bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative analysis of follicle‐stimulating hormone receptor in ovarian epithelial tumors: A novel approach to explain the field effect of ovarian cancer development in secondary mullerian systems
Authors: Wang Jun , Lin Lynne , Parkash Vinita , Schwartz Peter E. , Lauchlan Stuart C. , Zheng Wenxin
Published: December 2002

The role of FSHR expression in ovarian cancer development is not clear. We examined quantitative expression of FSHR in different types of OET, presumed precursor lesions and peritoneal implants and further discussed FSH as a key growth‐promotion factor for the process of ovarian epithelial tumorigenesis. Thirty‐five primary OET specimens, including 5 serous cystadenomas, 4 papillary serous cystadenomas, 9 SBTs and 17 serous carcinomas, were examined for quantitative FSHR expression. Ten paired samples (3 benign cystadenomas, 5 SBTs and 2 carcinomas) were obtained from several morphologically different areas, including benign‐looking, borderline and cancerous areas in the same OETs, and from the remaining ovarian tissue and contralateral ovaries. Competitive RT‐PCR was performed to measure the quantitative expression of FSHR in each tissue sample. FSHR expression levels were compared among nonpaired samples and within paired samples. We found that OSE had the lowest FSHR expression, whereas antral follicles had the highest level. Within benign OETs, papillary serous cystadenomas have 4.9‐fold higher FSHR levels than nonpapillary serous cystadenomas. SBTs had the highest level of FSHR expression, which was 12.8‐fold, 2.7‐fold and 2.4‐fold higher than that of serous cystadenomas, papillary serous cystadenomas and grade 1 carcinomas, respectively. A similarly high level of FSHR mRNA was found in peritoneal implants, which were associated with SBTs. FSHR levels among serous carcinomas decreased with an increase in carcinoma grade. Grade 3 carcinomas had the lowest FSHR level, which was similar to that of serous cystadenomas, while grade 1 carcinomas had 6.5‐fold higher FSHR levels than those in serous cystadenomas. Our results suggest that not only serum FSH but also FSHR in ovarian epithelium may play important roles in ovarian OET development. Both the receptor and ligand may act in a synergistic way to promote tumor growth. The observation that high FSHR levels are present in peritoneal implants suggests that FSH may also play a similar role in the development of peritoneal serous tumors. From this perspective, circulating FSH may be considered a driving force in the field effect theory for the development of both ovarian neoplasms and their associated peritoneal implants. However, the exact role of FSH and/or FSHR in the development of epithelial tumors arising in both the ovary and peritoneum needs further investigation. © 2002 Wiley‐Liss, Inc.
Cyclopentenyl cytosine primes SK‐N‐BE(2)c neuroblastoma cells for cytarabine toxicity
Authors: Bierau Jörgen , van Gennip Albert H. , Leen René , Helleman Jozien , Caron Huib N. , van Kuilenburg André B.P.
Published: December 2002

CPEC is a potent inhibitor of CTP synthetase and causes depletion of CTP and dCTP pools. AraC is an analog of dCyd and a chemotherapeutic agent. Here, we demonstrate that, upon incubation with CPEC, both the anabolism and cytostatic effect of AraC in SK‐N‐BE(2)c neuroblastoma cells were increased. Cotreatment of CPEC (50–250 nM) and AraC (37.5–500 nM) decreased the 4‐day ED50 value for AraC 2‐ to 8‐fold in the SK‐N‐BE(2)c cell line, while pretreatment with CPEC followed by incubation with AraC alone decreased the 4‐day ED50 value for AraC 1‐ to 19‐fold. Preincubation of SK‐N‐BE(2)c cells with 100 nM CPEC followed by incubation with 500 nM [3H]AraC increased the total amount of AraC nucleotides and incorporation of [3H]AraC into DNA by 392% and 337%, respectively, compared to non‐CPEC‐treated cells. When 20 nM [3H]AraC was used, the maximum incorporation of [3H]AraC into DNA was 1,378% compared to non‐CPEC‐treated cells. Incorporation of AraC into DNA correlated well with the accumulation of cells in S phase of the cell cycle caused by CPEC. DNA synthesis was almost completely inhibited (>91%) when 100 nM CPEC and 500 nM AraC were combined. CPEC alone and the combination of CPEC and AraC increased caspase‐3 activity 3‐fold, indicating induction of apoptosis in SK‐N‐BE(2)c cells. In contrast, AraC alone did not induce caspase‐3 activity. Our results demonstrate that low concentrations of CPEC profoundly increase the cytostatic properties of AraC toward SK‐N‐BE(2)c human neuroblastoma cells. © 2002 Wiley‐Liss, Inc.
Big firms waiting to grow? Franchisees in the pub sector
Authors: Lashley Conrad , Rowson Bill
Published: December 2002

Pub‐operating companies have undergone major changes in their business organization over recent years. One of the effects of the ‘Beer Orders’ has been to break up the large estates of pubs directly tied to a beer producer.

In many cases, the larger brewers have directly managed their estate of large high‐volume pubs and bars. More typically, however, companies control pubs in indirectly managed forms. Tenancies and leases offer the pub operator strategies that allow them to operate on a larger scale with less risk because the smaller firm takes the risk and also has the entrepreneurial motives to build the business.

In many ways, this limited form of franchising appears to offer many benefits as a business strategy because it enables the pub operator to trade at a higher scale and at lower risk. The problem is that many companies have a limited understanding of the motives of the small‐firm operators who are running their pubs as tenants or lessees.

Whilst the key motive for indirect forms of pub control was to maintain outlets for the beer product, these strategies are flawed when properties need to be run as retail outlets, intent on maximizing sales and business growth.

This paper explores some of the motives of the small firms who operate pubs via tenancy and lessee arrangements and the difficulties that exist between the pub‐operating companies and their small‐firm partners.

