bluuebunny/crossref_metadata_2025 huggingface dataset:
Functioning and Acceptance of Overtaking Assistant Design Tested in Driving Simulator Experiment
Authors: Hegeman Geertje , van der Horst Richard , Brookhuis Karel A. , Hoogendoorn Serge P.
Published: January 2008

This paper describes a driving simulator experiment to test the functioning and acceptance of a standardized overtaking assistant design. On a simulated two-lane road, 24 participants drove 15 min with and without a prototype overtaking assistant. The overtaking assistant calculated the available time to perform an overtaking maneuver, taking the preceding vehicle and opposing traffic into account. When it was safe to overtake, the assistant showed a green sign to participants; when it was not safe, a red sign was shown. The number of overtaking maneuvers performed in the base scenario (without assistance) did not vary significantly from that in the assistant scenario. Male participants, however, did overtake significantly more than female participants. The reported activation level of all participants had grown significantly after the run with the overtaking assistant, compared with a similar run without assistance. Participants’ ratings for the usefulness of the assistant and on how satisfying it was were both low; some participants thought the assistant was too careful (shows a red sign while it is safe to overtake), and others thought it was not careful enough (shows a green sign while it is not safe to overtake). The overtaking frequency of participants was not significantly related to sensation-seeking scores, which are highly related to risky driving. It was concluded that according to the performance of the overtaking maneuvers, it is possible to design a standardized overtaking assistant. However, it should be possible to improve the system to suit the different drivers’ perceptions better.
Adding Graphics to Dynamic Message Sign Messages
Authors: Wang Jyh-Hone , Hesar Siamak G. , Collyer Charles E.
Published: January 2008

A human factors study assessed the effects of adding graphics to dynamic message sign (DMS) messages. Two approaches employed in the assessment—a questionnaire survey and a video-based driving simulation experiment—are reported here along with the findings. The questionnaire surveyed drivers’ preferences concerning the addition of graphics to a text message, the color of the message, alternative graphic images, placement of the graphic image, image contrast, flashing, and the framing of graphic images. One hundred and twenty-seven subjects from Rhode Island participated in the survey. Statistical analysis of survey results showed strong preference for graphic-aided messages over text-only messages; amber-color messages over green- and red-color messages; and messages with graphic on the left side over others. The analysis also identified specific graphics to accompany certain text messages. Based on the survey results, a video-based driving simulation experiment was designed to test drivers’ responses to selected DMS messages surveyed in the questionnaire. Forty-eight subjects from different age groups with different native language backgrounds took part in the experiment. Results of the experiment showed that graphic-aided messages displayed in amber or green were responded to significantly faster than other settings. Older drivers’ responses were slower and less accurate than others; however, their responses improved significantly when the DMS messages were enhanced by graphics. It was also found that graphic-aided DMS messages helped improve the responses of non-native-English-speaking drivers.
Transportation Asset Management and Visualization Using Semantic Models and Google Earth
Authors: Darter Michael T. , Lasky Ty A. , Ravani Bahram
Published: January 2008

Transportation asset management is important in planning and resource allocation for infrastructure maintenance, operations, and improvements. This paper presents the design and initial implementation of the kernel of a software system for asset management with the use of nonproprietary standards and open source software with state-of-the-art visualization capabilities. An innovative software design is presented; it combines semantic models of mobile and stationary transportation assets with the visualization capabilities of Google Earth. Semantic models can represent complex relationships between diverse asset classes. Semantic query across asset classes and properties is also a key feature. Google Earth is used for visualization because of its accessibility to a wide range of users and ability to combine different types of data. A visualization server was developed that implements the semantic model. The model defines stationary and mobile assets, including culverts, end treatments, and real-time traffic sensors. Spatial and semantic queries are used to construct layers displayed within Google Earth. Results show that the developed semantic models facilitate integration of software and hardware systems. Semantic modeling, using resource description framework (RDF) and web ontology language (OWL), provides a richer transportation world model than is possible with existing object-oriented or relational methods. Definition of classes and properties with a standardized syntax allows separation of design and implementation.
Visualizing and Analyzing Activities in an Integrated Space-Time Environment
Authors: Yu Hongbo
Published: January 2008

An integrated space-time environment is demanded by activity-based travel studies to facilitate the investigation of spatial and temporal characteristics of activities. The current geographic information system (GIS), which has been successful in supporting trip-based travel analysis, does not include an explicit time representation and therefore is incapable of supporting activity-based travel analysis efficiently. This study proposes a temporal GIS design that incorporates the space-time path concept of Hägerstrand's time geography to facilitate the analysis of activities in a space-time context. The space-time path concept provides an efficient approach to organizing activities and travels in their space-time contexts and to supporting the investigation of spatiotemporal relationships between individuals. This study adopts the three-dimensional orthogonal space-time system in the temporal GIS design and develops representation and analysis functions related to space-time paths and individual activities. The proposed design is successfully implemented in a prototype system. The system provides an integrated space-time environment to effectively visualize activities and travels in their space-time contexts and analyze their spatiotemporal characteristics. Such a system offers useful tools to facilitate activity-based travel studies.
Methodology for Selection and Development of TransXML Schemas
Authors: Scarponcini Paul
Published: January 2008

