Biomedical subjects

H Akimoto

Publications and source records attributed to H Akimoto.

At least 37 records · Page 2Linked to original sources

PubMed2002

Search for new heavy particles in the WZ0 final state in pp collisions at square root[s] = 1.8 TeV.

We present the first general search for new heavy particles, X, which decay via X --> WZ0 --> e(nu)+jj as a function of M(X) and Gamma(X) in pp collisions at square root[s] = 1.8 TeV. No evidence is found for production of X in 110 pb(-1) of data collected by the Collider Detector at Fermilab. General cross section limits are set at the 95% C.L. as a function of mass and width of the new particle. The results are further interpreted as mass limits on the production of new heavy charged vector bosons which decay via W' --> WZ0 in an extended gauge model as a function of the width, Gamma(W'), and mixing factor between the W' and the standard model W bosons.

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PubMed2002

Study of B0 --> J/psiK(*)0pi(+)pi(-) decays with the collider detector at Fermilab.

We report a study of the decays B0 --> J/psiK(*)0pi(+)pi(-), which involve the creation of a uu or dd quark pair in addition to a b -->c(cs) decay. The data sample consists of 110 pb(-1) of pp collisions at square root[s] = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching fractions to be B(B0 --> J/psiK(*0)pi(+)pi(-)) = (6.6 +/- 1.9 +/- 1.1)x10(-4) and B(B0 --> J/psiK0pi(+)pi(-)) = (10.3 +/- 3.3 +/- 1.5)x10(-4). Evidence is seen for contributions from psi(2S)K(*)0, J/psiK0rho(0), J/psiK(*+)pi(-), and J/psiK1(1270).

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PubMed2002

Measurement of the strong coupling constant from inclusive jet production at the Tevatron pp collider.

We report a measurement of the strong coupling constant, alpha(s)(MZ), extracted from inclusive jet production in pp collisions at square root[s] = 1800 GeV. The QCD prediction for the evolution of alpha(s) with jet transverse energy ET is tested over the range 40<ET<450 GeV using ET for the renormalization scale. The data show good agreement with QCD in the region below 250 GeV. The value of alpha(s) at the mass of the Z0 boson averaged over the range 40<ET<250 GeV is found to be alpha(s)(MZ) = 0.1178+/-0.0001(stat)+0.0081(-0.0095)(expt. syst). The associated theoretical uncertainties are mainly due to the choice of renormalization scale ((+6%)(-4%)) and input parton distribution functions (5%).

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PubMed2002

Search for gluinos and scalar quarks in pp collisions at square root[s] = 1.8 TeV using the missing energy plus multijets signature.

We have performed a search for gluinos (g) and scalar quarks (q) in a data sample of 84 pb(-1) of pp collisions at square root[s] = 1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and three or more jets, a characteristic signature in R-parity-conserving supersymmetric models. The analysis has been performed "blind," in that the inspection of the signal region is made only after the predictions from standard model backgrounds have been calculated. Comparing the data with predictions of constrained supersymmetric models, we exclude gluino masses below 195 GeV/c2 (95% C.L.), independent of the squark mass. For the case m(q) approximately m(g), gluino masses below 300 GeV/c2 are excluded.

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PubMed2002

Epidural cooling for regional spinal cord hypothermia during most or all of descending thoracic or thoracoabdominal aneurysm repair.

