bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Pb(Zr, Ti)O3 thin films fabricated by plasma enhanced chemical vapor deposition on Ir-based electrodes
Authors: Lee Hee-Chul , Lee Won-Jong
Published: November 2002

Structural and electrical characteristics of Pb(Zr, Ti)O3 (PZT) ferroelectric thin films deposited on various Ir-based electrodes (Ir, IrO2, and Pt/IrO2) using electron cyclotron resonance plasma enhanced chemical vapor deposition were investigated. On the Ir electrode, stoichiometric PZT films with pure perovskite phase could be obtained over a very wide range of processing conditions. However, PZT films prepared on the IrO2 electrode contain a large amount of PbOx phases and exhibited high Pb-excess composition. The deposition characteristics were dependent on the behavior of PbO molecules on the electrode surface. The PZT thin film capacitors prepared on the Ir bottom electrode showed different electrical properties depending on top electrode materials. The PZT capacitors with Ir, IrO2, and Pt top electrodes showed good leakage current characteristics, whereas those with the Ru top electrode showed a very high leakage current density. The PZT capacitor exhibited the best fatigue endurance with an IrO2 top electrode. An Ir top electrode provided better fatigue endurance than a Pt top electrode. The PZT capacitor with an Ir-based electrode is thought to be attractive for the application to ferroelectric random access memory devices because of its wide processing window for a high-quality ferroelectric film and good polarization, fatigue, and leakage current characteristics.
Electron-temperature control in 915 MHz electron cyclotron resonance plasma
Authors: Itagaki N. , Kawai Y. , Kawakami S. , Ishii Nobuo
Published: November 2002

The electron temperature of a 915 MHz electron cyclotron resonance (ECR) plasma was controlled in a wide range by adjusting the incident microwave power when the gradient in the magnetic field strength near the resonant zone was gentle. From the numerical simulations of the microwave-power absorption, the electron temperature in an ECR plasma was found to change with changing spatial profiles of the power absorption. It was also suggested from our experimental and numerical results that the electron temperature is controlled by changing the gradient in the magnetic field strength and/or the microwave frequency because the power absorption profile may be changed with changing effective resonance zone width.
Temperature effect on growth of well-ordered thin Al2O3 film on NiAl(110)
Authors: Lay Thi Thi , Yoshitake M. , Mebarki B.
Published: November 2002

We have investigated the effect of temperature on the growth of thin Al2O3 film on NiAl(110) surface. 1200 L oxygen was adsorbed at temperatures 570, 620, 670, 700, and 720 K while the pressure was kept constant at 6.6×10−5 Pa. After oxygen absorption the specimen was subsequently annealed at 1070 K for epitaxial growth of crystalline oxide. Low energy electron diffraction (LEED) and Auger electron spectroscopy were used to characterize oxide formation and surface composition. LEED patterns showed that the crystallinity depended on temperature and the brightest crystalline oxide spots were obtained at temperature between 620 and 670 K. Temperature has little effect on film thickness. The average film thickness estimated was around 4 Å. Stoichiometry of O–Al bonds during oxygen absorption and realignment during annealing is important in epitaxial growth of well-ordered crystalline oxide.
Effect of carbon enrichment induced by photoresist on highly selective SiO2 etching
Authors: Chu Changwoong , Chi Kyeong-Koo , Moon Joo-Tae
Published: November 2002

We propose two models to discuss the behavior of the selective etching of SiO2 to the underlying Si3N4 with changing wafer surface temperatures. For this investigation, three specimens, SiO2, Si3N4, and poly-Si, which are nonpatterned, photoresist-patterned, and poly-silicon-patterned, respectively, have been etched in a surface wave plasma system equipped with an electrostatic chuck for wafer temperature control. The coolant temperature, which controls the wafer temperature, has been changed from −20 to 50 °C. For the nonpatterned wafer, the etch rates of SiO2, Si3N4, and poly-Si increase and the selectivities decreases with wafer temperature. However, for the samples patterned with either photoresist or poly-Si, the etch rates of SiO2 decrease with wafer temperature. The temperature rise also leads to an enhancement of selectivity of SiO2/Si3N4, and the steeper profile angles. The presence of a masking layer, even for the poly-Si-patterned samples, results in a different etching behavior. This is because the sticking probability of the polymer precursor becomes smaller on the sidewall of the profile with the temperature increase. Therefore the thickness of polymer on the sidewall of the contact hole decreases, and the thickness of polymer on the bottom increases as the wafer temperature goes up. Comparing photoresist-patterned samples with poly-Si-patterned ones, we can corroborate the role of the photoresist mask layer, which provides a higher carbon-to-fluorine ratio at the near surface. The carbon enrichment accelerates more steeply the etch rate decrement of the substrate layer. In summary, there are two main contributions attributed by the substrate temperature: changing the sticking coefficient of the fluorocarbon precursor and enhancing the photoresist erosion.
Correlation between structure, stress and deposition parameters in direct current sputtered zinc oxide films
Authors: Kappertz O. , Drese R. , Wuttig M.
Published: November 2002