Copyright © 2002 John Wiley & Sons, Ltd.
Evidence of worth in not‐for‐profit sector organizations
Authors: Harris Ian , Mainelli Michael , O'Callaghan Mary
Published: December 2002

The not‐for‐profit sector is a significant part of the economy. Such organizations have a duty to their stakeholders to provide evidence that they are using resources well.

The authors have substantial client work in this area and have conducted research among leaders of UK not‐for‐profit organizations in order to see to what extent such organizations provide evidence of worth. Indeed, this research presented here confirms the prominence of this objective.

Four themes emerge in discharging this goal as not‐for profit organizations strive to balance internal aspiration versus external imposition, outcomes not outputs, gathering evidence and communication, contribution, consensus and commitment.

There are four basic types of not‐for‐profit evidence based on the primary outcome; these are expanding frontiers, changing systems, service delivery and communitarian.

Information to validate evidence of worth may be categorized as risk control, reward enhancement or volatility‐reduction targets and outcomes. Copyright © 2002 John Wiley & Sons, Ltd.
Long‐ and short‐range interactions in native protein structures are consistent/minimally frustrated in sequence space
Authors: Miyazawa Sanzo , Jernigan Robert L.
Published: December 2002

We show that long‐ and short‐range interactions in almost all protein native structures are actually consistent with each other for coarse‐grained energy scales; specifically we mean the long‐range inter‐residue contact energies and the short‐range secondary structure energies based on peptide dihedral angles, which are potentials of mean force evaluated from residue distributions observed in protein native structures. This consistency is observed at equilibrium in sequence space rather than in conformational space. Statistical ensembles of sequences are generated by exchanging residues for each of 797 protein native structures with the Metropolis method. It is shown that adding the other category of interaction to either the short‐ or long‐range interactions decreases the means and variances of those energies for essentially all protein native structures, indicating that both interactions consistently work by more‐or‐less restricting sequence spaces available to one of the interactions. In addition to this consistency, independence by these interaction classes is also indicated by the fact that there are almost no correlations between them when equilibrated using both interactions and significant but small, positive correlations at equilibrium using only one of the interactions. Evidence is provided that protein native sequences can be regarded approximately as samples from the statistical ensembles of sequences with these energy scales and that all proteins have the same effective conformational temperature. Designing protein structures and sequences to be consistent and minimally frustrated among the various interactions is a most effective way to increase protein stability and foldability. Proteins 2003;50:35–43. © 2002 Wiley‐Liss, Inc.
A knowledge‐based scale for amino acid membrane propensity
Authors: Punta Marco , Maritan Amos
Published: December 2002

In this article, a membrane‐propensity scale for amino acids is derived using only two ingredients: (i) a set of transmembrane helices segments from membrane protein crystal structures and (ii) the request that each component of the set has a free energy lower than that of a typical soluble protein sequence of the same length. Although the most widely used hydropathy scales satisfy this request, we use an optimization procedure that allows for extraction of an optimal scale, which correlates equally well with those scales. We show that, if the choice of the sequence database is accurate, significant knowledge‐based scales, which are robust with respect to changes in the learning set, can be easily derived. The obtained scales can be used for transmembrane helices prediction. The predictive power of one of these scales is tested on membrane proteins, soluble proteins, and signal peptides databases, finding that its performances is comparable with those of the hydropathy scales. Proteins 2003;50:114–121. © 2002 Wiley‐Liss, Inc.
Ion permeation through the gramicidin channel: Atomically detailed modeling by the stochastic difference equation
Authors: Siva Koneshan , Elber Ron
Published: December 2002

Atomically detailed descriptions of ionic solution, membrane, and the gramicidin channel are used to compute molecular dynamics trajectories of ion permeation. The microsecond trajectories are calculated with the Stochastic Difference Equation (SDE), which provides approximate solutions to the equations of motions (with filtered high‐frequency modes) of extended timescales. The relative permeations of lithium, sodium, and potassium are estimated by using a novel, kinetic cycle protocol and are compared with experiment. The transport through native gramicidin and one fluoro‐valine variant is considered as well. Qualitative agreement between theory and experiment is obtained. The faster permeation rate of sodium compared to lithium is reproduced in the calculations. The calculations also reproduce the slower diffusion through a gramicidin with fluorinated valine compared to native gramicidin. The calculations are inconclusive about the relative rates of potassium and sodium. The experiment suggests that potassium permeates more quickly. We directly probe the kinetics of a biophysical process at a relevant time window without reducing the atomically detailed description of the system. The calculations were able to capture subtle balances between binding and diffusion that determine permeation rates. The same model gave the correct ordering of diffusion rates for cases in which electrostatic binding has opposite effects and must be supplemented by dynamic factors. Diffusion rates are faster when favorable electrostatic interactions of ions in the channel (compared to the solvent) are observed. Studies of a gramicidin variant suggest an opposite effect, in which permeation is faster for the less polar channel, indicating dynamic effects. Although both trends can be explained qualitatively, it is not possible to predict (before doing the SDE calculations) which factor is more important. Proteins 2003;50:63–80. © 2002 Wiley‐Liss, Inc.
Exponential decay kinetics in “downhill” protein folding
Authors: Hagen Stephen J.
Published: December 2002

The observation of single‐exponential kinetic phases in early stages of protein folding is often interpreted as evidence that these phases are rate limited by significant energy or entropy barriers. However, although the existence of large barriers reliably implies exponential kinetics, the reverse is not necessarily true. A simple model for the hydrophobic collapse of a chain molecule demonstrates that a barrierless or “downhill” diffusional relaxation can give rise to kinetics that are practically indistinguishable from a pure exponential. Within this model, even a highly nonlinear experimental probe such as resonance energy transfer (Förster transfer) could exhibit a large amplitude decay (greater than 90% in fluorescence) that deviates from a simple exponential by less than 0.5%. Only a detailed analysis of the dynamics is likely to reveal that a free energy barrier is absent. Proteins 2003;50:1–4. © 2002 Wiley‐Liss, Inc.
Virtual screening to enrich hit lists from high‐throughput screening: A case study on small‐molecule inhibitors of angiogenin
Authors: Jenkins Jeremy L. , Kao Richard Y. T. , Shapiro Robert
Published: December 2002

