9,198 research outputs found
Experimental investigation of the impact of optical injection on vital parameters of a gain-switched pulse source
An analysis of optical injection on a gain-switched distributed feedback (DFB) laser and its impact on pulse parameters that influence the performance of the pulse source in high-speed optical communication systems is presented in this paper. A range of 10 GHz in detuning and 5 dB in injected power has been experimentally identified to attain pulses, from an optically injected gain-switched DFB laser, with durations below 10 ps and pedestal suppression higher than 35 dB. These pulse features are associated with a side mode suppression ratio of about 30 dB and a timing jitter of less than 1 ps. This demonstrates the feasibility of using optical injection in conjunction with appropriate pulse compression schemes for developing an optimized and cost-efficient pulse source, based on a gain-switched DFB laser, for high-speed photonic systems
Annealing-induced reduction in nanoscale heterogeneity of thermally evaporated amorphous As2S3 films
The morphology and structural order of thermally deposited and annealed amorphous As2S3 films
have been investigated using high resolution transmission electron microscopy. It was found that
both the as-deposited and annealed films contained sparsely distributed nanocrystallites of the
orpiment As2S3 crystalline phase. However, from selected area electron diffraction both films
appeared amorphous. Fluctuation electron microscopy revealed that the as-deposited film contained
greater nanoscale inhomogeneity. Low temperature annealing reduced the nanoscale inhomogeneity
and resulted in a more homogeneous and energetically favorable network. The reduction in
nanoscale inhomogeneity upon low temperature annealing was accompanied by the appearance of
a first sharp diffraction peak in the diffraction pattern. This first-sharp diffraction peak has been
attributed to chemical ordering of interstitial voids. Our measurements suggest that this chemical
short-range ordering is associated with the dissolution of the energetically unfavorable larger
correlated structures that contribute to the inhomogeneity of the as-deposited film
Finding Eyewitness Tweets During Crises
Disaster response agencies have started to incorporate social media as a
source of fast-breaking information to understand the needs of people affected
by the many crises that occur around the world. These agencies look for tweets
from within the region affected by the crisis to get the latest updates of the
status of the affected region. However only 1% of all tweets are geotagged with
explicit location information. First responders lose valuable information
because they cannot assess the origin of many of the tweets they collect. In
this work we seek to identify non-geotagged tweets that originate from within
the crisis region. Towards this, we address three questions: (1) is there a
difference between the language of tweets originating within a crisis region
and tweets originating outside the region, (2) what are the linguistic patterns
that can be used to differentiate within-region and outside-region tweets, and
(3) for non-geotagged tweets, can we automatically identify those originating
within the crisis region in real-time
The synthesis and unexpected solution chemistry of thermochromic carborane-containing osmium half-sandwich complexes
YesThe functionalisation of the 16-electron complex [Os(η6-p-cymene)(1,2-dicarba-closo-dodecarborane-
1,2-dithiolato)] (1) with a series of Lewis bases to give the 18-electron complexes of general formula
[Os(η6-p-cymene)(1,2-dicarba-closo-dodecarborane-1,2-dithiolato)(L)] (L = pyridine (2), 4-dimethylaminopyridine
(3), 4-cyanopyridine (4), 4-methoxypyridine (5), pyrazine (6), pyridazine (7), 4,4’-bipyridine
(8) and triphenylphosphine (9)) is reported. All 18-electron complexes are in equilibrium in solution with
the 16-electron precursor, and thermochromic properties are observed in some cases (2, 3, 5, 8, and 9).
The binding constants and Gibbs free energies of the equilibria are determined using UV-visible titrations
and their stabilities investigated. Synthetic routes for forcing the formation of the 18-electron species are
proposed, and analytical methods to characterise the equilibria are described.We thank the Leverhulme Trust (Early Career Fellowship No. ECF-2013-414 to NPEB), and the University of Warwick (Grant No. RD14102 to NPEB)
Stringent Nucleotide Recognition by the Ribosome at the Middle Codon Position.
Accurate translation of the genetic code depends on mRNA:tRNA codon:anticodon base pairing. Here we exploit an emissive, isosteric adenosine surrogate that allows direct measurement of the kinetics of codon:anticodon University of California base formation during protein synthesis. Our results suggest that codon:anticodon base pairing is subject to tighter constraints at the middle position than at the 5'- and 3'-positions, and further suggest a sequential mechanism of formation of the three base pairs in the codon:anticodon helix
Doping influence of spin dynamics and magnetoelectric effect in hexagonal YLuMnO
We use inelastic neutron scattering to study spin waves and their correlation
with the magnetoelectric effect in YLuMnO. In the undoped
YMnO and LuMnO, the Mn trimerization distortion has been suggested to
play a key role in determining the magnetic structure and the magnetoelectric
effect. In YLuMnO, we find a much smaller in-plane
(hexagonal -plane) single ion anisotropy gap that coincides with a weaker
in-plane dielectric anomaly at . Since both the smaller in-plane
anisotropy gap and the weaker in-plane dielectric anomaly are coupled to a
weaker Mn trimerization distortion in YLuMnO comparing to
YMnO and LuMnO, we conclude that the Mn trimerization is responsible
for the magnetoelectric effect and multiferroic phenomenon in
YLuMnO.Comment: 5 pages, 5 figure
TGF-beta signaling proteins and the Protein Ontology
The Protein Ontology (PRO) is designed as a formal and principled Open Biomedical
Ontologies (OBO) Foundry ontology for proteins. The components of PRO extend from a classification of proteins on the basis of evolutionary relationships at the homeomorphic level to the representation of the multiple protein forms of a gene, including those resulting from alternative splicing, cleavage and/or posttranslational
modifications. Focusing specifically on the TGF-beta signaling proteins, we describe the building, curation, usage and dissemination of PRO. PRO provides a framework for the formal representation of protein classes and protein forms in the OBO Foundry. It is designed to enable data retrieval and integration and machine reasoning at the molecular level of proteins, thereby facilitating cross-species comparisons, pathway analysis, disease modeling and the generation of new hypotheses
Methylarsonous Acid Transport by Aquaglyceroporins
Many mammals methylate trivalent inorganic arsenic in liver to species that are released into the bloodstream and excreted in urine and feces. This study addresses how methylated arsenicals pass through cell membranes. We have previously shown that aquaglyceroporin channels, including Escherichia coli GlpF, Saccharomyces cerevisiae Fps1p, AQP7, and AQP9 from rat and human, conduct trivalent inorganic arsenic [As(III)] as arsenic trioxide, the protonated form of arsenite. One of the initial products of As(III) methylation is methylarsonous acid [MAs(III)], which is considerably more toxic than inorganic As(III). In this study, we investigated the ability of GlpF, Fps1p, and AQP9 to facilitate movement of MAs(III) and found that rat aquaglyceroporin conducted MAs(III) at a higher rate than the yeast homologue. In addition, rat AQP9 facilitates MAs(III) at a higher rate than As(III). These results demonstrate that aquaglyceroporins differ both in selectivity for and in transport rates of trivalent arsenicals. In this study, the requirement of AQP9 residues Phe-64 and Arg-219 for MAs(III) movement was examined. A hydrophobic residue at position 64 is not required for MAs(III) transport, whereas an arginine at residue 219 may be required. This is similar to that found for As(III), suggesting that As(III) and MAs(III) use the same translocation pathway in AQP9. Identification of MAs(III) as an AQP9 substrate is an important step in understanding physiologic responses to arsenic in mammals, including humans
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