34,704 research outputs found
Sub-femtosecond electron bunches created by direct laser acceleration in a laser wakefield accelerator with ionization injection
In this work, we will show through three-dimensional particle-in-cell
simulations that direct laser acceleration in laser a wakefield accelerator can
generate sub-femtosecond electron bunches. Two simulations were done with two
laser pulse durations, such that the shortest laser pulse occupies only a
fraction of the first bubble, whereas the longer pulse fills the entire first
bubble. In the latter case, as the trapped electrons moved forward and
interacted with the high intensity region of the laser pulse, micro-bunching
occurred naturally, producing 0.5 fs electron bunches. This is not observed in
the short pulse simulation.Comment: AAC 201
A randomised, controlled, double blind, non-inferiority trial of ultrasound-guided fascia iliaca block vs. spinal morphine for analgesia after primary hip arthroplasty
We performed a single centre, double blind, randomised, controlled, non-inferiority study comparing ultrasound-guided fascia iliaca block with spinal morphine for the primary outcome of 24-h postoperative morphine consumption in patients undergoing primary total hip arthroplasty under spinal anaesthesia with levobupivacaine. One hundred and eight patients were randomly allocated to receive either ultrasound-guided fascia iliaca block with 2 mg.kg−1 levobupivacaine (fascia iliaca group) or spinal morphine 100 μg plus a sham ultrasound-guided fascia iliaca block using saline (spinal morphine group). The pre-defined non-inferiority margin was a median difference between the groups of 10 mg in cumulative intravenous morphine use in the first 24 h postoperatively. Patients in the fascia iliaca group received 25 mg more intravenous morphine than patients in the spinal morphine group (95% CI 9.0–30.5 mg, p < 0.001). Ultrasound-guided fascia iliaca block was significantly worse than spinal morphine in the provision of analgesia in the first 24 h after total hip arthroplasty. No increase in side-effects was noted in the spinal morphine group but the study was not powered to investigate all secondary outcomes
Critical behavior at de-pinning of a driven disordered vortex matter in 2H-NbS2
We report unusual jamming in driven ordered vortex flow in 2H-NbS2.
Reinitiating movement in these jammed vortices with a higher driving force, and
halting it thereafter once again with a reduction in drive, unfolds a critical
behavior centered around the de-pinning threshold via divergences in the
lifetimes of transient states, validating the predictions of a recent
simulation study, which also pointed out a correspondence between plastic
de-pinning in vortex matter and the notion of random organization proposed in
the context of sheared colloids undergoing diffusive motion.Comment: Phys. Rev. B (in press, 2012). The paper has 14 pages of Text+ Refs.
with 4 figures. (Note as some of the figure files are large in size, to
enable faster download, the file size has been kept small and the figure
resolution are low. The online version of the paper to appear in PRB will
contain the higher resolution figures
Viral delivery of antioxidant genes as a therapeutic strategy in experimental models of amyotrophic lateral sclerosis.
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder with no effective treatment to date. Despite its multi-factorial aetiology, oxidative stress is hypothesized to be one of the key pathogenic mechanisms. It is thus proposed that manipulation of the expression of antioxidant genes that are downregulated in the presence of mutant SOD1 may serve as a therapeutic strategy for motor neuronal protection. Lentiviral vectors expressing either PRDX3 or NRF2 genes were tested in the motor neuronal-like NSC34 cell line, and in the ALS tissue culture model, NSC34 cells expressing the human SOD1(G93A) mutation. The NSC34 SOD1(G93A) cells overexpressing either PRDX3 or NRF2 showed a significant decrease in endogenous oxidation stress levels by 40 and 50% respectively compared with controls, whereas cell survival was increased by 30% in both cases. The neuroprotective potential of those two genes was further investigated in vivo in the SOD1(G93A) ALS mouse model, by administering intramuscular injections of adenoassociated virus serotype 6 (AAV6) expressing either of the target genes at a presymptomatic stage. Despite the absence of a significant effect in survival, disease onset or progression, which can be explained by the inefficient viral delivery, the promising in vitro data suggest that a more widespread CNS delivery is needed
Recurrent ~24 h Periods in RXTE ASM Data
Analysis of data from the Rossi X-ray Timing Explorer satellite's All Sky
Monitor instrument for several X-ray binary sources has identified a recurrent
\~24 h period. This period is sometimes highly significant, giving rise to the
possibility of it being identified as an orbital or super-orbital period.
