bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Thermosensitive Properties of Poly[(N‐vinylamide)‐co‐(vinyl acetate)]s and Their Hydrogels
Authors: Yamamoto Kazuya , Serizawa Takeshi , Akashi Mitsuru
Published: June 2003

Free radical copolymerization of water‐soluble N‐vinylamides such as N‐vinylacetamide (NVA) and N‐vinylformamide (NVF) with hydrophobic vinyl acetate (VAc) gave amphiphilic copolymers. The monomer reactivity ratios were determined as r1 = 5.8 and r2 = 0.68 (M1 = NVA, M2 = VAc) and r1 = 6.2 and r2 = 0.37 (M1 = NVF, M2 = VAc), respectively. The growing radical of the terminals of N‐vinylamides propagates more favorably for N‐vinylamide monomers than for VAc monomer, resulting in the possible formation of blocky copolymers. It is found that aqueous solutions of these amphiphilic copolymers exhibited a lower critical solution temperature (LCST), depending on their chemical composition, followed by coacervate formation above the LCST. Furthermore, thermosensitive hydrogels could be prepared by the free radical copolymerization of N‐vinylamide and VAc in the presence of the crosslinker butylenebis(N‐vinylacetamide) (Bis‐NVA). The swelling ratios of these hydrogels decreased with an immediate increase in temperature from 20 to 80 °C, and then reversibly increased with decreasing temperature. These hydrogels showed the same thermosensitive properties as linear copolymers of NVF and VAc.

Relationship between LCST and vinyl acetate content in poly(N‐vinylamide‐co‐VAc)s.

magnified image

Relationship between LCST and vinyl acetate content in poly(N‐vinylamide‐co‐VAc)s.
Initial boundary value problem for the evolution system of MHD type describing geophysical flow in three‐dimensional domains
Authors: Zhao Chunshan
Published: May 2003

The initial boundary value problem for the evolution system describing geophysical flow in three‐dimensional domains was considered. The existence and uniqueness of global strong solution to the evolution system were proved under assumption on smallness of data. Moreover, solvable compatibility conditions of initial data and boundary values which guarantee the existence and uniqueness of global strong solution were discussed. Copyright © 2003 John Wiley & Sons, Ltd.
A suitable computational strategy for the parametric analysis of problems with multiple contact
Authors: Boucard P. A. , Champaney L.
Published: May 2003

The aim of the present work is to develop an application of the LArge Time INcrement (LATIN) approach for the parametric analysis of static problems with multiple contacts. The methodology adopted was originally introduced to solve viscoplastic and large‐transformation problems. Here, the applications concern elastic, quasi‐static structural assemblies with local non‐linearities such as unilateral contact with friction. Our approach is based on a decomposition of the assembly into substructures and interfaces. The interfaces play the vital role of enabling the local non‐linearities, such as contact and friction, to be modelled easily and accurately. The problem on each substructure is solved by the finite element method and an iterative scheme based on the LATIN method is used for the global resolution. More specifically, the objective is to calculate a large number of design configurations. Each design configuration corresponds to a set of values of all the variable parameters (friction coefficients, prestress) which are introduced into the mechanical analysis. A full computation is needed for each set of parameters. Here we propose, as an alternative to carrying out these full computations, to use the capability of the LATIN method to re‐use the solution to a given problem (for one set of parameters) in order to solve similar problems (for the other sets of parameters). Copyright © 2003 John Wiley & Sons, Ltd.
A stacked chalcopyrite thin‐film tandem solar cell with 1.2 V open‐circuit voltage
Authors: Nishiwaki S. , Siebentritt S. , Walk P. , Ch. Lux‐Steiner M.
Published: May 2003

CuGaSe2(CGS) thin films were prepared on tin‐doped indium oxide (ITO) coated soda‐lime glass substrates by thermal co‐evaporation to fabricate transparent solar cells. The films consisted of columnar grains with a diameter of approximately 1 μm. Some deterioration of the transparency of the ITO was observed after deposition of the CGS film. The CGS solar cells were electrically connected in series with Cu(In,Ga)Se2(CIGS) solar cells and mechanically stacked on the CIGS cells to construct tandem cells. The tandem solar cell with the CGS cell as the top cell showed an efficiency of 7.4% and an open‐circuit voltage of 1.18 V (AM 1.5, total area). Copyright © 2003 John Wiley & Sons, Ltd.
High‐irradiance degradation tests on concentrator GaAs solar cells
Authors: Rey‐Stolle Ignacio , Algora Carlos
Published: May 2003

The present work summarises the results of an experiment of light‐soaking high‐concentrator MOVPE‐grown GaAs solar cells under monochromatic light (808 nm). The irradiance level was set so that the short‐circuit current obtained was 1100 times that produced with the AM1ċ5D spectrum at 1 kW/m2. This test caused no morphological changes in the devices. The main phenomenon discovered has been a slight increase with time of the reverse currentI02. This increase is analogous to that observed in similar degradation experiments based on high forward currents. In general, the results of these tests show that the drop in performance is very limited, supporting the idea that concentrator GaAs solar cells are rugged devices, capable of achieving long lifetimes in field operation. Copyright © 2003 John Wiley & Sons, Ltd.
Life‐cycle assessment of photovoltaic modules: Comparison of mc‐Si, InGaP and InGaP/mc‐Si solar modules
Authors: Meijer A. , Huijbregts M. A. J. , Schermer J. J. , Reijnders L.
Published: May 2003