“Hit lists” generated by high‐throughput screening (HTS) typically contain a large percentage of false positives, making follow‐up assays necessary to distinguish active from inactive substances. Here we present a method for improving the accuracy of HTS hit lists by computationally based virtual screening (VS) of the corresponding chemical libraries and selecting hits by HTS/VS consensus. This approach was applied in a case study on the target‐enzyme angiogenin, a potent inducer of angiogenesis. In conjunction with HTS of the National Cancer Institute Diversity Set and ChemBridge DIVERSet E (∼18,000 compounds total), VS was performed with two flexible library docking/scoring methods, DockVision/Ludi and GOLD. Analysis of the results reveals that dramatic enrichment of the HTS hit rate can be achieved by selecting compounds in consensus with one or both of the VS functions. For example, HTS hits ranked in the top 2% by GOLD included 42% of the true hits, but only 8% of the false positives; this represents a sixfold enrichment over the HTS hit rate. Notably, the HTS/VS method was effective in selecting out inhibitors with midmicromolar dissociation constants typical of leads commonly obtained in primary screens. Proteins 2003;50:81–93. © 2002 Wiley‐Liss, Inc.
Prediction of load–settlement relationship for large‐diameter piles
Authors: Xiao H. B. , Luo Q. Z. , Tang J. , Li Q. S.
Published: December 2002

An analytical solution for the bearing capacity of a large‐diameter pile is proposed based on the load transfer function in this paper. The load–settlement relationship or the P–S curve of such a pile can be determined by the proposed method for practical application. Comparison is made between the results obtained by the proposed method and the test data, and close agreement has been found, thus verifying the accuracy of the proposed method. It is noted that the most reliable approach to the determination of the vertical load capacity of a pile is to use the ­P–S curve, which is usually obtained through on‐site load test. However, for a large‐diameter pile (e.g. a diameter over 3 m), this kind of test requires a thousand tons of test load, which sometimes is impossible to provide. It is expected that the proposed method can be used in this kind of situation. Copyright © 2002 John Wiley & Sons, Ltd.
RIP4 (DIK/PKK), a novel member of the RIP kinase family, activates NF‐κB and is processed during apoptosis
Authors: Meylan Etienne , Martinon Fabio , Thome Margot , Gschwendt Michael , Tschopp Jürg
Published: December 2002

RIP1 and its homologs, RIP2 and RIP3, form part of a family of Ser/Thr kinases that regulate signal transduction processes leading to NF‐κB activation. Here, we identify RIP4 (DIK/PKK) as a novel member of the RIP kinase family. RIP4 contains an N‐terminal RIP‐like kinase domain and a C‐terminal region characterized by the presence of 11 ankyrin repeats. Overexpression of RIP4 leads to activation of NF‐κB and JNK. Kinase inactive RIP4 or a truncated version containing the ankyrin repeats have a dominant negative (DN) effect on NF‐κB induction by multiple stimuli. RIP4 binds to several members of the TRAF protein family, and DN versions of TRAF1, TRAF3 and TRAF6 inhibit RIP4‐induced NF‐κB activation. Moreover, RIP4 is cleaved after Asp340 and Asp378 during Fas‐induced apoptosis. These data suggest that RIP4 is involved in NF‐κB and JNK signaling and that caspase‐dependent processing of RIP4 may negatively regulate NF‐κB‐dependent pro‐survival or pro‐inflammatory signals.
Role of ubiquitination in retro‐translocation of cholera toxin and escape of cytosolic degradation
Authors: Rodighiero Chiara , Tsai Billy , Rapoport Tom A. , Lencer Wayne I.
Published: December 2002

Cholera toxin travels from the cell surface of affected mammalian cells to the endoplasmic reticulum (ER), where the A1 chain is released and retro‐translocated across the ER membrane into the cytosol. We have tested whether, as in other cases, retro‐translocation requires poly‐ubiquitination. We show that an A1 chain mutant that lacks lysines and has a blocked N‐terminus, and therefore cannot be ubiquitinated, remains active in vivo. The A1 chain is not degraded in the cytosol, as demonstrated by the fact that proteasome inhibitors do not stimulate its activity. When additional lysines are introduced into the A1 chain, moderate degradation by the proteasome is observed. The unfolded A1 chain rapidly refolds in vitro. These results show that poly‐ubiquitination is not required for retro‐translocation of all proteins across the ER membrane and indicate that the reason why the toxin escapes degradation in the cytosol may be both its paucity of lysines and its rapid refolding.
Dynamic behavior of transcription factors on a natural promoter in living cells
Authors: Becker Matthias , Baumann Christopher , John Sam , Walker Dawn A. , Vigneron Marc , McNally James G. , Hager Gordon L.
Published: December 2002

Through the use of photobleaching techniques, we examined the dynamic interaction of three members of the transcrsiption apparatus with a target promoter in living cells. The glucocorticoid receptor (GR) interacting protein 1 (GRIP‐1) exhibits a half maximal time for fluorescent recovery (τR) of 5 s, reflecting the same rapid exchange as observed for GR. In contrast, the large subunit (RPB1) of RNA polymerase II (pol II) required 13 min for complete fluorescence recovery, consistent with its function as a processive enzyme. We also observe a complex induction profile for the kinetics of GR‐stimulated transcription. Our results indicate that GR and GRIP‐1 as components of the activating complex are in a dynamic equilibrium with the promoter, and must return to the template many times during the course of transcriptional activation.
Attraction within the membrane
Authors: Helms Volkhard
Published: December 2002

