bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of quantitative techniques in anal sphincter electromyography
Authors: Podnar Simon , Vodušek David B. , Stålberg Erik
Published: September 2002

Data comparing results and utility of different quantitative electromyographic (EMG) techniques are limited. In the present study, we analyzed the EMG signal from the external anal sphincter (EAS) muscle using three techniques of motor unit potential (MUP) analysis, and a technique of interference pattern (IP) analysis. We examined 56 patients with damage to the cauda equina or conus medullaris, and 64 control subjects. Using manual‐MUP and multi‐MUP analysis about 20 MUPs, using a single‐MUP technique about 10 MUPs, and using turn/amplitude (T/A) analysis about 20 IP samples were obtained. The sensitivities of these techniques in distinguishing neuropathic from control muscles were calculated. The single‐MUP technique detected 63%, manual‐MUP 57%, and multi‐MUP analysis 62% of neuropathic muscles, and MUP parameters obtained by each of these differed significantly from the other. The sensitivity of T/A analysis of IP was 29%. Our results confirm the need for separate MUP normative data for each of the MUP analysis techniques, and favor them over the IP analysis technique. The normative data presented for the EAS muscle should improve and promote quantitative EMG in patients. © 2002 John Wiley & Sons, Inc. Muscle Nerve 25: 83–92, 2002
Brain aromatase is neuroprotective
Authors: Azcoitia Iñigo , Sierra Amanda , Veiga Sergio , Honda Shin‐ichiro , Harada Nobuhiro , Garcia‐Segura Luis M.
Published: September 2002

The expression of aromatase, the enzyme that catalyzes the biosynthesis of estrogens from precursor androgens, is increased in the brain after injury, suggesting that aromatase may be involved in neuroprotection. In the present study, the effect of inactivating aromatase has been assessed in a model of neurodegeneration induced by the systemic administration of neurotoxins. Domoic acid, at a dose that is not neurotoxic in intact male mice, induced significant neuronal loss in the hilus of the hippocampal formation of mice with reduced levels of aromatase substrates as a result of gonadectomy. Furthermore, the aromatase substrate testosterone, as well as its metabolite estradiol, the product of aromatase, were able to protect hilar neurons from domoic acid. In contrast, dihydrotestosterone, the 5α‐reduced metabolite of testosterone and a nonaromatizable androgen, was not. These findings suggest that aromatization of testosterone to estradiol may be involved in the neuroprotective action of testosterone in this experimental model. In addition, aromatase knock‐out mice showed significant neuronal loss after injection of a low dose of domoic acid, while control littermates did not, indicating that aromatase deficiency increases the vulnerability of hilar neurons to neurotoxic degeneration. The effect of aromatase on neuroprotection was also tested in male rats treated systemically with the specific aromatase inhibitor fadrozole and injected with kainic acid, a well characterized neurotoxin for hilar neurons in the rat. Fadrozole enhanced the neurodegenerative effect of kainic acid in intact male rats and this effect was counterbalanced by the administration of estradiol. Furthermore, the neuroprotective effect of testosterone against kainic acid in castrated male rats was blocked by fadrozole. These findings suggest that neuroprotection by aromatase is due to the formation of estradiol from its precursor testosterone. Finally, a role for local cerebral aromatase in neuroprotection is indicated by the fact that intracerebral administration of fadrozole enhanced kainic acid induced neurodegeneration in the hippocampus of intact male rats. These findings indicate that aromatase deficiency decreases the threshold for neurodegeneration and that local cerebral aromatase is neuroprotective. Brain aromatase may therefore represent a new target for therapeutic approaches to neurodegenerative diseases. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 318–329, 2001
Gap junctional coupling between progenitor cells at the retinal margin of adult goldfish
Authors: Tamalu Fuminobu , Chiba Chikafumi , Saito Takehiko
Published: September 2002

We prepared living slice preparations of the peripheral retina of adult goldfish to examine electrical membrane properties of progenitor cells at the retinal margin. Cells were voltage‐clamped near resting potential and then stepped to either hyperpolarizing or depolarizing test potentials using whole‐cell voltage‐clamp recordings. Electrophysiologically examined cells were morphologically identified by injecting both Lucifer Yellow (LY) and biocytin. All progenitor cells examined (n = 37) showed a large amount of passively flowing currents of either sign under suppression of the nonjunctional currents flowing through K+ and Ca2+ channels in the cell membrane. They did not exhibit any voltage‐gated Na+ currents. Cells identified by LY fills were typically slender. As the difference between the test potential and the resting potential increased, 13 out of 37 cells exhibited symmetrically voltage‐ and time‐dependent current decline on either sign at the resting potential. The symmetric current profile suggests that the current may be driven and modulated by the junctional potential difference between the clamping cell and its neighbors. The remaining 24 cells did not exhibit voltage dependency. A gap junction channel blocker, halothane, suppressed the currents. A decrease in extracellular pH reduced coupling currents and its increase enhanced them. Dopamine, cAMP, and retinoic acid did not influence coupling currents. Injection of biocytin into single progenitor cells revealed strong tracer coupling, which was restricted in the marginal region. Immature ganglion cells closely located to the retinal margin exhibited voltage‐gated Na+ currents. They did not reveal apparent tracer coupling. These results demonstrate that the marginal progenitor cells couple with each other via gap junctions, and communicate biochemical molecules, which may subserve or interfere with cellular differentiation. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 204–214, 2001
Optimal sampling of electrophysiological signals
Authors: Jaw Fu‐Shan
Published: September 2002

