429 research outputs found
Dynamic charge density correlation function in weakly charged polyampholyte globules
We study solutions of statistically neutral polyampholyte chains containing a
large fraction of neutral monomers. It is known that, even if the quality of
the solvent with respect to the neutral monomers is good, a long chain will
collapse into a globule. For weakly charged chains, the interior of this
globule is semi-dilute. This paper considers mainly theta-solvents, and we
calculate the dynamic charge density correlation function g(k,t) in the
interior of the globules, using the quadratic approximation to the
Martin-Siggia-Rose generating functional. It is convenient to express the
results in terms of dimensionless space and time variables. Let R be the blob
size, and let T be the characteristic time scale at the blob level. Define the
dimensionless wave vector q = R k, and the dimensionless time s = t/T. We find
that for q<1, corresponding to length scales larger than the blob size, the
charge density fluctuations relax according to g(q,s) = q^2(1-s^(1/2)) at short
times s < 1, and according to g(q,s) = q^2 s^(-1/2) at intermediate times 1 < s
0.1, where
entanglements are unimportant.Comment: 12 pages RevTex, 1 figure ps, PACS 61.25.Hq, reason replacement:
Expression for dynamic corr. function g(k,t) in old version was incorrect
(though expression for Fourier transform g(k,w) was correct, so the major
part of the calculation remains.) Also major textual chang
Geochemical analysis of bulk marine sediment by Inductively Coupled Plasma–Atomic Emission Spectroscopy on board the JOIDES Resolution
Geochemical analyses on board the JOIDES Resolution have been enhanced with the addition of a Jobin-Yvon Ultrace inductively coupled plasma-atomic emission spectrometer (ICP-AES) as an upgrade from the previous X-ray fluorescence facility. During Leg 199, we sought to both challenge and utilize the capabilities of the ICP-AES in order to provide an extensive bulk-sediment geochemical database during the cruise. These near real-time analyses were then used to help characterize the recovered sedimentary sequences, calculate mass accumulation rates of the different sedimentary components, and assist with cruise and postcruise sampling requests. The general procedures, sample preparation techniques, and basic protocol for ICP-AES analyses on board ship are outlined by Murray et al. (2000) in Ocean Drilling Program Tech Note, 29. We expand on those concepts and offer suggestions for ICP-AES methodology, calibration by standard reference materials, data reduction procedures, and challenges that are specific to the analysis of bulk-sediment samples. During Leg 199, we employed an extensive bulk-sediment analytical program of ~600 samples of varying lithologies, thereby providing several opportunities for refinement of techniques. We also discuss some difficulties and challenges that were faced and suggest how to alleviate such occurrences for sedimentary chemical analyses during future legs
Frequency-modulated atomic force microscopy localises viscoelastic remodelling in the ageing sheep aorta
We gratefully acknowledge funding from the Royal Society for the provision of an International Travel Grant for Collaboration (R112205) to RA, and Wellcome Trust Value in People Award to RA and MJS. MJS and BD gratefully acknowledge the support of the Medical Research Council (www.mrc.ac.uk: grant reference G1001398)
Sibling Rivalry among Paralogs Promotes Evolution of the Human Brain
Geneticists have long sought to identify the genetic changes that made us human, but pinpointing the functionally relevant changes has been challenging. Two papers in this issue suggest that partial duplication of SRGAP2, producing an incomplete protein that antagonizes the original, contributed to human brain evolution
Recent results on multiplicative noise
Recent developments in the analysis of Langevin equations with multiplicative
noise (MN) are reported. In particular, we:
(i) present numerical simulations in three dimensions showing that the MN
equation exhibits, like the Kardar-Parisi-Zhang (KPZ) equation both a weak
coupling fixed point and a strong coupling phase, supporting the proposed
relation between MN and KPZ;
(ii) present dimensional, and mean field analysis of the MN equation to
compute critical exponents;
(iii) show that the phenomenon of the noise induced ordering transition
associated with the MN equation appears only in the Stratonovich representation
and not in the Ito one, and
(iv) report the presence of a new first-order like phase transition at zero
spatial coupling, supporting the fact that this is the minimum model for noise
induced ordering transitions.Comment: Some improvements respect to the first versio
Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA
Deep--inelastic scattering events with a leading baryon have been detected by
the H1 experiment at HERA using a forward proton spectrometer and a forward
neutron calorimeter. Semi--inclusive cross sections have been measured in the
kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T
<= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV,
or a neutron with energy E' >= 160 GeV. The measurements are used to test
production models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi-inclusive cross sections in the
region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading
neutron data are used to estimate for the first time the structure function of
the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.
Correlations, soliton modes, and non-Hermitian linear mode transmutation in the 1D noisy Burgers equation
Using the previously developed canonical phase space approach applied to the
noisy Burgers equation in one dimension, we discuss in detail the growth
morphology in terms of nonlinear soliton modes and superimposed linear modes.
We moreover analyze the non-Hermitian character of the linear mode spectrum and
the associated dynamical pinning and mode transmutation from diffusive to
propagating behavior induced by the solitons. We discuss the anomalous
diffusion of growth modes, switching and pathways, correlations in the
multi-soliton sector, and in detail the correlations and scaling properties in
the two-soliton sector.Comment: 50 pages, 15 figures, revtex4 fil
Multiethnic meta-analysis identifies ancestry-specific and cross-ancestry loci for pulmonary function
Nearly 100 loci have been identified for pulmonary function, almost exclusively in studies of European ancestry populations. We extend previous research by meta-analyzing genome-wide association studies of 1000 Genomes imputed variants in relation to pulmonary function in a multiethnic population of 90,715 individuals of European (N = 60,552), African (N = 8429), Asian (N = 9959), and Hispanic/Latino (N = 11,775) ethnicities. We identify over 50 additional loci at genome-wide significance in ancestry-specific or multiethnic meta-analyses. Using recent fine-mapping methods incorporating functional annotation, gene expression, and differences in linkage disequilibrium between ethnicities, we further shed light on potential causal variants and genes at known and newly identified loci. Several of the novel genes encode proteins with predicted or established drug targets, including KCNK2 and CDK12. Our study highlights the utility of multiethnic and integrative genomics approaches to extend existing knowledge of the genetics of l
Customer emotions in service failure and recovery encounters
Emotions play a significant role in the workplace, and considerable attention has been given to the study of employee emotions. Customers also play a central function in organizations, but much less is known about customer emotions. This chapter reviews the growing literature on customer emotions in employee–customer interfaces with a focus on service failure and recovery encounters, where emotions are heightened. It highlights emerging themes and key findings, addresses the measurement, modeling, and management of customer emotions, and identifies future research streams. Attention is given to emotional contagion, relationships between affective and cognitive processes, customer anger, customer rage, and individual differences
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