bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural studies on MtRecA‐nucleotide complexes: Insights into DNA and nucleotide binding and the structural signature of NTP recognition
Authors: Datta S. , Ganesh N. , Chandra Nagasuma R. , Muniyappa K. , Vijayan M.
Published: January 2003

RecA protein plays a crucial role in homologous recombination and repair of DNA. Central to all activities of RecA is its binding to Mg+2‐ATP. The active form of the protein is a helical nucleoprotein filament containing the nucleotide cofactor and single‐stranded DNA. The stability and structure of the helical nucleoprotein filament formed by RecA are modulated by nucleotide cofactors. Here we report crystal structures of a MtRecA‐ADP complex, complexes with ATPγS in the presence and absence of magnesium as well as a complex with dATP and Mg+2. Comparison with the recently solved crystal structures of the apo form as well as a complex with ADP‐AlF4 confirms an expansion of the P‐loop region in MtRecA, compared to its homologue in Escherichia coli, correlating with the reduced affinity of MtRecA for ATP. The ligand bound structures reveal subtle variations in nucleotide conformations among different nucleotides that serve in maintaining the network of interactions crucial for nucleotide binding. The nucleotide binding site itself, however, remains relatively unchanged. The analysis also reveals that ATPγS rather than ADP‐AlF4 is structurally a better mimic of ATP. From among the complexed structures, a definition for the two DNA‐binding loops L1 and L2 has clearly emerged for the first time and provides a basis to understand DNA binding by RecA. The structural information obtained from these complexes correlates well with the extensive biochemical data on mutants available in the literature, contributing to an understanding of the role of individual residues in the nucleotide binding pocket, at the molecular level. Modeling studies on the mutants again point to the relative rigidity of the nucleotide binding site. Comparison with other NTP binding proteins reveals many commonalties in modes of binding by diverse members in the structural family, contributing to our understanding of the structural signature of NTP recognition. Proteins 2003;50:474–485. © 2003 Wiley‐Liss, Inc.
Matrix‐assisted laser desorption/ionization study of cationization of PEO‐PPP rod‐coil diblock polymers
Authors: Chen Hui , He Meiyu , Wan Xinhua , Yang Lifang , He Haifeng
Published: January 2003

Five PEO‐PPP rod‐coil diblock polymers were synthesized and characterized using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS). By using a series of alkali chlorides as cation salts, relative cation affinities were studied. Different cation affinities and shifts in molecular weight distributions were found as a result of changing the cation type and size. Also, a study of lithium cationization resulted in determination of a recommended quantity of lithium to be used. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of carbocysteine in human plasma by liquid chromatography/tandem mass spectrometry employing precolumn derivatization
Authors: Chen Xiaoyan , Zhong Dafang , Han Ying , Xie Zhiyong
Published: January 2003

A sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed to determine carbocysteine in human plasma using 2‐pyridylacetic acid as the internal standard (IS). The method employed derivatization with 10 M hydrochloric acid/methanol, which significantly improved the ionization efficiency of carbocysteine. After methanol‐induced protein precipitation of plasma samples, carbocysteine and the IS were derivatized and subjected to LC/MS/MS analysis using atmospheric pressure chemical ionization. The method has a lower limit of quantitation of 20 ng/mL for a 0.2‐mL plasma aliquot. The intra‐ and inter‐day precision (RSD), calculated from quality control (QC) samples, was less than 7%. The accuracy, determined using QC samples, was within ± 1%. The method offered increased sensitivity, selectivity and speed of analysis over existing methods. The method was utilized to support clinical pharmacokinetic studies of carbocysteine in volunteers following oral administration. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative characterization of differential ion suppression on liquid chromatography/atmospheric pressure ionization mass spectrometric bioanalytical methods
Authors: Avery Michael J.
Published: January 2003

Ion suppression is a known phenomenon in atmospheric pressure ionization mass spectrometry. These suppression effects have been shown to adversely affect the accuracy and precision of quantitative bioanalytical methods. This paper presents a simple procedure for determining the impact of differential ion suppression on bioanalytical methods that utilize atmospheric pressure ionization mass spectrometric (APIMS) detection. This procedure was applied to the assessment of two potential internal standards, and to determine selectivity issues for another analyte which was to be measured in multiple species. Copyright © 2002 John Wiley & Sons, Ltd.
Mass calibration of a matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer including the rise time of the delayed extraction pulse
Authors: Moskovets E. , Karger B. L.
Published: January 2003

To utilize fully modern MALDI‐TOF and TOF/TOF mass spectrometers with mass resolution exceeding 10 000 and 2 ppm precision of flight time measurements for high mass accuracy, the model of ion motion used in the mass calibration equation must be expanded. The standard three‐term equation providing up to 5–10 ppm (rms) mass accuracy with internal standards was modified with an additional term accounting for the finite rise time of the high‐voltage extraction pulse. This new four‐term calibration equation minimizes the effect of systematic error resulting from the fact that ion velocities are mass dependent due to the rise time of the extraction pulse. Applying this new calibration equation to a mass spectrum obtained in an axial MALDI‐TOF MS containing 70 peaks (sodiated PEG), each with a signal‐to‐noise ratio greater than 100, a mass accuracy of 1.6 ppm (rms) was obtained over the mass range 1.0–4.0 kDa compared with 3.6 ppm (rms) with the standard three‐term equation. The physical basis of the effects of the finite extraction pulse rise time on mass calibration is examined for axial MALDI‐TOF mass spectrometers, as well as for orthogonal acceleration TOF mass spectrometers. Copyright © 2002 John Wiley & Sons, Ltd.
Ion suppression in the determination of clenbuterol in urine by solid‐phase extraction atmospheric pressure chemical ionisation ion‐trap mass spectrometry
Authors: van Hout M. W. J. , Niederländer H. A. G. , de Zeeuw R. A. , de Jong G. J.
Published: January 2003

