bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mesoporous Pt/TiO2 Nanoarchitecture with Catalytic and Photocatalytic Functions
Authors: Wang Xinchen , Yu Jimmy C. , Yip Ho Yin , Wu Ling , Wong Po Keung , Lai Suk Yin
Published: March 2005

A novel metal/semiconductor nanocomposite with catalytic and photocatalytic functions has been prepared. The new material consists of highly dispersed platinum (Pt) nanoparticles embedded in a cubic mesoporous nanocrystalline anatase (meso‐nc‐TiO2) thin film. The porous thin film possesses a narrow pore‐size distribution and a large surface area. The diameter of the Pt cluster can be controlled to below 5 nm, and the high dispersion of these clusters gives rise to catalytic activity for the oxidation of carbon monoxide, an important reaction for automobile exhaust treatment. This novel ordered mesoporous Pt/TiO2 nanoarchitecture is also a promising photochemical material, as demonstrated by the photo‐driven killing of Micrococcus lylae cells on the film.
Roxarsone and transformation products in chicken manure: Determination by capillary electrophoresis‐inductively coupled plasma‐mass spectrometry
Authors: Rosal Charlita G. , Momplaisir Georges‐Marie , Heithmar Edward M.
Published: March 2005

The determination of the animal feed additive roxarsone (3‐nitro‐4‐hydroxyphenylarsonic acid) and six of its possible transformation products (arsenite, arsenate, monomethylarsonate, dimethylarsinate, 3‐amino‐4‐hydroxyphenylarsonic acid, and 4‐hydroxyphenylarsonic acid) in chicken manure was investigated using capillary electrophoresis‐inductively coupled plasma‐mass spectrometry (CE‐ICP‐MS). Initial method development was conducted using ultraviolet (UV) detection for ruggedness and time efficiency. Separation of these seven arsenic species was effected using a 20 mM phosphate buffer at pH 5.7. The CE‐ICP‐MS limits of detection in terms of As for each of the species was in the low µg·L−1 range, corresponding to absolute detection limits in the range 20–70 fg As (based on a 23 nL injection). Overall, the method developed in this study provides high selectivity and low limits of detection (1–3 µg·L−1 or low‐ppb, based on As), uses small sample volume (low nL), and produces minimal wastes.
Overexpression of genes on 16q associated with cisplatin resistance of testicular germ cell tumor cell lines
Authors: Wilson Charlotte , Yang Jinshu , Strefford Jon C. , Summersgill Brenda , Young Bryan D. , Shipley Janet , Oliver Tim , Lu Yong‐Jie
Published: March 2005

Testicular germ‐cell tumors (TGCTs) show exquisite sensitivity to cisplatin‐based chemotherapy, and therefore this is considered a good model system for studying the mechanism of chemotherapy resistance. Although the genetic alterations related to TGCT have been well studied, little is known about the genetic basis of chemotherapy resistance, which occurs in a small proportion of TGCTs. In this study, we investigated genomic and expression differences between three cisplatin‐sensitive and their paired cisplatin‐resistant lines using combined whole‐genome screen approaches. Comparative genomic hybridization (CGH) analysis on chromosomes revealed genetic differences between the resistant and parent cell lines in each pair, but did not show any consistent chromosome changes in all three lines. Microarray CGH analysis generated some additional information of DNA copy number gains and losses including some important oncogenes, tumor‐suppressor genes, and drug‐resistance‐related genes. However, no consistent genomic region changes were found in the three cell lines. Interestingly, when comparative expressed sequence hybridization, a technique for gene expression profiling along chromosomes, was applied, we discovered a consistently overexpressed chromosomal region in all three resistant lines compared with their parent lines. The minimum overlapping chromosomal region is at 16q22–23. Further definition of genes in this chromosomal region will aid our understanding of the mechanism of cisplatin resistance and may offer novel therapeutic targets. © 2005 Wiley‐Liss, Inc.
The growth of supply and demand of occupational‐based training and certification in the United States, 1990–2003
Authors: Carter Shani D.
Published: March 2005

The 1990s and early 2000s saw the increased development of advanced training, skills standards, and certification exams by private organizations in the United States. Employers began accepting these skill certifications in lieu of traditional on‐the‐job training, thereby encouraging employees to acquire more credentials. This article examines the increase in the number of skill certifications available, discusses legislative causes of these increases, and notes the current lack of published peer‐reviewed analyses of statistical reliability and validity of certification exams. It presents a call for future research to determine the usefulness of certification.
Development and validation of the learning transfer system inventory in Taiwan
Authors: Chen Hsin‐Chih , Holton III E. F. , Bates Reid
Published: March 2005

Due to globalization in recent years, organizations and the government in Taiwan take developing human expertise more seriously than ever before. However, human resource development evaluation practices in Taiwan have somewhat overlooked connecting training to transfer and organizational results. To help close the gap, organizations in Taiwan need a valid and reliable instrument to assess transfer issues. This study validated a research‐based instrument in the United States, the Learning Transfer System Inventory (LTSI), for use in Taiwan. A heterogeneous sample containing 583 responses from twenty organizations was collected. Through a rigorous translation process with qualitatively subjective, quantitatively objective, and pilot evaluations of the translation as well as common factor analyses, a Taiwan version of the LTSI (TLTSI), which contained fifteen statistically reliable factors, was validated. This study also extended the LTSI's generalizability and provided comparable measures of transfer systems between Taiwan and the United States. Translation issues, suggestions for improving the LTSI, implications for HRD, and future research directions are discussed.
Controlled release of heparin from polypyrrole‐poly(vinyl alcohol) assembly by electrical stimulation
Authors: Li Yali , Neoh K. G. , Kang E. T.
Published: March 2005

