Search for magnetic monopoles produced via the Schwinger mechanism.

Electrically charged particles can be created by the decay of strong enough electric fields, a phenomenon known as the Schwinger mechanism1. By electromagnetic duality, a sufficiently strong magnetic field would similarly produce magnetic monopoles, if they exist2. Magnetic monopoles are hypothetical fundamental particles that are predicted by several theories beyond the standard model3-7 but have never been experimentally detected. Searching for the existence of magnetic monopoles via the Schwinger mechanism has not yet been attempted, but it is advantageous, owing to the possibility of calculating its rate through semi-classical techniques without perturbation theory, as well as that the production of the magnetic monopoles should be enhanced by their finite size8,9 and strong coupling to photons2,10. Here we present a search for magnetic monopole production by the Schwinger mechanism in Pb-Pb heavy ion collisions at the Large Hadron Collider, producing the strongest known magnetic fields in the current Universe11. It was conducted by the MoEDAL experiment, whose trapping detectors were exposed to 0.235 per nanobarn, or approximately 1.8 × 109, of Pb-Pb collisions with 5.02-teraelectronvolt center-of-mass energy per collision in November 2018. A superconducting quantum interference device (SQUID) magnetometer scanned the trapping detectors of MoEDAL for the presence of magnetic charge, which would induce a persistent current in the SQUID. Magnetic monopoles with integer Dirac charges of 1, 2 and 3 and masses up to 75 gigaelectronvolts per speed of light squared were excluded by the analysis at the 95% confidence level. This provides a lower mass limit for finite-size magnetic monopoles from a collider search and greatly extends previous mass bounds.

First Search for Dyons with the Full MoEDAL Trapping Detector in 13 TeV pp Collisions.

The MoEDAL trapping detector consists of approximately 800 kg of aluminum volumes. It was exposed during run 2 of the LHC program to 6.46 fb^{-1} of 13 TeV proton-proton collisions at the LHCb interaction point. Evidence for dyons (particles with electric and magnetic charge) captured in the trapping detector was sought by passing the aluminum volumes comprising the detector through a superconducting quantum interference device (SQUID) magnetometer. The presence of a trapped dyon would be signaled by a persistent current induced in the SQUID magnetometer. On the basis of a Drell-Yan production model, we exclude dyons with a magnetic charge ranging up to five Dirac charges (5g_{D}) and an electric charge up to 200 times the fundamental electric charge for mass limits in the range 870-3120 GeV and also monopoles with magnetic charge up to and including 5g_{D} with mass limits in the range 870-2040 GeV.

Magnetic Monopole Search with the Full MoEDAL Trapping Detector in 13 TeV pp Collisions Interpreted in Photon-Fusion and Drell-Yan Production.

MoEDAL is designed to identify new physics in the form of stable or pseudostable highly ionizing particles produced in high-energy Large Hadron Collider (LHC) collisions. Here we update our previous search for magnetic monopoles in Run 2 using the full trapping detector with almost four times more material and almost twice more integrated luminosity. For the first time at the LHC, the data were interpreted in terms of photon-fusion monopole direct production in addition to the Drell-Yan-like mechanism. The MoEDAL trapping detector, consisting of 794 kg of aluminum samples installed in the forward and lateral regions, was exposed to 4.0 fb^{-1} of 13 TeV proton-proton collisions at the LHCb interaction point and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to or above the Dirac charge are excluded in all samples. Monopole spins 0, ½, and 1 are considered and both velocity-independent and-dependent couplings are assumed. This search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.

Search for Magnetic Monopoles with the MoEDAL Forward Trapping Detector in 13 TeV Proton-Proton Collisions at the LHC.

MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV proton-proton collisions using the trapping technique, extending a previous publication with 8 TeV data during LHC Run 1. A total of 222 kg of MoEDAL trapping detector samples was exposed in the forward region and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges exceeding half the Dirac charge are excluded in all samples and limits are placed for the first time on the production of magnetic monopoles in 13 TeV pp collisions. The search probes mass ranges previously inaccessible to collider experiments for up to five times the Dirac charge.

