bluuebunny/crossref_metadata_2025 huggingface dataset:
The key‐group method
Authors: Yarahmadi Bafghi A. R. , Verdel T.
Published: April 2003

This paper proposes an extension to the key‐block method, called ‘key‐group method’, that considers not only individual key blocks but also groups of collapsable blocks into an iterative and progressive analysis of the stability of discontinuous rock slopes. The basics of the key‐block method are recalled herein and then used to prove how key groups can be identified. We reveal that a key group must contain at least one basic key block, yet this condition is not entirely sufficient. The second block candidate for grouping must be another key block or a block whose movement‐preventing faces are common to one or more single key blocks.

We also show that the proposed method yields more realistic results than the basic key‐block method and a comparison with results obtained using a distinct element analysis demonstrates the ability of this new method. Copyright © 2003 John Wiley & Sons, Ltd.
Influence of prednisolone on β‐secretase enzyme activity in vitro
Authors: Ishikawa Kohtaro , Imai Yohsuke , Tokuda Takahiko , Ikeda Shu‐ichi
Published: April 2003

Epidemiological studies have shown that anti‐inflammatory medications decrease the incidence of Alzheimer's disease (AD). Our previous studies showed that a regimen of prednisolone decreased the amyloid β‐protein (Aβ) concentration in the cerebrospinal fluid of AD patients. However, the detailed mechanism by which prednisolone decreased the Aβ concentration is unknown. In the present study we tested whether prednisolone has a direct inhibitory activity against β‐secretase by using an in vitro enzyme assay system. β‐Secretase, a fluorogenic substrate of β‐secretase, and either prednisolone or β‐secretase inhibitor were coincubated, and then the increase in fluorescence intensity was monitored. Prednisolone (1×10−3M–1×10−9) had no effect on the β‐secretase activity, whereas β‐secretase inhibitor inhibited it. This result shows it to be unlikely that prednisolone has an effect on the intracerebral Aβ metabolism via the modulation of β‐secretase activity.
Thermal Decomposition of Energetic Materials 85: Cryogels of Nanoscale Hydrazinium Diperchlorate in Resorcinol‐Formaldehyde
Authors: Tappan Bryce C. , Brill Thomas B.
Published: April 2003

The objective of this work was to try to desensitize an energetic material by using sol‐gel processing and freeze drying to incorporate the energetic material into the fuel matrix on the nano (or at least submicron) particle size scale. Hydrazinium diperchlorate ([N2H6][ClO4]2 or HP2) and resorcinol‐formaldehyde (RF) were chosen as the oxidizer and fuel, respectively. Solid loading up to 88% HP2 was achieved by using the sol gel‐to‐cryogel method. Various weight percentages of HP2 in RF were characterized by elemental analysis, scanning electron (SEM) and optical microscopy, T‐jump/FTIR spectroscopy, DSC, and drop‐weight impact. SEM indicated that 20–50 nm diameter HP2 plates aggregated into porous 400–800 nm size clusters. Below 80% HP2 the cryogels are less sensitive to impact than physical mixtures having the same ratios of HP2 and RF. The decomposition temperatures of the cryogels are higher than that of pure HP2, which is consistent with their lower impact sensitivity. The heat of decomposition as measured at a low heating rate increases with increasing percentage of HP2. The cryogels and physical mixtures release similar amounts of energy, but the cryogels exhibit mainly a single exotherm by DSC whereas the physical mixtures showed a two‐step energy release. Flash pyrolysis revealed gaseous product ratios suggestive of more energy being released from the cryogels than the physical mixtures. Cryogels also burn faster by visual observation.
Configuration interaction study of the single‐electron transport in the vertical gated quantum dot
Authors: Adamowski J. , Bednarek S. , Szafran B.
Published: April 2003

A theoretical description is presented for a single‐electron transport through a vertical gated quantum dot. Using the configuration interaction method we study the correlation effects in the gated quantum dots. We have found that the electron‐electron correlation only slightly changes the single‐electron tunnelling conditions in the absence of an external magnetic field, but has a pronounced influence on the magnetic‐field induced phase transitions in few‐electron systems confined in quantum dots.
Exciton–LO‐phonon coupling in self‐organized InAs/GaAs quantum dots
Authors: Heitz R. , Schliwa A. , Bimberg D.
Published: April 2003

The exciton–LO‐phonon interaction in self‐organized quantum dots is investigated emphasizing the impact of realistic structural properties. The possibility to engineer the local charge density via the shape and composition profile of such strained quantum dots provides an unique opportunity to optimize the electronic and optical properties of a semiconductor nanostructure. Size‐selective luminescence, resonant Raman scattering, and time‐resolved luminescence experiments provide insight into the exciton‐LO‐phonon and exciton‐photon couplings in self‐organized quantum dots. The impact of the structural details is analyzed based on eight‐band k · p model calculations.
Large polaron absorption in high‐Tc cuprates
Authors: Calvani P.
Published: April 2003

