Study of the charge-exchange reactions\pi ^ - p \to (\pi ^0 ,\eta ,\eta \prime )n at 63 GeV

Muon electron pairs were detected in an Al multiplate spark chamber, exposed to a neutrino beam from the CERN PS. The leptons were not accompanied by other particles, except occasionally by protons. The background came mainly from muon associated π⁰ production, with one decay gamma lost. It was determined empirically, together with the small contribution from υ _e reactions. For electron energies above 2 GeV the background is 5.7±1.5 events, whereas 18 (μe)-candidates have been observed. Hence the effect is established, with a rate of about 10^?4 as compared to the muonic reactions above 3 GeV. Charm creation as the origin of this (μe)-production process is excluded; heavy neutral lepton production does not fit the kinematics observed. Instead the events are compatible with the two-body decay of an object with variable invariant mass of order 1 GeV, possibly resulting from axion interactions.     

Genetic screens and selections for small molecules based on a synthetic riboswitch that activates protein translation

Genetic selection provides the most powerful method to assay large libraries of biomolecules for function. However, harnessing the power of genetic selection for the detection of specific, nonendogenous small-molecule targets in vivo remains a significant challenge. The ability to genetically select for small molecules would provide a reaction-independent mechanism to clone biosynthesis genes from large DNA libraries and greatly facilitate the exploration of large libraries of mutant enzymes for improved synthetic capabilities including altered substrate specificities and enhanced regio- or stereoselectivities. While remarkable progress has been made in developing genetic methods to detect small molecules in vivo, many of these methods rely on engineering small-molecule-protein interactions which remains a difficult problem, and the potential for some of these systems to assay large libraries is limited by the low transformation efficiency and long doubling time of yeast relative to bacteria. Herein, we demonstrate that synthetic riboswitches that activate protein translation in response to a specific small molecule can be used to perform sensitive genetic screens and selections for the presence of small molecules in Escherichia coli. We further demonstrate that the exquisite molecular discrimination properties of aptamers selected in vitro translate directly into an in vivo genetic selection system. Finally, we demonstrate that a cell harboring a synthetic riboswitch with a particular ligand specificity can be selectively amplified from a million-fold larger pool of cells containing mutant riboswitches that respond to a closely related ligand, suggesting that it is possible to use genetic selection in E. coli to discover synthetic riboswitches with new ligand specificities from libraries of mutant riboswitches.     

A counterexample to a ‘simplex algorithm’ for convex bodies

A counterexample, in E ³, is given to the following conjecture. Suppose f ^* is a linear functional, and e an exposed point of a convex body K such that f ^* does not attain its maximum on K at e; then there is an f ^*-strictly increasing path in the one-skeleton of K emanating from e. The counterexample shows that a certain generalized simplex algorithm fails. Furthermore for a different linear functional f, there are no three disjoint f-strictly increasing paths in the one-skeleton of K leading to e.     

Complete subgraphs of the graphs of convex polytopes

It is shown that if three vertices of the graph G(l') of a convex 3-polytope P are chosen, then G(P) contains a refinement of the complete graph C₄ on four vertices, for which the three chosen vertices are principal (that is, correspond to vertices of C₄ in the refinement). In general, all four vertices may not be preassigned as principal. For dimensions d?4, simple (simplicial) d-polytopes are constructed whose graphs contain sets of three (four) vertices, which cannot all be principal in any refinement of C₄₊₁.     

Episodic paroxysmal laryngospasm: Voice and pulmonary function assessment and management

