bluuebunny/crossref_metadata_2025 huggingface dataset:
Unusual properties of the prespore‐specific enzyme, UDPgalactose:polysaccharide galactosyl transferase, of Dictyostelium discoideum
Authors: Nakahara Yasuo , Okamoto Koji
Published: November 2004

UDPgalactose:polysaccharide galactosyl‐transferase is the enzyme that is specifically localized in prespore cells of Dictyostelium discoideum and its activity sharply changes in response to differentiation and dedifferentiation. To clarify the nature of this enzyme, we first developed an improved assay method for the enzyme, and by using this method, we partially purified the enzyme through DEAE‐sepharose, phenyl‐sepharose and ATP‐sepharose chromatography. The apparent molecular mass of the enzyme was ca. 200 KDa (by non‐denaturing polyacrylamide gel gradient analysis) and the isoelectric point was around pH 7. The enzyme exhibited a hitherto undescribed property, that is the reaction proceeds faster at 0 °C than at 21 °C, with a smaller Km value and an unchanged Vmax value. This low‐temperature resistant property of the enzyme is consistent with the previous observation (Maeda 1984, J. Cell Sci. 69, 159–165) that prespore differentiation is favored at low temperatures. The reaction appears to proceed in a double displacement manner. ATP reversibly inhibited the enzyme with a Ki value of 2 mM, suggesting the possibility that ATP regulates its activity in vivo. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Species identification and comparative molecular and physiological analysis of Candida zemplinina and Candida stellata
Authors: Sipiczki Matthias
Published: November 2004

Strains of the recently described yeast species Candida zemplinina have been identified in botrytized grapes and musts in geographically distant areas. C. zemplinina is almost indistinguishable from C. stellata, another yeast common in fermenting botrytized wines. In this work a specific PCR‐RFLP method is described for the differentiation of the two species. It is also shown that both species have three chromosomes, display chromosomal length polymorphism, and C. zemplinina has a smaller genome. C. zemplinina is acidogenic, highly osmotolerant, grows much better than C. stellata in the presence of ethanol and at low temperatures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative evaluation of the Desoxycholate Agar Nissui Food Stamp and swab methods for estimating coliform organisms in poultry processing plants after cleaning in Japan
Authors: Kodaka Hidemasa , Goto Koichi , Umeki Kyuichi , Nishina Tokuhiro , Tokumaru Yoshikazu , Shinagawa Kunihiro , Konuma Hirotaka
Published: November 2004

Bacterial control in poultry processing plants is very important, but the swab method for estimating bacterial contamination is somewhat troublesome in routine work. We compared the Desoxycholate Agar Nissui Food Stamp (DA‐NFS) based on the agar contact method with the swab method to estimate coliform organisms from various equipments in four poultry processing plants after cleaning. Overall 104 surfaces for coliform organisms were evaluated. The results from 98 (94.2%) surfaces for coliform organisms were equivalent by the DA‐NFS and swab methods and there were no significant differences between two methods (P > 0.05). The correlation coefficient between the DA‐NFS and swab methods was 0.91. We conclude that the DA‐NFS could be useful for routine coliform organisms examination in poultry processing plants after cleaning in Japan. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Revivals for a two-level atom in a free space under bichromatic excitation
Authors: Kilin S Ya , Karlovich T B
Published: November 2004

A two level atom in a free space excited by a bichromatic symmetrical field is shown to display the property of revivals for relatively small frequency detunings and a large driving field amplitude.
Full vectorial finite element modal solution of curved optical
waveguides
Authors: Obayya S S A , Rahman B M A , Grattan K T V
Published: November 2004

Using a full vectorial finite element based beam
propagation method combined with the imaginary axis propagation
technique, the accurate calculation of the full vectorial leaky
modes of a curved optical waveguide is addressed. The numerical
precision of the proposed modal solution approach is supported by
excellent agreement with published results obtained using other
rigorous full vectorial approaches.
Functional Thin Polymer Films at High Pressure
Authors: Baba Akira , Kleideiter Gerd , Jakob Thomas , Knoll Wolfgang
Published: November 2004

Summary: A new thin‐film characterization setup was created based on the combination of a surface plasmon spectrometer with an electrochemical cell operated under high pressure of up to 200 MPa and at temperatures up to 120 °C. The examples given to document its performance include photoisomerization studies with poly(methyl methacrylate) (PMMA) films partly derivatized with disperse red (DR1), as well as, a preliminary account of the electropolymerization of EDOT under pressure and the assessment of the redox properties of the resulting thin PEDOT films.

Sketch of the high‐pressure electrochemistry surface plasmon cell.

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Sketch of the high‐pressure electrochemistry surface plasmon cell.
Highly Active Yttrium and Lanthanide Catalysts for Polymerization of Isobutene
Authors: Touchard Virginie , Spitz Roger , Boisson Christophe , Llauro Marie‐France
Published: November 2004

Summary: Highly active catalysts for isobutene polymerization were obtained by mixing silica with yttrium or lanthanide chloride salts. Solid catalysts were investigated using transmission electron microscopy and Raman spectroscopy. Both Lewis and Brönsted acid sites were detected on the surface. Polymers of low and medium molecular weight were prepared and their unsaturated chain ends were fully investigated by one‐ and two‐dimensional NMR analyses.

