bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrolysis of the amyloid β‐peptide (Aβ) 1–40 between Asp23–Val24 produces non‐aggregating fragments. An electrospray mass spectrometric study
Authors: Hosia Waltteri , Griffiths William J. , Johansson Jan
Published: February 2005

The aggregation of full‐length (residues 1–40) amyloid β‐peptide (Aβ) and fragments corresponding to residues 1–23 and 24–40 was studied by electrospray mass spectrometry, using gramicidin as a non‐aggregating reference. Following a lag period, Aβ(1–40) at 140 µM concentration aggregates with apparent first‐order kinetics. Under acidic conditions Aβ(1–40) undergoes spontaneous cleavage between Asp23–Val24 and to a lesser extent also at two other Asp–X motifs. Incubation in acidic H218O showed incorporation of 18O in fragment Aβ(1–23), confirming that the Asp23–Val24 peptide bond had been hydrolyzed. Incubation of synthetic Aβ(1–23) and Aβ(24–40) peptides with Aβ(1–40) showed that Aβ(24–40) remained in solution for several months, that Aβ(1–23) partly disappeared from solution, whereas Aβ(1–40) completely disappeared. Further, treatment of sedimentable aggregates formed after co‐incubation of the three peptides with hexafluoro‐2‐propanol or formic acid recovered the intensity of Aβ(1–40). These data support previous studies showing that the region of Aβ encompassing residues 16–24 is necessary for aggregation into amyloid fibrils. Copyright © 2005 John Wiley & Sons, Ltd.
Mass spectrometric analysis of head ganglia and neuroendocrine tissue of larval Galleria mellonella (Arthropoda, Insecta)
Authors: Huybrechts Jurgen , Verleyen Peter , Schoofs Liliane
Published: February 2005

A brain–retrocerebral complex–subesophageal ganglion acidified methanolic extract of 100 larval Galleria mellonella (greater wax moth) was prepared for the isolation and identification of (neuro)peptides. To reduce sample complexity, the isolated peptides were roughly separated using a single, conventional chromatographic separation step. Subsequently, screening of these fractions with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry in combination with nanoflow electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry resulted in the identification of 12 lepidopteran peptides. None of these had been previously isolated or characterized within this species. VIFTPKLamide encoded by the diapause hormone–pheromone biosynthesis activating neuropeptide precursor was for the first time isolated and biochemically identified in a tissue extract, providing irrefutable evidence of its expression in larval nervous tissue. Another pentapeptide, AMVRFamide, with no resemblance to other lepidopteran peptides, was de novo sequenced and is most related to the neuropeptide F peptide family. Copyright © 2005 John Wiley & Sons, Ltd.
Model Reduction in Emulsion Polymerization Using Hybrid First Principles/Artificial Neural Networks Models, 2
Authors: Arzamendi Gurutze , d'Anjou Alicia , Graña Manuel , Leiza José R. , Asua José M.
Published: February 2005

Summary: A “series” hybrid model based on material balances and artificial neural networks to predict the evolution of weight average molecular weight, $\overline M _{\rm w}$, in semicontinuous emulsion polymerization with long chain branching kinetics is presented. The core of the model is composed by two artificial neural networks (ANNs) that calculate polymerization rate, Rp, and instantaneous weight‐average molecular weight, $\overline M _{{\rm winst}}$ from reactor process variables. The subsequent integration of the material balances allowed to obtain the time evolution of conversion and $\overline M _{\rm w}$, along the polymerization process. The accuracy of the proposed model under a wide range of conditions was assessed. The low computer‐time load makes the hybrid model suitable for optimization strategies.

Effect of the monomer feed rate on $\overline M _{{\rm winst}}$.

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Effect of the monomer feed rate on $\overline M _{{\rm winst}}$.
A reduced‐size two‐layer bandpass filter
Authors: Djaiz Azzeddine , Denidni Tayeb A.
Published: February 2005

In this paper, a new design for a reduced‐size two‐layer bandpass filter is introduced. This filter is built using four resonators placed in two stacked microstrip layers. In this structure, each layer contains two resonators, and the coupling between the resonators in the upper layer and those in the lower one is achieved via two rectangular slots etched in a common ground plane placed between the two layers. Using this design, the size of the proposed filter can be significantly reduced. A design is fabricated and the measured results are described. These measurements demonstrate excellent agreement with the computer‐simulated predictions. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 512–515, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20683
Parallel‐coupled phase‐matched multiring optical filters
Authors: Schwelb Otto , Frigyes István
Published: February 2005

A periodic bandpass filter that is based on the phase‐matching principle and consists of several parallel‐coupled microrings is presented. The rings are identical in size; the coupling coefficients are chosen to provide maximally flat or equal ripple passband. Simulated filter characteristics exhibit steep roll‐off and large stopband rejection. Expressions are given to estimate the passband insertion loss and the stopband rejection level. The effects of loss and fabrication tolerances is examined. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 536–540, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20689
An improved optically controlled phase shifter on Si wafer
Authors: Li H. P. , Chan Kam Tai
Published: February 2005