Action potentials (APs) and field potentials (FPs) are commonly used to study functions of the brain. To facilitate their analysis, computer methods are often used. The high‐speed nature of APs and the large amount of data of FPs put stringent requirements on the sampling rate used. To determine optimal sampling rates for these signals a modified sampling equation is derived. This equation formulates the relationship among the order of the anti‐aliasing filter, the sampling rate, and the number of bits of quantization. For convenience, a table is also provided to reveal the optimal sampling rate for various combinations of filters and analog‐to‐digital converter cards commonly available. The recordings of compound action potentials, APs, and FPs were practically used to further examine this relationship. Under the specified conditions for the recording of these electrophysiological signals, their highest frequency contents are about 10 kHz, 9.3 kHz and 40 Hz, respectively. In conclusion, this paper provides a tutorial, quick reference, and step‐by‐step guide to sample a signal faithfully; that is, free from the contamination of aliasing errors no matter the spectrum of the signal is known. Also, the role of necessity of a high order anti‐aliasing filter is emphasized.
Alteration in glycoconjugate metabolism in CNS disorders ‐ role of isoprenoid pathway
Authors: Kurup Ravi Kumar Achutha , Devi Deepa , Augustine Jyothi , Kurup Parameswara Achutha
Published: September 2002

The isoprenoid pathway which is upregulated in neuropsychiatric disorders produces two metabolites which can regulate glycoconjugate metabolism ‐ dolichol (required for N‐glycosylation) and digoxin (endogenous membrane sodium‐potassium ATPase inhibitor producing magnesium depletion). It is known that Mg++ deficiency can influence glycoconjugate metabolism. The results showed an increase in the concentration of serum total glycosaminoglycan (GAG), glycolipids and carbohydrate component of glycoproteins and a decrease in the total GAG and carbohydrate component of glycoproteins in the Red blood cell (RBC) membrane suggesting their reduced incorporation into the membrane. The pattern of change in individual GAG in the serum was different, however heparan sulphate (HS) and chondroitin sulphate (ChS) increased in most of the disorders studied. The activity of GAG degrading enzymes and glycohydrolases showed significant increase in the serum in all the groups suggesting reduced lysosomal stability consequent to defective lysosomal membrane formation. The importance of altered glycoconjugate metabolism in the pathogenesis of multiple sclerosis, Parkinson's disease, schizophrenia, epilepsy and CNS gliomas is stressed.
Regulation or revenues? An analysis of local business licences, with a case study of the single business permit reform in Kenya
Authors: Devas Nick , Kelly Roy
Published: September 2002

Licensing of businesses by local governments is a common practice in many countries. While business licensing has its origins in regulation, it is often seen as little more than a revenue source for local government. This article reviews the potentially conflicting objectives of regulation and revenue generation, and outlines the various forms which local taxation of business has taken in a number of countries. In practice, the regulatory aspects of local business licensing in many developing countries are ineffective at best and counterproductive at worst, and there are pressures to sweep away most local business licences as part of deregulatory reform. Yet local governments in many countries are in dire need of revenue sources in order to finance local service provision. The article analyses the reforms that have been introduced to business licensing in Kenya. There, traditional business licences have been replaced with a Single Business Permit, with the twin objectives of increasing local revenues and reducing regulatory compliance costs on businesses. Initial results suggest that, while there have been some initial start‐up problems, both these objectives are being achieved. Copyright © 2001 John Wiley & Sons, Ltd.
Priority setting in agricultural research: beyond economic surplus methods
Authors: Smith Peter
Published: September 2002

The article examines the issue of priority setting in Third World agricultural research organizations, for those research sectors and topics which—mainly because of the difficulty of quantifying benefits—are outside the domain of economic surplus and benefit/cost techniques. The issue is redefined as one of processing ill‐structured decisions, i.e., decisions in which there is no unique, identifiable, objectively optimal solution. The implications of this for the concept of rational action in this field are explored, and the results used to define a practical approach. This centres on a radical review of the possible options and criteria in priority setting, using four techniques (challenge groups, repertory grid, creativity techniques and flow charting). The final section of the article examines the decision‐making aspects of these techniques in three priority‐setting contexts of increasing difficulty: within a department, where the issue is essentially one of technical choice between competing research lines; within a major institute or research sector, where there is substantial competition for resources; and in an institute or sector which is facing a crisis of resources or relevance. Copyright © 2001 John Wiley & Sons, Ltd.
Deregulation and the Racial Composition of Airlines
Authors: Agesa Jacqueline
Published: September 2002

Economic theory suggests that the enhanced product market competition of deregulation reduces employers' ability to discriminate when hiring. Recent studies of the effect of deregulation on racial employment in the naturally competitive trucking industry find that deregulation increased minority employment. This study examines the effect of deregulation on racial employment in the airline industry. Because deregulation transformed airlines from wasteful service competition to rigorous price competition, deregulation's effect on racial hiring in this continuously competitive industry is not apparent. This study finds that deregulation only modestly changed the racial composition of major airline occupations, which suggests that the change in market structure as a result of deregulation may largely determine the effect of regulatory reform on the racial composition of an industry. © 2001 by the Association for Public Policy Analysis and Management.
Photovoltaics literature survey (No. 8)
Authors: Keevers Mark J.
Published: September 2002

