13,427 research outputs found
Lower dimensional Yang-Mills theory as a laboratory to study the infrared regime
Lattice studies of the infrared regime of gauge theories are complicated by
the required extensive limits, the performed gauge fixing and the demand for
high statistics. Using a general power counting scheme for the infrared limit
of Landau gauge SU(N) Yang-Mills theory in arbitrary dimensions we show that
the infrared behavior of Greens functions is both qualitatively and
quantitatively similar in two, three and four spacetime dimensions. Therefore,
lower dimensional lattice simulations can serve as a simplified laboratory to
analyze the presently applied approximations and to obtain first results for
higher correlation functions.Comment: 7 pages, 6 figures; talk presented at Lattice 200
Specific immunotherapy in Albanian patients with anaphylaxis to hymenoptera venoms
Background: Severe allergic reactions during rush-specific immunotherapy (Rush-SIT) may occur in the treatment of hymenoptera sting allergy. The objective of the present study was to examine the characteristics of allergic reactions during Rush-SIT in a cohort of patients with allergy towards hymenoptera venom in the mediterranean population of Albania.
Methods: A retrospective study was performed using the clinical reports of 37 patients with venom of bee (apinae), wasp (vespidae, subfamily vespinae) or paperwasp (vespidae, subfamily polistinae) allergy treated with Rush-SIT between 1987 and 1996. After hymenoptera sting allergy diagnosis according to anamnesis and intracutaneous tests the patient were treated with Rush-SIT. The protocol lasted 3 - 4 d with an increase in the concentration from 0.01 microg/ml to 100 microg/ml. Anaphylactic reactions were classified according to the Mueller-classification.
Results: The frequency of reactions during Rush-SIT for bee-venom was 4.7% and for wasp-venom was 1.5% (p < 0.01). The mean frequency of reactions of Mueller grade II for the bee-venom Rush-SIT patients during the first 4 d (= 26 injections) was 0.73 and for the wasp-venom Rush-SIT patients 0.15. No patient experienced a third-degree reaction. 94.6% of the patient supported an end dose of 100 microg.
Conclusions: Rush-SIT is a reliable method for the treatment of anaphylactic reactions to hymenoptera venom even in less developed countries. Bee-venom Rush-SIT was found to cause higher numbers allergic reactions than wasp or paperwasp Rush-SIT
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A cleavage clock regulates features of lineage-specific differentiation in the development of a basal branching metazoan, the ctenophore Mnemiopsis leidyi
Background: An important question in experimental embryology is to understand how the developmental potential responsible for the generation of distinct cell types is spatially segregated over developmental time. Classical embryological work showed that ctenophores, a group of gelatinous marine invertebrates that arose early in animal evolution, display a highly stereotyped pattern of early development and a precocious specification of blastomere fates. Here we investigate the role of autonomous cell specification and the developmental timing of two distinct ctenophore cell types (motile compound comb-plate-like cilia and light-emitting photocytes) in embryos of the lobate ctenophore, Mnemiopsis leidyi. Results: In Mnemiopsis, 9 h after fertilization, comb plate cilia differentiate into derivatives of the E lineage, while the bioluminescent capability begins in derivatives of the M lineage. Arresting cleavage with cytochalasin B at the 1-, 2- or 4-cell stage does not result in blastomere death; however, no visible differentiation of the comb-plate-like cilia or bioluminescence was observed. Cleavage arrest at the 8- or 16-cell stage, in contrast, results in the expression of both differentiation products. Fate-mapping experiments indicate that only the lineages of cells that normally express these markers in an autonomous fashion during normal development express these traits in cleavage-arrested 8- and 16-cell stage embryos. Lineages that form comb plates in a non-autonomous fashion (derivatives of the M lineage) do not. Timed actinomycin D and puromycin treatments show that transcription and translation are required for comb formation and suggest that the segregated material might be necessary for activation of the appropriate genes. Interestingly, even in the absence of cytokinesis, differentiation markers appear to be activated at the correct times. Treatments with a DNA synthesis inhibitor, aphidicolin, show that the number of nuclear divisions, and perhaps the DNA to cytoplasmic ratio, are critical for the appearance of lineage-specific differentiation. Conclusion: Our work corroborates previous studies demonstrating that the cleavage program is causally involved in the spatial segregation and/or activation of factors that give rise to distinct cell types in ctenophore development. These factors are segregated independently to the appropriate lineage at the 8- and the 16-cell stages and have features of a clock, such that comb-plate-like cilia and light-emitting photoproteins appear at roughly the same developmental time in cleavage-arrested embryos as they do in untreated embryos. Nuclear division, which possibly affects DNA-cytoplasmic ratios, appears to be important in the timing of differentiation markers. Evidence suggests that the 60-cell stage, just prior to gastrulation, is the time of zygotic gene activation. Such cleavage-clock-regulated phenomena appear to be widespread amongst the Metazoa and these cellular and molecular developmental mechanisms probably evolved early in metazoan evolution
Transcriptional down-regulation of suppressor of cytokine signaling (SOCS)-3 in chronic obstructive pulmonary disease
Background: Tobacco is a leading environmental factor in the initiation of respiratory diseases and causes chronic obstructive pulmonary disease (COPD). Suppressor of cytokine signaling (SOCS) family members are involved in the pathogenesis of many inflammatory diseases and SOCS-3 has been shown to play an important role in the regulation, onset and maintenance of airway allergic inflammation indicating that SOCS-3 displays a potential therapeutic target for anti-inflammatory respiratory drugs development. Since chronic obstructive pulmonary disease (COPD) is also characterized by inflammatory changes and airflow limitation, the present study assessed the transcriptional expression of SOCS-3 in COPD.
