616 research outputs found
Renovation of Nitrogenous Wastewater Via Land Application
Removal of inorganic and organic nitrogen from wastewater prior to recharge of ground and surface waters can be accomplished by judicious land application. This study focused attention upon the feasibility of using sprinkler irrigation as the wastewater delivery system with coastal bermudagrass (Cynodon dactylon L.,var. coastal) pasture as the wastewater sink. One site was located on a Sawyer soil near El Dorado, while the other was located on a Savannah soil near Malvern. This report is limited to the renovation of surface waters. Results revealed that nitrogen concentration in runoff water from rainfall was substantially less than nitrogen concentration of the wastewater applied to the soil and similar to background levels. Such results support the consideration of land application as a viable wastewater disposal method
Characterization of 40-Gbit/s pulses generated using a lithium niobate modulator at 1550 nm using frequency resolved optical gating
The characteristics of 40-Gbit/s pulses generated by exploiting the nonlinear characteristics of a Mach-Zender Lithium Niobate modulator are presented. A high spectral resolution frequency resolved optical gating apparatus has been developed to allow for the complete characterization of the intensity and phase of these pulses. The use of these measurements to simplify the design and optimization of an 80-Gbit/s pulse source, based on this 40-Gbit/s source followed by a nonlinear fiber compressor and multiplexer, is also demonstrated
Optimization of optical data transmitters for 40-Gb/s lightwave systems using frequency resolved optical gating
The measurement technique of frequency resolved optical gating has been used to optimize the phase of a 40-GHz train of optical pulses generated using a continuous-wave laser gated with an external modulator. This technique will be vital for optimization of optical transmitters to be used in systems operating at 40 Gb/s and beyond, as standard measurement techniques will not suffice to optimize such high-speed systems
Imaging of Iso-frequency Contours via Resonance-Enhanced Scattering in Near-Pristine Photonic Crystals
The iso-frequency contours of a photonic crystal are important for predicting
and understanding exotic optical phenomena that are not apparent from
high-symmetry band structure visualizations. Here, we demonstrate a method to
directly visualize the iso-frequency contours of high-quality photonic crystal
slabs that shows quantitatively good agreement with numerical results
throughout the visible spectrum. Our technique relies on resonance-enhanced
photon scattering from generic fabrication disorder and surface roughness, so
it can be applied to general photonic and plasmonic crystals, or even
quasi-crystals. We also present an analytical model of the scattering process,
which explains the observation of iso-frequency contours in our technique.
Furthermore, the iso-frequency contours provide information about the
characteristics of the disorder and therefore serve as a feedback tool to
improve fabrication processes.Comment: 8 pages, 5 figure
Substrate-Independent Light Confinement in Bioinspired All-Dielectric Surface Resonators
Traditionally, photonic crystal slabs can support resonances that are strongly confined to the slab but also couple to external radiation. However, when a photonic crystal slab is placed on a substrate, the resonance modes become less confined, and as the index contrast between slab and substrate decreases, they eventually disappear. Using the scale structure of the Dione juno butterfly wing as an inspiration, we present a low-index zigzag surface structure that supports resonance modes even without index contrast with the substrate. The zigzag structure supports resonances that are contained away from the substrate, which reduces the interaction between the resonance and the substrate. We experimentally verify the existence of substrate-independent resonances in the visible wavelength regime. Potential applications include substrate-independent structural color and light guiding.United States. Army Research Office (W911NF-13-D-0001)Solid-State Solar-Thermal Energy Conversion Center (DE-SC0001299)National Science Foundation (U.S.) (1122374
Progress toward curing HIV infection with hematopoietic cell transplantation.
HIV-1 infection afflicts more than 35 million people worldwide, according to 2014 estimates from the World Health Organization. For those individuals who have access to antiretroviral therapy, these drugs can effectively suppress, but not cure, HIV-1 infection. Indeed, the only documented case for an HIV/AIDS cure was a patient with HIV-1 and acute myeloid leukemia who received allogeneic hematopoietic cell transplantation (HCT) from a graft that carried the HIV-resistant CCR5-∆32/∆32 mutation. Other attempts to establish a cure for HIV/AIDS using HCT in patients with HIV-1 and malignancy have yielded mixed results, as encouraging evidence for virus eradication in a few cases has been offset by poor clinical outcomes due to the underlying cancer or other complications. Such clinical strategies have relied on HIV-resistant hematopoietic stem and progenitor cells that harbor the natural CCR5-∆32/∆32 mutation or that have been genetically modified for HIV-resistance. Nevertheless, HCT with HIV-resistant cord blood remains a promising option, particularly with inventories of CCR5-∆32/∆32 units or with genetically modified, human leukocyte antigen-matched cord blood
Analyses of protein cores reveal fundamental differences between solution and crystal structures
There have been several studies suggesting that protein structures solved by
NMR spectroscopy and x-ray crystallography show significant differences. To
understand the origin of these differences, we assembled a database of
high-quality protein structures solved by both methods. We also find
significant differences between NMR and crystal structures---in the
root-mean-square deviations of the C atomic positions, identities of
core amino acids, backbone and sidechain dihedral angles, and packing fraction
of core residues. In contrast to prior studies, we identify the physical basis
for these differences by modelling protein cores as jammed packings of
amino-acid-shaped particles. We find that we can tune the jammed packing
fraction by varying the degree of thermalization used to generate the packings.
For an athermal protocol, we find that the average jammed packing fraction is
identical to that observed in the cores of protein structures solved by x-ray
crystallography. In contrast, highly thermalized packing-generation protocols
yield jammed packing fractions that are even higher than those observed in NMR
structures. These results indicate that thermalized systems can pack more
densely than athermal systems, which suggests a physical basis for the
structural differences between protein structures solved by NMR and x-ray
crystallography.Comment: 9 pages, 4 figure
Using physical features of protein core packing to distinguish real proteins from decoys
The ability to consistently distinguish real protein structures from
computationally generated model decoys is not yet a solved problem. One route
to distinguish real protein structures from decoys is to delineate the
important physical features that specify a real protein. For example, it has
long been appreciated that the hydrophobic cores of proteins contribute
significantly to their stability. As a dataset of decoys to compare with real
protein structures, we studied submissions to the bi-annual CASP competition
(specifically CASP11, 12, and 13), in which researchers attempt to predict the
structure of a protein only knowing its amino acid sequence. Our analysis
reveals that many of the submissions possess cores that do not recapitulate the
features that define real proteins. In particular, the model structures appear
more densely packed (because of energetically unfavorable atomic overlaps),
contain too few residues in the core, and have improper distributions of
hydrophobic residues throughout the structure. Based on these observations, we
developed a deep learning method, which incorporates key physical features of
protein cores, to predict how well a computational model recapitulates the real
protein structure without knowledge of the structure of the target sequence. By
identifying the important features of protein structure, our method is able to
rank decoys from the CASP competitions equally well, if not better than,
state-of-the-art methods that incorporate many additional features.Comment: 7 pages, 5 figure
Optimization of 40 Gbit/s transmission systems using frequency resolved optical gating characterization techniques
To achieve multiterabit/s capacities in long-haul transport networks, it is anticipated that wavelength division multiplexed (WDM) systems will be upgraded to operate at line rates of 40 Gbit/s. We have shown that by employing the FROG measurement technique to optimize the generation of optical pulses for use in a 40 Gbit/s soliton transmission link, we ensure that the performance of the overall system using the generated optical pulses is optimum
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