A higher conversion efficiency of photovoltaic modules does not automatically imply a lower environmental impact, when the life‐cycle of modules is taken into account. An environmental comparison is carried out between the production and use phase, except maintenance, of an indium–gallium–phosphide (InGaP) on multicrystalline silicon (mc‐Si) tandem module, a thin‐film InGaP cell module and a mc‐Si module. The evaluation of the InGaP systems was made for a very limited industrial production scale. Assuming a fourfold reuse of the GaAs substrates in the production of the thin‐film InGaP (half) modules, the environmental impacts of the tandem module and of the thin‐film InGaP module are estimated to be respectively 50 and 80% higher than the environmental impact of the mc‐Si module. The energy payback times of the tandem module, the thin‐film InGaP module and the mc‐Si module are estimated to be respectively 5.3, 6.3 and 3.5 years. There are several ways to improve the life‐cycle environmental performance of thin‐film InGaP cells, including improved materials efficiency in production and reuse of the GaAs wafer and higher energy efficiency of the metalorganic chemical vapour deposition process. Copyright © 2003 John Wiley & Sons, Ltd.
Developmental, gender, and practical considerations in scoring curriculum‐based measurement writing probes
Authors: Malecki Christine Kerres , Jewell Jennifer
Published: May 2003

The present study focused on CBM written language procedures by conducting an investigation of the developmental, gender, and practical considerations surrounding three categories of CBM written language scoring indices: production‐dependent, production‐independent, and accurate‐production. Students in first‐ through eighth‐grade generated a three‐minute writing sample in the fall and spring of the school year using standard CBM procedures. The writing samples were scored using all three types of scoring indices to assess the trends in scoring indices for students of varying ages and gender and of the time required to score writing samples using various scoring indices. With only one exception, older students outperformed younger students on all of the scoring indices. Although at the middle school level students' levels of writing fluency and writing accuracy were not closely associated, at the younger grade levels the CBM indices were significantly related. With regard to gender differences, girls outperformed boys on measures of writing fluency at all grade levels. The average scoring time per writing sample ranged from 1‐1/2 to 2‐1/2 minutes (depending on grade level). © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 379–390, 2003.
Assessment of Attention‐Deficit/Hyperactivity Disorder (ADHD): A comparative evaluation of five, commonly used, published rating scales
Authors: Demaray Michelle K. , Elting Jennifer , Schaefer Katherine
Published: May 2003

ADHD is one of the most common referrals to school psychologists and child mental health providers. Although a best practice assessment of ADHD requires more than the use of rating scales, rating scales are one of the primary components in the assessment of ADHD. Therefore, the goal of this paper is to provide the reader with a critical and comparative evaluation of the five most commonly used, narrow‐band, published rating scales for the assessment of ADHD. Reviews were conducted in four main areas: content and use, standardization sample and norms, scores and interpretation, and psychometric properties. It was concluded the rating scales with the strongest standardization samples and evidence for reliability and validity are the ADDES, the ADHD‐IV, and the CRS‐R. In determining which of these to use, the prospective users may want to reflect on their goals for the assessment. The ACTeRS and the ADHDT are not recommended for use because they are lacking crucial information in their manuals and have less well‐documented evidence of reliability and validity. Conclusions and recommendations for scale usage are discussed. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 341–361, 2003.
Design and Performance Evaluation of Low‐Volume PM2.5 Inlet for Analyzing Chemical Composition
Authors: Kim D. S. , Hong S. B. , Kim H. T. , Lee J. H. , Lee K. W.
Published: May 2003

A new PM2.5 inlet, based on the particle cup impactor configuration, was designed for sampling fine particles smaller than 2.5 μm in aerodynamic diameter and for operating at a flow rate of 5 l/min, as the devices, which are used to analyze the chemical composition of the particles, have good efficiency only at low‐volume flow rates. The performance of the inlet was evaluated in a test chamber, and the optimum dimensions of the particle cup impactor were determined by varying the nozzle‐to‐cup distance. Additional experiments covering flow rates between 3 and 10 l/min with particle sizes between 0.8 and 5.0 μm were carried out in the test chamber. The performance indicated that a nozzle‐to‐cup distance of 1.1 mm would yield a sharp size cutoff. The results from the tests showed that the inlet had a cutoff size of 2.55 μm in aerodynamic diameter at a flow rate of 5 l/min.
Transient effect of a free particle wave packet in the hydrodynamic formulation of the time‐dependent Schrödinger equation
Authors: Vadapalli Ravi K. , Weatherford Charles A. , Banicescu Ioana , Cariño Ricolindo L. , Zhu Jianping
Published: May 2003

This article scrutinizes anomalies in accuracy studies by Brook et al. Int J Quantum Chem 2001, 85, 263–271 for a moving free particle. These studies were carried out in the framework of the quantum trajectory method developed from Bohm's hydrodynamic formalism. These accuracy studies exhibited a strange behavior of the relative error in the probability density that apparently contradicts the quantum fluid dynamic formalism. It is found that improper initialization of the pseudoparticle velocities is responsible for the observed anomalies. This article presents a method for appropriate initialization of the pseudoparticle velocities. It also evaluates the accuracy of this method by reinvestigating accuracy studies by Brook et al. for a moving free particle. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 1–6, 2003
Theoretical study of 4‐, 5‐, 6‐, and 7‐member ring superphane cages with a metal atom inside
Authors: Mireles N. , Sansores L. E. , Martínez A. , Salcedo R.
Published: May 2003

