A mean field method with correlations determined by linear response

We introduce a new mean-field approximation based on the reconciliation of maximum entropy and linear response for correlations in the cluster variation method. Within a general formalism that includes previous mean-field methods, we derive formulas improving upon, e.g., the Bethe approximation and the Sessak-Monasson result at high temperature. Applying the method to direct and inverse Ising problems, we find improvements over standard implementations.Comment: 15 pages, 8 figures, 9 appendices, significant expansion on versions v1 and v

A comparative study of MTA solubility in various media

INTRODUCTION: Solubility of root filling materials is heavily influenced by the environment they are in contact with. This study compared the solubility of ProRoot MTA in deionized water and synthetic tissue fluid. MATERIALS & METHODS: Forty specimens of prepared MTA were immersed in deionized water and synthetic tissue fluid (20 samples each). The solubility was assessed after 7 and 28 days. Scanning electron microscope observation was also performed. The mean weight loss was evaluated using a digital scale. Data were analyzed using one-way ANOVA. Tukey test was performed for multiple comparisons. RESULTS: MTA solubility in synthetic tissue fluid was significantly lower than deionized water after 7 and 28 days (P<0.05). Secondary electron detectors revealed the presence of lumps and platelets on the surfaces of both specimens. Also, more voids were observed in specimen stored in deionized water. CONCLUSION: MTA dissolved faster in deionized water than synthetic tissue fluid. Despite this, the solubility of this material in both media was acceptable.

A Problem with Non-Abelian Duality

We investigate duality transformations in a class of backgrounds with non-Abelian isometries, i.e. Bianchi-type (homogeneous) cosmologies in arbitrary dimensions. Simple duality transformations for the metric and the antisymmetric tensor field, generalizing those known from the Abelian isometry (Bianchi I) case, are obtained using either a Lagrangian or a Hamiltonian approach. Applying these prescriptions to a specific conformally invariant \s-model, we show that no dilaton transformation leads to a new conformal background. Some possible ways out of the problem are suggested.Comment: 14pages, CERN-TH.6960/93 ROM2F/93/24 (One reference and one paragraph added

Human glutathione transferase T2-2 discloses some evolutionary strategies for optimization of the catalytic activity of glutathione transferases.

Steady state, pre-steady state kinetic experiments, and site-directed mutagenesis have been used to dissect the catalytic mechanism of human glutathione transferase T2-2 with 1-menaphthyl sulfate as co-substrate. This enzyme is close to the ancestral precursor of the more recently evolved glutathione transferases belonging to Alpha, Pi, and Mu classes. The enzyme displays a random kinetic mechanism with very low k(cat) and k(cat)/K(m)((GSH)) values and with a rate-limiting step identified as the product release. The chemical step, which is fast and causes product accumulation before the steady state catalysis, strictly depends on the deprotonation of the bound GSH. Replacement of Arg-107 with Ala dramatically affects the fast phase, indicating that this residue is crucial both in the activation and orientation of GSH in the ternary complex. All pre-steady state and steady state kinetic data were convincingly fit to a kinetic mechanism that reflects a quite primordial catalytic efficiency of this enzyme. It involves two slowly interconverting or not interconverting enzyme populations (or active sites of the dimeric enzyme) both able to bind and activate GSH and strongly inhibited by the product. Only one population or subunit is catalytically competent. The proposed mechanism accounts for the apparent half-site behavior of this enzyme and for the apparent negative cooperativity observed under steady state conditions. These findings also suggest some evolutionary strategies in the glutathione transferase family that have been adopted for the optimization of the catalytic activity, which are mainly based on an increased flexibility of critical protein segments and on an optimal orientation of the substrate

CONTROL DE DISPOSITIVOS INTRATUBARIOS ESSURE MEDIANTE ESTUDIO DE IMÁGENES

Objetivo: Comparar la efectividad en la detección y control del dispositivo intratubario (DIT) Essure por medio de la radiografía abdominopélvica y el ultrasonido. Método: Control de los primeros 5 casos de esterilización tubaria ambulatoria con Essure, después de 1 y 2 años de su inserción, mediante radiografía abdominopélvica y ecografía transvaginal. Resultados: Ambos exámenes de imágenes permitieron corroborar la presencia del dispositivo Essure en las 5 pacientes, al completar su primer y segundo año desde su inserción. Conclusión:Tanto la radiografía abdominopélvica como la ecografía transvaginal, permiten detectar y controlar la presencia del DIT Essure. El ultrasonido realizado por el ginecólogo en la consulta, puede reemplazar a la radiografía simple, como método de detección y control de los dispositivos intra-tubarios (Essure). Las ventajas comparativas permiten concluir que el ultrasonido, no irradia a la paciente y permite explorar el resto de la anatomía de los órganos sexuales internos durante el mismo procedimiento. Sin embargo, es de mayor costo que la radiografí

On the geometry of classically integrable two-dimensional non-linear sigma models

A master equation expressing the classical integrability of two-dimensional non-linear sigma models is found. The geometrical properties of this equation are outlined. In particular, a closer connection between integrability and T-duality transformations is emphasised. Finally, a whole new class of integrable non-linear sigma models is found and all their corresponding Lax pairs depend on a spectral parameter.Comment: 16 pages. Major changes (almost a new paper). To be published in Nuclear Physics B (2010

