bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(ethylene‐co‐methacrylic acid)–lithium ionomer as a compatibilizer for poly(ethylene terephthalate)/linear low‐density polyethylene blends
Authors: Retolaza A. , Eguiazábal J. I. , Nazábal J.
Published: December 2002

Poly(ethylene terephthalate) (PET)/linear low‐density polyethylene (LLDPE) blends (75/25), with contents of poly(ethylene‐co‐methacrylic acid) partially neutralized with lithium (PEMA–Li) that were systematically changed from 0 to 45% relative to the LLDPE, were obtained by direct injection molding in an attempt to (1) ameliorate the performance of the binary blend and (2) find the best compatibilizer content. PEMA–Li did not modify the PET or LLDPE amorphous‐phase compositions or the crystalline content of PET. However, PEMA–Li did lead to a nucleation effect and to the presence of a second smaller and less perfect crystalline structure. PET induced a fractional crystallization in LLDPE that remained in the presence of PEMA–Li and reduced the crystallinity of LLDPE. The ternary blends showed two similar dispersed LLDPE and PEMA–Li phases with small subparticles, probably PET, inside. The compatibilizing effect of PEMA–Li was clearly shown by the impressive increase in the break strain, along with only small decreases in the modulus of elasticity and in the tensile strength. With respect to the recycling possibilities of LLDPE, a ternary blend with the addition of 22.5% PEMA–Li, which led to very slight modulus and yield stress decreases with respect to the binary blend and a break strain increase of 480%, appeared to be the most attractive. However, the highest property improvement appeared with the addition of 37.5% PEMA–Li, which led to elasticity modulus and tensile strength decreases of only 9%, along with a very high break strain increase (760%). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1322–1328, 2003
Effect of polymer concentration on polarization switching in polysiloxane‐dispersed ferroelectric liquid crystals
Authors: Sumana G. , Raina K. K.
Published: December 2002

Ferroelectric liquid crystal–polysiloxane composite films were prepared after dissolving them in diethyl ether as a solvent. The crosslinking was done by adding room temperature vulcanizer (mixture of tetra ethoxy silane and dibutyl tin dilaurate) as curing agent. These composite films show good electro‐optic properties with switching times on the order of few milliseconds. The preliminary results show that these systems can be useful as functional materials in electronic displays. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1209–1215, 2003
An Empirical Comparison of Parametric and Semiparametric Cure Models
Authors: Peng Yingwei , Carriere K.C.
Published: December 2002

Parametric and semiparametric cure models have been proposed for cure proportion estimation in cancer clinical research. In this paper, several parametric and semiparametric models are compared, and their estimation methods are discussed within the framework of the EM algorithm. We show that the semiparametric PH cure model can achieve efficiency levels similar to those of parametric cure models, provided that the failure time distribution is well specified and uncured patients have an increasing hazard rate. Therefore the semiparametric model is a viable alternative to parametric cure models. When the hazard rate of uncured patients is rapidly decreasing, the estimates from the semiparametric cure model tend to have large variations and biases. However, all other models also tend to have large variations and biases in this case.
The Utilization of Kurtosis in the Estimation of the Parameters of the One‐Way Random Effects Model
Authors: Singh Housila P. , Shukla Sushil K. , Singh Sarjinder
Published: December 2002

This paper deals with the problem of estimating the components of the variance of one‐way random effects model under non‐normality situation using a prior knowledge of coefficient of kurtosis. We have suggested two classes of estimators $\hat \sigma _{(p)}^2 $ and $\hat \sigma _{(q)}^2 $ for the within and between variances respectively. Optimum estimators in the classes of $\hat \sigma _{(p)}^2 $ and $\hat \sigma _{(q)}^2 $ are identified with their mean squared errors formulae and compared with that of usual ANOVA unbiased and Shoukri, Tracy and Mian's (1990) estimators. It is found that the proposed estimators are more efficient than the ANOVA unbiased estimators and Shoukri, Tracy and Mian (1990) estimators.
Validation of Surrogate Endpoints in Multiple Randomized Clinical Trials with Discrete Outcomes
Authors: Renard Didier , Geys Helena , Molenberghs Geert , Burzykowski Tomasz , Buyse Marc
Published: December 2002

This article extends the work of Buyse et al. (2000) on the validation of surrogate endpoints in a meta‐analytic setting to the case of two discrete outcomes, the focus being on binary endpoints. The methodology entails fitting of a joint model for the surrogate and the true endpoints that includes several random effects. We propose to fit this model using a pairwise likelihood (PL) approach which seems better suited to the problem at hand than maximum likelihood or penalized quasi‐likelihood. The performance of the PL estimator is evaluated on the grounds of limited simulations and the methodology is illustrated on data from a meta‐analysis of five clinical trials comparing antipsychotic agents for the treatment of chronic schizophrenia.
Estimation of Spatial Variation in Risk Using Matched Case‐control Data
Authors: Jarner Mikala F. , Diggle Peter , Chetwynd Amanda G.
Published: December 2002

A common problem in environmental epidemiology is to estimate spatial variation in disease risk after accounting for known risk factors. In this paper we consider this problem in the context of matched case‐control studies. We extend the generalised additive model approach of Kelsall and Diggle (1998) to studies in which each case has been individually matched to a set of controls. We discuss a method for fitting this model to data, apply the method to a matched study on perinatal death in the North West Thames region of England and explain why, if spatial variation is of particular scientific interest, matching is undesirable.
Estimation of Poisson Rates with Misclassified Counts
Authors: Bratcher Thomas L. , Stamey James D.
Published: December 2002