Ion suppression effects were observed during the determination of clenbuterol in urine with solid‐phase extraction/multiple‐stage ion‐trap mass spectrometry (SPE/MS3), despite the use of atmospheric pressure chemical ionisation. During SPE, a polymeric stationary phase (polydivinylbenzene) was applied. Post‐cartridge infusion of analyte to the SPE eluate after the extraction of blank urine was performed to obtain a profile of the suppression. Single and multiple‐stage MS were performed to provide insight in the suppressing compounds. The ion suppression was mainly ascribed to two m/z values, but still no identification of the compounds was achieved from the multiple‐stage MS data. No ionisable and non‐ionisable complexes and/or precipitation of clenbuterol with matrix compounds were observed. A concentration dependence of the percentage of suppression was observed. Up to 70% of the signal was suppressed upon post‐cartridge infusion of 0.22 μg/mL (at 5 μL/min) clenbuterol into the eluate, and this decreased to about 4% at infusion of 22 μg/mL clenbuterol. Molecularly imprinted polymers were used to enhance the selectivity of the extraction. Although matrix components were still present after extraction, no interference of these compounds with the analyte was observed. However, the bleeding of the imprint from the polymer (brombuterol) caused significant ion suppression. Copyright © 2002 John Wiley & Sons, Ltd.
Local institutions and natural resource management in the South Tongu District of Ghana: a case study
Authors: Koku John E. , Gustafsson Jan‐Erik
Published: January 2003

This paper draws on secondary and primary data derived from a field survey undertaken in Torsukpo and Agbogbla communities in the South Tongu District of Ghana to discuss possibilities of enhancing the roles of local institutions in resource management. Key issues addressed in the paper include (i) limitations which share cropping (abunu‐abusa) as a local social institutional arrangement places on tenant farmers and (ii) the role of the District Assembly with specific reference to policy provisions placed at its disposal that could be used to formulate co‐operative strategies that may help mobilize and empower the local people for effective natural resources management. To complement efforts in this direction, the paper also highlights some possible ways in which NGOs could play more effective roles in facilitating development process in the district. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
Revisiting the logical and research considerations of competitive advantage
Authors: Arend Richard J.
Published: January 2003

This commentary addresses the main points made in the recent article by T. C. Powell on the logical and philosophical flaws in the main thesis of strategy research. Each one of Powell's three points is refutable. The main thesis of strategy research retains logical causation given a reasonable definition of the main explanatory variable. Strategy theory is falsifiable when the implied assumptions of the theory are exploited and the endogeneity of its explanatory variables is considered. The characterization of strategy research as pragmatic instrumentalism void of progress to the objective truth is a proposition without any logical or empirical support. Copyright © 2003 John Wiley & Sons, Ltd.
Entry mode, organizational learning, and R&D in foreign affiliates: evidence from Japanese firms
Authors: Belderbos René
Published: January 2003

This paper develops hypotheses concerning the role of entry mode and experience‐based organizational learning as determinants of the R&D intensity of foreign affiliates and tests these hypotheses on a sample of 420 Japanese manufacturing affiliates abroad. Entry mode has a major impact on R&D activities: the R&D intensities of acquired affiliates substantially exceed those in wholly owned greenfield affiliates, while the R&D intensities of minority owned ventures are higher if Japanese parent firms lack strong R&D capabilities at home. For greenfield operations, support is found for an incremental growth pattern of foreign R&D as a function of organizational learning and affiliate capability building. The results are consistent with the view that part of the explanation for Japanese firms' relative lack of involvement in overseas R&D must be sought in their status as ‘latecomers’ in the establishment of overseas manufacturing networks. At the same time, a number of Japanese firms have actively used foreign acquisitions and joint ventures to gain access to overseas technology and to establish overseas R&D capabilities at a faster pace. Copyright © 2002 John Wiley & Sons, Ltd.
Link between dopamine D1 and D2 receptors in rat and human striatal tissues
Authors: Seeman Philip , Tallerico Teresa
Published: January 2003

Many psychomotor behaviors depend on an interaction between dopamine D1 and D2 receptors. This study tested the hypothesis that agonist stimulation of dopamine D1 receptors leads to the conversion of D2 receptors from a state of high affinity for dopamine into a state of low affinity for dopamine. To test this hypothesis, dopamine was competed against [3H]raclopride for binding to rat and human striatal homogenates. Although the detection of high‐affinity states of the dopamine D2 receptor in rat or postmortem human striatum is normally difficult because the proportions of such sites are very low in the presence of physiological concentrations of sodium ions, the present work found that in the presence of 100 nM SCH 23390 to block D1 receptors, a significant proportion of D2 high‐affinity sites were unmasked and readily revealed to be 10–35% of the D2 population, illustrating the presence of a strong D1–D2 link in both rat and human striata. Synapse 47:250–254, 2003. © 2003 Wiley‐Liss, Inc.
Preproenkephalin mRNA expression in rat dorsal striatum induced by selective activation of metabotropic glutamate receptor subtype‐5
Authors: Parelkar Nikhil K. , Wang John Q.
Published: January 2003