13C NMR spectrum of a low‐molecular‐weight polyisobutene (high‐field resonance region).

image

13C NMR spectrum of a low‐molecular‐weight polyisobutene (high‐field resonance region).
Non‐linear analysis of shells with arbitrary evolving cracks using XFEM
Authors: Areias Pedro M. A. , Belytschko Ted
Published: November 2004

A new formulation and numerical procedures are developed for the analysis of arbitrary crack propagation in shells using the extended finite element method. The method is valid for completely non‐linear problems. Through‐the‐thickness cracks in sandwich shells are considered. An exact shell kinematics is presented, and a new enrichment of the rotation field is proposed which satisfies the director inextensibility condition. To avoid locking, an enhanced strain formulation is proposed for the 4‐node cracked shell element. A finite strain plane stress constitutive model based on the logarithmic corotational rate is employed. A cohesive zone model is introduced which embodies the special characteristics of the shell kinematics. Stress intensity factors are calculated for selected problems and crack propagation problems are solved. Copyright © 2004 John Wiley & Sons, Ltd.
Using spectral low rank preconditioners for large electromagnetic calculations
Authors: Duff I. S. , Giraud L. , Langou J. , Martin E.
Published: November 2004

For solving large dense complex linear systems that arise in electromagnetic calculations, we perform experiments using a general purpose spectral low rank update preconditioner in the context of the GMRES method preconditioned by an approximate inverse preconditioner. The goal of the spectral preconditioner is to improve the convergence properties by shifting by one the smallest eigenvalues of the original preconditioned system. Numerical experiments on parallel distributed memory computers are presented to illustrate the efficiency of this technique on large and challenging real‐life industrial problems. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical simulation of granular materials by an improved discrete element method
Authors: Fortin J. , Millet O. , de Saxcé G.
Published: November 2004

In this paper, we present an improved discrete element method based on the non‐smooth contact dynamics and the bi‐potential concept. The energy dissipated during the collisions is taken into account by means of restitution coefficients. The interaction between particles is modelled by Coulomb unilateral contact law with dry friction which is typically non‐associated: during the contact, the sliding vector is not normal to the friction cone. The main feature of our algorithm is to overcome this difficulty by means of the bi‐potential theory. It leads to an easy implement predictor–corrector scheme involving just an orthogonal projection onto the friction cone. Moreover the convergence test is based on an error estimator in constitutive law using the corner stone inequality of the bipotential. Then we present numerical simulations which show the robustness of our algorithm and the various possibilities of the software ‘MULTICOR’ developed with this approach. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and solution properties of poly(methacrylate)s with semipolar structures on the side chains
Authors: Hiwatashi Tomoaki , Hayama Kazuhide , Sawada Yoshiaki , Itoh Takahito
Published: November 2004

Poly{2‐(N,N‐dimethylamino)ethyl methacrylate [poly(DMMA)]}, which was prepared by radical polymerization initiated with dimethyl 2,2‐azobis(2‐methylpropionate), was reacted with hydrogen peroxide, diethyl sulfate, and chloroacetic acid to yield poly[N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)amine N‐oxide] [poly(DMANO)], poly[N‐ethyl‐N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)ammonium ethyl sulfate] [poly(EDMES)], and poly[N,N‐dimethyl‐N‐(2‐methacryloyloxy)ethylammonioacetate] [poly(DMEAA)] as ion‐containing water‐soluble polymers, respectively. The solution properties of these charged polymers were compared via the reduced viscosities of these three charged polymers in aqueous solutions as a function of the concentration. Poly(EDMES) showed typical polyelectrolyte behavior, and the other two polymers [poly(DMANO) and poly(DMEAA)] exhibited antipolyelectrolyte behavior. Furthermore, the antipolyelectrolyte behavior was different for poly(DMANO) and poly(DMEAA); that is, poly(DMANO) was less dependent on small electrolytes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 129–141, 2005
Synthesis of acid‐sensitive latices by ring‐opening metathesis polymerization
Authors: Quémener Damien , Héroguez Valérie , Gnanou Yves
Published: November 2004

This study describes the synthesis of polynorbornene colloidal particles able to release active molecules in response to pH change. Such functionalized polynorbornene latices with surface active molecules have been obtained by ring‐opening metathesis copolymerization in a dichloromethane/ethanol medium in the presence of α‐norbornenyl poly(ethylene oxide) macromonomer. Two different strategies of introduction of the active molecule—either at their periphery or at their core— have been contemplated. The particles have been characterized by both dynamic light scattering and transmission electron microscopy. Their size was found to range from 260 to 600 nm. The release of the active molecules was monitored by UV spectrometry. After 48 h in an appropriate HCl buffer (pH = 3) more than 80% of the initially linked active molecule was released. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 217–229, 2005
Copolymerization kinetics of N‐isopropylacrylamide and diethylene glycol monomethylether monomethacrylate determined by online NMR spectroscopy
Authors: Gramm Stefan , Komber Hartmut , Schmaljohann Dirk
Published: November 2004

