Magnesium alkyl reduced titanium (IV) chloride based polymerization catalysts: materials rich in magnesium chloride

Reduction of TiCl₄ with organomagnesiums either in the presence of preformed MgCl₂, or concurrently with the formation of MgCl₂ from chlorocarbons, yields materials which are active catalysts for the polymerization of propene and ethene. Transformation of these materials to a violet allotrope by heating with TiCl₄ gives materials much more active for propene polymerization, albeit stereoregulation is still not good. interestingly, these transformed materials show little advantage for ethene polymerization except at high temperatures. Use of a Lewis base does not give high stereoregulation with propene; although some advantage is gained activity is greatly diminished by this.     

Measurement of flow in small vessels by magnetic resonance phase mapping techniques: anin vitro andin vivo study

The measurement of blood flow in small arteries is a potential extension of magnetic resonance (MR) angiography. We have compared flow measurements based on MR phase mapping with those obtained by Doppler ultrasound and electromagnetic flowmetry in both phantom and animal models. Correlation between modalities was high forin vitro studies (R ²=0.93–0.98).In vivo, electrocardiogram-gated MR and Doppler ultrasound flow measurements compared to electromagnetic flowmetry showed fair correlation coefficients (R ²=0.73 and 0.66, respectively). However, limits of agreement indicated that in small vessels flow measured by the three modalities could differ by up to ±90 mL/min. For both models, arteries in the range of 3–6.5 mm in diameter produced complementary errors in area and velocity measurements in MR studies. Ungated MR studies showed a reduced agreement (R ²=0.88in vitro, 0.54in vivo), which may in part be due to poor sampling of the velocity pattern. The results show that the high correlation obtainedin vitro cannot be extrapolated to thein vivo situation, where additional physiological and anatomical variables are encountered.     

What the 2007 TAC Market Design Game tells us about effective auction mechanisms

This paper analyzes the entrants to the 2007 tac Market Design Game. We present a classification of the entries to the competition, and use this classification to compare these entries. The paper also attempts to relate market dynamics to the auction rules adopted by these entries and their adaptive strategies via a set of post-tournament experiments. Based on this analysis, the paper speculates about the design of effective auction mechanisms, both in the setting of this competition and in the more general case.     

NO and N2O emissions from savanna soils following the first simulated rains of the season

Data on the emissions of oxides of nitrogen from the soil during the early part of the wet season are reported for nutrient-rich and nutrient-poor sandy soils at Nylsvley, South Africa. The emissions of NO_x and N₂O following the first wetting event of the season are elevated relative to subsequent events. The observed high emission rates (76 ng N-NO m^-2 s^-1) are partially attributed to the sandiness of the soil, which permits NO to diffuse out of the soil rapidly. The pulse of high emissions following wetting is maintained for approximately 72 hours, thereafter continuing at around 20 ng NO m^-2 s^-1 while the soil remains moist. The initial pulse is suggested to be due to the accumulation of a substrate pool during the dry period, coupled with an inability of plants and microbes to use it effectively during the first few days after wetting. There were no significant differences in the peak or subsequent emission rates for either NO or N₂O between two sites of differing nitrogen mineralisation potentials. N₂O emissions averaged 8% of NO_x emissions. The enhanced emissions of NO_x which follow the first wetting after a prolonged dry period do not make a very large contribution to the annual gaseous N emission budget, but could be a significant contributor to the high tropospheric ozone levels observed over southern Africa in springtime.     

The Influence of a Phase Transition in Poly(oxyethylene)/Poly(oxypropylene)/Poly(oxyethylene) Block Copolymer Surfactants on the Properties of Material Adsorbed from Dilute Aqueous Solution

In this study the adsorption of poloxamer block copolymer surfactants to polystyrene latex has been studied at a range of temperatures. It has been noted previously that the adsorption first falls, then rises and falls again as the temperature is increased, due to the existence of a phase transition in aqueous solutions of these surfactants at specific temperatures, which may be a critical micelle temperature. The present study shows that the hydrophobicity of the surface changes in a manner related to the amount of poloxamer adsorbed (i.e. is greatly influenced by the temperature of adsorption in relation to the transition temperature). The coating layer thickness, however, is essentially unchanged by the temperature of adsorption (i.e. not related to the amount adsorbed), but is influenced by the temperature at which the sizing was undertaken. This is due to dehydration of the poly (oxyethylene) with increasing temperature. The data presented here provide a possible explanation for the changes in biological distribution of poloxamer coated particles which occur when they are injected into animals.     

