bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz quantum-cascade laser at λ≈100 μm using metal waveguide for mode confinement
Authors: Williams Benjamin S. , Kumar Sushil , Callebaut Hans , Hu Qing , Reno John L.
Published: September 2003

We report lasing at ∼3.0 THz (λ≈98–102 μm) in a quantum-cascade structure in which mode confinement is provided by a double-sided metal waveguide. The depopulation mechanism is based on resonant phonon scattering, as in our previous work. Lasing takes place in pulsed mode up to a heat-sink temperature of 77 K. The waveguide consists of metallic films placed above and below the 10-μm-thick multiple-quantum-well gain region, which gives low losses and a modal confinement factor of nearly unity. Fabrication takes place via low-temperature metallic wafer bonding and subsequent substrate removal using selective etching. This type of waveguide is expected to be increasingly advantageous at even longer wavelengths.
Shedding Light on the Conformation of Proteins and Other Macromolecules at an Interface
Authors: Gee Michelle L. , Smith Trevor A.
Published: September 2003

An attractive way to probe interfacial phenomena is through the utilization of total internal reflection-based spectroscopic methods, in which the evanescent field is used to photo-excite an absorbing species situated within the penetrating field. In this paper we discuss both absorbance and time-resolved fluorescence evanescent wave techniques that we have developed. We highlight how these techniques can be utilized successfully for interrogating the adsorption behaviour of proteins and polymers as a function of distance from a solid/solution interface into bulk solution. Information provided by these methods regarding how protein and polymer molecular conformation is affected by their adsorption/interaction at a surface is discussed with specific reference to poly(2-vinylpyridine), hen egg white lysozyme, and bovine serum albumin.
Biomimetic Honeycomb-Structured Surfaces Formed from Block Copolymers Incorporating Acryloyl Phosphorylcholine
Authors: Stenzel Martina H. , Davis Thomas P.
Published: September 2003

We report the preparation of biomimetic honeycomb-structured porous films. These regular arrays were obtained by casting block copolymers composed of polystyrene and poly(acryloyl phosphorylcholine), so that they mimicked a cell membrane. The size of the pores and regularity of the hexagonal array is strongly dependent on the block length. The block copolymers were prepared via RAFT (reversible addition fragmentation transfer) polymerization leading to well-defined products with a good control over block sizes.
Evolution of the coastal neospecies Zieria prostrata (Rutaceae) and its relationship to the Zieria smithii species complex
Authors: Hogbin Patricia M. , Crisp Michael D.
Published: September 2003

The endangered plant Zieria prostrata J.A.Armstrong (Rutaceae) is known from only four coastal headlands in northern New South Wales, Australia. The discovery of another headland Zieria form, Z. sp. aff. smithii, raised questions about the taxonomic status of Z. prostrata and its relationship to the Z. smithii Jacks. species complex. Morphometrics was used as the primary tool for investigating the relationship between Z.�prostrata and the Z. smithii species complex, while a genetic study utilising RAPD markers was used to assess the validity of the distinct evolutionary lineages implied by the morphometric analysis. Z. prostrata formed a distinct group in phenetic space based upon the morphometric data, but with an incomplete discontinuity between it and nearby populations of Z. smithii based upon the genetic data, implying that Z. prostrata may be considered a distinct but incipient species. While the morphometric data set suggested that Z. sp. aff. smithii may be worthy of subspecific status, the genetic data revealed that each headland population is likely to have originated independently from inland populations of Z. smithii. Therefore, the morphological similarity among populations of Z. sp. aff. smithii does not reflect evolutionary relatedness, but rather is likely to be a consequence of parallelism and active or rapid speciation. Z. sp. aff. smithii is therefore considered to be a headland ecotype of Z. smithii.
Land use effects on sorption of pesticides and their metabolites in sandy soils. I. Fenamiphos and two metabolites, fenamiphos sulfoxide and fenamiphos sulfone, and fenarimol and azinphos methyl
Authors: Oliver D. P. , Kookana R. S. , Salama R. B.
Published: September 2003

There is very limited information about the effect of land use on sorption behaviour of organic chemicals. It has been documented that clearing natural vegetation and cropping soil typically decreases the original organic carbon (OC) content of soil. Because OC is one of the major parameters controlling pesticide sorption, the effects of land use on the sorption behaviour of fenamiphos and its 2 main metabolites, fenamiphos sulfone (f. sulfone) and fenamiphos sulfoxide (f. sulfoxide), together with fenarimol and azinphos methyl were investigated. Based on sorption isotherms for a subset of soils, using a range of concentrations (2.5, 5.0, 7.5, and 10 mg/L), the use of a single concentration (2 mg/L) was considered adequate to determine sorption coefficients. Generally the Kd values for fenamiphos were significantly (P�<�0.005) higher than those of its 2 metabolites. The sorption coefficients decreased in the order: fenamiphos >> f. sulfone ≥� f. sulfoxide. As both metabolites can apparently move more easily through soil than fenamiphos, they would pose a greater risk to groundwater contamination. For all compounds, only weak relationships were determined between Kd and pH or %silt + clay. Similarly, the relationship between Kd and %OC was poor, when data from all soils were combined for analysis. However, a strong relationship was obtained between sorption coefficients and %OC for fenamiphos in market garden soils (r2 = 0.76***). This was also the case for azinphos methyl and fenarimol, particularly in soils under native vegetation (r2�=�0.71 and 0.73***, respectively). At a given OC content, the soils under Banksia bush generally showed greater sorption than those under market gardens. This effect became more pronounced with increasing OC content, suggesting that the nature and composition of the OC in soils under native vegetation are likely to be different from that in cultivated soils. Clearly the OC content is not an adequate parameter describing the complex interactions between pesticides and organic matter.
Land use effects on sorption of pesticides and their metabolites in sandy soils. II. Atrazine and two metabolites, deethylatrazine and deisopropylatrazine, and prometryne
Authors: Oliver D. P. , Kookana R. S. , Salama R. B. , Correll R.
Published: September 2003