The kinetics of the copolymerization of N‐isopropylacrylamide (NiPAAm) and diethylene glycol monomethylether monomethacrylate was followed by online 1H NMR spectroscopy. Two copolymerization reactions were sufficient to evaluate the kinetic data with the Extended‐Kelen–Tüdös method as well as the nonlinear least square method. The copolymerization parameter was determined as rNiPAAm = 0.70 and rDEGMA = 2.0. The higher reactivity of the methacrylate compared to the NiPAAm is in good agreement with other kinetic data of similar systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 142–148, 2005
Incompatibility of metam sodium with halogenated fumigants
Authors: Guo Mingxin , Yates Scott R , Papiernik Sharon K , Zheng Wei
Published: November 2004

Metam sodium (metam) is a widely used soil fumigant. Combined application of metam and other available fumigants is intended to produce synergic pesticidal effects for a broad spectrum of pest control in soil fumigation. This study aimed to test the compatibility of metam with the halogenated fumigants 1,3‐dichloropropene (1,3‐D), chloropicrin, methyl bromide, methyl iodide and propargyl bromide. Halogenated fumigants and metam were spiked simultaneously into organic solvents, water and moist soils, and metam‐induced degradation of these halogenated chemicals was evaluated. In all three media, the halogenated fumigants were incompatible with metam and degraded via rapid chemical reactions. The degradation rate varied with halogenated fumigant species and increased as the amount of metam present was increased. In moist soil, 15–95% of the halogenated fumigants were decomposed within 72 h by metam at a 1:1 molar ratio. Combined application of Telone C‐35 (62.5% 1,3‐D + 35% chloropicrin) at 265 mg kg−1 and Vapam (42% metam) at 567 mg kg−1 in soil resulted in complete disappearance of the applied chloropicrin and 20–38% of the 1,3‐D within 8 h. The results suggest that simultaneous application of halogenated fumigants and metam at the same soil depth will not maximize pest control. In practice, sequential treatment of soil or application at different soil depths is recommended when these two types of fumigants are used in combination. Copyright © 2004 Society of Chemical Industry
Conducting portions of GLP studies in GMP laboratories
Authors: Roberge Kristin
Published: November 2004

Good manufacturing practice (GMP) analytical laboratories are routinely used to conduct stability and concentration analyses of dose formulations for non‐clinical laboratory studies. There are many reasons for using GMP analytical laboratories including saving the overhead required for two or more separate laboratories. There are also several challenges that need to be addressed, however, to make this a successful transition. This paper discusses the challenges resulting from the differences in the GMP and good laboratory practice (GLP) regulations and some of the cultural challenges associated with such a major change. Some challenges are common to most major changes and some are specific to this situation. Finally, this paper will discuss some simple strategies to prepare the GMP analytical laboratory for conducting GLP studies. Copyright © 2004 John Wiley & Sons, Ltd.
Guidance on responding to FDA Warning Letters and possible enforcement consequences for clinical investigators and sponsors
Authors: Walters James P.
Published: November 2004

Under the Bio‐Research Monitoring Program, the United States Food and Drug Administration conducts oversight of clinical investigators, and pharmaceutical and medical device manufacturers who sponsor clinical trials used to support pre‐marketing applications submitted to the agency. Although the program focuses on investigators, inspections of violative clinical investigators can result in significant agency action against investigators and sponsors alike. The author discusses Warning Letters, provides guidance on how to respond to Warning Letters, and possible consequences of violative inspections. Copyright © 2004 John Wiley & Sons, Ltd.
What's new?
Authors: Broughton Harold Steven , Hattemer‐Apostel Rita
Published: November 2004

The What's New? section in the Quality Assurance Journal aims to draw attention to items of importance to QA professionals. There is usually a three‐month interval between final submission of manuscripts and distribution of the journal. For this issue, the entries in the What's New? section arise from the period of 1 June 2004 to 31 August 2004. If you feel that there is any other new information that should be brought to the attention of readers, please let us know by e‐mailing rha@verdandi.ch. Copyright © 2004 John Wiley & Sons, Ltd.
Strategies adopted and lessons learnt during the severe acute respiratory syndrome crisis in Singapore
Authors:   SARS Investigation Team from DMERI,   SGH
Published: November 2004

In Singapore, the military was actively involved in the containment of the outbreak of severe acute respiratory syndrome (SARS) last year. The outbreak started in February 2003 with three Singapore travellers to Hong Kong. At that time, nothing was known about the aetiological agent of the atypical pneumonia that was termed SARS. Unfortunately one of the travellers was a super‐spreader, defined as a person with high efficiency for virus transmission, and was responsible for the expansion of the national outbreak. Not only was the Singapore military involved in contact tracing of personnel and enforcement of home quarantine, military‐affiliated research institutes were also involved in providing diagnostic support. This review reconstructs the events that took place during the SARS outbreak, focusing on the special support arising from complementing the military‐affiliated laboratory with the public health laboratory. A description of the diagnostic findings is provided in chronological order. The review ends with lessons Singapore learnt from the SARS crisis, stressing the importance of national preparedness for future outbreaks. Copyright © 2004 John Wiley & Sons, Ltd.
A simple hybrid variance estimator for the Kaplan–Meier survival function
Authors: Borkowf Craig B.
Published: November 2004

