463 research outputs found
Where the Cathedrals and Bazaars Are: An Index of Open Source Software Activity and Potential
This article presents a framework to measure activity and potential for open source software development and use at a country level. The framework draws on interviews with experts in the open source software industry and numerous existing studies in the literature to identify relevant indicators. Several indices of diverse variable lists and weighting and aggregation methods were developed and tested for robustness. The results provide a first step toward more systematically understanding the current state of open source software internationally
Comments on the Fayet-Iliopoulos Term in Field Theory and Supergravity
A careful analysis of the Fayet-Iliopoulos (FI) model shows that its energy
momentum tensor and supersymmetry current are not gauge invariant. Since the
corresponding charges are gauge invariant, the model is consistent. However,
our observation about the currents gives a new perspective on its restrictive
renormalization group flow and explains why FI-terms never appear in dynamical
supersymmetry breaking. This lack of gauge invariance is at the root of the
complications of coupling the model to supergravity. We show that this is
possible only if the full supergravity theory (including all higher derivative
corrections) has an additional exact continuous global symmetry. A consistent
quantum gravity theory cannot have such symmetries and hence FI-terms cannot
appear. Our results have consequences for various models of particle physics
and cosmology.Comment: 14 pages. v2: references added and minor change
Functional Characteristics of the Gut Microbiome in C57BL/6 Mice Differentially Susceptible to Plasmodium yoelii
C57BL/6 mice are widely used for in vivo studies of immune function and metabolism in mammals. In a previous study, it was observed that when C57BL/6 mice purchased from different vendors were infected with Plasmodium yoelii, a causative agent of murine malaria, they exhibited both differential immune responses and significantly different parasite burdens: these patterns were reproducible when gut contents were transplanted into gnotobiotic mice. To gain insight into the mechanism of resistance, we removed whole ceca from mice purchased from two vendors, Taconic Biosciences (low parasitemia) and Charles River Laboratories (high parasitemia), to determine the combined host and microflora metabolome and metatranscriptome. With the exception of two Charles River samples, we observed 90% similarity in overall bacterial gene expression within vendors and 80% similarity between vendors. In total 33 bacterial genes were differentially expressed in Charles River mice (p-value \u3c 0.05) relative to the mice purchased from Taconic. Included among these, fliC, ureABC, and six members of the nuo gene family were overrepresented in microbiomes susceptible to more severe malaria. Moreover, 38 mouse genes were differentially expressed in these purported genetically identical mice. Differentially expressed genes included basigin, a cell surface receptor required for P. falciparum invasion of red blood cells. Differences in metabolite pools were detected, though their relevance to malaria infection, microbial community activity, or host response is not yet understood. Our data have provided new targets that may connect gut microbial activity to malaria resistance and susceptibility phenotypes in the C57BL/6 model organism
Nonresonant Semileptonic Heavy Quark Decay
In both the large N_c limit and the valence quark model, semileptonic decays
are dominated by resonant final states. Using Bjorken's sum rule in an
"unquenched" version of the quark model, I demonstrate that in the heavy quark
limit nonresonant final states should also be produced at a significant rate.
By calculating the individual strengths of a large number of exclusive two-body
nonresonant channels, I show that the total rate for such processes is highly
fragmented. I also describe some very substantial duality-violating suppression
factors which reduce the inclusive nonresonant rate to a few percent of the
total semileptonic rate for the finite quark masses of B decay, and comment on
the importance of nonresonant decays as testing grounds for very basic ideas on
the structure, strength, and significance of the quark-antiquark sea and on
quark-hadron duality in QCD.Comment: 51 pages, 2 Postscript figure
Emerging role of insulin with incretin therapies for management of type 2 diabetes
Type 2 diabetes mellitus (T2DM) is a progressive disease warranting intensification of treatment, as beta-cell function declines over time. Current treatment algorithms recommend metformin as the first-line agent, while advocating the addition of either basal-bolus or premixed insulin as the final level of intervention. Incretin therapy, including incretin mimetics or enhancers, are the latest group of drugs available for treatment of T2DM. These agents act through the incretin axis, are currently recommended as add-on agents either as second-or third-line treatment, without concurrent use of insulin. Given the novel role of incretin therapy in terms of reducing postprandial hyperglycemia, and favorable effects on weight with reduced incidence of hypoglycemia, we explore alternative options for incretin therapy in T2DM management. Furthermore, as some evidence alludes to incretins potentially increasing betacell mass and altering disease progression, we propose introducing these agents earlier in the treatment algorithm. In addition, we suggest the concurrent use of incretins with insulin, given the favorable effects especially in relation to weight gain
Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron
The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2]
for the proton and neutron have been determined from measurements of polarised
cross section asymmetries in deep inelastic scattering of 27.5 GeV
longitudinally polarised positrons from polarised 1H and 3He internal gas
targets. The data were collected in the region above the nucleon resonances in
the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the
proton the contribution to the generalised Gerasimov-Drell-Hearn integral was
found to be substantial and must be included for an accurate determination of
the full integral. Furthermore the data are consistent with a QCD
next-to-leading order fit based on previous deep inelastic scattering data.
Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte
Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction
Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H,
3He, and 14N targets has been studied by the HERMES experiment at squared
four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20
GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the
nuclear transparency, was found to decrease with increasing coherence length of
quark-antiquark fluctuations of the virtual photon. The data provide clear
evidence of the interaction of the quark- antiquark fluctuations with the
nuclear medium.Comment: RevTeX, 5 pages, 3 figure
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