bluuebunny/crossref_metadata_2025 huggingface dataset:
Typical failures in pyrolysis coils for ethylene cracking
Authors: Jakobi D. , Gommans R.
Published: October 2003

This paper points out the main failure mechanisms for tubes and outlet parts of pyrolysis furnace coils. In most cases there is a combination of factors which ultimately lead to the failure, e. g. carburization and creep ductility exhaustion. This results in bulging, bending and ovalisation of the tubes. Also, brittle fracture during furnace trips can result in large, longitudinal cracks on many tubes in the furnace.

The metallurgical background of the combined action of carburization and creep ductility exhaustion will be explained. Dense and stable oxide scales on the bore surface lower the amount of catalytic coke and also the carbon ingress into the alloy matrix (carburization). Carburization is also determined by the nickel content of the matrix. Creep ductility exhaustion is determined by the number of cycles (start/stop‐ and decoke cycles) and the nature (or severity) of these cycles.

Pyrolysis tube failures can be prevented by a combination of proper furnace operation, materials choice, regular inspections and good design.
Filamentous carbon formation caused by catalytic metal particles from iron oxide
Authors: Bonnet F. , Ropital F. , Berthier Y. , Marcus P.
Published: October 2003

The thermodynamic equilibrium between metallic iron, iron oxides, iron carbides and an hydrocarbon/hydrogen mixture was calculated at 600°C. On the basis of the metastable Fe‐C‐O phase diagram, both metallic iron and iron oxides can be directly converted into carbides in reducing and carburizing atmosphere. Thermogravimetric (ATG) measurements have been performed in iC4H10‐H2‐Ar atmosphere at 600°C on reduced and pre‐oxidised iron samples. The kinetic of coke formation was studied on both surface states by sequential exposure experiments. The initial stages of the transformation were characterised by scanning electron microscopy (SEM) observations and X‐ray diffraction (XRD) analysis. On a reduced surface, the results are consistent with the mechanism currently proposed to explain catalytic coke formation. Cementite (Fe3C) is formed on the iron surface after carbon supersaturation (ac > 1). The graphite deposition on its surface (ac = 1) induces its decomposition. Iron atoms from cementite diffuse through the graphite and agglomerate to small particles that act as catalysts for further carbon deposition. A new mechanism of catalytic particle formation is proposed when an oxide scale initially covers the iron surface. In the carburizing and reducing atmosphere, magnetite (Fe3O4) can be directly converted into cementite (Fe3C). XPS analysis confirm that, in this process, metallic iron is not an intermediary specie of the oxide/carbide reaction. At the same time, graphite deposition occurs at the metal/oxide interface through the cracks present in the oxide scale. Iron carbide in contact with graphite is partially decomposed and acts as catalyst for graphitic filaments growth.
Copolyester/layered silicate nanocomposites: The effect of the molecular size and molecular structure of the intercalant on the structure and viscoelastic properties of the nanocomposites
Authors: Kalgaonkar Rajendra A. , Jog Jyoti P.
Published: October 2003

The preparation of poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate)/layered silicate nanocomposites via a melt‐intercalation technique is reported. Layered silicates modified with different alkyl ammonium intercalants have been used for this purpose. A comparison is made between carefully chosen pairs of the nanocomposites, the choice depending on the cation‐exchange capacity or the intercalant concentration of the organically modified montmorillonite, to study the effects of the molecular size and molecular structure of the intercalant. The structure of the nanocomposites is characterized with wide‐angle X‐ray diffraction. The presence of well‐defined diffraction peaks and an observed increase in the interlayer spacing in the nanocomposites imply the formation of an intercalated hybrid. To investigate the viscoelastic behavior, these nanocomposites are also subjected to dynamic mechanical analysis. The dynamic mechanical properties show an increase in the storage modulus of the nanocomposites over the entire temperature range studied (except in the transition region from 68 to 78 °C) in comparison with that of the pristine polymer. The size of the intercalant molecule and the presence of functional groups capable of forming favorable interactions with the polymer govern the amount of polymer infiltrating the clay gallery space and control the increase in the modulus of the nanocomposite. The tan δ peak signifying the glass‐transition temperature shifts to lower temperatures in the nanocomposites. Interestingly, the nanocomposites show less damping than the pristine polymer. This behavior is understood in terms of the confinement of the polymer chains in the clay interlayer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3102–3113, 2003
The size and number of local free volumes in polypropylenes: A positron lifetime and PVT study
Authors: Kilburn D. , Bamford D. , Dlubek G. , Pionteck J. , Alam M. A.
Published: October 2003

The temperature dependence of the mean size of local free volumes in an amorphous atactic (aPP) and a semicrystalline syndiotactic polypropylene (sPP), and an amorphous ethylene‐propylene copolymer (E‐co‐P48) has been studied. Pressure‐volume‐temperature (PVT) experiments were performed for aPP, from which the hole fraction h of the Simha‐Somcynsky theory and the number density of holes were estimated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3089–3093, 2003
Development of the crystallinity and rigid amorphous fraction in cold‐crystallized isotactic polystyrene
Authors: Xu Hui , Ince B. Seyhan , Cebe Peggy
Published: October 2003

