Finiteness and Dual Variables for Lorentzian Spin Foam Models

We describe here some new results concerning the Lorentzian Barrett-Crane model, a well-known spin foam formulation of quantum gravity. Generalizing an existing finiteness result, we provide a concise proof of finiteness of the partition function associated to all non-degenerate triangulations of 4-manifolds and for a class of degenerate triangulations not previously shown. This is accomplished by a suitable re-factoring and re-ordering of integration, through which a large set of variables can be eliminated. The resulting formulation can be interpreted as a ``dual variables'' model that uses hyperboloid variables associated to spin foam edges in place of representation variables associated to faces. We outline how this method may also be useful for numerical computations, which have so far proven to be very challenging for Lorentzian spin foam models.Comment: 15 pages, 1 figur

Dual Computations of Non-abelian Yang-Mills on the Lattice

In the past several decades there have been a number of proposals for computing with dual forms of non-abelian Yang-Mills theories on the lattice. Motivated by the gauge-invariant, geometric picture offered by dual models and successful applications of duality in the U(1) case, we revisit the question of whether it is practical to perform numerical computation using non-abelian dual models. Specifically, we consider three-dimensional SU(2) pure Yang-Mills as an accessible yet non-trivial case in which the gauge group is non-abelian. Using methods developed recently in the context of spin foam quantum gravity, we derive an algorithm for efficiently computing the dual amplitude and describe Metropolis moves for sampling the dual ensemble. We relate our algorithms to prior work in non-abelian dual computations of Hari Dass and his collaborators, addressing several problems that have been left open. We report results of spin expectation value computations over a range of lattice sizes and couplings that are in agreement with our conventional lattice computations. We conclude with an outlook on further development of dual methods and their application to problems of current interest.Comment: v1: 18 pages, 7 figures, v2: Many changes to appendix, minor changes throughout, references and figures added, v3: minor corrections, 22 page

Coupling of spacetime atoms and spin foam renormalisation from group field theory

We study the issue of coupling among 4-simplices in the context of spin foam models obtained from a group field theory formalism. We construct a generalisation of the Barrett-Crane model in which an additional coupling between the normals to tetrahedra, as defined in different 4-simplices that share them, is present. This is realised through an extension of the usual field over the group manifold to a five argument one. We define a specific model in which this coupling is parametrised by an additional real parameter that allows to tune the degree of locality of the resulting model, interpolating between the usual Barrett-Crane model and a flat BF-type one. Moreover, we define a further extension of the group field theory formalism in which the coupling parameter enters as a new variable of the field, and the action presents derivative terms that lead to modified classical equations of motion. Finally, we discuss the issue of renormalisation of spin foam models, and how the new coupled model can be of help regarding this.Comment: RevTeX, 18 pages, no figure

Diagnostic Accuracy of Spanish Language Depression-Screening Instruments

PURPOSE To make decisions about implementing systematic depression screening, primary care physicians who serve Spanish-speaking populations need to know whether Spanish language depression-screening instruments are accurate. We aimed to review systematically the evidence regarding diagnostic accuracy of depression-screening instruments in Spanish-speaking primary care populations

Genome-wide analysis reveals PADI4 cooperates with Elk-1 to activate c-Fos expression in breast cancer cells.

Peptidylarginine deiminase IV (PADI4) catalyzes the conversion of positively charged arginine and methylarginine residues to neutrally charged citrulline, and this activity has been linked to the repression of a limited number of target genes. To broaden our knowledge of the regulatory potential of PADI4, we utilized chromatin immunoprecipitation coupled with promoter tiling array (ChIP-chip) analysis to more comprehensively investigate the range of PADI4 target genes across the genome in MCF-7 breast cancer cells. Results showed that PADI4 is enriched in gene promoter regions near transcription start sites (TSSs); and, surprisingly, this pattern of binding is primarily associated with actively transcribed genes. Computational analysis found potential binding sites for Elk-1, a member of the ETS oncogene family, to be highly enriched around PADI4 binding sites; and coimmunoprecipitation analysis then confirmed that Elk-1 physically associates with PADI4. To better understand how PADI4 may facilitate gene transactivation, we then show that PADI4 interacts with Elk-1 at the c-Fos promoter and that, following Epidermal Growth Factor (EGF) stimulation, PADI4 catalytic activity facilitates Elk-1 phosphorylation, histone H4 acetylation, and c-Fos transcriptional activation. These results define a novel role for PADI4 as a transcription factor co-activator

Numerical indications on the semiclassical limit of the flipped vertex

We introduce a technique for testing the semiclassical limit of a quantum gravity vertex amplitude. The technique is based on the propagation of a semiclassical wave packet. We apply this technique to the newly introduced "flipped" vertex in loop quantum gravity, in order to test the intertwiner dependence of the vertex. Under some drastic simplifications, we find very preliminary, but surprisingly good numerical evidence for the correct classical limit.Comment: 4 pages, 8 figure

