874 research outputs found
Spiky Strings on I-brane
We study rigidly rotating strings in the near horizon geometry of the 1+1
dimensional intersection of two orthogonal stacks of NS5-branes, the so called
I-brane background. We solve the equations of motion of the fundamental string
action in the presence of two form NS-NS fluxes that the I-brane background
supports and write down general form of conserved quantities. We further find
out two limiting cases corresponding to giant magnon and single spike like
strings in various parameter space of solutions.Comment: 17 pages, major restructuring of text, added a referenc
Single stage repair of a complex pathology: end stage ischaemic cardiomyopathy, ascending aortic aneurysm and thoracic coarctation
The not uncommon combination of ascending aortic pathology with late presenting coarctation is a difficult surgical challenge. The two stage approach is usually adopted. The necessity for cardiac transplantation adds to the complexity: a trans-sternal approach and single stage repair become mandatory
Space charge limited conduction with exponential trap distribution in reduced graphene oxide sheets
We elucidate on the low mobility and charge traps of the chemically reduced
graphene oxide (RGO) sheets by measuring and analyzing temperature dependent
current-voltage characteristics. The RGO sheets were assembled between source
and drain electrodes via dielectrophoresis. At low bias voltage the conduction
is Ohmic while at high bias voltage and low temperatures the conduction becomes
space charge limited with an exponential distribution of traps. We estimate an
average trap density of 1.75x10^16 cm^-3. Quantitative information about charge
traps will help develop optimization strategies of passivating defects in order
to fabricate high quality solution processed graphene devices.Comment: 6 pages, 3 figures, 1 tabl
Finite-gap equations for strings on AdS_3 x S^3 x T^4 with mixed 3-form flux
We study superstrings on AdS_3 x S^3 x T^4 supported by a combination of
Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three form fluxes, and construct
a set of finite-gap equations that describe the classical string spectrum.
Using the recently proposed all-loop S-matrix we write down the all-loop Bethe
ansatz equations for the massive sector. In the thermodynamic limit the Bethe
ansatz reproduces the finite-gap equations. As part of this derivation we
propose expressions for the leading order dressing phases. These phases differ
from the well-known Arutyunov-Frolov-Staudacher phase that appears in the pure
Ramond-Ramond case. We also consider the one-loop quantization of the algebraic
curve and determine the one-loop corrections to the dressing phases. Finally we
consider some classical string solutions including finite size giant magnons
and circular strings.Comment: 44 pages, 3 figures. v2: references and a discussion about
perturbative results adde
The Weak Gravity Conjecture and the Viscosity Bound with Six-Derivative Corrections
The weak gravity conjecture and the shear viscosity to entropy density bound
place constraints on low energy effective field theories that may help to
distinguish which theories can be UV completed. Recently, there have been
suggestions of a possible correlation between the two constraints. In some
interesting cases, the behavior was precisely such that the conjectures were
mutually exclusive. Motivated by these works, we study the mass to charge and
shear viscosity to entropy density ratios for charged AdS5 black branes, which
are holographically dual to four-dimensional CFTs at finite temperature. We
study a family of four-derivative and six-derivative perturbative corrections
to these backgrounds. We identify the region in parameter space where the two
constraints are satisfied and in particular find that the inclusion of the
next-to-leading perturbative correction introduces wider possibilities for the
satisfaction of both constraints.Comment: 24 pages, 6 figures, v2: published version, refs added, minor
clarificatio
Physics, Astrophysics and Cosmology with Gravitational Waves
Gravitational wave detectors are already operating at interesting sensitivity
levels, and they have an upgrade path that should result in secure detections
by 2014. We review the physics of gravitational waves, how they interact with
detectors (bars and interferometers), and how these detectors operate. We study
the most likely sources of gravitational waves and review the data analysis
methods that are used to extract their signals from detector noise. Then we
consider the consequences of gravitational wave detections and observations for
physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version
<http://www.livingreviews.org/lrr-2009-2
Engineering Mesophase Stability and Structure via Incorporation of Cyclic Terminal Groups
