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Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 2: Partially Sealed Configuration
Experimental results from a partially sealed squeeze film damper (SFD) test rig, executing a circular centered orbit are presented and discussed. A serrated piston ring is installed at the damper exit. This device involves a new sealing concept which produces high damping values while allowing for oil flow to cool the damper. In the partially sealed damper, large cavitation regions are observed in the pressure fields at orbit radii epsilon equals 0.5 and epsilon equals 0.8. The cavitated pressure distributions and the corresponding force coefficients are compared with a cavitated bearing solution. The experimental results show the significance of fluid inertia and vapor cavitation in the operation of squeeze film dampers. Squeeze film Reynolds numbers tested reach up to Re equals 50, spanning the range of contemporary applications
Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 1: Fully Open Ended Configuration
Measurements of pressure distributions and force coefficients were carried out in two types of squeeze film dampers, executing a circular centered orbit, an open-ended configuration, and a partially sealed one, in order to investigate the effect of fluid inertia and cavitation on pressure distributions and force coefficients. Dynamic pressure measurements were carried out for two orbit radii, epsilon 0.5 and 0.8. It was found that the partially sealed configuration was less influenced by fluid inertia than the open ended configuration
Infrared optical absorption spectra of CuO single crystals: Fermion-spinon band and dimensional crossover of the antiferromagnetic order
We have obtained mid-infrared optical absorption spectra of the S=1/2 quasi
one-dimensional CuO using polarized transmission measurement and interpreted
the spectra in terms of phonon assisted magnetic excitations. When the electric
field is parallel to the main antiferromagnetic direction a Delta shaped peak
is observed with the maximum at 0.23eV which is attributed to spinons along
Cu-O chains. At low temperatures in the antiferromagnetic phase another peak
appears at 0.16eV which is attributed to two-magnon absorption but the spinon
peak remains. This behavior is interpreted as due to a dimensional crossover
where the low temperature three-dimensional magnetic phase keeps short range
characteristics of a one-dimensional magnet.Comment: 5 pages, 5 figure
Infrared Hall conductivity of NaCoO
We report infrared Hall conductivity of
NaCoO thin films determined from Faraday rotation angle
measurements. exhibits two types of hole
conduction, Drude and incoherent carriers. The coherent Drude carrier shows a
large renormalized mass and Fermi liquid-like behavior of Hall scattering rate,
. The spectral weight is suppressed and disappears at T
= 120K. The incoherent carrier response is centered at mid-IR frequency and
shifts to lower energy with increasing T. Infrared Hall constant is positive
and almost independent of temperature in sharp contrast with the dc-Hall
constant.Comment: 5 Pages, 5 Figures. Author list corrected in metadata only, paper is
unchange
Comprehensive structural model of the mechanochemical cycle of a mitotic motor highlights molecular adaptations in the kinesin family
Kinesins are responsible for a wide variety of microtubule-based, ATP-dependent
functions. Their motor domain drives these activities but the molecular adaptations
that specify these diverse and essential cellular activities are poorly understood. It
has been assumed that the first identified kinesin - the transport motor kinesin-1 – is
the mechanistic paradigm for the entire superfamily, but accumulating evidence
suggests that this is not the case. To address the deficits in our understanding of the
molecular basis of functional divergence within the kinesin superfamily, we studied
kinesin-5s, which are essential mitotic motors whose inhibition blocks cell division.
Using cryo-electron microscopy and subnanometer resolution structure
determination, we have visualised conformations of microtubule-bound human
kinesin-5 motor domain at successive steps in its ATPase cycle. Following ATP
hydrolysis, nucleotide-dependent conformational changes in the active site are
allosterically propagated into rotations of the motor domain and uncurling of the drugbinding
loop L5. In addition, the mechanical neck-linker element that is crucial for
motor stepping undergoes discrete, ordered displacements. We also observed large
reorientations of the motor N-terminus that indicate its importance for kinesin-5
function through control of neck-linker conformation. A kinesin-5 mutant lacking this
N-terminus is enzymatically active, and ATP-dependent neck-linker movement and
motility is defective although not ablated. All these aspects of kinesin-5
mechanochemistry are distinct from kinesin-1. Our findings directly demonstrate the
regulatory role of the kinesin-5 N-terminus in collaboration with the motor’s structured
neck-linker, and highlight the multiple adaptations within kinesin motor domains that
tune their mechanochemistries according to distinct functional requirements
Spin/Orbital Pattern-Dependent Polaron Absorption in Nd(1-x)Sr(x)MnO3
We investigated optical properties of Nd(1-x)Sr(x)MnO3 (x= 0.40, 0.50, 0.55,
and 0.65) single crystals. In the spin/orbital disordered state, their
conductivity spectra look quite similar, and the strength of the mid-infrared
absorption peak is proportional to x(1-x) consistent with the polaron picture.
As temperature lowers, the Nd(1-x)Sr(x)MnO3 samples enter into various
spin/orbital ordered states, whose optical responses are quite different. These
optical responses can be explained by the spin/orbital ordering
pattern-dependent polaron hopping.Comment: 3 figures (gzipped
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