The transmission characteristics of an improved optically controlled microstrip interdigital gap structure on a high‐resistivity silicon substrate are reported. When irradiated with an optically controlled power as low as 8 mw, a maximum signal‐phase change of 37° is obtained while the signal amplitude remains nearly constant. The proposed device can potentially be used as an optically controlled phase shifter. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 540–541, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20690
Use of electromagnetic band‐gap materials for RCS reduction
Authors: Collardey S. , Tarot A‐C. , Pouliguen P. , Mahdjoubi K.
Published: February 2005

Most applications of electromagnetic band gap (EBG) concern antenna radiation or electromagnetic filters. In this paper, a metallic EBG structure is designed for stealth applications. We show how this structure allows us to reduce the radar cross section (RCS) of targets. An application of this kind of MEBG is the design of a radome allowing the reduction of antenna RCS. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 546–550, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20693
Direct noise characterization of microwave FET using 50Ω noise figure and Y‐parameter measurements
Authors: De Dominicis Marco , Giannini Franco , Limiti Ernesto , Serino Antonio
Published: February 2005

A fast and accurate method to determine the noise parameters of microwave FETs, based on a new expression of the device noise figure as a function of the Y‐parameters and two equivalent noise temperatures, is presented. The method requires only the measured small‐signal parameters and 50Ω noise figure, thus avoiding the extraction of the small‐signal equivalent circuit. It is particularly suitable for noise characterization of coplanar devices. Good agreement with the results of more conventional methods is demonstrated in a wide frequency range. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 565–569, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20698
Electromagnetic simulations of metallic materials using the mapped fourier PSTD algorithm
Authors: Gao Xiang , Mirotznik Mark S. , Prather Dennis W.
Published: February 2005

Previously, the regular Fourier pseudospectral time‐domain (PSTD) algorithm was recognized as mainly applicable to simulations of low‐contrast dielectric materials. In this paper, we discuss the difficulties in simulating high‐contrast and particularly metallic materials using the Fourier PSTD method. To overcome these difficulties, we use a nonuniform grid obtained from a specially designed mapping curve that can reduce the Gibbs phenomenon in the mapped space. The convergence property of this technique is then examined. We show dramatic improvements compared with regular Fourier PSTD and finite‐difference time‐domain (FDTD) methods on a uniform grid. As an example application, we apply our method to the modeling of the 2D scattering of a chrome‐projection lithography mask. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 569–575, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20699
Enhanced microstrip coupled‐line bandpass filter by means of EBG structures on the middle layer for spurious suppression
Authors: Weng Min‐Hung , Huang Tsung‐Hui , Hung Cheng‐Yuan
Published: February 2005

In this paper, a microstrip parallel‐coupled bandpass filter based on electromagnetic bandgap (EBG) structures to achieve spurious suppression is presented. The EBG loops of the middle layer add an extra stopband‐rejection mode to the 2nd and 3rd harmonics of the filter with attenuation losses of over than −30 dB, without affecting the center frequency and insertion loss of the originally designed filter. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 575–577, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20700
Mutual coupling in finite microstrip patch arrays
Authors: Xi Y. P. , Fang D. G. , Sun Y. X. , Chow Y. L.
Published: February 2005

Knowledge of the mutual interaction between antenna elements is of great importance for the design of practical antenna arrays, especially for phased arrays and ultra‐low side‐lobe arrays. In this paper, to fully take into consideration the mutual coupling in an array environment, a mutual‐impedance formula based on synthetic asymptote and variable separation [1] is used in an existing correction procedure in order to speed up the computation for microstrip patch arrays. The simulation results show that the performance of the finite microstrip patch arrays can be successfully predicted. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 577–581, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20701
NMR study of quinolizidine alkaloids: relative configurations, conformations
Authors: Le Phuong Mai , Martin Marie‐Thérèse , Van Hung Nguyen , Guénard Daniel , Sévenet Thierry , Platzer Nicole
Published: February 2005

Extracts of fruits and leaves of Connarus paniculatus afford six quinolizidine alkaloids which were identified as piptanthine, 18‐epipiptanthine, ormosanine, homoormosanine, podopetaline (monohydrochloride) and homopodopetaline on the basis of high‐field NMR studies. 1D and 2D NMR experiments provide complete assignments of the 1H and 13C spectra. In conjunction with detection of nuclear Overhauser effects (NOESY), these results allow detailed structure characterization including determination of relative configurations for the chiral sites and conformational analysis. Exchange phenomena involving nitrogen inversion were detected. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis and second‐order nonlinear optical properties of multifunctional polysiloxanes with sulfonyl‐based chromophores
Authors: Hua Jianli , Li Zhen , Long Kai , Qin Jingui , Li Shaojun , Ye Cheng , Lu Zuhong
Published: February 2005

