bluuebunny/crossref_metadata_2025 huggingface dataset:
On the processor scheduling problem in time warp synchronization
Authors: Quaglia Francesco , Cortellessa Vittorio
Published: May 2003

Time Warp is a synchronization mechanism for parallel/distributed simulation. It allows logical processes (LPs) to execute events without the guarantee of a causally consistent execution. Upon the detection of a causality violation, rollback procedures recover the state of the simulation to a correct value. When a rollback occurs there are two primary sources of performance loss: (1) CPU time must be spent for the execution of the rollback procedures and (2) waste of CPU time arises from the invalidation of event executions. In this paper we present a general framework for the problem of scheduling the next LP to be run on a processor in Time Warp simulations. The framework establishes a class of scheduling algorithms having the twofold aim to keep low the CPU time for the execution of the rollback procedures and also to guarantee low waste of time due to event executions invalidated by rollback. The combination of these two aims should actually lead to short completion time of Time Warp simulations.We collocate existing scheduling algorithms within the framework, pointing out how they miss previous aims, at least partially. Then we instantiate a Window-based Grain Sensitive (WGS) scheduling algorithm relying on the framework, which pursues the above twofold aim. We also identify the proper conditions, associated with the simulation model execution, under which any algorithm exploiting the framework structure is expected to benefit the performance of the Time Warp mechanism. Empirical evidence from an experimental study of WGS on classical benchmarks and on a mobile communication system simulation fully confirms the theoretical outcomes.
Rapid model parameterization from traffic measurements
Authors: Lan Kun-Chan , Heidemann John
Published: May 2003

The utility of simulations and analysis heavily relies on good models of network traffic. While network traffic constantly is changing over time, existing approaches typically take years from collecting trace, analyzing the data to finally generating and implementing models. In this paper, we describe approaches and tools that support rapid parameterization of traffic models from live network measurements. Rather than treating measured traffic as a time-series of statistics, we utilize the traces to estimate end-user behavior and network conditions to generate application-level simulation models. We also show multi-scaling analytic techniques are helpful for debugging and validating the model. To demonstrate our approaches, we develop structural source-level models for web and FTP traffic and evaluate their accuracy by comparing the outputs of simulation against the original trace. We also compare our work with existing traffic generation tools and show our approach is more flexible in capturing the heterogeneity of traffic. Finally, we automate and integrate the process from trace analysis to model validation for easy model parameterization from new data.
Modeling, simulation, sensitivity analysis, and optimization of hybrid systems
Authors: Barton Paul I. , Lee Cha Kun
Published: May 2003

Hybrid (discrete/continuous) systems exhibit both discrete state and continuous state dynamics which interact to such a significant extent that they cannot be decoupled and must be analyzed simultaneously. We present an overview of the work that has been done in the modeling, simulation, sensitivity analysis, and optimization of hybrid systems, paying particular attention to the interaction between discrete and continuous dynamics. A concise intuitive framework for hybrid system modeling is presented, together with discussions on robust state event location, transfer functions of the continuous state at discontinuities, parametric sensitivity analysis of hybrid systems, and challenges in optimization.
Rearchitecting the UML infrastructure
Authors: Atkinson Colin , Kühne Thomas
Published: May 2003

Metamodeling is one of the core foundations of computer-automated multiparadigm modeling. However, there is currently little agreement about what form the required metamodeling approach should take and precisely what role metamodels should play. This article addresses the problem by first describing some fundamental problems in the industry's leading metamodeling technology, the UML framework, and then explaining how this framework could be rearchitected to overcome these problems. Three main issues are identified in the current framework: the
dual classification
problem arising from the need to capture both the logical and physical classification of model elements, the
class/object duality
problem arising from the need to capture both the classlike and objectlike facets of some model elements, and the
replication of concepts
problem arising from the need to define certain concepts multiple times. Three main proposals for rearchitecting the UML framework to overcome these problems are then presented: the separation of logical and physical classification dimensions, the unification of the class and object facets of model elements, and the enhancement of the instantiation mechanism to allow definitions to transcend multiple levels. The article concludes with a discussion of other practical issues involved in rearchitecting the UML modeling framework in the proposed way.
Efficient multicast stream authentication using erasure codes
Authors: Park Jung Min , Chong Edwin K. P. , Siegel Howard Jay
Published: May 2003

We describe a novel method for authenticating multicast packets that is robust against packet loss. Our focus is to minimize the size of the communication overhead required to authenticate the packets. Our approach is to encode the hash values and the signatures with Rabin's Information Dispersal Algorithm (IDA) to construct an authentication scheme that amortizes a single signature operation over multiple packets. This strategy is especially efficient in terms of space overhead, because just the essential elements needed for authentication (i.e., one hash per packet and one signature per group of packets) are used in conjunction with an erasure code that is space optimal. Using asymptotic techniques, we derive the authentication probability of our scheme using two different bursty loss models. A lower bound of the authentication probability is also derived for one of the loss models. To evaluate the performance of our scheme, we compare our technique with four other previously proposed schemes using empirical results.
A propositional policy algebra for access control
Authors: Wijesekera Duminda , Jajodia Sushil
Published: May 2003

