398 research outputs found
EFFECT OF BIO-ENVIRONMENT AND CU ALLOYING ON ZINC IMPLANT BIOCOMPATIBILITY
Heart disease is the leading cause of death world-wide with coronary artery disease, or atherosclerosis, being the most common form of heart disease. To treat atherosclerosis, stenting is commonly used to widen or reopen narrowed arteries and restore proper blood flow to tissues. The industry standard stent is a bare-metal or drug-eluting stent. Both of these stent types are permanent and can have complications, including in-stent restenosis and thrombosis. Some of these complications would be reduced with bioresorbable stents. In this work, a possible bioresorbable Zn-Cu alloy for arterial stenting applications was investigated using a rodent wire implantation model.
In addition to needing different materials for stenting, the environment in which they are investigated needs to be taken into account. Most biocompatibility studies are done in young, healthy animals. However, the human patients they will be implanted in tend to be older and have comorbidities that could influence how the body responds. Therefore, two different animal models, of transgenic diseased mice and aged rats, were investigated for future material testing through wire implantation of pure platinum and zinc wires. In the diseased ApoE-/- mice, there was significantly more neointimal tissue growth, increased inflammation and smooth muscle cell (SMC) presence than healthy counterparts. In aged rats, there was a decrease in inflammation and SMC presence, but an increase in neointimal tissue area
Coulomb Drag in the Exciton Regime in Electron-Hole Bilayers
We report electrical transport measurements on GaAs/AlGaAs based
electron-hole bilayers. These systems are expected to make a transition from a
pair of weakly coupled two-dimensional systems to a strongly coupled exciton
system as the barrier between the layers is reduced. Once excitons form,
phenomena such as Bose-Einstein condensation of excitons could be observed. In
our devices, electrons and holes are confined in double quantum wells, and
carriers in the devices are induced with top and bottom gates leading to
variable density in each layer. Separate contact to each layer allows Coulomb
drag transport measurements where current is driven in one layer while voltage
is measured in the other. Coulomb drag is sensitive to interlayer coupling and
has been predicted to provide a strong signature of exciton condensation. Drag
measurement on EHBLs with a 30 nm barrier are consistent with drag between two
weakly coupled 2D Fermi systems where the drag decreases as the temperature is
reduced. When the barrier is reduced to 20 nm, we observe a consistent increase
in the drag resistance as the temperature is reduced. These results indicate
the onset of a much stronger coupling between the electrons and holes which
leads to exciton formation and possibly phenomena related to exciton
condensation.Comment: 12 pages, 3 figure
Charmonium-hadron interactions from QCD
The heavy quark system is an excellent probe to learn about the QCD dynamics
at finite density. First, we discuss the properties of the and
meson at finite nucleon density. We discuss why their properties should change
at finite density and then introduce an exact QCD relation among these hadron
properties and the energy momentum tensor of the medium. Second, we discuss
attempts to calculate charmonium-hadron total cross section using effective
hadronic models and perturbative QCD. We emphasize a recent calculation, where
the cross section is derived using QCD factorization theorem. We conclude by
discussing some challenges for SIS 200.Comment: 8 pages, Presented at 6th International Conference on Strange Quarks
in Matter: 2001: A Flavorspace Odyssey (SQM2001), Frankfurt, Germany, 25-29
Sep 2001, submitted to J. Phys.
Properties of D-mesons in nuclear matter within a self-consistent coupled-channel approach
The spectral density of the -meson in the nuclear environment is studied
within a self-consistent coupled-channel approach assuming a separable
potential for the bare meson-baryon interaction. The interaction,
described through a G-matrix, generates dynamically the (2593)
resonance. This resonance is the charm counterpart of the (1405)
resonance generated from the s-wave interaction in the I=0 channel.
