bluuebunny/crossref_metadata_2025 huggingface dataset:
Worldwide Field Applications of a Polymeric Gel System for Conformance Applications
Authors: Eoff L. , Dalrymple D. , Everett D. , Vasquez J.
Published: December 2007

Water production becomes a major problem as hydrocarbon-producing fields mature. Higher levels of water production result in increased levels of corrosion and scale, increased load on fluid-handling facilities, increased environmental concerns, and eventually well shut-in (with associated workover costs). Consequently, producing zones are often abandoned in an attempt to avoid water contact, even when the intervals still retain large volumes of recoverable hydrocarbons. Many polymer systems have been applied over the years to control undesired water production from hydrocarbon wells, with varying degrees of success.

For approximately eight years, a polymer gel system based on an acrylamide/t-butyl acrylate copolymer (PAtBA) crosslinked with polyethyleneimine (PEI) has been used successfully for various water shutoff applications. This article describes results from a sampling of over 200 jobs performed throughout the world, including the average results from more than 90 jobs performed in one geographic location alone. In addition to "standard" matrix treatments, results will be shown for other types of treatment, including a design to plug annular communication and a combination of sealant and temporary gel in an openhole horizontal completion. In addition, laboratory data pertaining to work aimed at increasing the temperature limit of the system will be presented. The upper placement temperature of the system originally was ~260°F. Data presented in this article indicates the development of a retarder system that allows the upper placement temperature to be raised to at least 350°F.
Applying Radial Acoustic Amplitude Signals To Predict Intervals of Sand-Stuck Tubing
Authors: Siems G. , Boudreaux S.
Published: December 2007

The reuse of existing well bores is a cost-saving technique used by oil and gas producers in mature fields. This process usually requires the removal of tubing and packers to allow the well to be deepened or sidetracked. The tubing removal process is often made difficult when the tubing is stuck inside the casing because of mechanical binding or binding caused by dehydrated mud or sand in the annulus between the tubing and casing. Conventional direct and indirect methods of finding the stuck point(s) along an interval of tubing, such as free-point indicator tools or acoustic attenuation measurements, have proved themselves useful in finding the point(s) where the tubing is stuck. However, when the sticking is caused by uncompacted sand that has entered the annular space between the tubing and casing, these conventional stuck-pipe indication methods are often inconclusive or misleading.

Technological advancements in the design and development of slim, 11116-in. outside diameter (OD), radial cement bond tools allow the application of a new measurement to find sand-stuck tubing intervals. These tools provide up to six independent, closely spaced acoustic attenuation measurements distributed radially around the tool body. When the recording operation is performed inside the tubing, the increased sensitivity of these tools to sound attenuation, as compared with conventional omnidirectional amplitude signals, allows sand intervals along the outside of the tubing to be distinguished from intervals where little or no sand is present. This information is used to select the best depth to sever or back-off the free tubing in order to reduce the interval length and expense associated with the washover process required to remove the remaining tubing from the wellbore.

An overview of conventional stuck-pipe recovery techniques is provided here, along with a brief explanation of applicable acoustic technology. A case study of a South Louisiana well is presented to demonstrate the application and illustrate the cost savings which can be gained by use of this very new technology.
Real-Time Field Surveillance and Well Services Management in a Large Mature Onshore Field: Case Study
Authors: Ormerod L. , Sardoff H. , Wilkinson J. , Erlendson B. , Cox B. , Stephenson G.
Published: December 2007

This paper describes the planning for, implementation of and results generated by a real-time field surveillance and well services management system, as it was deployed in an onshore mature field in California, USA. The motivation behind the deployment of this system was simultaneously to improve efficiency and reduce operating costs in this large field with over 1,000 wells.

The paper will describe how the business processes and supporting workflows were defined. This is an essential step before any technology can be deployed. The challenges of data management included not only the automatic handling of very large quantities of real-time data, but also the management of inventory and the integration of field level data with corporate level data. Historical data had to be brought into, and made compatible with the new system. The technologies required for this project included the software systems and the integration of these with remoteintelligent field sensors and data transmission systems.

The impact of the system has been material to the performance of the asset. Examples will be given of tangible improvements in performance across the disciplines of surveillance, production engineering, and well services. One critical factor to the successful deployment of this system includes the organizational changes needed to support the new working practices enabled by the system. The paper will discuss the required change management programs.

