bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersal Data and the Spread of Invading Organisms
Authors: Kot Mark , Lewis Mark A. , van den Driessche P.
Published: May 2006

Models that describe the spread of invading organisms often assume that the dispersal distances of propagules are normally distributed. In contrast, measured dispersal curves are typically leptokurtic, not normal. In this paper, we consider a class of models, integrodifference equations, that directly incorporate detailed dispersal data as well as population growth dynamics. We provide explicit formulas for the speed of invasion for compensatory growth and for different choices of the propagule redistribution kernel and apply these formulas to the spread of D. pseudoobscura. We observe that: (1) the speed of invasion of a spreading population is extremely sensitive to the precise shape of the redistribution kernel and, in particular, to the tail of the distribution; (2) fat—tailed kernels can generate accelerating invasions rather than constant—speed travelling waves; (3) normal redistribution kernels (and by inference, many reaction—diffusion models) may grossly underestimate rates of spread of invading populations in comparison with models that incorporate more realistic leptokurtic distributions; and (4) the relative superiority of different redistribution kernels depends, in general, on the precise magnitude of the net reproductive rate. The addition of an Allee effect to an integrodifference equation may decrease the overall rate of spread. An Allee effect may also introduce a critical range; the population must surpass this spatial threshold in order to invade successfully. Fat—tailed kernels and Allee effects provide alternative explanations for the accelerating rates of spread observed for many invasions.
Fractal Analyses of Animal Movement: A Critique
Authors: Turchin Peter
Published: May 2006

Several recent papers developed and applied a novel approach for the analysis of animal movement paths, based on calculating the paths' fractal dimensions. The estimated fractal dimension is used to describe the pattern of the interaction between animal movement and landscape heterogeneity, and possibly to extrapolate movement patterns of organisms across spatial scales. Here, I critically examine the key assumption of the fractal approach: that the estimated fractal dimension is constant over some biologically relevant range of spatial scales. Use of a correlated random walk as a null hypothesis for movement suggests that the fractal dimension should grade smoothly from near 1 at very small spatial scales to near 2 at very large spatial scales. Several empirical data sets exhibit a qualitative pattern in agreement with this prediction. I conclude that ecologists should avoid calculating and using the fractal dimension of movement paths, unless self—similarity (a constant fractal dimension) for some range of spatial scales is demonstrated. An alternative approach employing random—walk models provides a more powerful framework for translating individual movements in heterogeneous space into spatial dynamics of populations.
Top‐Down Cascade from a Bitrophic Predator in an Old‐Field Community
Authors: Moran Matthew D. , Rooney Thomas P. , Hurd L. E.
Published: May 2006

We tested the hypothesis that a bitrophic (third and fourth level) arthropod predator can exert a cascading, top—down influence on other arthropods and plants in an early successional old field. First—stadium mantids, Tenodera sinensis, were added to replicated open—field plots in numbers corresponding to naturally occurring egg hatch density and allowed to remain for $\approx 2$ mo. Sticky—trap dispersal barriers around both control and mantid—addition plots allowed us to monitor emigration of arthropods continuously during the experiment. Biomass of herbivores, carnivores, and plants, and abundances of arthropod taxa within plots were determined at the beginning, middle, and end of the experiment. The impact of mantids on the community was a top—down trophic cascade, beginning at the fourth trophic level and evident at each of the lower three levels. Mantids induced marked behavioral responses in other predators, but inteference among predators did not prevent the trophic cascade. The most common predators, cursorial spiders, emigrated from mantid addition plots in significantly greater numbers than from controls. This behavioral response may have resulted from avoidance of predation or competition. Mantids decreased biomass of herbivorous arthropods through predation, and this decrease in turn increased biomass of plants. Therefore, these generalist predators were able to decrease herbivory enough to affect plant growth. This and other recent studies indicate that top—down effects can be important in structuring terrestrial communities. Ours is the first example of a top—down cascade by a generalist arthropod predator in a nonagricultural ecosystem and illustrates the importance of detecting behavioral responses in studies of trophic interactions.
The Relationship Between Bite Rate and Local Forage Abundance in Wild Thomson's Gazelles
Authors: Bradbury Jack W. , Vehrencamp Sandra L. , Clifton Kenneth E. , Clifton Lisa M.
Published: May 2006

