bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of an MR‐compatible piezoelectric actuator for MR elastography
Authors: Uffmann Kai , Abicht Claus , Grote Wolfgang , Quick Harald H. , Ladd Mark E.
Published: December 2002

Magnetic Resonance (MR) elastography is a method for measuring tissue elasticity via phase images acquired with an MR scanner. The propagation of periodic mechanical waves through the tissue can be captured by means of a modified phase contrast sequence. These waves are generated with a mechanical oscillator (actuator) and coupled into the tissue through the skin. The actuator must be capable of generating a sinusoidal excitation with excellent phase and amplitude stability, while not disturbing the MR imaging process. In this work, an actuator based on a piezoelectric principle was developed. Based on the imaging evaluation of several material samples, the housing for the piezoelectric ceramic was constructed of aluminum. Smaller parts of the housing were manufactured from brass and titanium to fulfill the mechanical constraints. A lever was used to transfer the oscillation generated by the piezoelectric ceramic to the point of excitation. The lever amplifies the piezoelectric motion, allowing for a more compact design. Three different lever designs were characterized by an acceleration sensor both outside and inside the magnet. It was shown that the rigidity of the lever, as determined by its material and form, was decisive in determining the resonant frequency of the system and therefore the maximum practical frequency of operation. It was also shown that the motion of the oscillator is unaffected by the electromagnetic fields of the MR imager. The final design can be placed directly in the magnet bore within a few centimeters of the tissue volume to be imaged without generating significant artifacts. An amplitude range of 0–1 mm in the frequency range from 0 to over 300 Hz was achieved, sufficient for performing most MR elastography applications. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 239–254, 2002
Developmental and contextual influences on autonomic reactivity in young children
Authors: Alkon Abbey , Goldstein Lauren H. , Smider Nancy , Essex Marilyn J. , Kupfer David J. , Boyce W. Thomas
Published: December 2002

Studies of cardiovascular reactivity in young children have generally employed integrated, physiologically complex measures, such as heart rate and blood pressure, which are subject to the multiple influences of factors such as blood volume, hematologic status, thermoregulation, and autonomic nervous system (ANS) tone. Reactivity studies in children have rarely employed more differentiated, proximal measures of autonomic function capable of discerning the independent effects of sympathetic and parasympathetic responses. We describe 1) the development, validity, and reliability of a psychobiology protocol assessing autonomic reactivity to challenge in 3‐ to 8‐year‐old children; 2) the influences of age, gender, and study context on autonomic measures; and 3) the distributions of reactivity measures in a normative sample of children and the prevalences of discrete autonomic profiles. Preejection period (PEP) and respiratory sinus arrythmia (RSA) were measured as indices of sympathetic and parasympathetic nervous system reactivity, respectively, and autonomic profiles were created to offer summative indices of PEP and RSA response. Results confirmed the protocol's validity and reliability, and showed differences in autonomic reactivity by age and study context, but not by gender. The studies' findings offer guidelines for future research on autonomic reactivity in middle childhood and support the feasibility of examining sympathetic and parasympathetic responses to challenge in 3‐ to 8‐year‐old children. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 64–78, 2003.
The development of “roughness” in the play fighting of rats: A Laban Movement Analysis perspective
Authors: Foroud Afra , Pellis Sergio M.
Published: December 2002

With increasing age, rats, when play fighting, become rougher. In part, this change can be accounted for by the increasing likelihood of using adult‐typical fighting tactics. However, even when using the same tactics, adults appear rougher than juveniles in their play. In this study, videotaped sequences of play fighting in rats from the juvenile (30 days) to the post‐pubertal (70 days) period were analyzed using Laban Movement Analysis (LMA). Movement qualities called Effort Factors in LMA captured the character of some of this change. Juveniles tended to use Indulging Efforts, whereas older rats tended to use Condensing Efforts. The latter are related to performing movements that are more controlled. This greater level of control was also evident in the way older rats maintained postural support during play fights. When standing over supine partners, juveniles are more likely to stand on the partner with all four paws, reducing their postural stability, and hence ability to control their partner's movements. Older rats are more likely to place their hind paws on the ground, thus providing a firmer anchor for movements with their upper bodies and forepaws. These age‐related changes in behavior were found for both males and females. The findings lend support to a growing body of evidence that play fighting in the juvenile phase of rats is not just a more frequently occurring version of that present in adults, but rather, has unique organizational properties. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 35–43, 2003.
Categorization of infant‐directed speech: Development from 4 to 6 months
Authors: Spence Melanie J. , Moore David S.
Published: December 2002

To extend a previous finding that 6‐month‐old infants categorized low‐pass filtered infant‐directed (ID) utterances, we examined a) 6‐month‐old infants' categorization of more naturalistic, unfiltered ID utterances and b) the developmental progression of ID‐speech categorization. In Experiment 1, 6‐month‐olds heard seven different unfiltered tokens from one class of ID utterance (approving or comforting), followed by a novel token from either the same or an unfamiliar category. Infants recovered, responding only to the unfamiliar category token, suggesting that they categorized naturalistic ID utterances. Four‐month‐olds' categorization of filtered and unfiltered versions of the ID utterances was assessed in Experiments 2 and 4. Four‐month‐olds did not recover, responding to a test token from an unfamiliar class, suggesting that they did not categorize either filtered or unfiltered ID utterances. Experiment 3 demonstrated that 4‐month‐old infants' failure to categorize did not result from their inability to complete the procedure. These results suggest that infants' processing of ID speech changes from 4 to 6 months of age. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 42: 97–109, 2003.
Putting domain decomposition at the heart of a mesh‐based simulation process
Authors: Chow Peter , Addison Clifford
Published: December 2002