Group I metabotropic glutamate receptors (mGluR1 and mGluR5 subtypes) are positively coupled to phosphoinositide hydrolysis through G‐proteins and are densely expressed in medium‐sized projection neurons of striatum. Selective activation of Group I mGluRs upregulates preproenkephalin (PPE) mRNA expression in the rat dorsal striatum. This study investigated the role of one subtype of Group I receptors, mGluR5, in the regulation of PPE mRNA expression in the rat dorsal striatum using quantitative in situ hybridization. Unilateral injection of the mGluR5 selective agonist (RS)‐2‐Chloro‐5‐hydroxyphenylglycine (CHPG) into the dorsal striatum (caudoputamen) of chronically cannulated rats at doses of 50 and 200 nmol elevated basal levels of PPE mRNA in the injected dorsal striatum. The induction of PPE mRNA was evident at 1 h, remained at 3 h, and returned to normal level 6 h after CHPG injection. Pretreatment with an mGluR5 selective antagonist 2‐methyl‐6‐(phenylethynyl) pyridine hydrochloride (MPEP) at a dose of 10 mg/kg (i.p.) blocked CHPG‐stimulated PPE expression. MPEP also attenuated PPE expression induced by dopamine D2 receptor blockade with eticlopride (0.5 mg/kg, i.p.). Administration of MPEP alone had no significant effects on basal levels of PPE mRNA in the striatum. The results from the present study demonstrate that glutamatergic tone on mGluR5 possesses the ability to positively regulate PPE gene expression in striatal neurons in vivo. Moreover, activation of mGluR5 participates in the mediation of D2 antagonist‐induced PPE expression. Synapse 47:255–261, 2003. © 2003 Wiley‐Liss, Inc.
Relative levels of cytoprotection produced by analogs of choline and the role of α7‐nicotinic acetylcholine receptors
Authors: Jonnala Ramamohana R. , Graham John H. , Terry Jr. Alvin V. , Beach J. Warren , Young Jennifer A. , Buccafusco Jerry J.
Published: January 2003

Several analogs of the acetylcholine precursor molecule choline have been widely studied as potential false cholinergic neurotransmitters with the therapeutic goal of using them to limit cholinergic neurotransmission. More recently, choline itself has been shown to act as a full, if low potency, agonist at the α7 subtype of the nicotinic acetylcholine receptor. This pharmacological property has been associated with the ability of nicotine and other related α7 receptor agonists to offer neuroprotection in a variety of experimental models. We confirm here that choline offers a significant degree of protection against the cytotoxicity induced by growth factor deprivation in differentiated PC‐12 cells. Choline‐induced cytoprotection (∼1 mM) was about 3 orders of magnitude less potent than that for nicotine (EC50 = 0.7 μM). Choline also exhibited only about 40% of the full cytoprotective effect of nicotine. Ethyl substitution for choline's N‐methyl groups did not result in a significant improvement over choline as a cytoprotective agent. In contrast, pyrrolidinecholine exhibited much greater potency (EC50 = 20 μM) and increased efficacy (about 55% of nicotine's effect) than choline. Like choline and nicotine, pyrrolidinecholine fully displaced [125I]α‐bungarotoxin binding (Ki = 33 μM) and chronic exposure to the analog increased cell surface binding sites. The cytoprotective effects of the analog were completely inhibited by coincubation with methyllycaconitine (MLA), a selective α7‐nicotinic receptor antagonist. These findings are consistent with the possibility that the choline structure may serve as a template for the development of novel agents with both α7‐nicotinic agonist activity and potential neuroprotective ability, as many of these compounds, including pyrrolidinecholine, are transported along with choline into the central nervous system. Synapse 47:262–269, 2003. © 2003 Wiley‐Liss, Inc.
Down‐regulation of mGluR8 in pilocarpine epileptic rats
Authors: Kral T. , Erdmann E. , Sochivko D. , Clusmann H. , Schramm J. , Dietrich D.
Published: January 2003