Two new polysiloxanes (P1 and P2) with a high density of sulfonyl‐based chromophores were prepared by a new two‐step method. Poly[methyl‐3‐(9‐carbazolyl)propyl siloxane] was partially formulated by the standard Vilsmeier reaction, and formyl groups of high reactivity were condensed with cyanoacetylated chromophores; this yielded polysiloxanes P1 and P2 in almost complete conversions. Their structures were verified with 1H NMR, IR, and ultraviolet–visible spectra. P1 and P2 exhibited good solubility in common organic solvents and were thermally stable. The maximum absorptions appeared at about 452 and 390 nm for P1 and P2, respectively, in tetrahydrofuran; they were blueshifted about 42 and 8 nm, respectively, in comparison with those of the corresponding chromophores with a nitro acceptor and resulted in a wider transparency window. The P1 values of the nonlinear optical coefficient (d33), measured by in situ second harmonic generation, was 16.2 pm/V. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1317–1324, 2005
Cationic organoiron polyelectrolyte three‐arm stars
Authors: Abd‐El‐Aziz Alaa S. , Carruthers Sarrah A. , Todd Erin K. , Afifi Tarek H. , Gavina Jennilee M. A.
Published: February 2005

With nucleophilic aromatic substitution and ester condensation reactions, several new first‐generation dendrimers and star‐shaped molecules containing cationic cyclopentadienyl iron moieties were prepared. Although the solubility of the organoiron star‐shaped molecules with ether bridges in polar solvents was found to decrease with an increase in the size of the molecule, the addition of ester linkages resulted in a sharp decrease in the solubility, regardless of the size. The thermal behavior of these molecules was examined with differential scanning calorimetry and thermogravimetric analysis. The glass‐transition temperatures (Tg's) of these star‐shaped molecules ranged from 123 to 170 °C. However, the addition of the ester functionality allowed for an increase in the Tg's to 151–194 °C. The star‐shaped molecules were thermally stable up to 200 °C, above which a loss of the cationic cyclopentadienyl iron moieties occurred. Degradation of the ester chains started at 321 °C, and degradation of the ether chains started at 408 °C. Electrochemical studies of the ether star‐shaped molecules showed a reduction of the 18‐electron iron centers to 19‐electron centers. This redox system was reversible at low temperatures, whereas it was irreversible at room temperature. Moreover, an increase in the number of metal moieties caused an overlap and broadening of the redox wave. Viscosity studies showed a polyelectrolyte effect for the organoiron star‐shaped molecules. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1382–1396, 2005
Economic and herbicide use impacts of glyphosate‐resistant crops
Authors: Gianessi Leonard P
Published: February 2005

More than 95% of United States maize, cotton, soybean and sugarbeet acres are treated with herbicides for weed control. These products are used to improve the economic profitability of crop production for farmers. Since their introduction in 1996, over 75 million acres of genetically engineered glyphosate‐resistant crops have been planted, making up 80% of soybean acres and 70% of cotton acres in the USA. These genetically engineered crops have been adopted by farmers because they are perceived to offer greater economic benefits than conventional crop and herbicide programs. The adoption of glyphosate‐resistant crops has saved US farmers $1.2 billion associated with the costs of conventional herbicide purchases, application, tillage and hand weeding. With the adoption of glyphosate‐resistant sugarbeets on currently planted sugarbeet acres, US growers could potentially save an additional $93 million. The adoption of glyphosate‐resistant crops by US agriculture has reduced herbicide use by 37.5 million lbs, although the adoption of glyphosate‐resistant sugarbeets would dampen this reduction by 1 million lbs. Copyright © 2005 Society of Chemical Industry
Liquid-Handling Robotic Workstations for Functional Genomics
Authors: Lorenz Matthias G. O.
Published: February 2005

More and more functional genomics laboratories are willing to invest in robotic workstations due to the higher throughput liquid-handling intensive nature of the work. In this report, the features of robotic workstations important for functional genomics are discussed. Workstations for functional genomics are useful for replication of clone sets, PCR and sequencing set-up and clean-up, hit picking, gel loading, and nucleic acid purification procedures. Workstations not only increase throughput, but also ensure that assay steps are performed consistently, human error- and learning curve-free from run to run. Workstations fit on a laboratory bench and may have several robotic arms in different configurations. Available configurations include grippers and single-, oligo-, or multi-probe heads, with uniform or independent spanning, and liquid-level detection or tracking options. Most hardware and software packages can be designed for integration with other automated devices, building towards a fully automated system.
Integration of an Opto-Mechanical Mass Sensor with a Powder- Dispensing Device for Microgram Sensitivity
Authors: Cherng Jean-Pei Jeanie , Gonzalez-Zugasti Javier , Kane Nathan R. , Cima Michael J. , Lemmo Anthony V.
Published: February 2005

A novel sensor has been developed to measure the mass of very small amounts of powder that are manipulated by a unique dispensing device. The sensor quantifies the mass of the powder by detecting the change in resonant frequency of the dispensing device before and after the powder is released. The measured frequency shift is then correlated to the powder mass by a calibration curve. This paper presents the design and performance of the mass sensor tested with common pharmaceutical compounds. The sensor was demonstrated to measure powder mass between 30 to 70 μg with less than 2.9% standard deviation of error.
Advancing Parallel Solution Phase Library Synthesis through Efficient Purification, Quantitation, and Characterization Techniques
Authors: Noonan Jeffrey W. , Brown Joe N. , Kershaw Mark T. , Lew Richard M. , Lombardi Christopher J. , Mach Christopher J. , Shaw Kenneth R. , Sogge Scott R. , Virdee Susan
Published: February 2005