Thin ZnO and ZnO:Al films have been prepared by reactive dc magnetron sputtering, using both metallic and ceramic targets. The influence of oxygen flow and total pressure on film stress, structure, texture, and surface roughness has been examined. The properties of the films strongly depend on the deposition conditions, in particular the total pressure. Increasing the pressure from 0.5 to 2 Pa resulted in rougher, and less strained films. Increasing the oxygen flow at a constant total pressure led to a slight increase in stress, but had no visible effect on the surface roughness. Structural investigations by x-ray diffraction (XRD) showed that polycrystalline films with pronounced preferential orientation were formed. Most XRD-spectra showed a coexistence of strained and unstrained ZnO in wurtzite structure. The relative abundance of the relaxed phase is a function of the intrinsic stress only, and does not directly depend on deposition parameters. However, the deposition parameters determine the stress within the film, and thus influence the amount of the relaxed grains.
Study on time of flight property of uniform magnetic sector field analyzers up to the third-order approximation
Authors: Cheng Min , Tang Tiantong , Yao Zhenhua , Wang Zhenhua
Published: November 2002

Time of flight (TOF) is an important concept in many electron optical instruments including TOF analyzers and streak camera image tubes. In this article, successive approximation approach is applied to study the TOF properties of uniform magnetic sector field analyzers. The charged particle trajectories in the magnetic field analyzers are calculated up to the third-order approximation and the corresponding solutions are obtained. Therefore, the TOF properties of the uniform magnetic sector field analyzers are analytically derived up to the third-order approximation.
Dosimetry and mechanical accuracy of the first rotating gamma system installed in North America
Authors: Kubo Hideo D. , Araki Fujio
Published: November 2002

The purpose of this paper is to present the dosimetry and mechanical accuracy of the first rotating gamma system (RGS) installed in North America for stereotactic radiosurgery. The data were obtained during the installation, acceptance test procedure, and commissioning of the unit. The RGS unit installed at UC Davis Cancer Center has modifications on the source and collimator bodies from the earlier version of the Chinese RGS The differences between these two RGSs are presented. The absolute dose at the focal point was measured in a 16‐cm‐diam acrylic phantom using a small volume chamber, which was calibrated at the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UW‐ADCL). The dose in acrylic was then converted to a dose in water. A collimator output factor from each of the four different collimator sizes ranging from 4, 8, 14, and 18 mm was measured with (1) a smaller volume chamber and (2) approximately TLD chips in the same acrylic phantom. The Gafchromic films were used for the dose profile, collimator output factor, and mechanical/radiation field isocentricity measurements. The TLD chips were processed in‐house whereas Gafchromic films were processed both at the UW‐ADCL and in‐house. The timer error, timer accuracy, and timer linearity were also determined. The dose profiles were found to be similar between and The 4 mm collimator output factor of the was approximately 0.6, similar to that from in comparison to 0.8 in the report for a Leksell Model U Gamma‐Knife. The mechanical/radiation field isocentricity for and is found to be similar and is within 0.3 mm in both X and Y directions. In the Z direction, the beam center of the is shifted toward the sources by 0.75 mm from the mechanical isocenter whereas no data are available for Little dosimetric difference is found between and It is reported that has the same dosimetric and mechanical characteristics as the Model U Gamma‐Knife. Therefore, should be capable of achieving stereotactic radiosurgery with the same degree of dosimetric and mechanical accuracy as with the Gamma‐Knife.
Polymer gel dosimetry using a three‐dimensional MRI acquisition technique
Authors: Baras P. , Seimenis I. , Kipouros P. , Papagiannis P. , Angelopoulos A. , Sakelliou L. , Pappas E. , Baltas D. , Karaiskos P. , Sandilos P. , Vlachos L.
Published: November 2002

In this work, three‐dimensional (3‐D) MRI techniques are employed in N‐Vinylpyrrolidone‐Argon‐ (VIPAR‐) based polymer gel dosimetry. VIPAR gels were irradiated using a Nucletron microSelection HDR brachytherapy remote afterloading system with single source dwell position and intravascular brachytherapy irradiation protocols. A single VIPAR gel and a single irradiation are adequate to obtain the full calibration curve needed. The 3‐D dose distributions obtained with the 3‐D MRI method were found to be in good agreement with the corresponding Monte Carlo calculations, for brachytherapy and intravascular irradiations. The method allows the reconstruction of isodose contours over any plane, with increased spatial resolution and accuracy following a single MR acquisition. VIPAR gel measurements using a 3‐D MRI readout technique can be of particular use in the experimental dosimetry of brachytherapy sources, as well as for dose verification purposes when complex irradiation regimes and three‐dimensional dose gradients are investigated.
Analysis of mechanical sources of patient alignment errors in radiation therapy
Authors: Wyman Douglas R. , Ostapiak Orest Z. , Gamble Lisa M.
Published: November 2002