The Poisson assumption is popular when data arises in the form of counts. In many applications such counts are fallible. Little research has been done on the Poisson distribution when both false positives and false negatives are present. We present a model in this paper that corrects for misclassification of count data. Bayesian estimators are developed. We provide the actual posterior distributions via integration. Markov Chain Monte Carlo results, which are more convenient for large sample sizes, are utilized for inference.
Effect of phosphonate additive on crystallization of gypsum in phosphoric and sulfuric acid medium
Authors: El‐Shall H. , Rashad M.M. , Abdel‐Aal E.A.
Published: December 2002

Understanding the mechanisms of growth and inhibition during crystallization of calcium sulfate is of primary importance for many industrial applications. For instance, inhibition of the crystallization process may be required to prevent scale formation in pipes, boilers, heat exchangers, reactors, reverse osmosis membrane surfaces, cooling water systems, secondary oil recovery utilizing water flooding techniques and desalination evaporators, etc. On the other hand, control growth and morphology of gypsum crystals is desired in achieving higher filtration rate and higher productivity of phosphoric acid from phosphate rocks. In this regard, this basic study is carried out to understand effect of Aminotris (methylenephosphonic acid (ATMP) on calcium sulfate dihydrate (gypsum) crystallization. The time elapsed between the achievement of supersaturation and the appearance of a solid phase (termed as induction time) is measured under different supersaturation ratios ranging from 1.018 to 1.979. The data are used to calculate the surface energy, critical nucleus size, and crystal growth rates of gypsum under different conditions. The results show that, the induction time decreases exponentially with increasing the supersaturation ratio. In addition, the surface energy decreases with ATMP compared to the baseline (without ATMP). Interestingly, with addition of the ATMP, the crystals mean and median diameters are found to decrease. The inhibition efficiency ranges from 16% to 59% depending on supersaturation ratio.
Crystal growth of some urinary stone constituents: II. In‐vitro crystallization of hippuric acid
Authors: Ramachandran E. , Natarajan S.
Published: December 2002

Hippuric acid [C6H5CONHCH2COOH], one of the organic chemical constituents of urinary stone is crystallized in silica gel under suitable pH conditions by double diffusion method. The grown crystals were characterized by density measurement, Fourier transform infrared spectroscopy, X‐ray powder diffraction and thermogravimetric analysis.
Influence of thermal annealing on the composition and structural parameters of DC magnetron sputtered titanium dioxide thin films
Authors: Karunagaran B. , Rajendra Kumar R.T. , Mangalaraj D. , Narayandass Sa. K. , Mohan Rao G.
Published: December 2002

Titanium dioxide films have been deposited using DC magnetron sputtering technique. Films were deposited onto RCA cleaned p‐silicon substrates at the ambient temperature at an oxygen partial pressure of 7 × 10–5 mbar and sputtering pressure of 1 × 10 –3 mbar. The deposited films were annealed in the temperature range 673–873 K. The structure and composition of the films were confirmed using X‐ray diffraction and Auger electron spectroscopy. The structure of the films deposited at the ambient was found to be amorphous and the films annealed at 673 K and above were crystalline with anatase structure. The lattice constants, grain size, microstrain and the dislocation density of the film are calculated and correlated with annealing temperature.
Crystal structure and properties of [Cu(sac)2(py)3], a new example of a mononuclear complex with both N‐ and O‐bonded saccharinate ligands
Authors: Quinzani O. V. , Tarulli S. H. , Garcia‐Granda S. , Marcos C. , Baran E. J.
Published: December 2002

The crystal structure of the title complex has been determined by single X‐ray diffraction methods and refined to an R‐value of 0.0543. It crystallizes in the monoclinic P21/a space group with a = 21.1231(9), b = 9.4523(4), c = 16.1874(7) Å, β = 107.3706(3)° and Z = 4. The compound represents only the second known example of a simple mononuclear metal complex containing simultaneously N‐ and O‐bonded saccharinato ligands. Its infrared spectrum and thermal behavior are also briefly discussed.
Crystal structure analysis of Bis{(N,N′‐dimethylformamide)‐[μ‐bis‐N,N′‐(2‐oxybenzyl)‐1,3‐propanediaminato](μ‐asetato) nickel(II)}nickel(II)
Authors: Tatar Yildirim L. , Atakol O.
Published: December 2002

The title compound, a homotrinuclear NiII complex has been synthesized from ONNO type Schiff base reduced with the help of NaBH4. The structure of the complex, [Ni{Ni(CH3CO2) (C17H20N2O2) (C3H7NO)}2], was identified using elemental analysis, thermal analysis, IR spectroscopy and x‐ray diffraction techniques. It was established that although some bond lengths and angles changed with respect to previous complexes, the Ni…Ni distance was approximately the same.
Crystal structure of μ‐phenoxo bridged dicopper complex: {N‐[(2‐hydroxylato‐5‐methyl)benzyl‐(2′‐hydroxylato‐3′,5′‐dimethylbenzyl)]ethyl amine dicopper(II)}
Authors: Malathy Sony S. M. , Kuppayee M. , Ponnuswamy M. N. , Manonmani J. , Kandasamy M. , Fun Hoong‐Kun
Published: December 2002

