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D Keane

Publications and source records attributed to D Keane.

At least 37 records · Page 2Linked to original sources
PubMed2001

Directed flow of lambda hyperons in (2-6 )A GeV Au+Au collisions.

Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.

Journal Article↗
PubMed2001

Peripartum hysterectomy in the 1990s: any new lessons?

We aimed to identify the risk factors and subsequent maternal and perinatal outcome associated with the procedure of peripartum hysterectomy. This was a retrospective case review carried out at the National Maternity Hospital, Dublin, of all patients who underwent a peripartum hysterectomy from January 1990 to December 1999. Seventeen cases were performed during the study period from a total of 64 563 deliveries (0.03%). Mean maternal age was 34 years (21-43). There were no nulliparous patients. Eight patients had previous vaginal deliveries. The other nine had a history of previous caesarean section, four of whom had two or more caesarean sections. The indications for the hysterectomy were placenta praevia (5), secondary postpartum haemorrhage (3), abruptio placentae (3), atonic postpartum haemorrhage (2), placenta accreta (2), traumatic postpartum haemorrhage (1) and broad ligament haematoma (1). All patients received blood transfusions, 74% receiving more than 10 units. There were no maternal deaths. There were two neonatal deaths secondary to placental abruption (perinatal mortality rate 118/1000). In conclusion, there was no maternal death in this study but the associated maternal morbidity and perinatal mortality was high. More than half the cases were associated with previous caesarean section. The caesarean section rate is increasing worldwide for many reasons, including recent emphasis on maternal request. We recommend that caesarean section be performed only for valid clinical indications, which should help to reduce the problems associated with peripartum hysterectomy.

Journal Article↗
PubMed2000

Does HIV reporting by name deter testing? MESH Study Group.

OBJECTIVE: Name-based HIV reporting is controversial in the United States because of concerns that it may deter high-risk persons from being tested. We sought to determine whether persons at risk of HIV infection knew their state's HIV reporting policy and whether they had delayed or avoided testing because of it. DESIGN: A cross-sectional anonymous survey. METHODS: We interviewed 2404 participants in one of three high-risk groups: men who have sex with men (MSM), heterosexuals attending a sexually transmitted disease (STD) clinic, and street-recruited injection drug users (IDU). Participants were asked standardized questions about their knowledge of reporting policies and reasons for having delayed or avoided testing. We recruited in eight US states: four with name-based reporting and four without; all offered anonymous testing at certain sites. RESULTS: Fewer than 25% correctly identified their state's HIV reporting policy. Over 50% stated they did not know whether their state used name-based reporting. Of the total, 480 participants (20%) had never been tested. Of these, 17% from states with name-based reporting selected concern about reporting as a reason for not testing compared with 14% from states without name-based reporting (P = 0.5). Comparing previously tested participants from states with name-based reporting to those from states without, concern about HIV reporting was given as a reason for delaying testing by 26% compared with 13% of IDU (P < 0.001), and for 26% compared with 19% of MSM (P = 0.06). CONCLUSION: Most participants did not know their state's HIV reporting policy. Name-based reporting policies were not associated with avoiding HIV testing because of worry about reporting, although they may have contributed to delays in testing among some IDU.

AIDS Serodiagnosis↗
PubMed2000

Nuclear multifragmentation, percolation, and the fisher droplet model: common features of reducibility and thermal scaling

It is shown that the Fisher droplet model, percolation, and nuclear multifragmentation share the common features of reducibility (stochasticity in multiplicity distributions) and thermal scaling (one-fragment production probabilities are Boltzmann factors). Barriers obtained, for cluster production on percolation lattices, from the Boltzmann factors show a power-law dependence on cluster size with an exponent of 0.42+/-0.02. The EOS Collaboration Au multifragmentation data yield barriers with a power-law exponent of 0.68+/-0.03. Values of the surface energy coefficient of a low density nuclear system are also extracted.

Journal Article↗
PubMed2000

Antiflow of K(0)(s) mesons in 6A GeV Au + Au collisions

We have measured the sideward flow of neutral strange ( K(0)(s)) mesons in 6A GeV Au+Au collisions. A prominent antiflow signal is observed for an impact parameter range ( b less, similar7 fm) which spans central and midcentral events. Since the K(0)(s) scattering cross section is relatively small in nuclear matter, this observation suggests that the in-medium kaon vector potential plays an important role in high density nuclear matter.