NCHRP Project 20-64, TransXML, solicited the development of standard, public domain extensible markup language (XML) schemas for the exchange of transportation data as well as the creation of a framework for the development, validation, dissemination, and extension of current and future schemas. The methodology used for the selection and development of the initial set of TransXML schemas ensured their consistency, cohesiveness, and usefulness. Data flow diagrams of the design and construction process had previously been developed for the Minnesota Department of Transportation. They articulate steps in the design process as well as the flow of data between these steps. The diagrams were analyzed to discover candidate data flows that if supported by standardized XML schemas, could improve the design and construction process. The content and structure of the data identified were then modeled with unified modeling language (UML) class diagrams–roughly one UML package per data flow. Consensus of interested parties was achieved through the project website, including specific agreement on data elements and their associations. For each element, relevant attributes were decided, along with their cardinality and data type. For associations, relationship types, cardinalities, and roles were established. Diagrams for each area were compared to achieve consistency and to identify common elements, the latter being extracted into separate UML packages. XML schemas were then developed, based on the UML packages. The geography markup language (GML) was used as the framework for the schemas, building on predefined GML elements and following GML rules for developing application schemas. Sample applications were developed to demonstrate how the schemas support the data flows.
Mechanistic Comparison of Cement- and Bituminous-Stabilized Granular Base Systems
Authors: Berthelot Curtis , Marjerison Brent , Houston Gary , McCaig Jody , Warrener Stu , Gorlick Rock
Published: January 2008

The Saskatchewan, Canada, Department of Highways and Transportation is investigating alternative recycling and strengthening systems for inservice thin granular pavements. This research is being performed to improve the granular pavement structural integrity and to reduce the dependence on new source aggregates. A pilot project investigated the mechanistic-climatic laboratory characterization of materials used to construct test sections on Control Section Highway 15-11 (C.S. 15-11). This research demonstrated the use of ground-penetrating radar and falling weight deflection measurements to select uniform field test section locations. In situ recycled granular base was sampled and found to be a typical thin granular pavement requiring strengthening because it is relatively high in fine sand fraction and has a high portion of intermediate plastic clay fines. These two properties are known to cause marginal performance of granular bases in the field. This research showed that cement and bitu-minous stabilization significantly improved the mechanistic primary response and climatic durability properties of marginal granular base materials. However, it was found that the asphalt emulsion with cement stabilization showed the highest performance improvement. It also was found that the addition of cement to emulsified and foamed asphalt stabilization systems significantly improved the mechanistic-climatic durability of the marginal granular base aggregate. This study demonstrated the rapid triaxial tester to be a pragmatic and cost-efficient methodology to characterize the mechanistic constitutive relations of granular base materials for performing mechanistic road structural modeling.
Data-Driven Algorithms for Real-Time Adaptive Tuning of Offsets in Coordinated Traffic Signal Systems
Authors: Gettman Douglas , Shelby Steven G. , Head Larry , Bullock Darcy M. , Soyke Nils
Published: January 2008

A real-time adaptive control algorithm for tuning traffic signal offsets in a coordinated traffic signal system is presented. The algorithm described here is used in the Adaptive Control Software-Lite (ACS-Lite) adaptive control system. The algorithm uses a statistical average flow profile of traffic on the coordinated approaches to an intersection to assess when vehicles are arriving during the signal cycle. Alternative offset adjustments are evaluated by calculating how much of this flow profile is being captured by the green phase serving each coordinated approach. The algorithm considers the impact of the offset adjustment on traffic at the local intersection as well as on traffic at adjacent intersections that are also under ACS-Lite control. Simulation tests have quantitatively shown that this tuning approach can improve arterial progression performance relative to the quality of the initial baseline fixed offsets used in a traffic pattern. Several issues and areas for improvement of the algorithm are also identified and discussed.
VisSim-Based Genetic Algorithm Optimization of Signal Timings
Authors: Stevanovic Aleksandar , Martin Peter T. , Stevanovic Jelka
Published: January 2008

Genetic algorithm optimizations of traffic signal timings have been shown to be effective, continually outperforming traditional optimization tools such as Synchro and TRANSYT-7F. However, their application has been limited to scholarly research and evaluations. Only one tool has matured to a commercial deployment: direct CorSim optimization, a feature of TRANSYT-7F. A genetic algorithm formulation, VisSim-based genetic algorithm optimization of signal timings (VISGAOST), is presented; it builds on the best of the recorded methods by extending their capabilities. It optimizes four basic signal timing parameters with VisSim microsimulation as an evaluation environment. The program brings new optimization features not available in the direct CorSim optimization, such as the optimization of phasing sequences, multiple coordinated systems and uncoordinated intersections, fully actuated isolated intersections, and multiple time periods. The formulation has two features that enhance and reduce computational time: optimization resumption and parallel computing. The program has been tested on two VisSim networks: a hypothetical grid network and a real-world arterial of actuated–coordinated intersections in Park City, Utah. The results show that timing plans optimized by the genetic algorithm outperformed the best Synchro plans in both cases, reducing delay and stops by at least 5%.
Feasibility of Traffic Simulation for Decision Support in Real-Time Regional Traffic Management
Authors: Fries Ryan , Inamdar Imran , Chowdhury Mashrur , Taaffe Kevin , Ozbay Kaan
Published: January 2008