In computational mechanics analyses such as those in computational fluid dynamics and computational structure mechanics, some 60‐90% of total modelling time is taken by specifying and creating the model of the geometry and mesh. The rest of the time is spent in actual analyses and interpreting the results. This is especially true for industries such as aerospace and electronics, where 3D geometrically complex models with multiple physical processes are common. Advances in computational hardware and software have tended to increase the proportion of time spent in model creation, partly because such advances have made it feasible to solve hard and complex geometry problems in a timely fashion. This paper shows one way to exploit the advances in computation to reduce the model creation time and potentially the overall modelling time, namely the use of domain decomposition to define consistent and coherent global models based on existing component geometry and mesh models. In keeping with existing modelling processes the re‐engineering cost for the process is minimal. Copyright © 2002 John Wiley & Sons, Ltd.
Construction of interface conditions for solving the compressible Euler equations by non‐overlapping domain decomposition methods
Authors: Dolean Victorita , Nataf Frédéric , Lanteri Stéphane
Published: December 2002

In this work we examine the acceleration of the convergence of a non‐overlapping additive Schwarz‐type algorithm by modifying the transmission conditions applied to the subdomain interfaces. We have built generalized zero‐order interface conditions using the Smith theory of diagonalizing polynomial matrices. The numerical experiments confirmed qualitatively the behaviour in accordance with the theory, but we could not reproduce identically the results obtained in the continuous case. The preliminary results are very encouraging since they lead to a very good convergence rate for certain Mach numbers. Copyright © 2002 John Wiley & Sons, Ltd.
Current status of the molecular genetics of human prostatic adenocarcinomas
Authors: Karan Dev , Lin Ming‐Fong , Johansson Sonny L. , Batra Surinder K.
Published: December 2002

Molecular genetic mechanisms involved in the progression of prostate cancer are not well understood due to extensive tumor heterogeneity and lack of suitable models. New methods such as fluorescence in‐situ hybridization (FISH), comparative genomic hybridization (CGH) and microsatellite analysis have documented losses or gains on various chromosomes. Altered chromosomal regions have been associated with the activation of oncogenes and the inactivation of tumor suppressor genes or defects in mismatch repair (MMR) genes. It is suggested that increased genomic instability is associated with decreased androgen‐responsive and progressive behavior of human prostate tumors, but it remains unclear whether this genomic instability is causing the progression of cancer or is the consequence of cancer. Extended studies on hereditary prostate cancer have identified 7 prostate cancer susceptibility loci on several chromosomes, but no specific gene has been confined for a large proportion of susceptibility. In this review we summarize the ongoing molecular genetic events associated with the sporadic and hereditary prostate cancer development and progression. © 2002 Wiley‐Liss, Inc.
β2‐microglobulin aberrations in diffuse large B‐cell lymphoma of the testis and the central nervous system
Authors: Jordanova Ekaterina S. , Riemersma Sietske A. , Philippo Katja , Schuuring Ed , Kluin Philip M.
Published: December 2002

Human leukocyte antigen (HLA) class I molecules are expressed on the surface of all nucleated cells and present antigenic peptides to cytotoxic T cells, thereby playing an important role in initiating the cellular anti‐tumor immune response. We previously reported that loss of HLA class I expression in diffuse large B‐cell lymphoma (DLBCL) of the central nervous system (CNS) and the testis is a common event. Loss of expression and mutations of the light chain of the HLA class I molecule, β2‐microglobulin (β2m) have been described in a variety of human tumors and cell lines. In our study, we screened 15 DLBCL cases with a combined loss of HLA class I and β2m expression for mutations in the latter gene by direct sequencing. Frame shift mutations in repetitive sequences within the β2m gene leading to loss of functional β2m were detected in 2 cases. Loss of heterozygosity (LOH) and fluorescent in situ hybridization (FISH) analysis for chromosome 15 exhibited loss of the remaining copy of the β2m gene in both cases but also hemizygous deletions and monosomies in 6 additional cases. Since similar mutations in the β2m gene have been associated with microsatellite instability (MSI), we used 8 markers to study MSI involvement in DLBCL. Low MSI was more frequent (33%) as compared to nodal DLBCL (n=15) but did not correlate with the β2m mutations. Our data indicate that multiple mechanisms lead to downregulation of β2m and concomitant loss of HLA class I expression in DLBCL. © 2002 Wiley‐Liss, Inc.
Effect of methylenetetrahydrofolate reductase 677C→T polymorphism on toxicity and homocysteine plasma level after chronic methotrexate treatment of ovarian cancer patients
Authors: Toffoli Giuseppe , Russo Antonio , Innocenti Federico , Corona Giuseppe , Tumolo Salvatore , Sartor Franca , Mini Enrico , Boiocchi Mauro
Published: December 2002

