bluuebunny/crossref_metadata_2025_split huggingface dataset:
The structure of Pseudomonas P51 Cl‐muconate lactonizing enzyme: Co‐evolution of structure and dynamics with the dehalogenation function
Authors: Kajander Tommi , Lehtiö Lari , Schlömann Michael , Goldman Adrian 
Published: August 2003

AbstractBacterial muconate lactonizing enzymes (MLEs) catalyze the conversion of cis,cis‐muconate as a part of the β‐ketoadipate pathway, and some MLEs are also able to dehalogenate chlorinated muconates (Cl‐MLEs). The basis for the Cl‐MLEs dehalogenating activity is still unclear. To further elucidate the differences between MLEs and Cl‐MLEs, we have solved the structure of Pseudomonas P51 Cl‐MLE at 1.95 Å resolution. Comparison of Pseudomonas MLE and Cl‐MLE structures reveals the presence of a large cavity in the Cl‐MLEs. The cavity may be related to conformational changes on substrate binding in Cl‐MLEs, at Gly52. Site‐directed mutagenesis on Pseudomonas MLE core positions to the equivalent Cl‐MLE residues showed that the variant Thr52Gly was rather inactive, whereas the Thr52Gly‐Phe103Ser variant had regained part of the activity. These residues form a hydrogen bond in the Cl‐MLEs. The Cl‐MLE structure, as a result of the Thr‐to‐Gly change, is more flexible than MLE: As a mobile loop closes over the active site, a conformational change at Gly52 is observed in Cl‐MLEs. The loose packing and structural motions in Cl‐MLE may be required for the rotation of the lactone ring in the active site necessary for the dehalogenating activity of Cl‐MLEs. Furthermore, we also suggest that differences in the active site mobile loop sequence between MLEs and Cl‐MLEs result in lower active site polarity in Cl‐MLEs, possibly affecting catalysis. These changes could result in slower product release from Cl‐MLEs and make it a better enzyme for dehalogenation of substrate.
Innovation and Performance: Benchmarking Australian Firms
Authors: Feeny Simon , Rogers Mark 
Published: August 2003

AbstractThis article empirically analyses the link between innovation and performance using a sample of large Australian firms, with a specific aim of developing benchmarking tools. Innovation is measured by firms' investment in R&D and applications for patents, trademarks and designs. An innovation index is constructed to provide one method of benchmarking. The index incorporates a firm's innovative activities into a single figure after accounting for firm size. The index provides a ranking of the most innovative firms in Australia. A second method of benchmarking uses a stochastic production frontier. This type of analysis identifies the firms which are located closest to a ‘best practice innovation frontier’.
On the Popular Support for Progressive Taxation
Authors: Klor Esteban F. 
Published: August 2003

AbstractThe “popular support for progressive taxation theorem” (Marhuenda and Ortuño‐Ortín, 1995) provides an important formalization of the intuition that a majority of relatively poor voters over rich ones leads to progressive income taxation. Yet the theorem does not provide an equilibrium outcome. In addition, it assumes an overly restrictive domain of tax schedules and no incentive effects of income taxation. This paper shows that none of these assumptions of the theorem can be relaxed completely. Most notably, it is shown that a majority of poor voters does not imply progressive taxation in a more general policy space and that a regressive tax schedule may obtain a majority over a progressive one when individuals' income is endogenous.
Managing the future forest resource through designer trees
Authors: Todoroki C. L. , Carson S. D. 
Published: August 2003

AbstractWith today's tree improvement technology coupled with knowledge of the influence of forest management practices on tree growth and log quality, it is possible to manipulate tree form to engineer trees with specific characteristics. Theoretically we can create forest portfolios to optimize suitability for different end uses. We could design structural forests for optimal building materials, LongClears Forests for furniture and mouldings markets, or PulpWood Forests for pulp and paper industries. This project's goal was to explore methods for identifying tree characteristics that could be manipulated to optimize production of specific lumber products, namely LongClears. A model that works backwards from the targeted product through wood processing with linkage to forest management and genetic selection strategies is proposed. The model uses a combination of mathematical programming and operations research techniques including data envelopment analysis, log sawing optimization, and sawmill simulation to identify properties of the optimal log and designer tree.
Non‐linear matrix modeling of forest growth with permanent plot data: The case of uneven‐aged Douglas‐fir stands
Authors: Ralston R. , Buongiorno J. , Schulte B. , Fried J. 
Published: August 2003