State-of-the-art microscopic traffic simulation programs offer detailed modeling capabilities of vehicle interactions based on drivers, pedestrians, and highway elements. Consequently, these tools can help regional traffic management personnel make operational decisions by predicting future traffic conditions that result from incidents. This research sought to determine the effectiveness and timeliness of using a detailed microsimulation suite called Paramics to support personnel in a regional traffic management center in real-time decision making. Two sites in rural, high-crash areas of South Carolina were examined to see whether Paramics could provide decision information as quickly as desired by regional traffic management centers. Only certain combinations of incident durations and simulation accuracy satisfied the decision-time constraints for realtime decision support. Increasing the computational resources or reducing the size of the traffic network can provide decision support for longer incidents at higher accuracies and further allow microscopic traffic simulation to aid regional traffic management personnel in real-time decision making.
Evaluating Effects of Toll Strategies on Route Diversion and Travel Times for Origin–Destination Pairs in a Regional Transportation Network
Authors: Al-Deek Haitham , Chandra Srinivasa Ravi , Emam Emam B. , Klodzinski Jack
Published: January 2008

Congestion on freeway facilities is a growing menace. Interstate 4 (I-4) in the Central Florida region has been experiencing delays during peak hour; this has warranted research on traffic management strategies. The public, through the media, had proposed removing tolls on state toll roads to divert traffic from I-4. A microsimulation model, Paramics, was used to examine the potential impact of this proposal. SR-417 is a relatively uncongested toll road alternative to I-4. SR-528 is the east–west toll road connecting SR-417 and I-4. Commuters on SR-417 have to travel 15 mi longer and pay $5 compared with no monetary cost on I-4 for the same trip. The public and politicians are reluctant to toll I-4 to relieve congestion. The results from the simulation indicated that under recurring congestion conditions on I-4, removing tolls on SR-417 and SR-528 would not divert enough traffic from I-4 because of the 15-mi advantage. Under incident and lane closure scenarios on I-4 with toll reduction on SR-417 and SR-528, the travel time would increase on I-4. This result would prompt some diversion, with volumes and travel times increasing on SR-417. It was concluded that the amount of traffic that would be diverted from I-4 to the toll roads would not significantly relieve congestion on I-4. When specific origin–destination pairs were analyzed, average travel time savings on I-4 were only around 5 min. It was concluded that contrary to the media and public perception, toll reduction would only have a minimum impact on reducing I-4 congestion.
Spatial patterns of microsite colonisation on two young lava flows on Mount Hekla, Iceland
Authors: Cutler N.A. , Belyea L.R. , Dugmore A.J.
Published: January 2008

Questions: How does vegetation first establish on newly‐formed lava substrates? Do very small (cm) and meso‐scale (m) variations in the physical environment influence this process and subsequent vegetation development?

Location: Mount Hekla, southern Iceland (64°00’ N, 19°40’ W).

Methods: Data on vegetation structure and the incidence of ‘safe sites’ suitable for colonisation were collected from high and low points on the surfaces of lava flows emplaced during the 1991 and 2000 A.D. eruptions of Mount Hekla. Effects of flow age and meso‐topographic position on vegetation structure (moss cover, patch density, stem length) were assessed by two‐way analyses of variance. The distributions of colonisation events and available safe sites were analysed using point pattern techniques.

Results: Rapid colonisation of the lava surface was observed, despite stressful environmental conditions. The 1991 and 2000 flows differed significantly in vegetation structure, but there were no significant differences in moss cover, patch density and stem length between ‘high’ and ‘low’ sites.

Conclusions: Colonisation events are invariably associated with small‐scale irregularities on the surface of the lava. The colonisation process appears to be spatially random. Development of the moss ‘carpet’ proceeds by vertical thickening and lateral growth and coalescence of moss patches that establish in ‘safe sites’. This process is rapid, with close to 100% of available safe sites exploited within 20 years. Topographic position makes no difference to the very early stages of vegetation development and cannot be used to ‘forecast’ the later stages of development.
Clock genes may influence bipolar disorder susceptibility and dysfunctional circadian rhythm
Authors: Shi Jiajun , Wittke‐Thompson Jacqueline K. , Badner Judith A. , Hattori Eiji , Potash James B. , Willour Virginia L. , McMahon Francis J. , Gershon Elliot S. , Liu Chunyu
Published: January 2008