Historically, access to large numbers of quality compounds in a parallel solution phase library synthesis environment has been hindered by the inability to rapidly purify, quantitate, and characterize solution phase libraries in an efficient and cost effective manner. At Neurogen Corporation, we overcome these barriers by employing a collection of novel workstations in the High Speed Synthesis (HSS) group that are tightly integrated into our informatics architecture. This approach supports rapid and reliable instrument operation, rapid interpretation of results, and decision analysis for further downstream tasks and processing. Our movement of library samples and data from workstation to workstation facilitates synthesis throughput and the utilization of equipment, creating a cost-effective library production environment.
Evaluation of an Automated Cell Culture Incubator: The Autocell 200
Authors: Triaud F. , Darmon C. , Cariou Y. , Ferry N. , Le Neel T. , Clenet D. H. , Morin D. , Fraudeau C. , Blanchard D. , Truchaud A.
Published: February 2005

We evaluated the benefits of automation on the technical performance of a new automated cell culture incubator, the Autocell 200®, developed by Jouan SA. In addition, we assessed the potential interference of the embedded mechanical parts on cell culture growth. We measured a throughput of 150 plates loaded per hour, and 120 plates unloaded per hour, which is compatible with an external robotic handler. The mean time of robotic gate opening was 7 s. The gate pathway minimized climate disturbances inside the incubator. For CO2, we used a delay between opening events of 1 min. Biological assay results did not demonstrate a significant difference between the automated incubator and a traditional manual incubator, but we concluded that automation using the Autocell 200® could provide meaningful benefits for cell culture.
PERIODIC PEAKONS AND CALOGERO–FRANÇOISE FLOWS
Authors: Beals R. , Sattinger D. H. , Szmigielski J.
Published: February 2005

It has long been known that a number of periodic completely integrable systems are associated to hyperelliptic curves, for which the Abel map linearizes the flow (at least in part). We show that this is true for a relatively recent such system: the periodic discrete reduction of the shallow water equation derived by Camassa and Holm. The associated spectral problem has the same form and evolves in the same way as the spectral problem for a family of finite-dimensional non-periodic Hamiltonian flows introduced by Calogero and Françoise. We adapt the Weyl function method used earlier by us to solve the peakon problem to give an explicit solution to both the periodic discrete Camassa–Holm system and the (non-periodic) Calogero–Françoise system in terms of theta functions.

AMS 2000 Mathematics subject classification: Primary 35Q51; 37J35; 35Q53
An empirical‐stochastic, event‐based program for simulating inflow from a tributary network: Framework and application to the Sacramento River basin, California
Authors: Singer Michael Bliss , Dunne Thomas
Published: February 2005

A stochastic streamflow program was developed to simulate inflow to a large river from a network of gauged tributaries. The program uses historical streamflow data from major tributary gauges near their confluence with the main stem and combines them stochastically to represent spatial and temporal patterns in flood events. It incorporates seasonality, event basis, and correlation in flood occurrence and flood peak magnitude between basins. The program produces synchronous tributary inflow hydrographs, which when combined and routed, reproduce observed main stem hydrograph characteristics, including peak, volume, shape, duration, and timing. Verification of the program is demonstrated using daily streamflow data from primary tributary and main stem gauges in the Sacramento River basin, California. The program is applied to simulating flow at ungauged main stem locations, assessing risk in fluvial systems, and detecting bed level change.
Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction
Authors: Smith Richard L. , Böhlke John Karl , Garabedian Stephen P. , Revesz Kinga M. , Yoshinari Tadashi
Published: February 2005

Denitrification was measured within a nitrate‐contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 μM) and nitrous oxide (up to 143 μM) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small‐scale (15–24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down‐gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one‐dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036–0.047 μmol N (L aquifer)−1 d−1) was faster than the subsequent denitrification steps (0.013–0.016 μmol N (L aquifer)−1 d−1 for nitrous oxide and 0.013–0.020 μmol N (L aquifer)−1 d−1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down‐gradient before being completely consumed.
Impaired Protein Maturation of the Conjugate Export Pump Multidrug Resistance Protein 2 As A Consequence of A Deletion Mutation in Dubin–Johnson Syndrome
Authors: Keitel Verena , Kartenbeck Jürgen , Nies Anne T. , Spring Herbert , Brom Manuela , Keppler Dietrich
Published: February 2005

