1,993 research outputs found
Position and velocity space diffusion of test particles in stochastic electromagnetic fields
The two--dimensional diffusive dynamics of test particles in a random
electromagnetic field is studied. The synthetic electromagnetic fluctuations
are generated through randomly placed magnetised ``clouds'' oscillating with a
frequency . We investigate the mean square displacements of particles
in both position and velocity spaces. As increases the particles
undergo standard (Brownian--like) motion, anomalous diffusion and ballistic
motion in position space. Although in general the diffusion properties in
velocity space are not trivially related to those in position space, we find
that energization is present only when particles display anomalous diffusion in
position space. The anomalous character of the diffusion is only in the
non--standard values of the scaling exponents while the process is Gaussian.Comment: 10 pages, 4 figure
Proximate constraints on intruder detection in the dragonfly Perithemis tenera (Odonata: Libellulidae): effects of angle of approach and background
The implications of insects’ vision for territorial defense have been relatively little studied in the field. In the dragonfly Perithemis tenera Say we investigated whether either the angle at which an intruder was viewed by a territorial resident or the background against which it was viewed affected the detection of that intruder. Residents detected intruders at a greater distance if the intruders were directly in front of them; they also detected more intruders in front of them than from other angles. Intruders viewed against distant vegetation were detected more readily than were intruders against near vegetation. Residents detected more intruders viewed against distant vegetation than viewed against near vegetation; however, more intruders than expected were detected against near vegetation. The probability of detecting intruders depends on the angle at which they are viewed and the background behind them. Hence, there may be selection on territorial residents to adjust their orientation and space use to enhance their view of their territory and intruders
Proximate constraints on intruder detection in the dragonfly Perithemis tenera (Odonata: Libellulidae): effects of angle of approach and background
The implications of insects’ vision for territorial defense have been relatively little studied in the field. In the dragonfly Perithemis tenera Say we investigated whether either the angle at which an intruder was viewed by a territorial resident or the background against which it was viewed affected the detection of that intruder. Residents detected intruders at a greater distance if the intruders were directly in front of them; they also detected more intruders in front of them than from other angles. Intruders viewed against distant vegetation were detected more readily than were intruders against near vegetation. Residents detected more intruders viewed against distant vegetation than viewed against near vegetation; however, more intruders than expected were detected against near vegetation. The probability of detecting intruders depends on the angle at which they are viewed and the background behind them. Hence, there may be selection on territorial residents to adjust their orientation and space use to enhance their view of their territory and intruders
Teaching business ethics: Plato was right
Ethical lapses in major corporations continue to draw public attention to the specter of corporate misconduct. This paper presents a pedagogical approach that is designed to enhance student understanding and appreciation of the challenges that business leaders face when confronted with the conflict between the profit-maximizing demands of capitalism and the ethical expectations of society. This is an approach that fully acknowledges the seductive nature of unethical conduct in search of corporate rewards. This paper presents a method which can be applied both in undergraduate and graduate coursework, facilitates the examination of two corruption cases (Enron and WorldCom), and highlights short-term gain versus the eventual long-term pain of unethical behavior
Bayesian Inference of Transition Matrices from Incomplete Graph Data with a Topological Prior
Many network analysis and graph learning techniques are based on models of
random walks which require to infer transition matrices that formalize the
underlying stochastic process in an observed graph. For weighted graphs, it is
common to estimate the entries of such transition matrices based on the
relative weights of edges. However, we are often confronted with incomplete
data, which turns the construction of the transition matrix based on a weighted
graph into an inference problem. Moreover, we often have access to additional
information, which capture topological constraints of the system, i.e. which
edges in a weighted graph are (theoretically) possible and which are not, e.g.
transportation networks, where we have access to passenger trajectories as well
as the physical topology of connections, or a set of social interactions with
the underlying social structure. Combining these two different sources of
information to infer transition matrices is an open challenge, with
implications on the downstream network analysis tasks.
Addressing this issue, we show that including knowledge on such topological
constraints can improve the inference of transition matrices, especially for
small datasets. We derive an analytically tractable Bayesian method that uses
repeated interactions and a topological prior to infer transition matrices
data-efficiently. We compare it against commonly used frequentist and Bayesian
approaches both in synthetic and real-world datasets, and we find that it
recovers the transition probabilities with higher accuracy and that it is
robust even in cases when the knowledge of the topological constraint is
partial. Lastly, we show that this higher accuracy improves the results for
downstream network analysis tasks like cluster detection and node ranking,
which highlights the practical relevance of our method for analyses of various
networked systems.Comment: 22 pages, 13 figure
a smart nanofibrous material for adsorbing and detecting elemental mercury in air
Abstract. The combination of the affinity of gold for mercury and nanosized frameworks has allowed for the design and fabrication of novel kinds of sensors with promising sensing features for environmental applications. Specifically, conductive sensors based on composite nanofibrous electrospun layers of titania easily decorated with gold nanoparticles were developed to obtain nanostructured hybrid materials capable of entrapping and revealing gaseous elemental mercury (GEM) traces from the environment. The electrical properties of the resulting chemosensors were measured. A few minutes of air sampling were sufficient to detect the concentration of mercury in the air, ranging between 20 and 100 ppb, without using traps or gas carriers (LOD: 1.5 ppb). Longer measurements allowed the sensor to detect lower concentrations of GEM. The resulting chemosensors are expected to be low cost and very stable (due to the peculiar structure), requiring low power, low maintenance, and simple equipment
A cross-sectional study on prevalence and predictors of burnout among a sample of pharmacists employed in pharmacies in Central Italy
Burnout is defined as an occupational phenomenon linked to chronic workplace stress that has not been successfully managed and included among the factors influencing health status or contact with health services. Although several studies were performed for assessing this phenomenon, there is a lack of data on the prevalence of burnout and associated predictors, due to different definitions of the syndrome and heterogeneity of assessment methods. One of the well-known evidences on burnout is related to the highest risk professions, which include policemen, firemen, teachers, psychologists, medical students, nurses, physicians, and other health professionals, such as pharmacists. Objective. The aims of the present study were to (1) assess the occurrence of burnout syndrome among a sample of pharmacists employed in public and private pharmacies located in Rome province (Latium Region; central Italy); (2) evaluate the role of some potential predictors for the development of the syndrome. Materials and Methods. A questionnaire elaborated ad hoc was administered online to 2,000 members of the Association of Professional Pharmacists of Rome and its province and employed in public or private pharmacies. The questionnaire included the 14-item Shirom-Melamed Burnout Measure (SMBM) tool and questions on demographic characteristics and working conditions. Results. Physical exhaustion was the burnout dimension with the highest score; besides, approximately 11% of the studied pharmacists were categorized as having clinically relevant burnout levels (≥4.40). Several of the investigated variables significantly influenced the single burnout dimensions at the univariate analyses; multivariate analyses demonstrated that alcohol consumption and workplace location have a significant independent role on the overall SMBM index, while working time significantly influences clinically relevant burnout level. Conclusions. The results revealed that pharmacists are at risk of burnout, and thus, it is necessary to perform specific preventive intervention for managing this occupational threat
- …