The foraging of female Thomson's gazelles (Gazella thomsoni) on shortgrass plains was monitored over one annual cycle in southwestern Kenya. Sward dry green biomasses and protein densities were estimated regularly throughout the study site. Changes in protein densities with season and locale were strongly correlated with underlying changes in grass physiognomy: sward height and dry green bulk biomass density were particularly important and were found to vary inversely. The relationship between bite rates and underlying sward parameters varied with season: gazelle bite rates in the dry season were positively correlated with underlying dry green biomass and protein densities, as predicted by either the Process 1 or Process 2 foraging model of Spalinger and Hobbs. Nonlinear regressions of within—bout bite rates on these model equations significantly explained 21.8 and 23.7% of the dry season variance, respectively. In contrast, bite rates in the early wet season showed significant negative correlations with underlying protein densities: the fit of the within—bout bite rate data to Spalinger and Hobbs' Process 3 model explained 18.4% of the overall variation. The late wet season showed a flat (insignificant) relationship between bite rates and protein levels and was thus intermediate between early wet— and later dry—season patterns. Logistic regression of the type of correlation between bite rate and protein density (positive, flat, negative) on two principal components of grass physiognomy suggested that a component heavily weighting sward height was the major correlate of foraging process, whereas a second major component heavily weighting bulk density and other grass quality measures was less critical. At least during this single annual cycle, shorter swards were associated with Processes 1 or 2, whereas taller swards showed Process 3 foraging. One interpretation of these results is that sward height modulates bite mass, which in turn plays the major role in controlling foraging process. Whether the switching point remains the same in subsequent years or not, the results make it clear that the direction of the bite rate vs. foraging density relationship can change markedly with season, as predicted by the Spalinger and Hobbs models.
Plant Species Mediate Changes in Soil Microbial N in Response to Elevated CO2
Authors: Hungate Bruce A. , Canadell Josep , Chapin F. Stuart
Published: May 2006

The effect of elevated $\mathrm{CO}_2$ on plant—microbial interactions and nitrogen (N) cycling is critical to predicting plant growth responses to elevated $\mathrm{CO}_2$, because plant growth is often N—limited. We investigated whether the effects of elevated $\mathrm{CO}_2$ on plant—microbial N dynamics differed among six annual plant species; three European grasses that have invaded California grasslands, and one grass and two forbs native to California serpentine grassland. Elevated $\mathrm{CO}_2$ altered plant N pools and ${15}\mathrm{NH}_4+$ uptake, but the direction and magnitude of the changes were species dependent. The introduced grasses showed increased plant N pools and ${15}\mathrm{NH}_4+$ uptake, whereas the native species showed smaller increases or even decreases in plant N pools and $15{\mathrm{NH}_4+$ uptake. Under nutrient enrichment, soil microbial N and 15\mathrm{NH}_4+$ uptake differed among soils with different plant species, but they were not affected by elevated $\mathrm{CO}_2$. At low nutrients, elevated $\mathrm{CO}_2$ altered soil microbrial N and 15\mathrm{NH}_4+$ uptake, but the direction and magnitude of the changes were species dependent. The changes in soil microbial N were positively correlated with changes in the plant N pool, suggesting that there was no trade—off in N uptake between plants and microbes. The results also suggest that plant species composition will partly determine the direction of changes in soil N cycling in response to elevated $\mathrm{CO}_2$.
Nutrients in Senesced Leaves: Keys to the Search for Potential Resorption and Resorption Proficiency
Authors: Killingbeck Keith T.
Published: May 2006

Analyses of nitrogen and phosphorus in the senesced leaves of 89 species of deciduous and evergreen woody perennials were used (1) to discover the limits of ultimate potential resorption (maximal withdrawal of nutrients from senescing leaves), (2) to determine a means by which resorption can be categorized as complete or incomplete, (3) to develop the concept of resorption proficiency (measured as the levels to which nutrients have been reduced in senesced leaves), (4) to compare resorption in evergreen vs. deciduous species, (5) to assess the impact of phylogeny on resorption, (6) to compare resorption in actinorhizal vs. non—nitrogen—fixing species, and (7) to consider the efficacy of using multiple measures of resorption to answer questions regarding the function and evolution of this process, rather than relying solely on analyses of resorption efficiency (percentage reduction of nutrients between green and senesced leaves). Concentrations of 0.3% nitrogen and 0.01% phosphorus in senesced leaves represent ultimate potential resorption of these nutrients in woody perennials. Resorption proficiency and potential resorption were quantitatively defined in two models that describe both resorption that is maximal and biochemically complete, and that which is not. Resorption is highly proficient in plants that have reduced nitrogen and phosphorus in their senescing leaves to concentrations below 0.7% and 0.05%, respectively. An important feature of knowing the levels to which nutrients can be reduced in senescing leaves is that these values offer an objective gauge by which to measure the success of resorption as a nutrient conservation mechanism. Evergreens were significantly more proficient at resorbing phosphorus than were deciduous species (0.045% vs. 0.067% P in senesced leaves, respectively) and plants capable of symbiotic nitrogen fixation were significantly less proficient at resorbing nitrogen than were nonfixers (1.6% vs. 0.9% N in senesced leaves, respectively). Resorption proficiency appeared to parallel some phylogenic trends, yet the influence of phylogeny was not so significant as to overwhelm the effects of recent selection. The ability of plants to reduce nitrogen in senescing leaves was significantly correlated with their ability to reduce phosphorus. Measurement and analysis of resorption proficiency, when coupled with concurrent consideration of potential resorption and resorption efficiency, should facilitate and expedite the ongoing attempt to resolve complex questions regarding the environmental constraints that influence resorption, and the selection pressures that have directed the evolution of this process.
Maternal Manipulation of Offspring Phenotypes via Nest‐Site Selection in an Oviparous Lizard
Authors: Shine Richard , Harlow Peter S.
Published: May 2006

