Unidirectional reconstitution and characterization of purified Na+/proline transporter of Escherichia coli

A simple approach for large-scale purification and unidirectional reconstitution of the Na+/proline transporter of Escherichia coli (PutP) is described. The procedure is based on the insertion of a highly polar peptide composed of 17 amino acids including a 6His tag at the C-terminus of the transporter. Purification of the hybrid protein is achieved by Ni+-NTA affinity (purity >95%) and ion exchange chromatography (purity >99%). The purified transporter is reconstituted into preformed, detergent-destabilized liposomes. Detergent is removed slowly by adsorption to polystyrene beads. The highest activities [Vmax = 1.1 x 10(3) nmol min-1 (mg of protein)-1] are measured when Triton X100 is used for liposomes destabilization at a concentration corresponding to the onset of lipid solubilization. Site-directed labeling of PutP and site-specific proteolytic cleavage indicate that the transporter is inserted into proteoliposomes in an inside-out orientation. Reconstituted PutP is able to accumulate proline against a concentration gradient in the presence of an inwardly directed electrochemical Na+ or Li+ gradient, while a pH gradient does not affect transport. The apparent proline affinity of PutP in proteoliposomes is similar to the value determined with intact cells. Interestingly however, the apparent Na+ affinity of reconstituted PutP is reduced by a factor of about 25 compared to cells, suggesting a lower cation affinity on the cytosolic side of PutP relative to the outside.     

Mixed-dye staining method for protein detection in polyacrylamide gel electrophoresis using calconcarboxylic acid and rhodamine B

We have developed a new mixed-dye protein staining method that is simple, rapid, and sensitive. A freshly prepared mixture of calconcarboxylic acid (NN, 0.02%) and rhodamine B (RB, 0.04%) in 40% methanol/7% acetic acid, was used as a staining solution. RB acts as an auxiliary agent to inhibit the binding of NN to the gel matrix, reducing the background staining and therefore enhancing the protein staining by NN. This mixed-dye staining method reduces the total staining and destaining time to less than an hour, and increases the sensitivity to 25 ng of bovine serum albumin, which is greater than the 100 ng sensitivity limit of Coomassie Brilliant Blue R-250 (CBBR) staining.     

Prospects for magnetization of large PM rotors: conclusions from a development case study

A development feasibility study has been conducted for magnetizing the rotor of a 1.7 MVA, 20-r/min, permanent magnets (PMs) excited synchronous wind turbine generator. Various technical problem areas and their likely influence on the overall design concept, are reviewed. Thus, some particularly important problems are identified: KERI's conventional facilities ensure sufficient energy for magnetizing, pair by pair, of all the PMs of the rotor. A rotor and inductor optimal arrangement for a magnetizing system's configuration is required in order to avoid a wrong, strong magnetization of the neighboring poles. It is also necessary to take into account the mechanical strength of the magnetizing inductor winding to withstand electromagnetic forces. This paper presents the result of the analytical calculation of such a specialized inductor and a PC Spice-based software simulation of the magnetizer circuit; finally, a transient finite element method (FEM) simulation of the inductors connected by the external electric circuit has been done. All three methods confirm the possibility for a successful magnetization, pair by pair, of all rotor poles. Design proposals are detailed and conclusions are relevant for magnetizing large rotors with surface-mounted PMs in general.     

Design of concatenated space-time block codes using signal space diversity and the Alamouti scheme

New full-rate space-time block codes achieving full diversity for quadrature amplitude modulation (QAM) using an even number of transmit antennas over quasi-static Rayleigh fading channels are proposed. The proposed codes are constructed by serially concatenating unitary rotating precoders with the Alamouti code. The coding advantage of the proposed code for a codeword pair corresponding to any distinct input pair is shown to be greater than or equal to that of the ST-CR code.     

Experimental and Numerical Studies in a Vortex Tube

The present investigation deals with the study of the internal flow phenomena of the counter flow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.     

An oversampled digital PWM linearization technique for digital-to-analog conversion

An algorithmic-based linearization process for uniformly sampled digital pulsewidth modulation (PWM) is described. It is shown that linearization of the intrinsic distortion resulting in uniformly sampled PWM can be achieved by using a fractional delay digital filter embedded within a noise shaping re-quantizer. A technique termed direct PWM mapping is proposed as a pre-compensation filter scheme for applications in high-resolution digital-to-analog conversion.