Several previous studies suggest that dysfunction of circadian rhythms may increase susceptibility to bipolar disorder (BP). We conducted an association study of five circadian genes (CRY2, PER1‐3, and TIMELESS) in a family collection of 36 trios and 79 quads (Sample I), and 10 circadian genes (ARNTL, ARNTL2, BHLHB2, BHLHB3, CLOCK, CRY1, CSNK1D, CSNK1E, DBP, and NR1D1) in an extended family collection of 70 trios and 237 quads (Sample II), which includes the same 114 families but not necessarily the same individuals as Sample I. In Sample II, the Sibling‐Transmission Disequilibrium Test (sib‐tdt) analysis showed nominally significant association of BP with three SNPs within or near the CLOCK gene (rs534654, P = 0.0097; rs6850524, P = 0.012; rs4340844, P = 0.015). In addition, SNPs in the ARNTL2, CLOCK, DBP, and TIMELESS genes and haplotypes in the ARNTL, CLOCK, CSNK1E, and TIMELESS genes showed suggestive evidence of association with several circadian phenotypes identified in BP patients. However, none of these associations reached gene‐wide or experiment‐wide significance after correction for multiple‐testing. A multi‐locus interaction between rs6442925 in the 5′ upstream of BHLHB2, rs1534891 in CSNK1E, and rs534654 near the 3′ end of the CLOCK gene, however, is significantly associated with BP (P = 0.00000172). It remains significant after correcting for multiple testing using the False Discovery Rate method. Our results indicate an interaction between three circadian genes in susceptibility to bipolar disorder. © 2008 Wiley‐Liss, Inc.
Fuzzy logic‐based optimal control of a catalytic reformer
Authors: Manamalli D. , Kanagasabapathy P. , Dhivya K.
Published: January 2008

Catalytic naphtha reforming is an important process carried out in refineries for upgrading low‐octane naphtha to high‐octane gasoline. A reformer can meet many product demands through its wide range of design and flexibility in operation. This work deals with fuzzy logic‐based optimization of a catalytic reformer. This optimization requires an accurate process model that is valid over wide range of operating conditions. In this work, a simple kinetic model has been developed. This model gives the temperature and concentration profiles of three important hydrocarbons (naphthenes, paraffins, and aromatics) across the reactors. A fuzzy logic‐based optimal control scheme has been developed to maximize the aromatics yield, subject to constraints in inlet temperature of the reactors. Four fuzzy logic systems, one in forward path and three in feedback path, have been developed to give setpoints for temperature control loops of the three reactors. Finally, the results are compared with the conventional control scheme and the better performance of fuzzy logic‐based control is validated. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
New generation layered nanocomposites derived from ethylene‐co‐vinyl acetate and naturally occurring graphite
Authors: Jacob George Jinu , Bandyopadhyay Abhijit , Bhowmick Anil K.
Published: January 2008

New ethylene‐co‐vinyl acetate (EVA, with 60% vinyl acetate content) based nanocomposites were prepared with graphites modified by various techniques and a commercially available expanded graphite (EG). The infrared spectra and the surface energy measurements indicated better oxidation and higher surface energy of the graphite modified by mixed acids followed by high temperature treatment (GO). Interlayer space and surface area were increased as a result. EG possessed higher surface area. GO was found to distribute in finer tactoids of average thickness of 25 nm in the matrix, as compared with the unmodified graphite (UG), having average tactoid thickness more than 40 nm along with aggregation. EG also showed finer dispersion in the EVA matrix with some network formation. The dynamic mechanical and the mechanical properties were superior at the 2 wt % concentration of the GO, beyond which the improvement was less, possibly because of aggregation of GO. Greater EVA‐GO interaction at 2 wt % concentration was also supported from the swelling analysis, thermal conductivity, and the thermo‐oxidative degradation data of the hybrid composites. The melt viscosity was lower at 2 wt % GO concentration. EG based nanocomposites registered similar properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Homopolymer and copolymers of 4‐cyanophenyl acrylate with glycidyl methacrylate: Synthesis, characterization, thermal properties, and determination of monomer reactivity ratios
Authors: Vijayanand P. S. , Kato S. , Satokawa S. , Kojima T.
Published: January 2008

