2,084 research outputs found
Temperature dependence of the Kerr nonlinearity and two-photon absorption in a silicon waveguide at 1.55{\mu}m
We measure the temperature dependence of the two-photon absorption and
optical Kerr nonlinearity of a silicon waveguide over a range of temperatures
from 5.5 to 300 K at a wavelength of 1.55 {\mu}m. The two-photon absorption
coefficient is calculated from the power dependent transmission of a 4.9 ps
pulse. We observed a nearly two-fold decrease in the two-photon absorption
coefficient from 0.76 cm/GW at 300K to 0.42 cm/GW at 5.5 K. The Kerr
nonlinearity is inferred from the self-phase modulation induced spectral
broadening of the transmitted pulse. A smaller reduction in Kerr nonlinearity
from 5.2E-18 m^2/W at 300 K to 3.9E-18 m^2/W at 5.5 K is found. The increased
ratio of Kerr to absorptive nonlinearity at low temperatures indicates an
improved operation of devices that make use of a nonlinear phase shift, such as
optical switches or parametric photon-pair sources. We examine how the
heralding efficiency of a photon-pair source will change at low temperature. In
addition, the modelling and experimental techniques developed can readily be
extended to other wavelengths or materials of interest.Comment: 9 pages, 5 figure
Affimer Tagged Cubosomes: Targeting of Carcinoembryonic Antigen Expressing Colorectal Cancer Cells Using In Vitro and In Vivo Models.
Nanomedicines, while having been approved for cancer therapy, present many challenges such as low stability, rapid clearance, and nonspecificity leading to off-target toxicity. Cubosomes are porous lyotropic liquid crystalline nanoparticles that have shown great premise as drug delivery vehicles; however, their behavior in vivo is largely underexplored, hindering clinical translation. Here, we have engineered cubosomes based on the space group Im3m that are loaded with copper acetylacetonate as a model drug, and their surfaces are functionalized for the first time with Affimer proteins via copper-free click chemistry to actively target overexpressed carcinoembryonic antigens on LS174T colorectal cancer cells. Unlike nontargeted cubosomes, Affimer tagged cubosomes showed preferential accumulation in cancer cells compared to normal cells not only in vitro (2D monolayer cell culture and 3D spheroid models) but also in vivo in colorectal cancer mouse xenografts, while exhibiting low nonspecific absorption and toxicity in other vital organs. Cancerous spheroids had maximum cell death compared to noncancerous cells upon targeted delivery. Xenografts subjected to targeted drug-loaded cubosomes showed a 5–7-fold higher drug accumulation in the tumor tissue compared to the liver, kidneys, and other vital organs, a significant decrease in tumor growth, and an increased survival rate compared to the nontargeted group. This work encompasses the first thorough preclinical investigation of Affimer targeted cubosomes as a cancer therapeutic
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
Search for gravitational wave bursts in LIGO's third science run
We report on a search for gravitational wave bursts in data from the three
LIGO interferometric detectors during their third science run. The search
targets subsecond bursts in the frequency range 100-1100 Hz for which no
waveform model is assumed, and has a sensitivity in terms of the
root-sum-square (rss) strain amplitude of hrss ~ 10^{-20} / sqrt(Hz). No
gravitational wave signals were detected in the 8 days of analyzed data.Comment: 12 pages, 6 figures. Amaldi-6 conference proceedings to be published
in Classical and Quantum Gravit
The spatiotemporal dynamics of microglia across the human lifespan
Microglia, the brain’s resident macrophages, shape neural development and are key neuroimmune hubs in
the pathological signatures of neurodevelopmental disorders. Despite the importance of microglia, their
development has not been carefully examined in the human brain, and most of our knowledge derives
from rodents. We aimed to address this gap in knowledge by establishing an extensive collection of 97
post-mortem tissues in order to enable quantitative, sex-matched, detailed analysis of microglia across
the human lifespan. We identify the dynamics of these cells in the human telencephalon, describing waves
in microglial density across gestation, infancy, and childhood, controlled by a balance of proliferation and
apoptosis, which track key neurodevelopmental milestones. These profound changes in microglia are also
observed in bulk RNA-seq and single-cell RNA-seq datasets. This study provides a detailed insight into
the spatiotemporal dynamics of microglia across the human lifespan and serves as a foundation for elucidating how microglia contribute to shaping neurodevelopment in humans
Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change
While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends
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