671 research outputs found
Photonuclear reactions with Zinc: A case for clinical linacs
The use of bremsstrahlung photons produced by a linac to induce photonuclear
reactions is wide spread. However, using a clinical linac to produce the
photons is a new concept. We aimed to induce photonuclear reactions on zinc
isotopes and measure the subsequent transition energies and half-lives. For
this purpose, a bremsstrahlung photon beam of 18 MeV endpoint energy produced
by the Philips SLI-25 linac has been used. The subsequent decay has been
measured with a well-shielded single HPGe detector. The results obtained for
transition energies are in good agreement with the literature data and in many
cases surpass these in accuracy. For the half-lives, we are in agreement with
the literature data, but do not achieve their precision. The obtained accuracy
for the transition energies show what is achievable in an experiment such as
ours. We demonstrate the usefulness and benefits of employing clinical linacs
for nuclear physics experiments
DiffĂŒz bĂŒyĂŒk B-hĂŒcreli lenfomanın farklı immĂŒnofenotipik profillerinde apoptozis, proliferasyon durumu ve O6 metilguanin DNA metiltransferaz metilasyon profillerinin tespiti
Objective: Our aim was to investigate the expression of apoptosis-associated proteins (bcl-2, bcl-xl, bax, bak, bid), apoptotic index (AI) and proliferation index (PI) in germinal center B-cell-like immunophenotypic profile (GCB) and non-GCB of diffuse large B-cell lymphoma (DLBCL). Materials and Methods: The methylation status of the promoter region of O6-methylguanine-DNA yerine O6-methylguanine-DNA methyltransferase (MGMT) gene and its relation with immunophenotypic differentiation of DLBCLs were also investigated. 101 cases were classified as GCB (29 cases) or non-GCB (72 cases). Apoptosis-associated proteins and PI were determined by IHC, and TUNEL method was used to determine AI. MGMT methylation analysis was performed by real-time PCR. Results: The PI was significantly higher in GCB compared with non-GCB (p=0.011). Percentage of cells stained with bcl-6 was positively correlated with the percentage of cells expressing bcl-2 (p=0.023), AI (p=0.006) and PI (p<0.001), while a significant negative correlation was observed with the percentage of cells expressing bax (p=0.027). The percentage of cells stained with MUM1 showed a significantly positive correlation with the percentage of cells expressing bcl-xl (p=0.003), bid (p=0.002), AI (p<0.001), and PI (p=0.001). MGMT methylation analysis was performed in 95 samples, and methylated profile was found in 31 cases (32.6%). GCB was found in 6 cases (22.2%) and non-GCB was determined in 25 cases (36.8%) out of 31 with MGMT methylated samples. There was no significant association between MGMT methylation status and immunophenotypic profiles (p=0.173). Conclusion: These results suggest that bcl-6 protein expression may be responsible for the high PI in GCB. Additionally, we found that apoptosis-associated proteins were not significantly associated with immunophenotypic profiles
Bottom Production
We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999
CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O.
Schneider G.F. Tartarelli, P. Vikas (conveners
Physiological, Biochemical, and Transcriptional Responses to Single and Combined Abiotic Stress in Stress-Tolerant and Stress-Sensitive Potato Genotypes
Potato production is often constrained by abiotic stresses such as drought and high temperatures which are often present in combination. In the present work, we aimed to identify key mechanisms and processes underlying single and combined abiotic stress tolerance by comparative analysis of tolerant and susceptible cultivars. Physiological data indicated that the cultivars Desiree and Unica were stress tolerant while Agria and Russett Burbank were stress susceptible. Abiotic stress caused a greater reduction of photosynthetic carbon assimilation in the susceptible cultivars which was associated with a lower leaf transpiration rate. Oxidative stress, as estimated by the accumulation of malondialdehyde was not induced by stress treatments in any of the genotypes with the exception of drought stress in Russett Burbank. Stress treatment resulted in increases in ascorbate peroxidase activity in all cultivars except Agria which increased catalase activity in response to stress. Transcript profiling highlighted a decrease in the abundance of transcripts encoding proteins associated with PSII light harvesting complex in stress tolerant cultivars. Furthermore, stress tolerant cultivars accumulated fewer transcripts encoding a type-1 metacaspase implicated in programmed cell death. Stress tolerant cultivars exhibited stronger expression of genes associated with plant growth and development, hormone metabolism and primary and secondary metabolism than stress susceptible cultivars. Metabolite profiling revealed accumulation of proline in all genotypes following drought stress that was partially suppressed in combined heat and drought. On the contrary, the sugar alcohols inositol and mannitol were strongly accumulated under heat and combined heat and drought stress while galactinol was most strongly accumulated under drought. Combined heat and drought also resulted in the accumulation of Valine, isoleucine, and lysine in all genotypes. These data indicate that single and multiple abiotic stress tolerance in potato is associated with a maintenance of CO2 assimilation and protection of PSII by a reduction of light harvesting capacity. The data further suggests that stress tolerant cultivars suppress cell death and maintain growth and development via fine tuning of hormone signaling, and primary and secondary metabolism. This study highlights potential targets for the development of stress tolerant potato cultivars
Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions
We describe a measurement of the charge asymmetry of leptons from W boson
decays in the rapidity range 0 enu, munu events from
110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The
asymmetry data constrain the ratio of d and u quark momentum distributions in
the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry
predictions that use parton distribution functions obtained from previously
published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree
with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur
Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab
We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using
a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with
the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass
distribution is obtained that is consistent with W decay and inconsistent with
the background prediction by 3.3 standard deviations. From this peak we measure
the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the
presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet
channel.Comment: 20 pages, 4 figures, submitted to PR
Measurement of Dijet Angular Distributions at CDF
We have used 106 pb^-1 of data collected in proton-antiproton collisions at
sqrt(s)=1.8 TeV by the Collider Detector at Fermilab to measure jet angular
distributions in events with two jets in the final state. The angular
distributions agree with next to leading order (NLO) predictions of Quantum
Chromodynamics (QCD) in all dijet invariant mass regions. The data exclude at
95% confidence level (CL) a model of quark substructure in which only up and
down quarks are composite and the contact interaction scale is Lambda_ud(+) <
1.6 TeV or Lambda_ud(-) < 1.4 TeV. For a model in which all quarks are
composite the excluded regions are Lambda(+) < 1.8 TeV and Lambda(-) < 1. 6
TeV.Comment: 16 pages, 2 figures, 2 tables, LaTex, using epsf.sty. Submitted to
Physical Review Letters on September 17, 1996. Postscript file of full paper
available at http://www-cdf.fnal.gov/physics/pub96/cdf3773_dijet_angle_prl.p
Search for New Particles Decaying to Dijets at CDF
We have used 106 pb^-1 of data collected with the Collider Detector at
Fermilab to search for new particles decaying to dijets. We exclude at the 95%
confidence level models containing the following new particles: axigluons and
flavor universal colorons with mass between 200 and 980 GeV/c, excited quarks
with mass between 80 and 570 GeV/c^2 and between 580 and 760 GeV/c^2, color
octet technirhos with mass between 260 and 480 GeV/c^2, W' bosons with mass
between 300 and 420 GeV/c^2, and E_6 diquarks with mass between 290 and 420
GeV/c^2.Comment: 18 pages, 4 figures, 1 table. Submitted to Physical Review D Rapid
Communications. Postscript file of paper is also available at
http://www-cdf.fnal.gov/physics/pub97/cdf3276_dijet_search_prd_rc.p
Measurement of the top quark mass and top-antitop production cross section from dilepton events at the Collider Detector at Fermilab
We present an analysis of dilepton events originating from top-antitop
production in proton-antiproton collisions at sqrt{s}=1.8 TeV at the Fermilab
Tevatron Collider. The sample corresponds to an integrated luminosity of 109+-7
pb^{-1}. We observe 9 candidate events, with an estimated background of
2.4+-0.5 events. We determine the mass of the top quark to be M_top =
161+-17(stat.)+-10(syst.) GeV/c^2. In addition we measure a top-antitop
production cross section of 8.2+4.4-3.4 pb (where M_top = 175 GeV/c^2 has been
assumed for the acceptance estimate).Comment: 6 pages of text, 3 figure
Search for Chargino-Neutralino Associated Production at the Fermilab Tevatron Collider
We have searched in collisions at = 1.8 TeV for events
with three charged leptons and missing transverse energy. In the Minimal
Supersymmetric Standard Model, we expect trilepton events from
chargino-neutralino (\chione \chitwo) pair production, with subsequent decay
into leptons. We observe no candidate , ,
or events in 106 pb integrated
luminosity. We present limits on the sum of the branching ratios times cross
section for the four channels: \sigma_{\chione\chitwo}\cdot
BR(\chione\chitwo\to 3\ell+X) 81.5 \mgev\sp and
M_\chitwo > 82.2 \mgev\sp for , ~\mgev\sp and
M_\squark= M_\gluino.Comment: 9 pages and 3 figure
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