5,315 research outputs found
On 3-dimensional f-Kenmotsu manifolds and Ricci solitons
The aim of the present paper is to study 3-dimensional f-Kenmotsu manifolds and Ricci solitons. First, we give an example of a 3-dimensional f-Kenmotsu manifold. Then we consider a Riccisemisymmetric 3-dimensional f-Kenmotsu manifold and prove that a 3-dimensional f-Kenmotsu manifold is Ricci semisymmetric if and only if it is an Einstein manifold. Moreover, we investigate an η-parallel Ricci tensor in a 3-dimensional f-Kenmotsu manifold. Finally, we study Ricci solitons in a 3-dimensional f-Kenmotsu manifold.Метою даної статті є вивчення 3-вимірних f-многовидів Кенмоцу та солітонів Річчі. Спочатку наведено приклад 3-вимірного f-многовиду Кенмоцу. Потім розглянуто напівсиметричний за Річчі 3-вимірний f-многовид Кенмоцу i доведено, що 3-вимірний f-многовид Кенмоцу є напівсиметричним за Річчі тоді i тільки тоді, коли він є многовидом Ейнштейна. Також досліджено n-паралельний тензор Річчі у 3-вимірному f-многовиді Кенмоцу. Насамкінець, досліджено солітони Річчі у 3-вимірному f-многовиді Кенмоцу
Fractional Super Lie Algebras and Groups
n^{th} root of a Lie algebra and its dual (that is fractional supergroup)
based on the permutation group invariant forms are formulated in the Hopf
algebra formalism. Detailed discussion of -graided algebras is
done.Comment: 13 pages, detailed discussion of -graided is adde
Myosin V passing over Arp2/3 junctions: branching ratio calculated from the elastic lever arm model
Myosin V is a two-headed processive motor protein that walks in a
hand-over-hand fashion along actin filaments. When it encounters a filament
branch, formed by the Arp2/3 complex, it can either stay on the straight mother
filament, or switch to the daughter filament. We study both probabilities using
the elastic lever arm model for myosin V. We calculate the shapes and bending
energies of all relevant configurations in which the trail head is bound to the
actin filament before Arp2/3 and the lead head is bound either to the mother or
to the daughter filament. Based on the assumption that the probability for a
head to bind to a certain actin subunit is proportional to the Boltzmann factor
obtained from the elastic energy, we calculate the mother/daughter filament
branching ratio. Our model predicts a value of 27% for the daughter and 73% for
the mother filament. This result is in good agreement with recent experimental
data.Comment: 9 pages, 7 figures, to appear in Biophysical Journa
Elastic lever arm model for myosin V
We present a mechanochemical model for myosin V, a two-headed processive
motor protein. We derive the properties of a dimer from those of an individual
head, which we model both with a 4-state cycle (detached, attached with ADP.Pi,
attached with ADP and attached without nucleotide) and alternatively with a
5-state cycle (where the power stroke is not tightly coupled to the phosphate
release). In each state the lever arm leaves the head at a different, but
fixed, angle. The lever arm itself is described as an elastic rod. The chemical
cycles of both heads are coordinated exclusively by the mechanical connection
between the two lever arms. The model explains head coordination by showing
that the lead head only binds to actin after the power stroke in the trail head
and that it only undergoes its power stroke after the trail head unbinds from
actin. Both models (4- and 5-state) reproduce the observed hand-over-hand
motion and fit the measured force-velocity relations. The main difference
between the two models concerns the load dependence of the run length, which is
much weaker in the 5-state model. We show how systematic processivity
measurement under varying conditions could be used to distinguish between both
models and to determine the kinetic parameters.Comment: 15 pages, 15 figures, to appear in Biophys.
Core properties of alpha Cen A using asteroseismology
A set of long and nearly continuous observations of alpha Centauri A should
allow us to derive an accurate set of asteroseismic constraints to compare to
models, and make inferences on the internal structure of our closest stellar
neighbour. We intend to improve the knowledge of the interior of alpha Centauri
A by determining the nature of its core. We combined the radial velocity time
series obtained in May 2001 with three spectrographs in Chile and Australia:
CORALIE, UVES, and UCLES. The resulting combined time series has a length of
12.45 days and contains over 10,000 data points and allows to greatly reduce
the daily alias peaks in the power spectral window. We detected 44 frequencies
that are in good overall agreement with previous studies, and found that 14 of
these show possible rotational splittings. New values for the large and small
separations have been derived. A comparison with stellar models indicates that
the asteroseismic constraints determined in this study allows us to set an
upper limit to the amount of convective-core overshooting needed to model stars
of mass and metallicity similar to those of alpha Cen A.Comment: 8 pages, 11 figures, A&A accepte
Vwo-examenresultaten en succes in de propedeuse Rechten
Van een deel van de voltijdcohorten 2003 en 2004 Rechten waren eindexamencijfers en cijfers van het centraal schriftelijk bekend. Bij deze groepen studenten is onderzoek gedaan naar de relatie tussen de Vwo-prestaties en studiesucces (propedeuse na 1 jaar, na 2 jaar, gemiddeld cijfer voor eerstejaarsonderdelen). De correlatie van het gemiddelde voor het centraal schriftelijk met het gemiddelde cijfer voor eerstejaarsonderdelen bedraagt in de groep geslaagde studenten 0.53.VakpublicatieICLO
A Branched Kinetic Scheme Describes the Mechanochemical Coupling of Myosin Va Processivity in Response to Substrate
Myosin Va is a double-headed cargo-carrying molecular motor that moves processively along cellular actin filaments. Long processive runs are achieved through mechanical coordination between the two heads of myosin Va, which keeps their ATPase cycles out of phase, preventing both heads detaching from actin simultaneously. The biochemical kinetics underlying processivity are still uncertain. Here we attempt to define the biochemical pathways populated by myosin Va by examining the velocity, processive run-length, and individual steps of a Qdot-labeled myosin Va in various substrate conditions (i.e., changes in ATP, ADP, and Pi) under zero load in the single-molecule total internal reflection fluorescence microscopy assay. These data were used to globally constrain a branched kinetic scheme that was necessary to fit the dependences of velocity and run-length on substrate conditions. Based on this model, myosin Va can be biased along a given pathway by changes in substrate concentrations. This has uncovered states not normally sampled by the motor, and suggests that every transition involving substrate binding and release may be strain-dependent. © 2012 Biophysical Society
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