464 research outputs found
Dynamics of rapidly spinning blob-filaments: fluid theory with a parallel kinetic extension
Blob-filaments (or simply 'blobs') are coherent structures formed by
turbulence and sustained by nonlinear processes in the edge and scrape-off
layer (SOL) of tokamaks and other magnetically confined plasmas. The dynamics
of these blob-filaments, in particular their radial motion, can influence the
scrape-off layer width and plasma interactions with both the divertor target
and with the main chamber walls. Motivated by recent results from the XGC1
gyrokinetic simulation code reported on elsewhere [J. Cheng et al. submitted to
Nucl. Fusion and available at arXiv:2302.02877v1], a theory of rapidly spinning
blob-filaments has been developed. The theory treats blob filaments in the
closed flux surface region or the region that is disconnected from sheaths in
the SOL. It extends previous work by treating blob spin, arising from partially
or fully adiabatic electrons, as the leading order effect and retaining
inertial (ion charge polarization) physics in next order. Spin helps to
maintain blob coherency and affects the blob's propagation speed. Dipole charge
polarization, treated perturbatively, gives rise to blob-filaments with
relatively slow radial velocity, comparable to that observed in the
simulations. The theory also treats the interaction of rapidly spinning blob
filaments with a zonal flow layer. It is shown analytically that the flow layer
can act like a transport barrier for these structures. Finally parallel
electron kinetic effects are incorporated into the theory. Various asymptotic
parameter regimes are discussed and asymptotic expressions for the radial and
poloidal motion of the blob-filaments are obtained.Comment: 31 pages, 2 figures, accepted in the journal Physics of Plasmas 30,
072302 (2023
Oblique radiative shocks, including their interactions with nonradiative polytropic shocks
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98755/1/PhysPlasmas_18_056901.pd
Dispelling the myths of online education: learning via the information superhighway
There continues to be a perception that online education is inferior to traditional education. In the U.S. online learning is more developed than in the U.K. This paper provides insights into a U.S. provision and takes a close look at what are perceived as weaknesses of on line learning and argues that these are not necessarily inherent weaknesses of this form of educational delivery. Then, results of two major studies, undertaken in the U.S. are provided comparing the effectiveness of online education to traditional education as perceived by current MBA students and past graduates. Results of these studies suggest that students of MBA modules and MBA graduates perceive the quality and effectiveness of online education to be similar to, if not higher than, the quality and effectiveness of traditional modules and programmes
Hypoxia modulates the stem cell population and induces EMT in the MCF-10A breast epithelial cell line
A common feature among pre-malignant lesions is the induction of hypoxia through increased cell propagation and reduced access to blood flow. Hypoxia in breast cancer has been associated with poor patient prognosis, resistance to chemotherapy and increased metastasis. Although hypoxia has been correlated with factors associated with the latter stages of cancer progression, it is not well documented how hypoxia influences cells in the earliest stages of transformation. Using the immortalized MCF-10A breast epithelial cell line, we used hypoxic culture conditions to mimic reduced O2 levels found within early pre-malignant lesions and assessed various cellular parameters. In this non-transformed mammary cell line, O2 deprivation led to some changes not immediately associated with cancer progression, such as decreased proliferation, cell cycle arrest and increased apoptosis. In contrast, hypoxia did induce other changes more consistent with an increased metastatic potential. A rise in the CD44+CD24-/low-labeled cell sub-population along with increased colony forming capability indicated an expanded stem cell population. Hypoxia also induced cellular and molecular changes consistent with an epithelial-to-mesenchymal transition (EMT). Furthermore, these cells now exhibited increased migratory and invasive abilities. These results underscore the contribution of the hypoxic tumour microenvironment in cancer progression and dissemination
Docosahexaenoic acid counteracts palmitate-induced endoplasmic reticulum stress in C2C12 myotubes: Impact on muscle atrophy