Journal Article↗
PubMed2000

Sideward flow in Au+Au collisions between 2A and 8A GeV

Using the large acceptance Time Projection Chamber of experiment E895 at Brookhaven, measurements of collective sideward flow in Au+Au collisions at beam energies of 2A, 4A, 6A, and 8A GeV are presented in the form of in-plane transverse momentum and the first Fourier coefficient of azimuthal anisotropy v(1). These measurements indicate a smooth variation of sideward flow as a function of beam energy. The data are compared with four nuclear transport models which have an orientation towards this energy range. All four exhibit some qualitative trends similar to those found in the data, although none show a consistent pattern of agreement within experimental uncertainties.

Journal Article↗
PubMed2000

Bombarding energy dependence of pi(-) interferometry at the brookhaven AGS

We present the first excitation function of pi(-) intensity interferometry at Alternating Gradient Synchrotron (AGS) energies (2-8 A GeV). The sensitivity of the multidimensional correlation functions to the geometry and dynamics of the pion-emitting system provides a stringent test of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction dynamics is different in the model than in the data. A significantly increased pi(-) emission time scale, which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.

Journal Article↗
PubMed2000

Lead noise with an active-fixation defibrillation lead.

Inappropriate detection and therapy is the most common adverse effect of implantable cardioverter defibrillator therapy. One mechanism is lead artifact, which usually presents late and is due to stress and fatigue of the lead components. Our experience with a defibrillator lead (Endotak Endurance EZ leads, Models 0154/0155/0156) and its method of active fixation is described. Of 20 implants with this lead, four patients were found to have noise that resulted in inappropriate detections in three. No patient received therapy as a consequence of these detections. The artifact appeared soon after implant and resolved in three of four cases by 4 weeks. None of the 16 remaining patients developed noise after this time. This is a unique lead problem that resolves with time, but it may result in inappropriate therapies and difficult management decisions in high risk patients with ventricular arrhythmias.

Aged↗
PubMed1999

Name-based surveillance and public health interventions for persons with HIV infection. Multistate Evaluation of Surveillance for HIV Study Group.

Name-based surveillance of HIV infection is the law in 31 U.S. states but remains controversial. This policy can be advocated solely to support surveillance of the epidemic, but a frequent argument is that it also provides a public health benefit by allowing follow-up of HIV-infected persons. These persons can then receive timely medical care and can be assisted with notifying sex and needle-sharing partners. Few comparative data are available to evaluate the outcomes of these interventions. In five states with name-based surveillance of HIV infection, the Multistate Evaluation of Surveillance for HIV Study Group surveyed a cross-sectional probability sample of persons with AIDS who tested positive for HIV before the date of their AIDS diagnosis. Health department follow-up of a reported HIV infection was not associated with more timely receipt of medical care after a positive HIV test result. Only 8.6% of persons who delayed medical care after their first positive HIV test result gave concern about being reported by name as a reason; no person gave it as the main reason. Persons who were tested anonymously and those who were tested confidentially did not differ in the mean number of sex and needle-sharing partners notified: Those tested anonymously reported personally notifying 3.85 sex and needle-sharing partners, and those tested confidentially reported notifying-personally and through the health department-3.80 partners. Many researchers and policymakers believe that name-based surveillance of HIV infection will have positive or negative effects on partner notification and access to health care. These results suggest that the potential for such effects has been exaggerated.

Anonymous Testing↗
PubMed1999

Fast and simple purification of chemically modified hammerhead ribozymes using a lipophilic capture tag.

