Pathological tau leads to dementia and neurodegeneration in tauopathies, including Alzheimer’s disease. It has been shown to disrupt cellular and synaptic functions, yet its effects on the function ...of the intact neocortical network remain unknown. Using in vivo intracellular and extracellular recordings, we measured ongoing activity of neocortical pyramidal cells during various arousal states in the rTg4510 mouse model of tauopathy, prior to significant cell death, when only a fraction of the neurons show pathological tau. In transgenic mice, membrane potential oscillations are slower during slow-wave sleep and under anesthesia. Intracellular recordings revealed that these changes are due to longer Down states and state transitions of membrane potentials. Firing rates of transgenic neurons are reduced, and firing patterns within Up states are altered, with longer latencies and inter-spike intervals. By changing the activity patterns of a subpopulation of affected neurons, pathological tau reduces the activity of the neocortical network.
•Pathological tau disrupts the activity of single cells and neocortical networks•Pathological tau alters neocortical neuronal oscillatory patterns•Pathological tau affects firing patterns of neocortical pyramidal cells
Menkes-Caspi et al. show that the activity of cortical neurons is reduced in tau-transgenic mice, including in neurons without detectable pathological tau. The pathological effects on a group of neurons are amplified and propagated through the entire cortical network.
Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and ...efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic R ds,on , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale.
The sudden collapse of thawing soils in the Arctic might double the warming from greenhouse gases released from tundra, warn Merritt R. Turetsky and colleagues.
The double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results ...are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by C dv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method is proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.
Abstract The leadership of the National Lipid Association convened an Expert Panel to develop a consensus set of recommendations for patient-centered management of dyslipidemia in clinical medicine. ...An Executive Summary of those recommendations was previously published. This document provides support for the recommendations outlined in the Executive Summary. The major conclusions include (1) an elevated level of cholesterol carried by circulating apolipoprotein B-containing lipoproteins (non–high-density lipoprotein cholesterol and low-density lipoprotein cholesterol LDL-C, termed atherogenic cholesterol) is a root cause of atherosclerosis, the key underlying process contributing to most clinical atherosclerotic cardiovascular disease (ASCVD) events; (2) reducing elevated levels of atherogenic cholesterol will lower ASCVD risk in proportion to the extent that atherogenic cholesterol is reduced. This benefit is presumed to result from atherogenic cholesterol lowering through multiple modalities, including lifestyle and drug therapies; (3) the intensity of risk-reduction therapy should generally be adjusted to the patient's absolute risk for an ASCVD event; (4) atherosclerosis is a process that often begins early in life and progresses for decades before resulting a clinical ASCVD event. Therefore, both intermediate-term and long-term or lifetime risk should be considered when assessing the potential benefits and hazards of risk-reduction therapies; (5) for patients in whom lipid-lowering drug therapy is indicated, statin treatment is the primary modality for reducing ASCVD risk; (6) nonlipid ASCVD risk factors should also be managed appropriately, particularly high blood pressure, cigarette smoking, and diabetes mellitus; and (7) the measurement and monitoring of atherogenic cholesterol levels remain an important part of a comprehensive ASCVD prevention strategy.
Food insecurity has been associated with diverse developmental consequences for U.S. children primarily from cross-sectional studies. We used longitudinal data to investigate how food insecurity over ...time related to changes in reading and mathematics test performance, weight and BMI, and social skills in children. Data were from the Early Childhood Longitudinal Study-Kindergarten Cohort, a prospective sample of approximately21,000 nationally representative children entering kindergarten in 1998 and followed through 3rd grade. Food insecurity was measured by parent interview using a modification of the USDA module in which households were classified as food insecure if they reported >/=1 affirmative response in the past year. Households were grouped into 4 categories based on the temporal occurrence of food insecurity in kindergarten and 3rd grade. Children's academic performance, height, and weight were assessed directly. Children's social skills were reported by teachers. Analyses examined the effects of modified food insecurity on changes in child outcomes using lagged, dynamic, and difference (i.e., fixed-effects) models and controlling for child and household contextual variables. In lagged models, food insecurity was predictive of poor developmental trajectories in children before controlling for other variables. Food insecurity thus serves as an important marker for identifying children who fare worse in terms of subsequent development. In all models with controls, food insecurity was associated with outcomes, and associations differed by gender. This study provides the strongest empirical evidence to date that food insecurity is linked to specific developmental consequences for children, and that these consequences may be both nutritional and nonnutritional.