Certain radiation treatments, such as conformal and intensity modulated treatments, involve isocentric treatment fields delivered using multiple angles or continuous angulation of the gantry, collimator and table. At our institution, treatments involving three angles (gantry, collimator, and table) can, if uncorrected, exhibit misalignments of 2 mm or more on premarked field centers and borders on the patient surface during the initial setup on a linear accelerator (linac), even though the linac operates within allowable mechanical tolerances. This paper is an analysis of three principal mechanical sources of patient alignment errors observed on linacs: (i) errors in table and gantry angle, (ii) displacement of gantry rotational axis during gantry rotation, and (iii) displacement between collimator and table rotational axes. On patient surfaces, these small, systematic mechanical errors can each be expected to produce misalignments of up to 1.5 mm, increasing to over 2 mm with nearly horizontal fields delivered at nonzero table angles onto highly oblique patient surfaces. For the underlying target volumes, the mechanical errors can, in combination, be expected to produce target volume misalignments of up to 1 mm on newly installed linacs and 3 mm on older linacs. Thus, 1 mm appears to be a mechanical limit on the positional precision of radiation treatments.
The effect of spectra on calibration and measurement with mammographic ionization chambers
Authors: DeWerd L. A. , Micka J. A. , Laird R. W. , Pearson D. W. , O'Brien M. , Lamperti P.
Published: November 2002

Mammographic imaging uses x‐ray tubes with molybdenum, rhodium, or tungsten anodes with the produced bremsstrahlung filtered by thin sheets of molybdenum, rhodium, or aluminum. The National Institute of Standards and Technology, the Accredited Dosimetry Calibration Laboratories, and several manufacturers offer calibrations of mammography ionization chambers with reference x‐ray beams with different radiation qualities in the range 23–40 kVp. The energy response of ten commercially available chambers was determined for these reference radiation qualities using the Attix variable‐length free‐air chamber. The evaluated chambers are designed with thin entrance windows of varying thickness and composition. The chambers show variation in their air kerma response as a function of beam radiation quality. This response with beam radiation quality may affect the measurement of clinical beam half value layer (HVL) and the determination of the mean glandular dose. The combined effect of the chamber's energy dependence and HVL measurement affects the mean glandular dose calculation resulting in differences ranging from −1.8% to +2.5%.
Introduction of weighted structural complexity measures for analysis of noisy signals and introduction to nuclear medicine image processing
Authors: Poppe Björn
Published: November 2002

In this work a sensitive source detection algorithm for nuclear medicine imaging is presented. Special attention is given to weak sources with strength comparable to fluctuations of the underlying noise. The scaling‐index‐method (SIM) originally developed by Morfill et al. (Max‐Planck‐Institute for Extraterrestrial Physics) has been extended. The SIM assumes that the local point density in a sphere with radius r around a point in a discrete phase space follows the scaling law For a digitized image the points of this space are represented by the coordinates (x,y) and the gray‐level Because the scaling behavior of noise and signal points differs, discrimination between sources and noise is possible. In this work the author extends the SIM by applying weighting functions to the locally calculated scaling indices, which take into account the information available on the noise characteristics. Because of the poor photon density in nuclear medicine diagnostics the image quality is highly influenced by the statistical fluctuations inherent in radioactive decay. Consequently, only those changes in radiopharmaceutical distributions will be detectable for the observer, which are greater than statistical noise. On the other hand the detection of weak sources is one of the most important tasks in nuclear medicine diagnostics. Therefore in several clinical cases, such as total‐bone or thyroidal scintigraphy, the applicability of the developed algorithms is studied. This work documents that by using the proposed methods even weak sources hardly detectable for the examining physician are identified with a high significance. Furthermore the SIM allows to discriminate real sources from tomographic artefacts.
CONTINUOUS TIME-DEPENDENT MEASUREMENTS: QUANTUM ANTI-ZENO PARADOX WITH APPLICATIONS
Authors: BALACHANDRAN A. P. , ROY S. M.
Published: November 2002

We derive differential equations for the modified Feynman propagator and for the density operator describing time-dependent measurements or histories continuous in time. We obtain an exact series solution and discuss its applications. Suppose the system is initially in a state with density operator ρ(0) and the projection operator E(t) = U(t) EU†(t) is measured continuously from t = 0 to T, where E is a projector obeying Eρ(0)E = ρ(0) and U(t) a unitary operator obeying U(0) = 1 and some smoothness conditions in t. Then the probability of always finding E(t) = 1 from t = 0 to T is unity. Generically E(T) ≠ E and the watched system is sure to change its state, which is the anti-Zeno paradox noted by us recently. Our results valid for projectors of arbitrary rank generalize those obtained by Anandan and Aharonov for projectors of unit rank.
ON UNITARY TIME EVOLUTION IN GOWDY T3 COSMOLOGIES
Authors: CORICHI ALEJANDRO , CORTEZ JERÓNIMO , QUEVEDO HERNANDO
Published: November 2002

