bluuebunny/crossref_metadata_2025 huggingface dataset:
Fate of Effluent‐Borne Contaminants beneath Septic Tank Drainfields Overlying a Karst Aquifer
Authors: Katz Brian G. , Griffin Dale W. , McMahon Peter B. , Harden Harmon S. , Wade Edgar , Hicks Richard W. , Chanton Jeffrey P.
Published: July 2010

Groundwater quality effects from septic tanks were investigated in the Woodville Karst Plain, an area that contains numerous sinkholes and a thin veneer of sands and clays overlying the Upper Floridan aquifer (UFA). Concerns have emerged about elevated nitrate concentrations in the UFA, which is the source of water supply in this area of northern Florida. At three sites during dry and wet periods in 2007–2008, water samples were collected from the septic tank, shallow and deep lysimeters, and drainfield and background wells in the UFA and analyzed for multiple chemical indicators including nutrients, nitrate isotopes, organic wastewater compounds (OWCs), pharmaceutical compounds, and microbiological indicators (bacteria and viruses). Median NO3–N concentration in groundwater beneath the septic tank drainfields was 20 mg L−1 (8.0–26 mg L−1). After adjusting for dilution, about 25 to 40% N loss (from denitrification, ammonium sorption, and ammonia volatilization) occurs as septic tank effluent moves through the unsaturated zone to the water table. Nitrogen loading rates to groundwater were highly variable at each site (3.9–12 kg N yr−1), as were N and chloride depth profiles in the unsaturated zone. Most OWCs and pharmaceutical compounds were highly attenuated beneath the drainfields; however, five OWCs (caffeine, 1,7‐dimethylxanthine, phenol, galaxolide, and tris(dichloroisotopropyl)phosphate) and two pharmaceutical compounds (acetaminophen and sulfamethoxazole) were detected in groundwater samples. Indicator bacteria and human enteric viruses were detected in septic tank effluent samples but only intermittently in soil water and groundwater. Contaminant movement to groundwater beneath each septic tank system also was related to water use and differences in lithology at each site.
Chemistry and Transport of Metals from Entrenched Biosolids at a Reclaimed Mineral Sands Mining Site
Authors: Lasley Katrina K. , Evanylo Gregory K. , Kostyanovsky Kirill I. , Shang Chao , Eick Matthew , Lee Daniels W.
Published: July 2010

Deep row incorporation of biosolids is an alternative land treatment method whose typically high rates may result in elevated pollutant transport. The objectives of this research were to compare the effects of entrenched biosolids stabilization type and rate on heavy metal chemistry and mobility. Two rates each of Alexandria (Virginia) Sanitation Authority anaerobically digested (213 and 426 dry Mg ha−1) and Blue Plains (Washington, DC) lime‐stabilized (329 and 657 dry Mg ha−1) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia, in summer 2006. Vertical and lateral transport of heavy metals from the biosolids seams were determined by analyzing leachate collected in zero tension lysimeters below the trenches and suction lysimeters adjacent to the trenches. Silver, Cd, Pb, and Sn did not move vertically or laterally to any significant extent. During the 15‐mo period following entrenching, lime‐stabilized biosolids produced higher cumulative metal mass transport for Cu (967 g ha−1), Ni (171 g ha−1), and Zn (1027 g ha−1) than did the anaerobically digested biosolids and control. Barium mass loss was similar for both biosolids. All metals moved primarily with particulates. MINTEQA2 predicted that >70% of Cu was bound to fulvic acids, whereas >80% of Ba was found as Ba2+ As pH decreased with time, free ions of Zn decreased and the metal's association with fulvic acids increased. Largely insignificant transport of metals into the lysimeters demonstrated that biosolids‐borne heavy metals posed little risk to groundwater even when entrenched in very coarse‐textured soil.
Analysis of Polycyclic Aromatic Hydrocarbons and Their Oxygen‐Containing Derivatives and Metabolites in Soils
Authors: Bandowe Benjamin A. Musa , Wilcke Wolfgang
Published: July 2010

Although polycyclic aromatic hydrocarbons (PAHs) have been extensively studied, the knowledge of their oxygen‐containing derivatives and metabolites (OPAHs) in soils is limited. We modified and tested an existing analytical protocol involving pressurized liquid extraction of soil followed by fractionation of target compounds into PAHs and OPAHs on a silica gel column and gas chromatography/mass spectrometry–based separation and quantification. Polycyclic aromatic hydrocarbons and carbonyl‐OPAHs were quantified directly after separation on silica gel columns, and hydroxyl/carboxyl‐OPAHs were quantified after silylation with N,O‐bis(trimethylsilyl)trifluoroacetamide. Recoveries between 78 and 97% (relative standard deviation [RSD], 5–12%) were obtained for six carbonyl‐OPAHs, whereas 1,2‐acenaphthenequinone and 1,4‐naphthoquinone showed lower recoveries of 34 and 44% (RSD, 19 and 28%, respectively). Five hydroxyl/carboxyl‐OPAHs had recoveries between 36 and 70% (RSD, 13–46%), six others had between 2 and 7% (RSD, 8–25%), and nine were lost in sample preparation. Limits of detection ranged from 0.1 to 1.6 ng g−1 for OPAHs and from 0.01 to 0.56 ng g−1 for PAHs. The protocol was applied to soils from a former gasworks site, Berlin, an urban soil from Mainz, both in Germany, and a forest soil from near Manaus, Brazil. The sums of 34 PAH concentrations were 107,000, 3505, and 21 ng g−1; those of seven carbonyl‐OPAHs were 15,690, 170, and 7 ng g−1; and those of 11 hydroxyl/carboxyl‐OPAHs 518, 36, and 16 ng g−1 for Berlin, Mainz, and Manaus soils, respectively. Several OPAHs were present at concentrations higher than or equal to their parent PAHs, demonstrating the importance of OPAH measurement for the assessment of PAH‐related environmental risks.
Maximizing Ammonium Nitrogen Removal from Solution Using Different Zeolites
Authors: Penn Chad J. , Warren Jason G. , Smith Savannah
Published: July 2010