There is very limited information about the effect of land use on sorption behaviour of organic chemicals. The effects of land use on the sorption behaviour of prometryne, atrazine, and its 2 main metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), in sandy soils were studied. This study would provide fate data for these chemicals specifically for Australian soils. Sorption coefficients (Kd) were determined using batch studies and a single solution concentration (2 mg/L for atrazine, DEA, and DIA, and 3 mg/L for prometryne) after initially determining sorption isotherms for a subset of 6 soils for atrazine and prometryne using a range of concentrations. Generally, the Kd values for prometryne were significantly (P < 0.001) greater than for the other 3 compounds. There was no consistent trend in the Kd values for atrazine and the 2 metabolites. This study demonstrated that prometryne was least likely to pose a risk to groundwater contamination but in some cases both atrazine metabolites (DEA and DIA) were less sorbed in the soils than the parent compound. Consequently the metabolites could pose a greater risk to groundwater quality than the parent compound. In the surface soils, significantly (P < 0.05) greater Kd values were determined under native vegetation for DIA, atrazine and prometryne. In the subsurface soils significantly (P < 0.001) greater Kd values were observed under native vegetation for all 4 chemicals. This may be related to differences in the nature and type of OC content of soils under the 2 land uses. There were significant (P < 0.001) positive relationships for the market garden soils between Kd and OC for atrazine, DIA, and DEA (r2 = 0.85, 0.86, and 0.51, respectively). The relationship for prometryne and OC was not significant for all soils. The relationship between Koc and pH was significant (P < 0.001) for prometryne (r2 = 0.70 all soils, r2 = 0.64 native vegetation only). Prometryne Koc values were also fitted to a model to predict changes in sorption of ionic pesticides with changes in pH. The data fitted the predictive model reasonably well at pHw >5, but at more acidic pH values the data deviated from the model predictions suggesting an increase in the cationic form of the pesticide that readily bind to negatively charged clay particles rather than OC. This study demonstrated that land use significantly (P < 0.05) affected the sorption behaviour of DIA, atrazine, and prometryne. It also highlighted the potential risk that pesticide metabolites may pose in areas where groundwater is used as a drinking water supply. Clearly there is a need for the metabolites to be considered when establishing guidelines for drinking water.
Interaction effects of clay swelling and dispersion and CaCO3 content on saturated hydraulic conductivity
Authors: Keren Rami , Ben-Hur Meni
Published: September 2003

Typic Chromoxeret-sand and Lithic Ruptic Xerochrept-sand mixtures, of high sodicity, and containing 8 and ~0% CaCO3, respectively, were packed in columns and leached with electrolyte solutions. When a reference solution of 500 mmol/L was replaced successively with solutions containing 100, 50, 10, 5, and 1 mmol/L and then with deionised water (gradual leaching), the saturated hydraulic conductivity (Ks) decreased gradually to steady-state values, and no clay was observed in the leachate. Under deionised leaching, the relative Ks (Ks/Ks0) (the ratio between the observed Ks and that under leaching with the reference solution) in the Chromoxeret mixture at exchangeable sodium percentages (ESPs) of 30, 38, and 63 was 0.83, 0.47, and 0.41, respectively, and that in the Xerochrept mixture at ESPs of 23, 28, and 36 were 0.82, 0.71, and 0.39 respectively. When a solution of 50 mmol/L was replaced directly with deionised water (abrupt leaching), the Ks/Ks0 of the Chromoxeret mixture at the above ESPs dropped sharply to minimum values of 0.25, 0.18, and 0.11, respectively, and that of the Xerochrept mixture to 0.42, 0.04, and 0.13, respectively, and dispersed clay was observed in the leachate. It is hypothesised that the abrupt leaching with deionised water generated a steep concentration gradient between the solutions within and around the aggregates, leading to clay dispersion and rapid Ks/Ks0 reduction; under gradual leaching, no steep concentration gradient developed, there was no clay dispersion, and clay swelling caused gradual Ks/Ks0 reduction. In the Chromoxeret, the CaCO3 decreased the clay swelling and dispersion, and probably acted as a cementing agent that stabilised the soil aggregates against slaking during the initial wetting of the mixture.
A technique to assess small-scale heterogeneity of chemical properties in soil aggregates
Authors: Kirchhof G. , Daniel H.
Published: September 2003