In order to help keep readers up‐to‐date in the field each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn primarily from recent issues of IEEE Transactions on Electron Devices, Journal of Applied Physics, Progress in Photovoltaics, Solar Energy and Solar Energy Materials and Solar Cells, with additional journals surveyed if space permits. To assist the reader, the list is separated into broad categories, but please note these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality. If you have any suggestions please email Mark Keevers at markk@ psolar.com.au. Copyright © 2001 John Wiley & Sons, Ltd.
Nanoscale calorimetry of isolated polyethylene single crystals
Authors: Kwan A. T. , Efremov M. Yu. , Olson E. A. , Schiettekatte F. , Zhang M. , Geil P. H. , Allen L. H.
Published: September 2002

We used thin‐film differential scanning calorimetry to investigate the melting of isolated polyethylene single crystals with lamellar thicknesses of 12 ± 1 nm. We observed the melting of as few as 25 crystals. Over a wide number of crystals (25–2000 crystals), the heat of fusion was 40% larger than the bulk value. The melting temperature of the isolated single crystals was 123 ± 2 °C, 9 °C lower than that of the bulk material. We also measured the heat of fusion of quenched crystals (±15%) over a wide range of heating rates (20,000–100,000 K/s). Annealing the quenched crystals resulted in shifts in the endotherm peak by as much as 15 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1237–1245, 2001
Phospholipase A2 degradation products modulate epithelial and stromal 5α‐reductase activity of human benign prostatic hyperplasia in vitro
Authors: Weisser Heike , Ziemssen Tjalf , Krieg Michael
Published: September 2002

BACKGROUND

Recent studies have demonstrated the inhibition of 5α‐reductase activity in human prostate by phospholipases. Among those phospholipases, phospholipase A2 cleaves one of the acyl chains from phospholipids, thereby producing fatty acids and lysophospholipids such as LPC, LPS, and LPE. Therefore, we were interested in the effect of those lysophospholipids on 5α‐reductase activity in human benign prostatic hyperplasia (BPH).

METHODS

In a first set of experiments, cell homogenates were incubated with phospholipase A2 either in the presence or absence of albumin, which is known to bind fatty acids and lysophospholipids. Thereafter, the effect of lysophospholipids of known structure on 5α‐reductase activity was investigated.

RESULTS

In epithelium and stroma of human BPH, 5α‐reductase activity was inhibited in a dose‐dependent manner by phospholipase A2. In the presence of albumin, this inhibition was enhanced. In epithelium, LPC at low concentration yielded a dose‐dependent stimulation of 5α‐reductase activity up to 167%. At higher concentrations, epithelial as well as stromal 5α‐reductase activity was inhibited significantly. As indicated by results of enzyme kinetic analyses, the LPC‐mediated activation in the epithelium results from an increase of the active population of 5α‐reductase. In contrast, LPC reduces the affinity of epithelial 5α‐reductase to testosterone. LPE had no effect on epithelial 5α‐reductase, whereas stromal 5α‐reductase was inhibited in a dose‐dependent manner up to 46%. Finally, LPS stimulated epithelial and stromal 5α‐reductase activity; this stimulation was significantly stronger in epithelium (296%) than in stroma (163%). The LPC‐mediated effects could be neutralized by the addition of albumin.

CONCLUSIONS

The present data on BPH tissue suggest that lysophospholipids may play a specific and structure‐related role in the posttranslational regulation of human prostatic 5α‐reductase. Prostate 50: 4–14, 2002. © 2002 Wiley‐Liss, Inc.
Differential expression of matrix metalloproteinases and their tissue inhibitors in human primary cultured prostatic cells and malignant prostate cell lines
Authors: Zhang Ju , Jung Klaus , Lein Michael , Kristiansen Glen , Rudolph Birgit , Hauptmann Steffen , Schnorr Dietmar , Loening Stefan A. , Lichtinghagen Ralf
Published: September 2002

BACKGROUND

The aim was to investigate the expression of matrix metalloproteinases (MMPs), membrane type MMPs (MT‐MMPs), and their inhibitors (TIMPs) in human primary cultured prostatic cells and malignant prostate cell lines.

METHODS

Reverse transscription‐polymerase chain reaction‐based measurements of the mRNA levels of MMP‐2, MMP‐7, MT1‐MMP, MT3‐MMP, TIMP‐1, and TIMP‐2 in relation to the house‐keeping gene glyceraldehyde phosphate dehydrogenase were performed in cancerous and non‐cancerous prostatic tissue samples, in primary cell cultures of epithelial cells, in both fibroblasts, and smooth‐muscle cells as stromal cells, and in the human malignant prostatic cell lines DU‐145, LNCaP, and PC‐3.

RESULTS

MMP‐2 was mainly expressed in the stromal cells and MMP‐7 showed their highest values in the epithelial cells. MT1‐MMP, MT3‐MMP, TIMP‐1, and TIMP‐2 were found both in the stromal and in the epithelial cells, but there were some differences between the expressions in fibroblasts and smooth‐muscle cells. Different expressions were also observed between the cells deriving from the primary cell cultures, the benign cell line BPH‐1, and the malignant cell lines LNCaP, D‐145, and PC‐3.

