Simple modeling for conducted common-mode current in switching circuits

Common mode current strongly depends on stray capacitance of each circuit node, especially those with high dv/dt and di/dt. To build a simple model for conducted common mode current in switching circuit a computer software based on Partial Element Equivalent Circuit (PEEC) method is used to calculate the parasitic elements of the printed circuit board (PCB). Simulation results agree well with experimental results up to 10 MHz.published_or_final_versio

Cerebellar defects in Pdss2 conditional knockout mice during embryonic development and in adulthood

PDSS2 is a gene that encodes one of the two subunits of trans-prenyl diphosphate synthase that is essential for ubiquinone biosynthesis. It is known that mutations in PDSS2 can cause primary ubiquinone deficiency in humans and a similar disease in mice. Cerebellum is the most often affected organ in ubiquinone deficiency, and cerebellar atrophy has been diagnosed in many infants with this disease. In this study, two Pdss2 conditional knockout mouse lines directed by Pax2-cre and Pcp2-cre were generated to investigate the effect of ubiquinone deficiency on cerebellum during embryonic development and in adulthood, respectively. The Pdss2 f/-; Pax2-cre mouse recapitulates some symptoms of ubiquinone deficiency in infants, including severe cerebellum hypoplasia and lipid accumulation in skeletal muscles at birth. During early cerebellum development (E12.5-14.5), Pdss2 knockout initially causes the delay of radial glial cell growth and neuron progenitor migration, so the growth of mutant cerebellum is retarded. During later development (E15.5-P0), increased ectopic apoptosis of neuroblasts and impaired cell proliferation result in the progression of cerebellum hypoplasia in the mutant. Thus, the mutant cerebellum contains fewer neurons at birth, and the cells are disorganized. The developmental defect of mutant cerebellum does not result from reduced Fgf8 expression before E12.5. Electron microscopy reveals mitochondrial defects and increased autophagic-like vacuolization that may arise in response to abnormal mitochondria in the mutant cerebellum. Nevertheless, the mutant mice die soon after birth probably due to cleft palate and micrognathia, which may result from Pdss2 knockout caused by ectopic Pax2-cre expression in the first branchial arch. On the other hand, the Pdss2 f/-; Pcp2-cre mouse is healthy at birth but gradually loses cerebellar Purkinje cells and develops ataxia-like symptoms at 9.5months; thus this conditional knockout mouse may serve as a model for ubiquinone deficiency in adult patients. In conclusion, this study provides two mouse models of Pdss2 based ubiquinone deficiency. During cerebellum development, Pdss2 knockout results in severe cerebellum hypoplasia by impairing cell migration and eliciting ectopic apoptosis, whereas Pdss2 knockout in Purkinje cells at postnatal stages leads to the development of cerebellar ataxia. © 2011 Elsevier Inc.postprin

Quantum well intermixing for the fabrication of InGaAsN/GaAs lasers with pulsed anodic oxidation

Quantum well (QW) intermixing was carried out by post-growth rapid thermal annealing in InGaAsN/GaAs QW laser structures grown by solid-source molecular-beam epitaxy. The intensity and width of the photoluminescence peak showed a dependence on annealing temperature and time, and the maximum intensity and minimum linewidth were obtained after the wafer was annealed at 670 °C for 60 s. The peak luminescence energy blueshifted with increasing annealing time, although it plateaued at an annealing time that corresponded to that yielding the maximum luminescence intensity. The diffusion coefficient for indium was determined from a comparison between experimental data and modeling, but showed that QW intermixing alone was not sufficient to account for the relatively large blueshift after annealing. Defects related to the incorporation of nitrogen in the QW layer were responsible for the low photoluminescence efficiency in the as-grown samples and were annealed out during rapid thermal annealing. During annealing, nitrogen interstitials moved to vacancy sites within the QW and thus suppressed QW intermixing. After annealing wafers under conditions giving the maximum luminescence intensity, lasers were fabricated with pulsed anodic oxidation. © 2004 American Institute of Physics.published_or_final_versio

Conjugated polyelectrolyte nano field emission adlayers.