A non-perturbative canonical quantization of the Gowdy T3 polarized models is considered here. This approach profits from the equivalence between the symmetry reduced model and 2 + 1 gravity coupled to a massless real scalar field. The system is partially gauge fixed and a choice of internal time is made, for which the true degrees of freedom of the model reduce to a massless free scalar field propagating on a two-dimensional expanding torus. It is shown that the symplectic transformation that determines the classical dynamics cannot be unitarily implemented on the corresponding Hilbert space of quantum states. The implications of this result for both the quantization of fields on curved manifolds and other physically relevant questions regarding the initial singularity are discussed.
EFFECT OF MUONS ON THE PHASE TRANSITION IN MAGNETIZED PROTO-NEUTRON STAR MATTER
Authors: GUPTA ASHA , GUPTA V. K. , SINGH S. , ANAND J. D.
Published: November 2002

We study the effect of the inclusion of muons and the muon neutrinos on the phase transition from nuclear to quark matter in a magnetized proto-neutron star and compare our results with those obtained by us without the muons. We find that the inclusion of muons changes slightly the nuclear density at which transition occurs. However the dependence of this transition density on various chemical potentials, temperature and the magnetic field remains quantitatively the same.
BULK VISCOUS SOLUTIONS TO THE FIELD EQUATIONS AND THE DECELERATION PARAMETER-REVISITED
Authors: PRADHAN ANIRUDH , AOTEMSHI I.
Published: November 2002

We utilise a form for the Hubble parameter to generate a number of solutions to the Einstein field equations with variable cosmological constant and variable gravitational constant in the presence of a bulk viscous fluid. The Hubble law utilised yields a constant value for the deceleration parameter. A new class of solutions is presented in the Robertson–Walker spacetimes. The coefficient of bulk viscosity is assumed to be a power function of the mass density. For a class of solutions, the deceleration parameter is negative which is consistent with the supernovae Ia observations.
THE EFFECTIVE ENERGY-MOMENTUM TENSOR IN KALUZA–KLEIN GRAVITY WITH LARGE EXTRA DIMENSIONS AND OFF-DIAGONAL METRICS
Authors: PONCE DE LEON J.
Published: November 2002

We consider a version of Kaluza–Klein theory where the cylinder condition is not imposed. The metric is allowed to have explicit dependence on the "extra" coordinate(s). This is the usual scenario in brane-world and space-time-matter theories. We extend the usual discussion by considering five-dimensional metrics with off-diagonal terms. We replace the condition of cylindricity by the requirement that physics in four-dimensional space-time should remain invariant under changes of coordinates in the five-dimensional bulk. This invariance does not eliminate physical effects from the extra dimension but separates them from spurious geometrical ones. We use the appropriate splitting technique to construct the most general induced energy-momentum tensor, compatible with the required invariance. It generalizes all previous results in the literature. In addition, we find two four-vectors, [Formula: see text] and [Formula: see text], induced by off-diagonal metrics, that separately satisfy the usual equation of continuity in 4D. These vectors appear as source-terms in equations that closely resemble the ones of electromagnetism. These are Maxwell-like equations for an antisymmetric tensor [Formula: see text] that generalizes the usual electromagnetic one. This generalization is not an assumption, but follows naturally from the dimensional reduction. Thus, if[Formula: see text] could be identified with the electromagnetic tensor, then the theory would predict the existence of classical magnetic charge and current. The splitting formalism used allows us to construct 4D physical quantities from five-dimensional ones, in a way that is independent from how we choose our space-time coordinates from those of the bulk.
THE APPLICATION OF SUPRATHRESHOLD STOCHASTIC RESONANCE TO COCHLEAR IMPLANT CODING
Authors: STOCKS N. G. , ALLINGHAM D. , MORSE R. P.
Published: November 2002

In this paper we explore the possibility of using a recently discovered form of stochastic resonance - termed suprathreshold stochastic resonance - to improve speech comprehension in patients fitted with cochlear implants. A leaky-integrate-and-fire (LIF) neurone is used to model cochlear nerve activity when subject to electrical stimulation. This model, in principle, captures key aspects of temporal coding in analogue cochlear implants. Estimates for the information transmitted by a population of nerve fibres is obtained as a function of internal (neuronal) noise level. We conclude that SSR does indeed provide a possible mechanism by which information transmission along the cochlear nerve can be improved - and thus may well lead to improved speech comprehension.
CELLULAR AUTOMATON MODELS OF TUMOR DEVELOPMENT: A CRITICAL REVIEW
Authors: MOREIRA JOANA , DEUTSCH ANDREAS
Published: November 2002

Cancer development can be viewed as an example of spatio-temporal pattern formation. Several attempts have been made to model and predict malignant tumor behavior and also to account for immune system response and the impact of possible clinical treatments. Modeling started from a macroscopic perspective and developed towards cell-based approaches, from which cellular automaton (CA) models are an example.

