641 research outputs found
The Hagedorn Temperature and Partition Thermodynamics
We review the resonance gas formalism of hadron thermodynamics and recall
that an exponential increase of the resonance spectrum leads to a limiting
temperature of hadronic matter. We then show that the number p(n) of ordered
partitions of an integer n grows exponentially with n and satisfies the integer
counterpart of the statistical bootstrap equation. Considering the set of all
partitions as a Gibbs ensemble provides a partition thermodynamics which is
also governed by a limiting temperature, determined by the combinatorial
structure of the problem. Further associating intrinsic quantum numbers to
integers results in a phase diagram equivalent to that found in QCD for
hadronic matter as function of temperature and baryochemical potential.Comment: Dedicated to Rolf Hagedorn, 1919-2003. 11 pages, 3 figures. Final
version accepted for publication in the European Physical Journal
Novel coronary heart disease risk factors at 60-64 years and life course socioeconomic position: The 1946 British birth cohort.
Social disadvantage across the life course is associated with a greater risk of coronary heart disease (CHD) and with established CHD risk factors, but less is known about whether novel CHD risk factors show the same patterns. The Medical Research Council National Survey of Health and Development was used to investigate associations between occupational socioeconomic position during childhood, early adulthood and middle age and markers of inflammation (C-reactive protein, interleukin-6), endothelial function (E-selectin, tissue-plasminogen activator), adipocyte function (leptin, adiponectin) and pancreatic beta cell function (proinsulin) measured at 60-64 years. Life course models representing sensitive periods, accumulation of risk and social mobility were compared with a saturated model to ascertain the nature of the relationship between social class across the life course and each of these novel CHD risk factors. For interleukin-6 and leptin, low childhood socioeconomic position alone was associated with high risk factor levels at 60-64 years, while for C-reactive protein and proinsulin, cumulative effects of low socioeconomic position in both childhood and early adulthood were associated with higher (adverse) risk factor levels at 60-64 years. No associations were observed between socioeconomic position at any life period with either endothelial marker or adiponectin. Associations for C-reactive protein, interleukin-6, leptin and proinsulin were reduced considerably by adjustment for body mass index and, to a lesser extent, cigarette smoking. In conclusion, socioeconomic position in early life is an important determinant of several novel CHD risk factors. Body mass index may be an important mediator of these relationships
Identification of novel subgroup a variants with enhanced receptor binding and replicative capacity in primary isolates of anaemogenic strains of feline leukaemia virus
<b>BACKGROUND:</b>
The development of anaemia in feline leukaemia virus (FeLV)-infected cats is associated with the emergence of a novel viral subgroup, FeLV-C. FeLV-C arises from the subgroup that is transmitted, FeLV-A, through alterations in the amino acid sequence of the receptor binding domain (RBD) of the envelope glycoprotein that result in a shift in the receptor usage and the cell tropism of the virus. The factors that influence the transition from subgroup A to subgroup C remain unclear, one possibility is that a selective pressure in the host drives the acquisition of mutations in the RBD, creating A/C intermediates with enhanced abilities to interact with the FeLV-C receptor, FLVCR. In order to understand further the emergence of FeLV-C in the infected cat, we examined primary isolates of FeLV-C for evidence of FeLV-A variants that bore mutations consistent with a gradual evolution from FeLV-A to FeLV-C.<p></p>
<b>RESULTS:</b>
Within each isolate of FeLV-C, we identified variants that were ostensibly subgroup A by nucleic acid sequence comparisons, but which bore mutations in the RBD. One such mutation, N91D, was present in multiple isolates and when engineered into a molecular clone of the prototypic FeLV-A (Glasgow-1), enhanced replication was noted in feline cells. Expression of the N91D Env on murine leukaemia virus (MLV) pseudotypes enhanced viral entry mediated by the FeLV-A receptor THTR1 while soluble FeLV-A Env bearing the N91D mutation bound more efficiently to mouse or guinea pig cells bearing the FeLV-A and -C receptors. Long-term in vitro culture of variants bearing the N91D substitution in the presence of anti-FeLV gp70 antibodies did not result in the emergence of FeLV-C variants, suggesting that additional selective pressures in the infected cat may drive the subsequent evolution from subgroup A to subgroup C.<p></p>
<b>CONCLUSIONS:</b>
Our data support a model in which variants of FeLV-A, bearing subtle differences in the RBD of Env, may be predisposed towards enhanced replication in vivo and subsequent conversion to FeLV-C. The selection pressures in vivo that drive the emergence of FeLV-C in a proportion of infected cats remain to be established
Deformation of the N=Z nucleus 76Sr using beta-decay studies
A novel method of deducing the deformation of the N=Z nucleus 76Sr is
presented. It is based on the comparison of the experimental Gamow-Teller
strength distribution B(GT) from its beta decay with the results of QRPA
calculations. This method confirms previous indications of the strong prolate
deformation of this nucleus in a totally independent way. The measurement has
been carried out with a large Total Absorption gamma Spectrometer, "Lucrecia",
newly installed at CERN-ISOLDE.Comment: Accepted in Phys. Rev. Letter
Can a falling tree make a noise in two forests at the same time?
