Ceric and ferrous dosimeters show precision for 50-5000 rad range

Ammonium thiocyanate, added to the usual ferrous sulfate dosimeter solution, yielded a very stable, precise and temperature-independent system eight times as sensitive as the classical Fricke system in the 50 to 5000 rad range. The ceric dosimeters, promising for use in mixed radiation fields, respond nearly independently of LET

A stochastic control approach to no-arbitrage bounds given marginals, with an application to lookback options

We consider the problem of superhedging under volatility uncertainty for an investor allowed to dynamically trade the underlying asset, and statically trade European call options for all possible strikes with some given maturity. This problem is classically approached by means of the Skorohod Embedding Problem (SEP). Instead, we provide a dual formulation which converts the superhedging problem into a continuous martingale optimal transportation problem. We then show that this formulation allows us to recover previously known results about lookback options. In particular, our methodology induces a new proof of the optimality of Az\'{e}ma-Yor solution of the SEP for a certain class of lookback options. Unlike the SEP technique, our approach applies to a large class of exotics and is suitable for numerical approximation techniques.Comment: Published in at http://dx.doi.org/10.1214/13-AAP925 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Cyclic nucleotide-gated channels: structural basis of ligand efficacy and allosteric modulation

Most working proteins, including metabolic enzymes, transcription regulators, and membrane receptors, transporters, and ion channels, share the property of allosteric coupling. The term 'allosteric' means that these proteins mediate indirect interactions between sites that are physically separated on the protein. In the example of ligand-gated ion channels, the binding of a suitable ligand elicits local conformational changes at the binding site, which are coupled to further conformational changes in regions distant from the binding site. The physical motions finally arrive at the site of biological activity: the ion-permeating pore. The conformational changes that lead from the ligand binding to the actual opening of the pore comprise 'gating'. In 1956, del Castillo and Katz suggested that the competition between different ligands at nicotinic acetylcholine receptors (nAChRs) could be explained by formation of an intermediate, ligand-bound, yet inactive state of the receptor, which separates the active state of the receptor from the initial binding of the ligand (del Castillo & Katz, 1957). This 'binding-then-gating', two-step model went beyond the then-prevailing drug-receptor model that assumes a single bimolecular binding reaction, and paralleled Stephenson's conceptual dichotomy of 'affinity' and 'efficacy' (Stephenson, 1956). In 1965 Monod, Wyman and Changeux presented a simple allosteric model (the MWC model) (Monod et al. 1965) that explained the cooperative binding of oxygen to haemoglobin; it was adopted as an important paradigm for ligand-gated channels soon after its initial formulation (Changeux et al. 1967; Karlin, 1967; Colquhoun, 1973)

Generalised fractional diffusion equations for subdiffusion on arbitrarily growing domains

Many physical phenomena occur on domains that grow in time. When the timescales of the phenomena and domain growth are comparable, models must include the dynamics of the domain. A widespread intrinsically slow transport process is subdiffusion. Many models of subdiffusion include a history dependence. This greatly confounds efforts to incorporate domain growth. Here we derive the fractional partial differential equations that govern subdiffusion on a growing domain, based on a Continuous Time Random Walk. This requires the introduction of a new, comoving, fractional derivative.Comment: 12 pages, 1 figur

The prevalence of cocaine-associated chest pain in a London hospital

Objectives: To determine the prevalence of cocaine misuse in patients presenting to an Accident and Emergency department with chest pain. 4 of 12 FAEM abstracts www.emjonline.co

Mutations in M2 alter the selectivity of the mouse nicotinic acetylcholine receptor for organic and alkali metal cations

