426 research outputs found
Effect of CH4 addition on excess electron mobility in liquid Kr
No full textThe mobility μ of excess electrons has been measured in liquid mixtures of Kr and CH4 as a function of the electric field up to E~104 V/cm and of the CH4 concentration x up to x~10%, at a temperature T~125 K, fairly close to the normal boiling point of Kr (Tb~120 K) [Nucl. Instrum. Methods Phys. Res. A 430, 277 (1997)]. We present here new data extending the previous set in the low E region. At small E, μ appears to be quite independent of x. CH4 impurities prove to be less efficient in enhancing momentum transfer than liquified rare gas impurities Kr and Xe in liquid Ar. The dependence of μ on E at higher strengths is complicated. On the one hand, the addition of CH4 extends the range of E in which μ is field independent, by efficiently thermalizing the electrons. On the other hand, at the highest field, the presence of the impurities accomplishes a large increase of the electron drift velocity with respect to the pure liquid (up to a factor of 7 for the highest x). Moreover, at intermediate values of E, where electrons are epithermal, there appears to be a crossover between two different behaviors of μ as a function of E. The electric field strength at the crossover, E*, is well correlated with x. The behavior of μ can be rationalized in terms of a gas-kinetic model proposed to explain its concentration dependence in the liquified rare gas mixtures Ar-Kr and Ar-Xe. This analysis suggests that the observed crossover is related to the excitation of the first vibrational level of CH4
Particle identification in a LKr ionization chamber by multiple induced current measurements using the shape analysis of the signal
No full textCharged particle (π/K) separation in the momentum range 0.5-0.7 GeV/c using a new method of shape analysis of the signal from a liquid krypton ionization chamber has been studied experimentally. The detector has been exposed to pions and protons at the T11 test beam at CERN PS. The shape of preamplifier output signal has been recorded by a waveform digitizer and differentiated to obtain multiple measurements of induced current inside a 2 cm gap. Results on particle separation are presented and compared with a Monte Carlo simulation
Malignant vasovagal syncope: A randomised trial of metoprolol and clonidine
No full textObjective-To evaluate the efficacy of head up tilt guided treatment with metoprolol and clonidine in preventing the recurrence of syncope in patients with malignant vasovagal syncope. Patients-20 patients (9 men and 11 women, mean age 33 (SD 17), range 14 to 62 years) with severe symptoms. Design-Randomised double blind cross-over trial; efficacy was assessed by head up tilt testing. Results-Metoprolol was more effective than clonidine in abolishing syncope (19/20 v 1/20, P < 0.001) but clonidine showed some beneficial effects on time to syncope and severity of hypotension in 12 patients. During an average follow up of 15 (3) months there was a significant reduction in the recurrence of symptoms compared with the previous year in patients who had tilt up guided treatment (18 metoprolol, 1 clonidine). Conclusions-Treatment guided by head up tilting is a reliable method of treating patients with malignant vasovagal syndrome. Metoprolol was an effective long term treatment for preventing syncope. High doses were more effective and a careful dose titration period helped to minimise withdrawal symptoms and side effects
A Measurement of elastic J / psi photoproduction cross-section at fermilab E687.
