6,800 research outputs found
Preoperative predictors of knee range of motion during stair walking after total knee replacement
This paper discusses the preoperative predictors of knee range of motion during stair walking after total knee replacement. It was presented at the 17th Annual Meeting of the European Society of Movement Analysis for Adults and Children (ESMAC) in 2008
The X-ray Transient XTE J2012+381
We present optical and infrared observations of the soft X-ray transient
(SXT) XTE J2012+381 and identify the optical counterpart with a faint red star
heavily blended with a brighter foreground star. The fainter star is coincident
with the radio counterpart and appears to show weak H alpha emission and to
have faded between observations. The RXTE/ASM lightcurve of XTE J2012+381 is
unusual for an SXT in that after an extended linear decay, it settled into a
plateau state for about 40 days before undergoing a weak mini-outburst. We
discuss the nature of the object and suggest similarities to long orbital
period SXTs.Comment: 5 pages, 7 postscript figures included, uses mn.sty. Accepted for
publication in MNRA
Quantum turbulence at finite temperature: the two-fluids cascade
To model isotropic homogeneous quantum turbulence in superfluid helium, we
have performed Direct Numerical Simulations (DNS) of two fluids (the normal
fluid and the superfluid) coupled by mutual friction. We have found evidence of
strong locking of superfluid and normal fluid along the turbulent cascade, from
the large scale structures where only one fluid is forced down to the vorticity
structures at small scales. We have determined the residual slip velocity
between the two fluids, and, for each fluid, the relative balance of inertial,
viscous and friction forces along the scales. Our calculations show that the
classical relation between energy injection and dissipation scale is not valid
in quantum turbulence, but we have been able to derive a temperature--dependent
superfluid analogous relation. Finally, we discuss our DNS results in terms of
the current understanding of quantum turbulence, including the value of the
effective kinematic viscosity
Vortex density spectrum of quantum turbulence
The fluctuations of the vortex density in a turbulent quantum fluid are
deduced from local second-sound attenuation measurements. These measurements
are performed with a micromachined open-cavity resonator inserted across a flow
of turbulent He-II near 1.6 K. The power spectrum of the measured vortex line
density is compatible with a (-5/3) power law. The physical interpretation,
still open, is discussed.Comment: Submitted to Europhys. Let
The human milk protein-lipid complex HAMLET disrupts glycolysis and induces death in Streptococcus pneumoniae
HAMLET is a complex of human a-lactalbumin (ALA) and oleic acid and kills several Gram-positive bacteria by a mechanism that bears resemblance to apoptosis in eukaryotic cells. To identify HAMLET's bacterial targets, here we used Streptococcus pneumoniae as a model organism and employed a proteomic approach that identified several potential candidates. Two of these targets were the glycolytic enzymes fructose bis-phosphate aldolase (FBPA) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Treatment of pneumococci with HAMLET immediately inhibited their ATP and lactate production, suggesting that HAMLET inhibits glycolysis. This observation was supported by experiments with recombinant bacterial enzymes, along with biochemical and bacterial viability assays, indicating that HAMLET's activity is partially inhibited by high glucose-mediated stimulation of glycolysis but enhanced in the presence of the glycolysis inhibitor 2-deoxyglucose. Both HAMLET and ALA bound directly to each glycolytic enzyme in solution and solid phase assays and effectively inhibited their enzymatic activities. In contrast, oleic acid alone had little to no inhibitory activity. However, ALA alone also exhibited no bactericidal activity and did not block glycolysis in whole cells, suggesting a role for the lipid moiety in the internalization of HAMLET into the bacterial cells to reach its target(s). This was verified by inhibition of enzyme activity in whole cells after HAMLET but not ALA exposure. The results of this study suggest that part of HAMLET's antibacterial activity relates to its ability to target and inhibit glycolytic enzymes, providing an example of a natural antimicrobial agent that specifically targets glycolysis
Distribution of dust clouds around the central engine of NGC 1068
We studied the distribution of dust clouds around the central engine of NGC
1068 based on shifted-and-added 8.8 - 12.3 micron (MIR) multi-filter images and
3.0 - 3.9 micron (L-band) spectra obtained with the Subaru Telescope. In a
region of 100 pc (1.4") around the central peak, we successfully constructed
maps of color temperatures and emissivities of the MIR and L-band continua as
well as the 9.7 micron and 3.4 micron dust features with spatial resolutions of
26 pc (0.37") in the MIR and 22 pc (0.3") in the L-band. Our main results are:
1) color temperature of the MIR continuum scatters around the thermal
