bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo‐Viscoelastic Response of Polycarbonate Reinforced with Short Glass Fibers
Authors: Drozdov Aleksey D. , Al‐Mulla Adam , Gupta Rakesh K.
Published: June 2003

Observations are reported for oscillatory torsion tests at several temperatures ranging from room temperature to 100 °C on a polymer composite consisting of a polycarbonate matrix reinforced with short glass fibers. Constitutive equations are derived for the linear viscoelastic behavior of the polymer composite, which is treated as an equivalent heterogeneous network of chains bridged by junctions (entanglements and glass fibers). The network is thought of as an ensemble of meso‐regions with arbitrary shapes and sizes. With reference to the concept of cooperative relaxation, the time‐dependent response of an ensemble is associated with the rearrangement of meso‐domains. The rearrangement events occur at random times as meso‐regions are agitated by thermal fluctuations. Stress–strain relations for isothermal deformation of an ensemble of meso‐domains are derived by using the laws of thermodynamics. The governing equations are determined by five adjustable parameters that are found by fitting the experimental data. The effects of temperature and filler content on the material parameters are studied in detail.

The shear modulus G GPa versus the content of short glass fibers ν wt.‐%. Symbols: treatment of observations in oscillatory torsion tests at T = 25 (unfilled circles) and T = 100 °C (filled circles). Solid lines: approximation of the experimental data by Equation (27). Curve 1: G0 = 1.05, G1 = 3.83 × 10−2. Curve 2: G0 = 0.91, G1 = 3.65 × 10−2.

image

The shear modulus G GPa versus the content of short glass fibers ν wt.‐%. Symbols: treatment of observations in oscillatory torsion tests at T = 25 (unfilled circles) and T = 100 °C (filled circles). Solid lines: approximation of the experimental data by Equation (27). Curve 1: G0 = 1.05, G1 = 3.83 × 10−2. Curve 2: G0 = 0.91, G1 = 3.65 × 10−2.
A Method of Improving the Theoretical Basis of kp Determination from PLP‐SEC Measurements
Authors: Kornherr Andreas , Olaj Oskar Friedrich , Schnöll‐Bitai Irene , Zifferer Gerhard
Published: June 2003

Making use of hitherto ignored features (such as the peak width) contained in the chain‐length distributions of polymers prepared by pulsed‐laser polymerization (PLP), corrections are calculated from simulated chain‐length distributions for improving the accuracy of the “characteristic chain length” L0 data on which the evaluation of the propagation rate constant kp is based. These corrections refer to a wide range of chain lengths and primary radical production, slightly chain‐length‐dependent termination by disproportionation or combination, and a reasonable extent of axial dispersion introduced by the chromatographic device used in the evaluation of the chain‐length distribution. They can be applied to the point of inflection on the low‐molecular‐weight side of the extra peaks as well as to the peak maximum. The remaining mean error which, of course, concerns the evaluation of L0 only, is shown to be of the order of 1.0–1.5%, if the mode of termination is unknown, and comes down to about half that value if information on the mode of termination is available. Although all the other errors inherent in the size exclusion chromatography (SEC) method are still present, this method constitutes substantial progress with respect to the accuracy of determining kp data from PLP experiments followed by chromatographic analysis.

Hyper mass distributions calculated for L0 = 200, C = 5 and b = 0.16 for termination by disproportionation considering Poissonian and Gaussian broadening.

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Hyper mass distributions calculated for L0 = 200, C = 5 and b = 0.16 for termination by disproportionation considering Poissonian and Gaussian broadening.
Numerical techniques for the analysis of crack propagation in cohesive materials
Authors: Marfia S. , Sacco E.
Published: June 2003

The aim of the paper is the development, assessment and use of suitable numerical procedures for the analysis of the crack evolution in cohesive materials. In particular, homogeneous as well as heterogeneous materials, obtained by embedding short stiff fibres in a cohesive matrix, are considered. Two‐dimensional Mode I fracture problems are investigated. The cohesive constitutive law is adopted to model the process zone occurring at the crack tip. An elasto‐plastic constitutive relationship, able to take into account the processes of fibre debonding and pull‐out, is introduced to model the mechanical response of the short fibres.

Two numerical procedures, based on the stress and on the energy approach, are developed to investigate the crack propagation in cohesive as well as fibre‐reinforced materials, characterized by a periodic crack distribution. The results obtained using the stress and energy approaches are compared in order to evaluate the effectiveness of the procedures. Investigations on the size effect for microcracked periodic cohesive materials, and on the beneficial effects of the fibres in improving the composite material response, are developed. Copyright © 2003 John Wiley & Sons, Ltd.
Trajectory‐planning through interpolation by overlapping cubic arcs and cubic splines
Authors: du Plessis L. J. , Snyman J. A.
Published: June 2003

