Laboratory realization of relativistic pair-plasma beams.

Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN's Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.

Gastrointestinal Bleeding Secondary to Iliac Artery Pseudoaneurysm in a Patient With Remote Pancreas Transplant: A Case Report.

BACKGROUND: Vascular complications represent the most common cause of early graft failure after pancreatic transplantation (PT). Pseudoaneurysms are uncommon vascular complications that usually present within the first year post transplantation. CASE REPORT: A 49-year-old man with history of type 1 diabetes mellitus presented for evaluation with a 2-day history of painless hematochezia. He had undergone PT 4 years prior to presentation, which failed due to acute cellular rejection after 1 year. Both extended upper endoscopy and colonoscopy did not identify an active bleeding source. After an episode of massive hematochezia, he became hemodynamically unstable with peritoneal signs noted on physical examination. An abdominal angiogram was unable to identify active hemorrhage, and the patient was transferred to the operating room for open laparotomy. Exploration revealed a right common iliac artery pseudoaneurysm eroding into the pancreatic-ileal anastomosis, which required initial digital compression for initial hemostasis. After combined endovascular procedure with ballooning and stenting of the right iliac artery, optimal hemostasis was achieved without further episodes of hematochezia. DISCUSSION: Gastrointestinal bleeding (GIB) has been reported to occur in 11% of enteric-drained PT. Even though infectious causes have been reported, culprits are more commonly associated with vascular or enteric surgical anastomosis and usually occur within the early postoperative course. Here we report an uncommon cause of GIB, a late complication of PT, and review important points associated with the management of GIB, anatomy of PT, and potential etiologies for early and late GIB in the setting of PT.

Dislocation resistance of ProRoot Endo Sealer, a calcium silicate-based root canal sealer, from radicular dentine.

AIM: To examine the dislocation resistance of three root canal sealers from radicular dentine with and without immersion in a simulated body fluid (SBF), using a modified push-out test design that produced simulated canal spaces of uniform dimensions under identical cleaning and shaping conditions. METHODOLOGY: Sixty single-rooted caries-free human canine teeth were used. Standardized simulated canal spaces were created using 0.04 taper ProFile instruments along the coronal, middle and apical thirds of longitudinal tooth slabs. Following NaOCl/ethylenediamine tetra-acetic acid cleaning, the cavities were filled with ProRoot Endo Sealer, AH Plus Jet or Pulp Canal Sealer. After setting, half of the cavities were tested with a fibre-optic light-illuminated push-out testing device. The rest were immersed in SBF for 4 weeks before push-out evaluation. Failure modes were examined with stereomicroscopy and field emission (FE)-scanning electron microscopy. RESULTS: Location of the sealer-filled cavities did not affect push-out strengths. ProRoot Endo Sealer exhibited higher push-out strengths than the other two sealers particularly after SBF storage (P < 0.001). Failure modes were predominantly adhesive and mixed for Pulp Canal Sealer and AH Plus Jet, and predominantly cohesive for ProRoot Endo Sealer. Spherical amorphous calcium phosphate-like phases that spontaneously transformed into apatite-like phases were seen in the fractured specimens of ProRoot Endo Sealer after SBF storage. CONCLUSIONS: When tested in bulk without a main core, both 'sealer type' and 'SBF storage' were significant in affecting push-out results. The ProRoot Endo Sealer demonstrated the presence of spherical amorphous calcium phosphate-like phases and apatite-like phases (i.e. ex vivo bioactivity) after SBF storage.

Changes in resin-infiltrated dentin stiffness after water storage.

Plasticization of polymers by water sorption lowers their mechanical properties in a manner that is predictable by the polarity of their component resins. This study tested the hypothesis that when adhesive resins were used to create resin-infiltrated dentin, the reductions in their flexural moduli after water storage would be lowered proportional to their hydrophilic characteristics. Three increasingly hydrophilic resin blends were used to fabricate polymer beams and macro-hybrid layer models of resin-infiltrated dentin for testing with a miniature three-point flexure device, before and after 1-4 weeks of water storage. Flexural modulus reductions in macro-hybrid layers were related to, and more extensive than, reductions in the corresponding polymer beams. Macro-hybrid layers that were more hydrophilic exhibited higher percent reductions in flexural modulus, with the rate of reduction proportional to the Hoy's solubility parameters for total intermolecular attraction forces (delta(t)) and polar forces (delta(p)) of the macro-hybrid layers.

Insulin hypoglycemia and growth hormone secretion in sheep: a paradox revisited.

Although insulin-induced hypoglycemia is a potent stimulus for growth hormone (GH) secretion in humans, hypoglycemia was reported to suppress GH in sheep. We investigated whether GH suppression in sheep during insulin hypoglycemia resulted from the dose of insulin administered or the fed state of the animal. Saline or insulin (0.05, 0.2, 1.0, or 5.0 U/kg) intravenous boluses were administered to eight fasted ewes in a crossover experiment. In another experiment, four sheep were fed 2 h before intravenous administrations of either 0.2 or 5 U/kg of insulin. All doses of insulin resulted in comparable hypoglycemia, although the duration of hypoglycemia increased directly with insulin dose. Hypoglycemia in fasted animals stimulated GH secretion. The GH rise above baseline was inversely related to the insulin dose, and the insulin doses of 1 and 5 U/kg resulted in late suppression of GH below baseline concentrations. Insulin administration to fed animals caused an identical degree of hypoglycemia but no increase in GH. Insulin-hypoglycemia stimulates GH secretion in sheep in a manner similar to humans, and the response is dependent on both fed state and insulin dose.

Diet and exercise and gemfibrozil therapy for the management of dyslipidemia: a CEN study. Clinical Experience Network.

BACKGROUND: Dyslipidemia constitutes a serious health problem that should be diagnosed and treated by the family physician. Little is known about the efficacy of typical dietary therapy for patients with abnormal cholesterol levels. This study was the first large prospective family practice evaluation of the effectiveness of diet-and-exercise therapy followed by a pharmacologic intervention for those patients who remained dyslipidemic. METHODS: Patients who met standard criteria for cardiovascular disease risk based on lipid analysis were enrolled in a typical 6-week physician-directed diet-and-exercise program. Those patients who were still dyslipidemic after that period were started on 12 weeks of pharmacologic treatment with gemfibrozil. RESULTS: Of the 2992 patients screened, 1193 were eligible for participation in the study. The diet-and-exercise program led to a modest change in lipid values (average decrease in total cholesterol of 4.1%). Only 2% of the patients achieved desirable levels of all lipid values. Seven hundred thirty-nine subjects qualified for further therapy and were treated with gemfibrozil. Seventy patients discontinued drug therapy because of adverse effects. Those who completed 12 weeks of pharmacologic therapy had an additional 5.4% reduction in total cholesterol, 3.9% reduction in low-density lipoprotein cholesterol, 30.6% reduction in triglycerides, and a 17.2% increase in high-density lipoprotein cholesterol. CONCLUSIONS: These findings suggest that in a typical clinical setting, a nonpharmacologic intervention of diet and exercise may not produce the desired overall lipid changes in the majority of dyslipidemic patients.