Zeolite minerals are ideal for removing ammonium nitrogen (NH4+–N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch‐shaken system or a “tea bag” approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow‐through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch‐stirred compared to batch‐shaken systems, suggesting that diffusion between particles was rate‐limiting in the former system. Flow‐through cells possessing contact times >100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4+–K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4+–K+ exchange followed by a slower one and suggests the 100‐s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study.
Assessment of Total Maximum Daily Load Implementation Strategies for Nitrate Impairment of the Raccoon River, Iowa
Authors: Jha Manoj K. , Wolter Calvin F. , Schilling Keith E. , Gassman Philip W.
Published: July 2010

The state of Iowa requires developing total maximum daily loads (TMDLs) for over 400 water bodies that are listed on the 303(d) list of the impaired waters. The Raccoon River watershed, which covers approximately 9400 km2 of prime agriculture land and represents a typical Midwestern corn‐belt region in west‐central Iowa, was found to have three stream segments impaired by nitrate‐N. The Soil and Water Assessment Tool (SWAT) was applied to this watershed to facilitate the development of a TMDL. The modeling framework integrates SWAT with supporting software and databases on topography, land use and management, soil, and weather information. Annual and monthly simulated and measured streamflow and nitrate loads were strongly correlated. The watershed response was evaluated for a suite of watershed management scenarios where land use and management changes were made uniformly across the watershed. A scenario of changing the entire land to row crop resulted in an increased nitrate load of about 12% over the baseline condition at the watershed outlet. Results from the 15 nitrate load reduction strategies were found to reduce nitrate from <1% to about 85%, with the greatest potential reduction associated with changing the row crops to grassland. This research demonstrated the use of a modeling system to facilitate the analyses of TMDL implementation strategies, including the ability to target the most efficient allocation of alternative practices on a subwatershed basis.
Influence of Short Helical Tape on Local Convective Heat Transfer and Thermal Performance Characteristics in Turbulent Decaying Swirl Flow
Authors: Eiamsa-ard Smith , Kongkaitpaiboon Vichan , Wongcharee Khwanchit
Published: July 2010

This paper reports the experimental investigation of local convective heat transfer enhancement, flow friction and thermal performance factor behaviors in the tube fitted with the short helical tapes (SHTs) acting as decaying swirl flow generators. The tapes with three different helical tape angles (? = 90°, 135° and 180°) and three different channel numbers (N = 2, 3 and 4 channels) were tested under the uniform wall heat flux condition. The performance of each tape is compared with the performance of the plain tube subject to the same pumping power. The experimental results show that the heat transfer rates and friction factors of the tube with SHTs are respectively in range of 1.15 to 1.9 and 1.49 to 2.31 times of those in the plain, corresponding to thermal performances between 0.98 and 1.46. The correlations for Nusselt number (Nu) as a function of Reynolds number (Re), Prandtl number (Pr), helical tape angle (?) and the number of channel (N) are also developed.
Human Lung Cancer Risks from Radon – Part II – Influence from Combined Adaptive Response and Bystander Effects – a Microdose Analysis
Authors: Leonard Bobby E. , Thompson Richard E. , Beecher Georgia C.
Published: July 2010

In the prior Part I, the potential influence of the low level alpha radiation induced bystander effect (BE) on human lung cancer risks was examined. Recent analysis of adaptive response (AR) research results with a Microdose Model has shown that single low LET radiation induced charged particles traversals through the cell nucleus activates AR. We have here conducted an analysis based on what is presently known about adaptive response and the bystander effect (BE) and what new research is needed that can assist in the further evaluation human cancer risks from radon. We find that, at the UNSCEAR (2000) worldwide average human exposures from natural background and man-made radiations, the human lung receives about a 25% adaptive response protection against the radon alpha bystander damage. At the UNSCEAR (2000) minimum range of background exposure levels, the lung receives minimal AR protection but at higher background levels, in the high UNSCEAR (2000) range, the lung receives essentially 100% protection from both the radon alpha damage and also the endogenic, spontaneously occurring, potentially carcinogenic, lung cellular damage.
Assessment of rigid overlying strata failure in face mining
Authors: Jiránková Eva
Published: July 2010

The method of overlying strata failure assessment of extracted seams is based upon the simultaneous assessment of surface subsidence and seismic activity, considering the spatiatemporal progress of mining, depending on the character of the rock mass. The rigid overlying strata failure assessment results in finding whether a failure of the firm overlying rocks occurred or whether a strutting arch was formed over the mined-out area. The practical importance of the overlying strata failure assessment consists in determining the size of the mined-out area at which the com-plete failure of the rigid overlying strata occurred and in the assessment of the current stress condition of the overlying strata failure. The assessment method is applicable in deep mine workings where thick coal seams are being mined by means of the method of longwall mining with controlled caving. The results of this method are used to amend contemporary known methods of rock-burst protection, namely (regarding the use of surface measurements for the evaluation) in overlying strata areas.
Searching for Poetry: On Collective Collaboration in Wajdi Mouawad's Theatre
Authors: Meerzon Yana
Published: July 2010