The phase structure of crystalline isotactic polystyrene (iPS) has been investigated with temperature‐modulated differential scanning calorimetry (TMDSC), wide‐angle X‐ray scattering (WAXS), and Fourier transform infrared (FTIR) spectroscopy. Quenched amorphous samples have been cold‐crystallized at 140 or 170 °C for various crystallization times. The degree of crystallinity obtained from WAXS, with the ratio of the crystal peak intensity to the total peak intensity, shows excellent agreement with the crystallinity determined from TMDSC total heat flow endotherms. For the first time, FTIR results show that the absorbance peak ratio (I/I) has a linear correlation with the crystalline mass fraction (χc) for cold‐crystallized iPS according to the following relation: I/I = 0.54χc + 0.16. This relationship allows the crystallinity of iPS to be determined from infrared spectroscopy analyses in cases in which it is difficult to perform thermal or X‐ray measurements. On the basis of the measurements of the heat capacity increment at the glass transition, we find that a significant amount of the rigid amorphous fraction (RAF) coexists with the crystalline and mobile amorphous phases in cold‐crystallized iPS. The RAF increases systematically with the crystallization time, and a greater amount is formed at a lower crystallization temperature. A three‐phase model (crystalline phase, mobile amorphous phase, and rigid amorphous phase) is, therefore, appropriate for the interpretation of the structure of cold‐crystallized iPS. The origin of the low‐temperature endothermic peak (annealing peak) has been investigated with TMDSC and FTIR spectroscopy and has been shown to be due to irreversible relaxation of the RAF. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3026–3036, 2003
Copolyimides containing alicyclic and fluorinated groups: Characterization of the film microstructure
Authors: Pinel Eliette , Barthe Marie‐France , De Baerdemaeker Jérémie , Mercier Régis , Neyertz Sylvie , Albérola N. Dominique , Bas Corine
Published: October 2003

The microstructures of a series of copolyimide films were characterized with different experimental methods such as density measurements, X‐ray diffraction, ultraviolet‐visible spectrophotometry, positron annihilation spectroscopy, and dynamic mechanical analysis. The experimental data were linked to the chemical structures of the polymers and especially the alicyclic and fluorinated monomers. Some analysis responses were directly dependent on the fluorine atoms and, therefore, did not provide clear information about the microstructures. The chain organization in the amorphous films appeared to be significantly dependent on the effect of the casting solvent. The influence of the alicyclic group content was quite significant for a nonsubstituted diamine but was strongly attenuated with a fluorinated diamine. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2998–3010, 2003
Influence of the surface chemistry on the structural and mechanical properties of silica‐polymer composites
Authors: Boisvert Jean‐Philippe , Persello Jacques , Guyard Aurélien
Published: October 2003

Poly(vinyl alcohol) (PVA) composite films filled with nanometric, monodisperse, and spherical silica particles were prepared by the mixing of an aqueous PVA solution and SiO2 colloidal suspension and the evaporation of the solvent. Adjusting the solution pH to 5 and 9 controlled the PVA‐SiO2 interaction. Adsorption isotherms showed a higher PVA/surface affinity at a lower pH. This interaction influenced the composite structure and the particle distribution within the polymer matrix, which was investigated by small‐angle neutron scattering, electron microscopy, and swelling measurements. Most of the mechanical properties could be related to the composite structure, that is, the distribution of clusters within the polymer matrix. The progressive creation of a cluster network within the polymeric matrix as the silica volume fraction increased reduced the extensibility or swelling capacity of the composite. The effect was more acute at a higher pH, at which the surface interaction with PVA was weaker and promoted the interconnection between clusters. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3127–3138, 2003
Genome‐wide scan for prostate cancer susceptibility genes using families from the University of Michigan prostate cancer genetics project finds evidence for linkage on chromosome 17 near BRCA1
Authors: Lange Ethan M. , Gillanders Elizabeth M. , Davis Cralen C. , Brown W. Mark , Campbell Joel K. , Jones MaryPat , Gildea Derek , Riedesel Erica , Albertus Julie , Freas‐Lutz Diana , Markey Carol , Giri Veda , Dimmer Jennifer Beebe , Montie James E. , Trent Jeffrey M. , Cooney Kathleen A.
Published: October 2003

BACKGROUND

Previous linkage studies have suggested prostate cancer susceptibility genes located on chromosomes 1, 20, and X. Several putative prostate cancer candidate genes have also been identified including RNASEL, MSR1, and ELAC2. Presently, these linkage regions and candidate genes appear to explain only a small proportion of hereditary prostate cancer cases suggesting the need for additional whole genome analyses.

METHODS

A genome‐wide mode‐of‐inheritance‐free linkage scan, using 405 genetic markers, was conducted on 175 pedigrees, the majority containing three or more affected individuals diagnosed with prostate cancer. Stratified linkage analyses were performed based on previously established criteria.

RESULTS

Results based on the entire set of 175 pedigrees showed strong suggestive evidence for linkage on chromosome 17q (LOD = 2.36), with strongest evidence coming from the subset of pedigrees with four or more affected individuals (LOD = 3.27). Race specific analyses revealed strong suggestive evidence for linkage in our African‐American pedigrees on chromosome 22q (LOD = 2.35).

