2,453 research outputs found
Consistent and efficient output-streams management in optimistic simulation platforms
Get PDFOptimistic synchronization is considered an effective means for supporting Parallel Discrete Event Simulations. It relies on a speculative approach, where concurrent processes execute simulation events regardless of their safety, and consistency is ensured via proper rollback mechanisms, upon the a-posteriori detection of causal inconsistencies along the events' execution path. Interactions with the outside world (e.g. generation of output streams) are a well-known problem for rollback-based systems, since the outside world may have no notion of rollback. In this context, approaches for allowing the simulation modeler to generate consistent output rely on either the usage of ad-hoc APIs (which must be provided by the underlying simulation kernel) or temporary suspension of processing activities in order to wait for the final outcome (commit/rollback) associated with a speculatively-produced output. In this paper we present design indications and a reference implementation for an output streams' management subsystem which allows the simulation-model writer to rely on standard output-generation libraries (e.g. stdio) within code blocks associated with event processing. Further, the subsystem ensures that the produced output is consistent, namely associated with events that are eventually committed, and system-wide ordered along the simulation time axis. The above features jointly provide the illusion of a classical (simple to deal with) sequential programming model, which spares the developer from being aware that the simulation program is run concurrently and speculatively. We also show, via an experimental study, how the design/development optimizations we present lead to limited overhead, giving rise to the situation where the simulation run would have been carried out with near-to-zero or reduced output management cost. At the same time, the delay for materializing the output stream (making it available for any type of audit activity) is shown to be fairly limited and constant, especially for good mixtures of I/O-bound vs CPU-bound behaviors at the application level. Further, the whole output streams' management subsystem has been designed in order to provide scalability for I/O management on clusters. © 2013 ACM
The static electric polarizability of a particle bound by a finite potential well
Full text linkIn this paper we derive an expression for the static electric polarizability
of a particle bound by a finite potential well without the explicit use of the
continuum states in our calculations. This will be accomplished by employing
the elegant Dalgarno-Lewis perturbative technique.Comment: 14 Pages, 2 Table
A comprehensive analysis of the geometry of TDOA maps in localisation problems
Get PDFIn this manuscript we consider the well-established problem of TDOA-based
source localization and propose a comprehensive analysis of its solutions for
arbitrary sensor measurements and placements. More specifically, we define the
TDOA map from the physical space of source locations to the space of range
measurements (TDOAs), in the specific case of three receivers in 2D space. We
then study the identifiability of the model, giving a complete analytical
characterization of the image of this map and its invertibility. This analysis
has been conducted in a completely mathematical fashion, using many different
tools which make it valid for every sensor configuration. These results are the
first step towards the solution of more general problems involving, for
example, a larger number of sensors, uncertainty in their placement, or lack of
synchronization.Comment: 51 pages (3 appendices of 12 pages), 12 figure
Attaching Meaning to Sex: Attachment Styles and Possible Mediators of Safe Sex Behavior
Get PDFAttachment theory, first posited by Bowlby (1969, 1973, 1980), has been expanded and applied to many aspects of human development as well as to adult relationships. Hazan and Shaver (1987), for example, define romantic relationships as an interaction between caregiving, attachment, and sex. It would then be expected that attachment has an effect on sexual behavior, and indeed, Strachman and Impett (2009) have reported that anxious individuals are typically less likely to use condoms than avoidant individuals. This study attempted to explore the link between attachment and beliefs about sex and condom use as possible mediators for the differences seen in safe sex behavior. A one-time questionnaire assessing participants’ attachment styles, perceived barriers to condom use, reasons for engaging in sexual activity, perceptions of love and sex, and feelings of detachment was administered to 196 psychology students from the University of Mississippi and the University of Houston. A series of partial correlation analyses, controlling for gender, were run to analyze the relationships between attachment and these measures. Attachment anxiety was significantly correlated to engaging in unsafe sex because of partner barriers and a lack of access to condoms. It was also correlated to engaging in sex for intimacy, as a coping strategy, to affirm their own self-worth, for status among peers, and to please their partner. Attachment avoidance predicted engaging in sex for peer status, and was negatively correlated with having sex to foster intimacy
Background-deflection Brillouin microscopy reveals altered biomechanics of intracellular stress granules by ALS protein FUS
Get PDFAltered cellular biomechanics have been implicated as key photogenic triggers in age-related diseases. An aberrant liquid-to-solid phase transition, observed in in vitro reconstituted droplets of FUS protein, has been recently proposed as a possible pathogenic mechanism for amyotrophic lateral sclerosis (ALS). Whether such transition occurs in cell environments is currently unknown as a consequence of the limited measuring capability of the existing techniques, which are invasive or lack of subcellular resolution. Here we developed a non-contact and label-free imaging method, named background-deflection Brillouin microscopy, to investigate the three-dimensional intracellular biomechanics at a sub-micron resolution. Our method exploits diffraction to achieve an unprecedented 10,000-fold enhancement in the spectral contrast of single-stage spectrometers, enabling, to the best of our knowledge, the first direct biomechanical analysis on intracellular stress granules containing ALS mutant FUS protein in fixed cells. Our findings provide fundamental insights on the critical aggregation step underlying the neurodegenerative ALS disease
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