Biological membranes are fascinating two‐dimensional microenvironments that exhibit unique solvent behaviours due to their varying lipid composition. Although many important bioenergetic and signalling events involve the transient or permanent assembly of membrane protein complexes, the characterization of the thermodynamic and kinetic properties behind this assembly is just beginning. In particular, the molecular forces that govern protein association within these structures remain poorly understood. An understanding of the docking of transmembrane proteins to supramolecular complexes, which will make possible the development of predictive computational tools, will require detailed knowledge of interaction forces at the atomistic or residue level. Here, I review current data on supramolecular complexes in membrane environments and make a tentative comparison between assembly processes in membranes and those driven by the hydrophobic effect in water. This comparison suggests that, in addition to being controlled by specific characteristics of the lipid molecules themselves, molecular assembly in the membrane milieu also depends more generally on the entropy of the lipid fraction.
Sulfimidation of thio-ether crown systems: the X-ray crystal structure of the {[9-ane]S2S(NH2)}+, {[9-ane]SS(NH2)S(NH2)}2+, and {[9-ane]S(NH2)S2(μ-N)}2+ cations
Authors: Elsegood Mark RJ , Gilby Liam M , Holmes Kathryn E , Kelly Paul F
Published: December 2002

Treatment of the thio-ether crown [9-ane]S3 (1) with 1 equiv of O-mesitylsulfonylhydroxylamine (MSH) yields the water-soluble protonated sulfimide {[9-ane]S2S(NH2)}+ (2). Two equiv of MSH leads to the formation of {[9-ane]SS(NH2)S(NH2)}2+ (3), while excess MSH generates the {[9-ane]S(NH2)S2(μ-N)}2+ cation (4) (24 form as salts of the [Me3C6H2SO3] anion); the X-ray crystal structure of 2 and 3 confirms that one and two of the ring sulfurs, respectively, have been converted to terminal protonated sulfimides, while that of 4 reveals the presence of both terminal and bridging nitrogens.Key words: sulfur-nitrides, macrocycles, sulfimides, amination.
Self-assembly using stannylplatinum(IV) halide complexes as ligands for organotin halides
Authors: Janzen Michael C , Jennings Michael C , Puddephatt Richard J
Published: December 2002

The possibility of forming extended structures by self-association using transition metal halides as donors to organotin acceptors has been investigated. The stannylplatinum(IV) complex [PtClMe2(SnMe2Cl)(bu2bpy)] forms a 1:1 adduct [PtClMe2(SnMe2Cl)(bu2bpy)]·Me2SnCl2with Me2SnCl2in which the organoplatinum complex acts as a donor to the organotin halide. Similarly, [PtClMe2(SnMeCl2)(bu2bpy)] forms adducts [PtClMe2(SnMeCl2)(bu2bpy)]·MeSnCl3or [PtClMe2(SnMeCl2)(bu2bpy)]·Me2SnCl2, and [{PtClMe2(bu2bpy)}2(µ-SnCl2)] forms [{PtClMe2(bu2bpy)}2(µ-SnCl2)]·Me2SnCl2. Structure determinations on selected compounds show that the donor is the Pt-Cl group and the acceptor tin centre is 5-coordinate. In the similar bromo complex [PtBrMe2(SnMeBr2)(bu2bpy)]·Me2SnBr2both the Pt-Br and PtSn-Br groups coordinate to the Me2SnBr2acceptor with short (3.14 or 3.29 Å) and long (3.99 or 4.05 Å) contacts, respectively, so that the acceptor tin centre adopts distorted octahedral stereochemistry in the solid state and a folded polymeric structure is formed. Reaction of [{PtClMe2(bu2bpy)}2(µ-SnCl2)] with AgO3SCF3yields the complex [{PtClMe2(bu2bpy)}(µ-SnCl2){PtMe2(bu2bpy)O3SCF3}], which is fluxional in solution.Key words: platinum, tin, self-assembly, coordination chemistry, organometallics.
The addition of organometallic reagents to tetramesityldigermene
Authors: Fujdala Kyle L , Gracey David W.K , Wong Erica F , Baines Kim M
Published: December 2002

The thermolysis and photolysis of hexamesitylcyclotrigermane in the presence of ethylmagnesium bromide has been investigated. Under photochemical conditions, ethyldimesitylgermane, 1,2-diethyl-1,1,2-trimesityldigermane and ethyl-1,1,2,2-tetramesityldigermane were isolated and, under thermal conditions, 1,2,2-triethyl-1,1-dimesityl digermane and 2,2-diethyl-1,1,1-trimesityldigermane were isolated. The photolysis of hexamesitylcyclotrigermane in the presence of methyllithium has also been investigated. In both cases, the organometallic reagent adds to tetramesityl digermene and dimesitylgermylene formed by photochemical or thermal cleavage of the cyclotrigermane. In the case of the addition of the Grignard reagent, the resulting germyl Grignard reagent undergoes a facile ligand exchange reaction.Key words: digermene, germylene, Grignard reagents, alkyllithium reagents, germylmagnesium compounds, germyllithium compounds.
Supramolecular self-assembly through tellurium···halogen secondary bonds: A hexagonal grid of Te2Cl2 and Te6Cl6 rings in the solid state structure of 1,1,3-trichloro-2,4,5,6-tetrahydro-1H-1λ4-benzo[b]tellurophene
Authors: Zukerman-Schpector Julio , Haiduc Ionel , Camillo Robinson L , Comasseto João V , Cunha Rodrigo Luiz Oliveira R. , Jorge Alvim
Published: December 2002

