950 research outputs found
Effects of serum proteins on corrosion behavior of ISO 5832â9 alloy modified by titania coatings
Stainless steel ISO 5832â9 type is often used to
perform implants which operate in protein-containing physiological
environments. The interaction between proteins and
surface of the implant may affect its corrosive properties. The
aim of this work was to study the effect of selected serum
proteins (albumin and Îł-globulins) on the corrosion of ISO
5832â9 alloy (trade name M30NW) which surface was modified
by titania coatings. These coatings were obtained by solâ
gel method and heated at temperatures of 400 and 800 °C. To
evaluate the effect of the proteins, the corrosion tests were
performed with and without the addition of proteins with
concentration of 1 g Lâ1 to the physiological saline solution
(0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out
within 7 days. The following electrochemical methods were
used: open circuit potential, linear polarization resistance, and
electrochemical impedance spectroscopy. In addition, surface
analysis by optical microscopy and X-ray photoelectron spectroscopy
(XPS) method was done at the end of weekly corrosion
tests. The results of corrosion tests showed that M30NW
alloy both uncoated and modified with titania coatings exhibits
a very good corrosion resistance during weekly exposition
to corrosion medium. The best corrosion resistance in
0.9 % NaCl solution is shown by alloy samples modified by
titania coating annealed at 400 °C. The serumproteins have no
significant effect onto corrosion of investigated biomedical
steel. The XPS results confirmed the presence of proteins on
the alloy surface after 7 days of immersion in proteincontaining
solutions.The investigations were supported by the National Science Centre project No. N N507 501339. The authors gratefully acknowledge Dr. Janusz
Sobczak and Dr. hab. Wojciech Lisowski from Institute of Physical
Chemistry of PAS for XPS surface analyses
The effects of climatic fluctuations and extreme events on running water ecosystems
Most research on the effects of environmental change in freshwaters has focused on incremental changes in average conditions, rather than fluctuations or extreme events such as heatwaves, cold snaps, droughts, floods or wildfires, which may have even more profound consequences. Such events are commonly predicted to increase in frequency, intensity and duration with global climate change, with many systems being exposed to conditions with no recent historical precedent. We propose a mechanistic framework for predicting potential impacts of environmental fluctuations on running water ecosystems by scaling up effects of fluctuations from individuals to entire ecosystems. This framework requires integration of four key components: effects of the environment on individual metabolism, metabolic and biomechanical constraints on fluctuating species interactions, assembly dynamics of local food webs and mapping the dynamics of the meta-community onto ecosystem function. We illustrate the framework by developing a mathematical model of environmental fluctuations on dynamically assembling food webs. We highlight (currently limited) empirical evidence for emerging insights and theoretical predictions. For example, widely supported predictions about the effects of environmental fluctuations are: high vulnerability of species with high per capita metabolic demands such as large-bodied ones at the top of food webs; simplification of food web network structure and impaired energetic transfer efficiency; reduced resilience and top-down relative to bottom-up regulation of food web and ecosystem processes. We conclude by identifying key questions and challenges that need to be addressed to develop more accurate and predictive bio-assessments of the effects of fluctuations, and implications of fluctuations for management practices in an increasingly uncertain world
Diazepam and its metabolites in the mothers' and newborns' hair as a biomarker of prenatal exposure
Pregnant women are exposed to benzodiazepines for therapeutic purposes during gestation. The goal of this study was to evaluate prenatal exposure to benzodiazepines. Time of exposure during course of pregnancy is a significant aspect of fetal exposure to drugs. Benzodiazepine concentration assay in hair of mothers and newborns exposed prenatally to these drugs was performed in the studies. Development, validation and evaluation of benzodiazepine determination method in mothers and their newborns enables assessment of health risks for the child and implementation of adequate therapeutic procedures. We used A LC-ESI-MS/MS method that allowed determination of diazepam (the main benzodiazepine used by pregnant women was diazepam) and its metabolites (nordazepam, oxazepam) in hair of mothers and newborns. LOQ 10 pg/mg of hair was used in the study. Results: concentration of nordazepam was higher than parent drug (diazepam) and higher in newbornsâ hair when compared to mothersâ. The mean concentrations of diazepam in mothersâ hair were 31.6±36.0 and 34.1±42.4 pg/mg in the second and third trimester of pregnancy respectively. The mean concentration of diazepam in newbornsâ hair was higher and reached levels of 53.3±36.5 pg/mg. The mean concentration of nordazepam in the mothersâ hair corresponding to the second and third trimester was 52.9±48.1 and 89.9±122.8 pg/mg, respectively. Nordazepam in the newbornsâ hair was detected at the mean level of 108.1±144.2 pg/mg. It was concluded that diazepam and nordazepam are permanently incorporated into the hair structure. Presence of diazepam and its metabolites in newbornâs hair confirms that these benzodiazepines permeate placental barrier. Segmental analysis of mothersâ hair enabled the assessment of drug administration time. Diazepam and its metabolites determined in hair of newborns may serve as biomarkers of prenatal exposure to these drugs. The performed LC-MS/MS analysis was accurate enough to determine even low concentrations of benzodiazepines, at the level of few pg/mg of hair. Levels of diazepam detected in hair of newborns were higher than levels determined in mothers. This may confirm the fact, that fetusâs ability to metabolize diazepam is scarce. Nordazepam was found in higher concentrations in hair of newborns than in hair of mothers, which may suggest that it is cumulated in childâs organism. Other metabolites of diazepam - oxazepam and temazepam - were detected in very few cases, in low concentrations
DECam integration tests on telescope simulator
The Dark Energy Survey (DES) is a next generation optical survey aimed at
measuring the expansion history of the universe using four probes: weak
gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and
Type Ia supernovae. To perform the survey, the DES Collaboration is building
the Dark Energy Camera (DECam), a 3 square degree, 570 Megapixel CCD camera
which will be mounted at the Blanco 4-meter telescope at the Cerro Tololo
Inter- American Observatory. DES will survey 5000 square degrees of the
southern galactic cap in 5 filters (g, r, i, z, Y). DECam will be comprised of
74 250 micron thick fully depleted CCDs: 62 2k x 4k CCDs for imaging and 12 2k
x 2k CCDs for guiding and focus. Construction of DECam is nearing completion.
