bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Electrically Active Si-based Thin Films by Pulsed Laser Deposition of SiO/C Dual Targets
Authors: Ono Yusaburo , Kato Yushi , Akita Yasuyuki , Hosaka Makoto , Shiraishi Naoki , Yamaguchi Makoto , Sakata Osami , Yoshimoto Mamoru
Published: February 2009

We investigated the fabrication of Si nanocrystals, including thin films, by annealing the SiO/C/SiO thin films in an Ar atmosphere. The SiO/C/SiO trilayered thin films were deposited on α-Al2O3 (0001), Si (111), or ITO-coated borosilicate glass substrates at room temperature by pulsed laser deposition using dual sintered SiO and graphite targets. The SiO/C/SiO thin films subjected to heat treatment at 500°C included nanocrystalline Si. Measurements by synchrotron radiation X-ray diffraction indicated the formation of Si nanocrystals having a size of 5–10 nm. Fourier transform infrared spectra showed that Si–O stretching and vibrational peak intensities of the as-deposited thin film decreased remarkably after annealing. The C layer in the SiO/C/SiO trilayered thin films is considered to play a role in enhancing the chemical reaction that produces Si nanocrystals through reduction of SiO during heat treatment. The annealed SiO/C-based thin films, including Si nanocrystals, exhibited photosensitive conduction behavior in current–voltage measurements.
Ultrathin oxide films: CaO layers on BaO and SrO
Authors: Mohn Chris E , Allan Neil L. , Harding John H.
Published: February 2009

Prompted by renewed interest in the crystalline oxides-on-semiconductors interface, periodic density functional theory and atomistic simulation techniques are used to examine the formation of a layer of CaO on a BaO substrate. We examine how CaO islands which form at coverages less than 100% adjust to the substrate in which the cation-anion separation is substantially larger than in CaO itself. All Ca-O bond lengths in the island are shorter than that in bulk CaO. Corner O atoms in the islands are associated with particularly short Ca-O bond lengths, and the shape of the islands is dominated by (100) edges. Once formed, islands with intact edges will remain intact. Interactions between islands at larger coverages are also investigated and we see the formation of characteristic elliptical gaps and loops.
Structural complexity in AA′MM′O6 Perovskites. A Transmission Electron Microscopy Study
Authors: García-Martín Susana , Urones-Garrote Esteban , Knapp Meghan C. , King Graham , Woodward Patrick M.
Published: February 2009

We have prepared five perovskite compounds which have two different A-site cations and examined the ordering of the A-site lattice through powder X-ray diffraction, TEM, HRTEM, HAADF-STEM, STEM-EELS. NaLaTi2O6 and NaLaZr2O6 show no indication of cation ordering by XRD but TEM analysis reveals that the A-site cations are ordered into layers in nanometer domains which have perpendicular orientations of the layers. NaLaMgTeO6 has larger domains which can be detected by XRD. XRD has revealed that both NaLaMgWO6 and KLaMnWO6 have nearly complete long range layered ordering of the A-site cations. TEM microscopy has further shown that a compositional modulation exists in both compounds. NaLaMgWO6 organizes into alternating stripes ˜24Å wide that are compositionally distinct from each other. KLaMnWO6 shows similar behaviour except with a chessboard pattern.
Abnormal Grain Growth Behavior in Nanostructured Al Thin Films on SiO2/Si Substrates
Authors: Luce Flavia Piegas , Fichtner Paulo , Schelp Luiz Fernando , Zawislak Fernando
Published: February 2009

We report on the formation of nanocrystalline Al thin films (180 nm thick) via magnetron sputtering technique using a step-wise deposition concept where columnar growth is inhibited, giving place to the development of a nanocrystalline mosaic grain arrangement with characteristic diameters of ≈ 30 nm and small size dispersion. The thermal evolution of the grain size distributions is investigated by transmission electron microscopy (TEM) in samples annealed in high vacuum for 3600 s. For the temperature range 300 ≤ T ≤ 462 °C the system presents a 3-D regular growth behavior up to sizes ≈ 70 nm. For T = 475 °C a rather sharp transition from normal to abnormal grain growth occurs. The grains extend to the film thickness and present mean lateral dimensions of ≈ 1000 nm. The observed phenomenon is discussed in terms of a synergetic grain boundary mobility effect caused by the characteristics of the initial nanogranular grain boundary morphology.
Liquid Structures of Metallic Glass-forming Binary Zr Alloys
Authors: Mizuno Akitoshi , Akimoto Toshihiko , Watanabe Masahito , Kohara Shinji , Takata Masaki
Published: February 2009

We have analyzed liquid structures of the binary Zr-TM (TM=Pd, Cu, Ni) alloys as a function of composition to investigate relations with their glass-forming abilities. High-energy x-ray (E=113 keV) diffraction experiments were performed and a conical nozzle levitation (CNL) technique was applied to achieve a containerless condition for highly reactive melts with high temperature. Structure information of the liquid alloys has been obtained with the aid of reverse Monte Carlo simulation. A shoulder was found at high-Q side of the second peak for the structure factor for Zr70Pd30 as well as the Zr70Cu30 alloy and the Zr50Cu50 alloys, which can be indication of the formation of ISRO in the liquid alloys. Liquid Zr-Ni alloys shows an apparent difference in the structure factors between the Zr70Ni30 and the Zr50Ni50 alloys, which can be associated with the formation of the chemical short range ordering, whereas the Zr-Pd alloys show a typical random distribution of atoms.
Management of Mucin-Producing Cystic Neoplasms of the Pancreas
Authors: Fritz Stefan , Warshaw Andrew L. , Thayer Sarah P.
Published: February 2009

