Fat Fisher Zeroes

We show that it is possible to determine the locus of Fisher zeroes in the thermodynamic limit for the Ising model on planar (``fat'') phi4 random graphs and their dual quadrangulations by matching up the real part of the high and low temperature branches of the expression for the free energy. The form of this expression for the free energy also means that series expansion results for the zeroes may be obtained with rather less effort than might appear necessary at first sight by simply reverting the series expansion of a function g(z) which appears in the solution and taking a logarithm. Unlike regular 2D lattices where numerous unphysical critical points exist with non-standard exponents, the Ising model on planar phi4 graphs displays only the physical transition at c = exp (- 2 beta) = 1/4 and a mirror transition at c=-1/4 both with KPZ/DDK exponents (alpha = -1, beta = 1/2, gamma = 2). The relation between the phi4 locus and that of the dual quadrangulations is akin to that between the (regular) triangular and honeycomb lattices since there is no self-duality.Comment: 12 pages + 6 eps figure

Dynamics of elastocapillary rise

We present the results of a combined experimental and theoretical investigation of the surface-tension-driven coalescence of flexible structures. Specifically, we consider the dynamics of the rise of a wetting liquid between flexible sheets that are clamped at their upper ends. As the elasticity of the sheets is progressively increased, we observe a systematic deviation from the classical diffusive-like behaviour: the time to reach equilibrium increases dramatically and the departure from classical rise occurs sooner, trends that we elucidate via scaling analyses. Three distinct temporal regimes are identified and subsequently explored by developing a theoretical model based on lubrication theory and the linear theory of plates. The resulting free-boundary problem is solved numerically and good agreement is obtained with experiments

Identification of an Actin-Based Antidiabetic Action of Chromium in Skeletal Muscle

poster abstractWe recently demonstrated that cortical filamentous actin (F-actin) loss contributes to cellular insulin resistance induced by hyperinsulinemia. New animal and human analyses suggest a similar loss of F-actin is present in insulin-resistant skeletal muscle and results from cellular cholesterol accrual. Interestingly, we found that chromium picolinate (CrPic), a dietary supplement recognized to improve insulin action, lowers plasma membrane cholesterol in cultured adipocytes. Understanding whether CrPic can improve F-actin structure in insulinresistant skeletal muscle via lowering membrane cholesterol is not known, yet significant, as skeletal muscle is responsible for a large majority of insulin-stimulated glucose transport. In L6 myotubes stably expressing the insulin-responsive glucose transporter GLUT4 carrying an exofacial myc-epitope tag, acute insulin stimulation (20 min, 100 nM) increased myc-epitope labeling at the surface of intact cells by ~2-fold (P<0.05). In contrast, the ability of insulin to stimulate this process was inhibited 25% (P<0.05) by sustained exposure of L6 myotubes to insulin (12 h, 5 nM). Defects in insulin signaling did not readily account for the observed disruption. However, we found that insulin-induced insulin-resistant myotubes displayed a 28% elevation (P<0.05) in membrane cholesterol with a reciprocal 14% loss (P<0.05) in F-actin. This cholesterol/actin imbalance and insulin/GLUT4 dysfunction was corrected by the cholesterollowering action of CrPic. Mechanistically, CrPic increased the activity of the AMP-activated protein kinase (AMPK). Tests also revealed that other well-recognized activators of AMPK (e.g., AICAR, DNP) lowered membrane cholesterol and that, in a fashion similar to that witnessed for CrPic, improved regulation of GLUT4 in insulin-induced insulin-resistant myotubes. These data, as well as findings from ongoing siRNA-mediated AMPK knockdown experiments, are consistent with AMPK mediating its antidiabetic action by lowering cellular cholesterol. We predict that chromium, via AMPK activation, protects against cholesterol accrual that induces skeletal muscle F-actin loss and insulin resistance

Beavers, Castor canadensis, Feeding on Salmon Carcasses: Opportunistic Use of a Seasonally Superabundant Food Source