Security-sensitive environments protect their information resources against unauthorized use by enforcing access control mechanisms driven by access control policies. Due to the need to compare, contrast, and compose such protected information resources, access control policies regulating their manipulation need to be compared, contrasted, and composed. An algebra for manipulating such access control policies at a higher (propositional) level, where the operations of the algebra are abstracted from their specification details, is the subject of this paper. This algebra is applicable to policies that have controlled nondeterminism and
all or nothing
assignments of access privileges in their specification. These requirements reflect current practices in discretionary and role-based access control models. Therefore, the proposed algebra can be used to reason about role-based access control policies combined with other forms of discretionary policies. We show how to use algebraic identities to reason about consistency, completeness, and determinacy of composed policies using similar properties of their constituents.
A SMART scheduler for multimedia applications
Authors: Nieh Jason , Lam Monica S.
Published: May 2003

Real-time applications such as multimedia audio and video are increasingly populating the workstation desktop. To support the execution of these applications in conjunction with traditional non-real-time applications, we have created SMART, a Scheduler for Multimedia And Real-Time applications. SMART supports applications with time constraints, and provides dynamic feedback to applications to allow them to adapt to the current load. In addition, the support for real-time applications is integrated with the support for conventional computations. This allows the user to prioritize across real-time and conventional computations, and dictate how the processor is to be shared among applications of the same priority. As the system load changes, SMART adjusts the allocation of resources dynamically and seamlessly. It can dynamically shed real-time computations and regulate the execution rates of real-time tasks when the system is overloaded, while providing better value in underloaded conditions than previously proposed schemes.We have implemented SMART in the Solaris UNIX operating system and measured its performance against other schedulers commonly used in research and practice in executing real-time, interactive, and batch applications. Our experimental results demonstrate SMART's superior performance over fair queueing and UNIX SVR4 schedulers in supporting multimedia applications.
Rectilinear block placement using B*-trees
Authors: Wu Guang-Ming , Chang Yun-Chih , Chang Yao-Wen
Published: May 2003

Due to the layout complexity in modern VLSI designs, integrated circuit blocks may not be rectangular. However, literature on general rectilinear block placement is still quite limited. In this article, we present approaches for handling the placement for arbitrarily shaped rectilinear blocks using B*-trees [Chang et al. 2000]. We derive the feasibility conditions of B*-trees to guide the placement of rectilinear blocks. Experimental results show that our algorithm achieves optimal or near-optimal block placement for benchmarks with various shaped blocks.
Region proximity in metric spaces and its use for approximate similarity search
Authors: Amato Giuseppe , Rabitti Fausto , Savino Pasquale , Zezula Pavel
Published: May 2003

Similarity search structures for metric data typically bound object partitions by ball regions. Since regions can overlap, a relevant issue is to estimate the proximity of regions in order to predict the number of objects in the regions' intersection. This paper analyzes the problem using a probabilistic approach and provides a solution that effectively computes the proximity through realistic heuristics that only require small amounts of auxiliary data. An extensive simulation to validate the technique is provided. An application is developed to demonstrate how the proximity measure can be successfully applied to the approximate similarity search. Search speedup is achieved by ignoring data regions whose proximity to the query region is smaller than a user-defined threshold. This idea is implemented in a metric tree environment for the similarity range and "nearest neighbors" queries. Several measures of efficiency and effectiveness are applied to evaluate proposed approximate search algorithms on real-life data sets. An analytical model is developed to relate proximity parameters and the quality of search. Improvements of two orders of magnitude are achieved for moderately approximated search results. We demonstrate that the precision of proximity measures can significantly influence the quality of approximated algorithms.
Telefile
Authors: Sanders M.
Published: May 2003

The development of an on-line computer system for a savings bank institution is traced from the early conceptual needs of the bank to the consummation of design by The Teleregister Corporation. Both bank and equipment criteria are specified which led to the development of the Telefile System of The Teleregister Corporation.Operation of the on-line and off-line programs are described and statistics are cited for reliability and performance of the system. Benefits to the bank are discussed from the banker's point of view; an indication of future trends in the on-line savings bank field is also discussed.
Indexing and the A-notation
Authors: Barnett M. P.
Published: May 2003

Some methods of indexing sequentially stored elements of sparse multi-dimensional arrays are described in the scheme A notation.
The height of a random binary search tree
Authors: Reed Bruce
Published: May 2003

LetHnbe the height of a random binary search tree onnnodes. We show that there exist constants α = 4.311… and β = 1.953… such thatE(Hn) = αln n− βln ln n+O(1), We also show thatVar(Hn) =O(1).
Privacy through pseudonymity in user-adaptive systems
Authors: Kobsa Alfred , Schreck Jörg
Published: May 2003

