bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Molecules in Short‐ and Long‐Distance Proton Transfer Steps of Bacteriorhodopsin Proton Pumping
Authors: Bondar Ana‐Nicoleta , Smith Jeremy C.
Published: August 2009

The proton pumping cycle of bacteriorhodopsin consists of five consecutive proton transfer steps, in all of which water molecules are likely to play critical roles. Here we review the role of water molecules in bacteriorhodopsin function, with emphasis on computations of the retinal Schiff base deprotonation reaction and the open questions regarding the participation of water molecules in the longer‐distance proton transfer reactions.
Enzymatic H Transfers: Quantum Tunneling and Coupled Motion from Kinetic Isotope Effect Studies
Authors: Stojković Vanja , Kohen Amnon
Published: August 2009

Many hydrogen transfer processes exhibit nonclassical behavior due to inherent quantum mechanical properties of the hydrogen. Investigation of various enzymes under physiological conditions indicates that hydrogen transfer processes often show significant quantum mechanical behavior. Traditionally, this phenomenon was treated in terms of a tunneling correction to classical or semiclassical models. However, more recently, it has been observed that increasing numbers of enzymes yield data that cannot be rationalized by tunneling correction models. Observations such as large kinetic isotope effects (KIEs) with unusual temperature dependence, isotope effects on Arrhenius preexponential factors with values different from semiclassical predicted ranges, and small temperature‐independent KIEs for processes with significant energy of activation, could only be explained with full tunneling models for H transfer. Full tunneling models presume that the solvent or protein fluctuations generate a reactive configuration along the heavy‐atom coordinate, from which the hydrogen is transferred through quantum mechanical tunneling. These models are sometimes denoted as environmentally coupled tunneling (ECT) or Marcus‐like models, and they link protein dynamics to the catalyzed H transfer. Several enzymatic systems (dihydrofolate reductase, thymidylate synthase, and soybean lipoxygenase) are presented as case studies of proton, hydrogen, and hydride transfer.
Tautomerization in Condensed Phases and in Isolated Molecules
Authors: Waluk Jacek
Published: August 2009

We review our recent investigations of systems revealing single or double proton (hydrogen) transfer in the ground or electronically‐excited states. The results obtained for condensed phases are compared with the data provided by experiments carried out in the regime of molecular isolation, mainly by using supersonic jet spectroscopy techniques.

Both intra‐ and intermolecular processes have been studied. Four different bifunctional chromophores are discussed, all sharing a common feature of possessing a proton‐donating NH group and an acceptor nitrogen atom incorporated into a pyridine or pyrrolene ring.

Porphycene and derivatives reveal, when isolated, coherent double hydrogen transfer manifested by vibration‐specific tunneling splittings. In condensed phases, tautomerization occurs as a rate process; its dynamics can be probed by techniques using polarized light. Huge dependence of the tautomerization rate on the strength of intramolecular hydrogen bonds has been detected.

2‐(2′‐pyridyl)pyrrole provides a rare example of a molecule which undergoes both intramolecular excited‐state single proton transfer and a solvent‐assisted excited‐state double proton transfer reaction. Supersonic jet studies allowed us to identify the vibrational modes that enhance the tautomerization.

Photoinduced intramolecular proton transfer in 7‐(2′‐pyridyl)indole is accompanied by twisting of the proton donor and acceptor subunits. The reaction occurs faster in the supersonic beam than in room temperature solutions.

1H‐pyrrolo[3,2‐h]quinoline forms 1:1 and 1:2 complexes with alcohols and water. The stoichiometries and vibrational structure could be determined for jet‐isolated complexes. The 1:1 cyclic, doubly hydrogen‐bonded species reveal rapid photoinduced tautomerization both in condensed phases and when isolated in supersonic beams.
Isotope Effect of Proton/Deuteron Diffusion Constant in Ice
Authors: Uritski Anna , Presiado Itay , Huppert Dan
Published: August 2009

The isotope effect of the proton diffusion constant in ice Ih was studied by using a time‐resolved emission technique. For that purpose we used three photoactive molecules that are sensitive to the excess mobile proton in ice. We found that the diffusion constant isotope effect was smaller by less than a factor of two in the temperature range of 240–270 K. Previously, we reported that the proton diffusion constant in ice is very large, in fact, 10 times greater than that of water at 295 K.
Nitric Acid Dissociation at an Aqueous Surface: Occurrence and Mechanism
Authors: Wang Shuzhi , Bianco Roberto , Hynes James T.
Published: August 2009

Here we briefly review some highlights of our recent work on the acid dissociation of nitric acid HNO3 at an aqueous surface, a proton transfer reaction of interest not only from a fundamental perspective, but also in connection with heterogeneous chemistry in a wide range of atmospheric contexts. Two types of studies of the potential acid dissociation are discussed, quantum chemical reaction path calculations to assess the reaction free energy and Car‐Parrinello molecular dynamics simulations to assess the reaction feasibility. We discuss the agreement and disagreement between the predictions of these two calculations as a function of the initial location of the HNO3 molecule, ranging from a positioning on top of the aqueous surface to one several water layers below the surface. Special attention is given to the four key water solvent motions found to be necessary for the proton transfer reaction to occur. Finally, an Eigen cation, rather than a Zundel cation, is in all cases found to be predominant next to the nitrate ion in contact ion pairs produced in the acid dissociation. This predominance remains, although diminished, for solvent‐separated ion pairs.
Watershed Land Use Controls on Chemical Inputs to Lake Ontario Embayments
Authors: Chen Xiaoxia , Driscoll Charles T.
Published: August 2009