A new type of 5'-lipophilic capture tag is described, enabling the facile reverse phase HPLC purification of chemically modified hammerhead ribozymes (oligozymes) whilst still carrying the 2'-O-tert.-butyldimethylsilyl protection of the essential riboses. In its most convenient form, the capture tag consists of a simple diol, such as hexan-1,6-diol, which at one end is attached via a silyl residue to a highly lipophilic entity such as tocopherol (vitamin E) or cholesterol, and the other end is functionalized as a phosphoramidite. This lipophilic capture tag is added as the last residue in the solid-phase synthesis of chemically modified hammerhead ribozymes. Cleavage from the support and release of all protecting groups except for the silyl groups is achieved with ethanolamine/ethanol. The crude product is then loaded directly on to a reverse phase HPLC column. Separation of failure peaks from full length product is achieved easily using a short run time. The retarded product peak is collected, lyophilized, desilylated in the normal way and then desalted. This method removes the lipophilic capture tag yet leaves behind the hexanediol entity which helps protect the compound against degradation by 5'-exonucleases. The purity of the product as judged by analytical anion-exchange HPLC and capillary gel electrophoresis is generally better than 95% full-length, and yields of 2-4 mg from a 1 micromol scale synthesis are routine. In addition, the method can be readily scaled up, an important feature for the development of such chemically modified ribozymes as potential therapeutics.

Cholesterol↗
PubMed1999

Thromboembolic complications of cardiac radiofrequency catheter ablation: a review of the reported incidence, pathogenesis and current research directions.

INTRODUCTION: Radiofrequency catheter ablation (RFCA) has become established as an effective therapy for the treatment of many cardiac tachyarrhythmias. The principle limitation of conventional RFCA continues to be the risk of thromboembolism. This risk is of particular concern for the ongoing development of the catheter maze procedure for the treatment of atrial fibrillation, which currently involves the creation of extensive linear lesions in the left atrium. METHODS AND RESULTS: A Medline search of the literature over the last ten years was performed. Focused review of the reported thromboembolic complications of RFCA indicates an overall incidence of 0.6%. However, the risk is increased when ablation is performed in the left heart (1.8% to 2%) and for ventricular tachycardia (2.8%). It is of concern that intravenous heparin and the use of temperature feedback to control radiofrequency current do not eliminate the risk of thromboembolic events. CONCLUSION: The thromboembolic complications of RFCA are not eliminated by the treatment of intravenous herapin and mode of temperature control during ablation. Potential approaches to further reduce the risk of thromboembolism include the adjunctive administration of specific inhibitors of platelet activation and aggregation, intraprocedural intracardiac echocardiography, irrigated radiofrequency ablation, and cryoablation catheter systems.

Anticoagulants↗
PubMed1998

Multistate evaluation of anonymous HIV testing and access to medical care. Multistate Evaluation of Surveillance of HIV (MESH) Study Group.

CONTEXT: Infection with the human immunodeficiency virus (HIV) is the only infectious disease for which anonymous testing is publicly funded, an exception that has been controversial. OBJECTIVE: To assess whether anonymous HIV testing was associated with earlier HIV testing and HIV-related medical care than confidential HIV testing. DESIGN: Retrospective cohort. SETTING: Arizona, Colorado, Missouri, New Mexico, North Carolina, Oregon, and Texas. PARTICIPANTS: Probability sample of 835 new acquired immunodeficiency syndrome (AIDS) cases reported to the state health department's HIV/AIDS Reporting System from May 1995 through December 1996. All had responded to the AIDS Patient Survey; 643 had been tested confidentially for HIV, and 192 had been tested anonymously. MAIN OUTCOME MEASURES: First CD4+ cell count; number of days from HIV-positive test result to first HIV-related medical care, from first HIV-related medical care to AIDS, and from first HIV-positive test result to AIDS. RESULTS: Persons tested anonymously sought testing and medical care earlier in the course of HIV disease than did persons tested confidentially. Mean first CD4+ cell count was 0.427x 10(9)/L in persons tested anonymously vs 0.267x 10(9)/L in persons tested confidentially. Persons tested anonymously experienced an average of 918 days in HIV-related medical care before an AIDS diagnosis vs 531 days for persons tested confidentially. The mean time from learning they were HIV positive to the diagnosis of AIDS was 1246 days for persons tested anonymously vs 718 days for persons tested confidentially. After adjustment for the subject's age, sex, race/ethnicity, education, income, insurance status, HIV exposure group, whether the respondent had a regular source of care or symptoms at the time of the HIV test, and state residence, anonymous testing remained significantly associated with earlier entry into medical care (P<.001). CONCLUSION: Anonymous testing contributes to early HIV testing and medical care.

AIDS Serodiagnosis↗
PubMed1998

Nonpharmacologic therapies for atrial fibrillation.