During the last decade small lesions of the pancreas have been increasingly recognized in clinical practice. Among these lesions, mucin-producing cystic neoplasms represent a recently described and unique entity among pancreatic tumors. In 1996, the World Health Organization distinguished two different types of mucinous cystic tumors: intraductal papillary mucinous neoplasms (IPMNs) of the pancreas, which are characterized by mucin production, cystic dilation of the pancreatic ducts, and intrapapillary growth, and mucinous cystic neoplasms (MCNs), which are defined by ovarian-like stroma and in most cases do not communicate with pancreatic ducts. Further, IPMNs can be subdivided into main-duct type, mixed-type, and branch-duct type tumors. Older data did not distinguish among different subsets of cystic neoplasms of the pancreas, and consequently many databases were inconsistent. Histopathologically, both IPMNs and MCNs demonstrate a wide spectrum of cellular atypia ranging from mild mucinous hyperplasia to invasive adenocarcinoma. Because mucinous cystic neoplasms of the pancreas show significant differences in clinical behavior from patient to patient, knowledge of the clinicopathologic characteristics and natural history of specific subtypes of IPMNs and MCNs has become crucial for physicians working in the field of gastroenterology. The present work offers an overview of current and generally accepted clinical guidelines for the diagnosis and treatment of IPMNs and MCNs.
Stone Soup: Commentary on “Five Strategies for Accelerating the War on Cancer in an Era of Budget Deficits”
Authors: Young Robert C.
Published: February 2009

This commentary critically examines the five strategies proposed by the NCI to accelerate the war on cancer in this era of budget deficits.
Urocortin induces interleukin-6 release from rat cardiomyocytes through p38 MAP kinase, ERK and NF-κB activation
Authors: Huang Man , Kempuraj Duraisamy , Papadopoulou Nikoletta , Kourelis Taxiarchis , Donelan Jill , Manola Akrivi , Theoharides Theoharis C
Published: February 2009

CRH and its structurally related peptide urocortin (Ucn) are released under stress. Ucn is a potent agonist for CRH-receptor 2 (CRH-R2), which is strongly expressed in rodent heart. Stress induces Ucn mRNA expression in the heart, where it may be cardioprotective. However, increasing evidence indicates that Ucn may also have pro-inflammatory actions. Here, we show that neonatal rat cardiomyocytes express CRH-R2 by western blot analysis and Ucn induces interleukin-6 (IL-6) release in a time- and dose-dependent fashion. Ucn stimulates activation of ERK and p38 MAP kinases, while both MEK1 and p38 inhibitor block Ucn-induced IL-6 release. Ucn also activates nuclear factor kappa B (NF-κB) and a NF-κB inhibitor blocks Ucn-induced IL-6 release. Finally, the CRH-R antagonists α-helical (9–41) CRH and astressin-2B completely inhibit Ucn-induced IL-6 release, as well as activation of ERK, p38, and NF-κB. These findings indicate that Ucn induces IL-6 synthesis and release from neonatal rat cardiomyocytes. Our findings suggest that even though Ucn may confirm some protection on cardiomyocyte survival, it can also release IL-6, which is an independent risk factor for acute coronary syndrome. The precise role of cardiac Ucn in vivo remains to be elucidated.
Rain forest nutrient cycling and productivity in response to large‐scale litter manipulation
Authors: Wood Tana E. , Lawrence Deborah , Clark Deborah A. , Chazdon Robin L.
Published: February 2009

Litter‐induced pulses of nutrient availability could play an important role in the productivity and nutrient cycling of forested ecosystems, especially tropical forests. Tropical forests experience such pulses as a result of wet–dry seasonality and during major climatic events, such as strong El Niños. We hypothesized that (1) an increase in the quantity and quality of litter inputs would stimulate leaf litter production, woody growth, and leaf litter nutrient cycling, and (2) the timing and magnitude of this response would be influenced by soil fertility and forest age. To test these hypotheses in a Costa Rican wet tropical forest, we established a large‐scale litter manipulation experiment in two secondary forest sites and four old‐growth forest sites of differing soil fertility. In replicated plots at each site, leaves and twigs (<2 cm diameter) were removed from a 400‐m2area and added to an adjacent 100‐m2area. This transfer was the equivalent of adding 5–25 kg/ha of organic P to the forest floor. We analyzed leaf litter mass, [N] and [P], and N and P inputs for addition, removal, and control plots over a two‐year period. We also evaluated basal area increment of trees in removal and addition plots. There was no response of forest productivity or nutrient cycling to litter removal; however, litter addition significantly increased leaf litter production and N and P inputs 4–5 months following litter application. Litter production increased as much as 92%, and P and N inputs as much as 85% and 156%, respectively. In contrast, litter manipulation had no significant effect on woody growth. The increase in leaf litter production and N and P inputs were significantly positively related to the total P that was applied in litter form. Neither litter treatment nor forest type influenced the temporal pattern of any of the variables measured. Thus, environmental factors such as rainfall drive temporal variability in litter and nutrient inputs, while nutrient release from decomposing litter influences the magnitude. Seasonal or annual variation in leaf litter mass, such as occurs in strong El Niño events, could positively affect leaf litter nutrient cycling and forest productivity, indicating an ability of tropical trees to rapidly respond to increased nutrient availability.
Including intraspecific variability in functional diversity
Authors: Cianciaruso M. V. , Batalha M. A. , Gaston K. J. , Petchey O. L.
Published: February 2009