CONCLUSIONS

These exemplary results concerning different expressions of MMPs and TIMPs in cells from prostatic tissue suggest that a better insight into changes observed in prostatic tissue needs studies on cells cultured from the tissue. Prostate 50: 38–45, 2002. © 2002 Wiley‐Liss, Inc.
The action of phosphine against the eggs of phosphine‐resistant and ‐susceptible strains of Rhyzopertha dominica F
Authors: Rajendran Somiahnadar , Nayak Kirti R , Anjum Siddiqha Saba
Published: September 2002

The effect of phosphine at exposure periods of 24, 48 and 120 h on hatching and mortality of 0‐ to 1‐day‐old eggs of susceptible (TN6) and resistant (FC10) strains of Rhyzopertha dominica of field origin was investigated. The fumigant affected hatching in both the strains. In a 48‐h exposure at 27 (± 2) °C, the LD99 doses for the eggs of TN6 and FC10 were 0.56 and 3.25 mg litre−1, respectively. Significant reduction in hatching was observed in treated batches with progressive increase of phosphine dose in the first 2–3 days. On subsequent days the numbers hatching were often similar to those in controls, and sometimes exceeded control hatch, especially following a 5‐day exposure. A critical change in the order of susceptibility of egg and adult stages of the two strains was noticed. In 48‐h exposures, eggs of the susceptible strain were more tolerant than their adults, whilst the reverse was true in the resistant strain.

© 2001 Society of Chemical Industry
Amaranthus palmeri resistance and differential tolerance of Amaranthus palmeri and Amaranthus hybridus to ALS‐inhibitor herbicides
Authors: Burgos Nilda R , Kuk Yong‐In , Talbert Ronald E
Published: September 2002

Suspected imazaquin‐resistant accessions of Amaranthus palmeri were studied to determine the magnitude of resistance and cross‐resistance to acetolactate synthase (ALS)‐inhibiting herbicides and compare differential tolerance of A palmeri and Amaranthus hybridus to ALS inhibitors. Five of seven A palmeri accessions were resistant to imazaquin. The most imazaquin‐resistant accession, accession 7, also showed 74, 39 and 117 times higher resistance than the susceptible biotype to chlorimuron, diclosulam and pyrithiobac, respectively. Resistance to imazaquin and cross‐resistance to other ALS inhibitors in A palmeri was due to a less‐sensitive ALS enzyme. A palmeri was 70 times more tolerant to imazaquin than A hybridus. A palmeri was also seven times more tolerant to pyrithiobac than A hybridus. Differences in ALS enzyme sensitivity could not fully account for the high tolerance of A palmeri to imazaquin compared to A hybridus. Both species were equally affected by chlorimuron and diclosulam.

© 2001 Society of Chemical Industry
Time‐dependent density functional calculations of the Q‐like bands of phenylene‐linked free‐base and zinc porphyrin dimers
Authors: Yamaguchi Yoichi , Yokomichi Yasunori , Yokoyama Shiyoshi , Mashiko Shinro
Published: September 2002

Time‐dependent density functional theory (TDDFT) calculations have been performed on the excitation energies and oscillator strengths of the Q‐like bands of three structural isomers of phenylene‐linked free‐base (FBP) and zinc (ZnP) porphyrin dimers. The TDDFT calculated results on the low‐lying excited states of the reference monomers, FBP and ZnP, are in excellent agreement with previously calculated and experimental results. It is found that the 1,3‐ and 1,4‐phenylene‐linked dimers have monomerlike Q bands that are slightly red‐shifted compared to the monomers and new Q′ bands comprised of the cross‐linked excitations from the FBP (ZnP) ring to the ZnP (FBP) ring at considerably lower energies than the monomer Q bands. For the 1,2‐phenylene‐linked dimer, the direct π–π interaction between porphyrin rings caused by the van der Waals repulsion between them provides strong mixing of the Q′ bands with the Q bands, which causes its minimum excitation energy to be red‐shifted by 0.05 eV compared to the other isomers. The oscillator strengths of the Q′ bands are also unexpectedly found to be as strong as those of the Q bands in the dimers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 338–347, 2001
Phase behavior of C60 by computer simulation using ab‐initio interaction potential
Authors: Fartaria Rui P. S. , Silva Fernandes Fernando M. S. , Freitas Filomena F. M. , Rodrigues Pedro C. R.
Published: September 2002

A first‐principles intermolecular potential recently proposed by Pacheco and Ramalho [Phys Rev Lett 1997, 79, 3873–3876] has been used with the Gibbs ensemble and Gibbs–Duhem integration Monte Carlo methods to simulate the vapor–liquid and fluid–solid coexistence properties of C60. The critical properties were calculated by fitting the results to the laws of rectilinear diameters and order parameter scaling. The triple‐point properties were determined from the limiting behavior of the Gibbs ensemble vapor–liquid simulations at the lowest temperature range. A stable liquid phase is predicted for temperatures between 1570±20 and 2006±27 K and densities between 0.444±0.003 and 1.05±0.01 nm−3. The estimated critical and triple‐point pressures are, respectively, 35±6 and 5±16 bars. We show for the first time, to our knowledge, that it is possible, strictly by computer simulation, to estimate a triple point for C60 in accordance with the predictions of theoretical methods and the basic concepts of thermodynamics. The liquid and fluid radial distribution functions indicate the presence of solid or glasslike features. This may support the suggestion of a more cooperative interaction of clusters in C60. A comparison of our results with the data obtained by other authors is presented and discussed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 375–387, 2001
Mass spectrometric studies on pyridine‐piperazine‐containing ligands and their complexes with transition metals formed in solution
Authors: Nuutinen Jari M. J. , Purmonen Mikko , Ratilainen Jari , Rissanen Kari , Vainiotalo Pirjo
Published: September 2002

Electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI) methods were used to study open‐chain piperazine‐containing ligands (L) and their complexes formed with transition‐metal salts. ESI and MALDI measurements were performed with a Fourier transform ion cyclotron resonance (FT‐ICR) and a time‐of‐flight (TOF) mass spectrometer, respectively. Only singly charged complexes, between one ligand and one or several metal ions, were formed in the ESI measurements. Because the net charge was always one, one or several counterions were attached to the complex. Under ESI conditions, the complexes formed between the ligands and metal (Co, Ni, Cu, and Cd) salts were [L + M + X]+, [L + H + M + X2]+ and [L + M2 + X3]+ (M = metal ion, X = counterion). In collision induced dissociation reactions the [L + H + M + X2]+ complexes easily eliminated one proton and one counterion. Fragmentation pathways were more dependent on the metal ion than the ligand, and elimination of the second counterion occurred with one proton from copper and nickel complexes and with one proton and one hydrogen from cobalt complexes. Differences in the fragmentation of the complexes could be due to electronic configuration of the metal ion. In the MALDI measurements the ratio between the [L + H]+ and [L − H]+ ions varied with the matrix. Fragmentation of the ligands through elimination of 2‐methylpyridine end groups occurred with the aromatic matrices containing carboxylic acid and hydroxyl substituents. Ionization of the complexes was not successful with MALDI as the matrix molecules were also attached to the complexes. Copyright © 2001 John Wiley & Sons, Ltd.
Protection of fixed service receivers from the interference produced by the non‐geostationary satellites in a fixed satellite service network: a statistical interference analysis
Authors: Fortes José Mauro P. , Maldonado Jorge E. Amores
Published: September 2002

Until 1997, the power flux density (pfd) limits applicable to fixed satellite service (FSS) satellite transmitters to protect fixed service (FS) receivers operating in the same frequency band were those in Article 21 of the radio regulations. They were developed assuming that potentially interfering satellites in the FSS would only operate in the GSO. The need to revise these limits to allow for the protection of FS receivers from interference generated by non‐geostationary satellites has led to several studies, most of them based on the non‐realistic assumption that every visible satellite in a NGSO constellation produces the maximum allowed pfd level at the FS receive station location. To provide a quantitative indication of how pessimistic this assumption is, this paper considers a more realistic model in which the pfd entries reaching a given FS receiver location are characterized by statistically independent random variables. The probability density functions of these random variables depend on the operational characteristics of the NGSO network. The obtained results have also shown the need to consider some of the operational characteristics of NGSO satellite networks when evaluating the interference produced by their satellites. If these operational characteristics are not taken into account in the calculations, higher values of interference, that do not reflect the real interference environment, are obtained. Copyright © 2002 John Wiley & Sons, Ltd.
Electroluminescence spectra study of Au/Si/SiO2 superlattice/p‐Si structures with gamma irradiation
Authors: Ma S. Y. , Qin G. G. , Wang Y. Y. , He D. Y. , Liu X. Q.
Published: September 2002

Visible light emission can be observed from alternation‐magnetron‐sputtered Si/SiO2 superlattices (SSOSLs) when the forward bias exceeds 5 V. The electroluminescence (EL) spectra of Au/ amorphous Si/SiO2 superlattice/p‐Si structures with Si layers of nine different thicknesses showed a peak located at 650 nm. After the SSOSLs were irradiated by a 60Co radiative source, a new strong 470 nm blue peak emerged from the EL spectra in all the Au/ Si/SiO2 superlattice/p‐Si structures. We rule out the possibility that both the excitation and recombination processes of the observed EL are from the nanometre silicon layers, as described by the quantum confinement model. The experimental results can be explained by electrons from the Au electrode and holes from the p‐Si substrate tunnelling into the luminescence centres in the SiO2layers and recombining radiatively there. Copyright © 2001 John Wiley & Sons, Ltd.
Local conductivity study of TiO2 electrodes by atomic force microscopy
Authors: Jiang Feng Zhi , Zhang Dong She , Lin Yuan , Song Yan Lin , Xiao Xu Rui , Jiang Lei , Zhu Dao Ben
Published: September 2002

Titanium dioxide (TiO2) nanocrystalline porous film electrodes were prepared by the sol–gel method on indium–tin oxide (ITO) glass and chemically modified further by an aqueous solution of titanium tetrachloride for solar energy conversion application. The surface topography and local conductivity of the TiO2 films were investigated by atomic force microscopy and a simultaneous current mapping technique in the dark and under ultraviolet illumination, respectively. It was found that the conductivity of the films was improved by chemical treatment and the possible mechanism of the effect was discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Ultrathin Al layers on Si(111) and Si(100): structures and phase transitions
Authors: Gröger R. M. , Barczewski M. R.
Published: September 2002