In this paper, we propose a hybrid variance estimator for the Kaplan–Meier survival function. This new estimator approximates the true variance by a Binomial variance formula, where the proportion parameter is a piecewise non‐increasing function of the Kaplan–Meier survival function and its upper bound, as described below. Also, the effective sample size equals the number of subjects not censored prior to that time. In addition, we consider an adjusted hybrid variance estimator that modifies the regular estimator for small sample sizes. We present a simulation study to compare the performance of the regular and adjusted hybrid variance estimators to the Greenwood and Peto variance estimators for small sample sizes. We show that on average these hybrid variance estimators give closer variance estimates to the true values than the traditional variance estimators, and hence confidence intervals constructed with these hybrid variance estimators have more nominal coverage rates. Indeed, the Greenwood and Peto variance estimators can substantially underestimate the true variance in the left and right tails of the survival distribution, even with moderately censored data. Finally, we illustrate the use of these hybrid and traditional variance estimators on a data set from a leukaemia clinical trial. Published in 2004 by John Wiley & Sons, Ltd.
IEEE 802.11e/802.11k wireless LAN: spectrum awareness for distributed resource sharing
Authors: Mangold Stefan , Zhong Zhun , Hiertz Guido R. , Walke Bernhard
Published: November 2004

Coordinating priorities in wireless medium access is difficult when radio networks operate with contention‐based medium access. Contention‐based medium access protocols such as listen‐before‐talk are widely employed today, and for example used in the popular IEEE 802.11 protocol. Contention‐based protocols are used for wireless communication in unreliable radio environments such as the unlicensed frequency bands with their typically irregular and unpredictable interferences. However, to support time‐bounded traffic with a certain quality of service (QoS) support is extremely difficult, because it requires the knowledge of how aggressive other radio stations, which also contend for radio resources, access the medium. In this contribution, we discuss a new measurement in the IEEE 802.11k draft standard, together with the IEEE 802.11e draft standard for coordinating priorities. By combining the two extensions of IEEE 802.11, we develop an algorithm that allows radio stations to estimate the achievable throughput per radio station (the saturation throughput) in the presence of other radio stations. Our algorithm further allows predicting the saturation throughput per radio station in the presence of other non‐802.11 radio networks, because it only relies on the information about how the medium is used by other stations, i.e. for what duration other stations have to sense the medium as idle before initiating transmissions. The algorithm does not require knowledge about the contention‐parameters (like, e.g. minimum contention window sizes) used by other radio stations, and only relies on medium sensing information. For this reason, we refer to spectrum awareness in this work. We modify an existing model that was originally developed for calculating the saturation throughput in IEEE 802.11, to calculate the saturation throughput for IEEE 802.11e with one single priority. We then describe a new measurement, which is part of the IEEE 802.11k draft standard. The measurement provides information about medium access probabilities of other radio stations per contention window slots. These probabilities provide the information about how aggressive the medium is utilized by other stations. The probabilities are used in our model for approximating the saturation throughput per station and priority in the presence of other radio stations. As a result, with the help of the new model, a radio station is able to estimate its own expected saturation throughput. The comparison of the model with stochastic simulation stations indicates that our model approximates the saturation throughput per station and priority sufficiently in many scenarios, and hence allows to predict expected saturation throughputs per radio station. Copyright © 2004 John Wiley & Sons, Ltd.
A new risk index
Authors: Seydel R.
Published: November 2004

This paper contributes to the novel approach of a deterministic risk analysis. We introduce a risk index, which is designed such that large values of the index indicate a deterministic risk. The approach is illustrated by two examples. The new risk index allows to give the “risk area” a quantitative meaning.
Bounds on the effective conductivity of two‐dimensional N‐component isotropic and symmetric cell mixtures
Authors: Chinh Pham Duc
Published: November 2004

Variational perturbation approach is applied to derive upper and lower bounds on the effective conductivity of two‐dimensional isotropic quasisymmetric (or symmetric cell) N‐component media, which involve only the definite information about the volume proportions and properties of their components. The bounds appear to improve upon, or coincide (in case of circular cell subclass) with, the bounds constructed by an alternative variational approach. The general geometry‐dependent bounds for isotropic composites converge to yield the exact effective conductivity of the multi‐coated circles model.
Dugdale‐model for a ring‐shaped crack in a transtropic thick walled cylinder
Authors: Uyaner M.
Published: November 2004

In this study, a problem of a ring‐shaped crack contained in an infinitely long thick‐walled cylinder is considered. The problem is formulated for a transtropic (transversely isotropic) material by using integral transform technique under uniform load. The governing elasticity equation for the transtropic axisymmetric problem in cylindrical co‐ordinates was obtained in terms of a Love type stress function. Hankel and Fourier transforms were applied on the stress function because of the geometry of the configuration and boundary conditions. The stress function was expressed in terms of the governing equation. Using the boundary conditions, the problem reduced to a singular integral equation. This singular integral equation is solved by using the Gaussian Quadrature. Then the stress intensity factor at the crack tip was determined. The plastic zone widths are obtained by using the Dugdale model. The plastic zone widths are plotted for various ring‐shaped crack sizes and transtropic materials.
A phenomenological model for hysteresis in polycrystalline shape memory alloys
Authors: Kružík M. , Otto F.
Published: November 2004

