19,444 research outputs found
Inviscid limit of the active interface equations
We present a detailed solution of the active interface equations in the
inviscid limit. The active interface equations were previously introduced as a
toy model of membrane-protein systems: they describe a stochastic interface
where growth is stimulated by inclusions which themselves move on the
interface. In the inviscid limit, the equations reduce to a pair of coupled
conservation laws. After discussing how the inviscid limit is obtained, we turn
to the corresponding Riemann problem: the solution of the set of conservation
laws with discontinuous initial condition. In particular, by considering two
physically meaningful initial conditions, a giant trough and a giant peak in
the interface, we elucidate the generation of shock waves and rarefaction fans
in the system. Then, by combining several Riemann problems, we construct an
oscillating solution of the active interface with periodic boundaries
conditions. The existence of this oscillating state reflects the reciprocal
coupling between the two conserved quantities in our system.Comment: 22 pages, 11 figure
Investigating perceptions of cohesion, performance, and satisfaction in sport officiating groups
Since sport officials constitute instrumental groups, their perceptions of, and interactions with, group members likely influence their performance, satisfaction, and retention. This warrants investigation into sport officiating groups. Rationale/Purpose: (1) Examine the relationship between sport officialsâ cohesion, satisfaction, and performance; (2) Investigate sport officialsâ perceptions of cohesion across sports; and (3) Explore sport officialsâ perceptions of group processes. Design/Methodology/Approach: Using a cross-sectional design, participants (N = 228) completed a survey measuring perceptions of cohesion, performance, and satisfaction. Findings: Responses demonstrated consistent positive relationships between cohesion, performance, and satisfaction. Path analysis found that task cohesion predicted performance and satisfaction. Participants rated task cohesion higher than social cohesion, with American football highest and Association football lowest. Practical implications: Officiating organizations can use these results to reconsider assigning practices and develop strategies that improve cohesion, leading to increased performance and retention. Research contribution: Results highlight the need for sustained research to further understand how group processes influence sport officials and their performances. This study is novel as there is a dearth of research on how group dynamics influence sport officialsâ performances and retention.</p
Kinase pathways in dominant and subordinate ovarian follicles during the first wave of follicular development in sheep
Abstract The mechanism by which one or more dominant ovarian follicles continue development while other subordinate follicles regress is not known. The mitogen activated protein kinases (MAPKs) are a group of kinases that are activated by hormonal factors and form a cascade of processes that regulate cell growth, division and differentiation. The aim of the present experiment was to characterise the presence of the MAPKs, Erk 1/Erk 2 and Akt in healthy dominant follicles and regressing subordinate follicles. Following in vivo monitoring of ovarian follicle development, three ewes were ovariectomised and the follicular fluid and follicle wall (theca and granulosa cells) saved from the dominant and largest subordinate follicle. The dissected diameter and follicular fluid oestradiol concentration of the dominant follicle was larger (P < 0.01) than the largest subordinate follicle (6.5 ± 0.0 mm and 41.3 ± 4.9 ng/ml versus 4.7 ± 0.3 mm and 0.6 ± 0.4 ng/ml). Western blot analyses showed that there was more Akt (202.7 ± 6.4 versus 59.6 ± 32.7 units; P < 0.05) and Erk 1/Erk 2 (104.5 ± 10.6 versus 0.3 ± 0.2 units; P < 0.01) present in follicle wall samples from the dominant compared to the largest subordinate follicles. Phosphorylated forms of Akt and Erk 1/Erk 2 were detected in samples from dominant but not subordinate follicles. We suggest that signal transduction pathways involving Akt and Erk 1/Erk 2 may play an important role in determining the outcome of ovarian follicle growth and development in sheep
Metformin-mediated increase in DICER1 regulates microRNA expression and cellular senescence
Metformin, an oral hypoglycemic agent, has been used for
decades to treat type 2 diabetes mellitus. Recent studies indicate
that mice treated with metformin live longer and have fewer
manifestations of age-related chronic disease. However, the
molecular mechanisms underlying this phenotype are unknown.
Here, we show that metformin treatment increases the levels of
the microRNA-processing protein DICER1 in mice and in humans
with diabetes mellitus. Our results indicate that metformin
upregulates DICER1 through a post-transcriptional mechanism
involving the RNA-binding protein AUF1. Treatment with metformin
altered the subcellular localization of AUF1, disrupting its
interaction with DICER1 mRNA and rendering DICER1 mRNA
stable, allowing DICER1 to accumulate. Consistent with the role
of DICER1 in the biogenesis of microRNAs, we found differential
patterns of microRNA expression in mice treated with metformin
or caloric restriction, two proven life-extending interventions.