The title compound crystallizes in monoclinic space group C2/c with cell parameters a = 21.404(2), b = 13.962(1), c = 17.917(1)Å, β = 124.394(2)°, V = 4418.3(6)Å3, Z = 8, Dcal = 1.193Mg/m3 and T = 293 K. The structure was solved by Patterson method and refined by full‐matrix least‐squares procedures to final R = 0.0882 using 5253 observed reflections. The tetra coordinated copper atom have a slight distorted square planar geometry with the Cu‐Cu distance of 2.987(1)Å. The two six membered rings containing copper atom assume distorted sofa conformation. C‐H…π and C‐H…O type of intermolecular interactions play a role in stabilizing the crystal packing in addition to van der Waals forces.
Theory of DNA electrophoresis (∼ 1999 –2002 ½)
Authors: Slater Gary W. , Guillouzic Steve , Gauthier Michel G. , Mercier Jean‐François , Kenward Martin , McCormick Laurette C. , Tessier Frédéric
Published: December 2002

Over the last two decades, the introduction of new methods such as pulsed‐field gel electrophoresis and capillary array electrophoresis has made it possible to map and sequence entire genomes, including our own. The development of these experimental methods has been helped by the progress of theoretical and computational sciences, and the interactions between these threemodi operandiof modern science are still pushing the limits of our technologies. We now see a clear trend towards proteomics and microfluidic (even nanofluidic!) devices. In this review, we take a look at the progress of the field over the last 3 years using the glasses of the theoretical scientist and focusing mostly on new ideas and concepts. About a dozen different subfields are discussed and reviewed. We conclude by giving a commented list of some of the best review articles published over the last 2–3 years.
Polymeric monolithic stationary phases for capillary electrochromatography
Authors: Hilder Emily F. , Svec Frantisek , Fréchet Jean M. J.
Published: December 2002

This review summarizes the contributions of a number of groups working in the rapidly growing area of monolithic columns for capillary electrochromatography (CEC), with a focus on those prepared from synthetic polymers. Monoliths have quickly become a well‐established stationary phase format in the field of CEC. The simplicity of their in situ preparation method as well as the good control over their porous properties and surface chemistries make the monolithic separation media an attractive alternative to capillary columns packed with particulate materials. A wide variety of approaches as well as materials used for the preparation of the monolithic stationary phases are detailed. Their excellent chromatographic performance is demonstrated by numerous separations of different analytes.
Advances in sol‐gel based columns for capillary electrochromatography: Sol‐gel open‐tubular columns
Authors: Malik Abdul
Published: December 2002

The development of sol‐gel open‐tubular column technology in capillary electrochromatography (CEC) is reviewed. Sol‐gel column technology offers a versatile means of creating organic‐inorganic hybrid stationary phases. Sol‐gel column technology provides a general approach to column fabrication for microseparation techniques including CEC, and is amenable to both open‐tubular and monolithic columns. Direct chemical bonding of the stationary phase to the capillary inner walls provides enhanced thermal and solvent stability to sol‐gel columns. Sol‐gel stationary phases inherently possess higher surface area, and thus provide an effective one‐step alternative to conventional open‐tubular column technology. Sol‐gel column technology is applicable to both silica‐based and transition metal oxide‐based hybrid stationary phases, and thus, provides a great opportunity to utilize advanced material properties of a wide range of nontraditional stationary phases to achieve enhanced selectivity in analytical microseparations. A wide variety of stationary phase ligands can be chemically immobilized on the capillary inner surface using a single‐step sol‐gel procedure. Sol‐gel chemistry can be applied to design stationary phases with desired chromatographic characteristics, including the possibility of creating columns with either a positive or a negative charge on the stationary phase surface. This provides a new tool to control electroosmotic flow (EOF) in the column. Column efficiencies on the order of half a million theoretical plates per meter have been reported for sol‐gel open‐tubular CEC columns. The selectivity of sol‐gel stationary phases can be easily fine‐tuned by adjusting the composition of the coating sol solution. Open‐tubular columns have significant advantages over their packed counterparts because of the simplicity in column making and hassle‐free fritless operation. Open‐tubular CEC columns possess low sample capacity and low detection sensitivity. Full utilization of the analytical potential of sol‐gel open‐tubular columns will require a concomitant development in the area of high‐sensitivity detection technology.
Recent progress in the development, characterization and application of polymeric pseudophases for electrokinetic chromatography
Authors: Palmer Christopher P.
Published: December 2002

This review article details the development, characterization and application of polymeric materials as pseudostationary phases for electrokinetic chromatography over the past two years. Recent developments in cationic polymers and anionic siloxane, acrylamide and polymerized surfactants (micelle polymers) are reviewed. Also reviewed is recent progress in the development and characterization of chiral polymeric phases for chiral separations by electrokinetic chromatography, and application of a polymeric pseudophase with electrospray ionization mass spectrometric detection.
Recent progress in enantiomeric separation by capillary electrochromatography
Authors: Kang Jingwu , Wistuba Dorothee , Schurig Volker
Published: December 2002

Recent progress in enantiomeric separations by capillary electrochromatography (CEC) is reviewed. The development of simple and robust CEC column technologies plays an important role for popularization of CEC. During the last several years, various approaches for the preparation of enantioselective columns have been reported. Currently, the monolithic column technology (continuous beds) represents the most advanced approach for the preparation of CEC columns. The development of new chiral stationary phase used for CEC is another important issue in this field. Fundamental investigations on electrochromatographic behaviors of various CSPs are necessary in order to understand the separation mechanism and thus improve the separation performance. Some chiral stationary phases performed better under nonaqueous CEC conditions than reversed‐phase conditions. Coupling CEC with mass spectrometry (MS) provides a powerful tool for enantiomeric separation. Finally, some applications of enantiomeric separation by CEC are summarized.
Detection of submicrogram quantities of glycosaminoglycans on agarose gels by sequential staining with toluidine blue and Stains‐All
Authors: Volpi Nicola , Maccari Francesca
Published: December 2002