There is considerable interest in understanding the role of land use in controlling surface water quality. This study was conducted to assess the role of land cover in regulating temporal and spatial patterns in nutrients and major solutes in rivers that drain into Lake Ontario. Water samples were collected monthly from 22 river sites in subwatersheds of eight embayments along the New York coast of Lake Ontario over the period 2001–2003. Samples were analyzed for nutrients and major solutes. The land cover of the subwatersheds was varied, but largely a mixture of forest and agricultural lands. Rivers draining largely agricultural lands exhibited distinct seasonal patterns, particularly for nutrients. Nitrate and total nitrogen (TN) concentrations were generally low during the summer growing season, increased markedly during fall and decreased during winter and spring. Total phosphorus (TP), dissolved organic carbon (DOC), and most ion (Na+, K+, Ca2+, Mg2+, Cl−, SO42–) concentrations varied with seasonal discharge patterns. Distinct spatial patterns were observed in river solute concentrations that closely corresponded with land use. Solute concentrations increased markedly with increases in the percentage of the watershed occurring as agricultural lands. Such a pattern has been commonly observed for nutrients (e.g., TP, TN, NO3−), but this relationship was also evident for most non‐nutrient solutes (e.g., DOC, Ca2+, F−, SO42–), a pattern which has not previously been reported. These observations suggest that agricultural activities mobilize most major elements, enhancing transport across the temperate landscape and impacting downstream water resources, including embayments and the Lake Ontario ecosystem.
Diffuse Phosphorus Models in the United States and Europe: Their Usages, Scales, and Uncertainties
Authors: Radcliffe D.E. , Freer Jim , Schoumans Oscar
Published: August 2009

Today there are many well‐established computer models that are being used at different spatial and temporal scales to describe water, sediment, and P transport from diffuse sources. In this review, we describe how diffuse P models are commonly being used in the United States and Europe, the challenge presented by different temporal and spatial scales, and the uncertainty in model predictions. In the United States, for water bodies that do not meet water quality standards, a total maximum daily load (TMDL) of the pollutant of concern must be set that will restore water quality and a plan implemented to reduce the pollutant load to meet the TMDL. Models are used to estimate the current maximum daily and annual average load, to estimate the contribution from different nonpoint sources, and to develop scenarios for achieving the TMDL target. In Europe, the EC‐Water Framework Directive is the driving force to improve water quality and models are playing a similar role to that in the United States, but the models being used are not the same. European models are more likely to take into account leaching of P and the identification of critical source areas. Scaling up to the watershed scale has led to overparameterized models that cannot be used to test hypotheses regarding nonpoint sources of P or transport processes using the monitoring data that is typically available. There is a need for more parsimonious models and monitoring data that takes advantage of the technological improvements that allow nearly continuous sampling for P and sediment. Tools for measuring model uncertainty must become an integral part of models and be readily available for model users.
Phosphorus Retention in Riparian Buffers: Review of Their Efficiency
Authors: Hoffmann Carl Christian , Kjaergaard Charlotte , Uusi‐Kämppä Jaana , Hansen Hans Christian Bruun , Kronvang Brian
Published: August 2009

Ground water and surface water interactions are of fundamental importance for the biogeochemical processes governing phosphorus (P) dynamics in riparian buffers. The four most important conceptual hydrological pathways for P losses from and P retention in riparian buffers are reviewed in this paper: (i) The diffuse flow path with ground water flow through the riparian aquifer, (ii) the overland flow path across the riparian buffer with water coming from adjacent agricultural fields, (iii) irrigation of the riparian buffer with tile drainage water from agricultural fields where disconnected tile drains irrigate the riparian buffer, and (iv) inundation of the riparian buffer (floodplain) with river water during short or longer periods. We have examined how the different flow paths in the riparian buffer influence P retention mechanisms theoretically and from empirical evidence. The different hydrological flow paths determine where and how water‐borne P compounds meet and interact with iron and aluminum oxides or other minerals in the geochemical cycling of P in the complex and dynamic environment that constitutes a riparian buffer. The main physical process in the riparian buffer—sedimentation—is active along several flow paths and may account for P retention rates of up to 128 kg P ha−1 yr−1, while plant uptake may temporarily immobilize up to 15 kg P ha−1 yr−1 Retention of dissolved P in riparian buffers is not as pronounced as retention of particulate P and is often below 0.5 kg P ha−1 yr−1 Several studies show significant release of dissolved P (i.e., up to 8 kg P ha−1 yr−1).
Are Current Phosphorus Risk Indicators Useful to Predict the Quality of Surface Waters in Southern Manitoba, Canada?
Authors: Salvano Esther , Flaten Don N. , Rousseau Alain N. , Quilbe Renaud
Published: August 2009

