bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton-implantation-induced photoluminescence enhancement in self-assembled InAs/GaAs quantum dots
Authors: Ji Yalin , Chen Guibin , Tang Naiyun , Wang Qing , Wang X. G. , Shao J. , Chen X. S. , Lu W.
Published: April 2003

We have used proton-implantation-induced intermixing and a passivation effect to enhance the light-emission efficiency in multilayer InAs/GaAs quantum dots (QDs). Photoluminescence (PL) spectroscopy is used to study both the intermixing and passivation effects. Besides the blueshift of the luminescence peak due to the intermixing-induced energy band variation, a six times higher PL intensity increase is observed, relative to that of as-grown QDs, with a proton implantation dose of 5×1013 cm−2 followed by rapid thermal annealing at 700 °C. These effects are beneficial to both the quantum efficiency and the wavelength tuning of optoelectronic devices.
Multimode combined intense laser-induced electron acceleration and violent bunch compression
Authors: Wang P. X. , Tang Ch. X. , Huang Sh. J.
Published: April 2003

The ponderomotive potential structure of a multimode combined intense laser beam is studied. Using a three-dimensional test particle simulation, the interaction of slow electrons with the combined laser beam in vacuum is investigated. The calculation shows that electrons distributed on a large scale can be accelerated to relativistic energy in vacuum. A violent longitudinal bunch compression phenomenon is also presented and discussed.
Enhanced critical current density in overdoped HgBa2CaCu2O6+δ superconducting thin films
Authors: Xie Y. Y. , Wu J. Z.
Published: April 2003

Overdoped HgBa2CaCu2O6+δ (Hg-1212) high-temperature superconducting thin films have been synthesized in a fluorine-assisted cation-exchange process followed by postannealing in flowing oxygen. The overdoped Hg-1212 thin films have lowered superconducting transition temperature Tc of about 114–115 K. Critical current density Jc, however, is nearly twice as that for optimally doped Hg-1212 films. The enhancement in magnetic irreversible field Hirr has also been observed in the overdoped Hg-1212 films, while a similar scaling law of Hirr∼(1−T/Tc)n with n=1.2–1.3 in field range below 1 T was observed for both optimally doped and overdoped samples. Such a fluorine-assisted cation-exchange process, hence, provides a simple practical route for achieving high-current carrying Hg-1212 films on oxide and metal substrates.
Field-induced relaxation of bulk composition due to internal boundaries
Authors: Jamnik J. , Guo X. , Maier J.
Published: April 2003

The establishment of compositional variations in solids caused by an external electric field usually requires electrodes that block either electronic or ionic charge carriers. Here we present unambiguous experimental and theoretical evidence that the compositional variations can occur even in the case of completely nonblocking electrodes if grain boundaries are present. In addition to the proper grain boundary impedance arc characterized by the dielectric relaxation time, τ, a second arc occurs at much lower frequencies (τδ). It is shown that this low-frequency response refers to a chemical relaxation (Warburg diffusion) induced by the selectively blocking grain boundary. The effect is the analogue to the chemical relaxation induced by selectively blocking electrodes (cf. Wagner–Hebb polarization).
Magneto-optical investigations of single self-assembled InAs/InGaAlAs quantum dashes
Authors: Mensing T. , Worschech L. , Schwertberger R. , Reithmaier J. P. , Forchel A.
Published: April 2003

Small mesa structures with only a few self-assembled InAs dashes for optical studies were realized by electron-beam lithography and etching techniques. The heterostructure was grown by molecular-beam epitaxy lattice-matched to an InP substrate and consists of an In0.53Ga0.23Al0.24As layer embedding in the center 3.3 monolayers of InAs. By self-assembly InAs dashes were formed. At low temperatures, narrow emission lines associated with electron-hole pairs confined in single dashes are observed. Biexciton transitions with typical binding energies of about 3.5 meV are found. The diamagnetic shift and the Zeeman splitting of single excitons are studied in magnetic fields up to 8 T in Faraday configuration. A large variation of the exciton g factor with the emission energy of quantum dashes is observed.
Magnetic confinement of weakly ionized plasma with superconducting bulk magnets
Authors: Matsuzawa Hidenori , Ohishi Kazuya , Ishikawa Kazuhito , Morita Tomonori , Yoshikawa Masaaki , Ikuta Hiroshi , Mizutani Uichiro
Published: April 2003

This letter describes the application of single-domain superconducting bulk magnets as a plasma confinement. A through-hole was drilled at the center of a Sm123 bulk superconductor of 39 mm diameter and 17 mm thickness. When the sample was field cooled to 77 K, the resulting bulk magnet trapped a magnetic field of ∼0.65 T called a magnetic mirror, in the bore of the hole. The magnet was applied to a weakly ionized neon plasma column. Both the magnet and discharge glass tube were immersed in liquid nitrogen. The spatial distribution in the tube of red fluorescence of the plasma showed that the magnet certainly confined the plasma. These results would provide a clue to applications of the compact magnet of strong magnetic field.
Atomic-layer deposition of wear-resistant coatings for microelectromechanical devices
Authors: Mayer T. M. , Elam J. W. , George S. M. , Kotula P. G. , Goeke R. S.
Published: April 2003

