An SMR Topology with Suppressed DC Link Components and Predictive Line Current Waveshaping

A new switch-mode rectifier (SMR) topology has been developed and presented in this paper. Its advantages over other SMR topologies include: high input power factor, minimum input current distortion, elimination of dc link bus electrolytic capacitors, and minimization of switching stresses of high-frequency inverter stage components.     

Biosynthetic requirements for the repair of membrane damage in pressure-treated Escherichia coli.

Cells of Escherichia coli that survived pressure treatment at 400 MPa showed increased sensitivity to sodium deoxycholate or sodium chloride in the plating medium, implying that homeostatic or barrier functions associated with outer and cytoplasmic membranes, respectively, were impaired. Repair of such sublethal membrane damage occurred when cells were incubated at 37 degrees C in tryptone soya broth. Inhibitor studies indicated that repair of cytoplasmic membrane damage was energy-dependent and required RNA and protein synthesis, whereas repair of outer membrane damage occurred with no requirement for energy or RNA or protein synthesis.     

Analysis of supply voltage distortion effects on induction motoroperation

Many modern induction motor applications involve nonsinusoidal voltage supply. Under such operating conditions, the motor performance can be seriously affected while the standard equivalent circuit is no more adequate for the motor analysis. In this paper, a modified equivalent circuit topology is introduced, in order to account for the increased iron losses associated with the leakage flux and saturation in the motor, in presence of low order harmonics in the supply waveform. This equivalent circuit allows the prediction of the motor performance under nonsinusoidal operation. The proposed results have been checked by means of an experimental setup, comprising an inverter-fed 1.5 kW induction motor     

Homing of a group II intron from Lactococcus lactis subsp. lactis ML3

Ll.ltrB is a functional group II intron located within a gene (ltrB) encoding a conjugative relaxase essential for transfer of the lactococcal element pRSO1. In this work, the Ll.ltrB intron was shown to be an independent mobile element capable of inserting into an intronless allele of the ltrB gene. Ll.ltrB was not observed to insert into a deletion derivative of the ltrB gene in which the intron splice site was removed. In contrast, a second vector containing a 271-nucleotide segment of ltrB spanning the Ll.ltrB splice site was shown to be a proficient recipient of intron insertion. Efficient homing was observed in the absence of a functional host homologous recombination system. This work demonstrates that the Ll.ltrB intron is a novel site-specific mobile element in lactococci and that group II intron self-transfer is a mechanism for intron dissemination among bacteria.     

Nested self-similar wrinkling patterns in skins

Stiff thin films on soft substrates are both ancient and commonplace in nature; for instance, animal skin comprises a stiff epidermis attached to a soft dermis. Although more recent and rare, artificial skins are increasingly used in a broad range of applications, including flexible electronics, tunable diffraction gratings, force spectroscopy in cells, modern metrology methods, and other devices. Here we show that model elastomeric artificial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over five orders of magnitude in length scale, ranging from a few nanometres to a few millimetres. We provide a mechanism for the formation of this hierarchical wrinkling pattern, and quantify our experimental findings with both computations and a simple scaling theory. This allows us to harness the substrates for applications. In particular, we show how to use the multigeneration-wrinkled substrate for separating particles based on their size, while simultaneously forming linear chains of monodisperse particles.     

Rapid formation of soft hydrophilic silicone elastomer surfaces

We report on the rapid formation of hydrophilic silicone elastomer surfaces by ultraviolet/ozone (UVO) irradiation of poly(vinylmethyl siloxane) (PVMS) network films. Our results reveal that the PVMS network surfaces render hydrophilic upon only a short UVO exposure time (seconds to a few minutes). We also provide evidence that the brief UVO irradiation treatment does not cause dramatic changes in the surface modulus of the PVMS network. We compare the rate of formation of hydrophilic silicone elastomer surfaces made of PVMS to those of model poly(dimethyl siloxane) (PDMS) and commercial-grade PDMS (Sylgard-184). We find that relative to PVMS, 20 times longer UVO treatment times are needed to oxidize the PDMS network surfaces in order to achieve a comparable density of surface-bound hydrophilic moieties. The longer UVO treatment times for PDMS are in turn responsible for the dramatic increase in surface modulus of UVO treated PDMS, relative to PVMS. We also study the formation of self-assembled monolayers (SAMs) made of semifluorinated organosilane precursors on the PVMS-UVO and PDMS-UVO network surfaces. By tuning the UVO treatment times and by utilizing mono- and tri-functional organosilanes we find that while mono-functionalized organosilanes attach directly to the substrate, SAMs of tri-functionalized organosilanes form in-plane networks on the underlying UVO-modified silicone elastomer surface, even with only short UVO exposure times.     

A SANS Study of Organoclay Dispersions

Small-angle neutron scattering (SANS) is used to investigate the dispersion in toluene of various forms of the complex, Cloisite C15A. Cloisite is a commercially important exchanged clay prepared from montmorillonite and the cation di-tallow ammonium. Points discussed include estimates of the extent to which the complex is dispersed, the amount of organic clay platelet surface layer coverage, and possible network formation of the complex in the solvent. From power-law plots of the scattered neutron intensity versus the wave vector, it is estimated that C15A is well dispersed into clusters which consist of a stack of between three and seven di-tallow-coated montmorillonite platelets. The removal of excess di-tallow from the surface layer reduces the number of platelets in the cluster. Substitution of dimethydioctodecyl ammonium for the di-tallow molecule promotes network formation. It is demonstrated that SANS is a powerful tool for examining these complicated organic/inorganic systems.     

Effects of Switching Angle Phase Shift on PWM Techniques

The behavior of some well-known pulsewidth modulation (PWM) techniques is investigated under perturbation conditions of power semiconductor gating signals. An evaluation of different PWM techniques is performed considering the effect of PWM timing errors on the output spectra of switch-mode converters.