CONCLUSIONS

Genome‐wide analysis of a large set of prostate cancer families indicates new areas of the genome that may harbor prostate cancer susceptibility genes. Specifically, our linkage results suggest that there is a prostate cancer susceptibility gene on chromosome 17 that is independent of ELAC2. Further research including combined analyses of independent genome‐wide scan data may clarify the most important regions for future investigation. Prostate 57: 326–334, 2003. Published 2003 Wiley‐Liss, Inc.
ROC methodology within a monitoring framework
Authors: Parker Corette B. , DeLong Elizabeth R.
Published: October 2003

Receiver operating characteristic (ROC) methodology is widely used to evaluate and compare diagnostic tests. Generally, each diagnostic test is applied once to each subject in a population and the results, reported on a continuous scale, are used to construct the ROC curve. We extend the standard method to accommodate a framework in which the diagnostic test is repeated over time to monitor for occurrence of an event. Unlike the usual situation in which event status is static, the problem we address involves event status that is not constant over the monitoring period. Subjects generally are classified as non‐events, or controls, until they experience events that convert them to cases. Viewing the data as incomplete discrete failure time data with time‐varying covariates, potentially useful diagnostic markers can be related appropriately in time with the true condition and varying amounts of information per individual can be taken into account. The ROC curve provides an assessment of the performance of the test in combination with the schedule of testing. Within this framework, a computational simplification is introduced to calculate variances and covariances for the areas under the ROC curves. Periodic monitoring for reperfusion following thrombolytic treatment for acute myocardial infarction provides a detailed example, whereby the lengths of the testing interval combined with different diagnostic markers are compared. Copyright © 2003 John Wiley & Sons, Ltd.
Overlaps in Dimensions of Poverty
Authors: BRADSHAW JONATHAN , FINCH NAOMI
Published: October 2003

The Poverty and Social Exclusion Survey of Britain made it possible first time to explore poverty using three different measures applied at the same time on the same sample. The measures were: lacking socially perceived necessities; being subjectively poor and having a relatively low income. These approaches are all commonly used to identify the poor and to measure poverty but rarely if ever in combination. In this article we have found that there is little overlap in the group of people defined as poor by these dimensions. There are reasons for this lack of overlap, connected to the reliability and validity of the different measures. However the people who are defined as living in poverty by different measures of poverty are different. This inevitably means that the policy response to poverty will be different depending on which measure is employed.

We have attempted to analyse overlap in two ways. First, by exploring the dimensions of poverty cumulatively, we have found that, the more dimensions people are poor on, the more they are unlike the non-poor and the poor on only one dimension, in their characteristics and in their social exclusion. Second, by treating particular dimensions as meriting more attention than others, we explored three permutations of this type and concluded that, while each permutation were more unlike the non-poor than those poor on a single dimension, they were not as unlike the non-poor as the cumulatively poor were. These results indicate that accumulation might be a better way of using overlapping measures of poverty than by giving priority to one dimension over another.

The implication of the paper is that it is not safe to rely on one measure of poverty – the results obtained are just not reliable enough. Surveys, such as the Family Resources Survey or the European Community Household Panel, which are used to monitor the prevalence of poverty, need to be adapted to enable results to be triangulated – to incorporate a wider range of poverty measures.
Who Influences the Fed? Presidential Versus Congressional Leadership
Authors: Saeki Manabu , Shull Steven A.
Published: October 2003

This paper examines political influences over U.S monetary policy, analysed quarterly from 1953 to 2000. We use indicators of presidential and congressional ideology as predictors of actor preferences and as representative of overhead democracy. We also include several economic variables predicting percent change in the federal funds rate. While not surprised to find that economic conditions are important in explaining Fed decisionmaking, we also find that the theory of overhead democracy also contributes to the explanation. Initially, both presidential and congressional ideology are important but in a combined model, presidential variables wash out influence of congressional variables. Thus, we conclude that overhead democracy must be included in models predicting Fed decisionmaking.
The subject knowledge of secondary music PGCE applicants: a response
Authors: Spruce Gary
Published: October 2003

The introduction of a ‘Points for Debate’ section in BJME is a welcome innovation. It provides a context in which important aspects of music education can be discussed in a friendly and temperate manner. It is in this spirit that I offer this response to Vic Gammon's interesting article concerning the subject knowledge of intending PGCE music students and how such knowledge might be identified.
Enlivening analysis through performance: ‘Practising set theory’
Authors: Mawer Deborah
Published: October 2003

This is a sister article to one that appeared in this journal in 1999, which established benefits in coupling instrumental study and voice-leading analysis, primarily for performers but also for analysts. That analytical students too were more receptive to study when connected with their instrument was the cue for the present article; performance has much to offer the teaching/learning of non-tonal analytical techniques founded on the basic tenets of set theory. This article details an experimental curriculum, ‘Practising set theory’, tested at Lancaster University across 2001–2, in comparison with more traditional methods employed across 1995–2002, and in relation to the new ‘Music benchmark statement’ (2002). Beyond the specifics, it is hoped this research may interest other practitioners seeking alternative pedagogical approaches to parts of the Music curriculum perceived as difficult or especially demanding.
Cloud systems leading to flood events in Europe: an overview and classification
Authors: Porcú Federico , Caracciolo Clelia , Prodi Franco
Published: October 2003

Over recent years most European countries have experienced destructive precipitation events, many of which have generated floods resulting in the loss of lives and economic damage. Rather surprisingly, Europe has no common database for flood events, which continue to be monitored by different national and/or local authorities, with different criteria. In the light of this situation, the main aim of the present work is to propose a classification scheme for a European‐level flood database, in which severe flood episodes are related to meteorological conditions and mesoscale settings.

