800 research outputs found
Positive exchange bias in ferromagnetic La0.67Sr0.33MnO3 / SrRuO3 bilayers
Epitaxial La0.67Sr0.33MnO3 (LSMO)/ SrRuO3 (SRO) ferromagnetic bilayers have
been grown on (001) SrTiO3 (STO) substrates by pulsed laser deposition with
atomic layer control. We observe a shift in the magnetic hysteresis loop of the
LSMO layer in the same direction as the applied biasing field (positive
exchange bias). The effect is not present above the Curie temperature of the
SRO layer (), and its magnitude increases rapidly as the temperature is lowered
below . The direction of the shift is consistent with an antiferromagnetic
exchange coupling between the ferromagnetic LSMO layer and the ferromagnetic
SRO layer. We propose that atomic layer charge transfer modifies the electronic
state at the interface, resulting in the observed antiferromagnetic interfacial
exchange coupling.Comment: accepted to Applied Physics Letter
Nrt1 and Tna1-Independent Export of NAD+ Precursor Vitamins Promotes NAD+ Homeostasis and Allows Engineering of Vitamin Production
NAD+ is both a co-enzyme for hydride transfer enzymes and a
substrate of sirtuins and other NAD+ consuming enzymes.
NAD+ biosynthesis is required for two different regimens
that extend lifespan in yeast. NAD+ is synthesized from
tryptophan and the three vitamin precursors of NAD+: nicotinic
acid, nicotinamide and nicotinamide riboside. Supplementation of yeast cells
with NAD+ precursors increases intracellular
NAD+ levels and extends replicative lifespan. Here we show
that both nicotinamide riboside and nicotinic acid are not only vitamins but are
also exported metabolites. We found that the deletion of the nicotinamide
riboside transporter, Nrt1, leads to increased export of nicotinamide riboside.
This discovery was exploited to engineer a strain to produce high levels of
extracellular nicotinamide riboside, which was recovered in purified form. We
further demonstrate that extracellular nicotinamide is readily converted to
extracellular nicotinic acid in a manner that requires intracellular
nicotinamidase activity. Like nicotinamide riboside, export of nicotinic acid is
elevated by the deletion of the nicotinic acid transporter, Tna1. The data
indicate that NAD+ metabolism has a critical extracellular
element in the yeast system and suggest that cells regulate intracellular
NAD+ metabolism by balancing import and export of
NAD+ precursor vitamins
Flight Crew Alertness and Sleep Relative to Timing of In-Flight Rest Periods in Long-Haul Flights
BACKGROUND: In-flight breaks are used during augmented long-haul flight operations, allowing pilots a sleep opportunity. The U.S. Federal Aviation Administration duty and rest regulations restrict the pilot flying the landing to using the third rest break. It is unclear how effective these restrictions are on pilots’ ability to obtain sleep. We hypothesized there would be no difference in self-reported sleep, alertness, and fatigue between pilots taking the second vs. third rest breaks. METHODS: Pilots flying augmented operations in two U.S.-based commercial airlines were eligible for the study. Volunteers completed a survey at top-of-descent (TOD), including self-reported in-flight sleep duration, and Samn-Perelli fatigue and Karolinska Sleepiness Scale ratings. We compared the second to third rest break using noninferiority analysis. The influence of time of day (home-base time; HBT) was evaluated in 4-h blocks using repeated measures ANOVA. RESULTS: From 787 flights 500 pilots provided complete data. The second rest break was noninferior to the third break for self-reported sleep duration (1.5 6 0.7 h vs. 1.4 6 0.7 h), fatigue (2.0 6 1.0 vs. 2.9 6 1.3), and sleepiness (2.6 6 1.4 vs. 3.8 6 1.8) at TOD for landing pilots. Measures of sleep duration, fatigue, and sleepiness were influenced by HBT circadian time of day. DISCUSSION: We conclude that self-reported in-flight sleep, fatigue, and sleepiness from landing pilots taking the second in-flight rest break are equivalent to or better than pilots taking the third break. Our findings support providing pilots with choice in taking the second or third in-flight rest break during augmented operations
Relativistic mass distribution in event-anti-event system and ``realistic'' equation of state for hot hadronic matter
We find the equation of state which gives the value of
the sound velocity in agreement with the ``realistic'' equation of
state for hot hadronic matter suggested by Shuryak, in the framework of a
covariant relativistic statistical mechanics of an event--anti-event system
with small chemical and mass potentials. The relativistic mass distribution for
such a system is obtained and shown to be a good candidate for fitting hadronic
resonances, in agreement with the phenomenological models of Hagedorn, Shuryak,
{\it et al.} This distribution provides a correction to the value of specific
heat 3/2, of the order of 5.5\%, at low temperatures.Comment: 19 pages, report TAUP-2161-9
Towards resolution of the scalar meson nonet enigma
By the application of a linear mass spectrum to a composite system of both
the pseudoscalar and scalar meson nonets, we find three mass relations for the
masses of the scalar states which suggest the assignment for the
scalar meson nonet: Comment: 16 pages, LaTe
The Middle Way: East Asian masters students’ perceptions of critical argumentation in U.K. universities.