PURPOSE: Hypothermia has some protective effect against ischemia of the spinal cord in thoracoabdominal aneurysm repair. Its method is divided into systemic or regional cooling. Several experimental studies of the regional cooling of the spinal cord have been performed, however, clinical reports are few. The purpose of this study is to evaluate the effect and safety of perfusion cooling of the epidural space during thoracic or thoracoabdominal aortic replacement. METHODS: Between January 1998 to June 2001 37 patients (True aneurysm: 18 patients, type B aortic dissection: 19 patients) underwent thoracic or thoracoabdominal aortic replacement with an aid of epidural perfusion cooling. The age ranged from 23 to 78 years old with a mean age of 61 years old. Separate perfusion of upper and lower body was used in all cases. Temperature was lowered to around a 31 degrees C or 32 degrees C. In cases where proximal cross-clamping was danger, deep hypothermic circulatory arrest was used. RESULTS: Ten patients underwent most or all of descending thoracic aneurysm repair with no spinal cord injury and hospital death. Number of patients of the Crawford type I, type II, and type III were 14, 8 and 5 patients, respectively. One Crawford type II patients was complicated with postoperative spinal cord injury (2.7%). There was one hospital death (2.7%) in Crawford type III. The mean epidural cooling time was 150 minutes, and mean infusion volume of cold saline was 981 cc. The mean lowest cerebrospinal fluid (CSF) temperature was 24.3 degrees C, and mean temperature differences between nasopharynx and CSF was 6.3 degrees C. CONCLUSION: Perfusion cooling of the epidural space during most or all of the descending thoracic or thoracoabdominal aneurysm repair was effective in reducing postoperative spinal cord injury and a safe method in clinical situations.

Adult↗

PubMed2002

Myocardial protection of the pressure overload hypertrophied heart in human cardiac surgery by acceleration of anaerobic glycolysis.

BACKGROUND: Because of the decreased tolerance to ischemia and increased reperfusion injury in hypertrophied myocardium, myocardial hypertrophy is a well known risk factor for cardiac surgery. We have previously demonstrated in a left ventricular hypertrophy (LVH) model that a highly buffered cardioplegic solution (HBS) that provided glucose as a substrate and promoted anaerobic glycolysis during ischemia afforded superior myocardial protection when compared to standard formulations. And we reported the superiority of this cardioplegia in human cardiac surgery. METHODS: In this study, 16 patients with aortic stenosis (AS) and LVH receiving HBS were reviewed and compared to another patient group with AS and LVH who received either cold blood cardioplegia (CBC; n=5) or glucose insulin potassium (GIK; n=6). RESULTS: Postoperative cardiac index was better in the HBS group than the other two groups with similar or lower catecholamine. CK-MB was lower in HBS group than GIK group, but this was not significant. Only one DC cardioversion was required in the HBS group, whereas 2 DC in the CBC group and total 7 DC in the GIK group. CONCLUSIONS: We found that histidine buffered cardioplegic solution provided comparable or better pump performance after surgery with relatively lower inotropic requirement, less DC cardioversion and homologous blood requirements for left ventricular hypertrophied heart associated with aortic stenosis.

Aged↗

PubMed2002

[True aneurysm of the ascending aorta and/or aortic arch; determinants of late surgical outcome].

To identify significant predictors of late mortality, multivariate analysis were applied to the clinical outcome of 150 consecutive patients with true aneurysm of the ascending aorta and/or aortic arch operated between January, 1987 and December, 2000. Mean follow-up was 53.0 months with a total of 6,682 patient-months of follow-up. Multivariate analysis revealed that operation date (before December, 1996), presence of preoperative cerebrovascular disease, rupture and postoperative phrenic nerve palsy were independent determinants of late mortality. The overall 5-year and 10-year actuarial survival rates were 66.0% and 48.2%. The 5-year and 10-year event free rate of cardiovascular and/or cerebrovascular death were 88.9% and 71.7%. Preoperative evaluation of the brain, operation prior to aneurysm rupture and phrenic nerve protection during operation is necessary to improve long-term survival rate.

Adult↗

PubMed2002

[Recurrent low output syndrome after the weaning from mechanical circulatory support for postcardiotomy cardiogenic shock].