The acrylic monomer, 4‐cyanophenyl acrylate (CPA), was synthesized by reacting 4‐cyanophenol dissolved in methyl ethyl ketone (MEK) with acryloyl chloride in the presence of triethylamine as a catalyst. The homopolymer and copolymers were synthesized by using free‐radical techniques. Characterization by FTIR, 1H NMR, and 13C NMR spectroscopic analysis confirms the chemical structure. The solubility of the polymers was tested in various polar and nonpolar solvents. The polydispersity index values of polymers suggest a strong tendency for chain termination by disproportionation in all cases, and the tendency increases with the increasing GMA content in the feed. The initial decomposition temperatures for poly(GMA) (188°C), poly(CPA‐co‐GMA) (280°C), and poly(CPA) (290°C) reveal that the thermal stability of the copolymer increases with an increase in CPA content. DSC analysis showed Tg for poly(CPA) (25°C), poly(GMA) (74°C), and copolymer (0.4007 : 0.5993) (39°C) indicates that Tg of the copolymers decreases with the increase in CPA content. The copolymer composition was determined using 1H NMR spectra. The monomer reactivity ratios were determined by the application of linearization methods such as Fineman‐Ross (r1 = 0.5806, r2 = 0.6651), Kelen‐Tudos (r1 = 0.5442, r2 = 0.6472), and extended Kelen‐Tudos methods (r1 = 0.5372, r2 = 0.6352). The reactivity ratio values indicate that the copolymerization has a tendency to alternation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Novel poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers through atom transfer radical polymerization
Authors: Tharanikkarasu Kannan , Verma Hemant , Jang Wonbong , Lee Seok Kyu , Seo Jongchul , Baek Sanghyun , Han Haksoo
Published: January 2008

Poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers have been synthesized successfully through atom transfer radical polymerization of methyl methacrylate using telechelic bromo‐terminated polyurethane/CuBr/N,N,N,N″,N″‐pentamethyldiethylenetriamine initiating system. As the time increases, the number‐average molecular weight increases linearly from 6400 to 37,000. This shows that the poly methyl methacrylate blocks were attached to polyurethane block. As the polymerization time increases, both conversion and molecular weight increased and the molecular weight increases linearly with increasing conversion. These results indicate that the formation of the tri‐block copolymers was through atom transfer radical polymerization mechanism. Proton nuclear magnetic resonance spectral results of the triblock copolymers show that the molar ratio between polyurethane and poly (methyl methacrylate) blocks is in the range of 1 : 16.3 to 1 : 449.4. Differential scanning calorimetry results show Tg of the soft segment at −35°C and Tg of the hard segment at 75°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Strain rate effect on crystallinity variations in the double yield region of polyethylene
Authors: Manzur Angel
Published: January 2008

The double yield phenomenon was studied using numerous specimens uniaxially deformed up to different elongations of linear low‐density polyethylene samples. Extruded samples prepared under different conditions were deformed at 1, 10, and 50 mm/min. The crystallinity under stressed state was calculated using the wide‐angle X‐ray scattering technique. The crystallinity degrees of the samples without deformation were less than 55%. This parameter, as a function of the elongation, presented a multistep behavior. An increment before the first yield point and a decrement after this point; then, at higher elongation values around the second yield point, another decrement and an abrupt increment. The behavior was more notorious at intermediate and lower strain rates. The results around the second yield point were interpreted in terms of melting of the less perfect crystallites followed by a recrystallization process. These experimental findings show that the partial melting–recrystallization process is one of the main mechanisms of the double yield phenomenon. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Copolymerization of tetracyclododecene or norbornene with styrene in the presence of Ni(II) complex/MAO catalytic system: First example for transition metal catalyzed copolymerization of tetracyclododecene with styrene
Authors: Ogata Kenichi , Nishimura Naoya , Yunokuchi Tomoshige , Toyota Akinori
Published: January 2008

The first example for transition metal catalyzed copolymerization of tetracyclododecene (TD) with styrene as well as of norbornene (NB) with styrene was achieved by the use of nickel(II) complex in the presence of MAO. High cyclic olefin contents of these copolymers were showed by 1H NMR measurements. Their GPC curves are all unimodal and Mw/Mn ratio of both homo‐ and copolymer samples are rather narrow value. These results show that these homo‐ and copolymerization take place at a single active site. The cyclic olefin content in these copolymers could be changed by changing the comonomer feed ratio. TD/styrene copolymers showed higher Tg value than that for NB/styrene copolymers and the Tg value were increases with an increase of TD content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Nondegradative microextrusion of resorbable polyesters for pharmaceutical and biomedical applications: The cases of poly‐lactic‐acid and poly‐caprolactone
Authors: Perale G. , Pertici G. , Giordano C. , Daniele F. , Masi M. , Maccagnan S.
Published: January 2008

In recent years biodegradable polymers, particularly polyesters such as the poly(lactic acid) (PLA) and polycaprolactone (PCL), have gained high interests for their applicability in the biomedical and pharmaceutical fields where they're used for manufacturing various different resorbable devices, from tissue engineering scaffolds to controlled drug release systems. Despite many positive characteristics, processability of these materials still remains a critical issue as they easily tend to degrade during manufacturing. In this article we aimed to assess microextrusion as a nondegradative process for manufacturing PLA and PCL. The results we experimentally obtained, that are hereby presented, set a new point in the on‐going debate on degradation during processing of resorbable polymers as they allow to affirm that microextrusion leaves unmodified molecular weight distributions without producing any evident reductions in mean molecular weight. Microextrusion thus represents a risk‐free high molecular weight polymer processing solution for obtaining nondegraded products within pharmaceutical and biomedical production lines, such as for scaffolds for tissue engineering applications or drug delivery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Glomerular Hypertrophy in Offspring of Subtotally Nephrectomized Ewes
Authors: Brandon Amanda E. , Boyce Amanda C. , Lumbers Eugenie R. , Zimanyi Monika A. , Bertram John F. , Gibson Karen J.
Published: January 2008