A surface modification technique was developed for the covalent immobilization of poly(vinyl alcohol) (PVA)‐heparin hydrogel onto electrically conductive polypyrrole (PPY) film with the objective of achieving controlled release of heparin. First, aldehyde groups were introduced onto PPY film through poly(ethylene glycol) monomethacrylate graft copolymerization and subsequent oxidation in acetic anhydride and dimethyl sulfoxide mixture. Then, the prepared PVA‐heparin hydrogel was cast onto the PPY film and covalently immobilized to the film through the reaction between the aldehyde groups on the PPY film and the hydroxyl groups of PVA. X‐ray photoelectron spectroscopy was used to characterize the surface‐modified film after each stage. The strong attachment of the PVA‐heparin layer on the PPY film was confirmed by peel test and scanning electron microscopy. The release behavior of heparin from the substrate with and without electrical stimulation was studied and the experimental results showed that the heparin release rate from the prepared substrate using an electric current of 3.5 mA is twofold higher than that without current. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 171–181, 2005
Cartilage‐derived morphogenetic proteins induce osteogenic gene expression in the C2C12 mesenchymal cell line
Authors: Yeh Lee‐Chuan C. , Tsai Alicia D. , Lee John C.
Published: March 2005

Cartilage‐derived morphogenetic protein‐1, ‐2, and ‐3 (CDMP‐1, ‐2, and ‐3) are members of the bone morphogenetic protein (BMP) family and have been shown to exhibit a variety of biological activities. In the present study, effects of these CDMPs on the temporal and spatial expression of genes in the pluripotent mesenchymal cell line C2C12 were examined. Cells cultured in the presence of CDMPs lost the characteristic elongated shape of myoblasts. At the molecular level, CDMP treatment did not change the mRNA expression of MyoD, aggrecan, Six1, and tendin. Scleraxis mRNA level was reduced by CDMP treatment. CDMP‐1 and ‐3, but not CDMP‐2, stimulated expression of osteogenic markers, such as alkaline phosphatase (AP), osteocalcin (OC), BSP, and type I collagen, in a dose‐ and time‐dependent manner. With few exceptions, the three CDMPs changed, with different potencies, the expression profile of different members of the BMP family in a similar temporal pattern. Except at the late phase of treatment, CDMP treatment did not change the expression of ActR‐IA, BMPR‐IA, BMPR‐IB, BMPR‐II, and ALK‐7 mRNAs. Based on the current data, the CDMPs appear to be able to stimulate the C2C12 cells to differentiate into the osteoblast pathway. © 2005 Wiley‐Liss, Inc.
Development of a force field for Li2SiF6
Authors: Liivat Anti , Aabloo Alvo , Thomas John O.
Published: March 2005

A force field has been developed for Li2SiF6 for subsequent use in Molecular Dynamics (MD) simulations involving Li+ and SiF ions in a polymer electrolyte host. Both ab initio calculations and available empirical data have been used. The force field has been verified in simulations of the crystal structure of Li2SiF6 in two different space groups: P321 and P$\bar{3}$m1. The use of MD simulation to assess the correct space group for Li2SiF6 shows that it is probably P321. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 716–724, 2005
A structure/function study of polyaminoamide dendrimers as silica scale growth inhibitors
Authors: Demadis Konstantinos D
Published: March 2005

Dendrimers have attracted immense attention during the last decade due to their interesting properties both from a basic and an applied research viewpoint. Encapsulation of metal nanoparticles for catalysis, drug delivery and light harvesting are only some applications of dendrimers that are breaking new ground. A novel application of dendrimer technology is described in the present paper that relates to industrial water treatment. Industrial water systems often suffer from undesirable inorganic deposits. These can form either in the bulk or on metallic surfaces, such as heat exchangers or pipelines. Silica (SiO2) scale formation and deposition is a major problem in high‐silica‐containing cooling waters. Scale prevention rather than removal is highly desired. In this paper, benchtop screening tests on various silica inhibition chemistries are reported, with emphasis on materials with a dendrimeric structure. Specifically, the inhibition properties of commercially available STARBURST® polyaminoamide (PAMAM) dendrimers generations 0.5, 1, 1.5, 2, and 2.5 are investigated in detail together with other commonly‐used scale inhibitors. Experimental results show that inhibition efficiency largely depends on structural features of PAMAM dendrimers such as generation number and nature of the end groups. PAMAM dendrimers are effective inhibitors of silica scale growth at 40 ppm dosage levels. PAMAM dendrimers also act as silica nucleators, forming SiO2–PAMAM composites. This occurs because the SiO2 formed by incomplete inhibition interacts with cationic PAMAM‐1 and ‐2. The general scope of silica formation and inhibition in industrial waters is also discussed. Copyright © 2005 Society of Chemical Industry
Kinetics of phenol oxidation in a trickle bed reactor over active carbon catalyst
Authors: Eftaxias Athanasios , Font Josep , Fortuny Agusti , Fabregat Azael , Stüber Frank
Published: March 2005