A new path‐planning interpolation methodology is presented with which the user may analytically specify the desired path to be followed by any planar industrial robot. The user prescribes a set of nodal points along a general curve to be followed by the chosen working point on the end‐effector of the mechanism. Given these specified points along the path and additional prescribed kinematical requirements, Overlapping Cubic Arcs are fitted in the Cartesian domain and a cubic Spline interpolation curve is fitted in the time‐domain. Further user‐specified information is used to determine how the end‐effector orientation angle should vary along the specified curve. The proposed trajectory‐planning methodology is embodied in a computer‐algorithm (OCAS), which outputs continuous graphs for positions, velocities and accelerations in the time‐domain. If a varying end‐effector orientation angle is specified, the OCAS‐algorithm also generates continuous orientation angle, orientation angular velocity and orientation angular acceleration curves in the time‐domain. The trajectory‐planning capabilities of the OCAS‐algorithm are tested for cases where the prescribed nodal points lie along curves defined by analytically known non‐linear functions, as well as for nodal points specified along a non‐analytical (free‐form) test‐curve. The proposed trajectory‐planner may be implemented as part of kinematic and kinetic simulation software, and it also has the potential application for controlling machine tools in cutting along free‐form curves. Copyright © 2003 John Wiley & Sons, Ltd.
Accuracy of trisomy 18 screening using the second‐trimester triple test
Authors: Meier Chris , Huang Tianhua , Wyatt Philip R. , Summers Anne M.
Published: June 2003

Objective

To assess the accuracy of the calculated risk for trisomy 18 assigned to individual women screened with the second‐trimester triple test.

Methods

The study was based on 382 598 women screened in the Ontario Maternal Serum Screening Programme between October 1993 and September 2000. Of the women screened, 111 cases of trisomy 18 were identified. Originally, 92 874 women were screened using a risk cut‐off level method. Estimated risks of trisomy 18 were calculated by applying published population parameters for the remaining women screened using a fixed analyte cut‐off method.

Women were ranked according to their individual risk for trisomy 18 syndrome in decreasing order and divided into 12 groups. The mean calculated risks of having an affected pregnancy at term for each group were compared with the birth prevalence of the corresponding group after allowing for spontaneous fetal losses.

Results

Agreement between the mean calculated risks and the observed prevalence was seen across the entire risk range, although women identified as having high‐risk pregnancies had an actual prevalence that was somewhat lower than that estimated by the screen.

Conclusion

The calculated risk for trisomy 18 syndrome assigned to the individual woman on the basis of the risk cut‐off method accurately reflects their risk of having a term trisomy 18 syndrome pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.
Discordant prenatal diagnosis of trisomy 21 due to mosaic structural rearrangements of chromosome 21
Authors: Brisset Sophie , Aboura Azzedine , Audibert François , Costa Jean‐Marc , L'Herminé Aurore Coulomb , Gautier Valérie , Frydman René , Tachdjian Gérard
Published: June 2003

Objectives

Trisomy 21 mosaicism associated with a structural rearrangement of chromosome 21 is uncommon. We report on two prenatal diagnoses in which karyotypes showed mosaicism with an aberrant cell line, including a structural rearrangement of chromosome 21.

Methods

Both these cases were associated with increased nuchal translucency. Conventional and molecular cytogenetic analyses were performed on uncultured and cultured trophoblast and amniotic fluid cells.

Results

In Case 1, analysis of trophoblast cells revealed an abnormal karyotype of 47,XX,+mar.ish der(13/21)(D13Z1/D21Z1+)/46,XX. The amniocentesis showed a free non‐mosaic trisomy 21. In Case 2, the trophoblast direct analysis showed a normal male karyotype whereas the long‐term culture revealed a mosaicism for a dicentric long‐arm isochromosome 21: 46,XY,idic(21)(p11)/45,XY,−21/46,XY. Amniocentesis showed an unbalanced non‐mosaic karyotype 46,XY,idic(21)(p11) resulting therefore in trisomy for the long arm of chromosome 21.

Conclusion

Our cases underline the importance of combining the direct analysis and long‐term culture of trophoblast and emphasise the need for confirmatory studies in other tissues when mosaicism of structural rearrangement is encountered in chorionic villi. The meiotic and mitotic mechanisms of formation of these structural rearrangements of chromosome 21 are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Personality traits and academic examination performance
Authors: Chamorro‐Premuzic Tomas , Furnham Adrian
Published: June 2003

British university students (N = 247) completed the NEO‐PI‐R (Costa & McCrae, 1992) personality inventory at the beginning of their course and took several written examinations throughout their three‐year degree. Personality super‐traits (especially Conscientiousness positively, and Extraversion and Neuroticism negatively) were significantly correlated with examination grades and were found to account for around 15% of the variance. Primary traits were also examined and results showed significant correlations between a small number of these traits (notably dutifulness and achievement striving positively, and anxiety and activity negatively) and academic achievement. Furthermore, selected primary personality traits (i.e. achievement striving, self‐discipline, and activity) were found to explain almost 30% of the variance in academic examination performance. It is argued that personality inventory results may represent an important contribution to the prediction of academic success and failure in university (particularly in highly selective and competitive settings). Copyright © 2002 John Wiley & Sons, Ltd.
Communicating membrane surfaces used in modern nanoanalytics
Authors: Galla Hans‐Joachim , Hinz Andreas
Published: June 2003

Ein zentraler Aspekt im Leben jedes zellulären biologischen Systems ist der ständige Informationsaustausch zwischen der Außenwelt und den inneren Zellkompartimenten. Chemische Botenstoffe erreichen die zelluläre Oberfläche und binden an ihren entsprechenden membranständigen Rezeptor. Dieser durchläuft eine komformative Änderung, die dann ein chemisches oder elektrisches Signal im Innenraum der Zelle oder an der Zellmembran freisetzt. Diesem Grundprinzip folgen alle unsere Wahrnehmungssinne wie Geruch und Geschmack, aber auch Nervenreizleitung, der Sehprozess, Tastsinn oder das Hörvermögen folgen letztlich diesem Prinzip der Signaltransduktion. Das Vorbild biologische Membran mit der einzigartigen Möglichkeit der parallelen Detektion verschiedener Eingangssignale nutzt die moderne Bioanalytik. Mit nanobiotechnologischen Methoden können rezeptive Areale mit molekularer Dimension auf Festkörpern, z. B. Elektroden oder Halbleitern, aufgebracht werden. Solche sog. Biochips oder Biosensoren erlauben die spezifische Detektion von bioaktiven Substanzen in geringsten Konzentrationen. Potentiell pharmakologisch aktive Wirkstoffe können, ebenso wie die entsprechenden Rezeptoren, ermittelt werden. Anwendungen im Bereich der Genomic aber auch der Proteomic sind heute realisierbar.