Activation of presynaptic metabotropic glutamate receptors (mGluRs) leads to a powerful inhibition of glutamate release from many synaptic terminals throughout the CNS. mGluRs as autoreceptors are believed to provide a negative feedback system that prevents potentially toxic accumulation of glutamate in the extracellular space during synchronous synaptic activity such as epileptic seizures. In this study we analyzed the function of presynaptic mGluR8 on terminals of the lateral perforant pathway in the pilocarpine model of limbic epilepsy. Field excitatory postsynaptic potentials (fEPSPs) recorded in hippocampal slices of rats that developed spontaneous recurrent seizures after pilocarpine‐induced status epilepticus (SRS group) showed a significantly reduced sensitivity to Group III mGluR agonists and severe mossy fiber sprouting. The Group III mGluR agonist L(+)‐2‐amino‐4‐phosphonobutyric acid (L‐AP4, 10 μM) depressed fEPSPs in the SRS group only by 26 ± 21% compared to 50 ± 18% in untreated rats. Similarly, the mGluR8 preferring agonist (R,S)‐4‐phosphonophenylglycine (PPG, 5 μM) was significantly less effective in slices from SRS rats (43 ± 4% vs. 83 ± 5%). Concentration–response curves for L‐AP4 revealed that the EC50 values were not different between the control and SRS group (13 ± 7 μM vs. 9 ± 9 μM), while the maximal depressing effect was significantly reduced. The remaining depressing effect of L‐AP4 in the SRS group could be blocked by the Group III specific antagonists (RS)‐α‐methyl‐4‐phosphonophenylglycine (MPPG) and α‐methyl‐L‐AP4 (MAP4). Rats that did not develop SRS following pilocarpine‐induced status epilepticus were indistinguishable from control rats: fEPSPs were highly sensitive to L‐AP4 and there was no mossy fiber sprouting. The results show that pilocarpine‐induced status epilepticus can lead to a downregulation of mGluR8 and suggest that the condition of SRS is associated with a deteriorated autoregulation of glutamate release. Synapse 47:278–284, 2003. © 2003 Wiley‐Liss, Inc.
Tannery wastewater characterization and toxicity effects on Daphnia spp.
Authors: Cooman K. , Gajardo M. , Nieto J. , Bornhardt C. , Vidal G.
Published: January 2003

Tannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts. The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests. The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex. To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure. In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D. pulex (native species). Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840–27 600 mg L−1), chloride (1813–16 500 mg L−1), sulfate (230–35 200 mg L−1), and total solids (8600–87 100 mg L−1). All effluents showed extremely toxic effects on D. pulex, with 24‐h mean lethal values (LC50) ranging from 0.36% to 3.61%. The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76%. The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%–74%). The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg NNH3 L−1) and chloride (11 300 mg Cl− L−1) contents. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 45–51, 2003.
Acute and sublethal effects of two insecticides on earthworms (Lumbricus terrestris L.) under laboratory conditions
Authors: Mosleh Yahia Y. , Paris‐Palacios Séverine , Couderchet Michel , Vernet Guy
Published: January 2003

Earthworms (Lumbricus terrestris L.) were exposed to commercial formulations of endosulfan and aldicarb for 2, 7, and 15 days, and the LC10, LC25, and LC50 were determined. Worms were then exposed to LC10, LC25, and LC50 concentrations of endosulfan and LC10 and LC25 concentrations of aldicarb. The growth rate and total protein content were determined and related to endosulfan and aldicarb residues in soil and earthworms. Aldicarb was more toxic than endosulfan under the experimental conditions. The residues of endosulfan and aldicarb caused a significant reduction in the growth rate and total protein content of earthworms. The residues of endosulfan and aldicarb were monitored in soil and earthworms after 2, 7, and 15 days of exposure. The residues remaining in the soil after the experiments ranged between 37.75% and 68.54% of the applied concentration for endosulfan and between 10.13% and 67.71% of the applied concentration for aldicarb. Small amounts of both insecticides were detected in worms, and accumulation was more important for endosulfan. This study proposes the use of growth rate and total protein content as biomarkers for contamination by endosulfan and aldicarb. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 1–8, 2003.
The freshwater cyanobacterium Lyngbya aerugineo‐coerulea produces compounds toxic to mice and to mammalian and fish cells
Authors: Teneva Ivanka , Asparuhova Dafinka , Dzhambazov Balik , Mladenov Rumen , Schirmer Kristin
Published: January 2003

Despite a growing awareness of the presence of cyanobacterial toxins, knowledge about the ability of specific species to produce toxic compounds is still rather limited. It was the overall goal of the current work to investigate if probes derived from the freshwater species Lyngbya aerugineo‐coerulea (Kutz.) Gomont, a cyanobacterium frequently found in southern Europe and not previously investigated for the presence of bioactive compounds, were capable of eliciting in vivo and in vitro toxicity. The cyanobacterial extract revealed signs of neuro‐ as well as hepatotoxicity in mice, although these signs could not be explained by the well‐known respective cyanobacterial neuro‐ and hepatotoxins saxitoxin and microcystin. Cytotoxicity was elicited by the cyanobacterial extract in all mammalian cell lines tested. As well, the rainbow trout liver cell line, RTL‐W1, was found to be susceptible to the cytotoxic effects of the extract, although the cytotoxicity was dependent on temperature. In contrast, the cyanobacterial growth medium elicited cytotoxicity independent of temperature, leading to morphological changes indicative of alterations to the cytoskeleton. Overall, the results suggest that Lyngbya aerugineo‐coerulea is an important cyanobacterium to be considered for its potential to cause health risks on environmental exposure of it to mammals and fish. Applying a combination of mammalian and piscine cell line bioassays is a unique approach that, combined with chemical analysis, could be used in the future to identify the structure and cellular mechanisms of the as‐yet‐unknown toxic Lyngbya aerugineo‐coerulea metabolites in particular and to screen cyanobacterial extracts for their toxicity in general. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 9–20, 2003.
Depuration kinetics and persistence of the cyanobacterial toxin microcystin‐LR in the freshwater bivalve Unio douglasiae
Authors: Yokoyama Atsushi , Park Ho‐Dong
Published: January 2003

