Self-consistent tomography of the state-measurement Gram matrix

State and measurement tomography make assumptions about the experimental states or measurements. These assumptions are often not justified because state preparation and measurement errors are unavoidable in practice. Here we describe how the Gram matrix associated with the states and measurement operators can be estimated via semidefinite programming if the states and the measurements are so called globally completable. This is for instance the case if the unknown measurements are known to be projective and non-degenerate. The computed Gram matrix determines the states, and the measurement operators uniquely up to simultaneous rotations in the space of Hermitian matrices. We prove the reliability of the proposed method in the limit of a large number of independent measurement repetitions.Comment: We have completely rewritten the first version because new results from arXiv:1209.6499 allowed to significantly clearify the first submission. We have added some reference

Detecting projectivity in sheaves associated to representations of infinitesimal groups

Let G be an infinitesimal group scheme of finite height r and V(G) the scheme which represents 1-parameter subgroups of G. We consider sheaves over the projectivization P(G) of V(G) constructed from a G-module M. We show that if P(G) is regular then the sheaf H^[1](M) is zero if and only if M is projective. In general, H^[1] defines a functor from the stable module category and we prove that its kernel is a thick triangulated subcategory. Finally, we give examples of G such that P(G) is regular and indicate, in characteristic 2, the connection to the BGG correspondence. Along the way we will provide new proofs of some known results and correct some errors in the literature.Comment: 26 pages, grant acknowledgement, journal reference, and DOI added to previous versio

B Physics at D0

The Fermilab Tevatron (p pbar), operating at sqrt(s)=1.96 TeV, is a rich source of B hadrons. The large acceptance in terms of rapidity and transverse momentum of the charged particle tracking system and the muon system make the upgraded Run II D0 detector an excellent tool for B physics. In this article, we report on selected physics results based on the first 250 pb^-1 of Run II data. This includes results on the X(3872) state, semileptonic B decays, B hadron lifetimes, flavour oscillations, and the rare decay B_s -> mu^+ mu^-.Comment: 8 pages, 8 figures. To appear in the proceedings of the 39th Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Aosta Valley, Italy, 21-28 Mar 200

Microstructural Alterations in Hippocampal Subfields Mediate Age-Related Memory Decline in Humans.

Aging, even in the absence of clear pathology of dementia, is associated with cognitive decline. Neuroimaging, especially diffusion-weighted imaging, has been highly valuable in understanding some of these changes in live humans, non-invasively. Traditional tensor techniques have revealed that the integrity of the fornix and other white matter tracts significantly deteriorates with age, and that this deterioration is highly correlated with worsening cognitive performance. However, traditional tensor techniques are still not specific enough to indict explicit microstructural features that may be responsible for age-related cognitive decline and cannot be used to effectively study gray matter properties. Here, we sought to determine whether recent advances in diffusion-weighted imaging, including Neurite Orientation Dispersion and Density Imaging (NODDI) and Constrained Spherical Deconvolution, would provide more sensitive measures of age-related changes in the microstructure of the medial temporal lobe. We evaluated these measures in a group of young (ages 20-38 years old) and older (ages 59-84 years old) adults and assessed their relationships with performance on tests of cognition. We found that the fiber density (FD) of the fornix and the neurite density index (NDI) of the fornix, hippocampal subfields (DG/CA3, CA1, and subiculum), and parahippocampal cortex, varied as a function of age in a cross-sectional cohort. Moreover, in the fornix, DG/CA3, and CA1, these changes correlated with memory performance on the Rey Auditory Verbal Learning Test (RAVLT), even after regressing out the effect of age, suggesting that they were capturing neurobiological properties directly related to performance in this task. These measures provide more details regarding age-related neurobiological properties. For example, a change in fiber density could mean a reduction in axonal packing density or myelination, and the increase in NDI observed might be explained by changes in dendritic complexity or even sprouting. These results provide a far more comprehensive view than previously determined on the possible system-wide processes that may be occurring because of healthy aging and demonstrate that advanced diffusion-weighted imaging is evolving into a powerful tool to study more than just white matter properties

A Sharper discrepancy measure for post-election audits

Post-election audits use the discrepancy between machine counts and a hand tally of votes in a random sample of precincts to infer whether error affected the electoral outcome. The maximum relative overstatement of pairwise margins (MRO) quantifies that discrepancy. The electoral outcome a full hand tally shows must agree with the apparent outcome if the MRO is less than 1. This condition is sharper than previous ones when there are more than two candidates or when voters may vote for more than one candidate. For the 2006 U.S. Senate race in Minnesota, a test using MRO gives a $P$-value of 4.05% for the hypothesis that a full hand tally would find a different winner, less than half the value Stark [Ann. Appl. Statist. 2 (2008) 550--581] finds.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS171 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Efficacy of Probiotics for Reducing the Incidence of Lameness in Broilers Grown on Wire Flooring

Growing broilers on wire flooring provides an excellent experimental model for reproducibly triggering significant levels of lameness. In Pilot Study #1 using broilers from Line C grown on wire flooring, adding the Biomin probiotic PoultryStar® to the feed reduced the percentage of lameness by half when compared with broilers that received the control diet alone. In Pilot Study # 2 using broilers from Line B grown on wire flooring, adding the PoultryStar® probiotic reduced the percentage of lameness to 8% when compared with 28% lameness in broilers that received the control diet alone. The objective of this study was to conduct a replicated experiment to determine if probiotics consistently reduced the incidence of lameness in broilers reared on wire flooring. Male broiler chicks from Cobb-Vantress Line B were placed at 1 day of age in pens having flat wire flooring within environmental chambers 1 through 10 inside the Poultry Environmental Research Lab at the University of Arkansas Poultry Research Farm. On day 14, birds were culled to 50 per pen, yielding a density of 1ft²/chick. A corn and soybean meal-based diet formulated to meet minimum National Research Council standards (1994) for all ingredients was provided ad libitum as the control feed. Broilers in chambers 1, 3, 5, 7 and 9 were provided the control feed while chambers 2, 4, 6, 8 and 10 were provided the same feed mixed with the probiotic throughout the experiment (50 lbs of control feed blended with 12.5 g PoultryStar® probiotic). The birds in all pens were walked and observed for lameness every two days starting on day 15 and continuing until the end of the experiment on day 56. Birds unable or unwilling to walk were diagnosed as clinically lame and humanely euthanized with CO2 gas. They were then necropsied to assess sub-clinical lesion incidences including femoral head separation, femoral head transitional degeneration, femoral head necrosis, tibial head necrosis, and tibial dyschondroplasia. Findings from the study indicate that for broilers grown on wire flooring, diets containing the probiotic PoultryStar® consistently reduced the incidence of lameness when compared with birds fed the control diet alone

Making serine integrases work for us

DNA site-specific recombinases are enzymes (often associated with mobile DNA elements) that catalyse breaking and rejoining of DNA strands at specific points, thereby bringing about precise genetic rearrangements. Serine integrases are a group of recombinases derived from bacteriophages. Their unusual properties, including directionality of recombination and simple site requirements, are leading to their development as efficient, versatile tools for applications in experimental biology, biotechnology, synthetic biology and gene therapy. This article summarizes our current knowledge of serine integrase structure and mechanism, then outlines key factors that affect the performance of these phage recombination systems. Recently published studies, that have expanded the repertoire of available systems and reveal system-specific characteristics, will help us to choose the best integrases for envisaged applications