Low-Energy Signals from Kinetic Mixing with a Warped Abelian Hidden Sector

We investigate the detailed phenomenology of a light Abelian hidden sector in the Randall-Sundrum framework. Relative to other works with light hidden sectors, the main new feature is a tower of hidden Kaluza-Klein vectors that kinetically mix with the Standard Model photon and Z. We investigate the decay properties of the hidden sector fields in some detail, and develop an approach for calculating processes initiated on the ultraviolet brane of a warped space with large injection momentum relative to the infrared scale. Using these results, we determine the detailed bounds on the light warped hidden sector from precision electroweak measurements and low-energy experiments. We find viable regions of parameter space that lead to significant production rates for several of the hidden Kaluza-Klein vectors in meson factories and fixed-target experiments. This offers the possibility of exploring the structure of an extra spacetime dimension with lower-energy probes.Comment: (1+32) Pages, 13 Figures. v2: JHEP version (minor modifications, results unchanged

Two-Loop Soft Corrections and Resummation of the Thrust Distribution in the Dijet Region

The thrust distribution in electron-positron annihilation is a classical precision QCD observable. Using renormalization group (RG) evolution in Laplace space, we perform the resummation of logarithmically enhanced corrections in the dijet limit, $T\to 1$ to next-to-next-to-leading logarithmic (NNLL) accuracy. We independently derive the two-loop soft function for the thrust distribution and extract an analytical expression for the NNLL resummation coefficient $g_3$. To combine the resummed expressions with the fixed-order results, we derive the $\log(R)$-matching and $R$-matching of the NNLL approximation to the fixed-order NNLO distribution.Comment: 50 pages, 12 figures, 1 table. Few minor changes. Version accepted for publication in JHE

Stainable hepatic iron in 341 African American adults at coroner/medical examiner autopsy

BACKGROUND: Results of previous autopsy studies indicate that increased hepatic iron stores or hepatic iron overload is common in African Americans dying in hospitals, but there are no reports of hepatic iron content in other cohorts of African Americans. METHODS: We investigated the prevalence of heavy liver iron deposition in African American adults. Using established histochemical criteria, we graded Perls' acid ferrocyanide-reactive iron in the hepatocytes and Kupffer cells of 341 consecutive African American adults who were autopsied in the coroner/medical examiner office. Heavy staining was defined as grade 3 or 4 hepatocyte iron or grade 3 Kupffer cell iron. RESULTS: There were 254 men and 85 women (mean age ± 1 SD: 44 ± 13 y vs. 48 ± 14 y, respectively; p = 0.0255); gender was unstated or unknown in two subjects. Approximately one-third of subjects died of natural causes. Heavy staining was observed in 10.2% of men and 4.7% of women. 23 subjects had heavy hepatocyte staining only, six had heavy Kupffer cell staining only, and one had a mixed pattern of heavy staining. 15 subjects had histories of chronic alcoholism; three had heavy staining confined to hepatocytes. We analyzed the relationships of three continuous variables (age at death in years, hepatocyte iron grade, Kupffer cell iron grade) and two categorical variables (sex, cause of death (natural and non-natural causes)) in all 341 subjects using a correlation matrix with Bonferroni correction. This revealed two positive correlations: hepatocyte with Kupffer cell iron grades (p < 0.01), and male sex with hepatocyte iron grade (p < 0.05). We also analyzed the relationship of steatosis, inflammation, and fibrosis/cirrhosis in 30 subjects with heavy iron staining using a correlation matrix with Bonferroni correction. There were significant positive correlations of steatosis with inflammation (r = 0.5641; p < 0.01), and of inflammation with fibrosis/cirrhosis (r = 0.6124; p < 0.01). CONCLUSIONS: The present results confirm and extend previous observations that heavy liver iron staining is relatively common in African Americans. The pertinence of these observations to genetic and acquired causes of iron overload in African Americans is discussed

Functional imaging studies of cognition using 99mTc-HMPAO SPECT: empirical validation using the n-back working memory paradigm

{Purpose} Functional activation protocols are widely applied for the study of brain-cognition relations. Only few take advantage of the intrinsic characteristics of SPECT, particularly those allowing cognitive assessment outside of the camera, in settings close to the standard clinical or laboratory ones. The purpose of the study was to assess the feasibility of a split-dose activation protocol with 99mTc-HMPAO using low irradiation dose. {Materials and methods} A two-scans protocol was applied to 12 healthy young volunteers using 270 MBq of 99mTc-HMPAO per scan, with each image associated to a particular experimental condition of the verbal {n}-back working memory task (0-back, 2-back). Subtraction method was used to identify regional brain activity related to the task. {Results} Voxel-wise statistical analysis showed left lateralized activity associated with the 2-back task, compared to the 0-back task. Activated regions, mainly prefrontal and parietal, were similar to those observed in previous fMRI and 15O-PET studies. {Conclusion} The results support the use of 99mTc-HMPAO SPECT for the investigation of brain-cognition relations and demonstrate the feasibility of optimal quality images despite low radiopharmaceutical doses. The findings also acknowledge the use of HMPAO as a radioligand to capture neuro-energetic modulations linked to cognitive activity. They encourage extending the application of the described activation protocol to clinical populations

