246 research outputs found
IFN-gamma is associated with risk of Schistosoma japonicum infection in China.
Before the start of the schistosomiasis transmission season, 129 villagers resident on a Schistosoma japonicum-endemic island in Poyang Lake, Jiangxi Province, 64 of whom were stool-positive for S. japonicum eggs by the Kato method and 65 negative, were treated with praziquantel. Forty-five days later the 93 subjects who presented for follow-up were all stool-negative. Blood samples were collected from all 93 individuals. S. japonicum soluble worm antigen (SWAP) and soluble egg antigen (SEA) stimulated IL-4, IL-5 and IFN-gamma production in whole-blood cultures were measured by ELISA. All the subjects were interviewed nine times during the subsequent transmission season to estimate the intensity of their contact with potentially infective snail habitats, and the subjects were all re-screened for S. japonicum by the Kato method at the end of the transmission season. Fourteen subjects were found to be infected at that time. There was some indication that the risk of infection might be associated with gender (with females being at higher risk) and with the intensity of water contact, and there was evidence that levels of SEA-induced IFN-gamma production were associated with reduced risk of infection
EVH Black Holes, AdS3 Throats and EVH/CFT Proposal
Within class of generic black holes there are extremal black holes (with
vanishing Hawking temperature T) and vanishing horizon area Ah, but with finite
Ah/T ratio,the Extremal Vanishing Horizon (EVH) black holes. We study the near
horizon limit of a four dimensional EVH black hole solution to a generic
(gauged) Einstein-Maxwell dilaton theory and show that in the near horizon
limit they develop a throat which is a pinching orbifold limit of AdS3. This is
an extension of the well known result for extremal black holes the near horizon
limit of which contains an AdS2 throat. We show that in the near EVH near
horizon limit the pinching AdS3 factor turns to a pinching BTZ black hole and
that this near horizon limit is indeed a decoupling limit. We argue that the
pinching AdS3 or BTZ orbifold is resolved if the near horizon limit is
accompanied by taking the 4d Newton constant G4 to zero such that the
Bekenstein-Hawking entropy S = Ah/(4G4) remains finite. We propose that in this
limit the near horizon EVH black hole is dual to a 2d CFT. We provide pieces of
evidence in support of the EVH/CFT correspondence and comment on its connection
to the Kerr/CFT proposal and speculations how the EVH/CFT may be used to study
generic e.g. Schwarzchild-type black holes.Comment: 31 pages, 3 figures, JHEP styl
State-space Manifold and Rotating Black Holes
We study a class of fluctuating higher dimensional black hole configurations
obtained in string theory/ -theory compactifications. We explore the
intrinsic Riemannian geometric nature of Gaussian fluctuations arising from the
Hessian of the coarse graining entropy, defined over an ensemble of brane
microstates. It has been shown that the state-space geometry spanned by the set
of invariant parameters is non-degenerate, regular and has a negative scalar
curvature for the rotating Myers-Perry black holes, Kaluza-Klein black holes,
supersymmetric black holes, - configurations and the
associated BMPV black holes. Interestingly, these solutions demonstrate that
the principal components of the state-space metric tensor admit a positive
definite form, while the off diagonal components do not. Furthermore, the ratio
of diagonal components weakens relatively faster than the off diagonal
components, and thus they swiftly come into an equilibrium statistical
configuration. Novel aspects of the scaling property suggest that the
brane-brane statistical pair correlation functions divulge an asymmetric
nature, in comparison with the others. This approach indicates that all above
configurations are effectively attractive and stable, on an arbitrary
hyper-surface of the state-space manifolds. It is nevertheless noticed that
there exists an intriguing relationship between non-ideal inter-brane
statistical interactions and phase transitions. The ramifications thus
described are consistent with the existing picture of the microscopic CFTs. We
conclude with an extended discussion of the implications of this work for the
physics of black holes in string theory.Comment: 44 pages, Keywords: Rotating Black Holes; State-space Geometry;
Statistical Configurations, String Theory, M-Theory. PACS numbers: 04.70.-s
Physics of black holes; 04.70.Bw Classical black holes; 04.70.Dy Quantum
aspects of black holes, evaporation, thermodynamics; 04.50.Gh
Higher-dimensional black holes, black strings, and related objects. Edited
the bibliograph
Frequency of extreme Sahelian storms tripled since 1982 in satellite observations
The hydrological cycle is expected to intensify under global
warming, with studies reporting more frequent extreme rain
events in many regions of the world, and predicting increases in future flood frequency. Such early, predominantly mid-latitude observations are essential because of shortcomings within climate models in their depiction of convective rainfall. A globally important group of intense storms—mesoscale convective systems (MCSs)—poses a particular challenge, because they organize dynamically on spatial scales that cannot be resolved by conventional climate models. Here, we use 35 years of satellite observations from the West African Sahel to reveal a persistent increase in the frequency of the most intense MCSs. Sahelian storms are some of the most powerful on the planet, and rain gauges in this region have recorded a rise in ‘extreme’ daily rainfall totals. We find that intense MCS frequency is only weakly related to the multidecadal recovery of Sahel annual rainfall, but is highly correlated with global land temperatures. Analysis of trends across Africa reveals that MCS intensification is limited to a narrow band south of the Sahara desert. During this period, wet-season Sahelian temperatures have not risen, ruling out the possibility that rainfall has intensified in response to locally warmer conditions. On the other hand, the meridional temperature gradient spanning the Sahel has increased in recent decades, consistent with anthropogenic forcing driving enhanced Saharan warming. We argue that Saharan warming intensifies convection within Sahelian MCSs through increased wind shear and changes to the Saharan air layer. The meridional gradient is projected to strengthen throughout the twenty-first century, suggesting that the Sahel will experience particularly marked increases in extreme rain. The remarkably rapid intensification of Sahelian MCSs since the 1980s sheds new light on the response of organized tropical convection to global warming, and challenges conventional projections made by general circulation models