Infrared evidence for the existence of polaronic carriers in superconducting cuprates is reviewed. Absorption features like shake‐off bands in the mid‐infrared and extra‐phonon peaks in the far‐infrared can be easily resolved and studied in the insulating phase at low doping, where they are well described by the large polaron model. Recent data are in close agreement with the two‐step model of Devreese and coworkers. As the carrier density increases, polaron–polaron interactions have to be taken into account. A renormalized polaronic conductivity proposed by Tempere and Devreese well accounts for the experimental observations in the electron‐doped cuprate NCCO. In hole‐doped LSCO, however, when approaching the metallic phase the absorption spectra are dominated by huge peaks at extremely low frequencies, which indicate a cross‐over to a new regime. Indeed, those exotic spectral features are most probably related to the formation of dynamic charge stripes in the Cu–O planes.
InGaAs quantum dot excited states as determined by microphotoluminescence and resonant photoluminescence
Authors: Bissiri M. , Baldassarri Höger von Högersthal G. , Ochoa D. , Capizzi M. , Frigeri P. , Franchi S.
Published: April 2003

Microphotoluminescence and resonant photoluminescence experiments in a variety of InGaAs quantum dots (QD's) differing for size, shape, indium content, and growth technique are reported. In the case of large QD's, the excited state energies determined by the above mentioned two experimental techniques show a quite different dependence on the QD ground state energy. Possible causes of this disagreement are discussed.
Influence of polarization fields and depletion fields on photoluminescence of AlGaN/GaN multiple quantum well structures
Authors: Monemar B. , Haratizadeh H. , Paskov P. P. , Pozina G. , Holtz P. O. , Bergman J. P. , Kamiyama S. , Iwaya M. , Amano H. , Akasaki I.
Published: April 2003

We report on a detailed study of low temperature photoluminescence (PL) in Al0.07Ga0.93N/GaN multiple quantum wells (MQWs). The structures were grown on sapphire with the conventional low temperature AlN nucleation layer and thick GaN buffer layer. Several sets of 5 QW MQW samples were studied, one set with Si doping in the barriers up to or above the metallic limit. Nominally undoped MQW samples were also studied. The spectral behaviour of the doped samples was strongly affected by the near surface depletion field, causing overlap of different spectra from non‐equivalent QWs. The QWs closest to the surface are presumably inactive in some samples, due to a very high depletion field. For the case of undoped samples, on the other hand, the near surface QWs are active and most prominent in the PL spectra. The structure from discrete well width variations is here resolved in the PL spectra. The results demonstrate that for structures with no additional capping layer both the depletion field and the polarisation fields need to be considered in the interpretation of experimental data. The theoretically estimated fields in this work are consistent with the experimental spectra. The presence of localisation even in the case of metallic samples, as observed by a constant PL decay time independent of doping, is discussed in terms of penetration of the hole wave functions into the AlGaN barriers. This localisation is also manifested in a sizeable LO phonon coupling strength in all samples studied.
Application of Feynman path integration to the electron–plasmon interaction
Authors: Pinsook U. , Sa‐yakanit V.
Published: April 2003

We study a system of an electron interacting with plasmons using Feynman path integral method. The Lagrangian and then the action which describe the motion of the electron interacting with a harmonic field of the plasmons are derived. The interaction strength is embedded in a specific dielectric function and a corresponding plasmon spectrum. We have studied two models of the dielectric media proposed by Lundqvist and Overhauser. By using numerical integration and minimization, we evaluate the ground state energy and the effective mass of the system as a function of rs. We found that both models give similar ground state energy. There is a possibility that the theory would predict a phase transition in this system. The analytic expansion of the ground state energy in some extreme limits are investigated. The applications of theory to some excitations in a Fermi gas are discussed.
On the use of path integrals in micro‐electronic design
Authors: Schoenmaker W.
Published: April 2003

The design of micro‐electronic processes is done by running process splits that either consist of laboratory or clean‐room experiment or of computer experiments. In order to obtain optimal designs, in terms of high yield and having the specifications on target, the design space is explored using design‐of‐experiment and response‐surface methods. In this paper we present a new technique for performing continuous interpolation between the experimental points in order to determine non‐explored input settings. The method eliminates all bias which is traditionally built into the surface construction by assuming polynomial behavior by using the maximum entropy principle and by constructing numerical interpolation hyper surfaces. The technique is generic and can be applied also outside the field of microelectronic design.
Stochastic and numerical approaches to dissipative quantum dynamics: path integrals and beyond
Authors: Stockburger Jürgen T.
Published: April 2003

Recent advances using non‐Markovian stochastic techniques in the treatment of system–reservoir models of quantum dissipation are reviewed, outlining their derivation from the influence functional formalism and discussing their new features and potential applications. A coherent perspective of the salient features in the mathematical foundations of dissipative quantum mechanics, diverse established perturbative and numerical methods, and more recent non‐Markovian stochastic approaches is attempted.
Social Mobility from a Kinship Perspective: Rural Liaoning, 1789–1909
Authors: Campbell Cameron , Lee James
Published: April 2003

This paper examines the role of kin networks in intergenerational mobility in rural Liaoning, China, 1789–1909. Classic studies of social mobility in historical China based on the records of imperial examination candidates suggest that society was relatively fluid. It has been claimed, however, that associations between fathers' and sons' outcomes overestimate the fluidity of historical Chinese society because many men who achieved prominence had been helped by senior kin other than their fathers. We test these claims by applying event-history techniques to longitudinal, nominative household register data, measuring the effects of characteristics of kin on the chances of obtaining an official title. Even though distant kin influenced the chances of obtaining a title, kin networks did not monopolize opportunities. There was substantial downward mobility among the sons of prominent families, and high proportions of titleholders were new, in the sense of not having any senior kin who held titles.
Apolipoprotein E genotype and major depression in a community of older adults.
The Cache County Study
Authors: STEFFENS D. C. , NORTON M. C. , HART A. D. , SKOOG I. , CORCORAN C. , BREITNER J. C. S.
Published: April 2003

Background. The role of allelic variation in APOE, the genetic locus for apolipoprotein E, in geriatric depression is poorly understood. There are conflicting reports as to an association between the ε4 allele and depression in late life.

