Synthetic aspects of host-guest chemistry

Imperial Users onl

Development of the health and economic consequences of smoking interactive model

Objective-To describe the health and economic consequences of smoking model, a user friendly, web based tool, designed to estimate the health and economic outcomes associated with smoking and the benefits of smoking cessation. Results-An overview of the development of the model equations and user interface is given, and data from the UK are presented as an example of the model outputs. These results show that a typical smoking cessation strategy costs approximately pound 1200 per life year saved and pound 22 000 per death averted. Conclusions-The model successfully captures the complexity required to model smoking behaviour and associated mortality, morbidity, and health care costs. Furthermore, the interface provides the results in a simple and flexible way so as to be useful to a variety of audiences and to simulate a variety of smoking cessation methods

Very high energy gamma rays from the Crab Nebula

Observations of the Crab pulsar using the atmospheric Cerenkov technique were conducted for 22 hours. The light curve obtained shows a single peak at approximately the position of the expected main peak with a significance level of 3.2 sigma. The pulsed flux above 200 GeV is 2.5 + or - 0.8 x 10 to the 11th power cm(-2)s(-1)

Lentiviral manipulation of gene expression in human adult and embryonic stem cells

Human stem cells could revolutionize the field of medicine by providing a diverse range of cell types for tissue replacement therapies and drug discovery. To achieve this goal, genetic tools need to be optimized and developed for controlling and manipulating stem cells ex vivo. Here we describe a lentiviral delivery system capable of high infection rates in human mesenchymal and embryonic stem cells. The lentiviral backbone was modified to express mono- and bi-cistronic transgenes and was also used to deliver short hairpin ribonucleic acid for specific silencing of gene expression in human stem cells. We show that lentiviral transduction can be used to alter gene expression without altering the genes' ability to differentiate in vitro. These vectors will enable rapid analysis of gene function in stem cells and permit the generation of knock-in / knock-out models of human disease in the rapidly developing field of gene therapy

Two-stage clustering in genotype-by-environment analyses with missing data

Cluster analysis has been commonly used in genotype-by-environment (G x E) analyses, but current methods are inadequate when the data matrix is incomplete. This paper proposes a new method, referred to as two-stage clustering, which relies on a partitioning of squared Euclidean distance into two independent components, the G x E interaction and the genotype main effect. These components are used in the first and second stages of clustering respectively. Two-stage clustering forms the basis for imputing missing values in the G x E matrix so that a more complete data array is available for other GxE analyses. Imputation for a given genotype uses information from genotypes with similar interaction profiles. This imputation method is shown to improve on an existing nearest cluster method that confounds the G x E interaction and the genotype main effect

Cochlear Damage Affects Neurotransmitter Chemistry in the Central Auditory System

Tinnitus, the perception of a monotonous sound not actually present in the environment, affects nearly 20% of the population of the United States. Although there has been great progress in tinnitus research over the past 25 years, the neurochemical basis of tinnitus is still poorly understood. We review current research about the effects of various types of cochlear damage on the neurotransmitter chemistry in the central auditory system and document evidence that different changes in this chemistry can underlie similar behaviorally measured tinnitus symptoms. Most available data have been obtained from rodents following cochlear damage produced by cochlear ablation, loud sound, or ototoxic drugs. Effects on neurotransmitter systems have been measured as changes in neurotransmitter level, synthesis, release, uptake, and receptors. In this review, magnitudes of changes are presented for neurotransmitter-related amino acids, acetylcholine, and serotonin. A variety of effects have been found in these studies that may be related to animal model, survival time, type of cochlear damage, or methodology. The overall impression from the evidence presented is that any imbalance of neurotransmitter-related chemistry could disrupt auditory processing in such a way as to produce tinnitus

Properties of the Strange Axial Mesons in the Relativized Quark Model

We studied properties of the strange axial mesons in the relativized quark model. We calculated the $K_1$ decay constant in the quark model and showed how it can be used to extract the $K_1 (^3P_1) - K_1 (^1P_1)$ mixing angle ($\theta_K$) from the weak decay $\tau \to K_1 \nu_\tau$. The ratio $BR(\tau \to \nu_\tau K_1 (1270))/BR(\tau\to \nu_\tau K_1(1400))$ is the most sensitive measurement and also the most reliable since the largest of the theoretical uncertainties factor out. However the current bounds extracted from the TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain $-30^o \lesssim \theta_K \lesssim 50^o$ at 68\% C.L. We also calculated the strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube breaking model and extracted a $^3P_1 - ^1P_1$ mixing angle of $\theta_K \simeq 45^o$. Our analysis also indicates that the heavy quark limit does not give a good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex file uses revtex version 3 and epsfig, 4 postcript figures are attached. The full postcript version with embedded figures is available at ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.

Modern Geometry

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