1,368 research outputs found
On Recovering the Nonlinear Bias Function from Counts in Cells Measurements
We present a simple and accurate method to constrain galaxy bias based on the
distribution of counts in cells. The most unique feature of our technique is
that it is applicable to non-linear scales, where both dark matter statistics
and the nature of galaxy bias are fairly complex. First, we estimate the
underlying continuous distribution function from precise counts-in-cells
measurements assuming local Poisson sampling. Then a robust, non-parametric
inversion of the bias function is recovered from the comparison of the
cumulative distributions in simulated dark matter and galaxy catalogs.
Obtaining continuous statistics from the discrete counts is the most delicate
novel part of our recipe. It corresponds to a deconvolution of a (Poisson)
kernel. For this we present two alternatives: a model independent algorithm
based on Richardson-Lucy iteration, and a solution using a parametric skewed
lognormal model. We find that the latter is an excellent approximation for the
dark matter distribution, but the model independent iterative procedure is more
suitable for galaxies. Tests based on high resolution dark matter simulations
and corresponding mock galaxy catalogs show that we can reconstruct the
non-linear bias function down to highly non-linear scales with high precision
in the range of . As far as the stochasticity of the bias,
we have found a remarkably simple and accurate formula based on Poisson noise,
which provides an excellent approximation for the scatter around the mean
non-linear bias function. In addition we have found that redshift distortions
have a negligible effect on our bias reconstruction, therefore our recipe can
be safely applied to redshift surveys.Comment: 32 pages, 18 figures; submitted to Ap
Microscopic Magnetic Properties of (VTi)O near the Phase Boundary of the Metal-Insulator Transition
Magnetic susceptibility (chi) and V NMR have been measured in
(VTi)O near the phase boundary of the metal-insulator
transition. It is established that the transition from antiferromagnetic
insulating (AFI) to antiferromagnetic metallic phases near is not quantum critical but is discontinuous with a jump of the
transition temperature. In the AFI phase at 4.2 K, we observed the satellite in
the zero-field V NMR spectrum around 181 MHz in addition to the ``host''
resonance around 203 MHz. The satellite is also observable in the paramagnetic
metallic phase of the x = 0.055 sample. We associated the satellite with the V
sites near Ti which are in the V-like oxidation state but has different
temperature dependence of the NMR shift from that of the host V site. The host
d-spin susceptibility for x = 0.055 decreases below 60 K but remains
finite in the low-temperature limit.Comment: 9 pages, 4 eps figures; corrected the author lis
Small mitochondrial ARF (smARF) is located in both the nucleus and cytoplasm, induces cell death, and activates p53 in mouse fibroblasts
AbstractThe ARF transcript produces two proteins, the full-length ARF, p19ARF, and a short mitochondrial version, smARF. To explore the functional difference between the two, we generated GFP-fused expression vectors for each protein and introduced them into NIH3T3 murine fibroblasts, which sustains a global deletion in the INK4a locus but contains a functional p53 gene. GFP-p19ARF was located within the nucleolus as previously reported, whereas GFP-smARF was detected mainly in the nucleoplasm. GFP-smARF induced cell death although to a slightly lesser extent than p19ARF. GFP-smARF stabilized p53 thereby inducing expression of the target genes, MDM2 and p21. We suggest that smARF has functions other than mitochondria-mediated autophagy, and induces p53 expression and cell death via a novel mechanism
Continuous-wave and Q-switched microchip laser performance of Yb : Y3Sc2Al3O12 crystals
Optical properties of Yb:Y3Sc2Al3O12 crystal were investigated and compared with those from Yb:YAG crystals. The broad absorption and emission spectra of Yb:Y3Sc2Al3O12 show that this crystal is very suitable for laser-diode pumping and ultrafast laser pulse generation. Laser-diode pumped continuous-wave and passively Q-switched Yb:Y3Sc2Al3O12 lasers with Cr4+: YAG crystals as saturable absorber have been demonstrated for the first time. Continuous-wave output power of 1.12 W around 1032 nm ( multi-longitudinal modes) was measured with an optical-to-optical efficiency of 30%. Laser pulses with pulse energy of over 31 mu J and pulse width of 2.5 ns were measured at repetition rate of over 12.7 kHz; a corresponding peak power of over 12 kW was obtained. The longitudinal mode selection by a thin plate of Cr4+: YAG as an intracavity etalon was also observed in passively Q-switched Yb:Y3Sc2Al2O12 microchip lasers. (C) 2008 Optical Society of America
Low serum sodium concentration is a prognostic factor related to current blood glucose level in stable hemodialysis patients : an observational study
Background: A lot of risk factors for mortality have been proposed in hemodialysis patients. However, most of the findings were derived from the analyses using all of the hemodialysis patients. What we really want to know is the prognostic factor in stable hemodialysis patients who have good activities of daily living, because it is difficult to estimate their prognosis by physical appearance.
Methods: This is a 7-year observational study. The study involved registering 631 patients who had undergone hemodialysis for more than 1 year at enrollment and were still alive more than 1 year after it. Demographic and clinical data were collected to analyze the relationship with mortality. Moreover, the patients were age-stratified to investigate age-dependent prognostic factors.
Results: Low serum sodium concentration is an independent risk factor for all-cause and cardiovascular mortality common to a wide range of ages in stable hemodialysis patients. Causes of hyponatremia included the predialysis blood glucose level as well as the variables related to nutrition, inflammation, and fluid overload.
Conclusions: Low serum sodium concentration is a significant prognostic factor in stable hemodialysis patients. Low serum sodium concentration can be a clue to finding current poor glucose control in stable hemodialysis patients. Predialysis blood glucose level is one of the representative factors correlated with serum sodium concentration
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