Comparative efficacy and safety of pravastatin, nicotinic acid and the two combined in patients with hypercholesterolemia.

In a comparative study, 158 patients with type IIa or IIb primary hypercholesterolemia received either placebo, nicotinic acid extended-release capsules (0.5 to 1.0 g twice daily), pravastatin (40 mg at bedtime), or the combination for a short-term, 8-week period. A long-term, 88-week phase followed in which the addition of other lipid-lowering agents was permitted. During the short-term phase, low-density lipoprotein cholesterol levels were lower, in relation to baseline, with nicotinic acid treatment (-21%) than with placebo (P < or = 0.05), with pravastatin (-33%) than with either placebo (p < or = 0.001) or nicotinic acid (p < or = 0.05) and with combination therapy (-49%) than with the other 3 treatments (p < or = 0.05) at all weeks measured. At week 8, high-density lipoprotein cholesterol levels were increased, in relation to placebo, by nicotinic acid treatment (12%; p < or = 0.05), pravastatin therapy (13%; p < or = 0.01) and combination therapy (16%; p < or = 0.01). Adverse events were less frequent in the pravastatin and placebo groups (p < or = 0.05). In comparison with placebo, treatment with nicotinic acid resulted in significant increases in aspartate and alanine aminotransferase. The placebo and pravastatin groups did not differ significantly regarding adverse events or laboratory parameters. Similar results were observed in the long-term phase. Therefore, pravastatin is very effective and well tolerated in the treatment of type IIa or IIb primary hypercholesterolemia, and is superior to nicotinic acid in both efficacy and adverse event profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of acetylsalicylic acid to improve patency of subclavian to pulmonary artery Gore-Tex shunts.

In order to assess the influence of acetylsalicylic acid (ASA) on function and patency of Gore-Tex shunts, angiographic features of 62 Gore-Tex shunts were assessed, 31 without and 31 with postoperative ASA. Groups were selected on the basis of similar angiographic follow-up duration. Mean follow-up was 709 days for the group without ASA and 739 days for the group with it. The average daily dose of ASA was 4.5 mg/kg/day started a mean of 6.7 days after surgery. Clinical characteristics were similar between the two groups except for age at surgery which was 581 days in the group without ASA (operated between 1983 and 1987) and 303 days in the group with (operated between 1987 and 1991), reflecting the fact that patients were operated upon earlier after 1987. Preoperative Gore-Tex diameter was similar between the two groups, but three patients in the group with ASA had a Gore-Tex shunt as small as 4 mm. At angiography, four conduits were diagnosed as nonpatient (two in each group), 20 had a localized stenosis (11 of 28 in the group without ASA and nine of 23 in the group with ASA). Patency index (angiographic Gore-Tex diameter/preoperative Gore-Tex diameter) was similar in the two groups: 68.5% in the group without ASA and 69.7% in the group with ASA. Pulmonary artery growth index was 57% in the group without ASA and 91% in the group with ASA. No risk factor for thrombosis or decreased patency was found.(ABSTRACT TRUNCATED AT 250 WORDS)

HMG-CoA reductase inhibitors: a look back and a look ahead.