We propose a phenomenological model describing stress and temperature induced transformations in polycrystalline shape memory alloys. Polycrystallinity is mimicked on the level of a finite element discretization: Each element is treated as a single grain of a randomly chosen orientation. This heterogeneity destroys the undesirable effect of instantaneous transformation under spatially homogeneous loading or heating. We present various computational experiments on the hysteretic effects.
The Jewish Actor and the Theatre of Modernism in Germany
Authors: SHAHAR GALILI
Published: November 2004

This article explores images of the Jewish actor in modernist German theatre. It deals with the question of theatrical identities on the stages of the Weimar period and discusses the complexities of cultural stereotyping applied to actors of Jewish origin. Special attention will be devoted to the perspectives of the avant-garde used here in the historical sense of the term. In the second part of the article, individual actors such as Max Pallenberg, Alexander Granach and Fritz Kortner will be analysed with respect to certain physical or vocal characteristics deemed to be typically ‘Jewish’. In the final section Kafka's reactions to visiting Yiddish performers will be examined as an example of aesthetic (self)reflection on the question of Jewish identity and modernism.
Edward Bond and the Celebrity of Exile
Authors: SAUNDERS GRAHAM
Published: November 2004

A shibboleth has grown up around the work of Edward Bond. The tag ‘controversial dramatist’ has continued to dog both the man and his work. This article will hope to explore some of the contradictory, and sometimes frustrating manifestations that such ‘celebrity’ has produced. Since the reception of The War Plays [1985] by the Royal Shakespeare Company at the National Theatre Bond has largely withdrawn his work from mainstream British theatre. Since the late 1990s he has looked to a new home – La Colline Theatre – in France, to premiere new work and run retrospective seasons of older plays. Here, Bond's celebrity is of a different kind, and has allowed him to enhance and develop his work as a playwright, director and writer about theatre. While this article draws on secondary sources it also uses material based on personal correspondence with Edward Bond.
Plasmas observed near local noon in Jupiter's magnetosphere with the Galileo spacecraft
Authors: Frank L. A. , Paterson W. R.
Published: November 2004

Measurements of electron beams and thermal ions were achieved by the Galileo spacecraft during the later phases of its mission for three outbound passages of the local afternoon and noon sectors of Jupiter's magnetosphere. During the first two passages the spacecraft passed through the rigidly corotating plasma torus with outer boundary near 8 RJ, into the transition region from torus to plasma sheet, and then into the plasma sheet proper at distances beyond ∼25 RJ. Telemetry coverage for the third passage began in the transition region. At the outer boundary of the torus the ion densities and temperatures were ∼500 cm−3 and 106 K. In the transition region the ion densities decreased with increasing distance to 0.1 cm−3, and temperatures increased to 5 × 107 K. In the plasma sheet the ion densities were typically 0.1 cm−3 with temperatures of 108 K. The azimuthal component of plasma flow slows to ∼70% of the corotational value in the transition region. For the first two passages, strong radial flows toward Jupiter increase with increasing radial distances. For the third passage near local noon the plasma flows are considerably more stagnant than those at local evening. The variations in the flow suggest that the solar wind influence extends to radial distances in the range of 10 RJ. Electron beams parallel and antiparallel to the magnetic field were observed during the passages on field lines connected to the main auroral ring in the ionosphere. Major constraints on the heating/acceleration mechanism for the main ring are (1) the presence of the electron beams at and near the equator and (2) previous remote observations of emissions in the vicinity of the atmospheric methane layer. These constraints support a heating mechanism in this layer driven by magnetospheric convection without acceleration by field‐aligned electrostatic fields. At radial distances 30–44 RJ near local noon the plasma densities exhibited a System III effect, increasing once per planetary rotation near a longitude 300°. In addition, the finding of thermal ion beams directed parallel to the magnetic field near 20 RJ resolves the problem of radial force balance previously identified with Voyager measurements. That is, the outward centrifugal force for these beams is sufficient to balance the inward radial force of the magnetic field.
Late Quaternary environmental and climatic changes in central Europe as inferred from the composition of organic matter in annually laminated maar lake sediments
Authors: Fuhrmann Andreas , Fischer Thomas , Lücke Andreas , Brauer Achim , Zolitschka Bernd , Horsfield Brian , Negendank Jörg F. W. , Schleser Gerhard H. , Wilkes Heinz
Published: November 2004