The success of this project has clearly established that a "smart" solution integrating intelligent remote devices, communications networks and workflow management software can be successfully deployed on large, mature fields. The deployment process to achieve this has been assimilated and is now being reproduced in many other similar fields across North America. The paper will indicate some of the areas where this combination of technology and supporting change management will be expanded in the future.
Rapid sonic characterisation of sewer change and obstructions
Authors: Podd F.J. , Ali M.T.B. , Horoshenkov K.V. , Wood A.S. , Tait S.J. , Boot J.C. , Long R. , Saul A.J.
Published: December 2007

This paper reports on the development of a low-cost, rapidly deployable sensor for surveying live sewers for blockages and structural failures. The anticipated cost is an order of magnitude lower than current techniques. The technology is based on acoustic normal model decomposition, The instrument emits short coded acoustic signals which are reflected from any sewer wall defect. The acoustic signals can be short Gaussian pulses or longer sinusoidal sweeps and pseudo-random noise. The processing algorithms used on the reflected signal can predict the extent and geometry of the pipe deformation, and the locations and approximate size of common blockages. The effect of the water level on the frequency of the fundamental mode has also been investigated. It is shown that the technique can be adapted to work reliably in relatively large 600 mm diameter sewer pipes.
Impact of hydrodynamics on the precipitation efficiency – application to HARDTAC reactor
Authors: Génin A. , Essemiani K. , Lemoine C. , Barbier E. , Logette S.
Published: December 2007

Precipitation of gypsum is studied in a HARDTAC (High-Aspect Ratio, Draft-Tube, Agitated Crystallizer) reactor, which is considered as the core crystallization unit of lots of wastewater treatment systems. Coupling Computational Fluid Dynamics (CFD) and population balance modelling to simulate precipitation can be a useful tool to come to a decision about upstream and downstream units. In the present study, we aim to validate such approach by investigating gypsum precipitation in a HARDTAC pilot unit and comparing experiments results with simulation. Measured nucleation and growth kinetics are used to feed the model. A comparison between experiments and simulations is presented in the case of gypsum precipitation with a given set of operating conditions. Good agreement is obtained for species concentrations, gypsum mass fraction and volumetric mean diameter but some discrepancies still remain between measured and simulated crystal size distribution.
Effect of Modification Processes on Bond Energy of Asphalt Binders
Authors: Bhasin Amit , Howson Jonathan , Masad Eyad , Little Dallas N. , Lytton Robert L.
Published: December 2007

Performance of asphalt pavements depends on the properties of its constituent materials, mixture volumetrics, and external factors such as load and environment. An important material property that influences the performance of an asphalt mixture is the surface free energy of the asphalt binder and the aggregate. Surface free energy governs the adhesive bond strength between the asphalt binder and the aggregate as well as the cohesive bond strength of the asphalt binder. These bond energies in turn influence the resistance of the asphalt mixture to distresses such as fatigue cracking and moisture induced damage. Asphalt binders undergo several types of engineering and natural modifications that influence their chemical and mechanical properties. Three common examples of modifications are the addition of polymers, addition of additives (e.g., antistrip agents), and oxidative aging of the asphalt binder. This paper is part of a study conducted to examine the effect of different types of modifications on the surface free energy components of the asphalt binder. The change in surface free energy was used to calculate parameters that are related to the performance of the asphalt mixtures. Results from this study demonstrate that the magnitude and nature of change to the surface free energy and concomitant performance-related parameters varied significantly among different asphalt binders. For example, certain modifications improved the performance of some binders while adversely affecting the performance of others. The experiment and analysis methods presented in this study can be used to examine the influence of modifications on performance and optimize the engineering properties of binders and asphalt mixtures.
Thermal Sensitivity and Fatigue Life of Gap-Graded Asphalt Mixes Incorporating Crumb Rubber from Tire Waste
Authors: Gallego Juan , Castro María , Prieto Jorge N. , Vassallo Jose M.
Published: December 2007

The most usual asphalt mix applied for thin overlays on Spanish roads is produced with a gap-graded combination of aggregates and a polymer-modified binder. Nevertheless, reflective cracking usually affects the overlay so that the surface of the pavement soon begins to reveal a network of cracks. The brittleness and aging of asphalt mixes at low temperatures encourage the appearance and progress of these cracks. Asphalt mixes incorporating rubber from discarded tires are believed to control reflective cracking well. This paper presents a study performed on five gap-graded asphalt mixes, three containing rubber from tire waste. Every mix was tested at two stages of aging in accordance with the laboratory-accelerated aging processes proposed by SHRP. Dynamic moduli at several temperatures, ranging from −15°C to 40°C, and the fatigue life of each mix at 20°C were measured. The results are provided to help researchers build realistic models for studying reflective cracking as a function of the actual characteristics of the materials. The results show that the tire rubber, especially when incorporated by the wet process, enhances the fatigue life of the mixes. The thermal sensitivity of the mix decreases as the content of rubber arises, regardless of whether the rubber has been incorporated by the wet or the dry process. In addition, the paper reports the difficulties with the SHRP accelerated aging processes and raises some doubts about these aging processes when applied to rubberized asphalt mixes.
Effect of Calcareous Fillers on Bituminous Mix Aging
Authors: Bianchetto Hugo , Miró Rodrigo , Pérez-Jiménez Félix , Martínez Adriana H.
Published: December 2007