Superphanes are a relatively new type of molecules with interesting properties. The best example is [26](1,2,3,4,5,6)cyclophane. Superphane molecules with ring sizes ranging from 3 to 7 were previously studied by our group. It was shown that these cages have highly symmetrical structures and show the transannular effect. The same set of molecules is studied in this work but now with a metal atom inside the cage localized in the geometric center. Calculations were performed using Gaussian98 code at the B3LYP/6‐31++G level. For metal atoms the basis used was LANL2DZ. Symmetrical structures were found in all cases with both rings flat and parallel to each other. Bond lengths between C atoms on each ring suggests electron delocalization. There is a transannular effect but now the electronic flow involves the metal atom. This effect is in particular strong in compounds 1 and 2, whereas compound 3 shows an important interaction between the rings localized in the HOMO‐1 besides an important presence of the side‐chains. The same effect is observed in the case of compound 4, but now the interaction is in the LUMO+1. The delocalization in compound 1 suggests that the butadienyl fragments have some degree of aromatization. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 51–56, 2003
Computation on symmetry‐invariant bases
Authors: Wu Jian , Klein D. J. , Schmalz T. G.
Published: May 2003

There is standard methodology available to facilitate electronic structure computations on a space that is invariant under a symmetry group. Here, we focus on additional consequences that arise if the basis itself is invariant under the symmetry group (i.e., in the case that application of symmetry operations to each basis vector yields, up to proportionality, a single basis vector). In illustration of the formal development, examples are considered where the symmetries are point‐group symmetries and the basis vectors are Slater determinants over singly occupied atomic orbitals, as for an open‐shell valence bond (VB) model. Several other types of examples are mentioned, e.g., a basis of chemically motivated resonance structures, as for a VB model, or an orbital basis of atomic orbitals for a one‐electron Hückel‐type model. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 7–22, 2003
Theory of excitation energy transfer regarded as nonadiabatic transition 2: Calculational evidence of nonadiabatic interaction causing intermolecular excitation energy transfer
Authors: Okuno Yoshishige , Mashiko Shinro
Published: May 2003

To clarify whether the excitation energy transfer from a donor molecule or aggregate to a remote acceptor molecule or aggregate can be caused by nonadiabatic interaction as expected in our previous studies Okuno, Y. Chem Phys Lett 2001, 347, 138–142; Okuno, Y.; Mashiko, S. Int J Quantum Chem 2002, 90, 772–777, we carried out ab initio calculations for three donor–acceptor systems. Even when the acceptor is separated from the donor by 15 Å, it was found that nonadiabatic coupling elements have moderately large values in the nuclear configuration region where the potential energy surfaces at two excited states for the donor–acceptor system are close to each other; otherwise, the conical intersection between the two excited‐state potential energy surfaces appears. In addition, it was found that the adiabatic approximation for the donor–acceptor system holds in the nuclear configuration region in which the initial and final wave packets in the process of the excitation energy transfer lie. These findings lead to the conclusion that the excitation energy transfer between two remote molecules or aggregates can be caused by the nonadiabatic interaction. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 36–43, 2003
Theoretical investigation of the isomers photolysis reaction for chlorine nitrate
Authors: Zhou Zhengyu , Du Benni , Aiping Fu , Zhang Weichao
Published: May 2003

For the reactant ClONO2 the equilibrium geometry and energy have been calculated by using various density functional (DFT) theory methods. The harmonic vibrational frequencies were computed using the B3LYP method for the ground state of the reactant; the results were in good agreement with those of the experiment. It was shown that the DFT methods were superior to other ab initio methods in optimizing geometry and predicting vibrational frequencies. In the process of forming the products from the dissociation reactions of ClONO2, the results indicated it undergoes the TS2, but not the TS1 transition state. According to the relative energies of various species, the potential energy surface reflected intuitively the mechanisms of these dissociation reactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 44–50, 2003
Theoretical investigation of charge transfer excitation and charge recombination in acenaphthylene–tetracyanoethylene complex
Authors: Yi Hai‐Bo , Li Xiang‐Yuan , Yang Sheng‐Yong , Duan Xiao‐Hui
Published: May 2003

Ab initio calculations were performed to investigate the charge separation and charge recombination processes in the photoinduced electron transfer reaction between tetracyanoethylene and acenaphthylene. The excited states of the charge‐balanced electron donor–acceptor complex and the singlet state of ion pair complex were studied by employing configuration interaction singles method. The equilibrium geometry of electron donor–acceptor complex was obtained by the second‐order Møller–Plesset method, with the interaction energy corrected by the counterpoise method. The theoretical study of ground state and excited states of electron donor–acceptor complex in this work reveals that the S1 and S2 states of the electron donor–acceptor complexes are excited charge transfer states, and charge transfer absorptions that corresponds to the S0 → S1 and S0 → S2 transitions arise from π–π* excitations. The charge recombination in the ion pair complex will produce the charge‐balanced ground state or excited triplet state. According to the generalized Mulliken–Hush model, the electron coupling matrix elements of the charge separation process and the charge recombination process were obtained. Based on the continuum model, charge transfer absorption and charge transfer emission in the polar solvent of 1,2‐dichloroethane were investigated. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 23–35, 2003
Quantifying and evaluating the space overhead for alternative C++ memory layouts
Authors: Sweeney Peter F. , Burke Michael
Published: May 2003

This paper develops a formalism that precisely characterizes when class tables are required for C++ memory layouts. A memory layout is a particular choice of data structures for implementing run‐time support for object‐oriented languages. We use this formalism to quantify and evaluate, on a set of benchmarks, the space overhead for a set of C++ memory layouts. In particular, this paper studies the space overhead due to three language features: virtual dispatch, virtual inheritance, and dynamic typing. To date, there has been no scientific quantification or evaluation of C++ memory layouts. Our approach can help C++ implementors. This work has already influenced the memory layout design choices in IBM's Visual Age C++ V5 compiler.

