Weak Singular Hybrid Automata

The framework of Hybrid automata, introduced by Alur, Courcourbetis, Henzinger, and Ho, provides a formal modeling and analysis environment to analyze the interaction between the discrete and the continuous parts of cyber-physical systems. Hybrid automata can be considered as generalizations of finite state automata augmented with a finite set of real-valued variables whose dynamics in each state is governed by a system of ordinary differential equations. Moreover, the discrete transitions of hybrid automata are guarded by constraints over the values of these real-valued variables, and enable discontinuous jumps in the evolution of these variables. Singular hybrid automata are a subclass of hybrid automata where dynamics is specified by state-dependent constant vectors. Henzinger, Kopke, Puri, and Varaiya showed that for even very restricted subclasses of singular hybrid automata, the fundamental verification questions, like reachability and schedulability, are undecidable. In this paper we present \emph{weak singular hybrid automata} (WSHA), a previously unexplored subclass of singular hybrid automata, and show the decidability (and the exact complexity) of various verification questions for this class including reachability (NP-Complete) and LTL model-checking (PSPACE-Complete). We further show that extending WSHA with a single unrestricted clock or extending WSHA with unrestricted variable updates lead to undecidability of reachability problem

Explosion at Blaenhirwaun Colliery, Carmarthenshire Report

Report on the causes of, and circumstances attending, the explosion which occurred at Blaenhirwaun Colliery, Carmarthenshire, on 6th September, 1955.In accordance with the instructions given by your predecessor under the terms of Section 82 of the Coal Mines Act. 1911, I beg to submit my report on the causes of, and circumstances attending, the explosion which occurred on the "Q" face in the Lower Pumpquart seam at Blaenhirwaun colliery, Carmarthenshire, on 6th September, 1955, when four persons were killed and 13 others injured. One of the injured died in hospital on the 18th and another on the 30th September, 1955, bringing the death roll to six. On 23rd November. 1955, Mr. W. Lock Smith, H.M. Coroner for the Three Commotts District of the County of Carmarthen, sitting with a jury, concluded the holding of an Inquest on the bodies of the six deceased persons and recorded a verdict to the effect that all six had died from injuries accidentally received in a coal gas explosion, the cause of which had yet to be ascertained

Uniqueness and Non-uniqueness in the Einstein Constraints

The conformal thin sandwich (CTS) equations are a set of four of the Einstein equations, which generalize the Laplace-Poisson equation of Newton's theory. We examine numerically solutions of the CTS equations describing perturbed Minkowski space, and find only one solution. However, we find {\em two} distinct solutions, one even containing a black hole, when the lapse is determined by a fifth elliptic equation through specification of the mean curvature. While the relationship of the two systems and their solutions is a fundamental property of general relativity, this fairly simple example of an elliptic system with non-unique solutions is also of broader interest.Comment: 4 pages, 4 figures; abstract and introduction rewritte

Optical application and measurement of torque on microparticles of isotropic nonabsorbing material

We show how it is possible to controllably rotate or align microscopic particles of isotropic nonabsorbing material in a TEM00 Gaussian beam trap, with simultaneous measurement of the applied torque using purely optical means. This is a simple and general method of rotation, requiring only that the particle is elongated along one direction. Thus, this method can be used to rotate or align a wide range of naturally occurring particles. The ability to measure the applied torque enables the use of this method as a quantitative tool--the rotational equivalent of optical tweezers based force measurement. As well as being of particular value for the rotation of biological specimens, this method is also suitable for the development of optically-driven micromachines.Comment: 8 pages, 6 figure

Using benchtop experiments to teach dimensional analysis and analogue modeling to graduate geoscience students

The need for geoscience students to develop a quantitative skillset is ever increasing. However, this can be difficult to implement in university-style lecture courses in a way that is both manageable for the instructor and does not involve lengthy, potentially repetitive, question sheets for the students. Here, a method for teaching dimensional analysis, basic fluid dynamics, and the interpretation and scaling of experimental data is presented for a graduate student audience. The proposed method utilizes simple fluid dynamic benchtop experiments that require a small amount of teaching space and use readily available, low cost materials. Our analysis of student performance through pre- and post-tests demonstrates that students have a better knowledge of dimensional analysis, data interpretation and experimental design after the series of practical sessions compared to instruction through a single, passive lecture. We therefore show that simple benchtop experiments can be an effective way to improve and integrate quantitative learning into a graduate geoscience class

