Nonstationary Stochastic Resonance in a Single Neuron-Like System

Stochastic resonance holds much promise for the detection of weak signals in the presence of relatively loud noise. Following the discovery of nondynamical and of aperiodic stochastic resonance, it was recently shown that the phenomenon can manifest itself even in the presence of nonstationary signals. This was found in a composite system of differentiated trigger mechanisms mounted in parallel, which suggests that it could be realized in some elementary neural networks or nonlinear electronic circuits. Here, we find that even an individual trigger system may be able to detect weak nonstationary signals using stochastic resonance. The very simple modification to the trigger mechanism that makes this possible is reminiscent of some aspects of actual neuron physics. Stochastic resonance may thus become relevant to more types of biological or electronic systems injected with an ever broader class of realistic signals.Comment: Plain Latex, 7 figure

Light deflection by gravitational waves from localized sources

We study the deflection of light (and the redshift, or integrated time delay) caused by the time-dependent gravitational field generated by a localized material source lying close to the line of sight. Our calculation explicitly takes into account the full, near-zone, plus intermediate-zone, plus wave-zone, retarded gravitational field. Contrary to several recent claims in the literature, we find that the deflections due to both the wave-zone 1/r gravitational wave and the intermediate-zone 1/r^2 retarded fields vanish exactly. The leading total time-dependent deflection caused by a localized material source, such as a binary system, is proven to be given by the quasi-static, near-zone quadrupolar piece of the gravitational field, and therefore to fall off as the inverse cube of the impact parameter.Comment: 12 pages, REVTeX 3.0, no figur

Recognition of Tifinagh Characters using Self Organizing Map and Fuzzy k-Nearest Neighbor

In this paper we present a comparison between SOM (Self-Organization Map) neural network and Fuzzy Knearest Neighbor algorithms and their application to handwriting Tifinagh character recognition.The Box approach proposed in [1] is used for features extraction. Experimentation is carried out on a limited database of nearly 200 samples. The results showed that Fuzzy K-Nearest Neighbor had a very good performance

Solution heat treatment, forming and in-die quenching of a commercial sheet magnesium alloy into a complex-shaped component: experimentation and FE analysis

Interest in lightweight materials, particularly magnesium alloys, has increased significantly with rising efficiency requirements in the automotive sector. Magnesium is the lightest available structural metal, with a density approximately 35% lower than that of aluminium. The potential is great for magnesium to become a primary material used in future low carbon vehicle structures; however, there are significant obstacles, namely low ductility and formability, particularly at room temperature. The aim of this work is to present the feasibility of using the solution Heat treatment, Forming, and in-die Quenching (HFQ) process to produce complex shapes from a sheet magnesium alloy, and to use the results to verify a simulation of the process developed using commercial FE software. Uniaxial tensile tests were initially conducted to establish the optimum parameters for forming the part. Stamping trials were then carried out using these parameters, and a simulation set up modelling the forming operation. It was shown that the HFQ process could be used to form a successful component from this alloy, and that a good match was achieved between the results of the forming experiments and the simulation.The authors gratefully acknowledge the support from the EPSRC (Grant Ref: EP/I038616/1) for TARF-LCV: Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle Structures

To be or not to be a conodont. The controversial story of Pseudooneotodus and Eurytholia

The genus Pseudooneotodus (Drygant, 1974) is a genus of small and conical elements widely distributed from the Middle Ordovician to the Early Devonian throughout the world. Because of its unusual shape, Pseudooneotodus has long been considered enigmatic, and only in the late nineties of the last century the genus has been finally placed within conodonts according to histological data. This study investigates possible similarities between Pseudooneotodus and Eurytholia (Sutton et al., 2001), an incertae sedis genus of enigmatic plates with a phosphate composition. An association of over one hundred specimens of Pseudooneotodus beckmanni and Eurytholia bohemica was analyzed from conodont residues in two distinct geographical areas: the Prague Basin (Požáry and Mušlovka sections, Bohemia, Czech Republic) and the Carnic Alps (Rauchkofel Boden section, Austria). Through an investigation that combines the use of optical and electron microscopy (including focused ion beam scanning electron microscopy), X-ray microdiffraction, and trace element (HFSE) analysis by mass spectrometry, differences between these fossil groups were observed and compared with data resulting from typical conodonts (Dapsilodus obliquicostatus, Panderodus unicostatus and Wurmiella excavata) recovered from the same samples

The stability of modified gravity models

Conditions for the existence and stability of de Sitter space in modified gravity are derived by considering inhomogeneous perturbations in a gauge-invariant formalism. The stability condition coincides with the corresponding condition for stability with respect to homogeneous perturbations, while this is not the case in scalar-tensor gravity. The stability criterion is applied to various modified gravity models of the early and the present universe.Comment: 22 pages, LaTeX, to appear in Phys. Rev.