Friction and wear are major concerns in the performance and reliability of microelectromechanical systems (MEMS) devices employing sliding contacts. While many tribological coating materials are available, most traditional surface coating processes are unable to apply conformal coatings to the high aspect ratio (height/width) structures typical of MEMS devices. We demonstrate that thin, conformal, wear-resistant coatings can be applied to Si surface-micromachined structures by atomic-layer deposition (ALD). For this demonstration, we apply 10-nm-thick films of Al2O3 using a binary reaction sequence with precursors of trimethyl aluminum and water. Deposition is carried out in a viscous flow reactor at 1 Torr and 168 °C, with N2 as a carrier gas. Cross-section transmission electron microscopy analysis shows that films are uniform to within 5% on MEMS device structures with aspect ratio ranging from 0 to >100. Films are stoichiometric Al2O3, with no evidence of contamination from other species, and are amorphous. Preliminary friction and wear data show that ALD films have promising properties for application to MEMS devices.
Manager attention to multisource feedback
Authors: Greguras Gary J. , Ford John M. , Brutus Stéphane
Published: April 2003

Although research on multisource ratings indicates that different rater sources provide different information, little research has investigated how ratees attend to such information. Understanding how ratees attend to feedback information from different rater sources is important because such attention likely impacts subsequent behavior. Using a policy‐capturing design, managers (n = 213) completed scenarios in which supervisor, peer, and subordinate ratings were varied across different performance dimensions. Results indicated that ratees attended to all three rater sources, with supervisor ratings being attended to more than peer or subordinate ratings. Further, results indicated a significant interaction between rater source and performance dimension such that some rater sources were attended to more, for certain dimensions, than for others.
Reliable prediction of T‐cell epitopes using neural networks with novel sequence representations
Authors: Nielsen Morten , Lundegaard Claus , Worning Peder , Lauemøller Sanne Lise , Lamberth Kasper , Buus Søren , Brunak Søren , Lund Ole
Published: April 2003

In this paper we describe an improved neural network method to predict T‐cell class I epitopes. A novel input representation has been developed consisting of a combination of sparse encoding, Blosum encoding, and input derived from hidden Markov models. We demonstrate that the combination of several neural networks derived using different sequence‐encoding schemes has a performance superior to neural networks derived using a single sequence‐encoding scheme. The new method is shown to have a performance that is substantially higher than that of other methods. By use of mutual information calculations we show that peptides that bind to the HLA A*0204 complex display signal of higher order sequence correlations. Neural networks are ideally suited to integrate such higher order correlations when predicting the binding affinity. It is this feature combined with the use of several neural networks derived from different and novel sequence‐encoding schemes and the ability of the neural network to be trained on data consisting of continuous binding affinities that gives the new method an improved performance. The difference in predictive performance between the neural network methods and that of the matrix‐driven methods is found to be most significant for peptides that bind strongly to the HLA molecule, confirming that the signal of higher order sequence correlation is most strongly present in high‐binding peptides. Finally, we use the method to predict T‐cell epitopes for the genome of hepatitis C virus and discuss possible applications of the prediction method to guide the process of rational vaccine design.
Farmers and Their Languages: The First Expansions
Authors: Diamond Jared , Bellwood Peter
Published: April 2003

The largest movements and replacements of human populations since the end of the Ice Ages resulted from the geographically uneven rise of food production around the world. The first farming societies thereby gained great advantages over hunter-gatherer societies. But most of those resulting shifts of populations and languages are complex, controversial, or both. We discuss the main complications and specific examples involving 15 language families. Further progress will depend on interdisciplinary research that combines archaeology, crop and livestock studies, physical anthropology, genetics, and linguistics.
ALL-TO-ALL BROADCASTING ALGORITHMS ON HONEYCOMB NETWORKS AND APPLICATIONS
Authors: CARLE JEAN , MYOUPO JEAN-FREDERIC , SEME DAVID
Published: April 2003

This paper presents two simple all-to-all broadcasting algorithms on honeycomb mesh. Consider a network with n processors, one has personalized routing strategy at each node and it requires a 3n communication time complexity. This communication time can be reduced to n because the computation time is always assumed to be much lower than the communication time. The other is based on a Hamiltonian path and has a 2n communication time complexity. We show how they can be used to get parallel solutions to a class of problems on honeycomb networks, among others Prefix Sums, Maximal Vectors, Maximal Sum Subsegment, Parenthesis Matching, Decoding Binary Tree, and Sorting. In our knowledge, these all-to-all broadcast algorithms are the only ones so far exhibited on a honeycomb.
B LIFETIMES, MIXING AND CP VIOLATION AT CDF
Authors: PAULINI MANFRED
Published: April 2003

We review the status of bottom quark physics at the CDF experiment. The measurements reported are based on about 110 pb -1 of data collected at the Fermilab Tevatron [Formula: see text] Collider operating at [Formula: see text]. In particular, we review results on B hadron lifetimes, measurements of the time dependence of [Formula: see text] oscillations, and a search for CP violation in [Formula: see text] decays. Prospects for future B physics at CDF in the next run of the Tevatron Collider, starting in the year 2000, are also presented.
ON OPTIMALITY OF LOCAL CONTROL OF CHAOS
Authors: RICHTER HENDRIK
Published: April 2003

Local control stabilizes chaotic motions by applying a state feedback only within a possible strongly bounded state space region of control (SSRC). In this paper, we consider the question of when a local control is optimal. Therefore, a cost function is employed that accounts for two components: time and control force needed until stabilization occurs. We present analytical and numerical results on the dependency of the cost on the size of the SSRC and a weighting constant between the two components of the cost function.
ON A NONLINEAR COMMUNICATION SCHEME
Authors: CHOW S.-N. , DENG BO , HALE J. K.
Published: April 2003

