668 research outputs found
Effect of nanosize BaZrO3 inclusions on vortex parameters in YBaCuO
We report on the field dependence of the microwave complex resistivity data
in YBaCuO/BaZrO films grown by PLD at various BaZrO
content. The data, analyzed within a recently developed general framework for
the mixed-state microwave response of superconductors, yield the field
dependence of the fluxon parameters such as the vortex viscosity and the
pinning constant. We find that pinning undergoes a change of regime when the
BaZrO content in the target increases from 2.5 mol.% to 5 mol.%.
Simultaneously, the vortex viscosity becomes an increasing function of the
applied magnetic field. We propose a scenario in which flux lines are pinned as
bundles, and a crossover from dilute point pins to dense c-axis correlated
defects takes place between 2.5 and 5 mol.% in the BZO concentration. Our data
are inconsistent with vortices occupying mainly the BaZrO sites at low
fields, and suggest instead that vortices occupy both BaZrO sites and
interstitials in the YBaCuO matrix, even at low fields.Comment: Presented at EUCAS 2009, to be published in J. Phys.:Conf. Serie
College Students\u27 Perceived and Personal Mental Health Stigma : The Influence on Help-Seeking Attitudes and Intentions
Despite being vulnerable to mental health problems, college students are a population that is especially influenced by perceptions of peer mental health stigmatization (Quinn, Wilson, MacIntyre, & Tinklin, 2009), a known barrier to seeking mental health services (Corrigan, 2004a; Komiya, Good, & Sherrod, 2000; Vogel, Wade, & Haake, 2006), and the greatest barrier to college students (Evans, et al., 2007; Hepworth & Paxton, 2007; Martin, 2010). This paper begins with a thorough discussion of the participant population—undergraduate college students, including well established theories of college student development, and developmental challenges and issues that are faced. Mental health stigma is also explored in detail, including specific types and its role as a barrier to help-seeking behaviors. There is a negative impact on mental health through perceived public stigma (Andrews, Issakidis, & Carter, 2001; Komiya, Good, & Sherrod, 2000), yet, the amount of public stigma may be overestimated through misperception, as estimates are considerably greater than one’s own personal stigma (Eisenberg et al., 2009). Also, higher levels of perceived public stigma have been associated with lower levels of help-seeking (Eisenberg et al., 2009). This study gained a better understanding of the relationships and predictions between perceived and personal stigmas and helpseeking attitudes and intentions. Furthermore, this study accounted for the variable of social desirability in such relationships, as prior research has not. This paper presents justifications and discusses the specific methods used for the current study, as well as the findings. Finally, implications for clinical and educational use are presented along with implications for future research
Mixed-state microwave response in superconducting cuprates
We report measurements of the magnetic-field induced microwave complex
resistivity in REBaCuO thin films, with RE = Y, Sm.
Measurements are performed at 48 GHz by means of a resonant cavity in the
end-wall-replacement configuration. The magnetic field dependence is
investigated by applying a moderate (0.8 T) magnetic field along the c-axis.
The measured vortex state complex resistivity in
YBaCuO and SmBaCuO is
analyzed within the well-known models for vortex dynamics. It is shown that
attributing the observed response to vortex motion alone leads to
inconsistencies in the as-determined vortex parameters (such as the vortex
viscosity and the pinning constant). By contrast, attributing the entire
response to field-induced pair breaking leads to a nearly quantitative
description of the data.Comment: 6 pages, 4 figures, to be published in J. Supercond. as proceedings
of 8th HTSHFF (May 26th-29th, 2004, Begur, Spain
Anisotropy and directional pinning in YBaCuO with BaZrO3 nanorods
Measurements of anisotropic transport properties (dc and high-frequency
regime) of driven vortex matter in YBaCuO with elongated
strong-pinning sites (c-axis aligned, self-assembled BaZrO nanorods) are
used to demonstrate that the effective-mass angular scaling takes place only in
intrinsic physical quantities (flux-flow resistivity), and not in
pinning-related Labusch parameter and critical currents. Comparison of the
dynamics at different time scales shows evidence for a transition of the vortex
matter toward a Mott phase, driven by the presence of nanorods. The strong
pinning in dc arises partially from a dynamic effect.Comment: 4 pages, 4 figures. Accepted for publication on Applied Physics
Letters. With respect to v1: changed title, slightly shortene
Intestinal perforation after surgical treatment for incisional hernia. iatrogenic or idiopathic?