Method. Using a community based study of non-demented elders in Cache County, Utah, that included many very old individuals, we examined the relationship between APOE and late-onset (age >60) depression, with particular attention to possible age effects.

Results. There was no overall association between APOE and depression. However, there was a significant interaction effect of APOE and age such that the relationship of late-onset depression with respect to presence of the ε4 allele was larger among those 80 and older compared with those below age 80. Consistent with previous studies, women were more likely to experience late-onset depression than men.

Conclusions. Because we excluded prevalent cases of dementia, this pattern of relative risk with age may reflect the appearance of depressive symptoms as a prodrome of Alzheimer's disease or vascular dementia. Longitudinal studies should help to confirm or refute this explanation of the data.
Recurrent brief depression – more investigations in clinical samples are now required
Authors: BALDWIN DAVID S.
Published: April 2003

Classifications of depression based on secondary care samples may have little relevance in primary care settings, where many patients do not fulfil criteria for major depression; for example, through having depressive symptoms that are either too mild or too brief. And yet many such patients receive antidepressant treatments (antidepressants and various psychotherapies). At a time when the appropriate recognition and treatment of people with depressive symptoms is the subject of much discussion, and there is concern about the burgeoning number of new psychiatric diagnoses, the burden and hazards of depressive disorders need to be emphasized. The paper by Pezawas et al. (2003) (in this issue) reports the findings of an epidemiological study in adolescents and young adults, and provides a detailed description of the prevalence and features of one such disruptive disorder, namely recurrent brief depression.
The incidental ecotourist: measuring visitor impacts on endangered howler monkeys at a Belizean archaeological site
Authors: Grossberg Rebecca , Treves Adrian , Naughton-Treves Lisa
Published: April 2003

Conservationists are missing opportunities to protect species at mass tourism sites where wildlife itself is not the main tourist attraction. At such locations are ‘incidental ecotourists’, i.e. tourists with multiple interests who encounter wildlife or fragile ecosystems inadvertently. A case study from Lamanai Archaeological Reserve, Belize, reveals the motivations of incidental ecotourists and their impact on an endangered primate species, the black howler monkey, Alouatta pigra. Four hundred and seventy-one visitors were surveyed to assess their travel goals, conservation commitments, and reactions to viewing howler monkeys. Data were also collected on the behaviour of tourists and monkeys during encounters. More intense tourist interactions with howler monkeys were correlated with the number of tourists and the duration of the encounter; guided parties interacted more intensely than unguided parties. Tourists were largely unaware that these interactions may harm the howler monkeys. Qualitative observations of howler response to tourists suggest short- and long-term negative impacts. These impacts could be mitigated through more effective guide training, limiting tourist group size, and increasing entrance fees at the Reserve. Improving environmental education may reduce impacts and motivate some tourists to become advocates for conservation of endangered species.
D. N. MacKenzie (8th April 1926–13th Oct. 2001)
Authors: Meisterernst Desmond Durkin
Published: April 2003

D. N. MacKenzie was a scholar of Middle and Modern Iranian languages who has left an impressive body of publications.
GENERATING PICTURES USING RANDOM PERMITTING CONTEXT
Authors: EWERT SIGRID , VAN DER WALT ANDRIES
Published: April 2003

We use random context picture grammars to generate pictures through successive refinement. At any stage a picture consists of a shape divided into smaller shapes, each containing a variable or terminal. A variable may be rewritten according to a production of the underlying grammar, which entails either dividing the shape containing it into smaller shapes, or substituting a variable or terminal for it. A production may depend on context randomly distributed in the intermediate picture. Context is classified as either permitting or forbidding, the former enabling the application of a production, the latter inhibiting it. For visualization purposes every terminal is associated with a color, and its shape filled with that color.

We show examples of pictures generated with random context picture grammars. Then we concentrate on grammars which use permitting context only and present a pumping lemma for the corresponding picture sets.
TOWARDS THE SELF-CALIBRATION OF A MULTIVIEW RADIOGRAPHIC IMAGING SYSTEM FOR THE 3D RECONSTRUCTION OF THE HUMAN SPINE AND RIB CAGE
Authors: CHERIET F. , DANSEREAU J. , PETIT Y. , AUBIN C.-É. , LABELLE H. , DE GUISE J. AU.
Published: April 2003