A nonlinear communication scheme is presented. It is shown that a family of equations can be used for encoding and that synchronization can be maintained even though parameters are varied at the encoding end. It is also demonstrated that the idea of using the sensitive dependence on initial conditions of chaotic system for communication purposes can also be implemented for nonchaotic systems near the common boundary of basins of attraction for multiple attractors. Numerical simulations are also included.
NOISE REDUCTION INDUCED BY EXTERNAL NOISE OR PERIODIC SIGNAL IN A DYNAMICAL SYSTEM
Authors: GINZBURG SAUL L. , PUSTOVOIT MARK A. , GERASHCHENKO OLEG V.
Published: April 2003

We investigated, analytically and by analog simulation, a simple model system, an overdamped Kramers oscillator with two additive noise sources, internal white and external colored. We found that the magnetude of noise background in the spectrum of system outpit can decrease when the amplitude of external noise or periodic signal increases.
STATISTICAL EXPLANATION FOR THE OBSERVATION OF 1/f NOISE FROM BASICALLY DISCRETE FLUCTUATIONS
Authors: HÄRTLER GISELA
Published: April 2003

In this paper, we propose an original statistical explanation to interpret 1/ f noise consistently. It is shown that a sequence of noise signals is necessarily non-stationary if it is generated by stationary random walks at random time points. The variance of the signal distribution is random and the probability of the appearance of random increments in the k'th time interval (k > 1) is based on the intensities of a family of Poisson processes in the current time interval and on conditional probabilities generated in all previous time intervals. This leads to increasing expectations of the random variances in consecutive time intervals. As a consequence, the correlation of signals is random with time dependent expectations. The noise process is non-stationary and not first-order Markovian. Common estimation yields biased frequency spectra with increasing error variances appearing as 1/ f error spectra. Families of Poisson processes with jump probabilities characterized by a priori Beta distributions are investigated and the second moments of the resulting noise processes are conisdered. Simulated process yield spectral estimates with linearly increasing error variances.
LOW FREQUENCY NOISE CONVERSION IN FETS UNDER NONLINEAR OPERATION
Authors: DANNEVILLE F. , TAMEN B. , CAPPY A. , JURAVER J-B , LLOPIS O. , GRAFFEUIL J.
Published: April 2003

The conversion mechanisms of microscopic low frequency noise sources (e.g. generation-recombination noise sources) located in the channel of a FET (Field Effect Transistor), in the presence of a large RF signal, are investigated. It is shown that the base-band (low frequency) input gate noise voltage spectral density is strongly dependent on the magnitude of the input RF power applied to the FET. Moreover, the microscopic generation-recombination noise sources distributed along the channel are also responsible of up-converted input gate noise voltage spectral density around the RF frequency.
Human Heart-Type Fatty Acid-Binding Protein as an Early Diagnostic and Prognostic Marker in Acute Coronary Syndrome
Authors: Nakata Tomoaki , Hashimoto Akiyoshi , Hase Mamoru , Tsuchihashi Kazufumi , Shimamoto Kazuaki
Published: April 2003

Although heart-type fatty acid-binding protein (H-FABP) can be a marker of sarcolemmal injury due to acute myocardial ischemia, the diagnostic or prognostic value is not established in patients with acute chest pain. This multicenter prospective study aimed to determine the diagnostic and prognostic values of H-FABP in 133 patients presenting to an emergency room with suspected acute coronary syndrome (ACS) by comparing with those of conventional biomarkers. H-FABP and myoglobin had greater positive results than did creatine kinase-MB or troponin T. Receiver operating characteristics analysis revealed that H-FABP was the most reliable for detection of ACS and that H-FABP had the greatest sensitivities for identification of patients requiring emergency hospitalization, coronary angiography, and interventional therapy within 7 days among the biomarkers. Thus, H-FABP can be an early diagnostic and prognostic biochemical marker, particularly within the first 6 h from the onset of chest symptoms, in patients with chest pain at an emergency department.
Perceived Patient Comprehension in Acute and Chronic Cardiovascular Clinical Trials
Authors: Yuval Rita , Halon David A. , Flugelman Moshe Y. , Lewis Basil S.
Published: April 2003

An anonymous patient perception comprehension and satisfaction questionnaire was sent to 438 patients 1–3 months after they had participated in a clinical cardiovascular trial to examine the level of patient comprehension as perceived by the patient. We compared perceived comprehension in acute (acute myocardial infarction) and chronic (outpatient heart failure) clinical trials. Partially or fully completed questionnaires were received from 220 patients (70 chronic, 150 acute). The findings were similar in the 2 patient groups. Perceived full comprehension (understood most or all) of the trial was reported by 18 (27%) of chronic and 40 (31%) of 129 acute patients, while almost 20% of both groups reported little or no understanding of the trial. The level of comprehension was related to the recollected duration of explanation (p = 0.003 chronic, p < 0.001 acute). Perceived comprehension was not related to the personnel explaining the study (physician or nurse) or to whether the explanation as recollected was oral or written. However, in both acute and chronic patients, the majority (51% chronic; 63% acute) preferentially recalled the oral rather than written explanation of the trial. The very similar findings in the acute and chronic situation suggest that perceived understanding reflects human nature and willingness to be involved in medical issues. Considerable effort should be directed to improve the duration of explanation (particularly oral), if we are to achieve our goal of true informed consent in clinical cardiovascular trials.
In vitro Synergy Studies Using Aztreonam and Fluoroquinolone Combinations against Six Species of Gram-Negative Bacilli
Authors: Critchley Ian A. , Sahm Daniel F. , Kelly Laurie J. , Karlowsky James A.
Published: April 2003