We reviewed the cases of recurrent low output syndrome (LOS) after the weaning from mechanical circulatory support for postcardiotomy cardiogenic shock. Twelve patients were divide into 2 groups according to whether low output syndrome recurred or not, consisting of a recurrent low output syndrome (+) group [re-LOS (+) group, n = 6] and a recurrent low output syndrome (-) group [re-LOS (-) group, n = 6]. Between 2 groups, there was no statistical difference in preoperative left ventricular ejection fraction (LVEF), aortic closs-clamping time and cardiac index at the weaning from mechanical circulatory support. Only the LVEF at the weaning in the re-LOS (+) group was significantly less than that in the re-LOS (-) group (0.39 +/- 0.08 vs 0.62 +/- 0.19, p < 0.05). All patients in the re-LOS (-) group survived to discharge, while in the re-LOS (+) group, although 3 patients were re-supported by intra-aortic balloon pumping, 4 of 6 patients died of multiple organ failure and 2 survivors were in New York Heart Association class III. The results suggest that the key to survive to discharge after the weaning from mechanical circulatory support is whether the cardiac contraction could recover or not.

Aged↗

PubMed2002

[Aortobronchial fistula after replacement of descending thoracic aorta with ringed graft; report of a case].

A 79-year-old male patient complicated with aortobronchial fistula after replacement of descending thoracic aorta with ringed graft. He underwent replacement of the aortic arch using a four branched vascular graft and open stent grafting to replace the descending thoracic aorta after removing the ringed-graft through median sternotomy. This procedure is useful for patients as the left thoracotomy is risky and the distal anastomotic site of the descending thoracic aorta is too far to anastomose.

Aged↗

PubMed2001

Search for gluinos and squarks using like-sign dileptons in pp macro collisions at square root of s = 1.8 TeV.

We present results of the first search for like-sign dilepton ( e(+/-)e(+/-), e(+/-)mu(+/-), mu(+/-)mu(+/-)) events associated with multijets and large missing energy using 106 pb(-1) of data in pp macro collisions at square root of s = 1.8 TeV collected during 1992-1995 by the CDF experiment. Finding no events that pass our selection, we examine pair production of gluinos (tilde g) and squarks (tilde q) in a constrained framework of the minimal supersymmetric standard model. At tan beta = 2 and mu = -800 GeV/c(2), we set 95% confidence level limits of M(tilde g)>221 GeV/c(2) for M(tilde g) approximately M(tilde q), and M(tilde q)>168 GeV/c(2) for M(tilde q)>>M(tilde g), both with small variation as a function of mu.

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PubMed2001

Observation of diffractive J/psi production at the Fermilab Tevatron.

We report the first observation of diffractive J/psi(--> mu+mu-) production in pp collisions at root square[s] = 1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum p(mu)T>2 GeV/c within the pseudorapidity region /eta/ < 1.0, the ratio of diffractive to total J/psi production rates is found to be R(J/psi) = [1.45 +/- 0.25]%. The ratio R(J/psi)(x) is presented as a function of x-Bjorken. By combining it with our previously measured corresponding ratio R(jj)(x) for diffractive dijet production, we extract a value of 0.59 +/- 0.15 for the gluon fraction of the diffractive structure function of the proton.

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PubMed2001

Charged-particle multiplicity pp collisions at square root of (s) = 1.8 TeV.

We report on a measurement of the mean charged-particle multiplicity of jets in dijet events with dijet masses in the range 80-630 GeV/c(2), produced at the Tevatron in pp collisions with square root (s) = 1.8 TeV and recorded by the Collider Detector at Fermilab. The data are fit to perturbative-QCD calculations carried out in the framework of the modified leading log approximation and the hypothesis of local parton-hadron duality. The fit yields values for two parameters in that framework: the ratio of parton multiplicities in gluon and quark jets, r identical withN(g-jet)(partons)/N(q-jet)(partons) = 1.7+/-0.3, and the ratio of the number of charged hadrons to the number of partons in a jet, K(charged)(LPHD) identical with N(charged)(hadrons)/N(partons) = 0.57+/-0.11.

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PubMed2001

Search for quark-lepton compositeness and a heavy W' Boson using the enu channel in p p macro collisions at square root of [s] = 1.8 TeV.

