3,140 research outputs found
A Heuristic Framework for Next-Generation Models of Geostrophic Convective Turbulence
Many geophysical and astrophysical phenomena are driven by turbulent fluid
dynamics, containing behaviors separated by tens of orders of magnitude in
scale. While direct simulations have made large strides toward understanding
geophysical systems, such models still inhabit modest ranges of the governing
parameters that are difficult to extrapolate to planetary settings. The
canonical problem of rotating Rayleigh-B\'enard convection provides an
alternate approach - isolating the fundamental physics in a reduced setting.
Theoretical studies and asymptotically-reduced simulations in rotating
convection have unveiled a variety of flow behaviors likely relevant to natural
systems, but still inaccessible to direct simulation. In lieu of this, several
new large-scale rotating convection devices have been designed to characterize
such behaviors. It is essential to predict how this potential influx of new
data will mesh with existing results. Surprisingly, a coherent framework of
predictions for extreme rotating convection has not yet been elucidated. In
this study, we combine asymptotic predictions, laboratory and numerical
results, and experimental constraints to build a heuristic framework for
cross-comparison between a broad range of rotating convection studies. We
categorize the diverse field of existing predictions in the context of
asymptotic flow regimes. We then consider the physical constraints that
determine the points of intersection between flow behavior predictions and
experimental accessibility. Applying this framework to several upcoming devices
demonstrates that laboratory studies may soon be able to characterize
geophysically-relevant flow regimes. These new data may transform our
understanding of geophysical and astrophysical turbulence, and the conceptual
framework developed herein should provide the theoretical infrastructure needed
for meaningful discussion of these results.Comment: 36 pages, 8 figures. CHANGES: in revision at Geophysical and
Astrophysical Fluid Dynamic
The effect of 14 weeks of vitamin D3 supplementation on antimicrobial peptides and proteins in athletes
Heavy training is associated with increased respiratory infection risk and antimicrobial proteins are important in defence against oral and respiratory tract infections. We examined the effect of 14 weeks of vitamin D3 supplementation (5000 IU/day) on the resting plasma cathelicidin concentration and the salivary secretion rates of secretory immunoglobulin A (SIgA), cathelicidin, lactoferrin and lysozyme in athletes during a winter training period. Blood and saliva were obtained at the start of the study from 39 healthy men who were randomly allocated to vitamin D3 supplement or placebo. Blood samples were also collected at the end of the study; saliva samples were collected after 7 and 14 weeks. Plasma total 25(OH)D concentration increased by 130% in the vitamin D3 group and decreased by 43% in the placebo group (both P=0.001). The percentage change of plasma cathelicidin concentration in the vitamin D3 group was higher than in the placebo group (P=0.025). Only in the vitamin D3 group, the saliva SIgA and cathelicidin secretion rates increased over time (both P=0.03). A daily 5000 IU vitamin D3 supplement has a beneficial effect in up-regulating the expression of SIgA and cathelicidin in athletes during a winter training period which could improve resistance to respiratory infections
Recommended from our members
Disrupted CXCR2 Signaling in Oligodendroglia Lineage Cells Enhances Myelin Repair in a Viral Model of Multiple Sclerosis.
