1,053 research outputs found
Determination of spin and orbital magnetization in the ferromagnetic superconductor UCoGe
International audienceThe magnetism in the ferromagnetic superconductor UCoGe has been studied using a combination of magnetic Compton scattering, bulk magnetization, X-ray magnetic circular dichroism and electronic structure calculations, in order to determine the spin and orbital moments. The experimentally observed total spin moment, Ms, was found to be-0.24 ± 0.05 ”B at 5 T. By comparison with the total moment of 0.16 ± 0.01 ”B, the orbital moment, M l , was determined to be 0.40 ± 0.05 ”B. The U and Co spin moments were determined to be antiparallel. We find that the U 5f electrons carry a spin moment of Us â-0.30 ”B and that there is a Co spin moment of Cos â 0.06 ”B induced via hybridization. The ratio U l /Us, of â1.3 ± 0.3, shows the U moment to be itinerant. In order to ensure an accurate description of the properties of 5f systems, and to provide a critical test of the theoretical approaches, it is clearly necessary to obtain experimental data for both the spin and orbital moments, rather than just the total magnetic moment. This can be achieved simply by measuring the spin moment with magnetic Compton scattering and comparing this to the total moment from bulk magnetizatio
The effect of time delay in plant-pathogen interactions with host demography
Background: There is a need for valid and comprehensive measures of parental influence on children's energy balance-related behaviours (EBRB). Such measures should be based on a theoretical framework, acknowledging the dynamic and complex nature of interactions occurring within a family. The aim of the Family & Dietary habits (F&D) project was to develop a conceptual framework identifying important and changeable family processes influencing dietary behaviours of 13-15 year olds. A second aim was to develop valid and reliable questionnaires for adolescents and their parents (both mothers and fathers) measuring these processes. Methods: A stepwise approach was used; (1) preparation of scope and structure, (2) development of the F&D questionnaires, (3) the conducting of pilot studies and (4) the conducting of validation studies (assessing internal reliability, test-retest reliability and confirmatory factor analysis) using data from a cross-sectional study. Results: The conceptual framework includes psychosocial concepts such as family functioning, cohesion, conflicts, communication, work-family stress, parental practices and parental style. The physical characteristics of the home environment include accessibility and availability of different food items, while family meals are the sociocultural setting included. Individual characteristics measured are dietary intake (vegetables and sugar-sweetened beverages) and adolescents' impulsivity. The F&D questionnaires developed were tested in a test-retest (54 adolescents and 44 of their parents) and in a cross-sectional survey including 440 adolescents (13-15 year olds), 242 mothers and 155 fathers. The samples appear to be relatively representative for Norwegian adolescents and parents. For adolescents, mothers and fathers, the test-retest reliability of the dietary intake, frequencies of (family) meals, work-family stress and communication variables was satisfactory (ICC: 0.53-0.99). Barratt Impulsiveness Scale-Brief (BIS-Brief) was included, assessing adolescent's impulsivity. The internal reliability (Cronbach's alphas: 0.77/0.82) and test-retest reliability values (ICC: 0.74/0.77) of BIS-Brief were good. Conclusions: The conceptual framework developed may be a useful tool in guiding measurement and assessment of the home food environment and family processes related to adolescents' dietary habits, in particular and for EBRBs more generally. The results support the use of the F&D questionnaires as psychometrically sound tools to assess family characteristics and adolescent's impulsivity
Using grounded theory for theory building in operations management research:a study on inter-firm relationship governance
Purpose â Qualitative theory building approaches, such as grounded theory method (GTM), are still not very widespread and rigorously applied in operations management (OM) research. Yet it is agreed that more systematic observation of current industrial phenomena is necessary to help managers deal with their problems. The purpose of this paper is to provide an example to help guide other researchers on using GTM for theory building in OM research. Design/methodology/approach â A GTM study in the German automotive industry consisting of 31 interviews is followed by a validation stage comprising a survey (110 responses) and a focus group. Findings â The result is an example of conducting GTM research in OM, illustrated by the development of the novel collaborative enterprise governance framework for inter-firm relationship governance in the German automotive industry. Research limitations/implications â GTM is appropriate for qualitative theory building research, but the resultant theories need further testing. Research is necessary to identify the transferability of the collaborative enterprise governance concept to other industries than automotive, to other organisational areas than R&D and to product and service settings that are less complex and innovative. Practical implications â The paper helps researchers make more informed use of GTM when engaging in qualitative theory building research in OM. Originality/value â There is a lack of explicit and well-informed use of GTM in OM research because of poor understanding. This paper addresses this deficiency. The collaborative enterprise governance framework is a significant contribution in an area of growing importance within OM
Wetting films on chemically heterogeneous substrates
Based on a microscopic density functional theory we investigate the
morphology of thin liquidlike wetting films adsorbed on substrates endowed with
well-defined chemical heterogeneities. As paradigmatic cases we focus on a
single chemical step and on a single stripe. In view of applications in
microfluidics the accuracy of guiding liquids by chemical microchannels is
discussed. Finally we give a general prescription of how to investigate
theoretically the wetting properties of substrates with arbitrary chemical
structures.Comment: 56 pages, RevTeX, 20 Figure
The Correlated Colors of Transneptunian Binaries
We report resolved photometry of the primary and secondary components of 23
transneptunian binaries obtained with the Hubble Space Telescope. V-I colors of
the components range from 0.7 to 1.5 with a median uncertainty of 0.06
magnitudes. The colors of the primaries and secondaries are correlated with a
Spearman rank correlation probability of 99.99991%, 5 sigma for a normal
distribution. Fits to the primary vs. secondary colors are identical to within
measurement uncertainties. The color range of binaries as a group is
indistinguishable from that of the larger population of apparently single
transneptunian objects. Whatever mechanism produced the colors of apparently
single TNOs acted equally on binary systems. The most likely explanation is
that the colors of transneptunian objects and binaries alike are primordial and
indicative of their origin in a locally homogeneous, globally heterogeneous
protoplanetary disk.Comment: 28 pages, 4 figure, 4 tables. accepted to Icaru
The Vlasov limit and its fluctuations for a system of particles which interact by means of a wave field
In two recent publications [Commun. PDE, vol.22, p.307--335 (1997), Commun.