Linking species and ecosystems often relies on approaches that consider how the traits exhibited by species affect ecosystem processes. One method is to estimate functional diversity (FD) based on the dispersion of species in functional trait space. Individuals within a species also differ, however, and an unresolved challenge is how to include such intraspecific variability in a measure of functional diversity. Our solution is to extend an existing measure to variation among individuals within species. Here, simulations demonstrate how the new measure behaves relative to one that does not include individual variation. Individual‐level FD was less well associated with species richness than species‐level FD in a single trait dimension, because species differed in their intraspecific variation. However, in multiple trait dimensions, there was a strong association between individual‐ and species‐level FD and richness, because many traits result in a tight relationship between functional diversity and species richness. The correlation between the two FD measures weakened as the amount of intraspecific variability increased. Analyzing natural plant communities we found no relationship between species richness and functional diversity. In these analyses, we did not have to specify the source of intraspecific variation. In fact, the variation was only among individuals. The measure can, however, include differences in the amount of intraspecific variation at different sites, as we demonstrate. Including intraspecific variation should allow a more complete understanding of the processes that link individuals and ecosystems and provide better predictions about the consequences of extinctions for ecosystem processes.
Elicitation by design in ecology: using expert opinion to inform priors for Bayesian statistical models
Authors: Choy Samantha Low , O'Leary Rebecca , Mengersen Kerrie
Published: February 2009

Bayesian statistical modeling has several benefits within an ecological context. In particular, when observed data are limited in sample size or representativeness, then the Bayesian framework provides a mechanism to combine observed data with other “prior” information. Prior information may be obtained from earlier studies, or in their absence, from expert knowledge. This use of the Bayesian framework reflects the scientific “learning cycle,” where prior or initial estimates are updated when new data become available. In this paper we outline a framework for statistical design of expert elicitation processes for quantifying such expert knowledge, in a form suitable for input as prior information into Bayesian models. We identify six key elements: determining the purpose and motivation for using prior information; specifying the relevant expert knowledge available; formulating the statistical model; designing effective and efficient numerical encoding; managing uncertainty; and designing a practical elicitation protocol. We demonstrate this framework applies to a variety of situations, with two examples from the ecological literature and three from our experience. Analysis of these examples reveals several recurring important issues affecting practical design of elicitation in ecological problems.
Age‐specific reproduction and survival of individually marked Wood Thrushes, Hylocichla mustelina
Authors: Brown William P. , Roth Roland R.
Published: February 2009

Several nonexclusive, sometimes contradictory, hypotheses have been employed to explain age‐related changes in reproduction and survival among vertebrates. We evaluated these hypotheses with observations collected from a 31‐year study of individually marked Wood Thrushes (Hylocichla mustelina). Age‐specific fledgling production, survival probabilities, and derived life table columns are presented here. Additionally, we report “genetic value,” or the number of young remaining to be recruited into the breeding population by individuals of age x. Controlling for age of mate, the presence of some individuals in multiple years, and the effect of year of breeding, reproduction and survival peaked in middle‐aged birds of each sex and declined later in life for the oldest individuals. We could not exclude the selection hypothesis (removal of inferior individuals) as an explanation for improved female reproduction until middle age. The age at last reproduction was a significant determinant of age‐related reproductive success, indicating a disappearance of low‐quality individuals. Yearling females that did not successfully reproduce had greater within‐season emigration than all other age classes of each sex, regardless of the reproductive success of other classes. For males, we favored the constraint hypothesis (improved reproduction with experience) to explain greater reproductive output with increasing age until at least middle age. For each sex, the age of the mate independently influenced all measures of reproductive performance, but there was generally a linear or quadratic, rather than interactive, effect of the mate's age on reproduction. For both sexes, hypotheses of age‐related reproduction were only partially supported because of effects of senescence, or a decline in reproductive output or survival probabilities with increasing age. Senescence may confound attempts to examine or apply general hypotheses of age‐related reproduction that assume a monotonic relationship between age and reproduction or survival.
Demographic trade‐offs in a neutral model explain death‐rate–abundance‐rank relationship
Authors: Lin Kui , Zhang Da-Yong , He Fangliang
Published: February 2009