The aim of this paper is to explain phenomena associated with bitumen aging and to establish design patterns that contribute to optimizing the aging resistance of bituminous mixes on the basis of the rational addition of calcareous fillers (hydrated lime and limestone filler). The potential benefits of using fillers to improve aging resistance are well known. However, concepts related to the biphasic filler-bitumen system affecting some of the main characteristics of mixes are not always considered. In this paper, a new study procedure, Universal de Caracterización de Ligantes, a method for characterizing both conventional and polymer-modified binders developed at the Technical University of Catalonia, has been applied. In addition, the dynamic shear rheometer and nonroutine procedures such as macromolecular analysis (e.g., gel-permeation chromatography and infrared spectroscopy) were used to perform rheological tests. These techniques have provided greater insight into the causes and effects of aging on the basis of changes undergone by the bituminous binder. The obtained results show the advantages of incorporating calcareous fillers into bituminous mixes, provided that filler content does not exceed a critical concentration determined by the type of filler and binder to be used. Moreover, some variations on the concept of critical concentration of filler in bituminous mixes have been found, notably those resulting from the degree of mix aging and use of polymer-modified bitumens.
Bottleneck Identification and Calibration for Corridor Management Planning
Authors: Ban Xuegang (Jeff) , Chu Lianyu , Benouar Hamed
Published: December 2007

Corridor mobility improvements require a new approach to corridor management planning and operations. Recent investigations are aimed at improving the safety and efficiency of existing transportation systems by integrating state-of-the-art operational analysis (such as microsimulation) into more traditional corridor planning. One of the important elements in developing corridor management improvements is better bottleneck analysis. Such analyses play a crucial role in corridor management planning for both performance assessment and simulation model calibration. New approaches are proposed for bottleneck identification and calibration in simulation. Identification is conducted with percentile speeds based on data from multiple days. It turns out that this method is more appropriate for urban congested freeways than use of single-day data. The algorithm for bottleneck calibration represents the first attempt to rigorously calibrate bottlenecks in microsimulation. It is a three-step process–including visual assessment, bottleneck area matching, and detailed speed calibration–aiming to calibrate bottlenecks in three levels of detail. With the I-880 corridor network in the San Francisco Bay Area of California, it has been shown that the identification method can adequately identify corridor bottlenecks; the calibration procedure complements and improves the current practice of simulation calibration.
Modeling Reductions in Freeway Capacity due to Incidents in Microscopic Simulation Models
Authors: Hadi Mohammed , Sinha Prasoon , Wang Amy
Published: December 2007

Modeling the impacts of incidents on traffic flow operations is essential for the use of simulation programs to evaluate incident management alternatives. In particular, these programs must be able to model correctly the reductions in highway capacity that are due to incidents and the lane-changing behaviors of drivers ahead of incident locations. Although simulation models have been used for evaluating incident impacts, the abilities of these programs to model incidents have not been adequately assessed. Here the modeling of incidents in microscopic simulation models and the effects of calibration parameters on the simulated reductions in capacity due to incidents are examined. A basic freeway segment was simulated with three widely used microscopic simulation models: CorSim, VisSim, and AIMSUN. The three investigated simulation models allow the analyst to simulate incident blockages either explicitly or by using other events that have similar impacts on traffic operations at the incident locations. Calibration parameters of the three models were varied to determine if it is possible to calibrate the models to achieve target link capacity values for conditions both with and without incidents. The target capacity values used were those presented in the Highway Capacity Manual 2000, although any other target capacities could have been used. For all three models, there is a need to calibrate model parameters to produce acceptable reductions in capacity due to incidents. It is shown that this objective is possible with all investigated models. However, there is a need to introduce incident-specific time-variant calibration parameters in AIMSUN and VisSim. Recommendations are given regarding required improvements to the simulation programs to enhance their ability to model the reduction in capacity and the lane-changing behaviors at incident locations.
Modeling Duration of Lane Changes
Authors: Toledo Tomer , Zohar David
Published: December 2007

Lane changes significantly affect the characteristics of traffic flow. Lane-changing models are therefore important in microscopic traffic simulation. Existing lane-changing models emphasize the decision-making aspects of the task but generally neglect the detailed modeling of the lane-changing action itself and model it only as an instantaneous event. However, research indicates that lane-changing durations are on average in the range of 5 to 6 s. The omission of lane-changing durations from simulation models may have a significant impact on simulation outputs. Models of the duration of lane changes are presented. These models are estimated by using detailed vehicle trajectory data that were collected in naturalistic driving with high-mounted video cameras. Separate models are presented for passenger cars and for heavy vehicles and statistical tests are conducted for the similarity between the lane-change durations of the two vehicle types.
Empirical Analysis of Underlying Mechanisms and Variability in Car-Following Behavior
Authors: Kim Taehyung , Lovell David J. , Park Yongjin
Published: December 2007

Car-following models have been used in all microscopic traffic simulation modeling for almost half a century to describe the process of driver behavior in following each other in the traffic stream. In recent years, a detailed understanding of car-following behavior has become more essential for both the design and the assessment of advanced driver assistance systems, such as adaptive cruise control, to help improve appropriate algorithms and develop control strategies. However, previous experimental studies and models of car-following behavior have some important limitations, which make them inconsistent with real driving experience. Hence, this study aims to contribute to the better understanding of driving behavior in following a lead vehicle in car-following situations. Efforts have been made to disclose the problems and the limitations in previous experimental studies and models of car-following behavior; to build a new data collection system, including hardware and software architecture; and to investigate and discover the characteristics of real driving behavior in following a lead vehicle. It is hoped that the findings will provide clues to guide the construction of more realistic car-following models.
Hybrid Traffic Simulation with Adaptive Signal Control
Authors: Burghout Wilco , Wahlstedt Johan
Published: December 2007

