5,589 research outputs found
Effects of Magnetic Field on Josephson Current in SNS System
The effect of a magnetic field on Josephson current has been studied for a
superconductor/normal-metal/superconductor (SNS) system, where N is a
two-dimensional electron gas in a confining potential. It is found that the
dependence of Josephson currents on the magnetic field are sensitive to the
width of the normal metal. If the normal metal is wide and contains many
channels (subbands), the current on a weak magnetic field shows a dependence
similar to a Fraunhofer-pattern in SIS system and, as the field gets strong, it
shows another type of oscillatory dependence on the field resulting from the
Aharonov-Bohm interference between the edge states. As the number of channels
decreases (i.e. normal metal gets narrower), however, the dependence in the
region of the weak field deviates from a clear Fraunhofer pattern and the
amplitude of the oscillatory dependence in the region of the strong field is
reduced.Comment: 14 pages, 9 figure
Orbital Magnetism and Current Distribution of Two-Dimensional Electrons under Confining Potential
The spatial distribution of electric current under magnetic field and the
resultant orbital magnetism have been studied for two-dimensional electrons
under a harmonic confining potential V(\vecvar{r})=m \omega_0^2 r^2/2 in
various regimes of temperature and magnetic field, and the microscopic
conditions for the validity of Landau diamagnetism are clarified. Under a weak
magnetic field (\omega_c\lsim\omega_0, \omega_c being a cyclotron frequency)
and at low temperature (T\lsim\hbar\omega_0), where the orbital magnetic
moment fluctuates as a function of the field, the currents are irregularly
distributed paramagnetically or diamagnetically inside the bulk region. As the
temperature is raised under such a weak field, however, the currents in the
bulk region are immediately reduced and finally there only remains the
diamagnetic current flowing along the edge. At the same time, the usual Landau
diamagnetism results for the total magnetic moment. The origin of this dramatic
temperature dependence is seen to be in the multiple reflection of electron
waves by the boundary confining potential, which becomes important once the
coherence length of electrons gets longer than the system length. Under a
stronger field (\omega_c\gsim\omega_0), on the other hand, the currents in
the bulk region cause de Haas-van Alphen effect at low temperature as
T\lsim\hbar\omega_c. As the temperature gets higher (T\gsim\hbar\omega_c)
under such a strong field, the bulk currents are reduced and the Landau
diamagnetism by the edge current is recovered.Comment: 15 pages, 11 figure
Cryptotomography: reconstructing 3D Fourier intensities from randomly oriented single-shot diffraction patterns
We reconstructed the 3D Fourier intensity distribution of mono-disperse
prolate nano-particles using single-shot 2D coherent diffraction patterns
collected at DESY's FLASH facility when a bright, coherent, ultrafast X-ray
pulse intercepted individual particles of random, unmeasured orientations. This
first experimental demonstration of cryptotomography extended the
Expansion-Maximization-Compression (EMC) framework to accommodate unmeasured
fluctuations in photon fluence and loss of data due to saturation or background
scatter. This work is an important step towards realizing single-shot
diffraction imaging of single biomolecules.Comment: 4 pages, 4 figure
Procedural Complications During Early Versus Late Endovascular Treatment in Acute Stroke: Frequency and Clinical Impact
BACKGROUND AND PURPOSE: Endovascular treatment (EVT) in acute ischemic stroke is effective in the late time window in selected patients. However, the frequency and clinical impact of procedural complications in the early versus late time window has received little attention. METHODS: We retrospectively studied all acute ischemic strokes from 2015 to 2019 receiving EVT in the Acute Stroke Registry and Analysis of Lausanne. We compared the procedural EVT complications in the early (<6 hours) versus late (6-24 hours) window and correlated them with short-term clinical outcome. RESULTS: Among 695 acute ischemic strokes receiving EVT (of which 202 were in the late window), 113 (16.3%) had at least one procedural complication. The frequency of each single, and for overall procedural complications was similar for early versus late EVT (16.2% versus 16.3%, Padj=0.90). Procedural complications lead to a significantly less favorable short-term outcome, reflected by the absence of National Institutes of Health Stroke Scale improvement in late EVT (delta-National Institutes of Health Stroke Scale-24 hours, -2.5 versus 2, Padj=0.01). CONCLUSIONS: In this retrospective analysis of consecutive EVT, the frequency of procedural complications was similar for early and late EVT patients but very short-term outcome seemed less favorable in late EVT patients with complications