Background: Combination antimicrobial therapy is often necessary to eradicate infections caused by gram-negative bacteria. Methods: To evaluate the potential benefit of aztreonam and fluoroquinolone combination therapy, the activity of aztreonam in combination with ciprofloxacin, gatifloxacin, levofloxacin and moxifloxacin was assessed using checkerboard testing for four clinical isolates of each of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloacae, Burkholderia cepacia and Pseudomonas aeruginosa.Results: All aztreonam and fluoroquinolone combinations demonstrated additive activity [fractional inhibitory concentration (FIC) index >0.5–4] or synergy (FIC index ≤0.5) for all 24 isolates tested. Aztreonam plus ciprofloxacin was the most effective combination, demonstrating synergy against 16.7% of isolates (2 P. mirabilis, 1 E. cloacae, 1 B. cepacia). Aztreonam in combination with moxifloxacin was synergistic against 2 isolates (P. mirabilis, E. cloacae), and in combination with gatifloxacin against 1 isolate (E. cloacae). Aztreonam and levofloxacin demonstrated only additive activity. Conclusion: Additive activity was observed for the majority of the aztreonam and fluoroquinolone combinations tested against six species of gram-negative bacilli. Synergy involving aztreonam and fluoroquinolone combinations was less common than additive activity and was isolate dependent. Although in vivo clinical successes have been documented using aztreonam in combination with other agents, confirmation by laboratory techniques requires further investigation.
Detection of Macrolide Resistance in Streptococcus pneumoniae
Authors: Kimura Taku , Horii Toshinobu , Morita Motoki , Muramatsu Hideaki , Kanno Takashi , Maekawa Masato
Published: April 2003

We determined the susceptibilities of recent clinical isolates of Streptococcus pneumoniae to 19 antibiotics. The frequency of erythromycin nonsusceptibility was high, i.e. 8/13 (61.5%), 10/14 (71.4%) and 11/11 isolates (100%) from 13 penicillin-susceptible, 14 penicillin-intermediate and 11 penicillin-resistant S. pneumoniae, respectively. Macrolide resistance was detected by polymerase chain reaction (PCR) and disk diffusion methods. Of these erythromycin-nonsusceptible pneumococcal isolates, 13/29 (44.8%) isolates contained genomic copies of mefA and showed non-‘D’-shaped zones of inhibition observed around rokitamycin and/or clindamycin disks. Sixteen out of 29 isolates (55.2%) contained copies of ermB and showed typical ‘D’-shaped zones of inhibition, except one isolate. Although the macrolide resistance determinants, mefA and ermB, could be identified by PCR and disk diffusion methods, PCR methods were more reliable in elucidating these determinants. The susceptibility pattern to 14-, 15- and 16-membered macrolides and clindamycin differed between the mefA+ and ermB+ isolates. All isolates were susceptible to levofloxacin, sparfloxacin and vancomycin. The MICs of sitafloxacin were lowest among the fluoroquinolones examined for 38 isolates.
A Parametric Manipulation of Factors Affecting Task-induced Deactivation in Functional Neuroimaging
Authors: McKiernan Kristen A. , Kaufman Jacqueline N. , Kucera-Thompson Jane , Binder Jeffrey R.
Published: April 2003

Task-induced deactivation (TID) refers to a regional decrease in blood flow during an active task relative to a “resting” or “passive” baseline. We tested the hypothesis that TID results from a reallocation of processing resources by parametrically manipulating task difficulty within three factors: target discriminability, stimulus presentation rate, and short-term memory load. Subjects performed an auditory target detection task during functional magnetic resonance imaging (fMRI), responding to a single target tone or, in the short-term memory load conditions, to target sequences. Seven task conditions (a common version and two additional levels for each of the three factors) were each alternated with “rest” in a block design. Analysis of covariance identified brain regions in which TID occurred. Analyses of variance identified seven regions (left anterior cingulate/superior frontal gyrus, left middle frontal gyrus, right anterior cingulate gyrus, left and right posterior cingulate gyrus, left posterior parieto-occipital cortex, and right precuneus) in which TID magnitude varied across task levels within a factor. Follow-up tests indicated that for each of the three factors, TID magnitude increased with task difficulty. These results suggest that TID represents reallocation of processing resources from areas in which TID occurs to areas involved in task performance. Short-term memory load and stimulus rate also predict suppression of spontaneous thought, and many of the brain areas showing TID have been linked with semantic processing, supporting claims that TID may be due in part to suspension of spontaneous semantic processes that occur during “rest” (Binder et al., 1999). The concept that the typical “resting state” is actually a condition characterized by rich cognitive activity has important implications for the design and analysis of neuroimaging studies.
When Seeing Is Not Believing: Children's Understanding of Humans' and Non-Humans' Use of Background Knowledge in Interpreting Visual Displays
Authors: Barrett Justin , Newman Roxanne Moore , Richert Rebekah
Published: April 2003

