3,037 research outputs found
Non-abelian D=11 Supermembrane
We obtain a U(M) action for supermembranes with central charges in the Light
Cone Gauge (LCG). The theory realizes all of the symmetries and constraints of
the supermembrane together with the invariance under a U(M) gauge group with M
arbitrary. The worldvolume action has (LCG) N=8 supersymmetry and it
corresponds to M parallel supermembranes minimally immersed on the target M9xT2
(MIM2). In order to ensure the invariance under the symmetries and to close the
corresponding algebra, a star-product determined by the central charge
condition is introduced. It is constructed with a nonconstant symplectic
two-form where curvature terms are also present. The theory is in the strongly
coupled gauge-gravity regime. At low energies, the theory enters in a
decoupling limit and it is described by an ordinary N=8 SYM in the IR phase for
any number of M2-branes.Comment: Contribution to the Proceedings of the Dubna International SQS'09
Workshop ("Supersymmetries and Quantum Symmetries-2009", July 29 - August 3,
2009. 12pg, Late
Supersymmetric exact sequence, heat kernel and super KdV hierarchy
We introduce the free N=1 supersymmetric derivation ring and prove the
existence of an exact sequence of supersymmetric rings and linear
transformations. We apply necessary and sufficient conditions arising from this
exact supersymmetric sequence to obtain the essential relations between
conserved quantities, gradients and the N=1 super KdV hierarchy. We combine
this algebraic approach with an analytic analysis of the super heat operator.We
obtain the explicit expression for the Green's function of the super heat
operator in terms of a series expansion and discuss its properties. The
expansion is convergent under the assumption of bounded bosonic and fermionic
potentials. We show that the asymptotic expansion when of the Green's
function for the super heat operator evaluated over its diagonal generates all
the members of the N=1 super KdV hierarchy.Comment: 20 pages, to be published in JM
Social pedagogy as a model to provide support for siblings of children with intellectual disabilities: A report of the views of the children and young people using a sibling support group.
The experiences of non-disabled children growing up with a sibling with an intellectual disability vary considerably, with reported impact ranging from increased mental health problems through evaluations of life enhancement. However, there is evidence that the net impact is neutral to positive, which was supported by the findings of this report of a service evaluation survey. The value of providing support to those young siblings is however clear. An established method of support is within a group of peers who also have a sibling with an intellectual disability, though no specific method for running this type of group has yet been fully explored. This article reports the views of 39 children taking part in such a group, analysing their perspective through a proposed model for the operation of sibling groups: social pedagogy. It was found that the closer the group's activities were to social pedagogy, the more supported the children and young people felt
A Meiotic Checkpoint Alters Repair Partner Bias to Permit Inter-sister Repair of Persistent DSBs
Accurate meiotic chromosome segregation critically depends on the formation of inter-homolog crossovers initiated by double-strand breaks (DSBs). Inaccuracies in this process can drive aneuploidy and developmental defects, but how meiotic cells are protected from unscheduled DNA breaks remains unexplored. Here we define a checkpoint response to persistent meiotic DSBs in C. elegans that phosphorylates the synaptonemal complex (SC) to switch repair partner from the homolog to the sister chromatid. A key target of this response is the core SC component SYP-1, which is phosphorylated in response to ionizing radiation (IR) or unrepaired meiotic DSBs. Failure to phosphorylate (syp-16A) or dephosphorylate (syp-16D) SYP-1 in response to DNA damage results in chromosome non-dysjunction, hyper-sensitivity to IR-induced DSBs, and synthetic lethality with loss of brc-1BRCA1. Since BRC-1 is required for inter-sister repair, these observations reveal that checkpoint-dependent SYP-1 phosphorylation safeguards the germline against persistent meiotic DSBs by channelling repair to the sister chromatid.Cancer Research UK FC0010048UK Medical Research Council FC0010048Wellcome Trust FC0010048Ministerio de EconomĂa y Competitividad BFU2016-75058-PEuropean Research Council ERC2014 AdG669898 TARLOO
The role of science in physical natural hazard assessment : report to the UK Government by the Natural Hazard Working Group
Following the tragic Asian tsunami on 26 December 2004, the Prime Minister asked
the Government’s Chief Scientific Adviser, Sir David King, to convene a group of
experts (the Natural Hazard Working Group) to advise on the mechanisms that could
and should be established for the detection and early warning of global physical
natural hazards.
2. The Group was asked to examine physical hazards which have high global or regional
impact and for which an appropriate early warning system could be put in place. It
was also asked to consider the global natural hazard frameworks currently in place
and under development and their effectiveness in using scientific evidence; to
consider whether there is an existing appropriate international body to pull together
the international science community to advise governments on the systems that need
to be put in place, and to advise on research needed to fill current gaps in knowledge.
The Group was asked to make recommendations on whether a new body was
needed, or whether other arrangements would be more effective
The response of perennial and temporary headwater stream invertebrate communities to hydrological extremes
The headwaters of karst rivers experience considerable hydrological variability, including spates and streambed drying. Extreme summer flooding on the River Lathkill (Derbyshire, UK) provided the opportunity to examine the invertebrate community response to unseasonal spate flows, flow recession and, at temporary sites, streambed drying. Invertebrates were sampled at sites with differing flow permanence regimes during and after the spates. Following streambed drying at temporary sites, dewatered surface sediments were investigated as a refugium for aquatic invertebrates. Experimental rehydration of these dewatered sediments was conducted to promote development of desiccation-tolerant life stages. At perennial sites, spate flows reduced invertebrate abundance and diversity, whilst at temporary sites, flow reactivation facilitated rapid colonisation of the surface channel by a limited number of invertebrate taxa. Following streambed drying, 38 taxa were recorded from the dewatered and rehydrated sediments, with Oligochaeta being the most abundant taxon and Chironomidae (Diptera) the most diverse. Experimental rehydration of dewatered sediments revealed the presence of additional taxa, including Stenophylax sp. (Trichoptera: Limnephilidae) and Nemoura sp. (Plecoptera: Nemouridae). The influence of flow permanence on invertebrate community composition was apparent despite the aseasonal high-magnitude flood events
Formal Analysis of Linear Control Systems using Theorem Proving
Control systems are an integral part of almost every engineering and physical
system and thus their accurate analysis is of utmost importance. Traditionally,
control systems are analyzed using paper-and-pencil proof and computer
simulation methods, however, both of these methods cannot provide accurate
analysis due to their inherent limitations. Model checking has been widely used
to analyze control systems but the continuous nature of their environment and
physical components cannot be truly captured by a state-transition system in
this technique. To overcome these limitations, we propose to use
higher-order-logic theorem proving for analyzing linear control systems based
on a formalized theory of the Laplace transform method. For this purpose, we
have formalized the foundations of linear control system analysis in
higher-order logic so that a linear control system can be readily modeled and
analyzed. The paper presents a new formalization of the Laplace transform and
the formal verification of its properties that are frequently used in the
transfer function based analysis to judge the frequency response, gain margin
and phase margin, and stability of a linear control system. We also formalize
the active realizations of various controllers, like
Proportional-Integral-Derivative (PID), Proportional-Integral (PI),
Proportional-Derivative (PD), and various active and passive compensators, like
lead, lag and lag-lead. For illustration, we present a formal analysis of an
unmanned free-swimming submersible vehicle using the HOL Light theorem prover.Comment: International Conference on Formal Engineering Method
- …