bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractSelected 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

AbstractWidespread 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

AbstractThe 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

AbstractThe 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

AbstractPurposeTo 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 MethodsOne 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.ResultsInterobserver 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.ConclusionFluoro‐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

AbstractFollowing 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 imageBound 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

AbstractWe 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

AbstractObjective: 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

AbstractParkinson'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

AbstractResults 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

AbstractStrengthening 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.
Fermionic path integrals and local anomalies
Authors: Roepstorff G. 
Published: April 2003

AbstractNo 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

AbstractOver 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

AbstractWe 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

AbstractCharged 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.
On‐column digestion of proteins in aqueous‐organic solvents
Authors: Slysz Gordon W. , Schriemer David C. 
Published: April 2003

AbstractProteolytic digestion is an important step in protein identification by peptide mass mapping and tandem mass spectrometry (MS/MS)‐based peptide sequencing. Traditional methods of protein digestion require extended incubation times and have difficulty with proteolytically resistant proteins. Here, we describe a method in which a protein solution was combined with a mixed aqueous‐organic solution (methanol, isopropanol, or acetonitrile) and passed through a microcolumn containing immobilized trypsin. Myoglobin sequence coverage was high (>85%) in all three solvents, and differences in spectra were seen among the different solution conditions. Notably, methanol‐based digestions produced fewer missed cleavages while acetonitrile‐based digestions produced the most peptides and the most intense mass spectra. Flow rates through the column were varied from 0.5 to 15 μL/min, corresponding to column residence times of 78 and 2.6 s, respectively. All flow rates produced high sequence coverage of myoglobin, although, at higher flow rates, more missed cleavages were observed. No significant increase in undigested myoglobin was observed with flow rates up to 15 μL/min. The described method was applied to the digestion of human transferrin (hTf), a proteolytically resistant protein. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric (MALDI‐TOFMS) analysis detected 42 peptides covering 46% of the hTf sequence. The traditional aqueous method resulted in 12 peptides (8% sequence coverage) only when high concentrations of trypsin were used. Lastly, digestion of low nanomolar myoglobin was shown to produce detectable peptides and resulted in a correct database hit. Thus, we demonstrate a method that is capable of rapid on‐line digestion, thereby lending itself to high‐throughput identification of proteins. Copyright © 2003 John Wiley & Sons, Ltd.
A simplified recursive formulation for the dynamic analysis of spatial mechanisms in point coordinates
Authors: Attia H.A. 
Published: April 2003

AbstractIn the present study, a recursive formulation for generating the equations of motion of spatial mechanisms with revolute and/or spherical joints is presented. The method uses the concepts of linear and angular momentums to generate the rigid body equations of motion in terms of the Cartesian coordinates of a dynamically equivalent constrained system of particles, without introducing any rotational coordinates and the corresponding rotational transformation matrix. It eliminates the necessity of distributing the external forces and couples over the equivalent system of particles. For the open‐chain system, the equations of motion are generated recursively along the serial chains. Closed‐chain system is transformed to open‐chain by cutting suitable kinematic joints and introducing cut‐joint constraints. The method is simple and suitable for computer implementation. An example is chosen to demonstrate the generality and simplicity of the developed formulation.
Air flow influences on local climate: observed United Kingdom climate variations
Authors: Osborn Timothy J. , Jones Philip D. 
Published: April 2003

AbstractIdentifying and removing the influence of atmospheric circulation variability on central England temperature increases the statistical significance of warming trends in spring, autumn and the annual mean over the last 50 years. The trends are more detectable because the circulation changes contribute greatly to the ‘noise’ of interannual to interdecadal variability, but induce only small multi‐decadal trends (the ‘signal’). Factoring out the circulation can thus enhance the signal‐to‐noise ratio. For precipitation, the recent enhancement in the difference between summer rainfall in south‐east England and winter precipitation in northern Scotland can partly be explained by atmospheric circulation variability over the past 40 years (particularly the increase in the North Atlantic Oscillation index from the 1960s to the early 1990s). Copyright © 2000 Royal Meteorological Society.