The wet air oxidation of phenol over a commercial active carbon catalyst was studied in a trickle bed reactor (TBR) in the temperature and oxygen partial pressure ranges of 120–160 °C and 0.1–0.2 MPa, respectively. The performance of the active carbon was compared in terms of phenol and COD destruction. The weight change of active carbon due to reaction was also measured. Finally, oxic phenol adsorption isotherms were assessed in batch conditions at 25, 125 and 160 °C. In order to use the conversion data obtained from the TBR for a kinetic study, special care was taken to check the kinetic control in the TBR experiments. Several kinetic models including power law or Langmuir–Hinshelwood expressions were considered to describe the catalytic oxidation of phenol over active carbon. The simple power law model with first order dependence on both phenol and oxygen concentration predicted satisfactorily the experimental data not only over the entire range of operating conditions studied, but also outside its validity range. Copyright © 2005 Society of Chemical Industry
Motion estimation for sequential medical images using a deformable model
Authors: Kurabayashi Yew , Kagei Seiichiro , Gotoh Toshiyuki , Iwasawa Tae
Published: March 2005

The gradient method, which is a conventional method of motion analysis, has the problem that artifacts appear near contours or edges with a large brightness gradient. Another method, which applies a deformable model to the deforming object, has the opposite problem, namely, that the accuracy of estimation is degraded in areas with small brightness gradients. In order to handle such problems, this paper proposes a new deformable model in which the motion of each part of a pliantly deforming object is estimated. In this method, a term based on local optimization is added to the interframe energy following the conventional definition, so that the shape and the motion minimizing the energy are simultaneously determined. More accurate estimation of the motion is realized owing to the multiplicative effect of the term based on the brightness gradient composing the interframe external energy, and the term based on local optimization. The proposed method is applied to time‐series chest MR images and its effectiveness is verified. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(4): 27–36, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20146
Multilevel selection: the evolution of cooperation in non‐kin groups
Authors: Goodnight Charles J.
Published: March 2005

Hamilton's (1964a, 1964b) landmark papers are rightly recognized as the formal basis for our understanding of the evolution of altruistic traits. However, Hamilton's equation as he originally expressed it is simplistic. A genetically oriented approach to studying multilevel selection can provide insights into how the terminology and assumptions used by Hamilton can be generalized. Using contextual analysis I demonstrated that Hamilton's rule actually embodies three distinct processes, group selection, individual selection, and transmission genetics or heritability. Whether an altruistic trait will evolve depends the balance of all of these factors. The genetical approach, and particularly, contextual analysis provides a means of separating these factors and examining them one at a time. Perhaps the greatest issue with Hamilton's equation is the interpretation of r. Hamilton (1964a) interpreted this as relatedness. In this paper I show that what Hamilton called relatedness is more generally interpreted as the proportion for variance among groups, and that many processes in addition to relatedness can increase the variance among groups. I also show that the evolution of an altruistic trait is driven by the ratio of the heritability at the group level to the heritability at the individual level. Under some circumstances this ratio can be greater than 1. In this situation altruism can evolve even if selection favoring selfish behavior is stronger than selection favoring altruism.
Climatological annual cycle of upper ocean oxygen content anomaly
Authors: Garcia Hernan E. , Boyer Tim P. , Levitus Sydney , Locarnini Ricardo A. , Antonov John I.
Published: March 2005

The climatological annual cycle of oxygen content anomaly of the 0–100 m depth layer for major ocean basins is described using Fourier analysis of objectively analyzed monthly O2 anomaly values on a 1° grid (70°S–70°N). The largest seasonal changes in O2 content anomaly occur in the extra‐tropics in the 30° to 60° latitude belt of each hemisphere. The magnitude of the global cycle is dominated by the Pacific Ocean. The annual and semi‐annual harmonics account for most (>90%) of the annual cycle of the monthly O2 content anomaly. The magnitude of the annual harmonic is largest in the upper 75 m layer except in the tropics and high latitudes. The annual harmonic accounts for >90% of the variance of the zonally integrated monthly O2 content anomaly.
Radiative‐convective model of warming Mars with artificial greenhouse gases
Authors: Marinova Margarita M. , McKay Christopher P. , Hashimoto Hirofumi
Published: March 2005

Artificial greenhouse gases could be used to warm Mars in order to make it habitable. Here we present new laboratory measurements of the thermal infrared absorption spectra of seven artificial greenhouse gases (CF4, C2F6, C3F8, SF6, CF3Cl, CF3Br, CF2Cl2) at concentrations from 10−7 up to unity. We used a radiative‐convective multilayer model to compute the warming caused by a mixture of the four fluorine‐based greenhouse gases. The results show that for current Mars, C3F8 produces the largest warming: 0.56 K and 33.5 K for partial pressures of 10−3 Pa and 1 Pa, respectively. Averaged over partial pressures from 0.01 to 1 Pa, the range of most interest for planetary ecosynthesis, CF4, C2F6, and SF6 were 17%, 49%, and 48% as effective as C3F8, respectively. The optimal mixture of the four fluorine‐based greenhouse gases, taking into account the overlapping of their absorption bands, was 16% more effective than pure C3F8, averaged over the range 0.01 Pa to 1 Pa. Energy balance calculations suggest that the addition of ∼0.2 Pa of the best greenhouse gases mixture or ∼0.4 Pa of C3F8 would shift the equilibrium to the extent that CO2 would no longer be stable at the Martian poles and a runaway greenhouse effect would result.
The common cuckoo Cuculus canorus and its cavity nesting host, the redstart Phoenicurus phoenicurus: a peculiar cuckoo‐host system?
Authors: Rutila Jarkko , Latja Raimo , Koskela Kimmo
Published: March 2005

