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

3-D seismic exploration for the Victorio Peak treasure

In January of 1994, we conducted an extensive seismic experiment to find caverns under Victorio Peak, a bioherm reef structure located approximately 80 miles northeast of Las Cruces, New Mexico. Within Victorio Peak there is reputed to be an extensive network of caverns, tunnels and fissures that contain a large and varied treasure consisting of gold bars, Spanish armor, jewels, coins, and human skeletons. We used an array of seismic sources that included a sledgehammer on the surface of the mountain, a sledgehammer impacting on the walls of two deep fissures within the mountain, as well as blasting caps located in boreholes drilled into the mountain. Approximately 2,000 source positions were recorded by 120 receiver channels consisting of geophones cemented into fissure walls and hydrophones deployed in a deep horizontal borehole drilled at the base of the mountain. The data analysis consisted of measuring reduced traveltime and amplitude of the direct arrival and isolating those source/receiver pairs that exhibited anomalously large direct arrival traveltimes and/or low amplitudes. We have currently identified and located a major amplitude anomaly under the peak that will be drilled and explored during the summer of 1994

Constitutive activation of nuclear factor‐E2‐related factor 2 induces biotransformation enzyme and transporter expression in livers of mice with hepatocyte‐specific deletion of Kelch‐like ECH‐associated protein 1

Chemicals that activate nuclear factor‐E2‐related factor 2 (Nrf2) often increase multidrug‐resistance‐associated protein (Mrp) expression in liver. Hepatocyte‐specific deletion of Kelch‐like ECH‐associated protein 1 (Keap1) activates Nrf2. Use of hepatocyte‐specific Keap1 deletion represents a nonpharmacological method to determine whether constitutive Nrf2 activation upregulates liver transporter expression in vivo. The mRNA, protein expression, and localization of several biotransformation and transporters were determined in livers of wild‐type and hepatocyte‐specific Keap1‐null mice. Sulfotransferase 2a1/2, NADP(H):quinone oxidoreductase 1, cytochrome P450 2b10, 3a11, and glutamate–cysteine ligase catalytic subunit expression were increased in livers of Keap1‐null mice. Organic anion‐transporting polypeptide 1a1 expression was nearly abolished, as compared to that detected in livers of wild‐type mice. By contrast, Mrp 1–5 mRNA and protein levels were increased in Keap1‐null mouse livers, with Mrp4 expression being more than 15‐fold higher than wild types. In summary, Nrf2 has a significant role in affecting Oatp and Mrp expressions

Lorentzian spin foam amplitudes: graphical calculus and asymptotics

The amplitude for the 4-simplex in a spin foam model for quantum gravity is defined using a graphical calculus for the unitary representations of the Lorentz group. The asymptotics of this amplitude are studied in the limit when the representation parameters are large, for various cases of boundary data. It is shown that for boundary data corresponding to a Lorentzian simplex, the asymptotic formula has two terms, with phase plus or minus the Lorentzian signature Regge action for the 4-simplex geometry, multiplied by an Immirzi parameter. Other cases of boundary data are also considered, including a surprising contribution from Euclidean signature metrics.Comment: 30 pages. v2: references now appear. v3: presentation greatly improved (particularly diagrammatic calculus). Definition of "Regge state" now the same as in previous work; signs change in final formula as a result. v4: two references adde

Geometric Algorithm for Abelian-Gauge Models

Motivated by the sign problem in several systems, we have developed a geometric simulation algorithm based on the strong coupling expansion which can be applied to abelian pure gauge models. We have studied the algorithm in the U(1) model in 3 and 4 dimensions, and seen that it is practical and is similarly efficient to the standard heat-bath algorithm, but without the ergodicity problems which comes from the presence of vortices. We have also applied the algorithm to the Ising gauge model at the critical point, and we find hints of a better asymptotic behaviour of the autocorrelation time, which therefore suggests the possibility of a smaller dynamical critical exponent with respect to the standard heat-bath algorithm.Comment: 16 pages, 11 figure

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

Patient Navigators Connecting Patients to Community Resources to Improve Diabetes Outcomes

BACKGROUND: Despite the recognized importance of lifestyle modification in reducing risk of developing type 2 diabetes and in diabetes management, the use of available community resources by both patients and their primary care providers (PCPs) remains low. The patient navigator model, widely used in cancer care, may have the potential to link PCPs and community resources for reduction of risk and control of type 2 diabetes. In this study we tested the feasibility and acceptability of telephone-based nonprofessional patient navigation to promote linkages between the PCP office and community programs for patients with or at risk for diabetes. METHODS: This was a mixed-methods interventional prospective cohort study conducted between November 2012 and August 2013. We included adult patients with and at risk for type 2 diabetes from six primary care practices. Patient-level measures of glycemic control, diabetes care, and self-efficacy from medical records, and qualitative interview data on acceptability and feasibility, were used. RESULTS: A total of 179 patients participated in the study. Two patient navigators provided services over the phone, using motivational interviewing techniques. Patient navigators provided regular feedback to PCPs and followed up with the patients through phone calls. The patient navigators made 1028 calls, with an average of 6 calls per patient. At follow-up, reduction in HbA1c (7.8 ± 1.9% vs 7.2 ± 1.3%; P = .001) and improvement in patient self-efficacy (3.1 ± 0.8 vs 3.6 ± 0.7; P < .001) were observed. Qualitative analysis revealed uniformly positive feedback from providers and patients. CONCLUSIONS: The patient navigator model is a promising and acceptable strategy to link patient, PCP, and community resources for promoting lifestyle modification in people living with or at risk for type 2 diabetes

Exotic Corn Lines with Increased Resistant Starch and Impact on Starch Thermal Characteristics

Ten parent corn lines, including four mutants (dull sugary2, amyloseextender sugary2, amylose-extender dull, and an amylose-extender with introgressed Guatemalen germplasm [GUAT ae]) and six lines with introgressed exotic germplasm backgrounds, were crossed with each other to create 20 progeny crosses to increase resistant starch (RS) as a dietary fiber in corn starch and to provide materials for thermal evaluation. The resistant starch 2 (RS2) values from the 10 parent lines were 18.3–52.2% and the values from the 20 progeny crosses were 16.6–34.0%. The %RS2 of parents was not additive in the offspring but greater RS2 in parents was correlated to greater RS2 in the progeny crosses (r = 0.63). Differential scanning calorimetry (DSC) measured starch thermal characteristics, revealing positive correlations of peak gelatinization temperature and change in enthalpy with %RS2 (r = 0.65 and r = 0.67, P ≤ 0.05); however, % retrogradation (a measure of RS3) and retrogradation parameters did not correlate with %RS2. The %RS2 and onset temperature increased with the addition of the ae gene, likely because RS delays gelatinization