The neutral theory of biodiversity has been criticized for its neglect of species differences. Yet it is much less heeded that S. P. Hubbell's definition of neutrality allows species to differ in their birth and death rates as long as they have an equal per capita fitness. Using the lottery model of competition we find that fitness equalization through birth–death trade‐offs can make species coexist longer than expected for demographically identical species, whereas the probability of monodominance for a species under zero‐sum neutral dynamics is equal to its initial relative abundance. Furthermore, if newly arising species in a community survive preferentially they are more likely to slip through the quagmire of rareness, thus creating a strong selective bias favoring their community membership. On the other hand, high‐mortality species, once having gained a footing in the community, are more likely to become abundant due to their compensatory high birth rates. This unexpected result explains why a positive association between species abundance and per capita death rate can be seen in tropical‐forest communities. An explicit incorporation of interspecific trade‐offs between birth and death into the neutral theory increases the theory's realism as well as its predictive power.
The brighter side of soils: Quantum dots track organic nitrogen through fungi and plants
Authors: Whiteside Matthew D. , Treseder Kathleen K. , Atsatt Peter R.
Published: February 2009

Soil microorganisms mediate many nutrient transformations that are central in terrestrial cycling of carbon and nitrogen. However, uptake of organic nutrients by microorganisms is difficult to study in natural systems. We assessed quantum dots (fluorescent nanoscale semiconductors) as a new tool to observe uptake and translocation of organic nitrogen by fungi and plants. We conjugated quantum dots to the amino groups of glycine, arginine, and chitosan and incubated them with Penicillium fungi (a saprotroph) and annual bluegrass (Poa annua) inoculated with arbuscular mycorrhizal fungi. As experimental controls, we incubated fungi and bluegrass samples with substrate‐free quantum dots as well as unbound quantum dot substrate mixtures. Penicillium fungi, annual bluegrass, and arbuscular mycorrhizal fungi all showed uptake and translocation of quantum dot‐labeled organic nitrogen, but no uptake of quantum dot controls. Additionally, we observed quantum dot‐labeled organic nitrogen within soil hyphae, plant roots, and plant shoots using field imaging techniques. This experiment is one of the first to demonstrate direct uptake of organic nitrogen by arbuscular mycorrhizal fungi.
3‐D maps of tree canopy geometries at leaf scale
Authors: Sinoquet Hervé , Pincebourde Sylvain , Adam Boris , Donès Nicolas , Phattaralerphong Jessada , Combes Didier , Ploquin Stéphane , Sangsing Krissada , Kasemsap Poonpipope , Thanisawanyangkura Sornprach , Groussier-Bout Géraldine , Casas JérÔme
Published: February 2009

The geometrical structure of plant canopies has many implications for plant functioning, microclimatic conditions, and plant‐pathogen/herbivore interactions. Plant geometry can be described at several scales. At the finest scale, canopy structure includes the shape, size, location, and orientation of each organ in the canopy. This data set reports the three‐dimensional (3‐D) geometry of a set of fruit and rubber trees at the leaf scale. A 3‐D magnetic digitizer was used to measure the spatial coordinates and the orientation angles of each leaf, namely, the midrib azimuth and inclination angles, and the rolling angle of leaf lamina around the midrib. In addition, for most trees, branching or flush order is given as well as the ranking of leaves along branches and the leaf identity of leaflets in compound‐leaved trees. Leaf length was also measured for most trees. Leaf width was measured or estimated based on allometric relationships. Leaf area was derived from allometric relationships with leaf length and width. The data set includes the 3‐D geometry of six trees: one apple, two mangos, two rubbers, and one walnut. Plant height ranged from 1.6 m for mango trees to 5.3 m for the large rubber tree. The number of leaves ranged from 895 for the small rubber tree to 26,283 for the apple tree. Total leaf area ranged from 3.6 m2 for the small rubber tree to 36.4 m2 for the apple tree. Most of the data were used to show how canopy geometry determines light interception and subsequently plant primary production and fruit yield. The data set was also used to test the quality of innovative methods for canopy structure description at tree scale. The apple tree was used to study the thermal environment of a leaf miner insect, to show how canopy geometry leads to a strongly heterogeneous risk of mortality, in particular under heat‐wave conditions. Overall, our data set provides explicit plant architectures suitable for spatial modeling of plant physiological ecology and plant–herbivore interactions, allowing us to determine the mechanisms through which climate impacts biological and ecological processes involved in these functions.
Coexistence of annual plants: Generalist seed predation weakens the storage effect
Authors: Kuang Jessica J. , Chesson Peter
Published: February 2009

We investigate the effect of seed predation on the coexistence of competing annual plants. We demonstrate a role for predation that is opposite to the conventional wisdom that predation promotes coexistence by reducing the intensity of competition. In the common situation where competitive coexistence involves intraspecific competition exceeding interspecific competition, predation can undermine coexistence by reducing the overall magnitude of competition, replacing competition with “apparent competition” in a way that does not lead to differential intraspecific and interspecific effects. We demonstrate this outcome in the case where coexistence occurs by “the storage effect” in a variable environment. The storage effect arises when the environment interacts with competition to create opportunities for species to increase from low density. Critical to the storage effect is positive covariance between the response of population growth to the environment and its response to competition, when a species is at high density. This outcome prevents species at high density from taking advantage of favorable environmental conditions. A species at low density has lower covariance and can take advantage of favorable environmental conditions, giving it an advantage over a high‐density species, fostering its recovery from low density. Hence, species coexistence is promoted. Here we find that density‐dependent predation lowers population densities, and so weakens competition, replacing competition with apparent competition, which does not covary with the environment. As a consequence, covariance between environment and competition is weakened, reducing the advantage to a species at low density. The species still strongly interact through the combination of competition and apparent competition, but the reduced low‐density advantage reduces their ability to coexist. Although this result is demonstrated specifically for the storage effect with a focus on annual plant communities, the principles involved are general ones.
Modeling misidentification errors in capture–recapture studies using photographic identification of evolving marks
Authors: Yoshizaki Jun , Pollock Kenneth H. , Brownie Cavell , Webster Raymond A.
Published: February 2009

