The Charm Content of W+1 Jet Events as a Probe of the Strange Quark Distribution Function

We investigate the prospects for measuring the strange quark distribution function of the proton in associated $W$ plus charm quark production at the Tevatron. The $W+c$ quark signal produced by strange quark -- gluon fusion, $sg\rightarrow W^-c$ and $\bar sg\rightarrow W^+\bar c$, is approximately 5\% of the inclusive $W+1$ jet cross section for jets with a transverse momentum $p_T(j)>10$~GeV. We study the sensitivity of the $W$ plus charm quark cross section to the parametrization of the strange quark distribution function, and evaluate the various background processes. Strategies to identify charm quarks in CDF and D\O \ are discussed. For a charm tagging efficiency of about 10\% and an integrated luminosity of 30~pb$^{-1}$ or more, it should be possible to constrain the strange quark distribution function from $W+c$ production at the Tevatron.Comment: submitted to Phys. Lett. B, Latex, 12 pages + 4 postscript figures encoded with uufile, FSU-HEP-930812, MAD/TH/93-6, MAD/PH/788. A postscript file with text and embedded figures is available via anonymous ftp at hepsg1.physics.fsu.edu, file is /pub/keller/fsu-hep-930812.p

The magnetic field topology associated to two M flares

On 27 October, 2003, two GOES M-class flares occurred in the lapse of three hours in active region NOAA 10486. The two flares were confined and their associated brightenings appeared at the same location, displaying a very similar shape both at the chromospheric and coronal levels. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (HASTA, Kanzelhoehe Solar Observatory, TRACE) and coronal (TRACE) observations. By combining our data analysis with a model of the coronal magnetic field, we compute the magnetic field topology associated to the two M flares. We find that both events can be explained in terms of a localized magnetic reconnection process occurring at a coronal magnetic null point. This null point is also present at the same location one day later, on 28 October, 2003. Magnetic energy release at this null point was proposed as the origin of a localized event that occurred independently with a large X17 flare on 28 October, 2003, at 11:01 UT. The three events, those on 27 October and the one on 28 October, are homologous. Our results show that coronal null points can be stable topological structures where energy release via magnetic reconnection can happen, as proposed by classical magnetic reconnection models.Comment: 14 pages, 7 figure

A retrospective evaluation of the impact of a dedicated obstetric and neonatal transport service on transport times within an urban setting

OBJECTIVE:To determine whether the establishment of a dedicated obstetric and neonatal flying squad resulted in improved performance within the setting of a major metropolitan area.DESIGN AND SETTING:The Cape Town metropolitan service of the Emergency Medical Services was selected for a retrospective review of the transit times for the newly implemented Flying Squad programme. Data were imported from the Computer Aided Dispatch programme. Dispatch, Response, Mean Transit and Total Pre-hospital times relating to the obstetric and neonatal incidents was analysed for 2005 and 2008. RESULTS: There was a significant improvement between 2005 and 2008 in all incidents evaluated. Flying Squad dispatch performance improved from 11.7% to 46.6% of all incidents dispatched within 4 min (p < 0.0001). Response time performance at the 15-min threshold did not demonstrate a statistically significant improvement (p = 0.4), although the improvement in the 30-min performance category was statistically significant in both maternity and neonatal incidents. Maternity incidents displayed the greatest improvement with the 30-min performance increasing from 30.3% to 72.9%. The analysis of the mean transit times demonstrated that neonatal transfers displayed the longest status time in all but one of the categories. Even so, the introduction of the Flying Squad programme resulted in a reduction in a total pre-hospital time from 177 to 128 min. CONCLUSION: The introduction of the Flying Squad programme has resulted in significant improvement in the transit times of both neonatal and obstetric patients. In spite of the severe resource constraints facing developing nations, the model employed offers significant gains

Beyond information seeking:Consumers' online deliberation about the risks and benefits of red meat

Successfully engaging consumers in a dialogue may provide opportunities for better tailored and more effective communication about food-related risks and benefits. Using an online deliberation concept and software, VIZZATA™, we explored the validity of a behavioral measure of deliberation in an online environment in the context of consumers’ perceptions and information seeking about the risks and benefits of red meat. Participants from Belgium, Portugal and the United Kingdom (n = 150) were given the opportunity to engage in an asynchronous interaction with the research team about the information provided. Online deliberation was operationalized as an individual metric based on the number of questions asked in relation to the information, the number of comments left, the number of glossary terms accessed, and the time spent on deliberative activity. This operationalization provided a coherent measure of deliberation which was positively correlated with information recall about the risks and benefits of red meat. Participants who perceived the information about red meat risks and benefits as too complex engaged less with the information. The study herewith presents a novel method of investigating consumers’ deliberation about food issues that conceptualizes consumer engagement as more than just information seeking

The Composition of Cosmic Rays at the Knee

The observation of a small change in spectral slope, or 'knee' in the fluxes of cosmic rays near energies 10^15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review some modern experimental measurements of this region was held at the Adler Planetarium in Chicago, USA in June 2000. This paper summarizes the results presented at this workshop and the discussion of their interpretation in the context of hadronic models of atmospheric airshowers.Comment: 36 pages, 10 figure