A hybrid mesoscopic-microscopic model is implemented that applies microscopic simulation to areas of specific interest while simulating a large surrounding network in lesser detail with a mesoscopic model. The hybrid model integrates VisSim, a microscopic traffic simulation model, and Mezzo, a recently developed mesoscopic model. The hybrid model is applied on a network in which Mezzo simulates the entire area (6,000 links) of Stockholm, Sweden, and VisSim simulates the area of specific interest, containing three intersections with adaptive signal control with bus-priority functions. The adaptive signal control and bus-priority functions are simulated by a separate signal controller simulator (EC-1 simulator) that interacts with the hybrid Mezzo-VisSim model and thereby provides the actual signal changes that would take place in the field. Two alternative control schemes are evaluated with the hybrid setup: the original fixed-time control and the new adaptive control. The results show clear improvement in terms of travel times, delays, and stops with the new adaptive control scheme. They also show that although these improvements for the local (microlevel) area attract additional traffic from the surrounding (mesolevel) area, the net effects both locally and networkwide remain positive in terms of travel times, average number of stops, and delay. Moreover, this study demonstrates the advantages of hybrid simulation in evaluation of complicated adaptive traffic control in which both local detailed effects and network effects need to be studied.
Calibration of Microscopic Traffic Simulation Models
Authors: Balakrishna Ramachandran , Antoniou Constantinos , Ben-Akiva Moshe , Koutsopoulos Haris N. , Wen Yang
Published: December 2007

A mathematical framework and a solution approach are presented for the simultaneous calibration of the demand and supply parameters and inputs to microscopic traffic simulation models as well as a large-scale application emphasizing practical issues. Microscopic traffic simulation models provide detailed estimates of evolving network conditions by modeling time-varying demand patterns and individual drivers' detailed behavioral decisions. Such models are composed of elements that simulate different demand and supply processes and their complex interactions. Several model inputs (such as origin-destination flows) and parameters (car-following and lane-changing coefficients) must be specified before these simulation tools can be applied, and their values must be determined so that the simulation output accurately replicates the reality reflected in traffic measurements. A methodology is presented here for simultaneously estimating all microscopic simulation model parameters by using general traffic measurements. A large-scale case study for the calibration of the MITSimLab microscopic traffic simulation model by using the network of Lower Westchester County, New York, is employed to demonstrate the feasibility, application, and benefits of the proposed methodology.
Application of Cross-Nested Logit Route Choice Model in Stochastic User Equilibrium Traffic Assignment
Authors: Bekhor Shlomo , Reznikova Lena , Toledo Tomer
Published: December 2007

Most stochastic user equilibrium (SUE) model applications reported in the literature are based on the multinomial logit (MNL) model. This paper presents a SUE assignment based on the cross-nested logit (CNL) route choice model, which can better represent route choice behavior. The paper develops path-based algorithms to solve the CNL-SUE problem based on adaptation of the disaggregate simplicial decomposition method. The algorithms differ for the step-size determination; three different methods are considered. The algorithms are tested in two well-known networks. Two main tests are conducted: (a) the impact of the CNL model parameters on the assignment results is analyzed and (b) the differences between the CNL-SUE and the MNL-SUE solutions are investigated. The results indicate that the path-based algorithm with Armijo's step-size rule outperforms other step-size determinations. This paper indicates that depending on the model parameters, particularly the nesting coefficient, the CNL-SUE path flows may be quite different from the MNL-SUE path flows.
Modeling Route Choice Behavior
Authors: Prato Carlo Giacomo , Bekhor Shlomo
Published: December 2007

Most route choice models are related to revealed choice behavior and are estimated by adding alternative paths to observed routes. This paper focuses on the effects of choice set composition in route choice modeling by designing an experimental analysis of actual route choice behavior of individuals driving habitually from home to work in an urban network. The numerical analysis concentrates on a qualitative perspective, by considering path sets built with different generation techniques, and a quantitative perspective, by accounting for path sets constructed with sample size reduction from each initial choice set. Comparison of prediction accuracy across different choice sets suggests that a recently developed branch and bound algorithm generates heterogeneous routes that allow for estimating models with better prediction abilities with respect to the outcomes of the drivers' actual choices. Further, comparison of route choice models across different choice set compositions indicates that nonnested structures, such as C-logit and path size logit, yield more robust parameter estimates.
Ohio Long-Distance Travel Model
Authors: Erhardt Gregory D. , Freedman Joel , Stryker Andrew , Fujioka Heather , Anderson Rebekah
Published: December 2007