User-adaptive applications cater to the needs of each individual computer user, taking for example users' interests, level of expertise, preferences, perceptual and motoric abilities, and the usage environment into account. Central user modeling servers collect and process the information about users that different user-adaptive systems require to personalize their user interaction.Adaptive systems are generally better able to cater to users the more data their user modeling systems collect and process about them. They therefore gather as much data as possible and "lay them in stock" for possible future usage. Moreover, data collection usually takes place without users' initiative and sometimes even without their awareness, in order not to cause distraction. Both is in conflict with users' privacy concerns that became manifest in numerous recent consumer polls, and with data protection laws and guidelines that call for parsimony, purpose-orientation, and user notification or user consent when personal data are collected and processed.This article discusses security requirements to guarantee privacy in user-adaptive systems and explores ways to keep users anonymous while fully preserving personalized interaction with them. User anonymization in personalized systems goes beyond current models in that not only users must remain anonymous, but also the user modeling system that maintains their personal data. Moreover, users' trust in anonymity can be expected to lead to more extensive and frank interaction, hence to more and better data about the user, and thus to better personalization. A reference model for pseudonymous and secure user modeling is presented that meets many of the proposed requirements.
Get your product used in anger!
Authors: Myhill Carl
Published: May 2003

Some months ago, Carl wrote to an email list about a bike light and a new requirement that he had discovered after using the light "in anger." "Anger!" I thought. "What a perfect topic for The Whiteboard! Use a product, get mad about its design, and take advantage of your anger to derive important but hidden requirements." It was only on receiving Carl's first draft that I discovered he wasn't talking about anger at all. In the UK, to use something "in anger" means to use it for real. But in fact, Carl does get angry about bad design. And I think that's a good thing.---
Elizabeth Buie
The eXtensible Rule Markup Language
Authors: Lee Jae Kyu , Sohn Mye M.
Published: May 2003

XRML explicates the rules implicitly embedded in Web pages, enabling software agents to process the rules automatically.
Affinity to infinity in peer-to-peer knowledge platforms
Authors: Tiwana Amrit
Published: May 2003

Adapting the social paradigm of face-to-face human communication, they promote ad hoc knowledge exchange among peers, leveraging individual expertise at the periphery of the network.
Real-time taxi dispatching using Global Positioning Systems
Authors: Liao Ziqi
Published: May 2003

Hailing a taxi in Singapore now employs the latest positioning technology for matching passengers with the nearest available cabs, thus achieving greater productivity and customer satisfaction.
Life beyond the bubbles
Authors: Tsichritzis Dennis
Published: May 2003

The technology, Internet, bandwidth, and content bubbles all burst, scattering not only broken dreams but new seeds of innovation and enterprise.
Introduction
Authors: Rubin Aviel D.
Published: May 2003

In the time span of just a few years, wireless local area networking went from being a novelty to revolutionizing the way many organizations connect their computers. Visit any major department store, hospital, or office building, and you will encounter 802.11 cards in all of the PCs and access points hanging from the ceiling. The speed with which wireless networking has caught on is not surprising, as 802.11b offers up to 11Mbps of bandwidth, and a range of several hundred feet. Newer standards, such as 802.11g, promise five times the speed. Multiple wireless access points can be easily installed on the same network to increase the coverage area, so that an entire building can be easily connected. Conversely, wiring buildings with Ethernet is expensive and limits the locations from which networked computers can be used.
Protection against methacholine-induced bronchospasm: salbutamol pMDIversusClickhaler® DPI
Authors: Newhouse M.T. , Patel P. , Parry-Billings M.
Published: May 2003

Passive dry-powder inhalers (DPIs) have been developed as an alternative to pressurised metered-dose inhalers (pMDIs) to improve aerosol delivery on inhalation and eliminate the need for propellants. However, new DPI formulations of generic drugs must be rigorously compared with conventional pMDI therapy.

This randomised, double-blind, double-dummy, placebo-controlled, seven-way crossover study evaluated bronchoprotection from methacholine challenge in order to compare a novel salbutamol DPI (Clickhaler®) with a reference salbutamol pMDI (Ventolin®). Adult asthma patients with airway hyperresponsiveness to methacholine (provocative concentration of methacholine causing a 20% fall in the forced expiratory volume in one second (PC20) <4 mg·mL−1) were treated on separate days with 0, 100, 200 or 400 µg of salbutamolviathe DPI or pMDI. Methacholine challenge was performed before and after salbutamol treatment and the PC20ratios analysed by Finney's bioassay to test for therapeutic equivalence of the inhalers.

Eighteen patients completed the study and showed significant dose-related responses to salbutamol. The relative potency of DPI:pMDI was 1.29 (90% confidence interval 1.04–1.63). There were no treatment differences in safety (cardiac frequency, blood pressure, adverse events).

Methacholine-challenge methodology provides a sensitive bioassay and has demonstrated therapeutic equivalence of the salbutamol Clickhaler® dry-powder inhaler with the conventional salbutamol pressurised metered-dose inhaler.
Social position and mortality from respiratory diseases in males and females
Authors: Prescott E. , Godtfredsen N. , Vestbo J. , Osler M.
Published: May 2003

Although social differences in respiratory diseases are considerable, few studies have focused on this disease entity using mortality as an outcome. Does mortality from respiratory disease, including chronic obstructive pulmonary disease (COPD) differ with social position measured by education, income, housing and employment grade?

The study population consisted of 26,392 males and females from pooling of two population studies in the Copenhagen area. Data was linked with information from social registers in Statistics Denmark. The relationship between socioeconomic factors and risk of death from respiratory disease and COPD was assessed with an average duration of follow-up of 12 yrs.