We have shown that fetuses whose mothers underwent subtotal nephrectomy (STNx) before pregnancy had high urine flow rates and sodium excretions, but lower hematocrits, plasma chloride, and plasma renin levels compared with controls. To see if these functional differences in utero persist after birth and are the result of altered renal development, we studied 8 lambs born to STNx mothers (STNxL) and 10 controls (ConL) in the second week of life. These lambs were of similar body weights, nose–rump lengths and abdominal girths. Their kidney weights were not different (ConL 36.1 ± 1.9 vs. STNxL 39.8 ± 3.3 g), nor were kidney dimensions or glomerular number (ConL 423,520 ± 22,194 vs. STNxL 429,530 ± 27,471 glomeruli). However, STNxL had 30% larger glomerular volumes (both mean and total, P < 0.01) and there was a positive relationship between total glomerular volume and urinary protein excretion (P < 0.05) in STNxL. Despite this change in glomerular morphology, glomerular filtration rate, tubular function, urine flow, and sodium excretion rates were not different between STNxL and ConL, nor were plasma electrolytes, osmolality, and plasma renin levels. Thus while many of the functional differences seen in late gestation were not present at 1–2 weeks after birth, the alteration in glomerular size and its relationship to protein excretion suggests that exposure to this altered intrauterine environment may predispose offspring of mothers with renal dysfunction to renal disease in adult life. Anat Rec, 291:318–324, 2008. © 2008 Wiley‐Liss, Inc.
Cellular dynamics and tissue interactions of the dura mater during head development
Authors: Gagan Jeffrey R. , Tholpady Sunil S. , Ogle Roy C.
Published: January 2008

During development and growth of the neurocranium, the dura mater regulates events in the underlying brain and overlying skull by the release of soluble factors and cellular activity. Morphogenesis of the cranial bones and sutures is dependent on tissue interactions with the dura mater, which control the size and shape of bones as well as sutural patency. Development of the brain also involves interactions with dura mater: secretion of stromal derived factor 1 (SDF‐1) is a critical event in directing migration of the external granular layer precursors of the cerebellar cortex and the Cajal‐Retzius (CR) cells of the cerebral cortex. The dura mater is also required for growth of the hippocampal dentate gyrus. Wnt1Cre/R26R transgenic reporter mice were used to study the origin and fates of the cells of dura mater during head development. The dura mater of mammals is derived entirely from the cranial neural crest. Beginning around neonatal day 10 (N 10), the dura mater is infiltrated by cells derived from paraxial mesoderm, which later come to predominate. Over the course of infancy, the neural crest–derived cells of the dura mater become sequestered in niche‐like distribution characteristic of stem cells. Simultaneously, dura mater cells underlying the sagittal suture migrate upward into the mesodermally‐derived mesenchyme separating the parietal bones. Although initially the parietal bones are formed entirely from paraxial mesoderm, the cellular composition gradually becomes chimeric and is populated mainly by neural crest–derived cells by N 30. This occurs as a consequence of osteoblastic differentiation at the dura mater interface and intravasation of neural crest–derived osteoclastic and other hematopoietic precursors. The isolated cells of the dura mater are multipotent in vitro, giving rise to osteoblasts, neuronal cells and other derivatives characteristic of cranial neural crest, possibly reflecting the multipotent nature of dura mater cells in vivo. Birth Defects Research (Part C) 81:297–304, 2007. © 2008 Wiley‐Liss, Inc.
Synthetic tissue biology: Tissue engineering meets synthetic biology
Authors: Sia Samuel K. , Gillette Brian M. , Yang Genevieve J.
Published: January 2008

We propose the term “synthetic tissue biology” to describe the use of engineered tissues to form biological systems with metazoan‐like complexity. The increasing maturity of tissue engineering is beginning to render this goal attainable. As in other synthetic biology approaches, the perspective is bottom‐up; here, the premise is that complex functional phenotypes (on par with those in whole metazoan organisms) can be effected by engineering biology at the tissue level. To be successful, current efforts to understand and engineer multicellular systems must continue, and new efforts to integrate different tissues into a coherent structure will need to emerge. The fruits of this research may include improved understanding of how tissue systems can be integrated, as well as useful biomedical technologies not traditionally considered in tissue engineering, such as autonomous devices, sensors, and manufacturing. Birth Defects Research (Part C) 81:354–361, 2007. © 2008 Wiley‐Liss, Inc.
Developmental biology and tissue engineering
Authors: Marga Francoise , Neagu Adrian , Kosztin Ioan , Forgacs Gabor
Published: January 2008