An experimental investigation of the large-strain tensile behavior of neat and rubber-toughened polycarbonate

The large-strain tensile behavior of polycarbonate and polycarbonate filled with several volume fractions (f) of rubber particles is studied via an optical technique. Digital image correlation is used to determine, in two dimensions, the local displacement gradients and full-field displacements during a uniaxial tension test. Full-field strain contours, macroscopic true stress-strain behavior, and local volumetric strain are reduced from the raw test data. Full-field strain contours exhibit a decreasing degree of localization with increasing f. The true stress-strain results show a decrease in modulus, yield stress, post-yield strain softening, and subsequent strain hardening with increasing f. The volumetric strain decreases with increasing f as well. In the case of the neat polymer, comparisons are made to a three-dimensional finite element simulation.     

Utility Wind Integration and Operating Impact State of the Art

In only six years, from 2000 to 2006, wind energy has become a significant resource on many electric utility systems, with nearly 74 000 MW of nameplate capacity installed worldwide at the end of 2006. Wind energy is now "utility scale" and can affect utility system planning and operations for both generation and transmission. The utility industry in general, and transmission system operators in particular, are beginning to take note. At the end of 2005, the Power Engineering Society (PES) published a special issue of its Power & Energy Magazine that focused on integrating wind into the power system. This paper provides a summary and update on many of the salient points from that special issue about the current state of knowledge regarding utility wind integration issues.     

ARTIFICIAL INTELLIGENCE GOES MOBILE

New mobile computing technologies require new paradigms for infrastructure and interaction with mobile and networked devices. For building smart mobile companions for new intelligent services, a number of challenges have to be addressed. We argue that artificial intelligence is a key to a new generation of mobile systems. In this introduction to AI in mobile systems, we present some of the challenges and solutions in this exciting field of research.     

Model driven middleware: A new paradigm for developing distributed real-time and embedded systems

Distributed real-time and embedded (DRE) systems have become critical in domains such as avionics (e.g., flight mission computers), telecommunications (e.g., wireless phone services), tele-medicine (e.g., robotic surgery), and defense applications (e.g., total ship computing environments). These types of system are increasingly interconnected via wireless and wireline networks to form systems of systems. A challenging requirement for these DRE systems involves supporting a diverse set of quality of service (QoS) properties, such as predictable latency/jitter, throughput guarantees, scalability, 24x7 availability, dependability, and security that must be satisfied simultaneously in real-time. Although increasing portions of DRE systems are based on QoS-enabled commercial-off-the-shelf (COTS) hardware and software components, the complexity of managing long lifecycles (often ∼15-30 years) remains a key challenge for DRE developers and system integrators. For example, substantial time and effort is spent retrofitting DRE applications when the underlying COTS technology infrastructure changes.This paper provides two contributions that help improve the development, validation, and integration of DRE systems throughout their lifecycles. First, we illustrate the challenges in creating and deploying QoS-enabled component middleware-based DRE applications and describe our approach to resolving these challenges based on a new software paradigm called Model Driven Middleware (MDM), which combines model-based software development techniques with QoS-enabled component middleware to address key challenges faced by developers of DRE systems — particularly composition, integration, and assured QoS for end-to-end operations. Second, we describe the structure and functionality of CoSMIC (Component Synthesis using Model Integrated Computing), which is an MDM toolsuite that addresses key DRE application and middleware lifecycle challenges, including partitioning the components to use distributed resources effectively, validating software configurations, assuring multiple simultaneous QoS properties in real-time, and safeguarding against rapidly changing technology.