The meteorological systems relating to the most severe events (22 events) over a five‐year period (1992–1996) were analysed using Meteosat imagery and conventional meteorological data. Most of the observed events were related to extra tropical cyclone development. The results are discussed in terms of conceptual models currently used for extra tropical cyclones: the structure and dynamics of Atlantic cyclones can very often be interpreted in terms of well‐ known conceptual models, while characteristics of Mediterranean systems are not fully rendered by current descriptions. Our study underpins the need to improve the knowledge of Mediterranean systems, possibly introducing new conceptual models and/or refining the current ones. Copyright © 2003 Royal Meteorological Society
Wind speed‐up in the Dover Straits with the Met Office New Dynamics Model
Authors: Capon Rachel Anne
Published: October 2003

It is part of British sailing and forecasting folklore that the wind speed increases in the Dover Straits when there is an established wind‐flow –westerly/south‐westerly or easterly/north‐easterly –along the English Channel. However the underlying mechanism of the phenomenon is unclear. We have used the Met Office ‘New Dynamics’ mesoscale model to perform a case study on an occasion when this phenomenon was observed in the Channel but not forecast well by the operational model, UM 4.5. Results are presented showing the sensitivity of forecasts to horizontal resolution (down to 2 km) and to vertical resolution. We probe the physical mechanism of the Channel jet by altering the surrounding orography and the land or sea surface roughness. Both the orography and the surface roughness are shown to influence the jet formation. Copyright © 2003 Royal Meteorological Society
Thermal advection, vorticity advection and potential vorticity advection in extra‐tropical, synoptic‐scale development
Authors: Carroll E B
Published: October 2003

The role of thermal advection in development is examined in its different guises, from the frontal cyclone model of the Bergen School, through the ideas of Sutcliffe and Petterssen, to the quasi‐geostrophic omega equation, system‐relative isentropic analysis and the potential vorticity (PV) perspective. The PV formulation of the omega equation introduced by Hoskins et al. (1985) is used, together with a simple quasi‐geostrophic numerical model, to compare system relative isentropic upgliding with full vertical velocity. The PV approach is compared with the application of the traditional omega equation, particularly with regard to cancellation between vorticity/potential vorticity and thermal advection terms. An equivalence is proved between the traditional form of the omega equation and the diagnosis of vertical velocity via ageostrophic motion, with the contribution from thermal advection being identified with the vertical motion that arises from isallobaric ageostrophic motion. Copyright © 2003 Royal Meteorological Society
The origin of captive Galápagos tortoises based on DNA analysis: implications for the management of natural populations
Authors: Burns Catherine E. , Ciofi Claudio , Beheregaray Luciano B. , Fritts Thomas H. , Gibbs James P. , Márquez Cruz , Milinkovitch Michel C. , Powell Jeffrey R. , Caccone Adalgisa
Published: October 2003

Giant tortoises once thrived throughout the Galápagos archipelago, but today three island populations are extinct, only one individual survives from the island of Pinta, and several populations are critically endangered. We established the geographic origin of 59 captive tortoises housed at the Charles Darwin Research Station in the Galápagos Islands in an effort to find a mate for the sole survivor from Pinta (‘Lonesome George’) and to augment the number of breeders in other imperilled populations. By comparison with an extensive database of mtDNA control region (CR) haplotypes and nine microsatellites, we determined the geographic and evolutionary origin of the captive individuals. All individuals had CR haplotypes and multilocus microsatellite genotypes identical to or closely related to known haplotypes from natural populations. No obvious mate was found for Lonesome George, although we found several captive individuals carrying an evolutionarily close but geographically distinct mtDNA haplotype. Tortoises with mtDNA haplotypes closely related to another at‐risk population (San Cristóbal) were also identified. These individuals could be considered as candidates for augmentation of natural populations or captive‐breeding programmes and exemplify how molecular techniques can provide insights for the development of endangered species management plans.
Fragmentation of Asia's remaining wildlands: implications for Asian elephant conservation
Authors: Leimgruber P. , Gagnon J. B. , Wemmer C. , Kelly D. S. , Songer M. A. , Selig E. R.
Published: October 2003