OBJECTIVES: This review is a follow-up to the Vancouver Symposium on hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors held in May 1990 (Can J Cardiol 1992;8 [Supplement A]: March 1992). The aim is to provide an update on the issues discussed at the time, focusing primarily on aspects of practical importance for the clinician and new developments. DATA SOURCES: The available literature on HMG-CoA reductase inhibitors from May 1990 to May 1991 was systematically reviewed. DATA SELECTION: The review focuses especially on human studies which provide a better understanding of mechanisms of action, pharmacokinetics, efficacy, safety and tolerance, as well as structure-function relationships. CONCLUSIONS: A look back indicates that HMG-CoA reductase inhibitors, as a class, appear to be safe and effective for long term use and constitute a major drug addition for the control of hypercholesterolemia. Combination therapy may enhance effectiveness but close monitoring is needed when used in conjunction with fibrates and nicotinic acid because of potential muscle toxicity. A look ahead uncovers new properties that may be of potential benefit in the treatment of atherosclerosis, hypertension, cholelithiasis, mild renal disease and possibly thrombogenesis and cancer. In view of the fact that the magnitude of low density lipoprotein cholesterol lowering is commensurate with the degree of atherosclerosis regression, HMG-CoA reductase inhibitors provide a unique tool for the control of aggressive atherosclerotic vascular disease and for secondary prevention of coronary artery disease.

[Treatment of congenital pulmonary valve stenosis by percutaneous valvuloplasty]. / Traitement du rétrécissement pulmonaire valvulaire congénital par valvuloplastie percutanée.

The purpose of this study was to evaluate the efficacy technique and follow-up results of balloon valvuloplasty for congenital valvular pulmonary stenosis. Percutaneous dilatation was performed in 48 patients aged 0.5 to 21 years (m = 7.5 yrs) from two pediatric cardiology centers (Lyon and Montreal). The right ventricular peak systolic pressure ranged from 42 to 180 mmHg (m = 93) before dilatation and fell from 24 to 105 mmHg (m = 48) immediately after dilatation. The pulmonary valvular peak systolic pressure gradient ranged from 22 to 156 mmHg (m = 73) and fell to 4 to 70 mmHg (m = 27) after the procedure (P less than 0.001). Follow-up continuous doppler data was available from 33 patients at 1 to 37 months (m = 9.2 months) after dilatation. The maximal instantaneous gradient from right ventricle pulmonary artery ranged from 0 to 74 mmHg (m = 27).

Postoperative evaluation after end-to-end subclavian-left coronary artery anastomosis in anomalous left coronary artery.

In most instances of anomalous left coronary artery originating from the pulmonary artery, surgical treatment is recommended. Because establishment of a direct systemic to coronary blood flow is expected to provide the best recovery of left ventricular function, various corrective procedures have been proposed. Subclavian-left coronary artery anastomosis appears to be a logical approach. Four patients operated on at Sainte-Justine Hospital, at an average age of 33 months (27 to 44), with an end-to-end subclavian-left coronary artery anastomosis were evaluated 6 to 46 months postoperatively. The anastomosis was patent in all cases. End-diastolic volume index (74.6 +/- 24.7 versus 122.7 +/- 15.3 ml/m2) and ejection fraction (0.58 +/- 0.07 versus 0.33 +/- 0.06) were improved significantly. Subclavian-left coronary artery anastomosis appears to meet the main criteria for an optimal physiologic correction of anomalous left coronary artery: restoration of a two-coronary artery system, improvement of left ventricular function, and likelihood of long-term patency.

Comparison of cardiovascular adjustments to exercise in adolescents 8 to 15 years of age after correction of tetralogy of fallot, ventricular septal defect or atrial septal defect.

Surgical correction of tetralogy of Fallot (TF) has generally been associated with a reduced maximal exercise tolerance, possibly related to the ventriculotomy inherent to the intracardiac repair procedure. This study documents the exercise hemodynamics of a group of patients operated on for TF who showed similar clinical and functional characteristics, and compares these responses to those of age-matched patients operated on for an isolated ventricular septal defect (VSD) or atrial septal defect (ASD) in an attempt to better understand the role of the ventriculotomy in the exercise limitation. Thirty patients, ages 12 to 19 years, operated on before 5 years of age for complete repair of TF (n = 13), VSD (n = 7) or ASD (n = 10) and 10 age-matched control subjects underwent a progressive maximal cycling test to determine the maximal oxygen uptake (VO2 max), and completed submaximal cycling at intensities of 33 and 66% VO2 max, respectively, to determine the cardiac output (CO2-rebreathing). No significant differences in VO2 max were observed (TF = 37.6 +/- 10; VDS = 34.0 +/- 9.2; ASD = 36.5 +/- 7; controls = 41.3 +/- 6.0 ml/kg/min). The maximal heart rate, however, remained lower in all patient groups in comparison with control subjects (p less than or equal to 0.05) (TF = 178 +/- 14; VSD = 172 +/- 17; ASD = 179 +/- 16; controls = 191 +/- 12 beats/min).(ABSTRACT TRUNCATED AT 250 WORDS)