Many phosphorus (P) risk indicators have been developed to assess the risk of P loss from agricultural land to surface water. Most of these indicators are designed for land and climates where rainfall‐induced erosion of particulate P from sloping landscapes is the main process of P transport. No indicators have been validated in the Canadian Prairies, where P losses are driven by snowmelt‐driven runoff over nearly level landscapes and frozen soils. The objective of this project was to evaluate the relationship between water quality data for P from 14 watersheds and three existing P risk indicators for their potential use in the southern Manitoba prairie region of Canada. None of the indicators, including Birr and Mulla's P Index, a preliminary P risk indicator for Manitoba, and a preliminary version of Canada's National Indicator of Risk of Water Contamination by Phosphorus, was significantly correlated with mean concentrations of total P in water or P export per hectare. Although erosion risk was a significant factor influencing the value of these indexes, erosion risk was not correlated with either measure of P loss in these watersheds. Several other watershed characteristics, including average soil test P concentrations, livestock density, proportion of land in annual crops, and the land's inherent capability for agricultural production, were strongly correlated with P concentrations in water (r = 0.80***, r = 0.63**, 0.76***, and ‐0.70**, respectively). Therefore, these types of P risk indicators require modifications to estimate the risk of P loss under the soil, landscape, and climatic conditions of southern Manitoba.
Base Flow Nutrient Discharges from Lower Delmarva Peninsula Watersheds of Virginia, USA
Authors: Stanhope Jennifer W. , Anderson Iris C. , Reay William G.
Published: August 2009

Proper management of shallow coastal systems, which are vulnerable to nutrient enrichment, requires knowledge of land use impacts on nutrient discharges. This study quantified base flow nutrient concentrations and yields for 1 yr (May 2001–April 2002) from 14 first‐order streams on the Virginia Eastern Shore (VaES) on the Delmarva Peninsula and assessed their relationships with land cover and soil drainage class in their watersheds. Base flow water discharge rates (1.4–31.5 cm yr−1) were likely lower than the long‐term average due to a severe drought. Seasonal mean nitrate concentrations were higher in winter, while mean dissolved organic carbon and ammonium concentrations were higher in summer. Annual base flow‐weighted mean total dissolved nitrogen (TDN) concentrations were positively related to percent (%) agricultural land cover (r2 = 0.43; p = 0.02) and % very poorly drained soils (r2 = 0.51; p = 0.009) and negatively related to % forested land cover (r2 = 0.54; p = 0.005). Patterns of base flow TDN yields were similar to those of concentrations but were also positively related to % developed land cover (r2 = 0.40; p = 0.03). Agricultural and developed land covers, together with very poorly drained soil, accounted for 91% of the variability of TDN yields (p = 0.0001). Using a multiple regression model, the base flow TDN loading rate to a coastal lagoon on the VaES, a system vulnerable to nutrient enrichment, was estimated to be 28,170 kg N yr−1
Peroxidase‐Mediated Polymerization of 1‐Naphthol: Impact of Solution pH and Ionic Strength
Authors: Bhandari Alok , Xu Fangxiang , Koch David E. , Hunter Robert P.
Published: August 2009

Peroxidase‐mediated oxidation has been proposed as a treatment method for naphthol‐contaminated water. However, the impact of solution chemistry on naphthol polymerization and removal has not been documented. This research investigated the impact of pH and ionic strength on peroxidase‐mediated removal of 1‐naphthol in completely mixed batch reactors. The impact of hydrogen peroxide to 1‐naphthol ratio and activity of horseradish peroxidase was also studied. Size exclusion chromatography was used to estimate the molecular weight distribution of oligomeric products, and liquid chromatography/mass spectrometry was used to estimate product structure. Naphthol transformation decreased with ionic strength, and substrate removal was lowest at neutral pHs. Solution pH influenced the size and the composition of the oligomeric products. An equimolar ratio of H2O2:naphthol was sufficient for optimal naphthol removal. Polymerization products included naphthoquinones and oligomers derived from two, three, and four naphthol molecules. Our results illustrate the importance of water chemistry when considering a peroxidase‐based approach for treatment of naphthol‐contaminated waters.
Speciation and Mobility of Arsenic in Agricultural Lime
Authors: Schmidt Gerald T. , Lui Ka Hei , Kersten Michael
Published: August 2009