A sensitive method has been developed for the visualization of nonradiolabelled glycosaminoglycans resolved by agarose gel electrophoresis using staining with toluidine blue followed by Stains‐All procedure. This method, which can detect as little as 10 ng of a single species, can be used to stain a few micrograms of a complex polysaccharide mixture. The combination of agarose gel electrophoresis and sequential toluidine blue/Stains‐All staining can be applied to the analysis of all the complex glycosaminoglycans (i.e., heparin, heparan sulfate, chondroitin/dermatan sulfate) and nonsulfated polyanions (i.e., hyaluronate, defructosylated capsular polysaccharide K4) as well as to comparisons of specificities of the glycosaminoglycan‐degrading enzymes and the identification and quantification of the contaminations of other polysaccharides within glycosaminoglycan preparations with great sensitivity (about 0.1%). Furthermore, this method can be used to stain low‐molecular‐mass fractions and oligosaccharides derived from the natural polyanions, such as heparin. This procedure may be particularly valuable in situations where the availability of glycosaminoglycan is very limited.
Revisiting electroblotting of immobilized pH gradient gels: A new protocol for studying post‐translational modification of proteins
Authors: Poland Julia , Böhme Axel , Schubert Kathrin , Sinha Pranav
Published: December 2002

Currently, one of the most important techniques in proteome analysis is two‐dimensional electrophoresis that is widely used for separation of thousands of different protein spots. Nevertheless, characterization of special aspects in protein patterns, e.g., separation of protein isoforms generated by post‐translational modifications, requires individual detection methods, e.g., immunoblotting. Blotting of proteins after fractionation in immobilized pH gradients has always caused some problems. In this paper we present an optimized protocol for immunoblotting after isoelectric focusing using immobilized pH gradient (IPG) strips cast on Net‐Fix as an internal support that is permeable to electric current. The focusing procedure can be carried out in commonly used IPG systems, e.g., the IPGphor by Amersham Biosciences, where electrically assisted rehydration can be performed. This may be of interest for many laboratories, because the same system as used for the first dimension of two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) is involved. As an example, we describe separation and detection of up to seven isoforms of recombinant erythropoietin β using semidry blotting of IPG strips and visualization by chemiluminescence detection.
Analysis of benzo[a]pyrene diol epoxide‐DNA adducts by capillary zone electrophoresis‐ electrospray ionization‐mass spectrometry in conjunction with sample stacking
Authors: Willems An V. , Deforce Dieter L. , Van den Eeckhout Elfriede G. , Lambert Willy E. , Van Peteghem Carlos H. , De Leenheer André P. , Van Bocxlaer Jan F.
Published: December 2002

Benzo[a]pyrene diol epoxide (BPDE) was reacted in vitro with (2'‐deoxy)nucleotides and with calf thymus DNA. The modified DNA was enzymatically hydrolyzed to the 5'‐monophosphate nucleotides using deoxyribonuclease I (DNA‐ase I), nuclease P1 and snake venom phosphodiesterase (SVP). Most of the unmodified nucleotides were removed using solid phase extraction (SPE) in a polystyrene divinylbenzene copolymer. Three adducts could be detected and identified using capillary zone electrophoresis(negative)‐ion electrospray ionization‐mass spectrometry (CZE‐(—)‐ESI‐MS) in conjunction with sample stacking. This way, not only a BPDE‐dGMP adduct [(M—H)— at m/z 648], a well‐known nucleotide adduct, could be retrieved, but also a BPDE‐dAMP [(M—H)— at m/z 632] and a BPDE‐dCMP adduct [(M—H)— at m/z 608] could be detected for the first time. The presence of the prominent ion at m/z 195 (the deoxyribose‐phosphate ion) in the three low‐energy collision‐activated decomposition (CAD) spectra indicated that the adducts were formed through base‐alkylation. CZE‐positive ion ESI‐MS/MS experiments were performed to obtain further information on base‐alkylation. The absence of the loss of NH3 from the nucleobase in each CAD spectrum points to an alkylated exocyclic NH2 position of the nucleobase. So, the three adducts could be identified as BPDE‐N2‐dGMP, BPDE‐N6‐dAMP and BPDE‐N4‐dCMP using CZE‐ESI‐MS and CZE‐ESI‐MS/MS.
Enantioseparation of chiral aromatic amino acids by capillary electrophoresis in neutral and charged cyclodextrin selector modes
Authors: La Sookie , Ahn Sungyeon , Kim Jung‐Han , Goto Junichi , Choi One‐Kyun , Kim Kyoung‐Rae
Published: December 2002

