403 research outputs found
Prevalence of Clostridium difficile toxin genes in Pretoria
The hypervirulent polymerase chain reaction (PCR) ribotype 027 strain of Clostridium difficile produces toxins A, B and a binary
toxin. Toxin detection kits are commonly used in diagnostic laboratories, but have been unsuccessful in detecting all of the
relevant C. difficile strains, and the toxins produced. In this study, conventional PCR was used to detect the presence of the genes
of toxin A, toxin B and the binary toxin of C. difficile. Eighty-four frozen (collected between 2006-2007) and 13 fresh (collected in
2010) stool specimens, obtained in Pretoria, were analysed. The genes for toxin A, toxin B and the binary toxin were detected in
one of the fresh stool specimens. This may have implications for healthcare facilities, and suggests the possible emergence of
the highly virulent PCR ribotype 027 strain of C. difficile in Pretoria. This emphasises the importance of continuous surveillance
and monitoring of C. difficile outbreaks.http://www.sajei.co.za/index.php/SAJEIay201
SAT-Based Synthesis Methods for Safety Specs
Automatic synthesis of hardware components from declarative specifications is
an ambitious endeavor in computer aided design. Existing synthesis algorithms
are often implemented with Binary Decision Diagrams (BDDs), inheriting their
scalability limitations. Instead of BDDs, we propose several new methods to
synthesize finite-state systems from safety specifications using decision
procedures for the satisfiability of quantified and unquantified Boolean
formulas (SAT-, QBF- and EPR-solvers). The presented approaches are based on
computational learning, templates, or reduction to first-order logic. We also
present an efficient parallelization, and optimizations to utilize reachability
information and incremental solving. Finally, we compare all methods in an
extensive case study. Our new methods outperform BDDs and other existing work
on some classes of benchmarks, and our parallelization achieves a super-linear
speedup. This is an extended version of [5], featuring an additional appendix.Comment: Extended version of a paper at VMCAI'1
The temporal dynamics of Arc expression regulate cognitive flexibility
YesNeuronal activity regulates the transcription and
translation of the immediate-early gene Arc/Arg3.1,
a key mediator of synaptic plasticity. Proteasomedependent
degradation of Arc tightly limits its
temporal expression, yet the significance of this
regulation remains unknown. We disrupted the temporal
control of Arc degradation by creating an Arc
knockin mouse (ArcKR) where the predominant Arc
ubiquitination sites were mutated. ArcKR mice had
intact spatial learning but showed specific deficits
in selecting an optimal strategy during reversal
learning. This cognitive inflexibility was coupled to
changes in Arc mRNA and protein expression resulting
in a reduced threshold to induce mGluR-LTD and
enhanced mGluR-LTD amplitude. These findings
show that the abnormal persistence of Arc protein
limits the dynamic range of Arc signaling pathways
specifically during reversal learning. Our work
illuminates how the precise temporal control of activity-dependent
molecules, such as Arc, regulates synaptic
plasticity and is crucial for cognition.Open access funded by Biotechnology and Biological Sciences Research Counci
Stability of circular orbits of spinning particles in Schwarzschild-like space-times
Circular orbits of spinning test particles and their stability in
Schwarzschild-like backgrounds are investigated. For these space-times the
equations of motion admit solutions representing circular orbits with particles
spins being constant and normal to the plane of orbits. For the de Sitter
background the orbits are always stable with particle velocity and momentum
being co-linear along them. The world-line deviation equations for particles of
the same spin-to-mass ratios are solved and the resulting deviation vectors are
used to study the stability of orbits. It is shown that the orbits are stable
against radial perturbations. The general criterion for stability against
normal perturbations is obtained. Explicit calculations are performed in the
case of the Schwarzschild space-time leading to the conclusion that the orbits
are stable.Comment: eps figures, submitted to General Relativity and Gravitatio
Recommended from our members
Tomonaga–Luttinger liquid behavior and spinon confinement in YbAlO 3
Low dimensional quantum magnets are interesting because of the emerging collective behavior arising from strong quantum fluctuations. The one-dimensional (1D) S = 1/2 Heisenberg antiferromagnet is a paradigmatic example, whose low-energy excitations, known as spinons, carry fractional spin S = 1/2. These fractional modes can be reconfined by the application of a staggered magnetic field. Even though considerable progress has been made in the theoretical understanding of such magnets, experimental realizations of this low-dimensional physics are relatively rare. This is particularly true for rare-earth-based magnets because of the large effective spin anisotropy induced by the combination of strong spin–orbit coupling and crystal field splitting. Here, we demonstrate that the rare-earth perovskite YbAlO3 provides a realization of a quantum spin S = 1/2 chain material exhibiting both quantum critical Tomonaga–Luttinger liquid behavior and spinon confinement–deconfinement transitions in different regions of magnetic field–temperature phase diagram