Agricultural liming materials are used to correct soil acidity and to improve plant growth and microbial functionality. A relatively low‐grade agricultural lime was found to contain up to 125 mg kg−1 arsenic (As), which is above any fertilizing materials code threshold. The color of the milled material is brown due to ample oxide dendrites. Microprobe elemental maps confirmed that these accessory oxide mineral phases are responsible for the elevated As concentrations in the limestone. The black Mn‐bearing dendrites contain minor amounts of As, whereas the brown Fe‐bearing dendrites contain the major part of the As inventory, with an Fe/As molar ratio around 100. Because the elemental maps represent only a few sample regions of interest (ROI), the results are corroborated by a bulk five‐step sequential extraction of the lime, which suggests that a majority of the As is bound to acid‐reducible phases. Because repartitioning of the As oxyanion during extraction cannot be ruled out, X‐ray absorption spectroscopy with micrometer resolution (μ‐XAS) was used as a solid‐state speciation analysis approach. The μ‐XAS results at the Fe K‐edge for the selected ROIs revealed the brown dendrites to consist of ferrihydrite and goethite, whereas those at the As K‐edge revealed that the pentavalent As species arsenate predominates, with As‐Fe distance and coordination indicating binding as a mononuclear inner‐spheric adsorbate complex. Batch experiments with soil exposed to submerged conditions of up to 41 d revealed a negligible As release rate from the lime (approximately 40 ng kg−1 d−1). The results of this study corroborate regulatory codes that set the permissible As content in agricultural lime relative to the respective Fe content.
Mineral‐nitrogen Leaching and Ammonia Volatilization from a Rice–Rapeseed System as Affected by 3,4‐Dimethylpyrazole Phosphate
Authors: Li Hua , Chen Yingxu , Liang Xinqiang , Lian Yanfeng , Li Wenhong
Published: August 2009

3,4‐Dimethylpyrazole phosphate (DMPP) was validated as an effective nitrification inhibitor to reduce nitrate leaching. Its effects on ammonia (NH3) volatilization were not clear, especially on farmland scale with crop rotations. In this study, on‐farm experiments at the Jiaxing (JX) and Yuhang (YH) sites in Taihu Lake Basin, China were conducted to evaluate the effect of DMPP application on mineral nitrogen (N) (NH4–N and NO3–N) leaching and NH3 volatilization losses in a rice–rapeseed cropping system. Treatments included urea alone (UA), urea + 1% DMPP (UD), and no fertilizer (CK). The results show that DMPP reduced NO3–N leaching fluxes by 44.9 to 59.9% and increased NH4–N leaching fluxes by 13.0 to 33.3% at two sites during rice and rape seasons compared with urea alone. Reductions in mineral‐N leaching fluxes by DMPP in two seasons at the JX and YH sites were 9.5 and 14.3 kg N ha−1, respectively, compared with UA treatment. The application of DMPP had no significant effects on NH3 volatilization loss fluxes at either site. The rice and rapeseed yields were 5.3 to 7.4% higher in UD plots than in UA plots at two sites. These results that indicate DMPP could reduce leaching losses of mineral‐N from crop fields and promote grain yields by conserving more applied N in soil in rice–rapeseed rotation systems.
Fresh Water Leaching of Alkaline Bauxite Residue after Sea Water Neutralization
Authors: Menzies Neal W. , Fulton Ian M. , Kopittke Rosemary A. , Kopittke Peter M.
Published: August 2009

Processing of bauxite to extract alumina produces a strongly alkaline waste, bauxite refining residue, which is commonly stored in engineered structures. Once full, these waste dumps must be revegetated. In many alumina refineries, the waste is separated into fine‐textured red mud and coarse‐textured residue sand (RS). The sand component has physical characteristics that make it a suitable plant growth medium, provided the adverse chemical characteristics can be addressed. Neutralization of the highly saline‐sodic RS with sea water lowers pH, reduces Na saturation, and adds plant nutrients. However, sea water–neutralized RS remains saline sodic and needs fresh water leaching before use as a plant growth medium. Columns containing sea water–neutralized RS were leached with 30 m depth‐equivalent of fresh water to evaluate the effects of rainfall on the RS and its leachate. Entrained cations were rapidly displaced by the fresh water, lowering salinity to non–plant‐limiting levels (≤0.3 dS m−1). The percentage of the effective cation exchange capacity (ECEC) saturated by Na decreased from 71 to 62% due to a reduction in soil solution ionic strength (causing a decrease in the ECEC) and the preferential displacement of Na+ (and K+) from the exchange. Fresh water leaching increased pH (leachate pH increased from 8.0 to 10.1). This pH increase is attributed to the slow dissolution of the Na‐containing mineral sodalite. Under the current experimental conditions, the application of 30 m depth‐equivalent of leaching reduced the total RS sodalite content by <10%.
Nitrogen, Tillage, and Crop Rotation Effects on Carbon Dioxide and Methane Fluxes from Irrigated Cropping Systems
Authors: Alluvione Francesco , Halvorson Ardell D. , Del Grosso Stephen J.
Published: August 2009