The main objective of this study was to develop a 3D reconstruction technique of the spine and rib cage of idiopathic scoliotic patients using the self-calibration of the imaging system. The proposed approach computes the intrinsic and extrinsic parameters of the radiographic setup with respect to the global coordinate system used at Ste-Justine Hospital. Our approach determines an optimal estimate of the geometrical parameters of the imaging system from a nonlinear minimization of the mean square distance between the observed and analytical projections of a set of matched points identified on a pair of radiographic views. The accuracy of the optimal estimate for the intrinsic parameters was significantly improved when geometric knowledge such as the known length of detectable straight bars is incorporated as a set of equality constraints in the optimization process. Furthermore, in order to retrieve the 3D structure of interest in the global coordinate system, a reference plane including the origin of the global coordinate system is specified. Computer simulations were performed to evaluate the self-calibration procedure and to determine the minimum knowledge required to obtain an accurate 3D reconstruction for clinical applications. An in vitro validation on real images of a dry cadaveric human spine showed that the method is feasible and reaches the expected accuracy.
ROBUST MOTION TRAJECTORY ESTIMATION FOR LONG IMAGE SEQUENCES WITH APPLICATIONS TO MOTION COMPENSATED PREDICTION
Authors: GIBSON DAVID , SPANN MICHAEL
Published: April 2003

This paper presents a new approach for the estimation of motion trajectories from image sequences. This approach is seen to be similar to both "token tracking" feature-based methods, and "block based" region-matching approaches. Initially, a parametric motion trajectory model is formulated, and the motion trajectory estimation problem is conveniently cast into a Markov Random Field (MRF) framework which allows a priori motion constraints to be expressed. A three-stage optimization algorithm is presented, and a recursive estimation approach is developed. A method for the robust detection of areas of occlusion is presented, as are comparative results to show the relative success of this motion estimation approach. Although robustly computed motion trajectories show great promise in many motion-related areas of computer vision, this paper illustrates their use in the context of motion compensated prediction as part of a video compression algorithm.
PLANAR STRONG VISIBILITY
Authors: FINK EUGENE , WOOD DERICK
Published: April 2003

Strong visibility is a generalization of standard visibility, defined with respect to a fixed set of line orientations. We investigate computational properties of this generalized visibility, as well as the related notion of strong convexity, and describe algorithms for the following tasks:

1. Testing the strong visibility of two points in a polygon.

2. Finding the strong convex hull of a point set or polygon.

3. Constructing the strong kernel of a polygon.

4. Identifying the points that are strongly visible from a given point.
Effect of competitor density on the aggressiveness of juvenile white seabream (Diplodus sargus cadenati de la Paz, Bauchot and Daget, 1974)
Authors: Caballero Catalina , Castro‐Hdez José J.
Published: April 2003

The number of aggressive interactions displayed by juveniles of Diplodus sargus cadenati increases progressively in proportion to the number of intruders, with an upper threshold of more than 16 to 18 intruder fish. Beyond this density, resident aggressiveness decreases. The number of aggressive interactions that the resident fish devotes to expelling each intruder shows a clear and significant tendency to decrease as competitor density increases. The resident fish is incapable of rapidly evaluating the outweighing of its capacity for defense. Moreover, the strategy of aggressive defense of the resource against the density of competitors does not seem to be only profitability criteria dependent, but rather there is also a significant influence of the ability to fight shown by the resident. Aggr. Behav. 29:279–284, 2003. © 2003 Wiley‐Liss, Inc.
Overlap and correlates of different types of aggression among adults: Results from a cross‐sectional survey in Bogotá, Colombia
Authors: Duque Luis Fernando , Klevens Joanne , Ramirez Clemencia
Published: April 2003

Our objective is to establish the prevalence and overlap among different forms of violence and the importance of known correlates of aggression in Bogotá, Colombia. Our method is a cross‐sectional household survey of violence amongst a random sample (n=3007) of the general population between the ages of 15 and 60. In this population the more severe forms of aggression tend to appear concurrently with the less severe forms. Multivariate analyses of the data show that a family history of crime, physical aggression among family members, lack of clarity of parental norms, beliefs justifying the use of violence, and alcohol consumption are the main correlates of verbal and physical aggression independent of age, gender and social class. Although the findings are limited by the cross‐sectional design, exclusion of the institutionalized population, and reliance on retrospective self‐reports, they provide population‐based estimates of different forms of aggression and support for known correlates of aggression in a Latin American context. Aggr. Behav. 29:191–201, 2003. © 2003 Wiley‐Liss, Inc.
Improved Rhodium Hydrogenation Catalysts Immobilized on Oxidic Supports
Authors: Merckle C. , Blümel J.
Published: April 2003

Wilkinson‐type rhodium hydrogenation catalysts immobilized on oxidic supports via mono‐ and bidentate phosphine linkers have been studied by 31P solid‐state NMR, and their recycling stability and lifetime with respect to hydrogenation of 1‐dodecene, 2‐cyclohexen‐1‐one, and 4‐bromostyrene have been improved substantially.
Synthesizing homelessness research: trends, lessons and prospects
Authors: Anderson Isobel
Published: April 2003

This article presents an overview of some of the key trends emerging from homelessness research to date, lessons to be learned, and some thoughts on the future prospects for homelessness research. Homelessness research draws on a number of academic disciplines, in an international context, and using a wide range of research methods. There is a significant theoretical and empirical research evidence base for understanding the nature and causes of homelessness, and a developing body of research on the impact of intervention strategies. Key challenges for the future include the development of truly multi‐disciplinary research and truly international comparative research, as well as greater scientific rigour in both policy oriented and scholarly led research on homelessness. Copyright © 2003 John Wiley & Sons, Ltd.
Percutaneous closure of coronary pulmonary arterial fistula using catheterization laboratory trash
Authors: Trehan Vijay Kumar , Arora Ramesh , Mukhopadhyay Saibal , Nair Girish M. , Rangasetty Umamahesh C. , Yusuf Jamal , Chandrashekhar
Published: April 2003