The metal/silicon system Al/Si(111)‐7 × 7 was studied by our group with spot‐profile analysis low‐energy electron diffraction (SPA‐LEED), reflection high‐energy electron diffraction (RHEED) and scanning force microscopy (SFM), with emphasis on temperature‐dependent order–disorder phase transitions of the surface structures. A review of the Al/Si(111) system describes our results in context with the findings of others. An improved phase formation diagram, including earlier results, is deduced. Between the submonolayer phases and the thick films a cluster phase (the δ‐phase) was found that exists in a coverage range of 1–10 monolayers, showing intriguing temperature‐dependent effects. At coverages above 20 monolayers the behaviour changes to that of thick films. Although the Al/Si(100) system has completely different reconstructions below one monolayer, the same δ‐phase as on Si(111) appears at one monolayer, with similar thermal behaviour. Copyright © 2001 John Wiley & Sons, Ltd.
Row structure in metal‐induced Si(111) surface reconstructions
Authors: Jin Kui‐juan , Sanders Barry C. , Pan Shao‐hua , Yang Guo‐zhen
Published: September 2002

We demonstrate that quantum size effects play a crucial role in the row structure of metal‐induced Si(111) reconstruction by identifying the ‘magic’ widths of the metal adsorbates with the minima of electron energy as a function of adsorbate width. Without any adjustable parameters, we obtain accurate agreement with all recent results for Si(111)‐4 × 1‐In and Si(111)‐3 × 1‐M (M = Li, Na, K, Rb, Ag) structures. This new and simple physical picture of electron energies in metal adsorbates provides a universal quantitative model for describing the row structures of metal‐induced Si(111) surface reconstructions. Copyright © 2001 John Wiley & Sons, Ltd.
Chain‐length‐adjusted assembly of substituted porphyrins on graphite
Authors: Wang Hongna , Wang Chen , Zeng Qingdao , Xu Shandong , Yin Shuxia , Xu Bo , Bai Chunli
Published: September 2002

A series of alkyloxyphenyl‐substituted porphyrins were synthesized, and their adsorption and assembling behaviour on a highly oriented pyrolytic graphite (HOPG) surface were studied by scanning tunneling microscope (STM) in ambient conditions. A characteristic stripe‐like structure was observed from these samples. In high‐resolution images, we found that within the stripe structure porphyrin cores are arranged side by side with each other and the alkyl chains interdigitate to form a uniform alkane lamella. This high stability and close‐packed assembly is attributed to van der Waals interactions between the alkyl chains and the graphite substrate, which substantially increases the desorption barrier of the combined molecules. This observation illustrates that molecular alkylation is an effective method to obtain stable low‐dimensional molecular assemblies. Copyright © 2001 John Wiley & Sons, Ltd.
Molecular dynamics study for structural stability of the interface at elevated temperatures
Authors: Zhao S. J. , Wang S. Q. , Ye H. Q.
Published: September 2002

The high‐temperature structure of the Σ = 5 bicrystalline interface of B2 NiAl with a large boundary plane is investigated by molecular dynamics simulations on parallel computers. It is observed that the atoms in the grain boundary region tend to form clusters in a thermal structural disorder transition, which is initiated at a temperature well below the thermodynamic melting point Tm (∼0.52 Tm). The number and size of the clusters are monitored over a wide temperature range including Tm. Below Tm, the number and size of the clusters increase continuously with increasing temperature. When the temperature is up to Tm, the abrupt growth of the clusters induces melting. Once above Tm, the number and size of the clusters decrease significantly upon raising the temperature. The calculations of the potential energy also indicate that the thermal disorder transition is a continuous process, in contrast to the first‐order melting transformation. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of surface physicochemical properties on the tribological properties of liquid paraffin film in the nanoscale
Authors: Shen Mingwu , Luo Jianbin , Wen Shizhu
Published: September 2002

Effects of different coatings on the tribological properties of very thin oil films in the nanoscale were investigated. The film thickness and friction force were measured by the technique of relative optical interference intensity (ROII) and a stress–strain force measuring system with high precision. The results indicate that the film thickness complies with the elastohydrodynamic theory in the high‐speed region but it differs from the theory in the low‐speed region. The physicochemical properties of coating surfaces have a great effect on the tribological properties of the oil film in the nanoscale. The coating with higher surface energy gives rise to a thicker film and a higher friction coefficient. The reasons for enhancement in the friction coefficient of the oil film in the nanoscale are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Chemical structure and interface reaction of LaCoO3/Si thin‐film system
Authors: Zhang Yingxia , Zhu Yongfa , Ye Xiaoyan , Cao Lili
Published: September 2002

An LaCoO3 thin film was prepared on Si(111) substrate successfully using an amorphous heteronuclear complex, LaCo(DTPA)·6H2O, as a precursor. The surface chemical structures and interface reaction of LaCoO3/Si thin film were studied by XPS and AES techniques. The AES depth profile analysis indicated that the composition of the LaCoO3 thin film was relatively homogeneous with depth. Interface diffusion and chemical reaction took place at the interface between the LaCoO3 layer and the Si substrate during thermal treatment. The linear least‐squares fitting of the AES depth profile analysis indicated that the LaCoO3 decomposed into simple a oxide of La and Co at the interface. An SiO2 species also formed at the interface when the sample was treated at relatively high temperature. Interface diffusion and reaction were intensified with increasing calcination temperature and time. When the temperature was <650 °C, the interface species were mainly La2O3 and CoO simple oxides. After the temperature reached 700 °C, the interface species were La2O3, CoO and SiO2. Copyright © 2001 John Wiley & Sons, Ltd.
Transmission electron microscopy studies of microstructures of silica–zirconia membranes for gas separation
Authors: Kato T. , Sasaki Y. , Osada K. , Hirayama T. , Saka H.
Published: September 2002