Simultaneous enantioseparations of 15 racemic aromatic amino acids and L‐mimosine for their chiral discrimination were achieved by neutral selector‐modified capillary electrophoresis (CE) and by charged selector‐modified CE. Among the diverse cyclodextrins (CDs) examined, hydroxypropyl (HP)‐α‐CD as the neutral selector and highly sulfated (HS)‐γ‐CD as the charged selector provided best chiral environments of different enantioselectivities. Fairly good enantiomeric resolutions were achieved with the HP‐α‐CD mode except for racemic 6‐hydroxy‐3,4‐dihydroxyphenylalanine, threo‐3,4‐dihydroxyphenylserine and homophenylalanine while high‐resolution separations of all the enantiomeric pairs were achieved in the HS‐γ‐CD mode except that L‐mimosine was not detected and a partial resolution (0.6) for threo‐3,4‐dihydroxyphenylserine enantiomers. Relative migration times to that of internal standard under the respective optimum conditions were characteristic of each enantiomer with good precision (% RSD: 0.7–3.8), thereby enabling to cross‐check the chemical identification of aromatic amino acids and also their chiralities. The method linearity was found to be adequate (r> 0.99) for the chiral assay of the aromatic amino acids investigated. When applied to extracts of three plant seeds, nonprotein amino acids such as L‐mimosine (42 νg/g) from Mimosa pudica Linné, and L‐3,4‐dihydroxyphenylalanine (268 νg/g) from Vicia faba were positively detected along with L‐tryptophan, L‐phenylalanine and L‐tyrosine.
What cardiovascular defect does my prenatal mouse mutant have, and why?
Authors: Conway Simon J. , Kruzynska‐Frejtag Agnieszka , Kneer Paige L. , Machnicki Michal , Koushik Srinagesh V.
Published: December 2002

Summary: Since the advent of mouse targeted mutations, gene traps, an escalating use of a variety of complex transgenic manipulations, and large‐scale chemical mutagenesis projects yielding many mutants with cardiovascular defects, it has become increasingly evident that defects within the heart and vascular system are largely responsible for the observed in utero lethality of the embryo and early fetus. If a transgenically altered embryo survives implantation but fails to be born, it usually indicates that there is some form of lethal cardiovascular defect present. A number of embryonic organ and body systems, including the central nervous system, gut, lungs, urogenital system, and musculoskeletal system appear to have little or no survival value in utero (Copp, 1995). Cardiovascular abnormalities include the failure to establish an adequate yolk‐sac vascular circulation, which results in early lethality (E8.5–10.5); poor cardiac function (E9.0–birth); failure to undergo correct looping and chamber formation of the primitive heart tube (E9.0–11.0); improper septation, including division of the common ventricle and atria and the establishment of a divided outflow tract (E11.0–13.0); inadequate establishment of the cardiac conduction system (E12.0–birth); and the failure of the in utero cardiovascular system to adapt to adult life (birth) and close the interatrial and aorta‐pulmonary trunk shunts that are required for normal fetal life. Importantly, the developmental timing of lethality is usually a good indicator of both the type of the cardiovascular defect present and may also suggest the possible underlying cause/s. The purpose of this review is both to review the literature and to provide a beginner's guide for analysing cardiovascular defects in mouse mutants. genesis 35:1–21, 2003. © 2002 Wiley‐Liss, Inc.
Consequences of knocking out BMP signaling in the mouse
Authors: Zhao Guang‐Quan
Published: December 2002

Summary: During the past two decades, a significant amount of data has been accumulated revealing the intriguing functions of bone morphogenetic proteins (BMPs) in all aspects of embryonic development and organogenesis. Numerous genes encoding BMPs, BMP receptors, and their downstream signal transducers have been mutated in the mouse through targeted mutagenesis. This review focuses on what is known about the role of BMP signaling in gastrulation, mesoderm formation, left–right asymmetry, neural patterning, skeletal and limb development, organogenesis, and gametogenesis as revealed by BMP‐signaling mutants. genesis 35:43–56, 2003. © 2002 Wiley‐Liss, Inc.
Prediction of seasonal snow accumulation in cold climate forests
Authors: Pomeroy J. W. , Gray D. M. , Hedstrom N. R. , Janowicz J. R.
Published: December 2002

Accumulation of snow under forest canopies is known to decline with increasing canopy density and leaf area because of snow interception and sublimation in the canopy. Seasonal snow accumulation measurements, collected over a decade from various forest stands in western Canada, were used to test and develop methods to relate forest snow accumulation to stand properties and observations of either small‐clearing seasonal snow accumulation or seasonal snowfall. At sub‐stand scales, the variability of seasonal snow accumulation was not well related to stand leaf area, seasonal interception or small‐clearing seasonal snow accumulation. At the stand scale, physically based snow interception equations predicted seasonal snow accumulation from the stand leaf area and the seasonal snow accumulation or snowfall in adjacent clearings. A simple parametric form of these equations showed the sensitivity of seasonal snow accumulation to leaf area at the forest stand scale and suggested a relationship to extrapolate snow accumulation or snowfall measurements from clearings to forests. These relationships, developed from Canadian boreal forest observations, are consistent with Kuz'min's (1960. Formirovanie Snezhnogo Pokrova i Metody Opredeleniya Snegozapasov. Gidrometeoizdat: Leningrad) relationship between accumulation and canopy density derived from Russian observations, suggesting a good degree of transferability. Copyright © 2002 Crown in the right of Canada. Published by John Wiley & Sons Ltd.
Simulation of ice phenology on Great Slave Lake, Northwest Territories, Canada
Authors: Ménard Patrick , Duguay Claude R. , Flato Greg M. , Rouse Wayne R.
Published: December 2002

A one‐dimensional thermodynamic lake ice model (Canadian Lake Ice Model or CLIMo) is used to simulate ice phenology on Great Slave Lake (GSL) in the Mackenzie River basin, Northwest Territories, Canada. Model simulations are validated against freeze‐up and break‐up dates, as well as ice thickness and on‐ice snow depth measurements made in situ at three sites on GSL (Back Bay near Yellowknife, 1960–91; Hay River, 1965–91; Charlton Bay near Fort Reliance, 1977–90). Freeze‐up and break‐up dates from the lake ice model are also compared with those derived from SSM/I 85 GHz passive microwave imagery over the entire lake surface (1988–99).