Episodic paroxysmal laryngospasm (EPL) is a sign of laryngeal dysfunction, often without a specific organic etiology, which can masquerade as asthma, vocal fold paralysis, or a functional voice disorder. The intermittent respiratory distress of EPL may precipitate an apparent upper airway obstructive emergency, resulting in unnecessary endotracheal intubation, cardiopulmonary resuscitation, or tracheostomy. During 27 months, seven women and three men, ages 30–76 years, were assessed by a high diagnostic index of suspicion, an intensive history including psychosocial factors, physical examination of the airways, provocative asthma testing, and swallowing studies. Videolaryngoscopy, stroboscopy, and pulmonary flow-volume loop testing were definitive. The classic appearance was paradoxic inspiratory adduction of the anterior vocal folds with a posterior diamond-shaped glottic gap. During an attack of stridor or wheezing, attenuation of the inspiratory flow rate as depicted by the flow-volume loop suggested partial extrathoracic upper airway obstruction. Swallowing evaluation by videolaryngoscopy and videoesophagography may uncover gastroesophageal reflux disease. Hallmarks of management include patient and family education by observation of laryngoscopic videos, a specific speech therapy program, psychotherapy, and medical treatment of associated disorders. Electromyography may become a valuable future adjunct. Unlike laryngeal dystonia, patients with EPL do not benefit from botulinum toxin type A.     

Estimating a Markov Transition Matrix from Observational Data

Markov chains are frequently used in Operational Research to describe how a system changes over time, its behaviour being governed by its transition matrix. This paper describes a technique for finding a maximum likelihood estimate for such a transition matrix when a system is observed at infrequent time intervals. The technique is called the EM Algorithm which, for this kind of problem, has distinct advantages over other methods of optimization.     

A partial-wave analysis of the reaction π−p → K+K−n measured on a polarized target at ∼18 GeV/c

The reaction π^?p→K⁺K^?n has been studied on a hydrogen target (27 000 events) at 18.4 GeV/c and on a polarized target (54 000 events) at 17.2 GeV/c. A combination of results of both experiments allows a partial-wave analysis of the K⁺K^? system between 1.1 and 1.74 GeV mass without any model assumptions. In general our fits yield unique solutions. Using results of our previous analysis of π⁺π^? final states and assuming the dominance of the positive G-parity states in the K⁺K^? system, the branching ratios $\text{BR}\text{(}\text{K}\text{K}\text{/ππ)}$ of partial waves into $\text{K}\text{K}\text{and}\text{ππ}$ are determined. The S-wave appears to be mainly a broad ε (1300) with $\text{BR}\text{(}\text{K K}\text{/ππ) = 0.068}{}_{\mathrm{?0.021}}{}^{\mathrm{+0.017}}$. The weak P-wave can be described by a tail of the $\text{?(770)}\text{with BR}\text{(}\text{K K}\text{/ππ) = 0.081}{}_{\mathrm{?0.025}}{}^{\mathrm{+0.029}}$. The D-wave is interpreted in terms of a superposition of f(1270) + A₂(1310) + f′(1515) resonances. The fit yields $\text{BR}\text{(}\text{K K}\text{/ππ) = 0.069}{}_{\mathrm{?0.031}}{}^{\mathrm{+0.023}}$ for the f(1270) and BR(ππ/all) = 0.027_?0.013^+0.071 for the f′(1515). The F-wave shows the g(1690) meson with $\text{BR}\text{(}\text{K K}\text{/ππ) = 0.191}{}_{\mathrm{?0.037}}{}^{\mathrm{+0.040}}$. All the above values refer to the t bin between 0.01 and 0.20 (GeV/c)². Some results are also given for the high-t region.     

Evidence for a spin-5 boson resonance at 2300 MeV

Evidence is given for the existence of a spin-5 boson resonance from the analysis of the reaction π^?p→K⁺K^?n at 62 GeV incident momentum. A simplified amplitude analysis with a Breit-Wigner ansatz leads to a mass 2307 ± 6 MeV and a width of 245 ± 20 MeV. The quantum numbers of the resonance are J^P = 5^?, C = ?1, and very probably I^G = 1⁺.     

Modelling toolkit to assist with introducing a stepped care system design in mental health care

We describe a modelling toolkit that was developed with the aim of assisting those responsible for introducing stepped care systems to local mental health services in the UK. The toolkit was pre-populated with real patient flow data collected from four sites that piloted the stepped care system design. Two analytical models were developed and coded as part of the toolkit to provide insights concerning workload, patient throughput, and changes in waiting times and waiting list size. An interface was built to allow users to specify their own stepped care system and input their own estimates or data of service demands and capacities at different steps. Despite the challenges and limitations, the use of modelling to inform the design of new service configurations is an important step in the right direction and we would recommend this as a reasonable way forward.