198 research outputs found
Attitude of Polotsk state university students to the transition to distance learning during the pandemic covid-19
The opinion of students of Polotsk State University regarding the organization of the educational process during the COVID-19 pandemic is considered. The negative and positive aspects of this form of education are noted. Special attention is paid to the discipline "Physical Culture", as in the conditions of home self-isolation and forced restriction of physical activity, the need for physical activity increases significantly
Attitude of Polotsk state university students to the transition to distance learning during the pandemic covid-19
The opinion of students of Polotsk State University regarding the organization of the educational process during the COVID-19 pandemic is considered. The negative and positive aspects of this form of education are noted. Special attention is paid to the discipline "Physical Culture", as in the conditions of home self-isolation and forced restriction of physical activity, the need for physical activity increases significantly
Carbon Supported Polyaniline as Anode Catalyst: Pathway to Platinum-Free Fuel Cells
The effectiveness of carbon supported polyaniline as anode catalyst in a fuel
cell (FC) with direct formic acid electrooxidation is experimentally
demonstrated. A prototype FC with such a platinum-free composite anode
exhibited a maximum room-temperature specific power of about 5 mW/cm2Comment: 11 pages, 3 Postscript figures, atricle tex styl
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
Structure of a double ubiquitin-like domain in the talin head: a role in integrin activation
Talin is a 270-kDa protein that activates integrins and couples them to cytoskeletal actin. Talin contains an N-terminal FERM domain comprised of F1, F2 and F3 domains, but it is atypical in that F1 contains a large insert and is preceded by an extra domain F0. Although F3 contains the binding site for β-integrin tails, F0 and F1 are also required for activation of β1-integrins. Here, we report the solution structures of F0, F1 and of the F0F1 double domain. Both F0 and F1 have ubiquitin-like folds joined in a novel fixed orientation by an extensive charged interface. The F1 insert forms a loop with helical propensity, and basic residues predicted to reside on one surface of the helix are required for binding to acidic phospholipids and for talin-mediated activation of β1-integrins. This and the fact that basic residues on F2 and F3 are also essential for integrin activation suggest that extensive interactions between the talin FERM domain and acidic membrane phospholipids are required to orientate the FERM domain such that it can activate integrins
A computational analysis of the dynamic roles of talin, Dok1, and PIPKI for integrin activation
Integrin signaling regulates cell migration and plays a pivotal role in
developmental processes and cancer metastasis. Integrin signaling has been
studied extensively and much data is available on pathway components and
interactions. Yet the data is fragmented and an integrated model is missing. We
use a rule-based modeling approach to integrate available data and test
biological hypotheses regarding the role of talin, Dok1 and PIPKI in integrin
activation. The detailed biochemical characterization of integrin signaling
provides us with measured values for most of the kinetics parameters. However,
measurements are not fully accurate and the cellular concentrations of
signaling proteins are largely unknown and expected to vary substantially
across different cellular conditions. By sampling model behaviors over the
physiologically realistic parameter range we find that the model exhibits only
two different qualitative behaviours and these depend mainly on the relative
protein concentrations, which offers a powerful point of control to the cell.
Our study highlights the necessity to characterize model behavior not for a
single parameter optimum, but to identify parameter sets that characterize
different signaling modes
Structural and biophysical properties of the integrin-associated cytoskeletal protein talin
Talin is a large cytoskeletal protein (2541 amino acid residues) which plays a key role in integrin-mediated events that are crucial for cell adhesion, migration, proliferation and survival. This review summarises recent work on the structure of talin and on some of the structurally better defined interactions with other proteins. The N-terminal talin head (approx. 50 kDa) consists of an atypical FERM domain linked to a long flexible rod (approx. 220 kDa) made up of a series of amphipathic helical bundle domains. The F3 FERM subdomain in the head binds the cytoplasmic tail of integrins, but this interaction can be inhibited by an interaction of F3 with a helical bundle in the talin rod, the so-called “autoinhibited form” of the molecule. The talin rod contains a second integrin-binding site, at least two actin-binding sites and a large number of binding sites for vinculin, which is important in reinforcing the initial integrin–actin link mediated by talin. The vinculin binding sites are defined by hydrophobic residues buried within helical bundles, and these must unfold to allow vinculin binding. Recent experiments suggest that this unfolding may be mediated by mechanical force exerted on the talin molecule by actomyosin contraction
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