Wesentliche Voraussetzung für einen solchen breiten Einsatz ist aber die gezielte Herstellung der rezeptiven Oberflächen. Dazu müssen Biomoleküle (Lipide, Proteine oder Nukleinsäuren) definiert so auf die Oberfläche aufgebracht werden, dass sie sowohl im Hinblick auf Orientierung als auch laterale Organisation die Bauprinzipien der biologischen Membran als rezeptive Oberfläche nachempfinden [1]. Die physikalischen Prinzipien, die zu einer solchen organisierten Oberflächenbelegung führen, sind bekannt. Die Kombination aus Wasserstoffbrückenbindungen sowie elektrostatischer und hydrophober Wechselwirkungen bestimmen den Aufbau der organisierten Schichten [2]. Die Synthese der Bausteine und die Entwicklung neuer Techniken zu deren Aufbringung auf die sonst unspezifische Sensoroberfläche sind Herausforderungen der Nanobiotechnologie. Die Kombination aus Kenntnis der biologischen Prinzipien, chemischer Synthesefertigkeit und Entwicklung neuer hochauflösender physikalischer Methoden erlaubt schon heute die Handhabung und die Analyse einzelner Moleküle.
Kostengünstige TiN‐Schichten für tribologische Anwendungen
Authors: Strauss G. N. , Pulker H. K. , Meyer M. , Hatto P. , Davis C. , Jehn H. , Balzer M. , Misiano C. , Silipo V. , Olzi E. , Molena R. , Passareti F.
Published: June 2003

Ein Hauptziel dieser Arbeit war die Adaptierung bzw. Entwicklung eines plasma unterstützten PVD Prozesses zur Herstellung von kostengünstigen TiN Schichten für tribologische Anwendungen bei Prozessdrücken bis zu 10‐1 mbar. Dabei wurde ausgehend von industriell eingesetzten PVD Prozessen, wie Plasma unterstütztes Magnetron Sputtern, Reaktives Ionenplattieren bzw. Arc‐Verdampfung, versucht, durch Prozess‐Adaptierung und Wahl geeigneter Prozessfenster, beständige und qualitativ hochwertige TiN Hartstoffschichten, selbst bei hohen Prozessdrücken, zu erzeugen. Zur qualitativen Beurteilung der verschiedenen Prozesse bei den unterschiedlichen Prozessparametern wurde neben der Schichtcharakterisierung (Schichtdickenverteilung, Morphologie, Härte, tribologische Eigenschaften) auch eine Analyse der Prozessplasmen durchgeführt und versucht die erzielten Schichteigenschaften mit den eingestellten Prozessparametern und den gemessenen Plasmaeigenschaften, wie Ionenart, Ionenstromdichte und Energieverteilung der Ionen, in Korrelation zu bringen. Die unterschiedlichen Prozesse wurden mittels eines Plasmamonitoring Systems (PPM421 von Inficon) und eines Faraday Cup Systems untersucht und die ermittelten Plasmaeigenschaften gegenüber gestellt und diskutiert. Die Untersuchungen wurden im Rahmen eines europäischen BriteEuram Projektes TIPCOAT BE‐3815/Contract BRPR‐CT97‐0397 durchgeführt.
Ramanspectroscopic Characterization of ultra‐thin nano‐protective Carbon Films for the Magnetic Storage Industry
Authors: v. Gradowski M. , Schneider H.‐H. , Jacoby B. , Ohr R. , Hilgers H.
Published: June 2003

Raman‐Spektroskopie ist eine Standard‐Methode zur strukturellen Charakterisierung ultra‐dünner (<10 nm) amorpher Kohlenstoffschichten, die als Korrosions‐ und tribologische Schutzschichten in der Magnetspeichertechnologie eingesetzt werden. Sie basiert auf der inelastischen Streuung von monochromatischem Licht an Molekülen und liefert wertvolle Informationen über die Bindungsstruktur der Schichten.

Das Raman‐Spektrum amorpher Kohlenstoffe ist im wesentlichen durch zwei Schwingungsmoden (D‐ und G‐Peak) im Bereich von 1350 cm‐1 – 1600 cm‐1 gekennzeichnet, deren Position und Intensität zur Analyse der Kohlenstoffbindung verwendet werden. Bei den hier vorgestellten Untersuchungen an ultra‐dünnen Kohlenstoffschichten, die bei grünem (λgrün = 514.5 nm) und ultraviolettem (λUV = 244 nm) Laserlicht stattfanden, wurde die Abhängigkeit des G‐Peaks von der einfallenden Wellenlänge (G‐Dispersion) zur Bindungscharakterisierung ausgenutzt. Dabei bedeutet eine hohe G‐Dispersion eine starke dreidimensionale Vernetzung der Kohlenstoffschicht und einen entsprechend hohen sp3‐Gehalt.