Habitat loss and fragmentation are main causes for Asian elephant population declines. We mapped wildlands ‐ large, unfragmented and undeveloped areas ‐ asking: (1) Where are the largest wildlands that constitute elephant habitats? (2) What proportion of these wildlands is protected? (3) What is their potential for elephant conservation? Our study demonstrates that wildlands constitute only 51% of the Asian elephant range. Myanmar has the largest wildland (∼170,000 km2), followed by Thailand and India. In Principal Components Analysis (PCA), the first two components explained 73% of the variation in fragmentation among ranges. We identified three fragmentation clusters from the PCA. Cluster A contains large ranges with unfragmented wildlands; cluster B includes ranges with well‐developed transportation networks and large human populations; and cluster C contains ranges with severely fragmented wildlands. In cluster A, we identified four ranges with elephant populations >1000 animals: ARYO, MYUC, BNMH and BITE. Together with ranges that support >1000 elephants in cluster B, these A ranges have great potential for long‐term elephant conservation. We propose that fragmentation clusters and population size can be used to identify different elephant monitoring and management zones.
Phylogeography and genetic diversity of the critically endangered Przewalski's gazelle
Authors: Lei Runhua , Hu Zhiang , Jiang Zhigang , Yang Wenlong
Published: October 2003

The Przewalski's gazelle (Procapra przewalskii) is critically endangered and has experienced significant decline in population numbers in the past, and now survives in four isolated populations: the Bird Island, Hudong‐Ketu, Yuanzhe and Shadao‐Gahai populations. To understand better the effect of habitat fragmentation and geographical isolation on gene flow and genetic variation, and uncover genetic units for conservation, we examined the hypervariable region (420 bp) of the mitochondrial DNA control region of 29 Przewalski's gazelles from four localities distributed throughout their present geographical range. Phylogenetic analysis consistently revealed four distinct mtDNA lineages within Przewalski's gazelle, with each lineage restricted to a single geographical location. The study revealed a marked divergence of lineages from the Bird Island population relative to other populations, which corresponds to the geographical association. The nucleotide diversity within populations was very low (less than 0.004). The value of Nm was less than 0.3 individuals per generation, indicating low gene flow between populations. It was suggested that the Yuanzhe, Hudong‐Ketu and Shadao‐Gahai populations be managed as a conservation unit because of their genetic and geographical closeness.
Continued CO2 outgassing in an upwelling area off northern Chile during the development phase of El Niño 1997–1998 (July 1997)
Authors: Torres Rodrigo , Turner David R. , Rutllant José , Lefèvre Nathalie
Published: October 2003

Carbonate system parameters were measured in the upper 200 m of the water column during July 1997 in an upwelling area off northern Chile (22.6°–24°S), and the CO2 fluxes were estimated. At this time (during the onset of El Niño 1997–1998), the water column that feeds the coastal upwelling was less dense, warmer, and saltier than in non‐El Niño winters. Nevertheless, the major vertical gradients in pH, total inorganic carbon (CT), carbon dioxide fugacity (fCO2), and apparent oxygen utilization (AOU) remained confined to the upper 100 m of the water column, so that the active upwelling forced by southerly winds caused the upwelling of CO2‐rich water leading a CO2 flux from the ocean to the atmosphere. However, these fluxes were found to be highly variable. Grid surveys 2 weeks apart show a change in CO2 flux from +3.9 mol C m−2 yr−1 to +0.4 mol C m−2 yr−1: the change is thought to be associated with a pulsed upwelling forcing in combination with an active biological uptake of CO2. This high short‐term variability of CO2 fluxes makes it difficult to assess the interannual variability of CO2 outgassing in this area based on low‐frequency direct CO2 observations. The fact that the oxycline, whose location usually coincides with the carboncline, also remained within the upper 100 m during the remarkably warm 1972 and 1983 El Niño winters seems to imply that the CO2 outgassing during those warm periods can be as strong as we report for 1997 under similar upwelling favorable winds.
Phytoplankton growth and microzooplankton grazing in high‐nutrient, low‐chlorophyll waters of the equatorial Pacific: Community and taxon‐specific rate assessments from pigment and flow cytometric analyses
Authors: Landry Michael R. , Brown Susan L. , Neveux Jacques , Dupouy Cécile , Blanchot Jean , Christensen Stephanie , Bidigare Robert R.
Published: October 2003

Phytoplankton growth and microzooplankton grazing rates were investigated using the seawater dilution technique during a French Joint Global Ocean Flux Study cruise focusing on grazing processes in the high‐nutrient, low‐chlorophyll equatorial Pacific at 180° (Etude du Broutage en Zone Equatoriale, October–November, 1996). Raw rate estimates based on spectrofluorometric and high‐performance liquid chromatography pigment analyses were typically in close agreement, but most showed substantial imbalances in growth and grazing. Flow cytometric (FCM) analyses were used both as an alternate approach for distinguishing populations and as a means for adjusting pigment‐based growth estimates for changes in cellular chlorophyll content and biovolume. Total chlorophyll a (Tchl a) gave mean community growth rates of 0.76 d−1 at 30 m and 0.27 d−1 at 60 m. Grazing rates averaged 0.56 and 0.15 d−1 at the two depths, respectively, and 69% of phytoplankton growth overall. For the prokaryotic picophytoplankter, Prochlorococcus (PRO), rate estimates from dv‐chl a and FCM cell counts generally indicated balanced growth and grazing and therefore close grazing control by microzooplankton. At the equator, rate estimates from dv‐chl a averaged 0.6–0.7 d−1 at 30 m and 0.25–0.26 at 60 m and were consistent with inferences based on diel pigment variations in the 30–70 m depth range. Phytoplankton production estimates from experimentally determined rates and microscopical assessments of autotrophic carbon at 30 m (mean = 19 mg C m−3 d−1) agreed well with contemporaneous measurements by 14C uptake. Diatom growth rate estimates (1.0–1.6 d−1), constrained by contemporaneous measurements of silicate uptake, implied a relatively small biomass (10–45 nmol C L−1) with high rates of turnover and recycling.
Comment on “Effects of fast and slow solar wind on the correlation between interplanetary medium and geomagnetic activity” by P. Ballatore
Authors: Wang C. B. , Chao J. K.
Published: October 2003