Education was strongly associated with respiratory mortality in both sexes. The association was stronger in later birth cohorts comparing the highest level of education (>11 yrs) with the lowest (<8 yrs). Although smoking rates were inversely associated with the level of education, the social gradient was not affected by adjustment for smoking. In males, but not in females, there was an additional effect of other indicators of social position,i.e.employment grade (white collarversusblue collar), household income, housing conditions (less than one person per roomversusmore), and cohabitation (cohabitingversusliving alone). Similar results were found for mortality from COPD.

The results confirm the existence of a strong social gradient in respiratory mortality and chronic obstructive pulmonary disease, which is independent of smoking and is stronger in males. Social disadvantage is a potentially avoidable cause of death from respiratory disease and further research is needed to explain the excess risk in the socioeconomically disadvantaged.
Pulmonary perfusion quantified by electron-beam computed tomography: effects of hypoxia and inhaled NO
Authors: Jones A.T. , Hansell D.M. , Evans T.W.
Published: May 2003

Patients with acute lung injury may benefit from the manipulation of pulmonary blood flow using inhaled nitric oxide (iNO) to optimise ventilation/perfusion matching. Current techniques for studying changes in regional pulmonary perfusion are difficult to apply clinically. This study therefore investigated the potential of electron-beam computed tomography (EBCT) to quantify the effects of hypoxia and iNO on regional pulmonary perfusion in five healthy subjects.

Contrast-enhanced sections were obtained sequentially under conditions of normoxia, hypoxia (fractional concentration of oxygen in inspired gas (FI,O2) 0.12) and hypoxia, with iNO (14.8 parts per million (ppm)) administered during inspiration in the supine position. Regions of interest were placed along the nondependent to dependent axis and values for relative perfusion derived.

Under normoxic conditions a vertical gradient of perfusion existed, which became less apparent due to increased perfusion in nondependent regions after the induction of hypoxia (FI,O20.12). The addition of iNO (FI,O20.12 and NO 14.8 ppm) increased perfusion in all regions of the lung section, suggesting redistribution of pulmonary perfusion from other regions of the lung. Absolute values of perfusion were comparable to those documented with existing techniques.

The use of a high spatial-resolution technique confirmed the presence of marked perfusion heterogeneity between anatomically close regions of lung.
Structural mimicry in the phage [phis]21 N peptide–boxB RNA complex
Authors: CILLEY CHRISTOPHER D. , WILLIAMSON JAMES R.
Published: May 2003

We determined the solution structure of a 22-amino-acid peptide from the amino-terminal domain of the bacteriophage [phis]21 N protein in complex with its cognate 24-mer boxB RNA hairpin using heteronuclear magnetic resonance spectroscopy. The N peptide binds as an α-helix and interacts predominately with the major groove side of the 5′ half of the boxB RNA stem-loop. This binding interface is defined by surface complementarity of polar and nonpolar interactions, and little sequence-specific recognition. The [phis]21 boxB loop (CUAACC) has hydrogen bond and backbone torsions typical of the “U-turn” motif, as well as base stacking of the last 4 nt, and a hydrogen bonded C:C pair closing the loop. The exposed face of the [phis]21 boxB loop, in complex with the N peptide, is strikingly similar to the GNRA tetraloop-like folds of the related λ and P22 bacteriophage N peptide–boxB RNA complexes. The N peptide–boxB complexes of the various phage, while individually distinct, provide similar structural features for interactions with the Escherichia coli host factors to enable antitermination.
Single‐Crystalline Scroll‐Type Nanotube Arrays of Copper Hydroxide Synthesized at Room Temperature
Authors: Zhang W. , Wen X. , Yang S. , Berta Y. , Wang Z.L.
Published: May 2003

A novel nanolayer‐rolled tubular structure of Cu(OH)2 has been grown in solution at ambient temperature and pressure. Significantly, the Cu(OH)2 nanotubes are phase‐pure single crystallites and are arrayed uniformly on copper substrates (see Figure). The reaction conditions for the fabrication of the nanotube arrays are examined and possible growth mechanisms are discussed.
Triacylglycerol and phospholipid fatty acids of the silverleaf whitefly: Composition and biosynthesis
Authors: Buckner James S. , Hagen Marcia M.
Published: May 2003