We carried out uptake and depuration experiments in the laboratory to investigate the effects of temperature (15°C and 25°C) on the depuration kinetics and persistence of a cyanobacterial toxin, microcystin‐LR (MCYST‐LR), in a freshwater bivalve, Unio douglasiae. Bivalves were fed toxic Microcystis cells in the 15‐day uptake experiment and nontoxic diatoms in the following 15‐day depuration experiment. Each bivalve's hepatopancreas was lyophilized and extracted with a butanol:methanol:water solution for analysis of MCYST‐LR by high‐performance liquid chromatography. The toxin in the organ accumulated rapidly after the beginning of the uptake experiment and reached approximately steady‐state conditions on day 5 at concentrations of 130 ± 11 μg g−1 dry weight at 15°C and 250 ± 40 μg g−1 at 25°C. In the depuration experiments MCYST‐LR was eliminated asymptotically from the tissue. The values of the depuration rate constant (kd), calculated with a first‐order one‐compartment model, were found to be 0.142 ± 0.044 day−1 at 15°C and 0.226 ± 0.046 day−1 at 25°C. The depuration Q10 value from 15°C to 25°C equaled 1.6. This study was the first to reveal the kinetics of depuration for MCYST‐LR in a bivalve. The results show that MCYST‐LR may be eliminated slowly in autumn and winter and persist in the tissue until spring. Thus, in terms of toxicokinetics, the risk to people of being poisoned by bivalves would increase if toxic blooms occur in autumn. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 61–67, 2003.
The elasticity of single kettin molecules using a two‐bead laser‐tweezers assay
Authors: Leake Mark C. , Wilson David , Bullard Belinda , Simmons Robert M.
Published: January 2003

Kettin is a high molecular mass protein of insect muscle associated with thin filaments and α‐actinin in the Z‐disc. It is thought to form a link between thin and thick filaments towards its C‐terminus, contributing significantly to passive sarcomere stiffness. Here the elastic properties were characterised by mechanical stretches on an antibody‐delimited region of the single molecule using two independent optical traps capable of exerting forces up to 150 pN. Step‐like events were observed in the force–extension relationships consistent with the unfolding of Ig domains at moderate force and refolding of these domains at significantly higher forces than have been observed for related modular proteins.
The preliminary development of a new self‐report measure for OCD in young people
Authors: Shafran Roz , Frampton Ian , Heyman Isobel , Reynolds Martina , Teachman Bethany , Rachman S.
Published: January 2003

The aim of this study was to develop a reliable self‐report instrument to assess obsessive–compulsive disorder (OCD) in young people. The children's Obsessional Compulsive Inventory (CHOCI) had good internal consistency, criterion validity and was significantly correlated with the Children's Yale‐Brown Obsessive Compulsive Scale (CY‐BOCS). This preliminary new measure could serve to provide a more efficient and accessible way of assessing OCD in young people.
WELFARE COST OF MONETARY AND FISCAL POLICY SHOCKS
Authors: Evans Lynne , Kenc Turalay
Published: January 2003

This paper provides estimates of the welfare cost of volatility attributable to monetary and fiscal policy shocks. It uses a continuous-time stochastic dynamic general equilibrium model based on a recursive utility function that disentangles risk aversion from intertemporal substitution. We find that monetary and fiscal policy shocks may lead to opposite welfare effects: negative for monetary growth shocks, but positive for government expenditure shocks. Furthermore, we find that welfare costs are sensitive to the parameter values chosen for risk aversion and intertemporal substitution, and we conclude that welfare costs are potentially much larger than that found by Lucas, forcing some modification of the policy conclusions associated with Lucas's pioneering work.
Combined High-Resolution and Analytical TEM Studies of Phase-Separated
Alloys
Authors: Wu C. K. , Marshall A. F. , Thomas G. , Sinclair R.
Published: January 2003

The determination of composition variations due to alloy phase
transformations has long been of interest to materials scientists. In this
paper, data obtained in the same alloy system using conventional x-ray
diffraction analysis, high resolution lattice imaging and the analytical
technique of STEM/EDS are compared, and their application to various systems
is discussed. Composition is experimentally correlated with lattice
parameter measurements or, for species of similar sizes, determined by
assuming Vegard's law. X-ray diffraction gives a more accurate lattice
parameter measurement but the information is averaged over a large specimen
volume and cannot be used for coherent precipitate systems. Lattice imaging,
on the other hand, resolves lattice spacings in microareas (<20 Å) of the
structure, but is limited in accuracy by magnification determination,
imaging conditions and precision in measuring fringe
spacings.1 STEM/EDS, with a resolution under
optimum conditions of 100-200 Å, is a more direct technique for composition
determination since the characteristic x-ray intensity produced by the
specimen is directly proportional to the composition. However, a number of
spurious events may occur to alter the x-ray intensities seen by the
detector and accuracy depends greatly on the experimental conditions and the
nature of the specimen.2
A Simple Low-Vacuum Environmental Cell
Authors: Ervin Matthew H.
Published: January 2003