The Dubin–Johnson syndrome is an inherited disorder characterized by conjugated hyperbilirubinemia. The deficient hepatobiliary transport of anionic conjugates is caused by the absence of a functional multidrug–resistance protein 2 (MRP2, symbol ABCC2) from the apical (canalicular) membrane of hepatocytes. Mechanisms underlying this deficiency may include rapid degradation of mutatedMRP2messenger RNA (mRNA) or impaired MRP2 protein maturation and trafficking. We investigated the consequences of the mutation MRP2Δ(R,M), which leads to the loss of 2 amino acids from the second ATP–binding domain of MRP2. The MRP2Δ(R,M) mutation is associated with the absence of the MRP2 glycoprotein from the apical membrane of hepatocytes. Transfection of mutatedMRP2complementary DNA (cDNA) led to an MRP2Δ(R,M) protein that was only core glycosylated, sensitive to endoglycosidase H digestion, and located in the endoplasmic reticulum (ER) of transfected HEK293 and HepG2 cells. This indicated that deletion of Arg1392 and Met1393 leads to impaired maturation and trafficking of the protein from the ER to the Golgi complex. Inhibition of proteasome function resulted in a paranuclear accumulation of the MRP2Δ(R,M) protein, suggesting that proteasomes are involved in the degradation of the mutant protein. This is the first mutation in Dubin–Johnson syndrome shown to cause deficient MRP2 maturation and impaired sorting of this glycoprotein to the apical membrane.
Response to “Comment on ‘Excitations in photoactive molecules from quantum Monte Carlo’ ” [J. Chem. Phys. 122, 087101 (2005)]
Authors: Filippi Claudia , Buda Francesco
Published: February 2005

We find that regions of the excited state potential energy surface of formaldimine, which are accessible from the Franck-Condon configuration, are incorrectly described by the restricted open-shell Kohn-Sham (ROKS) approach. In these regions, the deviations of the ROKS energies from the time-dependent density functional theory results are not a simple shift. Contrary to what is argued in the Comment by Doltsinis and Fink [J. Chem. Phys.XX, XXX (2004)], these differences can play a role in the excited state molecular dynamics of formaldimine at finite temperature.
Ionic microgels as model systems for colloids with an ultrasoft electrosteric repulsion: Structure and thermodynamics
Authors: Gottwald D. , Likos C. N. , Kahl G. , Löwen H.
Published: February 2005

We present a theoretical analysis of the structural properties and phase behavior of spherical, loosely cross-linked ionic microgels that possess a low monomer concentration. The analysis is based on the recently derived effective interaction potential between such particles [A. R. Denton, Phys. Rev. E 67, 011804 (2003)]. By employing standard tools from the theory of the liquid state, we quantitatively analyze the pair correlations in the fluid and find anomalous behavior above the overlap concentration, similar to the cases of star-branched neutral and charged polymers. We also employ an evolutionary algorithm in order to predict the crystalline phases of the system without any a priori assumptions regarding their symmetry class. A very rich phase diagram is obtained, featuring two reentrant melting transitions and a number of unusual crystal structures. At high densities, both the Hansen–Verlet freezing criterion [J.-P. Hansen and L. Verlet, Phys. Rev. 184, 151 (1969)] and the Lindemann melting criterion [F. A. Lindemann, Phys. Z. 11, 609 (1910)] lose their validity. The topology of the phase diagram is altered when the steric interactions between the polymer segments become strong enough, in which case the lower-density reentrant melting disappears and the region of stability of the fluid is split into two disconnected domains, separated by intervening fcc and bcc regions.
Pressure dependence of viscosity
Authors: Schmelzer Jürn W. P. , Zanotto Edgar D. , Fokin Vladimir M.
Published: February 2005

We reanalyze the pressure dependence of viscosity of liquids of constant composition under isothermal conditions. Based exclusively on very general considerations concerning the relationship between viscosity and “free volume,” we show that, at moderate values of pressure, viscosity increases, as a rule, with increasing pressure, provided the liquid is in stable or metastable (undercooled) equilibrium states. However, even if the behavior of the viscosity is governed by free volume effects, deviations from a positive pressure dependence are possible, when the liquid’s thermal expansion coefficient is negative. We derive an equation that allows one to quantitatively determine the pressure dependence of viscosity, which requires, in the simplest case, only the knowledge of the temperature dependence of viscosity at constant pressure, the thermal expansion coefficient, and the isothermal compressibility of the liquid. As an example, the negative pressure dependence of water in the range of temperatures 0–4°C and of several silicate liquids, such as albite, jadeite, dacite, basalts, etc., could be explained in such a way. Other glass-forming liquids initially (for moderate pressures) show a positive pressure dependence of viscosity that changes to a negative one when subjected to high (∼GPa) isostatic pressure. A detailed analysis of water and already mentioned silicate melts at GPa pressures shows that, in addition to free volume effects, other pressure induced structural transformations may have to be accounted for in a variety of cases. By this reason, the theoretical analysis is extended (i) in order to describe the pressure dependence of viscosity for systems that are in frozen-in thermodynamic nonequilibrium states (glasses, i.e., undercooled liquids below the glass transition temperature Tg) and (ii) to systems which undergo, in addition to variations of the free volume, pressure induced changes of other structural parameters. In such cases a decrease of viscosity with increasing pressure may occur, in principle, even if the thermal expansion coefficient is positive. In this way, the present analysis grants a general tool to estimate the pressure dependence of viscosity and supposedly settles the controversy in the current literature.
Fabrication of submicron size electrode via nonetching method for metal ion detection
Authors: Kim Younghun , Choi Inhee , Kang Sung Koo , Lee Jeongjin , Yi Jongheop
Published: February 2005

