343 research outputs found
Ferromagnetism and interlayer exchange coupling in short period (Ga,Mn)As/GaAs superlattices
Magnetic properties of (Ga,Mn)As/GaAs superlattices are investigated. The
structures contain magnetic (Ga,Mn)As layers, separated by thin layers of
non-magnetic GaAs spacer. The short period GaMnAs/GaAs
superlattices exhibit a paramagnetic-to-ferromagnetic phase transition close to
60K, for thicknesses of (Ga,Mn)As down to 23 \AA. For
GaMnAs/GaAs superlattices of similar dimensions, the Curie
temperature associated with the ferromagnetic transition is found to oscillate
with the thickness of non magnetic spacer. The observed oscillations are
related to an interlayer exchange interaction mediated by the polarized holes
of the (Ga,Mn)As layers.Comment: REVTeX 4 style; 4 pages, 2 figure
Mathematically Gifted Adolescents Have Deficiencies in Social Valuation and Mentalization
Many mathematically gifted adolescents are characterized as being indolent, underachieving and unsuccessful despite their high cognitive ability. This is often due to difficulties with social and emotional development. However, research on social and emotional interactions in gifted adolescents has been limited. The purpose of this study was to observe differences in complex social strategic behaviors between gifted and average adolescents of the same age using the repeated Ultimatum Game. Twenty-two gifted adolescents and 24 average adolescents participated in the Ultimatum Game. Two adolescents participate in the game, one as a proposer and the other as a responder. Because of its simplicity, the Ultimatum Game is an apt tool for investigating complex human emotional and cognitive decision-making in an empirical setting. We observed strategic but socially impaired offers from gifted proposers and lower acceptance rates from gifted responders, resulting in lower total earnings in the Ultimatum Game. Thus, our results indicate that mathematically gifted adolescents have deficiencies in social valuation and mentalization
Optimizing HVAC Control to Improve Building Comfort and Energy Performance
This paper demonstrates the benefits of optimal
control in well-designed and operated buildings using
a case study. The case study building was built in
2001. The HVAC and control systems have been
installed with state-of-the-art equipment which
include a terminal box temperature integrated
minimum airflow reset. The building has been used
and operated based on the design intents. This paper
presents both the existing and the optimal control
schedules, which include the VAV box operation
schedule, AHUs optimal control, chiller and chilled
water pump control, and boiler and hot water pump
control. The measured hourly HVAC electricity
consumption shows that annual savings of up to 40%
can be achieved with an optimal control schedule
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High-temperature magnetic anomalies in Sr-doped La manganite structures
The temperature dependence of the magnetization M, susceptibility {chi}, and magnetoresistance MR for 3 perovskite-variant manganite structures were studied: monoclinic (x=0.075) and orthorhombic (x=0. 125) La{sub 1-x}Sr{sub x}MnO{sub 3}, and tetragonal layered La{sub 2- 2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x=0.4) with x also indicating the nominal fraction of Mn{sup 4+}. In each case, evidence is found for unusual magnetic states at temperatures T above their primary magnetic transitions. In the first case, the high-T {chi} deviates from Curie-Weiss expectations, in the second case the MR extends to high T, and in the last, M and {chi} exhibit short-range anomalies at high T. This suggests that a key feature of these systems is the existence of multiple magnetic energy scales, independent of structure, dimensionality, or doping levels
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Impact of COVID-19 on Formal Education: An International Review of Practices and Potentials of Open Education at a Distance.
In terms of scale, shock, and disenfranchisement, the disruption to formal education arising from COVID-19 has been unprecedented. Anecdotally, responses from teachers and educators around the world range from heightened caution to being inspired by distance education as the 'new normal.' Of all the challenges, face-to-face and formal teaching have been most heavily affected. Despite some education systems demonstrating resilience, a major challenge is sustaining quality and inclusiveness in formal education suddenly delivered at a distance. In probing these issues, this article profiles international perspectives on the role of open education in responding to the impact on formal school and higher education caused by the COVID-19 pandemic. We proceed by highlighting and analysing practices and case studies from 13 countries representing all global regions, identifying and discussing the challenges and opportunities that have presented themselves. Reports cover the period from the beginning of 2020 until 11 March 2021, the first anniversary of the COVID-19 outbreak as declared by the World Health Organization. In our comparative study, we identify seven key aspects of which three (missing infrastructure and sharing OER, open education and access to OER, and urgent need for professional development and training for teachers) are directly related to open education at a distance. After comparing examples of existing practice, we make recommendations and offer insights into how open education strategies can lead to interventions that are effective and innovative¿to improve formal education at a distance in schools and universities in the future
Somatic Pairing of Chromosome 19 in Renal Oncocytoma Is Associated with Deregulated ELGN2-Mediated Oxygen-Sensing Response
Chromosomal abnormalities, such as structural and numerical abnormalities, are a common occurrence in cancer. The close association of homologous chromosomes during interphase, a phenomenon termed somatic chromosome pairing, has been observed in cancerous cells, but the functional consequences of somatic pairing have not been established. Gene expression profiling studies revealed that somatic pairing of chromosome 19 is a recurrent chromosomal abnormality in renal oncocytoma, a neoplasia of the adult kidney. Somatic pairing was associated with significant disruption of gene expression within the paired regions and resulted in the deregulation of the prolyl-hydroxylase ELGN2, a key protein that regulates the oxygen-dependent degradation of hypoxia-inducible factor (HIF). Overexpression of ELGN2 in renal oncocytoma increased ubiquitin-mediated destruction of HIF and concomitantly suppressed the expression of several HIF-target genes, including the pro-death BNIP3L gene. The transcriptional changes that are associated with somatic pairing of chromosome 19 mimic the transcriptional changes that occur following DNA amplification. Therefore, in addition to numerical and structural chromosomal abnormalities, alterations in chromosomal spatial dynamics should be considered as genomic events that are associated with tumorigenesis. The identification of EGLN2 as a significantly deregulated gene that maps within the paired chromosome region directly implicates defects in the oxygen-sensing network to the biology of renal oncocytoma
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