5MHz PWM-controlled current-mode resonant DC-DC converter using GaN-FETs

In this paper, the method of the realization of a MHz level switching frequency DC-DC converter for high power-density is presented. For high power-density, Gallium Nitride field effect transistor (GaN-FET) and current-mode resonant DC-DC converter are adopted. In addition, the proposed pulse width modulation (PWM) control method which is suitable for the isolated current-mode resonant DC-DC converter operated at MHz level switching frequency, and the novel primary-side zero voltage switching (ZVS) turn on method for the proposed PWM control are presented. Some experiments have been done with 5MHz isolated DC-DC converter which has GaN-FET, and the total volume of the circuit is 16.14cm3. With the proposed PWM control method, input voltage range is 36-44V, and maximum load current range is 8A at Vi = 44V. The primary-side ZVS turn on is confirmed, and the maximum power-efficiency is 89.4%.7th International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014; Hiroshima; Japan; 18 May 2014 through 21 May 201

Enhanced Hydrolyisis of Lignocellulosic Biomass Assisted by a Combination of Acidic Ionic Liquids and Microwave Heating

Lignocellulosic biomass was hydrolyzed by combining an acidic ionic liquid, 1-(1-butylsulfonic)-3-methylimidazolium hydrogen sulfate, and microwave heating, resulting in high glucose yields and short reaction times. This new approach achieved 40% glucose yield from bagasse within 12 min at 160°C; whereas, almost no glucose was yielded with a well-known method involving H2SO4 and conventional heating within 30 min at the same temperature. It was confirmed that the reaction temperature significantly affected glucose yield and reaction rate; whereas, the concentration of the acidic ionic liquid only affected the reaction rate. Three kinds of lignocellulosic biomass, including bagasse (herbaceous biomass), eucalyptus (hardwood), and Japanese cedar (softwood), were examined. Glucose yield was in the range of 30–40%, indicating that the present method effectively hydrolyzes various kinds of lignocellulosic biomasses

High frequency PWM-controlled current-mode resonant DC-DC converter with boost conversion

In this paper, a new pulse width modulation (PWM) control method for the isolated current-mode resonant converter with a fixed switching frequency is presented. The circuit topology is the same as a conventional resonant converter with synchronous rectification and without any additional components. The control technique for the output voltage regulation is proposed with the unique PWM control for synchronously-rectifying switches. By using the transformer\u27s leakage inductance and the PWM control, the boost conversion can be realized. Also, the zero-voltage switching (ZVS) operation can be done for primary switches, simultaneously. Some experiments have been done with 5MHz isolated DC-DC converter which has Gallium Nitride field effect transistor (GaN-FET).2013 15th European Conference on Power Electronics and Applications, EPE 2013; Lille; France; 2 September 2013 through 6 September 201

Five-Megahertz PWM-Controlled Current-Mode Resonant DC?DC Step-Down Converter Using GaN-HEMTs

High power efficiency and high power density are required in regulated isolated dc-dc converters. In this paper, a novel pulsewidth modulation (PWM) control method that is suitable for an isolated current-mode resonant dc-dc converter operated at a megahertz-level switching frequency is proposed. The output voltage with the proposed method can be regulated with no additional components at a fixed switching frequency. In addition, the zero-voltage switching (ZVS) of primary-side switches at turn on can be maintained. The principle of the proposed method and the method of the ZVS operation in the proposed method are explained. Some experiments have been performed with a 5-MHz isolated step-down dc-dc converter using gallium nitride high-electron-mobility transistors; the output voltage is 12 V, and the total volume of the circuit is 16.14 cm3. With the proposed PWM control method, the input voltage range is 42-45.5 V, and the maximum load current range is 10 A at Vi = 45.5 V. The ZVS of the primary-side switches at turn on is confirmed in all experimental regions, and the maximum power efficiency is 89.2%

Association of fruit, pericarp, and epidermis traits with surface autofluorescence in green peppers

We investigated the association of blue fluorescence (excitation at 365 nm) with the traits of the fruit, pericarp, and epidermis in green peppers. The fruits were manually classified into two groups based on fluorescence brightness. The dark fluorescence group showed the accumulation of blue-absorbing pigments and a thicker cuticular structure, suggesting epidermal development

