Join-Reachability Problems in Directed Graphs

For a given collection G of directed graphs we define the join-reachability graph of G, denoted by J(G), as the directed graph that, for any pair of vertices a and b, contains a path from a to b if and only if such a path exists in all graphs of G. Our goal is to compute an efficient representation of J(G). In particular, we consider two versions of this problem. In the explicit version we wish to construct the smallest join-reachability graph for G. In the implicit version we wish to build an efficient data structure (in terms of space and query time) such that we can report fast the set of vertices that reach a query vertex in all graphs of G. This problem is related to the well-studied reachability problem and is motivated by emerging applications of graph-structured databases and graph algorithms. We consider the construction of join-reachability structures for two graphs and develop techniques that can be applied to both the explicit and the implicit problem. First we present optimal and near-optimal structures for paths and trees. Then, based on these results, we provide efficient structures for planar graphs and general directed graphs

Monte Carlo algorithm based on internal bridging moves for the atomistic simulation of thiophene oligomers and polymers

We introduce a powerful Monte Carlo (MC) algorithm for the atomistic simulation of bulk models of oligo- and poly-thiophenes by redesigning MC moves originally developed for considerably simpler polymer structures and architectures, such as linear and branched polyethylene, to account for the ring structure of the thiophene monomer. Elementary MC moves implemented include bias reptation of an end thiophene ring, flip of an internal thiophene ring, rotation of an end thiophene ring, concerted rotation of three thiophene rings, rigid translation of an entire molecule, rotation of an entire molecule and volume fluctuation. In the implementation of all moves we assume that thiophene ring atoms remain rigid and strictly co-planar; on the other hand, inter-ring torsion and bond bending angles remain fully flexible subject to suitable potential energy functions. Test simulations with the new algorithm of an important thiophene oligomer, {\alpha}-sexithiophene ({\alpha}-6T), at a high enough temperature (above its isotropic-to-nematic phase transition) using a new united atom model specifically developed for the purpose of this work provide predictions for the volumetric, conformational and structural properties that are remarkably close to those obtained from detailed atomistic Molecular Dynamics (MD) simulations using an all-atom model. The new algorithm is particularly promising for exploring the rich (and largely unexplored) phase behavior and nanoscale ordering of very long (also more complex) thiophene-based polymers which cannot be addressed by conventional MD methods due to the extremely long relaxation times characterizing chain dynamics in these systems

A case of an accessory testicular artery

Dissection of an adult male cadaver revealed the presence of an accessory left testicular artery in addition to the normal right and left testicular arteries. In this case the accessory left testicular artery originated from the ventrolateral wall of the descending aorta. The origin was located between the superior mesenteric artery and the left renal vein. The accessory artery continued to course from the aorta laterally toward the superior ventral portion of the left kidney and then passed ventrally to the kidney on its course inferiorly to the pelvic region. Communication was observed between the accessory left testicular artery and the left renal artery. This variation of gonadal vasculature is of interest from the point of view of its embryogenesis, and possible clinical significance

Evaluation of Compton scattering sequence reconstruction algorithms for a portable position sensitive radioactivity detector based on pixelated Cd(Zn)Te crystals

We present extensive simulation studies on the performance of algorithms for the Compton sequence reconstruction used for the development of a portable spectroscopic instrument (COCAE), with the capability to localize and identify radioactive sources, by exploiting the Compton scattering imaging. Various Compton Sequence reconstruction algorithms have been compared using a large number of simulated events. These algorithms are based on Compton kinematics, as well as on statistical test criteria that exploit the redundant information of events having two or more photon interactions in the active detector's volume. The efficiency of the best performing technique is estimated for a wide range of incident gamma-ray photons emitted from point-like gamma sources.Comment: 16 pages, 17 figure

Anatomical variations of the superficial and deep palmar arches

The use of radial arteries as an arterial bypass conduit is an invasive procedure which is becoming popular among various medical centres. The greatest risk associated with harvesting the radial artery is ischaemia of the soft tissues of the hand. In this study we dissected 200 hands derived from 100 formalin-fixed cadavers in order to identify arterial patterns that will allow safe removal of the radial artery for use in bypass procedures. A complete superficial palmar arch (SPA) was found in 90% of the cases and divided into 5 types, while the remaining 10% possessed an incomplete palmar arch. Types of SPA are designated by the letter S. In type S-I (40%), the SPA is formed by anastomosis of the superficial volar branch of the radial artery to the ulnar artery. Type S-II (35%) is formed entirely of the ulnar artery. Type S-III (15%) is formed by anastomosis of the ulnar and median arteries. Type S-IV (6%) is formed by anastomosis of the ulnar, radial, and median arteries and Type S-V (4%) is formed by a branch of the deep palmar arch (DPA) communicating with the SPA.DPA was identified in all specimens and classified into three types, all designated by the letter D. Type D-I (60%) is formed by anastomosis of the deep volar branch of the radial artery and the inferior deep branch of the ulnar branch. Type D-II (30%) is formed by anastomosis of the deep volar branch of the radial artery and the superior deep branch of the ulnar artery. Type D-III (10%) is formed by anastomosis of the deep volar branch of the radial artery with both deep branches of the ulnar artery. This data could provide an important source of information for vascular surgeons harvesting radial arteries

Predictive modelling of thermo-active tunnels in London Clay

Thermo-active structures are underground facilities which enable the exchange of thermal energy between the ground and the overlying buildings, thus providing renewable means of space heating and cooling. Although this technology is becoming increasingly popular, the behaviour of geotechnical structures under additional thermal loading is still not fully understood. This paper focuses on the use of underground tunnels as thermo-active structures and explains their behaviour through a series of finite element analyses based on an existing case study of isothermal tunnels in London Clay. The bespoke finite element codeI CFEP is adopted which is capable of simulating the fully coupled thermo-hydro-mechanical behaviour of porous materials. The complex coupled interactions between the tunnel and the surrounding soil are explored bycomparing results from selected types of coupledand uncoupled simulations. It is demonstratedthat: (1) the thermally-induceddeformation of the tunnel and the ground are more critical design aspects than the thermally-induced forces in the tunnel lining, and (2) the modelling approach in terms of the type of analysis, as well as the assumed permeability of the tunnel lining, have a significant effect on the computed tunnel response and,hence, must be chosen carefull

The ansa subclavia: a review of the literature

The ansa subclavia, subclavian loop, Vieussens’ ansa or Vieussens’ loop is a nerve cord that connects the middle cervical and inferior cervical sympathetic ganglia, forming a loop around the subclavian artery. The structure of the ansa subclavia is evolutionarily conserved from rats, guinea pigs, the porcine species and dogs to humans. A common application in physiological studies is to electrically stimulate the ansa subclavia in animal models as a robust protocol to modulate stimulatory cardiac sympathetic input. Despite a large number of physiological studies utilizing the ansa subclavia, only very brief descriptions have been devoted to it in standard anatomy texts. An extensive search found only one report in the English language literature concerning the anatomy of the ansa subclavia. The aim of this report, therefore, was to provide a comprehensive review of the clinical anatomy of the ansa subclavia and to discuss its potential physiological functions