Some bounds for the spectral radius of a coxeter transformation

Let △ be finite quiver (=oriented, connected graph) without oriented cycles. Let k be any field. The path albebra k[△] is a hereditary algebra, see [7]. The study of this kind of algebras had played a central role in the development of the Representation Theory of Algebras, ..

Classical Signal Model for Quantum Channels

Recently it was shown that the main distinguishing features of quantum mechanics (QM) can be reproduced by a model based on classical random fields, so called prequantum classical statistical field theory (PCSFT). This model provides a possibility to represent averages of quantum observables, including correlations of observables on subsystems of a composite system (e.g., entangled systems), as averages with respect to fluctuations of classical (Gaussian) random fields. In this note we consider some consequences of PCSFT for quantum information theory. They are based on the observation \cite{W} of two authors of this paper that classical Gaussian channels (important in classical signal theory) can be represented as quantum channels. Now we show that quantum channels can be represented as classical linear transformations of classical Gaussian signa

A study on PDC drill bits quality

The quality of innovating PDC (Polycrystalline Diamond Compact) bits materials needs to be determined with accuracy by measuring cutting efficiency and wear rate, both related to the overall mechanical properties. An original approach is developed to encompass cutting efficiency and wear contribution to the overall sample quality. Therefore, a lathe-type test device was used to abrade specific samples from various manufacturers. Post-experiment analyzes are based on models establishing coupled relationships between cutting and friction stresses related to the drag bits excavation mechanism. These models are implemented in order to evaluate cutting efficiency and to estimate wear of the diamond insert. Phase analysis by XRD and finite element simulations were performed to explain the role of physicochemical parameters on the calculated quality factor values. Four main properties of PDC material were studied to explain quality results obtained in this study: cobalt content in samples that characterizes hardness/fracture toughness compromise, undesired phase as tungsten carbide weakening diamond structure, diamond grains sizes and residual stresses distribution affecting abrasion resistance

Brownian Entanglement

We show that for two classical brownian particles there exists an analog of continuous-variable quantum entanglement: The common probability distribution of the two coordinates and the corresponding coarse-grained velocities cannot be prepared via mixing of any factorized distributions referring to the two particles in separate. This is possible for particles which interacted in the past, but do not interact in the present. Three factors are crucial for the effect: 1) separation of time-scales of coordinate and momentum which motivates the definition of coarse-grained velocities; 2) the resulting uncertainty relations between the coordinate of the brownian particle and the change of its coarse-grained velocity; 3) the fact that the coarse-grained velocity, though pertaining to a single brownian particle, is defined on a common context of two particles. The brownian entanglement is a consequence of a coarse-grained description and disappears for a finer resolution of the brownian motion. We discuss possibilities of its experimental realizations in examples of macroscopic brownian motion.Comment: 18 pages, no figure

Robonaut 2 - Initial Activities On-Board the ISS

Robonaut 2, or R2, arrived on the International Space Station in February 2011 and is currently undergoing testing in preparation for it to become, initially, an Intra-Vehicular Activity (IVA) tool and then evolve into a system that can perform Extra-Vehicular Activities (EVA). After the completion of a series of system level checks to ensure that the robot traveled well on-board the Space Shuttle Atlantis, ground control personnel will remotely control the robot to perform free space tasks that will help characterize the differences between earth and zero-g control. For approximately one year, the fixed base R2 will perform a variety of experiments using a reconfigurable task board that was launched with the robot. While working side-by-side with human astronauts, Robonaut 2 will actuate switches, use standard tools, and manipulate Space Station interfaces, soft goods and cables. The results of these experiments will demonstrate the wide range of tasks a dexterous humanoid can perform in space and they will help refine the methodologies used to control dexterous robots both in space and here on earth. After the trial period that will evaluate R2 while on a fixed stanchion in the US Laboratory module, NASA plans to launch climbing legs that when attached to the current on-orbit R2 upper body will give the robot the ability to traverse through the Space Station and start assisting crew with general IVA maintenance activities. Multiple control modes will be evaluated in this extra-ordinary ISS test environment to prepare the robot for use during EVAs. Ground Controllers will remotely supervise the robot as it executes semi-autonomous scripts for climbing through the Space Station and interacting with IVA interfaces. IVA crew will locally supervise the robot using the same scripts and also teleoperate the robot to simulate scenarios with the robot working alone or as an assistant during space walks

Beaming into the News: A System for and Case Study of Tele-Immersive Journalism

We show how a combination of virtual reality and robotics can be used to beam a physical representation of a person to a distant location, and describe an application of this system in the context of journalism. Full body motion capture data of a person is streamed and mapped in real time, onto the limbs of a humanoid robot present at the remote location. A pair of cameras in the robot's 'eyes' stream stereoscopic video back to the HMD worn by the visitor, and a two-way audio connection allows the visitor to talk to people in the remote destination. By fusing the multisensory data of the visitor with the robot, the visitor's 'consciousness' is transformed to the robot's body. This system was used by a journalist to interview a neuroscientist and a chef 900 miles distant, about food for the brain, resulting in an article published in the popular press

Born's rule from measurements of classical signals by threshold detectors which are properly calibrated

The very old problem of the statistical content of quantum mechanics (QM) is studied in a novel framework. The Born's rule (one of the basic postulates of QM) is derived from theory of classical random signals. We present a measurement scheme which transforms continuous signals into discrete clicks and reproduces the Born's rule. This is the sheme of threshold type detection. Calibration of detectors plays a crucial role.Comment: The problem of double clicks is resolved; hence, one can proceed in purely wave framework, i.e., the wave-partcile duality has been resolved in favor of the wave picture of prequantum realit

A Model of the Potential Distribution of Striga hermonthica in the African Continent and its Prospection under Climate Change

The genus Striga (Orobanchaceae) comprises parasitic weeds recognised as a major problem for crop production in sub-Saharan Africa. Striga hermonthica is an obligate parasite of pearl millet, sorghum and other important crops in semi-arid and arid regions of the tropics, producing millions of hectares of yield loses and a great impact on human welfare in the rural areas where it occurs. Under the present situation and the possible scenarios within the framework of climate change Striga hermonthica’s current and future distribution needs to be estimated urgently, in order to efficiently target available prevention and management strategies. Using the maximum entropy (Maxent) approach for modelling species’ distributions, our research focuses on better describe the present distribution of Striga hermonthica and to predict potential future areas where this dangerous parasite could spread in the African continent

Dna methylation changes in fibromyalgia suggest the role of the immune‐inflammatory response and central sensitization

Fibromyalgia (FM) has been explained as a result of gene‐environment interactions. The present study aims to verify DNA methylation differences in eleven candidate genome regions previously associated to FM, evaluating DNA methylation patterns as potential disease biomarkers. DNA methylation was analyzed through bisulfite sequencing, comparing 42 FM women and their 42 healthy sisters. The associations between the level of methylation in these regions were further explored through a network analysis. Lastly, a logistic regression model investigated the regions potentially associated with FM, when controlling for sociodemographic variables and depressive symptoms. The analysis highlighted significant differences in the GCSAML region methylation between patients and controls. Moreover, seventeen single CpGs, belonging to other genes, were significantly different, however, only one cytosine related to GCSAML survived the correction for multiple comparisons. The network structure of methylation sites was different for each group; GRM2 methylation represented a central node only for FM patients. Logistic regression revealed that depressive symptoms and DNA methylation in the GRM2 region were significantly associated with FM risk. Our study encourages better exploration of GCSAML and GRM2 functions and their possible role in FM affecting immune, inflammatory response, and central sensitization of pain