The limited efficacy and proarrhythmic risks of antiarrhythmic drug therapies for atrial fibrillation have led to the exploration of a wide spectrum of alternative therapeutic approaches. The diversity of the approaches is warranted by the current absence of a single procedure that can safely and effectively cure atrial fibrillation. The interventional therapies that are currently under most active development include implantable atrial defibrillator therapy, prophylactic atrial pacing in combination with drug therapy, multisite regional pace-entrainment of atrial fibrillation by rapid pacing, atrial surgery, and catheter ablation for atrial fibrillation. The current limitations of these procedures include: (1) for the implantable atrial defibrillator--patient tolerance of low energy shocks and early recurrence of atrial fibrillation; (2) for prophylactic pacing-limited efficacy in a small proportion of the total atrial fibrillation population; (3) for multisite regional pace-entrainment--lack of proved efficacy and difficulty in the expansion and merging of the entrained regions; (4) for atrial surgery--highly invasive as a stand-alone procedure; and (5) for catheter ablation-lack of proved long-term efficacy, shortcomings of currently available technology, and risk of thromboembolic stroke. It is evident that more basic and clinical research as well as technologic innovation are needed. However, it is likely that some of these new therapies, possibly in combination with antiarrhythmic drug therapy, will offer considerable clinical benefit to selected patients with symptomatic atrial fibrillation.

Atrial Fibrillation↗
PubMed1998

Neutron yields from 435 MeV/nucleon Nb stopping in Nb and 272 MeV/nucleon Nb stopping in Nb and Al.

Neutron fluences were measured from 435 MeV/nucleon Nb ions stopping in a Nb target and 272 MeV/nucleon Nb ions stopping in targets of Nb and Al for neutrons above 20 MeV and at laboratory angles between 3 degrees and 80 degrees. The resultant spectra were integrated over angles to produce neutron energy distributions and over energy to produce neutron angular distributions. The total neutron yields for each system were obtained by integrating over the angular distributions. The angular distributions from all three systems are peaked forward, and the energy distributions from all three systems show an appreciable yield of neutrons with velocities greater than the beam velocity. Comparison of the total neutron yields from the two Nb + Nb systems suggests that the average neutron multiplicity decreases with decreasing projectile energy. Comparison of the total yields from the two 272 MeV/nucleon systems suggests that the total yields show the same dependence on projectile and target mass number as do total inclusive neutron cross sections. The data are compared with Boltzmann-Uehling-Uhlenbeck model calculations.

Aluminum↗
PubMed1997

Comparison of coronary luminal quantification obtained from intracoronary ultrasound and both geometric and videodensitometric quantitative angiography before and after balloon angioplasty and directional atherectomy.

BACKGROUND: Debate exists regarding the relationship between angiographic and intracoronary ultrasound (ICUS) measurements of minimal luminal cross-sectional area after coronary intervention. We investigated this and the factors that may influence it by using ICUS and quantitative angiography. METHODS AND RESULTS: Patients who underwent successful balloon angioplasty (n=100) or directional atherectomy (n=50) were examined by using ICUS and quantitative angiography (edge-detection [ED] and videodensitometry [VID]) before and after intervention. Luminal damage postintervention was qualitatively graded into three categories based on angiographic results (smooth lumen, haziness, or dissection). Correlation of minimal luminal cross-sectional area measurements by ICUS and ED was .59 before and .47 after balloon angioplasty. Correlation between ICUS and VID was .50 before and .63 after balloon angioplasty. Postintervention, the difference between ICUS and VID was less than the difference between ICUS and ED (P<.01). Additionally, the correlation was .74 between ICUS and ED measurements and .78 between ICUS and VID measurements in the smooth lumen group, .46 and .63, respectively, in the presence of haziness, and .26 and .46, respectively, in lesions with dissection. Similar results were obtained after directional atherectomy: the agreement between ICUS and quantitative angiography deteriorated according to the degree of vessel damage, but less so with VID than ED. CONCLUSIONS: Complex morphological changes induced by intervention may contribute to discordance between the two quantitative imaging techniques. In the absence of ICUS, VID may be a complementary technique to ED in lesions with complex morphology after balloon angioplasty and directional atherectomy.

Aged↗