We report a case of coronary pulmonary arterial fistula that was successfully occluded by packing the fistula with thrombogenic floppy tips of used percutaneous transluminal coronary angioplasty guidewires instead of conventional steel coils. Cathet Cardiovasc Intervent 2003;59:49–51. © 2003 Wiley‐Liss, Inc.
Impact of angina class on inhibition of platelet aggregation following clopidogrel loading in patients undergoing coronary intervention: Do we need more aggressive dosing regimens in unstable angina?
Authors: Soffer Daniel , Moussa Issam , Harjai Kishore J. , Boura Judith A. , Dixon Simon R. , Grines Cindy L. , O'Neill William W. , Roubin Gary S. , Moses Jeffrey W.
Published: April 2003

Pretreatment with thienopyridines has been shown to improve clinical outcomes in patients undergoing percutaneous coronary intervention (PCI). We determine the impact of angina class on inhibition of platelet aggregation (IPA) following clopidogrel loading. Seventy‐two patients (mean age, 64 ± 11 years; 76% male) were pretreated with 450 mg of clopidogrel at least 3 hr prior to PCI. All patients received ASA 325 mg prior to the procedure. Patients were classified into two groups according to angina class: group 1 = stable angina or Braunwald class 1 unstable angina (UA; n = 33); group 2 = Braunwald class 2 or 3 UA (n = 39). IPA was measured prior to PCI, with the Ichor point‐of‐care platelet analyzer (Helena Laboratories, Beaumont, TX), using 20 μM of ADP. Group 2 patients were more likely to have prior MI (54% vs. 27%; P = 0.023), prior CABG (33% vs. 5%; P = 0.046), and received IV heparin (64% vs. 27%; P = 0.0018). Mean IPA was significantly lower in group 2 compared to group 1 (19% ± 22% vs. 32% ± 22%; P = 0.004). In multivariate analysis, higher angina class was independently associated with lower IPA (P = 0.018). Patients with UA undergoing PCI have a lower IPA following clopidogrel loading with 450 mg. This may indicate the possibility of clopidogrel resistance in such patients. Cathet Cardiovasc Intervent 2003;59:21–25. © 2003 Wiley‐Liss, Inc.
Windows into the future: How lessons from Hollywood will shape the music industry
Authors: Bhatia G. Krishan , Gay Richard C. , Honey W. Ross
Published: April 2003

For several years, new digital technologies and startup companies have put the music industry in a defensive posture by driving innovation and disrupting established format, pricing, and distribution standards. However, with Napster now defanged, the major labels that dominate the industry are reclaiming the spotlight and taking proactive steps to secure their place in the online music arena.
2,7,12,17‐Tetra(p‐butylphenyl)‐3,6,13,16‐tetraazaporphycene: The First Example of a Straightforward Synthetic Approach to a New Class of Photosensitizing Macrocycles
Authors: Nonell Santi , Borrell José I. , Borrós Salvador , Colominas Carles , Rey Oscar , Rubio Noemí , Sánchez‐García David , Teixidó Jordi
Published: April 2003

Selected on the basis of computational studies and synthetic feasibility, the title compound 9c has been obtained by cross‐coupling of 4,4′‐bis(p‐butylphenyl)‐2,2′‐biimidazole‐5,5′‐dicarbaldehyde (28c) followed by oxidative aromatization. The introduction of a Suzuki coupling protocol opens the way to 2,7,12,17‐tetraryl‐substituted 3,6,13,16‐tetraazaporphycenes avoiding the development of a de novo synthesis whenever a new peripheral substituent is desired. As predicted by computational studies, oxidation of the non‐aromatic precursor 33c to yield the azaporphycene macrocycle 9c is more favourable than in the case of porphycene itself. The absorption spectrum of 9c shows a substantial bathochromic shift relative to porphycene 1a, revealing a synergism between aza substitution in the macrocycle and phenyl substitution at its periphery. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Privatizing canal irrigation
Authors: Svendsen Mark , Gonzalez Fernando , Johnson Sam
Published: April 2003

Widespread dissatisfaction with state management of canal irrigation systems has focused intense interest on potential private sector remedies for the problems afflicting the sector. Privatization promises a number of benefits—lower operating costs, increased productivity, innovation, mobilization of capital, higher service quality, and larger service areas.

However, canal irrigation is a natural monopoly, where the large capital investments required preclude multiple private service providers in a given service area. Nevertheless, the paper argues that there are a number of ways to take advantage of positive features of the private sector, without wasteful duplication of infrastructure or leaving farmers at the mercy of greedy investors. Three primary options—renewable management contracts, franchises, and self‐provision of services by clients—are described and illustrated.

Another way to examine possibilities for privatization is to look at the types of organizations that provide irrigation services. The defining aspects of an organization are governance, source of funds, economic motive, and type of staff. The paper defines a set of five types of service providers based on these characteristics. These types are departments, authorities, districts, associations, and public utilities. The characteristics of each are discussed, with examples.