To explore 3- to 7-year-old children's developing understanding of human and non-human minds, a battery of "background knowledge" tasks was administered to 51 American children. The children were asked to speculate about how three other intentional agents (mother, dog, and God) would understand various visual displays. First, children answered when they themselves did not understand the displays, then they answered after they had been given information necessary to understand the displays. Results revealed that children begin to understand the role of background knowledge around the same age that they pass false-belief tasks; and that before thoroughly understanding the role of background knowledge they already begin to discriminate between different types of minds. By age four, children began to show some understanding that because of having different minds than people, God is more able and dogs are less able to understand some visual displays even with full visual access.
Numerical diagnosis of a small, quasi‐tropical cyclone over the western Mediterranean: Dynamical vs. boundary factors
Authors: Homar V. , Romero R. , Stensrud D. J. , Ramis C. , Alonso S.
Published: April 2003

A small, quasi‐tropical cyclone occurred on 12 September 1996 over the western Mediterranean. Intense convective activity over the region during this period also produced a tornado outbreak in the Balearic Islands and torrential precipitation over eastern mainland Spain.

Mesoscale model runs properly simulate the cyclone formation and show convection and heavy precipitation following the cyclone trajectory during its eastward progression. A sensitivity study examining the upper‐level dynamic forcing, latent‐ and sensible‐heat fluxes from the sea, and orography is conducted. A potential‐vorticity (PV) inversion technique is used to reduce the amplitude of the upper‐level trough in the model initial conditions. The results show that neither the orography nor the sensible‐heat flux from the sea play a significant role during this particular cyclone development. Conversely, both the latent‐heat flux and the upper‐level trough are shown to be crucial for low‐level cyclogenesis. Features common to hurricane‐like polar lows are found for the cyclone, and an analysis of the precise role of the upper‐level structures and the convective development is conducted.

A factor‐separation technique is used to determine the individual effects of the aforementioned factors, as well as their interaction. At the first stage of the cyclogenesis, the upper‐level PV anomaly enhanced the low‐level circulation of the synoptic‐scale low and enhanced the latent‐heat flux from the sea. During its mature stage, the circulation associated with the small‐scale cyclone enhanced the latent‐heat flux from the sea, thereby helping to maintain the development of deep convection, and inducing further cyclone deepening by diabatic heating. This scenario has many similarities with the air–sea interaction instability mechanism. Thus, the joint action of the upper‐level anomaly, as a spin‐up agent, and the latent‐heat flux, as a sustainer of convection, emerges as the primary factor for the genesis and evolution of the small quasi‐tropical cyclone. Copyright © 2003 Royal Meteorological Society
Size‐Controlled Synthesis and Catalytic Performance of Pt Nanoparticles in Micro‐ and Mesoporous Silica Prepared Using Supercritical Solvents
Authors: Wakayama H. , Setoyama N. , Fukushima Y.
Published: April 2003

A novel impregnation process using a supercritical fluid (SCF) solvent to generate size‐controlled Pt nanoparticles in micro‐ and mesoporous silica hosts with a uniform pore size (see Figure) is presented. The size of the Pt nanoparticles decreases with the pore size of silica hosts, and the SCFs are shown to be excellent solvents for the introduction of nanoparticles into fine spaces on a nanometer scale.
Synthesis of Novel Nickel Sulfide Submicrometer Hollow Spheres
Authors: Hu Y. , Chen J. , Chen W. , Lin X. , Li X.
Published: April 2003

Nickel sulfide uniform hollow spheres (see scanning electron microscopy image, Figure) have been successfully synthesized by γ‐irradiation of a PMMA–CS2–ethanol aqueous solution that contains NiSO4·6H2O at room temperature. Calculation shows that the diameter of the NiS hollow spheres is 500 nm and the thickness of shell is ∼ 20 nm. A possible growth mechanism is also presented.
Solid‐state polymerization of poly(ethylene terephthalate). I. Experimental study of the reaction kinetics and properties
Authors: Kim T. Y. , Lofgren E. A. , Jabarin S. A.
Published: April 2003

The solid‐state polymerization (SSP) reaction kinetics of poly(ethylene terephthalate) were investigated in connection with the initial precursor intrinsic viscosity (IV; molecular weight). Evaluations were performed with otherwise equivalent precursors melt‐polymerized to IVs of 0.50, 0.56, and 0.64 dL/g. The changes in the molecular weight and other properties were monitored as functions of the reaction times at solid‐state temperatures of 160–230°C. Precursors with higher initial molecular weights exhibited higher rates of SSP than those with lower initial values, as discussed in connection with the levels of crystallinity and the carboxyl and hydroxyl end‐group composition. Activation energies decreased at temperatures above 200°C, and this indicated a change in the SSP reaction mechanism. At temperatures of 200–230°C, similar activation energies were required for the polymerization of all three precursors. Lower temperature polymerizations, from 160 to 200°C, required higher activation energies for all precursors, with the 0.50‐IV material requirement almost twice as high as that calculated for the higher IV precursors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 197–212, 2003
Some properties of styrene‐based ionomers. I
Authors: Suchocka‐Gałaś K.
Published: April 2003