Credible forecasts of long-distance travel are an important tool for evaluating proposed intercity transportation improvements, including intercity highway and transit projects. Although researchers have studied the topic and have developed frameworks for modeling long-distance travel behavior, these research models have not been integrated into comprehensive model systems used for a wide range of applications. This paper presents a long-distance travel model that bridges the gap between research and practice. It is based on a rigorous behavioral framework that models the unique aspects of long-distance travel, such as a less regular frequency of trips and a different set of modal alternatives. The model structure includes the choice of whether to travel, the selection of the days on which to travel, scheduling to a specific time of day, destination choice, and mode choice. The model is sensitive to important descriptive variables, including the demographic characteristics of travelers, the attractiveness of possible destinations, and the levels of service of air, transit, and highway networks. It has been successfully implemented as part of the Ohio statewide model, which also features an advanced tour-based model of short-distance travel. Through this integration, it allows for behavioral consistency within the entire model system and competition among all travelers for transportation capacity. Lessons are learned about the data needs and research needs to further improve long-distance travel models.
Data Security
Authors: De Capitani di Vimercati Sabrina , Samarati Pierangela , Jajodia Sushil
Published: December 2007

The problem of protecting information has existed since information has been managed. Ensuring protection against threats to data security requires a variety of measures. This article focuses, in particular, on the protection of information against possible violations by users, insiders or intruders.
Fault‐Tolerant Software
Authors: Lyu Michael R. , Cai Xia
Published: December 2007

Fault tolerance is the survival attribute of a system or component to continue operating as required despite the manifestation of hardware or software faults. Fault‐tolerant software delivers continuous service complying with the relevant specification in the presence of faults typically by employing either single‐version software techniques or multiple‐version software techniques. We address four key perspectives for fault‐tolerant software: historical background, techniques, modeling schemes, and applications.
Regression Analysis
Authors: Weisberg Sanford
Published: December 2007

In statistics, regression is the study of the changes in the distribution of a response as the values of predictors of it are varied. Regression models are used in virtually all areas of science and represent fundamental tools in understanding data.

Simple and multiple linear regression methodology are the basic tools of regression analysis. These methods can be used with only minimal assumptions and are described in this article. Linear regression is not always appropriate, for example, if the response is a category or a count. For these cases, specialized methods have been developed. More recent developments in regression include nonparametric, semiparametric approaches, among others.
Visual Software Engineering
Authors: Zhang Kang , Kong Jun , Cao Jiannong
Published: December 2007

Graphical notations, such as data flow diagrams and class diagrams, are widely used in software design and development. While being easy to understand and convenient to use, these graphical notations are not amendable to automated verification and transformation. This article provides an overview on visual assistance in software engineering, and it focuses on a graph grammar approach to visual software modeling, architectural design, and evolution. A graph grammar enables a high‐level abstraction of the general organization of a class of software architectures, and it forms a basis for formal analysis and transformations. In this approach, software verification is performed through a syntax analyzer. Architectural evolution is achieved by applying predefined transformation rules.
Primary Efficacy Endpoint
Authors: Follmann Dean A
Published: December 2007

At its core, a clinical trial is designed to test a specific primary hypothesis. The primary efficacy endpoint in a clinical trial is a clinical or laboratory outcome measured in an individual after randomization that allows one to test the primary hypothesis and provides the means of assessing whether a therapy is effective compared with its control. A primary endpoint can be measured once or repeatedly over time, or may comprise several kinds of individual measurements. Once a primary endpoint is selected, statistical methods of analysis to test the primary hypothesis can be determined and sample size calculations can be performed to ensure the trial is properly powered. Because of the key role of the primary endpoint in the design and analysis of a trial, it is critical that it be chosen carefully. A primary efficacy endpoint must be precisely specified in advance and should(1)address the primary objective,(2)be ascertainable in all patients,(3)be “fair” to each study arm,(4)have demonstrated or accepted relevance for the population and intervention(s) of the trial, and(5)be sensitive to meaningful changes in a patient's health.
Influence of potassium humate on the swelling properties of a poly(acrylic acid‐co‐acrylamide)/ potassium humate superabsorbent composite
Authors: Chu Mo , Zhu Shu‐Quan , Huang Zhan‐Bin , Li Hua‐Min
Published: December 2007

A novel superabsorbent composite, poly(acrylic acid‐co‐acrylamide)/potassium humate (PAA‐AM/KHA), was prepared by aqueous solution polymerization from acrylic acid, acrylamide, and potassium humate (KHA) with N,N′‐methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of incorporated KHA on the water absorbency, swelling rate, and reswelling capability were investigated. The swelling property of PAA‐AM/KHA in various saline solutions was studied systematically. The results show that the comprehensive properties and especially salt‐resistant ability of PAA‐AM/KHA were enhanced. There was a linear relationship between the saturated water absorbency and the minus square root of the ionic strength of the external medium, and the water absorbency of PAA‐AM/KHA in various salt solutions had the following order: NH4Cl(aq) = KCl(aq) = NaCl(aq) > MgCl2(aq) > CaCl2(aq) > AlCl3(aq) > FeCl3(aq). Moreover, the polymeric net structure of PAA‐AM/KHA was examined with respect to that of poly(acrylic acid‐co‐acrylamide). The results indicate that the polymeric net of PAA‐AM/KHA was improved by the introduction of a moderate amount of KHA into the superabsorbent composite and made more suitable for agriculture and horticulture applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Excimer and electromer suppression of tetraphenylsilane‐based blue‐light‐emitting polymers
Authors: Lee Rong‐Ho , Wang Ying‐Yu
Published: December 2007