Aufgrund des Hysterese‐Effektes, der zur Folge hat, dass sich zwei Raman‐Spektren ähneln können, obgleich die jeweiligen Kohlenstoffschichten ganz verschiedene Strukturen besitzen, sind diese Informationen bei reinen Einwellenlängen‐Untersuchungen nicht zugänglich. Die hier vorgestellte Duale‐Methode umgeht den Hysterese‐Effekt und ermöglicht durch Korrelationen mit den Ergebnissen verschiedener Analyseverfahren eine qualitative Abschätzung des sp3‐Gehaltes und der Massendichte beliebiger Kohlenstoffsysteme. Darüberhinaus bietet eine ramanspektroskopische Untersuchung im UV‐Bereich die Möglichkeit einer Stickstoffquantifizierung der Schutzschichten. Hierzu dient die relative Intensität einer Bande bei 2200 cm‐1 als Maß für den Stickstoffgehalt.

Der große Vorteil der Raman‐Spektroskopie ist die Schnelligkeit der Methode. Die reine Messzeit beträgt maximal 1.5 min, weshalb sie sich hervorragend als Methode zur Prozeßkontrolle und Prozessoptimierung eignet. Außerdem ist sie eine zerstörungsfreie Technik, so dass die untersuchten Magnetspeicherplatten und ‐köpfe nach einer raman‐spektroskopischen Analyse unbeschadet weiter verwendet werden können.
Optical, electrical and acoustic films deposited by the Double Ring Magnetron
Authors: Bartzsch Hagen , Frach Peter , Goedicke Klaus
Published: June 2003

Für zahlreiche Anwendungen in Optik, Elektronik und Sensorik werden dünne dielektrische Schichten eingesetzt. Üblicherweise werden diese durch Bedampfung, aktivierte Bedampfung, HF‐Sputtern oder CVD‐Techniken hergestellt. In vorliegender Veröffentlichung wird die Abscheidung solcher Schichten durch das reaktive Puls‐Magnetron‐Sputtern dargestellt. Dieses Verfahren ermöglicht nicht nur die Schichtabscheidung mit einer zehnfach höheren Rate im Vergleich zu den konventionellen Verfahren, sondern bietet wichtige neue Möglichkeiten zur Beeinflussung des Schichtwachstums. So kann die Zusammensetzung der Schicht während des Abscheideprozesses verändert und ein komplettes optisches Schichtsystem ohne Unterbrechung des Plasmaprozesses erzielt werden. Auch lässt sich der Beschuss des Substrates mit energiereichen Teilchen in weiten Grenzen durch die Pulsparameter steuern, um beispielsweise durch starken Teilchenbeschuss besonders dichte Schichten zu erzielen oder Schichten bei geringem Beschuss auf temperaturempfindlichen Substraten abzuscheiden.

Anhand von Beispielen aus der Abscheidung laseroptischer Schichten, elektrischer Isolationsschichten und funktioneller Schichten für Oberflächenwellenbauelemente wird gezeigt, wie diese neuen technologischen Möglichkeiten vorteilhaft für die Herstellung innovativer Schichtsysteme eingesetzt werden. Das zur Schichtabscheidung eingesetzte Doppel‐Ring‐Magnetron ermöglicht es dabei aufgrund der Überlagerung der Schichtdickenverteilungen zweier konzentrischer Entladungen, stationär Schichten mit einer Homogenität besser als ± 1 % auf 8”‐Substraten abzuscheiden.
LARGE DEVIATIONS ANALYSIS OF A COUPLED-PROCESSORS SYSTEM
Authors: Hordijk Arie , Popov Nikolai
Published: June 2003

In this article, we derive closed-form expressions of the large
deviations local rate function in terms of the arrival and service
parameters for the zero path in exponential queueing networks
corresponding to a coupled-processors system.
SUBSTRATE INFLUENCE IN CREOLES AND THE ROLE OF TRANSFER IN SECOND LANGUAGE ACQUISITION
Authors: Siegel Jeff
Published: June 2003

This article discusses how research on language transfer in the field of SLA can help to explain the origins of substrate influence in creoles and provide answers to more difficult questions concerning the distribution and verification of substrate features. First, it argues against the view that both SLA and transfer are not involved in the genesis of pidgin and creole languages. Then the view is presented that, as described in the SLA literature, transfer is not just a consequence of second language learning but also of second language use, and it serves as a communication strategy when the need arises. Such a strategy may be used by speakers of either a prepidgin or an already established pidgin when its functional use is being rapidly extended. Sociolinguistic perspectives on transfer in SLA, described next, throw some light onto the question of why substrate features remain in pidgins and creoles. Research on transfer in SLA also provides important insights into the specific factors that may have affected substrate influence in creoles. Evidence is presented that some transfer constraints discovered in SLA research—rather than other proposed factors such as so-called functional expendability—still provide the best explanation for the absence of particular substrate features in creoles. Finally, it is shown that tests proposed for verifying instances of L1 influence in interlanguage could be adapted for verifying instances of substrate influence in creoles.
The contribution of parents and siblings to antisocial and depressive behavior in adolescents: A double jeopardy coercion model
Authors: COMPTON KRISTI , SNYDER JAMES , SCHREPFERMAN LYNN , BANK LEW , SHORTT JOANN WU
Published: June 2003