In this article, we first introduce the general concept of CA systems. Then, we review CA models of tumor development, focusing on avascular and vascular growth, tumor invasion and angiogenesis. Finally, a comparative analysis of the models as well as criteria for designing new CA models are provided and future perspectives are outlined.
EVOLUTION OF COOPERATION IN A SPATIAL PRISONER'S DILEMMA
Authors: SCHWEITZER FRANK , BEHERA LAXMIDHAR , MÜHLENBEIN HEINZ
Published: November 2002

We investigate the spatial distribution and the global frequency of agents who can either cooperate or defect. The agent interaction is described by a deterministic, non-iterated prisoner's dilemma game, further each agent only locally interacts with his neighbors. Based on a detailed analysis of the local payoff structures we derive critical conditions for the invasion or the spatial coexistence of cooperators and defectors. These results are concluded in a phase diagram that allows us to identify five regimes, each characterized by a distinct spatiotemporal dynamics and a corresponding final spatial structure. In addition to the complete invasion of defectors, we find coexistence regimes with either a majority of cooperators in large spatial domains, or a minority of cooperators organized in small non-stationary domains or in small clusters. The analysis further allowed a verification of computer simulation results by Nowak and May (1993). Eventually, we present simulation results of a true 5-person game on a lattice. This modification leads to non-uniform spatial interactions that may even enhance the effect of cooperation.
SUSTAINABLE AIR TRANSPORT: IDENTIFYING POSSIBILITIES FOR TECHNOLOGICAL REGIME SHIFTS IN AIRCRAFT CONSTRUCTION
Authors: DE HAAN ALEXANDER , MULDER KAREL
Published: November 2002

This paper analyses the historic genesis and further development of the dominant technological regime in civil passenger aircraft design, the civil jet engine aircraft. The emergence of the civil jet airliner cannot simply be explained as a technological necessity. Historically, more options were available which are still considered attractive for various niche applications in air transport. To reach sustainable long(er) range passenger transport, we will need radical new technological options; the dominant technological regime of civil jet aircraft design only produces incrementally more efficient aircraft. The paper analyses the history of the civil jet aircraft design regime in order to clarify the factors that contributed to the success of this regime, thereby also prohibiting a technological regime shift. It discusses options for new regimes in civil aviation, and draws conclusions regarding a path that could lead to sustainable air transport.
Effects of UV-B Radiation on Terrestrial and Aquatic Primary Producers
Authors: Day Thomas A. , Neale Patrick J.
Published: November 2002

▪ Abstract  Ozone depletion by anthropogenic gases has increased the atmospheric transmission of solar ultraviolet-B radiation (UV-B, 280–315 nm). Our understanding of the consequencences of enhanced UV-B levels on primary producers has grown dramatically over the past 20 years, but it has been hampered by how realistically experimental UV-B exposures mimic ozone-depletion scenarios. Overcoming these shortcomings will require sophisticated and creative approaches. Biological weighting functions and solar spectral irradiance estimates are critical in evaluating effects and require more attention. Whereas UV screening compounds in terrestrial and aquatic producers commonly increase with UV-B exposure, the implications, while potentially far reaching, are unclear. Photosynthesis is more sensitive to UV-B in phytoplankton than in terrestrial plants, probably owing to less effective screening in phytoplankton. Productivity of terrestrial plants is usually unaffected by enhanced UV-B, although reduced growth has been observed and may increase in magnitude over successive years. Aquatic productivity is often compromised by short-term exposures to enhanced UV-B, and long-term assessments are complicated by the dynamic nature of aquatic systems and by nonlinear responses. Recent work examining UV-B effects on multiple trophic levels suggests that outcomes will be diverse and difficult to predict. Such effects may lead to feedbacks on primary producers.
Neopolyploidy in Flowering Plants
Authors: Ramsey Justin , Schemske Douglas W.
Published: November 2002

▪ Abstract  Here we review the biology of early generation neopolyploids and discuss the profound changes that accompany their formation. Newly formed auto- and allopolyploids exhibit considerable meiotic complexity, including multivalent pairing, multisomic inheritance, and the production of unbalanced gametes. The cytogenetic behavior of allopolyploids and autopolyploids differ statistically, but are more similar than commonly believed. The progeny of neopolyploids include a high frequency of aneuploids, pseudoeuploids and homeologue-recombinant genotypes that may contribute to the phenotypic variability observed in early generation polyploids. We find no evidence to support the traditional view that autopolyploids possess lower fertility than allopolyploids, casting doubt on the paradigm that allopolyploids should be more frequent due to their inherent fertility. The fertility of early generation polyploids increases rapidly, owing largely to selection against meiotic configurations that generate unbalanced gametes. Neopolyploids are commonly differentiated from progenitors by a combination of morphological, phenological and life-history characteristics. Further progress toward understanding polyploid evolution will require studies in natural populations that can evaluate the demographic and larger ecological significance of the cytogenetic and phenotypic character of neopolyploids.
The (Super)Tree of Life: Procedures, Problems, and Prospects
Authors: Bininda-Emonds Olaf R. P. , Gittleman John L. , Steel Mike A.
Published: November 2002