The identification and composition of the fatty acids of the major lipid classes (triacylglycerols and phospholipids) within Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) nymphs were determined. Comparisons were made to fatty acids from the internal lipids of B. argentifolii adults. The fatty acids, as ester derivatives, were analyzed by capillary gas chromatography (CGC) and CGC‐mass spectrometry (MS). All lipid classes contained variable distributions of eight fatty acids: the saturated fatty acids, myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), arachidic acid (20:0); the monounsaturated fatty acids, palmitoleic acid (16:1), oleic acid (18:1); the polyunsaturated fatty acids, linoleic acid (18:2), linolenic acid (18:3). Fourth instar nymphs had 5–10 times the quantities of fatty acids as compared to third instar nymphs and 1–3 times the quantities from adults. The fatty acid quantity differences between fourth and third instar nymphs were related to their size and weight differences. The percentage compositions for fatty acids from each lipid class were the same for the pooled groups of third and fourth instar nymphs. For nymphs and adults, triacylglycerols were the major source of fatty acids, with 18:1 and 16:0 acids as major components and the majority of the polyunsaturated fatty acids, 18:2 and 18:3 were present in the two phospholipid fractions, phosphatidylethanolamine and phosphatidylcholine. Evidence was obtained that whiteflies indeed synthesize linoleic acid and linolenic acid de novo: radiolabel from [2‐14C] acetate was incorporated into 18:2 and 18:3 fatty acids of B. argentifolii adults and CGC‐MS of pyrrolidide derivatives established double bonds in the Δ9,12 and Δ9,12,15 positions, respectively. Arch. Insect Biochem. Physiol. 53:66–79, 2003. Published 2003 Wiley‐Liss, Inc.
Induction of glutathione S‐transferases activities in Drosophila melanogaster exposed to phenol
Authors: Shen S. , Chien Y. , Chien C.
Published: May 2003

Studying the toxic effects of long‐term exposing fruit flies to phenol is the object of this study. The induction of the glutathione S‐transferases enzymatic activities, the change in the amount of mRNA related to phenol exposure, the change in survival rate of adult fruit flies, and the chemical interaction between phenol and benzene were the problems to be investigated. Glutathione S‐transferases were separated by affinity chromatography and the mRNAs levels were quantified by reverse‐transcription polymerase chain reaction. Long‐term feeding phenol to wild type fruit flies had caused some toxic effects included increasing the resistance to phenol toxicity, lowering the benzene toxicity, and induction of glutathione S‐transferases enzymatic activities. But no significant change in the amount of glutathione S‐transferases GstD1 and GstD5 mRNAs had occurred. From these results, we concluded that fruit flies could develop resistance to phenol by decreasing its toxicity; phenol was a inducer of glutathione S‐transferases; phenol could increase the glutathione S‐transferases enzymatic activities by increasing the amount of proteins; phenol exposure could decrease the benzene toxicity; no new glutathione S‐transferase isozyme subunit was induced; and the level of GstD1 and GstD5 mRNAs did not significantly increase in phenol‐treated strain. Arch. Insect Biochem. Physiol. 53:80–91, 2003. © 2003 Wiley‐Liss, Inc.
EphA4 provides repulsive signals to developing cochlear ganglion neurites mediated through ephrin‐B2 and ‐B3
Authors: Brors Dominik , Bodmer Daniel , Pak Kwang , Aletsee Christoph , Schäfers Maria , Dazert Stefan , Ryan Allen F.
Published: May 2003

The ephrins and Eph receptors make up two large families of bi‐directional signaling molecules that are known to play a role in the development of the nervous system. Recently, expression of EphA4 in the developing cochlea was shown, with strong expression in cells lining the osseous spiral lamina (OSL) through which afferent dendrites must pass to reach the organ of Corti (OC). It was also demonstrated that ephrin‐B2 and ‐B3, both of which are known to interact with EphA4, are expressed by spiral ganglion (SG) neurons. To investigate the functional role of EphA4 in the development of inner ear neurons, neonatal rat SG explants were cultured for 72 hours on uniformly coated surfaces or near stripes of EphA4/IgG‐Fc‐chimera. Control explants were cultured on or near IgG‐Fc and EphA1/IgG‐Fc‐chimera. To assess the roles of ephrin‐B2 and ‐B3 in EphA4 signaling, SG explants were cultured with or without anti‐ephrin‐B2 and/or ‐B3 blocking antibodies. Growth patterns of SG neurites at the border of EphA4 receptor stripes showed repulsion, characterized by turning, stopping and/or reversal. In the case of IgG‐Fc and EphA1, the neurites grew straight onto the stripes. Treatment with either anti‐ephrin‐B2 or ‐B3 blocking antibodies significantly reduced the repulsive effect of an EphA4 stripe. Moreover, when both antibodies were used together, neurites crossed onto EphA4 stripes with no evidence of repulsion. The results suggest that EphA4 provides repulsive signals to SG neurites in the developing cochlea, and that ephrin‐B2 and ‐B3 together mediate this response. J. Comp. Neurol. 462:90–100, 2003. © 2003 Wiley‐Liss, Inc.
Differential expression of angiogenic and vasodilatory factors by invasive trophoblast giant cells depending on depth of invasion
Authors: Hemberger Myriam , Nozaki Tadashige , Masutani Mitsuko , Cross James C.
Published: May 2003