Applying our approach to a set of five benchmarks, we demonstrate that the impact of object‐oriented space overhead can vary dramatically between applications (ranging from 0.42% to 99.79% for our benchmarks). In particular, applications whose object space is dominated by instances of classes that heavily use object‐oriented language features will be significantly impacted by the choice of a memory layout. Copyright © 2003 John Wiley & Sons, Ltd.
Investigating the use of analysis contracts to improve the testability of object‐oriented code
Authors: Briand L. C. , Labiche Y. , Sun H.
Published: May 2003

A number of activities involved in testing software are known to be difficult and time consuming. Among them is the definition and coding of test oracles and the isolation of faults once failures have been detected. Through a thorough and rigorous empirical study, we investigate how the instrumentation of contracts could address both issues. Contracts are known to be a useful technique in specifying the precondition and postcondition of operations and class invariants, thus making the definition of object‐oriented analysis or design elements more precise. It is one of the reasons the Object Constraint Language (OCL) was made part of the Unified Modeling Language. Our aim in this paper is to reuse and instrument contracts to ease testing. A thorough case study is run where we define OCL contracts, instrument them using a commercial tool and assess the benefits and limitations of doing so to support the automated detection of failures and the isolation of faults. As contracts can be defined at various levels of detail, we also investigate the cost and benefit of using contracts at different levels of precision. We then draw practical conclusions regarding the applicability of the approach and its limitations. Copyright © 2003 John Wiley & Sons, Ltd.
Odyssey: a high‐performance clustered video server
Authors: Wu Min‐You , Shu Wei , Lin Chow‐Sing
Published: May 2003

Video servers are essential in video‐on‐demand and other multimedia applications. In this paper, we present our high‐performance clustered CBR video server, Odyssey. Odyssey is a server connecting PCs with switched Ethernet. It provides efficient support for normal play and interactive browsing functions such as fast‐forward and fast‐backward. We designed a set of algorithms for scheduling, synchronization and admission control, which results in a high utilization of resources. Odyssey is able to deliver a large number of video streams. Copyright © 2003 John Wiley & Sons, Ltd.
Alpha 4 nicotinic acetylcholine receptor subunit links cholinergic to brainstem monoaminergic neurotransmission
Authors: Cucchiaro Giovanni , Commons Kathryn G.
Published: May 2003

Agonists of nicotinic receptors containing the α4‐subunit produce antinociception accompanied by several adverse side effects. The purpose of this study was to determine the distribution of the α4‐subunit of nicotinic acetylcholine receptors (nAChR) in brainstem monoaminergic nuclei that may contribute to these effects using dual labeling immunofluorescence methods. The α4‐subunit immunoreactivity was enriched in serotonergic (nucleus raphe magnus, pallidus, obscurus, and dorsalis) and noradrenergic (A5, locus coeruleus (LC), A7) areas associated with antinociception, where it was commonly colocalized with serotonin (5‐HT) or tyrosine hydroxylase (TH) immunoreactivity. However, it was also noted that α4 was present in all other brainstem monoaminergic nuclei examined (adrenergic C1–C3, noradrenergic A1–α4, dopamine A9 and A10, nucleus raphe medianus). To determine if α4 agonists could impact neural activity in brainstem, monoaminergic nuclei that are associated with antinociception, the expression of c‐Fos in response to the systemic administration of epibatidine (2.5, 5, or 10 μg/kg) was examined. Epibatidine produced a robust (2–5‐fold) increase in c‐Fos expression, which was not dose dependent, in all of these areas examined except the nucleus raphe magnus. These results suggest that the α4 subunit is positioned to mediate the effects of acetylcholine widely across many, if not all, monoaminergic neurons in the brainstem. These observations emphasize the potential involvement of noradrenergic, as well as serotonergic mechanisms in epibatidine's analgesic effects, and they also suggest that even selective α4 ligand may have widespread effects on brain monoamine neurotransmission. Synapse 49:195–205, 2003. © 2003 Wiley‐Liss, Inc.
Differential regulation by stimulants of neocortical expression of mrt1, arc, and homer1a mRNA in the rats treated with repeated methamphetamine
Authors: Fujiyama Ko , Kajii Yasushi , Hiraoka Shuichi , Nishikawa Toru
Published: May 2003

