2,370 research outputs found
Nambu monopoles in lattice Electroweak theory
We considered the lattice electroweak theory at realistic values of
and and for large values of the Higgs mass. We investigated
numerically the properties of topological objects that are identified with
quantum Nambu monopoles. We have found that the action density near the Nambu
monopole worldlines exceeds the density averaged over the lattice in the
physical region of the phase diagram. Moreover, their percolation probability
is found to be an order parameter for the transition between the symmetric and
the broken phases. Therefore, these monopoles indeed appear as real physical
objects. However, we have found that their density on the lattice increases
with increasing ultraviolet cutoff. Thus we conclude, that the conventional
lattice electroweak theory is not able to predict the density of Nambu
monopoles. This means that the description of Nambu monopole physics based on
the lattice Weinberg - Salam model with finite ultraviolet cutoff is
incomplete. We expect that the correct description may be obtained only within
the lattice theory that involves the description of TeV - scale physics.Comment: LATE
A novel approach to light-front perturbation theory
We suggest a possible algorithm to calculate one-loop n-point functions
within a variant of light-front perturbation theory. The key ingredients are
the covariant Passarino-Veltman scheme and a surprising integration formula
that localises Feynman integrals at vanishing longitudinal momentum. The
resulting expressions are generalisations of Weinberg's infinite-momentum
results and are manifestly Lorentz invariant. For n = 2 and 3 we explicitly
show how to relate those to light-front integrals with standard energy
denominators. All expressions are rendered finite by means of transverse
dimensional regularisation.Comment: 10 pages, 5 figure
Looking back and moving forward
This chapter brings together the research on teacher resilience and approaches to supporting resilience and wellbeing discussed in this volume. As many of the approaches utilised aspects of the BRiTE and Staying BRiTE projects, I highlight common themes as well as the different ways the authors developed and implemented their work to reflect their specific contexts and participants. I also reflect on broader issues related to conceptualisation of resilience, consider where responsibility for resilience lies, and explore future directions. The chapter also provides some insights regarding the collegial collaboration that has made the body of work possible
On the accuracy of language trees
Historical linguistics aims at inferring the most likely language
phylogenetic tree starting from information concerning the evolutionary
relatedness of languages. The available information are typically lists of
homologous (lexical, phonological, syntactic) features or characters for many
different languages.
From this perspective the reconstruction of language trees is an example of
inverse problems: starting from present, incomplete and often noisy,
information, one aims at inferring the most likely past evolutionary history. A
fundamental issue in inverse problems is the evaluation of the inference made.
A standard way of dealing with this question is to generate data with
artificial models in order to have full access to the evolutionary process one
is going to infer. This procedure presents an intrinsic limitation: when
dealing with real data sets, one typically does not know which model of
evolution is the most suitable for them. A possible way out is to compare
algorithmic inference with expert classifications. This is the point of view we
take here by conducting a thorough survey of the accuracy of reconstruction
methods as compared with the Ethnologue expert classifications. We focus in
particular on state-of-the-art distance-based methods for phylogeny
reconstruction using worldwide linguistic databases.