MTHFR is a critical enzyme that regulates the metabolism of folate and methionine, both of which are important factors in DNA methylation and synthesis. Subjects with the 677C→T variant have impaired remethylation of Hcy to methionine that could determine hyperhomocysteinemia. Remethylation of Hcy into methionine and DNA methylation are also affected by MTX treatment. Thus, a combined effect between MTX and reduced activity of the MTHFR 677C→T polymorphism could occur, leading to toxicity. In a clinical trial, 43 ovarian cancer patients were treated with low doses of MTX. During MTX therapy, 12 patients (27.9%) developed G3/4 WHO toxicity. In these 12 patients, we observed 6 G3/4 thrombocytopenias, 1 G3 neutropenia, 1 G3 anemia, 9 G3 mucositis cases and 1 G4 mucositis case. A significant association was observed between toxicity and TT MTHFR 677 genotype (p < 0.0001). G3/4 toxicity occurred in 10 of 13 (77%), 1 of 17 (6%) and 1 of 13 (8%) patients with the TT, CT and CC MTHFR genotypes, respectively. According to the logistic regression model, patients with the TT genotype had a relative risk of 42.0 (95% CI 4.2–418.6) of developing G3/4 toxicity compared to patients with the CC and CT genotypes. Patients with the TT genotype had Hcy plasma levels after MTX therapy significantly (p = 0.0001) higher than basal levels (mean ± SD = 16.71 ± 4.72 vs. 12.48 ± 3.57 μmol/l); moreover, they also had higher Hcy plasma levels after MTX than patients with other MTHFR 677 genotypes (CC mean ± SD = 9.87 ± 3.61 μmol/l and CT mean ± SD = 11.48 ± 3.13 μmol/l). Finally, significant associations were observed between G3/4 WHO toxicity and higher Hcy plasma levels after MTX treatment (p = 0.0004). In conclusion, our data suggest that the TT MTHFR 677 genotype is associated with marked MTX‐induced hyperhomocysteinemia and could represent a pharmacogenetic marker for toxicity after chronic treatment with low doses of MTX. © 2002 Wiley‐Liss, Inc.
The art of ‘good conversations’: a strategy to negotiate succession within South Asian family firms
Authors: Janjuha‐Jivraj Shaheena , Woods Adrian
Published: December 2002

A large proportion of the Asian business community in Britain is experiencing generational succession for the first time. [Within the context of this paper Asian refers to businesses whose founders originate from the Indian sub‐continent.] This paper explores the impact of transition within this group by incorporating family dynamics and influencing cultural factors.

Successional transition within family businesses is acknowledged as a turbulent period. Most academic work on succession originates from Anglo‐Saxon research polarizing the family and business.

Typical approaches to succession are grounded in stage development models. This paper argues that succession is a process that cannot be guided by adopting such approaches due to the interaction of family and business.

This paper proposes ‘Good Conversations’ (Bird, 1990) as a means of preparing to negotiate succession. Copyright © 2002 John Wiley & Sons, Ltd.
Implicit solvent models for flexible protein–protein docking by molecular dynamics simulation
Authors: Wang Ting , Wade Rebecca C.
Published: December 2002

The suitability of three implicit solvent models for flexible protein–protein docking by procedures using molecular dynamics simulation is investigated. The three models are (i) the generalized Born (GB) model implemented in the program AMBER6.0; (ii) a distance‐dependent dielectric (DDD) model; and (iii) a surface area‐dependent model that we have parameterized and call the NPSA model. This is a distance‐dependent dielectric model modified by neutralizing the ionizable side‐chains and adding a surface area‐dependent solvation term. These solvent models were first tested in molecular dynamics simulations at 300 K of the native structures of barnase, barstar, segment B1 of protein G, and three WW domains. These protein structures display a range of secondary structure contents and stabilities. Then, to investigate the performance of the implicit solvent models in protein docking, molecular dynamics simulations of barnase/barstar complexation, as well as PIN1 WW domain/peptide complexation, were conducted, starting from separated unbound structures. The simulations show that the NPSA model has significant advantages over the DDD and GB models in maintaining the native structures of the proteins and providing more accurate docked complexes. Proteins 2003;50:158–169. © 2002 Wiley‐Liss, Inc.
Structural plasticity of thermophilic serine hydroxymethyltransferases
Authors: Paiardini Alessandro , Gianese Giulio , Bossa Francesco , Pascarella Stefano
Published: December 2002

Serine hydroxymethyltransferase (SHMT) catalyzes the reversible cleavage of serine to form glycine and monocarbonic groups, essential in several biosynthetic pathways. The availability of crystallographic structures of SHMT from mesophilic organisms and information produced by the genomic projects prompted the analysis of the adaptation of SHMT to “extreme” environments, such as high temperatures, by exploitation of structural data from thermophilic organisms. The sequences of 10 thermophilic/hyperthermophilic SHMTs were multiply aligned to 53 mesophilic homologs and analyzed by a comparative approach, examining the amino acid compositions and preferred residue exchanges between mesophiles and extremophiles. The structural basis of the observed exchanges was further investigated through the application of homology modeling to the 10 extremophilic SHMTs. The results of this study indicate that, in SHMT, thermal stability can be achieved mainly through three strategies: (i) increased number of charged residues at the protein surface; (ii) increased hydrophobicity of the protein core; and (iii) substitution of thermolabile residues exposed to the solvent. Additional features of the archaeal SHMTs, for which no structural data are available yet, were also investigated to explain their quaternary assemblage and the interaction with modified folates. Proteins 2003;50:122–134. © 2002 Wiley‐Liss, Inc.
Effects of partner's ability on the achievement and conceptual organization of high‐achieving fifth‐grade students
Authors: Carter Glenda , Jones M. Gail , Rua Melissa
Published: December 2002