Geochemical (elemental analysis, bulk δ13CTOC, thermal degradation techniques, molecular analysis of n‐alkanes) and microscopic investigations (maceral analysis, vitrinite reflectance) were performed (1) to characterize the organic matter (OM) in sediments from two maar lakes in the Westeifel volcanic field, Germany, and (2) to discuss paleoenvironmental processes which have controlled the accumulation and preservation of OM. The annually laminated sediments show a wide range of organic carbon contents between 0.3 and 21.4% TOC and Hydrogen Index values between 80 and 501 mg HC/g TOC. Well‐developed laminations mirror suboxic to anoxic bottom waters. Diagnostic compounds in the pyrolysates and microscopic analysis permit discrimination between the principal OM sources, and their variations over time provide important evidence for the reconstruction of the environmental histories of the lakes and their watershed. The significance of terrigenous OM is reflected by the occurrence of methoxyphenols in the insoluble as well as mid‐ and long‐chain n‐alkanes in the soluble OM which are indicative of land plant or macrophyte input to the lakes. The relative abundance of certain homologues together with the amount of terrigenous macerals can be used to show differences in higher plant input and vegetation changes through time. During the Pleniglacial and Younger Dryas period, high‐reflecting reworked OM was introduced by soil erosion in an environment with relatively open vegetation. The alkylphenols in the pyrolysates originate partly from the microbial reworking of proteinaceous tyrosine moieties and/or reflect a direct contribution from cyanobacteria. We assume that variations in the carbon isotopic composition of OM are mainly due to changes in the lake's primary productivity with the exception of the Pleniglacial. Various forms of land use are reflected by increasing amounts of terrigenous particles as well as chemical plant markers from 500 varve years B.P. until present. The organic geochemical and microscopic data correlate well with other proxy information about climate‐dependent fluctuations in the ecosystem of the studied sites.
230Th in the Andaman Sea: Rapid deep‐sea renewal
Authors: Okubo Ayako , Obata Hajime , Nozaki Yoshiyuki , Yamamoto Yoshiyuki , Minami Hideki
Published: November 2004

230Th activities were determined in seawater collected from the Bay of Bengal and the Andaman Sea. The Andaman Sea is a semi‐closed basin that is isolated from the Bay of Bengal by the Andaman‐Nicobar Ridge. The noticeable trend in the vertical distribution of 230Th activity in the Andaman Sea is its uniformity below 1250 m depth. We applied the scavenging‐mixing model to this vertical profile in the Andaman Sea, and estimated the upper limit of renewal time to be 6 yr. We compared 210Pb/226Ra ratios among deep waters of various oceanic basins to constrain the application of 230Th as a tracer of deep‐water renewal. The 210Pb/226Ra ratios were almost identical for the deep‐water of the Andaman Sea and the inflow water from the Bay of Bengal, suggesting that the deep water in the Andaman Sea is replaced rapidly without bottom scavenging effects on the 210Pb/226Ra ratio.
Modeling the time‐evolving plasma in the inner magnetosphere: An empirical approach
Authors: Orsini S. , Milillo A. , Mura A.
Published: November 2004

The global plasma distribution in the inner magnetosphere is directly related to the time‐evolving magnetospheric and solar wind conditions. However, it is difficult to derive a realistic global picture of the inner magnetosphere from in situ spacecraft measurements. In this study we approach this intriguing task by analyzing the H+ spectra from CRRES Magnetospheric Ion Composition Spectrometer (MICS) and Low‐Energy Magnetospheric Ion Composition Sensor (LOMICS) experiments (L shell between 3 and 9 and energies between 4 and 400 keV) during a large period including storm times as well as quiet times and by best fitting these proton spectra with those obtained via the empirical model proposed by Milillo et al. [2001]. The procedure is performed by tuning a subset of the model parameters in order to reconstruct the trend of the experimental data at the given location. It is shown that the profile versus time of the selected model parameters (strictly linked to the plasma distribution characteristics) is well correlated to the geomagnetic indexes. In particular, the storm‐time development of both the diffused population at high energies and the convected/injected particles in the range of tens of keVs are highlighted. Subsequently, the trend of the proton distributions on a global scale is reconstructed by means of the mentioned empirical model. Finally, the macroscopic features and their developments on a global scale are analyzed in terms of energy density, electric potential, and equatorial current density.
Angle effect in laser nanopatterning with particle-mask
Authors: Wang Z. B. , Hong M. H. , Luk'yanchuk B. S. , Lin Y. , Wang Q. F. , Chong T. C.
Published: November 2004

Parallel nanostructuring of substrate surface with particle-mask is a promising technology that may significantly improve the patterning speed under single laser pulse irradiation. In this paper, the influence of the incidence wave angle on the pattern structures is investigated. Polystyrene spherical particles were deposited on the surface in a monolayer form by self-assembly. The sample was then irradiated with 248nm KrF laser at different incidence angles α. It is found that nanostructures can be formed at different positions with different incidence angles. Both round-shape and comet-shape nanostructures can be produced. By varying the incidence angles, the depth of the nanostructures can also be controlled. To explain the different nanostructures produced at different angles, the intensity field distributions under the particle were calculated according to an exact model for light scattering by a sphere on the substrate (P. A. Bobbert and J. Vlieger, Physica A 137A, 209 1986). The main equation in the original model was reformed for the ease of numerical simulation. A method was proposed to calculate the total electric and magnetic field as an extension to the model. The theoretical results are in good agreement with the experimental results.
Full potential linearized augmented plane wave investigations of structural and electronic properties of pyrochlore systems
Authors: Terki R. , Feraoun H. , Bertrand G. , Aourag H.
Published: November 2004