In order to assess the accuracy of the inferred trees we introduce and
characterize two generalizations of standard definitions of distances between
trees. Based on these scores we quantify the relative performances of the
distance-based algorithms considered. Further we quantify how the completeness
and the coverage of the available databases affect the accuracy of the
reconstruction. Finally we draw some conclusions about where the accuracy of
the reconstructions in historical linguistics stands and about the leading
directions to improve it.Comment: 36 pages, 14 figure
Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons
We report on the generation of coherent phonon polaritons in ZnTe, GaP and
LiTaO using ultrafast optical pulses. These polaritons are coupled modes
consisting of mostly far-infrared radiation and a small phonon component, which
are excited through nonlinear optical processes involving the Raman and the
second-order susceptibilities (difference frequency generation). We probe their
associated hybrid vibrational-electric field, in the THz range, by
electro-optic sampling methods. The measured field patterns agree very well
with calculations for the field due to a distribution of dipoles that follows
the shape and moves with the group velocity of the optical pulses. For a
tightly focused pulse, the pattern is identical to that of classical Cherenkov
radiation by a moving dipole. Results for other shapes and, in particular, for
the planar and transient-grating geometries, are accounted for by a convolution
of the Cherenkov field due to a point dipole with the function describing the
slowly-varying intensity of the pulse. Hence, polariton fields resulting from
pulses of arbitrary shape can be described quantitatively in terms of
expressions for the Cherenkov radiation emitted by an extended source. Using
the Cherenkov approach, we recover the phase-matching conditions that lead to
the selection of specific polariton wavevectors in the planar and transient
grating geometry as well as the Cherenkov angle itself. The formalism can be
easily extended to media exhibiting dispersion in the THz range. Calculations
and experimental data for point-like and planar sources reveal significant
differences between the so-called superluminal and subluminal cases where the
group velocity of the optical pulses is, respectively, above and below the
highest phase velocity in the infrared.Comment: 13 pages, 11 figure
Genetic Modulation of Lipid Profiles following Lifestyle Modification or Metformin Treatment: the Diabetes Prevention Program
Weight-loss interventions generally improve lipid profiles and reduce cardiovascular disease risk, but effects are variable and may depend on genetic factors. We performed a genetic association analysis of data from 2,993 participants in the Diabetes Prevention Program to test the hypotheses that a genetic risk score (GRS) based on deleterious alleles at 32 lipid-associated single-nucleotide polymorphisms modifies the effects of lifestyle and/or metformin interventions on lipid levels and nuclear magnetic resonance (NMR) lipoprotein subfraction size and number. Twenty-three loci previously associated with fasting LDL-C, HDL-C, or triglycerides replicated (P=0.04–1×10). Except for total HDL particles (r=−0.03, P=0.26), all components of the lipid profile correlated with the GRS (partial |r|=0.07–0.17, P=5×10–1×10). The GRS was associated with higher baseline-adjusted 1-year LDL cholesterol levels (β=+0.87, SEE±0.22 mg/dl/allele, P=8×10−5, P=0.02) in the lifestyle intervention group, but not in the placebo (β=+0.20, SEE±0.22 mg/dl/allele, P=0.35) or metformin (β=−0.03, SEE±0.22 mg/dl/allele, P=0.90; P=0.64) groups. Similarly, a higher GRS predicted a greater number of baseline-adjusted small LDL particles at 1 year in the lifestyle intervention arm (β=+0.30, SEE±0.012 ln nmol/L/allele, P=0.01, P=0.01) but not in the placebo (β=−0.002, SEE±0.008 ln nmol/L/allele, P=0.74) or metformin (β=+0.013, SEE±0.008 nmol/L/allele, P=0.12; P = 0.24) groups. Our findings suggest that a high genetic burden confers an adverse lipid profile and predicts attenuated response in LDL-C levels and small LDL particle number to dietary and physical activity interventions aimed at weight loss
Wideband THz time domain spectroscopy based on optical rectification and electro-optic sampling
We present an analytical model describing the full electromagnetic propagation in a THz time-domain spectroscopy (THz-TDS) system, from the THz pulses via Optical Rectification to the detection via Electro Optic-Sampling. While several investigations deal singularly with the many elements that constitute a THz-TDS, in our work we pay particular attention to the modelling of the time-frequency behaviour of all the stages which compose the experimental set-up. Therefore, our model considers the following main aspects: (i) pump beam focusing into the generation crystal; (ii) phase-matching inside both the generation and detection crystals; (iii) chromatic dispersion and absorption inside the crystals; (iv) Fabry-Perot effect; (v) diffraction outside, i.e. along the propagation, (vi) focalization and overlapping between THz and probe beams, (vii) electro-optic sampling. In order to validate our model, we report on the comparison between the simulations and the experimental data obtained from the same set-up, showing their good agreement