1,1,3-Trichloro-2,4,5,6-tetrahydro-1H-1λ4-benzo[b]tellurophene (a = 8.807(1), b = 14.495(2), c = 9.263(1) Å, β = 110.18(1)°; P21/a, Z= 4, R[F 2 > 2σ(F 2)] = 0.0383), prepared by reacting 1-ethynyl-1-cyclohexanol with tellurium tetrachloride, displays a hexagonal grid structure made of four-membered Te2Cl2 and 12-membered Te6Cl6 rings formed by self-assembly of Cl-Te-Cl rods through Te···Cl secondary bonds into a supramolecular 2D network. The comparison with structurally related compounds reveals that 2D layers can also be formed by similar self-assembly of eight-membered Te4I4 rings alone or in a combination of four-membered Te2I2 with eight-membered Te4I4 rings.Key words: diorganotellurium(IV), supramolecular 2D assembly, self-assembly, secondary bonding.
Palladium and platinum complexes of L-PhePhos: Acetyl-p-(diphenylphosphino)-L-phenylalanine methyl ester  a chiral ligand for transition metal complexation
Authors: Iyengar Vineeth , Galka Patrycja V , Pletsch Andreas , Kraatz Heinz-Bernhard
Published: December 2002

The crystal structure of the new phenylalanine-based phosphino amino acid L-PhePhos and its reactivity to form the Pd and Pt complexes (L-PhePhos)PdCl2 and (L-PhePhos)PtCl2 is reported. A new platinum hydride was quantitatively formed in the reaction of (L-PhePhos)PtCl2 with NaBH4.Key words: phosphine, amino acid, hydride, platinum, palladium, structure.
Linear and nonlinear optical responses of a dye anchored to gold nanoparticles dispersed in liquid and polymeric matrixes
Authors: Vargas-Baca Ignacio , Brown Andrew P , Andrews Mark P , Galstian Tigran , Li Yuejun , Vali Hojatollah , Kuzyk Mark G
Published: December 2002

The compound [4-CH3C6H4-SS-CH2CH2-N(CH3)C6H4C(C6H4N(CH3)2)-4)2]Cl (1a) consists of the triarylmethyl chromophore of crystal violet appended to an organic disulfide, to entail direct attachment of this dye to gold surfaces. Addition of 1a to colloidal dispersions of the metal produced a stable dispersion in methanolwater mixtures. Transmission electron microscopy of Freeze-Fracture sections shadowed with carbon and platinum confirmed that the dispersion remains unaggregated. Local-field effects and coupling to the surface plasmon of gold magnified the interaction of the chromophore with optical fields. A large oscillator strength in the visible spectrum (f ca. 35) and a first hyperpolarizability (β ca. 1026 esu, hyper-Rayleigh scattering) were observed as the colloid adsorbed dye molecules. A Hill-type analysis indicated that the adsorption process is cooperative. This combination of organic chromophore and nanoparticle was adapted for incorporation into PMMA-based composite films whose electrooptic coefficient (r113 = 2.20 pm V1) is larger than the sum of the individual contributions of dye and metallic particles.Key words: chromophores, colloids, gold, local-field effects, nonlinear optical materials.
Condensed versus open channel structures in cysteic acid coordination frameworks containing d10-d10 dimers
Authors: Riley Patrick J , Reid Jennifer L , Côté Adrien P , Shimizu George K
Published: December 2002

Single crystal X-ray structures have been obtained for [Ag(L-cysteic acid)][Formula: see text] (1) and [Ag(L-cysteic acid)(H2O)][Formula: see text] (2) These compounds represent the first two structurally characterized complexes of cysteic acid. Network 1 is shown to adopt an infinite two-dimensional structure, describable as one-dimensional ribbons cross-linked into layers. The basic building block is a doubly carboxylate-bridged silver(I) dimer. Compound 1 crystallizes in the monoclinic space group P21 (a = 5.5066(3) Å, b = 7.5761(4) Å, c = 16.644(1) Å, β = 94.335(1)°). Compound 2, while differing chemically from 1 by only one water molecule, forms a three-dimensional structure built upon the same core dimer unit as that observed in 1. In 2, these units assemble in a different manner via the weak interactions and form a channel structure in which the guest water molecules are included. Compound 2 crystallizes in the monoclinic space group P21 (a = 8.120(2) Å, b = 9.805(2) Å, c = 9.204(2) Å, β = 98.45(3)°).Key words: silver, carboxylates, sulfonates, coordination polymer.
The neutral diradical 5,5'-bis(1,3,2,4-dithiadiazolyl) [-], the first main group radical to exhibit a dramatic increase in paramagnetism on mechanical grinding
Authors: Antorrena Guillermo , Brownridge Scott , Cameron T Stanley , Palacio Fernando , Parsons Simon , Passmore Jack , Thompson Laurence K , Zarlaida Fitri
Published: December 2002