Some properties of styrene‐based ionomers containing alkali metal salts of acrylic acid or methacrylic acid have been investigated. A study has been conducted to examine the influence of the acidic content and nature (acrylic or methacrylic) and the nature of the alkali metal salt on the glass transition temperature, density, melt index and activation energy of a flow of the styrene‐based ionomers. The present studies have indicated that the temperature of glass transition (Tg) of sodium ionomers increases as the sodium content rises and the region of the glass transition broadens. The Tg's of the styrene‐acrylic acid (S‐AA) ionomers do not depend on the nature of the alkali metal introduced into the copolymer. The density of films rises with the content of acid or salt introduced to the polystyrene chain. The melt index of the investigated ionomers depends on the amount and type of the introduced acid and salt as well as on the molecular weight of the initial copolymer. The energy of activation of the flow is independent of the polymer molecular weight; however, the energy of activation of flow of the ionomers increases with larger ionic radii of the introduced alkali metal. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 55–62, 2003
Direct polycondensation of N‐trimellitylimido‐L‐isoleucine with aromatic diamines
Authors: Mallakpour Shadpour , Hajipour Abdol‐Reza , Hassan Shahmohammadi Mohammad
Published: April 2003

N‐Trimellitylimido‐L‐isoleucine (3) was prepared from the reaction of trimellitic anhydride with L‐isoleucine [L‐2‐amino‐3‐methylvalerianic acid or (2S,3S)‐2‐amino‐3‐methyl‐n‐valerinic acid] in an N,N‐dimethylformamide solution at the refluxing temperature. The direct polycondensation reaction of the monomer imide diacid (3) with 1,4‐phenylenediamine, 4,4′‐diaminodiphenylmethane, 4,4′‐diaminodiphenylsulfone, diaminodiphenylether, 1,5‐naphthalendiamine, 2,4‐diaminotoluene, and 1,3‐phenylenediamine was performed in a medium consisting of triphenyl phosphite, N‐methyl‐2‐pyrolidone (NMP), pyridine, and calcium chloride. The polycondensation was performed under two different conditions: in one method, the reaction mixture was heated in an NMP solution at 60, 90, and then 130°C for different periods of time, and in the other method, the reaction mixture was refluxed only for 1 min in the same solvent. The resulting poly(amide imide)s (PAIs), with inherent viscosities of 0.21–0.37 dL/g, were obtained in high yields. All of these compounds were fully characterized by IR spectra, elemental analyses, and specific rotation measurements. Some structural characterizations and physical properties of these new optically active PAIs were examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 116–122, 2003
Characterization of polyelectrolyte effect in poly(acrylic acid) solutions
Authors: Fernandes A. L. P. , Martins R. R. , da Trindade Neto C. G. , Pereira M. R. , Fonseca J. L. C.
Published: April 2003

The viscometric behavior of poly(acrylic acid) solutions, as well as their ion transport properties, were monitored as a function of polymer concentration and the addition of KOH in nonisoionic conditions. Polyelectrolyte effect was studied and characterized by conductivimetry as well as viscometric properties at the infinite dilution limit. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 191–196, 2003
Interaction of antitumoral 9‐aminoacridine drug with DNA and dextran sulfate studied by fluorescence and surface‐enhanced Raman spectroscopy
Authors: Murza Adrian , Alvarez‐Méndez Sergio , Sanchez‐Cortes Santiago , Garcia‐Ramos Jose V.
Published: April 2003

Fluorescence spectroscopy and surface‐enhanced Raman spectroscopy are applied to study the interaction of the drug 9‐aminoacridine (9AA) with DNA and dextran sulfate. The effect of the electrostatic interaction between the positively charged 9AA and negatively charged groups in relation to the excimer or exciplex emission is investigated. The exciplex emission of 9AA is connected to the intercalation of this drug between nucleic base residues. The importance of negative groups in this interaction is evaluated by using dextran and dextran sulfate as model polymers. The existence of negative charges seems to induce an increase of the drug concentration in the vicinity of the polymers. The role of electrostatic attraction in the 9AA dimerization is confirmed by the excimer emission of 9AA in the presence of dextran sulfate. In the case of DNA, the phosphate groups may induce the drug approach to the DNA chain, but the exciplex fluorescence emission could be due to a charge transfer between the drug and adenine‐rich sequences of DNA. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 174–184, 2003
Hydration of hyaluronan polysaccharide observed by IR spectrometry. II. Definition and quantitative analysis of elementary hydration spectra and water uptake
Authors: Haxaire K. , Maréchal Y. , Milas M. , Rinaudo M.
Published: April 2003

We recorded a series of spectra of sodium hyaluronan (HA) films that were in equilibrium with their surrounding humid atmosphere. The hygrometry of this atmosphere extended from 0 to 0.97% relative humidity. We performed a quantitative analysis of the corresponding series of hydration spectra that are the difference spectra of the film at a defined hygrometry minus the spectrum of the dried film (hygrometry = 0). The principle of this analysis is to use this series of hydration spectra to define a limited number (four) of “elementary hydration spectra” over which we can decompose all hydration spectra with good accuracy. This decomposition, combined with the measurements of the numbers of H2O molecules at the origin in these elementary hydration spectra of the three characteristic vibrational bands of H2O, allowed us to calculate the hydration number under different relative humidity conditions. This number compares well with that determined by thermogravimetry. Furthermore, the decomposition defines for each hygrometry value which chemical mechanisms represented by elementary hydration spectra are active. This analysis is pursued by determining for the elementary hydration spectra the number of hydrogen bonds established by each of the four alcohol groups found in each disaccharide repeat unit before performing the same analysis for amide and carboxylate groups. These results are later utilized to discuss the structure of HA at various stages of hydration. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 149–161, 2003
FT‐Raman spectroscopy as diagnostic tool of Congo red binding to amyloids
Authors: Iconomidou Vassiliki A. , Chryssikos Georgios D. , Gionis Vassilis , Hoenger Andreas , Hamodrakas Stavros J.
Published: April 2003