Mothers may be able to manipulate the phenotypes of their progeny not only via direct pathways (e.g., allocation of nutrients and energy), but also indirectly, by inducing particular developmental pathways through selection of nest sites and thus, incubation conditions. In the field, female skinks (Bassiana duperreyi) in montane southeastern Australia select nest sites with specific thermal characteristics–especially, a high mean temperature and a high diel range in temperature. Monitoring of 14 natural nests throughout most of the incubation period revealed considerable differences among nests in both means and variances of thermal regimes. Laboratory experiments on this species show that both the mean and the variance of incubation temperatures profoundly influence developmental rates (and hence, incubation periods) as well as the body shape, activity levels, thermo—regulatory behavior, and running speeds of the hatchlings. Hence, a female's selection of a particular nest site can substantially modify both the time of emergence of the hatchlings, and the morphology and behavior of her offspring. Even within a single nest, minor differences among eggs in their depth below the ground surface will directly affect thermal variance, and so may strongly influence rates of embryogenesis and the phenotype of the hatchling. The effects of thermal variance (independent of the mean) on embryonic development rates and hatchling phenotypes suggest that data from constant—temperature incubation in the laboratory should be interpreted with caution
The Role and Importance of Recruitment Variability to a Guild of Tide Pool Fishes
Authors: Pfister Catherine A.
Published: May 2006

In a guild of tide pool fishes on the outer coast of Washington State, USA, recruitment varied both temporally (seasonally and interannually) and spatially (over intervals of 4—5 km, across a maximum of 30 km of shoreline). Using census data and mark—recapture data, I studied the demography of four species of tide pool sculpins with the goal of understanding how variability in recruitment affected adult population patterns. I found that, although adult populations reflected well the most recent recruitment pulse for the two most common species, adult population growth rate was the most sensitive to changes in survivorship rates. Similarly, analyses of the effect that variance in each demographic parameter had on variability in subsequent adult population size also showed a disproportionate effect of adult survivorship on adult population sizes. In other words, high variability in a demographic estimate did not always result in high variability in population size. Negative density dependence was documented for all species, suggesting that recruitment effects are dampened by postrecruitment events. Thus, although recruitment events could be detected in the adult population for short time periods, postrecruitment events appeared to dampen the effects of seasonal recruitment pulses in these nearshore fishes.
Effects of Food Availability and Density on Red Squirrel (Sciurus Vulgaris) Reproduction
Authors: Wauters Luc A. , Lens Luc
Published: May 2006

Density—dependent reproductive rate may be the result of all individuals in a population suffering reduced fecundity when density increases (Lack 1954), or it may be the result of a lower proportion of individuals living in favorable places at high density (Andrewartha and Birch 1954). We used a key—factor analysis to investigate whether reproductive rate in two red squirrel (Sciurus vulgaris) populations was density dependent. Four k values were determined, indicating offspring mortality caused by: adult females not entering oestrus (k1), oestrous females not giving birth (k2), lactating females failing to wean offspring (k3), and mortality in litters of successful females (k4). We also investigated the effect of food availability on the different k values and tested predictions of the two contrasting hypotheses (Lack vs. Andrewartha and Birch) by examining the mechanisms of density dependence. The reproductive performance of female squirrels was monitored over 18 breeding seasons in a coniferous forest and over 16 breeding seasons in a deciduous forest. In the coniferous forest, annual variation in pine seed abundance only affected k4, which was only weakly related to total mortality of offspring (K). In the deciduous woodland, however, the key factors k2 and k3, which were strongly related with total K, were inversely correlated with food abundance. In the coniferous forest, only k2 was female density dependent, and breeding failure before parturition occurred primarily among floaters, which were more numerous at high density. In the deciduous forest, annual and seasonal variation in the number of floaters caused density dependence in fecundity (k1). Increased breeding failure of lactating females (k3) with high female density was positively correlated with the number of floaters and with the proportion of females occupying poor quality home ranges. We concluded that density—dependent reproduction in red squirrels can be caused by two mechanisms: a direct density effect of more floaters at high female density, and an effect of habitat heterogeneity, with more females occupying poor territories at high densities, resulting in low breeding success. That reduced fecundity or breeding failure at high densities occurred mainly in female squirrels not occupying good territories, and that annual and seasonal variation in litter size of successful females was not density dependent, supported the predictions of the Andrewartha and Birch (1954) hypothesis.
Ecological Correlates of Labile Sex Expression in the Orchid Catasetum Viridiflavum
Authors: Zimmerman Jess K.
Published: May 2006

