Photodegradation of Anthracene and Benzo[a]anthracene in Polar and Apolar Media: New Pathways of Photodegradation

The photochemical reactions of anthracene and benzo[a]anthracene polycyclic aromatic hydrocarbons (PAHs) in polar and apolar solvents (cyclohexane and water/acetonitrile) were studied using spectroscopic and chromatographic techniques. These homogenous photolysis experiments are used as simplified models to compare PAHs photochemistry in water and oil (or oil films). Moreover, these processes were to some extent used as model in literature in order to study those occurring on particulate matter and aerosol surfaces. In both media, new photochemical reaction products were found. Generally, the reaction rate in the polar medium is faster than that in the apolar medium, and the photodegradation quantum yields increase with increasing polarity of the medium. HPLC-absorption/emission analysis confirmed the literature reports that mainly oxygenated photoproducts, such as PAH-hydroxides, were formed. The novelty of this article is that GC-MS data revealed the presence of new photoproducts that have not yet been described. This simplified model system allowed us to characterize the product distribution, thus simplifying the interpretation of the photodegradation mechanism. The identification of new photofragmentation paths, originating by irradiation of primary PAH photoproducts, may suggest an innovative way of remediation triggered by light.     

Blinding struts, Part 2: Towards a simplified design method

The companion paper described how concrete blinding can be used to prop retaining walls in cut and cover excavations prior to the completion of the base slab. In addition, it was demonstrated that the behaviour of blinding struts can be accurately predicted with nonlinear finite element analysis (NLFEA) if the strut properties and ground profile are known. This paper presents a simple design-oriented analytical model which can be used for blinding struts as an alternative to NLFEA. The simplified model is shown to give comparable results to NLFEA and is attractive for design since it allows the effect of variations in imperfection amplitude and length to be rapidly assessed. A case study is presented which illustrates the use of the method and demonstrates that relatively thin blinding struts can resist the maximum axial forces likely to be encountered in cut and cover excavations.     

Seismic FRP retrofit of circular single-column bents using a ductility wrap envelope to alter failure modes

The target displacement ductility requirements for circular reinforced concrete (R/C) single-column bridge bents are considered using a proposed multi-failure mode algorithm to determine the required thickness of fiber reinforced polymer wraps (FRPs). The procedure is developed using two in-house computer algorithms, PACCC (Plastic Analysis of Circular Concrete Columns) and PACCC-FRP, to generate a moment-curvature analysis using circular segments and subsequent failure mode predictions in single-column bents for both FRP-wrapped and unwrapped circular R/C sections. The results of the study were verified against published experimental tests at the ultimate force-deflection states of R/C sections and also against three commercial “software test beds”. The study uses PACCC-FRP to show that single-columns experiencing a brittle failure may be retrofitted with FRP wraps in order to increase the displacement ductility and satisfy target ductility values within the Ductility Wrap Envelope (DWE), or wrap-saturation level, as established herein.     

Multiscale modelling of the circulatory system: a preliminary analysis

In this paper we show how numerical solutions of human cardiovascular system may be devised by coupling models having different physical dimensions. One of the aspects of circulatory system is indeed its multiscale nature. Local flow features may have a global effect on circulation. For instance, a stenosis caused by an atherosclerotic plaque may change the overall characteristic of the vessels involved, and consequently have significant influence on the flow in the whole system. Hence, it lays the interest to set up a numerical device that could represent accurately both local and systemic features. For that, it is needed to couple different model scales. From lumped models (which are traditionally described by means of an electrical network analog) to local models based on 2D or 3D Navier-Stokes equations, passing through intermediate 1D models. In this paper, the different assumptions underlying these models, some mathematical issues related to their coupling and preliminary numerical results are presented. Received: 30 April 1999 / Accepted: 17 June 1999     

Dynamics Identification in Evolution Models Using Radial Basis Functions

The problem of identifying an unknown function of the state of an evolution model with differential equations is considered in the framework of a minimization problem. The well-posedness of this minimization problem as well as unique solvability is proven. The analysis of the dependence of the identified function on the data is presented by means of the derivative of the “data–to–function” mapping. Moreover, the infinite dimensional function space, where the unknown function is sought, is discretized by suitable radial basis functions that are chosen such that optimal approximation results are obtained. The numerical treatment of a representative evolution model and the application to a bio-chemical model illustrate the proposed approach.     