The structural and electronic properties of La2Zr2O7 and La2Hf2O7 pyrochlore compounds were investigated using the first principles full-potential linearized augmented plane wave method within the density functional theory. In this approach, the generalized gradient approximation was used for the exchange-correlation potential. We have optimized the internal structure parameter and then calculated the ground-state energy, the lattice constant, the bulk modulus, and its pressure derivative. The interatomic distances and angles were also determined. The results are in good agreement with available experimental measurements. Our electronic structure calculations predict a direct band gap at the Γ point; the nature of chemical bonding is dominated by the presence of ionic character. Furthermore, both La2Zr2O7 and La2Hf2O7 compounds are found to be insulating, which is in good agreement with experimental data.
Magnetotransport properties of two-dimensional electron gas in AlSb∕InAs quantum well structures designed for device applications
Authors: Zverev V. N. , Muhammad M. , Rahman S. , Debray P. , Saglam M. , Sigmund J. , Hartnagel H. L.
Published: November 2004

The mobility and the sheet electron density of two-dimensional electron gas in AlSb∕InAs quantum well structures optimized for device applications were measured in the temperature range 4.2K<T<90K. A maximum electron mobility μ=3.24×105 was found at 4.2K at a sheet electron density n2D=1.1×1012cm−2. Measurements of the integral quantum Hall and Shubnikov-de Haas oscillations in the temperature range 0.07–9K were also carried out to obtain additional information on the characteristics of the two-dimensional electron gas. The electron effective mass m* and the effective electron g-factor g* were determined from these measurements and found to be, respectively, 0.032m0 and 14.6. The latter is in good agreement with the recent experimental data obtained from cyclotron resonance and titled magnetic-field experiments.
Effect of the magnetic field on the melting transition of H2O and D2O measured by a high resolution and supersensitive differential scanning calorimeter
Authors: Inaba Hideaki , Saitou Tetsuya , Tozaki Ken-ichi , Hayashi Hideko
Published: November 2004

The magnetic effect on the melting transition of H2O and D2O was measured by using a high resolution and supersensitive differential scanning calorimeter working in a magnetic bore. The melting temperature of H2O and D2O at 6T was 5.6 and 21.8mK higher than that without the magnetic field, respectively. The temperature shifts of the melting transition of H2O and D2O were proportional to the square of the magnetic field. The temperature shifts of the melting transition due to the magnetic field did not obey the magneto-Clapeyron equation quantitatively. A dynamic effect due to the magnetic field was discussed for an alternative interpretation.
Effects of lanthanum doping on the dielectric properties of Ba(Fe0.5Nb0.5)O3 ceramic
Authors: Chung Chao-Yu , Chang Yen-Hwei , Chen Guo-Ju
Published: November 2004

The relaxor type of ferroelectric material Ba(FeNb)1∕2O3, which has a partially disordered perovskite structure, has been characterized and shown a maximum plateau of the dielectric permittivity depending upon the temperature. The dielectric constant at a low frequency is up to 30 000 at room temperature. While the single-phase La-doped Ba(FeNb)1∕2O3, Ba1−xLax(Fe1∕2Nb1∕2)1−x∕4O3(0⩽x⩽0.2) has a monoclinic structure solid solutions up to x⩽0.2, the lattice parameters decrease with an increasing La concentration. The temperature dependence of the dielectric constant of the La-doped Ba(FeNb)1∕2O3 was measured with different La contents, showing that the dielectric permittivity is higher than 105 at an 8mol% La concentration. The present dielectric dispersion was interpreted on the basis of the interfacial polarization at the grain-boundary region.
Efficient organic solar cells by penetration of conjugated polymers into perylene pigments
Authors: Nakamura Jun-ichi , Yokoe Chiho , Murata Kazuhiko , Takahashi Kohshin
Published: November 2004

We report here efficient air-stable p-n heterojunction organic solar cells with a structure consisting of an n-type insoluble perylene pigment penetrated by a p-type-conjugated polymer, where the interfacial area for photocurrent generation increases. The solar cells are easily produced by infiltrating a soluble-conjugated polymer intentionally into an opening among insoluble microcrystalline perylene layer under a saturated chloroform vapor. This approach can be regarded as an alternative convenient way to achieve bulk heterojunction solar cells. The cell performance is further enhanced by inserting an additional layer between the electrode and the photoactive layer to confine exciton in the photoactive layer. The overall attempt to improve the cell performance, so far, results in maximum quantum efficiency up to 45% under illumination of 485-nm monochromatic light and power conversion efficiency up to 1.9% under a simulated solar light (AM1.5) with a 100mWcm−2 intensity. The approach is promising to achieve practical efficiency because tuning the opening size can further widen the photoactive area.
A model for electromigration-induced degradation mechanisms in dual-inlaid copper interconnects: Effect of interface bonding strength
Authors: Sukharev Valeriy , Zschech Ehrenfried
Published: November 2004