Long‐term effects of tillage intensity, N fertilization, and crop rotation on carbon dioxide (CO2) and methane (CH4) flux from semiarid irrigated soils are poorly understood. We evaluated effects of: (i) tillage intensity [no‐till (NT) and conventional moldboard plow tillage (CT)] in a continuous corn rotation; (ii) N fertilization levels [0–246 kg N ha−1 for corn (Zea mays L.); 0 and 56 kg N ha−1 for dry bean (Phaseolus vulgaris L.); 0 and 112 kg N ha−1 for barley (Hordeum distichon L.)]; and (iii) crop rotation under NT soil management [corn‐barley (NT‐CB); continuous corn (NT‐CC); corn‐dry bean (NT‐CDb)] on CO2 and CH4 flux from a clay loam soil. Carbon dioxide and CH4 fluxes were monitored one to three times per week using vented nonsteady state closed chambers. No‐till reduced (14%) growing season (154 d) cumulative CO2 emissions relative to CT (NT: 2.08 Mg CO2–C ha−1; CT: 2.41 Mg CO2–C ha−1), while N fertilization had no effect. Significantly lower (18%) growing season CO2 fluxes were found in NT‐CDb than NT‐CC and NT‐CB (11.4, 13.2 and 13.9 kg CO2–C ha−1d−1 respectively). Growing season CH4 emissions were higher in NT (20.2 g CH4 ha−1) than in CT (1.2 g CH4 ha−1). Nitrogen fertilization and cropping rotation did not affect CH4 flux. Implementation of NT for 7 yr with no N fertilization was not adequate for restoring the CH4 oxidation capacity of this clay loam soil relative to CT plowed and fertilized soil.
International Phosphorus Workshop: Diffuse Phosphorus Loss to Surface Water Bodies—Risk Assessment, Mitigation Options, and Ecological Effects in River Basins
Authors: Kronvang Brian , Rubæk Gitte H. , Heckrath Goswin
Published: August 2009

Agriculture is a major source of P to the aquatic environment in many countries. Although efforts have been made to improve the P utilization in agricultural production, which is reflected in modestly declining P surpluses in many countries, increasing agricultural P surpluses are still observed in some countries. The IPW5 Special Submission included in this issue addresses and discusses four key topics that emerged from the workshop: (i) managing agricultural P losses–effectiveness, uncertainties, and costs; (ii) P modeling at different scales; (iii) functioning of riparian buffers; (iv) ecological responses to P loadings and impacts of climate change. Each of these four topics interacts with each other as well as with the four tiers of the P Transfer Continuum (Source, Mobilization, Transport, and Ecological Effects). In this review paper we highlight the main outcomes of the workshop and the special collection of eight papers. Moreover, we identify the main gaps in our knowledge and future research directions on P, which are linked to important issues such as addressing scale effects, improved P models with the ability to quantify uncertainty, the linking of P losses with ecological effects, and climate change.
The Search for Meaning after Pregnancy Loss: An Autoethnography
Authors: Leith Valerie M. Sheach
Published: August 2009

The focus of this autoethnography is the often hidden and marginalized experience of pregnancy loss. Through an exploration of “the search for meaning” in the aftermath of three different losses over a period of 9 years, I seek to problematize Western discourses which, influenced by Enlightenment ideals, adhere to linear notions of progress. Such discourses can be argued to sustain an imperative to create positive meaning from traumatic life experience, to gain beneficial insight from suffering, and ultimately to triumph over adversity. In articulating a messier and more ambiguous story, the difficulties of living through and voicing experience, which fails to conform to such a framework, is highlighted.
Understanding and Consulting with Inconsolable Organizations
Authors: Stein Howard F.
Published: August 2009

Contrary to their widely touted and expected benefits to organizations, the various forms of “managed social change” (e.g., downsizing, RIFing, reengineering, restructuring, outsourcing) over the past quarter century have had widespread devastating psychological effects on those fired, on those who survived the firings, on those whose roles were dramatically changed, and on their families and communities. The result has often been what I call “inconsolable organizations,” that is, workplaces mired in loss and grief. Inconsolable organizations emerge where recurrent traumatic change has occurred together with the often officially-enforced “inability to mourn” the massive losses—not only of others, but of one's very self and self-worth. A tentative model is proposed, one that situates organizational inconsolability relative to other dimensions of adaptation to traumatic change. Recommendations are offered for assisting organizations in these circumstances.
Conception of Crossed Populations: Application in Cyclopoida Taxonomy
Authors: Monchenko V. , Samchyshyna L.
Published: August 2009

Conception of Crossed Populations: Application in Cyclopoida Taxonomy

The conception of crossed populations in wide practice of taxonomic investigations in Cyclopoida is used for the first time. Applying this conception in taxonomy of cyclopoid copepods we based on revealed facts of the coexistence of sibling species which keep a little morphological hiatus. Hence, next pairs of species we consider as independent ones:Eucyclops speratus(Lilljeborg) andE. serrulatus(Lilljeborg);Paracyclops poppei(Rehberg) andP. fimbriatus(Fischer);Megacyclops latipes(Lowndes),M. viridis(Jurine) andM. gigas(Claus);Diacyclops clandestinus(Kiefer) andD. languidoides(Lilljeborg);D. hypnicola(Gurney) andD. languidoides(Lilljeborg);D. odessanus(Schmankevitsch) andD. bicuspidatus(Claus);Microcyclops rubellus(Lilljeborg) andM. varicans(Sars);Halicyclops septentrionalis(Kiefer) andH. neglectus(Kiefer). Facts of coexistence ofAcanthocyclops americanus(Marsh) and its formA. americanusf.spinosa(Monchenko) differing by only one qualitative feature (spine or seta on outer edge on endopodite P4 distal segment) that has no transitive manifestation do not allow us to consider morphological formA. americanusf.spinosaas a separated species from the typeA. americanus.
Graph Compression by BFS
Authors: Apostolico Alberto , Drovandi Guido
Published: August 2009

