Kappa-symmetric SL(2,R) covariant D-brane actions

A superspace formulation of IIB supergravity which includes the field strengths of the duals of the usual physical one, three and five-form field strengths as well as the eleven-form field strength is given. The superembedding formalism is used to construct kappa-symmetric SL(2,R) covariant D-brane actions in an arbitrary supergravity background.Comment: 20 pages. Minor clarification in text. References adde

Impact-ionization and noise characteristics of thin III-V avalanche photodiodes

It is, by now, well known that McIntyre\u27s localized carrier-multiplication theory cannot explain the suppression of excess noise factor observed in avalanche photodiodes (APDs) that make use of thin multiplication regions. We demonstrate that a carrier multiplication model that incorporates the effects of dead space, as developed earlier by Hayat et al. provides excellent agreement with the impact-ionization and noise characteristics of thin InP, In/sub 0.52/Al/sub 0.48/As, GaAs, and Al/sub 0.2/Ga/sub 0.8/As APDs, with multiplication regions of different widths. We outline a general technique that facilitates the calculation of ionization coefficients for carriers that have traveled a distance exceeding the dead space (enabled carriers), directly from experimental excess-noise-factor data. These coefficients depend on the electric field in exponential fashion and are independent of multiplication width, as expected on physical grounds. The procedure for obtaining the ionization coefficients is used in conjunction with the dead-space-multiplication theory (DSMT) to predict excess noise factor versus mean-gain curves that are in excellent accord with experimental data for thin III-V APDs, for all multiplication-region widths

Terawatt-scale sub-10-fs laser technology - key to generation of GW-level attosecond pulses in X-ray free electron laser

We propose a technique for the production of attosecond X-ray pulses which is based on the use of X-ray SASE FEL combined with a femtosecond laser system. A few-cycle optical pulse from a Ti:sapphire laser interacts with the electron beam in a two-period undulator resonant to 800 nm wavelength and produces energy modulation within a slice of the electron bunch. Following the energy modulator the electron beam enters the X-ray undulator and produces SASE radiation. Due to energy modulation the frequency is correlated to the longitudinal position within the few-cycle-driven slice of SASE radiation pulse. The largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. The selection of single-spike pulses is achieved by using a crystal monochromator after the X-ray undulator. Our studies show that the proposed technique is capable to produce 300 attoseconds long single pulses with GW-level output power in the 0.1 nm wavelength range, and is applicable to the European X-Ray Laser Project XFEL and the Linac Coherent Light Source at SLAC.Comment: 19 pages, 13 figure

A new technique to generate 100 GW-level attosecond X-ray pulses from the X-ray SASE FELs

We propose a scheme for generation of single 100 GW 300-as pulse in the X-ray free electron laser with the use of a few cycles optical pulse from Ti:sapphire laser system. Femtosecond optical pulse interacts with the electron beam in the two-period undulator resonant to 800 nm wavelength and produces energy modulation within a slice of the electron bunch. Following the energy modulator the electron beam enters the first part of the baseline gap-adjustable X-ray undulator and produces SASE radiation with 100 MW-level power. Due to energy modulation the frequency is correlated to the longitudinal position within the few-cycle-driven slice of the SASE radiation pulse. The largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. After the first undulator the electron beam is guided through a magnetic delay which we use to position the X-ray spike with the largest frequency offset at the "fresh" part of the electron bunch. After the chicane the electron beam and the radiation produced in the first undulator enter the second undulator which is resonant with the offset frequency. In the second undulator the seed radiation at reference frequency plays no role, and only a single (300 as duration) spike grows rapidly. The final part of the undulator is a tapered section allowing to achieve maximum output power 100-150 GW in 0.15 nm wavelength range. Attosecond X-ray pulse is naturally synchronized with its fs optical pulse which reveals unique perspective for pump-probe experiments with sub-femtosecond resolution.Comment: 14 pages, 13 fig

Biomarker analyses of clinical outcomes in patients with advanced hepatocellular carcinoma treated with Sorafenib with or without Erlotinib in the SEARCH Trial

Purpose: Sorafenib is the current standard therapy for advanced HCC, but validated biomarkers predicting clinical outcomes are lacking. This study aimed to identify biomarkers predicting prognosis and/or response to sorafenib, with or without erlotinib, in HCC patients from the phase 3 SEARCH trial. Experimental Design: 720 patients were randomized to receive oral sorafenib 400 mg BID plus erlotinib 150 mg QD or placebo. Fifteen growth factors relevant to the treatment regimen and/or to HCC were measured in baseline plasma samples. Results: Baseline plasma biomarkers were measured in 494 (69%) patients (sorafenib plus erlotinib, n=243; sorafenib plus placebo, n=251). Treatment arm–independent analyses showed that elevated HGF (HR, 1.687 [high vs low expression]; endpoint multiplicity adjusted [e-adj] P=0.0001) and elevated plasma VEGF-A (HR, 1.386; e-adj P=0..0377) were significantly associated with poor OS in multivariate analyses, and low plasma KIT (HR, 0.75 [high vs low]; P=0.0233; e-adj P=0.2793) tended to correlate with poorer OS. High plasma VEGF-C independently correlated with longer TTP (HR, 0.633; e-adj P=0.0010) and trended toward associating with improved disease control rate (univariate:OR, 2.047; P=0.030; e-adj P=0.420). In 67% of evaluable patients (339/494), a multimarker signature of HGF, VEGF-A, KIT, epigen, and VEGF-C correlated with improved median OS in multivariate analysis (HR, 0.150; P<0.00001). No biomarker predicted efficacy from erlotinib. Conclusions: Baseline plasma HGF, VEGF-A, KIT, and VEGF-C correlated with clinical outcomes in HCC patients treated with sorafenib with or without erlotinib. These biomarkers plus epigen constituted a multimarker signature for improved OS

