2,064 research outputs found
Tailoring optical fields emitted by nanometric sources
Here we study a simple way of controlling the emitted fields of
sub-wavelength nanometric sources. The system consists of arrays of
nanoparticles (NPs) embedded in optical active media. The key concept is the
careful tuning of NP's damping factors, which changes the eigenmode's decay
rates of the whole array. This, at long time, leads to a locking of relative
phases and frequencies of individual localized-surfaces-plasmons (LSPs) and,
thus, controlls the emitted field. The amplitude of the LSP's oscillations can
be kept constant by embedding the system in optical active media. In the case
of full loss compensation, this implies that, not only the relative phases, but
also the amplitudes of the LSPs remain fixed, leading us, additionally, to
interpret the process as a new example of synchronization. The proposed
approach can be used as a general way of controlling and designing the
electromagnetic fields emitted by nanometric sources, which can find
applications in optoelectronic, nanoscale lithography and probing microscopy
Using a Gridded Global Dataset to Characterize Regional Hydroclimate in Central Chile
Central Chile is facing dramatic projections of climate change, with a consensus for declining precipitation, negatively affecting hydropower generation and irrigated agriculture. Rising from sea level to 6000 m within a distance of 200 km, precipitation characterization is difficult because of a lack of long-term observations, especially at higher elevations. For understanding current mean and extreme conditions and recent hydroclimatological change, as well as to provide a baseline for downscaling climate model projections, a temporally and spatially complete dataset of daily meteorology is essential. The authors use a gridded global daily meteorological dataset at 0.25° resolution for the period 1948â2008, adjusted by monthly precipitation observations interpolated to the same grid using a cokriging method with elevation as a covariate. For validation, daily statistics of the adjusted gridded precipitation are compared to station observations. For further validation, a hydrology model is driven with the gridded 0.25° meteorology and streamflow statistics are compared with observed flow. The high elevation precipitation is validated by comparing the simulated snow extent to Moderate Resolution Imaging Spectroradiometer (MODIS) images. Results show that the daily meteorology with the adjusted precipitation can accurately capture the statistical properties of extreme events as well as the sequence of wet and dry events, with hydrological model results displaying reasonable agreement with observed streamflow and snow extent. This demonstrates the successful use of a global gridded data product in a relatively data-sparse region to capture hydroclimatological characteristics and extremes
Gyrokinetic studies of core turbulence features in ASDEX Upgrade H-mode plasmas
Gyrokinetic validation studies are crucial in developing confidence in the
model incorporated in numerical simulations and thus improving their predictive
capabilities. As one step in this direction, we simulate an ASDEX Upgrade
discharge with the GENE code, and analyze various fluctuating quantities and
compare them to experimental measurements. The approach taken is the following.
First, linear simulations are performed in order to determine the turbulence
regime. Second, the heat fluxes in nonlinear simulations are matched to
experimental fluxes by varying the logarithmic ion temperature gradient within
the expected experimental error bars. Finally, the dependence of various
quantities with respect to the ion temperature gradient is analyzed in detail.
It is found that density and temperature fluctuations can vary significantly
with small changes in this parameter, thus making comparisons with experiments
very sensitive to uncertainties in the experimental profiles. However,
cross-phases are more robust, indicating that they are better observables for
comparisons between gyrokinetic simulations and experimental measurements
UBQLN4 Represses Homologous Recombination and Is Overexpressed in Aggressive Tumors
Genomic instability can be a hallmark of both human genetic disease and cancer. We identify a deleterious UBQLN4 mutation in families with an autosomal recessive syndrome reminiscent of genome instability disorders. UBQLN4 deficiency leads to increased sensitivity to genotoxic stress and delayed DNA double-strand break (DSB) repair. The proteasomal shuttle factor UBQLN4 is phosphorylated by ATM and interacts with ubiquitylated MRE11 to mediate early steps of homologous recombination-mediated DSB repair (HRR). Loss of UBQLN4 leads to chromatin retention of MRE11, promoting non-physiological HRR activity in vitro and in vivo. Conversely, UBQLN4 overexpression represses HRR and favors non-homologous end joining. Moreover, we find UBQLN4 overexpressed in aggressive tumors. In line with an HRR defect in these tumors, UBQLN4 overexpression is associated with PARP1 inhibitor sensitivity. UBQLN4 therefore curtails HRR activity through removal of MRE11 from damaged chromatin and thus offers a therapeutic window for PARP1 inhibitor treatment in UBQLN4-overexpressing tumors
Primer registro del género y la especie Zefevazia peruana (Boucomont, 1902) (Coleoptera: Bolboceratidae: Bolboceratinae) para Ecuador
The first report of the genus and species Zefevazia peruana (Boucomont, 1902) for Ecuador is presented. The species is previously known only from a few localities in northern Peru, and is now also recorded from Santa Elena, southern Ecuador. This report represents the northernmost record of the genus and species.Se presenta el primer reporte del gĂ©nero y la especie Zefevazia peruana (Boucomont, 1902) para Ecuador. La especie es conocida previamente de unas pocas localidades en el norte de PerĂș, y ahora tambiĂ©n es registrada en Santa Elena, sur de Ecuador. Este reporte representa el registro mĂĄs al norte del gĂ©nero y la especie
Role of coherence in quantum-dot-based nanomachines within the Coulomb blockade regime
During the last decades, quantum dots within the Coulomb blockade regime of
transport have been proposed as essential building blocks for a wide variety of
nanomachines. This includes thermoelectric devices, quantum shuttles, quantum
pumps, and even quantum motors. However, in this regime, the role of quantum
mechanics is commonly limited to provide energy quantization while the working
principle of the devices is ultimately the same as their classic counterparts.
Here, we study quantum-dot-based nanomachines in the Coulomb blockade regime,
but in a configuration that resembles the quantum mechanics' paradigmatic
experiment: the double-slit. We show that the coherent superposition of states
appearing in this configuration can be used as the basis for different forms of
"true" quantum machines. We analyze the efficiency of these machines against
different non-equilibrium sources (bias voltage, temperature gradient, and
external driving) and the factors that limit it, including decoherence and the
role of the different orders appearing in the adiabatic expansion of the
charge/heat currents.Comment: 16 pages, 7 figure
Redox-Active Nanomaterials For Nanomedicine Applications
Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials
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