A dual coercion model of family processes associated with the development of antisocial and depressive behavior during adolescence was assessed, using an at-risk sample of families and children. Consistent with the model, involvement in family coercion during childhood and adolescence increased both boys' and girls' risk for antisocial behavior in adolescence and girls' risk for depressive behavior. Coercive family processes served as a link between older and younger siblings' antisocial behavior. Childhood exposure to maternal depression predicted boys' and girls' depressive behavior 10 years later, but this association was not mediated by coercion. The data suggest that family risk factors and processes for antisocial development are similar for boys and girls but pathways to depression may be gender specific.
Depressive symptoms across adolescence and young adulthood in men: Predictions from parental and contextual risk factors
Authors: KIM HYOUN K. , CAPALDI DEBORAH M. , STOOLMILLER MIKE
Published: June 2003

The current study examined the course of depressive symptoms of young men from early adolescence through young adulthood using a growth model approach and the influence of early parental (i.e., depressive symptoms, antisocial behaviors, substance use) and contextual (i.e., family income and parental marital transitions) risk factors on both the level of depressive symptoms in early adolescence and on changes over a 10-year period, controlling for young men's early antisocial behavior. On average, depressive symptoms of the youths tended to decrease slightly as they reached young adulthood. Among the parental and contextual risk factors, parent's marital transitions was the most significant predictor for the level of depressive symptoms in early adolescence. Parent's marital transitions and family income were also significantly related to changes in depressive symptoms. As hypothesized, there was a significant interaction effect of paternal and maternal depressive symptoms on depressive symptoms in early adolescence and on changes over time. Maternal depressive symptoms were related to the son's depressive symptoms only when the father's depressive symptoms were also high. The results also suggested that parenting practices did not mediate the effects of the parental and contextual risk factors on the development of depressive symptoms among young men.
Helping Clinicians Find Resolution after a Medical Error
Authors: POLLACK CRAIG , BAYLEY CAROL , MENDIOLA MICHAEL , McPHEE STEPHEN
Published: June 2003

Clinicians, operating within complex systems, make mistakes, as people
do in every human endeavor, and when they do, patients are sometimes harmed.
One important question is how we as clinicians can find resolution in the
wake of an error. The published literature has divided errors into those
caused by “systems” and by “individuals.” But
whereas both “systems” and “individual” approaches
are important in understanding the cause of an error, neither alone can
fully lead to resolution once an error has occurred. Instead, both are
necessary to understand, resolve, and prevent errors.
The Other Side of Professionalism: Doctor-to-Doctor
Authors: CONNELLY JULIA E.
Published: June 2003

What do the terms “profession, professional, professionalism”
mean in 2002? One dictionary defines profession as “a calling
requiring specialized knowledge and often long and intensive academic
preparation,” and it defines professionalism as “the conduct,
aims, or qualities that characterize or make a profession or professional
person.” These definitions are appealingly simple. Complexity arises
when we add the term “medical” as in the medical profession, a
medical professional, or medical professionalism; and, here a specific
understanding of “the conduct, aims, and qualities that
characterize” the field of medicine is required. To complicate matters,
professionalism applies to both the profession as a whole as well as the
individual professional persons, such as the physicians.
Determining Futility
Authors: d'ORONZIO JOSEPH C.
Published: June 2003

The challenge of determining that therapeutic intervention is futile is
a recurrent ethical theme in critical care medicine. The process by which
that determination is reached often involves demanding collaborative and
interdisciplinary conversation and deliberation within the context of
hospital policy, including ethics committee guidelines. The subsequent
decision as to what happens next depends on resources, such as palliative
care services, hospice, other hospital protocols, and, of course, family
support.
Abstracts of Note: The Bioethics Literature
Authors: Iserson Kenneth V.
Published: June 2003

This section is meant to be a mutual effort. If you find an
article you think should be abstracted in this section, do not
be bashful—submit it for consideration to feature editor
Kenneth V. Iserson care of CQ. If you do not like the editorial
comments, this will give you an opportunity to respond in the
letters section. Your input is desired and anticipated.
Self-awareness after traumatic brain injury: A comparison
of measures and their relationship to executive functions
Authors: BOGOD NICHOLAS M. , MATEER CATHERINE A. , MACDONALD STUART W.S.
Published: June 2003

Poor awareness of deficit is common after brain injury. Recent
literature has examined various tools for measurement of this
phenomenon; the most widely used being self–other rating
scales. Although self–other scale measures have face
validity, their criterion-related validity has not been adequately
demonstrated, and there is little information as to whether
and how they relate to other neuropsychological measures. The
present study compared measurement of awareness by the Dysexecutive
(DEX) Questionnaire self–other rating scale with the
Self-Awareness of Deficits Interview (SADI), a semistructured
interview measure. Evaluation of awareness by these measures
was compared to tests of executive functioning and IQ. Results
indicated significant, albeit marginal relationships between
the two measures, and better correlation of the SADI with measures
of frontal lobe functioning. The SADI also predicted injury
severity. (JINS, 2003, 9, 450–458.)
The Hand Movement Test as a tool in neuropsychological
assessment: Interpretation within a working memory theoretical
framework
Authors: FRENCHAM KATHERINE A.R. , FOX ALLISON M. , MAYBERY MURRAY T.
Published: June 2003

