696 research outputs found
Intermodal Energy Transfer in a Tapered Optical Fiber: Optimizing Transmission
We present an experimental and theoretical study of the energy transfer
between modes during the tapering process of an optical nanofiber through
spectrogram analysis. The results allow optimization of the tapering process,
and we measure transmission in excess of 99.95% for the fundamental mode. We
quantify the adiabaticity condition through calculations and place an upper
bound on the amount of energy transferred to other modes at each step of the
tapering, giving practical limits to the tapering angle.Comment: 29 pages, 17 figure
Ultrahigh Transmission Optical Nanofibers
We present a procedure for reproducibly fabricating ultrahigh transmission
optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode
transmissions of 99.95 0.02%, which represents a loss from tapering of
2.6 10 dB/mm when normalized to the entire stretch. When
controllably launching the next family of higher-order modes on a fiber with
195 mm stretch, we achieve a transmission of 97.8 2.8%, which has a loss
from tapering of 5.0 10 dB/mm when normalized to the
entire stretch. Our pulling and transfer procedures allow us to fabricate
optical nanofibers that transmit more than 400 mW in high vacuum conditions.
These results, published as parameters in our previous work, present an
improvement of two orders of magnitude less loss for the fundamental mode and
an increase in transmission of more than 300% for higher-order modes, when
following the protocols detailed in this paper. We extract from the
transmission during the pull, the only reported spectrogram of a fundamental
mode launch that does not include excitation to asymmetric modes; in stark
contrast to a pull in which our cleaning protocol is not followed. These
results depend critically on the pre-pull cleanliness and when properly
following our pulling protocols are in excellent agreement with simulations.Comment: 32 pages, 10 figures, accepted to AIP Advance
Gravitational Lorentz Force and the Description of the Gravitational Interaction
In the context of a gauge theory for the translation group, we have obtained,
for a spinless particle, a gravitational analog of the Lorentz force. Then, we
have shown that this force equation can be rewritten in terms of magnitudes
related to either the teleparallel or the riemannian structures induced in
spacetime by the presence of the gravitational field. In the first case, it
gives a force equation, with torsion playing the role of force. In the second,
it gives the usual geodesic equation of General Relativity. The main conclusion
is that scalar matter is able to feel anyone of the above spacetime geometries,
the teleparallel and the metric ones. Furthermore, both descriptions are found
to be completely equivalent in the sense that they give the same physical
trajectory for a spinless particle in a gravitational field.Comment: Equations (44)-(47) correcte
Patterning graphene nanostripes in substrate-supported functionalized graphene: A promising route to integrated, robust, and superior transistors
It is promising to apply quantum-mechanically confined graphene systems in
field-effect transistors. High stability, superior performance, and large-scale
integration are the main challenges facing the practical application of
graphene transistors. Our understandings of the adatom-graphene interaction
combined with recent progress in the nanofabrication technology indicate that
very stable and high-quality graphene nanostripes could be integrated in
substrate-supported functionalized (hydrogenated or fluorinated) graphene using
electron-beam lithography. We also propose that parallelizing a couple of
graphene nanostripes in a transistor should be preferred for practical
application, which is also very useful for transistors based on graphene
nanoribbon.Comment: Frontiers of Physics (2012) to be publishe
The effectiveness of convalescent plasma and hyperimmune immunoglobulin for the treatment of severe acute respiratory infections of viral etiology: a systematic review
Background: Administration of convalescent plasma, serum, or hyperimmune immunoglobulin may be of clinical benefit for treatment of severe acute respiratory infections (SARIs) of viral etiology. We conducted a systematic review and exploratory meta-analysis to assess the overall evidence.
Methods: Healthcare databases and sources of grey literature were searched in July 2013. All records were screened against the protocol eligibility criteria, using a 3-stage process. Data extraction and risk of bias assessments were undertaken.
Results: We identified 32 studies of SARS coronavirus infection and severe influenza. Narrative analyses revealed consistent evidence for a reduction in mortality, especially when convalescent plasma is administered early after symptom onset. Exploratory post hoc meta-analysis showed a statistically significant reduction in the pooled odds of mortality following treatment, compared with placebo or no therapy (odds ratio, 0.25; 95% confidence interval, .14–.45; I(2) = 0%). Studies were commonly of low or very low quality, lacked control groups, and at moderate or high risk of bias. Sources of clinical and methodological heterogeneity were identified.
Conclusions: Convalescent plasma may reduce mortality and appears safe. This therapy should be studied within the context of a well-designed clinical trial or other formal evaluation, including for treatment of Middle East respiratory syndrome coronavirus CoV infection
Genomic selection in commercial perennial crops: applicability and improvement in oil palm (Elaeis guineensis Jacq.)
Genomic selection (GS) uses genome-wide markers to select individuals with the desired overall combination of breeding traits. A total of 1,218 individuals from a commercial population of Ulu Remis x AVROS (UR x AVROS) were genotyped using the OP200K array. The traits of interest included: shellto- fruit ratio (S/F, %), mesocarp-to-fruit ratio (M/F, %), kernel-to-fruit ratio (K/F, %), fruit per bunch (F/B, %), oil per bunch (O/B, %) and oil per palm (O/P, kg/palm/year). Genomic heritabilities of these traits were estimated to be in the range of 0.40 to 0.80. GS methods assessed were RR-BLUP, Bayes A (BA), Cπ (BC), Lasso (BL) and Ridge Regression (BRR). All methods resulted in almost equal prediction accuracy. The accuracy achieved ranged from 0.40 to 0.70, correlating with the heritability of traits. By selecting the most important markers, RR-BLUP B has the potential to outperform other methods. The marker density for certain traits can be further reduced based on the linkage disequilibrium (LD). Together with in silico breeding, GS is now being used in oil palm breeding programs to hasten parental palm selection
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