The present work was conducted to obtain clues for the possible roles of a novel stimulant‐inducible gene mrt1 (methamphetamine‐responsive transcript 1) encoding a PDZ‐PX protein in stimulant‐induced behavioral sensitization. In the young adult rats, repeated daily treatment with methamphetamine (4 mg/kg, intraperitoneally, once a day) for 5 days caused an enhanced behavioral response to methamphetamine: behavioral sensitization. The 5‐day intermittent administration of MAP upregulated the basal expression of mrt1 transcripts and eliminated the increasing effects of a challenge dose of MAP (1.6 mg/kg, i.p.) or cocaine (30 mg/kg, i.p.) on mrt1 expression on day 14 of withdrawal in the neocortex that has been considered to be composed of a neuron circuit implicated in the sensitization phenomenon. In contrast, the basal expression of other stimulant‐inducible and plasticity‐related genes arc and homer1a and the ability of MAP or cocaine challenge to augment the amounts of their transcripts were not affected by the repeated MAP regimen in the cortical area. These findings suggest the differential regulation by stimulant of neocortical mrt1, arc, and homer1a expression in the behaviorally sensitized animals and supports the view that stimulant induction of mrt1 may be involved in the early molecular signalings for stimulant sensitization. Synapse 49:143–149, 2003. © 2003 Wiley‐Liss, Inc.
[11C]‐NS 4194 versus [11C]‐DASB for PET imaging of serotonin transporters in living porcine brain
Authors: Jensen Svend B. , Smith Donald F. , Bender Dirk , Jakobsen Steen , Peters Dan , Nielsen Elsebet Ø. , Olsen Gunnar M. , Scheel‐Krüger Jørgen , Wilson Alan , Cumming Paul
Published: May 2003

In vitro, the novel diazabicyclononane NS 4194 has several thousand‐fold selectivity for blocking the transport into rat brain synaptosomes of [3H]‐serotonin in comparison to [3H]‐dopamine or [3H]‐noradrenaline. We have prepared [11C]‐NS 4194 in order to test its properties for PET imaging of brain serotonin transporters in comparison with the well‐documented tracer [11C]‐DASB. Both compounds had rapid clearance from blood to brain of living pigs. The apparent equilibrium distribution volumes in cerebellum were 35 ml g−1 for [11C]‐NS 4194 and 11 ml g−1 for [11C]‐DASB. Pretreatment of pigs with citalopram did not reduce the uptake of either tracer in cerebellum, validating the use of that tissue as a nonbinding reference tissue for kinetic analysis of specific binding. The binding potential (pB) calculated for [11C]‐NS 4194 using arterial input models was close to 0.5 in the telencephalon, and was 60% displaced by citalopram. However, the reference tissue method of Lammertsma was unsuited to calculate pB for this tracer, apparently due to its excessive nonspecific binding. In contrast to the relatively homogeneous binding of [11C]‐NS 4194, the pB of [11C]‐DASB ranged from 0.6 in frontal cortex to 2 in the mesencephalon when calculated by the method of Lammertsma. Parametric maps of the pB of [11C]‐DASB showed a pattern consistent with the known distribution of serotonin transporters in pig brain in vitro, and there was a uniform displacement of 80% of the specific binding after citalopram treatment in vivo. In conclusion, [11C]‐DASB is in several respects superior to [11C]‐NS 4194 for the detection of serotonin uptake sites by PET. Synapse 49:170–177, 2003. © 2003 Wiley‐Liss, Inc.
Higher in vivo muscarinic‐2 receptor distribution volumes in aging subjects with an apolipoprotein E‐ϵ4 allele
Authors: Cohen Robert M. , Podruchny Teresa A. , Bokde Arun L.W. , Carson Richard E. , Herscovitch Peter , Kiesewetter Dale O. , Eckelman William C. , Sunderland Trey
Published: May 2003

The apolipoprotein E‐ϵ4 allele confers an increased susceptibility to age‐related memory problems and Alzheimer's disease. Abnormalities in the cholinergic system are also likely contributors to memory deficits associated with aging and AD. To determine the effect of the APOE‐ϵ4 allele on the muscarinic component of the cholinergic system of aging subjects, 10 healthy subjects with APOE‐ϵ4 alleles (APOE‐ϵ4+) and 10 without (APOE‐ϵ4‐), ranging in age from 52 to 75 years, were tomographically scanned with the F‐18‐labeled muscarinic‐2 (M2) selective agonist, 3‐(3‐(3‐[18F]Flouropropyl)thio)‐1,2,5‐thiadiazol‐4‐yl)‐1,2,5,6‐tetrahydro‐1‐methylpyridine ([18F]FP‐TZTP). The distribution volumes (VT) of [18F]FP‐TZTP were determined by compartmental modeling of partial volume and free fraction corrected PET scans. Regional cerebral blood flow (rCBF) measurements with H215O were also performed. Global Gray VT (840 ± 155 ml plasma/ml tissue) was greater in APOE‐ϵ4+ subjects than APOE‐ϵ4‐ subjects (660 ± 113 ml plasma/ml tissue, P = 0.01), and previously studied younger subjects. There were no significant differences between the groups with respect to rCBF, but within the APOE‐ϵ4+ group there was a trend for subjects with the higher Global Gray VTs to have lower Global Gray CBFs (r = −0.65, P < 0.06). A lower concentration of acetylcholine in the synapse of APOE‐ϵ4+ older individuals is a likely explanation for the greater [18F]FP‐TZTP distribution volumes. Synapse 49:150–156, 2003. Published 2003 Wiley‐Liss, Inc.
Synaptic organization of monosynaptic connections from mesencephalic trigeminal nucleus neurons to hypoglossal motoneurons in the rat
Authors: Zhang Jingdong , Pendlebury William W. , Luo Pifu
Published: May 2003