We examined redstart Phoenicurus phoenicurus populations over a period of fifteen years to study interactions between the cuckoo Cuculus canorus and its cavity‐nesting host. Over 380 redstart nests were checked and more than 100 cuckoo eggs were found during the study period. The average parasitism rate was 20%. The cuckoos’ breeding success was extremely low, only 18 chicks surviving to the fledgling stage. When redstarts were parasitized experimentally with artificial cuckoo eggs, they rejected eight percent of mimetic eggs and 44% of non‐mimetic eggs. We were not able to record any rejection of the real cuckoo eggs. However, about 30% of the real cuckoo eggs were found outside the redstart's nest cup. This could be the result of laying failures by the cuckoo, rather than of a strong rejection behaviour by the redstart. We suggest that redstarts’ cavity nesting itself was a factor that reduced the cost of the parasitism dramatically. Firstly, it makes it difficult for the female cuckoo to lay her egg correctly in the nest and secondly, it is more difficult for the cuckoo chick to evict the host's eggs or nestlings effectively from the nest. Only 54% of the cuckoo chicks were able to evict all the host eggs or chicks from the nest. When reared in mixed broods, cuckoo chicks survived only in every second case to fledgling age, while at least one redstart chick from every brood managed to leave the nest.
Nocturnal migratory flight initiation in reed warblers Acrocephalus scirpaceus: effect of wind on orientation and timing of migration
Authors: Åkesson Susanne , Walinder Göran , Karlsson Lennart , Ehnbom Sophie
Published: March 2005

We used radio‐telemetry to study autumn migratory flight initiation and orientation in relation to wind and air pressure in a nocturnal passerine migrant, the reed warbler Acrocephalus scirpaceus at Falsterbo, southwest Sweden. The majority of the reed warblers departed in the expected migratory direction towards south of southwest, while a low number of the birds took off in reverse directions between north and east. Flight directions at departure correlated with wind directions. These correlations were particularly prominent at higher wind speeds but were absent at wind speeds below 4 m/s. Birds departing in the expected migratory direction compensated completely for wind drift. The reed warblers preferred to depart during nights with tailwinds and when air pressure was increasing suggesting that reed warblers are sensitive to winds and air pressure and select favourable wind conditions for their migratory flights. Since air pressure as well as velocity and direction of the wind are correlated with the passage of cyclones, a combination of these weather variables is presumably important for the birds' decision to migrate and should therefore be considered in optimal migration models.
Sex‐biased nestling mortality in the Montagu's harrier Circus pygargus
Authors: Arroyo Beatriz
Published: March 2005

I evaluate causes and patterns of nestling mortality in a sexually dimorphic species, the Montagu's harrier Circus pygargus, and their relationship with sex and condition. Starvation was apparently the main reason for nestling death. Condition of birds that died was lower than those that survived. Both probability of nestling death and the proportion of nestlings that died within a brood increased with the number of hatched nestlings in a brood, and with increasing hatching date. For the nestlings that died after being sexed, when controlling for brood effects, probability of death was significantly related to nestling sex, with smaller males having a higher probability of dying. The probability of nestling death if hatched late in the season was relatively greater for males than for females. There was also a significant interaction between sex and hatching date on nestling condition: the decline in condition if hatched late in the season was steeper for males than for females. Males did not have a higher probability of death when having more sisters: neither the probability of brood reduction nor the proportion of nestlings that died were significantly related to within‐brood sex ratio. Results suggest that mortality may partly result from sibling competition: females, being the larger sex, might be better able to compete for food within a brood than their male siblings. Additionally, smaller males may be less able to recover from periods of declining body weight.
Does avian winter fat storage integrate temperature and resource conditions? A long‐term study
Authors: Rogers Christopher M. , Reed Amanda K.
Published: March 2005