We report observations of Beavers (Castor canadensis) foraging and feeding on discarded Chinook Salmon (Oncorhynchus tshawytscha) carcasses within the confines of the Susitna River drainage in southcentral Alaska on three separate occasions between 1999 and 2004. In all three instances, Beavers were observed actively seeking out freshly discarded carcasses or transporting &ldquo;fresh&rdquo; salmon carcasses in their mouths. In one instance, Beavers were seen using their dextrous forefeet to &ldquo;handle&rdquo; chunks of salmon while hunched over carcasses and in this case we actually witnessed Beavers &ldquo;chewing&rdquo; and ingestion was assumed. In the other two instances, Beavers were observed swimming with salmon carcasses in their mouths. Though unique within the framework of Beaver foraging ecology, we suggest this behavior may be a fairly common strategy employed by Beavers in Alaskan streams and rivers to take advantage of a seasonally superabundant source of protein

They Saw a Protest : Cognitive Illiberalism and the Speech-Conduct Distinction

“Cultural cognition” refers to the unconscious influence of individuals’ group commitments on their perceptions of legally consequential facts. We conducted an experiment to assess the impact of cultural cognition on perceptions of facts relevant to distinguishing constitutionally protected “speech” from unprotected “conduct.” Study subjects viewed a video of a political demonstration. Half the subjects believed that the demonstrators were protesting abortion outside of an abortion clinic, and the other half that the demonstrators were protesting the military’s “don’t ask, don’t tell” policy outside a military recruitment center. Subjects of opposing cultural outlooks who were assigned to the same experimental condition (and thus had the same belief about the nature of the protest) disagreed sharply on key “facts”—including whether the protestors obstructed and threatened pedestrians. Subjects also disagreed sharply with those who shared their cultural outlooks but who were assigned to the opposing experimental condition (and hence had a different belief about the nature of the protest). These results supported the study hypotheses about how cultural cognition would affect perceptions pertinent to the speech-conduct distinction. We discuss the significance of the results for constitutional law and liberal principles of self governanc generally

Methionine synthase interreplacement in diatom cultures and communities : implications for the persistence of B12 use by eukaryotic phytoplankton

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 58 (2013): 1431–1450, doi:10.4319/lo.2013.58.4.1431.Three proteins related to vitamin B12 metabolism in diatoms were quantified via selected reaction monitoring mass spectrometry: B12-dependent and B12-independent methionine synthase (MetH, MetE) and a B12 acquisition protein (CBA1). B12-mediated interreplacement of MetE and MetH metalloenzymes was observed in Phaeodactylum tricornutum where MetH abundance was highest (0.06 fmol µg−1 protein) under high B12 and MetE abundance increased to 3.25 fmol µg−1 protein under low B12 availability. Maximal MetE abundance was 60-fold greater than MetH, consistent with the expected ∼ 50–100-fold larger turnover number for MetH. MetE expression resulted in 30-fold increase in nitrogen and 40-fold increase in zinc allocated to methionine synthase activity under low B12. CBA1 abundance was 6-fold higher under low-B12 conditions and increased upon B12 resupply to starved cultures. While biochemical pathways that supplant B12 requirements exist and are utilized by organisms such as land plants, B12 use persists in eukaryotic phytoplankton. This study suggests that retention of B12 utilization by phytoplankton results in resource conservation under conditions of high B12 availability. MetE and MetH abundances were also measured in diatom communities from McMurdo Sound, verifying that both these proteins are expressed in natural communities. These protein measurements are consistent with previous studies suggesting that B12 availability influences Antarctic primary productivity. This study illuminates controls on expression of B12-related proteins, quantitatively assesses the metabolic consequences of B12 deprivation, and demonstrates that mass spectrometry–based protein measurements yield insight into the functioning of marine microbial communities.This work was supported by National Science Foundation (NSF) Antarctic Sciences awards 0732665, 1103503, and 0732822; NSF Division of Ocean Science awards 0752291, 0928414, and 1031271; The Gordon and Betty Moore Foundation; Center for Microbial Oceanography Research and Education; an NSF Graduate Research Fellowship (2007037200); and an Environmental Protection Agency Science To Achieve Results (EPA-STAR) Fellowship to E.M.B. (F6E720324)

Quantifying Laryngopharyngeal Reflux in Singers: Perceptual and Objective Findings