Misidentification of animals is potentially important when naturally existing features (natural tags) are used to identify individual animals in a capture–recapture study. Photographic identification (photoID) typically uses photographic images of animals' naturally existing features as tags (photographic tags) and is subject to two main causes of identification errors: those related to quality of photographs (non‐evolving natural tags) and those related to changes in natural marks (evolving natural tags). The conventional methods for analysis of capture–recapture data do not account for identification errors, and to do so requires a detailed understanding of the misidentification mechanism. Focusing on the situation where errors are due to evolving natural tags, we propose a misidentification mechanism and outline a framework for modeling the effect of misidentification in closed population studies. We introduce methods for estimating population size based on this model. Using a simulation study, we show that conventional estimators can seriously overestimate population size when errors due to misidentification are ignored, and that, in comparison, our new estimators have better properties except in cases with low capture probabilities (<0.2) or low misidentification rates (<2.5%).
Invasive fire ants alter behavior and morphology of native lizards
Authors: Langkilde Tracy
Published: February 2009

Nonnative species introductions are becoming more common, but long‐term consequences of the novel pressures imposed by invaders on native species remain poorly known. The red imported fire ant,Solenopsis invicta, is an invasive species with potential global impact. Comparison of lizards across the invasive range within the United States reveals novel antipredator strategies and altered morphologies that mitigate potentially lethal attack by these ants, within 70 years of their introduction. The likelihood that adult lizards will behaviorally respond to fire ant attack increases with time since invasion, but hatchlings exhibit high levels of antipredator behavior irrespective of their site of origin. Adults and hatchlings from sites invaded longer ago also have relatively longer hind limbs. This trait increases the effectiveness of behavioral strategies for removing ants and is likely an adaptive response to minimize envenomation during attack. The observed changes are not correlated with habitat, exposure to fire ants, or latitude, arguing against phenotypic plasticity and learning as causal mechanisms, and museum specimens show that morphological differences were not evident prior to fire ant invasion. These data contribute to our growing awareness that ecological invasions can prompt adaptive responses, altering the nature of interactions between invaders and the natives they contact.
Synergistic cytotoxic effect of tetrachlorocatechol and sodium azide in Escherichia coli: Toxicity, metabolism, and mechanistic aspects
Authors: Levy Smadar , Chevion Mordechai
Published: February 2009

Pentachlorophenol (PCP) is used in industrial and domestic applications, including as a biocide and a wood preservative. Metabolism of PCP undergoes oxidative dechlorination, forming tetrachlorocatechol (TCC) and tetrachlorohydroquinone (TCHQ). Both sodium azide (NaN3) and TCC appear naturally in soil. None of them are cytotoxic by themselves or facilitate autooxidation. Here, we show that their combination leads to synergistic cytotoxicity (>6 log bacterial killing) to Escherichia coli. The rate of oxygen consumption in a cell-free system showed that NaN3 increases TCC oxidation by 520-fold. The synergism coefficient to cells was calculated as 96 or greater, and we have shown the formation of a new compound. It is suggested that the intermediate species, o-tetrachlorosemiquinine, and an unknown, nitrogen-centered free radical, both visualized by electron-spin resonance, are harmful species responsible for the synergistic cytotoxicity of TCC/NaN3, rather than the endproduct formed during the reaction. Desferoxamine and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide offered nearly complete protection, but through radical scavenging rather than through chelating properties. The mechanism of damage for TCC compared to its analogue, TCHQ, were investigated, and whereas the cellular damage of TCHQ/NaN3 is through a site-specific mechanism, in the case of TCC/NaN3 it is through the accumulation of the component(s) in the bacterial cell membrane, eventually leading to dysfunction, as evidenced by electron microscopy.
Pseudospin symmetry and a double ring-shaped spherical harmonic oscillator potential
Authors: Zhang Min-Cang
Published: February 2009

A new double ring-shaped spherical harmonic oscillator potential is presented. The pseudospin symmetry in this system is investigated by solving the Dirac equation with equal mixture of scalar and vector potentials with opposite signs. The normalized spinor wave function and energy equation are obtained and some particular cases are discussed.
Liquidus surface projection of the Fe–Co–C ternary system in the iron-rich corner
Authors: Haddad Farida , Eddine Amara Sif , Kesri Rafika
Published: February 2009

In the present work, the liquidus projection of the Fe – Co – C ternary system is plotted in the iron-rich corner using differential thermal analysis, optical microscopy, scanning electron microscopy and X-ray diffraction. This projection contains three primary crystallisation phases (δ(Fe), γ(Fe) and graphite) as well as two univariant lines: peritectic L + δ(Fe) γ(Fe) and eutectic L γ(Fe) + Cgraphite.
Catalytic performance of Fe-, Pd-, and Pd–Fe- mordenites in simulated hydrocarbon-selective catalytic reduction of N2O by methane in a model flue-gas from nitric acid plants
Authors: Lee Sungkyu , Hye Seo Min , Cho Sung-Su , Kang Kyoung-Hoon , Kim Jong-Min , Seon Hong Hyun , Yun Yongseung , Ahn Jae-Hwan
Published: February 2009