CXCR2 is a chemokine receptor expressed on oligodendroglia that has been implicated in the pathogenesis of neuroinflammatory demyelinating diseases as well as enhancement of the migration, proliferation, and myelin production by oligodendroglia. Using an inducible proteolipid protein (Plp) promoter-driven Cre-loxP recombination system, we were able to assess how timed ablation of Cxcr2 in oligodendroglia affected disease following intracranial infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV). Generation of Plp-Cre-ER(T)::Cxcr2flox/flox transgenic mice (termed Cxcr2-CKO mice) allows for Cxcr2 to be silenced in oligodendrocytes in adult mice following treatment with tamoxifen. Ablation of oligodendroglia Cxcr2 did not influence clinical severity in response to intracranial infection with JHMV. Infiltration of activated T cells or myeloid cells into the central nervous system (CNS) was not affected, nor was the ability to control viral infection. In addition, the severity of demyelination was similar between tamoxifen-treated mice and vehicle-treated controls. Notably, deletion of Cxcr2 resulted in increased remyelination, as assessed by g-ratio (the ratio of the inner axonal diameter to the total outer fiber diameter) calculation, compared to that in vehicle-treated control mice. Collectively, our findings argue that CXCR2 signaling in oligodendroglia is dispensable with regard to contributing to neuroinflammation, but its deletion enhances remyelination in a preclinical model of the human demyelinating disease multiple sclerosis (MS).IMPORTANCE Signaling through the chemokine receptor CXCR2 in oligodendroglia is important for developmental myelination in rodents, while chemical inhibition or nonspecific genetic deletion of CXCR2 appears to augment myelin repair in animal models of the human demyelinating disease multiple sclerosis (MS). To better understand the biology of CXCR2 signaling on oligodendroglia, we generated transgenic mice in which Cxcr2 is selectively ablated in oligodendroglia upon treatment with tamoxifen. Using a viral model of neuroinflammation and demyelination, we demonstrate that genetic silencing of CXCR2 on oligodendroglia did not affect clinical disease, neuroinflammation, or demyelination, yet there was increased remyelination. These findings support and extend previous findings suggesting that targeting CXCR2 may offer a therapeutic avenue for enhancing remyelination in patients with demyelinating diseases
Laboratory model of electrovortex flow with thermal gradients, for liquid metal batteries
We present a novel laboratory setup for studying the fluid dynamics in liquid
metal batteries (LMBs). LMBs are a promising technology suited for grid-scale
energy storage, but flows remain a confounding factor in determining their
viability. Two important drivers of flow are thermal gradients, caused by
internal heating during operation, and electrovortex flow (EVF), induced by
diverging current densities. Our setup explores thermal gradients and
electrovortex flow separately and in combination in a cylindrical layer of
liquid gallium, simulating the behavior in a single layer of an LMB. In this
work, we discuss the design principles underlying our choices of materials,
thermal control, and current control. We also detail our diagnostic tools -
thermocouple measurements for temperature and Ultrasonic Doppler Velocimetry
(UDV) probes for velocities - and the design principles which go into choosing
their placement on the setup. We also include a discussion of our
post-processing tools for quantifying and visualizing the flow. Finally, we
validate convection and EVF in our setup: we show that scaling relationships
between the nondimensional parameters produced by our data agree well with
theory and previous studies.Comment: 13 pages, 9 figure
Laboratory Exploration of Heat Transfer Regimes in Rapidly Rotating Turbulent Convection
We report heat transfer and temperature profile measurements in laboratory
experiments of rapidly rotating convection in water under intense thermal
forcing (Rayleigh number as high as ) and unprecedentedly
strong rotational influence (Ekman numbers as low as ).
Measurements of the mid-height vertical temperature gradient connect
quantitatively to predictions from numerical models of asymptotically rapidly
rotating convection, separating various flow phenomenologies. Past the limit of
validity of the asymptotically-reduced models, we find novel behaviors in a
regime we refer to as rotationally-influenced turbulence, where rotation is
important but not as dominant as in the known geostrophic turbulence regime.