Excimer and electromer suppression of tetraphenylsilane‐derivative‐based blue polymer light‐emitting devices (PLEDs) was investigated. Tetraphenylsilane with a rigid bulky structure certainly but not completely suppressed excimer formation among polymer‐chain segments. A poor solvent, toluene, resulted in excimer formation in the solid film during the spin‐coating process, which could not be suppressed by the incorporation of a bulky moiety onto the polymer backbone. In addition, electromers or electroplexes formed by the strong interaction between the oxadiazole and diphenyl(4‐tolyl)amine groups could not be prevented by the tetraphenylsilane moiety. The influences of the bulky moiety, bipolar unit, and device fabrication conditions on the suppression of excimers or electromers in PLEDs are discussed in detail. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites
Authors: Maity J. , Jacob C. , Das C. K. , Singh R. P.
Published: December 2007

Composites consisting of high density polyethylene (HDPE) reinforced with randomly oriented chopped Twaron fibers (both fluorinated and nonfluorinated) show a significant increase in mechanical and thermal properties. To increase the better fiber matrix adhesion, the Twaron fiber is surface fluorinated using elemental fluorine. The surface of the Twaron fiber becomes very rough and the diameter of Twaron fiber increases from ∼ 12 to 14 μm after fluorination. The composites were prepared using solution method to overcome the damage of the fiber. The tensile strength and the Young's modulus increases with increasing fiber content. The tensile strength and modulus of modified fiber (fluorinated Twaron fiber) composites is much higher than nonmodified fiber composites indicating that there is better mechanical interlocking between the modified fiber and the matrix. Thermal properties obtained from DSC and DTA‐TG analysis of the fluorinated fiber composites are also improved. Contact angle measurements, as well as the surface energy measurements, indicate that the composites are more wettable and is maximum for fluorinated fiber composites i.e., surface energy for fluorinated fiber composites is highest. Crystallinity is also higher for fluorinated fiber composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Synthesis of a new tetrafunctional monomer, 1,4‐di(2‐hydroxy‐3‐methacryloyloxypropoxy)phenol, and its copolymerization
Authors: Grochowicz Marta , Bartnicki Andrzej , Gawdzik Barbara
Published: December 2007

The new aromatic tetrafunctional methacrylate monomer, 1,4‐di(2‐hydroxy‐3‐methacryloyloxypropoxy) phenol, and its application for the synthesis of porous microspheres have been presented. It was copolymerized with trimethylolpropane trimethacrylate in the presence of pore‐forming diluents mixture (chlorobenzene and 1‐decanol). The results indicate that composition of diluents mixture influence porous structure of copolymers. The porous structure of the copolymer obtained in the presence of 50% chlorobenzene was studied in detail. The results show that pore volume and the most probable pore size diameters determined for the copolymer in the dry and in the wetted states are different. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Blending PP with PA6 industrial wastes: Effect of the composition and the compatibilization
Authors: Jaziri Mohamed , Barhoumi Najoua , Massardier Valérie , Mélis Flavien
Published: December 2007

Blending polypropylene to recycled PA6 industrial wastes at different compositions, with and without compatibilizer PPgMA was produced in a corotating twin screw extruder where, polypropylene acts as the polymer matrix and polyamide as the dispersed phase. Several techniques were used to investigate the morphology, thermal, viscoelastic and tensile properties of these blend. Binary PP/PA6 blends showed the presence of PA6 particles dispersed in the PP continuous phase and exhibited a coarse morphology. Increasing PA6 contents in the blend increased their crystallinity and their size and improved the tensile properties at weak deformation. In addition to compatibilizer PPgMA, the morphology shows lower diameters and a decrease in size of the dispersed PA6 particles. The interfacial adhesion was also improved, as a result of the creation of an interphase that was formed by the interaction between the formed PPgPA6 copolymer in situ and both phases. This interphase induced an improvement in tensile properties. The PPgPA6 copolymer generated by the interphase was identified with DMA analysis thanks to an additional transition in loss modulus curves. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Enantio‐ and diastereoselective syntheses of cyclic Cα‐tetrasubstituted α‐amino acids and their use to induce stable conformations in short peptides
Authors: Maity Prantik , König Burkhard
Published: December 2007

Cα‐Tetrasubstituted α‐amino acids are widely used to design and prepare peptides and peptide mimics with constrained conformations. Subcategories of these compounds are cyclic Cα‐tetrasubstituted α‐amino acids, in which both α‐substituents are covalently connected. This survey presents recent advances in the synthesis and application of cyclic Cα‐tetrasubstituted α‐amino acids in a systematic order beginning with cyclopropane amino acids, continuing with four, five, six membered rings, and ring structures larger than six‐membered. We discuss synthetic routes to the cyclic Cα‐tetrasubstituted α‐amino acids and their use as conformation determining elements in peptides. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 8–27, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Physical injuries in the dissecting room
Authors: Cornwall Jon , Stringer Mark D.
Published: December 2007