TLR9 ligation in pancreatic stellate cells promotes tumorigenesis
Modulation of Toll-like receptor (TLR) signaling can have protective or protumorigenic effects on oncogenesis depending on the cancer subtype and on specific inflammatory elements within the tumor milieu. We found that TLR9 is widely expressed early during the course of pancreatic transformation and that TLR9 ligands are ubiquitous within the tumor microenvironment. TLR9 ligation markedly accelerates oncogenesis, whereas TLR9 deletion is protective. We show that TLR9 activation has distinct effects on the epithelial, inflammatory, and fibrogenic cellular subsets in pancreatic carcinoma and plays a central role in cross talk between these compartments. Specifically, TLR9 activation can induce proinflammatory signaling in transformed epithelial cells, but does not elicit oncogene expression or cancer cell proliferation. Conversely, TLR9 ligation induces pancreatic stellate cells (PSCs) to become fibrogenic and secrete chemokines that promote epithelial cell proliferation. TLR9-activated PSCs mediate their protumorigenic effects on the epithelial compartment via CCL11. Additionally, TLR9 has immune-suppressive effects in the tumor microenvironment (TME) via induction of regulatory T cell recruitment and myeloid-derived suppressor cell proliferation. Collectively, our work shows that TLR9 has protumorigenic effects in pancreatic carcinoma which are distinct from its influence in extrapancreatic malignancies and from the mechanistic effects of other TLRs on pancreatic oncogenesis
Meningeal Relapse of Nodular Lymphocyte Predominant Hodgkin Lymphoma Transformed to T-Cell/Histiocyte-Rich Large B-Cell Lymphoma: A Case Report.
Central nervous system involvement in Hodgkin lymphoma is extremely rare, especially in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), which usually carries a favorable prognosis. Here we report a case of a young patient with NLPHL, who developed a progressive and fatal neurological deterioration requiring a very extensive work-up including two biopsies to obtain the diagnosis of T-cell/histiocyte-rich large B-cell lymphoma like transformation. This report, which includes post-mortem analysis, highlights the correlations between clinical, radiological, and biological data but also the difficulties encountered in reaching the correct diagnosis
Early-versus-Late Endovascular Stroke Treatment: Similar Frequencies of Nonrevascularization and Postprocedural Cerebrovascular Complications in a Large Single-Center Cohort Study.
Endovascular treatment of acute ischemic stroke is now performed more frequently in the late window in radiologically selected patients. However, little is known about whether the frequency and clinical impact of incomplete recanalization and postprocedural cerebrovascular complications differ between early and late windows in the real world.
We retrospectively reviewed all patients with acute ischemic stroke receiving endovascular treatment within 24 hours from 2015 to 2019 and included in the Acute STroke Registry and Analysis of Lausanne. We compared rates of incomplete recanalization and postprocedural cerebrovascular complications (parenchymal hematoma, ischemic mass effect, and 24-hour re-occlusion) in the early (<6 hours) versus late window (6-24 hours, including patients with unknown onset) populations and correlated them with the 3-month clinical outcome.
Among 701 patients with acute ischemic stroke receiving endovascular treatment, 29.2% had late endovascular treatment. Overall, incomplete recanalization occurred in 56 patients (8%), and 126 patients (18%) had at least 1 postprocedural cerebrovascular complication. The frequency of incomplete recanalization was similar in early and late endovascular treatment (7.5% versus 9.3%, adjusted P =.66), as was the occurrence of any postprocedural cerebrovascular complication (16.9% versus 20.5%, adjusted P = .36). When analyzing single postprocedural cerebrovascular complications, rates of parenchymal hematoma and ischemic mass effect were similar (adjusted P = .71, adjusted P = .79, respectively), but 24-hour re-occlusion seemed somewhat more frequent in late endovascular treatment (4% versus 8.3%, unadjusted P = .02, adjusted P = .40). The adjusted 3-month clinical outcome in patients with incomplete recanalization or postprocedural cerebrovascular complications was comparable between early and late groups (adjusted P = .67, adjusted P = .23, respectively).