This paper reports on the individual activity and selectivity of Fe-, Pd- and Pd – Fe-mordenite catalysts prepared by wet Fe-ion exchange and Pd-ion impregnation for N2O reduction using simulated hydrocarbon-selective catalytic reduction operation conditions of nitric acid plants. Laboratory-scale data on the activity, selectivity and characterization of Fe-, Pd-, and Pd – Fe-mordenite catalysts for conversion of N2O have been obtained under the simulated hydrocarbon-selective catalytic reduction operating condition in the temperature range of 325 – 400 °C encountered in nitric acid plant tail gases. More specifically, Pd-, Fe- and Pd – Fe-mordenite catalysts with Si/Al ratios of 10.25 – 10.65 were prepared. Wet ion-exchange methodology was used to prepare Fe-mordenite catalyst, whilst Pd-ion impregnation was used to prepare Pd-, and Pd – Fe-mordenite catalysts. Catalytic activities could not be consistently correlated with and explained by X-ray absorption near edge spectroscopy spectra. Further analysis by temperature-programmed desorption of ammonia was performed to explain higher catalytic activity of Pd – Fe-mordenite compared to Fe-, and Pd-mordenites. Higher catalytic activity of Pd – Fe-mordenite is most probably attributable to the presence of strong Lewis type acid centers as manifested by a TPD spectrum peak at about 300 °C.
Microstructure and some properties of FeCr25Co15 alloy subjected to plastic deformation by complex load
Authors: Korneva Anna , Bieda Magdalena , Korznikowa Galija , Sztwiertnia Krzysztow , Korznikov Aleksandr
Published: February 2009

The microstructural, mechanical and magnetic properties of FeCr25Co15 alloy were examined after upset followed by torsion. Deformation was carried out at temperatures that corresponded to the appearance of α + γ phases. During the process, the initial lamellar microstructure of the material was transformed into a globular one. In the sample sections parallel to the upsetting direction a gradient microstructure, with a layer of submicron grains in the highest deformation zone, was formed. The thickness of the zone did not significantly depend on the deformation temperature. Measurements of the mechanical properties after magnetic treatment showed that the plasticity and strength of the deformed samples increased in comparison with the high coercive state.
The effect of cooling rate on the microstructure and mechanical properties of Mg–Zn–Gd-based alloys
Authors: Liu Yong , Yuan Guangyin , Yin Jian , Lu Chen , Ding Wenjiang , Jiang J. Z.
Published: February 2009

The microstructure and mechanical properties of Mg3.5Zn0.6Gd and Mg3.5Zn0.6Gd1.5Cu alloys were investigated under different solidification conditions. The microstructure and phase constitutions of alloys were characterized using optical microscopy, scanning electron microscopy, X-ray diffraction and differential thermal analysis. The results indicate that the cooling rate plays an important role in grain refinement and phase constitutions of Mg – Zn – Gd alloys. In the cooling rate range from 4.8 K s− 1to 18.5 K s− 1for the Mg – Zn – Gd system, higher content of the icosahedral phase (I-phase) was obtained under the condition of higher cooling rate which accelerated the nucleation and growth of the I-phase. Under the cooling rate of 18.5 K s− 1, the mechanical properties of the Mg3.5Zn0.6Gd alloy were further improved by the high I-phase content due to its unique icosahedral structure, in addition to the contribution of grain refinement.
Study of fatigue dislocation structures in [233] coplanar double-slip-oriented copper single crystals using SEM electronic channelling contrast
Authors: Zhou Yang , Li Xiao-Wu , Yang Rui-Qing
Published: February 2009

Dislocation structures in fatigued [] coplanar double-slip-oriented copper single crystals were studied using the electron channelling contrast technique in scanning electron microscopy, especially focusing on the observations of the microstructures of persistent slip bands and deformation bands. It was found that, at low plastic strain amplitudes (γpl ≤ 3.4 × 10– 4), the dislocation structures of the [] copper single crystal comprise a majority of elongated veins and a few elongated cells along the primary slip plane (111). As γpl increases to 6.2 × 10– 4, a special persistent slip band structure consisting of irregular dislocation cells, rather than generally-observed ladders in single-slip crystals, was found to form, which is responsible for the occurrence of a quasi-plateau in the cyclic stress – strain curve of the [] crystal. When γpl ≤ 3.5 × 10– 3, different dislocation microstructures in deformation bands, such as wall-like features, dislocation walls, elongated cells and dense dislocation cells, were found in the cyclically saturated [] crystal. Effects of the crystallographic orientation, the applied plastic strain amplitude, the accumulated plastic strain and the strain localization in the crystal on the microstructure of deformation bands are summarized and discussed.
σ-phase morphologies and their effect on mechanical properties of duplex stainless steels
Authors: Pohl Michael , Storz Oliver , Glogowski Thomas
Published: February 2009