Ballatore [2002] has investigated the correlations between the interplanetary medium and the geomagnetic indices Kp and Dst for different ranges of solar wind speed. She found that the correlation coefficients obtained for data points corresponding to a solar wind slower than 550 km s−1 are equal to or slightly higher than the global correlations. The observations show generally lower correlation coefficients for solar wind speeds greater than 550 km s−1. From these results she verified that at high solar wind speeds the processes responsible for the energy transfer between the interplanetary medium and the magnetosphere saturate. We have recalculated the correlation coefficients using the most recent OMNI data and found, contrary to her results, that the global correlation coefficients between Kp, Dst, and the interplanetary parameters are generally higher than the correlations obtained for data points corresponding to different solar wind speed intervals. From statistical tests we demonstrate that the correlations for solar wind speeds greater than 550 km s−1 are not significantly different from the correlations in other solar wind speed intervals. There is insufficient evidence to show that, from an investigation of the correlation coefficients between the interplanetary medium and the geomagnetic indices Kp and Dst, a threshold exists at a solar wind speed of ∼550 km s−1 for the coupling of the interplanetary‐magnetosphere system. This conclusion is also supported by analysis of the correlations between the time derivation of Dst and the interplanetary medium.
Climatological analysis of tornado report counts using a hierarchical Bayesian spatiotemporal model
Authors: Wikle Christopher K. , Anderson Christopher J.
Published: October 2003

Recent evidence suggests that tornado report counts for monthly or longer periods may be correlated to climate indices in space and time. However, the climatological analysis of tornado reports is complicated by reporting errors, by the non‐Gaussian nature of count data and rare events, and by the presence of spatial and temporal correlation. Typically, such factors have not been formally included in the underlying statistical model used for inferential decisions. We present an analysis in which a statistical model is constructed so that the aforementioned characteristics of tornado reports are explicitly accommodated in the model structure. In particular, a hierarchical Bayesian framework is considered, in which the various complicated structures are considered in a series of conditional models, formally linked by basic probability rules. This formalism allows one to evaluate characteristics of the spatiotemporal variability of an underlying (unobservable) tornado count process given the noisy observations (tornado reports). In addition, one can consider the effects of exogenous climate processes on this tornado count process. We find that an index of El Niño activity is significantly associated with tornado reports over the continental U.S. and that there is substantial regional variability in this relationship. In addition, we find evidence of temporal trends in tornado counts, with spatial variation in the magnitude and sign of the trend.
Intrusive mechanism of the 2002 NE‐Rift eruption at Mt. Etna (Italy) inferred through continuous microgravity data and volcanological evidences
Authors: Branca Stefano , Carbone Daniele , Greco Filippo
Published: October 2003

In October 2002 a new eruption began at Etna. Lava flows were issued from two different fissure systems on the NE and S flanks of the volcano. A continuous microgravity sequence, acquired at a station on the N slope (2800 m a.s.l.), shows a marked decrease (about 400 μGal in less than one hour) about 4 hours before lava was first emitted from the eruptive fissures along the NE‐Rift. This anomaly reversed soon afterward at a high rate. The strong gravity decrease is interpreted as the opening, by external forces, of a shallow fracture system 1 km W of the gravity station. Magma from the central conduit entered the new fracture system passively, and propagated through it towards lower portions of the NE‐Rift. Both the arrangement of the new fracture system and the eruptive dynamics are in keeping with the inferred intrusive mechanism.
Reply to Comment on “Effects of fast and slow solar wind on the correlations between interplanetary medium and geomagnetic activity” by C. B. Wang and J. K. Chao
Authors: Ballatore Paola
Published: October 2003

