852 research outputs found

    Characterizing aging in the human brainstem using quantitative multimodal MRI analysis.

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    Aging is ubiquitous to the human condition. The MRI correlates of healthy aging have been extensively investigated using a range of modalities, including volumetric MRI, quantitative MRI (qMRI), and diffusion tensor imaging. Despite this, the reported brainstem related changes remain sparse. This is, in part, due to the technical and methodological limitations in quantitatively assessing and statistically analyzing this region. By utilizing a new method of brainstem segmentation, a large cohort of 100 healthy adults were assessed in this study for the effects of aging within the human brainstem in vivo. Using qMRI, tensor-based morphometry (TBM), and voxel-based quantification (VBQ), the volumetric and quantitative changes across healthy adults between 19 and 75 years were characterized. In addition to the increased R2* in substantia nigra corresponding to increasing iron deposition with age, several novel findings were reported in the current study. These include selective volumetric loss of the brachium conjunctivum, with a corresponding decrease in magnetization transfer and increase in proton density (PD), accounting for the previously described “midbrain shrinkage.” Additionally, we found increases in R1 and PD in several pontine and medullary structures. We consider these changes in the context of well-characterized, functional age-related changes, and propose potential biophysical mechanisms. This study provides detailed quantitative analysis of the internal architecture of the brainstem and provides a baseline for further studies of neurodegenerative diseases that are characterized by early, pre-clinical involvement of the brainstem, such as Parkinson’s and Alzheimer’s diseases

    Factorization of e+e- Event Shape Distributions with Hadronic Final States in Soft Collinear Effective Theory

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    We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory.Comment: 21 pages. Journal version. Defined an explicit thrust axis operator; clarified meaning of a delta function operato

    The Plasma Cholesterol in Nephritis: Observations on a Short Series of Cases

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    1. While the majority of workers consider the normal range of the cholesterol content of the plasma to lie between 130 and 200 mgms. per 100 ccs. , the results of this investigation suggest that the upper normal limit frequently exceeds the accepted figure. 2. In acute nephritis the main findings ares (a) While the level of cholesterol may or may not be unduly high, recovery is accompanied by a decrease. (b) A tardy fall is associated with a slow or incomplete recovery. (c) The degree of oedema is not proportional to the amount of cholesterol in the plasma. (d) The onset of convulsions is not closely related to an abnormal cholesterol content; where nitrogen retention is present (one case) the cholesterol content is normal. 3. Chronic Interstitial nephritis. (a) In this type of nephritis, the plasma cholesterol is within normal limits, unless very pronounced arterial degeneration is present. b) The onset of uraemia is accompanied by a fall in the cholesterol level. (c) Recovery from uraemia is attended by a rise in the cholesterol content. 4. Arterio Sclerosis. (a) In this condition, where a renal lesion is present, the cholesterol value is constantly high. 5. Chronic Parenchymatous Nephritis. (a) The plasma cholesterol is raised to a greater degree in this type of nephritis than in any other. (b) Oedema is usually associated with hypercholesterin-aemia, but occasional exceptions may occur. 6. The Mixed Type of Nephritis. No constant values are found in this group, but the average figure is above normal. 7. In Renal Conditions other than nephritis, no hyper-cholesterinaemia is found. 8. Cardiac cases with oedema shew no increase in plasma cholesterol. The main diagnostic value of cholesterol estimations is in the differentiation between renal and cardiac oedema. In this connection, it should be noted that the differentiation is most certain in chronic cases, where a high value will almost certainly be obtained in the presence of a renal lesion. In acute cases, the test is not so trustworthy, but a high value favours the diagnosis of nephritis. In almost all cases, the necessary differentiation can be made from a single estimation. In the second place, a single estimation is of value in establishing a diagnosis of uraemia but it is obviously necessary to consider this finding in conjunction with the other clinical features of the case. The test is of value, in the third place, in that it supplies an aid to prognosis in renal cases. For this purpose, a single estimation is insufficient and a series of observations must be made. In interpreting the behaviour of the cholesterol, the type of nephritis must be borne in mind. Thus in an acute nephritis a fall in the cholesterol level is a favourable sign, whereas in chronic nephritis, a fall is generally unfavourable, and associated with the onset of uraemia. Conversely, a rise in cholesterol in acute nephritis suggests the development of a more permanent lesion, while in chronic nephritis especially of the interstitial type, a rise frequently coincides with clinical improvement. Additional information can be obtained by noting the rate of fall in cases of acute nephritis, a slow fall indicating a tardy recovery. The above conclusions relate to the practical application of the test, but it is of interest to note the relationship of the cholesterol content of the plasma to nitrogen retention, and to oedema. The cholesterol value, in general, varies inversely with the nitrogen retention. As regards the relationship to oedema, this has been dealt with in detail in the different groups, but on the whole no direct proportion exists between the two. The results of this investigation shew that cholesterol estimations have a definite diagnostic and prognostic value in the study of nephritis

    Alcohol Sale Status and Homicide Victimization in Kentucky, 2005-2012: Is There a Spatial Association?