A new method is presented which allows the separation of the soil aggregate exterior from the aggregate core. The method employs a combination of aggregate freezing with rapid separation of aggregate exteriors using ultrasonic energy. The factors influencing the thickness of the removed aggregate surface layer include water content of the aggregate prior to freezing, temperature difference between that of the frozen aggregate and that of the liquid it is submerged in during sonification, sonification time and energy, and the type of the immersion liquid. The success of the method and the thickness of the removed aggregate surface were examined using barium (Ba2+) as a tracer. Barium (as BaCl2) is rapidly absorbed by soil and is present at only very low levels in natural soils. Surface layers of 0.2–0.4 cm thickness were successfully removed from aggregates of 1–4�cm diameter. Two examples are given from soils in northern NSW to demonstrate the occurrence of small-scale hetero-geneity in soil chemical properties. Compared with the surface fraction, a 4–7% higher calcium concentration was found in the core fraction of a clay loam soil (Dermosol). Conversely, on a cracking clay soil (Vertosol), atrazine concentration was around 15 times greater in the aggregate surface fractions compared with core fractions. Compared with the traditional estimation of soil chemical properties on homogenised bulk soil samples, it is suggested that separate analysis of aggregate surface and core fractions could provide useful additional information on the relationships between soil properties and environmental responses.
Is there a meaningful definition of sustainability?
Authors: Owens Susan
Published: September 2003

Although the concept of ‘sustainable development’ has been hailed for its reconciliatory poten- tial, it has failed in practice to resolve enduring conflicts. Exploring the evolution of the concept—from its 19th-century antecedents through Brundtland to contemporary ‘Panglossian’ interpretations—the paper argues that difficulties of implementation are not transient but have deep roots. No conception of sustainable development can be adopted without making fundamental ethical and political choices, but the debate about such choices is nevertheless of great importance. It is argued that we should abandon our search for a singular, consensual definition of sustainability, but try as best we can to make progress in the absence of consensus.
Finite element modelling of contracting skeletal muscle
Authors: Oomens C. W. J. , Maenhout M. , van Oijen C. H. , Drost M. R. , Baaijens F. P.
Published: September 2003

To describe the mechanical behaviour of biological tissues and transport processes in biological tissues, conservation laws such as conservation of mass, momentum and energy play a central role. Mathematically these are cast into the form of partial differential equations. Because of nonlinear material behaviour, inhomogeneous properties and usually a complex geometry, it is impossible to find closed-form analytical solutions for these sets of equations. The objective of the finite element method is to find approximate solutions for these problems.

The concepts of the finite element method are explained on a finite element continuum model of skeletal muscle. In this case, the momentum equations have to be solved with an extra constraint, because the material behaves as nearly incompressible. The material behaviour consists of a highly nonlinear passive part and an active part. The latter is described with a two-state Huxley model. This means that an extra nonlinear partial differential equation has to be solved. The problems and solutions involved with this procedure are explained. The model is used to describe the mechanical behaviour of a tibialis anterior of a rat. The results have been compared with experimentally determined strains at the surface of the muscle. Qualitatively there is good agreement between measured and calculated strains, but the measured strains were higher.
Approaches to the structural modelling of insect wings
Authors: Wootton R. J. , Herbert R. C. , Young P. G. , Evans K. E.
Published: September 2003

Insect wings lack internal muscles, and the orderly, necessary deformations which they undergo in flight and folding are in part remotely controlled, in part encoded in their structure. This factor is crucial in understanding their complex, extremely varied morphology. Models have proved particularly useful in clarifying the facilitation and control of wing deformation. Their development has followed a logical sequence from conceptual models through physical and simple analytical to numerical models. All have value provided their limitations are realized and constant comparisons made with the properties and mechanical behaviour of real wings. Numerical modelling by the finite element method is by far the most time–consuming approach, but has real potential in analysing the adaptive significance of structural details and interpreting evolutionary trends. Published examples are used to review the strengths and weaknesses of each category of model, and a summary is given of new work using finite element modelling to investigate the vibration properties and response to impact of hawkmoth wings.
Inverse and forward dynamics: models of multi–body systems
Authors: Otten E.
Published: September 2003

Connected multi–body systems exhibit notoriously complex behaviour when driven by external and internal forces and torques. The problem of reconstructing the internal forces and/or torques from the movements and known external forces is called the ‘inverse dynamics problem’, whereas calculating motion from known internal forces and/or torques and resulting reaction forces is called the ‘forward dynamics problem’. When stepping forward to cross the street, people use muscle forces that generate angular accelerations of their body segments and, by virtue of reaction forces from the street, a forward acceleration of the centre of mass of their body. Inverse dynamics calculations applied to a set of motion data from such an event can teach us how temporal patterns of joint torques were responsible for the observed motion. In forward dynamics calculations we may attempt to create motion from such temporal patterns, which is extremely difficult, because of the complex mechanical linkage along the chains forming the multi–body system.