Reduction of [([Formula: see text])2][As6]2with triphenylantimony and tetrabutylammonium chloride produced the diradical 5,5'-bis(1,3,2,4-dithiadiazolyl) [[Formula: see text]-[Formula: see text]] in high yield as a black solid with widely ranging magnetic susceptibilities (e.g., 0.6 to 2.6 μB), which on oxidation with AsF5regenerated [([Formula: see text])2][AsF6]2. The identity of [[Formula: see text]-[Formula: see text]] was established from EPR, vibrational, and mass spectra. Ab initio molecular orbital [MPW1PW91/6-311G(2df)] calculations show the lowest energy structure to consist of two coplanar rings separated by a CC single bond (1.444 Å), reflected in the comparison of the vibrational spectra of the diradical with that of [([Formula: see text])2][AsF6]2and the calculated spectra. Confidence in the calculated [MPW1PW91/6-311G(2df)] structure of the diradical is supported by the excellent agreement between the calculated and X-ray single crystal structure geometries of [[Formula: see text]]2and [([Formula: see text])2]2+in [([Formula: see text])2][AsF6]2. The molecular orbitals indicate the diradical is essentially disjoint, confirmed by a very small (0.07 kJ mol1) GVB-PP(TC-SCF)/6-311G* calculated singlettriplet energy gap. Accordingly, the EPR spectrum of the diradical (in tetrahydrofuran, 293 K) shows a simple 3-line pattern (g = 2.0043, a(14N) = 1.11 mT) with no observable exchange coupling between the two radical centers. Mechanical grinding of the diradical results in a large increase in paramagnetism (e.g., from 1.03 to 2.55 μB) that is unprecedented in main group chemistry. The X-ray diffraction data of the ground and unground powder are consistent with a second order phase change on grinding. Attempts to obtain crystals of the diradical by sublimation led instead to numerous decomposition and rearrangement products, including 4-cyano-1,2,3,5-dithiadiazolyl [NC-[Formula: see text]], monoclinic space group C2/c, a = 9.46(2) Å, b = 7.625(5) Å, c = 13.17(2) Å, β = 107.94(4)°, Z = 8. The structure consists of axially symmetric, co-facial, cis dimers linked to form strands through two sets of C[Formula: see text]Nδ···Sδ+contacts. More efficient and larger scale preparations of [SNS][AsF6] and [([Formula: see text])2][AsF6]2are reported. Key words: 5,5'-bis(1,3,2,4-dithiadiazolyl), diradical, paramagnetism, mechanical grinding, second order phase change, 4-cyano-1,2,3,5-dithiadiazolyl.
Formation and decomposition of the Sb(III)/Li cage [{Sb(P-t-Bu)3}2Li6·6THF]
Authors: Bashall Alan , García Felipe , Lawson Gavin T , McPartlin Mary , Rothenberger Alexander , Woods Anthony D , Wright Dominic S
Published: December 2002

The heterometallic Sb(III)/Li cage complex [{Sb(P-t-Bu)3}2Li6·6THF] (1) is obtained by the low-temperature (<0°C) reaction of Sb(NMe2)3 with t-BuPHLi (1:3 equiv) in THF. Thermolysis of this reaction solution leads to the formation of the bicyclic distibane [(t-BuP)3Sb]2 (2). 31P NMR spectroscopic studies reveal that this process involves initial formation of [(t-BuP)3Sb] and [t-Bu(H)PP-t-Bu] anions. Complexes 1 and 2 have been characterized in the solid state by X-ray diffraction studies.Key words: antimony, lithium, cage.
Structural studies of dithiatetrazocines: X-ray crystal structures of the symmetric dithiatetrazocines p-XC6H4CN4S2CC6H4X [X = NO2, Br] and the first unsymmetric dithiatetrazocine, p-BrC6H4CN4S2CC6H4NO2
Authors: Bond Andrew D , Haynes Delia A , Rawson Jeremy M
Published: December 2002

Oxidation of equimolar amounts of [p-BrC6H4CNSSN]Cl and [p-O2NC6H4CNSSN]Cl with elemental O2 in the presence of Ph3Sb in MeCN yields a mixture of the symmetric dithiatetrazocines, O2NC6H4CN4S2CC6H4NO2 (1) and BrC6H4CN4S2CC6H4Br (2) as well as the unsymmetrically substituted derivative BrC6H4CN4S2CC6H4NO2 (3). The structures of compounds 13 are determined by X-ray diffraction: 1 crystallizes in the monoclinic space group P21/c (a = 8.6397(4), b = 5.8359(4), c = 14.9767(11) Å, β = 92.088(4)°) with half a molecule in the asymmetric unit; 2 crystallizes in the triclinic space group P[Formula: see text] (a = 6.5330(5), b = 8.2084(6), c = 14.7264(9) Å, α = 84.483(4)°, β = 77.112(4)°, γ = 87.879(3)°); 3 was found to crystallize in two forms: recrystallization from CH2Cl2 at room temperature yielded a solvent-free, triclinic phase, space group P[Formula: see text] (a = 6.5060(9), b = 7.0739(9), c = 9.1164(8) Å, α = 81.860(3)°, β = 83.406(5)°, γ = 66.589(5)°), whereas cooling a solution to 5°C yielded a solvated form, 3·CH2Cl2, which crystallizes in the monoclinic space group P21/m (a = 6.179(1), b = 10.960(2), c = 13.884(3) Å, β = 92.69(3)°). The NO2···Br intermolecular interactions observed in the unsolvated structure of 3 are disrupted in the solvate structure; the CH2Cl2 molecule in the latter is aligned such that its molecular dipole interacts with both nitro and bromo groups, retaining a molecular chain motif. The structures are discussed in relation to their semi-empirically calculated molecular electrostatic potentials and calculations of intermolecular interactions using van der Waals forces combined with an electrostatic point charge model.Key words: dithiatetrazocine, crystal structure, crystal engineering, molecular electrostatic potential.
OPTIMIZATION AND STATISTICAL ANALYSIS OF EVOLUTIONARY DYNAMICS IN THE SK SPIN GLASS MODEL
Authors: CAMPOS PAULO R. A. , DE OLIVEIRA VIVIANE M.
Published: December 2002

In this work we perform a statistical analysis of the evolutionary events in a modified version of the Sherrigton–Kirkpatrick model that takes into account the neutrality effect in the landscape. The evolutionary events correspond to abrupt changes in the fitness of the population after long period of stasis. The distribution of these events and its dependence on the set of parameters of the model are investigated. We also examine the performance of the optimization process looking at the temporal evolution of average and maximum fitness in the population.
ARE FOREST FIRES PREDICTABLE?
Authors: MALARZ K. , KACZANOWSKA S. , KUŁAKOWSKI K.
Published: December 2002

