106 research outputs found
A century of social wasp occupancy trends from natural history collections: spatiotemporal resolutions have little effect on model performance
1. The current dearth of longâterm insect population trends is a major obstacle to conservation. Occupancy models have been proposed as a solution, but it remains unclear whether they can yield longâterm trends from natural history collections, since specimen records are normally very sparse. A common approach for sparse data is to coarsen its spatial and/or temporal resolution, although coarsening risks violating model assumptions.
2. We (i) test whether occupancy trends of three social wasp (Hymenoptera: Vespidae: Vespinae) species â the common wasp (Vespula vulgaris), the German wasp (Vespula germanica) and the European hornet (Vespa crabro) â have changed in England between 1900 and 2016, and (ii) test the effect of spatiotemporal resolution on the performance of occupancy models using very sparse data. All models are based on an integrated dataset of occurrence records and natural history collection specimen records.
3. We show that occupancy models can yield longâterm speciesâspecific trends from very sparse natural history collection specimens. We present the first quantitative trends for three Vespinae species in England over 116âyears. Vespula vulgaris and V. germanica show stable trends over the time series, whilst V. crabro's occupancy decreased from 1950 to 1970 and increased since 1970. Moreover, we show that spatiotemporal resolution has little effect on model performance, although coarsening the spatial grain is an appropriate method for achieving enough records to estimate longâterm changes.
4. With the increasing availability of biological records, the model formulation used here has the potential to provide novel insights by making use of natural history collections' unique specimen assemblages
From QFT to DCC
A quantum field theoretical model for the dynamics of the disoriented chiral
condensate is presented. A unified approach to relate the quantum field theory
directly to the formation, decay and signals of the DCC and its evolution is
taken. We use a background field analysis of the O(4) sigma model keeping
one-loop quantum corrections (quadratic order in the fluctuations). An
evolution of the quantum fluctuations in an external, expanding metric which
simulates the expansion of the plasma, is carried out. We examine, in detail,
the amplification of the low momentum pion modes with two competing effects,
the expansion rate of the plasma and the transition rate of the vacuum
configuration from a metastable state into a stable state.We show the effect of
DCC formation on the multiplicity distributions and the Bose-Einstein
correlations.Comment: 34 pages, 10 figure
DCC dynamics with the SU(3) linear sigma model
The SU(3) extension of the linear sigma model is employed to elucidate the
effect of including strangeness on the formation of disoriented chiral
condensates. By means of a Hartree factorization, approximate dispersion
relations for the 18 scalar and pseudoscalar meson species are derived and
their self-consistent solution makes it possible to trace out the thermal path
of the two order parameters as well as delineate the region of instability
within which spontaneous pair creation becomes possible. The results depend
significantly on the employed sigma mass, with the highest values yielding the
largest regions of instability. An approximate solution of the equations of
motion for the order parameter in scenarios emulating uniform scaling
expansions show that even with a rapid quench only the pionic modes grow
unstable. Nevertheless, the rapid and oscillatory relaxation of the order
parameters leads to enhanced production of both pions and (to a lesser degree)
kaons.Comment: 29 pages, RevTeX, 11 postscript figures, discussion about anomaly
term adde
Linking the chiral and deconfinement phase transitions
We show that the electric glueball becomes critical at the end-point of the
deconfinement phase transition in finite temperature QCD. Based on this
observation and existing lattice data, we argue that the chiral phase
transition at a zero quark mass and the deconfinement phase transition at an
infinite quark mass are continuously connected by the glueball-sigma mixing.Comment: 4 pages, terminology corrected. To appear in Phys. Rev.