The paper Ballatore [2002] (the paper commented) shows that the statistical significance of the correlations between the interplanetary parameters and the geomagnetic indices (Kp or Dst) is generally less significant during the fastest solar wind. On the other hand, at these fast solar wind periods, the significance of the Kp versus Dst correlation is equal to or higher than during slower solar wind. These results, together with further observations related to substorm periods and with previously published findings, are interpreted in terms of a difference in the interplanetary‐magnetospheric coupling for solar wind faster or slower than a certain threshold (identified between about 500 and 600 km/s). Specifically, it is suggested that a possible linear approximation of the geomagnetic‐interplanetary coupling is more appropriate during solar wind speed (Vsw) slower than this threshold, being nonlinear processes more dominant during the fastest speeds. This reply highlights that the correlation coefficients shown by Wang and Chao [2003] are in agreement with these findings. In addition, Wang and Chao show that the statistical significance of the difference between the correlation coefficients for Vsw ≥ 550 km/s and those for Vsw < 550 km/s would indicate that the interplanetary‐geomagnetic correlations during the fastest speeds are not significantly different from those at slower Vsw ranges. Here we give evidence of the fact that according to the common definition of this parameter, the calculation of the significance of the difference between two correlation coefficients made by Wang and Chao is wrong. Moreover, Wang and Chao recalculate the correlations between the interplanetary parameters and the ΔDst instead of Dst; in fact they note that the time derivative of this index (not the index itself) is driven by the interplanetary medium. Here we note that on the contrary, they show that the correlation coefficients between interplanetary parameters and Dst are larger than those obtained using ΔDst and we suggest a possible interpretation in terms of nonlinearity.
Stardust: Comet and interstellar dust sample return mission
Authors: Brownlee D. E. , Tsou P. , Anderson J. D. , Hanner M. S. , Newburn R. L. , Sekanina Z. , Clark B. C. , Hörz F. , Zolensky M. E. , Kissel J. , McDonnell J. A. M. , Sandford S. A. , Tuzzolino A. J.
Published: October 2003

Stardust, the 4th Discovery mission launched in February 1999, will collect coma samples from the recently deflected comet 81P/Wild 2 on 2 January 2004 and return them to Earth on 15 January 2006 for detailed laboratory analyses. Stardust will be the first mission to bring samples back to Earth from a known comet and also the first to bring back contemporary interstellar particles recently discovered. These samples should provide important insights into the nature and amount of dust released by comets, the roles of comets in planetary systems, clues to the importance of comets in producing dust in our zodiacal cloud as well as circumstellar dust around other stars, and the links between collected meteoritic samples with a known cometary body. Samples are collected in newly invented continuous gradient density silica aerogel. Stardust is facilitated by a magnificent trajectory designed to accomplish a complex and ambitious flyby sample return mission within the Discovery program restrictions. The remaining science payload, which provides important context for the captured samples, includes a time‐of‐flight spectrometer measuring the chemical and isotopic composition of dust grains; a polyvinylidene fluoride dust flux monitor determining dust flux profiles; a CCD camera for imaging Wild 2 coma and its nucleus; a shared X band transponder providing two‐way Doppler shifts to estimate limits to Wild 2 mass and integrated dust fluence; and tracking of the spacecraft's attitude sensing for the detection of large particle impacts. The graphite composite spacecraft brings the collected sample back to Earth by a direct reentry in a capsule.
The modified Stroop paradigm as a measure of selective attention towards pain‐related stimuli among chronic pain patients: a meta‐analysis
Authors: Roelofs Jeffrey , Peters Madelon L. , Zeegers Maurice P. A. , Vlaeyen Johan W. S.
Published: October 2003

Although the modified Stroop paradigm is considered to be a prominent paradigm for investigating selective attention in emotional disorders, relatively few studies have applied this paradigm to examine selective attention in chronic pain patients. Moreover, the results from these studies are not robust. The purpose of this article is to review the evidence for attentional bias in chronic pain patients, by means of a meta‐analysis. Data from five studies were pooled and summarized into a mean difference (MD). Significant MD estimations (in milliseconds) were found for both sensory pain words (MD = 26.7; 95% confidence interval (CI) 10.0–42.9) and affective pain words (MD = 28.1; 95% CI 0.4–55.8). Meta‐regression analysis indicated that methodological quality did not significantly affect the pooled MD estimation for both sensory pain words and affective pain words. Thus, the results from the present meta‐analysis on studies applying the modified Stroop paradigm suggest that chronic pain patients selectively attend to both pain sensory and pain affective stimuli. Furthermore, the MD estimation did not depend on the methodological quality, tentatively indicating that even though studies differed in methodology, the results were rather consistent. Implications of the results are discussed. © 2002 European Federation of chapters of the International Association for the Study of Pain. Published by Elsevier Science Ltd. All rights reserved.
Involvement of N‐methyl‐D‐aspartate receptors in nociception in the cyclophosphamide‐induced vesical pain model in the conscious rat
Authors: Méen Murielle , Coudoré‐Civiale Marie‐Ange , Parry Laurent , Eschalier Alain , Boucher Michel
Published: October 2003

We previously showed that the intraperitoneal (i.p.) administration of 200 mg/kg cyclophosphamide, an antitumoral agent, modified the behaviour of rats with cystitis induced by acrolein, a toxic urinary by‐product of cyclophosphamide. This behaviour, (namely decreased breathing rate, closing of the eyes, and specific postures), was scored to indirectly assess the nociception elicited by the cystitis and to use this experimental model as a vesical pain model. Here we investigated the involvement of the N‐methyl‐D‐aspartate (NMDA) receptors and thus of the excitatory amino acid system in this model.