Inverse Association between trans Isomeric and Long-Chain Polyunsaturated Fatty Acids in Pregnant Women and Their Newborns: Data from Three European Countries
Background: trans unsaturated fatty acids are thought to interfere with essential fatty acid metabolism. To extend our knowledge of this phenomenon, we investigated the relationship between trans isomeric and long-chain polyunsaturated fatty acids (LCPUFA) in mothers during pregnancy and in their infants at birth. Methods: Fatty acid composition of erythrocyte phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was determined in Spanish (n = 120), German (n = 78) and Hungarian (n = 43) women at the 20th and 30th week of gestation, at delivery and in their newborns. Results: At the 20th week of gestation, the sum of trans fatty acids in PE was significantly (p < 0.01) lower in Hungarian [0.73 (0.51), % wt/wt, median (IQR)] than in Spanish [1.42 (1.36)] and German [1.30 (1.21)] women. Docosahexaenoic acid (DHA) values in PE were significantly (p < 0.01) higher in Hungarian {[}5.65 (2.09)] than in Spanish [4.37 (2.60)] or German [4.39 (3.3.2)] women. The sum of trans fatty acids significantly inversely correlated to DHA in PCs in Spanish (r = -0.37, p < 0.001), German (n = -0.77, p < 0.001) and Hungarian (r = -0.35, p < 0.05) women, and in PEs in Spanish (r = -0.67, p < 0.001) and German (r = -0.71, p < 0.001), but not in Hungarian (r = -0.02) women. Significant inverse correlations were seen between trans fatty acids and DHA in PEs at the 30th week of gestation (n = 241, r = -0.52, p < 0.001), at delivery (n = 241, r = -0.40, p < 0.001) and in cord lipids (n = 218, r = -0.28, p < 0.001). Conclusion: Because humans cannot synthesize trans isomeric fatty acids, the data obtained in the present study support the concept that high maternal trans isomeric fatty acid intake may interfere with the availability of LCPUFA both for the mother and the fetus. Copyright (C) 2011 S. Karger AG, Base
Cross-genotype AR3-specific neutralizing antibodies confer long-term protection in injecting drug users after HCV clearance
Background & AimsUnderstanding immune protection against hepatitis C virus (HCV) infection is necessary for designing an effective vaccine. A number of broadly-reactive, neutralizing antibodies have been isolated from B cells of HCV-infected subjects. However, it remains unclear whether B cells producing such antibodies contribute to the clearance and long-term immune protection against HCV.MethodsWe analysed the B-cell repertoire of thirteen participants from the Amsterdam Cohort Study among injecting drug users with a median follow-up of 17.5 years. Five subjects ultimately became chronically infected either after primary infection or after reinfection. Eight subjects, at the end of study follow-up, were HCV RNA negative following spontaneous clearance of one or multiple infections. From each subject, 10,000 CD27+IgG+ B cells, collected 0.75 year after HCV infection, were cultured to characterize the antibody repertoire.ResultsUsing a multiplex flow cytometry-based assay to study the antibody binding to E1E2 from genotype 1 to 6, we found that a high frequency of cross-genotype antibodies was associated with spontaneous clearance of one or multiple infections (p-value=0.03). Epitope specificity of these cross-genotype antibodies was determined by alanine mutant scanning in four subjects, who were HCV RNA negative following spontaneous clearance of one or multiple infections. Interestingly, the cross-genotype antibodies were mainly AR3-specific and showed cross-neutralizing activity against HCV. In addition to AR3 antibodies, three subjects developed antibodies recognizing AR4 of which one monoclonal antibody showed cross-neutralizing capacity.ConclusionsTogether, these data suggest that a strong B-cell response producing cross-genotype and neutralizing antibodies, especially targeting AR3, contribute to HCV clearance and long-term immune protection against HCV
Covariant Light-Front Approach for s-wave and p-wave Mesons: Its Application to Decay Constants and Form Factors
We study the decay constants and form factors of the ground-state s-wave and
low-lying p-wave mesons within a covariant light-front approach. Numerical
results of the form factors for transitions between a heavy pseudoscalar meson
and an s-wave or p-wave meson and their momentum dependence are presented in
detail. In particular, form factors for heavy-to-light and B to D**
transitions, where D** denotes generically a p-wave charmed meson, are compared
with other model calculations. The experimental measurements of the decays B^-
to D** pi^- and B to D D**_s are employed to test the decay constants of D**_s
and the B to D** transition form factors. The heavy quark limit behavior of the
decay constants and form factors is examined and it is found that the
requirement of heavy quark symmetry is satisfied. The universal Isgur-Wise (IW)
functions, one for s-wave to s-wave and two for s-wave to p-wave transitions,
are obtained. The values of IW functions at zero recoil and their slope
parameters can be used to test the Bjorken and Uraltsev sum rules.Comment: 59 pages, 6 figures. Version to appear in Phys. Rev. D. Changes are:
(i) D_s to phi transition form factors are discussed and compared with the
recent FOCUS measurements and (ii) zero mode effects are clarifie
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