Contrasting prefrontal cortex contributions to episodic memory dysfunction in behavioural variant frontotemporal dementia and alzheimer's disease

Recent evidence has questioned the integrity of episodic memory in behavioural variant frontotemporal dementia (bvFTD), where recall performance is impaired to the same extent as in Alzheimer's disease (AD). While these deficits appear to be mediated by divergent patterns of brain atrophy, there is evidence to suggest that certain prefrontal regions are implicated across both patient groups. In this study we sought to further elucidate the dorsolateral (DLPFC) and ventromedial (VMPFC) prefrontal contributions to episodic memory impairment in bvFTD and AD. Performance on episodic memory tasks and neuropsychological measures typically tapping into either DLPFC or VMPFC functions was assessed in 22 bvFTD, 32 AD patients and 35 age- and education-matched controls. Behaviourally, patient groups did not differ on measures of episodic memory recall or DLPFC-mediated executive functions. BvFTD patients were significantly more impaired on measures of VMPFC-mediated executive functions. Composite measures of the recall, DLPFC and VMPFC task scores were covaried against the T1 MRI scans of all participants to identify regions of atrophy correlating with performance on these tasks. Imaging analysis showed that impaired recall performance is associated with divergent patterns of PFC atrophy in bvFTD and AD. Whereas in bvFTD, PFC atrophy covariates for recall encompassed both DLPFC and VMPFC regions, only the DLPFC was implicated in AD. Our results suggest that episodic memory deficits in bvFTD and AD are underpinned by divergent prefrontal mechanisms. Moreover, we argue that these differences are not adequately captured by existing neuropsychological measures

False recognition in behavioral variant frontotemporal dementia and Alzheimer's Disease - Disinhibition or amnesia?

Episodic memory recall processes in Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD) can be similarly impaired, whereas recognition performance is more variable. A potential reason for this variability could be false-positive errors made on recognition trials and whether these errors are due to amnesia per se or a general over-endorsement of recognition items regardless of memory. The current study addressed this issue by analysing recognition performance on the Rey Auditory Verbal Learning Test (RAVLT) in 39 bvFTD, 77 AD and 61 control participants from two centers (India, Australia), as well as disinhibition assessed using the Hayling test. Whereas both AD and bvFTD patients were comparably impaired on delayed recall, bvFTD patients showed intact recognition performance in terms of the number of correct hits. However, both patient groups endorsed significantly more false-positives than controls, and bvFTD and AD patients scored equally poorly on a sensitivity index (correct hits—false-positives). Furthermore, measures of disinhibition were significantly associated with false positives in both groups, with a stronger relationship with false-positives in bvFTD. Voxel-based morphometry analyses revealed similar neural correlates of false positive endorsement across bvFTD and AD, with both patient groups showing involvement of prefrontal and Papez circuitry regions, such as medial temporal and thalamic regions, and a DTI analysis detected an emerging but non-significant trend between false positives and decreased fornix integrity in bvFTD only. These findings suggest that false-positive errors on recognition tests relate to similar mechanisms in bvFTD and AD, reflecting deficits in episodic memory processes and disinhibition. These findings highlight that current memory tests are not sufficient to accurately distinguish between bvFTD and AD patients

Inhaled ambient-level traffic-derived particulates decrease cardiac vagal influence and baroreflexes and increase arrhythmia in a rat model of metabolic syndrome

Background: Epidemiological studies have linked exposures to ambient fine particulate matter (PM2.5) and traffic with autonomic nervous system imbalance (ANS) and cardiac pathophysiology, especially in individuals with preexisting disease. It is unclear whether metabolic syndrome (MetS) increases susceptibility to the effects of PM2.5. We hypothesized that exposure to traffic-derived primary and secondary organic aerosols (P + SOA) at ambient levels would cause autonomic and cardiovascular dysfunction in rats exhibiting features of MetS. Male Sprague Dawley (SD) rats were fed a high-fructose diet (HFrD) to induce MetS, and exposed to P + SOA (20.4 ± 0.9 μg/m3) for 12 days with time-matched comparison to filtered-air (FA) exposed MetS rats; normal diet (ND) SD rats were separately exposed to FA or P + SOA (56.3 ± 1.2 μg/m3). Results: In MetS rats, P + SOA exposure decreased HRV, QTc, PR, and expiratory time overall (mean effect across the entirety of exposure), increased breathing rate overall, decreased baroreflex sensitivity (BRS) on three exposure days, and increased spontaneous atrioventricular (AV) block Mobitz Type II arrhythmia on exposure day 4 relative to FA-exposed animals receiving the same diet. Among ND rats, P + SOA decreased HRV only on day 1 and did not significantly alter BRS despite overall hypertensive responses relative to FA. Correlations between HRV, ECG, BRS, and breathing parameters suggested a role for autonomic imbalance in the pathophysiologic effects of P + SOA among MetS rats. Autonomic cardiovascular responses to P + SOA at ambient PM2.5 levels were pronounced among MetS rats and indicated blunted vagal influence over cardiovascular physiology. Conclusions: Results support epidemiologic findings that MetS increases susceptibility to the adverse cardiac effects of ambient-level PM2.5, potentially through ANS imbalance. Electronic supplementary material The online version of this article (doi:10.1186/s12989-017-0196-2) contains supplementary material, which is available to authorized users