▪ Abstract  Supertree construction is a new, rigorous approach for combining phylogenetic information to produce more inclusive phylogenies. It has been used to provide some of the largest, most complete phylogenies for diverse groups (e.g., mammals, flowering plants, and dinosaurs) at a variety of taxonomic levels. We critically review methods for assembling supertrees, discuss some of their more interesting mathematical properties, and describe the strengths and limitations of the supertree approach. To document the need for supertrees in biology, we identify how supertrees have already been used beyond the systematic information they provide to examine models of evolution, test rates of cladogenesis, detect patterns of trait evolution, and extend phylogenetic information to biodiversity conservation.
The Mesozoic Radiation of Birds
Authors: Chiappe Luis M. , Dyke Gareth J.
Published: November 2002

▪ Abstract  Until recently, most knowledge of the early history of birds and the evolution of their unique specializations was based on just a handful of diverse Mesozoic taxa widely separated in time and restricted to marine environments. Although Archaeopteryx is still the oldest and only Jurassic bird, a wealth of recent discoveries combined with new phylogenetic analyses have documented the divergence of a number of lineages by the beginning of the Cretaceous. These and younger Cretaceous fossils have filled much of the morphological chasm that existed between Archaeopteryx and its living counterparts, providing insights into the evolutionary development of feathers and other important features of the avian flight system. Dramatic new perceptions of the life history, growth and development of early birds have also been made possible by the latest data. Although no primitive birds are known to have survived beyond the end of the Cretaceous, the present fossil record provides no evidence for a sudden disappearance. Likewise, a Mesozoic origin for extant birds remains controversial.
The Quality of the Fossil Record: Implications for Evolutionary Analyses
Authors: Kidwell Susan M. , Holland Steven M.
Published: November 2002

▪ Abstract  Advances in taphonomy and stratigraphy over the past two decades have dramatically improved our understanding of the causes, effects, and remedies of incompleteness in the fossil record for the study of evolution. Taphonomic research has focused on quantifying probabilities of preservation across taxonomic groups, the temporal and spatial resolution of fossil deposits, and secular changes in preservation over the course of the Phanerozoic. Stratigraphic research has elucidated systematic trends in the formation of sedimentary gaps and permanent stratigraphic records, the quantitative consequences of environmental change and variable rock accumulation rates over short and long timescales, and has benefited from greatly improved methods of correlation and absolute age determination. We provide examples of how these advances are transforming paleontologic investigations of the tempo and mode of morphologic change, phylogenetic analysis, and the environmental and temporal analysis of macroevolutionary patterns.
Specification issues in stratified variance component ordinal response models
Authors: Grilli Leonardo , Rampichini Carla
Published: November 2002

The paper presents some criteria for the specification of ordinal variance component models when the units are grouped in a limited number of strata. The base model is specified using a latent variable approach, allowing the first level variance, the second level variance, and the thresholds to vary according to the strata. However this model is not identifiable. The paper discusses some alternative assumptions that overcome the identification problem and illustrates a general strategy for model selection. The proposed methodology is applied to the analysis of course programme evaluations based on student ratings, referring to three different schools of the University of Florence. The adopted model takes into account both the ordinal scale of the ratings and the hierarchical nature of the phenomenon. In this framework, the specification of the latent variable distributions is crucial, since a different first level variance among the schools would substantially change the interpretation of model parameters, as confirmed by the limited simulation study presented in the paper.
Sensitivity of Building Loss Estimates to Major Uncertain Variables
Authors: Porter Keith A. , Beck James L. , Shaikhutdinov Rustem V.
Published: November 2002

This paper examines the question of which sources of uncertainty most strongly affect the repair cost of a building in a future earthquake. Uncertainties examined here include spectral acceleration, ground-motion details, mass, damping, structural force-deformation behavior, building-component fragility, contractor costs, and the contractor's overhead and profit. We measure the variation (or swing) of the repair cost when each basic input variable except one is taken at its median value, and the remaining variable is taken at its 10th and at its 90th percentile. We perform this study using a 1960s highrise nonductile reinforced-concrete moment-frame building. Repair costs are estimated using the assembly-based vulnerability (ABV) method. We find that the top three contributors to uncertainty are assembly capacity (the structural response at which a component exceeds some damage state), shaking intensity (measured here in terms of damped elastic spectral acceleration, Sa), and details of the ground motion with a given Sa.
Thermal and microstructural analysis of orthogonal cutting of a low alloyed carbon steel using an infrared—charge-coupled device camera technique
Authors: M'Saoubi R , Le Calvez C , Changeux B , Lebrun J L
Published: November 2002

In the present investigation, an analysis of the thermal aspects associated with the machining of low alloyed carbon steel is carried out. A new technique, based on the use of an infrared—charge-coupled device (CCD) camera, has been developed to determine the complete distribution of temperatures at the cutting edge of the tool. Special attention is paid to the study of the influence of the tool nature, geometry and cutting parameters on the temperature distribution in the cutting zone. The role of workpiece material treatment has also been studied and the existence of a correlation between tool/chip interface temperatures and microstructure evolution of the material during cutting has been discussed in terms of phase transformation observations. The experimental thermal analysis of metal cutting is completed with a finite element model that permits the heat transfer mechanisms in the cutting zone to be analysed and the influence of various parameters such as cutting speed, feed rate or material properties to be understood.
Finite element modelling of decompression after isostatic pressing
Authors: Henderson R J , Moriarty B
Published: November 2002