Noninvasive predictors of presence and grade of esophageal varices in viral cirrhotic patients

Predicting the presence and the grade of varices by non-invasive methods is likely to predict the need for prophylactic beta blockers or endoscopicvariceal ligation. The factors related to the presence of varices are not  well-defined. Therefore, the present study has been undertaken to determine the appropriateness of the various factors in predicting the existence and also the grade of esophageal varices. Patients with  diagnosis of liver cirrhosis due to hepatitis C or B were included in a retrospective study between January 2001 and January 2010. All the  patients underwent detailed clinical evaluation, appropriate investigations, imaging studies (ultrasound with Doppler) and endoscopy at our center. Five variables considered relevant to the presence and grade of varices were tested using univariate and multivariate analysis (logistic regression). Three hundred and seventy two patients with viral liver cirrhosis were included, with 192 (51.6%) males. Platelet count and abundance of ascites were significantly associated with the presence of esophageal varices. However, abundance of ascites, prothrombin time, diameter of the spleen and portal vein were significantly associated with a large varice. In  multivariate analysis, platelet count inferior to 100000 was associated with presence of varices (p=0.04) and only abundance of ascites was associated with large varice. Low Platelet count (< or equal 100000) is associated with the presence of varices in viral cirrhotic patients and abundance of ascites is correlated with the presence of large varices

Dosimetric Evaluation of PSMA PET-Delineated Dominant Intraprostatic Lesion Simultaneous Infield Boosts

Purpose: Prostate cancer is multifocal. However, there often exists a single dominant focus in the gland responsible for driving the biology of the disease. Dose escalation to the dominant lesion is a proposed strategy to increase tumor control. We applied radiobiological modeling to evaluate the dosimetric feasibility and benefit of dominant intraprostatic lesion simultaneous in-field boosts (DIL-SIB) to the gross tumor volume (GTV), defined using a novel molecular positron emission tomography (PET) probe (18F-DCFPyL) directed against prostate specific membrane antigen (PSMA). Methods and Materials: Patients with clinically localized, biopsy-proven prostate cancer underwent preoperative [ F]-DCFPyL PET/computed tomography (CT). DIL-SIB plans were generated by importing the PET/CT into the RayStation treatment planning system. GTV-PET for the DIL-SIB was defined by the highest %SUVmax (percentage of maximum standardized uptake value) that generated a biologically plausible volume. Volumetric arc–based plans incorporating prostate plus DIL-SIB treatment were generated. Tumor control probability (TCP) and normal tissue complication probability (NTCP) with fractionation schemes and boost doses specified in the FLAME (Investigate the Benefit of a Focal Lesion Ablative Microboost in Prostate Cancer; NCT01168479), PROFIT (Prostate Fractionated Irradiation Trial; NCT00304759), PACE (Prostate Advances in Comparative Evidence; NCT01584258), and hypoFLAME (Hypofractionated Focal Lesion Ablative Microboost in prostatE Cancer 2.0; NCT02853110) protocols were compared. Results: Comparative DIL-SIB plans for 6 men were generated from preoperative [ F]-DCFPyL PET/CT. Median boost GTV volume was 1.015 cm (0.42-1.83 cm ). Median minimum (D99%) DIL-SIB dose for F35 , F20 , F5 , and F5 were 97.3 Gy, 80.8 Gy, 46.5 Gy, and 51.5Gy. TCP within the GTV ranged from 84% to 88% for the standard plan and 95% to 96% for the DIL-SIB plans. Within the rest of the prostate, TCP ranged from 89% to 91% for the standard plans and 90% to 92% for the DIL-SIB plans. NTCP for the rectum NTCP was similar for the DIL-SIB plans (0.3%-2.7%) compared with standard plans (0.7%-2.6%). Overall, DIL-SIB plans yielded higher uncomplicated TCP (NTCP, 90%-94%) versus standard plans (NTCP, 83%-85%). Conclusions: PSMA PET provides a novel approach to define GTV for SIB-DIL dose escalation. Work is ongoing to validate PSMA PET-delineated GTV through correlation to coregistered postprostatectomy digitized histopathology. 18 18 3 3 BS BS BS BS

Non-chaotic dynamics in general-relativistic and scalar-tensor cosmology

In the context of scalar-tensor models of dark energy and inflation, the dynamics of vacuum scalar-tensor cosmology are analysed without specifying the coupling function or the scalar field potential. A conformal transformation to the Einstein frame is used and the dynamics of general relativity with a minimally coupled scalar field are derived for a generic potential. It is shown that the dynamics are non-chaotic, thus settling an existing debate.Comment: 20 pages, LaTeX, to appear in Class. Quantum Gra

Pandemic catch-22: the role of mobility restrictions and institutional inequalities in halting the spread of COVID-19

Countries across the world responded to the COVID-19 pandemic with what might well be the set of biggest state-led mobility and activity restrictions in the history of humankind. But how effective were these measures across countries? Compared to multiple recent studies that document an association between such restrictions and the control of the contagion, we use an instrumental variable approach to estimate the causal effect of these restrictions on mobility, and the growth rate of confirmed cases and deaths during the first wave of the pandemic. Using the level of stringency in the rest of the world to predict the level of stringency of the restriction measures in a country, we show while stricter contemporaneous measures affected mobility, stringency in seven to fourteen days mattered most for containing the contagion. Heterogeneity analysis, by various institutional inequalities, reveals that even though the restrictions reduced mobility more in relatively less-developed countries, the causal effect of a reduction in mobility was higher in more developed countries. We propose several explanations. Our results highlight the need to complement mobility and activity restrictions with other health and information measures, especially in less-developed countries, to combat the COVID-19 pandemic effectively