Golgi Outpost Synthesis Impaired by Toxic Polyglutamine Proteins Contributes to Dendritic Pathology in Neurons
Dendrite aberration is a common feature of neurodegenerative diseases caused by protein toxicity, but the underlying mechanisms remain largely elusive. Here, we show that nuclear polyglutamine (polyQ) toxicity resulted in defective terminal dendrite elongation accompanied by a loss of Golgi outposts (GOPs) and a decreased supply of plasma membrane (PM) in Drosophila class IV dendritic arborization (da) (C4 da) neurons. mRNA sequencing revealed that genes downregulated by polyQ proteins included many secretory pathway-related genes, including COPII genes regulating GOP synthesis. Transcription factor enrichment analysis identified CREB3L1/CrebA, which regulates COPII gene expression. CrebA overexpression in C4 da neurons restores the dysregulation of COPII genes, GOP synthesis, and PM supply. Chromatin immunoprecipitation (ChIP)-PCR revealed that CrebA expression is regulated by CREB-binding protein (CBP), which is sequestered by polyQ proteins. Furthermore, co-overexpression of CrebA and Rac1 synergistically restores the polyQ-induced dendrite pathology. Collectively, our results suggest that GOPs impaired by polyQ proteins contribute to dendrite pathology through the CBP-CrebA-COPII pathway. ? 2017 The Author(s)113Ysciescopu
Evolution of cosmological perturbations in non-singular string cosmologies
In a class of non-singular cosmologies derived from higher-order corrections
to the low-energy bosonic string action, we derive evolution equations for the
most general cosmological scalar, vector and tensor perturbations. In the large
scale limit, the evolutions of both scalar and tensor perturbations are
characterised by conserved quantities, the usual curvature perturbation in the
uniform-field gauge and the tensor-type perturbed metric. The vector
perturbation is not affected, being described by the conservation of the
angular momentum of the fluid component in the absence of any additional
dissipative process. For the scalar- and tensor-type perturbations, we show
how, given a background evolution during kinetic driven inflation of the
dilaton field, we can obtain the final power spectra generated from the vacuum
quantum fluctuations of the metric and the dilaton field during the inflation.Comment: 11 pages, 2 figures, submitted to Phys. Rev.
Social Media, Gender and the Mediatisation of War: Exploring the German Armed Forces’ Visual Representation of the Afghanistan Operation on Facebook
Studies on the mediatisation of war point to attempts of governments to regulate the visual perspective of their involvements in armed conflict – the most notable example being the practice of ‘embedded reporting’ in Iraq and Afghanistan. This paper focuses on a different strategy of visual meaning-making, namely, the publication of images on social media by armed forces themselves. Specifically, we argue that the mediatisation of war literature could profit from an increased engagement with feminist research, both within Critical Security/Critical Military Studies and within Science and Technology Studies that highlight the close connection between masculinity, technology and control. The article examines the German military mission in Afghanistan as represented on the German armed forces’ official Facebook page. Germany constitutes an interesting, and largely neglected, case for the growing literature on the mediatisation of war: its strong antimilitarist political culture makes the representation of war particularly delicate. The paper examines specific representational patterns of Germany’s involvement in Afghanistan and discusses the implications which arise from what is placed inside the frame of visibility and what remains out of its view
Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology
notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations
Measurement of the ttbar Production Cross Section in ppbar collisions at sqrt s = 1.96 TeV in the All Hadronic Decay Mode
We report a measurement of the ttbar production cross section using the
CDF-II detector at the Fermilab Tevatron. The analysis is performed using 311
pb-1 of ppbar collisions at sqrt(s)=1.96 TeV. The data consist of events
selected with six or more hadronic jets with additional kinematic requirements.
At least one of these jets must be identified as a b-quark jet by the
reconstruction of a secondary vertex. The cross section is measured to be
sigma(tbart)=7.5+-2.1(stat.)+3.3-2.2(syst.)+0.5-0.4(lumi.) pb, which is
consistent with the standard model prediction.Comment: By CDF collaboratio
- …