Cold isostatic pressing, where a rubber bag is filled with ceramic powder, sealed and subjected to hydrostatic pressure, is a method of forming ceramic components with near-net shape. One problem associated with the pressing of complex shapes is that the compact may be cracked after pressing, leading to rejection of the component. In this paper the role of the rubber bag during decompression is investigated using the finite element method. Simulations of both the compaction and the decompression stages of the pressing process are presented and the results demonstrate that excessive distortion of the rubber bag can lead to tensile stresses within the compact that are sufficient to cause cracking of the compact. Methods for alleviating this problem including the modification of the bag geometry are discussed.
Consanguinity and hearing impairment in developing countries: a custom to be discouraged
Authors: Zakzouk Siraj
Published: November 2002

Consanguineous marriage is a tradition which is commonly practised among Asian, African, and Latin American communities whether they are living in their own countries or settled in Europe or the USA.

These communities, in addition to their custom of interrelated marriage, have large families and are a rapidly growing population. The siblings of consanguineous marriages have a significantly higher incidence of autosomal recessive diseases including hearing impairment.

Two epidemiological surveys were carried out 10 years apart. There were 6 421 subjects from Riyadh City and 9 540 from all other parts of the Kingdom of Saudi Arabia. A random sample was examined otologically and a questionnaire was filled in that included age, sex, family relation, number of siblings, etc. ENT examination and audiological assessment were performed. Consanguinity was found among 22 per cent as first cousins and 23 per cent as second cousins in the first survey. In the second survey 19 per cent were first cousins and 28 per cent second cousins. The rate of consanguinity was 45 per cent in the first survey and 47 per cent in the second. The prevalence of hereditary sensorineural hearing loss (SNHL) was 66.07 per cent and 36.6 per cent in the first and second survey respectively.

The incidence of hereditary hearing impairment is very high in developing countries compared to developed countries. Prevention is essential to reduce the incidence of genetic hearing loss. Consanguinity should be discouraged through health education of the public about the adverse effect of interrelated marriage. Genetic counselling, premarital and antenatal screening are to be applied whenever possible, at least for those at risk of developing genetic diseases including hearing impairment.
Prevalence of Galen’s anastomosis: an anatomical and comparative study
Authors: Furlan Julio C. , Brandão Lenine G. , Ferraz Alberto R.
Published: November 2002

An anatomical study of 50 fresh adult human cadavers was performed in order to verify prevalence of Galen’s anastomosis (GA) and to evaluate whether factors such as gender, ethnicity, side of the neck, and individual stature may interfere with GA prevalence. The results were analysed using the Chi-square test, Student t-test, and F-Snedecor test. GA was observed in 87 of 100 dissections. There was no statistically significant difference regarding GA prevalence between groups separated by ethnicity (p = 0.853), gender (p = 0.198), side of the neck (p = 0.766), or individual height (p = 0.199). Therefore, the GA was a frequent anatomical finding, and this result was not influenced by any studied factor. Comparing our data with previous studies, we also concluded that the GA seems to play an important role in the innervation of the larynx, even though its function remains unclear. Also, it is reasonable to consider GA a constant anatomical constituent.
Is the English National Health Service meeting the needs of mentally distressed Chinese women?
Authors: Green Gill , Bradby Hannah , Chan Anita , Lee Maggy , Eldridge Kimmy
Published: November 2002

Objectives: To identify barriers to communication between health care workers and Chinese women living in England, a group who are known to use the National Health Service (NHS) less than other ethnic groups; to consider whether such barriers lead to inequitable access to NHS mental health treatment; and to determine the extent to which this results from institutional racism. Method: A purposive sample of 42 Chinese women living in South-East England aged 29-60 years derived from a primary care group, two secondary mental health service providers and three Chinese associations. Subjects had all consulted a general practitioner and had either experienced mental distress ( n = 24) and/or had used traditional Chinese medicine ( n = 25). Results: Communication with health care professionals was hindered by a lack of common language and an absence of shared concepts concerning the causes and manifestations of health and illness, particularly mental health. This lack of communication resulted in delayed diagnoses, misunderstood treatment regimens and deterred women from (re-)presenting to the NHS. Among our informants, these types of problem were more acute for those women who were most marginalised from English-language culture. Conclusions: Linguistic and conceptual problems explain Chinese women's relatively poor access to mental health services. The continuing failure to tackle systematically these communication problems through the routine provision of interpretation and advocacy services lays the health care system open to the charge of 'institutional racism'.
How to compare results after surgery or radiation for localized prostate carcinoma
Authors: D'Amico Anthony V.
Published: November 2002

In addressing the clinically relevant question regarding prostate specific antigen (PSA) outcome data in the study presented by Vicini and colleagues in this issue of Cancer, the author concurs with Vicini et al. that only a randomized trial powered to assess survival ultimately can answer the important question of the relative efficacy of surgery versus various forms of radiation therapy in the management of patients with localized prostate carcinoma. In addition, the author points out that one posttreatment clinical parameter, the posttreatment PSA doubling time, has emerged from both the surgical literature and the radiation literature as a potential candidate for predicting the likelihood of death from prostate carcinoma after primary treatment failure.