Morphogenesis implies the controlled spatial organization of cells that gives rise to tissues and organs in early embryonic development. While morphogenesis is under strict genetic control, the formation of specialized biological structures of specific shape hinges on physical processes. Tissue engineering (TE) aims at reproducing morphogenesis in the laboratory, i.e., in vitro, to fabricate replacement organs for regenerative medicine. The classical approach to generate tissues/organs is by seeding and expanding cells in appropriately shaped biocompatible scaffolds, in the hope that the maturation process will result in the desired structure. To accomplish this goal more naturally and efficiently, we set up and implemented a novel TE method that is based on principles of developmental biology and employs bioprinting, the automated delivery of cellular composites into a three‐dimensional (3D) biocompatible environment. The novel technology relies on the concept of tissue liquidity according to which multicellular aggregates composed of adhesive and motile cells behave in analogy with liquids: in particular, they fuse. We emphasize the major role played by tissue fusion in the embryo and explain how the parameters (surface tension, viscosity) that govern tissue fusion can be used both experimentally and theoretically to control and simulate the self‐assembly of cellular spheroids into 3D living structures. The experimentally observed postprinting shape evolution of tube‐ and sheet‐like constructs is presented. Computer simulations, based on a liquid model, support the idea that tissue liquidity may provide a mechanism for in vitro organ building. Birth Defects Research (Part C) 81:320–328, 2007. © 2008 Wiley‐Liss, Inc.
Synthesis, Structures and DFT Calculations on Alkaline‐Earth Metal Azide‐Crown Ether Complexes
Authors: Brown Michael D. , Davis Martin F. , Dyke John M. , Ferrante Francesco , Levason William , Ogden J. Steven , Webster Michael
Published: January 2008

The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown‐6)(N3)2(MeOH)], [Sr([15]crown‐5)(N3)2(H2O)], [Ca([15]crown‐5)(N3)2(H2O)] and [Sr([15]crown‐5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including κ1‐, μ‐1,3‐ and linkages via H‐bonded water molecules, in addition to azide ions. The [Ba([18]crown‐6)(N3)2(MeOH)]⋅1/3 MeOH contains dinuclear cations with three μ‐1,3‐NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional theory (DFT). This has allowed the effects of the crystal lattice to be investigated. A study of the MNterminal metal–azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal–azide bond to be investigated in each case. As in our earlier work on alkali metal azide‐crown ether complexes, the bonding in the alkaline‐earth complexes is believed to be predominantly ionic or ion‐dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre, and minimising ligand–ligand repulsions.
Enantioselective Decarboxylation of β‐Keto Esters with Pd/Amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis
Authors: Kukula Pavel , Matoušek Václav , Mallat Tamas , Baiker Alfons
Published: January 2008

The kinetics and mechanisms of one‐pot cascade reactions of racemic β‐keto esters to give chiral ketones in the presence of Pd/C‐chiral amino alcohol catalyst systems were studied. Transformation of 2‐methyl‐1‐tetralone‐2‐carboxylic acid benzyl ester (1) into 2‐methyl‐1‐tetralone (4) in the presence of Pd/C and cinchona alkaloids or ephedrine was chosen as a model reaction. After the first reaction step, the Pd‐catalysed debenzylation of 1 to afford the corresponding β‐keto acid (2), there are two possible reaction routes that may be catalysed by the chiral amino alcohol in solution or by Pd0 sites on the metal surface in cooperation with the adsorbed amino alcohol. The reaction intermediate 2 was synthesized, and the kinetics of decarboxylation were followed by NMR, UV and IR spectroscopy. The studies revealed that the role of Pd is to trigger the reaction series by deprotection of 1. The subsequent dominant reaction route from the racemic β‐keto acid 2 to the chiral ketone 4 is catalysed by the chiral amino alcohol in the liquid phase. It is shown that kinetic resolution of the diastereomeric salt of rac‐2 and the chiral amino alcohol plays a key role in the enantioselection. High enantioselectivity necessitates an amino alcohol/rac‐2 ratio of at least 2. A high ratio favours the formation of 1:1 amino alcohol/acid diastereomeric complexes, and the second amino alcohol molecule may be responsible for the enantioselective protonation of 2 in the diastereomeric complex.
Facile, One‐Step Production of Niacin (Vitamin B3) and Other Nitrogen‐Containing Pharmaceutical Chemicals with a Single‐Site Heterogeneous Catalyst
Authors: Raja Robert , Thomas John Meurig , Greenhill‐Hooper Michael , Ley Steven V. , Almeida Paz Filipe A.
Published: January 2008

