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On the boundary-layer structure of patterns of convection in rectangular-planform containers
This paper considers the structure of steady-state solutions of the Swift–Hohenberg
equation describing convection in shallow rectangular-planform containers heated
from below. The lateral dimensions of the planform are assumed to be much larger
than the characteristic wavelength of convection. Results are restricted to patterns
composed of rolls orthogonal to the sides of the rectangle in which case convection
sets in at a critical value of the Rayleigh number in the form of rolls parallel to
the shorter sides. This primary bifurcation from the conductive state of no motion
produces a solution which subsequently undergoes a secondary bifurcation in which
the low-amplitude motion near the shorter sides is replaced locally by cross-rolls
perpendicular to the sides. This results in the formation of grain boundaries (or
domain boundaries) within the fluid which mark the division between the different
roll orientations.With increasing Rayleigh number the grain boundaries approach the sides of the
rectangle and a boundary-layer structure is formed. In the present paper the method
of matched asymptotic expansions is used to determine this boundary-layer structure
and to predict the location of the grain boundaries. An interesting feature of the
solution is that the grain boundaries develop significant curvature and bend into the
corners of the rectangle, where the local solution is also determined.The results are compared with numerical computations of the secondary solution
branch and with previous numerical and experimental work.</jats:p
Resting respiratory tract dendritic cells preferentially stimulate T helper cell Type 2(Th2) responses and require obligatory cytokine signals for induction of Th1 immunity
Consistent with their role in host defense, mature dendritic cells (DCs) from central lymphoid organs preferentially prime for T helper cell type 1 (Th1)-polarized immunity. However, the “default” T helper response at mucosal surfaces demonstrates Th2 polarity, which is reflected in the cytokine profiles of activated T cells from mucosal lymph nodes. This study on rat respiratory tract DCs (RTDCs) provides an explanation for this paradox. We demonstrate that freshly isolated RTDCs are functionally immature as defined in vitro, being surface major histocompatibility complex (MHC) II lo, endocytosishi, and mixed lymphocyte reactionlo, and these cells produce mRNA encoding interleukin (IL)-10. After ovalbumin (OVA)-pulsing and adoptive transfer, freshly isolated RTDCs preferentially stimulated Th2-dependent OVA-specific immunoglobulin (Ig)G1 responses, and antigen-stimulated splenocytes from recipient animals produced IL-4 in vitro. However, preculture with granulocyte/macrophage colony stimulating factor increased their in vivo IgG priming capacity by 2–3 logs, inducing production of both Th1- and Th2-dependent IgG subclasses and high levels of IFN-γ by antigen-stimulated splenocytes. Associated phenotypic changes included upregulation of surface MHC II and B7 expression and IL-12 p35 mRNA, and downregulation of endocytosis, MHC II processing– associated genes, and IL-10 mRNA expression. Full expression of IL-12 p40 required additional signals, such as tumor necrosis factor α or CD40 ligand. These results suggest that the observed Th2 polarity of the resting mucosal immune system may be an inherent property of the resident DC population, and furthermore that mobilization of Th1 immunity relies absolutely on the provision of appropriate microenvironmental costimuli
Magnetization of Charge-ordered la(2-x)sr(x)nio(4+delta)
We report magnetization measurements on La(2-x)Sr(x)NiO(4+ delta) single
crystals, with 0 < x < 0.5. Glassy behaviour associated with the formation of
spin-charge stripes, and a separate spin-glass phase at low temperatures were
observed. We have also found a `memory effect' in the magnetic field --
temperature history, which is found to be suppressed in the low temperature
spin state of the x = 0.33 crystal.Comment: 2 pages, 2 figures. Presented at ICM2003 to appear in J. Magn. Magn.