The paper explores the learning experiences of East Asian masters students in dealing with Western academic norms of critical thinking in classroom debate and assignment writing. The research takes a cultural approach, and employs grounded theory and case study methodology, the aims being for students to explain their perceptions of their personal learning journeys. The data suggest that the majority of students interviewed rejected full academic acculturation into Western norms of argumentation. They instead opted for a ‘Middle Way’ that synergizes the traditional cultural academic values held by many East Asian students with those elements of Western academic norms that are perceived to be aligned with these. This is a relatively new area of research which represents a challenge for British lecturers and students
Negotiating professional and social voices in research principles and practice
This paper draws on work conducted for a qualitative interview based study which explores the gendered racialised and professional identifications of health and social care professionals. Participants for the project were drawn from the professional executive committees of recently formed Primary Care Trusts. The paper discusses how the feminist psychosocial methodological approach developed for the project is theoretically, practically and ethically useful in exploring the voices of those in positions of relative power in relation to both health and social care services and the social relations of gender and ethnicity. The approach draws on psychodynamic accounts of (defended) subjectivity and the feminist work of Carol Gilligan on a voice-centred relational methodology. Coupling the feminist with the psychosocial facilitates an emphasis on voice and dialogic communication between participant and researcher not always captured in psychosocial approaches which tend towards favouring the interviewer as ‘good listener’. This emphasis on dialogue is important in research contexts where prior and ongoing relationships with professional participants make it difficult and indeed undesirable for researchers to maintain silence
Gender, age and the MBA: An analysis of extrinsic and intrinsic career benefits
Against the background of an earlier UK study, this paper presents the findings of a Canadian based survey of career benefits from the MBA. Results indicate firstly that gender and age interact to influence perceptions of career outcomes (young men gain most in terms of extrinsic benefits of career change and pay), and secondly that both men and women gain intrinsic benefits from the MBA. However, intrinsic benefits vary by gender: men in the study were more likely to say they gained confidence from having a fuller skill set while women were more likely to say they gained confidence from feelings of self worth; men emphasised how they had learned to give up control while women argued that they had gained a ‘voice’ in the organization. The role of the MBA in career self- management and the acquisition of key skills are examined as well as the implications for the design of programmes in meeting the varied need of men and women in different age groups
Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering
We report a significant enhancement of the upper critical field of
different samples alloyed with nonmagnetic impurities. By studying
films and bulk polycrystals with different resistivities , we show a
clear trend of increase as increases. One particular high
resistivity film had zero-temperature well above the
values of competing non-cuprate superconductors such as and Nb-Ti. Our
high-field transport measurements give record values and for high resistivity films and
for untextured bulk polycrystals. The highest
film also exhibits a significant upward curvature of , and
temperature dependence of the anisotropy parameter opposite to that of single crystals: decreases as the
temperature decreases, from to .
This remarkable enhancement and its anomalous temperature dependence
are a consequence of the two-gap superconductivity in , which offers
special opportunities for further increase by tuning of the impurity
scattering by selective alloying on Mg and B sites. Our experimental results
can be explained by a theory of two-gap superconductivity in the dirty limit.
The very high values of observed suggest that can be made
into a versatile, competitive high-field superconductor.Comment: An updated version of the paper (12/12/2002)that was placed on
cond-mat on May 7 200
Strange Meson Enhancement in PbPb Collisions
The NA44 Collaboration has measured yields and differential distributions of
K+, K-, pi+, pi- in transverse kinetic energy and rapidity, around the
center-of-mass rapidity in 158 A GeV/c Pb+Pb collisions at the CERN SPS. A
considerable enhancement of K+ production per pi is observed, as compared to
p+p collisions at this energy. To illustrate the importance of secondary hadron
rescattering as an enhancement mechanism, we compare strangeness production at
the SPS and AGS with predictions of the transport model RQMD.Comment: 11 pages, including 4 figures, LATE
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