The uterine bed undergoes remarkable changes during pregnancy, including proliferation and decidualization of the uterine stroma and remodeling and angiogenesis of the maternal vasculature. Fetal‐derived trophoblast giant cells invade into the uterus where they gain access to the maternal blood circulation to ensure sufficient nutrient supply of the embryo. In serial sections through early‐ to mid‐gestation conceptuses, we have determined the exact distance of trophoblast invasion and the expression of angiogenic, vasodilatory, and anticoagulative factors that are likely to influence remodeling and redirection of the maternal circulatory system. Trophoblast derivatives were detected at a distance as far as ∼300 μm from the placental border, where they are allocated exclusively along the mid‐line of the decidua. The farthest invading cells characteristically expressed proliferin and proliferin‐related protein, hormones that affect endothelial cell migration and vascularization. Occasionally, these cells replaced the normal vascular endothelium and acquired a “pseudo‐endothelial” shape. Complete vascular disintegration was observed 50–80 μm outside of the placental border where maternal blood was entirely lined by a trophoblast giant cell‐derived network of blood sinuses. This transition in blood space lining correlated with trophoblast expression of various vasodilatory and anticoagulative factors that are likely to promote blood flow toward the placenta. Analysis of teratocarcinoma‐like tumors demonstrated that trophoblast giant cell‐induced promotion and redirection of blood flow is not restricted to the uterine environment. These results show that trophoblast giant cells have the intrinsic capacity to attract and increase blood flow and to gradually displace the vascular endothelium resulting in the formation of canals entirely lined by trophoblast cells. Developmental Dynamics 227:185–191, 2003. © 2003 Wiley‐Liss, Inc.
Differential expression of β3 integrin gene in chick and mouse cranial neural crest cells
Authors: Pietri Thomas , Thiery Jean Paul , Dufour Sylvie
Published: May 2003

RNA in situ hybridization on early chicken embryos revealed that the β3 integrin gene started to be expressed after Hamburger and Hamilton (HH) stage 6 in the presumptive epidermis adjacent to the neural plate, before closure of the neural tube. The β3 integrin gene was also strongly expressed in cephalic neural crest cells at the same stage in which they begin their migration but disappeared progressively in these cells along the route they take to the branchial arches. The gene was weakly expressed in the differentiating cranial neural crest cells. The αVβ3 integrin protein complex was also mainly detected in the migratory cephalic neural crest cells. However, during early mouse embryogenesis and in contrast to the chick, the β3 integrin gene was expressed in the foregut diverticulum and in the heart and not in the cephalic neural crest cells. Therefore, the difference in the β3 integrin expression suggests that mouse and chicken cranial neural crest cells may have distinct integrin requirements during their ontogenesis. Developmental Dynamics 227:309–313, 2003. © 2003 Wiley‐Liss, Inc.
Thyroid transcription factor (TTF) ‐1 regulates the expression of midkine (MK) during lung morphogenesis
Authors: Reynolds Paul R. , Mucenski Michael L. , Whitsett Jeffrey A.
Published: May 2003

Midkine (MK) is a 13‐kDa heparin‐binding growth factor that is thought to mediate developmental processes, including vasculogenesis, cell migration, and proliferation in various organs. To determine whether MK plays a role during lung morphogenesis, immunostaining for MK was assessed in mouse lung from embryonic day (E) 13 to postnatal day (PN) 24. MK was detected in mesenchymal and respiratory epithelial cells of the peripheral mouse lung from E13.0 to E15.5. From E18.5 to PN1, MK was observed primarily in epithelial cells lining conducting airways and peripheral lung saccules. By PN10, expression was no longer observed in respiratory epithelial cells but was readily detected in small blood vessels in the alveolar region of the lung. Although most respiratory epithelial cells uniformly expressed MK before E13.0, MK was restricted to subsets of cells by E18.5, colocalizing with the Clara cell secretory protein (CCSP) marker in conducting airways and with pro‐SPC, a marker specific for alveolar type II pneumocytes. By PN10, MK was not detected in respiratory epithelial cells of the conducting airways and was closely associated with capillary networks. The sites of intense MK staining in the respiratory epithelial cells correlated with sites of expression of thyroid transcription factor (TTF) ‐1, a transcription factor regulating formation and gene expression in the lung parenchyma. TTF‐1 enhanced transcription of the mouse MK gene promoter, acting on TTF‐1 regulatory elements located in the 5′‐region of the gene. Furthermore, MK expression was not detected in lungs of TTF‐1 null mice. TTF‐1 regulates expression of MK in the lung. The temporal/spatial distribution of midkine is consistent with a potential role in paracrine signaling during lung morphogenesis. Developmental Dynamics 227:227–237, 2003. © 2003 Wiley‐Liss, Inc.
Enantiomerically Pure (R)‐ and (S)‐15‐Hydroxy[2.2]paracyclophane‐4‐carbaldehyde (iso‐FHPC): A Novel Parent Compound for Planar Chiral Ligands
Authors: Rozenberg Valeria I. , Antonov Dmitrii Yu. , Sergeeva Elena V. , Vorontsov Evgenii V. , Starikova Zoya A. , Fedyanin Ivan V. , Schulz Christian , Hopf Henning
Published: May 2003

The planar chiral 15‐hydroxy[2.2]paracyclophane‐4‐carbaldehyde (2, iso‐FHPC) was synthesized and resolved via its Schiff bases 8 by using the enantiomers of α‐phenylethylamine. The absolute configurations of the enantiomers of 2 were determined by a combined X‐ray diffraction and chemical correlation study. Derivatives 9, the first representatives of cyclophane‐derived aminophenols with a pseudo‐gem arrangement of the functional groups were synthesized. All new chiral compounds can be regarded as prospective ligands for asymmetric synthesis and catalysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Laser Flash Photolysis of Disulfonyldiazomethanes: Partitioning between Hetero‐Wolff Rearrangement and Intramolecular Carbene Oxidation by a Sulfonyl Group
Authors: Bucher Götz , Strehl Anja , Sander Wolfram
Published: May 2003

