200 v superjunction N-type lateral insulated-gate bipolar transistor with improved latch-up characteristics

This paper evaluates the technique used to improve the latching characteristics of the 200 V n-type superjunction (SJ) lateral insulated-gate bipolar transistor (LIGBT) on a partial silicon-on-insulator. SJ IGBT devices are more prone to latch-up than standard IGBTs due to the presence of a strong pnp transistor with the p layer serving as an effective collector of holes. The initial SJ LIGBT design latches at about 23 V with a gate voltage of 5 V with a forward voltage drop (VON) of 2 V at 300 Acm2. The latch-up current density is 1100 Acm2. The latest SJ LIGBT design shows an increase in latch-up voltage close to 100 V without a significant penalty in VON. The latest design shows a latch-up current density of 1195 A cm2. The enhanced robustness against static latch-up leads to a better forward bias safe operating area. © 1963-2012 IEEE.

α-Synuclein senses lipid packing defects and induces lateral expansion of lipids leading to membrane remodeling.

There is increasing evidence for the involvement of lipid membranes in both the functional and pathological properties of α-synuclein (α-Syn). Despite many investigations to characterize the binding of α-Syn to membranes, there is still a lack of understanding of the binding mode linking the properties of lipid membranes to α-Syn insertion into these dynamic structures. Using a combination of an optical biosensing technique and in situ atomic force microscopy, we show that the binding strength of α-Syn is related to the specificity of the lipid environment (the lipid chemistry and steric properties within a bilayer structure) and to the ability of the membranes to accommodate and remodel upon the interaction of α-Syn with lipid membranes. We show that this interaction results in the insertion of α-Syn into the region of the headgroups, inducing a lateral expansion of lipid molecules that can progress to further bilayer remodeling, such as membrane thinning and expansion of lipids out of the membrane plane. We provide new insights into the affinity of α-Syn for lipid packing defects found in vesicles of high curvature and in planar membranes with cone-shaped lipids and suggest a comprehensive model of the interaction between α-Syn and lipid bilayers. The ability of α-Syn to sense lipid packing defects and to remodel membrane structure supports its proposed role in vesicle trafficking.

CdS/CdSe lateral heterostructure nanobelts by a two-step physical vapor transport method.

The two-dimensional heterostructure nanobelts with a central CdSe region and lateral CdS structures are synthesized by a two-step physical vapor transport method. The large growth rate difference between lateral CdS structures on both +/- (0001) sides of the CdSe region is found. The growth anisotropy is discussed in terms of the polar nature of the side +/- (0001) surfaces of CdSe. High-resolution transmission electron microscopy reveals the CdSe central region covered with non-uniform CdS layer/islands. From micro-photoluminescence measurements, a systematic blueshift of emission energy from the central CdSe region in accordance with the increase of lateral CdS growth temperature is observed. This result indicates that the intermixing rate in the CdSe region with CdS increases with the increase of lateral CdS growth temperature. In conventional CdSSe ternary nanostructures, morphology and emission wavelength were correlated parameters. However, the morphology and emission wavelength are independently controllable in the CdS/CdSe lateral heterostructure nanobelts. This structure is attractive for applications in visible optoelectronic devices.

Electrospun fiber - Hydrogel composites for nucleus pulposus tissue engineering

New materials are needed to replace degenerated intervertebral disc tissue and to provide longer-term solutions for chronic back-pain. Replacement tissue potentially could be engineered by seeding cells into a scaffold that mimics the architecture of natural tissue. Many natural tissues, including the nucleus pulposus (the central region of the intervertebral disc) consist of collagen nanofibers embedded in a gel-like matrix. Recently it was shown that electrospun micro- or nano-fiber structures of considerable thickness can be produced by collecting fibers in an ethanol bath. Here, randomly aligned polycaprolactone electrospun fiber structures up to 50 mm thick are backfilled with alginate hydrogels to form novel composite materials that mimic the fiber-reinforced structure of the nucleus pulposus. The composites are characterized using both indentation and tensile testing. The composites are mechanically robust, exhibiting substantial strain-to-failure. The method presented here provides a way to create large biomimetic scaffolds that more closely mimic the composite structure of natural tissue. © 2012 Materials Research Society.

Lateral and Axial Capacity of Monopiles for Offshore Wind Turbines

Offshore wind has enormous worldwide potential to generate increasing amounts of clean, renewable energy. Monopile foundations are considered to be viable in supporting larger offshore wind turbines in shallow to medium depth waters. In this paper, the lateral and axial response of monopiles installed in undrained clays of varying shear strength and stiffness is investigated using three-dimensional finite element analysis. A combination of axial and lateral loads expected at an offshore wind farm located in a water depth of 30 m has been used in the analysis. Numerically derived monopile axial capacities will be compared to those calculated using an established method in the literature. In addition, the lateral monopile capacity will be determined at ultimate limit state and compared to that at the serviceability limit state. Through a parametric study, it will be shown that with the exception of extremely high axial loads that border on monopile axial capacities, variation in axial loads does not have a significant effect on the ultimate lateral capacity and lateral displacement of monopiles. © 2013 Indian Geotechnical Society.