To rise above the basic performance floor provided by a public bureaucracy, an institutional structure including private elements requires a supporting policy environment. Critical elements of a supportive environment include policy stability, legal respect for contracts and agreements, and reasonably impartial regulation, allocation, and adjudication. In the absence of a sufficiently supportive national governance environment, private elements in the irrigation management system are unlikely to flourish or, conversely, may have the ability to take advantage of weaker parties. Copyright © 2003 John Wiley & Sons, Ltd.
Chemometric study of liquid water simulations. I. The parameters of the TIP4P model potential
Authors: Hernandes Marcelo Zaldini , Da Silva João Bosco P. , Longo Ricardo L.
Published: April 2003

The multivariate chemometric techniques two level factorial design (TLFD) and principal component analysis (PCA) were used to investigate the TIP4P model potential behavior with respect to perturbations on all intermolecular interaction parameters. The effects of these perturbations were calculated for the enthalpy of vaporization, the density, the first maximum of the radial distribution functions of the OH and OO pairs, and the second maximum of the radial distribution function of the OH pair obtained from Monte Carlo simulations of liquid water at 25°C. The principal effects were quantified and rationalized in terms of the pair‐wise interaction potential of the TIP4P model. They also corroborate previously published sensitivity analysis results using molecular dynamics and other model potentials. In addition, significant interaction effects between some parameters of the TIP4P model potential were observed and quantified, which hardly could be obtained without such a statistic approach. These interaction effects are very regular and systematic, and their behavior has not been encountered in other chemometric studies and cannot be rationalized in terms of the functional form of the pair‐wise potential. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 973–981, 2003
Recognition promoted by Zn2+ between phenanthroline bridging polyaza ligands and nucleotides — Zn2+ acts as ‘messenger’ between the receptor and substrate
Authors: Guo Yanhe , Ge Qingchun , Lin Hai , Lin Huakuan , Zhu Shourong , Zhou Changyue
Published: April 2003

The stability constants of the supramolecular complexes formed between L
(a,b,c,d) or their Zn2+ complexes, and adenosine 5′‐triphosphate (ATP) in aqueous solution were determined by potentiometric titrations (25 °C, I = 0.1 mol dm−3 KNO3). The results show that protonated aliphatic‐substituted L

a,d and aromatic‐substituted L

b,c ligands and/or Zn(II) ion can efficiently recognition the substrate, ATP. All of the equilibrium studies, 1H and 31P nuclear magnetic resonance spectra indicate that multiple interactions, including coordination, π‐stacking, ion‐pairing, H‐bonding, and possible ion‐π‐donor, hydrophobic and even van der Waals interactions exist in the Zn(II)–L–ATP systems. On the other hand, the recognition of the substrates by the protonated ligands was significantly promoted by the addition of Zn(II), which leads to coordination competition between the mixed ligands, L and nucleotide. In Zn(II)/L/ATP systems the tendency for phosphate chain to receive proton and metal ion increases, facilitating the cleavage of the phosphate chain of the nucleotide. Copyright © 2003 John Wiley & Sons, Ltd.
Atherosclerotic disease distribution in carotid and vertebrobasilar arteries: Clinical experience in 100 patients undergoing fluoro‐triggered 3D Gd‐MRA
Authors: Ersoy Hale , Watts Richard , Sanelli Pina , Zimmerman Robert D. , Kent K. Craig , Bush Harry L. , Prince Martin R.
Published: April 2003

Purpose

To determine how often three‐dimensional gadolinium‐enhanced magnetic resonance angiography (3D Gd‐MRA) shows disease outside of the standard two‐dimensional time‐of‐flight magnetic resonance angiography (2D TOF‐MRA) imaging volume.

Materials and Methods

One hundred consecutive patients with known or suspected cerebrovascular disease were examined using fluoro‐triggered 3D Gd‐MRA with a 1.5 Tesla scanner. All vessel segments from the aortic arch to the circle of Willis were independently evaluated for the presence of occlusive disease, ulceration, aneurysm, and anatomic variations by two radiologists blinded to clinical information. Branch vessel and circle of Willis visibility were also assessed. Kappa statistics were calculated to determine interobserver agreement.

Results

Interobserver agreement for the degree of stenosis was good to excellent (κ = 0.83–1.0). Disagreement was more frequent in the cases of mild stenoses and was less frequent for stenoses ≥ 50%. In 38% of the patients, 3D Gd‐MRA demonstrated either ulcerated plaques in carotid arteries (N = 14) or stenosis ≥ 50% in great vessel (N = 20) and/or vertebral artery (N = 38) origins, none of which can be readily evaluated on standard TOF‐MRA.

Conclusion

Fluoro‐triggered 3D Gd‐MRA provides a comprehensive evaluation of the carotid arteries including all vessel segments from the aortic arch to the circle of Willis. J. Magn. Reson. Imaging 2003;17:545–558. © 2003 Wiley‐Liss, Inc.
Studies of Adsorption of Diblock Copolymers from Non‐Selective Solvent by Scheutjens‐Fleer Theory and Monte Carlo Simulation, 2
Authors: Guo Lian , Chen Ting , Liu Honglai , Hu Ying
Published: April 2003

Following our previous Monte Carlo simulation work on the adsorption of diblock copolymer from a non‐selective solvent, the well‐established Scheutjens‐Fleer (SF) mean field theory is employed in this work to investigate the same system. Extensive comparisons between the Monte Carlo simulation and the SF theory are presented in two consecutive papers. In this second paper, the microstructure of adsorbed chains will be examined and discussed. After carefully inspecting various microstructure information including bound fraction, surface coverage, density profiles of the adsorbed segments corresponding to tails, loops and trains, and size distributions of these individual adsorption configurations, we observe that a systematic deviation between the theory and the simulation exists despite qualitative agreements between them. An in‐depth investigation and discussion on the source and the degree of this kind of deviation has been presented after we inspected the effect of adsorption energy, chain composition f and bulk concentration on the adsorption layer properties. Our results further corroborate that the deviation between the SF theory and Monte Carlo simulation can be attributed to two major factors: the allowance of the direct chain back‐folding and the random mixing approximation.