Dissection of human cadavers remains an important element of learning anatomy in many medical and dental schools. During this activity, students are introduced to the safe handling of surgical instruments. The frequency, type, and mechanism of associated injuries are unknown. We undertook a retrospective cohort analysis of dissecting‐room accidents during a 6‐year period (2001–2006). Injury rates were adjusted to account for exposure risk. A total of 55 injuries, all minor, were recorded in 53 students, representing an overall injury rate of less than 4 injuries per 1,000 hr of dissection. Twenty‐four injuries were documented in third‐year medical students, 13 in second‐year medical students, 10 in second‐year dental students, and 8 in third‐year science students. There was a statistically significant difference in injury rates between the groups due to a higher than expected rate among second‐year medical students and a lower than expected rate among third‐year medical students (P < 0.01). At least 38 (69%) injuries were from a scalpel blade. A further three injuries were from bone spicules. All except two injuries affected the hand. In conclusion, it is unusual for students to injure themselves in the dissecting room. Injuries tend to be minor and largely related to scalpel blades. A greater awareness of hazards due to sharps and safe handling techniques may reduce the risks of minor injury and better prepare students for future clinical practice. Clin. Anat. 21:82–85, 2008. © 2007 Wiley‐Liss, Inc.
Adsorption of Methyl tert‐butyl Ether on Perfluorooctyl Alumina Adsorbents – High Concentration Range
Authors: Ebadi A. , Soltan Mohammadzadeh J. S. , Khudiev A.
Published: December 2007

The performance of two types of perfluorooctyl alumina (PFOAL) adsorbents prepared using γ‐alumina (PFOALA) and alumina‐active‐basic® (PFOALB) is reported. The equilibrium adsorption behavior of the adsorbents was studied for adsorption of methyl tert‐butyl ether (MTBE) in a wide range (5–1000 mg/L) of aqueous phase MTBE concentrations. The monolayer adsorption capacities were 3.3 and 3.5 mg MTBE/g adsorbent, and the maximum adsorption capacities were 7.1 and 6.3 mg MTBE/g adsorbent for PFOALA and PFOALB, respectively. The application of Freundlich, Langmuir, BET and BDDT (the general form of BET) isotherms were compared for the modeling of aqueous adsorption of MTBE on the surface of PFOAL adsorbents. It was shown that adsorption of MTBE on the surface of PFOAL is a type IV van der Waals adsorption, which is best modeled by the general form of the BET (BDDT) multilayer adsorption isotherm.
Tuning the Charge Distribution and Photoswitchable Properties of Cobalt–Dioxolene Complexes by Using Molecular Techniques
Authors: Beni Alessandra , Dei Andrea , Laschi Serena , Rizzitano Mario , Sorace Lorenzo
Published: December 2007

A series of cobalt complexes [Co(Mentpa)(diox)]PF6⋅sol (diox=3,5‐di‐tert‐butyl‐1,2‐dioxolene; sol=ethanol, toluene; tpa=tris(2‐pyridylmethyl)amine) were prepared by using tripod‐like Mentpa (n=0, 1, 2, 3), derived from tpa by successive introduction of methyl groups into the 6‐position of the pyridine moieties, as an ancillary ligand. The steric hindrance induced by this substitution modulates the redox properties of the metal acceptor, thus determining the charge distribution of the metal–dioxolene moiety at room temperature. All of these complexes were characterised by using diffractometric studies, electronic spectroscopic analysis, and magnetic susceptibility measurements. In the solid state, the [Co(Mentpa)(diox)]+ ions (n=0, 1) can be described as diamagnetic cobalt(III)–catecholato derivatives, whereas a cobalt(II)–semiquinonato description seems appropriate for the paramagnetic [Co(Me3tpa)(diox)]+ complex. The complex [Co(Me2tpa)(diox)]PF6⋅C2H5OH undergoes entropy‐driven valence tautomeric interconversion at room temperature. Optically induced valence tautomerism was observed by irradiation of [Co(Mentpa)(diox)]PF6 complexes (n=0, 1, 2) at cryogenic temperatures. The different relaxation kinetics of the photoinduced metastable phases are related to the respective free‐energy changes of the interconversion, as estimated by cyclic voltammetric experiments at room temperature, and to the different lattice interactions, as supported by structural data. These results show the importance of molecular techniques for controlling the relaxation properties of photoinduced metastable species. At the same time, this behaviour strongly suggests that this paradigm exhibits intrinsic limits because of the less controllable factors that affect the process.
The resolution of five racemic α‐lactams by HPLC
Authors: Yu Hui , Hur Kyu , Lengyel István , Cesare Victor
Published: December 2007