Methods: Real-time PCR was performed to assess quantitative changes in bronchial biopsies of COPD patients in comparison to unaffected controls.
Results: SOCS-3 was significantly down-regulated in COPD at the transcriptional level while SOCS-4 and SOCS-5 displayed no change.
Conclusions: It can be concluded that the presently observed inhibition of SOCS-3 mRNA expression may be related to the dysbalance of cytokine signaling observed in COPD
Spectrum of scalar and pseudoscalar glueballs from functional methods
We provide results for the spectrum of scalar and pseudoscalar glueballs in
pure Yang-Mills theory using a parameter-free fully self-contained truncation
of Dyson-Schwinger and Bethe-Salpeter equations. The only input, the scale, is
fixed by comparison with lattice calculations. We obtain ground state masses of
and for the scalar and pseudoscalar
glueballs, respectively, and and for the
corresponding first excited states. This is in very good quantitative agreement
with available lattice results. Furthermore, we predict masses for the second
excited states at and . The quality of the
results hinges crucially on the self-consistency of the employed input. The
masses are independent of a specific choice for the infrared behavior of the
ghost propagator providing further evidence that this only reflects a
nonperturbative gauge completion.Comment: 13 pages, 10 figs.; v2: extended version with a meson calculation to
illustrate the extrapolation, unified scale setting in comparison, agrees
with published versio
Algorithmic derivation of functional renormalization group equations and Dyson-Schwinger equations
We present the Mathematica application DoFun which allows to derive
Dyson-Schwinger equations and renormalization group flow equations for n-point
functions in a simple manner. DoFun offers several tools which considerably
simplify the derivation of these equations from a given physical action. We
discuss the application of DoFun by means of two different types of quantum
field theories, namely a bosonic O(N) theory and the Gross-Neveu model.Comment: 40 pages, 12 figs.; corresponds to published versio
Multiscale nature of hysteretic phenomena: Application to CoPt-type magnets
We suggest a workable approach for the description of multiscale
magnetization reversal phenomena in nanoscale magnets and apply it to CoPt-type
alloys. We show that their hysteretic properties are governed by two effects
originating at different length scales: a peculiar splitting of domain walls
and their strong pinning at antiphase boundaries. We emphasize that such
multiscale nature of hysteretic phenomena is a generic feature of nanoscale
magnetic materials.Comment: 4 pages (revtex 4), 2 color EPS figure
Fe-Ti-V-(P) resources in the Upper Zone of the Bushveld Complex, South Africa
The Bushveld Complex in South Africa is the largest layered intrusion on Earth. Its upper part is known for huge resources of iron, titanium, vanadium and phosphorus. Associated with the layered character of the rocks, these resources are enriched at certain levels of the intrusion, which makes it important to understand the formation processes of those layers. In this paper we give an introduction and overview of recent debates and challenges
One-dimensional Ising ferromagnet frustrated by long-range interactions at finite temperatures
We consider a one-dimensional lattice of Ising-type variables where the
ferromagnetic exchange interaction J between neighboring sites is frustrated by
a long-ranged anti-ferromagnetic interaction of strength g between the sites i
and j, decaying as |i-j|^-alpha, with alpha>1. For alpha smaller than a certain
threshold alpha_0, which is larger than 2 and depends on the ratio J/g, the
ground state consists of an ordered sequence of segments with equal length and
alternating magnetization. The width of the segments depends on both alpha and
the ratio J/g. Our Monte Carlo study shows that the on-site magnetization
vanishes at finite temperatures and finds no indication of any phase
transition. Yet, the modulation present in the ground state is recovered at
finite temperatures in the two-point correlation function, which oscillates in
space with a characteristic spatial period: The latter depends on alpha and J/g
and decreases smoothly from the ground-state value as the temperature is
increased. Such an oscillation of the correlation function is exponentially
damped over a characteristic spatial scale, the correlation length, which
asymptotically diverges roughly as the inverse of the temperature as T=0 is
approached. This suggests that the long-range interaction causes the Ising
chain to fall into a universality class consistent with an underlying
continuous symmetry. The e^(Delta/T)-temperature dependence of the correlation
length and the uniform ferromagnetic ground state, characteristic of the g=0
discrete Ising symmetry, are recovered for alpha > alpha_0.Comment: 12 pages, 7 figure
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