Lipid accumulation in skeletal muscle results in dysregulation of protein meta- bolism and muscle atrophy. We previously reported that treating C2C12 myo- tubes with palmitate (PA), a saturated fatty acid, increases the overall rate of proteolysis via activation of the ubiquitin-proteasome and autophagy systems; co-treatment with the omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) prevents the PA-induced responses. Others have reported that PA induces endoplasmic reticulum (ER) stress which initiates the unfolded pro- tein response (UPR), a collective group of responses that can lead to activa- tion of caspase-mediated proteolysis and autophagy. Presently, we tested the hypothesis that DHA protects against PA-induced ER stress/UPR and its atro- phy-related responses in muscle cells. C2C12 myotubes were treated with 500 lmol/L PA and/or 100 lmol/L DHA for 24 h. Proteins and mRNA asso- ciated with ER stress/UPR, autophagy, and caspase-3 activation were evalu- ated. PA robustly increased the phosphorylation of protein kinase R (PKR)- like ER kinase (PERK) and eukaryotic initiation factor 2a (eIF2a). It also increased the mRNAs encoding activating transcription factor 4 (ATF4), spliced X-box binding protein 1 (XBP1s), C/EBP homologous protein (CHOP), and autophagy-related 5 (Atg5) as well as the protein levels of the PERK target nuclear factor erythroid 2-related factor (Nrf2), CHOP, and cleaved (i.e., activated) caspase-3. Co-treatment with DHA prevented all of the PA-induced responses. Our results indicate that DHA prevents PA- induced muscle cell atrophy, in part, by preventing ER stress/UPR, a process that leads to activation of caspase-mediated proteolysis and an increase in expression of autophagy-related genes
Instabilities of one-dimensional stationary solutions of the cubic nonlinear Schrodinger equation
The two-dimensional cubic nonlinear Schrodinger equation admits a large
family of one-dimensional bounded traveling-wave solutions. All such solutions
may be written in terms of an amplitude and a phase. Solutions with piecewise
constant phase have been well studied previously. Some of these solutions were
found to be stable with respect to one-dimensional perturbations. No such
solutions are stable with respect to two-dimensional perturbations. Here we
consider stability of the larger class of solutions whose phase is dependent on
the spatial dimension of the one-dimensional wave form. We study the spectral
stability of such nontrivial-phase solutions numerically, using Hill's method.
We present evidence which suggests that all such nontrivial-phase solutions are
unstable with respect to both one- and two-dimensional perturbations.
Instability occurs in all cases: for both the elliptic and hyperbolic nonlinear
Schrodinger equations, and in the focusing and defocusing case.Comment: Submitted: 13 pages, 3 figure
Nucleon Spin Fluctuations and the Supernova Emission of Neutrinos and Axions
In the hot and dense medium of a supernova (SN) core, the nucleon spins
fluctuate so fast that the axial-vector neutrino opacity and the axion
emissivity are expected to be significantly modified. Axions with
m_a\alt10^{-2}\,{\rm eV} are not excluded by SN~1987A. A substantial transfer
of energy in neutrino-nucleon () collisions is enabled which may alter
the spectra of SN neutrinos relative to calculations where energy-conserving
collisions had been assumed near the neutrinosphere.Comment: 8 pages. REVTeX. 2 postscript figures, can be included with epsf.
Small modifications of the text, a new "Note Added", and three new
references. To be published in Phys. Rev. Let
Aspirin Use and Incident Cardiovascular Disease, Kidney Failure, and Death in Stable Kidney Transplant Recipients: A Post Hoc Analysis of the Folic Acid for Vascular Outcome Reduction in Transplantation (FAVORIT) Trial
Cardiovascular disease (CVD) is the leading cause of death in kidney transplant recipients. Whether aspirin may reduce the risk for CVD, death, and kidney failure outcomes is uncertain
Randomized controlled trial of a health plan-level mood disorders psychosocial intervention for solo or small practices
Background: Mood disorders represent the most expensive mental disorders for employer-based commercial health plans. Collaborative care models are effective in treating chronic physical and mental illnesses at little to no net healthcare cost, but to date have primarily been implemented by larger healthcare organizations in facility-based models. The majority of practices providing commercially insured care are far too small to implement such models. Health plan-level collaborative care treatment can address this unmet need. The goal of this study is to implement at the national commercial health plan level a collaborative care model to improve outcomes for persons with mood disorders. Methods/Design A randomized controlled trial of a collaborative care model versus usual care will be conducted among beneficiaries of a large national health plan from across the country seen by primary care or behavioral health practices. At discharge 344 patients identified by health plan claims as hospitalized for unipolar depression or bipolar disorder will be randomized to receive collaborative care (patient phone-based self-management support, care management, and guideline dissemination to practices delivered by a plan-level care manager) or usual care from their provider. Primary outcomes are changes in mood symptoms and mental health-related quality of life at 12 months. Secondary outcomes include rehospitalization, receipt of guideline-concordant care, and work productivity. Discussion This study will determine whether a collaborative care model for mood disorders delivered at the national health plan level improves outcomes compared to usual care, and will inform a business case for collaborative care models for these settings that can reach patients wherever they receive treatment. Trial registration ClinicalTrials.gov Identifier: NCT02041962; registered January 3, 2014
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