The Angular Distribution of Photoneutrons From O16

The relative importance of competing reaction channels in the photo-excitation of the giant resonance in O16 has been studied by measurement of the angular distribution of the emitted photo-neutrons through the corresponding energy range using a multi-angle neutron time of flight spectrometer installed at the Kelvin Laboratory of the University of Glasgow. Design factors for the spectrometer are discussed with regard to optimisation of energy resolution and counting rates under the constraints of the source, and the obtainable accuracy of normalisation between neutron detectors at different angles has been measured, A reliable method of calibration of the neutron energy scale at each angle is described and corrections to the neutron spectra for absorption by materials in the flight path have been made. The energy dependent efficiency of the neutron detectors is calculated in an appendix by a Monte Carlo technique using a new measurement of the scintillation response curve for recoil protons. Angular distributions of photoneutrons from the D2 (gamma,n)p reaction with 26.9 MeV bremsstrahlung have been measured and are found to agree with previously published results and theoretical predictions to within the expected accuracy. This is taken as confirmation of good angular normalisation in the system. Measurements by the author of the angular distributions of photo-neutrons from 26.9 MeV bremsstrahlung on O16 are presented and absolute cross sections have been obtained with respect to that known for deuterium. Photoproton data from other authors is analysed in a similar way for comparison with the photoneutron results. In the E1 approximation, the relative intensity of s/d wave admixture is found to follow the resonance structure for both protons and neutrons and the corresponding phase difference is found to vary about the value expected from optical model predictions. The E2 cross section has been extracted from the data and is found to rest mainly in two broad states centred at about 23 MeV and 24.7 MeV, while a Barker-Mann analysis shows the isospin impurity in the O16 giant resonance to be small and to be mainly associated with the regions of E2 strength. The pure 1p1h dipole approximation fails to describe these features and the observed splitting of the giant resonance in O16 but the presence of more complicated excitations is shown to be more consistent with experiment

Frustration of crystallisation by a liquid–crystal phase

Frustration of crystallisation by locally favoured structures is critically important in linking the phenomena of supercooling, glass formation, and liquid-liquid transitions. Here we show that the putative liquid-liquid transition in n-butanol is in fact caused by geometric frustration associated with an isotropic to rippled lamellar liquid-crystal transition. Liquid-crystal phases are generally regarded as being “in between” the liquid and the crystalline state. In contrast, the liquid-crystal phase in supercooled n-butanol is found to inhibit transformation to the crystal. The observed frustrated phase is a template for similar ordering in other liquids and likely to play an important role in supercooling and liquid-liquid transitions in many other molecular liquids

Renal fibrosis in feline chronic kidney disease: known mediators and mechanisms of injury

Chronic kidney disease (CKD) is a common medical condition of ageing cats. In most cases the underlying aetiology is unknown, but the most frequently reported pathological diagnosis is renal tubulointerstitial fibrosis. Renal fibrosis, characterised by extensive accumulation of extra-cellular matrix within the interstitium, is thought to be the final common pathway for all kidney diseases and is the pathological lesion best correlated with function in both humans and cats. As a convergent pathway, renal fibrosis provides an ideal target for the treatment of CKD and knowledge of the underlying fibrotic process is essential for the future development of novel therapies. There are many mediators and mechanisms of renal fibrosis reported in the literature, of which only a few have been investigated in the cat. This article reviews the process of renal fibrosis and discusses the most commonly cited mediators and mechanisms of progressive renal injury, with particular focus on the potential significance to feline CKD