Application of Heavy-Metal-Free Pd/C Catalyst for the Oxidative Dehydrogenation of Sodium Lactate to Pyruvate in an Aqueous Phase under Pressurized Oxygen

According to previous reports, the oxidative dehydrogenation of lactic acid to pyruvic acid in an aqueous phase does not proceed with Pd/C, while Pd/C doped with Te or Pb has catalytic activity at atmospheric pressure and 363 K in an aqueous NaOH solution at a pH of 8. Since use of heavy metals, such as Te or Pb, is inconsistent with green chemistry, a heavy-metal-free Pd/C catalyst is employed in the present study. The oxidative dehydrogenation of sodium lactate to sodium pyruvate in an aqueous phase at 358 K under pressurized oxygen at 1 MPa proceeded favorably using Pd/C with no adjustment of solution pH. Under pressurized oxygen, the catalytic activity of Pd/C was similar to that of Pd/C doped with either Te or Pb. This result suggests that a heavy-metal-free Pd/C catalytst might also be applied to other catalytic reactions. As an alternative to doping Pd/C with Te or Pb, the dissolution of gaseous oxygen into the reaction solution significantly enhanced the catalytic activity of Pd/C. To show the contribution of the dissolution of gaseous oxygen, the effects of the volume of oxygen in the reactor (stainless autoclave) on the reaction rate and the activity were examined. The activation parameters thus obtained reveal that the volume of oxygen in the reactor is a more important determinant of catalytic activity than the activation of the reaction itself

Reactive oxygen species induce chondrocyte hypertrophy in endochondral ossification

Chondrocyte hypertrophy during endochondral ossification is a well-controlled process in which proliferating chondrocytes stop proliferating and differentiate into hypertrophic chondrocytes, which then undergo apoptosis. Chondrocyte hypertrophy induces angiogenesis and mineralization. This step is crucial for the longitudinal growth and development of long bones, but what triggers the process is unknown. Reactive oxygen species (ROS) have been implicated in cellular damage; however, the physiological role of ROS in chondrogenesis is not well characterized. We demonstrate that increasing ROS levels induce chondrocyte hypertrophy. Elevated ROS levels are detected in hypertrophic chondrocytes. In vivo and in vitro treatment with N-acetyl cysteine, which enhances endogenous antioxidant levels and protects cells from oxidative stress, inhibits chondrocyte hypertrophy. In ataxia telangiectasia mutated (Atm)–deficient (Atm−/−) mice, ROS levels were elevated in chondrocytes of growth plates, accompanied by a proliferation defect and stimulation of chondrocyte hypertrophy. Decreased proliferation and excessive hypertrophy in Atm−/− mice were also rescued by antioxidant treatment. These findings indicate that ROS levels regulate inhibition of proliferation and modulate initiation of the hypertrophic changes in chondrocytes

Clusters of internally primed transcripts reveal novel long noncoding RNAs

Non- protein- coding RNAs ( ncRNAs) are increasingly being recognized as having important regulatory roles. Although much recent attention has focused on tiny 22- to 25- nucleotide microRNAs, several functional ncRNAs are orders of magnitude larger in size. Examples of such macro ncRNAs include Xist and Air, which in mouse are 18 and 108 kilobases ( Kb), respectively. We surveyed the 102,801 FANTOM3 mouse cDNA clones and found that Air and Xist were present not as single, full- length transcripts but as a cluster of multiple, shorter cDNAs, which were unspliced, had little coding potential, and were most likely primed from internal adenine- rich regions within longer parental transcripts. We therefore conducted a genome- wide search for regional clusters of such cDNAs to find novel macro ncRNA candidates. Sixty- six regions were identified, each of which mapped outside known protein- coding loci and which had a mean length of 92 Kb. We detected several known long ncRNAs within these regions, supporting the basic rationale of our approach. In silico analysis showed that many regions had evidence of imprinting and/ or antisense transcription. These regions were significantly associated with microRNAs and transcripts from the central nervous system. We selected eight novel regions for experimental validation by northern blot and RT- PCR and found that the majority represent previously unrecognized noncoding transcripts that are at least 10 Kb in size and predominantly localized in the nucleus. Taken together, the data not only identify multiple new ncRNAs but also suggest the existence of many more macro ncRNAs like Xist and Air