Bound fraction PA as a function of f. \bar \varepsilon _{{\rm Aa}} = 0.5 (▵), 0.8 (⋄), 1.0 (•), 1.2 (○), 1.5 (□): MC results; line a, b, c, d, e: corresponding SF results.

magnified image

Bound fraction PA as a function of f. \bar \varepsilon _{{\rm Aa}} = 0.5 (▵), 0.8 (⋄), 1.0 (•), 1.2 (○), 1.5 (□): MC results; line a, b, c, d, e: corresponding SF results.
Calcium influx by hypertonicity through the voltage‐dependent calcium channels
Authors: Toshimi Hattori
Published: April 2003

We found out before the facts that propylene glycol (PG) raises the intracellular calcium concentration ([Ca2+]i) and that hypertonicity induced by PG is involved in the [Ca2+]i rise. The present study was conducted for the purpose of determining whether the Ca2+ influx through the Ca2+ channels is related to the rise in [Ca2+]i incuded by hypertonicity. A Ca2+‐free saline and all of the Ca2+ channel blockers CdCl2 (0.1 mM), o‐conotoxin GVIA (1 µM), verapamil (10 µM), and nicardipine (10 µM) significantly decreased the [Ca2+]i raised by hypertonicity. Bay K 8644 (4 µM), a Ca2+ channel activator, potentially increased the [Ca2+]i raised by hypertonic salines. The results described above lead me to the conclusion that the Ca2+ influx through the voltage‐dependent Ca2+ channels is involved in the hypertonicity‐induced [Ca2+]i rise.
Early contrast sensitivity loss and oxidative damage in healthy heavy smokers
Authors: Hepsen Ibrahim F. , Uz Efkan , Sogut Sadik , Büyükba Sadik , Akyol Omer
Published: April 2003

Objective: The purpose of this study was 1) to evaluate visual functions and the activities of antioxidant enzymes in plasma and erythrocytes in smokers in comparison with non‐smokers, 2) to evaluate the correlations between visual functions and the oxidant/antioxidant system. We hypothesized that the changes in antioxidant system and consequently lipid peroxidation depend on smoking may affect sophisticated visual tests including contrast sensitivity (CS) and pattern visual evoked potentials (PVEP)

Subjects: This non‐randomised control study included 24 chronic, heavy smokers who were smoking more than 20 cigarettes per day at least for last 10 years. Sixteen age and sex‐matched, healthy, non‐smokers were taken as controls. All volunteer subjects were accumulated from the outpatient clinic. To rule out the effect of alcoholism and malnutrition, we chose young, healthy heavy smokers who maintained adequate diet and who had no alcohol consumption history.

Following visual acuity and color vision tests, all subjects were applied to CS and PVEP tests. Values of CS, N75‐P100 amplitude and P100 wave latency were compared between the study and control subjects. Superoxide dismutase (SOD) and catalase (CAT) activities in plasma and erythrocytes were determined by spectrophotometer. Plasma malondialdehyde (MDA) level, as an end product of lipid peroxidation, was assessed by spectrofluorometric method.

Results: CS was determined to be significantly reduced in smokers compared to non‐smokers, although central vision and PVEP responses were not affected. Erythrocyte SOD activity and plasma MDA levels were significantly increased in smokers compared to controls. There were positive correlations between plasma SOD and erythrocyte SOD; CS and erythrocyte SOD; and CS and plasma SOD.

Conclusions: The results suggest the possible association between early CS loss and increase in antioxidant enzyme activities thus reflecting an increased oxidative damage due to cumulative effect of chronic smoking. Elevated concentrations of lipid peroxidation products in the plasma of smokers may directly show the increased oxidative damage in these subjects.
Involvement of nitric oxide in Parkinson's disease: Emphasis on sex difference in prevalence
Authors: Taskiran Dilek , Nazliel Bijen , Irkec Ceyla , Kutay Fatma Z. , Pogun Sakire
Published: April 2003

Parkinson's disease (PD) is characterized by severe movement disorders. Excessive production of reactive oxygen species has been implicated as a possible mediator of neurodegenerative changes in nigrostriatal neurons in PD. Nitric oxide (NO) has received substantial attention among pathophysiological factors underlying glutamate neurotoxicity in neurodegenerative disorders including PD. PD is more prevalent in men than in women by an approximate 3:2 ratio; the nitrergic systems are also more active in males than females. In this study, NO2−+NO3− (stable metabolites of NO) levels were determined in sera of PD patients (n=20) and control subjects (n=16). NO2−+NO3− Levels were higher in PD patients compared to controls, and in males compared to females. Furthermore, there was a correlation between age and NO metabolites in females but not in males. These data support a role for NO in PD and provide further evidence for sex differences in NO activity that may underlie neurodegenerative disorders.
Thermal Decomposition of Energetic Materials 84: Pyrolysis of 5‐Substituted 1,3,5‐Trinitrohexahydropyrimidines
Authors: Roos Brian D. , Brill Thomas B.
Published: April 2003