Awareness and control of canine leishmaniosis: A survey among Spanish and French veterinarians

Zoonotic visceral leishmaniasis (ZVL) is a parasitic disease affecting dogs and humans, which is transmitted by female sandflies. Over the last decade, disease prevalence has increased fivefold in parts of southern Europe, where an estimated 2.5 million dogs are infected. This increase is mainly due to an expansion in sandfly distribution due to climate change and to the greater numbers of dogs travelling among European countries. To combat the spread of ZVL in Europe, international guidelines have been drawn up that describe strategies to prevent, control and monitor the disease. To investigate whether these strategies are being implemented in the field, we conducted an online survey among veterinarians in Spain (endemic for ZVL) and France (south: emerging; north: non-endemic). Of the 889 respondents, 459 veterinarians completed all questions. Although 60% of all veterinarians were aware of the current ZVL increase in Europe, 70% were not familiar with any guidelines for controlling the disease. Most of their preventive and treatment actions were, however, in line with intervention strategies recommended by the guidelines. From the veterinarians in this survey, 76% had received no reports regarding confirmed cases of canine leishmaniosis (CanL) or human visceral leishmaniasis in their region or country. The fact that 88% of confirmed cases of clinical CanL were not reported suggests inadequate disease monitoring and evaluation. We therefore recommend that an easy-to-use and accessible international online network be developed, where both veterinarians and physicians can report confirmed cases of leishmaniosis in dogs and humans. This is crucial for monitoring, controlling and preventing the further spread of ZVL in Europe at regional, national and international level

On the covariance of the Dirac-Born-Infeld-Myers action

A covariant version of the non-abelian Dirac-Born-Infeld-Myers action is presented. The non-abelian degrees of freedom are incorporated by adjoining to the (bosonic) worldvolume of the brane a number of anticommuting fermionic directions corresponding to boundary fermions in the string picture. The proposed action treats these variables as classical but can be given a matrix interpretation if a suitable quantisation prescription is adopted. After gauge-fixing and quantisation of the fermions, the action is shown to be in agreement with the Myers action derived from T-duality. It is also shown that the requirement of covariance in the above sense leads to a modified WZ term which also agrees with the one proposed by Myers.Comment: 18 pages. Minor alterations to the text; references adde

Managing information cycles for intra-organisational coordination of humanitarian logistics

As the humanitarian aid sector is expanding, the need for enhancing coordination capabilities increases as well. This holds especially for the area of logistics, because humanitarian operations typically take place in unstable and risky environments, where infrastructure is poor, while staff turnover is high. The effectiveness of humanitarian logistics critically depends on the availability and quality of logistics support information, but data is often scarce and ICT support to remote areas is limited. The challenges caused by these constraints call for conceptual insight into the intra-organisational coordination process in humanitarian aid. In order to assess current practice of intra-organisational logistics information management for humanitarian aid, we combine humanitarian logistics and organisational literatures to develop a model that ties in information cycles with activity cycles that ultimately should lead to value creation. The model serves as a basis to analyse coordination practice at the Dutch filial of Médecins Sans Frontiéres (MSF-Holland) and develop implications for research and practice

Local well-posedness for membranes in the light cone gauge

In this paper we consider the classical initial value problem for the bosonic membrane in light cone gauge. A Hamiltonian reduction gives a system with one constraint, the area preserving constraint. The Hamiltonian evolution equations corresponding to this system, however, fail to be hyperbolic. Making use of the area preserving constraint, an equivalent system of evolution equations is found, which is hyperbolic and has a well-posed initial value problem. We are thus able to solve the initial value problem for the Hamiltonian evolution equations by means of this equivalent system. We furthermore obtain a blowup criterion for the membrane evolution equations, and show, making use of the constraint, that one may achieve improved regularity estimates.Comment: 29 page

The non-abelian D-brane effective action through order α′4\alpha'{}^4

Requiring the existence of certain BPS solutions to the equations of motion, we determine the bosonic part of the non-abelian D-brane effective action through order $\alpha'{}^4$. We also propose an economic organizational principle for the effective action.Comment: 12 pages, 2 figures, JHEP styl