Laser flash photolysis of bis(phenylsulfonyl)diazomethane (1a) and ditosyldiazomethane (1b) leads to the formation of sulfonylsulfenes 8a/8b (λmax = 310 nm). Non‐first‐order kinetics and non‐linear Stern−Volmer behavior suggest the formation of another transient species also absorbing at λ = 310 nm. Based on the results of DFT calculations, these species are tentatively identified as dithiocarbonate S,S,S′‐trioxides 12a/b, which are formed from the oxathiirene S‐oxides 9a/b. The latter compounds bear the characteristics of masked carbenes (τ estimated as 700 ps) and are quenched by methanol and cyclooctene. Singlet disulfonylcarbenes 2a/b are not predicted to be minima, since all attempts at optimizing the geometry of 2a led to 9a instead. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Propyne Iminium Salts and Phosphorus(III) Nucleophiles: Synthesis of (3‐Morpholinoallenyl)phosphanes and ‐phosphane Oxides or 1‐(Morpholinopropargyl)phosphanes and ‐phosphonates
Authors: Reisser Martin , Maier Alexandra , Maas Gerhard
Published: May 2003

Treatment of 4‐(1,3‐diphenyl‐l‐propynylidene)morpholinium triflate (1a) with the neutral phosphorus nucleophiles Me3Si−PPh2, Me3Si−P(Ph)C5H11, and Me3SiO−PPh2 affords (3‐morpholinoallenyl)phosphanes 4 and 5 and (3‐morpholinoallenyl)phosphane oxide 11, respectively. In contrast to these conjugate addition reactions at the ambident propyne iminium moiety of 1a, nucleophilic attack by Me3Si−PEt2 and Me3SiO−P(OEt)2 takes place at the iminium function and gives (1‐morpholinopropargyl)phosphane 6 and (1‐morpholinopropargyl)phosphonate 12, respectively. Propyne iminium salt 1b reacts with Me3Si−PPh2 to form (3‐morpholino‐1,3‐butadienyl)phosphane oxide 8. The bis(donor)‐substituted allene 4 is transformed by oxidation of the phosphorus substituent into the push‐pull substituted allenylphosphane oxide 11. Treatment of allene 4 with elemental sulfur results in the formation of betaine 16, which undergoes [3+2] cycloaddition reactions with acetylenic esters to afford 5‐benzylidene‐4,5‐dihydrothiophenes 17 and 18. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Signaling to and from radial glia
Authors: Campbell Kenneth
Published: May 2003

Radial glia represent the major glial cell type in the developing CNS and perform many essential functions, which range from acting as neural precursors to providing physical substrates for newborn neurons to migrate on. Previous work has shown that cell‐cell signaling is important for the development of the radial glial phenotype. In particular, signals from newborn neurons appear to contribute significantly to the formation of this cell type. In addition, radial glia may be involved in reciprocal signaling roles that contribute to regional patterning and differentiation in the developing CNS. GLIA 43:44–46, 2003. © 2003 Wiley‐Liss, Inc.
Astrocytes as support for axonal regeneration in the central nervous system of mammals
Authors: Privat A.
Published: May 2003

Reactive astrocytes are one of the main impediments for axonal regeneration in the central nervous system of mammals. Using mice KO for GFAP and vimentin, we show that reinnervation occurs after an hemisection of the spinal cord, mainly through sprouting of controlateral intact serotoninergic and cortico‐spinal axons, thanks to the absence of glial reactivity. This reinnervation is paralleled by the restoration of impaired locomotion of the ipselateral hindleg. Future applications to spinal cord injured patients are discussed. GLIA 43:91–93, 2003. © 2003 Wiley‐Liss, Inc.
Fibrin as a matrix for grafting 2‐hydroxyethyl methacrylate: Preparation and characterization of the graft and its in vivo evaluation for wound healing
Authors: Sathian J. , Sastry T. P. , Suguna L. , Lakshminarayana Y. , Radhakrishnan G.
Published: May 2003

In this work, fibrin was used as a substrate to graft 2‐hydroxyethyl methacrylate (HEMA) by free radical polymerization using potassium persulfate and sodium metabisulfite as redox initiators. The extent of grafting the synthetic polymer on the biopolymer was studied under various experimental conditions, and the optimum factors for affording maximum grafting were standardized. The graft, fib‐g‐p[HEMA], was characterized by Fourier transform infrared, scanning electron microscopy, and X‐ray diffraction studies. The graft exhibited a higher shelf life than native fibrin. The biocompatibility of the graft has been tested by in vivo studies and the results, in terms of collagen formation and wound size, proved its suitability for wound healing. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 435–440, 2003
Gas plasma etching of PEO/PBT segmented block copolymer films
Authors: Olde Riekerink M. B. , Claase M. B. , Engbers G. H. M. , Grijpma D. W. , Feijen J.
Published: May 2003