Synaptological characteristics of synapses between axonal boutons of the trigeminal mesencephalic nucleus (Vme) neurons and the hypoglossal nucleus (XII) motoneurons (MNs) were studied using biotinylated dextran amine (BDA) anterograde labeling combined with horseradish peroxidase (HRP) retrograde transport in the rat. BDA was initially iontophoresed into Vme unilaterally and 7 days later HRP was injected into the anterior two‐thirds of the ipsilateral tongue. After histochemical reactions, BDA anterogradely labeled boutons were seen to appose closely to somata and dendrites of HRP retrogradely labeled MNs in XII by light microscopy. A total of 212 BDA‐labeled Vme boutons were examined ultrastructurally, which had an average diameter of 1.3 ± 0.4 μm and contain small clear spherical vesicles. Eighty‐eight percent of Vme boutons (187/212) synapsed on dendrites of HRP‐labeled XII MNs. Twenty‐five Vme boutons (25/212, 12%) made synapses with somata of HRP‐labeled XII MNs. Thirty‐five percent (74/212) of BDA‐labeled Vme boutons were also contacted by unlabeled P‐type terminals. Presynaptic P‐type terminals contained spherical (47%, 35/74), pleomorphic (43%, 32/74), and flattened (10%, 7/74) synaptic vesicles. Thus, P‐type terminals (as a presynaptic element), BDA‐labeled Vme boutons, and XII MNs constitute axoaxodendritic and axoaxosomatic synaptic triads. There are four types of synaptic microcircuits in XII neuropil: synaptic convergence, synaptic divergence, presynaptic inhibition synaptic circuits, and feedforward regulation circuits. This detailed ultrastructure examination of the synaptic organization between Vme neurons and XII MNs provides insights into the synaptic mechanisms of the trigeminal proprioceptive afferents involved in the jaw–tongue reflex and coordination during oral motor behaviors. Synapse 49:157–169, 2003. © 2003 Wiley‐Liss, Inc.
Stressor controllability modulates stress‐induced serotonin but not dopamine efflux in the nucleus accumbens shell
Authors: Bland Sondra T. , Twining Carin , Watkins Linda R. , Maier Steven F.
Published: May 2003

The ability of an organism to control a stressor can modulate many of the consequences of stress. Previous research indicates that uncontrollable stress (inescapable shock, IS) activates serotonergic (5‐HT) neurons of the dorsal raphe nucleus (DRN) to a greater degree than controllable stress (escapable shock, ES), potentiating 5‐HT efflux in the DRN and in target regions. Previous research also indicates that IS selectively affects dopamine (DA) efflux. The present study measured 5‐HT and DA efflux in the NAc shell during IS or ES using in vivo microdialysis. Male Sprague Dawley rats with probes in the NAc shell were dialysed while subjected to 100 1.0 mA tailshocks. Rats were run in yoked pairs in wheel‐turn boxes such that one rat (ES) in the pair could terminate the shock received by both himself and his yoked (IS) partner by a behavioral response. No stress controls remained in the dialysis bowls. 5‐HT efflux selectively increased during IS, and remained increased throughout as well as after the stress session. There was no effect of stress on DA efflux. These results indicate that the NAc 5‐HT response is preferentially sensitive to stress and can be modulated by stressor controllability. Synapse 49:206–208, 2003. © 2003 Wiley‐Liss, Inc.
Cytoskeletal changes in the hippocampus following restraint stress: Role of serotonin and microtubules
Authors: Bianchi Massimiliano , Heidbreder Christian , Crespi Francesco
Published: May 2003

The aetiology of depression is associated with depletion in central levels of serotonin (5‐HT). Hence, a major effect of antidepressant drugs is to increase synaptic 5‐HT levels. Stressful conditions have also been shown to affect neuronal plasticity and 5‐HT neurotransmission in the hippocampus. Neuronal plasticity, which is typically referred to as a structural adaptation of neurons to functional requirements, requires more dynamic forms of microtubules (cytoskeletal component). The α‐tubulin, which is the major component of microtubules, can be postranslationally modified and both the tyrosinated (tyr‐tub) and acetylated (acet‐tub) forms are considered markers of more dynamic or more stable microtubules, respectively. The aim of the present work was to investigate the expression of tyr‐tub and acet‐tub in the hippocampus of rats submitted to either acute (6 h for 1 day) or sub‐chronic (6 h for 4 days every day) restraint stress. In addition, ex vivo hippocampal 5‐HT levels were monitored by differential pulse voltammetry to analyse the influence of both stress conditions upon 5‐HT levels. Our results showed that the expression of tyr‐tub in the hippocampus was significantly decreased to 70 ± 7% following sub‐chronic restraint stress (P < 0.01). In contrast, acute and sub‐chronic restraint stress increased the hippocampal expression of acet‐tub to 139 ± 11% and 145 ± 11% of control, respectively. Finally, 5‐HT levels were significantly increased (P < 0.05) to 142 ± 15% and 135 ± 11% following acute and sub‐chronic restraint stress, respectively. The stress‐induced cytoskeletal changes observed in the present study suggest that the microtubular network is a potential new pathway that may increase our understanding of stress‐related events. Synapse 49:188–194, 2003. © 2003 Wiley‐Liss, Inc.
Monoamine oxidase A imaging in peripheral organs in healthy human subjects
Authors: Fowler Joanna S. , Logan Jean , Wang Gene‐Jack , Franceschi Dinko , Volkow Nora D. , Telang Frank , Pappas Naomi , Ferrieri Richard , Shea Colleen , Garza Victor , Xu Youwen , King Payton , Schlyer David , Gatley S. John , Ding Yu‐Shin , Warner Donald , Netusil Noelwah , Carter Pauline , Jayne Millard , Alexoff David , Zhu Wei , Vaska Paul
Published: May 2003

