies. We show that such a confined helix stays stable without the presence of an external magnetic field. The magnetic stability is determined by the energy minimization and is a result of an internal m...