Abstract Various organizations and agencies have issued recommendations for the management of dyslipidemia. Although many commonalities exist among them, material differences are present as well. The ...leadership of the National Lipid Association (NLA) convened an Expert Panel to develop a consensus set of recommendations for patient-centered management of dyslipidemia in clinical medicine. The current Executive Summary highlights the major conclusions in Part 1 of the recommendations report of the NLA Expert Panel and includes: (1) background and conceptual framework for formulation of the NLA Expert Panel recommendations; (2) screening and classification of lipoprotein lipid levels in adults; (3) targets for intervention in dyslipidemia management; (4) atherosclerotic cardiovascular disease risk assessment and treatment goals based on risk category; (5) atherogenic cholesterol—non–high-density lipoprotein cholesterol and low-density lipoprotein cholesterol—as the primary targets of therapy; and (6) lifestyle and drug therapies intended to reduce morbidity and mortality associated with dyslipidemia.
Arm inductor in a modular multilevel converter (MMC) is used to limit the circulating current and dc short circuit fault current. The circulating current in MMC is dominated by second-order harmonic, ...which can be largely reduced with circulating current suppressing control. By analyzing the mechanism of the circulating current suppressing control, it is found that the circulating current at switching frequency becomes the main harmonic when suppression control is implemented. Unlike the second-order harmonic that circulates only within the three phases, switching frequency harmonic also flows through the dc side and may further cause high-frequency dc voltage harmonic. This paper develops the theoretical relationship between the arm inductance and switching frequency circulating current, which can be used to guide the arm inductance selection. The experimental results with a downscaled MMC prototype verify the existence of the switching frequency circulating current and its relationship with arm inductance.
A robust and modular synthesis of ynamides Mansfield, Steven J; Campbell, Craig D; Jones, Michael W ...
Chemical communications (Cambridge, England),
02/2015, Letnik:
51, Številka:
16
Journal Article
Recenzirano
Odprti dostop
A flexible, modular ynamide synthesis is reported that uses trichloroethene as an inexpensive two carbon synthon. A wide range of amides and electrophiles can be converted to the corresponding ...ynamides, importantly including acyclic carbamates, hindered amides, and aryl amides. This method thus overcomes many of the limitations of other approaches to this useful functionality.
This paper identifies extra junction capacitances and switching commutation loops introduced by line-frequency devices (i.e., non-active every other half line cycle) in three-level ac/dc converters ...and investigates the corresponding effects. Junction capacitances and power loops are well known as the key factors that impact converter switching loss and device stress, thus influence device selection, power stage layout, and thermal design. By examining switching transients of the commonly used T-shaped and I-shaped three-level converters, the cause and mechanism of the extra junction capacitances and power loops are presented. The impacts on switching loss, device voltage stress, and ac-side voltage/current distortion are respectively reported and analyzed. A loss calculation scheme for the three-level converter to include that extra loss is proposed. A power layout scheme to mitigate the device voltage stress is provided. Compensation and modeling of the voltage and current distortion are also proposed. Experimental results conducted on several types of three-level converter prototypes including a gallium nitride based 115 <inline-formula><tex-math notation="LaTeX">V_{{\text{ac}}}{\text{/650}}</tex-math></inline-formula> V dc /1.5-kW/450-kHz Vienna-type rectifier and a SiC mosfet based 1-kV/10-kW/280-kHz three-level active neutral-point-clamped inverter confirm the presented effects and verify the associated analysis and solutions.
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