We report on the characterisation of a number of liquid–crystalline materials featuring cyclic terminal groups, which lead to significant enhancements in the temperature range of the mesomorphic state. Materials with only short terminal chains are able to support lamellar mesophase formation by appending a large terminal cyclic unit at the end of a short spacer composed of methylene units. X-ray scattering experiments reveal that the layer spacings of the lamellar smectic phase are significantly larger when a cyclic end-group is present than for equivalent linear unsubstituted materials, but there is no effect on orientational order. Fully atomistic molecular dynamics simulations faithfully reproduce experimental layer spacings and orientational order parameters, and indicate that the cyclic terminal units spontaneously segregate into diffuse sub-layers and thus cause the increased layer spacing. This shape segregation predicted by molecular dynamics simulations is observed in the crystalline solid state by X-ray diffraction
Fluids in cosmology
We review the role of fluids in cosmology by first introducing them in
General Relativity and then by applying them to a FRW Universe's model. We
describe how relativistic and non-relativistic components evolve in the
background dynamics. We also introduce scalar fields to show that they are able
to yield an inflationary dynamics at very early times (inflation) and late
times (quintessence). Then, we proceed to study the thermodynamical properties
of the fluids and, lastly, its perturbed kinematics. We make emphasis in the
constrictions of parameters by recent cosmological probes.Comment: 34 pages, 4 figures, version accepted as invited review to the book
"Computational and Experimental Fluid Mechanics with Applications to Physics,
Engineering and the Environment". Version 2: typos corrected and references
expande
From whole bodies to single cells : a guide to transcriptomic approaches for ecology and evolutionary biology
Funding: The authors were assisted by a Special Topics Network (STN) grant from the European Society for Evolutionary Biology (ESEB) to facilitate networking of the European Drosophila Population Genomics consortium (DrosEU; https://droseu.net/). SG and NP are supported by a Deutsche Forschungsgemeinschaft grant (GR 4495/4-1, PO 1648/7-1, PO 1648/4-1). MGR is supported by Natural Environment Research Council, UK (NE/V001566/1). CS is supported by the Austrian Science Funds (P32935, P33734, W1225). TF is supported by the Swiss National Science Foundation (310030_219283, FZEB-0-214654, 31003A-182262). JG is supported by grant PID2020-115874GB-I00 funded by MCIN/AEI/10.13039/501100011033 and from grant 2021 SGR 00417 funded by Departament de Recerca i Universitats, Generalitat de Catalunya. MK was supported by the grant 322980 from The Research Council of Finland.RNA sequencing (RNAseq) methodology has experienced a burst of technological developments in the last decade, which has opened up opportunities for studying the mechanisms of adaptation to environmental factors at both the organismal and cellular level. Selecting the most suitable experimental approach for specific research questions and model systems can, however, be a challenge and researchers in ecology and evolution are commonly faced with the choice of whether to study gene expression variation in whole bodies, specific tissues, and/or single cells. A wide range of sometimes polarised opinions exists over which approach is best. Here, we highlight the advantages and disadvantages of each of these approaches to provide a guide to help researchers make informed decisions and maximise the power of their study. Using illustrative examples of various ecological and evolutionary research questions, we guide the readers through the different RNAseq approaches and help them identify the most suitable design for their own projects.Peer reviewe
Emerging issues and current trends in assistive technology use 2007-1010: practising, assisting and enabling learning for all
Following an earlier review in 2007, a further review of the academic literature relating to the uses of assistive technology (AT) by children and young people was completed, covering the period 2007-2011. As in the earlier review, a tripartite taxonomy: technology uses to train or practise, technology uses to assist learning and technology uses to enable learning, was used in order to structure the findings. The key markers for research in this field and during these three years were user involvement, AT on mobile mainstream devices, the visibility of AT, technology for interaction and collaboration, new and developing interfaces and inclusive design principles. The paper concludes by locating these developments within the broader framework of the Digital Divide
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