A metal ion detector with a submicron size electrode was fabricated by atomic force microscopy lithography using a pre-programmed voltage and a nonetching method. The square frame of the mesa pattern was functionalized by (aminopropyl)triethoxysilane for the metal ion detection, and the remaining portion was used as an electrode by the self-assembly of (3-mercaptopropyl)trimethoxysialne for Au metal deposition. In this module, no metal lining or lead line was required, because the conductive tip (mobile electrode) was in direct contact with the gold-deposited mesa portion (fixed electrode). The conductance changed with the quantity of adsorbed copper ions, due to electron tunneling between the mobile and surface electrodes.
Electrochemical control and selection of the structural and magnetic properties of cobalt nanowires
Authors: Darques M. , Piraux L. , Encinas A. , Bayle-Guillemaud P. , Popa A. , Ebels U.
Published: February 2005

In this letter we present a convenient way of controlling the direction of the uniaxial magnetocrystalline anisotropy in arrays of electrodeposited hcp Co nanowires. Combining electron microscopy and ferromagnetic resonance measurements, it is shown that using an appropriate pH of the electrolytic solution, the hcp c axis can be oriented parallel or perpendicular to the wires axes simply by changing the deposition current density or deposition rate. This reorientation of the c axis leads to a drastic change in overall magnetic anisotropy as the crystal anisotropy either competes for perpendicular oriented c axis or adds to the shape anisotropy for parallel oriented c axis.
Efficient polarized injection luminescence in forward-biased ferromagnetic-semiconductor junctions at low spin polarization of current
Authors: Bratkovsky A. M. , Osipov V. V.
Published: February 2005

We consider electron tunneling from a nonmagnetic n-type semiconductor (n-S) into a ferromagnet (FM) through a very thin forward-biased Schottky barrier resulting in efficient extraction of electron spin from a thin n-S layer near FM-S interface at low spin polarization of the current. We show that this effect can be used for an efficient polarization radiation source in a heterostructure where the accumulated spin-polarized electrons are injected from n-S and recombine with holes in a quantum well. The radiation polarization depends on a bias voltage applied to the FM-S junction.
Effect of nitrogen on gain and efficiency in InGaAsN quantum-well lasers
Authors: Palmer D. J. , Smowton P. M. , Blood P. , Yeh Jeng-Ya , Mawst L. J. , Tansu Nelson
Published: February 2005

We compare the gain and radiative efficiency characteristics of an InGaAsN and an InGaAs laser structure where the devices are identical except for the nitrogen content and emission wavelength. We find that the inclusion of nitrogen has little impact on the gain spectra except for the required shift to longer wavelength and that the intrinsic gain-radiative current characteristics may be slightly better for the nitrogen-containing materials. The radiative efficency is reduced by a factor of 4 in the samples containing nitrogen due to increased nonradiative recombination.
The Structure of Sensory Events and the Accuracy of Time Judgments
Authors: Grondin Simon , Roussel Marie-Eve , Gamache Pierre-Luc , Roy Martin , Ouellet Bastien
Published: February 2005

We investigated how does the structure of empty time intervals influence temporal processing. In experiment 1, the intervals to be discriminated were the silent durations marked by two sensory signals, both lasting 10 or 500 ms; these signals were two identical flashes (intramodal: VV), or one visual flash (V) followed by an auditory tone (A) (intermodal: VA). For the range of duration under investigation (standards = 0.2, 0.6, 1, or 1.4 s), the results indicated that both the marker length and sensory mode influenced discrimination, but no interaction between these variables or between one of these variables and standard duration was significant. In experiment 2, we compared, for each of four marker-type conditions (VV, AA, VA, AV; and standard = 1 s), intervals marked by two 10 ms signals with intervals marked by unequal signal length (markers 1 and 2 lasting 10 and 500 ms, or 500 and 10 ms). As in experiment 1, the results revealed significant marker-mode and marker-length effects, but no significant interaction between these variables. Experiment 3 showed that, for the same conditions as in experiment 2, perceived duration is not influenced by marker length and that the variability of interval reproductions does not depend on the perceived duration of intervals. The results are discussed in the light of a single-clock hypothesis: marker-length and marker-mode effects are presented as being non-temporal sources of variability associated mainly with sensory and memory processes.
Predictability and the Dynamics of Position Processing in the Flash-Lag Effect
Authors: Vreven Dawn , Verghese Preeti
Published: February 2005

Several models have been proposed to account for the flash-lag effect. One criterion for evaluating alternative models is to consider the separate effects of motion predictability and flash predictability. We first established that flash predictability has an impact on the size of the perceived spatial offset in the flash-lag illusion. We then examined motion predictability by varying the consistency of the motion trajectory. Both manipulations affected the magnitude of the flash-lag illusion. These outcomes suggest that the perception of position is a dynamic process that can be modulated by explicit cues in advance of the flash and by the temporal integration of position information over a consistent motion trajectory. A complete explanation of the flash-lag effect must specify how flash predictability and motion predictability modulate position-processing mechanisms.
Reduced response of insecticide-resistant aphids and attraction of parasitoids to aphid alarm pheromone; a potential fitness trade-off
Authors: Foster S.P. , Denholm I. , Thompson R. , Poppy G.M. , Powell W.
Published: February 2005