Intestinal perforation (IP) is a life-threatening gastroenterological condition requiring urgent surgical care, which may present itself as an uncommon complication following incisional hernia repair surgery, most often because of iatrogenic traumatism occurring during the procedure. However, we report a case where a spontaneous onset can be hypothesised. A 60-years-old patient underwent repair of an abdominal laparocele, through rectus abdominis muscle plasty, 5Â years after development of an incisional hernia due to exploratory laparotomy for the treatment of acute appendicitis. Xipho-pubic scar was excised and umbilicus and supra-umbilical hernia sac dissected, a linear median incision was performed along the sub-umbilical linea alba, reaching preperitoneal plane to assess any intestinal loop adherence to the abdominal wall. After limited viscerolysis, abdominal wall defect was corrected by 'rectus abdominis muscle plasty' and umbilicus reconstruction by Santanelli technique. Postoperative course was uneventful until Day 29, with sudden onset of epigastric pain, fever and bulge. Sixty cubic centimeter pus was drained percutaneously and cavity was rinsed with a 50% H2O2 and H2O V-V solution until draining clear fluid. Symptoms recurred two days later, while during rinsing presented dyspnoea. X-Ray and CT scan diagnosed IP, and she underwent under emergency an exploratory laparotomy, leading to right hemicolectomy extended to last ileal loops and middle third of the transverse, right monolateral salpingo-ovariectomy and a temporary ileostomy by general surgeon. Twenty-three days later an ileostomy reversal surgery was performed and 8 days after she was discharged. At latest follow-up patient showed fair conditions, complaining abdominal pain and diarrhoea, attributable to the extensive intestinal resection. IP following incisional hernia repair, is reported as uncommon and early postoperative complication. In our case, the previous regular postoperative course with late onset lead us to hypothesise a possible idiopathic etiopathogenesis, because of a strangulation followed by gangrene and abscess formation, which might begin before the incisional hernia repair and unnoticed at the time surgery was performed
Nonlinear c-axis transport in Bi_2Sr_2CaCu_2O_(8+d) from two-barrier tunneling
Motivated by the peculiar features observed through intrinsic tunneling
spectroscopy of BiSrCaCuO mesas in the normal state,
we have extended the normal state two-barrier model for the c-axis transport
[M. Giura et al., Phys. Rev. B {\bf 68}, 134505 (2003)] to the analysis of
curves. We have found that the purely normal-state model reproduces all
the following experimental features: (a) the parabolic -dependence of
in the high- region (above the conventional pseudogap temperature),
(b) the emergence and the nearly voltage-independent position of the "humps"
from this parabolic behavior lowering the temperature, and (c) the crossing of
the absolute curves at a characteristic voltage . Our
findings indicate that conventional tunneling can be at the origin of most of
the uncommon features of the c axis transport in
BiSrCaCuO. We have compared our calculations to
experimental data taken in severely underdoped and slightly underdoped
BiSrCaCuO small mesas. We have found good agreement
between the data and the calculations, without any shift of the calculated
dI/dV on the vertical scale. In particular, in the normal state (above
) simple tunneling reproduces the experimental dI/dV quantitatively.
Below quantitative discrepancies are limited to a simple rescaling of
the voltage in the theoretical curves by a factor 2. The need for such
modifications remains an open question, that might be connected to a change of
the charge of a fraction of the carriers across the pseudogap opening.Comment: 7 pages, 5 figure
Microwave properties of DyBa_2Cu_3O_(7-x) monodomains and related compounds in magnetic fields
We present a microwave characterization of a DyBaCuO
single domain, grown by the top-seeded melt-textured technique. We report the
(a,b) plane field-induced surface resistance, , at 48.3 GHz,
measured by means of a cylindrical metal cavity in the end-wall-replacement
configuration. Changes in the cavity quality factor Q against the applied
magnetic field yield at fixed temperatures. The temperature
range [70 K ; T_c] was explored. The magnetic field 0.8 T was
applied along the c axis. The field dependence of does not
exhibit the steep, step-like increase at low fields typical of weak-links. This
result indicates the single-domain character of the sample under investigation.
exhibits a nearly square-root dependence on H, as expected for
fluxon motion. From the analysis of the data in terms of motion of Abrikosov
vortices we estimate the temperature dependences of the London penetration
depth and the vortex viscosity , and their zero-temperature
values 165 nm and 3 10 Nsm, which are
found in excellent agreement with reported data in YBaCuO
single crystals. Comparison of microwave properties with those of related
samples indicate the need for reporting data as a function of T/T_c in order to
obtain universal laws.Comment: 6 pages, 4 figures, LaTeX, submitted to Journal of Applied Physic
Surgical pneumothorax under spontaneous ventilation-effect on oxygenation and ventilation
Surgical pneumothorax allows obtaining comfortable surgical space for minimally invasive thoracic surgery, under spontaneous ventilation and thoracic epidural anesthesia, without need to provide general anesthesia and neuromuscular blockade. One lung ventilation (OLV) by iatrogenic lung collapse, associated with spontaneous breathing and lateral position required for the surgery, involves pathophysiological consequences for the patient, giving rise to hypoxia, hypercapnia, and hypoxic pulmonary vasoconstriction (HPV). Knowledge of these changes is critical to safely conduct this type of surgery. Surgical pneumothorax can be now considered a safe technique that allows the realization of minimally invasive thoracic surgery in awake patients with spontaneous breathing, avoiding the risks of general anesthesia and ensuring a more physiological surgical course
Tunnel and thermal c-axis transport in BSCCO in the normal and pseudogap state
We consider the problem of c-axis transport in double-layered cuprates, in
particular with reference to BiSrCaCuO
compounds. We exploit the effect of the two barriers on the thermal and tunnel
transport. The resulting model is able to describe accurately the normal state
c-axis resistivity in BiSrCaCuO, from the
underdoped side up to the strongly overdoped. We extend the model, without
introducing additional parameters, in order to allow for the decrease of the
barrier when an external voltage bias is applied. The extended model is found
to describe properly the c-axis resistivity for small voltage bias above the
pseudogap temperature , the c-axis resistivity for large voltage bias
even below , and the differential curves taken in mesa structures.Comment: 12 pages, 6 figures. Submitted to Superconductor Science and
Technolog
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