Seismic data reveal eastern Black Sea Basin structure

Rifted continental margins are formed by progressive extension of the lithosphere. The development of these margins plays an integral role in the plate tectonic cycle, and an understanding of the extensional process underpins much hydrocarbon exploration. A key issue is whether the lithosphere extends uniformly, or whether extension varies\ud with depth. Crustal extension may be determined using seismic techniques. Lithospheric extension may be inferred from the waterloaded subsidence history, determined from\ud the pattern of sedimentation during and after rifting. Unfortunately, however, many rifted margins are sediment-starved, so the subsidence history is poorly known.\ud To test whether extension varies between the crust and the mantle, a major seismic experiment was conducted in February–March 2005 in the eastern Black Sea Basin (Figure 1), a deep basin where the subsidence history is recorded\ud by a thick, post-rift sedimentary sequence. The seismic data from the experiment indicate the presence of a thick, low-velocity zone, possibly representing overpressured sediments. They also indicate that the basement and\ud Moho in the center of the basin are both several kilometers shallower than previously inferred. These initial observations may have considerable impact on thermal models of the petroleum system in the basin. Understanding\ud the thermal history of potential source rocks is key to reducing hydrocarbon exploration risk. The experiment, which involved collaboration between university groups in the United Kingdom, Ireland, and Turkey, and BP and\ud Turkish Petroleum (TPAO), formed part of a larger project that also is using deep seismic reflection and other geophysical data held by the industry partners to determine the subsidence history and hence the strain evolution of\ud the basin

Interference of the T cell and antigen-presenting cell costimulatory pathway using CTLA4-Ig (abatacept) prevents Staphylococcal enterotoxin B pathology

Abstract Staphylococcal enterotoxin B (SEB) is a bacterial superantigen that binds the receptors in the APC/T cell synapse and causes increased proliferation of T cells and a cytokine storm syndrome in vivo. Exposure to the toxin can be lethal and cause significant pathology in humans. The lack of effective therapies for SEB exposure remains an area of concern, particularly in scenarios of acute mass casualties. We hypothesized that blockade of the T cell costimulatory signal by the CTLA4-Ig synthetic protein (abatacept) could prevent SEB-dependent pathology. In this article, we demonstrate mice treated with a single dose of abatacept 8 h post SEB exposure had reduced pathology compared with control SEB-exposed mice. SEB-exposed mice showed significant reductions in body weight between days 4 and 9, whereas mice exposed to SEB and also treated with abatacept showed no weight loss for the duration of the study, suggesting therapeutic mitigation of SEB-induced morbidity. Histopathology and magnetic resonance imaging demonstrated that SEB mediated lung damage and edema, which were absent after treatment with abatacept. Analysis of plasma and lung tissues from SEB-exposed mice treated with abatacept demonstrated significantly lower levels of IL-6 and IFN-γ (p &amp;lt; 0.0001), which is likely to have resulted in less pathology. In addition, exposure of human and mouse PBMCs to SEB in vitro showed a significant reduction in levels of IL-2 (p &amp;lt; 0.0001) after treatment with abatacept, indicating that T cell proliferation is the main target for intervention. Our findings demonstrate that abatacept is a robust and potentially credible drug to prevent toxic effects from SEB exposure.</jats:p

Evolving Regulation of Corporate Governance and the Implications for D&O Liability: The United States and Australia

This Article compares the modern corporate regulatory environments in the United States and Australia, including an analysis of the climate for Directors & Officers (D & O) liability coverage. Comparing these regulations across two large markets with similar historical bases for assessing director and officer liability allows us to explore which reforms may be more effective as new scandals emerge

Contribution of biomass fires to black carbon supply in a tropical river basin assessed using a Lagrangian atmospheric transport model and MODIS burned area product

Black carbon (BC) is known to be a potential sink of carbon for the global carbon cycle, particularly if long-term ocean stores are reached. Fluvial transport to the oceans can occur through the dissolution of BC in river water. Evidence from the Paraiba do Sul river basin, Brazil suggests that river DBC concentration is related to charcoal formed during the deforestation of the Brazilian Atlantic Forest. However, we highlight several key potential sources of BC to the basin that are yet to be considered. We hypothesize that external biomass fires are a source of BC to the basin on the basis that BC released from them can be transported over large distances before being deposited. This hypothesis is tested by quantifying the number of biomass fires intercepted by trajectories en route to the basin using the HYSPLIT model and a MODIS burned area dataset. We then create a Black Carbon Fallout Index (BCFI) which is rationalized by our assumption that atmospheric BC delivery to the basin is proportional to the number of interceptions of air masses en route to the basin. Our results suggest that the BC fallout from air masses reaching the basin in the dry season can explain 50% of the variance in DBC measured in the PSR channel during a subsequent collection campaign (p<.001). Spatial and temporal variations in the supply of BC to the basin throughout the dry season may in part be linked to the fires associated with the cultivation of sugarcane in southeast Brazil