Response to the alarm pheromone, (E)-β-farnesene, produced by many species of aphids, was assessed in laboratory bioassays using an aphid pest, Myzus persicae (Sulzer), and its primary endoparasitoid, Diaeretiella rapae (McIntosh). This was done in three separate studies, the first investigating responses of a large number of M. persicae clones carrying different combinations of metabolic (carboxylesterase) and target site (kdr) insecticide resistance mechanisms, and the other two investigating the responses of young virgin female adult parasitoids. In M. persicae, both insecticide resistance mechanisms were associated with reduced repellence suggesting that each has a pleiotropic effect on aphid behaviour. In contrast, D. rapae females were attracted to the alarm pheromone source. The implications of this apparent fitness trade-off for the evolution and dynamics of insecticide resistance, and the potential for using beneficial insects to combat resistance development are discussed.
Analysis of spatial patterns at a geographical scale over north-western Europe from point-referenced aphid count data
Authors: Cocu N. , Conrad K. , Harrington R. , Rounsevell M.D.A.
Published: February 2005

The spatial analysis by distance indices (SADIE) technique was developed to evaluate the spatial pattern of point-referenced count data as well as the spatial association between two sets of data sharing the same point locations. This paper presents an analysis of spatial patterns in aphid count data and the association of these data with climate across north-west Europe. The paper tests the applicability of the technique to large geographical areas. Aggregation and cluster indices were calculated for the total annual abundance of the peach–potato aphid Myzus persicae (Sulzer) and for the annual mean rainfall and temperature at aphid monitoring sites. Association indices demonstrated the stability in time of aphid spatial structures and the correlation between aphid density and climate patterns. Groups of relatively large numbers of aphids, termed patches, and groups of relatively small numbers of aphids, termed gaps, were located and their mean size estimated. The aphid patterns were quite stable in time and the spatial patterns of temperature and rainfall were weakly associated with M. persicae annual abundance. Similarities were observed between the results of SADIE and those from the more widely used technique of spatial autocorrelation (SAC). However, the SADIE association index has the advantage of quantifying the possible associations between aphid data and the factors that determine population distribution. Thus, high temperature and low rainfall were identified as environmental factors that were positively associated with aphid abundance across north-west Europe.
Inverse association between body mass and frequency of milk consumption in children
Authors: Barba Gianvincenzo , Troiano Ersilia , Russo Paola , Venezia Antonella , Siani Alfonso
Published: February 2005

Recent studies have shown an inverse association between the level of dietary Ca, particularly from dairy sources, and body weight in adults; there is, however, a paucity of data regarding this relationship in children. We therefore investigated this issue in 1087 children who underwent body weight and height measurement during a survey on childhood obesity. Lifestyle and dietary habits were investigated by a questionnaire. After excluding children who were following a dietary regimen for any reason, 884 children (M:F 451:433; age 7·5 (sd 2·1) years) were selected. Milk consumption was pooled into four frequency categories: poor (≤1/week; n 125), moderate (>1 but ≤5–6/week; n 133), regular (1/d; n 408) and high (≥2/d; n 218). The frequency of consumption of milk was inversely and significantly associated (t=–2·64, P=0·003) with age- and sex-specific BMI z-scores by linear regression analysis, controlling for sex, age, physical activity, birth weight and parental overweight and education. The statistical association remained significant (t=–2·831, P=0·005) after the inclusion of children consuming only skimmed milk (n 91). Milk consumption was still significantly and inversely associated with BMI z score (t=–2·791, P=0·005) in the whole-milk consumers when controlling for age and the frequency of consumption of various foods; this association was no longer significant (P=0·21) when children consuming skimmed milk were included in the analysis. This is the first report showing a significant inverse association between frequency of milk consumption and body mass in children. Regardless of the mechanisms involved, our results might encourage further research on this issue and might have important implications for the prevention of obesity.
Retinoid metabolism in the rat small intestine
Authors: Thomas Simmy , Prabhu Ramamoorthy , Balasubramanian Kunissery A.
Published: February 2005

Vitamin A (retinol) is essential for epithelial cell growth, differentiation and proliferation. The absorption of retinol occurs in the small intestine, and the metabolism of this vitamin is not well studied in this organ. The intestinal epithelium has a high rate of cell proliferation and differentiation, and the present study looked at the level of retinoids and metabolizing enzymes involved in their interconversion along the villus–crypt axis under normal conditions. Intestine was removed from control rats, and enterocytes at various stages of maturation and differentiation were quantified by the metal chelation method. Using HPLC, various retinoid concentrations in the cell homogenate and the metabolizing enzymes in the cytosol were quantified. The proliferating crypt cells were found to have a higher level of retinoic acid as well as of the enzymes involved in its formation, such as retinaldehyde oxidase and retinol dehydrogenase, compared with the villus cells, suggesting a possible role for this compound in intestinal epithelial cell proliferation and differentiation. The high level of retinol and high retinaldehyde reductase activity in the villus cells suggest the important role played by this enzyme in the conversion of dietary β-carotene to retinol via retinaldehyde. In summary, this study has given for the first time a detailed analysis of the retinoid levels and metabolizing enzymes in different cell populations in the rat small intestinal epithelium.
CsmA, a Class V Chitin Synthase with a Myosin Motor-like Domain, Is Localized through Direct Interaction with the Actin Cytoskeleton inAspergillus nidulans
Authors: Takeshita Norio , Ohta Akinori , Horiuchi Hiroyuki
Published: February 2005