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    To date, the association between the alcohol sale status of decedents’ residence and alcohol-related homicide victimization have not been studied as far as we know. The current study aims to: i) determine whether homicide victims who were residents of wet counties had higher odds of testing positive for alcohol than their counterparts in moist or dry counties after adjusting for confounders; ii) determine whether homicides and alcohol-related homicides tend to cluster spatially; iii) determine whether the aforementioned associations exist only in highly-populated counties. A multilevel logistic regression analysis was used to analyze the data on homicide victims in the Kentucky Violent Death Reporting System from 2005 to 2012. Spatial statistics were used to determine the spatial autocorrelation in rates of homicides and alcohol-related homicides. Overall, 944 homicide victims were included. The male to female ratio was 3:1. About 32.8% of homicide victims tested positive for alcohol. About 33.0% of homicide decedents who were residents in wet counties tested positive for alcohol compared to 32.5% of their counterparts in moist/dry counties. Residence in wet counties was associated with a statistically insignificant increase in the unadjusted odds ratio (OR) of alcohol-related homicide victimization (OR=1.20, 95% CI=0.81-1.77) as well as the adjusted odds (aOR=1.33, 95% CI=0.83-2.12). There was no association between population size and alcohol-related homicide rate

    The influence of substrate temperature on growth of para-sexiphenyl thin films on Ir{111} supported graphene studied by LEEM

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    The growth of para-sexiphenyl (6P) thin films as a function of substrate temperature on Ir{111} supported graphene flakes has been studied in real-time with Low Energy Electron Microscopy (LEEM). Micro Low Energy Electron Diffraction (\mu LEED) has been used to determine the structure of the different 6P features formed on the surface. We observe the nucleation and growth of a wetting layer consisting of lying molecules in the initial stages of growth. Graphene defects -- wrinkles -- are found to be preferential sites for the nucleation of the wetting layer and of the 6P needles that grow on top of the wetting layer in the later stages of deposition. The molecular structure of the wetting layer and needles is found to be similar. As a result, only a limited number of growth directions are observed for the needles. In contrast, on the bare Ir{111} surface 6P molecules assume an upright orientation. The formation of ramified islands is observed on the bare Ir{111} surface at 320 K and 352 K, whereas at 405 K the formation of a continuous layer of upright standing molecules growing in a step flow like manner is observed.Comment: 9 pages, 7 figures, Revised Version as accepted for publication in Surface Scienc

    Alcohol sale status and homicide victimization in Kentucky, 2005-2012: Is there a spatial association?

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    To date, the association between the alcohol sale status of decedents’ residence and alcohol-related homicide victimization have not been studied as far as we know. The current study aims to: i) determine whether homicide victims who were residents of wet counties had higher odds of testing positive for alcohol than their counterparts in moist or dry counties after adjusting for confounders; ii) determine whether homicides and alcohol-related homicides tend to cluster spatially; iii) determine whether the aforementioned associations exist only in highly-populated counties. A multilevel logistic regression analysis was used to analyze the data on homicide victims in the Kentucky Violent Death Reporting System from 2005 to 2012. Spatial statistics were used to determine the spatial autocorrelation in rates of homicides and alcohol-related homicides. Overall, 944 homicide victims were included. The male to female ratio was 3:1. About 32.8% of homicide victims tested positive for alcohol. About 33.0% of homicide decedents who were residents in wet counties tested positive for alcohol compared to 32.5% of their counterparts in moist/dry counties. Residence in wet counties was associated with a statistically insignificant increase in the unadjusted odds ratio (OR) of alcohol-related homicide victimization (OR=1.20, 95% CI=0.81-1.77) as well as the adjusted odds (aOR=1.33, 95% CI=0.83-2.12). There was no association between population size and alcohol-related homicide rate
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