116 research outputs found
Field-Assisted and Thermionic Contributions to Conductance in SnO2 Thick-Films
A deep analysis of conductance in nanostructured SnO2 thick films has been performed. A model for field-assisted thermionic barrier crossing is being proposed to explain the film conductivity. Themodel has been applied to explain the behavior of resistance in vacuum of two sets of nanostructured thick-films with grains having two well-distinct characteristic radii (R = 25nm and R = 125 nm). In the first case the grain radius is shorter than the depletion region width, a limit at which overlapping of barriers takes place, and in the second case it is longer. The behavior of resistance in the presence of dry air has been explained through the mechanism of barrier modulation through gas chemisorption.Fil: MalagĂș, C.. Universita Di Ferrara; ItaliaFil: Carotta, M. Cristina. Universita Di Ferrara; ItaliaFil: Martinelli, Giuliano. Universita Di Ferrara; ItaliaFil: Ponce, Miguel Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; ArgentinaFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; ArgentinaFil: Aldao, Celso Manuel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; Argentin
Crystal deflector for highly efficient channeling extraction of a proton beam from accelerators
The design and manufacturing details of a new crystal deflector for proton beams are reported. The technique allows one to manufacture a very short deflector along the beam direction (2 mm). Thanks to that, multiple encounters of circulating particles with the crystal are possible with a reduced probability of multiple scattering and nuclear interactions per encounter. Thus, drastic increase in efficiency for particle extraction out of the accelerator was attained (85%) on a 70 GeV proton beam. We show the characteristics of the crystal deflector and the technology behind it
FABRICATION OF CRYSTALS FOR CHANNELING OF PARTICLES IN ACCELERATOR
Abstract Channelling in bent crystals is technique with high potential to steer charged-particle beams for several applications in accelerators. Channeling and related techniques underwent significant progress in the last years. Distinctive features of performance increase was the availability of novel ideas other than new techniques to manufacture the crystal for channeling. We propose two methods to fabricate crystals through silicon micromachining techniques, i.e., isotropic or anisotropic silicon etchings. Characterization of the crystals accomplished for both methods to highlight that the crystals are free of lattice damage induced by the preparation. Crystals prepared by both kinds of methodologies were positively tested at the external line H8 of the SPS with 400 GeV protons for investigation on planar and axial channelings as well as on single and multiple volume reflection experiments by the H8-RD22 collaboration
Fabrication of Crystals for Channeling of Particles in Accelerators
Channelling in bent crystals is technique with high potential to steer charged-particle beams for several applications in accelerators. Channeling and related techniques underwent significant progress in the last years. Distinctive features of performance increase was the availability of novel ideas other than new techniques to manufacture the crystal for channeling. We propose two methods to fabricate crystals through silicon micromachining techniques, i.e., isotropic or anisotropic silicon etchings. Characterization of the crystals accomplished for both methods to highlight that the crystals are free of lattice damage induced by the preparation. Crystals prepared by both kinds of methodologies were positively tested at the external line H8 of the SPS with 400 GeV protons for investigation on planar and axial channelings as well as on single and multiple volume reflection experiments by the H8-RD22 collaboration
Mast Cells in Peritoneal Fluid From Women With Endometriosis and Their Possible Role in Modulating Sperm Function
Endometriosis is a local pelvic inflammatory process, frequently associated with infertility, with altered function of immune-related cells in the peritoneal environment. Mast cells are known to be key players of the immune system and have been recently involved in endometriosis and in infertility, with their mediators directly suppressing sperm motility. In this study, we evaluated the mast cell population and their mediators in the peritoneal fluid of infertile patients with endometriosis and their impact on human sperm motility. Peritoneal fluids, collected by laparoscopy from 11 infertile patients with endometriosis and 9 fertile controls were evaluated for the presence of mast cells, tryptase levels and their effect on sperm motility. Furthermore, an in vitro model of mast cells-sperm interaction in peritoneal fluid was set up, using LAD2 cell line as a mast cell model, and analyzed from a functional as well as a morphological point of view. Mast cell peritoneal fluid population and its main mediator, tryptase, is more represented in endometriosis confirming an involvement of these cells in this disease. Anyway it appears unlikely that tryptase enriched peritoneal fluid, which fails to inhibit sperm motility, could contribute to endometriosis associated infertility. Despite of this, sperm interaction with the mast cell surface (LAD2) induced a significantly mast cell-degranulation response in the peritoneal fluid from endometriosis which could directly modulate sperm function other than motility. This evidence lead us to suppose that there is, between these elements, an interrelationship which deserves further studies