Chorion is the major component of silkmoth eggshell. More than 95% of its dry mass consists of the A and B families of low molecular weight structural proteins, which have remarkable mechanical and chemical properties protecting the oocyte and developing embryo from environmental hazards. We present data from FT‐Raman spectroscopy of silkmoth chorion and amyloid‐like fibrils formed from peptide analogues of chorion proteins, both unstained and stained by Congo red. The results show that FT‐Raman spectroscopy is not a straightforward diagnostic tool for the specific interactions of Congo red with amyloids: a dilute aqueous solution of the Congo red dye at pH 5.5 and a thin solid film of the dye cast from this solution exhibit the same “diagnostic” Raman shifts relative to the neat Congo red dry powder as do amyloid fibrils formed from peptide analogues of chorion proteins stained by Congo red. An important consequence of this finding is that these shifts of the Raman active modes of Congo red are probably due to the formation of supramolecular dye aggregates in the presence of water. Therefore, this is not an appropriate diagnostic test for Congo red binding to amyloids. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 185–192, 2003
Gene selection in arthritis classification with large‐scale microarray expression profiles
Authors: Sha Naijun , Vannucci Marina , Brown Philip J. , Trower Michael K. , Amphlett Gillian , Falciani Francesco
Published: April 2003

The use of large‐scale microarray expression profiling to identify predictors of disease class has become of major interest. Beyond their impact in the clinical setting (i.e. improving diagnosis and treatment), these markers are also likely to provide clues on the molecular mechanisms underlining the diseases. In this paper we describe a new method for the identification of multiple gene predictors of disease class. The method is applied to the classification of two forms of arthritis that have a similar clinical endpoint but different underlying molecular mechanisms: rheumatoid arthritis (RA) and osteoarthritis (OA). We aim at both the classification of samples and the location of genes characterizing the different classes. We achieve both goals simultaneously by combining a binary probit model for classification with Bayesian variable selection methods to identify important genes. We find very small sets of genes that lead to good classification results. Some of the selected genes are clearly correlated with known aspects of the biology of arthritis and, in some cases, reflect already known differences between RA and OA. Copyright © 2003 John Wiley & Sons, Ltd.
Approximating L2‐invariants and the Atiyah conjecture
Authors: Dodziuk Józef , Linnell Peter , Mathai Varghese , Schick Thomas , Yates Stuart
Published: April 2003

Let G be a torsion‐free discrete group, and let ℚ denote the field of algebraic numbers in ℂ. We prove that ℚG fulfills the Atiyah conjecture if G lies in a certain class of groups D, which contains in particular all groups that are residually torsion‐free elementary amenable or are residually free. This result implies that there are no nontrivial zero divisors in ℂG. The statement relies on new approximation results for L2‐Betti numbers over ℚG, which are the core of the work done in this paper. Another set of results in the paper is concerned with certain number‐theoretic properties of eigenvalues for the combinatorial Laplacian on L2‐cochains on any normal covering space of a finite CW complex. We establish the absence of eigenvalues that are transcendental numbers whenever the covering transformation group is either amenable or in the Linnell class 𝒞. We also establish the absence of eigenvalues that are Liouville transcendental numbers whenever the covering transformation group is either residually finite or more generally in a certain large bootstrap class 𝒢. © 2003 Wiley Periodicals, Inc.
A convenient synthetic route to mannose 6‐phosphonate—cholesteryl conjugate
Authors: Vidal Sébastien , Morère Alain , Montero Jean‐Louis
Published: April 2003

A multistep synthesis of a mannose 6‐phosphonate‐based glycolipid is described involving (1) a one‐carbon chain elongation at the 6‐position of mannose, followed by (2) phosphonation, using tris(trimethylsilyl)phosphite. This method was shown to e efficient and provides a general route to various mannose 6‐phosphonate‐based compounds for the design of drug delivery systems. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:241–246, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10134
Psychosocial problems in Parkinson's disease: Evaluation of a disease‐specific questionnaire
Authors: Spliethoff‐Kamminga Noëlle G.A. , Zwinderman Aeilko H. , Springer Machiel P. , Roos Raymund A.C.
Published: April 2003

Our objective was to evaluate the BELA‐P‐k, a questionnaire for measuring psychosocial problems and need for help in Parkinson's disease (PD) patients. The Belastungsfragebogen Parkinson kurzversion (BELA‐P‐k) was translated from German into Dutch. It consists of 19 items distributed over four subscales: achievement capability/physical symptoms, fear/emotional functioning, social functioning and partner‐bonding/family, with a “Bothered by” (Bb) and a “Need for Help” (NfH) score. The BELA‐P‐k was tested for cultural differences, relevance, and feasibility in a pilot study (n = 10) and compared in a validation study (n = 54) with the Sickness Impact Profile, the COOP/WONCA Functional Health Assessment Charts and the Loneliness Questionnaire. All questionnaires were administered in person at home, in a prescribed order. The BELA‐P‐k was completed by 64 patients with PD. The internal‐consistency reliability coefficients for the total Bb (0.90) and NfH (0.93) scales were excellent. The internal consistency of the subscales exceeded the 0.70 standard except for the “Bothered by partner‐bonding/family scale” (0.61). Almost all BELA‐P‐k subscales correlated highly (P < 0.001) with the corresponding scales of the standard quality‐of‐life indices. There was no significant relationship between disease severity (Hoehn and Yahr) and the BELA‐P‐k. We conclude that the BELA‐P‐k is a relevant, reliable and valid measure for assessing psychosocial problems and need for help of PD patients. © 2003 Movement Disorder Society
Microscopic description of information transfer from a qudit to reservoir
Authors: Štelmachovič P. , Ziman M. , Bužek V.
Published: April 2003