Niacin (3‐picolinic acid), which is extensively used as vitamin B3 in foodstuffs and as a cholesterol‐lowering agent, along with other oxygenated products of the picolines, 4‐methylquinoline, and a variety of pyrimidines and pyridazines, may be produced in a single‐step, environmentally benign fashion by combining single‐site, open‐structure, heterogeneous catalysts with a solid source of active oxygen, namely acetyl peroxyborate (APB), in the absence of an organic solvent. The high activities, selectivities, and the relatively mild conditions employed with this single‐site heterogeneous catalyst, coupled with ease of transport, storage, and stability of the solid oxidant, augurs well for the future use of APB in conjunction with other open‐structure, single‐site catalysts for fine‐chemical, pharmaceutical, and agrochemical applications.
Light‐Harvesting Supramolecular Porphyrin Macrocycle Accommodating a Fullerene–Tripodal Ligand
Authors: Kuramochi Yusuke , Satake Akiharu , Itou Mitsunari , Ogawa Kazuya , Araki Yasuyuki , Ito Osamu , Kobuke Yoshiaki
Published: January 2008

Trisporphyrinatozinc(II) (1–Zn) with imidazolyl groups at both ends of the porphyrin self‐assembles exclusively into a light‐harvesting cyclic trimer (N‐(1–Zn)3) through complementary coordination of imidazolyl to zinc(II). Because only the two terminal porphyrins in 1–Zn are employed in ring formation, macrocycle N‐(1–Zn)3 leaves three uncoordinated porphyrinatozinc(II) groups as a scaffold that can accommodate ligands into the central pore. A pyridyl tripodal ligand with an appended fullerene connected through an amide linkage (C60–Tripod) was synthesized by coupling tripodal ligand 3 with pyrrolidine‐modified fullerene, and this ligand was incorporated into N‐(1–Zn)3. The binding constant for C60–Tripod in benzonitrile reached the order of 108 M−1. This value is ten times larger than those of pyridyl tetrapodal ligand 2 and tripodal ligand 3. This behavior suggests that the fullerene moiety contributes to enhance the binding of C60–Tripod in N‐(1–Zn)3. The fluorescence of N‐(1–Zn)3 was almost completely quenched (≈97 %) by complexation with C60–Tripod, without any indication of the formation of charge‐separated species or a triplet excited state of either porphyrin or fullerene in the transient absorption spectra. These observations are explained by the idea that the fullerene moiety of C60–Tripod is in direct contact with the porphyrin planes of N‐(1–Zn)3 through fullerene–porphyrin π–π interactions. Thus, C60–Tripod is accommodated in N‐(1–Zn)3 with a π–π interaction and two pyridyl coordinations. The cooperative interaction achieves a sufficiently high affinity for quantitative and specific introduction of one equivalent of tripodal guest into the antenna ring, even under dilute conditions (≈10−7 M) in polar solvents such as benzonitrile. Additionally, complete fluorescence quenching of N‐(1–Zn)3 when accommodating C60–Tripod demonstrates that all of the excitation energy collected by the nine porphyrins migrates rapidly over the macrocycle and then converges efficiently on the fullerene moiety by electron transfer.
ChemInform Abstract: Boron Cluster Cations: Transition from Planar to Cylindrical Structures.
Authors: Oger Esther , Crawford Nathan R. M. , Kelting Rebecca , Weis Patrick , Kappes Manfred M. , Ahlrichs Reinhart
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: High‐Pressure Synthesis and Structures of New Barium Chromium Sulfides, BaCr4S7 and Ba2Cr5S10, with New Type Face‐Sharing CrS6 Structure Units.
Authors: Fukuoka Hiroshi , Miyaki Yuji , Yamanaka Shoji
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: High‐Pressure δ‐Al(OH)3 and δ‐AlOOH Phases and Isostructural Hydroxides/Oxyhydroxides: New Structural Insights from High‐Resolution 1H and 27 NMR.
Authors: Xue Xianyu , Kanzaki Masami
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Pressure‐Induced Splitting and Buckling of Cu—O Chains in the Low‐Dimensional Structure of SrCuO2.
Authors: Zhang Fuxiang , Wang Jianwei , Becker Udo , Lian Jie , Hu Jingzhu , Saxena Surendra , Ewing Rodney C.
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Hydrogen Encapsulation in a Silicon Clathrate Type I Structure: Na5.5(H2)2.15Si46: Synthesis and Characterization.
Authors: Neiner Doinita , Okamoto Norihiko L. , Condron Cathie L. , Ramasse Quentin M. , Yu Ping , Browning Nigel D. , Kauzlarich Susan M.
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis, Structural Characterization, and Reactivity of Organolanthanides Derived from a New Chiral Ligand, (R)‐Bis(pyrrol‐2‐ylmethyleneamino)‐1,1′‐binaphthyl.
Authors: Xiang Li , Wang Qiuwen , Song Haibin , Zi Guofu
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: 5,5‐Dimethyl‐2‐phenylamino‐2‐oxazoline as an Effective Chiral Auxiliary for Asymmetric Alkylations.
Authors: Le Thanh Nguyen , Nguyen Quynh Pham Bao , Kim Jae Nyoung , Kim Taek Hyeon
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Reaction Between ortho‐Hydroxy Aromatic Aldehydes and Dialkyl Acetylenedicarboxylates in the Presence of Silica Gel in Solvent‐Free Conditions.
Authors: Noshiranzadeh Nader , Ramazani Ali
Published: January 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.