The aim of the presented study is to investigate the influence of the different σ-phase morphologies on the mechanical, wear and corrosive behaviour of the duplex stainless steel 1.4462 (X2CrNiMoN 22 5 3). Different amounts of σ-phase were precipitated in tensile, impact strength, wear and corrosion samples by annealing at 750 °C, 850 °C and 938 °C. σ-phase shows a detrimental influence on the impact strength and the corrosion behaviour. To a very limited extent it can be used to slightly raise the strength under quasi-static load and to improve the wear resistance. Finally, it can be concluded that σ-phase has more unfavourable influences on the material' behaviour than advantageous ones. Therefore, it should be avoided in duplex stainless steels.
Microstructural and acoustic damage analysis and finite element stress simulation of air plasma-sprayed thermal barrier coatings under thermal cycling
Authors: Trunova Olena , Bednarz Piotr , Herzog Roland , Beck Tilmann , Singheiser Lorenz
Published: February 2009

Degradation evolution and failure mechanisms of air plasma-sprayed thermal barrier coatings during thermal cycling were investigated using microstructural and acoustic emission analysis. The microcrack evolution observed suggests that the life-time is governed by the kinetics of crack formation, growth and linking of individual cracks. The damage in the thermal barrier coatings mainly occurs during cooling due to thermal-expansion mismatch stresses at the metal – ceramic interface. The effect of the minimum cycling temperature on the lifetime was found to be much more pronounced than that of a variation in cooling rate. Experimental results were supported by finite element modeling of the stress distribution at the metal – ceramic interface during cooling at different rates.
Thermal, mechanical and fretting fatigue of silicon nitride
Authors: Schwind Thomas , Schalk Thomas , Kerscher Eberhard , Beck Tilmann , Lang Karl-Heinz , Löhe Detlef
Published: February 2009

Tools for hot wire rolling are exposed to high thermal, mechanical and tribological loadings during service. Ceramic materials such as silicon nitride possess good mechanical and tribological properties up to temperatures where most of today' roller materials do not exhibit acceptable reliability. In the present paper basic mechanical properties under thermal and mechanical loading as well as the damage behaviour of Si3N4 have been investigated in high cycle thermal fatigue and dynamic as well as cyclic four point bending tests. In fretting fatigue tests the behaviour of Si3N4 under near-service conditions, as they appear during application in the hot wire rolling process, has been analysed. It is shown that in the temperature range investigated pure thermally induced loading leads to the same damage mechanism as pure mechanical loading and therefore thermally induced stresses can be directly added to any mechanical loading. The isothermal four point bending tests confirm the existence of a cyclic fatigue effect. With the fretting fatigue experiments the limits of high-performance ceramics such as Si3N4 are shown. Under the complex loading, surface flaws are produced leading to a severe lifetime reduction compared to plain mechanical and thermal loading.
Innovative materials for energy technology
Authors: Möslang Anton , Adelhelm Christel , Heidinger Roland
Published: February 2009

High performance materials are indispensable for economical and environmentally acceptable operation of fusion power and innovative fission reactor systems. In order to provide materials design data for short term needs of the ITER Test Blanket Modules and for a Fusion Demonstration Reactor, the international fusion materials community is concentrating their R&D work mainly on the four reduced-activation structural materials 8 – 9 CrWTa ferritic/martensitic steels, V – Ti – Cr alloys, W alloys and SiCf/SiC composites as well as on functional materials such as CVD diamond windows. Besides the development of the European reduced activation reference steel EUROFER, emphasis will be placed on synergies between fusion and fission materials R&D, namely the development of ductile oxide dispersion strengthened ferritic/martensitic steels with nano-scaled Y2O3 or Y2Ti2O7 particles that increase not only high temperature strength but also substantially the microstructural stability against irradiation embrittlement and high temperature ageing. Finally, the corrosion behaviour of zirconium-1.5 wt.% tin alloy, a well established cladding material for nuclear fuel rods, will be shown in different environments.
Investigation of surface fatigue of thermally sprayed micro- and nanocrystalline cylinder wall coatings by means of cavitation testing
Authors: Hahn Mareike , Fischer Alfons
Published: February 2009

The future demands of diesel engines require new options for low-friction and wear-resistant materials in order to increase efficiency and achieve environmentally sound solutions. Efforts are made to improve the performance and reduce the weight of engine blocks by coating the aluminium cylinder bores using thermal-spray processes. Thus, along with other means, today nanocrystalline coatings are considered when looking for the desired combination of structural, productional, and topographical properties. Besides sufficient tribological properties it is important that the composite (base material and coating) allows for prolonged endurance under cyclic mechanical and thermal stresses. Prior to engine tests these coatings are characterised in the laboratory by means of bench tests for adhesive tensile strength, tribological properties and fatigue of the composite. Cavitation tests should reveal the tribological stability of these coatings and their ability to resist high-frequency cyclic impact stresses. The objective in this investigation is to describe the cavitation behaviour and the influence of voids such as pores or oxides.
The running-in of amorphous hydrocarbon tribocoatings: a comparison between experiment and molecular dynamics simulations
Authors: Pastewka L. , Moser S. , Moseler M. , Blug B. , Meier S. , Hollstein T. , Gumbsch P.
Published: February 2009

