6,659 research outputs found
Motor regulation results in distal forces that bend partially disintegrated Chlamydomonas axonemes into circular arcs
The bending of cilia and flagella is driven by forces generated by dynein
motor proteins. These forces slide adjacent microtubule doublets within the
axoneme, the motile cytoskeletal structure. To create regular, oscilla- tory
beating patterns, the activities of the axonemal dyneins must be coordinated
both spatially and temporally. It is thought that coordination is mediated by
stresses or strains, which build up within the moving axoneme, and somehow
regulate dynein activity. While experimenting with axonemes subjected to mild
proteolysis, we observed pairs of doublets associate with each other and form
bends with almost constant curvature. By model- ing the statics of a pair of
filaments, we show that the activity of the motors concentrates at the distal
tips of the doublets. Furthermore, we show that this distribution of motor
activity accords with models in which curvature, or curvature-induced normal
forces, regulates the activity of the motors. These observations, together with
our theoretical analysis, provide evidence that dynein activity can be
regulated by curvature or normal forces, which may, therefore, play a role in
coordinating the beating of cilia and flagella
Detailed analysis of quantum phase transitions within the algebra
We analyze in detail the quantum phase transitions that arise in models based
on the algebraic description for bosonic systems with two types of
scalar bosons. First we discuss the quantum phase transition that occurs in
hamiltonians that admix the two dynamical symmetry chains
and by diagonalizing the problem exactly in the
basis. Then we apply the coherent state formalism to determine the energy
functional. Finally we show that a quantum phase transition of a different
nature, but displaying similar characteristics, may arise also within a single
chain just by including higher order terms in the hamiltonian.Comment: 5 figure
Avaliação preliminar da reação de cultivares de trigo a brusone em condições de campo.
bitstream/item/119385/1/FOL-06040.pd
Avaliação preliminar da reação de cultivares de trigo à brusone em condições de campo.
bitstream/item/84366/1/CNPT-COM.-TEC.-1-88.pd
Totem: a case study in HEP
It is being proved that the neurochip \Totem{} is a viable solution for high
quality and real time computational tasks in HEP, including event
classification, triggering and signal processing. The architecture of the chip
is based on a "derivative free" algorithm called Reactive Tabu Search (RTS),
highly performing even for low precision weights. ISA, VME or PCI boards
integrate the chip as a coprocessor in a host computer. This paper presents: 1)
the state of the art and the next evolution of the design of \Totem{}; 2) its
ability in the Higgs search at LHC as an example.Comment: Latex, elsart.sty, 5 pages, talk presented by I.Lazzizzera at CHEP97
(Berlin, April 1997
Cross-cultural validation and measurement invariance of the Short Grit scale (Grit-S): preliminary results.
Preliminary results of a cross-cultural validation of the Grit -
Analysis of a fluvial groynes system on hydraulic scale model
River morphodynamics and sediment transportSediment-structure interactio
Geometric invariant theory approach to the determination of ground states of D-wave condensates in isotropic space
A complete and rigorous determination of the possible ground states for
D-wave pairing Bose condensates is presented, using a geometrical invariant
theory approach to the problem. The order parameter is argued to be a vector,
transforming according to a ten dimensional real representation of the group
{\bf O}{\bf U}. We determine the equalities
and inequalities defining the orbit space of this linear group and its symmetry
strata, which are in a one-to-one correspondence with the possible distinct
phases of the system. We find 15 allowed phases (besides the unbroken one),
with different symmetries, that we thoroughly determine. The group-subgroup
relations between bordering phases are pointed out. The perturbative sixth
degree corrections to the minimum of a fourth degree polynomial -invariant
free energy, calculated by Mermin, are also determined.Comment: 27 revtex pages, 2 figures, use of texdraw; minor changes in the
bibliography and in Table II
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