We administered dizocilpine (0.01 to 0.1 mg/kg intravenously (i.v.) and 1 to 20 μg/rat intrathecally (i.t.)) and ketamine (5 and 10 mg/kg i.v. and 50 to 1000 μg/rat i.t.), two non‐competitive NMDA receptor antagonists that bind to the channel site, and AP‐5 (0.01 to 1 mg/kg i.v. and 20 to 500 μg/rat i.t), a competitive antagonist that binds to the glutamate site. Whichever the route of administration (i.v. or i.t.), dizocilpine dose‐relatedly reduced the behavioural disorders induced by cyclophosphamide. Systemic ketamine also dose‐dependently, though transiently, reduced the effects of cyclophosphamide, but ketamine i.t. and AP‐5 i.v. and i.t. did not induce any reduction of these effects.

These results (i) demonstrate that in the cyclophosphamide‐induced vesical pain model NMDA receptors are involved in the nociception, as shown by the effects of dizocilpine and systemic ketamine, (ii) reveal marked differences in the data obtained with various NMDA receptor antagonists, possibly due to their physicochemical properties, to the animal pain model used, to the noxious stimulus applied or to any combination of these factors. © 2002 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Science Ltd. All rights reserved.
A model for persistent hole burned spectra and hole growth kinetics that includes photoproduct absorption: Application to free base phthalocyanine in hyperquenched glassy ortho-dichlorobenzene at 5 K
Authors: Reinot T. , Dang N. C. , Small G. J.
Published: October 2003

Persistent nonphotochemical and photochemical hole burning of the S0→S1 origin absorption bands of chromophores in amorphous hosts such as glasses, polymers and proteins at low temperatures have been used to address a number of problems that range from structural disorder and configurational tunneling to excitation energy transfer and charge separation in photosynthetic complexes. Often the hole burned spectra are interfered by photoproduct (antihole) absorption. To date there has been no systematic approach to modeling hole burned spectra and the dispersive kinetics of zero-phonon hole growth that accounts for the antihole. A “master” equation that does so is presented. A key ingredient of the equation is a time-dependent, two-dimensional site excitation frequency distribution function (SDF) of the zero-phonon lines. Prior to hole burning (t=0) the SDF is that of the educt sites. For t>0 the SDF describes both educt and photoproduct sites and allows for burning of the latter that revert to the educt sites from which they originate (light-induced hole filling). Our model includes linear electron–phonon coupling and the three distributions that lead to dispersive hole growth kinetics, the most important of which is the distribution for the parameter λ associated with tunneling between the bistable configurations of the chromophore-host system that are interconverted by hole burning. The master equation is successfully applied to free base phthalocyanine (Pc) in hyperquenched glassy ortho-dichlorobenzene (DCB) at 5 K. The mechanism of hole burning is photochemical and involves tautomerization of the two protons at the center of the macrocycle (Pc) that occurs in the S1(Qx) and/or T1(Qx) state of Pc. A single set of parameter values (some of which are determined directly from the hole burned spectra) provides a satisfactory description of the dependence of the hole burned spectra and hole growth kinetics on the location of the burn frequency within the inhomogeneously broadened Qx absorption band. The hole growth kinetics are found to be quite highly dispersive, although to a lesser degree than the kinetics for free base phthalocyanine tetrasulphonate in hyperquenched glassy water [Reinot et al., J. Lumin. 98, 183 (2002)]. The dispersion is attributed to structural heterogeneity of solvent molecules in the inner shell that leads to a distribution of chromophore-host interactions that affect the height of the barrier separating the two tautomers. The new master equation should also prove useful with no additional assumptions or modifications for interpretation of nonphotochemical hole burned spectra.
A many-body interatomic potential for ionic systems: Application to MgO
Authors: Tangney P. , Scandolo S.
Published: October 2003

An analytic representation of the short-range repulsion energy in ionic systems is described that allows for the fact that ions may change their size and shape depending on their environment. This function is extremely efficient to evaluate relative to previous methods of modeling the same physical effects. Using a well-defined parametrization procedure we have obtained parameter sets for this energy function that reproduce closely the density functional theory potential energy surface of bulk MgO. We show how excellent agreement can be obtained with experimental measurements of phonon frequencies and temperature and pressure dependences of the density by using this effective potential in conjunction with ab initio parametrization.
Molecular dynamics study of the melting of nitromethane
Authors: Agrawal Paras M. , Rice Betsy M. , Thompson Donald L.
Published: October 2003

Molecular dynamic studies of melting of nitromethane have been carried out using two methods: (1) void-nucleated melting with the gradual heating of the lattice and (2) equilibration of coexisting liquid and solid phases. The results are in near agreement with each other; the small difference is attributed to the hysteresis effect associated with the direct heating process. The values of the melting temperature Tm computed by using the intermolecular interaction potential of Sorescu et al. [J. Phys. Chem. B 104, 8406 (2000)] are found to be in good agreement with the experimental data at various values of pressure ranging from 1 atm to 30 kbar. The computed values of the melting temperature satisfy the Simon–Glatzel equation P(kbar)=aTmb+c, where a=1.597×10−5, b=2.322, c=−6.74, and Tm is in kelvin. A comparison of computed Tm with and without the presence of molecular vibrations reveals that Tm is insensitive to the intramolecular interaction term of the potential energy function, but depends strongly on the intermolecular interactions, particularly the Coulombic term (i.e., the partial charges on atoms).