AbstractUneven‐aged forest management is acquiring increasing importance throughout the world as an alternative to clear cutting. Simple stage‐structured matrix models can be used to predict the growth of uneven‐aged stands, and they are easily incorporated in optimization analysis. Parameters of these models can be estimated from readily available permanent plot data. Such a growth and yield model is presented for mixed, uneven‐aged Douglas‐fir and hardwood stands. The model was calibrated with data from 66 permanent plots in Oregon and Washington. The density‐dependent matrix model predicts the number of trees by diameter class and species type, softwood or hardwood. The parameters are based on individual tree growth equations, individual tree mortality equations, and stand ingrowth equations. The individual tree equations are a function of tree diameter, stand density, species, and site index. The stand‐level ingrowth equations are a function of stand density. The model was validated in the short term by comparing the number of trees in each diameter and species class at the time of the second inventory with the number predicted by the model, given conditions at the first inventory. A long‐term validation of the model was also done by comparing the steady‐state stand structure and stand volume with those observed for old‐growth stands. The model was applied to show the effects of different cutting cycles on productivity, diversity of tree species and size, and financial returns. The results suggest that uneven‐aged management of the Douglas‐fir forest type in the Pacific Northwest can be as productive as even‐aged management, with the added benefits of continuous cover forestry.
Can mature patch constraints mitigate the fragmenting effects of harvest opening size restrictions?
Authors: Rebain S. , McDill M. E. 
Published: August 2003

AbstractHarvest scheduling models often include maximum harvest opening size constraints, a restriction generally imposed for legal or policy reasons. The maximum harvest opening size restriction can greatly affect the spatial layout of the forest, with the dispersed harvesting increasing forest fragmentation. Because they can offset the negative impacts of maximum harvest opening size constraints, mature patch size constraints, which require a certain amount of the forest to be in patches meeting both minimum size and age requirements, have also been included in these models. This paper looks at the economic and spatial effects of ten harvest scheduling formulations with these two constraint sets on 21 hypothetical forest landscapes. Analyses of their age‐class distributions, border distributions, and patch size distributions at the end of a 60‐year planning horizon confirm that maximum harvest opening size constraints tend to fragment forest landscapes and that mature patch constraints can significantly reduce these effects.
Syllable-Pattern-Based Unknown-Morpheme Segmentation and Estimation for Hybrid Part-of-Speech Tagging of Korean
Authors: Lee Gary Geunbae , Cha Jeongwon , Lee Jong-Hyeok 
Published: August 2003

Most errors in Korean morphological analysis and part-of-speech (POS) tagging are caused by unknown morphemes. This paper presents a syllable-pattern-based generalized unknown-morpheme-estimation method with POSTAG (POStech TAGger), 1 which is a statistical and rule-based hybrid POS tagging system. This method of guessing unknown morphemes is based on a combination of a morpheme pattern dictionary that encodes general lexical patterns of Korean morphemes with a posteriori syllable trigram estimation. The syllable trigrams help to calculate lexical probabilities of the unknown morphemes and are utilized to search for the best tagging result. This method can guess the POS tags of unknown morphemes regardless of their numbers and/or positions in an eojeol (a Korean spacing unit similar to an English word), which is not possible with other systems for tagging Korean. In a series of experiments using three different domain corpora, the system achieved a 97% tagging accuracy even though 10% of the morphemes in the test corpora were unknown. It also achieved very high coverage and accuracy of estimation for all classes of unknown morphemes. 1 The binary code of POSTAG is open to the public for research and evaluation purposes at http://nlp.postech.ac.kr/. Follow the link OpenResources→DownLoad.
Interfacial Phenomena of Newspaper Fiber-Reinforced Polypropylene Composite, Part I: The Development of Interfacial Interaction
Authors: Hon David N.-S. , Ren Shan 
Published: August 2003

In the process of developing interfacial interaction between newspaper fiber (NPF) and polypropylene (PP) by an intensive mixing, the morphological and microstructural characteristics which influence the mechanical behavior of the mixture were investigated by means of a scanning electron microscope (SEM) and a rheometer. The effects of mixing temperature and moisture content in the NPF on the mechanical behavior were elucidated. The development of interfacial interaction took place in two stages, in which the first stage took place over a relatively short time. In this stage, the fiber was not uniformly dispersed in the melted PP matrix. A fully developed interfacial interaction was not developed until the second stage. In this stage, the fiber was uniformly dispersed into the matrix and coated with PP. The mechanical strength of the composite was maximized in the second stage of mixing.
Shape Control with Karhunen-Loéve-Decomposition: Theory and Experimental Results
Authors: Zhang Weihua , Michaelis Bernd 
Published: August 2003