The environmental cell device discussed in this paper provides
a modest low-vacuum scanning electron microscopy (SEM) capability
to a standard SEM without requiring additional pumping. This
environmental cell confines a volume of low vacuum in contact
with the sample surface using a container that has an aperture
for admitting the primary electron beam. The aperture is large
enough to permit a limited field of view of the sample, and
small enough to limit the outflow of gas into the SEM chamber
to that which can be accommodated by the standard SEM pumping
system. This environmental cell also functions as a gaseous
detector device.
Simultaneous Mechanical Loading and Confocal Reflection
Microscopy for Three-Dimensional Microbiomechanical Analysis
of Biomaterials and Tissue Constructs
Authors: Voytik-Harbin Sherry L. , Roeder Blayne A. , Sturgis Jennifer E. , Kokini Klod , Robinson J. Paul
Published: January 2003

At present, mechanisms by which specific structural and mechanical
properties of the three-dimensional extracellular matrix
microenvironment influence cell behavior are not known. Lack
of such knowledge precludes formulation of engineered scaffolds
or tissue constructs that would deliver specific growth-inductive
signals required for improved tissue restoration. This article
describes a new mechanical loading–imaging technique that
allows investigations of structural–mechanical properties
of biomaterials as well as the structural–mechanical basis
of cell–scaffold interactions at a microscopic level and
in three dimensions. The technique is based upon the integration
of a modified, miniature mechanical loading instrument with
a confocal microscope. Confocal microscopy is conducted in a
reflection and/or fluorescence mode for selective visualization
of load-induced changes to the scaffold and any resident cells,
while maintaining each specimen in a “live,” fully
hydrated state. This innovative technique offers several advantages
over current biomechanics methodologies, including simultaneous
visualization of scaffold and/or cell microstructure in
three dimensions during mechanical loading; quantification of
macroscopic mechanical parameters including true stress and
strain; and the ability to perform multiple analyses on the
same specimen. This technique was used to determine the
structural–mechanical properties of three very different
biological materials: a reconstituted collagen matrix, a
tissue-derived biomaterial, and a tissue construct representing
cells and matrix.
A Single-Tilt TEM Stereomicroscopy Technique for Crystalline
Materials
Authors: McCabe Rodney J. , Misra Amit , Mitchell Terence E. , Alexander Kathleen B.
Published: January 2003

A new single-tilt technique for performing TEM stereomicroscopy
of strain fields in crystalline materials has been developed. The
technique is a weak beam technique that involves changing the value
of g and/or sg while
tilting across a set of Kikuchi bands. The primary benefit of
the technique is it can be used with single-tilt TEM specimen
holders including many specialty holders such as in situ
straining, heating, and cooling holders. Standard stereo-TEM
techniques are almost always limited to holders allowing two
degrees of rotational freedom (i.e., double-tilt or
tilt/rotation holders). An additional benefit of the new
technique is that it eliminates the need to focus with the specimen
height control. These advantages make it useful for stereo viewing
or for quantitative stereomicroscopy provided necessary
consideration is given to errors that may result from the technique.
Electron Ionization Cross Sections for Atomic Subshells
Authors: Rez Peter
Published: January 2003

Ionization of atoms is the first step in many analytical
procedures. The cross section for ionizing a particular atomic
shell is essential for calculating the magnitude of analytical
signals. Calculations using atomic wave functions for various
shells of all elements relevant for X-ray microanalysis over
a range of electron energies up to 400 keV were performed. The
calculations for high energies above threshold can be considerably
simplified by using the mathematical form of the Bethe ridge
that dominates the scattering in this region. Corrections for
exchange at low energies above threshold are incorporated in
these calculations. A selection of results showing the effects
of different approximations on ionization cross sections for
K, L, and M shells is presented.
Advances in Pathology, Microscopy, and Molecular Morphology
series: Gold and Silver Staining: Techniques in Molecular Staining
Morphology. Series Editors: Gerhard W. Hacker, Ph.D. and Jiang
Gu, M.D., Ph.D. CRC Press, Boca Raton, Florida; London; New
York; Washington, DC; 2002, 246 pages (Hardback, alkaline paper,
catalog no. 1392, US$139.95). ISBN 0-8493-1392-9
Authors: Tiekotter Ken
Published: January 2003

One of the most interesting aspects of this book is the frequency
at which the contributing authors are found in the references
at the end of not one, but usually several chapters: this is
by no means a mistake. Editors Hacker and Gu have assembled
a wealth of expertise from well-known individuals in the fields
of autometallography, immunogold-silver staining and molecular
morphology. Composed of 16 chapters with a total of 32 contributing
authors, the material is presented in a very well organized
and coherent format.
Application and Quantitative Validation of Computer-Automated Three-Dimensional Counting of Cell Nuclei
Authors: Shain William , Kayali Soraya , Szarowski Donald , Davis-Cox Margaret , Ancin Hakan , Bhattacharjya Anoop K. , Roysam Badrinath , Turner James N.
Published: January 2003