Patterns of sex expression were studied in a natural population of the epiphytic orchid Catasetum viridiflavum on Barro Colorado Island (BCI), Panama. Data on gender and flowering frequency were collected for 2 yr from 186 orchids occurring in both young (70—100 yr old) and mature forests. The distribution of phenotypic gender ratio was strongly bimodal in the population, and sex ratios were significantly affected by forest age. In the young forest was statistically indistinguishable from 1:1. Gender in C. viridiflavum is largely determined by light intensity. Females occurred most frequently in open canopies,and males predominated in closed canopies. Experimental shading of developing inflorescences of well—illuminated plants duplicated this pattern, suggesting sex expression is controlled by cues received by the developing inflorescence. Small, but significant effects of plant size on gender were also detected. Forty—two percent of plants occurred on dead, decaying wood (mostly standing dead trees), while the remainder occurred on live trees. Substrate type and canopy openness are correlated because dead trees present no canopy to shade epiphytes on them. Differences in sex ratio due to forest type resulted from a more frequent occurrence of plants on standing dead trees in the young vs. the mature forest. Theory for the evolution of environmental sex determination (ESD) assumes that environment affects reproductive success (RS), but that the relationship between RS and environment is different for males and females. Light availability and substrate were investigated for their effects on two components of RS, flowering frequency and vegetative growth. C. viridiflavum on dead, decaying wood flowered more often than those on live trees, but no significant effect due to canopy openness was detected. The influence of substrate and light availability on estimated rates of vegetative growth varied from year to year, but increased rates were associated with either dead, decaying wood or high light intensities in at least 1 yr. Thus, explanations for the evolution of ESD in C. viridiflavum must include potential effects of both substrate type and light environment on male and female RS. Plants growing on dead, decaying wood in an open habitat that produced fruit exhibited reduced vegetative growth compared to nonfruiting plants, indicating there is long—term cost to fruit production in C. viridiflavum. In forest habitats, females setting fruit on live trees did not flower in the following year. Most nonfruiting females on this substrate type, as well as fruiting and nonfruiting plants on dead trees, flowered in the following year. Although sample sizes supporting this pattern were small, it is consistent with the hypothesis that sex differences in costs of reproduction in response to changes in substrate (and correlated changes in light availability) may explain the evolution of ESD in C.viridiflavum.
Mediators reveal their essential techniques for successful settlements
Authors: Goldberg Stephen B.
Published: May 2006

What makes for mediation success? In the first of two parts, Stephen B. Goldberg, of Chicago, who surveyed dozens of mediators, recounts the neutrals' tales of how they were able to get parties to come to terms and avoid prolonging disputes. The techniques discussed in the interviews will act as a guide for neutrals to use in establishing rapport among mediation participants
Properties of the n‐overlap vector and n‐overlap similarity theory
Authors: Egghe L.
Published: May 2006

In the first part of this article the author defines the n‐overlap vector whose coordinates consist of the fraction of the objects (e.g., books, N‐grams, etc.) that belong to 1, 2, …, n sets (more generally: families) (e.g., libraries, databases, etc.). With the aid of the Lorenz concentration theory, a theory of n‐overlap similarity is conceived together with corresponding measures, such as the generalized Jaccard index (generalizing the well‐known Jaccard index in case n 5 2). Next, the distributional form of the n‐overlap vector is determined assuming certain distributions of the object's and of the set (family) sizes. In this section the decreasing power law and decreasing exponential distribution is explained for the n‐overlap vector. Both item (token) n‐overlap and source (type) n‐overlap are studied. The n‐overlap properties of objects indexed by a hierarchical system (e.g., books indexed by numbers from a UDC or Dewey system or by N‐grams) are presented in the final section. The author shows how the results given in the previous section can be applied as well as how the Lorenz order of the n‐overlap vector is respected by an increase or a decrease of the level of refinement in the hierarchical system (e.g., the value N in N‐grams).
Memex at 60: Internet or iPod?
Authors: Veith Richard H.
Published: May 2006

It has been 61 years since the 1945 Memex article, and so much has changed since then that we might well wonder whether the article is still worth looking at. It certainly inspired some of the leading figures in information technology, but now it seems to be cited either for things it did not really say, or because everything it proposed has been pretty much accomplished, albeit with alternate technology. If we take another look at the Memex description, though, there are a few key ideas that can still be goals in terms of an easy‐to‐use personal collection that is a supplement to one's own memory. Perhaps in today's terms, the device would be a combination of the iPod design and a tablet computer. As such, it could function as a handy information pod, with certain Memex features, serving as an extended personal memory.
“Head‐to‐head comparison between sirolimus‐eluting and paclitaxel‐eluting stents in patients with complex coronary artery disease: An intravascular ultrasound study”
Authors: Červinka Pavel , Costa Marco A. , Angiolillo Dominick J. , Špaček Radim , Bystroň Marian , Kvašňák Martin , Veselka Josef , Nanda Hitesh , Futamatsu Hideki , Futamatsu Kino
Published: May 2006

Background:

The aim of this study was to assess neointimal hyperplasia following sirolimus‐eluting (SES) and paclitaxel‐eluting stents (PES) implantation in a patients with complex coronary disease.

Method:

Between January to December 2004, 70 patients were enrolled in this study (SES = 37; PES = 33. The primary objective was to assess the efficacy of SES and PES on neointimal proliferation inhibition in patients with complex coronary lesions by volumetric 3D intravascular ultrasound (IVUS) assessment at six‐month follow‐up.

Results:

Baseline clinical, demographic or angiographic characteristics were well balanced in both groups. All procedures as well as hospitalisation were uneventful. The percentage of B2/C lesions in our study was >90% in both groups. The IVUS‐assessed in‐stent mean neointimal hyperplasia volume was significantly lower in lesions treated with SES compared to PES (4.1 ± 11 mm3 vs. 17.4 ± 23 mm3, p < 0.002) at 6 month follow‐up. No difference in both MACE (3.0 versus 6.0%, p = NS) and restenosis (5.4 versus 9.1%, p = NS) were found. The in‐segment late loss at six month was 0.26 mm in the SES and 0.48 mm in the PES group (p = NS).