Monoamine oxidase (MAO) catalyzes the oxidative deamination of many biogenic and dietary amines. Though studies of MAO have focused mainly on its regulatory role in the brain, MAO in peripheral organs also represents a vast mechanism for detoxifying vasoactive compounds as well as for terminating the action of physiologically active amines, which can cross the blood brain barrier. Indeed, robust central and peripheral MAO activity is a major requirement in the safe use of many CNS drugs, particularly antidepressants, and thus an awareness of the MAO inhibitory potential of drugs is essential in therapeutics. In this study, we examined the feasibility of quantifying MAO A in peripheral organs in healthy human subjects using comparative positron emission tomography (PET) imaging with carbon‐11 (t1/2: 20.4 min) labeled clorgyline ([11C]clorgyline) a suicide inactivator of MAO A and its deuterium labeled counterpart ([11C]clorgyline‐D2). Heart, lungs, kidneys, thyroid, and spleen showed a robust deuterium isotope effect characteristic of MAO and the magnitude of the effect was similar to that of trancylcypromine, an irreversible MAO inhibitor used in the treatment of depression. Liver time‐activity curves were not affected by deuterium substitution precluding the estimation of liver MAO in vivo. In organs showing an isotope effect, MAO A is greatest in the lungs and kidneys followed by the thyroid and heart. This method, which has been previously applied in the human brain, opens the possibility to also directly assess the effects of different variables including smoking, dietary substances, drugs, disease, and genetics on peripheral MAO A in humans. Synapse 49:178–187, 2003. Published 2003 Wiley‐Liss, Inc.
Hierarchical mobility database overflow control
Authors: Xiao Yang
Published: May 2003

In a 3G cellular network, the gateway location registers (GLRs), the visitor location registers (VLRs) and the home location registers (HLRs) form a three‐level mobility database structure. An HLR database is used to record mobile users' permanent subscription information. A VLR database is used to temporarily hold the subscription information of the roaming users who visit the service area of the VLR. A GLR is deployed at the edge of a visited network handling the location management of a roaming subscriber in a visited network without involving the HLR, and holding users' temporary subscription information when the mobile user is within the service area of the GLR. When users leave the GLR/VLR service area, the corresponding records in the GLR/VLR are deleted. Owing to mobility, a GLR/VLR database may overflow at some time periods when the number of visitors significantly increases in the GLR/VLR area. If the GLR/VLR is full, the registration procedure fails and the system cannot deliver services to incoming users under the existing cellular technology. This issue is called GLR/VLR overflow.

In this paper, we propose a hierarchical database overflow control mechanism in 3G cellular networks to effectively eliminate the GLR/VLR overflow problem, and incoming users can continuously use the service with insignificant extra overhead. An analytic model is proposed to investigate the performance of the hierarchical database overflow control scheme. Our study not only shows that the probability of VLR overflow is very small but also shows that among the VLR overflow cases, there is a very small probability of GLR overflow. In other words, the overhead in terms of causing both local and remote/international signaling traffic by exercising our approach is very small. Copyright © 2003 John Wiley & Sons, Ltd.
Handoff performance in wireless DS‐CDMA networks
Authors: Mišić Jelena , Mišić Vojislav B. , Tang Yat Kwan
Published: May 2003

This paper analyses the performance of DS‐CDMA networks in the presence of call handoffs. We show that a handoff may violate the SINR requirements for other users, and thus cause an outage in the target cell. We propose to use the probability of such events as a possible metric for quality of service in networks with multiple traffic types, and derive the corresponding QoS parameters. A two‐level admission policy is defined: in tier 1 policy, the network capacity is calculated on the basis of the bound on outage probability. However, this policy does not suffice to prevent outage events upon handoffs for various traffic types, and henceforth, we propose an extension that reserves extra bandwidth for handoff calls, thus ensuring that handoff calls will not violate the outage probability bound. The overhead imposed by the extension is negligible, as the complete two‐tier admission control algorithm is executed only when a call is admitted into the network. Once admitted, calls can freely execute handoffs using the reserved bandwidth. The modified second‐tier bandwidth reservation policy is adaptive with respect to the traffic intensity and user's mobility and we show that it can provide satisfactory call (flow) quality during its lifetime. Analytical results for the QoS have been verified by the simulations. Copyright © 2002 John Wiley & Sons, Ltd.
A batch‐update strategy for the distributed HLRs architecture in PCS networks
Authors: Hwang Hang‐Wen , Tseng Chien‐Chao , Chang Ming‐Feng
Published: May 2003

Owing to the increasing population of mobile subscribers, the rapidly expanding signaling traffic has become a challenge to the mobility management in PCS networks. Multiple database schemes to reduce signal traffic and to solve the bottleneck problem of the singlehome location register(HLR) architecture have been proposed by many researchers. However, in most of the multiple location databases or HLR systems, extra signaling is required for the multiple database updates. We propose a batch‐update strategy, instead of the immediate update method, for the location‐tracking schemes with replication to reduce the signaling overhead. In this paper, we first introduce a distributed HLRs architecture in which each HLR is associated with a localized set of VLRs and the location registrations and queries are processed locally. Then we propose our batch‐update strategy and present two pointing schemes for inter‐HLR call deliveries. The numerical result shows that our approach can effectively decrease the signaling cost of location registration and call delivery compared with the IS‐41 standard. Copyright © 2002 John Wiley & Sons, Ltd.
BER performance of MQAM withL‐branch MRC diversity reception over correlated Nakagami‐mfading channels
Authors: Patterh Manjeet S. , Kamal T. S. , Sohi B. S.
Published: May 2003