Targeting BMI-1 to deplete antibody-secreting cells in autoimmunity

Objectives. B cells drive the production of autoreactive antibodysecreting cells, ASCs, in autoimmune diseases such as Systemic Lupus Erythematosus, SLE, and Sjogren, s syndrome, causing long-, term organ damage. Current treatments for antibody-mediated autoimmune diseases target B cells or broadly suppress the immune system. However, pre-existing long-lived ASCs are often refractory to treatment, leaving a reservoir of autoreactive cells that continue to produce antibodies. Therefore, the development of novel treatment methods targeting ASCs is vital to improve patient outcomes. Our objective was to test whether targeting the epigenetic regulator BMI-, could deplete ASCs in autoimmune conditions in vivo and in vitro. Methods. Use of a BMI-, inhibitor in both mouse and human autoimmune settings was investigated. Lyn, mice, a model of SLE, were treated with the BMI-, small molecule inhibitor PTC-, before assessment of ASCs, serum antibody and immune complexes. To examine human ASC survival, a novel human fibroblast-based assay was established, and the impact of PTC-, on ASCs derived from Sjogren, s syndrome, patients was evaluated. Results. BMI-, inhibition significantly decreased splenic and bone marrow ASCs in Lyn, mice. The decline in ASCs was linked to aberrant cell cycle gene expression and led to a significant decrease in serum IgG, immune complexes and anti-DNA IgG. PTC-, was also efficacious in reducing ex vivo plasma cell survival from both Sjogren, s syndrome, patients and age-matched healthy donors. Conclusion. These data provide evidence that inhibiting BMI-, can deplete ASC in a variety of contexts and thus BMI-, is a viable therapeutic target for antibody-mediated autoimmune diseases.Jack Polmear, Lauren Hailes, Moshe Olshansky, Maureen Rischmueller, Elan L'Estrange-Stranieri, Anne L Fletcher, Margaret L Hibbs, Vanessa L Bryant, Kim L Good-Jacobso

A model for net-baryon rapidity distribution

In nuclear collisions, a sizable fraction of the available energy is carried away by baryons. As the baryon number is conserved, the net-baryon $B-\bar{B}$ retains information on the energy-momentum carried by the incoming nuclei. A simple and consistent model for net-baryon production in high energy proton-proton and nucleus-nucleus collisions is presented. The basic ingredients of the model are valence string formation based on standard PDFs with QCD evolution and string fragmentation via the Schwinger mechanism. The results of the model are presented and compared with data at different centre-of-mass energies and centralities, as well as with existing models. These results show that a good description of the main features of net-baryon data is possible in the framework of a simplistic model, with the advantage of making the fundamental production mechanisms manifest.Comment: 9 pages, 12 figures; in fig. 11 a) the vertical scale was correcte

Svestka's Research: Then and Now

Zdenek Svestka's research work influenced many fields of solar physics, especially in the area of flare research. In this article I take five of the areas that particularly interested him and assess them in a "then and now" style. His insights in each case were quite sound, although of course in the modern era we have learned things that he could not readily have envisioned. His own views about his research life have been published recently in this journal, to which he contributed so much, and his memoir contains much additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a contribution to a Topical Issue in Solar Physics, based on the presentations at this meeting (Editors Lyndsay Fletcher and Petr Heinzel

Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Molecular interactions of the plasma membrane calcium ATPase 2 at pre- and post-synaptic sites in rat cerebellum.

The plasma membrane calcium extrusion mechanism, PMCA (plasma membrane calcium ATPase) isoform 2 is richly expressed in the brain and particularly the cerebellum. Whilst PMCA2 is known to interact with a variety of proteins to participate in important signalling events [Strehler EE, Filoteo AG, Penniston JT, Caride AJ (2007) Plasma-membrane Ca(2+) pumps: structural diversity as the basis for functional versatility. Biochem Soc Trans 35 (Pt 5):919-922], its molecular interactions in brain synapse tissue are not well understood. An initial proteomics screen and a biochemical fractionation approach identified PMCA2 and potential partners at both pre- and post-synaptic sites in synapse-enriched brain tissue from rat. Reciprocal immunoprecipitation and GST pull-down approaches confirmed that PMCA2 interacts with the post-synaptic proteins PSD95 and the NMDA glutamate receptor subunits NR1 and NR2a, via its C-terminal PDZ (PSD95/Dlg/ZO-1) binding domain. Since PSD95 is a well-known partner for the NMDA receptor this raises the exciting possibility that all three interactions occur within the same post-synaptic signalling complex. At the pre-synapse, where PMCA2 was present in the pre-synapse web, reciprocal immunoprecipitation and GST pull-down approaches identified the pre-synaptic membrane protein syntaxin-1A, a member of the SNARE complex, as a potential partner for PMCA2. Both PSD95-PMCA2 and syntaxin-1A-PMCA2 interactions were also detected in the molecular and granule cell layers of rat cerebellar sagittal slices by immunohistochemistry. These specific molecular interactions at cerebellar synapses may allow PMCA2 to closely control local calcium dynamics as part of pre- and post-synaptic signalling complexes