Improvised dialogue, Wajdi Mouawad claims, does not constitute a production-forming part in his creative process. It is collective collaboration that informs his experience as a playwright and as a director. For each show he produces, Mouawad creates a new collective that he leads in dreaming up the situations and characters of a future play. Thus, unlike in the practice of collective creation, when a company is subjected to complex power-related issues, the collaboration in Mouawad's theatre is used as playwright's laboratory and excludes the uncertainty of authorship. The theatre of poetry sees dramatic text as the ultimate outcome of a collective effort. Here everything and everybody is called to serve the lyricism, the rhythms and the sound design of the text to be embodied on the stage and graphically laid out on the page.
Staggered Chromosomal Hybrid Zones in the House Mouse: Relevance to Reticulate Evolution and Speciation
Authors: Gündüz İslam , Pollock Christianne L. , Giménez Mabel D. , Förster Daniel W. , White Thomas A. , Sans-Fuentes Maria A. , Hauffe Heidi C. , Ventura Jacint , López-Fuster María José , Searle Jeremy B.
Published: July 2010

In the house mouse there are numerous chromosomal races distinguished by different combinations of metacentric chromosomes. These may come into contact with each other and with the ancestral all-acrocentric race, and form hybrid zones. The chromosomal clines that make up these hybrid zones may be coincident or separated from each other (staggered). Such staggered hybrid zones are interesting because they may include populations of individuals homozygous for a mix of features of the hybridising races. We review the characteristics of four staggered hybrid zones in the house mouse and discuss whether they are examples of primary or secondary contact and whether they represent reticulate evolution or not. However, the most important aspect of staggered hybrid zones is that the homozygous populations within the zones have the potential to expand their distributions and become new races (a process termed ‘zonal raciation’). In this way they can add to the total ‘stock’ of chromosomal races in the species concerned. Speciation is an infrequent phenomenon that may involve an unusual set of circumstances. Each one of the products of zonal raciation has the potential to become a new species and by having more races increases the chance of a speciation event.
Future Intentions Regarding Quitting and Reducing Cigarette Use in a Representative Sample of Canadian Daily Smokers: Implications for Public Health Initiatives
Authors: Cunningham John A. , Selby Peter L.
Published: July 2010

Pre-cessation reduction is associated with quitting smoking. However, many smokers reduce the amount consumed but may not quit altogether. Using a representative sample of adult current daily smokers, this project explored future intentions of smokers regarding cigarette consumption. This information is important because it can provide a framework within which to plan tobacco cessation initiatives. A random digit dialing telephone survey was conducted of 889 Canadian current daily smokers, 18 years and older. The response rate was 65% (of households with a smoker in residence, 65% agreed to participate). Analyses focused on the 825 respondents who smoked at least 10 cigarettes per day at some point in their lives. As part of this survey, respondents were asked their future plans about their smoking (maintain, increase, reduce, quit). Of these 825 respondents, the majority of respondents had plans to change their cigarette use, with 55% planning to quit, 18.8% to reduce and 22.5% to maintain the amount they smoked (3.4% did not know and 2 respondents planned to increase). Most smokers who planned to reduce their smoking saw it as a step towards quitting smoking completely. These results present a picture of smokers, the majority of whom appear to be in some form of transition. Many smokers planned to reduce, of which the overwhelming majority saw their reduction as a step towards quitting. Opportunities exist to capitalize on these intentions to change in efforts to promote tobacco cessation.
Emerging Families of Ion Channels Involved in Urinary Bladder Nociception
Authors: Araki Isao , Yoshiyama Mitsuharu , Kobayashi Hideki , Mochizuki Tsutomu , Du Shuqi , Okada Yusaku , Takeda Masayuki
Published: July 2010

The expression of multiple ion channels and receptors is essential for nociceptors to detect noxious stimuli of a thermal, mechanical or chemical nature. The peripheral sensory transduction systems of the urinary bladder include sensory nerve endings, urothelial cells and others whose location is suitable for transducing mechanical and chemical stimuli. There is an increasing body of evidence implicating the Deg/ENaC and TRP channel families in the control of bladder afferent excitability under physiological and pathological conditions. Pharmacological interventions targeting these ion channels may provide a new strategy for the treatment of pathological bladder sensation and pain.
Wireless Sensor Networks for Oceanographic Monitoring: A Systematic Review
Authors: Albaladejo Cristina , Sánchez Pedro , Iborra Andrés , Soto Fulgencio , López Juan A. , Torres Roque
Published: July 2010

Monitoring of the marine environment has come to be a field of scientific interest in the last ten years. The instruments used in this work have ranged from small-scale sensor networks to complex observation systems. Among small-scale networks, Wireless Sensor Networks (WSNs) are a highly attractive solution in that they are easy to deploy, operate and dismantle and are relatively inexpensive. The aim of this paper is to identify, appraise, select and synthesize all high quality research evidence relevant to the use of WSNs in oceanographic monitoring. The literature is systematically reviewed to offer an overview of the present state of this field of study and identify the principal resources that have been used to implement networks of this kind. Finally, this article details the challenges and difficulties that have to be overcome if these networks are to be successfully deployed.
Exploiting the Autofluorescent Properties of Photosynthetic Pigments for Analysis of Pigmentation and Morphology in Live Fremyella diplosiphon Cells
Authors: Bordowitz Juliana R. , Montgomery Beronda L.
Published: July 2010