While the Kaufman Hand Movements Test (KHMT) is argued to be
sensitive to cognitive impairment secondary to various forms
of brain dysfunction in adults, it is unknown which cognitive
processes it addresses. Dual-task research has employed tasks
similar to the KHMT to determine whether such tasks assess (1)
verbal or visuospatial memory, or (2) a proposed additional
short-term memory component, movement memory. However findings
consistent with both hypotheses have been reported. Experiment
1 involved 24 participants completing a hand movement task and
a letter span task under articulatory suppression, finger movement
and no interference conditions. Performance on both the hand
movement task and letter span task was significantly reduced
by articulatory suppression. In Experiment 2, 16 participants
were administered the hand movement task and a Corsi span task
under articulatory suppression, finger movement, spatial tapping,
and no interference. Again, hand movement span was most reduced
by articulatory suppression, in contrast to Corsi span which
was most reduced by spatial tapping. Hand movement task performance
was therefore assumed to rely upon verbal recoding strategies
and thus the proposition of an additional component of movement
memory was not supported. (JINS, 2003, 9,
633–641.)
Compositional Averaging of Backscatter Intensities in Compounds
Authors: Donovan John J. , Pingitore Nicholas E. , Westphal Andrew
Published: June 2003

We present high-precision measurements of pure element stable isotope
pairs that demonstrate mass has no influence on the backscattering of
electrons at typical electron microprobe energies. The traditional
prediction of average backscatter intensities in compounds was
pragmatically based on elemental mass fractions. Our isotopic
measurements establish that this approximation has no physical basis.
We propose an alternative model to mass fraction averaging, based on
the number of electrons or protons, termed “electron
fraction,” which predicts backscatter yield better than mass
fraction averaging. We also present an improved backscatter (electron
loss) factor based on a modified electron fraction average for the ZAF
atomic number correction that provides a significant analytical
improvement, especially where large atomic number corrections are
required.
Characterization of Contacting Boundaries between Nanoparticles
with LACBED
Authors: Yao Yiming , Thölén Anders R.
Published: June 2003

The boundary parameters between contacting spherical bcc-Fe particles
have been characterized with the Large Angle Convergent Beam Electron
Diffraction (LACBED) technique. The average accuracy of measurements
can reach 0.07°. The rotation parameters are interpreted using
matrix algebra and evaluated according to the CSL model. The deviation
between the experimental results and the reference misorientations
given in the CSL model is determined. It is possible to reveal
preferential misorientations between irregularly shaped particles with
a size less than 100 nm. The method can be applied to nanoparticles and
nanocrystalline materials with a wide range of grain orientations, and
it is possible to modify it into an automatic method for TEM
measurements.
Lightning current identification over a conducting ground plane
Authors: Delfino Federico , Procopio Renato , Rossi Mansueto , Verolino Luigi
Published: June 2003

One of the most significant lightning‐related quantities is the return stroke current, which is defined as the spatial and temporal distribution of the lightning current after the contact between the leader of the discharge and the ground is established. Gaining information about the return stroke current is of prime importance for the general investigation into the lightning physics as well as for the determination of the correct expression of the electromagnetic field associated with the phenomenon. In this paper we propose an inverse procedure for the reconstruction of the proper waveform of the return stroke current, starting from the measurement of the vertical component of the electric field it produces at different locations on the ground and making use of the integral equation expressing the link between field and current. The ground is assumed to be conductive, and the general Sommerfeld's theory for the vertical antenna radiation over a lossy half‐space is adopted for the calculation of the field. It is shown that the unknown current distribution along the channel can be identified if it is suitably expanded by means of a modified basis of Chebyshev polynomials. The proposed approach is validated by means of the numerical simulation of the classical MTLE (Modified Transmission Line Exponential) engineering model, and an analysis on the role played by ground conductivity in the identification process is carried out.
Prediction of diversity statistics on terrestrial microwave links
Authors: Paulson Kevin S.
Published: June 2003

The average annual rain attenuation statistics experienced by individual microwave links are well understood. ITU‐R models exist for the prediction of these statistics, and they are used to assign power levels to links to achieve the desired availability. The performance of networks such as mulithop links or links utilizing route, frequency or time diversity, is considerably more complex, and only superficial guidance is available for their design. The complexity arises from the correlation of rain attenuation experienced by the various individual links in the network. To understand and predict the performance of these networks, it is necessary to understand the spatial and temporal correlation of rain intensity. This paper uses a model for the high‐resolution spatial and temporal variation of rain intensity proposed by Paulson [2002]. This model allows the direct calculation of all the first and second order, temporal, statistics of rain attenuation experienced by pairs of microwave links, when the link system is covered by single rain events. The model is used to develop expressions for the joint rain attenuation distribution for pairs of links and hence expressions for diversity improvement for networks spanning small areas. These predictions are compared to diversity statistics measured from a database of radar images covering the southern United Kingdom.
Automatic processing of high‐rate, high‐density multibeam echosounder data
Authors: Calder B. R. , Mayer L. A.
Published: June 2003