Hyperhomocysteinemia and Mortality after Coronary Artery Bypass Grafting
BACKGROUND: The independent prognostic impact, as well as the possible causal role, of hyperhomocysteinemia (HHcy) in coronary artery disease (CAD) is controversial. No previous study specifically has addressed the relationship between HHcy and mortality after coronary artery bypass grafting (CABG) surgery. The aim of this study is to evaluate the prognostic impact of HHcy after CABG surgery. METHODOLOGY AND PRINCIPAL FINDINGS: We prospectively followed 350 patients who underwent elective CABG between May 1996 and May 1999. At baseline, fasting total homocysteine (tHcy) levels were measured in all participants, and a post-methionine loading (PML) test was performed in 77.7% of them (nâ=â272). After a median follow-up of 58 months, 33 patients (9.4%) had died, 25 because of cardiovascular events. HHcy, defined by levels higher than the 90(th) percentile (25.2 ”mol/L) of the population's distribution, was significantly associated to total and cardiovascular mortality (Pâ=â0.018 [log-rank test 5.57]; Pâ=â0.002 [log-rank test 9.76], respectively). The PML test had no prognostic value. After multiple adjustment for other univariate predictors by Cox regression, including statin therapy (the most powerful predictor in uni-/multivariate analyses), high-sensitivity C Reactive Protein (hs-CRP) levels, and all known major genetic (MTHFR 677CâT polymorphism) and non-genetic (B-group vitamin status and renal function) tHcy determinants, HHcy remained an independent prognostic factor for mortality (HRs: 5.02, 95% CIs 1.88 to 13.42, Pâ=â0.001). CONCLUSIONS: HHcy is an important prognostic marker after CABG, independent of modern drug therapy and biomarkers
Electroweak Symmetry Breaking and Precision Tests with a Fifth Dimension
We perform a complete study of flavour and CP conserving electroweak
observables in a slight refinement of a recently proposed five--dimensional
model on R^4XS^1/Z_2, where the Higgs is the internal component of a gauge
field and the Lorentz symmetry is broken in the fifth dimension.
Interestingly enough, the relevant corrections to the electroweak observables
turn out to be of universal type and essentially depend only on the value of
the Higgs mass and on the scale of new physics, in our case the
compactification scale 1/R. The model passes all constraints for 1/R > 4.7 TeV
at 90% C.L., with a moderate fine--tuning in the parameters. The Higgs mass
turns out to be always smaller than 200 GeV although higher values would be
allowed, due to a large correction to the T parameter. The lightest non-SM
states in the model are typically colored fermions with a mass of order 1-2
TeV.Comment: 26 pages, 7 figures; v2, minor corrections, one reference added; v3,
version to appear in Nucl. Phys.
Prespecified Risk Criteria Facilitate Adequate Discharge and LongâTerm Outcomes After Transfemoral Transcatheter Aortic Valve Implantation
Background
Despite the availability of guidelines for the performance of transcatheter aortic valve implantation (TAVI), current treatment pathways vary between countries and institutions, which impact on the mean duration of postprocedure hospitalization.
Methods and Results
This was a prospective, multicenter registry of 502 patients to validate the appropriateness of discharge timing after transfemoral TAVI, using prespecified risk criteria from FASTâTAVI (Feasibility and Safety of Early Discharge After Transfemoral [TF] Transcatheter Aortic Valve Implantation), based on hospital events within 1âyear after discharge. The end pointâa composite of allâcause mortality, vascular accessârelated complications, permanent pacemaker implantation, stroke, cardiac rehospitalization, kidney failure, and major bleedingâwas reached in 27.0% of patients (95% CI, 23.3â31.2) within 1 year after intervention; 7.5% (95% CI, 5.5â10.2) had inâhospital complications before discharge and 19.6% (95% CI, 16.3â23.4) within 1 year after discharge. Overall mortality within 1 year after discharge was 7.3% and rates of cardiac rehospitalization 13.5%, permanent pacemaker implantation 4.2%, any stroke 1.8%, vascularâaccessârelated complications 0.7%, lifeâthreatening bleeding 0.7%, and kidney failure 0.4%. Composite events within 1 year after discharge were observed in 18.8% and 24.3% of patients with low risk of complications/early (â€3 days) discharge and high risk and discharged late (>3 days) (concordant discharge), respectively. Event rate in patients with discordant discharge was 14.3% with low risk but discharged late and increased to 50.0% in patients with high risk but discharged in â€3 days.
Conclusions
The FASTâTAVI risk assessment provides a tool for appropriate, riskâbased discharge that was validated with the 1âyear event rate after transfemoral TAVI.
Registration
URL:
https://www.ClinicalTrials.gov
; Unique identifier: NCT02404467
Erratum to: "Double volume reflection of a proton beam by a sequence of two bent crystals" [Phys. Lett. B 658 (2008) 109]
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