The Web Graph is a large-scale graph that does not fit in main memory, so that lossless compression methods have been proposed for it. This paper introduces a compression scheme that combines efficient storage with fast retrieval for the information in a node. The scheme exploits the properties of the Web Graph without assuming an ordering of the URLs, so that it may be applied to more general graphs. Tests on some datasets of use achieve space savings of about 10% over existing methods.
The Economics of Gasification: A Market-Based Approach
Authors: Abadie Luis M. , Chamorro José M.
Published: August 2009

This paper deals with the economics of gasification facilities in general and IGCC power plants in particular. Regarding the prospects of these systems, passing the technological test is one thing, passing the economic test can be quite another. In this respect, traditional valuations assume constant input and/or output prices. Since this is hardly realistic, we allow for uncertainty in prices. We naturally look at the markets where many of the products involved are regularly traded. Futures markets on commodities are particularly useful for valuing uncertain future cash flows. Thus, revenues and variable costs can be assessed by means of sound financial concepts and actual market data. On the other hand, these complex systems provide a number of flexibility options (e.g., to choose among several inputs, outputs, modes of operation, etc.). Typically, flexibility contributes significantly to the overall value of real assets. Indeed, maximization of the asset value requires the optimal exercise of any flexibility option available. Yet the economic value of flexibility is elusive, the more so under (price) uncertainty. And the right choice of input fuels and/or output products is a main concern for the facility managers. As a particular application, we deal with the valuation of input flexibility. We follow the Real Options approach. In addition to economic variables, we also address technical and environmental issues such as energy efficiency, utility performance characteristics and missions (note that carbon constraints are looming). Lastly, a brief introduction to some stochastic processes suitable for valuation purposes is provided.
Behavioral Changes Based on a Course in Agroecology: A Mixed Methods Study
Authors: Harms Kristyn , King James , Francis Charles
Published: August 2009

This study evaluated and described student perceptions of a course in agroecology to determine if participants experienced changed perceptions and behaviors resulting from the Agroecosystems Analysis course. A triangulation validating quantitative data mixed methods approach included a written survey comprised of both quantitative and open‐ended questions as well as observations by the authors. Qualitative data garnered from the 2001–2007 daily evaluations were analyzed to locate and categorize central factors essential for the development of an experiential learning environment (n = 140). Study participants consisted of students and instructors who participated in the course, with matched non‐participant subjects serving as the control group for baseline comparisons (n = 66). Quantitative responses were analyzed using item analysis and ANCOVA. Qualitative responses were coded in accordance with grounded theory research practices. Although there was no significant difference between the responses of the course participants and the control group, five causal conditions were identified as playing a major role in creating an experiential environment more conducive to behavior change: hands‐on experience, emotional response, human interaction, self‐efficacy, and intensity of experience. Based on the research conclusions, five additional causal conditions were added to create a more comprehensive, effective model for creating an agricultural environment more conducive to experiential learning: length of course, appropriateness and rigor of curriculum, learner‐centered curriculum, ongoing education, and metacognitive processes. A comprehensive grounded theory model was presented, and recommendations for future course design and research were identified.
Laser Bending of Aluminum Foam Sandwich Panels
Authors: Guglielmotti Alessandro , Quadrini, Fabrizio , Squeo Erica Anna , Tagliaferri Vincenzo
Published: August 2009

Aluminum foam sandwich panels were laser bent by means of a diode laser. Two panels different in thickness were used in bending tests; the effect of the main process parameters (laser power and scan velocity) on the bending efficiency was investigated as well as the contribution of the panel skin, and the protective gas. As a result, a very good formability was observed for the laser processed panels.
Lipid‐Like Nanoparticles for Small Interfering RNA Delivery to Endothelial Cells
Authors: Cho Seung‐Woo , Goldberg Michael , Son Sun Mi , Xu Qiaobing , Yang Fan , Mei Ying , Bogatyrev Said , Langer Robert , Anderson Daniel G.
Published: August 2009

Here, nanoparticles composed of lipid‐like materials (lipidoids) to facilitate non‐viral delivery of small interfering RNA (siRNA) to endothelial cells (ECs) are developed. Nanoparticles composed of siRNA and lipidoids with small size (∼200 nm) and positive charge (∼34 mV) are formed by self‐assembly of lipidoids and siRNA. Ten lipidoids are synthesized and screened for their ability to facilitate the delivery of siRNA into ECs. Particles composed of leading lipidoids show significantly better delivery to ECs than a leading commercially available transfection reagent, Lipofectamine 2000. As a model of potential therapeutic application, nanoparticles composed of the top performing lipidoid, NA114, are studied for their ability to deliver siRNA targeting anti‐angiogenic factor (SHP‐1) to human ECs. Silencing of SHP‐1 expression significantly enhances EC proliferation and decreases EC apoptosis under a simulated ischemic condition.
Atomic‐Layer Graphene as a Saturable Absorber for Ultrafast Pulsed Lasers
Authors: Bao Qiaoliang , Zhang Han , Wang Yu , Ni Zhenhua , Yan Yongli , Shen Ze Xiang , Loh Kian Ping , Tang Ding Yuan
Published: August 2009