To understand, predict and sometimes control multi–body systems, we may want to have mathematical expressions for them. The Newton–Euler, Lagrangian and Featherstone approaches have their advantages and disadvantages. The simulation of collisions and the inclusion of muscle forces or other internal forces are discussed. Also, the possibility to perform a mixed inverse and forward dynamics calculation are dealt with. The use and limitations of these approaches form the conclusion.
How to perform measurements in a hovering animal's wake: physical modelling of the vortex wake of thehawkmoth,Manduca sexta
Authors: Tytell Eric D. , Ellington Charles P.
Published: September 2003

The vortex wake structure of the hawkmoth,Manduca sexta, was investigated using a vortex ring generator. Based on existing kinematic and morphological data, a piston and tube apparatus was constructed to produce circular vortex rings with the same size and disc loading as a hovering hawkmoth. Results show that the artificial rings were initially laminar, but developed turbulence owing to azimuthal wave instability. The initial impulse and circulation were accurately estimated for laminar rings using particle image velocimetry; after the transition to turbulence, initial circulation was generally underestimated. The underestimate for turbulent rings can be corrected if the transition time and velocity profile are accurately known, but this correction will not be feasible for experiments on real animals. It is therefore crucial that the circulation and impulse be estimated while the wake vortices are still laminar. The scaling of the ring Reynolds number suggests that flying animals of about the size of hawkmoths may be the largest animals whose wakes stay laminar for long enough to perform such measurements during hovering. Thus, at low advance ratios, they may be the largest animals for which wake circulation and impulse can be accurately measured.
Nitrogen Deficiency Increases Volicitin-Induced Volatile Emission, Jasmonic Acid Accumulation, and Ethylene Sensitivity in Maize
Authors: Schmelz Eric A. , Alborn Hans T. , Engelberth Juergen , Tumlinson James H.
Published: September 2003

Insect herbivore-induced plant volatile emission and the subsequent attraction of natural enemies is facilitated by fatty acid-amino acid conjugate (FAC) elicitors, such as volicitin [N-(17-hydroxylinolenoyl)-l-glutamine], present in caterpillar oral secretions. Insect-induced jasmonic acid (JA) and ethylene (E) are believed to mediate the magnitude of this variable response. In maize (Zea mays) seedlings, we examined the interaction of volicitin, JA, and E on the induction of volatile emission at different levels of nitrogen (N) availability that are known to influence E sensitivity. N availability and volicitin-induced sesquiterpene emission are inversely related as maximal responses were elicited in N-deficient plants. Plants with low N availability demonstrated similar volatile responses to volicitin (1 nmol plant-1) and JA (100 nmol plant-1). In contrast, plants with medium N availability released much lower amounts of volicitin-induced sesquiterpenes compared with JA, suggesting an alteration in volicitin-induced JA levels. As predicted, low N plants exhibited greater sustained increases in wound- and volicitin-induced JA levels compared with medium N plants. N availability also altered volicitin-E interactions. In low N plants, E synergized volicitin-induced sesquiterpene and indole emission 4- to 12-fold, with significant interactions first detected at 10 nL L-1 E. Medium N plants demonstrated greatly reduced volicitin-E interactions. Volicitin-induced sesquiterpene emission was increased by E and was decreased by pretreatment the E perception inhibitor 1-methylcyclopropene without alteration in volicitin-induced JA levels. N availability influences plant responses to insect-derived elicitors through changes in E sensitivity and E-independent JA kinetics.
Class I Chitinase and β-1,3-Glucanase Are Differentially Regulated by Wounding, Methyl Jasmonate, Ethylene, and Gibberellin in Tomato Seeds and Leaves
Authors: Wu Chun-Ta , Bradford Kent J.
Published: September 2003

Class I chitinase (Chi9) and β-1,3-glucanase (GluB) genes are expressed in the micropylar endosperm cap of tomato (Lycopersicon esculentum) seeds just before radicle emergence through this tissue to complete germination. In gibberellin (GA)-deficient mutant (gib-1) seeds, expression of Chi9 and GluB mRNA and protein is dependent upon GA. However, as expression occurs relatively late in the germination process, we investigated whether the genes are induced indirectly in response to tissue wounding associated with endosperm cap weakening and radicle protrusion. Wounding and methyl jasmonate (MeJA) induced Chi9 expression, whereas ethylene, abscisic acid, sodium salicylate, fusicoccin, or β-aminobutyric acid were without effect. Chi9 expression occurred only in the micropylar tissues when seeds were exposed to MeJA or were wounded at the chalazal end of the seed. Expression of Chi9, but not GluB, mRNA was reduced in germinating seeds of the jasmonate-deficient defenseless1 tomato mutant and could be restored by MeJA treatment. Chi9 expression during germination may be associated with “wounding” from cell wall hydrolysis and weakening in the endosperm cap leading to radicle protrusion, and jasmonate is involved in the signaling pathway for this response. Among these treatments and chemicals (other than GA), only MeJA and wounding induced a low level of GluB expression in gib-1 seeds. However, MeJA, wounding, and particularly ethylene induced both genes in leaves, whereas GA induced only Chi9 in leaves. Although normally expressed simultaneously during tomato seed germination, Chi9 and GluB genes are regulated distinctly and tissue specifically by hormones and wounding.
Negative Regulation of Abscisic Acid Signaling by theFagus sylvaticaFsPP2C1 Plays A Role in Seed Dormancy Regulation and Promotion of Seed Germination
Authors: González-García Mary Paz , Rodríguez Dolores , Nicolás Carlos , Rodríguez Pedro Luis , Nicolás Gregorio , Lorenzo Oscar
Published: September 2003