Theoretical models of short‐term avian behaviour suggest that small birds adaptively balance the ecological costs and benefits of winter fat to maximize survival probability. When low starvation risk eliminates benefit but not cost of fat, birds are leaner than when under high starvation risk. Most models focus on single factors affecting starvation risk and subsequent choice of adaptive body mass; however, in complex environments, more than one factor affects starvation risk. To test for multiple interacting factors affecting fat reserves, long‐term geographical data on winter fat in a ground‐feeding finch, the dark‐eyed junco Junco hyemalis were analyzed. Two measures of fat were used: (1) visible subcutaneous fat class, and (2) body mass residuals left after age, sex and wing length effects were factored out. Site means for fat measures were obtained from juncos visiting supplemental feeding sites in midwest and northwest North America. In backward elimination regression of fat class, the temperature‐snowfall interaction term and its constituent variables, proximate temperature (averaged over capture day and the preceding ten days) and snowfall (frequency over the same time interval) were significant explanators of variation. Snowfall frequency is considered to be a surrogate measure of resource deterioration. The interaction term, also found in backward regression of body mass residuals, showed that as temperature declined at low snowfall frequency, less fat was deposited than when temperature declined at high snowfall frequency. Thus, in a recently cold environment suggesting relatively high resource predictability, perceived starvation risk is low, and less costly fat is needed to reduce starvation risk compared to a cold and unpredictable resource environment. The analysis of mass residuals also yielded a significant effect of daylength, suggesting an underlying fattening programme independent of proximate environmental conditions. A longitudinal study of junco fat stores indicated that individual environmental responses contributed significantly to midwinter fat peaks. These results agree with predictions of a synergistic model of adaptive fat regulation in small birds by suggesting that a ground‐feeding bird may maximize winter survival probability by integrating multiple environmental factors affecting starvation risk.
Foraging of multimammate mice, Mastomys natalensis, under different predation pressure: cover, patch‐dependent decisions and density‐dependent GUDs
Authors: Mohr Katrine , Vibe‐Petersen Solveig , Lau Jeppesen Leif , Bildsøe Mogens , Leirs Herwig
Published: March 2005

Patch use under predation risk often results in a change of feeding behaviour in the prey animals. However, such changes only appear if the animals are able to assess under which predation pressure they live. We investigated patch use of Mastomys natalensis under different conditions of avian predation pressure.  

In replicated maize field plots in Morogoro, Tanzania, avian predators were allowed under natural conditions (control), attracted with perches and nest boxes or kept out with nets. During four one‐week periods in late 1999, we measured rodent feeding decisions with the giving‐up density (GUD) method. Trays with known amounts of millet seeds in sand were placed in pairs, one of them under a cover, the other one in the open. M. natalensis mice were expected to give up sooner in the open trays than in those with cover. We hypothesised that M. natalensis mice could assess the ambient predation pressure leading to larger difference in GUD between covered and non‐covered trays in the plots where predators were attracted. We also made video recordings of the rodent activity at a pair of trays in each treatment.

The GUD‐values were significantly lower for the covered trays but predation pressure did not affect this difference. The video observations showed that in the control and netted plots the animals visited trays equally frequently regardless of the cover, while the visits in the predator‐attracted plots occurred significantly more often in the covered trays. We conclude that M. natalensis can assess the ambient predation pressure and adapt its behaviour at a feeding patch. However, the variation in predation pressure in our experiment was not obvious from the GUD. Moreover, we found a strong relation between rodent density and GUD, which may mask variations in perceived predation pressure. Similar GUD values may be reached in different ways and we present models to investigate whether animals’ decision to forage at a food patch is only affected by the seed density at that patch, not by that at a neighbour patch.
Microgeographical variation in brown trout reproductive traits: possible effects of biotic interactions
Authors: Olsen Esben Moland , Vøllestad Leif Asbjørn
Published: March 2005

This study documents substantial variation in reproductive traits among populations of stream‐dwelling brown trout (Salmo truttaL.) at a very small geographic scale. Within two streams, we found a parallel pattern of variation, where females living above major waterfalls produced fewer and larger eggs than conspecifics from below the waterfalls. Four additional streams were represented with either a below‐waterfall site (n=2) or an above‐waterfall site (n=2). When these streams were included in the analyses, there was no consistent difference in reproductive traits between females from above‐ and below‐waterfall sites. There was no significant difference in total reproductive investment among sites within streams, but considerable variation among streams. Female first‐year growth rates was estimated from scales, and differed significantly among populations. Within streams, females from below waterfalls experienced higher first‐year growth rates as compared to females from above the waterfalls. Within seven out of eight populations, egg size increased significantly with increasing female body length. Within three populations, we found evidence for a trade‐off between offspring size and offspring number, as a negative association between fecundity and egg size independently of adult body size. Within three populations egg size decreased significantly with increasing maternal first‐year growth, independently of adult body size. We suggest that the within‐stream differences in offspring size/number strategies are influenced by population density and growth effects. Earlier, we have shown that population densities are consistently lower below the waterfalls in these streams. The Alpine bullhead (Cottus poecilopus) is found only below the waterfalls and could influence brown trout demography.
Mechanisms underlying shoal composition in the Trinidadian guppy, Poecilia reticulata
Authors: Croft D. P. , Arrowsmith B. J. , Bielby J. , Skinner K. , White E. , Couzin I. D. , Magurran A. E. , Ramnarine I. , Krause J.
Published: March 2005

Free‐ranging groups are frequently assorted by phenotypic characters. However, very little is known about the underlying processes that determine this structuring. In this study, we investigate the mechanisms underlying the phenotypic composition of shoals of guppies (Poecilia reticulata) in a high‐predation stream in Trinidad's Northern Mountain Range. We collected 57 entire wild shoals, which were strongly assorted by body length. Shoal encounters staged within an experimental arena showed shoal fission (but not fusion) events to be an important mechanism in generating phenotypic assortment. In the wild, fission and fusion between guppy shoals occurred extremely frequently and thus are unlikely to constrain the opportunities for shoal assortment. However, fission and fusion processes occur under the restrictions imposed by the distribution of individuals within the environment. We observed size specific segregation within the habitat in three dimensions, providing a passive mechanism that contributes to the maintenance of the observed homogeneity of group composition. Furthermore sex differences were found in social behaviour. Individual male guppies switched between shoals more frequently than females and left a shoal more often than females. We argue that shoal composition is determined by habitat segregation on a medium spatial scale and by fission/fusion processes on a small spatial scale (with sex‐specific shoal dynamics adding a additional layer of complexity).
Patch shape and orientation influences on seagrass epifauna are mediated by dispersal abilities
Authors: Tanner Jason E.
Published: March 2005