This study investigated high‐achieving fifth‐grade students' achievement gains and conceptual reorganization during a unit on convection. Specifically, the achievement and cognitive gains that occurred as a result of interactions of high‐achieving students with a high‐achieving or low‐achieving laboratory partner were compared. The study design included an instructional sequence of three dyadic inquiry investigations related to convection currents as well as pre‐ and postassessments consisting of a multiple‐choice test, card sorting task, construction of a concept map, and an interview. Results showed no significant differences for achievement of high‐achieving students regardless of the partner's achievement level and only slight differences in conceptual reorganization. The implications of this study for heterogeneous grouping and construction of knowledge by dyads is discussed. © 2002 Wiley Periodicals, Inc. Sci Ed 87:94–111, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10031
Earthquake damageability criteria for due diligence investigations
Authors: Thiel C. C.
Published: December 2002

Earthquake vulnerability is an important financial issue in evaluating the acceptability of a property as a security for a loan or for an equity position. Such analyses are usually performed as part of the due diligence assessment of the property. Probable loss (PL) and scenario loss (SL), for both design basis and maximum capable earthquakes, were assessed to determine their utility in damageability analyses. Evaluations were made for a range of building damageabilities and for 14 sites throughout the United States that are representative of seismic hazard from very high to low. Portfolios from one to 16 buildings are considered. The analysis indicates that none of the damageability criteria is sufficient to distinguish between good and bad buildings to be securities for loans or to be good risks for equity investment for general use throughout the United States. Scenario upper loss (SUL) and probable loss (PL) values are consistently very stringent criteria for individual buildings in moderate‐risk and high‐risk regions, while scenario expected loss (SEL) values are too lenient in moderate risk areas. PL and SUL criteria are much too stringent at the 20% threshold level to be used generally, except for a group of well‐designed buildings. They can be acceptable if threshold values for acceptance are set to be above 20%. The SEL criterion is evaluated as not adequate to discriminate between good and bad damageability buildings by itself. It can work well in combination with a stability criterion so that buildings with poor predicted earthquake performance are eliminated based on stability, not damageability. It is recommended that combined criteria be used for fiduciary evaluation that includes both an assessment of the stability of the buildings and a damageability assessment to achieve a balanced, consistent evaluation of the suitability of the buildings as securities or as investments. Four alternative acceptance criteria are recommended for due diligence assessments. It is recommended that all due diligence reports include evaluations of scenario and probable losses for each building and the group so that they can enter into the decision process for the property. Copyright © 2002 John Wiley & Sons, Ltd.
Forensic studies of a large cover‐plate steel moment‐resisting connection
Authors: Whittaker Andrew , Gilani Amir , Takhirov Shakhzod , Ostertag Claudia
Published: December 2002

A large‐size, single‐sided cover plate connection composed of a built‐up BW36×670 column and a W36×359 rolled beam section was tested in a custom‐made test fixture using the SAC Phase I loading protocol. A trapezoidal plate was used as top flange reinforcement and a rectangular plate was used as bottom flange reinforcement. The test specimen failed catastrophically at a story drift angle of 1.7% and a beam plastic rotation of 0.009 radian by fracture through the beam top flange and beam web. An ABAQUS nonlinear finite element model of the connection was prepared and analyzed. The ABAQUS data indicate that the likelihood of brittle or ductile fracture at the observed crack initiation site is very low. Fractographic and microstructure studies were conducted after testing. The fractographic analysis of the failure surface showed that the fracture initiated at the toe of a fillet weld that joined the top cover plate to the beam flange. The microstructure analysis around the crack initiation site revealed laminations in the base metal at the crack initiation site. Copyright © 2002 John Wiley & Sons, Ltd.
T‐DNA integration into the Arabidopsis genome depends on sequences of pre‐insertion sites
Authors: Brunaud Véronique , Balzergue Sandrine , Dubreucq Bertrand , Aubourg Sébastien , Samson Franck , Chauvin Stéphanie , Bechtold Nicole , Cruaud Corinne , DeRose Richard , Pelletier Georges , Lepiniec Loïc , Caboche Michel , Lecharny Alain
Published: December 2002

A statistical analysis of 9000 flanking sequence tags characterizing transferred DNA (T‐DNA) transformants in Arabidopsis sheds new light on T‐DNA insertion by illegitimate recombination. T‐DNA integration is favoured in plant DNA regions with an A‐T‐rich content. The formation of a short DNA duplex between the host DNA and the left end of the T‐DNA sets the frame for the recombination. The sequence immediately downstream of the plant A‐T‐rich region is the master element for setting up the DNA duplex, and deletions into the left end of the integrated T‐DNA depend on the location of a complementary sequence on the T‐DNA. Recombination at the right end of the T‐DNA with the host DNA involves another DNA duplex, 2–3 base pairs long, that preferentially includes a G close to the right end of the T‐DNA.
Telomere architecture
Authors: Rhodes Daniela , Fairall Louise , Simonsson Tomas , Court Robert , Chapman Lynda
Published: December 2002

Telomeres are protein–DNA complexes that cap chromosome ends and protect them from being recognized and processed as DNA breaks. Loss of capping function results in genetic instability and loss of cellular viability. The emerging view is that maintenance of an appropriate telomere structure is essential for function. Structural information on telomeric proteins that bind to double and single‐stranded telomeric DNA shows that, despite a lack of extensive amino‐acid sequence conservation, telomeric DNA recognition occurs via conserved DNA‐binding domains. Furthermore, telomeric proteins have multidomain structures and hence are conformationally flexible. A possibility is that telomeric proteins take up different conformations when bound to different partners, providing a simple mechanism for modulating telomere architecture.
Pentafluorophenyl and phenyl substituted azidoborates
Authors: Fraenk Wolfgang , Klapötke Thomas M , Krumm Burkhard , Nöth Heinrich , Suter Max , Vogt Martin , Warchhold Marcus
Published: December 2002

