268 research outputs found
Core-shell Structured Composite Silica Micro- and Nanoparticles with Ability Release a De fined Quantity „on Demand“
The aim of this work was the preparation of biocompatible micro- and nanoparticles with a hollow in-terrior. The particles must be able to encapsulate and store a chemical payload for a certain time, followed by the release on demand of this payload. In our previous work [13] we have prepared silica microparticles with a hollow core and found that the diffusion across the mesoporous silica shell was strongly dependent on temperature. In this work, we used this dependence and attached iron oxide nanoparticles on the sur-face of the silica shell to create composite iron oxide/silica particles. The iron oxide nanoparticles were able to heat up in the presence of an alternating magnetic field. This property allowed us to use magnetic field as a tool for remote control of diffusion across the particle shell. To avoid spontaneous leakage of encapsu-lated payload in time, we have modified the surface of the composite micropaticles with a layer of palm oil. Palm oil is a phase change material which is solid under 37 °C. We showed that the resultant composite particles are able to store a payload for several months and release a defined quantity on demand by the application of a magnetic field. The particles were characterised in shape, size, heating ability and their mass transport properties.
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Research Activities for the DORIS Contribution to the Next International Terrestrial Reference Frame
For the preparation of ITRF2008, the IDS processed data from 1993 to 2008, including data from TOPEX/Poseidon, the SPOT satellites and Envisat in the weekly solutions. Since the development of ITRF2008, the IDS has been engaged in a number of efforts to try and improve the reference frame solutions. These efforts include (i) assessing the contribution of the new DORIS satellites, Jason-2 and Cryosat2 (2008-2011), (ii) individually analyzing the DORIS satellite contributions to geocenter and scale, and (iii) improving orbit dynamics (atmospheric loading effects, satellite surface force modeling. . . ). We report on the preliminary results from these research activities, review the status of the IDS combination which is now routinely generated from the contributions of the IDS analysis centers, and discuss the prospects for continued improvement in the DORIS contribution to the next international reference frame
The event generator DECAY4 for simulation of double beta processes and decay of radioactive nuclei
The computer code DECAY4 is developed to generate initial energy, time and
angular distributions of particles emitted in radioactive decays of nuclides
and nuclear (atomic) deexcitations. Data for description of nuclear and atomic
decay schemes are taken from the ENSDF and EADL database libraries. The
examples of use of the DECAY4 code in several underground experiments are
described.Comment: 8 pages, 1 fi
Dynamic Critical Phenomena of Polymer Solutions
Recently, a systematic experiment measuring critical anomaly of viscosity of
polymer solutions has been reported by H. Tanaka and his co-workers
(Phys.Rev.E, 65, 021802, (2002)). According to their experiments, the dynamic
critical exponent of viscosity y_c drastically decreases with increasing the
molecular weight. In this article the kinetic coefficients renormalized by the
non-linear hydrodynamic interaction are calculated by the mode coupling theory.