The medium modification of the D-meson spectral density due to the Pauli
blocking of intermediate states as well as due to the dressing of the D-mesons,
nucleons and pions is investigated. We observe that the inclusion of
coupled-channel effects and the self-consistent dressing of the -meson
results in an overall reduction of the in-medium -meson changes compared to
previous work which neglect those effects.Comment: 23 pages, 10 figures, submitted for publicatio
Posttransplantation malignancy in a patient presenting with weight loss and changed bowel habits: a case report
BACKROUND: Advancements in immunosuppressive therapy have significantly improved patient and graft survival following renal transplantation. This is paralleled by an increasing occurrence of posttransplantation malignancy. CASE PRESENTATION: We report on a patient who presented with a history reminding of colon cancer seven years after receiving a kidney transplant. Initial diagnostic imaging seemed to confirm this diagnosis showing a constricting colonic lesion. To our surprise, colonoscopy findings were unremarkable. Review of the imaging studies revealed that the tumor-like picture was caused by the renal graft impressing the intestine. The following search for malignancy in other locations resulted in the diagnosis of glioblastoma multiforme of which the patient died several weeks later. CONCLUSION: Follow-up of renal transplant patients must include screening tests directed at tumor detection. Imaging studies and other tests in this patient group should be interpreted by physicians who are familiar with transplant related peculiarities
Forging Partnerships in Health Care: Process and Measuring Benefits
Universally, there is concern that much academic learning has dealt mainly in theory, removing knowledge from context with a resultant lack of practical experience. Here, the catalyst for strengthening university-community engagement, emanated from a desire to foster greater propensity within students to make connections between their academic courses and responsibility toward the community and people in need, and thus develop enhanced skills in social interaction, teamwork and effectiveness. This paper explores a variety of models of university-community engagement that aim to achieve and model good practice in policy making and planning around healthcare education and service development. Ways of integrating teaching and learning with community engagement, so there is reciprocal learning with significant benefits to the community, students, the university and industry are described. The communities of engagement for a transdisciplinary approach in healthcare are defined and the types of collaborative partnerships are outlined, including public/private partnerships, service learning approaches and regional campus engagement. The processes for initiating innovation in this field, forging sustainable partnerships, providing cooperative leadership and building shared vision are detailed. Measuring shared and sustained benefits for all participants is examined in the context of effecting changes in working relationships as well as the impact on students in terms of increased personal and social responsibility, confidence and competence. For the health professions, it is considered vital to adopt this approach in order to deliver graduates who feel aware of community needs, believe they can make a difference, and have a greater sense of community responsibility, ethic of service and more sophisticated understandings of social contexts. In the longer term, it is proposed the strategy will deliver a future healthcare workforce that is more likely to have a strengthened sense of community, social and personal responsibility and thus effect positive social change
Procalcitonin as marker of infection in patients with Goodpasture's syndrome is misleading
Abstract Background. Procalcitonin (PCT) is routinely measured to differentiate autoimmune disorders from infection. There are reports, however, where PCT is high in the absence of infection, i.e. in vasculitis. To investigate the value of PCT in Goodpasture's syndrome, we reviewed the charts of patients with Goodpasture's syndrome who were treated from 1996 to 2006. Methods. PCT (normal range <0.5 ng/ml) was measured with an immunoluminometric assay, C-reactive protein (CRP; normal range <5 mg/l) with nephelometry. Anti-glomerular basement membrane antibodies (normal range <1:10) were measured with ELISA
Density imbalance effect on the Coulomb drag upturn in an electron-hole bialyer
A low-temperature upturn of the Coulomb drag resistivity measured in an
undoped electron-hole bilayer (uEHBL) device, possibly manifesting from exciton
formation or condensation, was recently observed. The effects of density
imbalance on this upturn are examined. Measurements of drag as a function of
temperature in a uEHBL with a 20 nm wide AlGaAs barrier layer
at various density imbalances are presented. The results show drag increasing
as the density of either two dimensional system was reduced, both within and
above the upturn temperature regime. A comparison of the data with numerical
calculations of drag in the presence of electron-hole pairing fluctuations,
which qualitatively reproduce the drag upturn behavior, is also presented. The
calculations, however, predict a peak in drag at matched densities, which is
not reflected by the measurements.Comment: 4 pages, 4 figures, submitted to PRB Rapi
Theory of sound attenuation in glasses: The role of thermal vibrations
Sound attenuation and internal friction coefficients are calculated for a
realistic model of amorphous silicon. It is found that, contrary to previous
views, thermal vibrations can induce sound attenuation at ultrasonic and
hypersonic frequencies that is of the same order or even larger than in
crystals. The reason is the internal-strain induced anomalously large
Gr\"uneisen parameters of the low-frequency resonant modes.Comment: 8 pages, 3 figures; to appear in PR
Molecular and biochemical alterations in tubular epithelial cells of patients with isolated methylmalonic aciduria
Methylmalonic acidurias (MMAurias) are a group of inherited disorders in the catabolism of branched-chain amino acids, odd-chain fatty acids and cholesterol caused by complete or partial deficiency of methylmalonyl-CoA mutase (mut0 and mut- subtype respectively) and by defects in the metabolism of its cofactor 5′-deoxyadenosylcobalamin (cblA, cblB or cblD variant 2 type). A long-term complication found in patients with mut0 and cblB variant is chronic tubulointerstitial nephritis. The underlying pathomechanism has remained unknown. We established an in vitro model of tubular epithelial cells from patient urine (hTEC; 9 controls, 5 mut0, 1 cblB). In all human tubular epithelial cell (hTEC) lines we found specific tubular markers (AQP1, UMOD, AQP2). Patient cells showed disturbance of energy metabolism in glycolysis, mitochondrial respiratory chain and Krebs cycle in concert with increased reactive oxygen species (ROS) formation. Electron micrographs indicated increased autophagosome production and endoplasmic reticulum stress, which was supported by positive acridine orange staining and elevated levels of LC3 II, P62 and pIRE1. Screening mTOR signaling revealed a release of inhibition of autophagy. Patient hTEC produced and secreted elevated amounts of the pro-inflammatory cytokine IL8, which was highly correlated with the acridine orange staining. Summarizing, hTEC of MMAuria patients are characterized by disturbed energy metabolism and ROS production that lead to increased autophagy and IL8 secretio
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