Dynamic mean field theory is applied to the problem of forest fires. The starting point is the Monte Carlo simulation in a lattice of a million cells. The statistics of the clusters is obtained by means of the Hoshen–Kopelman algorithm. We get the map pn → pn + 1, where pn is the probability of finding a tree in a cell, and n is the discrete time. We demonstrate that the time evolution of p is chaotic. The arguments are provided by the calculation of the bifurcation diagram and the Lyapunov exponent. The bifurcation diagram reveals several windows of stability, including periodic orbits of length three, five and seven. For smaller lattices, the results of the iteration are in qualitative agreement with the statistics of the forest fires in Canada in the years 1970–2000.
LATTICE-GAS AUTOMATA FOR THE PROBLEM OF KINETIC THEORY OF GAS DURING FREE EXPANSION
Authors: KHOTIMAH SITI NURUL , ARIF IDAM , LIONG THE HOUW
Published: December 2002

The lattice-gas method has been applied to solve the problem of kinetic theory of gas in the Gay–Lussac–Joule experiment. Numerical experiments for a two-dimensional gas were carried out to determine the number of molecules in one vessel (Nr), the ratio between the mean square values of the components of molecule velocity [Formula: see text], and the change in internal energy (ΔU) as a function of time during free expansion. These experiments were repeated for different sizes of an aperture in the partition between the two vessels.

After puncturing the partition, the curve for the particle number in one vessel shows a damped oscillation for about half of the total number. The oscillations do not vanish after a sampling over different initial configurations. The system is in nonequilibrium due to the pressure equilibration, and here the flow is actually compressible. The equilibration time (in time steps) decreases with decreased size of aperture in the partition. For very small apertures (equal or less than [Formula: see text] lattice units), the number of molecules in one vessel changes with time in a smooth way until it reaches half of the total number; their curves obey the analytical solution for quasi-static processes. The calculations on [Formula: see text] and ΔU also support the results that the equilibration time decreases with decreased size of aperture in the partition.
HS3D, A DATASET OF HOMO SAPIENS SPLICE REGIONS, AND ITS EXTRACTION PROCEDURE FROM A MAJOR PUBLIC DATABASE
Authors: POLLASTRO PASQUALE , RAMPONE SALVATORE
Published: December 2002

The aim of this work is to describe a cleaning procedure of GenBank data, producing material to train and to assess the prediction accuracy of computational approaches for gene characterization. A procedure (GenBank2HS3D) has been defined, producing a dataset (HS3D — Homo Sapiens Splice Sites Dataset) of Homo Sapiens Splice regions extracted from GenBank (Rel.123 at this time). It selects, from the complete GenBank Primate Division, entries of Human Nuclear DNA according with several assessed criteria; then it extracts exons and introns from these entries (actually 4523 + 3802). Donor and acceptor sites are then extracted as windows of 140 nucleotides around each splice site (3799 + 3799). After discarding windows not including canonical GT–AG junctions (65 + 74), including insufficient data (not enough material for a 140 nucleotide window) (686 + 589), including not AGCT bases (29 + 30), and redundant (218 + 226), the remaining windows (2796 + 2880) are reported in the dataset. Finally, windows of false splice sites are selected by searching canonical GT–AG pairs in not splicing positions (271 937 + 332 296). The false sites in a range +/- 60 from a true splice site are marked as proximal. HS3D, release 1.2 at this time, is available at the Web server of the University of Sannio: .
DENSITY FUNCTIONAL THEORY ON FLOATING SPHERICAL GAUSSIAN ORBITAL METHOD
Authors: PAKIARI A. H. , MOHAJERI A.
Published: December 2002

This research is an introduction to density functional theory (DFT), which has been designed for Floating Spherical Gaussian Orbital (FSGO) method for the first time. Our principal objective is to apply a combination of energy functionals to the FSGO densities. The functionals used are separated into exchange and correlation parts. For the exchange part the Becke exchange that includes gradient correction is used. The correlation part has been carried out using Lee, Yang and Parr gradient-corrected functional. Three goals are investigated in this research. Is it possible to apply DFT in the FSGO procedure to obtain the electronic structure of chemical species? Second, is it a stable condition, from the variational point of view, during optimization of exponents and coefficients of each Gaussian? Thirdly, when the two above questions are encouraging, are the results consistent with other results in the literature? In this research we are looking for acceptable answers to the above questions.
3D PULSATILE FLOW WITH THE LATTICE BOLTZMANN BGK METHOD
Authors: ARTOLI A. M. , HOEKSTRA A. G. , SLOOT P. M. A.
Published: December 2002

We present detailed analysis of the accuracy of the lattice Boltzmann BGK method in simulating pulsatile flow in a 2D channel and a 3D tube. For the 2D oscillatory flow, we have observed a half time-steps shift between the theory and the simulation, that enhances the accuracy at least one order of magnitude. For 3D tube flow, we have tested the accuracy of the lattice Boltzmann BGK method in recovering the Womersley solution for pulsatile flow in a rigid tube with a sinusoidal pressure gradient. The obtained flow parameters have been compared to the analytical solutions. The influence of different boundary conditions such as the bounce-back and inlet-outlet boundary conditions on the accuracy was studied. Relative errors of the order of 0.001 in 2D with the bounce back on the nodes have been achieved. For the 3D simulations, it has been possible to reduce the error from 15% with the simple bounce-back to less than 5% with a curved boundary condition.
A NEW METHOD FOR CALCULATING THE FUNCTIONAL DERIVATIVE δTc/δα2F(Ω): APPLICATION TO MgB2
Authors: MITROVIĆ BOŽIDAR
Published: December 2002