The azidoborates [(C6F5)4nB(N3)n] (n = 13) (13) were synthesized by reacting the corresponding borane with [R]N3 (R = Me4N, Ph4P). To study the influence of the electron withdrawing C6F5-substituent on the boron atom, [Me4N][(C6H5)3BN3] (4) was also prepared. All compounds were fully characterized by IR, Raman, and multinuclear NMR spectroscopy in addition to characterization by single crystal diffraction analyses.Key words: azidoborate, pentafluorophenyl, multinuclear NMR spectroscopy, X-ray crystallography.
Triply bridged dicopper-bis(trimethylsilylchalcogenolates): Synthesis and characterization of the series of helical complexes [(Me3SiE-Cu)2(µ-Ph2PCCPPh2-κ2P)3] (E = S, Se, Te)
Authors: Wallbank Andrew I , Corrigan John F
Published: December 2002

The copper-chalcogenolates [(Me3SiE-Cu)2(µ-Ph2PC[Formula: see text]CPPh2-κ2P)3] (1, E = S; 2, E = Se; 3, E = Te) have been prepared in good yield from [(OAcCu)2(µ-Ph2PC[Formula: see text]CPPh2-κ2P)3] and E(SiMe3)2at low temperatures. Complexes 13 contain two pendant -ESiMe3moieties bonded to copper(I) centres, which are also bridged by three didentate ligands to form helical structures. Complexes 13 have been characterized by single crystal crystallographic and spectroscopic methods.Key words: copper, chalcogen, helical, trimethylsilyl groups, phosphinoacetylene.
Structural interrelationships between the bis(pentamethylcyclopentadienyl)arsenic(III) and antimony(III) cations and their precursor chlorides
Authors: Wiacek Robert J , Jones Jamie N , Macdonald Charles LB , Cowley Alan H
Published: December 2002

The chloropnictines (η-C5Me5)2AsCl (1), (η-C5Me5)2SbCl (2), and (η-C5Me5)2BiCl (3) have been prepared by treatment of the appropriate element trichloride with LiC5Me5. X-ray crystallographic assays establish that in the case of 1, both C5Me5 rings are attached to As in an η1(σ) fashion. In 2 and 3, the C5Me5 rings are π delocalized and feature tri- and pentahapto ring binding, respectively, to the group 15 element. Conversion of 1 and 2 to the salts [As(η-C5Me5)2][AlCl4] (4) and [Sb(η-C5Me5)2][AlCl4] (5) was effected by reaction with the stoichiometric quantity of Al2Cl6. The X-ray crystal structure of 4 is surprisingly complex and features four independent ion pairs in the asymmetric unit with a variety of hapticities for the π-bonded C5Me5 rings. The structure of the stibocenium cation of 5 involves bis(η4) attachment of the π-bonded C5Me5 rings.Key words: main group metallocenes, arsocenium cations, stibocenium cations, group 15 pentamethylcyclopentadienyl chlorides.
The coordination chemistry of o,o'-i-Pr2C6H3-bis(imino)acenaphthene to group 13 trihalides
Authors: Jenkins Hilary A , Dumaresque Carla L , Vidovic Dragoslav , Clyburne Jason AC
Published: December 2002

The preparation of several complexes of the diimine ligand o,o'-i-Pr2C6H3-bis(imino)acenaphthene (Ar-BIAN (1)) with group 13 trihalides (EX3, E = B, Al, Ga; X = Cl, Br) is reported. Four compounds with the general formula [(Ar-BIAN)(EX2)][EX4] (2) have been prepared and isolated. Two complexes have been crystallographically characterized: [(Ar-BIAN)(BCl2)][BCl4] (orthorhombic, P212121, a = 10.408(3) Å, b = 14.376(4) Å, c = 30.908(8) Å, Z = 4) and [(Ar-BIAN)(GaCl2)][GaCl4] (monoclinic, P21/m, a = 9.0822(7) Å, b = 15.390(1) Å, c = 15.458(1) Å, β = 92.519(2)°, Z = 2). Attempts to prepare diazametaloles via reduction of the [(Ar-BIAN)(EX2)][EX4] compounds using sodium or potassium have thus far been unsuccessful.Key words: boron, aluminium, gallium, complex, crystal structure, heterocycle.
Studies on electrochemical and coordination behaviour of phosphiniminocyclotrithiazenes
Authors: Swarnalatha U , Sivaramakrishna A , Venkatachalam C S , Rao MN Sudheendra , Inoue Tomonori , Ueda Tadaharu , Hojo Masashi
Published: December 2002

