Early signaling defects in human T cells anergized by T cell presentation of autoantigen.

Major histocompatibility complex class II-positive human T cell clones are nontraditional antigen-presenting cells (APCs) that are able to simultaneously present and respond to peptide or degraded antigen, but are unable to process intact protein. Although T cell presentation of peptide antigen resulted in a primary proliferative response, T cells that had been previously stimulated by T cells presenting antigen were completely unresponsive to antigen but not to interleukin 2 (IL-2). In contrast, peptide antigen presented by B cells or DR2+ L cell transfectants resulted in T cell activation and responsiveness to restimulation. The anergy induced by T cell presentation of peptide could not be prevented by the addition of either autologous or allogeneic B cells or B7+ DR2+ L cell transfectants, suggesting that the induction of anergy could occur in the presence of costimulation. T cell anergy was induced within 24 h of T cell presentation of antigen and was long lasting. Anergized T cells expressed normal levels of T cell receptor/CD3 but were defective in their ability to release [Ca2+]i to both alpha CD3 and APCs. Moreover, anergized T cells did not proliferate to alpha CD2 monoclonal antibodies or alpha CD3 plus phorbol myristate acetate (PMA), nor did they synthesize IL-2, IL-4, or interferon gamma mRNA in response to either peptide or peptide plus PMA. In contrast, ionomycin plus PMA induced both normal proliferative responses and synthesis of cytokine mRNA, suggesting that the signaling defect in anergized cells occurs before protein kinase C activation and [Ca2+]i release

Topological measures for the analysis of wireless sensor networks

Concepts such as energy dependence, random deployment, dynamic topological update, self-organization, varying large number of nodes are among many factors that make WSNs a type of complex system. However, when analyzing WSNs properties using complex network tools, classical topological measures must be considered with care as they might not be applicable in their original form. In this work, we focus on the topological measures frequently used in the related field of Internet topological analysis. We illustrate their applicability to the WSNs domain through simulation experiments. In the cases when the classic metrics turn out to be incompatible, we propose some alternative measures and discuss them based on the WSNs characteristics.Comment: 3rd International Conference on Ambient Systems (ANT), Networks and Technologies, Niagara Falls : Canada (2012

Studying and Treating Schizophrenia Using Virtual Reality: A New Paradigm

Understanding schizophrenia requires consideration of patients’ interactions in the social world. Misinterpretation of other peoples’ behavior is a key feature of persecutory ideation. The occurrence and intensity of hallucinations is affected by the social context. Negative symptoms such as anhedonia, asociality, and blunted affect reflect difficulties in social interactions. Withdrawal and avoidance of other people is frequent in schizophrenia, leading to isolation and rumination. The use of virtual reality (VR)—interactive immersive computer environments—allows one of the key variables in understanding psychosis, social environments, to be controlled, providing exciting applications to research and treatment. Seven applications of virtual social environments to schizophrenia are set out: symptom assessment, identification of symptom markers, establishment of predictive factors, tests of putative causal factors, investigation of the differential prediction of symptoms, determination of toxic elements in the environment, and development of treatment. The initial VR studies of persecutory ideation, which illustrate the ascription of personalities and mental states to virtual people, are highlighted. VR, suitably applied, holds great promise in furthering the understanding and treatment of psychosis

M22: A [Fe/H] Abundance Range Revealed

Intermediate resolution spectra at the Ca II triplet have been obtained for 55 candidate red giants in the field of the globular cluster M22 with the VLT/FORS instrument. Spectra were also obtained for a number of red giants in standard globular clusters to provide a calibration of the observed line strengths with overall abundance [Fe/H]. For the 41 M22 member stars that lie within the V-V_HB bounds of the calibration, we find an abundance distribution that is substantially broader than that expected from the observed errors alone. We argue that this broad distribution cannot be the result of differential reddening. Instead we conclude that, as has long been suspected, M22 is similar to omega Cen in having an intrinsic dispersion in heavy element abundance. The observed M22 abundance distribution rises sharply to a peak at [Fe/H] = -1.9 with a broad tail to higher abundances: the highest abundance star in our sample has [Fe/H] = -1.45 dex. If the unusual properties of omega Cen have their origin in a scenario in which the cluster is the remnant nucleus of a disrupted dwarf galaxy, then such a scenario likely applies also to M22.Comment: 29 pages, 9 figures, accepted for publication in the Astrophysical Journa

Critical animal and media studies: Expanding the understanding of oppression in communication research

Critical and communication studies have traditionally neglected the oppression conducted by humans towards other animals. However, our (mis)treatment of other animals is the result of public consent supported by a morally speciesist-anthropocentric system of values. Speciesism or anthroparchy, as much as any other mainstream ideologies, feeds the media and at the same time is perpetuated by them. The goal of this article is to remedy this neglect by introducing the subdiscipline of Critical Animal and Media Studies. Critical Animal and Media Studies takes inspiration both from critical animal studies – which is so far the most consolidated critical field of research in the social sciences addressing our exploitation of other animals – and from the normative-moral stance rooted in the cornerstones of traditional critical media studies. The authors argue that the Critical Animal and Media Studies approach is an unavoidable step forward for critical media and communication studies to engage with the expanded circle of concerns of contemporary ethical thinking