Conclusions:

The present study showed reduced neointimal proliferation after sirolimuseluting as compared to paclitaxel‐eluting stents in patients with complex coronary artery disease. Both SES and PES were associated with low rate of angiographic restenosis or major adverse cardiovascular events. © 2006 Wiley‐Liss, Inc.
A comparison of several methods for haplotype frequency estimation and haplotype reconstruction for tightly linked markers from general pedigrees
Authors: Zhang Kui , Zhao Hongyu
Published: May 2006

Haplotype inference for tightly linked markers from general pedigrees remains a challenging problem. Only a few methods are available to efficiently and accurately estimate haplotype frequencies and reconstruct haplotypes for a large number of tightly linked markers from general pedigrees in the presence of missing data, and their performance has not been carefully and extensively evaluated. In this paper, we compare four published methods for haplotype reconstruction and frequency estimation for tightly linked markers from general pedigrees, including HAPLORE, GENEHUNTER, PedPhase, and MERLIN. We review these methods and discuss the differences between them in terms of the models and computational strategies employed. We assess their performance based on simulations using pedigrees and haplotypes on tightly linked single nucleotide polymorphisms from real studies. We investigate the effect of several factors, including the missing rate, the departure from Hardy‐Weinberg Equilibrium, and the sample size, on the accuracy for haplotype inference. We also compare these methods with a widely used method for haplotype inference from unrelated individuals, PHASE, by treating individuals within a pedigree as unrelated samples. This comparison allows us to investigate the relative efficiency in haplotype inference using pedigree data. Our results indicate that incorporation of pedigree information can improve the precision for haplotype frequency estimation and the accuracy for haplotype reconstruction. Among four haplotyping methods capable of analyzing general pedigrees, HAPLORE and MERLIN have comparable performance and outperform the other two methods in almost all situations. Genet. Epidemiol. © 2006 Wiley‐Liss, Inc.
A review of metal release in the food industry
Authors: Jellesen M. S. , Rasmussen A. A. , Hilbert L. R.
Published: May 2006

The objective of this review is to outline literature on metal release in the food industry. Key results are reviewed from publications with high scientific level as well as papers with focus on industrial aspects. Examples of food products with a corrosive effect are given, and cases concerning processes, storing equipment as well as cleaning and sanitising procedures are reviewed. Stainless steel is the most widely used metallic material in the food industry; however other metals and their alloys are also briefly treated. The review deals with phenomena mainly relating to electrochemical corrosion, but also examples of material degradation as a consequence of wear and corrosive wear are presented.
Locking and hourglass phenomena in an element‐free Galerkin context: the B‐bar method with stabilization and an enhanced strain method
Authors: Recio D. P. , Jorge R. M. Natal , Dinis L. M. S.
Published: May 2006

The meshless methods, namely the element‐free Galerkin method (EFGM), when they first appeared claimed that volumetric locking and hourglass were avoided. This was not the case and both phenomena occur in the EFGM. In the context of the finite element method (FEM) these phenomena were widely studied. In this work, forms of avoiding the locking phenomenon will be presented; a formulation based on the enhanced strain method will be introduced in the EFGM and the B‐bar method will be implemented under the scope of the EFGM. Secondly, to render this method more robust, a stabilization technique will be implemented avoiding hourglass. Several examples are solved to probe the efficiency of these techniques. Copyright © 2006 John Wiley & Sons, Ltd.
Original crosslinking of poly(vinylidene fluoride) via trialkoxysilane‐containing cure‐site monomers
Authors: Guiot J. , Ameduri B. , Boutevin B. , Lannuzel T.
Published: May 2006

The synthesis of fluorinated monomers bearing an ω‐trialkoxysilane function (4,5,5‐trifluoropent‐4‐ene‐1‐trimethoxysilane and 4,5,5‐trifluoropent‐4‐ene‐1‐triethoxysilane), their radical copolymerization with vinylidene fluoride (VDF), and the crosslinking of resulting copolymers are presented. The silicon‐containing fluoromonomers were prepared from a three step‐reaction from ClCF2CFClI, last step being the hydrosilylation of 1,1,2‐trifluoro‐1,4‐pentadiene with trialkoxysilane. The copolymerizations of these silicon‐containing fluoromonomers with VDF led to original PVDF bearing pendant trialkoxysilane functions. Their microstructures, characterized by NMR showed that VDF was the more incorporated. These latter ones were crosslinked in the presence of moisture at 200 °C leading to insoluble materials stable in solvents, oils, water, and to acids. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3896–3910, 2006
Dimethacrylate derivatives of dimer acid
Authors: Trujillo‐Lemon Marianela , Ge Junhao , Lu Hui , Tanaka Jiro , Stansbury Jeffrey W.
Published: May 2006