We measured the permeability ratios (PX/PNa) of 3 wild-type, 1 hybrid, 2 subunit-deficient, and 22 mutant nicotinic receptors expressed in Xenopus oocytes for alkali metal and organic cations using shifts in the bi-ionic reversal potential of the macroscopic current. Mutations at three positions (2', 6', 10') in M2 affected ion selectivity. Mutations at position 2' (alpha Thr244, beta Gly255, gamma Thr253, delta Ser258) near the intracellular end of M2 changed the organic cation permeability ratios as much as twofold and reduced PCs/PNa and PK/PNa by 16-18%. Mutations at positions 6' and 10' increased the glycine ethyl ester/Na+ and glycine methyl ester/Na+ permeability ratios. Two subunit alterations also affected selectivity: omission of the delta subunit reduced PCs/PNa by 16%, and substitution of Xenopus delta for mouse delta increased Pguanidinium/PNa more than twofold and reduced PCs/PNa by 34% and PLi/PNa by 20%. The wild-type mouse receptor displayed a surprising interaction with the primary ammonium cations; relative permeability peaked at a chain length equal to four carbons. Analysis of the organic permeability ratios for the wild-type mouse receptor shows that (a) the diameter of the narrowest part of the pore is 8.4 A; (b) the mouse receptor departs significantly from size selectivity for monovalent organic cations; and (c) lowering the temperature reduces Pguanidinium/PNa by 38% and Pbutylammonium/PNa more than twofold. The results reinforce present views that positions -1' and 2' are the narrowest part of the pore and suggest that positions 6' and 10' align some permeant organic cations in the pore in an interaction similar to that with channel blocker, QX-222

Tris+/Na+ permeability ratios of nicotinic acetylcholine receptors are reduced by mutations near the intracellular end of the M2 region

Tris+/Na+ permeability ratios were measured from shifts in the biionic reversal potentials of the macroscopic ACh-induced currents for 3 wild- type (WT), 1 hybrid, 2 subunit-deficient, and 25 mutant nicotinic receptors expressed in Xenopus oocytes. At two positions near the putative intracellular end of M2, 2' (alpha Thr244, beta Gly255, gamma Thr253, delta Ser258) and -1', point mutations reduced the relative Tris+ permeability of the mouse receptor as much as threefold. Comparable mutations at several other positions had no effects on relative Tris+ permeability. Mutations in delta had a greater effect on relative Tris+ permeability than did comparable mutations in gamma; omission of the mouse delta subunit (delta 0 receptor) or replacement of mouse delta with Xenopus delta dramatically reduced relative Tris+ permeability. The WT mouse muscle receptor (alpha beta gamma delta) had a higher relative permeability to Tris+ than the wild-type Torpedo receptor. Analysis of the data show that (a) changes in the Tris+/Na+ permeability ratio produced by mutations correlate better with the hydrophobicity of the amino acid residues in M2 than with their volume; and (b) the mole-fraction dependence of the reversal potential in mixed Na+/Tris+ solutions is approximately consistent with the Goldman- Hodgkin-Katz voltage equation. The results suggest that the main ion selectivity filter for large monovalent cations in the ACh receptor channel is the region delimited by positions -1' and 2' near the intracellular end of the M2 helix

Life-limiting fetal conditions: Are Australian student midwives prepared? A mixed-methods survey

Aim: To document current teaching methods, curriculum, and perceived educational preparation related to the teaching of life-limiting fetal conditions, termination, and perinatal palliative care to Australian student midwives. Background: Australian women receiving a diagnosis of a life-limiting fetal condition are generally offered a choice between termination of pregnancy and perinatal palliative care. Midwives are often involved with caring for these women. What Australian student midwives are being taught about life-limiting fetal conditions, termination of pregnancy, and perinatal palliative care during their entry-to-practice program is unknown. Design: This study utilised a mixed-methods descriptive approach for data collection and analysis. Methods: Academic Leads of all Australian entry-to-practice midwifery programs received a questionnaire exploring topics taught, teaching time, teacher role, and perceived effectiveness of student preparation. Data was analysed statistically and thematically. Results: Twelve of 24 Academic Leads responded (50%); only five stated their programs taught all three areas. More respondents taught about termination of pregnancy (10/12) than perinatal palliative care (7/12). On average 5.8 ( ± 2.8) total hours was spent teaching about life-limiting fetal conditions, termination of pregnancy, and perinatal palliative care during the entire midwifery program, with a range of 1 – 10 h. The free-text data identified three central themes: lack of value within the curriculum; disconnect between the university and the placement hospital; and preparation for practice. Most (10/12) Academic Leads did not believe student midwives are prepared to care for affected families. Conclusions: Entry-to-practice midwifery programs vary considerably in their education surrounding life-limiting fetal conditions, however teaching hours overall were low and most Academic leads did not feel (or know if) their students were adequately prepared. Further research is required to determine if early career midwives find their university education in life-limiting fetal conditions adequate preparation for practice, and to then remediate identified deficiencies