See also pages 2126–35.
An interinstitutional and interspecialty comparison of treatment outcome data for patients with prostate carcinoma based on predefined prognostic categories and minimum follow‐up
Authors: Vicini Frank A. , Martinez Alvaro , Hanks Gerald , Hanlon Alex , Miles Brian , Kernan Ken , Beyers David , Ragde Haakon , Forman Jeffrey , Fontanesi James , Kestin Larry , Kovacs Gyorgy , Denis Louis , Slawin Kevin , Scardino Peter
Published: November 2002

BACKGROUND

The optimal management of patients with clinically localized prostate carcinoma remains undefined due in part to the absence of well‐designed, prospective, randomized trials. The current study was conducted to compare and contrast outcomes with different forms of therapy for patients with prostate carcinoma who were treated at several institutions using predefined prognostic categories.

METHODS

A retrospective study of 6877 men with prostate carcinoma who were treated between 1989 and 1998 at 7 different institutions with 6 different types of therapy was conducted. Five‐year actuarial rates of prostate specific antigen (PSA) failure were calculated based on predefined prognostic categories, which included combinations of pretreatment PSA level, tumor stage, and Gleason score. In addition, outcome was calculated using consistent biochemical failure definitions and a minimum, median length of follow‐up.

RESULTS

Substantial differences in outcome were observed for the same type of treatment and at the same institution, depending on the number of prognostic variables used to define treatment groups. However, estimates of 5‐year PSA outcomes after all forms of therapy for low‐risk and intermediate‐risk patient groups were remarkably similar (regardless of the type of treatment) when all three pretreatment variables were used to define prognostic categories. For patients in high‐risk groups, the 5‐year PSA outcomes were suboptimal, regardless of the treatment technique used.

CONCLUSIONS

The current data suggest that interinstitutional and interspecialty comparisons of treatment outcome for patients with prostate carcinoma are possible but that results must be based on all major prognostic variables to be meaningful. Analyzed in this fashion, 5‐year PSA results were similar for patients in low‐risk and intermediate‐risk groups, regardless of the form of therapy. Findings from prospective, randomized trials using survival (cause specific and overall) as the end point for judging treatment efficacy and longer follow‐up will be needed to validate these findings and to identify the most appropriate management option for patients with all stages of disease. Cancer 2002;95:2126–35. © 2002 American Cancer Society.

DOI 10.1002/cncr.10919
Potential marker of oral squamous cell carcinoma aggressiveness detected by fluorescence in situ hybridization in fine‐needle aspiration biopsies
Authors: Miyamoto Ryozo , Uzawa Narikazu , Nagaoka Shunya , Nakakuki Koichi , Hirata Yasushi , Amagasa Teruo
Published: November 2002

BACKGROUND

Amplification of chromosome 11q13 is a frequent event in carcinogenesis of the head and neck squamous cell carcinomas including oral carcinoma.

METHODS

Fluorescence in situ hybridization (FISH), using a BAC clone specific for the cyclin D1 gene (CCND1), was performed on specimens obtained by fine‐needle aspiration biopsy (FNAB) from 50 patients with primary oral squamous cell carcinomas (OSCCs.).

RESULTS

The CCND1 numerical aberration was identified in 21 (42.0%) of 50 patients with primary OSCCs. The CCND1 amplification was determined in 16 (32.0%) of these patients. Immunohistochemical staining revealed that all 21 tumors showing the CCND1 numerical aberration overexpressed the CCND1 protein. The CCND1 numerical aberration was associated significantly with histopathologic grading (P = 0.032), the mode of invasion (P = 0.047), the presence of cancer cells at the resection margin (P = 0.033), pathologic lymph nodestatus (P = 0.045), disease recurrence (P = 0.004), and survival (P = 0.004). The disease‐free and overall survival period of patients with the CCND1 numerical aberration was significantly shorter than that of patients without the CCND1 numerical aberration (P = 0.0016 and P = 0.0019, respectively). Moreover, a multivariate analysis showed that the CCND1 numerical aberration retained an independent prognostic value.

CONCLUSIONS

The CCND1 numerical aberration is useful both as a prognostic indicator that is independent of the TNM classification, and an indicator to assist in determination of the appropriate treatment for patients with OSCCs. Analysis of the CCND1 numerical aberration using FISH on FNABs may be a useful and practical method for predicting aggressive tumors, recurrence, and clinical outcome in patients with OSCCs. Cancer 2002;95:2152–9. © 2002 American Cancer Society.

DOI 10.1002/cncr.10929