The optical conductance of monolayer graphene is defined solely by the fine structure constant, α = $e^2 /\hbar c$ (where e is the electron charge, $\hbar $ is Dirac's constant and c is the speed of light). The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero‐gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, use of atomic layer graphene as saturable absorber in a mode‐locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the graphene thickness. These results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers. Graphene as a laser mode locker can have many merits such as lower saturation intensity, ultrafast recovery time, tunable modulation depth, and wideband tunability.
Wet and Dry Adhesion Properties of Self‐Selective Nanowire Connectors
Authors: Ko Hyunhyub , Zhang Zhenxing , Chueh Yu‐Lun , Ho Johnny C. , Lee Jongho , Fearing Ronald S. , Javey Ali
Published: August 2009

Here, the wet and dry adhesion properties of hybrid Ge/parylene nanowire (NW) connectors are examined. The ability of the NW connectors to bind strongly even under lubricating conditions, such as mineral oil, sheds light on the dominant role of van der Waals interactions in the observed adhesion. The superhydrophobic surface of the NW connectors enables the wet, self‐cleaning of contaminant particles from the surface, similar to the lotus effect. In addition, the effect of NW length on the shear adhesion strength, repeated usability, and robustness of the connectors, all critical properties for applications that require reversible binding of components, is examined.
Inkjet Printing—Process and Its Applications
Authors: Singh Madhusudan , Haverinen Hanna M. , Dhagat Parul , Jabbour Ghassan E.
Published: August 2009

In this Progress Report we provide an update on recent developments in inkjet printing technology and its applications, which include organic thin‐film transistors, light‐emitting diodes, solar cells, conductive structures, memory devices, sensors, and biological/pharmaceutical tasks. Various classes of materials and device types are in turn examined and an opinion is offered about the nature of the progress that has been achieved.
Bioorthogonal Chemistry: Fishing for Selectivity in a Sea of Functionality
Authors: Sletten Ellen M. , Bertozzi Carolyn R.
Published: August 2009

The study of biomolecules in their native environments is a challenging task because of the vast complexity of cellular systems. Technologies developed in the last few years for the selective modification of biological species in living systems have yielded new insights into cellular processes. Key to these new techniques are bioorthogonal chemical reactions, whose components must react rapidly and selectively with each other under physiological conditions in the presence of the plethora of functionality necessary to sustain life. Herein we describe the bioorthogonal chemical reactions developed to date and how they can be used to study biomolecules.
Mathematical model for mixing index in gas–solid fluidized bed: an analysis
Authors: Sahoo Abanti , Rana Subal
Published: August 2009

An available theoretical model for mixing index in gas‐solid fluidized bed has been analyzed for further modification and improvement. Assumption of 50% bed material moving in the upward direction and rest 50% in the downward direction considered for the above model (the counter‐flow circulation model) has been analyzed for optimum result. A computer program was run for different bed conditions by varying operating parameters, namely, the mixture composition, fractions of bed materials, minimum fluidization velocity of the jetsam particles and that of the bed materials (i.e. mixture of the jetsam and the flotsam particles). The developed model was solved by finite difference (central differencing). Fraction of the bed material moving in the upward direction was varied from 0 to 100% and the minimum fluidization velocity was varied within the Umf of the flotsam to that of the jetsam particles (i.e. 0.465–1.0335 m/s). Optimum fraction of bed materials with respect to its distribution (as per the earlier proposed model) in the upward and downward streams during the fluidization process was found to be 20 and 80%, respectively. The modified model was validated by conducting experiments on fluidization and studying the mixing characteristics of regular homogeneous materials (sago) in a 15 × 100 cm cylindrical column. Fairly good agreement was observed between the values of mixing index obtained from the proposed modified model and the experimental observations. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Characterization of an uneven DBD reactor for diesel PM removal
Authors: Yao Shuiliang , Kodama Satoshi , Yamamoto Shin , Fushimi Chihiro , Madokoro Kazuhiko , Mine Chieko , Fujioka Yuichi
Published: August 2009

An uneven dielectric barrier discharge (DBD) reactor of 21 electrode pairs that can improve the energy efficiency for the removal of particulate matter (PM) from a diesel engine is characterized. Ninety percent of PM (about 0.48 g/h) is removed by plasma discharges at an energy injection of 90 W into an exhaust gas (40 Nm3/h with PM emission rate 0.53 g/h). The discharge properties and relations of PM removal and energy efficiency with energy injection are given. The fuel penalty due to the use of the uneven DBD reactor is estimated. Comparison with other types of DBD reactors is carried out. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Synthesis and properties of random copolymers of 2,2‐dimethyltrimethylene carbonate and ethylene carbonate catalyzed by lanthanide tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)
Authors: Xu Ning , Liu Xin , Liu Yixin , Zhu Weipu , Chen Feng , Shen Zhiquan
Published: August 2009