While there have been theoretical arguments supporting the importance of the shape and orientation of habitat patches for determining species abundances, there have been few empirical demonstrations that these processes actually operate. Instead, most field studies have focussed on the importance of patch area, isolation and edge effects. I demonstrate that passively dispersed seagrass epifauna respond to the shape and orientation of artificial seagrass patches when currents, the dispersal mechanism, are strong, but not when they are weak. Orientation is important because animals dispersing via tidally induced water currents move predominantly in a single direction, and thus patches oriented across the current intercept more potential colonists than do those patches oriented perpendicular to the current. Currents less affect taxa that actively disperse, or that are relatively sedentary. Fish species that tend to use intertidal areas at high tide, however, were more abundant in patches perpendicular to shore (and parallel to the current), presumably because these patches offer the greatest amount of edge to animals undergoing tidal migrations.
Multiple Pathways Used for the Targeting of Thylakoid Proteins in Chloroplasts
Authors: Robinson Colin , Thompson Simon J. , Woolhead Cheryl
Published: March 2005

The assembly of the chloroplast thylakoid membrane requires the import of numerous proteins from the cytosol and their targeting into or across the thylakoid membrane. It is now clear that multiple pathways are involved in the thylakoid‐targeting stages, depending on the type of protein substrate. Two very different pathways are used by thylakoid lumen proteins; one is the Sec pathway which has been well‐characterised in bacteria, and which involves the threading of the substrate through a narrow channel. In contrast, the more recently characterised twin‐arginine translocation (Tat) system is able to translocate fully folded proteins across this membrane. Recent advances on bacterial Tat systems shed further light on the structure and function of this system. Membrane proteins, on the other hand, use two further pathways. One is the signal recognition particle‐dependent pathway, involving a complex interplay between many different factors, whereas other proteins insert without the assistance of any known apparatus. This article reviews advances in the study of these pathways and considers the rationale behind the surprising complexity.
Characterizing organic matter of soil aggregate coatings and biopores by Fourier transform infrared spectroscopy
Authors: Ellerbrock R. H. , Gerke H. H.
Published: March 2005

In some soils, aggregate coatings and walls of biopores differ in the content of clay and organic carbon from that of the aggregate interiors or the soil matrix. The composition of the organic matter on aggregates and on the surfaces of biopores is largely unknown. We have compared the composition of organic matter between inner and outer parts of aggregates and between biopore walls and the soil matrix in a loamy arable soil and a sandy forest one. Hot‐water‐ and sodium‐pyrophosphate‐extractable organic matter was analysed by Fourier transform infrared (FT‐IR) spectroscopy. For the sandy forest soil, the FT‐IR spectra showed that organic matter from the walls of root channels contains fewer functional groups with absorption bands at 1740–1710 cm−1 and 1640–1600 cm−1 than that from burrow fillings. For the arable soil, the content of these functional groups in hot‐water‐soluble organic matter from the coatings is less than in that from the interiors in the topsoil, and the reverse is so in the subsoil, probably because water‐soluble organic matter containing these functional groups has moved from topsoil to subsoil. The results indicate that root channels in the forest soil have more reactive zones in an otherwise relatively inert sandy matrix, whereas aggregate coatings in the arable subsoil have a greater cation exchange capacity and a greater sorption potential for hydrophobic substances than the aggregate interiors.
Acoustic properties of sediments saturated with gas hydrate, free gas and water
Authors: Gei Davide , Carcione José M.
Published: March 2005

We obtain the wave velocities and quality factors of gas‐hydrate‐bearing sediments as a function of pore pressure, temperature, frequency and partial saturation. The model is based on a Biot‐type three‐phase theory that considers the existence of two solids (grains and gas hydrate) and a fluid mixture. Attenuation is described with the constant‐Q model and viscodynamic functions to model the high‐frequency behaviour. We apply a uniform gas/water mixing law that satisfies Wood's and Voigt's averages at low and high frequencies, respectively. The acoustic model is calibrated to agree with the patchy‐saturation theory at high frequencies (White's model). Pressure effects are accounted by using an effective stress law for the dry‐rock moduli and permeabilities. The dry‐rock moduli of the sediment are calibrated with data from the Cascadia margin. Moreover, we calculate the depth of the bottom simulating reflector (BSR) below the sea floor as a function of sea‐floor depth, geothermal gradient below the sea floor, and temperature at the sea floor.
Complete necrosis of allograft ureter after cadaveric renal transplantation
Authors: Sinha Manish , Lewis Malcolm A. , Riad Hany , Webb Nicholas J. A.
Published: March 2005