Two types of silica–zirconia amorphous membranes were synthesized on the outer surface of porous alumina supports using the sol–gel method. The molar ratios of ZrO2 in SiO2 were 15 and 25 mol.%, respectively. Transmission electron microscopy (TEM) specimens of the membranes were prepared in a focused ion beam system. The microstructural characterizations were achieved by TEM and the chemical compositions of the amorphous material were analysed by energy‐dispersive x‐ray spectroscopy (EDX). Structural investigation of both membranes using TEM revealed two structures: continuous pores ∼100 nm in diameter in the amorphous material filling the crevices of the porous alumina supports; and layered structures of amorphous film on the porous alumina support formed by the coating process. Because the former structure has such large continuous pores, gases should be separated in the layered amorphous film. Therefore, the amorphous film on the porous alumina support should play the most important role in the gas separation mechanism. Furthermore, Zr/Si ratios of those amorphous films were revealed by TEM and EDX. They were constant for the 15% ZrO2–SiO2 membrane but not constant for the 25% ZrO2–SiO2 membrane. Copyright © 2001 John Wiley & Sons, Ltd.
Environmental dependence of thermal oxidation behaviour of silicon nanocrystallites
Authors: Zhu Y. , Ong P. P.
Published: September 2002

Three kinds of nanosilicon crystallites were prepared by different methods in high vacuum. All of them were composed of tiny silicon crystallites that initially were only mildly oxidized before annealing, but their behaviour upon annealing in a vacuum differed substantially, depending on the environment in which they resided. X‐ray photoelectron spectroscopy analyses revealed that the unencapsulated nanoparticles tended to oxidize quite quickly, whereas the nanoparticles sandwiched between layers of Al2O3 matrices were oxidized very slowly even under intense annealing. In the zinc/silicon nanocrystalline mixture, oxidation of the Si0 state was even faster than that of the intermediate Si +1,+2 and +3 states. Both the stability and formation processes of the Si O bonds in the partially oxidized states differed considerably with different environmental surroundings. However, in all cases, the Si O bonds of the fully oxidized Si+4 state remained the most stable, to which the less oxidized states tend to gravitate eventually. Copyright © 2001 John Wiley & Sons, Ltd.
Adhesion activation of Twaron® aramid fibres studied with low‐energy ion scattering and x‐ray photoelectron spectroscopy
Authors: de Lange P. J. , Akker P. G. , Maas A. J. H. , Knoester A. , Brongersma H. H.
Published: September 2002

The properties of the interphase between Twaron® aramid fibres and polymer matrix systems can be optimized by a surface treatment process of the fibres. In this work, x‐ray photoelectron spectroscopy and low‐energy ion scattering have been used to analyse the surface layers, whereas the adhesion was measured by a bundle pull‐out experiment. From the results, we succeeded in establishing a relation between the surface treatment, the resulting chemical/elemental surface composition and the adhesion to an epoxy matrix. Copyright © 2001 John Wiley & Sons, Ltd.
Probing the ex situ morphology of Ge islands on Si(001): AFM and XPS inelastic peak shape analysis
Authors: Cohen Simonsen A. , Tougaard S. , Hansen J. L. , Nylandsted Larsen A.
Published: September 2002

The dependence of morphology on growth temperature for Ge islands on Si(001) is studied ex situ using XPS inelastic peak shape analysis and atomic force microscopy (AFM). A systematic study is performed with temperatures of 200 °C, 550 °C and 700 °C and Ge nominal coverages of 5, 10 and 20 Å. By peak shape analysis of the Ge 2p and Si KLL spectra, islanding is found and the average island morphology is characterized quantitatively. The island morphology shows systematic trends with both temperature and Ge coverage. At fixed Ge dosage, increasing substrate temperature leads to taller and narrower islands, whereas for fixed temperatures both the island height and width increase with increasing Ge dosage. By AFM, the island morphology is resolved laterally and the size distribution of islands is found to depend strongly on temperature. Correlating the AFM and XPS results shows that they are complementary and consistent. Oxidation of the nanostructures is investigated by core‐level chemical shifts and the in‐depth distribution of oxygen is determined. There is substantial Ge oxidation and essentially no Si oxide is found. Copyright © 2001 John Wiley & Sons, Ltd.
Visualization of reconstituted solenoid chromatin structure by tapping mode atomic force microscopy
Authors: Liu Dage , Wang Chen , Li Junwei , Wang Zhigang , Xu Bo , Wei Zhongqing , Lin Zhang , Qin Jingfen , Cao Enhua , Bai Chunli
Published: September 2002