Dimethacrylate monomers are used in a wide variety of crosslinked polymer applications, including adhesives, coatings, dental restoratives, and stereolithography. The advantages of rapid curing and good mechanical properties offered by these materials are countered by problems with dimensional changes during polymerization and long‐term physical instability resulting from water sorption and loss of residual unreacted monomer. In this work, several examples of hydrophobic monomers based on a dimer acid structure were synthesized, and their monomeric and homopolymer properties were evaluated. The photopolymerization reactivity and conversion were investigated with near‐infrared spectroscopy. Studies of the volumetric shrinkage, water sorption, and water contact angle and three‐point‐bend testing of the homopolymers were also carried out, with the results compared with those of commonly used dimethacrylate monomers. The new monomers produced higher degrees of conversion combined with lower polymerization shrinkage and water sorption values in comparison with conventional monomers. The relatively low crosslink density of dimethacrylates constructed from dimer acid produced polymers with high flexibility and low modulus, as expected; however, changes in the functionality of the group linking the dimer acid core with the methacrylate end groups induced significant property differences. On the basis of the properties demonstrated by the dimer acid monomers and their homopolymers, these new materials appear well suited for applications such as coatings and adhesives. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3921–3929, 2006
Variation Mode and Effect Analysis: a Practical Tool for Quality Improvement
Authors: Johansson Per , Chakhunashvili Alexander , Barone Stefano , Bergman Bo
Published: May 2006

This paper describes a statistically based engineering method, variation mode and effect analysis (VMEA), that facilitates an understanding of variation and highlights the product/process areas in which improvement efforts should be targeted. An industrial application is also described to illustrate how the VMEA can be used for quality improvement purposes. Copyright © 2006 John Wiley & Sons, Ltd.
Relationships Among Control Charts Used with Feedback Control
Authors: Runger George , Testik Murat Caner , Tsung Fugee
Published: May 2006

Feedback control is common in modern manufacturing processes and there is a need to combine statistical process control in such systems. Typical types of assignable causes are described and fault signatures are calculated. A fault signature can be attenuated by the controller and an implicit confounding among faults of different types is discussed. Furthermore, the relationships between various control statistics are developed. Control charts have been proposed previously for deviations from target and for control adjustments. We describe why one or the other can be effective in some cases, but that neither directly incorporates the magnitude (or signature) of an assignable cause. Various disturbance models and control schemes, both optimal and non‐optimal, are included in a mathematically simple model that obtains results through properties of linear filters. We provide analytical results for a widely‐used model of feedback control. Copyright © 2006 John Wiley & Sons, Ltd.
Thermosensitive Y‐Shaped Micelles of Poly(oleic acid‐Y‐N‐isopropylacrylamide) for Drug Delivery
Authors: Li Yong‐Yong , Zhang Xian‐Zheng , Kim Gwang‐Chol , Cheng Han , Cheng Si‐Xue , Zhuo Ren‐Xi
Published: May 2006

A novel thermosensitive amphiphilic copolymer comprised of two hydrophobic poly(oleic acid) (POA) segments and one hydrophilic poly(N‐isopropylacrylamide) (PNIPAAm) segment was designed and synthesized. The structure of the copolymer was confirmed as Y‐shaped by FTIR, 1H NMR, and SEC‐MALLS analysis. A cytotoxicity study shows that the P(OA‐Y‐NIPAAm) copolymer exhibits good biocompatibility. The copolymer may self‐assemble into micelles in water, with the hydrophobic POA segments at the cores of micelles and the hydrophilic PNIPAAm segments as the outer shells. The resulting micelles demonstrate temperature sensitivity with a lower critical solution temperature (LCST) of 31.5 °C and a critical micelle concentration (CMC) of 12.6 mg L−1. Transmission electron microscopy (TEM) shows that the micelles exhibit a nanospheric morphology within a narrow size range of ≈10–30 nm. A study of controlled release reveals that the self‐assembled micelles have great potential as drug carriers.
Critical Oxide Thickness for Efficient Single‐Walled Carbon Nanotube Growth on Silicon Using Thin SiO2 Diffusion Barriers
Authors: Simmons Jason M. , Nichols Beth M. , Marcus Matthew S. , Castellini Olivia M. , Hamers Robert J. , Eriksson Mark A.
Published: May 2006

The ability to integrate carbon nanotubes, especially single‐walled carbon nanotubes, seamlessly onto silicon would expand their range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single‐walled carbon nanotubes on bare silicon and on ultrathin oxides is greatly inhibited due to the formation of a noncatalytic silicide. Using X‐ray photoelectron spectroscopy, we show that silicide formation occurs on ultrathin oxides due to thermally activated metal diffusion through the oxide. Silicides affect the growth of single‐walled nanotubes more than multi‐walled nanotubes due to the increased kinetics at the higher single‐walled nanotube growth temperature. We demonstrate that nickel and iron catalysts, when deposited on clean silicon or ultrathin silicon dioxide layers, begin to form silicides at relatively low temperatures, and that by 900 °C, all of the catalyst has been incorporated into the silicide, rendering it inactive for subsequent single‐walled nanotube growth. We further show that a 4‐nm silicon dioxide layer is the minimum diffusion barrier thickness that allows for efficient single‐walled nanotube growth.
Short‐term efficacy of pharmacotherapeutic interventions in osteoarthritic knee pain: A meta‐analysis of randomised placebo‐controlled trials
Authors: Bjordal Jan Magnus , Klovning Atle , Ljunggren Anne Elisabeth , Slørdal Lars
Published: May 2006

Background: Pain is the most debilitating symptom in osteoarthritis of the knee (OAK).