Recently Ziman et al. [3] have introduced a concept of a universal quantum homogenizer which is a quantum machine that takes as an input a system qubit initially in an arbitrary state ρ and a set of N reservoir qubits initially prepared in the same state ξ. The homogenizer realizes, in the limit sense, the transformation such that at the output each qubit is in an arbitrarily small neighbourhood of the state ξ irrespective of the initial states of the system and the reservoir qubits. In this paper we generalize the concept of quantum homogenization for qudits, that is, for d‐dimensional quantum systems. We prove that the partial swap operation induces a contractive map with the fixed point which is the original state of the reservoir. Finally we propose an optical realization of the quantum homogenization.
Controlled decoherence in an atom interferometer
Authors: Cronin A.D. , Kokorowski D.A. , Roberts T.D. , Pritchard D.E.
Published: April 2003

We observe controlled decoherence in an atom interferometer, in which exposure to one environment changes the rate of decoherence in a subsequent environment.
Pauli tomography: complete characterization of a single qubit device
Authors: Mazzei A. , Ricci M. , De Martini F. , D'Ariano G.M.
Published: April 2003

We present the first full experimental characterization of a single‐qubit device. This method uses a Pauli Process Tomography at the output of the device and needs only a single entangled state at the input, which works as all possible input states in quantum parallel. The method can be easily extended to any n‐qubits processing device.
Quantum degenerate potassium‐rubidium mixtures
Authors: Modugno G. , Roati G. , Inguscio M.
Published: April 2003

We report on the production of quantum degenerate mixtures of potassium and rubidium isotopes, by means of evaporative cooling in a magnetic trap. Specifically, we produce a Bose–Bose mixture with 41K and 87Rb and Fermi–Bose mixture with 40K and 87Rb. Application of association schemes in these systems may allow the production of degenerate gases of heteronuclear molecules of both bosonic and fermionic character. Ultracold dipolar molecules have been recognized as a viable candidate for the implementation of quantum computing.
Classical information transfer over noisy quantum channels
Authors: Macchiavello C. , Palma G.M.
Published: April 2003

We study the role of entanglement in the transmission of classical information over noisy quantum channels. We show that entanglement leads to an enhancement of the mutual information when the transmission channel is not memoryless.
Experimental evidence of multimode non‐classical light emission using OPOs
Authors: Maître A. , Treps N. , Martinelli M. , Ducci S. , Fabre C.
Published: April 2003

Any spatial measurement below the quantum standard limit requires multitransverse non‐classical light beams which can be produced by a transverse degenerate OPO. A multimode beam is characterized by a non uniform transverse repartition of noise. Using this criterion, we prove experimentally that a confocal Optical Parametric Oscillator emits a multimode non‐classical field.
Studies of femtosecond time‐bin entangled qubits for quantum communications
Authors: Marcikic I. , de Riedmatten H. , Tittel W. , Scarani V. , Acin A. , Tanzilli S. , Zbinden H. , Gisin N.
Published: April 2003

We create pairs of non‐degenerate time‐bin entangled photons at telecom wavelengths with ultra‐short pump pulses. Entanglement is shown by performing Bell kind tests of the Franson type with visibilities of up to 91 time‐bin entanglement can easily be protected from decoherence as encountered in optical fibers, this experiment opens the road for complex quantum communication protocols over long distances.
Rabi oscillations, Ramsey fringes and spin echoes in an electrical circuit
Authors: Vion D. , Aassime A. , Cottet A. , Joyez P. , Pothier H. , Urbina C. , Esteve D. , Devoret M.H.
Published: April 2003

We present a superconducting tunnel junction circuit which behaves as a controllable atom, and whose ground and first excited state form an effective spin 1/2. By applying microwave pulses, we have performed on this circuit experiments demonstrating the controlled manipulation of the spin : Rabi precession, Ramsey interferences, and spin echoes.
Kicked rotor in Wigner phase space
Authors: Bienert M. , Haug F. , Schleich W.P. , Raizen M.G.
Published: April 2003

We develop the Wigner phase space representation of a kicked particle for an arbitrary but periodic kicking potential. We use this formalism to illustrate quantum resonances and anti‐resonances.
Momentum changes due to quantum localization
Authors: Short A.J.
Published: April 2003

The momentum changes caused by localization are a central feature of wave‐particle duality. Investigating these changes in more detail, we find that single‐slit diffraction relies on a form of `interaction‐free' scattering, and that an ideal which‐way measurement can be made without any back‐reaction on the detector. We also consider Kim and Shih's recent realization of Popper's experiment, involving diffraction of entangled particles, and offer an explanation for the results.