The temperature gradients collapse to a Rayleigh-number scaling as
in this new regime. It is bounded from above by a critical convective Rossby
number independent of domain aspect ratio , clearly
distinguishing it from well-studied rotation-affected convection.Comment: 14 pages, 7 figure
Recommended from our members
Experimental pub crawl from Rayleigh–Bénard to magnetostrophic convection
The interplay between convective, rotational and magnetic forces defines the dynamics within the electrically conducting regions of planets and stars. Yet their triadic effects are separated from one another in most studies, arguably due to the richness of each subset. In a single laboratory experiment, we apply a fixed heat flux, two different magnetic field strengths and one rotation rate, allowing us to chart a continuous path through Rayleigh-Bénard convection (RBC), two regimes of magnetoconvection, rotating convection and two regimes of rotating magnetoconvection, before finishing back at RBC. Dynamically rapid transitions are determined to exist between jump rope vortex states, thermoelectrically driven magnetoprecessional modes, mixed wall- and oscillatory-mode rotating convection and a novel magnetostrophic wall mode. Thus, our laboratory 'pub crawl' provides a coherent intercomparison of the broadly varying responses arising as a function of the magnetorotational forces imposed on a liquid-metal convection system
Final-State Phases in Baryon-Antibaryon Decays
The recent observation of the decay \ob \to \Lambda_c^+ \bar p suggests
that related decays may soon be visible at colliders. It is shown how
these decays can shed light on strong final-state phases and amplitudes
involving the spectator quark, both of which are normally expected to be small
in B decays.Comment: 14 pages, LaTeX, 2 figures, submitted to Phys. Rev. D, references and
discussion of helicity amplitudes adde
Probing Lepton Flavor Violation at Future Colliders
Supersymmetric theories with significant lepton flavor violation have
and nearly degenerate. In this case, pair production
of and at LEPII and at
the Next Linear Collider leads to the phenomenon of slepton oscillations, which
is analogous to neutrino oscillations. The reach in and gives a probe of lepton flavor violation which is significantly more
powerful than the current bounds from rare processes, such as . Polarizable beams and the mode at the NLC are found to
be promising options.Comment: 10 pages, 3 figures, RevTeX, minor corrections, published versio
Masses and Mixings in a Grand Unified Toy Model
The generation of the fermion mass hierarchy in the standard model of
particle physics is a long-standing puzzle. The recent discoveries from
neutrino physics suggests that the mixing in the lepton sector is large
compared to the quark mixings. To understand this asymmetry between the quark
and lepton mixings is an important aim for particle physics. In this regard,
two promising approaches from the theoretical side are grand unified theories
and family symmetries. In this note we try to understand certain general
features of grand unified theories with Abelian family symmetries by taking the
simplest SU(5) grand unified theory as a prototype. We construct an SU(5) toy
model with family symmetry
that, in a natural way, duplicates the observed mass hierarchy and mixing
matrices to lowest approximation. The system for generating the mass hierarchy
is through a Froggatt-Nielsen type mechanism. One idea that we use in the model
is that the quark and charged lepton sectors are hierarchical with small mixing
angles while the light neutrino sector is democratic with larger mixing angles.
We also discuss some of the difficulties in incorporating finer details into
the model without making further assumptions or adding a large scalar sector.Comment: 21 pages, 2 figures, RevTeX, v2: references updated and typos
corrected, v3: updated top quark mass, comments on MiniBooNE result, and
typos correcte
Differential Effects of Cold Atmospheric Plasma in the Treatment of Malignant Glioma
Objective
Cold atmospheric plasma (CAP) has recently been shown to selectively target cancer cells with minimal effects on normal cells. We systematically assessed the effects of CAP in the treatment of glioblastoma. Methods
Three glioma cell lines, normal astrocytes, and endothelial cell lines were treated with CAP. The effects of CAP were then characterized for viability, cytotoxicity/apoptosis, and cell cycle effects. Statistical significance was determined with student\u27s t-test. Results
CAP treatment decreases viability of glioma cells in a dose dependent manner, with the ID50 between 90-120 seconds for all glioma cell lines. Treatment with CAP for more than 120 seconds resulted in viability less than 35% at 24-hours posttreatment, with a steady decline to less than 20% at 72-hours. In contrast, the effect of CAP on the viability of NHA and HUVEC was minimal, and importantly not significant at 90 to 120 seconds, with up to 85% of the cells remained viable at 72-hours post-treatment. CAP treatment produces both cytotoxic and apoptotic effects with some variability between cell lines. CAP treatment resulted in a G2/M-phase cell cycle pause in all three cell lines. Conclusions
This preliminary study determined a multi-focal effect of CAP on glioma cells in vitro, which was not observed in the non-tumor cell lines. The decreased viability depended on the treatment duration and cell line, but overall was explained by the induction of cytotoxicity, apoptosis, and G2/M pause. Future studies will aim at further characterization with more complex pre-clinical models
- …