Abstract:  Complete necrosis of a transplant ureter is a rare complication that needs to be considered early in cases of severe graft dysfunction if successful surgical intervention and restoration of graft function is to be achieved. We report on two cases of this complication occurring in children and discuss the surgical management. Surgical exploration of grafts where there is an early sudden decline in function is imperative as routine imaging will not exclude this potentially treatable problem.
The use of art therapy to detect depression and post‐traumatic stress disorder in pediatric and young adult renal transplant recipients
Authors: Wallace Jo , Yorgin Peter D. , Carolan Richard , Moore Heather , Sanchez Jaime , Belson Amir , Yorgin Lisa , Major Cyd , Granucci Laura , Alexander Steve , Arrington Doris
Published: March 2005

Abstract:  Pediatric and young adult renal transplant recipients may experience feelings of depression and emotional trauma. A study was conducted to (1) determine the prevalence of depression and emotional trauma and (2) assess the utility of the Formal Elements of Art Therapy Scale (FEATS). Sixty‐four renal transplant recipients, 6–21 yr of age, were evaluated using self‐report measures (CDI and Davidson) and art‐based assessments. Subject art was analyzed by art therapists using seven of the 14 elements of the (FEATS), to assess depression. Unlike CDI and Davidson self‐report testing, all patients were able to complete the art‐based directives. When self‐report measures and art‐based assessments were combined, 36% of the study population had testing results consistent with depression and/or post‐traumatic stress. The FEATS assessments identified a subset of patients who were not identified using the self‐report measures. There was a correlation between CDI and Davidson scores (p < 0.0001), Davidson scores correlated with hospital days (p = 0.05), and FEATS correlated with height Z score (p = 0.04) and donor type (p = 0.01). Patients who required psychological interventions including antidepressant therapy, psychological counseling and psychiatric hospitalization during the year after the study were identified as depressed. Sensitivity for FEATS and CDI were 22 and 50% respectively. The results suggest that while art therapy may be of utility in the identification of pediatric and young adult transplant recipients who are suffering from depression, FEATS analysis appears to lack sufficient sensitivity to warrant its use in this population. Study of other quantitative art‐based assessment techniques may be warranted.
Active site residues and mechanism of UDP‐glucose dehydrogenase
Authors: Ge Xue , Penney Lisa C. , van de Rijn Ivo , Tanner Martin E.
Published: March 2005

UDP‐glucose dehydrogenase catalyzes the NAD+‐dependent twofold oxidation of UDP‐glucose to give UDP‐glucuronic acid. A sequestered aldehyde intermediate is produced in the first oxidation step and a covalently bound thioester is produced in the second oxidation step. This work demonstrates that the Streptococcus pyogenes enzyme incorporates a single solvent‐derived oxygen atom during catalysis and probably does not generate an imine intermediate. The reaction of UDP‐[6′′,6′′‐di‐2H]‐d‐glucose is not accompanied by a primary kinetic isotope effect, indicating that hydride transfer is not rate determining in this reaction. Studies with a mutant of the key active site nucleophile, Cys260Ala, show that it is capable of both reducing the aldehyde intermediate, and oxidizing the hydrated form of the aldehyde intermediate but is incapable of oxidizing UDP‐glucose to UDP‐glucuronic acid. In the latter case, a ternary Cys260Ala/aldehyde intermediate/NADH complex is presumably formed, but it does not proceed to product as both release and hydration of the bound aldehyde occur slowly. A washout experiment demonstrates that the NADH in this ternary complex is not exchangeable with external NADH, indicating that dissociation only occurs after the addition of a nucleophile to the aldehyde carbonyl. Studies on Thr118Ala show that the value of kcat is reduced 160‐fold by this mutation, and that the reaction of UDP‐D‐[6′′,6′′‐di‐2H]‐glucose is now accompanied by a primary kinetic isotope effect. This indicates that the barriers for the hydride transfer steps have been selectively increased and supports a mechanism in which an ordered water molecule (H‐bonded to Thr118) serves as the catalytic base in these steps.
UDP‐galactose 4‐epimerase fromKluyveromyces fragilis
Authors: Brahma Amrita , Bhattacharyya Debasish
Published: March 2005

UDP‐galactose 4‐epimerases from the yeastKluyvero‐myces fragilisandEscherichia coliare both homodimers but the molecular mass of the former (75 kDa/subunit) is nearly double that of the latter (39 kDa/subunit). Protein databank sequence homology revealed the possibility of mutarotase activity in the excess mass of the yeast enzyme. This was confirmed by three independent assay protocols. With the help of specific inhibitors and chemical modification reagents, the catalytic sites of epimerase and mutarotase were shown to be distinct and independent. Partial proteolysis with trypsin in the presence of specific inhibitors, 5′‐UMP for epimerase and galactose for mutarotase, protected the respective activities. Similar digestion with double inhibitors cleaved the molecule into two fragments of 45 and 30 kDa. After separation by size‐exclusion HPLC, they manifested exclusively epimerase and mutarotase activities, respectively. Epimerases fromKluyveromyces lactis var lactis,Pachysolen tannophilusandSchizosaccharomyces pombialso showed associated mutarotase activity distinct from the constitutively formed mutarotase activity. Thus, the bifunctionality of homodimeric yeast epimerases of 65–75 kDa/subunit appears to be universal. In addition to the inducible bifunctional epimerase/mutarotase,K. fragiliscontained a smaller constitutive monomeric mutarotase of ≈ 35 kDa.
Protein assembly of photosystem II and accumulation of subcomplexes in the absence of low molecular mass subunits PsbL and PsbJ
Authors: Suorsa Marjaana , Regel Ralph E. , Paakkarinen Virpi , Battchikova Natalia , Herrmann Reinhold G. , Aro Eva‐Mari
Published: March 2005