Electrochemical (polarographic, cyclic voltammetric, and coulometric) and coordination behaviour of several symmetrically and unsymmetrically substituted phosphiniminocyclotrithiazenes have been studied. Polarograms of R3PN-S3N3(R = C6H5, p-ClC6H4, p-H3CC6H4, and (OC4H8N)), Ph2(OC4H8N)PN-S3N3, and Ph(OC4H8N)2PN-S3N3give two cathodic waves. Cyclic voltammograms of Ph3PN-S3N3(1) and (OC4H8N)3PN-S3N3(2) reveal nearly the same oxidation peak potential but different reduction potentials. Controlled potential electrolysis of 1 and 2 at +0.6 V indicates exocyclic cleavage and ring degradation. Cathodic reduction behaviour of Ph3PN-S3N3suggests the possibility for the formation of 1,5-(Ph3PN)2S4N4under electrochemical conditions. Reaction of nickel chloride hexahydrate with heterocycle 1 in 1:2 molar ratio in acetonitrile affords the complex, [Ni(S2N2H)2] (A) (90% yield) and [Ph3PNH2]Cl salt as products. Analogous reactions with other ligands of this type (two symmetrical (sym.) and three unsymmetrical (unsym.)) except 2 also give A, while ligand 2 reacts with anhyd NiCl2in an equimolar ratio to afford a dark green, square-planar complex ((OC4H8N)3PN-S3N·NiCl2(B)) whose ESCA results assist in providing its coordination details. The study reveals a high tendency of these heterocycles to different types of ring cleavage. Key words: phosphiniminocyclotrithiazenes, polarography and cyclic voltammetry, substituent effect, nickel complexes, ESCA.
Characterization of indirect 31P-31P spin-spin coupling and phosphorus chemical shift tensors in pentaphenylphosphinophosphonium tetrachlorogallate, [Ph3P-PPh2][GaCl4]
Authors: Gee Myrlene , Wasylishen Roderick E , Ragogna Paul J , Burford Neil , McDonald Robert
Published: December 2002

Phosphorus chemical shift and 31P,31P spin-spin coupling tensors have been characterized for pentaphenylphosphinophosphonium tetrachlorogallate, [Ph3P-PPh2][GaCl4], using solid-state 31P NMR spectroscopy. Spectra obtained with magic-angle spinning yield the isotropic value of the indirect spin-spin coupling, |1J(31P,31P)iso|, 323 ± 2 Hz, while 2D spin-echo and rotational resonance experiments provide the effective dipolar coupling constant, Reff, 1.70 ± 0.02 kHz, and demonstrate that Jiso is negative. Within experimental error, the effective dipolar coupling constant and Jiso are unchanged at 120°C. The anisotropy in 1J(31P,31P), ΔJ, has been estimated by comparison of Reff and the value of the dipolar coupling constant, RDD, calculated from the PP bond length as determined by X-ray diffraction. It is concluded that |ΔJ| is small, with an upper limit of 300 Hz. Calculations of 1J(31P,31P) for model systems H3P-PH+2 and (CH3)3P-P(CH3)+2 using density functional theory as well as multiconfigurational self-consistent field theory (H3P-PH+2) support this conclusion. The experimental spin-spin coupling parameters were used to analyze the 31P NMR spectrum of a stationary powder sample and provide information about the phosphorus chemical shift tensors. The principal components of the phosphorus chemical shift tensor for the phosphorus nucleus bonded to three phenyl groups are δ11 = 36 ppm, δ22 = 23 ppm, and δ33 = 14 ppm with an experimental error of ±2 ppm for each component. The components are oriented such that δ33 is approximately perpendicular to the PP bond while δ11 forms an angle of 31° with the PP bond. For the phosphorus nucleus bonded to two phenyl groups, the principal components of the phosphorus chemical shift tensor are δ11 = 23 ppm, δ22 = 8 ppm, and δ33 = 68 ppm with experimental errors of ±2 ppm. In this case, δ33 is also approximately perpendicular to the PP bond; however, δ22 is close to the PP bond for this phosphorus nucleus, forming an angle of 13°. The dihedral angle between the δ33 components of the two phosphorus chemical shift tensors is 25°. Results from ab initio calculations are in good agreement with experiment and suggest orientations of the phosphorus chemical shift tensors in the molecular frame of reference.Key words: Nuclear magnetic resonance spectroscopy, phosphorus chemical shift tensors, 31P-31P J-coupling tensors, density functional theory, multiconfigurational self-consistent field theory, phosphinophosphonium salts.
CONFIDENCE LIMITS WITH MULTIPLE CHANNELS AND ARBITRARY PROBABILITY DISTRIBUTIONS FOR SENSITIVITY AND EXPECTED BACKGROUND
Authors: PERROTTA ANDREA
Published: December 2002

A MC method is proposed to compute upper limits, in a pure Bayesian approach, when the errors associated to the experimental sensitivity and to the expected background content are not Gaussian distributed or not small enough to apply the usual approximations. It is relatively easy to extend the procedure to the multichannel case (for instance when different decay branchings, or luminosities or experiments have to be combined). Some of the searches for supersymmetric particles performed in the DELPHI experiment at the LEP electron–positron collider use such a procedure to propagate the systematics into the calculation of the cross-section upper limits. One of these searches will be described as an example.
MARKET SIMULATION WITH HIERARCHICAL INFORMATION FLUX
Authors: SCHULZE CHRISTIAN
Published: December 2002

We assume the market price to diffuse in a hierarchical comb of barriers, the heights of which represent the importance of new information entering the market. We find fat tails with the desired exponent for the price change distribution, and effective multifractality for intermediate times.
AN ADAPTATION MODEL FOR SIMULATION OF AGING PROCESS
Authors: RAUDYS Š.
Published: December 2002

To analyze aging processes, a concept based on these hypotheses was utilized: maturation and aging are affected by external influences and are related to the system's ability to learn, to adapt to sudden environmental changes rapidly and survive. To simulate the maturation and aging processes of systems, individuals and populations, a perceptron to classify two notably different classification tasks was trained. After lengthy training to learn the first task, the magnitudes of the perceptron's weights increase. The presence of nonlinearity in the output of the perceptron causes a saturation of the cost function. Saturation reduces the capability to learn a new task rapidly. The aging curves obtained show a rise and fall character. Factors that can be utilized to control re-training curves were considered. A new model allows us to analyze the aging process as a natural phenomenon that helps populations to survive in everlastingly changing environments was also introduced.
Conductive fibers based on poly(ethylene terephthalate)–polyaniline composites manufactured by electrochemical polymerization
Authors: Hirase Ryuji , Hasegawa Masaru , Shirai Masamitsu
Published: December 2002