On Parallel Computation of Blood Flow in Human Arterial Network Based on 1-D Modelling

In this study, parallel computation of blood flow in a 1-D model of human arterial network has been carried out employing a Taylor Galerkin Finite Element Method. Message passing interface libraries have been used on Origin 2000 SGI machine. A Greedy strategy for load-distribution has been devised and data-flow graphs necessary for parallelization have been generated. The performance of parallel implementation measured in terms of speedup and efficiency factors is found to be good. Further, the parallel code is used in simulating the propagation of pressure and velocity waveforms in our 1-D arterial model for two different inflow pressure pulses. Also, the influence of consideration of terminal resistance on pressure and velocity waveforms have been analyzed.     

Structured data clouding across multiple webs

The variety of web resources available to users for their business or personal needs is growing, spanning from fast, short, ready-to-consume news/posts to well-structured, formal ontology instances of the Semantic Web. In this context, users require to retrieve very fast all available prominent information about target entities regarding events, people, situations and similar. In this paper, we introduce the notion of inCloud (information Cloud) and we propose an approach to web resource clouding for the construction of inClouds. inClouds are built for a target entity of interest by distinguishing, also in a visual way, how much prominent the retrieved web resource(s) are with respect to the target entity and by organizing web resources according to their reciprocal levels of closeness. An application of the proposed approach to a collection of real web resources about movies is presented. Applicability and evaluation issues are also discussed.     

Multipath routing and rate-controlled video encoding in wireless video surveillance networks

Video surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper—to bring down the overall system cost and increase feasibility, scalability, and performance—is to propose a new architecture for a wireless video surveillance network, whose telecommunication infrastructure is based on a wireless mesh network, and where video sources are able to estimate network bandwidth and consequently control their output rate. Multipath routing is applied in such a way that at least part of the information arrives at its destination even if a wireless link is shielded (maliciously or not). A case study is considered to discuss the performance of the proposed architecture, analyzing a comparison between single-path and multipath approaches.     

A high-repetition rate scheme for synchrotron-based picosecond laser pump/x-ray probe experiments on chemical and biological systems in solution

We present the extension of time-resolved optical pump/x-ray absorption spectroscopy (XAS) probe experiments towards data collection at MHz repetition rates. The use of a high-power picosecond laser operating at an integer fraction of the repetition rate of the storage ring allows exploitation of up to two orders of magnitude more x-ray photons than in previous schemes based on the use of kHz lasers. Consequently, we demonstrate an order of magnitude increase in the signal-to-noise of time-resolved XAS of molecular systems in solution. This makes it possible to investigate highly dilute samples at concentrations approaching physiological conditions for biological systems. The simplicity and compactness of the scheme allows for straightforward implementation at any synchrotron beamline and for a wide range of x-ray probe techniques, such as time-resolved diffraction or x-ray emission studies.     

Active load with cross-coupled bulk for high-gain high-CMRR nanometer CMOS differential stages

Nanometer CMOS technologies are characterized by low intrinsic gain and limited rejection to common-mode disturbances, issues that analog designers must counteract through nonconventional circuit solutions able to operate under sub–1-V supply voltages. In this letter, an approach originally proposed as a common-mode control loop for body-driven amplifiers is exploited by cross-connecting the bulk terminals of the active-load transistors of a source-coupled pair to sensibly improve its small-signal performance. A design example in 65-nm process supplied from 750 mV shows that the presented solution offers both a nominal 20-dB increase in differential gain and 29-dB increase in CMRR, as compared with the standard counterpart.