It is a commonplace to claim that quantum mechanics supports the old idea
that a tree falling in a forest makes no sound unless there is a listener
present. In fact, this conclusion is far from obvious. Furthermore, if a
tunnelling particle is observed in the barrier region, it collapses to a state
in which it is no longer tunnelling. Does this imply that while tunnelling, the
particle can not have any physical effects? I argue that this is not the case,
and moreover, speculate that it may be possible for a particle to have effects
on two spacelike separate apparatuses simultaneously. I discuss the measurable
consequences of such a feat, and speculate about possible statistical tests
which could distinguish this view of quantum mechanics from a ``corpuscular''
one. Brief remarks are made about an experiment underway at Toronto to
investigate these issues.Comment: 9 pp, Latex, 3 figs, to appear in Proc. Obsc. Unr. Conf.; Fig 2
postscript repaired on 26.10.9
Early growth response gene-2 (Egr-2) regulates the development of B and T cells
The study was supported by Arthritis Research UK.
Copyright @ 2011 Li et al.BACKGROUND: Understanding of how transcription factors are involved in lymphocyte development still remains a challenge. It has been shown that Egr-2 deficiency results in impaired NKT cell development and defective positive selection of T cells. Here we investigated the development of T, B and NKT cells in Egr-2 transgenic mice and the roles in the regulation of distinct stages of B and T cell development. METHODS AND FINDINGS: The expression of Egr1, 2 and 3 were analysed at different stages of T and B cell development by RT-PCT and results showed that the expression was strictly regulated at different stages. Forced expression of Egr-2 in CD2+ lymphocytes resulted in a severe reduction of CD4+CD8+ (DP) cells in thymus and pro-B cells in bone marrow, which was associated with reduced expression of Notch1 in ISP thymocytes and Pax5 in pro-B cells, suggesting that retraction of Egr-2 at the ISP and pro-B cell stages is important for the activation of lineage differentiation programs. In contrast to reduction of DP and pro-B cells, Egr-2 enhanced the maturation of DP cells into single positive (SP) T and NKT cells in thymus, and immature B cells into mature B cells in bone marrow. CONCLUSIONS: Our results demonstrate that Egr-2 expressed in restricted stages of lymphocyte development plays a dynamic, but similar role for the development of T, NKT and B cells.This article is provided by the Brunel Open Access publishing fund
The Legacy of Rolf Hagedorn: Statistical Bootstrap and Ultimate Temperature
In the latter half of the last century, it became evident that there exists
an ever increasing number of different states of the so-called elementary
particles. The usual reductionist approach to this problem was to search for a
simpler infrastructure, culminating in the formulation of the quark model and
quantum chromodynamics. In a complementary, completely novel approach, Hagedorn
suggested that the mass distribution of the produced particles follows a
self-similar composition pattern, predicting an unbounded number of states of
increasing mass. He then concluded that such a growth would lead to a limiting
temperature for strongly interacting matter. We discuss the conceptual basis
for this approach, its relation to critical behavior, and its subsequent
applications in different areas of high energy physics.Comment: 25 pages, 5 figures; to appear in R. Hagedorn and J. Rafelski (Ed.),
"Melting Hadrons, Boiling Quarks", Springer Verlag 201
Resection of the liver for colorectal carcinoma metastases - A multi-institutional study of long-term survivors
In this review of a collected series of patients undergoing hepatic resection for colorectal metastases, 100 patients were found to have survived greater than five years from the time of resection. Of these 100 long-term survivors, 71 remain disease-free through the last follow-up, 19 recurred prior to five years, and ten recurred after five years. Patient characteristics that may have contributed to survival were examined. Procedures performed included five trisegmentectomies, 32 lobectomies, 16 left lateral segmentectomies, and 45 wedge resections. The margin of resection was recorded in 27 patients, one of whom had a positive margin, nine of whom had a less than or equal to 1-cm margin, and 17 of whom had a greater than 1-cm margin. Eighty-one patients had a solitary metastasis to the liver, 11 patients had two metastases, one patient had three metastases, and four patients had four metastases. Thirty patients had Stage C primary carcinoma, 40 had Stage B primary carcinoma, and one had Stage A primarycarcinoma. The disease-free interval from the time of colon resection to the time of liver resection was less than one year in 65 patients, and greater than one year in 34 patients. Three patients had bilobar metastases. Four of the patients had extrahepatic disease resected simultaneously with the liver resection. Though several contraindications to hepatic resection have been proposed in the past, five-year survival has been found in patients with extrahepatic disease resected simultaneously, patients with bilobar metastases, patients with multiple metastases, and patients with positive margins. Five-year disease-free survivors are also present in each of these subsets. It is concluded that five-year survival is possible in the presence of reported contraindications to resection, and therefore that the decision to resect the liver must be individualized. Β© 1988 American Society of Colon and Rectal Surgeons
Ecological implications of a flower size/number trade-off in tropical forest trees
Peer reviewedPublisher PD
The emergence of international food safety standards and guidelines: understanding the current landscape through a historical approach
Following the Second World War, the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) teamed up to construct an International Codex Alimentarius (or 'food code') which emerged in 1963. The Codex Committee on Food Hygiene (CCFH) was charged with the task of developing microbial hygiene standards, although it found itself embroiled in debate with the WHO over the nature these standards should take. The WHO was increasingly relying upon the input of biometricians and especially the International Commission on Microbial Specifications for Foods (ICMSF) which had developed statistical sampling plans for determining the microbial counts in the final end products. The CCFH, however, was initially more focused on a qualitative approach which looked at the entire food production system and developed codes of practice as well as more descriptive end-product specifications which the WHO argued were 'not scientifically correct'. Drawing upon historical archival material (correspondence and reports) from the WHO and FAO, this article examines this debate over microbial hygiene standards and suggests that there are many lessons from history which could shed light upon current debates and efforts in international food safety management systems and approaches
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