Results of slow and fast pyrolysis were compared for 1,3,5‐trinitrohexahydropyrimidine compounds in which the 5‐position was substituted by H, CH3, NO2, CH2ONO2, and CH2N3. IR and Raman spectroscopy were used to identify and quantify all of the gaseous products. The decomposition process appears to be initiated by reactions at the 5‐position of the ring. The gases produced are rather similar for all of the compounds, however the different functional groups impart their own signature on the concentrations of several products.
Structural rehabilitation of columns with reinforced concrete jacketing
Authors: Júlio E S , Branco F , Silva V D
Published: April 2003

Strengthening and rehabilitation by reinforced concrete jacketing of columns is assessed, considering different practical aspects: anchoring and slab crossing of the added longitudinal reinforcement, interface surface preparation, spacing of added stirrups, temporary shoring of the structure and addition of new concrete. Recent research on these topics and the main recommendations to achieve good RC jacketing are presented. Copyright © 2003 John Wiley & Sons, Ltd.
On peculiarities and pit falls in path integrals
Authors: 't Hooft Gerard
Published: April 2003

Path integrals can be rigorously defined only in low dimensional systems where the small distance limit can be taken. Particularly non‐trivial models in more than four dimensions can only be handled with considerable amount of speculation. In this lecture we try to put these various aspects in perspective.
Quantum mechanical momentum and energy balance equations for transport of charge carriers
Authors: Magnus W.
Published: April 2003

In this paper some basic features of electrical transport are discussed in terms of quantum mechanical energy and momentum balance equations. The latter are presented as an appropriate tool for the investigation of carrier transport in electric circuits containing mesoscopic active areas in the presence of inhomogeneous electromagnetic fields.
Fermionic path integrals and local anomalies
Authors: Roepstorff G.
Published: April 2003

No doubt, the subject of path integrals proved to be an immensely fruitful human, i.e. Feynman's idea. No wonder it is more timely than ever. Some even claim that it is the most daring, innovative and revolutionary idea since the days of Heisenberg and Bohr. It is thus likely to generate enthusiasm, if not addiction among physicists who seek simplicity together with perfection. Professor Devreese's long‐lasting interest in, if not passion on the subject stems from his firm conviction that, beyond being the tool of choice, path integration provides the key to all quantum phenomena, be it in solid state, atomic, molecular or particle physics as evidenced by the impressive list of publications at the address http://lib.ua.ac.be/AB/a867.html. In this note, I review a pitfall of fermionic path integrals and a way to get around it in situations relevant to the Standard Model of particle physics.
Quantum Monte Carlo: What can random numbers tell us about correlated quantum systems?
Authors: Rombouts S. , Heyde K.
Published: April 2003

Over the past decades, quantum Monte Carlo methods have proven to be very valuable for the study of quantum‐mechanical many‐body systems. The basic ingredient of theses methods is a decomposition of the imaginary‐time evolution operator into path integrals. These paths can then be sampled using Monte Carlo techniques. Though very successful for bosons, these methods often have troubles in dealing with fermions: the fermionic antisymmetry leads to a ‘sign problem’. One approach, the auxiliary‐field method, has yielded slightly better results in dealing with the sign problem. Some recent developments on this method are highlighted. As a case study, it is applied to a pairing model for Fe nuclei, where indications are found for a phase transition related to nucleon–nucleon pairing.
Path integral Monte Carlo for dissipative many‐body systems
Authors: Capriotti Luca , Cuccoli Alessandro , Fubini Andrea , Tognetti Valerio , Vaia Ruggero
Published: April 2003

We address the possibility of performing numerical Monte Carlo simulations for the thermodynamics of quantum dissipative systems. Dissipation is considered within the Caldeira–Leggett formulation, which describes the system in the path‐integral formalism through the inclusion of an influence action that is bilocal and quadratic in the system's coordinates. At a first sight the usual direct approach of discretizing the path integral could seem feasible, but complications arise when one tries to introduce a physically meaningful dissipation kernel: in particular its imaginary‐time dependence turns out to be severely singular and difficult to evaluate analytically, in spite of the simple expressions for its Matsubara components. We therefore propose to face the numerical problem using Fourier path‐integral Monte Carlo, that can be formulated in two different ways: transforming the continuous paths and then truncating the high Fourier components (with possible improvements upon the truncation procedure), or performing the Fourier transformation upon the discretized paths. The latter choice leads to a simpler formulation and allows for a better control of the extrapolation to the limit of infinite Trotter number. The method is implemented for a single nonlinear particle with Ohmic dissipation and for a ϕ4 chain with Drude‐like dissipation.
Charged complexes at the surface of liquid helium
Authors: Dyugaev A. M. , Grigoriev P. D. , Wyder P.
Published: April 2003

Charged clusters in liquid helium in an external electric field form a two‐dimensional system below the helium surface. This 2D system undergoes a phase transition from a liquid to a Wigner crystal at rather high temperatures. Contrary to the electron Wigner crystal, the Wigner lattice of charged clusters can be detected directly.