We predict that the critical divergence of viscosity should be suppressed with
increasing the molecular weight. The diffusion constant and the dynamic
structure factor are also calculated. The present results explicitly show that
the critical dynamics of polymer solutions should be affected by an extra
spatio-temporal scale intrinsic to polymer solutions, and are consistent with
the experiment of Tanaka, et al.Comment: 17 pages, 2 figures, to be published in J.Phys.Soc.Jp
Measurements of Differential Reflectivity in Snowstorms and Warm Season Stratiform Systems
The organized behavior of differential radar reflectivity (ZDR) is documented in the cold regions of a wide variety of stratiform precipitation types occurring in both winter and summer. The radar targets and attendant cloud microphysical conditions are interpreted within the context of measurements of ice crystal types in laboratory diffusion chambers in which humidity and temperature are both stringently controlled. The overriding operational interest here is in the identification of regions prone to icing hazards with long horizontal paths. Two predominant regimes are identified: category A, which is typified by moderate reflectivity (from 10 to 30 dBZ) and modest +ZDR values (from 0 to +3 dB) in which both supercooled water and dendritic ice crystals (and oriented aggregates of ice crystals) are present at a mean temperature of −13°C, and category B, which is typified by small reflectivity (from −10 to +10 dBZ) and the largest +ZDR values (from +3 to +7 dB), in which supercooled water is dilute or absent and both flat-plate and dendritic crystals are likely. The predominant positive values for ZDR in many case studies suggest that the role of an electric field on ice particle orientation is small in comparison with gravity. The absence of robust +ZDR signatures in the trailing stratiform regions of vigorous summer squall lines may be due both to the infusion of noncrystalline ice particles (i.e., graupel and rimed aggregates) from the leading deep convection and to the effects of the stronger electric fields expected in these situations. These polarimetric measurements and their interpretations underscore the need for the accurate calibration of ZDR.United States. Federal Aviation Administration (Air Force Contract FA8721-05-C-0002
Arctic sea ice simulation in the PlioMIP ensemble
Eight general circulation models have simulated the mid-Pliocene warm period (mid-Pliocene, 3.264 to 3.025 Ma) as part of the Pliocene Modelling Intercomparison Project (PlioMIP). Here, we analyse and compare their simulation of Arctic sea ice for both the pre-industrial period and the mid-Pliocene. Mid-Pliocene sea ice thickness and extent is reduced, and the model spread of extent is more than twice the pre-industrial spread in some summer months. Half of the PlioMIP models simulate ice-free conditions in the mid-Pliocene. This spread amongst the ensemble is in line with the uncertainties amongst proxy reconstructions for mid-Pliocene sea ice extent. Correlations between mid-Pliocene Arctic temperatures and sea ice extents are almost twice as strong as the equivalent correlations for the pre-industrial simulations. The need for more comprehensive sea ice proxy data is highlighted, in order to better compare model performances
Dynamic light scattering study on phase separation of a protein-water mixture: Application on cold cataract development in the ocular lens
We present a detailed dynamic light scattering study on the phase separation
in the ocular lens emerging during cold cataract development. Cold cataract is
a phase separation effect that proceeds via spinodal decomposition of the lens
cytoplasm with cooling. Intensity auto-correlation functions of the lens
protein content are analyzed with the aid of two methods providing information
on the populations and dynamics of the scattering elements associated with cold
cataract. It is found that the temperature dependence of many measurable
parameters changes appreciably at the characteristic temperature ~16+1 oC which
is associated with the onset of cold cataract. Extending the temperature range
of this work to previously inaccessible regimes, i.e. well below the phase
separation or coexistence curve at Tcc, we have been able to accurately
determine the temperature dependence of the collective and self-diffusion
coefficient of proteins near the spinodal. The analysis showed that the
dynamics of proteins bears some resemblance to the dynamics of structural
glasses where the apparent activation energy for particle diffusion increases
below Tcc indicating a highly cooperative motion. Application of ideas
developed for studying the critical dynamics of binary protein/solvent
mixtures, as well as the use of a modified Arrhenius equation, enabled us to
estimate the spinodal temperature Tsp of the lens nucleus. The applicability of
dynamic light scattering as a non-invasive, early-diagnostic tool for ocular
diseases is also demonstrated in the light of the findings of the present
paper
Benchmarking homogenization algorithms for monthly data
The COST (European Cooperation in Science and Technology) Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME) has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies. The algorithms were validated against a realistic benchmark dataset. Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including i) the centered root mean square error relative to the true homogeneous values at various averaging scales, ii) the error in linear trend estimates and iii) traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve precipitation data. Moreover, state-of-the-art relative homogenization algorithms developed to work with an inhomogeneous reference are shown to perform best. The study showed that currently automatic algorithms can perform as well as manual ones
Paternal Origins and Migratory Episodes of Domestic Sheep
Deng et al. show that domestic sheep harbor four Y chromosome lineages and early expansions of sheep were associated with the segregation of primitive and fat-tailed phenotypes as well as traits selected for different purposes
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