Aim and methods: To determine the short‐term pain‐relieving effects of seven commonly used pharmacological agents for OAK pain by performing a systematic review of randomised placebo‐controlled trials.

Results: In total, 14,060 patients in 63 trials were evaluated. Opioids and oral NSAIDs therapy in patients with moderate to severe pain (mean baseline 64.3 and 72.8mm on VAS respectively) had maximum efficacies compared to placebo at 2–4 weeks of 10.5mm [95% CI: 7.4–13.7] and 10.2mm [95% CI: 8.8–11.2] respectively. The efficacy of opioids may be inflated by high withdrawal rates (24–50%) and “best‐case” scenarios reported in intention‐to‐treat analyses. In patients with moderate pain scores on VAS (mean range from 51 to 57mm), intra‐articular steroid injections and topical NSAIDs had maximum efficacies at 1–3 weeks of 14.5mm [95% CI: 9.7–19.2] and 11.6 mm [95% CI: 7.4–15.7], respectively. Paracetamol, glucosamin sulphate and chondroitin sulphate had maximum mean efficacies at 1–4 weeks of only 4.7mm or lower.

Heterogeneity tests revealed that best efficacy values of topical NSAIDs may be slightly deflated, while data for oral NSAIDs may be slightly inflated due to probable patient selection bias.

Conclusion: Clinical effects from pharmacological interventions in OAK are small and limited to the first 2–3 weeks after start of treatment. The pain‐relieving effects over placebo in OAK are smaller than the patient‐reported thresholds for relevant improvement.
Habitat association of plaice, sole, and lemon sole in the English Channel
Authors: Hinz Hilmar , Bergmann Melanie , Shucksmith Richard , Kaiser Michel J. , Rogers Stuart I.
Published: May 2006

Flatfish have been the subject of scientific research since the beginning of the 19th century, but information on specific habitat requirements of adult life stages is incomplete. This study investigates the association between benthic habitat and the adult life stage of three flatfish species (plaice, sole, and lemon sole). Data from groundfish surveys spanning nine years were used to identify three distinct site groups: sites where a species was consistently abundant, sites of variable or low abundance, and sites at which no fish were caught. We hypothesize that these three site groups should represent a gradient in habitat suitability from highly suitable to unsuitable. Habitat parameters for each site group and species are described and analysed. Besides large-scale physical parameters, the importance of structuring epifauna and prey availability was investigated. Plaice and sole showed similar trends for most abiotic parameters, whereas lemon sole was found over distinctly different habitats. Sediment associations differed between the three species. No clear association was found between flatfish abundance, structuring epifauna, and prey availability within this study. Contradictory results between prey abundance assessed by grab samples and the nutritive state of plaice suggested that the sampling scale used might have been inappropriate to determine prey availability accurately. Plaice appear to sample prey more effectively at the appropriate spatial scales, so the nutritive state of the fish might be a more reliable indicator for prey availability and thus habitat quality.
Mitochondrial DNA analyses of narrow-barred Spanish mackerel (Scomberomorus commerson) suggest a single genetic stock in the ROPME sea area (Arabian Gulf, Gulf of Oman, and Arabian Sea)
Authors: Hoolihan John P. , Anandh Prem , van Herwerden Lynne
Published: May 2006

We studied the genetic stock structure of Scomberomorus commerson (locally called kingfish) using restriction fragment length polymorphism (RFLP) and direct sequencing analyses of mtDNA samples from seven locations within the ROPME sea area (Arabian Gulf, Gulf of Oman, and Arabian Sea). A 475-bp segment from the D-loop region was screened in 218 samples using six restriction enzymes, resulting in 22 composite haplotypes. Mean nucleotide diversity for the seven populations was 0.025 (±0.000). An AMOVA comparison among groups of individuals inside and outside the Gulf showed 0.49% variation (p = 0.201), whereas the variation of populations within these groups was 0.05% (p = 0.408). The mean FST value for population pairwise comparisons was 0.010. To further resolve genealogies, sequence analysis was performed on a 330-bp fragment from the same segment for 193 fish. The genetic variance estimated across all populations was similar to the RFLP data, indicating a homogeneous distribution consistent with a single intermingling genetic stock. Based on the genetic marker tested, the null hypothesis that kingfish within the ROPME sea area constitutes a single stock cannot be rejected, but considering that a few migrating fish can reduce heterogeneity to where genetic drift is undetectable, panmixia cannot be confirmed. The results cautiously suggest that adopting a single-stock model and regional shared management are appropriate for sustainable long-term use of this important resource. More rigorous genetic testing using additional neutral markers, and mark-recapture experiments to detect spatial movement patterns, are recommended to further elucidate any stock substructure.
Ligamentous Reconstruction of Scapholunate Dislocation through a Double Dorsal and Palmar Approach
Authors: MARCUZZI A. , ACCIARO A. LETI , CASERTA G. , LANDI A.
Published: May 2006