Effect of Native American ancestry on iron-related phenotypes of Alabama hemochromatosis probands with HFE C282Y homozygosity

BACKGROUND: In age-matched cohorts of screening study participants recruited from primary care clinics, mean serum transferrin saturation values were significantly lower and mean serum ferritin concentrations were significantly higher in Native Americans than in whites. Twenty-eight percent of 80 Alabama white hemochromatosis probands with HFE C282Y homozygosity previously reported having Native American ancestry, but the possible effect of this ancestry on hemochromatosis phenotypes was unknown. METHODS: We compiled observations in these 80 probands and used univariate and multivariate methods to analyze associations of age, sex, Native American ancestry (as a dichotomous variable), report of ethanol consumption (as a dichotomous variable), percentage transferrin saturation and log(e )serum ferritin concentration at diagnosis, quantities of iron removed by phlebotomy to achieve iron depletion, and quantities of excess iron removed by phlebotomy. RESULTS: In a univariate analysis in which probands were grouped by sex, there were no significant differences in reports of ethanol consumption, transferrin saturation, log(e )serum ferritin concentration, quantities of iron removed to achieve iron depletion, and quantities of excess iron removed by phlebotomy in probands who reported Native American ancestry than in those who did not. In multivariate analyses, transferrin saturation (as a dependent variable) was not significantly associated with any of the available variables, including reports of Native American ancestry and ethanol consumption. The independent variable quantities of excess iron removed by phlebotomy was significantly associated with log(e )serum ferritin used as a dependent variable (p < 0.0001), but not with reports of Native American ancestry or reports of ethanol consumption. Log(e )serum ferritin was the only independent variable significantly associated with quantities of excess iron removed by phlebotomy used as a dependent variable (p < 0.0001) (p < 0.0001; ANOVA of regression). CONCLUSION: We conclude that the iron-related phenotypes of hemochromatosis probands with HFE C282Y homozygosity are similar in those with and without Native American ancestry reports

Targeting murine heart and brain: visualisation conditions for multi-pinhole SPECT with 99mTc- and 123I-labelled probes

The study serves to optimise conditions for multi-pinhole SPECT small animal imaging of (123)I- and (99m)Tc-labelled radiopharmaceuticals with different distributions in murine heart and brain and to investigate detection and dose range thresholds for verification of differences in tracer uptake.A Triad 88/Trionix system with three 6-pinhole collimators was used for investigation of dose requirements for imaging of the dopamine D(2) receptor ligand [(123)I]IBZM and the cerebral perfusion tracer [(99m)Tc]HMPAO (1.2-0.4 MBq/g body weight) in healthy mice. The fatty acid [(123)I]IPPA (0.94 +/- 0.05 MBq/g body weight) and the perfusion tracer [(99m)Tc]sestamibi (3.8 +/- 0.45 MBq/g body weight) were applied to cardiomyopathic mice overexpressing the prostaglandin EP(3) receptor.In vivo imaging and in vitro data revealed 45 kBq total cerebral uptake and 201 kBq cardiac uptake as thresholds for visualisation of striatal [(123)I]IBZM and of cardiac [(99m)Tc]sestamibi using 100 and 150 s acquisition time, respectively. Alterations of maximal cerebral uptake of [(123)I]IBZM by >20% (116 kBq) were verified with the prerequisite of 50% striatal of total uptake. The labelling with [(99m)Tc]sestamibi revealed a 30% lower uptake in cardiomyopathic hearts compared to wild types. [(123)I]IPPA uptake could be visualised at activity doses of 0.8 MBq/g body weight.Multi-pinhole SPECT enables detection of alterations of the cerebral uptake of (123)I- and (99m)Tc-labelled tracers in an appropriate dose range in murine models targeting physiological processes in brain and heart. The thresholds of detection for differences in the tracer uptake determined under the conditions of our experiments well reflect distinctions in molar activity and uptake characteristics of the tracers

Small-animal SPECT and SPECT/CT: application in cardiovascular research

Preclinical cardiovascular research using noninvasive radionuclide and hybrid imaging systems has been extensively developed in recent years. Single photon emission computed tomography (SPECT) is based on the molecular tracer principle and is an established tool in noninvasive imaging. SPECT uses gamma cameras and collimators to form projection data that are used to estimate (dynamic) 3-D tracer distributions in vivo. Recent developments in multipinhole collimation and advanced image reconstruction have led to sub-millimetre and sub-half-millimetre resolution SPECT in rats and mice, respectively. In this article we review applications of microSPECT in cardiovascular research in which information about the function and pathology of the myocardium, vessels and neurons is obtained. We give examples on how diagnostic tracers, new therapeutic interventions, pre- and postcardiovascular event prognosis, and functional and pathophysiological heart conditions can be explored by microSPECT, using small-animal models of cardiovascular disease