326 research outputs found
Optical properties of the charge-density-wave polychalcogenide compounds Te (=Nd, Sm and Gd)
We investigate the rare-earth polychalcogenide Te (=Nd, Sm and
Gd) charge-density-wave (CDW) compounds by optical methods. From the absorption
spectrum we extract the excitation energy of the CDW gap and estimate the
fraction of the Fermi surface which is gapped by the formation of the CDW
condensate. In analogy to previous findings on the related Te (n=2 and
3) families, we establish the progressive closing of the CDW gap and the
moderate enhancement of the metallic component upon chemically compressing the
lattice
Fermi Surface reconstruction in the CDW state of CeTe3 observed by photoemission
CeTe3 is a layered compound where an incommensurate Charge Density Wave (CDW)
opens a large gap (400 meV) in optimally nested regions of the Fermi Surface
(FS), whereas other sections with poorer nesting remain ungapped. Through
Angle-Resolved Photoemission, we identify bands backfolded according to the CDW
periodicity. They define FS pockets formed by the intersection of the original
FS and its CDW replica. Such pockets illustrate very directly the role of
nesting in the CDW formation but they could not be detected so far in a CDW
system. We address the reasons for the weak intensity of the folded bands, by
comparing different foldings coexisting in CeTe3
Charge density wave formation in Te (=Nd, Sm and Gd)
The rare earth () tellurides Te have a crystal structure
intermediate between that of Te and Te, consisting of alternating
single and double Te planes sandwiched between Te block layers. We have
successfully grown single crystals of NdTe, SmTe and
GdTe from a self flux, and describe here the first evidence for charge
density wave formation in these materials. The superlattice patterns for all
three compounds are relatively complex, consisting at room temperature of at
least two independent wavevectors. Consideration of the electronic structure
indicates that to a large extent these wave vectors are separately associated
with sheets of the Fermi surface which are principally derived from the single
and double Te layers.Comment: 10 pages, 6 figure
The p53 codon 72 PRO/PRO genotype may be associated with initial central visual field defects in Caucasians with primary open angle glaucoma
Background: Loss of vision in glaucoma is due to apoptotic retinal ganglion cell loss. While p53 modulates apoptosis, gene
association studies between p53 variants and glaucoma have been inconsistent. In this study we evaluate the association
between a p53 variant functionally known to influence apoptosis (codon 72 Pro/Arg) and the subset of primary open angle
glaucoma (POAG) patients with early loss of central visual field.
Methods: Genotypes for the p53 codon 72 polymorphism (Pro/Arg) were obtained for 264 POAG patients and 400 controls
from the U.S. and in replication studies for 308 POAG patients and 178 controls from Australia (GIST). The glaucoma patients
were divided into two groups according to location of initial visual field defect (either paracentral or peripheral). All cases
and controls were Caucasian with European ancestry.
Results: The p53-PRO/PRO genotype was more frequent in the U.S. POAG patients with early visual field defects in the
paracentral regions compared with those in the peripheral regions or control group (p = 2.761025). We replicated this
finding in the GIST cohort (p = 7.361023, and in the pooled sample (p = 6.661027) and in a meta-analysis of both the US
and GIST datasets (1.361026, OR 2.17 (1.58–2.98 for the PRO allele).
Conclusions: These results suggest that the p53 codon 72 PRO/PRO genotype is potentially associated with early
paracentral visual field defects in primary open-angle glaucoma patients.NHMRC: This study was supported by National Institutes of Health/National Eye Institute grants: R01EY015872 (Wiggs), R01EY015473 (Pasquale), P30EY014104
(Wiggs), Research to Prevent Blindness (Wiggs, Pasquale, Realini), the Harvard Glaucoma Center of Excellence (Wiggs, Pasquale), The Massachusetts Lions Eye
Research Fund (Wiggs, Pasquale), National Health & Medical Research Council Project grant 229960, the Ophthalmic Research Institute of Australia, and Glaucoma
Australia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Microscopic View on Short-Range Wetting at the Free Surface of the Binary Metallic Liquid Gallium-Bismuth: An X-ray Reflectivity and Square Gradient Theory Study
We present an x-ray reflectivity study of wetting at the free surface of the
binary liquid metal gallium-bismuth (Ga-Bi) in the region where the bulk phase
separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the
evolution of the microscopic structure of wetting films of the Bi-rich,
low-surface-tension phase along different paths in the bulk phase diagram. A
balance between the surface potential preferring the Bi-rich phase and the
gravitational potential which favors the Ga-rich phase at the surface pins the
interface of the two demixed liquid metallic phases close to the free surface.
This enables us to resolve it on an Angstrom level and to apply a mean-field,
square gradient model extended by thermally activated capillary waves as
dominant thermal fluctuations. The sole free parameter of the gradient model,
i.e. the so-called influence parameter, , is determined from our
measurements. Relying on a calculation of the liquid/liquid interfacial tension
that makes it possible to distinguish between intrinsic and capillary wave
contributions to the interfacial structure we estimate that fluctuations affect
the observed short-range, complete wetting phenomena only marginally. A
critical wetting transition that should be sensitive to thermal fluctuations
seems to be absent in this binary metallic alloy.Comment: RevTex4, twocolumn, 15 pages, 10 figure
Non-compartment model to compartment model pharmacokinetics transformation meta-analysis – a multivariate nonlinear mixed model
Background
To fulfill the model based drug development, the very first step is usually a model establishment from published literatures. Pharmacokinetics model is the central piece of model based drug development. This paper proposed an important approach to transform published non-compartment model pharmacokinetics (PK) parameters into compartment model PK parameters. This meta-analysis was performed with a multivariate nonlinear mixed model. A conditional first-order linearization approach was developed for statistical estimation and inference.
Results
Using MDZ as an example, we showed that this approach successfully transformed 6 non-compartment model PK parameters from 10 publications into 5 compartment model PK parameters. In simulation studies, we showed that this multivariate nonlinear mixed model had little relative bias (<1%) in estimating compartment model PK parameters if all non-compartment PK parameters were reported in every study. If there missing non-compartment PK parameters existed in some published literatures, the relative bias of compartment model PK parameter was still small (<3%). The 95% coverage probabilities of these PK parameter estimates were above 85%.
Conclusions
This non-compartment model PK parameter transformation into compartment model meta-analysis approach possesses valid statistical inference. It can be routinely used for model based drug development
Groundwater of Rome
This paper describes the contents of the new Hydrogeological Map of the City of Rome (1:50,000 scale). The map extends to the entire municipality (1285 km2) and is based on both the most recent scientific studies on the groundwater field and new survey activities carried out in order to fill the data gaps in several areas of the examined territory. The map is the result of a combination of different urban groundwater expertise and Geographic Information System (GIS)-based mapping performed using the most recent available data and has been produced with the intention of furnishing the City of Rome with the most recent and updated information regarding groundwater
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