The Finite Element Method is a powerful method that can be used to describe the dynamic behavior of mechanical systems. The most crucial problem to use this method is the large degree of freedom in FE-models. It is very difficult or even impossible to design controllers. Consequently, it is necessary to reduce the model. However, the model reduction deals only with the state variables, therefore the model reduction is not sufficient for the shape control, because a great number of reference and measured data are needed for the shape description and control. In [Zhang, W. and Michaelis, B. 2000. “Shape Control with Karhunen-Loève-Decomposition,” 11th Int. Conference on Adaptive Structures and Technologies, Nagoya, Japan, October 23-26, pp. 119-126.], we have developed a new method using the Karhunen-Loève-Decomposition to realize the shape control. In this paper, we will first give the theory briefly and then the experimental results.
Cost-benefit analysis of mollusc eating in a shorebird I. Foraging and processing costs estimated by the doubly labelled water method
Authors: Piersma Theunis , Dekinga Anne , Gils Jan A. van , Achterkamp Bart , Visser G. Henk 
Published: August 2003

SUMMARYAlthough the energy costs of foraging and food processing in vertebrates may be considerable, they have rarely been quantified separately. Here we present estimates for both cost factors based on a series of trials with a shorebird, the red knot Calidris canutus, fed natural and artificial prey types under naturalistic but fully controlled indoor aviary conditions. During eight 1-day trials we successfully manipulated the extent to which the five red knots were (1) actively probing and walking (i.e. foraging) and (2)actually ingesting prey (i.e. processing food) that was (3) either hard-shelled or not (i.e. crushing). Energy expenditures, estimated by the doubly labelled water (DLW) method, calibrated for use in this particular condition, varied between 1.5 and 4 W. A hierarchical analysis of variance indicated that the crushing of hard-shelled prey entailed no extra cost. We arrived at the following breakdown of cost components under the thermoneutral conditions of the experiment: a cost of active rest/maintenance of 1.665 W, an additional cost of foraging of 0.602 W and an additional digestive processing cost of 1.082 W. These cost levels are all well within the range of expectation and are consistent with the results of a separate outdoor aviary experiment in which the thermostatic costs needed separate estimation. On the basis of the cost and performance functions of gizzards of different mass, it was shown that under the conditions of this experiment the red knots expended the bare minimum for a balanced budget, maintaining the smallest possible gizzard. Under field conditions a larger gizzard would be required.
Cost-benefit analysis of mollusc-eating in a shorebird II. Optimizing gizzard size in the face of seasonal demands
Authors: van Gils Jan A. , Piersma Theunis , Dekinga Anne , Dietz Maurine W. 
Published: August 2003

SUMMARY
Aiming to interpret functionally the large variation in gizzard masses of red knots Calidris canutus, we experimentally studied how the digestive processing rate is influenced by the size of the gizzard. During their non-breeding season, red knots feed on hard-shelled molluscs, which they ingest whole and crush in their gizzard. In three experiments with captive birds we tested predictions of the hypothesis that gizzard size, viathe rate of shell crushing and processing, constrains intake rate in red knots(against the alternative idea that external handling times constrain intake rate). Gizzard size within individual birds was manipulated by varying the hardness of the diet on offer, and was confirmed by ultrasonography. The results upheld the `shell-crushing hypothesis' and rejected the `handling time hypothesis'. Intake rates on with-shell prey increased with gizzard size, and decreased with shell mass per prey. Intake rates on soft (without shell) prey were higher than on with-shell prey and were unaffected by gizzard size. Offering prey that were heavily shelled relative to their flesh mass led to energy intake rates that were marginally sufficient to balance the daily energy budget within the time that is naturally available in a tidal system. We predicted the optimal gizzard sizes that are required to either (1) balance energy income with energy expenditure, or (2) to maximise net daily energy intake. The gizzard mass of free-living red knots in the Wadden Sea is such that it maximises daily net energy intake in spring when fuelling for migration, while it balances energy budget throughout the remainder of the year.
Interindividual variation of eye optics and single object resolution in bumblebees
Authors: Spaethe Johannes , Chittka Lars 
Published: August 2003

SUMMARY
In the eusocial bumblebees, distinct size variation occurs within the worker caste of a colony. We show that there are pronounced differences in compound eye optical quality between individual workers in Bombus terrestris. Using scanning electron microscopy and antidromic illumination techniques (the pseudopupil method), we demonstrate that large workers have extended facet diameters in conjunction with reduced interommatidial angles. Thus, both overall sensitivity and image resolution are superior in such individuals. Behavioural tests show that a 33% increase in body size is accompanied by 100% greater precision in single target detection. This improvement in spatial resolving power is much stronger than that predicted by surveying ommatidial arrays, indicating that measuring eye optics alone is insufficient for predictions of single object resolution,unless combined with behavioural tests. We demonstrate that in small bees the minimum number of ommatidia involved in target detection is seven, while in large workers a single ommatidium is sufficient for target detection. These findings have implications for foraging and division of labour in social insects.
The retina ofManduca sexta: rhodopsin expression, the mosaic of green-, blue- and UV-sensitive photoreceptors, and regional specialization
Authors: White Richard H. , Xu Huihong , Münch Thomas A. , Bennett Ruth R. , Grable Erin A. 
Published: August 2003