Amorphous hydrocarbon (a-C: H) films have enormous potential as low friction, wear resistant coatings. Here, we present a plasma assisted chemical vapour deposition process for a-C: H that exhibits growth rates of 100 nm min– 1 and higher. The tribological performance of the resulting a-C: H films has been studied experimentally by reciprocating sliding of an a-C: H-coated Si3N4 ball on an a-C: H-coated 100Cr6 steel substrate and by subsequent micro Raman spectroscopy of the wear track. Running-in of the coatings is observed and characterised by a rapid decrease in the friction coefficient accompanied by a significant increase in sp2 hybridisation in the wear track. In order to gain a deeper understanding of the underlying running-in mechanisms, the sliding of two a-C: H films under a load of 5 GPa has been studied by classical molecular dynamics employing a range-corrected Brenner bond-order potential. The simulations reproduce the experimental trends and explain the running-in by a combination of smoothing and chemical passivation of both tribosurfaces. Consequently, both mechanisms should be controlled in order to produce tribological coatings for applications with optimum energy-efficiency.
Development of high power density cathode materials for Li-ion batteries
Authors: Ketterer Bernt , Vasilchina Hristina , Seemann Klaus , Ulrich Sven , Besser Heino , Pfleging Wilhelm , Kaiser Tatjana , Adelhelm Christel
Published: February 2009

Cathode material for Li-ion batteries can be synthesised by r.f. magnetron sputtering of LiCoO2 targets in a pure Ar plasma. This technique is suitable for large-scale implementation in foil coating set-ups. By choosing the process parameters and by employing post heat treatment nanocrystalline, stoichiometrical LiCoO2 films can be fabricated which exhibit the desired high temperature phase. The determination of the elementary composition is possible by optical emission spectroscopy including plasma stimulation and carrier gas temperature extraction. The proof of crystal structure is carried out by X-ray diffraction and Raman spectroscopy. Heat treatment can be conventionally realised in a furnace or by laser impact. With regard to increasing the power density, the surface of the cathode material can be enhanced six-fold by laser-assisted surface patterning.
Determination of v–K curves from lifetime tests with reloaded survivals
Authors: Fett Theo , Riva Marco , Hoffmann Michael J. , Oberacker Rainer , Munz Dietrich
Published: February 2009

Lifetime tests under static load are often carried out in order to determine the relation v(K) of subcritical crack growth. Depending on the scatter behaviour of the most serious cracks in a specimen a number of immediate failures can occur during load application and some specimens will not fracture within a certain maximum lifetime limit. In order to get additional information on subcritical crack growth behaviour, the authors recommend performing lifetime tests at an increased load level. Appropriate procedures for the evaluation of such tests will be outlined. First, the procedure is explained for the simple case of the power-law crack growth relation. Then, a modified lifetime evaluation is proposed that needs no special crack growth law. The methods described are applied to static lifetime measurements on SiAlON in distilled water at 20 °C as the environment.
Tensile properties of L12 intermetallic foils fabricated by cold rolling
Authors: Kaneno Yasuyuki , Myoki Tadamichi , Takasugi Takayuki
Published: February 2009

Polycrystalline L12-type Ni3(Si,Ti), Ni3Al and Co3Ti alloys prepared through thermomechanical processing from arc-melted ingots were successfully cold-rolled to thin foils with a thickness of less than 200 m. The cold-rolling with over 90 % reduction in thickness was possible without providing intermediate annealing. The cold-rolled foils showed high tensile strength (∼2 GPa) at room temperature although no plastic elongation was observed. The tensile strength of the annealed foils generally decreased acquiring a certain level of fracture strain. Room temperature fracture strain increased with increasing annealing temperature, and reached to 30 – 40 % by a high temperature annealing at 1173 K. Among three kinds of intermetallic alloys, the Ni3(Si, Ti) foil annealed around at 900 K exhibited an extremely high tensile strength and yield strength (over 2 GPa) with a reasonable fracture strain. Also, it was found that the fully-recrystallized Ni3(Si, Ti) and Co3Ti foils showed a strength anomaly at intermediate testing temperature. The observed tensile properties, especially tensile strength at low temperature as well as at high temperature for the present L12 intermetallic foils, were found to be superior to those for the conventional alloys such as nickel based alloys and stainless steels.
Microstructure and room temperature mechanical properties of Hf and Sn-doped Nb-20Ti-5Cr-3Al-18Si alloy
Authors: Guo J. T. , Tian Y. X. , Sheng L. Y. , Zhou L. Z. , Ye H. Q.
Published: February 2009

In this paper, the effects of Sn and Hf additions on microstructures and room temperature mechanical properties of Nb-20Ti-5Cr-3Al-18Si alloy were investigated. The Sn addition has no significant effect on the microstructure of the alloy. Sn is preferentially partitioned in (Nb, Ti)ss rather than (Nb, Ti)5Si3. The addition of Sn decreases the solubility of Cr in (Nb, Ti)ss. The addition of Hf causes coarsening of the eutectic structure of (Nb, Ti)ss and (Nb, Ti)5Si3 and the formation of the Hf-rich γ(Nb, Ti)5Si3 along phase boundaries. With the addition of Sn the strength of the alloy decreases, while its ductility increases slightly. The Hf addition simultaneously improves strength and ductility of the alloy. The relationships between composition, microstructure and properties are discussed.