Integrated primary care for patients with mental and physical multimorbidity: cluster randomised controlled trial of collaborative care for patients with depression comorbid with diabetes or cardiovascular disease

PublishedOpen Access ArticleObjective To test the effectiveness of an integrated collaborative care model for people with depression and long term physical conditions. Design Cluster randomised controlled trial. Setting 36 general practices in the north west of England. Participants 387 patients with a record of diabetes or heart disease, or both, who had depressive symptoms (≥10 on patient health questionaire-9 (PHQ-9)) for at least two weeks. Mean age was 58.5 (SD 11.7). Participants reported a mean of 6.2 (SD 3.0) long term conditions other than diabetes or heart disease; 240 (62%) were men; 360 (90%) completed the trial. Interventions Collaborative care included patient preference for behavioural activation, cognitive restructuring, graded exposure, and/or lifestyle advice, management of drug treatment, and prevention of relapse. Up to eight sessions of psychological treatment were delivered by specially trained psychological wellbeing practitioners employed by Improving Access to Psychological Therapy services in the English National Health Service; integration of care was enhanced by two treatment sessions delivered jointly with the practice nurse. Usual care was standard clinical practice provided by general practitioners and practice nurses. Main outcome measures The primary outcome was reduction in symptoms of depression on the self reported symptom checklist-13 depression scale (SCL-D13) at four months after baseline assessment. Secondary outcomes included anxiety symptoms (generalised anxiety disorder 7), self management (health education impact questionnaire), disability (Sheehan disability scale), and global quality of life (WHOQOL-BREF). Results 19 general practices were randomised to collaborative care and 20 to usual care; three practices withdrew from the trial before patients were recruited. 191 patients were recruited from practices allocated to collaborative care, and 196 from practices allocated to usual care. After adjustment for baseline depression score, mean depressive scores were 0.23 SCL-D13 points lower (95% confidence interval −0.41 to −0.05) in the collaborative care arm, equal to an adjusted standardised effect size of 0.30. Patients in the intervention arm also reported being better self managers, rated their care as more patient centred, and were more satisfied with their care. There were no significant differences between groups in quality of life, disease specific quality of life, self efficacy, disability, and social support. Conclusions Collaborative care that incorporates brief low intensity psychological therapy delivered in partnership with practice nurses in primary care can reduce depression and improve self management of chronic disease in people with mental and physical multimorbidity. The size of the treatment effects were modest and were less than the prespecified effect but were achieved in a trial run in routine settings with a deprived population with high levels of mental and physical multimorbidity. Trial registration ISRCTN80309252.National Institute for Health ResearchCollaboration for Leadership in Applied Health ResearchCare for Greater Mancheste

A Soluble Guanylate Cyclase–Dependent Mechanism Is Involved in the Regulation of Net Hepatic Glucose Uptake by Nitric Oxide in Vivo

OBJECTIVE We previously showed that elevating hepatic nitric oxide (NO) levels reduced net hepatic glucose uptake (NHGU) in the presence of portal glucose delivery, hyperglycemia, and hyperinsulinemia. The aim of the present study was to determine the role of a downstream signal, soluble guanylate cyclase (sGC), in the regulation of NHGU by NO. RESEARCH DESIGN AND METHODS Studies were performed on 42-h–fasted conscious dogs fitted with vascular catheters. At 0 min, somatostatin was given peripherally along with 4× basal insulin and basal glucagon intraportally. Glucose was delivered at a variable rate via a leg vein to double the blood glucose level and hepatic glucose load throughout the study. From 90 to 270 min, an intraportal infusion of the sGC inhibitor 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ) was given in −sGC (n = 10) and −sGC/+NO (n = 6), whereas saline was given in saline infusion (SAL) (n = 10). The −sGC/+NO group also received intraportal SIN-1 (NO donor) to elevate hepatic NO from 180 to 270 min. RESULTS In the presence of 4× basal insulin, basal glucagon, and hyperglycemia (2× basal ), inhibition of sGC in the liver enhanced NHGU (mg/kg/min; 210–270 min) by ∼55% (2.9 ± 0.2 in SAL vs. 4.6 ± 0.5 in −sGC). Further elevating hepatic NO failed to reduce NHGU (4.5 ± 0.7 in −sGC/+NO). Net hepatic carbon retention (i.e., glycogen synthesis; mg glucose equivalents/kg/min) increased to 3.8 ± 0.2 in −sGC and 3.8 ± 0.4 in −sGC/+NO vs. 2.4 ± 0.2 in SAL (P < 0.05). CONCLUSIONS NO regulates liver glucose uptake through a sGC-dependent pathway. The latter could be a target for pharmacologic intervention to increase meal-associated hepatic glucose uptake in individuals with type 2 diabetes