Fremyella diplosiphon is a freshwater, filamentous cyanobacterium that exhibits light-dependent regulation of photosynthetic pigment accumulation and cellular and filament morphologies in a well-known process known as complementary chromatic adaptation (CCA). One of the techniques used to investigate the molecular bases of distinct aspects of CCA is confocal laser scanning microscopy (CLSM). CLSM capitalizes on the autofluorescent properties of cyanobacterial phycobiliproteins and chlorophyll a. We employed CLSM to perform spectral scanning analyses of F. diplosiphon strains grown under distinct light conditions. We report optimized utilization of CLSM to elucidate the molecular basis of the photoregulation of pigment accumulation and morphological responses in F. diplosiphon.
Emergence of Anthrax Edema Toxin as a Master Manipulator of Macrophage and B Cell Functions
Authors: Gnade Bryan T. , Moen Scott T. , Chopra Ashok K. , Peterson Johnny W. , Yeager Linsey A.
Published: July 2010

Anthrax edema toxin (ET), a powerful adenylyl cyclase, is an important virulence factor of Bacillus anthracis. Until recently, only a modest amount of research was performed to understand the role this toxin plays in the organism’s immune evasion strategy. A new wave of studies have begun to elucidate the effects this toxin has on a variety of host cells. While efforts have been made to illuminate the effect ET has on cells of the adaptive immune system, such as T cells, the greatest focus has been on cells of the innate immune system, particularly the macrophage. Here we discuss the immunoevasive activities that ET exerts on macrophages, as well as new research on the effects of this toxin on B cells.
Geographic variation in primary sex allocation per flower within and among 12 species of Pedicularis (Orobanchaceae): Proportional male investment increases with elevation
Authors: Guo Hui , Mazer Susan J. , Du Guozhen
Published: July 2010

• Premise of the study: The study of geographic variation in ecologically important traits within and among taxa is a first step toward understanding the environmental factors that contribute to population differentiation and species divergence. This study examines variation in mean sex allocation per flower (androecium mass/gynoecium mass) among 49 wild populations representing 12 Pedicularis species across an elevation gradient on the eastern Tibetan Plateau.

• Methods: We used population means to evaluate sources of variation in per‐flower sex allocation within and across species. In particular, we evaluate the relative influence of intrinsic (i.e., plant size, estimated as aboveground stem biomass) vs. extrinsic factors affecting mean sex allocation among populations.

• Key results: Mean sex allocation per flower (the relative investment in male floral organs) is negatively correlated with mean plant size; populations of large plants produce relatively female‐biased flowers. This relationship between mean plant size and mean sex allocation is not statistically significant, however, when the effect of elevation is controlled statistically. Among populations within and across species, mean sex allocation increases with elevation. This relationship persists even when the effect of mean plant size is controlled statistically. Factors associated with increasing elevation appear to favor genotypes and/or taxa with male‐biased flowers.

• Conclusion: Extrinsic environmental conditions may be more important than intrinsic resource status in determining patterns of geographic variation in mean sex allocation among populations or species of Pedicularis. We cannot conclude whether the effect of elevation on mean sex allocation is the result of environmentally induced plasticity, genetically based adaptation, or species sorting, but it is only partly mediated by mean plant size.
A case study of modified interactions with symbionts in a hybrid mediterranean orchid
Authors: Schatz Bertrand , Geoffroy Alexandre , Dainat Benjamin , Bessière Jean‐Marie , Buatois Bruno , Hossaert‐McKey Martine , Selosse Marc‐André
Published: July 2010

•Premise of the study: Most studies on orchid hybrids examine separately the effects of hybridization on interactions with pollinators or with mycorrhizal fungi. Here, we simultaneously investigated both interactions in the mediterranean food‐deceptiveOrchis simia,O. anthropophora, and their hybrid (O. ×bergonii) and tested a possible breakdown of coevolution using a multidisciplinary approach.

•Methods: We compared leaf growth, seed viability, emitted scent, and mycorrhizal fungi (species and rate of infection) among these three taxa.

•Key results: We show that leaf surface is greater in adult hybrids than in the parental species, suggesting a heterosis effect for vegetative growth. We demonstrate that flowers of the two parental species emit well‐differentiated bouquets of volatile organic compounds, while hybrids emit larger quantities, accumulating most compounds of the two parental species. However, hybrids fail to attract pollinators and have a 10 times lower fruit set. We determined that closely related Tulasnellales are mycorrhizal in the three taxa, suggesting that the mycorrhizal partner does not impair hybrid survival. We propose an interpretative model forO. ×bergoniicompared with its parents.

•Conclusions: In hybrids, carbon resources normally devoted to reproduction may be reallocated to the mycorrhizal symbiosis as a result of the disruption of the pollination interaction in hybrids. Higher mycorrhizal infection may in turn enhance vegetative growth and scent emission. Such interplay between the two obligate biotic interactions yields new insights into hybridization among orchids.
The age and diversification of the angiosperms re‐revisited
Authors: Bell Charles D. , Soltis Douglas E. , Soltis Pamela S.
Published: July 2010

• Premise of the study: It has been 8 years since the last comprehensive analysis of divergence times across the angiosperms. Given recent methodological improvements in estimating divergence times, refined understanding of relationships among major angiosperm lineages, and the immense interest in using large angiosperm phylogenies to investigate questions in ecology and comparative biology, new estimates of the ages of the major clades are badly needed. Improved estimations of divergence times will concomitantly improve our understanding of both the evolutionary history of the angiosperms and the patterns and processes that have led to this highly diverse clade.