Exact and closed form generalized expressions for bit error rate (BER) of M‐ary quadrature amplitude modulation (MQAM) withL‐branch maximal ratio combining (MRC) space diversity reception in fading channels are derived and analyzed. The fading channels are modeled as identical but correlated frequency‐nonselective slow Nakagami‐mfading channels corrupted by additive white Gaussian noise (AWGN). Analytical results obtained are in terms of few finite range integrals with an integrand composed of elementary functions. Because of their simple form, these analytical results readily allow numerical evaluation in cases of practical interest. The results are also general enough to include Nakagami‐mfading channels with and without correlation, no diversity system, Rayleigh fading channels with and without correlation, and AWGN as special cases. The numerical results for the case of 16QAM are shown graphically and also in tabular form in order to examine the effects of fading severity, order of diversity, and branch correlation on the BER performance. The two correlation models considered are constant correlation model and exponential correlation model. One may be interested to know how the BER of MQAM is related to symbol error rate (SER) of MQAM. Therefore, the BER results obtained in this paper are also compared with that obtained directly from the SER. It is expected that the analytical results presented in this paper will provide a convenient tool for design and analysis of a radio communication system with space diversity reception in uncorrelated and correlated fading environment. Copyright © 2002 John Wiley & Sons, Ltd.
A HiperLAN II frame processor implementation
Authors: Vasilakopoulou E. P. , Papadopoulos G. D. , Karastergios G. E.
Published: May 2003

In recent years, wireless access networks offer an alternative method for connecting subscribers to the global communication network. Several high‐speed Wireless LAN's (WLAN) standards have emerged and among them the ETSI BRAN HiperLAN II standard is distinguished for its performance and QoS support.

This paper, starting with a short overview of HiperLAN II main features and Medium Access (MAC) protocol, presents the architecture of an implemented high‐speed Frame Processor that realizes the medium access control (MAC) protocol of the HiperLAN II standard. The main goal of the Frame Processor is the real‐time management of the air interface as well as to bridge the upper network layers with the wireless world, relieving the data link control (DLC) layer of time‐consuming tasks such as slot map allocation extraction, bit‐by‐bit processing of data units, framing and synchronization. Copyright © 2003 John Wiley & Sons, Ltd.
Radio resource management schemes for combined GSM/GPRS mobile systems
Authors: Konstantinopoulou C. N. , Koutsopoulos K. A. , Demestichas P. P. , Theologou M. E. , Lyberopoulos G. L.
Published: May 2003

Data services like Web browsing, e‐mail and file transfer are becoming more and more popular in cellular systems. In contemporary systems like Global System for Mobile communications (GSM), data transfer has been circuit‐switched, that is, physical resources are allocated to a user for the entire call/session duration. However, this is inefficient in case of bursty traffic, where bursts are separated by long intervals of inactivity. This has been the main reason for the introduction of General Packet Radio Service (GPRS), which on the one hand acts as a mobile access network to the Internet, while on the other hand it enables the operator to offer a wide variety of value‐added services [Wireless Access Protocol (WAP) over GPRS, e/m‐banking, e/m‐commerce, push services, etc.] efficiently.

However, in contemporary commercial implementations of GPRS the radio resource allocation algorithm does not take into account the Quality of Service (QoS)‐related service characteristics—although such information is exchanged between the terminal and the network—and consequently all service requests are treated the same way (‘best effort’). In this paper, we propose and evaluate via a simulation platform various Radio Resource Management (RRM) schemes capable of differentiating the handling of ‘service requests’ (in uplink and downlink), taking into account the GPRS‐related QoS parameters (precedence, reliability, delay, mean and peak throughput). The evaluation is performed for a range of voice (circuit‐switched) traffic loads, number of Transmit Receive eXchange (TRXs), offered data (packet‐switched) services characteristics, number of dedicated Packet Data Channels (PDCHs), and so on, taking into account the respective QoS requirements for both service types (circuit‐ and packet‐switched). Copyright © 2003 John Wiley & Sons, Ltd.
LEO satellite communication networks—a routing approach
Authors: Makki S. A. M. , Pissinou Niki , Daroux Philippe
Published: May 2003

In the modern world of telecommunications, the concept of wireless global coverage is of the utmost importance. However, real global coverage can only be achieved by satellite systems. Until recently, the satellites were in geostationary orbit and their high altitude could not allow real‐time communication such as cellular networks. The development of LEO satellite networks seems to overcome this limit. However, LEO satellite systems have specific characteristics that need to be taken into account. In the same manner, the TCP/IP standard was developed for terrestrial network. The need is then to come up with a solution that would permit the use of TCP/IP on LEO satellite networks without losing too many packets.

The idea is to develop a routing algorithm that maximizes the RTT delays compared to the TCP timer granularity. For that matter, we use an FSA‐based link assignment that simulates the satellite constellation as a fixed network for a predetermined time interval. In this configuration, the problem becomes a static routing problem where an algorithm can find the best solution. Copyright © 2003 John Wiley & Sons, Ltd.