Further analysis has revealed the same period in a number of other X-ray
sources. As a result this period has been discounted as spurious, described
variously as arising from daily variations in background levels and beating
between the sampling period and long-term secular trends in the light curves.
We present here an analysis of the spurious periods and show that the dominant
mechanism is in fact spectral leakage of low-frequency power present in the
light curves.Comment: 9 Pages, 10 figures, 1 table, submitted to PASA 20th December 2004.
Added 1 page of text and 3 figures to clarify results and discussion.
Resubmitted 16th May 2005. Accepted 25th June 200
Electrochemical characterization of systems for secondary battery application Second quarterly report, Aug. - Oct. 1966
Multisweep cyclic voltammetry for electrochemical characterization of systems for secondary battery applicatio
Anomalous local magnetic field distribution and strong pinning in CaFe1.94Co0.06As2 single crystals
Magneto-optical imaging of a single crystal of CaFe1.94Co0.06As2, shows
anomalous remnant magnetization within Meissner like regions of the
superconductor. The unconventional shape of the local magnetization hysteresis
loop suggests admixture of superconducting and magnetic fractions governing the
response. Near the superconducting transition temperature, local magnetic field
exceeds the applied field resulting in a diamagnetic to positive magnetization
transformation. The observed anomalies in the local magnetic field distribution
are accompanied with enhanced bulk pinning in the CaFe1.94Co0.06As2 single
crystals. We propose our results suggest a coexistence of superconductivity and
magnetic correlations.Comment: 6 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1201.369
Electrical coupling of neuro-ommatidial photoreceptor cells in the blowfly
A new method of microstimulation of the blowfly eye using corneal neutralization was applied to the 6 peripheral photoreceptor cells (R1-R6) connected to one neuro-ommatidium (and thus looking into the same direction), whilst the receptor potential of a dark-adapted photoreceptor cell was recorded by means of an intracellular microelectrode. Stimulation of the photoreceptor cells not impaled elicited responses in the recorded cell of about 20% of the response elicited when stimulating the recorded cell. This is probably caused by gap junctions recently found between the axon terminals of these cells. Stimulation of all 6 cells together yielded responses that were larger and longer than those obtained with stimulation of just the recorded cell, and intensity-response curves that deviated more strongly from linearity. Evidence is presented that the resistance of the axon terminal of the photoreceptor cells quickly drops in response to a light flash, depending on the light intensity. Incorporating the cable properties of the cell body and the axon, the resistance of the gap junctions, and the (adapting) terminal resistance, a theoretical model is presented that explains the measurements well. Finally, it is argued that the gap junctions between the photoreceptor cells may effectively uncouple the synaptic responses of the cells by counteracting the influence of field potentials.
Microgastrinae (Hymenoptera: Braconidae) parasitizing Epirrita autumnata (Lepidoptera: Geometridae) larvae in Fennoscandia with description of Cotesia autumnatae Shaw, sp. n.
The microgastrine subset of hymenopteran parasitoids of the geometrid Epirrita
autumnata is investigated in Fennoscandia. Ecology, including population dynamics,
of the moth has been intensively studied in northern and mountainous
Finland, Norway and Sweden. Recently supported hypotheses about the causes
of its cyclic population dynamics stress the role of parasitoids, while the
parasitoid complex with some 15 species is insufficiently known. The complex
includes four solitarymicrogastrine species, Protapanteles anchisiades (Nixon),
P. immunis (Wesmael), Cotesia salebrosa (Marshall) and C. autumnatae Shaw,
sp. n. Here, we provide detailed figures for the latter, which is morphologically
close to C. jucunda (Marshall), and describe the species as new to science. We
also providemore general habitus figures of the other three species, as well as an
identification key for the four species, aiming to aid recognition of these species
by ecologists dealingwithmicrogastrine parasitoids of E. autumnata and their alternative
geometrid hosts
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