Interestingly, several microRNAs previously associated with
senescence and aging, including miR-20a, miR-34a, miR-130a,
miR-106b, miR-125, and let-7c, were found elevated. In agreement
with these findings, treatment with metformin decreased
cellular senescence in several senescence models in a DICER1-
dependent manner. Metformin lowered p16 and p21 protein
levels and the abundance of inflammatory cytokines and oncogenes
that are hallmarks of the senescence-associated secretory
phenotype (SASP). These data lead us to hypothesize that
changes in DICER1 levels may be important for organismal aging
and to propose that interventions that upregulate DICER1
expression (e.g., metformin) may offer new pharmacotherapeutic
approaches for age-related disease
D3/D7 Quark-Gluon Plasma with Magnetically Induced Anisotropy
We study the effects of the temperature and of a magnetic field in the setup
of an intersection of D3/D7 branes, where a large number of D7 branes is
smeared in the transverse directions to allow for a perturbative solution in a
backreaction parameter. The magnetic field sources an anisotropy in the plasma,
and we investigate its physical consequences for the thermodynamics and energy
loss of particles probing the system. In particular we comment on the
stress-energy tensor of the plasma, the propagation of sound in the directions
parallel and orthogonal to the magnetic field, the drag force of a quark moving
through the medium and jet quenching.Comment: 29 pages + appendices, 5 figures. v2 Version to appear in JHEP, with
minor revisions, references added and typos correcte
Technicolor and Beyond: Unification in Theory Space
The salient features of models of dynamical electroweak symmetry breaking are
reviewed. The ideal walking idea is introduced according to which one should
carefully take into account the effects of the extended technicolor dynamics on
the technicolor dynamics itself. The effects amount at the enhancement of the
anomalous dimension of the mass of the techniquarks allowing to decouple the
Flavor Changing Neutral Currents problem from the one of the generation of the
top mass. Precision data constraints are reviewed focussing on the latest
crucial observation that the S-parameter can be computed exactly near the upper
end of the conformal window (Conformal S-parameter) with relevant consequences
on the selection of nature's next strong force. We will then introduce the
Minimal Walking Technicolor (MWT) models. In the second part of this review we
consider the interesting possibility to marry supersymmetry and technicolor.
The reason is to provide a unification of different extensions of the standard
model. For example, this means that one can recover, according to the
parameters and spectrum of the theory distinct extensions of the standard
model, from supersymmetry to technicolor and unparticle physiscs. A surprising
result is that a minimal (in terms of the smallest number of fields)
supersymmetrization of the MWT model leads to the maximal supersymmetry in four
dimensions, i.e. N=4 SYM.Comment: Extended version of the PASCOS10 proceedings for the Plenary Tal
Glassy timescale divergence and anomalous coarsening in a kinetically constrained spin chain
We analyse the out of equilibrium behavior of an Ising spin chain with an
asymmetric kinetic constraint after a quench to a low temperature T. In the
limit T\to 0, we provide an exact solution of the resulting coarsening process.
The equilibration time exhibits a `glassy' divergence \teq=\exp(const/T^2)
(popular as an alternative to the Vogel-Fulcher law), while the average domain
length grows with a temperature dependent exponent, \dbar ~ t^{T\ln 2}. We show
that the equilibration time \teq also sets the timescale for the linear
response of the system at low temperatures.Comment: 4 pages, revtex, includes two eps figures. Proof of energy barrier
hierarchy added. Version to be published in Phys Rev Let
Improvement of arterial oxygenation in free-ranging moose (Alces alces) immobilized with etorphine-acepromazine-xylazine
Assessment of the LeadCareÂź Plus for Use on Scandinavian Brown Bears (Ursus arctos)
publishedVersio
Three-Dimensional Microfluidic Tri-Culture Model of the Bone Marrow Microenvironment for Study of Acute Lymphoblastic Leukemia
Acute lymphoblastic leukemia (ALL) initiates and progresses in the bone marrow, and as such, the marrow microenvironment is a critical regulatory component in development of this cancer. However, ALL studies were conducted mainly on flat plastic substrates, which do not recapitulate the characteristics of marrow microenvironments. To study ALL in a model of in vivo relevance, we have engineered a 3-D microfluidic cell culture platform. Biologically relevant populations of primary human bone marrow stromal cells, osteoblasts and human leukemic cells representative of an aggressive phenotype were encapsulated in 3-D collagen matrix as the minimal constituents and cultured in a microfluidic platform. The matrix stiffness and fluidic shear stress were controlled in a physiological range. The 3-D microfluidic as well as 3-D static models demonstrated coordinated cell-cell interactions between these cell types compared to the compaction of the 2-D static model. Tumor cell viability in response to an antimetabolite chemotherapeutic agent, cytarabine in tumor cells alone and tri-culture models for 2-D static, 3-D static and 3-D microfluidic models were compared. The present study showed decreased chemotherapeutic drug sensitivity of leukemic cells in 3-D tri-culture models from the 2-D models. The results indicate that the bone marrow microenvironment plays a protective role in tumor cell survival during drug treatment. The engineered 3-D microfluidic tri-culture model enables systematic investigation of effects of cell-cell and cell-matrix interactions on cancer progression and therapeutic intervention in a controllable manner, thus improving our limited comprehension of the role of microenvironmental signals in cancer biology
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