A series of poly(ethylene oxide)/poly(butylene terephthalate) (PEO/PBT) segmented block copolymer films was treated with a radio‐frequency carbon dioxide (CO2) or with argon (Ar) plasma. The effects of (preferential) etching on surface structure, topography, chemistry, and wettability were studied by scanning electron microscopy, atomic force microscopy, X‐ray photoelectron spectroscopy, and contact angle measurements. In all cases, a granular‐type nanostructure was formed after prolonged CO2 plasma etching. Ar plasma etching generally did not lead to significant changes in surface structure. Regarding surface chemistry, CO2 plasma treatment caused surface oxidation and oxidative degradation of the films while Ar plasma etching resulted mainly in the preferential removal of PEO blocks. The wettability of all films significantly increased after plasma treatment because of the creation of polar functional groups at the surface. Preliminary goat bone‐marrow cell compatibility experiments have shown that all plasma‐treated PEO/PBT films induced a greatly enhanced cell adhesion and/or growth compared to untreated biomaterials. This improvement was attributed to changes in surface chemistry during plasma etching rather than to changes in surface structure. These results show that plasma‐treated PEO/PBT copolymers have a high potential as scaffolds for bone tissue regeneration. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 417–428, 2003
Relationship between damage accumulation and mechanical property degradation in cortical bone: Microcrack orientation is important
Authors: Akkus Ozan , Knott David F. , Jepsen Karl J. , Davy Dwight T. , Rimnac Clare M.
Published: May 2003

The accumulation of damage and the associated degradation of the mechanical properties of cortical bone are postulated to contribute to age‐, disease‐, overuse‐, and disuse‐related skeletal fragilities. Therefore, gaining insight into the relationship between damage and degradation processes is essential in understanding the etiology of skeletal fractures. In investigating this relationship, the damage measure ideally needs to account for the size, the distribution density, and the orientation of microcracks. Existing measures of damage address the size and distribution density of microcracks; however, the orientation of cracks has not been well‐investigated. Because the overall orientation of microcracks determines the material axis along which the greatest degradation will be experienced, we hypothesized that the incorporation of the relative orientation between microcracks and loading direction will improve the significance of the relationship between damage accumulation and material property degradation. A three‐cycle damage protocol was used to induce tensile damage and to quantify the degradation of the elastic modulus of specimens from human donor femoral cortical bone (a 24‐year‐old and a 72‐year‐old man). Microcracks were evaluated by en bloc basic fuchsin staining of specimens after testing. The length (Li) and the orientation with respect to the loading direction (βi) of each crack were quantified by a video microscopy system. Three damage measures were quantified for each specimen: the number of linear microcracks (Cr #), the sum of the crack lengths (ΣLi) accounting for the microcrack size alone, and the sum of the projected crack length [ΣLPi = ΣLicos(βi)] accounting for both crack size and orientation. Inclusion of the orientation parameter improved the coefficient of determination between damage accumulation and the degradation of the elastic modulus: the coefficient of determination of the sum of the projected crack length (R2 = 0.239) was 60% greater than that of the sum the projected crack length (R2 = 0.149) and 33% greater than that of the number of linear microcracks (R2 = 0.180). We conclude that microcrack orientation is an essential physical variable in the relationship between damage accumulation and degradation of mechanical properties of cortical bone tissue. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 482–488, 2003
Identification, characterization, and expression of a novel α‐tropomyosin isoform in cardiac tissues in developing chicken
Authors: Zajdel Robert W. , Denz Christopher R. , Lee Sung , Dube Syamalima , Ehler Elisabeth , Perriard Evylene , Perriard Jean‐Claude , Dube Dipak K.
Published: May 2003

Tropomyosins are present in various muscle (skeletal, cardiac, and smooth) and non‐muscle cells with different isoforms characteristic of specific cell types. We describe here a novel smooth/striated chimeric isoform that was expressed in developing chick heart in addition to the classically described TM‐4 type. This novel α‐Tm tropomyosin isoform, designated as α‐Tm‐2, contains exon 2a (in place of exon 2b). The known striated muscle isoform (α‐Tm‐1) was also expressed in embryonic hearts along with the striated muscle isoform of TM‐4. In adult heart, TM‐4 was expressed, however, expression of both α‐Tm‐1 and α‐Tm‐2 isoforms was drastically reduced or downregulated. Interestingly, we were unable to detect the expression of α‐Tm‐2 in embryonic and adult skeletal muscle, however, the α‐Tm‐1 isoform is expressed in embryonic and adult skeletal muscle. Examination of other possible isoforms of the α‐TM gene, i.e., α‐smooth muscle tropomyosin (α‐Sm), α‐Fibroblast‐1 (α‐F1), and α‐Fibroblast‐2 (α‐F2) revealed expression in embryonic hearts and a significant reduction of each of these isoforms in adult heart. In order to elucidate the role of the newly discovered tropomyosin isoform in chicken, we ectopically expressed the GFP fusion protein of α‐Tm‐1 and α‐Tm‐2 separately into cardiomyocytes isolated from neonatal rats. Each isoform was incorporated into organized myofibrils. Our results suggest that the α‐TM gene may undergo both positive and negative transcriptional control in chicken hearts during development. © 2003 Wiley‐Liss, Inc.