This study examines the relationship between laryngopharyngeal reflux (LPR) symptoms and oropharyngeal pH levels in singers. We hypothesized that reported symptoms would correlate with objective measures of pH levels from the oropharynx, including the number and total duration of reflux episodes. Twenty professional/semiprofessional singers completed the Reflux Symptom Index (RSI) and underwent oropharyngeal pH monitoring. Mild, moderate, or severe pH exposure was recorded during oropharyngeal pH monitoring. Correlations were performed to examine potential relationships between reflux symptoms and duration of LPR episodes. Symptom severity did not correlate with pH levels; however, we found a number of covariances of interest. Large sample sizes are necessary to determine if true correlations exist. Our results suggest that singers may exhibit enhanced sensitivity to LPR and may therefore manifest symptoms, even in response to subtle changes in pH. This study emphasizes the importance of sensitive and objective measures of reflux severity as well as consideration of the cumulative time of reflux exposure in addition to the number of reflux episodes

Chromium Enhances Insulin Responsiveness via AMPK

Trivalent chromium (Cr3+) is known to improve glucose homeostasis. Cr3+ has been shown to improve plasma membrane-based aspects of glucose transporter GLUT4 regulation and increase activity of the cellular energy sensor 5′ AMP-activated protein kinase (AMPK). However, the mechanism(s) by which Cr3+ improves insulin responsiveness and whether AMPK mediates this action is not known. In this study we tested if Cr3+ protected against physiological hyperinsulinemia-induced plasma membrane cholesterol accumulation, cortical filamentous actin (F-actin) loss and insulin resistance in L6 skeletal muscle myotubes. In addition, we performed mechanistic studies to test our hypothesis that AMPK mediates the effects of Cr3+ on GLUT4 and glucose transport regulation. Hyperinsulinemia-induced insulin-resistant L6 myotubes displayed excess membrane cholesterol and diminished cortical F-actin essential for effective glucose transport regulation. These membrane and cytoskeletal abnormalities were associated with defects in insulin-stimulated GLUT4 translocation and glucose transport. Supplementing the culture medium with pharmacologically relevant doses of Cr3+ in the picolinate form (CrPic) protected against membrane cholesterol accumulation, F-actin loss, GLUT4 dysregulation and glucose transport dysfunction. Insulin signaling was neither impaired by hyperinsulinemic conditions nor enhanced by CrPic, whereas CrPic increased AMPK signaling. Mechanistically, siRNA-mediated depletion of AMPK abolished the protective effects of CrPic against GLUT4 and glucose transport dysregulation. Together these findings suggest that the micronutrient Cr3+, via increasing AMPK activity, positively impacts skeletal muscle cell insulin sensitivity and glucose transport regulation

Understanding verbal fluency in healthy aging, Alzheimer’s disease, and Parkinson’s disease

This is the author's accepted manuscript. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.• Objective: Verbal fluency measures are frequently part of batteries designed to assess executive function, but are also used to assess semantic processing ability or word knowledge. The goal of the present study was to identify the cognitive components underlying fluency performance. • Method: Healthy young and older adults, adults with Parkinson’s disease, and adults with Alzheimer’s disease performed letter, category, and action fluency tests. Performance was assessed in terms of number of items generated, clustering, and the time course of output. A series of neuropsychological assessments were also administered to index verbal ability, working memory, executive function, and processing speed as correlates of fluency performance. • Results: Findings indicated that regardless of the particular performance measure, young adults performed the best and adults with Alzheimer’s disease performed most poorly, with healthy older adults and adults with Parkinson’s disease performing at intermediate levels. The exception was the action fluency task, where adults with Parkinson’s disease performed most poorly. The time course of fluency performance was characterized in terms of slope and intercept parameters and related to neuropsychological constructs. Speed of processing was found to be the best predictor of performance, rather than the efficiency of executive function or semantic knowledge. • Conclusions: Together, these findings demonstrate that the pattern of fluency performance looks generally the same regardless of how performance is measured. In addition, the primary role of processing speed in performance suggests that the use of fluency tasks as measures of executive function or verbal ability warrants reexamination.This work was conducted with grant support from the Kansas City Life Sciences Institute. Additional support was provided by the Digital Electronics Core of the Center for Biobehavioral Neurosciences in Communication Disorders, grant number P30 DC-005803, for assistance with the development of the digital ink assessment