4,212 research outputs found
Sac1p mediates the adenosine triphosphate transport into yeast endoplasmic reticulum that is required for protein translocation.
Protein translocation into the yeast endoplasmic reticulum requires the transport of ATP into the lumen of this organelle. Microsomal ATP transport activity was reconstituted into proteoliposomes to characterize and identify the transporter protein. A polypeptide was purified whose partial amino acid sequence demonstrated its identity to the product of the SAC1 gene. Accordingly, microsomal membranes isolated from strains harboring a deletion in the SAC1 gene (sac1 delta) were found to be deficient in ATP-transporting activity as well as severely compromised in their ability to translocate nascent prepro-alpha-factor and preprocarboxypeptidase Y. Proteins isolated from the microsomal membranes of a sac1 delta strain were incapable of stimulating ATP transport when reconstituted into the in vitro assay system. When immunopurified to homogeneity and incorporated into artificial lipid vesicles, Sac1p was shown to reconstitute ATP transport activity. Consistent with the requirement for ATP in the lumen of the ER to achieve the correct folding of secretory proteins, the sac1 delta strain was shown to have a severe defect in transport of procarboxypeptidase Y out of the ER and into the Golgi complex in vivo. The collective data indicate an intimate role for Sac1p in the transport of ATP into the ER lumen
Conformal Toda theory with a boundary
We investigate sl(n) conformal Toda theory with maximally symmetric
boundaries. There are two types of maximally symmetric boundary conditions, due
to the existence of an order two automorphism of the W(n>2) algebra. In one of
the two cases, we find that there exist D-branes of all possible dimensions 0
=< d =< n-1, which correspond to partly degenerate representations of the W(n)
algebra. We perform classical and conformal bootstrap analyses of such
D-branes, and relate these two approaches by using the semi-classical light
asymptotic limit. In particular we determine the bulk one-point functions. We
observe remarkably severe divergences in the annulus partition functions, and
attribute their origin to the existence of infinite multiplicities in the
fusion of representations of the W(n>2) algebra. We also comment on the issue
of the existence of a boundary action, using the calculus of constrained
functional forms, and derive the generating function of the B"acklund
transformation for sl(3) Toda classical mechanics, using the minisuperspace
limit of the bulk one-point function.Comment: 42 pages; version 4: added clarifications in section 2.2 and
footnotes 1 and
Cosmological Birefringence: an Astrophysical test of Fundamental Physics
We review the methods used to test for the existence of cosmological
birefringence, i.e. a rotation of the plane of linear polarization for
electromagnetic radiation traveling over cosmological distances, which might
arise in a number of important contexts involving the violation of fundamental
physical principles. The main methods use: (1) the radio polarization of radio
galaxies and quasars, (2) the ultraviolet polarization of radio galaxies, and
(3) the cosmic microwave background polarization. We discuss the main results
obtained so far, the advantages and disadvantages of each method, and future
prospects.Comment: To appear in the Proceedings of the JENAM 2010 Symposium "From
Varying Couplings to Fundamental Physics", held in Lisbon, 6-10 Sept. 201
On AGT description of N=2 SCFT with N_f=4
We consider Alday-Gaiotto-Tachikawa (AGT) realization of the Nekrasov
partition function of N=2 SCFT. We focus our attention on the SU(2) theory with
N_f=4 flavor symmetry, whose partition function, according to AGT, is given by
the Liouville four-point function on the sphere. The gauge theory with N_f=4 is
known to exhibit SO(8) symmetry. We explain how the Weyl symmetry
transformations of SO(8) flavor symmetry are realized in the Liouville theory
picture. This is associated to functional properties of the Liouville
four-point function that are a priori unexpected. In turn, this can be thought
of as a non-trivial consistency check of AGT conjecture. We also make some
comments on elementary surface operators and WZW theory.Comment: 18 pages. v2, a misinterpretation in the gauge theory side has been
corrected; title and introduction were changed accordingl
The Combinatorics of Alternating Tangles: from theory to computerized enumeration
We study the enumeration of alternating links and tangles, considered up to
topological (flype) equivalences. A weight is given to each connected
component, and in particular the limit yields information about
(alternating) knots. Using a finite renormalization scheme for an associated
matrix model, we first reduce the task to that of enumerating planar
tetravalent diagrams with two types of vertices (self-intersections and
tangencies), where now the subtle issue of topological equivalences has been
eliminated. The number of such diagrams with vertices scales as for
. We next show how to efficiently enumerate these diagrams (in time