Results show a very good agreement between observed and simulated ice thickness and freeze‐up/break‐up dates over the 30–40 years of observations, particularly for the Back Bay and Hay River sites. CLIMo simulates the ice thickness and annual freeze‐up/break‐dates with a mean error of 7 cm and 4 days respectively. However, some limitations have been identified regarding the rather simplistic approach used to characterize the temporal evolution of snow cover on ice. Future model improvements will therefore focus on this particular aspect, through linkage or coupling to a snow model. Copyright © 2002 John Wiley & Sons, Ltd.
The influence of thermal, hydrologic, and snow deformation mechanisms on snow water equivalent pressure sensor accuracy
Authors: Johnson Jerome B. , Schaefer Garry L.
Published: December 2002

A 5 year field study was conducted to determine the mechanisms that cause snow water equivalent (SWE) pressure sensor measurement errors. The objective is to establish design and installation criteria to develop an accurate electronic SWE pressure sensor that minimizes errors. We monitored a 3 m snow pillow and installed three prototype electronic SWE sensors of our own design to examine how SWE errors occur. We also measured the heat flux through the prototype sensors and the soil, snow temperature, soil moisture content, and soil thermal conductivity. The SWEs of snow cores were used to assess the accuracy of the snow pillow and prototype sensors. Experimental results indicate that SWE measurement errors occur only when the snow–SWE sensor and/or the snow–soil interfaces are at the melting temperature. The magnitude of SWE errors is related to the diameter of the sensor and the difference in heat flux through the sensor and the surrounding soil. SWE over‐measurement errors occur when the heat flux through the sensor is less than through the surrounding soil, producing a snowmelt rate on the sensor that is less than on the adjacent soil. SWE under‐measurement errors occur when the heat flux through the sensor is greater than through the surrounding soil. The most severe SWE measurement errors occur during the transition from winter to spring, when the snow cover first reaches an isothermal condition causing a maximum difference in snowmelt rate between an SWE sensor and the surrounding soil. SWE measurement errors are reduced by increasing the SWE sensor diameter, matching the thermal properties of the soil and SWE sensor, allowing water to flow through the sensor, and using a surface cover to diffuse heat into the adjacent soil. SWE measurement errors relax through snow creep mechanisms that redistribute the snow load equally between the sensor and surrounding soil. Published in 2002 by John Wiley & Sons Ltd.
Simulating wind fields and snow redistribution using terrain‐based parameters to model snow accumulation and melt over a semi‐arid mountain catchment
Authors: Winstral Adam , Marks Danny
Published: December 2002

In mountainous regions, wind plays a prominent role in determining snow accumulation patterns and turbulent heat exchanges, strongly affecting the timing and magnitude of snowmelt runoff. In this study, digital terrain analysis was employed to quantify aspects of the upwind topography related to wind shelter and exposure, to efficiently develop a distributed time‐series of snow accumulation rates and wind speeds to force a distributed snow model. Parameters are presented that determined each grid cell's topographic exposure and potential for drift development relative to observed winds. Using meteorological data taken from both an exposed and a sheltered site in the Reynolds Mountain East watershed (0·38 km2) in southwestern Idaho, the terrain parameters were used to distribute rates of snow accumulation and wind speeds at an hourly time step for input to ISNOBAL, an energy and mass balance snow model. Model runs were initiated prior to the development of the seasonal snow cover and continued through complete meltout for the 1986 (precipitation 128% of average), 1987 (66%), and 1989 (108%) water years. A comprehensive dataset consisting of a time series of aerial photographs taken during meltout, measured runoff, and snow data from the sheltered meteorological site were used to validate the simulations. ISNOBAL forced with accumulation rates and wind fields generated from the applied terrain parameterizations accurately modelled the observed snow distribution (including the formation of drifts and scoured wind‐exposed ridges) and snowmelt runoff for all three years of study. By contrast, ISNOBAL forced with spatially constant accumulation rates and wind speeds taken from the sheltered meteorological site, a typical snow‐monitoring site, overestimated peak snowmelt inputs and tended to underestimate snowmelt inputs prior to the runoff peak. Published in 2002 by John Wiley & Sons, Ltd.
Melatonin inhibits the contractile effect of vanadate in the isolated pulmonary arterial rings of rats: Possible role of hydrogen peroxide
Authors: Nagi Mahmoud N. , Mansour Mahmoud A. , Al‐shabanah Othman A. , El‐Kashef Hassan A.
Published: December 2002