FsPP2C1 was previously isolated from beech (Fagus sylvatica) seeds as a functional protein phosphatase type-2C (PP2C) with all the conserved features of these enzymes and high homology to ABI1, ABI2, and PP2CA, PP2Cs identified as negative regulators of ABA signaling. The expression of FsPP2C1 was induced upon abscisic acid (ABA) treatment and was also up-regulated during early weeks of stratification. Furthermore, this gene was specifically expressed in ABA-treated seeds and was hardly detectable in vegetative tissues. In this report, to provide genetic evidence on FsPP2C1 function in seed dormancy and germination, we used an overexpression approach in Arabidopsis because transgenic work is not feasible in beech. Constitutive expression of FsPP2C1 under the cauliflower mosaic virus 35S promoter confers ABA insensitivity in Arabidopsis seeds and, consequently, a reduced degree of seed dormancy. Additionally, transgenic 35S:FsPP2C1 plants are able to germinate under unfavorable conditions, as inhibitory concentrations of mannitol, NaCl, or paclobutrazol. In vegetative tissues, Arabidopsis FsPP2C1 transgenic plants show ABA-resistant early root growth and diminished induction of the ABA-response genes RAB18 and KIN2, but no effect on stomatal closure regulation. Seed and vegetative phenotypes of Arabidopsis 35S:FsPP2C1 plants suggest that FsPP2C1 negatively regulates ABA signaling. The ABA inducibility of FsPP2C1 expression, together with the transcript accumulation mainly in seeds, suggest that it could play an important role modulating ABA signaling in beechnuts through a negative feedback loop. Finally, we suggest that negative regulation of ABA signaling by FsPP2C1 is a factor contributing to promote the transition from seed dormancy to germination during early weeks of stratification.
Differential Regulation of Glucose-6-Phosphate Dehydrogenase Isoenzyme Activities in Potato
Authors: Hauschild Rüdiger , von Schaewen Antje
Published: September 2003

In plants, Glc-6-phosphate dehydrogenase (G6PDH) isoenzymes are present in the cytosol and in plastids. The plastidic enzymes (P1 and P2) are subject to redox regulation, but mechanisms that adjust cytosolic G6PDH activity are largely unknown. We adopted a leaf disc system for monitoring the effects of various conditions on G6PD isoform expression and enzyme activities in potato (Solanum tuberosum). Cytosolic G6PDH activity remained constant during water incubation in the dark. In continuous light or in the presence of metabolizable sugars in the dark, cytosolic G6PDH activity increased 6-fold within 24 h. Cycloheximide incubation demonstrated that enhanced cytosolic G6PDH activity depends on de novo protein synthesis. Osmotic change, phosphate sequestration, or oxidative stress did not affect cytosolic G6PDH activity. Furthermore, enzyme activity and protein contents closely followed the corresponding mRNA levels. Together with the fact that multiple SURE elements are present in the promoter region of the gene, these results suggest that cytosolic G6PDH activity is regulated by sugar availability at the transcriptional level. Plastidic G6PDH activity stayed constant during water incubation in the light and dropped to minimal levels within 6 h in the dark. Conversely, plastidic G6PDH activity of leaf discs incubated on Paraquat rose to 10-fold higher levels, which was not prevented by cycloheximide. Similar increases were found with nitrite, nitrate, or sulfate. No major changes in protein or mRNA contents of the plastidic P1 and P2 isoforms were registered. K  m (Glc-6-phosphate) values of plastidic G6PDH activity differed between samples incubated on water or Paraquat, suggesting posttranslational modification of the plastidic enzyme(s). Immunoprecipitation of 32P-labeled samples with P1 isoform-specific antibodies showed that the chloroplast enzyme is subject to protein phosphorylation. Obviously, in extended dark periods, G6PDH activity in the stroma is restricted but can be stimulated in response to high demands for NADPH.
Properties of Fructan:Fructan 1-Fructosyltransferases from Chicory and Globe Thistle, Two Asteracean Plants Storing Greatly Different Types of Inulin
Authors: Vergauwen Rudy , Van Laere André , Van den Ende Wim
Published: September 2003