This study provides a quantitative validation of qualitative automated three-dimensional (3-D) analysis methods reported earlier. It demonstrates the applicability and quantitative accuracy of our method to detect, characterize, and count Feulgen stained cell nuclei in two tissues (hippocampus and testes). A laser-scanned confocal light microscope was used to record 3-D images i which our algorithms automatically identified individual nuclei from the optical sections given an estimate of minimum
nuclear size. The hippocampal data sets were also manually counted independently by five trained observers
using the STERECON 3-D image reconstruction system. The automated and manual counts were compared. A nucleus-by-nucleus comparison of the manual and automated counts verified that the automated analysis was accurate and reproducible, and permitted additional quantitative analyses not available from manual methods. The algorithms also identified subpopulations of nuclei within the hippocampal samples, and haploid and diploid nuclei in the testes. Our methods were shown to be repeatable, accurate, and more consistent than manual counting.
Fluorescence Microscopy and Fluorescent Probes, Vol. 2, Edited by Jan Slavík
1998. Plenum Press, New York and London. 292 pages. (hardback, $95.00)
Authors: Herman Brian
Published: January 2003

In June of 1995, the first conference on Fluorescent Microscopy
and Fluorescent Probes was held in the beautiful city
of Prague in the Czech Republic and the proceedings of that
meeting were published by Plenum Press in 1996 (Fluorescence
Microscopy and Fluorescent Probes, Vol. 1, edited by
Jan Slavík). Based on the success of the first conference, a
second conference was held two years later again in Prague,
and this book is the proceedings of that meeting.
Characterization of the Absolute Crystal Polarity across Twin Boundaries in Gallium Phosphide Using Convergent-Beam Electron Diffraction
Authors: Cohen Dov , McKernan Stuart , Carter C. Barry
Published: January 2003

The measurement of absolute crystal polarity is crucial to understanding the structural properties of many planar defects in compound semiconductors. Grain boundaries, including twin boundaries, in the sphalerite lattice are uniquely characterized by the crystallographic misorientation of individual grains and the direction of the crystal polarity in domains adjoining the grain boundary. To evaluate crystal polarity in gallium phosphide (GaP), asymmetrical interference contrast in convergent-beam electron-diffraction (CBED) patterns was used to ascertain the nature and direction of polar bonds. The direction of the asymmetry in the electron diffraction reflections was correlated with the crystal polarity of a sample with known polarity. The CBED
technique was applied to determine the polar orientation of grains adjoining Σ = 3 coherent and lateral twin
boundaries in polycrystalline GaP.
Improvement in Quantitative X-ray Microanalysis of Biological Cryosections
Authors: Schultz Michael , Rudolf Frank , Gallitelli Maria-Fiora
Published: January 2003

The accuracy of Na measurements in biological cryosections has been improved through replacement of the 8 μm Be window of the Si(Li) detector with a Super Atmospheric Thin Window (SuperATW) window mounted on a germanium electron microscope (GEM) detector. Greater accuracy of Ca measurements was also attained when a GEM detector instead of an Si(Li) detector was used for analysis of total Ca concentrations in cardiac muscle. Although the advantage of improved sensitivity for Na and Ca is lost in spot mode analysis because of the overriding contribution of biological variability, this advantage becomes important in X-ray mapping. We compared the two systems by analyzing cryosections of identical biological material under
comparable conditions. We found that Si contamination in thin biological cryosections is unpredictable; it may be widespread and differ in degree in various cell compartments of the same cell. Hence, a correction for Si contamination should be included in the calculations of elemental concentrations. We suggest here a procedure for measuring and subtracting Si contamination from elemental spectra.
A direct optimization method for calculating density functionals and exchange–correlation potentials from electron densities
Authors: Wu Qin , Yang Weitao
Published: January 2003

A direct optimization method is developed for the computation of the Kohn–Sham kinetic energy density functional Ts from a given electron density and the exchange–correlation potential vxc if this density is from a ground state. The method is based on the construction of a variational functional of the one-electron potential. This functional is derived from the conventional Levy constrained-search formulation and is shown to be closely related to the Lieb functional construction. The one-electron potential is expanded in terms of some fixed terms plus a linear expansion in a basis set. The determination of the Kohn–Sham kinetic energy for an input density is then turned into the maximization of this functional of potential. The analytic first and second derivatives of the variational functional with respect to the linear basis set expansion coefficients and also the nonlinear parameters in the basis set are derived. This enables very efficient iterative optimization of the potential and hence the calculation of Ts and vxc. The efficiency and accuracy of the method is shown in the numerical implementation for atomic and molecular calculations with Gaussian basis set expansions both for molecular orbitals and for one-electron potentials. Finally, this direct optimization method is extended to general density functionals and the analytic derivatives are also developed for use in optimization methods.
Short chains at surfaces and interfaces: A quantitative comparison between density-functional theories and Monte Carlo simulations
Authors: Müller M. , MacDowell L. G. , Yethiraj A.
Published: January 2003