No full textE687 COLLABORATIO
Cardioverter-defibrillatori impiantati per via transvenosa: esperienza clinica all'impianto e durante il follow-up [Transvenous cardioverter-defibrillators: clinical experience at implantation and follow-up]
No full textThirty-seven patients with ventricular tachyarrhythmias refractory to antiarrhythmic drug treatment, guided by electrophysiological testing, were submitted to implantation of a cardioverter-defibrillator by the transvenous technique. Mean age was 55 +/- 14 years and the underlying heart disease was coronary heart disease in 24 patients, cardiomyopathy or other etiologies in 11 patients. In 2 patients ventricular arrhythmias were idiopathic. Left ventricular ejection fraction was < or equal to 40% in 65% of the patients. The following devices were implanted: CPI Ventak P in 2 patients, Ventak P2 in 9 patients, Ventak PRx in 9 patients, Ventak PRxII in 2 patients, Telectronics Guardian ATP III 4215 in 9 patients, Siemens Siecure in 5 patients, Medtronic Jewel PCD in 1 patient. At implantation defibrillation threshold was lower with biphasic shocks than with monophasic shocks (17.0 +/- 3.2 vs 20.9 +/- 3.8 J, p < 0.003) and the need for subcutaneous patches was lower when biphasic shocks were employed. Operative and perioperative mortality were 0% and no significant complications were observed. During the follow-up (16 +/- 11 months) 35% of the patients had appropriate shocks and 93% of the patients with antitachycardia pacing availability (n = 15) had effective antitachycardia pacing interventions. The following complications were observed: lead failure in 4 patients (3 insulation breaks and 1 elongation for stretching), late lead dislodgement in 2 patients, lead recall in 1 patient, all of which required reintervention. Inappropriate shocks occurred in 30% of the patients and were related to lead failure, supraventricular arrhythmias or alternating current interference. During the follow-up one patient died of sudden death and one was submitted to heart transplantation. In conclusion, implantation of a cardioverter-defibrillator by the transvenous technique is a procedure relatively free from complications. During the follow-up lead failure appears to be one of the most relevant complications. Antitachycardia pacing allows effective termination of ventricular tachycardias without cardioversion, with a better compliance
[Idiopathic atrial fibrillation: clinical-instrumental characterization and thromboembolic risk]. FT Fibrillazione atriale idiopatica: caratterizzazione clinico-strumentale e rischio tromboembolico.
No full textNinety-two patients with diagnosis of lone atrial fibrillation (AF) were retrospectively identified by our in-hospital records. Among the 92 patients, 62 were males and 30 females. Mean age was 50 +/- 15 years (range 13-81). In 30% of the patients mild to moderate systemic hypertension was present. None had thyroid dysfunction. At the time of our first clinical observation, AF showed the following characteristics: recurrent AF in 58% of the cases (53 patients), chronic AF in 16% of the cases (15 patients) and first episode of AF in 26% of the cases (24 patients). Patient's symptoms were: palpitation in 73% of the cases, dyspnea in 24%, asthenia in 22%, chest pain in 19%, dizziness in 19% and syncope in 9% of the cases. In 9% of the subjects AF was asymptomatic. Recurrent AF presented with more than one episode per day in 12% of the cases, one per week in 16% of the cases, one-two episodes in 1 month in 8% of the cases and between two and six episodes in 1 year in 33% of the cases. Cross-sectional echocardiography, evidenced a higher prevalence of left atrial enlargement in patients with chronic AF (7/15 cases = 47%) either compared to subjects with recurrent AF (5/53 cases = 9%, p < 0.005) or compared to subjects with a first episode of AF (3/24 cases = 11%, p < 0.05). Echocardiographic signs of left ventricular dysfunction (left ventricular enlargement or hypokinesia) were found in 27% of the patients with chronic AF and in 8% of the other two groups (NS).(ABSTRACT TRUNCATED AT 250 WORDS
Identification of polymorphisms in the rabbit melanocortin 4 receptor gene and association with finishing weight in a commercial rabbit population
No full textMelanocortin 4 receptor (MC4R) is a member of the G proteincoupled receptor (GPCR) superfamily consisting of seven transmembrane domains with an extracellular NH2 tail and an intracellular COOH terminus. MC4R is mainly expressed in the hypothalamus in which plays a key role in controlling energy homeostasis and food intake with effects on body weight and fat deposition. Polymorphisms in the melanocortin 4 receptor (MC4R) gene have been already associated with growth performance in different species, like pigs, cattle, sheep and chicken and in humans several mutations cause severe obesity. For these reasons MC4R can be considered a candidate gene to identify markers associated with production traits in rabbits. In this study we resequenced 1729 bp of the MC4R gene in 31 rabbits from different breeds and lines and identified ten polymorphisms: one was a missense mutation (p.G34D), located in a conserved position of the extracellular tail of the MC4R protein. The missense mutation was genotyped in 516 performance tested rabbits of a commercial paternal line under selection for growth efficiency. Association analysis indicated that rabbits with the less frequent genotype in this population (DD) had a lighter weight at 70 postnatal days than animals with genotype GD (P<0.10) and animals with genotype GG (P<0.05). This result may confirm the important roles of variability in the MC4R gene in affecting growth and related traits across species
A Wide band photon beam at the Fermilab Tevatron to study heavy flavors.
No full textE687 COLLABORATIO
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