Remarkably, within the Asteraceae, a species-specific fructan pattern can be observed. Some species such as artichoke (Cynara scolymus) and globe thistle (Echinops ritro) store fructans with a considerably higher degree of polymerization than the one observed in chicory (Cichorium intybus) and Jerusalem artichoke (Helianthus tuberosus). Fructan:fructan 1-fructosyltransferase (1-FFT) is the enzyme responsible for chain elongation of inulin-type fructans. 1-FFTs were purified from chicory and globe thistle. A comparison revealed that chicory 1-FFT has a high affinity for sucrose (Suc), fructose (Fru), and 1-kestose as acceptor substrate. This makes redistribution of Fru moieties from large to small fructans very likely during the period of active fructan synthesis in the root when import and concentration of Suc can be expected to be high. In globe thistle, this problem is avoided by the very low affinity of 1-FFT for Suc, Fru, and 1-kestose and the higher affinity for inulin as acceptor substrate. Therefore, the 1-kestose formed by Suc:Suc 1-fructosyltransferase is preferentially used for elongation of inulin molecules, explaining why inulins with a much higher degree of polymerization accumulate in roots of globe thistle. Inulin patterns obtained in vitro from 1-kestose and the purified 1-FFTs from both species closely resemble the in vivo inulin patterns. Therefore, we conclude that the species-specific fructan pattern within the Asteraceae can be explained by the different characteristics of their respective 1-FFTs. Although 1-FFT and bacterial levansucrases clearly differ in their ability to use Suc as a donor substrate, a kinetic analysis suggests that 1-FFT also works via a ping-pong mechanism.
Peer Relations Across Contexts: Individual‐Network Homophily and Network Inclusion In and After School
Authors: Kiesner Jeff , Poulin François , Nicotra Eraldo
Published: September 2003

Peer relations across 2 contexts (in school and after school) were examined for 577 participants, approximately 12 years old, from 3 middle schools in Milan, Italy. The primary research questions were: Do peer networks from different contexts uniquely contribute to explaining variance in individual behavior? Do measures of peer preference and peer network inclusion across contexts uniquely contribute to explaining individual depressive symptoms? Structural equation models showed that both the in‐school and the after‐school peer networks uniquely contributed to explaining variance in 2 types of individual problem behavior (in‐school problem behavior, after‐school delinquency), and that similarity with the 2 peer networks varied according to behaviors specific to each context and across gender. Finally, both in‐school and after‐school peer network inclusion contributed to explaining variance in depressive symptoms, after controlling for classroom peer preference.
Modeling the Impacts of Child Care Quality on Children's Preschool Cognitive Development
Authors:   National Institute of Child Health and Human Development Early Child Care Research Network, Duncan Greg J.
Published: September 2003

The National Institute of Child Health and Human Development (NICHD) Study of Early Child Care compared 3 statistical methods that adjust for family selection bias to test whether child care type and quality relate to cognitive and academic skills. The methods included: multiple regression models of 54‐month outcomes, change models of differences in 24‐ and 54‐month outcomes, and residualized change models of 54‐month outcomes adjusting for the 24‐month outcome. The study was unable to establish empirically which model best adjusted for selection and omitted‐variable bias. Nevertheless, results suggested that child care quality predicted cognitive outcomes at 54 months, with effect sizes of .04 to .08 for both infant and preschool ages. Center care during preschool years also predicted outcomes across all models.
Blasting Open a Choice Space: Learning Inflectional Morphology for NLP
Authors: McShane Marjorie , Nirenburg Sergei
Published: September 2003

This article discusses the various aspects of designing a system for eliciting knowledge about language from informants. For each design aspect, various options for implementation are presented, along with their pros, cons, and repercussions for other parts of the knowledge elicitation system. A running example throughout the text is taken from the paradigmatic morphology elicitation module of a system called Boas, which elicits knowledge to support a machine translation system. The main point of the article is an argument about the necessity to analyze the design choice space for complex natural language processing (NLP) systems early, comprehensively, and overtly.
Analytical Predictive Bayesian Assessment of Occupational Injury Risk: Municipal Solid Waste Collectors
Authors: Englehardt James D. , Huren An  , Fleming Lora E. , Bean Judy A.
Published: September 2003

Unlike other waste streams, municipal solid waste (MSW) is collected manually, and MSW collection has recently been found to be among the highest‐risk occupations in the United States. However, as for other occupational groups, actual total injury rates, including the great majority of injuries not compensated and those compensated by other insurance, are not known. In this article a predictive Bayesian method of assessing total injury rates from available information without computation is presented, and used to assess the actual numbers of musculoskeletal and dermal injuries requiring clinical care of MSW workers in Florida. Closed‐form predictive Bayesian distributions that narrow progressively in response to information, representing both uncertainty and variability, are presented. Available information included workers' compensation (WC) data, worker population data, and safety records for one private and one public collection agency. Subjective input comprised epidemiological and medical judgment based on a review of 165 articles. The number of injuries was assessed at 3,146 annually in Florida, or 54 ± 18 injuries per 100 workers per year with 95% confidence. Further, WC data indicate that the injury rate is 50% higher for garbage collectors specifically, indicating a rate of approximately 80 per 100 workers. Results, though subject to uncertainty in worker numbers and classification and reporting bias, agreed closely with a survey of 251 MSW collectors, of whom 75% reported being injured (and 70% reported illness) within the past 12 months. The approach is recommended for assessment of total injury rates and, where sufficient information exists, for the more difficult assessment of occupational disease rates.
Do Reports on Drinking Water Quality Affect Customers' Concerns? Experiments in Report Content
Authors: Johnson Branden B.
Published: September 2003