The resolution of five racemic α‐lactams (1a‐d,g) using HPLC is reported. Five different Pirkle‐type stationary phases were tested. The enantiomers of α‐lactams containing the trityl group (1a‐d) were separated (selectivity factors ranging from 1.08 to 1.20) using a mobile phase of hexane/2‐propanol:98/2 and a stationary phase consisting of the 3,5‐dinitroaniline derivative of (S)‐valine with a urea linkage. Among the dialkyl‐substituted α‐lactams (1e‐g), only 1,3‐di‐tert‐butylaziridinone (1g) could be resolved, but only partially (selectivity factor = 1.07), with a mobile phase of hexane/1,2‐dichloroethane:95/5 and the stationary phase consisting of the 3,5‐dinitrobenzoic acid derivative of (R)‐1‐naphthylglycine. Chirality, 2008. © 2007 Wiley‐Liss, Inc.
Kleine nicht‐kodierende Ribonukleinsäuren. In Eukaryoten
Authors: Overhoff Marita
Published: December 2007

Die in den letzten Jahren entdeckten kleinen nicht kodierenden RNAs, wie siRNAs, miRNAs und rasiRNAs, regulieren auf unterschiedliche Art und Weise zelluläre Ereignisse, wie z.B. die Differenzierung einer Zelle. Obwohl sie an sehr vielen Prozessen beteiligt sind, wurden sie lange Zeit übersehen und erst jetzt beginnt man die gesamte Bandbreite der Regulation durch diese RNAs zu erahnen. Die genauen Mechanismen der Regulation durch die kleinen RNAs sind zum Teil noch nicht bekannt, trotzdem soll dieser Übersichtsartikel schon jetzt einen kleinen Einblick in die faszinierende Welt der kleinen RNAs geben.
Die molekularen Grundlagen heterogener Katalyse
Authors: Welter Kira
Published: December 2007

Den diesjährigen Nobelpreis für Chemie erhielt Gerhard Ertl, emeritierter Direktor des Berliner Fritz‐Haber‐Instituts. Mit seiner Arbeit legte der deutsche Physiko‐Chemiker die wissenschaftlichen Grundlagen für das Verständnis von heterogen katalytisierten Prozessen und trug wie kaum ein Anderer zur Entwicklung der modernen Oberflächenchemie bei. Die Auszeichnung bekam der gebürtige Stuttgarter genau an seinem 71. Geburtstag.
Reporter gene imaging using radiographic contrast from nonradioactive iodide sequestered by the sodium–iodide symporter
Authors: Brown Stephen L. , Freytag Svend O. , Barton Kenneth N. , Flynn Michael J. , Peck Donald J. , Dragovic Aleksandar F. , Jin Ryan , Yeni Yener N. , Fyhrie David P. , Les Clifford M. , Zhu Guopei , Kolozsvary Andrew , Pitchford Wayne C. , Nathanson S. David , Fenstermacher Joseph D. , Kim Jae Ho
Published: December 2007

The hypothesis that the human sodium–iodide symporter, NIS, can be used to detect NIS expression using standard radiological techniques was tested using adenoviral transduced NIS expression in human tumor xenografts grown in mice and in a naive dog prostate. Nonradioactive iodide was administered systemically to animals that 1–3 days previously had received a local injection of a replication‐competent adenovirus expressing NIS under the control of the CMV promoter. The distribution of radiopacity was assessed in mouse tumors using micro‐CT and a clinical X‐ray machine and in the prostate of an anesthetized dog using a clinical spiral CT. Iodide sequestration and NIS expression were measured using X‐ray spectrochemical analysis and fluorescence microscopy, respectively. Radiographic contrast due to NIS gene expression that was observed indicates the technique has potential for use in preclinical rodent tumor studies but probably lacks sensitivity for human use. Copyright © 2007 John Wiley & Sons, Ltd.
Granular cell tumor of the neurohypophysis: Report of a case with intraoperative cytologic diagnosis
Authors: Policarpio‐Nicolas Maria Luisa C. , Le Brian H. , Mandell James W. , Lopes M. Beatriz S.
Published: December 2007

Cytological techniques including touch and smear preparations are very useful diagnostic modality in the evaluation of central nervous system (CNS) lesions and, in many instances, may be effectively used as the sole modality of tissue preparation for intraoperative consultation. Cytologic preparations offer many advantages over frozen sections for CNS specimens. These include selective examination of multiple areas from small biopsy specimens, superior preservation and details of cellular morphology, fewer artifacts, faster results, and improved cost‐effectiveness. We describe the cytologic diagnosis of a granular cell tumor (GCT) of the neurohypophysis in a 33‐year‐old male who presented with headache and blurred vision. CT scan revealed an enlarged sella with a 2.15 × 2.0 cm pituitary lesion. Transsphenoidal resection of the mass was performed and submitted for intraoperative consultation. Smears and touch preparations were made on a portion of the mass that showed uniform polygonal cells with round to ovoid nuclei and abundant eosinophilic granular cytoplasm. An intraoperative cytological diagnosis of “favor GCT” was rendered. The histologic sections of the remaining material confirmed the diagnosis. Although GCT of the neurohypophysis is very rare, a specific intraoperative cytological diagnosis is possible. We report the clinical, cytological, and pathological findings of a GCT affecting the neurohypophysis. Diagn. Cytopathol. 2008;36:58–63. © 2007 Wiley–Liss, Inc.