The effect and possible mechanism of action of vanadate on the isolated pulmonary arterial rings of normal rats were studied. Pulmonary arterial rings contracted in response to vanadate (0.1–1 mM) in a concentration‐dependent manner. Preincubation of the pulmonary arterial rings with 1 mM melatonin significantly reduced the contractile effect of vanadate by more than 60%. Furthermore, addition of hydrogen peroxide (50 μM) or enzymatic generation of hydrogen peroxide by the addition of glucose oxidase (10 U/mL) to the medium containing glucose produced remarkable increases in the pulmonary arterial tension, 46.2 ± 7.3 and 78.7 ± 9.7 g tension/g tissue, respectively. Similarly, incubation of the pulmonary arterial rings with 1 mM melatonin significantly reduced the contractile responses of the arterial rings to hydrogen peroxide and glucose/glucose oxidase to 25.7 ± 2.9 and 24.7 ± 4.4 g tension/g tissue, respectively. Vanadate, in vitro, significantly stimulated the oxidation of NADH by xanthine oxidase, and the rate of oxidation was increased by increasing either time or vanadate concentration. Similarly, addition of melatonin to a reaction mixture containing xanthine oxidase and vanadate significantly inhibited the rate of NADH oxidation in a concentration‐dependent fashion. The results of the present study indicated that vanadate induced contraction in the isolated pulmonary arterial rings, which was significantly reduced by melatonin. Furthermore, the contractile effect of vanadate on the pulmonary arterial rings may be attributed to the intracellular generation of hydrogen peroxide. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:273–278, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10049
A dynamic role for the Ah receptor in cell signaling? Insights from a diverse group of Ah receptor interacting proteins
Authors: Carlson David B. , Perdew Gary H.
Published: December 2002

The aryl hydrocarbon (Ah) receptor (AhR) is a member of the basic helix‐loop‐helix PER‐ARNT‐SIM (PAS) transcription factor family. Consistent with the notion that PAS proteins are biological sensors, AhR binding to Ah toxicants induces or represses transcription of a wide range of genes and results in a cascade of toxic responses. However, an endogenous role for AhR in development and homeostasis is supported by (1) the discovery of low affinity, endogenous ligands; (2) studies demonstrating a role for the receptor in development of liver and vascular systems, that were established using mice lacking AhR expression; and (3) the presence of functional dioxin‐responsive elements in promoter regions of genes involved in cellular growth and differentiation. A large body of recent literature has implicated AhR in multiple signal transduction pathways. AhR is known to interact with signaling pathways that are mediated by estrogen receptor and other hormone receptors, hypoxia, nuclear factor κB, and retinoblastoma protein. In addition, AhR complexes may affect cellular signaling through interactions with various other regulatory and signaling proteins, including PAS heterodimerization partners (ARNT), chaperone and immunophilin‐like proteins (e.g. HSP90, XAP2/ARA9/AIP, p23), protein kinases and phosphatases (e.g. tyrosine kinases, casein kinase 2, protein kinase C), and coactivators (e.g. SRC‐1, RIP 140, CBP/p300). Here we summarize the types of molecular cross talk that have been identified between AhR and cell signaling pathways. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:317–325, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10051
Conflict values and team relationships: conflict's contribution to team effectiveness and citizenship in China
Authors: Tjosvold Dean , Hui Chun , Ding Daniel Z. , Hu Junchen
Published: December 2002

Although conflict has traditionally been considered destructive, especially in collectivist societies like China, recent studies indicate that valuing and approaching conflict can contribute to effective teamwork. A hundred and six pairs of employees and their leaders were recruited from State Owned Enterprises in Shanghai and Nanjing. Employees described their conflict values and relationships. Their immediate supervisors rated the effectiveness of their teams and the extent of their citizenship behavior. Results indicate that positive conflict attitudes and approaching conflict can contribute to strong relationships, which in turn strengthen team effectiveness and employee citizenship. Findings suggest that how conflict values affect relationships and outcomes are more differentiated than originally expected. Results were interpreted as supporting the traditional idea that relationships are critical for effective organization work in China but also challenging future research to understand the processes by which conflict has a positive contribution to work relationships. Copyright © 2003 John Wiley & Sons, Ltd.
Immersion corrosion tests on metal‐salt hydrate pairs used for latent heat storage in the 48 to 58°C temperature range
Authors: Cabeza L.F. , Roca J. , Nogués M. , Mehling H. , Hiebler S.
Published: December 2002

Efficient energy storage is one of the biggest problems facing alternative energy technologies. In whatever form the energy is stored, an alternative energy system usually requires a storage buffer between carrying energy input and the varying energy demand regime at the output end of the system. A method of energy storage is the use of the latent heat from Phase Change Materials (PCMs), for example salt hydrates. In this paper we tested the corrosion resistance of five commercial metals (aluminum, brass, copper, steel and stainless steel) in contact with two salt hydrates, commonly used as PCM, with a melting temperature in the range of 48 to 58°C (sodium acetate trihydrate and sodium thiosulfate pentahydrate) in experiments with a duration up to 70 days. The results demonstrated that brass and copper should be avoided when sodium acetate trihydrate is used in long term applications, but aluminum, steel and stainless steel can be used without problem. When the salt hydrate used is sodium thiosulfate pentahydrate, brass and copper should not be used in any case, aluminum and stainless steel can be used, and steel in contact with graphite should be monitored because corrosion could appear after some time of use.
Transactivation of ErbB1 and ErbB2 receptors by angiotensin II in normal human prostate stromal cells
Authors: Lin Jianqing , Freeman Michael R.
Published: December 2002

BACKGROUND

Heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) is synthesized primarily in the stromal compartment of the human prostate and may regulate stromal as well as epithelial cell growth and survival. The primary cognate HB‐EGF receptor, ErbB1, has been shown recently to be transactivated by G‐protein coupled receptors (GPCRs) through regulated proteolytic cleavage of the membrane‐bound, precursor form of HB‐EGF. Previous studies have demonstrated that human prostate tissue, especially tissue from benign prostatic hyperplasia (BPH), has high angiotensin converting enzyme activity, and a high density of angiotensin (Ang) receptors in periurethral stromal cells. Because the pressor peptide Ang II signals through GPCRs, we tested the possibility that Ang II could transactivate ErbB1/ErbB2 in human prostate stromal (hPS) cells.