The Safe Drinking Water Act Amendments of 1996 required U.S. utilities to report on drinking water quality to their customers annually, beginning in fall 1999, on the assumption that such reports would alert them to quality problems and perhaps mobilize pressure for improvement. A random sample of New Jersey customers read alternative versions of a water quality report, in an experiment on reactions to water quality information under U.S. Environmental Protection Agency (USEPA) rules. Experiment design was 2 × 3 + 1: two versions each—one with, one without, a violation of a health standard—of a report that was (1) Qualitative (without water quality numbers, thus not meeting USEPA rules); (2) Basic, with minimal information meeting the rules; or (3) Extended, adding reading aids and utility performance information; plus a control instrument without any hypothetical report. Results of ANOVA suggest the reports will have less effect than hoped or feared. These manipulations were successful: people reading the Qualitative versions were less likely to say that the report gave the amounts of substances found in the water, and those reading Violation versions were more likely to report a violation of a health standard. The main differences in responses to the report involved the judged adequacy of the information, and to a lesser extent responses on a Concern scale (constructed from measures of concern, judged risk, clean‐up intentions, distrust of utility information, and doubt that the utility was doing all it could to improve water quality). Overall judgments of water quality and utility performance did not change, either relative to the controls or in before versus after responses. Qualitative reports performed worse than others, confirming the decision to have utilities report actual contaminant levels. Extended reports did only slightly better than the Basic versions on these measures. Many respondents had trouble identifying the presence or absence of substance amounts or violations, despite their seeming obviousness (e.g., in a “bottom line” summary on the front page of each report), suggesting many were not processing this information carefully. However, the pattern of responses for those who accurately identified the presence or absence of substance amounts or violations did not differ substantially from that for the group as a whole. Generic risk beliefs (serious local environmental problems; lack of control over risks to one's health) dominated demographic variables, attitudes toward utility water quality or trustworthiness, and the content and format of water quality reports in influencing concern about drinking water quality. Previous empirical and theoretical evidence for lack of change in public risk attitudes due to one‐time or infrequent communications—e.g., role of personal experience, perseverance of prior trust or distrust—seems to be confirmed for annual water quality reports.
Assessing Perceptions of Synergistic Health Risk: A Comparison of Two Scales
Authors: Hampson Sarah E. , Andrews Judy A. , Barckley Maureen , Lee Michael E. , Lichtenstein Edward
Published: September 2003

Two approaches to measuring perceptions of synergistic risk were compared, one using the traditional Likert scale, the other using an anchored, relative scale. Perception of synergistic risk was defined as rating the combined hazard as more risky than each of its constituent single hazards. In a within‐subjects design, a convenience sample from the community (N= 604) rated three hazard combinations and their constituents: Driving while Intoxicated (familiar, high synergy), Radon and Smoking (unfamiliar, high synergy), and Smoking and Driving (familiar, low synergy), on both scales. The relative scale was expected to be a more sensitive measure of synergy than the Likert scale. The effects of item order (single hazards rated first versus combined hazards rated first) were examined between subjects. Driving while Intoxicated was perceived by the large majority of participants as a synergistic risk on both scales, but neither of the other two combined hazards were rated synergistically on either scale. The relative scale demonstrated a slight advantage over the Likert scale, and presenting the single hazards first for the relative scale produced more synergistic ratings. It is recommended that anchored, relative scales be used to measure synergy and that single hazards be presented prior to the combined hazards when using relative scales.
Data Available for Evaluating the Risks and Benefits of MTBE and Ethanol as Alternative Fuel Oxygenates
Authors: Williams Pamela R. D. , Cushing Colleen A. , Sheehan Patrick J.
Published: September 2003

The wide‐scale use of methyl tertiary butyl ether (MTBE) in gasoline has resulted in substantial public controversy and action to ban or control its use due to perceived impacts on water quality. Because oxygenates are still required under federal law, considerable research has focused on ethanol as a substitute for MTBE. In this article, we summarize the currently available literature on the air and water quality risks and benefits of MTBE versus ethanol as alternative fuel oxygenates. We find that MTBE‐fuel blends are likely to have substantial air quality benefits; ethanol‐fuel blends appear to offer similar benefits, but these may be at least partially negated because of ethanol's propensity to increase emissions and ambient concentrations of some air contaminants. Releases of gasoline containing either MTBE or ethanol could have an impact on some drinking water sources, although the impacts associated with MTBE tend to relate to aesthetics (i.e., taste and odor), whereas the impacts associated with ethanol generally relate to health risk (i.e., greater exposure to gasoline constituents such as benzene). It is likely that these water quality impacts will be outweighed by the air quality benefits associated with MTBE and perhaps ethanol use, which affect a much larger population. A lack of data on environmental exposures and associated health impacts hinders the completion of a comprehensive quantitative risk‐benefit analysis, and the available air and water quality data should be evaluated in a broader risk‐management context, which considers the potential life‐cycle impacts, costs, and feasibility associated with alternative fuel oxygenates.
Military Tribunals: A Sorry History
Authors: Fisher Louis
Published: September 2003

