On the reproducibility of hippocampal MEGA-sLASER GABA MRS at 7T using an optimized analysis pipeline

Magnetic Resonance Materials in Physics, Biology and Medicine - GABA is the most important inhibitory neurotransmitter. Thus, variation in its concentration is connected to a wide variety of...     

Synthesis of general impedance with simple dc/dc converters for power processing applications

A general impedance synthesizer using a minimum number of switching converters is studied in this paper. We begin with showing that any impedance can be synthesized by a circuit consisting of only two simple power converters, one storage element (e.g. capacitor) and one dissipative element (e.g. resistor) or power source. The implementation of such a circuit for synthesizing any desired impedance can be performed by (i) programming the input current given the input voltage such that the desired impedance function is achieved, (ii) controlling the amount of power dissipation (generation) in the dissipative element (source) so as to match the required active power of the impedance to be synthesized. Then, the instantaneous power will be automatically balanced by the storage element. Such impedance synthesizers find a lot of applications in power electronics. For instance, a resistance synthesizer can be used for power factor correction (PFC), a programmable capacitor or inductor synthesizer (comprising small high‐frequency converters) can be used for control applications. Copyright © 2007 John Wiley & Sons, Ltd.     

La doped PZT 60/40 films by MOD technology

Abstract

Ferroelectric La doped PZT 60/40 thin films with uniform composition have been synthesized using metallo-organic precursor solutions. These metallo-organic precursors have been stored for more than four years and are very stable in ambient conditions, compared to the sol-gel solutions. The structural properties of these films have been studied using X-ray diffraction and atomic force microscopy. The excellent ferroelectric properties of the films, such as less than 10% polarization loss after 10¹¹ cycles, low leakage current of 3·06×10^?12 A at 2 V, and small separation of polarization peaks in a voltage loop by the small-signal measurement, are attributed to the high quality of the metalloorganic solutions used in this study, which have been carefully home-synthesized. The oxygen vacancy in the films was reduced by optimizing the annealing conditions, and to minimize the blocking oxygen vacancy at the interface by Pt electrodes a suitable amount of La ions was doped. We suggest that greater attention should be paid to the elimination/minimization of the oxygen vacancy in the ferroelectric PZT films instead of using oxide electrodes, which allow a relatively larger leakage current flowing through the films and the electrodes.     

基于小波变换和自相关分析的电力电缆故障测距

随着电力电缆应用的增多,对电缆故障测距的精度要求也不断提高.文中分析了行波法故障测距存在误差的原因,在此基础上引入小波变换和自相关分析.运用小波变换进行信号滤波和奇异性检测,运用自相关分析为前者提供约束条件,从而实现故障的自动精确测距,并给出了实现该程序的流程图.试验结果表明,此方法可取得较高的故障测距精度.     

多区域互联电力系统输电服务边际电价理论

建立了一个多区域全交流互联电力系统最优潮流模型 (M-OPF),发展了一种基于最优潮流的灵敏度分析方法,该方法可以提供在参数变化同时保持最优解情况下电力系统运行状况的变化信息。M-OPF问题求最优解时,通常有一部分不等式约束条件。在计及不等式约束条件的最优解邻近进行灵敏度分析来计算灵敏度系数。它们是通过产生一个Kuhn-Tucker条件的线性近似来求得的。文中提出用区域发电成本对母线需求及功率交换的灵敏度信息来计算边际转运价格。     

Calculation of steady‐state solution of parallel‐connected buck converters with active current sharing and its parameter sensitivity

In this paper, the effect of active current‐sharing control on the steady‐state operation of parallel‐connected buck converters is investigated. The system under study consists of N voltage‐mode‐controlled buck converters connected in parallel. Three kinds of active current‐sharing schemes are considered, namely, master–slave scheme with automatic master, master–slave scheme with dedicated master, and democratic scheme. Using the principle of charge balance, the mechanism of the operating point drift arising from active current sharing is examined. A general formulation of the steady‐state solution under active current sharing is derived. Moreover, detailed parameter sensitivity analysis is performed to evaluate the effect of parameters' variation on the operating point. The results from sensitivity analysis can be used to categorize parameters for facilitating practical design. Computer simulations are presented to verify the analytical results. Copyright © 2010 John Wiley & Sons, Ltd.     

Predicting conversion to dementia of the Alzheimer’s type in a healthy control sample: The power of errors in stroop color naming.