• Methods: We simultaneously estimated the age of the angiosperms and the divergence times of key angiosperm lineages, using 36 calibration points for 567 taxa and a “relaxed clock” methodology that does not assume any correlation between rates, thus allowing for lineage‐specific rate heterogeneity.

• Key results: Based on the analysis for which we set fossils to fit lognormal priors, we obtained an estimated age of the angiosperms of 167–199 Ma and the following age estimates for major angiosperm clades: Mesangiospermae (139–156 Ma); Gunneridae (109–139 Ma); Rosidae (108–121 Ma); Asteridae (101–119 Ma).

• Conclusions: With the exception of the age of the angiosperms themselves, these age estimates are generally younger than other recent molecular estimates and very close to dates inferred from the fossil record. We also provide dates for all major angiosperm clades (including 45 orders and 335 families [208 stem group age only, 127 both stem and crown group ages], sensu APG III). Our analyses provide a new comprehensive source of reference dates for major angiosperm clades that we hope will be of broad utility.
Population biology of two rare fern species: long life and long‐lasting stability
Authors: Bucharová Anna , Münzbergová Zuzana , Tájek Přemysl
Published: July 2010

• Premise of the study: This study describes the population dynamics of two rare fern species and evaluates the prospects of their survival. This is the first detailed demography study of ferns using transition matrix models. The study species, Asplenium adulterinum and A. cuneifolium, are restricted to serpentine rocks and differ in ploidy level and partly in habitat requirements. Both species are of interest in nature conservation.

• Methods: Single life‐history traits were evaluated and transition matrix models were used to describe the dynamics of the populations. Population growth rates, elasticity values, and life‐table response experiments were used to compare the dynamics between species, years, and different habitat types. Predicted population performance based on models was compared with real data on population growth.

• Key Results: All populations of both species are growing. Stable stage distribution based on stochastic simulation corresponds to current stage distribution. The most critical phase of the life cycle is stasis of large adult plants. Reproduction is of low importance. Extinction probability of small populations is low. Mean life span of individuals of both species is 30–50 yr. When compared with real data, the model successfully predicted population performance over 10 yr.

• Conclusion: Populations in the study region are not endangered, and current population dynamics are stable. Differences in life‐history traits between species, probability of extinction between species and habitat, and different ploidy—and, thus, probably different dispersal ability—suggest the existence of metapopulation dynamics.
INVESTIGATION OF STATIONARY SOLUTIONS OF VISCOELASTIC MELT SPINNING EQUATIONS AND STABILITY WITH RESPECT TO INCREASING VISCOELASTICITY
Authors: Dhadwal R. , Kudtarkar S. K.
Published: July 2010

The one‐dimensional equations governing the formation of viscoelastic fibers using Giesekus constitutive equation were studied. Existence and uniqueness of stationary solutions was shown and relation between the stress at the spinneret and the take‐up velocity was found. Further, the value of the Giesekus model parameter for which the fibre exhibits Newtonian behaviour was found analytically. Using numerical simulations it was shown that below this value of the parameter the fluid shows extension thickening behaviour and above, extension thinning. In this context, by simulating the non‐stationary equations the effect of viscoelasticity on the stability of the spinning process was studied.
Análisis de componentes de material frágil por medio de métodos numéricos
Authors: Rubio M. D. , Crespo C. J. , Jakel R. , Dietz P. , Villellas A. , Doblaré M.
Published: July 2010

Los materiales frágiles deben sus características al elevado número de microgrietas producidas en su conformación. Es por ello por lo que han ido apareciendo una serie de criterios de cálculo específicos para estos materiales que se basan en cálculos de tipo probabilista y en las propiedades del material definidas por Weibull. En el I.M.W. (Clausthal, Alemania) se ha desarrollado un programa de cálculo de resistencia de piezas de estos materiales, por ejemplo cerámicas, que trabaja como subprocesador de un programa de elementos finitos, MARC, de forma que permite analizar la probabilidad de vida de las piezas según tres criterios generales y criterios de mecánica de fractura (once para elementos de volumen y seis para elementos de superficie). Asimismo, el programa permite calcular la probabilidad de fallo, según estos criterios en el caso de que se realicen cálculos con carga aplicada durante intervalos de tiempo, y realizar cálculos de factores de seguridad con los que se ha diseñado la pieza.
Tecnología de fabricación de arrabio con la inyección de combustibles y otros materiales por toberas en el horno alto. I Parte. Características de los combustibles auxiliares y su influencia en el proceso del horno alto
Authors: García L. , Cores A. , Formoso A. , Babich A. , Yaroshevskii S.
Published: July 2010