Multibeam echosounders (MBES) are currently the best way to determine the bathymetry of large regions of the seabed with high accuracy. They are becoming the standard instrument for hydrographic surveying and are also used in geological studies, mineral exploration and scientific investigation of the earth's crustal deformations and life cycle. The significantly increased data density provided by an MBES has significant advantages in accurately delineating the morphology of the seabed, but comes with the attendant disadvantage of having to handle and process a much greater volume of data. Current data processing approaches typically involve (computer aided) human inspection of all data, with time‐consuming and subjective assessment of all data points. As data rates increase with each new generation of instrument and required turn‐around times decrease, manual approaches become unwieldy and automatic methods of processing essential. We propose a new method for automatically processing MBES data that attempts to address concerns of efficiency, objectivity, robustness and accuracy. The method attributes each sounding with an estimate of vertical and horizontal error, and then uses a model of information propagation to transfer information about the depth from each sounding to its local neighborhood. Embedded in the survey area are estimation nodes that aim to determine the true depth at an absolutely defined location, along with its associated uncertainty. As soon as soundings are made available, the nodes independently assimilate propagated information to form depth hypotheses which are then tracked and updated on‐line as more data is gathered. Consequently, we can extract at any time a “current‐best” estimate for all nodes, plus co‐located uncertainties and other metrics. The method can assimilate data from multiple surveys, multiple instruments or repeated passes of the same instrument in real‐time as data is being gathered. The data assimilation scheme is sufficiently robust to deal with typical survey echosounder errors. Robustness is improved by pre‐conditioning the data, and allowing the depth model to be incrementally defined. A model monitoring scheme ensures that inconsistent data are maintained as separate but internally consistent depth hypotheses. A disambiguation of these competing hypotheses is only carried out when required by the user. The algorithm has a low memory footprint, runs faster than data can currently be gathered, and is suitable for real‐time use. We call this algorithm CUBE (Combined Uncertainty and Bathymetry Estimator). We illustrate CUBE on two data sets gathered in shallow water with different instruments and for different purposes. We show that the algorithm is robust to even gross failure modes, and reliably processes the vast majority of the data. In both cases, we confirm that the estimates made by CUBE are statistically similar to those generated by hand.
Anomalous seismograms generated by an intermediate‐depth earthquake: Unusual scattering sources in the upper mantle of central Japan
Authors: Lin Cheng‐Horng , Ando Masataka , Fujii Naoyuki , Yamaoka Koshun , Tadokoro Keiichi , Jin An‐Shu , Obara Kazusige , Ishida Mizuho
Published: June 2003

Strong scattering sources were detected in the upper mantle beneath central Japan from seismic data recorded by the high‐sensitivity seismograph network (Hi‐net). Anomalous seismograms, consisting of many strong later phases whose amplitudes did not decay significantly with time, were observed from an intermediate‐depth earthquake. A comparison of those anomalous seismograms with others generated by other deep earthquakes shows that major scattering sources may exist predominately in the upper mantle, not in the crust. Three possible candidates have been considered as the sources of scattering in the upper mantle including magma conduits, the previous collision zone and slab melting. Although seismic waves may be scattered strongly from each potential candidate, a region associate with slab melting might be more suitable for generating the anomalous seismogram due to the existence of abundant melting spots within the subducted Philippine Sea slab that is extremely young and hot beneath central Japan.
Galactic cosmic ray transport in the global heliosphere
Authors: Florinski V. , Zank G. P. , Pogorelov N. V.
Published: June 2003

We present a new axisymmetric model of the heliosphere that includes three principal particle species (plasma with magnetic field, interstellar neutral atoms, and galactic cosmic rays). Unlike previous modulation models, which necessarily included a modulation boundary, we study the entry of the galactic cosmic rays into the heliosphere directly from the local interstellar medium population. An important improvement over previous global heliospheric models is that a kinetic description for the cosmic rays is used instead of the usual fluid approach. We compute the cosmic‐ray diffusion coefficients from quasi‐linear theory, assuming a constant (but different) power spectrum of the fluctuations in both the solar wind and the interstellar medium. Our results show that low‐energy particles are strongly attenuated by the magnetic wall in the inner heliosheath and do not reach the termination shock. The model predicts small cosmic rays gradients in most of the heliosphere, implying little modification to the termination and bow shocks. The exception is the inner heliosheath region, where cosmic‐ray gradients are large and the energetic particles can, consequently, affect the plasma flow. Particle spectra in the inner heliosphere are found to be in agreement with the observations. We also find that the inner heliospheric galactic cosmic‐ray population is not sensitive to the upwind‐downwind asymmetry of the termination shock.
Short‐ and long‐term effects of GPS measured crustal deformation rates along the south central Andes
Authors: Khazaradze Giorgi , Klotz Jürgen
Published: June 2003

In this study we present the contemporary crustal deformation field along the central and southern Andes (17–42°S) estimated from four Global Positioning System (GPS) campaigns conducted in 1994–1997. We find that the majority of the observed crustal deformation field is relatively homogenous: roughly parallel to the plate convergence direction with decreasing velocities away from the trench. We attribute this type of deformation pattern to the interseismic phase of an earthquake deformation cycle caused by 100% locking of the thrust interface between the subducting Nazca and the overriding South American plates. We have also detected a strong postseismic deformation signal in the vicinity of the 1995 Mw8.0 Antofagasta (22–26°S) and 1960 Mw9.5 Chile (38–43°S) earthquakes. This type of deformation can be described as short‐term in nature compared to geological timescales. The above conclusions are based on the results of the three‐dimensional (3‐D) Andean Elastic Dislocation Model (AEDM). By subtracting the AEDM‐predicted deformation rates from the observations we obtained a residual velocity field that highlights the postseismic as well as more long‐term deformation effects. For example, we find strong evidence for the continuing crustal shortening across the back arc, reaching its maximum (4 mm/yr) in the very north of our study area. In addition, between latitudes 29°S and 34°S, there is an indication of E‐W oriented extension within the forearc, in accordance with the recent geologic findings for the N‐S oriented normal faulting.
Coulomb stress changes at calderas: Modeling the seismicity of Campi Flegrei (southern Italy)
Authors: Troise Claudia , Pingue Folco , De Natale Giuseppe
Published: June 2003