In this paper, tapping mode atomic force microscopy was applied to visualize the higher order chromatin structure reconstituted from calf thymus DNA and calf thymus whole histone in vitro. All the revealed reconstituted chromatin structures consisted of similar well‐defined subunits. In some of the chromatin structures, four to six subunits per turn were wrapped right‐handed to form a flattened solenoid with a height distribution of 12 ± 2 nm; and the other Y‐ and V‐shaped chromatin structures were formed by aggregation of these solenoids, which presented similar heights as the solenoids. Typical atomic force microscopy (AFM) images revealed relatively regular solenoid structure (containing six nucleosomes per turn) with a ratio of diameter to pitch of 3 : 1, which is in good agreement with that of 30 : 11 in the chromatin solenoid model proposed by Finch and Klug. Bio‐gel elution was used to separate reconstituted chromatin from uncombined histone particles, which proved to be helpful for the AFM imaging of the higher order chromatin structure with nearly no disturbance of histone particles and salt in the background. The AFM observations showed that the higher order chromatin structure was preserved well enough during the bio‐gel elution process. The cause for the stability of higher order chromatin structure during the bio‐gel elution was analysed. Electron microscopy analysis and circular dichroism spectroscopy investigation of the DNA–histone complexes indicated the formation of ordered aggregates. Copyright © 2001 John Wiley & Sons, Ltd.
Learning across the life cycle: Experimentation and performance among the hollywood studio heads
Authors: Miller Danny , Shamsie Jamal
Published: September 2002

Guided by notions from the literature on organizational learning, this paper investigates how product line experimentation and organizational performance change across the careers of top managers. Its subjects are the studio heads who ran all the major Hollywood film studios from 1936 to 1965. The study found first, that product line experimentation declines over the course of executive tenures; second, that there is an inverse U‐shaped relationship between top executive tenure and an organization's financial performance; and third, that product line experimentation is more likely to benefit financial performance late in top executives' tenures. These findings are consistent with a three‐stage ‘executive life cycle’. During the early years of their tenures, top managers experiment intensively with their product lines to learn about their business; later on their accumulated knowledge allows them to reduce experimentation and increase performance; finally, in their last years, executives reduce experimentation still further, and performance declines. Copyright © 2001 John Wiley & Sons, Ltd.
Llun—a high‐level debugger for generated parsers
Authors: Glass S. , Ince D. , Fergus E.
Published: September 2002

Parser generators such as yacc have been used in a large number of applications, not just those that involve compiler writing. This has meant that these tools are being used increasingly by nonspecialist developers. A consequence of this is that good support is required for debugging a grammar and its generated parser(s). This paper describes Llun, a debugging tool that visualizes the operation of a generated parser at both a high‐level and a low‐level. Llun is superior to other parser visualization products by virtue of the high‐level facilities it offers. The paper describes some of the problems encountered using parser generators, outlines a visualization system which addresses a number of the problems and uses a taxonomy developed by Price to categorize the system. Copyright © 2001 John Wiley & Sons, Ltd.
Investigation of genotoxic effect of taxol plus radiation on mice bone marrow cells
Authors: Özkan Lütfi , Egeli Ünal , Tunca Berrin , Aydemir Nilüfer , Çeçener Gülşah , Akpinar Gürler , Ergül Emel , Çimen Çiğdem , Özuysal Sema , Kahraman‐Çetintaş Sibel , Engin Kayihan , Ahmed Mansoor M.
Published: September 2002

In this study, we investigated the genotoxic effect of taxol, radiation, or taxol plus radiation on highly proliferative normal tissue‐bone marrow cells of Swiss albino mice. Swiss‐albino mice, 3–4 months old, were used in this study. Taxol was administered bolus intravenously through the tail vein. Radiation was given by using a linear accelerator. There were four treatment categories, which had a total of 34 groups. Each group consisted of five animals. The first was the control category that had one group (n = 5). The second treatment category was taxol alone, which had three groups as per taxol dose alone (n = 15). The third treatment category was radiation alone, which had three groups as per the radiation dose (n = 15). The fourth treatment category was taxol plus radiation, which had 27 groups as per combined radiation dose plus taxol dose concentration and as per pre‐treatment timing sequence of taxol before radiation (n = 135). Mice were sacrificed 24 h after taxol or radiation or combined administration using ether anesthesia. The cells were then dropped on two labeled slides, flamed, air dried, and stained in 7% Giemsa; 20–30 well‐spread mitotic metaphases were analyzed for each animal; the cells with chromosome breaks, acentric fragments, and rearrangements were evaluated on ×1,000 magnification with light microscope (Zeiss axioplan). The mitotic index was determined by counting the number of mitotic cells among 1,000 cells per animal. Differences between groups were evaluated with Student’s t‐test statistically. Taxol caused a dose‐dependent increase in chromosomal aberrations (P = 0.027). Similarly, radiation caused a dose‐dependent increase in chromosomal aberrations (P = 0.003) and decreased mitotic index (P = 0.002). In combination, there were a small enhancements at the 40 mg/kg taxol dose level and at 0.25 and 0.5 Gy radiation doses in the 48 h group. However, an increase in chromosomal aberrations was observed after 48 hours of taxol exposure when compared 12 or 24 h of taxol exposure (P = 0.001 and P = 0.019). These findings suggest that taxol at the high doses with low dose radiation caused radiosensitizing effect in bone marrow cells. Forty‐eight‐hour pretreatment of taxol exposure followed by radiation caused significant induction of chromosomal aberrations and a reduction of mitotic index when compared to other taxol timing sequence. Teratogenesis Carcinog. Mutagen. 22:1–11, 2002. © 2002 Wiley‐Liss, Inc.