SUMMARYSpectral sensitivities of individual photoreceptors in the compound eye of Manduca sexta were verified by immunocytochemistry, and the retinal mosaic was mapped, using polyclonal antisera raised against amino-terminal sequences of three identified rhodopsins: P520, P450 and P357. Retinulae are composed of a small proximal cell and seven or eight elongate cells extending across the retina. In each retinula, one or two elongate dv cells oriented in the dorsal-ventral axis of the retinal lattice express either P450 or P357. Six elongate ap and ob cells in the anterior-posterior and oblique axes express P520. The small proximal pr cell also appears to express P520. The retinal mosaic is regionalized into three distinct domains: ventral and dorsal domains that divide the main retina, and a large dorsal rim area. The immunocytochemical data provide a high-resolution map of the Manduca retina that confirms and refines earlier low-resolution ERG spectral sensitivity measurements. The dorsal and ventral domains, separated at a well-defined equatorial border, are distinguished by differences in the proportion of blue-sensitive dv cells: these cells dominate the ventral retina but are less abundant in the dorsal retina. Green-sensitive ap and ob receptors are uniformly distributed across the dorsal and ventral domains, and UV-sensitive dv cells are fairly uniformly distributed because many retinulae in the dorsal domain contain only one dv cell. Similarly, dorsal rim retinulae contain only the ventral member of the dv pair of receptors, two-thirds of which express P357. Otherwise,dorsal rim receptors express none of the three sequenced Manducaopsins; they must express rhodopsins that have yet to be cloned.
The integration of energy and nitrogen balance in the hummingbirdSephanoides sephaniodes
Authors: López-Calleja M. Victoria , Fernández María José , Bozinovic Francisco 
Published: August 2003

SUMMARYFloral nectars are rich in energy but contain only traces of amino acids,and it has been hypothesized that arthropods may be an important source of energy and amino acids for hummingbirds. We studied the nitrogen requirements of hummingbirds as well as how they use small arthropods to satisfy their nitrogen and energy requirements and how organ mass varies with nitrogen intake. Non-reproductive green-backed firecrowns Sephanoides sephaniodes were maintained for 10 days on diets containing 0%, 0.96%,1.82%, 4.11% and 11.1% nitrogen (dry-matter basis). A second group of individuals were fed with varying amounts of nitrogen-free nectar supplemented with fruit flies. Finally, non-reproductive hummingbirds were captured as a control group for analysis of organ mass and size as well as fat content.The maintenance nitrogen requirement of green-backed firecrowns determined by regression was 1.42 mg N day-1, yet they required nearly 10 mg N day-1 to maintain body mass. When arthropods were available, we observed that hummingbirds required approximately 150 fruit flies to maintain body mass, which corresponds to a 5% nitrogen diet. Interestingly, when nectar was restricted (to 4 ml day-1), or was absent, arthropods alone were not able to satisfy the body mass balance requirements of hummingbirds,suggesting that arthropods are not adequate as an energy source. In the group offered an 11.1% nitrogen diet, the size and surface of the small intestine,and liver and kidney mass increased in comparison with the control group(non-reproductive field hummingbirds) or the nitrogen-free group, suggesting a nitrogen overload. Our results are in agreement with other studies showing low nitrogen requirements by nectarivores. An important point to stress is that nitrogen digestibility declined in the 11.1% nitrogen diet, which strongly supports our nitrogen absorption saturation hypothesis.
Form and function of the bulbus arteriosus in yellowfin tuna (Thunnus albacares): dynamic properties
Authors: Braun Marvin H. , Brill Richard W. , Gosline John M. , Jones David R. 
Published: August 2003

SUMMARY
The bulbus arteriosus of the teleost heart possesses a static inflation curve that is r-shaped over the in vivo pressure range. To examine the possible significance of this in living animals, we recorded arterial blood pressure from anaesthetized yellowfin tuna and utilized a video dimensional analyser to simultaneously record changes in bulbar diameter. By plotting the changes in pressure against the changes in diameter, it was possible to create dynamic pressure-diameter (P-D) loops as well as calculate the instantaneous volume changes within the bulbus. The dynamic P-D loops showed the same features exhibited by static inflation. When nearly empty, a small stroke volume caused a large increase in blood pressure, while around systolic pressure large changes in volume resulted in small changes in pressure. We conclude that these features allow the bulbus to maintain ventral aortic flows and pressures over a large range of volumes.