2,161 research outputs found
Compact graphene mode-locked wavelength-tunable erbium-doped fiber lasers: from all anomalous dispersion towards all normal dispersion
Soliton operation and soliton wavelength tuning of erbium-doped fiber lasers
mode locked with atomic layer graphene was experimentally investigated under
various cavity dispersion conditions. It was shown that not only wide range
soliton wavelength tuning but also soltion pulse width variation could be
obtained in the fiber lasers. Our results show that the graphene mode locked
erbium-doped fiber lasers provide a compact, user friendly and low cost
wavelength tunable ultrahsort pulse source
Universal quantum gates based on a pair of orthogonal cyclic states: Application to NMR systems
We propose an experimentally feasible scheme to achieve quantum computation
based on a pair of orthogonal cyclic states. In this scheme, quantum gates can
be implemented based on the total phase accumulated in cyclic evolutions. In
particular, geometric quantum computation may be achieved by eliminating the
dynamic phase accumulated in the whole evolution. Therefore, both dynamic and
geometric operations for quantum computation are workable in the present
theory. Physical implementation of this set of gates is designed for NMR
systems. Also interestingly, we show that a set of universal geometric quantum
gates in NMR systems may be realized in one cycle by simply choosing specific
parameters of the external rotating magnetic fields. In addition, we
demonstrate explicitly a multiloop method to remove the dynamic phase in
geometric quantum gates. Our results may provide useful information for the
experimental implementation of quantum logical gates.Comment: 9 pages, language revised, the publication versio
Evaluation of the BCS Approximation for the Attractive Hubbard Model in One Dimension
The ground state energy and energy gap to the first excited state are
calculated for the attractive Hubbard model in one dimension using both the
Bethe Ansatz equations and the variational BCS wavefunction. Comparisons are
provided as a function of coupling strength and electron density. While the
ground state energies are always in very good agreement, the BCS energy gap is
sometimes incorrect by an order of magnitude, particularly at half-filling.
Finite size effects are also briefly discussed for cases where an exact
solution in the thermodynamic limit is not possible. In general, the BCS result
for the energy gap is poor compared to the exact result.Comment: 25 pages, 5 Postscript figure
SRSF1-dependent nuclear export of C9ORF72 repeat-transcripts: targeting toxic gain-of-functions induced by protein sequestration as a selective therapeutic strategy for neuroprotection
Microsatellite repeat expansions cause several incurable and lethal neurodegenerative disorders including
ataxias, myotonic dystrophy, Huntington's disease and C9ORF72-linked amyotrophic lateral sclerosis (ALS) and
frontotemporal dementia (FTD). Abnormal repeat transcripts generated from the expanded loci are substrates
of repeat-associated non-AUG (RAN) translation, an unconventional form of translation leading to the
production of polymeric repeat proteins with cytotoxic and aggregating properties. The mechanisms involved in
the pathogenesis of microsatellite repeat expansion disorders remain a hotly debated topic. They are shared
between toxic loss/gain of functions due to intranuclear RNA foci that sequesters RNA-binding proteins and
RAN translation of repeat proteins in the cytoplasm. We recently elucidated the molecular mechanism driving
the nuclear export of C9ORF72 repeat transcripts and showed for the first time that this pathway can be
manipulated to confer neuroprotection. Strikingly, we discovered that intron-retaining C9ORF72 repeat
transcripts hijack the physiological NXF1-dependent export pathway by selective RNA-repeat sequestration of
SRSF1. Antagonizing SRSF1 and the nuclear export of C9ORF72 repeat transcripts promoted in turn the
survival of patient-derived motor neurons and suppressed neurodegeneration-associated motor deficits in
Drosophila (Hautbergue et al. Nature Communications 2017; 8:16063). In this invited Research Highlight review,
we aim to place this work in the context of our previous studies on the nuclear export of mRNAs, provide a
summary of the published research and highlight the significance of these findings as a novel therapeutic
strategy for neuroprotection in C9ORF72-ALS/FTD. In addition, we emphasize that protein sequestration, often
thought as of inducing loss-of-function mechanisms, can also trigger unwanted protein interactions and toxic
gain-of-functions
Specific detection of Pythium aphanidermatum from hydroponic nutrient solution by booster PCR with DNA primers developed from mitochondrial DNA
Pythium aphanidermatum causes damping-off and root rot of vegetable crops in hydroponic systems. A DNA probe was isolated and modified from a library of HindIII-digested mitochondrial DNA of P aphanidermatum that strongly hybridized to DNA of R aphanidermatum and weakly hybridized to DNA of Pythium deliense. Cross-hybridizing sequences were absent from DNA of plants and other related fungi. The probe detected as little as 5 ng of P. aphanidermatum DNA and 250 ng of P deliense DNA in slot-blot assays. P. aphanidermatum was detected by a hybridization assay of total DNA extracted directly from infected roots. A pair of oligonucleotide primers P1 and RP2, which allowed amplification of a specific 0.65 kb DNA fragment of P. aphanidernatum using polymerase chain reaction (PCR), was designed from a specific DNA probe. Specific amplification of this fragment from P. aphanidermatum was highly sensitive, detecting template DNA as low as 0.1 pg total DNA by booster PCR. Specific booster PCR amplification using P1 and RP2 was successful in detecting P. aphanidermatum in naturally infected nutrient solution and roots of vegetables in a field hydroponic system
Theory of Melting and the Optical Properties of Gold/DNA Nanocomposites
We describe a simple model for the melting and optical properties of a
DNA/gold nanoparticle aggregate. The optical properties at fixed wavelength
change dramatically at the melting transition, which is found to be higher and
narrower in temperature for larger particles, and much sharper than that of an
isolated DNA link. All these features are in agreement with available
experiments. The aggregate is modeled as a cluster of gold nanoparticles on a
periodic lattice connected by DNA bonds, and the extinction coefficient is
computed using the discrete dipole approximation. Melting takes place as an
increasing number of these bonds break with increasing temperature. The melting
temperature corresponds approximately to the bond percolation threshold.Comment: 5 pages, 4 figure. To be published in Phys. Rev.