Node-node distance distribution for growing networks

We present the simulation of the time evolution of the distance matrix. The result is the node-node distance distribution for various kinds of networks. For the exponential trees, analytical formulas are derived for the moments of the distance distribution.Comment: presented during the 37-th Polish Physicists' Meeting, Gdansk, Poland, 15-19 Sep. 2003, 6 pages, 3 figure

Complex Independent Component Analysis of Frequency-Domain Electroencephalographic Data

Independent component analysis (ICA) has proven useful for modeling brain and electroencephalographic (EEG) data. Here, we present a new, generalized method to better capture the dynamics of brain signals than previous ICA algorithms. We regard EEG sources as eliciting spatio-temporal activity patterns, corresponding to, e.g., trajectories of activation propagating across cortex. This leads to a model of convolutive signal superposition, in contrast with the commonly used instantaneous mixing model. In the frequency-domain, convolutive mixing is equivalent to multiplicative mixing of complex signal sources within distinct spectral bands. We decompose the recorded spectral-domain signals into independent components by a complex infomax ICA algorithm. First results from a visual attention EEG experiment exhibit (1) sources of spatio-temporal dynamics in the data, (2) links to subject behavior, (3) sources with a limited spectral extent, and (4) a higher degree of independence compared to sources derived by standard ICA.Comment: 21 pages, 11 figures. Added final journal reference, fixed minor typo

ON COMPUTING UPPER LIMITS TO SOURCE INTENSITIES

A common problem in astrophysics is determining how bright a source could be and still not be detected. Despite the simplicity with which the problem can be stated, the solution involves complex statistical issues that require careful analysis. In contrast to the confidence bound, this concept has never been formally analyzed, leading to a great variety of often ad hoc solutions. Here we formulate and describe the problem in a self-consistent manner. Detection significance is usually defined by the acceptable proportion of false positives (the TypeI error), and we invoke the complementary concept of false negatives (the TypeII error), based on the statistical power of a test, to compute an upper limit to the detectable source intensity. To determine the minimum intensity that a source must have for it to be detected, we first define a detection threshold, and then compute the probabilities of detecting sources of various intensities at the given threshold. The intensity that corresponds to the specified TypeII error probability defines that minimum intensity, and is identified as the upper limit. Thus, an upper limit is a characteristic of the detection procedure rather than the strength of any particular source and should not be confused with confidence intervals or other estimates of source intensity. This is particularly important given the large number of catalogs that are being generated from increasingly sensitive surveys. We discuss the differences between these upper limits and confidence bounds. Both measures are useful quantities that should be reported in order to extract the most science from catalogs, though they answer different statistical questions: an upper bound describes an inference range on the source intensity, while an upper limit calibrates the detection process. We provide a recipe for computing upper limits that applies to all detection algorithms.Comment: 30 pages, 12 figures, accepted in Ap

On the origin of the stellar halo and multiple stellar populations in the globular cluster NGC 1851

We propose that the observed stellar halo around the globular cluster (GC) NGC 1851 is evidence for its formation in the central region of its defunct host dwarf galaxy. We numerically investigate the long-term dynamical evolution of a nucleated dwarf galaxy embedded in a massive dark matter halo under the strong tidal field of the Galaxy. The dwarf galaxy is assumed to have a stellar nucleus (or a nuclear star cluster) that could be the progenitor for NGC 1851. We find that although the dark matter halo and the stellar envelope of the host dwarf of NGC 1851 can be almost completely stripped during its orbital evolution around the Galaxy, a minor fraction of stars in the dwarf can remain trapped by the gravitational field of the nucleus. The stripped nucleus can be observed as NGC 1851 with no/little dark matter whereas stars around the nucleus can be observed as a diffuse stellar halo around NGC 1851. The simulated stellar halo has a symmetric distribution with a power-law density slope of ~ -2 and shows no tidal tails within ~200pc from NGC 1851. We show that two GCs can merge with each other to form a new nuclear GC embedded in field stars owing to the low stellar velocity dispersion of the host dwarf. This result makes no assumption on the ages and/or chemical abundances of the two merging GCs. Thus the observed stellar halo and characteristic multiple stellar populations in NGC 1851 suggest that NGC 1851 could have formed initially in the central region of an ancient dwarf galaxy.Comment: 15 pages, 12 figures, accepted in MNRA

Stellar over-densities in the halo: the extent of the Virgo over-density

We map the three dimensional extent of the Virgo Over-density by combining distance information from RR Lyrae variables and projected spatial information from SEKBO (Keller et al. 2008) and Sloan Digital Sky Survey (SDSS) DR6 photometry. The Virgo Over-density is seen to comprise two filaments 14.5 x 3 degrees and 10 x 3 degrees and a circular structure 3 degrees in diameter. Together the three features span 38 degrees of right ascension and declinations of +2 to -15 degrees. RR Lyrae variables place the two filamentary features at heliocentric distances of 20 and 17 kpc respectively, with projected dimensions of 5 x 1 kpc and 3 x 1 kpc.Comment: 6 pages, 5 figures, MNRAS accepte