The frequency of incomplete recanalization and of cerebrovascular complications occurring after endovascular treatment is similar in early and well-selected late patients receiving endovascular treatment. Our results demonstrate the technical success and safety of endovascular treatment in well-selected late patients with acute ischemic stroke
A systematic review on health resilience to economic crises
Background The health effects of recent economic crises differ markedly by population group. The objective of this systematic review is to examine evidence from longitudinal studies on factors influencing resilience for any health outcome or health behaviour among the general population living in countries exposed to financial crises. Methods We systematically reviewed studies from six electronic databases (EMBASE, Global Health, MEDLINE, PsycINFO, Scopus, Web of Science) which used quantitative longitudinal study designs and included: (i) exposure to an economic crisis; (ii) changes in health outcomes/behaviours over time; (iii) statistical tests of associations of health risk and/or protective factors with health outcomes/behaviours. The quality of the selected studies was appraised using the Quality Assessment Tool for Quantitative Studies. PRISMA reporting guidelines were followed. Results From 14,584 retrieved records, 22 studies met the eligibility criteria. These studies were conducted across 10 countries in Asia, Europe and North America over the past two decades. Ten socio-demographic factors that increased or protected against health risk were identified: gender, age, education, marital status, household size, employment/occupation, income/ financial constraints, personal beliefs, health status, area of residence, and social relations. These studies addressed physical health, mortality, suicide and suicide attempts, mental health, and health behaviours. Women’s mental health appeared more susceptible to crises than men’s. Lower income levels were associated with greater increases in cardiovascular disease, mortality and worse mental health. Employment status was associated with changes in mental health. Associations with age, marital status, and education were less consistent, although higher education was associated with healthier behaviours. Conclusions Despite widespread rhetoric about the importance of resilience, there was a dearth of studies which operationalised resilience factors. Future conceptual and empirical research is needed to develop the epidemiology of resilience
Bone cylinder plug and coil technique for accurate pedicle localization in thoracic spine surgery: A technical note.
Intraoperative identification of the correct level during thoracic spine surgery is essential to avoid wrong-level procedures. Despite technological progress, intraoperative imaging modalities for identifying the correct thoracic spine level remain unreliable and often lead to wrong-level surgery. To counter potential wrong-level operations, here, we have proposed a novel pedicle/bone cylinder marking technique for use in the thoracic spine utilizing biplanar fluoroscopy and confirmed with computed tomography (CT).
First, under fluoroscopic guidance, a bone cylinder is removed from the correct thoracic pedicle. Next, endovascular coils are packed into the cancellous bone defect followed by reinsertion of the bony plug. The patient then undergoes a CT scan of the entire thoracolumbosacral spine to precisely identify the marked level before surgery.
We utilized this bone cylinder plug/coil technique to identify the T9-T10 level in a 56-year-old female with a soft thoracic disc herniation. The index thoracic pedicle was successfully localized before performing the unilateral minimally invasive laminectomy followed by the transpedicular thoracic disc excision.
The bone cylinder plug/coil technique is a safe and effective method for marking the correct level in thoracic spine surgery, while also reducing the operative time
Prospective Investigation of Markers of Elevated Delirium Risk (PRIMED Risk) study protocol: a prospective, observational cohort study investigating blood and cerebrospinal fluid biomarkers for delirium and cognitive dysfunction in older patients [version 1; peer review: awaiting peer review]
BACKGROUND: Delirium is a common post-operative complication, particularly in older adults undergoing major or emergency procedures. It is associated with increased length of intensive care and hospital stay, post-operative mortality and subsequent dementia risk. Current methods of predicting delirium incidence, duration and severity have limitations. Investigation of blood and cerebrospinal fluid (CSF) biomarkers linked to delirium may improve understanding of the underlying pathophysiology, particularly with regard to the extent this is shared or distinct with underlying dementia. Together, these have the potential for development of better risk stratification tools and perioperative interventions. /
METHODS: 200 patients over the age of 70 scheduled for surgery with routine spinal anaesthetic will be recruited from UK hospitals. Their cognitive and functional baseline status will be assessed pre-operatively by telephone. Time-matched CSF and blood samples will be taken at the time of surgery and analysed for known biomarkers of neurodegeneration and neuroinflammation. Patients will be assessed daily for delirium until hospital discharge and will have regular cognitive follow-up for two years. Primary outcomes will be change in modified Telephone Interview for Cognitive Status (TICS-m) score at 12 months and rate of change of TICS-m score. Delirium severity, duration and biomarker levels will be treated as exposures in a random effects linear regression models. PRIMED Risk has received regulatory approvals from Health Research Authority and London – South East Research Ethics Committee. /
DISCUSSION: The main anticipated output from this study will be the quantification of biomarkers of acute and chronic contributors to cognitive impairment after surgery. In addition, we aim to develop better risk prediction models for adverse cognitive outcomes
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