Should a Sentinel Node Biopsy Be Performed in Patients with High-Risk Breast Cancer?
A negative sentinel lymph node (SLN) biopsy spares many breast cancer patients the complications associated with lymph node irradiation or additional surgery. However, patients at high risk for nodal involvement based on clinical characteristics may remain at unacceptably high risk of axillary disease even after a negative SLN biopsy result. A Bayesian nomogram was designed to combine the probability of axillary disease prior to nodal biopsy with customized test characteristics for an SLN biopsy and provides the probability of axillary disease despite a negative SLN biopsy. Users may individualize the sensitivity of an SLN biopsy based on factors known to modify the sensitivity of the procedure. This tool may be useful in identifying patients who should have expanded upfront exploration of the axilla or comprehensive axillary irradiation
Electroactive biofilms: new means for electrochemistry
This work demonstrates that electrochemical reactions can be catalysed by the natural biofilms that form on
electrode surfaces dipping into drinking water or compost. In drinking water, oxygen reduction was monitored with
stainless steel ultra-microelectrodes under constant potential electrolysis at )0.30 V/SCE for 13 days. 16 independent experiments were conducted in drinking water, either pure or with the addition of acetate or dextrose. In
most cases, the current increased and reached 1.5–9.5 times the initial current. The current increase was attributed to
biofilm forming on the electrode in a similar way to that has been observed in seawater. Epifluorescence microscopy
showed that the bacteria size and the biofilm morphology depended on the nutrients added, but no quantitative
correlation between biofilm morphology and current was established. In compost, the oxidation process was
investigated using a titanium based electrode under constant polarisation in the range 0.10–0.70 V/SCE. It was
demonstrated that the indigenous micro-organisms were responsible for the current increase observed after a few
days, up to 60 mA m)2. Adding 10 mM acetate to the compost amplified the current density to 145 mA m)2 at 0.50 V/SCE. The study suggests that many natural environments, other than marine sediments, waste waters and
seawaters that have been predominantly investigated until now, may be able to produce electrochemically active
biofilm
Longitudinal broadening of near side jets due to parton cascade
Longitudinal broadening along direction on near side in
two-dimensional () di-hadron correlation
distribution has been studied for central Au+Au collisions at =
200 GeV, within a dynamical multi-phase transport model. It was found that the
longitudinal broadening is generated by a longitudinal flow induced by strong
parton cascade in central Au+Au collisions, in comparison with p+p collisions
at = 200 GeV. The longitudinal broadening may shed light on the
information about strongly interacting partonic matter at RHIC.Comment: 5 pages, 4 figures; accepted by Eur. Phys. J.
Tight bounds on the competitive ratio on accomodating sequences for the seat reservation problem
The unit price seat reservation problem is investigated. The seat reservation problem is the problem of assigning seat numbers on-line to requests for reservations in a train traveling through stations. We are considering the version where all tickets have the same price and where requests are treated fairly, i.e., a request which can be fulfilled must be granted. For fair deterministic algorithms, we provide an asymptotically matching upper bound to the existing lower bound which states that all fair algorithms for this problem are frac{1{2-competitive on accommodating sequences, when there are at least three seats. Additionally, we give an asymptotic upper bound of frac{7{9 for fair randomized algorithms against oblivious adversaries. We also examine concrete on-line algorithms, First-Fit and Random, for the special case of two seats. Tight analyses of their performance are given
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