Search for lepton flavor violating decays of a heavy neutral particle in p-pbar collisions at root(s)=1.8 TeV

We report on a search for a high mass, narrow width particle that decays directly to e+mu, e+tau, or mu+tau. We use approximately 110 pb^-1 of data collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence of lepton flavor violating decays is found. Limits are set on the production and decay of sneutrinos with R-parity violating interactions.Comment: Figure 2 fixed. Reference 4 fixed. Minor changes to tex

Newly formed cystic lesions for the development of pneumomediastinum in Pneumocystis jirovecii pneumonia

<p>Abstract</p> <p>Background</p> <p><it>Pneumocystis jirovecii</it>, formerly named <it>Pneumocystis carinii</it>, is one of the most common opportunistic infections in human immunodeficiency virus (HIV)-infected patients.</p> <p>Case presentations</p> <p>We encountered two cases of spontaneous pneumomediastinum with subcutaneous emphysema in HIV-infected patients being treated for <it>Pneumocystis jirovecii </it>pneumonia with trimethoprim/sulfamethoxazole.</p> <p>Conclusion</p> <p>Clinicians should be aware that cystic lesions and bronchiectasis can develop in spite of trimethoprim/sulfamethoxazole treatment for <it>P. jirovecii </it>pneumonia. The newly formed bronchiectasis and cyst formation that were noted in follow up high resolution computed tomography (HRCT) but were not visible on HRCT at admission could be risk factors for the development of pneumothorax or pneumomediastinum with subcutaneous emphysema in HIV-patients.</p

Modelling the impact of toxic and disturbance stress on white-tailed eagle (Haliaeetus albicilla) populations

Several studies have related breeding success and survival of sea eagles to toxic or non-toxic stress separately. In the present investigation, we analysed single and combined impacts of both toxic and disturbance stress on populations of white-tailed eagle (Haliaeetus albicilla), using an analytical single-species model. Chemical and eco(toxico)logical data reported from laboratory and field studies were used to parameterise and validate the model. The model was applied to assess the impact of ∑PCB, DDE and disturbance stress on the white-tailed eagle population in The Netherlands. Disturbance stress was incorporated through a 1.6% reduction in survival and a 10–50% reduction in reproduction. ∑PCB contamination from 1950 up to 1987 was found to be too high to allow the return of white-tailed eagle as a breeding species in that period. ∑PCB and population trends simulated for 2006–2050 suggest that future population growth is still reduced. Disturbance stress resulted in a reduced population development. The combination of both toxic and disturbance stress varied from a slower population development to a catastrophical reduction in population size, where the main cause was attributed to the reduction in reproduction of 50%. Application of the model was restricted by the current lack of quantitative dose–response relationships between non-toxic stress and survival and reproduction. Nevertheless, the model provides a first step towards integrating and quantifying the impacts of multiple stressors on white-tailed eagle populations

America's Rural Hospitals: A Selective Review of 1980s Research

We review 1980s research on American rural hospitals within the context of a decade of increasing restrictiveness in the reimbursement and operating environments. Areas addressed include rural hospital definitions, organizational and financial performance, and strategic management activities. The latter category consists of hospital closure, diversification and vertical integration, swing-bed conversion, sole community provider designation, horizontal integration and multihospital system affiliation, marketing, and patient retention. The review suggests several research needs, including: developing more meaningful definitions of rural hospitals, engaging in methodologically sound work on the effects of innovative programs and strategic management activities—including conversion of the facility itself—on rural hospital performance, and completing studies of the effects of rural hospital closure or conversion on the health of the communities served.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74857/1/j.1748-0361.1990.tb00682.x.pd

Momentum distribution of charged particles in jets in dijet events in p(p)over-bar collisions at root s=1.8 TeV and comparisons to perturbative QCD predictions

Inclusive momentum distributions of charged particles in restricted cones around jet axes were measured in dijet events with invariant dijet masses in the range 80 to 600 GeV/c(2). Events were produced at the Fermilab Tevatron in p (p) over bar collisions with a center of mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The results were compared to perturbative QCD calculations carried out in the framework of the modified leading log approximation (MLLA) and assuming local parton-hadron duality. It was shown that the data follow theoretical predictions quite well over the whole range of the jet energies included in this analysis. We extracted the MLLA cutoff scale Q(eff) and found a value of 230+/-40 MeV. The theoretical prediction of E(jet)sin theta(c) scaling, where theta(c) is the cone opening angle, was experimentally observed for the first time. From the MLLA fits to the data, two more parameters were extracted: the ratio of parton multiplicities in gluon and quark jets, r=N-partons(g-jet)/N-partons(q-jet)=1.9+/-0.5, and the ratio of the number of charged hadrons to the number of predicted partons in a jet, K-LPHD(charged)=N-hadrons(charged)/N-partons=0.56+/-0.10

Search for the supersymmetric partner of the top quark in dilepton events from p(p)over-bar collisions at root s=1.8 TeV

We have searched for the supersymmetric partner of the top quark (stop) in 107 pb^{-1} of p-pbar collisions at \sqrt{s}= 1.8 TeV collected by the Collider Detector at Fermilab (CDF). Within the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM) each of the pair-produced stops is assumed to decay into a lepton, bottom quark and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We calculate a 95% confidence level (C.L.) upper limit on the stop production cross section, which excludes stop masses in the region (80<m_{\stop}<135 GeV/c^2) in the mass plane of stop versus sneutrino.Comment: 7 pages, 5 figures. Submitted to Physical Review Letter

Central pseudorapidity gaps in events with a leading antiproton at the Fermilab tevatron (p)over-barp collider

We report a measurement of the fraction of events with a large pseudorapidity gap Deltaeta within the pseudorapidity region available to the proton dissociation products X in (p) over bar +p--&gt;(p) over bar +X. For a final state (p) over bar of fractional momentum loss xi((p) over bar) and 4-momentum transfer squared t((p) over bar) within 0.063 is found to be 0.246+/-0.001 (stat)+/-0.042 (syst) [0.184+/-0.001 (stat)+/-0.043 (syst)]. Our results are compared with gap fractions measured in minimum bias (p) over barp collisions and with theoretical expectations

Search for a W(') boson decaying to a top and bottom quark pair in 1.8 TeV p(p)over-bar collisions

We report the results of a search for a W(') boson produced in p (p) over bar collisions at a center-of-mass energy of 1.8 TeV using a 106 pb(-1) data sample recorded by the Collider Detector at Fermilab. We observe no significant excess of events above background for a W(') boson decaying to a top and bottom quark pair. In a model where this boson would mediate interactions involving a massive right-handed neutrino (nu(R)) and have standard model strength couplings, we use these data to exclude a W(') boson with mass between 225 and 536 GeV/c(2) at 95\% confidence level for M(W)(')>M(nuR) and between 225 and 566 GeV/c(2) at 95\% confidence level for M(W)(')<M(nuR)