19 research outputs found
New bounds for the free energy of directed polymers in dimension 1+1 and 1+2
We study the free energy of the directed polymer in random environment in
dimension 1+1 and 1+2. For dimension 1, we improve the statement of Comets and
Vargas concerning very strong disorder by giving sharp estimates on the free
energy at high temperature. In dimension 2, we prove that very strong disorder
holds at all temperatures, thus solving a long standing conjecture in the
field.Comment: 31 pages, 4 figures, final version, accepted for publication in
Communications in Mathematical Physic
Quantum field theory of metallic spin glasses
We introduce an effective field theory for the vicinity of a zero temperature
quantum transition between a metallic spin glass (``spin density glass'') and a
metallic quantum paramagnet. Following a mean field analysis, we perform a
perturbative renormalization-group study and find that the critical properties
are dominated by static disorder-induced fluctuations, and that dynamic
quantum-mechanical effects are dangerously irrelevant. A Gaussian fixed point
is stable for a finite range of couplings for spatial dimensionality ,
but disorder effects always lead to runaway flows to strong coupling for . Scaling hypotheses for a {\em static\/} strong-coupling critical field
theory are proposed. The non-linear susceptibility has an anomalously weak
singularity at such a critical point. Although motivated by a perturbative
study of metallic spin glasses, the scaling hypotheses are more general, and
could apply to other quantum spin glass to paramagnet transitions.Comment: 16 pages, REVTEX 3.0, 2 postscript figures; version contains
reference to related work in cond-mat/950412
Observation of X(3872) production in pp collisions at âs=7TeV
Using 34.7 pbâ1 of data collected with the LHCb
detector, the inclusive production of the X(3872) meson in
pp collisions at âs = 7 TeV is observed for the first time.
Candidates are selected in the X(3872)âJ/ÏÏ+Ïâ decay
mode, and used to measure Ï(ppâX(3872)+anything)B(X(3872)âJ/ÏÏ+Ïâ) = 5.4 ±1.3 (stat)±0.8 (syst) nb, where Ï(pp âX(3872) + anything) is the inclusive production cross section of X(3872) mesons with rapidity in the range 2.5â4.5 and transverse momentum in the range 5â20 GeV/c. In addition the masses of both the X(3872) and Ï(2S) mesons, reconstructed in the J/ÏÏ+Ïâ final state, are measured to be mX(3872) = 3871.95± 0.48 (stat)±0.12 (syst) MeV/c2 and
mÏ(2S) = 3686.12±0.06 (stat) ±0.10 (syst) MeV/c2
Generation of a large combinatorial library of the immunoglobulin repertoire in phage lambda
A novel bacteriophage lambda vector system was used to express in Escherichia coli a combinatorial library of Fab fragments of the mouse antibody repertoire. The system allows rapid and easy identification of monoclonal Fab fragments in a form suitable for genetic manipulation. It was possible to generate, in 2 weeks, large numbers of monoclonal Fab fragments against a transition state analog hapten. The methods described may supersede present-day hybridoma technology and facilitate the production of catalytic and other antibodies
The Functional Expression of Antibody Fv Fragments in Ischhuchia coli: Improved Vectors and a Generally Applicable Purification Technique
Internal and External Change Agents
A survey questionnaire was designed and distributed to samples of internal and external change agents which measured the extent to which they professed values traditionally associated with the field of OD. The survey also included questions concerning the types of interventions utilised in the change programmes that respondents had been associated with in the previous five years as well as how these programmes had been evaluated. As predicted, external change agents were more likely to profess traditional OD values and to be associated with change programmes which included human processual interventions. Contrary to expectations, internal change agents were less likely than external change agents to be associated with the utilisation of technostructural interventions. Support was also generated for the prediction that internal change agents are more likely to carry out extensive programme evaluations
Mutation analysis of the MCHR1 gene in human obesity.
Objective: The importance of the melanin-concentrating hormone (MCH) system for regulation of energy homeostasis and body weight has been demonstrated in rodents. We analysed the human MCH receptor 1 gene (MCHR1) with respect to human obesity. Design: This consisted of genomic screening of 13.4 kb encompassing the MCHR1 in extremely obese German children and adolescents and association analyses for two coding single nucleotide polymorphisms (SNPs). To confirm initial positive association results, additional association studies and transmission disequilibrium tests in further German, Danish, French and American samples were conducted. Selected SNPs were investigated using functional in vitro studies and reporter gene assays. Methods: Single-stranded conformation polymorphism analysis, re-sequencing, PCR-restriction fragment length polymorphism analyses, tetra-primer amplification refractory mutation systems, matrix-assisted laser desorption/ionization time of flight mass spectrometry and reporter gene assays were carried out as well as measuring inositol phosphate formation, inhibition of cAMP formation and activation of p42/44 MAP kinase. Results: We identified 11 infrequent variations and two SNPs in the MCHR1 coding sequence and 18 SNPs (eight novel) in the flanking sequence. Association and transmission disequilibrium with obesity were detected for several SNPs in independent study groups of German obese children and adolescents and controls. In two German samples, encompassing 4056 and 295 individuals, trends towards association with obesity were detected. Findings in a second epidemiological German sample and in Danish, French and American samples were negative. Functional in vitro studies as well as reporter gene assays revealed no significant results. Conclusion: Our initial association of MCHR1 alleles/haplotype detected might be related to juvenile-onset obesity, conditional on a particular genetic and/or environmental background. Alternatively, we could not exclude the possibility that the initially detected association represented a false positive finding. © 2005 Society of the European Journal of Endocrinology