Random copolymers of 2,2‐dimethyltrimethylene carbonate and ethylene carbonate (EC) were synthesized with lanthanide tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)s [Ln(DBMP)3; Ln = La, Nd, Sm, or Dy] as catalysts, among which La(DBMP)3 showed the highest activity. Poly(2,2‐dimethyltrimethylene carbonate‐co‐ethylene carbonate)s [poly(DTC‐co‐EC)]s with high molecular weights were prepared at room temperature and characterized with 1H‐NMR and size exclusion chromatography. The thermal behavior and crystalline properties of the poly(DTC‐co‐EC)s were analyzed with differential scanning calorimetry, thermogravimetric analysis, and X‐ray diffraction. The crystallinity and melting temperatures of the poly(DTC‐co‐EC)s both decreased with increasing EC content in the copolymers. The mechanical properties of these copolymers were also investigated with dynamic mechanical analysis and tensile strength measurements, which revealed that a reduction of the glass‐transition temperature and great enhancement of the tensile properties could be achieved with higher EC contents. These improvements in the thermal and mechanical properties indicate potential applications in biomedical research for novel polycarbonates. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Microwave‐initiated synthesis of polyacrylamide grafted sodium alginate: Synthesis and characterization
Authors: Sen Gautam , Singh Ram Prakash , Pal Sagar
Published: August 2009

Microwave‐initiated synthesis of polyacrylamide‐grafted sodium alginate, a graft copolymer with wide variety of applications has been reported in this study. The effect of reaction parameters (i.e., irradiation time and monomer concentration) onto the percentage grafting has been investigated. The resulting polymer has been characterized by a variety of characterization techniques such as intrinsic viscosity measurement, Fourier transform infrared spectra,13C NMR spectra, elemental analysis, thermogravimetric analysis, molecular weight determination using static light scattering analysis, and scanning electron micrographs. Further, the flocculation efficiency of this graft copolymer has been investigated in coal suspension. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Epoxidized natural rubber–alumina nanoparticle composites: Optimization of mixer parameters via response surface methodology
Authors: Mohamad Noraiham , Muchtar Andanastuti , Ghazali Mariyam Jameelah , Mohd Dahlan HJ. , Azhari Che Husna
Published: August 2009

Epoxidized natural rubber–alumina nanoparticle composites were prepared by melt compounding with an internal mixer for a constant filler loading of 10 phr. Mixer parameters such as the mixing temperature, mixing time, and rotor speed were screened and optimized with response surface methodology to maximize the impact strength. The parameters were selected as three independent variables and the impact strength (J/m) was selected as the response in a screening factor study. The mixing temperature and its interaction terms were identified as insignificant factors with a P value greater than 0.0500. The optimum calculated values of the tested variables (rotor speed and mixing time) for the maximum impact strength were found to be a rotor speed of 60 rpm and a mixing time of 6 min with a predicted impact strength of 208.88 J/m. These predicted optimum parameters were tested in real experiments. The final impact strength was found to be close to the predicted value of 215.84 J/m, with only a 3.33% deviation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Characterization of polyurethane resins by FTIR, TGA, and XRD
Authors: Trovati Graziella , Sanches Edgar Ap , Neto Salvador Claro , Mascarenhas Yvonne P. , Chierice Gilberto O.
Published: August 2009

Fourier Transformed Infrared Spectroscopy, Thermogravimetric Analysis, and X‐ray Diffractometry have been used to investigate the rigid, semi rigid, and soft polyurethane (PU) forms, which were developed by the Group of Analytic Chemistry and Technology of Polymers ‐ USP ‐ São Carlos. The –NCO/–OH ratios were 0.6, 0.5, and 0.3% for rigid, semi rigid, and soft PUs, respectively, showing that different ratios cause differences in thermal behaviors and crystalline structures of the synthesized PU resins. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
The impact of flare on disease costs of patients with systemic lupus erythematosus
Authors: Zhu Tracy Y. , Tam Lai‐shan , Lee Vivian W.‐Y. , Lee Kenneth K.‐C. , Li Edmund K.
Published: August 2009

Objective

To evaluate both direct and indirect costs of systemic lupus erythematosus (SLE) patients with and without flares from a societal perspective, and to investigate the impact of the severity and clinical manifestations of flares on direct/indirect costs.

Methods

A retrospective cost‐of‐illness study was performed on 306 SLE patients. Participants completed questionnaires on sociodemographics, employment status, and out‐of‐pocket expenses. Health resources consumption was recorded by chart review and patient self‐reported questionnaire. The total number of flares and involved organs during the preceding 12 months were recorded. Multiple linear regression was performed to determine the cost predictors.

Results

Patients with flares were younger, had shorter disease duration, and had higher disease activity at the time of the assessment. The overall incidence of lupus flares was 0.24 episodes per patient‐year. Patients with flares used more health care resources and incurred significantly higher annual direct and indirect costs. The mean total costs per patient‐year were 2‐fold higher for patients with flares ($22,580 versus $10,870 [2006 US dollars]; P < 0.0005). Multiple regression analysis showed that the number of flares was an independent explanatory variable associated with increased direct costs. Patients with multiorgan flares or renal/neuropsychiatric flares incurred higher direct costs compared with those with single‐organ flares or with other organ flares.

Conclusion

Patients with flares incur higher direct and indirect costs compared with those without flares. Major organ flares incur higher disease costs than other organ flares. Treatments that effectively control disease activity and prevent flares, especially major organ flares, may reduce the high costs associated with flare in SLE.