The protein assembly and stability of photosystem II (PSII) (sub)complexes were studied in mature leaves of four plastid mutants of tobacco (Nicotiana tabacumL), each having one of thepsbEFLJoperon genes inactivated. In the absence ofpsbL, no PSII core dimers or PSII–light harvesting complex (LHCII) supercomplexes were formed, and the assembly of CP43 into PSII core monomers was extremely labile. The assembly of CP43 into PSII core monomers was found to be necessary for the assembly of PsbO on the lumenal side of PSII. The two other oxygen‐evolving complex (OEC) proteins, PsbP and PsbQ, were completely lacking in ΔpsbL. In the absence ofpsbJ, both intact PSII core monomers and PSII core dimers harboring the PsbO protein were formed, whereas the LHCII antenna remained detached from the PSII dimers, as demonstrated by 77 K fluorescence measurements and by the lack of PSII–LHCII supercomplexes. The ΔpsbJmutant was characterized by a deficiency of PsbQ and a complete lack of PsbP. Thus, both the PsbL and PsbJ subunits of PSII are essential for proper assembly of the OEC. The absence ofpsbEandpsbFresulted in a complete absence of all central PSII core and OEC proteins. In contrast, very young, vigorously expanding leaves of allpsbEFLJoperon mutants accumulated at least traces of D2, CP43 and the OEC proteins PsbO and PsbQ, implying developmental control of the expression of the PSII core and OEC proteins. Despite severe problems in PSII assembly, the thylakoid membrane complexes other than PSII were present and correctly assembled in allpsbEFLJoperon mutants.
Volkensin from Adenia volkensii Harms (kilyambiti plant), a type 2 ribosome‐inactivating protein
Authors: Chambery Angela , Di Maro Antimo , Monti Maurilia M. , Stirpe Fiorenzo , Parente Augusto
Published: March 2005

Volkensin, a type 2 ribosome‐inactivating protein from the roots of Adenia volkensii Harms (kilyambiti plant) was characterized both at the protein and nucleotide level by direct amino acid sequencing and cloning of the gene encoding the protein. Gene sequence analysis revealed that volkensin is encoded by a 1569‐bp ORF (523 amino acid residues) without introns, with an internal linker sequence of 45 bp. Differences in residues present at several sequence positions (reproduced after repeated protein sequence analyses), with respect to the gene sequence, suggest several isoforms for the volkensin A‐chain. Based on the crystallographic coordinates of ricin, which shares a high sequence identity with volkensin, a molecular model of volkensin was obtained. The 3D model suggests that the amino acid residues of the active site of the ricin A‐chain are conserved at identical spatial positions, including Ser203, a novel amino acid residue found to be conserved in all known ribosome‐inactivating proteins. The sugar binding site 1 of the ricin B‐chain is also conserved in the volkensin B‐chain, whilst in binding site 2, His246 replaces Tyr248. Native volkensin contains two free cysteinyl residues out of 14 derived from the gene sequence, thus suggesting a further disulphide bridge in the B chain, in addition to the inter‐ and intrachain disulphide bond pattern common to other type 2 ribosome‐inactivating proteins.
Interstitial charge states in boron-implanted silicon
Authors: Jung M. Y. L. , Kwok Charlotte T. M. , Braatz Richard D. , Seebauer E. G.
Published: March 2005

It is becoming increasingly clear that simulation models of transient enhanced diffusion (TED) in silicon need to incorporate interstitial charging effects accurately in order to adequately reproduce experimental data near the surface and near the underlying junction. However, in the case of boron TED, the relevant charge states and ionization levels of both boron and silicon interstitial atoms are known only imperfectly. The present work attempts to describe this behavior more accurately via simulations of implanted profiles that employ a model whose kinetic parameters have been determined with considerable confidence by rigorous systems methods. The results suggest that B has two relevant charge states: (+) and (−). The corresponding states for Si are (++) and (0). The effective ionization levels for B and Si are 0.33±0.05 and 0.12±0.05eV above the valence band maximum, respectively.
A theory of metamaterials based on periodically loaded transmission lines: Interaction between magnetoinductive and electromagnetic waves
Authors: Syms R. R. A. , Shamonina E. , Kalinin V. , Solymar L.
Published: March 2005

The propagation of waves in a metamaterial consisting of split ring resonators (SRRs) and metallic rods is considered in several steps. The first involves the rods in isolation, the second the SRRs in isolation, and the third a combination of the two, which includes the coupling between neighboring SRRs and allows the propagation of magnetoinductive (MI) waves. The mathematical formulation is based on a conventional description of loaded transmission lines. A dispersion equation is derived to show the main features of known experimental results, including all the stop bands and passbands, the latter exhibiting both forward and backward waves. The interaction between electromagnetic and MI waves is presented in the form of a coupled dispersion equation. The applicability of the approaches based on negative material parameters is discussed.