The surface and interfacial properties of a molecular liquid composed of short linear chains are investigated using molecular density-functional theories. The molecules are modeled as spherical sites connected by springs, and each site interacts with other sites and the surfaces with a modified Lennard-Jones interaction. In the density-functional theories, the ideal gas free energy functional is treated exactly (using a partial enumeration scheme) and the excess (over ideal gas) free energy functional is treated using a weighted density approximation (WDA). The latter requires the thermodynamic properties of the homogeneous fluid and a prescription for the weighting function. The thermodynamics of the homogeneous system is described via Wertheim’s perturbation theory, and various approximations for the weighting function in the WDA are tested. We find that for the theory to be accurate, it is important to decompose the excess free energy function into a repulsive and an attractive part, with different approximations for the two parts. Results from several approximations are in good agreement with Monte Carlo simulations for the chain conformations, density oscillations (packing) in the vicinity of surfaces, and the surface tension, for both liquid–vapor interfaces and attractive surfaces.
Plasmons of a two-dimensional electron gas in the presence of spin orbit interaction
Authors: Xu W.
Published: January 2003

A theoretical study of the collective excitation associated with plasmon modes is presented for a two-dimensional electron gas in the presence of spin orbit (SO) interaction induced by the Rashba effect. In such a case, the plasmon excitation can be achieved via intra- and inter-SO electronic transitions. As a result, three branches of the plasmon oscillations can be observed. It is found that inter-SO plasmons depend strongly on sample parameters and, at a long-wavelength limit, are optic-like, in contrast to intra-SO ones. The interesting features of these plasmon modes are examined.
Single-domain properties of 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 single crystals under electric field bias
Authors: Zhang Rui , Jiang Bei , Cao Wenwu
Published: January 2003

We report a complete set of material properties of single-domain, relaxor-based 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 [PMN–33%PT] single crystals. Because the single-domain state is unstable in natural conditions, a bias electric field of 0.2 MV/m was applied along the dipole direction of the rhombohedral phase during the measurements. It was found that the electromechanical coupling coefficient k33 and the piezoelectric constant d33 for single-domain PMN–33%PT are 69% and 190 pC/N, respectively. Both of them are much smaller than those of multidomain PMN–33%PT poled along [001] direction. However, the shear piezoelectric constant d15 of single-domain PMN–33%PT reaches 4100 pC/N, which is much higher than that of multidomain PMN–33%PT.
An advanced Monte Carlo method for the equilibration of model long-chain branched polymers with a well-defined molecular architecture: Detailed atomistic simulation of an H-shaped polyethylene melt
Authors: Karayiannis Nikos Ch. , Giannousaki Ageliki E. , Mavrantzas Vlasis G.
Published: January 2003

With few exceptions, atomistic simulation work on polymers has been limited to linear chain systems. The main reason for this is the inability of existing Monte Carlo (MC) methods to equilibrate the short- and long-length scale characteristics of nonlinear polymers without destroying their complex molecular architecture. We report here the first MC simulation of a well-defined model long-chain branched polymer, the H-shaped polyethylene melt, in full atomistic detail. The simulation has been executed with an advanced set of chain connectivity-altering moves based on the end-bridging [Pant and Theodorou, Macromolecules 28, 7224 (1995); Mavrantzas et al., Macromolecules 32, 5072 (1999)] and double-bridging [Karayiannis et al., Phys. Rev. Lett. 88, 105503 (2002); Karayiannis et al., J. Chem. Phys. 117, 5465 (2002)] algorithms. The new scheme provides excellent system equilibration at all length scales. The new method opens up the way toward the simulation of other nonlinear polymer systems where chain branching is precisely known (such as stars and combs) and the study of their unique thermodynamic and rheological properties from first principles.
Causation and Gerrymandered World Lines: A Critique of Salmon
Authors: Choi Sungho
Published: January 2003

In this paper I examine Salmon's response to two counterexamples to his conserved quantity (CQ) theory of causation. The first counterexample that I examine involves a time-wise gerrymandered world line of a series of patches of wall that is absorbing energy as a result of being illuminated in an astrodome. Salmon says that since the gerrymandered world line does not fulfill his “no-interaction requirement,” his CQ theory does not suffer from the counterexample. But I will argue that his response fails both at a theoretical level and at a practical level. In so doing I point out a problem for CQ theorists’ definition of a causal interaction. The second counterexample is concerned with a time-wise gerrymandered world line of a series of patches that are in shadow, in Hitchcock's well-known example. Salmon's response is based on a principle that Salmon thinks is derivable from the concept of a conserved quantity. However, I argue that the principle has a counterexample.
Contextual Unanimity and the Units of Selection Problem
Authors: Glennan Stuart
Published: January 2003

Sober and Lewontin's critique of genic selectionism is based upon the principle that a unit of selection should make a context-independent contribution to fitness. Critics have effectively shown that this principle is flawed. In this paper I show that the context independence principle is an instance of a more general principle for characterizing causes,called the contextual unanimity principle. I argue that this latter principle, while widely accepted, is erroneous. What is needed is to replace the approach to causality characterized by the contextual unanimity criterion with an approach based on the concept of causal mechanism. After sketching such an approach, I show how it can be used to shed light on the units of selection problem.
Genetic Relatedness and the Evolution of Altruism
Authors: Okasha Samir
Published: January 2003

In their recent book, Elliott Sober and David Wilson (1998) argue that evolutionary biologists have wrongly regarded kinship as the exclusive means by which altruistic behavior can evolve, at the expense of other mechanisms. I argue that Sober and Wilson overlook certain genetical considerations which suggest that kinship is likely to be a more powerful means for generating complex altruistic adaptations than the alternative mechanisms they propose.