In order to verify that the camera meets technical specifications for DES and
to reduce the time required to commission the instrument, we have constructed a
full sized telescope simulator and performed full system testing and
integration prior to shipping. To complete this comprehensive test phase we
have simulated a DES observing run in which we have collected 4 nights worth of
data. We report on the results of these unique tests performed for the DECam
and its impact on the experiments progress.Comment: Proceedings of the 2nd International Conference on Technology and
Instrumentation in Particle Physics (TIPP 2011). To appear in Physics
Procedia. 8 pages, 3 figure
Chaotic Motion Around Prolate Deformed Bodies
The motion of particles in the field of forces associated to an axially
symmetric attraction center modeled by a monopolar term plus a prolate
quadrupole deformation is studied using Poincare surface of sections and
Lyapunov characteristic numbers. We find chaotic motion for certain values of
the parameters, and that the instability of the orbits increases when the
quadrupole parameter increases. A general relativistic analogue is briefly
discussed.Comment: RevTEX, 7 eps figures, To appear in Phys Rev E (March 2001
Mechanisms of the Vertical Secular Heating of a Stellar Disk
We investigate the nonlinear growth stages of bending instability in stellar
disks with exponential radial density profiles.We found that the unstable modes
are global (the wavelengths are larger than the disk scale lengths) and that
the instability saturation level is much higher than that following from a
linear criterion. The instability saturation time scales are of the order of
one billion years or more. For this reason, the bending instability can play an
important role in the secular heating of a stellar disk in the direction.
In an extensive series of numerical -body simulations with a high spatial
resolution, we were able to scan in detail the space of key parameters (the
initial disk thickness , the Toomre parameter , and the ratio of dark
halo mass to disk mass ). We revealed three distinct
mechanisms of disk heating in the direction: bending instability of the
entire disk, bending instability of the bar, and heating on vertical
inhomogeneities in the distribution of stellar matter.Comment: 22 pages including 8 figures. To be published in Astronomy Letters
(v.29, 2003
Theoretical Directional and Modulated Rates for Direct SUSY Dark Matter Detection
Exotic dark matter together with the vacuum energy (cosmological constant)
seem to dominate in the flat Universe. Thus direct dark matter detection is
central to particle physics and cosmology. Supersymmetry provides a natural
dark matter candidate, the lightest supersymmetric particle (LSP). Furthermore
from the knowledge of the density and velocity distribution of the LSP, the
quark substructure of the nucleon and the nuclear structure (form factor and/or
spin response function), one is able to evaluate the event rate for LSP-nucleus
elastic scattering. The thus obtained event rates are, however, very low. So it
is imperative to exploit the two signatures of the reaction, namely the
modulation effect, i.e. the dependence of the event rate on the Earth's motion,
and the directional asymmetry, i.e. the dependence of the rate on the the
relative angle between the direction of the recoiling nucleus and the sun's
velocity. These two signatures are studied in this paper employing various
velocity distributions and a supersymmetric model with universal boundary
conditions at large tan(beta).Comment: 11 LATEX pages, 1 table and 4 ps figures included. Paper presented in
DARK2002, Fourth Heidelberg International Conference on Dark Matter in Astro-
and Particle Physics, Cape Town, South Africa, 4-9 February, 2002, to appear
in the proceedings (to be published by Springer Verlag
Dark matter and Colliders searches in the MSSM
We study the complementarity between dark matter experiments (direct
detection and indirect detections) and accelerator facilities (the CERN LHC and
a TeV Linear Collider) in the framework of the
constrained Minimal Supersymmetric Standard Model (MSSM). We show how
non--universality in the scalar and gaugino sectors can affect the experimental
prospects to discover the supersymmetric particles. The future experiments will
cover a large part of the parameter space of the MSSM favored by WMAP
constraint on the relic density, but there still exist some regions beyond
reach for some extreme (fine tuned) values of the supersymmetric parameters.
Whereas the Focus Point region characterized by heavy scalars will be easily
probed by experiments searching for dark matter, the regions with heavy
gauginos and light sfermions will be accessible more easily by collider
experiments. More informations on both supersymmetry and astrophysics
parameters can be thus obtained by correlating the different signals.Comment: 25 pages, 10 figures, corrected typos and reference adde
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