The local seismicity occurring at Campi Flegrei caldera during a recent unrest (1982–1984) has been modeled in terms of Coulomb stress changes due to magma chamber overpressure, superimposed on a background tensile regional stress. The computations, performed by a finite element method in heterogeneous axial‐symmetric elastic models, also take into account the effects of the caldera structure on stress distribution. Coulomb stress changes have been obtained for the best oriented focal mechanisms, determined for the total applied stress, i.e., local change plus background regional stress. The results demonstrate a very good correlation between positive Coulomb stress changes and earthquake locations. Furthermore, there is a good agreement between observed focal mechanisms and the optimally oriented mechanisms as predicted by the model. The obtained results represent not only a fundamental contribution toward understanding mechanisms of seismic generation at Campi Flegrei and other calderas but also demonstrate that Coulomb stress changes in volcanic areas can be very effective, because of the high intensity, and deserve more attention than generally paid.
Komatiites, kimberlites, and boninites
Authors: Arndt Nicholas
Published: June 2003

When the mantle melts, it produces ultramafic magma if the site of melting is unusually deep, the degree of melting is unusually high, or the source is refractory. For such melting to happen, the source must be unusually hot or very rich in volatiles. Differing conditions produce a spectrum of ultramafic magma types. Komatiites form by high degrees of melting, at great depths, of an essentially anhydrous source. Barberton‐type komatiites are moderately high degree melts from a particularly hot and deep source; Munro‐type komatiites are very high degree melts of a slightly cooler source. Kimberlites result from low‐degree melting, also at great depth, of sources rich in incompatible elements and CO2 + H2O. They become further enriched through interaction with overlying asthenospheric or lithospheric mantle. Boninites form by hydrous melting of metasomatized mantle above a subduction zone. Just like basalts, the different types of ultramafic magma, and the conditions in which they form, are readily identified using major and trace element criteria.
Imaging the complexity of an active normal fault system: The 1997 Colfiorito (central Italy) case study
Authors: Chiaraluce L. , Ellsworth W. L. , Chiarabba C. , Cocco M.
Published: June 2003

Six moderate magnitude earthquakes (5 < Mw < 6) ruptured normal fault segments of the southern sector of the North Apennine belt (central Italy) in the 1997 Colfiorito earthquake sequence. We study the progressive activation of adjacent and nearby parallel faults of this complex normal fault system using ∼1650 earthquake locations obtained by applying a double‐difference location method, using travel time picks and waveform cross‐correlation measurements. The lateral extent of the fault segments range from 5 to 10 km and make up a broad, ∼45 km long, NW trending fault system. The geometry of each segment is quite simple and consists of planar faults gently dipping toward SW with an average dip of 40°–45°. The fault planes are not listric but maintain a constant dip through the entire seismogenic volume, down to 8 km depth. We observe the activation of faults on the hanging wall and the absence of seismicity in the footwall of the structure. The observed fault segmentation appears to be due to the lateral heterogeneity of the upper crust: preexisting thrusts inherited from Neogene's compressional tectonic intersect the active normal faults and control their maximum length. The stress tensor obtained by inverting the six main shock focal mechanisms of the sequence is in agreement with the tectonic stress active in the inner chain of the Apennine, revealing a clear NE trending extension direction. Aftershock focal mechanisms show a consistent extensional kinematics, 70% of which are mechanically consistent with the main shock stress field.
Internal tide scattering at seamounts, ridges, and islands
Authors: Johnston T. M. Shaun , Merrifield Mark A.
Published: June 2003

The scattering of mode‐1 internal tides from idealized Gaussian topography in a nonrotating ocean with constant and realistic stratifications is examined with a primitive equation numerical model. Incident mode‐1 energy fluxes of 20 and 2000 W m−1 are used to examine the linear regime and a more realistic situation. Simulations using two‐dimensional or infinite ridges compare well with ray tracing methods and illustrate how the size and shape of the topography influence wave scattering. The height affects energy transmission and reflection, while the slope and width determine the conversion of low‐mode internal tides into beams or higher modes. Three‐dimensional topographic scattering is considered for seamounts, finite‐width ridges, and islands. Scattering from finite ridges focuses wave energy directly downstream, while scattering from seamounts produces azimuthal energy dispersion. Scattering to higher wave modes occurs in the lee of near‐critical and supercritical seamounts and ridges. Nonlinear interactions transfer energy into the mode‐1 M4 internal tide. The Mellor‐Yamada level‐2.5 submodel parameterizes turbulent mixing. For the near‐critical and supercritical ridges with realistic stratification, elevated mixing is found over the leading edge of the topography and along a tidal beam up to the first surface bounce. A transition from a beam structure near the topography to a low‐mode structure farther away occurs due to an increased contribution from the mode‐1 internal tide as it refracts around the topography and not due to turbulent dissipation. Internal tide scattering at topography leads to a loss of energy to mixing and to a redistribution of energy flux in space, frequency, and mode number.