Mat
Magnetic Order and Dynamics in Stripe-Ordered La2-xSrxNiO4
We have studied magnetic correlations in several compositions of
stripe-ordered La2-xSrxNiO4. In this paper we show how polarized-neutron
scattering has helped uncover important features of the magnetic ordering and
spin dynamics. In particular, polarization analysis has enabled us (1) to
characterize a spin reorientation transition, (2) to identify anisotropy gaps
in the spin excitation spectrum, and (3) to investigate an anomalous dip in the
spin-wave intensity suggestive of coupling between collective spin and charge
excitations.Comment: 4 pages, 3 figs. Presented at PNSXM, Venice. To appear in Physica
High speed video capture for mobile phone cameras
We consider an electromechanical model for the operation of a voice coil motor in a mobile phone camera, with the aim of optimizing how a lens can be moved to a desired focusing motion. Although a methodology is developed for optimizing lens shift, there is some concern about the experimentally-determined model parameters that are at our disposal. Central to the model is the value of the estimated magnetic force constant, Kf: its value determines how far it is actually possible to move lens, but it appears that, from the value given, it would not be possible to shift the lens through the displacements desired. Furthermore, earlier experiments have also estimated the value of the back EMF constant, Kg , to be roughly five times greater than Kf, even though we present two theoretical arguments that show that Kf = Kg: a conclusion supported by readily-available manufacturers’ data
Quantum-to-classical crossover of mesoscopic conductance fluctuations
We calculate the system-size-over-wave-length () dependence of
sample-to-sample conductance fluctuations, using the open kicked rotator to
model chaotic scattering in a ballistic quantum dot coupled by two -mode
point contacts to electron reservoirs. Both a fully quantum mechanical and a
semiclassical calculation are presented, and found to be in good agreement. The
mean squared conductance fluctuations reach the universal quantum limit of
random-matrix-theory for small systems. For large systems they increase
at fixed mean dwell time . The universal
quantum fluctuations dominate over the nonuniversal classical fluctuations if
. When expressed as a ratio of time scales, the
quantum-to-classical crossover is governed by the ratio of Ehrenfest time and
ergodic time.Comment: 5 pages, 5 figures: one figure added, references update
Neutron scattering study of the effects of dopant disorder on the superconductivity and magnetic order in stage-4 La_2CuO_{4+y}
We report neutron scattering measurements of the structure and magnetism of
stage-4 La_2CuO_{4+y} with T_c ~42 K. Our diffraction results on a single
crystal sample demonstrate that the excess oxygen dopants form a
three-dimensional ordered superlattice within the interstitial regions of the
crystal. The oxygen superlattice becomes disordered above T ~ 330 K, and a fast
rate of cooling can freeze-in the disordered-oxygen state. Hence, by
controlling the cooling rate, the degree of dopant disorder in our
La_2CuO_{4+y} crystal can be varied. We find that a higher degree of quenched
disorder reduces T_c by ~ 5 K relative to the ordered-oxygen state. At the same
time, the quenched disorder enhances the spin density wave order in a manner
analogous to the effects of an applied magnetic field.Comment: 4 figures included in text; submitted to PR
Experimental preparation of Werner state via spontaneous parametric down-conversion
We present an experiment of preparing Werner state via spontaneous parametric
down-conversion and controlled decoherence of photons in this paper. In this
experiment two independent BBO (beta-barium borate) crystals are used to
produce down-conversion light beams, which are mixed to prepare Werner state.Comment: 6 pages, 4 figures and 2 table
Transient thermal characterization of suspended monolayer MoS
We measure the thermal time constants of suspended single layer molybdenum
disulfide drums by their thermomechanical response to a high-frequency
modulated laser. From this measurement the thermal diffusivity of single layer
MoS is found to be 1.14 10 m/s on average. Using a
model for the thermal time constants and a model assuming continuum heat
transport, we extract thermal conductivities at room temperature between 10 to
40 W/(mK). Significant device-to-device variation in the thermal
diffusivity is observed. Based on statistical analysis we conclude that these
variations in thermal diffusivity are caused by microscopic defects that have a
large impact on phonon scattering, but do not affect the resonance frequency
and damping of the membrane's lowest eigenmode. By combining the experimental
thermal diffusivity with literature values of the thermal conductivity, a
method is presented to determine the specific heat of suspended 2D materials,
which is estimated to be 255 104 J/(kgK) for single layer MoS
The relationship between fetal growth and retinal nerve fiber layer thickness in a cohort of young adults
Purpose: To explore relationships between patterns of fetal anthropometric growth, as reflective of fetal wellbeing, and global retinal nerve fiber layer (RNFL) thickness measured in young adulthood.
Methods: Participants (n = 481) from within a Western Australian pregnancy cohort study underwent five serial ultrasound scans during gestation, with fetal biometry measured at each scan. Optic disc parameters were measured via spectral-domain optical coherence tomography imaging at a 20-year follow-up eye examination. Generalized estimating equations were used to evaluate differences in global RNFL thickness between groups of participants who had undergone similar growth trajectories based on fetal head circumference (FHC), abdominal circumference (FAC), femur length (FFL), and estimated fetal weight (EFW).
Results: Participants with consistently large FHCs throughout gestation had significantly thicker global RNFLs than those with any other pattern of FHC growth (P = 0.023), even after adjustment for potential confounders (P = 0.037). Based on model fit statistics, FHC growth trajectory was a better predictor of global RNFL thickness than birth weight or head circumference at birth. RNFL thickness did not vary significantly between groups of participants with different growth trajectories based on FAC, FFL, or EFW.
Conclusions: FHC growth is associated with RNFL thickness in young adulthood and, moreover, is a better predictor than either birth weight or head circumference at birth.
Translational Relevance: This research demonstrates an association between intrauterine growth and long-term optic nerve health, providing a basis for further exploring the extent of the influence of fetal wellbeing on clinical conditions linked to RNFL thinning
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