METHODS

Primary and early passage hPS cells were used as an in vitro model. Cells were stimulated by recombinant HB‐EGF or Ang II and total cell lysates were harvested for immunoprecipitation and Western blot. Cell growth was measured by [3H]thymidine incorporation assay and 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyl‐tetrazoliumbromide (MTT) assay.

RESULTS

Ang II receptors AT1 and AT2 were expressed in hPS cells. ErbB1 and ErbB2 receptors were activated by HB‐EGF. Furthermore, Ang II was able to transactivate both ErbB1 and ErbB2, and this transactivation activity could be abolished by pretreatment with [Glu‐52]‐diphtheria toxin/CRM197, a specific inhibitor of HB‐EGF bioactivity. Consistent with its transactivation activity, Ang II modestly promoted hPS cell growth and this effect was abolished by pretreatment with the ErbB1 antagonist AG1478.

CONCLUSION

These experiments suggest a regulatory role for Ang II in the prostate stroma and implicate the endogenous stromal growth factor HB‐EGF as a mediator of Ang II signaling in the prostate. Prostate 54: 1–7, 2003. © 2002 Wiley‐Liss, Inc.
ALCAM/CD166 is up‐regulated in low‐grade prostate cancer and progressively lost in high‐grade lesions
Authors: Kristiansen Glen , Pilarsky Christian , Wissmann Christoph , Stephan Carsten , Weissbach Lothar , Loy Volker , Loening Stefan , Dietel Manfred , Rosenthal André
Published: December 2002

BACKGROUND

Activated leukocyte cell adhesion molecule (ALCAM, CD166) is expressed in various tissues, including malignant melanoma, prostate cancer cell lines, and prostate cancer. We aimed to clarify the expression patterns of ALCAM in normal and malignant prostate tissue.

METHODS

RNA from 54 matched pairs of microdissected prostate tissue (tumor and normal) was hybridized to a custom built 4K GeneChip. Frozen section immunohistochemistry was used to confirm the ALCAM expression.

RESULTS

Chip‐based transcript analysis revealed an up‐regulation of ALCAM in prostate cancer in 22% of cases. Immunohistochemistry showed a focally raised ALCAM expression in 81% and a decreased expression in 19% of cases. These expression patterns correlated significantly with Gleason tumor grade: ALCAM up‐regulation was found in most low‐grade tumors (Gleason grade 1–3), whereas down‐regulation occurred preferentially in high‐grade tumors (Gleason grade 4 and 5), although up‐regulation of ALCAM expression was preserved in two Gleason grade 5 tumors.

CONCLUSION

ALCAM expression is commonly disturbed in prostate cancer, which might indicate a role of ALCAM in the progression of this disease. Prostate 54: 34–43, 2003. © 2002 Wiley‐Liss, Inc.
Insider trading as a vehicle to appropriate rent from R&D
Authors: Coff Russell W. , Lee Peggy M.
Published: December 2002

While most insider trading is routine and legal, investors still treat it as new information about the firm's prospects—they assume that trades reflect managers' attempts to profit from their private information. This article explores insider trading as a mechanism to appropriate rent from R&D advances. We analyze stock price reactions to over 134,000 insider‐trading events and find that insider purchases generate larger positive stock price reactions for R&D‐intensive firms. Investors seem to assume that managers use insider trading to appropriate rent from R&D breakthroughs. We discuss how shareholders may prefer this rent appropriation mechanism over other forms of compensation that directly reduce the firm's income. Copyright © 2002 John Wiley & Sons, Ltd.
Dynamic capabilities and the emergence of intraindustry differential firm performance: insights from a simulation study
Authors: Zott Christoph
Published: December 2002

This paper explores how the dynamic capabilities of firms may be linked to differential firm performance within an industry. A formal model is presented in which dynamic capabilities are treated as a set of routines guiding the evolution of a firm's resource configuration. The model centers on the endogenous choice firms make between resource deployment through imitation and experimentation in order to generate alternative resource configurations. Three performance‐relevant attributes of dynamic capabilities are proposed: timing, cost, and learning of resource deployment. Theoretical propositions are developed that suggest how these attributes contribute to the emergence of differential intraindustry firm performance. Simulation analysis offers insights into the trajectories of evolutionary change engendered by dynamic capability, and serves to refine the theoretical propositions. It is found that timing, cost, and learning effects foster the emergence of robust performance differences among firms with strikingly similar dynamic capabilities. Moreover, the results show that even small initial differences among firms can generate significant intraindustry differential firm performance, especially when the effects of timing, cost and learning are combined. Copyright © 2002 John Wiley & Sons, Ltd.
PVD metallisation of polymer films for electronic application
Authors: Müller R. , Kindle‐Hasse B. , Siefert W.
Published: December 2002

Die stetig fortschreitende Miniaturisierung in der Aufbau‐ und Verbindungstechnik macht den Einsatz neuer Strukturierungstechniken und Basismaterialien für einen zudem ständig wachsenden Massenmarkt erforderlich. Die neue Generation von Basismaterialien muss ein hohes Maß an Zuverlässigkeiten hinsichtlich der FPC‐Richtlinien erfüllen, um Produktinnovationen am Massenmarkt zu ermöglichen. Insbesondere die langzeitstabile Haftfestigkeit, die für den Einsatz der Flexmaterialien in einem breiten Applikationsumfeld notwendig ist, ist Gegenstand weiterer Entwicklungsbemühungen.