equilibrium temperature with the central engine as the heat source while that
of the L-band continuum is higher and independent upon distance from the
central engine; 2) the peak of the 9.7 micron silicate absorption feature is
shifted to a longer wavelength at some locations; 3) the ratio of the optical
depths of the dust features is different from the Galactic values and show
complicated spatial distribution; and 4) there is a pie shaped warm dust cloud
as an enhancement in the emissivity of the MIR continuum extending about 50 pc
to the north from the central engine. We speculate that material falls into the
central engine through this cloud.Comment: 26 pages, 9 figures. Accepted for publication on Ap
High Resolution Imaging of the Magnetic Field in the central parsec of the Galaxy
We discuss a high resolution (FWHM~ 0.45 arcsec) image of the emissive
polarization from warm dust in the minispiral in the Galactic Centre and
discuss the implications for the magnetic field in the dusty filaments. The
image was obtained at a wavelength of 12.5 microns with the CanariCam multimode
mid-infrared imager on the Gran Telescopio Canarias. It confirms the results
obtained from previous observations but also reveals new details of the
polarization structures. In particular, we identify regions of coherent
magnetic field emission at position angles of ~45 deg to the predominantly
north--south run of field lines in the Northern Arm which may be related to
orbital motions inclined to the general flow of the Northern Arm. The luminous
stars that have been identified as bow-shock sources in the Northern Arm do not
disrupt or dilute the field but are linked by a coherent field structure,
implying that the winds from these objects may push and compress the field but
do not overwhelm it. The magnetic field in the the low surface brightness
regions in the East-West Bar to the south of SgrA* lies along the Bar, but the
brighter regions generally have different polarization position angles,
suggesting that they are distinct structures. In the region of the Northern Arm
sampled here, there is only a weak correlation between the intensity of the
emission and the degree of polarization. This is consistent with saturated
grain alignment where the degree of polarization depends on geometric effects,
including the angle of inclination of the field to the line of sight and
superposition of filaments with different field directions, rather than the
alignment efficiency.Comment: 9 pages, 3 figures, Proceedings of Cosmic Dust X, held in Mitaka,
Japan in August 201
Mesoscale Equipartition of kinetic energy in Quantum Turbulence
The turbulence of superfluid helium is investigated numerically at finite
temperature. Direct numerical simulations are performed with a "truncated HVBK"
model, which combines the continuous description of the
Hall-Vinen-Bekeravich-Khalatnikov equations with the additional constraint that
this continuous description cannot extend beyond a quantum length scale
associated with the mean spacing between individual superfluid vortices. A good
agreement is found with experimental measurements of the vortex density.
Besides, by varying the turbulence intensity only, it is observed that the
inter-vortex spacing varies with the Reynolds number as , like the
viscous length scale in classical turbulence. In the high temperature limit,
Kolmogorov's inertial cascade is recovered, as expected from previous numerical
and experimental studies. As the temperature decreases, the inertial cascade
remains present at large scales while, at small scales, the system evolves
towards a statistical equipartition of kinetic energy among spectral modes,
with a characteristic velocity spectrum. The accumulation of superfluid
excitations on a range of mesoscales enables the superfluid to keep dissipating
kinetic energy through mutual friction with the residual normal fluid, although
the later becomes rare at low temperature. It is found that most of the
superfluid vorticity can concentrate on these mesoscales at low temperature,
while it is concentrated in the inertial range at higher temperature. This
observation should have consequences on the interpretation of decaying
turbulence experiments, which are often based on vortex line density
measurements.Comment: 6 pages, 5 figure
Fluctuation-Dissipation Relations of a Tunnel Junction Driven by a Quantum Circuit
We derive fluctuation-dissipation relations for a tunnel junction driven by a
high impedance microwave resonator, displaying strong quantum fluctuations. We
find that the fluctuation-dissipation relations derived for classical forces
hold, provided the effect of the circuit's quantum fluctuations is incorporated
into a modified non-linear curve. We also demonstrate that all
quantities measured under a coherent time dependent bias can be reconstructed
from their dc counterpart with a photo-assisted tunneling relation. We confirm
these predictions by implementing the circuit and measuring the dc current
through the junction, its high frequency admittance and its current noise at
the frequency of the resonator.Comment: Publisehd as Physical Review Letters, 114, 12680
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