La inyección de combustibles por toberas en el horno alto es una práctica utilizada en la mayoría de los hornos con el objetivo principal de reducir el consumo de coque por tonelada de arrabio fabricado. La naturaleza de estos combustibles es muy diversa y es función de los recursos de cada país y del precio del combustible. En la actualidad, la práctica más extendida es la inyección de carbón (pulverizado y granulado) y cada vez es mayor el número de hornos con instalaciones para la inyección de carbón.
Producción y tratamiento de películas de Si1-xGex mediante técnicas asistidas por láser de excímero
Authors: Castro J. , Chiussi S. , Serra J. , León B. , Pérez-Amor M. , Martelli S. , Larciprete R. , Frangis N.
Published: July 2010

El creciente interés que suscita la búsqueda de nuevas técnicas para la obtención de materiales semiconductores, compatibles con la tecnología del silicio, ha llevado a desarrollar un sistema de depósito y postprocesado en alto vacío (HV) de Si-Ge mediante técnicas asistidas por láser excímero. Se han obtenido películas amorfas de germanio mediante el depósito químico en fase vapor inducido por láser (LCVD), que posteriormente han sido recristalizadas con uso de la inducción de epitaxia por medio de láser pulsado (PLIE). Las películas depositadas sobre substratos de silicio fueron caracterizadas mediante XRD, HREM y Raman, revelándose que son amorfas con un alto grado de homogeneidad. Se ha estudiado la morfología y la estequiometría de las muestras por medio de XRD, HREM y XPS tras el tratamiento para inducir la cristalinidad de la aleación sobre el substrato de silicio, observándose la dependencia del grado de heteroepitaxia y variación de la composición en la aleación, con el número y la energía de los pulsos del láser.
Producción de recubrimientos de fosfato cálcico mediante ablación láser para aplicaciones biomédicas
Authors: Mayor M. B. , Arias J. L. , García-Sanz F. J. , Pou J. , León-Camacho B. , Pérez-Amor M.
Published: July 2010

Los fosfatos cálcicos apatíticos se utilizan como recubrimientos para mejorar la fijación de implantes ortopédicos y dentales. La técnica comercial para la producción de estos recubrimientos (plasma-spray) presenta problemas de adherencia y control de propiedades físico-químicas. En esta comunicación, se presenta la ablación láser como alternativa para solventar estos problemas. El sistema de ablación consiste en una cámara de vacío llena de vapor de agua hasta la presión deseada. El haz de un láser excímero de ArF se focaliza en un blanco de hidroxiapatito, depositándose el recubrimiento en un substrato paralelo al blanco mantenido a una cierta temperatura. Las propiedades físico-químicas del material se analizaron por espectroscopia infrarroja por transformada de Fourier (FT-IR), difracción de rayos X (XRD), microscopía electrónica de barrido (SEM) y espectroscopia de rayos X por dispersión de energías (EDX). Basándose en estos resultados, se escogieron dos tipos de recubrimientos para determinar su biocompatibilidad in vitro.
Depósito de capas de nitruro de carbono mediante ablación láser
Authors: Soto R. , González P. , Pou J. , León B. , Pérez-Amor M.
Published: July 2010

Se presenta la preparación de capas finas de nitruro de carbono mediante la ablación de diferentes tipos de blancos (grafito, guanazol) en una atmósfera reactiva de amoniaco utilizando un láser de excímero de ArF (193 nm). Las capas se han depositado sobre diferentes soportes (obleas de silicio y aluminio) y se han analizado empleando técnicas de caracterización básicas como la espectroscopia infrarroja mediante transformada de Fourier (FTIR), espectroscopia de rayos X por dispersión de energía (EDX) y perfilometría. Se ha realizado, para los dos blancos utilizados, un estudio comparativo de la influencia de la presión total de amoniaco en la velocidad de depósito, composición y propiedades del material obtenido. Se ha observado en ambos casos la progresiva incorporación de nitrógeno en las capas con el aumento de la presión de amoniaco, estando el nitrógeno enlazado al carbono en diferentes configuraciones (enlaces simples, dobles y/o triples). La utilización del blanco de guanazol se muestra más eficiente en la incorporación de nitrógeno en las capas y en la formación de enlaces simples de C-N.
Limpieza de obras de arte con láser de Nd:YAG
Authors: Flores T. , Ponce L. , Moreno B. , Arronte M. , Fernández M. , García C.
Published: July 2010

La limpieza de obras de arte por láser presenta una serie de ventajas sobre técnicas tradicionales de restauración. En el presente trabajo se describen la técnica empleada y los mecanismos físicos que explican el proceso de ablación de contaminantes. Se reportan los resultados alcanzados en la limpieza de estatuas de mármol y alabastro, así como en la restauración de pintura al óleo. En este último caso, se emplea por primera vez el láser de Nd:YAG con resultados ventajosos.
Estudio del endurecimiento superficial por láser de fundiciones grises
Authors: Maco A. L. , Belzunce F. J.
Published: July 2010

Se ha realizado el endurecimiento superficial con láser de tres fundiciones grises de diferente composición química, cuantificándose las variaciones microestructurales introducidas, las profundidades afectadas por el tratamiento y la variación de dureza lograda al modificar tanto la densidad de potencia como la velocidad de pasada. Siempre que la densidad de energía aportada con el láser supere un cierto valor crítico, se obtiene una capa superficial que llega a fundir en el tratamiento, dando lugar a una estructura ledeburítica de muy alta dureza, obteniéndose, por debajo de ella, una segunda capa, también muy dura, de fundición martensítica.
Determinaçao da absorçao do feixe láser em ensaios de refusao em regime continuo
Authors: Lima M. , Wagnière J. D.
Published: July 2010

[pt] Este trabalho estuda a absorção do feixe laser sobre a superfície de um ferro fundido branco por meio de ensaios calorimétricos. Um láser de CO2, trabalhando no modo contínuo, foi utilizado para produzir um traço refundido sobre a superfície de um ferro fundido branco em intervalos de velocidade de varredura do feixe entre 0,01 e 1,00 cm/s. O registro da temperatura em função do tempo foi realizada por três termopares fixados à superfície inferior da amostra. Verificou-se que cerva de 13 % da radiação incidente sobre a superfície da amostra é absorvida em forma de calor, para um feixe com 0,65 mm de diâmetro, idependentemente da velocidade de varredura do feixe. No caso do feixe com diâmetro de 1,11 mm, a absorção cai para cerca de 11 %.