Six patients, were treated for scapholunate dissociation by reconstruction of both the palmar and dorsal parts of the scapholunate interosseous ligament through a combined palmar and dorsal approach. The mean active range of motion of the wrist at final follow-up was 44° of flexion and 58° of extension and the mean hand grip strengths was 88% of that of the contralateral hand. The average time to return to work was 105 days and the mean DASH score at a mean follow-up of 32 months was 18. At follow-up, radiographs showed maintenance of the anatomical reduction of the scapholunate articulation in all cases and the scapholunate angle was normal in five patients.
Revisiting Russian and Polish elite value orientations: Are the elites still committed to the original goals of post-communist transitions?
Authors: Levintova Ekaterina
Published: May 2006

This article investigates the extent of continuity and discontinuity of the original political, economic, and foreign policy value orientations of Russian and Polish post-Communist elites. I conclude that during the post-Communist period the Russian elite shifted the priorities from pro-democratic to authoritarian positions, engaged in a debate over the most desirable foreign policy course, and ultimately chose a pragmatically independent direction, but remained loyal to original beliefs in the free market. In Poland, with its cyclical rotation of governments, original pro-democratic and pro-Western elite value orientations survive to this day, while the issue of preferred economic model is contested and highly sensitive to electoral cycles.
Pathophysiology and therapy for haemoglobinopathies; Part II: thalassaemias
Authors: Urbinati Fabrizia , Madigan Catherine , Malik Punam
Published: May 2006

Thalassaemias result from mutations of the globin genes that cause reduced or absent haemoglobin production and thus interfere with the critical function of oxygen delivery. They represent the most common single-gene disorders, with 4.83% of the world population carrying globin gene variants. Reduced or absent α-globin (α-thalassaemia) or β-globin (β-thalassaemia) leads to anaemia and multifaceted clinical syndromes. In this second of two reviews on the pathophysiology of haemoglobinopathies, we describe the clinical features, pathophysiology and molecular basis of α- and β-thalassaemias. We then discuss current targeted therapies, including the new oral iron chelators, which, along with chronic transfusions, constitute the mainstay of symptomatic therapy for the majority of patients. Finally, we describe potentially curative therapies, such as bone marrow transplant, and discuss some of the outstanding research studies and questions, including the upcoming field of gene therapy for β-thalassaemia. An accompanying article on haemoglobinopathies (Part I) focuses on sickle cell disease.
Anreizanalyse intensiver Nutzung von Computern in der Freizeit
Authors: Rheinberg Falko , Tramp Nadine
Published: May 2006

Zusammenfassung. Was bringt intensive Computernutzer dazu, ihre Freizeit am Rechner zu verbringen, und gibt es hierbei Unterschiede zwischen verschiedenen Nutzertypen? N = 271 Personen nahmen an einer online Befragung zu Anreizen freizeitlicher Computernutzung teil. Durch ausgewählte Internetverteiler waren gezielt besonders engagierte Computernutzer angesprochen worden (M = 3,9 Freizeitstunden am Rechner pro Tag). Für diese Nutzer fanden sich (in der Reihenfolge ihres Gewichtes) folgende Anreizfaktoren: Zugehörigkeit/Gemeinschaft; Kompetenzerleben; Vielseitigkeit/Nutzen; Langeweilevermeidung; rebellische Illegalitätstendenz. Gruppiert nach ihren bevorzugten Nutzungsweisen fanden sich drei Nutzertypen: Zweckorientierte Nutzer (58%), Hacker (= Eindringen in fremde Systeme ohne Schädigungsabsicht, 22%) und Cracker (Eindringen mit Schädigungsabsicht, 20%). Diese Nutzertypen unterschieden sich deutlich in ihrem Anreizprofil. Hacking und Cracking, nicht aber zweckorientierte Nutzungsweisen waren korreliert mit Flow-Erleben und positiver Aktivierung am Rechner. Die Ergebnisse sind nicht repräsentativ für alle Freizeitnutzer. Sie beziehen sich auf eine gezielt rekrutierte Stichprobe besonders engagierter Computernutzer, die über spezifische Netzwerke (z.B. relevante Fachschaften, Chaos Computer Club) erreichbar sind.
Fine‐resolution simulation of the channel structures and propagation features of intracloud lightning
Authors: Tan Yongbo , Tao Shanchang , Zhu Baoyou
Published: May 2006

Intracloud lightning discharges are simulated in 12.5 m (fine) and 250 m (coarse) resolution for 2‐dimensional domain by using an improved Stochastic Lightning Model. Simulation results indicate that the bi‐level branched channel structure, horizontal extending ranges and maximum vertical electric field changes obtained from fine resolution lightning model are in better agreement with previously observed data than those from coarser model. The IC flash channels from fine lightning model have the fractal feature with fractal dimension of 1.43, and propagation tendency is dependent on the potential distribution. In addition, fine resolution lightning modeling shows that after IC flash initiation at the boundary between positive and negative potential zones, potential wells attract the leaders of opposite polarity into the central area and prevent their outward expansion. Leaders can propagate throughout regions of net charge of the opposite polarity, but they avoid the isolated charge areas of the same polarity.