) by using a transfer matrix method. We give results for various
generating functions up to 22 crossings. We then comment on their large-order
asymptotic behavior.Comment: proceedings European Summer School St-Petersburg 200
Towards personalised management of atherosclerosis via computational models in vascular clinics: technology based on patient-specific simulation approach
The development of a new technology based on patient-specific modelling for personalised healthcare in the case of atherosclerosis is presented. Atherosclerosis is the main cause of death in the world and it has become a burden on clinical services as it manifests itself in many diverse forms, such as coronary artery disease, cerebrovascular disease/stroke and peripheral arterial disease. It is also a multifactorial, chronic and systemic process that lasts for a lifetime, putting enormous financial and clinical pressure on national health systems. In this Letter, the postulate is that the development of new technologies for healthcare using computer simulations can, in the future, be developed as in-silico management and support systems. These new technologies will be based on predictive models (including the integration of observations, theories and predictions across a range of temporal and spatial scales, scientific disciplines, key risk factors and anatomical sub-systems) combined with digital patient data and visualisation tools. Although the problem is extremely complex, a simulation workflow and an exemplar application of this type of technology for clinical use is presented, which is currently being developed by a multidisciplinary team following the requirements and constraints of the Vascular Service Unit at the University College Hospital, London
Higher Equations of Motion in Boundary Liouville Field Theory
In addition to the ordinary bulk higher equations of motion in the boundary
version of the Liouville conformal field theory, an infinite set of relations
containing the boundary operators is found. These equations are in one-to-one
correspondence with the singular representations of the Virasoro algebra. We
comment on the possible applications in the context of minimal boundary
Liouville gravity.Comment: 18 page
Climate Change and Childhood Respiratory Health: A Call to Action for Paediatricians
Climate change (CC) is one of the main contributors to health emergencies worldwide. CC appears to be closely interrelated with air pollution, as some pollutants like carbon dioxide (CO2), nitrogen oxides (NOx) and black carbon are naturally occurring greenhouse gases. Air pollution may enhance the allergenicity of some plants and, also, has an adverse effect on respiratory health. Children are a uniquely vulnerable group that suffers disproportionately from CC burden. The increasing global warming related to CC has a big impact on plants' lifecycles, with earlier and longer pollen seasons, as well as higher pollen production, putting children affected by asthma and allergic rhinitis at risk for exacerbations. Extreme weather events may play a role too, not only in the exacerbations of allergic respiratory diseases but, also, in favouring respiratory infections. Even though paediatricians are already seeing the impacts of CC on their patients, their knowledge about CC-related health outcomes with specific regards to children's respiratory health is incomplete. This advocates for paediatricians' increased awareness and a better understanding of the CC impact on children's respiratory health. Having a special responsibility for children, paediatricians should actively be involved in policies aimed to protect the next generation from CC-related adverse health effects. Hence, there is an urgent need for them to take action and successfully educate families about CC issues. This paper aims at reviewing the evidence of CC-related environmental factors such as temperature, humidity, rainfall and extreme events on respiratory allergic diseases and respiratory infections in children and proposing specific actionable items for paediatricians to deal with CC-related health issues in their clinical practice
The SKA and "High-Resolution" Science
"High-resolution", or "long-baseline", science with the SKA and its
precursors covers a broad range of topics in astrophysics. In several research
areas, the coupling between improved brightness sensitivity of the SKA and a
sub-arcsecond resolution would uncover truly unique avenues and opportunities
for studying extreme states of matter, vicinity of compact relativistic
objects, and complex processes in astrophysical plasmas. At the same time, long
baselines would secure excellent positional and astrometric measurements with
the SKA and critically enhance SKA image fidelity at all scales. The latter
aspect may also have a substantial impact on the survey speed of the SKA, thus
affecting several key science projects of the instrument.Comment: JENAM-2010: Invited talk at JENAM session S7: The Square Kilometre
Array: Paving the way for the new 21st century radio astronomy paradigm; 9
page
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