[es] Se estudia la absorción del rayo láser por la superficie de una fundición blanca utilizando ensayos calorimétricos. Se utilizó un láser tipo CO2 trabajando en modo continuo. Se realizaron trazos refundidos continuos en la superficie de la fundición blanca con velocidad de desplazamiento del haz láser comprendida entre 0,01 y 1,00 cm/s. Para el registro de la temperatura en función del tiempo se utilizaron tres termopares colocados sobre la superficie de la muestra. Se comprobó que, aproximadamente, el 13 % de la radiación incidente sobre la superficie de la muestra es absorbida en forma de calor, para un haz láser de 0,65 mm de diámetro, independientemente de la velocidad de paso del mismo. En el caso del haz láser de 1,11 mm de diámetro, la absorción disminuye a valores próximos al 11 %.
Tratamiento térmico superficial del acero U8 mediante láser de Nd:YAG
Authors: Ceballos-Ruano J. S. , Muñiz G. , Sagaró R. , Barja B. , Torres C.
Published: July 2010

Utilizando un láser continuo de Nd: YAG se procedió al endurecimiento superficial del acero U8. Se expone la metodología empleada en el trabajo para la determinación de los parámetros del proceso sobre la base de la documentación existente y a las pruebas realizadas. Se logra explicar el fenómeno observado para ilustrar los limites de operación de los parámetros del proceso a pesar de las limitaciones y simplificaciones realizadas. Se muestra que en el proceso de endurecimiento térmico superficial del acero U8 la profundidad endurecida está estrechamente vinculada con la potencia incidente (P) en la zona de interacción, el diámetro del haz (d) y la velocidad de barrido del haz del láser (ν) sobre la probeta por la relación P√dν. El experimento fue diseñado estadísticamente y permitió obtener durezas superiores a los 500 HV en espesores de 0,15 mm.
Texturado superficial de silicio mediante láser pulsado
Authors: Ponce L. , Castellanos A. , Arronte M. , Flores T. , Rodríguez E. , León R. , Montaigne A.
Published: July 2010

Se realiza el texturado de superficies de silicio con un láser pulsado mediante la formación de una estructura periódica inducida por láser (LIPSS). Se caracteriza el proceso mediante reflectancia dinámica, determinándose el umbral de formación de la estructura. Se caracteriza el nivel de texturado midiendo la reflectancia espectral de las muestras antes y después del tratamiento. El valor medio de la reflectancia espectral disminuye hasta el 6 %.
Recubrimientos superficiales con láseres de diodos de alta potencia
Authors: Molpeceres J. L. , Tomás M. J. , Pérez B. , Leal L.
Published: July 2010

La posibilidad de disponer actualmente de láseres de diodos con una potencia de emisión óptica superior a 1 kW permite abordar un gran número de aplicaciones en el ámbito del procesado de materiales con láser, dominado tradicionalmente por los láseres de CO2 y Nd:YAG. En el presente trabajo, se muestra la aplicación de los láseres de diodos de alta potencia al recubrimiento de materiales metálicos con aleaciones de base cobalto y níquel. Se describen las características del sistema empleado y se muestran los resultados obtenidos.
Propiedades de óxidos cerámicos procesados con laser
Authors: Virto M. , Peña J. I. , Díez J. C. , De la Fuente G. F.
Published: July 2010

La utilización de equipos láser como fuente de calor para el procesado de cerámicas presenta importantes ventajas, como el alcanzar temperaturas muy elevadas, próximas a los 3000 C, efectuar tratamientos muy localizados en superficies sin afectar el volumen del material, así como la realización de tratamientos en zonas de difícil acceso, entre muchas otras.
La fusión zonal asistida por láser constituye actualmente una de las técnicas más versátiles en el campo del crecimiento cristalino; la elevada absorción de la energía láser generada con sistemas CO2 y YAG:Nd en el interior de un compacto cerámico permite su eficaz transformación en monocristal, como es el caso del ZrO2 y Al2O3, eutéctico monocristalino de dos o más fases, caso del ZrO2-CaO, o policristal texturado como el superconductor Bi2Sr2CaCu2O8. La flexibilidad de control de los parámetros de crecimiento permite obtener productos con propiedades muy atractivas para su utilización en dispositivos de diversa naturaleza y de gran interés comercial.
Una introducción a las aplicaciones industriales de los láseres. Aspectos económicos y nuevos desarrollos
Authors: Orza J. M.
Published: July 2010