[Cardiac pacemakers in children. 15 years' experience]. / Stimulateurs cardiaques chez l'enfant. Expérience de 15 ans.

Between 1971 and 1986, 85 pacemakers were implanted at the St Justine Hospital, Montreal, in 57 young patients (25 girls, 32 boys) then aged from one day to 23 years (mean 10.3 years). The patients were followed up for periods ranging from 15 days to 13.5 years (mean 4.5 years); 119 epicardial electrodes were positioned by thoracotomy in 52 patients and by sternotomy in 5 patients; the 85 pacemaker cases were placed in the left retroperitoneal cavity. The pacemakers were programmed in modes VVI (28), AAI (1) and DDD (28). The indications for pacemaker implantation were: complete atrioventricular block in 39 cases (postoperative 16, congenital 22, acquired 1), sinus node disease in 17 cases (postoperative 13, cardiomyopathy 3, normal heart 1) and Romano-Ward syndrome in 1 case. Operated heart diseases which required pacemaker implantation were: D-transposition of the great arteries in 17 cases (complete atrioventricular block 7, sinus node disease 10), tricuspid valve atresia in 3 cases (sinus node disease 3) and tetralogy of Fallot in 3 cases (complete atrioventricular block 3). Twenty-four patients underwent a total of 33 reoperations: 21 changes of battery, 12 changes of electrodes (6 for fibrosis, 6 for breakage). Only one patient developed infection of the pacemaker case. Altogether, the incidence of complications (infection and/or breakage) was low in this series, regardless of the pacing mode. Pacing in children is now an acceptable treatment with low risk provided the indications are well selected.

Electrophysiologic effects and long-term efficacy of bepridil for recurrent supraventricular tachycardias.

Thirteen patients underwent electrophysiologic evaluation for recurrent supraventricular tachycardia (SVT). The effects of intravenous bepridil (4 mg/kg) were evaluated during the initial study in 5 patients, and 12 patients underwent repeat study 7 to 10 days later taking oral bepridil, 300 to 400 mg/day. Intravenous bepridil increased the pacing cycle length inducing atrioventricular (AV) (276 +/- 43 vs 334 +/- 31 ms, p less than 0.01) and ventriculoatrial (VA) block (268 +/- 34 vs 310 +/- 35 ms, p less than 0.001), the retrograde refractory period of the accessory pathway (251 +/- 17 vs 295 +/- 25 ms, p less than 0.05) and the ventricular refractory period (216 +/- 17 vs 226 +/- 11 ms, p less than 0.05), and prevented induction of sustained SVT in 3 patients. Oral bepridil increased the sinus cycle length (723 +/- 64 vs 800 +/- 118 ms, p less than 0.05), corrected QT (403 +/- 14 vs 431 +/- 21 ms, p less than 0.05) and the pacing cycle inducing AV (288 +/- 63 vs 353 +/- 78 ms, p less than 0.01) and VA block (271 +/- 31 vs 408 +/- 124 ms, p less than 0.01). It prolonged the refractory period of the atrium (195 +/- 29 vs 233 +/- 36 ms, p less than 0.05), AV node (264 +/- 35 vs 303 +/- 22 ms, p less than 0.05), ventricle (221 +/- 16 vs 245 +/- 21 ms, p less than 0.01), accessory pathway in the AV (290 +/- 47 vs 329 +/- 54 ms, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)