On the nature of the finite-temperature transition in QCD
We discuss the nature of the finite-temperature transition in QCD with N_f
massless flavors. Universality arguments show that a continuous (second-order)
transition must be related to a 3-D universality class characterized by a
complex N_f X N_f matrix order parameter and by the symmetry-breaking pattern
[SU(N_f)_L X SU(N_f)_R]/Z(N_f)_V -> SU(N_f)_V/Z(N_f)_V, or [U(N_f)_L X
U(N_f)_R]/U(1)_V -> U(N_f)_V/U(1)_V if the U(1)_A symmetry is effectively
restored at T_c. The existence of any of these universality classes requires
the presence of a stable fixed point in the corresponding 3-D Phi^4 theory with
the expected symmetry-breaking pattern. Otherwise, the transition is of first
order. In order to search for stable fixed points in these Phi^4 theories, we
exploit a 3-D perturbative approach in which physical quantities are expanded
in powers of appropriate renormalized quartic couplings. We compute the
corresponding Callan-Symanzik beta-functions to six loops. We also determine
the large-order behavior to further constrain the analysis. No stable fixed
point is found, except for N_f=2, corresponding to the symmetry-breaking
pattern [SU(2)_L X SU(2)_R]/Z(2)_V -> SU(2)_V/Z(2)_V equivalent to O(4) ->
O(3). Our results confirm and put on a firmer ground earlier analyses performed
close to four dimensions, based on first-order calculations in the framework of
the epsilon=4-d expansion. These results indicate that the finite-temperature
phase transition in QCD is of first order for N_f>2. A continuous transition is
allowed only for N_f=2. But, since the theory with symmetry-breaking pattern
[U(2)_L X U(2)_R]/U(1)_V -> U(2)_V/U(1)_V does not have stable fixed points,
the transition can be continuous only if the effective breaking of the U(1)_A
symmetry is sufficiently large.Comment: 30 pages, 3 figs, minor correction
Disordered macrophage cytokine secretion underlies impaired acute inflammation and bacterial clearance in Crohn's disease
The cause of Crohn's disease (CD) remains poorly understood. Counterintuitively, these patients possess an impaired acute inflammatory response, which could result in delayed clearance of bacteria penetrating the lining of the bowel and predispose to granuloma formation and chronicity. We tested this hypothesis in human subjects by monitoring responses to killed Escherichia coli injected subcutaneously into the forearm. Accumulation of 111In-labeled neutrophils at these sites and clearance of 32P-labeled bacteria from them were markedly impaired in CD. Locally increased blood flow and bacterial clearance were dependent on the numbers of bacteria injected. Secretion of proinflammatory cytokines by CD macrophages was grossly impaired in response to E. coli or specific Toll-like receptor agonists. Despite normal levels and stability of cytokine messenger RNA, intracellular levels of tumor necrosis factor (TNF) were abnormally low in CD macrophages. Coupled with reduced secretion, these findings indicate accelerated intracellular breakdown. Differential transcription profiles identified disease-specific genes, notably including those encoding proteins involved in vesicle trafficking. Intracellular destruction of TNF was decreased by inhibitors of lysosomal function. Together, our findings suggest that in CD macrophages, an abnormal proportion of cytokines are routed to lysosomes and degraded rather than being released through the normal secretory pathway
Last Call for RHIC Predictions
This paper contains the individual contributions of all speakers of the
session on 'Last Call for RHIC Predictions' at Quark Matter 99, and a summary
by the convenor.Comment: 56 pages, psfig, epsf, epsfig, graphicx style files required,
Proceedings of the XIV Int. Conf. on Nucleus-Nucleus Collisions, Quark Matter
99, Torino, Italy, May 10 - 15, 1999. Typographical mistakes corrected and
figure numbers change
Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at GeV
We present first measurements of the evolution of the differential transverse
momentum correlation function, {\it C}, with collision centrality in Au+Au
interactions at GeV. {\it C} exhibits a strong dependence
on collision centrality that is qualitatively similar to that of number
correlations previously reported. We use the observed longitudinal broadening
of the near-side peak of {\it C} with increasing centrality to estimate the
ratio of the shear viscosity to entropy density, , of the matter formed
in central Au+Au interactions. We obtain an upper limit estimate of
that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.
The PHENIX Experiment at RHIC
The physics emphases of the PHENIX collaboration and the design and current
status of the PHENIX detector are discussed. The plan of the collaboration for
making the most effective use of the available luminosity in the first years of
RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program
available at http://www.rhic.bnl.gov/phenix
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
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