Diffraction of inelastically scattered electrons in tungsten at low energies

Diffraction of inelastically scattered electrons in tungsten at low energie

Efficient Gene Targeting Mediated by Adeno-Associated Virus and DNA Double-Strand Breaks

Gene targeting is the in situ manipulation of the sequence of an endogenous gene by the introduction of homologous exogenous DNA. Presently, the rate of gene targeting is too low for it to be broadly used in mammalian somatic cell genetics or to cure genetic diseases. Recently, it has been demonstrated that infection with recombinant adeno-associated virus (rAAV) vectors can mediate gene targeting in somatic cells, but the mechanism is unclear. This paper explores the balance between random integration and gene targeting with rAAV. Both random integration and spontaneous gene targeting are dependent on the multiplicity of infection (MOI) of rAAV. It has previously been shown that the introduction of a DNA double-stranded break (DSB) in a target gene can stimulate gene targeting by several-thousand-fold in somatic cells. Creation of a DSB stimulates the frequency of rAAV-mediated gene targeting by over 100-fold, suggesting that the mechanism of rAAV-mediated gene targeting involves, at least in part, the repair of DSBs by homologous recombination. Absolute gene targeting frequencies reach 0.8% with a dual vector system in which one rAAV vector provides a gene targeting substrate and a second vector expresses the nuclease that creates a DSB in the target gene. The frequencies of gene targeting that we achieved with relatively low MOIs suggest that combining rAAV vectors with DSBs is a promising strategy to broaden the application of gene targeting

Chimeric nucleases stimulate gene targeting in human cells

Gene targeting is a powerful technique to introduce genetic change into the genome of eukaryotic cells. It is widely used to create defined mutations in murine embryonic stem cells and theoretically could be used to create or repair mutations in somatic cells. In this way gene targeting could be a powerful form of gene correction type gene therapy. Despite its potential, gene targeting has not been widely used in somatic cells because of its low efficiency. We report on a system based on the correction of a mutated GFP gene that allows the efficient study of gene targeting in somatic cells. Using this system we show that gene targeting is stimulated over 2000-fold by the introduction of a DNA double-stranded break in the target locus (DSB-GT). We find that the rate of DSB-GT can be increased by increasing the amount of repair substrate, the amount of homology between the gene target and repair substrate, and by increasing the frequency of double-stranded break creation. When we optimize conditions for DSB-GT we obtain targeting rates of 3-5%. Finally, we show that chimeric nucleases, protein fusions between zinc finger DNA binding domains and the endonuclease domain of the Fokl restriction enzyme, can stimulate gene targeting in the genome of human somatic cells by several-thousand fold. Our data provides a paradigm for the use of gene targeting as a form of gene therapy for monogenic diseases

Estimation of gloss from rough surface parameters

Gloss is a quantity used in the optical industry to quantify and categorize materials according to how well they scatter light specularly. With the aid of phase perturbation theory, we derive an approximate expression for this quantity for a one-dimensional randomly rough surface. It is demonstrated that gloss depends in an exponential way on two dimensionless quantities that are associated with the surface randomness: the root-mean-square roughness times the perpendicular momentum transfer for the specular direction, and a correlation function dependent factor times a lateral momentum variable associated with the collection angle. Rigorous Monte Carlo simulations are used to access the quality of this approximation, and good agreement is observed over large regions of parameter space.Comment: 5 page

What is the housing with care ‘offer’ and who is it for? Written for the Housing Learning and Improvement Network (LIN)

Published to coincide with the International Day of Older Persons, this viewpoint explores some of the findings from Adult Social Services Environments and Settings (ASSET), a research project that was funded by the NIHR School for Social Care Research from February 2012 to April 2014. The project explored how adult social care services are commissioned and delivered in extra care housing and retirement villages. It is a timely paper, coming hot off the heels of the recent Commission on Long Term Care, chaired by former Care Services Minister, Paul Burstow MP. This recommended greater clarification on what constitutes housing with care

Approximating the Nonlinear Newsvendor and Single-Item Stochastic Lot-Sizing Problems When Data Is Given by an Oracle

The single-item stochastic lot-sizing problem is to find an inventory replenishment policy in the presence of discrete stochastic demands under periodic review and finite time horizon. A closely related problem is the single-period newsvendor model. It is well known that the newsvendor problem admits a closed formula for the optimal order quantity whenever the revenue and salvage values are linear increasing functions and the procurement (ordering) cost is fixed plus linear. The optimal policy for the single-item lot-sizing model is also well known under similar assumptions. In this paper we show that the classical (single-period) newsvendor model with fixed plus linear ordering cost cannot be approximated to any degree of accuracy when either the demand distribution or the cost functions are given by an oracle. We provide a fully polynomial time approximation scheme for the nonlinear single-item stochastic lot-sizing problem, when demand distribution is given by an oracle, procurement costs are provided as nondecreasing oracles, holding/backlogging/disposal costs are linear, and lead time is positive. Similar results exist for the nonlinear newsvendor problem. These approximation schemes are designed by extending the technique of K-approximation sets and functions.National Science Foundation (U.S.) (Contract CMMI-0758069)United States. Office of Naval Research (Grant N000141110056

Targeting the absence: Homozygous DNA deletions as immutable signposts for cancer therapy

Many cancers harbor homozygous DNA deletions (HDs). In contrast to other attributes of cancer cells, their HDs are immutable features that cannot change during tumor progression or therapy. I describe an approach, termed deletion-specific targeting (DST), that employs HDs (not their effects on RNA/protein circuits, but deletions themselves) as the targets of cancer therapy. The DST strategy brings together both existing and new methodologies, including the ubiquitin fusion technique, the split-ubiquitin assay, zinc-finger DNA-recognizing proteins and split restriction nucleases. The DST strategy also employs a feedback mechanism that receives input from a circuit operating as a Boolean OR gate and involves the activation of split nucleases, which destroy DST vector in normal (nontarget) cells. The logic of DST makes possible an incremental and essentially unlimited increase in the selectivity of therapy. If DST strategy can be implemented in a clinical setting, it may prove to be curative and substantially free of side effects