We present searches for quark-lepton compositeness and a heavy W' boson at high electron-neutrino transverse mass. We use approximately 110 pb(-1) of data collected in p p macro collisions at square root of [s] = 1.8 TeV by the CDF Collaboration during 1992-1995. The data are consistent with standard model expectations. Limits are set on the quark-lepton compositeness scale Lambda, the ratio of partial cross sections sigma(W'-->enu)/sigma(W-->enu), and the mass of a W' boson with standard model couplings. We exclude Lambda<2.81 TeV and a W' boson with mass below 754 GeV/c(2) at the 95% confidence level. Combining with our previously published limit obtained using the muon channel, we exclude a W' boson with mass below 786 GeV/c(2) at the 95% confidence level.

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PubMed2001

Double diffraction dissociation at the Fermilab Tevatron collider.

We present results from a measurement of double diffraction dissociation in pp collisions at the Fermilab Tevatron collider. The production cross section for events with a central pseudorapidity gap of width Deltaeta(0)>3 (overlapping eta = 0) is found to be 4.43+/-0.02(stat)+/-1.18(syst) mb [ 3.42+/-0.01(stat)+/-1.09(syst) mb] at square root of (s) = 1800[630] GeV. Our results are compared with previous measurements and with predictions based on Regge theory and factorization.

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PubMed2001

Measurement of d sigma/dM and forward-backward charge asymmetry for high-mass Drell-Yan e(+)e(-) pairs from pp macro collisions at square root of s = 1.8 TeV.

We report on a measurement of the mass dependence of the forward-backward charge asymmetry, A(FB), and production cross section d sigma/dM for e(+)e(-) pairs with mass M(ee)>40 GeV/c(2). The data sample consists of 108 pb(-1) of pp macro collisions at square root of s = 1.8 TeV taken by the Collider Detector at Fermilab during 1992-1995. The measured asymmetry and d sigma/dM are compared with the predictions of the standard model and a model with an extra Z' gauge boson.

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PubMed2001

Measurement of the top quark p(T) distribution.

We have measured the p(T) distribution of top quarks that are pair produced in pp collisions at sqrt[s] = 1.8 TeV using a sample of tt decays in which we observe a single high- p(T) charged lepton, a neutrino, and four or more jets. We use a likelihood technique that corrects for the experimental bias introduced due to event reconstruction and detector resolution effects. The observed distribution is consistent with the standard model prediction. We use these data to place limits on the production of high- p(T) top quarks suggested in some models of anomalous top quark pair production.

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PubMed2001

Search for neutral supersymmetric Higgs bosons in pp collisions at sqrt[s] = 1.8TeV.

We present the results of a search for neutral Higgs bosons produced in association with b quarks in pp-->bb(phi)-->bbb final states with 91+/-7 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV recorded by the Collider Detector at Fermilab. We find no evidence of such a signal and the data are interpreted in the context of the neutral Higgs sector of the minimal supersymmetric extension of the standard model. With basic parameter choices for the supersymmetric scale and the stop-quark mixing, we derive 95% C.L. lower mass limits for neutral Higgs bosons for tan(beta) values in excess of 35.

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PubMed2001

Production of chi(c1) and chi(c2) in pp collisions at sqrt[S] = 1.8 TeV.

We have measured the ratio of prompt production rates of the charmonium states chi(c1) and chi(c2) in 110 pb(-1) of pp collisions at sqrt[s] = 1.8 TeV. The photon from their decay into J/psi(gamma) is reconstructed through conversion into e+e- pairs. The energy resolution this technique provides makes the resolution of the two states possible. We find the ratio of production cross sections sigma(chi(c2))/sigma(chi(c1)) = 0.96+/-0.27(stat)+/-0.11(syst) for events with pT(J/psi) > 4.0 GeV/c, /eta(J/psi)/ < 0.6, and pT(gamma) > 1.0 GeV/c.

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