Lateral response of monopiles using centrifuge testing and finite element analysis

Offshore wind capacity is expected to grow exponentially over the next decade resulting in the production of a considerable amount of renewable energy. Monopiles are currently the most popular type of foundation for supporting offshore wind turbines in shallow to medium depth waters. In this paper, the load-deformation response of a 3.8 m diameter monopile installed in soft clays when subjected to axial and lateral loading is investigated using centrifuge testing and soil pore-fluid coupled three-dimensional finite element analysis. Monopile deformation is principally assessed in terms of its lateral displacements and bending moments. Its behaviour as a short rigid pile is discussed using concepts such as its rotation at mudline and the pile depth at which pivoting occurs. © 2014 Taylor & Francis Group.

Centrifuge testing of monopiles subject to cyclic lateral loading

Monopiles supporting offshore wind turbines are subjected to cyclic lateral loading. The properties of the applied cyclic lateral load are known to have an effect on the accumulation of permanent displacement and rotation at the pile head. The results of centrifuge testing on model piles show that certain loading regimes lead to the development of locked in soil stresses around the pile. These locked in soil stresses change the stiffness of the monopile response to cyclic lateral loading and the natural frequency of the pile-soil system. © 2014 Taylor & Francis Group.

Lateral spreading-induced abutment rotation in the 2011 Christchurch earthquake: Observations and analysis

A series of strong earthquakes near Christchurch, New Zealand, occurred between September 2010 and December 2011, causing widespread liquefaction throughout the city's suburbs. Lateral spreading developed along the city's Avon River, damaging many of the bridges east of the city centre. The short-to medium-span bridges exhibited a similar pattern of deformation, involving back-rotation of their abutments and compression of their decks. By explicitly considering the rotational equilibrium of the abutments about their point of contact with the rigid bridge decks, it is shown that relatively small kinematic demands from the laterally spreading backfill soil are needed to initiate pile yielding, and that this mode of deformation should be taken into account in the design of the abutments and abutment piles.

800V lateral IGBT in bulk Si for low power compact SMPS applications

An 800V rated lateral IGBT for high frequency, low-cost off-line applications has been developed. The LIGBT features a new method of adjusting the bipolar gain, based on a floating N+ stripe in front of the P+ anode/drain region. The floating N+ layer enhances the carrier recombination at the anode/drain side of the drift region resulting in a very significant decrease in the turn-off speed and substantially lower overall losses. Switching speeds as low as 140ns at 25oC and 300ns at 125oC have been achieved with corresponding equivalent Rdson at 125oC below 90mω.cm2. A fully operational AC-DC converter using a controller with an integrated LIGBT+depletion mode MOSFET chip has been designed and qualified in plastic SOP8 packages and used in 5W, 65kHz SMPS applications. The device is fabricated in 0.6μm bulk silicon CMOS technology without any additional masking steps. © 2013 IEEE.

200V superjunction lateral IGBT fabricated on partial SOI

A 200V lateral insulated gate bipolar transistor (LIGBT) was successfully developed using lateral superjunction (SJ) in 0.18μm partial silicon on insulator (SOI) HV process. The results presented are based on extensive experimental measurements and numerical simulations. For an n-type lateral SJ LIGBT, the p layer in the SJ drift region helps in achieving uniform electric field distribution. Furthermore, the p-pillar contributes to the on-state current. Furthermore, the p-pillar contributes to sweep out holes during the turn-off process, thus leading to faster removal of plasma. To realize this device, one additional mask layer is required in the X-FAB 0.18μm partial SOI HV process. © 2013 IEEE.

Residual plastids of bleached mutants of Euglena gracilis and their effects on the expression of nucleus-encoded genes

Bleached mutants of Euglena gracilis were obtained by treatment with ofloxacin (Ofl) and streptomycin (Sm) respectively. As shown by electron microscopy, the residual plastids contain prothylakoids in an Ofl mutant, and the highly developed and tightly stacked membranous structure found in cells of two Sm, mutants. Nine genes of the plastid genome were examined with PCR, showing that ribosomal protein genes and most other plastid genes were lost in all but one Sm mutant. Using differential display and RT-PCR, it was shown that chloroplast degeneration could cause changes in transcription of certain nucleus-encoded genes during heterotrophic growth in darkness.

Analysis of lateral current spreading in solar cell devices by spatially-resolved electroluminescence

Spatially-resolved electroluminescence (EL) images from solar cells contain information of local current distribution. By theoretical analysis of the EL intensity distribution, the current density distribution under a certain current bias and the sheet resistance can be obtained quantitatively. Two-dimensional numerical simulation of the current density distribution is employed to a GaInP cell, which agrees very well with the experimental results. A reciprocity theorem for current spreading is found and used to interpret the EL images from the viewpoint of current extraction. The optimization of front electrodes is discussed based on the results. (C) 2010 American Institute of Physics. [doi:10.1063/1.3431390]