Here we report on a straightforward and rapid means of enhancing the field electron emission performance of nascent vertically aligned multi-walled carbon nanotubes by introducing a polar zwitterionic conjugated polyelectrolyte adlayer at the vacuum-emitter interface. We attribute the observed 66% decrease in turn-on electric field to the augmented emitter micro-morphology and shifted surface band structure. The composite emitters can be optically modulated by exploiting the absorption cross-section of the solution cast adlayer, which increases the local carrier concentration which broadens the effective electrostatic shape of the emitter during optical excitation. Assessment via scanning anode field emission microscopy reveals a 25% improvement in DC time stability, a significant reduction in long-term hysteresis shift, and a threefold increase in bandwidth during pulsed mode operation.Oppenheimer TrustThis is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/c6nh00071

Minimizing Non-selective Nanowrinkles of Reduced Graphene Oxide Laminar Membranes for Enhanced NaCl Rejection

Reduced graphene oxide membranes (rGOMs) have been intensively studied for desalination and molecular sieving applications, benefiting from their selective and stable two-dimensional (2D) nanochannels. However, their performance is usually over-rated because of the limited understanding of nanowrinkles. In this study, we tuned 2D nanochannels and nanowrinkles in rGOMs to improve their performance and revealed the underlying role of nanowrinkles for water and salt separation. A good trade-off between water permeance (1.05 LMH/bar) and NaCl rejection (83%) was obtained in rGOMs thermally treated in air (Air-rGO), compared with their counterparts synthesized via thermal treatment in vacuum (Va-rGO) and HI vapor reduction (HI-rGO). Instead of the narrow and impermeable 2D nanochannels in Va-rGO and HI-rGO, 5-10 nm-sized nanowrinkles were evident to transport water and salts without selectivity, leading to the low water permeance and NaCl rejection. For Air-rGO membranes, however, the smaller and fewer nanowrinkles retarded the NaCl transfer and the slightly narrowed 2D nanochannels maintained the fast water flow, contributing to the high NaCl rejection and water permeance, respectively. This study provides new insights into the mass transport mechanism in nanowrinkles of rGOMs and advances the design of 2D membranes for desalination, molecular/ionic sieving, and other environmental applications

Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms

A scanning electron microscope survey was initiated to determine if the previously reported findings of “dinosaurian soft tissues” could be identified in situ within the bones. The results obtained allowed a reinterpretation of the formation and preservation of several types of these “tissues” and their content. Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids. Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone

Atomic-scale combination of germanium-zinc nanofibers for structural and electrochemical evolution

Alloys are recently receiving considerable attention in the community of rechargeable batteries as possible alternatives to carbonaceous negative electrodes; however, challenges remain for the practical utilization of these materials. Herein, we report the synthesis of germanium-zinc alloy nanofibers through electrospinning and a subsequent calcination step. Evidenced by in situ transmission electron microscopy and electrochemical impedance spectroscopy characterizations, this one-dimensional design possesses unique structures. Both germanium and zinc atoms are homogenously distributed allowing for outstanding electronic conductivity and high available capacity for lithium storage. The as-prepared materials present high rate capability (capacity of similar to 50% at 20 C compared to that at 0.2 C-rate) and cycle retention (73% at 3.0 C-rate) with a retaining capacity of 546 mAh g(-1) even after 1000 cycles. When assembled in a full cell, high energy density can be maintained during 400 cycles, which indicates that the current material has the potential to be used in a large-scale energy storage system

Genotypes and haplotypes of the VEGF gene and survival in locally advanced non-small cell lung cancer patients treated with chemoradiotherapy