A novel method of manufacturing composite conductive fibers was developed through electrochemical polymerization with an apparatus consisting of insulating fibers, cotton fabrics as electrolytic solution holders, an electrolytic solution, and planer electrodes. By this method, poly(ethylene terephthalate) (PET) fibers coated with polyaniline (PAN) were prepared readily and yielded PET–PAN composite conductive fibers (PPCFs). The content of PAN in PPCFs increased with an increase in both the aniline concentration in the electrolytic solution and the polymerization voltage, although it did not depend on the load applied to the electrodes. Observations of the PPCF surface by scanning electron microscopy confirmed that the formation processes of PPCFs could be divided into three steps: (1) fine (nanometer‐size) granular PAN was generated from the anode and adsorbed onto the PET fiber surface, (2) the size of the granular PAN increased up to about 90 nm in a short time, and (3) the granular PAN was linked together to form networks. The conductivity of PPCFs increased with an increasing content of PAN networks. The surface resistance of the PPCF fabric was about 3 × 105 Ω/□ at a PAN content of approximately 2 wt %. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1073–1078, 2003
Co‐evolution of user and organizational interfaces: A longitudinal case study of WWW dissemination of national statistics
Authors: Marchionini Gary
Published: December 2002

The data systems, policies and procedures, corporate culture, and public face of an agency or institution make up its organizational interface. This case study describes how user interfaces for the Bureau of Labor Statistics web site evolved over a 5‐year period along with the larger organizational interface and how this co‐evolution has influenced the institution itself. Interviews with BLS staff and transaction log analysis are the foci in this analysis that also included user information‐seeking studies and user interface prototyping and testing. The results are organized into a model of organizational interface change and related to the information life cycle.
Iterative substructuring methods for incompressible non‐isothermal flows and its application to indoor air flow simulation
Authors: Knopp T. , Lube G. , Gritzki R. , Rösler M.
Published: December 2002

The parallel solution of the incompressible Navier–Stokes equations coupled with the energy equation is considered. For turbulent flows, the k/ε model together with a modified wall‐function concept is used. The iterative process requires the fast solution of advection–diffusion reaction and Oseen‐type problems. These linearized problems are discretized using stabilized finite element methods. We apply a coarse–granular iterative substructuring method which couples the subdomain problems via Robin‐type interface conditions. Then we apply the approach to the simulation of indoor air flow problems. Copyright © 2002 John Wiley & Sons, Ltd.
An algebraic 2‐level domain decomposition preconditioner with applications to the compressible Euler equations
Authors: Sala Marzio
Published: December 2002

A domain decomposition technique to solve large‐scale aerodynamics problems on unstructured grids is investigated. The linear system, arising when an implicit time‐advancing scheme is used, is preconditioned using a Schwarz‐based method. The key idea of the Schwarz preconditioner is to solve (approximately) a linear problem on each subdomain, then to exchange information only with neighbouring subdomains. Unfortunately, the performance of the Schwarz‐type preconditioner deteriorates as the number of processors grows. So, in this case, a key element for obtaining a scalable preconditioner is to provide acoarse leveloperator. Since many of the coarse operators proposed in literature are difficult to implement on unstructured 2D and 3D meshes, a purely algebraic procedure, that requires the entries of the matrix only, has been developed. This procedure may be seen as an Algebraic MultiGrid (AMG) method applied as a coarse grid correction operator. The key idea is to take advantage of the use of local data of domain decomposition preconditioners, and of the automatic coarsening procedures of AMG methods.

Two possible schemes to introduce the coarse grid operator will be described. Both cases have been implemented and tested in a distributed parallel environment, using the MPI library. It will be shown that for suitable values of the rank of the coarse grid operator it is possible to obtain a considerable reduction in the number of iterations compared to the Schwarz preconditioner without coarse operator. Copyright © 2002 John Wiley & Sons, Ltd.
Wnt‐5a and G‐protein signaling are required for collagen‐induced DDR1 receptor activation and normal mammary cell adhesion
Authors: Dejmek Janna , Dib Karim , Jönsson Marzieh , Andersson Tommy
Published: December 2002

The collagen‐induced phosphorylation of discoidin domain receptor 1 (DDR1) in Wnt‐5a‐expressing HB2 mammary cells was effectively inhibited by pertussis toxin, but not by cholera toxin or antibodies blocking β1 integrins. Moreover, pertussis toxin reduced adhesion of the cells to collagen by approximately 50%, and antibodies against β1 integrins had a similar effect that was in fact additive to that of pertussis toxin. Cholera toxin had accordingly no such effect on adhesion. By comparison, pertussis toxin did not influence adhesion of Wnt‐5a‐antisense HB2 cells or MCF‐7 mammary tumor cells, neither of which express Wnt‐5a or exhibit activation of DDR1. In accordance with these results, direct mastoparan‐induced activation of G‐proteins in Wnt‐5a‐deficient MCF‐7 cells enabled collagen‐induced phosphorylation of DDR1 and enhanced their adhesion. The inactive analogue mastoparan‐17 had no such effects on MCF‐7 cells nor did active mastoparan affect adhesion of Wnt‐5a‐expressing HB2 cells. A possible explanation for how DDR1, a receptor tyrosine kinase (RTK), potentiates mammary cell adhesion comes from our observations that pertussis toxin also inhibited the recruitment of the cytoskeletal regulator phosphatidylinositol 3‐kinase (PI3K) to DDR1 as well as its phosphorylation/activation. In accordance with that, the PI3K inhibitor wortmannin significantly impaired adhesion of normal Wnt‐5a‐expressing HB2 cells but had little effect on adhesion of Wnt‐5a‐antisense HB2 cells. Thus, a Gi/o‐protein signaling pathway mediates the effect of Wnt‐5a expression by enabling collagen‐induced activation of DDR1, which, in parallel with β1 integrins, regulates adhesion of mammary cells. © 2002 Wiley‐Liss, Inc.
Quantification of expression of netrins, slits and their receptors in human prostate tumors
Authors: Latil Alain , Chêne Laurent , Cochant‐Priollet Béatrix , Mangin Philippe , Fournier Georges , Berthon Philippe , Cussenot Olivier
Published: December 2002