Photodisintegration of He into p+t
The two-body photodisintegration of He into a proton and a triton has
been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson
Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system
in the energy range from 0.35 to 1.55 GeV were incident on a liquid He
target. This is the first measurement of the photodisintegration of He
above 0.4 GeV. The differential cross sections for the He
reaction have been measured as a function of photon-beam energy and
proton-scattering angle, and are compared with the latest model calculations by
J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the
calculations that include three-body mechanisms, thus confirming their
importance. These results reinforce the conclusion of our previous study of the
three-body breakup of He that demonstrated the great importance of
three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22
postscrip figure
First Measurement of Beam-Recoil Observables Cx and Cz in Hyperon Photoproduction
Spin transfer from circularly polarized real photons to recoiling hyperons
has been measured for the reactions and
. The data were obtained using the CLAS
detector at Jefferson Lab for center-of-mass energies between 1.6 and 2.53
GeV, and for . For the , the
polarization transfer coefficient along the photon momentum axis, , was
found to be near unity for a wide range of energy and kaon production angles.
The associated transverse polarization coefficient, , is smaller than
by a roughly constant difference of unity. Most significantly, the {\it
total} polarization vector, including the induced polarization ,
has magnitude consistent with unity at all measured energies and production
angles when the beam is fully polarized. For the this simple
phenomenology does not hold. All existing hadrodynamic models are in poor
agreement with these results.Comment: 28 pages, 18 figures, Submitted to Physical Review
B Cells Participate in Thymic Negative Selection of Murine Auto-reactive CD4+ T Cells
It is well documented that thymic epithelial cells participate in the process of negative selection in the thymus. In recent years it was reported that also dendritic cells enter the thymus and contribute to this process, thus allowing for the depletion of thymocytes that are specific to peripherally expressed self-antigens. Here we report that also B cells may take part in the elimination of auto-reactive thymocytes. Using a unique mouse model we show that B cells induce negative selection of self-reactive thymocytes in a process that leads to the deletion of these cells whereas regulatory T cells are spared. These findings have direct implication in autoimmunity, as expression of a myelin antigen by B cells in the thymus renders the mice resistant to autoimmune inflammation of the CNS
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Studying Language Change Using Price Equation and Pólya-urn Dynamics
Language change takes place primarily via diffusion of linguistic variants in a population of individuals. Identifying selective pressures on this process is important not only to construe and predict changes, but also to inform theories of evolutionary dynamics of socio-cultural factors. In this paper, we advocate the Price equation from evolutionary biology and the Pólya-urn dynamics from contagion studies as efficient ways to discover selective pressures. Using the Price equation to process the simulation results of a computer model that follows the Pólya-urn dynamics, we analyze theoretically a variety of factors that could affect language change, including variant prestige, transmission error, individual influence and preference, and social structure. Among these factors, variant prestige is identified as the sole selective pressure, whereas others help modulate the degree of diffusion only if variant prestige is involved. This multidisciplinary study discerns the primary and complementary roles of linguistic, individual learning, and socio-cultural factors in language change, and offers insight into empirical studies of language change
An Indirect Cue of Predation Risk Counteracts Female Preference for Conspecifics in a Naturally Hybridizing Fish Xiphophorus birchmanni
Mate choice is context dependent, but the importance of current context to interspecific mating and hybridization is largely unexplored. An important influence on mate choice is predation risk. We investigated how variation in an indirect cue of predation risk, distance to shelter, influences mate choice in the swordtail Xiphophorus birchmanni, a species which sometimes hybridizes with X. malinche in the wild. We conducted mate choice experiments to determine whether females attend to the distance to shelter and whether this cue of predation risk can counteract female preference for conspecifics. Females were sensitive to shelter distance independent of male presence. When conspecific and heterospecific X. malinche males were in equally risky habitats (i.e., equally distant from shelter), females associated primarily with conspecifics, suggesting an innate preference for conspecifics. However, when heterospecific males were in less risky habitat (i.e., closer to shelter) than conspecific males, females no longer exhibited a preference, suggesting that females calibrate their mate choices in response to predation risk. Our findings illustrate the potential for hybridization to arise, not necessarily through reproductive “mistakes”, but as one of many potential outcomes of a context-dependent mate choice strategy
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