<p>Abstract</p> <p>Background</p> <p>Vascular endothelial growth factor (VEGF) is a major mediator of angiogenesis involving in carcinogenesis, including lung cancer. We hypothesized that <it>VEGF </it>polymorphisms may affect survival outcomes among locally advanced non-small cell lung cancer (LA-NSCLC) patients.</p> <p>Methods</p> <p>We genotyped three potentially functional <it>VEGF </it>variants [-460 T > C (rs833061), -634 G > C (rs2010963), and +936 C > T (rs3025039)] and estimated haplotypes in 124 Caucasian patients with LA-NSCLC treated with definitive radiotherapy. We used Kaplan-Meier log-rank tests, and Cox proportional hazard models to evaluate the association between <it>VEGF </it>variants and overall survival (OS).</p> <p>Results</p> <p>Gender, Karnofsky's performance scores (KPS) and clinical stage seemed to influence the OS. The variant C genotypes were independently associated with significantly improved OS (CT+CC vs. TT: adjusted hazard ratio [HR] = 0.58; 95% confidence interval [CI] = 0.37-0.92, <it>P </it>= 0.022), compared with the <it>VEGF </it>-460 TT genotype.</p> <p>Conclusions</p> <p>Our study suggests that <it>VEGF </it>-460 C genotypes may be associated with a better survival of LA-NSCLC patients after chemoradiotherapy. Large studies are needed to confirm our findings.</p

The effect of S-substitution at the O6-guanine site on the structure and dynamics of a DNA oligomer containing a G:T mismatch

The effect of S-substitution on the O6 guanine site of a 13-mer DNA duplex containing a G:T mismatch is studied using molecular dynamics. The structure, dynamic evolution and hydration of the S-substituted duplex are compared with those of a normal duplex, a duplex with Ssubstitution on guanine, but no mismatch and a duplex with just a G:T mismatch. The S-substituted mismatch leads to cell death rather than repair. One suggestion is that the G:T mismatch recognition protein recognises the S-substituted mismatch (GS:T) as G:T. This leads to a cycle of futile repair ending in DNA breakage and cell death. We find that some structural features of the helix are similar for the duplex with the G:T mismatch and that with the S-substituted mismatch, but differ from the normal duplex, notably the helical twist. These differences arise from the change in the hydrogen-bonding pattern of the base pair. However a marked feature of the S-substituted G:T mismatch duplex is a very large opening. This showed considerable variability. It is suggested that this enlarged opening would lend support to an alternative model of cell death in which the mismatch protein attaches to thioguanine and activates downstream damage-response pathways. Attack on the sulphur by reactive oxygen species, also leading to cell death, would also be aided by the large, variable opening

Thin film Gallium nitride (GaN) based acoustofluidic Tweezer: Modelling and microparticle manipulation.

Gallium nitride (GaN) is a compound semiconductor which shows advantages in new functionalities and applications due to its piezoelectric, optoelectronic, and piezo-resistive properties. This study develops a thin film GaN-based acoustic tweezer (GaNAT) using surface acoustic waves (SAWs) and demonstrates its acoustofluidic ability to pattern and manipulate microparticles. Although the piezoelectric performance of the GaNAT is compromised compared with conventional lithium niobate-based SAW devices, the inherited properties of GaN allow higher input powers and superior thermal stability. This study shows for the first time that thin film GaN is suitable for the fabrication of the acoustofluidic devices to manipulate microparticles with excellent performance. Numerical modelling of the acoustic pressure fields and the trajectories of mixtures of microparticles driven by the GaNAT was performed and the results were verified from the experimental studies using samples of polystyrene microspheres. The work has proved the robustness of thin film GaN as a candidate material to develop high-power acoustic tweezers, with the potential of monolithical integration with electronics to offer diverse microsystem applications.Engineering and Physical Sciences Research Council Grant numbers: EP/P002803/1, EP/P018998/1, Natural Science Basic Research Program of Shaanxi Province/2020JQ-233, Fundamental Scientific Research of Central Universities/3102017OQD116, Engineering and Physical Sciences Research Council fellowship /EP/N01202X/2, Royal Society / IEC/NSFC/170142, IE161019, Natural Science Foundation of China/61704017, Dalian Science and Technology Innovation Fund/2018J11CY00