We present a new method for calculating the functional derivative of the superconducting transition temperature Tc with respect to the electron–phonon coupling function α2F(Ω). The method relies on a highly efficient procedure for finding the largest eigenvalue and the corresponding eigenvector of a Hermitian matrix. The convergence problems that arise in the calculation of δTc/δα2F(Ω) for systems with low Tc and a large maximum phonon frequency Ωmax using the method based on the pair-breaking parameter are eliminated. We apply the new method of calculating δTc/δα2F(Ω) to MgB2, to the prototype strong coupling superconductor Pb and to weak coupling (BCS) superconductor Al.
A FAMILY OF CONTROLLABLE CELLULAR AUTOMATA FOR PSEUDORANDOM NUMBER GENERATION
Authors: GUAN SHENG-UEI , ZHANG SHU
Published: December 2002

In this paper, we present a family of novel Pseudorandom Number Generators (PRNGs) based on Controllable Cellular Automata (CCA) CCA0, CCA1, CCA2 (NCA), CCA3 (BCA), CCA4 (asymmetric NCA), CCA5, CCA6 and CCA7 PRNGs. The ENT and DIEHARD test suites are used to evaluate the randomness of these CCA PRNGs. The results show that their randomness is better than that of conventional CA and PCA PRNGs while they do not lose the structure simplicity of 1D CA. Moreover, their randomness can be comparable to that of 2D CA PRNGs. Furthermore, we integrate six different types of CCA PRNGs to form CCA PRNG groups to see if the randomness quality of such groups could exceed that of any individual CCA PRNG. Genetic Algorithm (GA) is used to evolve the configuration of the CCA PRNG groups. Randomness test results on the evolved CCA PRNG groups show that the randomness of the evolved groups is further improved as compared with any individual CCA PRNG.
Low‐modulus siloxane–polyurethanes. Part II. Effect of chain extender structure on properties and morphology
Authors: Adhikari Raju , Gunatillake Pathiraja A. , McCarthy Simon J. , Bown Mark , Meijs Gordon F.
Published: December 2002

A series of six polyurethanes were prepared to study the effect of silicon chain extender structure on properties and morphology of siloxane–polyurethanes. Polyurethanes were prepared by a two‐step bulk polymerization without a catalyst. The soft segment of the polyurethanes was based on an 80:20 (w/w) mixture of α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS, MW 966) and poly(hexamethylene) oxide (MW 714). The hard segment was based on 4,4′‐methylenediphenyl diisocyanate (MDI) and a 60:40 molar mixture of 1,4‐butanediol (BDO) and a silicon chain extender. Silicon chain extenders (SCE) investigated were 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD), 1,3‐bis(3‐hydroxypropyl)1,1,3,3‐tetramethyldisiloxane (BPTD), 1,4‐bis(3‐hydroxypropyl)1,1,3,3‐tetramethyldisilylethylene (HTDE), 1,3‐bis(6‐hydroxyethoxypropyl)1,1,3,3‐tetramethyldisiloxane (BETD). All polyurethanes were clear and transparent with number average molecular weights between 72,000 to 116,000. Incorporation of the silicon chain extender resulted in polyurethanes with low‐modulus and high elongation. This was achieved without significant compromise in ultimate tensile strength in all cases, except BETD. Differential scanning calorimetry (DSC) results showed that the silicon chain extenders did not significantly disrupt the hard segment crystallinity, but exhibited a unique morphological feature where SCE‐based hard segments formed separate domains, which may be the primary reason for achieving low modulus without significant compromise in strength. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1092–1100, 2003
Reactive extrusion of polypropylene with supercritical carbon dioxide: Free radical grafting of maleic anhydride
Authors: Dorscht B. M. , Tzoganakis C.
Published: December 2002

A reactive extrusion process for the functionalization of polypropylene with maleic anhydride in the presence of supercritical carbon dioxide was studied. Supercritical carbon dioxide was used in this reactive extrusion system to reduce the viscosity of the polypropylene melt phase by forming a polymer–gas solution in order to promote better mixing of the reactants. Subsequently, the effect of supercritical carbon dioxide on the level of grafting, product homogeneity, and molecular weight was evaluated. Analysis of the products revealed that the use of supercritical carbon dioxide led to improved grafting when high levels of maleic anhydride were used. The experimental results showed no evidence of an improvement in the homogeneity of the product, while melt flow rate measurements showed a reduction in the degradation of polypropylene during the grafting reaction when low levels of maleic anhydride were employed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1116–1122, 2003
Banking (on) different forms of symbolic capital
Authors: Cronin Blaise , Shaw Debora
Published: December 2002

The accrual of symbolic capital is an important aspect of academic life. Successful capital formation is commonly signified by the trappings of scholarly distinction or acknowledged status as a public intellectual. We consider and compare three potential indices of symbolic capital: citation counts, Web hits, and media mentions. Our findings, which are domain specific, suggest that public intellectuals are notable by their absence within the information studies community.
Complementary user‐centered methodologies for information seeking and use: System's design in the Biological Information Browsing Environment (BIBE)
Authors: Heidorn P. Bryan , Mehra Bharat , Lokhaiser Mary F.
Published: December 2002

Complementary, socially grounded, user‐centered methodologies are being used to design new information systems to support biodiversity informatics. Each of the methods—interviews, focus groups, field observations, immersion, and lab testing—has its own strengths and weaknesses. Methods vary in their ability to reveal the automatic processes of experts (that need to be learned by novices), data richness, and their ability to help interpret complex information needs and processes. When applied in concert, the methods provide a much clearer picture of the use of information while performing a real life information‐mediated task. This picture will be used to help inform the design of a new information system, Biological Information Browsing Environment (BIBE). The groups being studied are high school students, teachers, and volunteer adult groups performing biodiversity surveys. In this task the people must identify and record information about many species of flora and fauna. Most of the information tools they use for training and during the survey are designed to facilitate the difficult species identification task.