Recently, DCC (Deleted in Colorectal Cancer) protein has been forwarded as a receptor for netrin. The Netrin/DCC complex is critical for axon guidance and cell migration. In the developing nervous system, netrin protein secreted by midline cells attracts commissural axons by activating the DCC receptor on growth cones. This attraction can be switched to repulsion or silenced completely, depending on the DCC binding partner. The potential suppressor function of DCC in prostate tumorigenesis, through a still unknown mechanism, prompted us to quantify the expression of several genes involved in this axon guidance pathway. The relative expression levels of DCC, NEO1, NTN1, NTN2L, NTN4, UNC5C, Slit1, Slit2, Slit3, Robo1 and Robo2 were simultaneous quantified in 48 tumors and 7 normal prostate tissues by using real‐time quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR). A reduction in DCC, NEO1, NTN1 and NTN4 expression was observed in prostate tumors, while many of the same prostate tumors over‐expressed either Slit genes or their receptors, Robo. © 2002 Wiley‐Liss, Inc.
Activation of T cells via tumor antigen specific chimeric receptors: The role of the intracellular signaling domain
Authors: Losch Florian O. , Müller Ralph , Mutschler Bettina , Neri Dario , Natali Pier Giorgio , Reth Michael , Carsetti Rita
Published: December 2002

T cells engineered to express hybrid receptors with antibody defined specificity can successfully be targeted to tumor cells. In order to select intracellular domains of chimeric receptors capable of efficiently activate T cells in vitro and in vivo, we compared the function of receptors, which share the same extracellular antigen‐binding part, joined to different intra‐cellular signal transduction units. The antigen binding domain of the receptors was a single‐chain fragment of a monoclonal antibody, which recognize a High Molecular Weight Melanoma‐Associated Antigen with high affinity. The intracellular tails were derived from the T‐cell receptor ζ chain (TCR‐ζ), from the B‐cell receptor Ig‐α molecule and from a mutated Ig‐α molecule able of stronger signal transduction. We compared the activity of the different chimeric receptors at a single‐cell level by using a T‐cell line that expressed an activation‐dependent EGFP‐reporter gene. Upon cross‐linking with immobilized antibodies, all receptors were able to induce EGFP expression in the majority of the T cells. In contrast, EGFP expression was induced by contact to melanoma cells in vitro only in T cells that expressed the chimeric receptor that contained the TCR‐ζ intracellular tail. In these T cells, the co‐expression of chimeric receptors that contain a mutated Ig‐α tail lowers the threshold of T‐cell activation and facilitates tumor recognition in vitro and in vivo. Given their specificity and efficiency, T cells grafted with these type of receptors may represent potential candidates for cancer passive immunotherapy. © 2002 Wiley‐Liss, Inc.
Infiltrating immune cells, but not tumour cells, express FasL in non‐small cell lung cancer: No association with prognosis identified in 3‐year follow‐up
Authors: Toomey Deirdre , Smyth Gordon , Condron Claire , Kelly James , Byrne Ann‐Marie , Kay Elaine , Conroy Ronan M. , Broe Patrick , Bouchier‐Hayes David
Published: December 2002

Non‐small cell lung cancer (NSCLC) remains a difficult disease to treat and independent prognostic markers other than tumour stage and histology have not emerged. The immune cell content of solid tumours has been associated with tumour regression and at times, tumour progression. The involvement of immune cells in prognosis of NSCLC is poorly described. Poor immune responses within solid tumours have been linked with tumour production of immunosuppressive cytokines. Tumour expression of FasL is thought to disarm responses through the transduction of a death signal in Fas‐expressing T cells. The existence of the ‘tumour counterattack’ in vivo has been questioned. We undertook to measure T cell and macrophage infiltration of the tumour bed in NSCLC and report the association between immune cell content and prognosis in a limited, 3‐year analysis of survival (n = 113). In addition we investigated FasL expression (n = 45). T cells and macrophages were found to frequently infiltrate lung tumours, albeit in small numbers. Generally there were more T cells infiltrating than macrophages. T cell and macrophage numbers were not associated with prognosis. Lung tumours were found not to express FasL, although occasional immune cells surrounding tumour cells were strongly positive. FasL expression was not associated with prognosis in this series. Thus, immune cells infiltrating NSCLC are not capable of suppressing tumour growth, nor are they associated with tumour progression. We report that lung tumours do not express the FasL, and that although some immune cells are FasL positive, this is not a reflection of general immune cell activation. © 2002 Wiley‐Liss, Inc.