1,667 research outputs found
Critical State Flux Penetration and Linear Microwave Vortex Response in YBa_2Cu_3O_{7-x} Films
The vortex contribution to the dc field (H) dependent microwave surface
impedance Z_s = R_s+iX_s of YBa_2Cu_3O_{7-x} thin films was measured using
suspended patterned resonators. Z_s(H) is shown to be a direct measure of the
flux density B(H) enabling a very precise test of models of flux penetration.
Three regimes of field-dependent behavior were observed: (1) Initial flux
penetration occurs on very low field scales H_i(4.2K) 100Oe, (2) At moderate
fields the flux penetration into the virgin state is in excellent agreement
with calculations based upon the field-induced Bean critical state for thin
film geometry, parametrized by a field scale H_s(4.2K) J_c*d 0.5T, (3) for very
high fields H >>H_s, the flux density is uniform and the measurements enable
direct determination of vortex parameters such as pinning force constants
\alpha_p and vortex viscosity \eta. However hysteresis loops are in
disagreement with the thin film Bean model, and instead are governed by the low
field scale H_i, rather than by H_s. Geometric barriers are insufficient to
account for the observed results.Comment: 20 pages, LaTeX type, Uses REVTeX style files, Submitted to Physical
Review B, 600 dpi PostScript file with high resolution figures available at
http://sagar.physics.neu.edu/preprints.htm
Microwave Current Imaging in Passive HTS Components by Low-Temperature Laser Scanning Microscopy (LTLSM)
We have used the LTLSM technique for a spatially resolved investigation of
the microwave transport properties, nonlinearities and material inhomogeneities
in an operating coplanar waveguide YBa_2Cu_3O_{7-\delta} (YBCO) microwave
resonator on an LaAlO_3 (LAO) substrate. The influence of twin-domain blocks,
in-plane rotated grains, and micro-cracks in the YBCO film on the nonuniform rf
current distribution were measured with a micrometer-scale spatial resolution.
The impact of the peaked edge currents and rf field penetration into weak links
on the linear device performance were studied as well. The LTLSM capabilities
and its future potential for non-destructive characterization of the microwave
properties of superconducting circuits are discussed.Comment: 8 pages, 9 figures, 2-column format, presented at High Temperature
Superconductors in High Frequency Fields 2004, Journal of Superconductivity
(in press
Freely decaying weak turbulence for sea surface gravity waves
We study numerically the generation of power laws in the framework of weak
turbulence theory for surface gravity waves in deep water. Starting from a
random wave field, we let the system evolve numerically according to the
nonlinear Euler equations for gravity waves in infinitely deep water. In
agreement with the theory of Zakharov and Filonenko, we find the formation of a
power spectrum characterized by a power law of the form of .Comment: 4 pages, 3 figure
The etiology of mathematical and reading (dis)ability covariation in a sample of Dutch twins
The genetic etiology of mathematical and reading (dis)ability has been studied in a number of distinct samples, but the true nature of the relationship between the two remains unclear. Data from the Netherlands Twin Register was used to determine the etiology of the relationship between mathematical and reading (dis)ability in adolescent twins. Ratings of mathematical and reading problems were obtained from parents of over 1500 twin pairs. Results of bivariate structural equation modeling showed a genetic correlation around .60, which explained over 90% of the phenotypic correlation between mathematical and reading ability. The genetic model was the same for males and females
Beyond Prejudice as Simple Antipathy: Hostile and Benevolent Sexism Across Cultures
The authors argue that complementary hostile and benevolent componen:s of sexism exist ac ro.ss
cultures. Male dominance creates hostile sexism (HS). but men's dependence on women fosters
benevolent sexism (BS)-subjectively positive attitudes that put women on a pedestal but reinforce their
subordination. Research with 15,000 men and women in 19 nations showed that (a) HS and BS are
coherenl constructs th at correlate positively across nations, but (b) HS predicts the ascription of negative
and BS the ascription of positive traits to women, (c) relative to men, women are more likely to reject
HS than BS. especially when overall levels of sexism in a culture are high, and (d) national averages on
BS and HS predict gender inequal ity across nations. These results challenge prevailing notions of
prejudice as an antipathy in that BS (an affectionate, patronizing ideology) reflects inequality and is a
cross-culturally pervasive complement to HS
Heritability and genome-wide linkage scan of subjective happiness
Causes of individual differences in happiness, as assessed with the Subjective Happiness Scale, are investigated in a large of sample twins and siblings from the Netherlands Twin Register. Over 12,000 twins and siblings, average age 24.7 years (range 12 to 88), took part in the study. A genetic model with an age by sex design was fitted to the data with structural equation modeling in Mx. The heritability of happiness was estimated at 22% for males and 41% in females. No effect of age was observed. To identify the genomic regions contributing to this heritability, a genome-wide linkage study for happiness was conducted in sibling pairs. A subsample of 1157 offspring from 441 families was genotyped with an average of 371 micro-satellite markers per individual. Phenotype and genotype data were analyzed in MERLIN with multipoint variance component linkage analysis and age and sex as covariates. A linkage signal (logarithm of odds score 2.73, empirical p value 0.095) was obtained at the end of the long arm of chromosome 19 for marker D19S254 at 110 cM. A second suggestive linkage peak was found at the short arm of chromosome 1 (LOD of 2.37) at 153 cM, marker D1S534 (empirical p value of .209). These two regions of interest are not overlapping with the regions found for contrasting phenotypes (such as depression, which is negatively associated with happiness). Further linkage and future association studies are warranted
Embryonic morphological development is delayed in pregnancies ending in a spontaneous miscarriage
Lymphoid tumours and breast cancer in ataxia telangiectasia; substantial protective effect of residual ATM kinase activity against childhood tumours
BACKGROUND: Immunodeficiency in ataxia telangiectasia (A-T) is less severe in patients expressing some mutant or normal ATM kinase activity. We, therefore, determined whether expression of residual ATM kinase activity also protected against tumour development in A-T. METHODS: From a total of 296 consecutive genetically confirmed A-T patients from the British Isles and the Netherlands, we identified 66 patients who developed a malignant tumour; 47 lymphoid tumours and 19 non-lymphoid tumours were diagnosed. We determined their ATM mutations, and whether cells from these patients expressed any ATM with residual ATM kinase activity. RESULTS: In childhood, total absence of ATM kinase activity was associated, almost exclusively, with development of lymphoid tumours. There was an overwhelming preponderance of tumours in patients <16 years without kinase activity compared with those with some residual activity, consistent with a substantial protective effect of residual ATM kinase activity against tumour development in childhood. In addition, the presence of eight breast cancers in A-T patients, a 30-fold increased risk, establishes breast cancer as part of the A-T phenotype. CONCLUSION: Overall, a spectrum of tumour types is associated with A-T, consistent with involvement of ATM in different mechanisms of tumour formation. Tumour type was influenced by ATM allelic heterogeneity, residual ATM kinase activity and age
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