A physical model and a simulation algorithm are used to predict an electromigration-(EM-) induced void nucleation and growth in dual-inlaid copper interconnect. Incorporation of all important atom migration driving forces into the mass balance equation and its solution together with solution of the coupled electromagnetics, heat transfer, and elasticity problems allows to simulate EM-induced degradation in a variety of dual-inlaid copper interconnect segments characterized by different dominant channels for mass transport. The interface bonding strengths, significantly influencing the interface diffusivity and consequently the mass transport along interfaces, result in completely different degradation and failure pictures for the weak and strengthened copper∕capping layer interfaces. Strengthening of the top interface of inlaid copper interconnect metal line is a promising way to prolong the EM lifetime. The results of the numerical simulation have been proven experimentally by the EM degradation studies on the fully embedded dual-inlaid copper interconnect test structures. EM-induced void formation, movement, and growth in a copper interconnect were continuously monitored in an in situ scanning electron microscopy experiment. The correspondence between simulation results and experimental data indicates the applicability of the developed model for optimization of the physical and electrical design rules. Simulation-based optimization of the interconnect architecture, segment geometry, material properties, and some of the process parameters can generate on-chip interconnect systems with a high immunity to EM-induced failures.
Nature of nonlinear imprint in ferroelectric films and long-term prediction of polarization loss in ferroelectric memories
Authors: Tagantsev Alexander K. , Stolichnov Igor , Setter Nava , Cross Jeffrey S.
Published: November 2004

The phenomenon of polarization imprint consisting of the development of a preferential polarization state in ferroelectric films is known as one of the major issues impacting the development of high density ferroelectric memories. According to the commonly accepted scenario, the imprint is related to the charge injection and charge accumulation in the nearby-electrode passive layer of the ferroelectric film. Recent studies demonstrated that the coercive voltage shift induced by the imprint exhibits a nonlinear time dependence in a logarithmic scale. This result was interpreted as the presence of two different imprint mechanisms characterized by different activation energies. In the present work, an analytical theory of the injection scenario of imprint is developed. The charge accumulation at the interface is shown to provoke a voltage offset and polarization loss which are nonlinearly dependent on the time in logarithmic scale. This result is obtained for different charge injection mechanisms including Schottky, Pool-Frenkel, and tunneling scenarios. Thus, it is shown that a single imprint mechanism can be responsible for a nolinear (in logarithmic scale) time dependence of the voltage offset and polarization loss. Additionally, the temperature dependence of the logarithmic rate of imprint is shown to be nonexponential. The developed model ties together the time and temperature dependences of imprint. For the experimental verification of the model a study of imprint has been performed on (111) Pb(Zr,Ti)O3 film capacitors with temperatures ranging from 25 to 150°C and exposure times up to 1000h. It has been found that the theory developed adequately describes the obtained experimental data. Based upon the theoretical and experimental results a test for ferroelectric memories is proposed, which enables the long-term prediction of polarization loss caused by imprint for a wide temperature range and for different operating voltages.
General theory of carrier lifetime in semiconductors with multiple localized states
Authors: Debuf Didier
Published: November 2004

The Shockley-Read-Hall rate equations determine the average carrier transitions via a single-level defect in the band gap of a nondegenerate semiconductor. In the present work the differential rate equations for multiple levels, or localized states systems, are derived from first principles. These multiple level systems comprise the multiple discrete defects system and the coupled or excited states system. The solution for the single-level rate equations, developed recently for transient decay, is represented by an infinite series of monoexponential terms, the frequencies or inverse time constants of which are a linear combination of the fundamental frequencies ω=1∕τ. For the multiple localized state solution expressions for the fundamental time constants τ1+k are derived for m states with k=1,2,…,m without an approximation at a given temperature for an excess carrier concentration below nondegenerate doping, arbitrary uniform doping concentration NA,D, defect level concentration Nk, cross section σnk,pk, and energy level Ek. Verification of the set of rate equations for each system is performed by comparing the analysis of the numerical solution for component time constants with the prediction of the theory. The variation of the fundamental time constant τ1 with excess carrier concentration indicates the behavior of minority carrier trapping.
Low-temperature elastic and piezoelectric constants of paratellurite (α-TeO2)
Authors: Ledbetter Hassel , Leisure Robert G. , Migliori Albert , Betts Jon , Ogi Hirotsugu
Published: November 2004

We report paratellurite’s 300-10-K elastic constants Cij, six constants reflecting tetragonal symmetry (P422 point group). The quantity e142∕k11, where e14 denotes the sole independent piezoelectric constant and k11 denotes a dielectric constant, was determined over the same temperature range. All the principal Cij show approximately regular temperature-change behavior: increasing with decreasing temperature, the increases being 2%–10%. One derived elastic constant, C′=(C11−C12)∕2, a shear constant, shows strongly anomalous temperature behavior, decreasing continuously during cooling to 10K, the total decrease being 5%. The quantity e142∕k11 was essentially independent of temperature. Obtained by resonant-ultrasound spectroscopy, our results differ from previous studies, none of which went to 10K, a temperature region of much practical interest for this material. From the near-zero-temperature elastic constants, we derive a Debye temperature of 235K. The slope dC′∕dT yields a negative Gruneisen parameter γ=−0.9, close to the specific-heat value.