The analysis of Raman optical activity spectra of proteins

Measurement of the Raman optical activity (ROA) spectra of biomolecules has become an experimental possibility due to significant advances in the available technology, and its successful implementation into the ROA instruments at the University of Glasgow. The ease with which the ROA spectra of biological molecules can be successfully measured lends itself perfectly to the ever-growing demand for biomolecular structural information, especially in the context of proteomics and the Human Genome Project. ROA spectroscopy is able to probe the chiral peptide backbone of proteins, and as such the ROA spectrum of a protein contains a wealth of structural information from within the whole molecule, across the whole vibrational spectrum. As well as containing detailed information from specific structural elements such as sections of secondary structure and motifs, the ability of ROA to see the molecule as a whole also enables the global fold of the protein to be deduced from the ROA spectrum. The development of the analysis of ROA spectra has largely been based upon the correlation of ROA spectra of proteins of known structure with structural information from alternative sources, chiefly X-ray crystallography and multidimensional nuclear magnetic resonance (NMR). As the database of ROA spectra of polypeptides and proteins has grown, it has been possible to tighten up the assignment of ROA spectral bands and band patterns to aspects of known structural content. With a basis for the correlation between the ROA spectrum and the known crystal structure (or NMR structure) being well established, it is possible to interpret the ROA spectra of proteins that do not have (for whatever reason) well defined structures. This means that ROA spectroscopy can provide invaluable structural information for proteins that are precluded from analysis by other techniques, and also cast new light on the structures of proteins that have not been well defined. In order to fully interpret an ROA spectrum of a protein, it is necessary to be familiar with protein structure and the ROA experiment as a whole. Analysing an ROA spectrum is a detailed and highly subjective process. Depending on the experience of the analyst, the information contained within the spectra can be extracted readily or not so readily. For this reason, it would be desirable to develop a technique that is capable of interpreting not only individual spectra, but also whole data sets in a manner that is independent of the analyst, and therefore independent of any preconceptions (or inexperience) the analyst may have. This project presents an up-to-date collection of newly obtained ROA spectra of a large number of proteins across a range of structural class types. In addition, the statistical technique of principal component analysis (PflA) has been used as a tool for the analysis of this new data. It is hoped that the result of this work will provide a basis for the future analysis of protein ROA spectra that is both mathematically rigorous and convenient

Amanita drummondii and A. quenda (Basidiomycota), two new species from Western Australia, and an expanded description of A. walpolei

Three species of Amanita Pers. are documented from Western Australia. Amanita drummondii E.M.Davison is described from the south-west region; it appears to be widespread but infrequent. Amanita quenda E.M.Davison is described from the Perth Metropolitan area. Amanita walpolei O.K.Mill. is redescribed to include additional collections, drawing attention to the presence of clamp connections in all tissues. A BLASTn search has shown that there are no exact matches of the nuclear ribosomal internal transcribed spacer (ITS) region of each species with those in GenBank

The role of depletion of dimethyl sulfoxide before autografting: on hematologic recovery, side effects, and toxicity

AbstractCryopreservation of stem cells after collection from peripheral blood or bone marrow for autologous transplantation necessitates protection with dimethyl sulfoxide (DMSO). Unfortunately, DMSO, when infused with the thawed cell suspension, may induce serious complications and side effects. To assess whether depletion of DMSO before autografting affects safety and efficacy, 56 consenting consecutive patients treated with high-dose chemotherapy and autologous blood stem cell transplantation were assigned to obtain either an untreated or DMSO-depleted autograft. On the day of transplantation, the cryopreserved cells were thawed and infused to the patient either immediately or after washing 3 times in normal saline supplemented with 6% anticoagulant citrate dextrose solution. Cell count with viability, clonogenic assay, and phenotyping were performed before and after thawing and after washing. Hematologic recovery, side effects, and complications were recorded. The in vitro and clinical data on 56 patients show that the depletion of DMSO in vitro before autografting does not induce a significant loss of cell number, viability, colony-forming unit-granulocyte-macrophage activity, or number of CD34+ cells. Furthermore, it leads to a safe and sustained engraftment. The complications and side effects, as recorded by continuous monitoring, were substantially less; however, the procedure takes 3 to 4 hours of laboratory work per patient

Phonon drag thermopower and weak localization

Previous experimental work on a two-dimensional (2D) electron gas in a Si-on-sapphire device led to the conclusion that both conductivity and phonon drag thermopower $S^g$ are affected to the same relative extent by weak localization. The present paper presents further experimental and theoretical results on these transport coefficients for two very low mobility 2D electron gases in $\delta-$doped GaAs/Ga$_x$Al$_{1-x}$As quantum wells. The experiments were carried out in the temperature range 3-7K where phonon drag dominates the thermopower and, contrary to the previous work, the changes observed in the thermopower due to weak localization were found to be an order of magnitude less than those in the conductivity. A theoretical framework for phonon drag thermopower in 2D and 3D semiconductors is presented which accounts for this insensitivity of $S^g$ to weak localization. It also provides transparent physical explanations of many previous experimental and theoretical results.Comment: 19 page Revtex file, 3 Postscript figur

Compilation of extended recursion in call-by-value functional languages

This paper formalizes and proves correct a compilation scheme for mutually-recursive definitions in call-by-value functional languages. This scheme supports a wider range of recursive definitions than previous methods. We formalize our technique as a translation scheme to a lambda-calculus featuring in-place update of memory blocks, and prove the translation to be correct.Comment: 62 pages, uses pi

Sex Differences in Endothelial Progenitor Cells and Circulating Endothelial Cells in Response to Acute Exercise

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