Se reproducen algunas cifras del mercado de láseres en 1997. Se pasa revista a treinta años de procesado de materiales metálicos con láseres de alta potencia. Se hace una referencia especial a los programas europeos de I+D y se plantean, finalmente, algunas cuestiones sobre la evolución previsible de aquí al año 2000.
Efecto de las condiciones de corte de un láser de Nd:YAG sobre la estructura y microcomposición de la superficie de aceros inoxidables
Authors: Ramírez A. , Pascual J. , Lasema J. , Moya M. V. , Zapatero J. , Fernández T.
Published: July 2010

Se presenta un estudio de la influencia de los parámetros de procesado láser (distribución temporal, distribución espacial y velocidad) en la calidad de acabado y microestructura de aceros inoxidables austeníticos. Se ha utilizado un láser Nd:YAG con nitrógeno como gas de protección, analizándose los resultados mediante SEM, microsonda electrónica y análisis metalográfico. Para una distribución espacial fija (10 %), y una frecuencia de 500 Hz, el aumento de la distribución temporal produce mayor potencia, lo que permite trabajar a velocidades más altas. La calidad del acabado aumenta al hacerlo la velocidad de corte. El corte de acero 304 con láser a velocidades superiores a 0,0033 m/s y potencias inferiores a 1.000 W usando nitrógeno a 18 bar no produce modificaciones apreciables en la estructura.
Soldadura laser de chapa fina de aço carbono e aço galvanizado
Authors: Peças P. , Gouveia H. , Quintino L.
Published: July 2010

Este artigo descreve os resultados da investigação da soldadura laser de CO2 de chapa fina de acó carbono (simples e galvanizado), em diferentes combinações de espessura. A soldadura laser é um processo de elevado potencial no fabrico de tailored-blanks (sub-conjuntos para posterior enformação, constituidos por varias partes de diferentes materiais e espessuras) para a indústria automóvel.
São analisados os aspectos de optimização paramétrica, de qualidade metalúrgica da junta soldada e das deformações resultantes da soldadura. São descritos os mecanismos desenvolvidos de fixação das chapas e protecção gasosa, por forma a minimizar os defeitos típicos na soldadura laser de chapa fina como o desalinhamento e da soldadura laser de chapa galvanizada como os poros e a volatilização do zinco. Por fim apresentam-se resultados da avaliação da qualidade da soldadura do ponto de vista qualitativo através da norma DIN 8563, e do pontos de vista quantitativo através de ensaios de tracção, dureza e corrosão.
Estudio del nivel de protección contra la corrosión de un hormigón polimérico
Authors: García E. , Valle E.
Published: July 2010

El objetivo de este estudio es determinar a nivel laboratorio el grado de protección contra la corrosión que puede ofrecer un hormigón polimérico de base poliéster desarrollado en el Instituto de Investigaciones Eléctricas (HE), empleando las técnicas electroquímicas de impedancia faradaica y ruido electroquímico.
Comportamiento del acero AISI-SAE 8615 frente al proceso de nitrocarburación ferrítica, utilizando urea-metanol
Authors: Barrena M. I. , Castro A.
Published: July 2010

El presente trabajo muestra el comportamiento del acero aleado de bajo contenido de carbono, AISISAE 8615, cuando se somete a un proceso de nitrocarburación ferrítica, a la temperatura de 570ºC y un tiempo de 3 h. La atmósfera reactiva ha sido generada mediante goteo variable de metanol y urea dentro del horno, utilizando distintas velocidades de flujo. Las capas nitrocarburadas fueron evaluadas mediante técnicas de microscopía óptica. Con el fin de conocer la extensión de las capas nitrocarburadas obtenidas, se realizaron medidas de microdureza y se determinaron los porcentajes de carbono en el proceso mediante espectroscopia de emisión. Se han encontrado las condiciones de flujo óptimo de la mezcla anteriormente comentada y se ha observado cómo su variación influye en el espesor de la capa nitrocarburada.
Ecuación de vida de herramienta en el punzonado de chapa de acero inoxidable 18-8
Authors: Faura F. , López J. , Sanes J. , García A.
Published: July 2010

En el presente artículo se presenta un modelo de ecuación de vida de herramientas para punzonado circular de chapa de acero inoxidable 18-8 (1 mm de espesor). Se han analizado inicialmente los diferentes estudios que previamente han abordado este problema. Posteriormente, teniendo en cuenta los experimentos realizados recientemente, se propone una formulación simple para predecir con Habilidad suficiente la vida de la herramienta. Para este propósito se han examinado los diferentes parámetros que afectan al proceso de desgaste, infiriendo a partir de estos, los parámetros fundamentales que lo regulan y sobre los cuales se han configurado las diferentes ecuaciones. Los ensayos fueron realizados en una prensa de 20 t y una velocidad de punzonado de 150 golpes/min. Los materiales de los punzones usados en los ensayos fueron AISI A2 y AISI D2 con diámetros comprendidos entre 1,5 y 10 mm. Los ensayos se realizaron para juegos de corte comprendidos entre un 5 y 20 % del espesor de la chapa.
Tecnología de fabricación de arrabio con inyección de combustibles y otros materiales por toberas en el horno alto. III parte. Inyección de mezclas combustibles y otros materiales no combustibles
Authors: García L. , Cores A. , Formoso A. , Babich A. , Yaroshevskii S.
Published: July 2010

Se analiza la inyección de materiales no combustibles (minerales de hierro, fundentes, escorias, arenas ilmeníticas), residuos siderúrgicos, plásticos y otros, tanto de forma individual como en mezcla con carbón pulverizado. Según las características de los materiales inyectados se pueden introducir variaciones en la operación del horno alto.