After 9/11, President George W. Bush authorized the creation of military tribunals to try those who assisted in the terrorist attacks on New York City and Washington, DC. His military order closely tracked the model established by President Franklin D. Roosevelt, who appointed a military tribunal in 1942 to try eight German saboteurs. In Ex parte Quirin (1942), the Supreme Court unanimously upheld Roosevelt's tribunal. The Bush administration relies heavily on this judicial precedent, but military tribunals in U.S. history have generally been hostile to civil liberties, procedural due process, and elementary standards of justice.
The War Power and Its Limits
Authors: Kassop Nancy
Published: September 2003

President Bush defined the September 11, 2001 terrorist attacks as “acts of war.” His response was to promulgate policies, domestic and foreign, geared to protect against any future attacks against the United States. He urged swift passage of legislation that delegated vast new powers to the executive branch through the USA Patriot Act and two use‐of‐force resolutions, issued an executive order authorizing military tribunals, and announced a new national security strategy of preemption. These policies centralized power in the executive branch, and shifted it from Congress and the courts.
Presidential Authority to Detain “Enemy Combatants”
Authors: Elsea Jennifer K.
Published: September 2003

The Bush administration claims that the law of war and Supreme Court precedent support the president's authority to detain U.S. citizens, incommunicado and without filing a criminal charge, as “enemy combatants.” The administration views this power as inherent in the president's commander‐in‐chief authority, and that congressional authorization, while unnecessary, is implied in statute. This article surveys the history of presidential efforts to deal with threats to the national security through preventive detention measures, and concludes that congressional authorization has always been necessary to validate such measures within the United States.
The Law: Walker v. Cheney: Legal Insulation of the Vice President from GAO Investigations
Authors: Halstead T. J.
Published: September 2003

In Walker v. Cheney, the District Court for the District of Columbia held that the General Accounting Office lacked standing to sue the vice president to compel the release of information pertaining to the administration's National Energy Policy Development Group. The court's decision brought an abrupt end to a highly publicized conflict between the executive and legislative branches, and legally insulated the Office of the Vice President from GAO's investigation. Despite the ramifications of the decision, the comptroller general did not pursue an appeal, leaving open significant questions regarding the scope of congressional oversight authority.
Electrical characteristics of ZrO2 prepared by electrochemical anodization of Zr in an ammonium tartrate electrolyte
Authors: Jeon Sanghun , Hwang Hyunsang
Published: September 2003

An investigation of the electrical characteristics of ultrathin ZrO2 formed by anodization in an ammonium tartrate electrolyte is reported. Compared with low temperature thermal oxidation, the formation of zirconium oxide by anodization shows self-limiting oxidation behavior with an increase in time, and, thus, provides superior control of the oxide thickness. The growth of anodized oxide inhibits aggressive oxidation by blocking the flow of current through a dielectric since the location at which the oxide forms would become a region of high resistance. The equivalent oxide thickness of ultrathin zirconium oxide by anodization within an acceptable dispersion was scaled down to 11.4 Å with leakage current density of less than 1.5×10−3 A/cm2 at Vfb of −1 V. The density of the interface state and fixed charge density of zirconium oxide using the anodization process are also discussed.
Study of C4F8/N2 and C4F8/Ar/N2 plasmas for highly selective organosilicate glass etching over Si3N4 and SiC
Authors: Hua Xuefeng , Wang X. , Fuentevilla D. , Oehrlein G. S. , Celii F. G. , Kirmse K. H. R.
Published: September 2003

We report the effect of N2 addition to C4F8 and C4F8/Ar discharges on plasma etching rates of organosilicate glass (OSG) and etch stop layer materials (Si3N4 and SiC), and the results of surface chemistry studies performed in parallel. N2 addition exhibits different effects in C4F8 and C4F8/Ar plasmas, which may be explained by a higher plasma density, electron temperature, and possibly, the presence of argon metastable species in the C4F8/Ar plasma, all of which serve to dissociate N2 more effectively. When N2 is added to a C4F8/Ar plasma, a reduction of the steady-state fluorocarbon surface layer thickness, one of the key parameters that controls the etching rate and etching selectivity on partially etched samples, is observed. This effect leads to a loss of etching selectivity for C4F8/Ar/N2 discharges. Adding N2 to C4F8 plasmas without Ar enhances the steady-state fluorocarbon layer thickness. X-ray photoelectron spectroscopy analysis shows, in this case, that there is an important change in the stoichiometry of either passively deposited films or the fluorination reaction layers formed on etching samples: A significant amount of nitrogen is incorporated in the fluorocarbon film for deposited films, which implies that CxNy needs to be removed to achieve an etching condition. The incorporation of nitrogen in fluorocarbon films could reduce the etchant supply for Si3N4, or OSG, from the gas phase, especially for C4F8/Ar/N2 plasmas, but not for SiC owing to the differences of the chemical compositions. SiO2 and Si are also studied for comparison materials. The etching behavior of SiO2 is similar to that of OSG and Si3N4, while Si behaves more similar to SiC during fluorocarbon etching. In addition, a comparison of N2 and O2 addition to C4F8 or C4F8/Ar plasma in terms of consequences on etching behavior of the aforementioned materials is presented.