In the present study, we investigated which cognitive functions in older adults at Time A are predictive of conversion to dementia of the Alzheimer’s type (DAT) at Time B. Forty-seven healthy individuals were initially tested in 1992–1994 on a trial-by-trial computerized Stroop task along with a battery of psychometric measures that tap general knowledge, declarative memory, visual–spatial processing, and processing speed. Twelve of these individuals subsequently developed DAT. The errors on the color incongruent trials (along with the difference between congruent and incongruent trials) and changes in the reaction time distributions were the strongest predictors of conversion to DAT, consistent with recent arguments regarding the sensitivity of these measures. Notably in the psychometric measures, there was little evidence of a difference in declarative memory between converters and nonconverters, but there was some evidence of changes in visual-spatial processing. Discussion focuses on the accumulating evidence suggesting a role of attentional control mechanisms as an early marker for the transition from healthy cognitive aging to DAT. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Raman spectroscopic study of the microstructure of carbon films developed from cobalt chloride‐modified polyacrylonitrile

Polyacrylonitrile (PAN) was modified with cobalt chloride at 90°C for 5 min. The carbon films prepared from original and modified PAN films were carbonized up to 1300°C. The structure of the resulting carbon film was studied using X‐ray diffraction and Raman spectroscopy. The stacking size obtained from X‐ray diffraction approaches the L_c value of the resulting carbon films as the heat treatment temperature increased. The mean average carbon basal planes in crystalline (Lc/d) also increased with increasing pyrolysis temperature. Raman spectra confirmed the progressive structural ordering as treatment temperature increased. During pyrolysis, a substantial decrease in the intensity of the band near the 1350 cm⁻¹ region was observed, indicating a decrease in the disordered structure. The crystal size (L_a) of the resulting carbon films also showed a remarkable increase with increased heat treatment temperature. The resulting carbon films developed from the modified PAN films had higher L_c and L_a than those developed from the original PAN film. It was established that cobalt catalyzes graphitization of amorphous carbon during pyrolysis. This modification not only promoted the growth of crystal size but also increased the close packing of the carbon basal planes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2219–2225, 1999     

Enhancer RNA Profiling in Smoking and HPV Associated HNSCC Reveals Associations to Key Oncogenes

Smoking and HPV infection are known causes for the vast majority of head and neck squamous cell carcinomas (HNSCC) due to their likelihood of causing gene dysregulation and genomic alterations. Enhancer RNAs (eRNAs) are non-coding RNAs that are known to increase nearby and target gene expression, and activity that has been suggested to be affected by genetic and epigenetic alterations. Here we sought to identify the effects of smoking and HPV status on eRNA expression in HNSCC tumors. We focused on four patient cohorts including smoking/HPV+, smoking/HPV−, non-smoking/HPV+, and non-smoking/HPV− patients. We used TCGA RNA-seq data from cancer tumors and adjacent normal tissue, extracted eRNA read counts, and correlated these to survival, clinical variables, immune infiltration, cancer pathways, and genomic alterations. We found a large number of differentially expressed eRNA in each patient cohort. We also found several dysregulated eRNA correlated to patient survival, clinical variables, immune pathways, and genomic alterations. Additionally, we were able to find dysregulated eRNA nearby seven key HNSCC-related oncogenes. For example, we found eRNA chr14:103272042–103272430 (eRNA-24036), which is located close to the TRAF3 gene to be differentially expressed and correlated with the pathologic N stage and immune cell populations. Using a separate validation dataset, we performed differential expression and immune infiltration analysis to validate our results from the TCGA data. Our findings may explain the association between eRNA expression, enhancer activity, and nearby gene dysregulation.     

The Potential Role of Spermine and Its Acetylated Derivative in Human Malignancies

Polyamines are essential biomolecules for normal cellular metabolism in humans. The roles of polyamines in cancer development have been widely discussed in recent years. Among all, spermine alongside with its acetylated derivative, N¹, N¹²-Diacetylspermine, demonstrate a relationship with the diagnosis and staging of various cancers, including lung, breast, liver, colorectal and urogenital. Numerous studies have reported the level of spermine in different body fluids and organ tissues in patients with different types of cancers. Currently, the role and the underlying mechanisms of spermine in cancer development and progression are still under investigation. This review summarized the roles of spermine in cancer development and as a diagnostic, prognostic and therapeutic tool in various cancers.