Math. Phys., vol.203, p.1--19 (1999)], A. Komech, M. Kunze and H. Spohn studied
the joint dynamics of a classical point particle and a wave type generalization
of the Newtonian gravity potential, coupled in a regularized way. In the
present paper the many-body dynamics of this model is studied. The Vlasov
continuum limit is obtained in form equivalent to a weak law of large numbers.
We also establish a central limit theorem for the fluctuations around this
limit.Comment: 68 pages. Smaller corrections: two inequalities in sections 3 and two
inequalities in section 4, and definition of a Banach space in appendix A1.
Presentation of LLN and CLT in section 4.3 improved. Notation improve
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si
detectors to search for Weakly Interacting Massive Particles (WIMPs) via their
elastic-scattering interactions with nuclei while discriminating against
interactions of background particles. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of CDMS data from 1998 and 1999 with a relaxed
fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent
with an earlier analysis with a more restrictive fiducial-volume cut.
Twenty-three WIMP candidate events are observed, but these events are
consistent with a background from neutrons in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.Comment: 40 pages, 49 figures (4 in color), submitted to Phys. Rev. D;
v.2:clarified conclusions, added content and references based on referee's
and readers' comments; v.3: clarified introductory sections, added figure
based on referee's comment
ADAMTS19-associated heart valve defects: Novel genetic variants consolidating a recognizable cardiac phenotype
Recently, ADAMTS19 was identified as a novel causative gene for autosomal recessive heart valve disease (HVD), affecting mainly the aortic and pulmonary valves. Exome sequencing and data repository (CentoMD) analyses were performed to identify patients with ADAMTS19 variants (two families). A third family was recognized based on cardiac phenotypic similarities and SNP array homozygosity. Three novel loss of function (LoF) variants were identified in six patients from three families. Clinically, all patients presented anomalies of the aortic/pulmonary valves, which included thickening of valve leaflets, stenosis and insufficiency. Three patients had (recurrent) subaortic membrane, suggesting that ADAMTS19 is the first gene identified related to discrete subaortic stenosis. One case presented a bi-commissural pulmonary valve. All patients displayed some degree of atrioventricular valve insufficiency. Other cardiac anomalies included atrial/ventricular septal defects, persistent ductus arteriosus, and mild dilated ascending aorta. Our findings confirm that biallelic LoF variants in ADAMTS19 are causative of a specific and recognizable cardiac phenotype. We recommend considering ADAMTS19 genetic testing in all patients with multiple semilunar valve abnormalities, particularly in the presence of subaortic membrane. ADAMTS19 screening in patients with semilunar valve abnormalities is needed to estimate the frequency of the HVD related phenotype, which might be not so rare
The first ultracompact Roche lobe-filling hot subdwarf binary
We report the discovery of the first short period binary in which a hot subdwarf star (sdOB) fills its Roche lobe and started mass transfer to its companion. The object was discovered as part of a dedicated high-cadence survey of the Galactic Plane named the Zwicky Transient Facility and exhibits a period of Porb=39.3401(1) min, making it the most compact hot subdwarf binary currently known. Spectroscopic observations are consistent with an intermediate He-sdOB star with an effective temperature of Teff=42,400±300 K and a surface gravity of log(g)=5.77±0.05. A high-signal-to noise GTC+HiPERCAM light curve is dominated by the ellipsoidal deformation of the sdOB star and an eclipse of the sdOB by an accretion disk. We infer a low-mass hot subdwarf donor with a mass MsdOB=0.337±0.015 Mâ and a white dwarf accretor with a mass MWD=0.545±0.020 Mâ. Theoretical binary modeling indicates the hot subdwarf formed during a common envelope phase when a 2.5â2.8 Mâ star lost its envelope when crossing the Hertzsprung Gap. To match its current Porb, Teff, log(g), and masses, we estimate a post-common envelope period of Porbâ150 min, and find the sdOB star is currently undergoing hydrogen shell burning. We estimate that the hot subdwarf will become a white dwarf with a thick helium layer of â0.1 Mâ and will merge with its carbon/oxygen white dwarf companion after â17 Myr and presumably explode as a thermonuclear supernova or form an R CrB star
Magnetic Field Amplification in Galaxy Clusters and its Simulation
We review the present theoretical and numerical understanding of magnetic
field amplification in cosmic large-scale structure, on length scales of galaxy
clusters and beyond. Structure formation drives compression and turbulence,
which amplify tiny magnetic seed fields to the microGauss values that are
observed in the intracluster medium. This process is intimately connected to
the properties of turbulence and the microphysics of the intra-cluster medium.
Additional roles are played by merger induced shocks that sweep through the
intra-cluster medium and motions induced by sloshing cool cores. The accurate
simulation of magnetic field amplification in clusters still poses a serious
challenge for simulations of cosmological structure formation. We review the
current literature on cosmological simulations that include magnetic fields and
outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure
- âŠ