One of the essential features of fungal morphogenesis is the polarized synthesis of cell wall components such as chitin. The actin cytoskeleton provides the structural basis for cell polarity in Aspergillus nidulans, as well as in most other eukaryotes. A class V chitin synthase, CsmA, which contains a myosin motor-like domain (MMD), is conserved among most filamentous fungi. The ΔcsmA null mutant showed remarkable abnormalities with respect to cell wall integrity and the establishment of polarity. In this study, we demonstrated that CsmA tagged with 9× HA epitopes localized near actin structures at the hyphal tips and septation sites and that its MMD was able to bind to actin. Characterization of mutants bearing a point mutation or deletion in the MMD suggests that the interaction between the MMD and actin is not only necessary for the proper localization of CsmA, but also for CsmA function. Thus, the finding of a direct interaction between the chitin synthase and the actin cytoskeleton provides new insight into the mechanisms of polarized cell wall synthesis and fungal morphogenesis.
Developmental Activation of the Rb–E2F Pathway and Establishment of Cell Cycle-regulated Cyclin-dependent Kinase Activity during Embryonic Stem Cell Differentiation
Authors: White Josephine , Stead Elaine , Faast Renate , Conn Simon , Cartwright Peter , Dalton Stephen
Published: February 2005

To understand cell cycle control mechanisms in early development and how they change during differentiation, we used embryonic stem cells to model embryonic events. Our results demonstrate that as pluripotent cells differentiate, the length of G1phase increases substantially. At the molecular level, this is associated with a significant change in the size of active cyclin-dependent kinase (Cdk) complexes, the establishment of cell cycle-regulated Cdk2 activity and the activation of a functional Rb–E2F pathway. The switch from constitutive to cell cycle-dependent Cdk2 activity coincides with temporal changes in cyclin A2 and E1 protein levels during the cell cycle. Transcriptional mechanisms underpin the down-regulation of cyclin levels and the establishment of their periodicity during differentiation. As pluripotent cells differentiate and pRb/p107 kinase activities become cell cycle dependent, the E2F–pRb pathway is activated and imposes cell cycle-regulated transcriptional control on E2F target genes, such as cyclin E1. These results suggest the existence of a feedback loop where Cdk2 controls its own activity through regulation of cyclin E1 transcription. Changes in rates of cell division, cell cycle structure and the establishment of cell cycle-regulated Cdk2 activity can therefore be explained by activation of the E2F–pRb pathway.
Road Fund Tax Compliance: An Analysis of Enhancement Strategies
Authors: Eger Robert J. , Hackbart Merl M.
Published: February 2005

This paper focuses on a continuing concern of tax administrators, which is the selection of the most efficient means of ensuring tax law compliance. The selection of the most efficient enforcement techniques and strategies can reduce compliance costs, enhance revenues, and support a culture of voluntary tax law compliance. This paper reports on a national study of state compliance efforts regarding state motor fuel taxes and motor vehicle registration fees, which are major sources of revenue for state Road Funds. Because of special complexities and unique interstate cooperation efforts, the compliance efficiency assessment focuses on the commercial carrier taxpayer group.
The life cycle of Henneguya nuesslini Schuberg & Schröder, 1905 (Myxozoa) involves a triactinomyxon‐type actinospore
Authors: Kallert D M , Eszterbauer E , El‐Matbouli M , Erséus C , Haas W
Published: February 2005

The life cycle of the histozoic myxozoan parasite Henneguya nuesslini was investigated in two salmonid host species. Naïve brown trout, Salmo trutta, and brook trout, Salvelinus fontinalis, were experimentally infected in two trials by triactinomyxon type actinospores from naturally infected Tubifex tubifex. In exposed common carp, Cyprinus carpio, no myxospore production was detected. The parasite formed cysts with mature myxospores in the connective tissue of the fish 102 days post‐exposure. The morphology of both actinosporean and myxosporean stages was described by light microscopy and a 1417‐bp fragment of the 18S rDNA gene was sequenced. Sequence analysis confirmed the absolute congruence of the two developmental stages and assisted in determining species identity. Host range, tissue specificity and myxospore measurements provided sufficiently distinctive features to confirm species validity and were thus crucial for identification. The triactinomyxon spores had 16 secondary germ cells, unique dimensions, a very opaque sporoplasm matrix and three conspicuously protruding, pyriform polar capsules. This is the first record of a Henneguya sp. life cycle with a triactinomyxon‐type actinospore, which suggests a close relationship with the Myxobolus group and a polyphyletic origin of the genus Henneguya.