bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Intramolecular Hydroamination of Unactivated Alkenes Catalysed by Butyllithium
Authors: Ates Ali , Quinet Coralie 
Published: April 2003

AbstractIn this communication, we wish to report some preliminary results demonstrating, for the first time, that intramolecular hydroamination of unactivated alkenes can be performed efficiently using small quantities of nBuLi as the pre‐catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003
Cover Picture: 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 (Eur. J. Org. Chem. 9/2003)
Authors: Nonell Santi , Borrell José I. , Borrós Salvador , Colominas Carles , Rey Oscar , Rubio Noemí , Sánchez‐García David , Teixidó Jordi 
Published: April 2003

AbstractThe cover picture shows a three‐dimensional model of 2,7,12,17‐tetra(p‐butylphenyl)‐3,6,13,16‐tetraazaporphycene, the first example of a new class of sensitizing porphyrinoid macrocycles. Starting from glyoxal and ammonia, the synthetic methodology includes Suzuki and McMurry couplings, using the depicted tetrabromobiimidazole as the key intermediate. The macrocycle has excellent light absorption properties in the red and near‐infrared regions (600−800 nm), an attractive feature for biomedical applications such as photodynamic therapy. Details are discussed in the article by J. Teixidó et al. on p. 1635 ff.
Volume‐selective 3D turbo spin echo imaging for vascular wall imaging and distensibility measurement
Authors: Crowe Lindsey A. , Gatehouse Peter , Yang Guang Zhong , Mohiaddin Raad H. , Varghese Anitha , Charrier Clare , Keegan Jennifer , Firmin David N. 
Published: April 2003

AbstractPurposeTo use a volume‐selective 3D turbo spin echo (TSE) technique to image the carotid artery wall and measure distensibility.Materials and MethodsA high‐resolution volume‐selective 3D TSE sequence has been developed. Volume selection is accomplished by orthogonal gradients for the 90° and 180° excitations and allows a 3D volume of vessel wall to be imaged in a relatively short time. The technique has been developed to allow imaging at any defined phase of the cardiac cycle so that the vascular function and distensibility can be studied.ResultsScan efficiency is increased by the reduced phase encode field of view (FOV) (ky steps) by the use of selective volume excitation. Significantly more slices (kz phase encode steps) for vessel coverage can be acquired with the same scan time as that of the conventional sequence while maintaining signal‐to‐noise ratio (SNR) levels. The practical value of the technique was demonstrated on 10 normal subjects with high‐resolution vessel distensibility measurements of the carotid arteries.ConclusionA volume‐selective TSE method has been used for carotid artery wall imaging and measurement of distensibility in normal subjects. Larger coverage of the vessel, and therefore more information for clinical diagnostics, was achieved with the same overall scan time with an SNR comparable to that of 2D full FOV images. J. Magn. Reson. Imaging 2003;17:572–580. © 2003 Wiley‐Liss, Inc.
The key‐group method
Authors: Yarahmadi Bafghi A. R. , Verdel T. 
Published: April 2003

AbstractThis 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

AbstractEpidemiological 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractInfrared 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

AbstractMicrophotoluminescence 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

AbstractWe 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

AbstractWe 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

AbstractThe 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

AbstractRecent 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.
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.
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.
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

AbstractThe 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

AbstractOur 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

AbstractWilkinson‐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

AbstractThis 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

AbstractWe 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

AbstractPretreatment 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.