Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr

The recent discovery of magnetism within the family of exfoliatable van der Waals (vdW) compounds has attracted considerable interest in these materials for both fundamental research and technological applications. However, current vdW magnets are limited by their extreme sensitivity to air, low ordering temperatures, and poor charge transport properties. Here the magnetic and electronic properties of CrSBr are reported, an air-stable vdW antiferromagnetic semiconductor that readily cleaves perpendicular to the stacking axis. Below its Néel temperature, T_N = 132 ± 1 K, CrSBr adopts an A-type antiferromagnetic structure with each individual layer ferromagnetically ordered internally and the layers coupled antiferromagnetically along the stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL) reveal that the electronic gap is Δ_E = 1.5 ± 0.2 eV with a corresponding PL peak centered at 1.25 ± 0.07 eV. Using magnetotransport measurements, strong coupling between magnetic order and transport properties in CrSBr is demonstrated, leading to a large negative magnetoresistance response that is unique among vdW materials. These findings establish CrSBr as a promising material platform for increasing the applicability of vdW magnets to the field of spin-based electronics.     

SPT Hammer Energy Ratio versus Drop Height

Automatic trip hammers have advantages for standard penetration test (SPT) of consistent drop height and low friction loss during hammer fall. These advantages, however, generate high energy transfer ratios (ER), typically about 90%. This efficiency causes lower sensitivity and higher energy correction coefficients, CE. To reduce ER and CE and to increase the sensitivity of SPT conducted at the Wildlife Liquefaction Array (WLA) and the Garner Valley Downhole Array, instrumented Network for Earthquake Engineering Simulation sites, a 127?mm (5.00?in.) long sleeve was placed in the hammer mechanism to reduce the drop height from 762?mm (30?in.) to 635?mm (25in.). To calibrate the energy for these drop heights, measurements were made for a series of SPT tests in Borehole X2 at WLA on November 21, 2003. For these SPT, sleeves were inserted with lengths of 50?mm (2?in.), 127?mm (5?in.) 177?mm (7?in.), and no sleeve. Resulting drop heights were 762?mm (30?in.), 711?mm (28?in.), 635?mm (25?in.), and 584?mm (23?in.). Results indicate that: (1) ER increases with rod length as expected; (2) corrections for rod length, CR, increased with rod length in accordance with CR published in 2001 by Youd et al.; and (3) for lengths greater than 6?m, ER increased approximately linearly with drop height. Average ER30 [ER based on a 762?mm (30?in.) drop height] were 43% for a 584?mm (23?in.) drop, 60% for a 635?mm (25?in.) drop, 84% for 711?mm (28?in.) drop, and 89% for a 762?mm (30?in.) drop.     

Leadership and the fate of organizations.

This article concerns the real-world importance of leadership for the success or failure of organizations and social institutions. The authors propose conceptualizing leadership and evaluating leaders in terms of the performance of the team or organization for which they are responsible. The authors next offer a taxonomy of the dependent variables used as criteria in leadership studies. A review of research using this taxonomy suggests that the vast empirical literature on leadership may tell us more about the success of individual managerial careers than the success of these people in leading groups, teams, and organizations. The authors then summarize the evidence showing that leaders do indeed affect the performance of organizations--for better or for worse--and conclude by describing the mechanisms through which they do so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

(R)-alpha-lipoic acid-supplemented old rats have improved mitochondrial function, decreased oxidative damage, and increased metabolic rate

A diet supplemented with (R)-lipoic acid, a mitochondrial coenzyme, was fed to old rats to determine its efficacy in reversing the decline in metabolism seen with age. Young (3 to 5 months) and old (24 to 26 months) rats were fed an AIN-93M diet with or without (R)-lipoic acid (0.5% w/w) for 2 wk, killed, and their liver parenchymal cells were isolated. Hepatocytes from untreated old rats vs. young controls had significantly lower oxygen consumption (P<0. 03) and mitochondrial membrane potential. (R)-Lipoic acid supplementation reversed the age-related decline in O2 consumption and increased (P<0.03) mitochondrial membrane potential. Ambulatory activity, a measure of general metabolic activity, was almost threefold lower in untreated old rats vs. controls, but this decline was reversed (P<0.005) in old rats fed (R)-lipoic acid. The increase of oxidants with age, as measured by the fluorescence produced on oxidizing 2',7'-dichlorofluorescin, was significantly lowered in (R)-lipoic acid supplemented old rats (P<0.01). Malondialdehyde (MDA) levels, an indicator of lipid peroxidation, were increased fivefold with age in cells from unsupplemented rats. Feeding rats the (R)-lipoic acid diet reduced MDA levels markedly (P<0.01). Both glutathione and ascorbic acid levels declined in hepatocytes with age, but their loss was completely reversed with (R)-lipoic acid supplementation. Thus, (R)-lipoic acid supplementation improves indices of metabolic activity as well as lowers oxidative stress and damage evident in aging.     

Are trauma victims susceptible to "false memories?"

Laboratory studies using word-list paradigms have provided evidence that nontraumatized individuals falsely recall or recognize events that never occurred. In the present study, H. L. Roediger and K. B. McDermott's false-memory paradigm (1995) was utilized to examine possible source monitoring deficits in individuals with PTSD. Traumatized individuals with PTSD were compared with traumatized individuals without PTSD and with nontraumatized control participants. Participants heard lists of related words (e.g., bed, night) that were associates of a critical nonpresented word (e.g., sleep) and were given immediate free recall and later recognition tests. Traumatized participants with and without PTSD generated more false recalls of critical nonpresented words than did nontraumatized participants. False recall was related to trait anxiety and PTSD severity. The results are consistent with a general source-monitoring deficit in trauma-exposed individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modelling and management of smart microgrid for rural electrification in sub-saharan Africa: The case of Nigeria

Access to electricity is still a challenge in many parts of sub-Saharan Africa. In Nigeria, over 70% of the rural dwellers do not have access to electricity. The purpose of this paper is to examine the potential of a smart microgrid for off-grid rural electrification in Nigeria. A combination of design thinking and model-based design methodology is employed to select a suitable microgrid configuration and to develop a smart microgrid model. A system consisting of a solar photovoltaic array, battery energy storage and a diesel generator is selected, and the model is developed in Simulink. Demand data from 10 rural communities in Nigeria are used to validate the performance of the model and the potential for demand management is considered. The use of energy efficient light bulbs is found to reduce the peak electricity demand of the case study communities by 42 to 76%. Combining the proposed system with the use of LED bulbs makes the system to have 56 to 81% less net present cost than a system with a diesel generator alone and incandescent light bulbs. The proposed smart microgrid is found to be more suitable for off-grid rural electrification in Nigeria than diesel generators which are currently used for off-grid electrification in Nigeria.