bluuebunny/crossref_metadata_2025 huggingface dataset:
The Method of Fundamental Solutions for Solving Exterior Axisymmetric Helmholtz Problems with High Wave-Number
Authors: Chen Wen , Lin Ji , Chen C.S.
Published: June 2013

In this paper, we investigate the method of fundamental solutions (MFS) for solving exterior Helmholtz problems with high wave-number in axisymmetric domains. Since the coefficient matrix in the linear system resulting from the MFS approximation has a block circulant structure, it can be solved by the matrix decomposition algorithm and fast Fourier transform for the fast computation of large-scale problems and meanwhile saving computer memory space. Several numerical examples are provided to demonstrate its applicability and efficacy in two and three dimensional domains.
B-Spline Gaussian Collocation Software for Two-Dimensional Parabolic PDEs
Authors: Li Zhi , Muir Paul
Published: June 2013

In this paper we describe newB-spline Gaussian collocation software for solving two-dimensional parabolic partial differential equations (PDEs) defined over a rectangular region. The numerical solution is represented as a bi-variate piecewise polynomial (using a tensor productB-spline basis) with time-dependent unknown coefficients. These coefficients are determined by imposing collocation conditions: the numerical solution is required to satisfy the PDE and boundary conditions at images of the Gauss points mapped onto certain subregions of the spatial domain. This leads to a large system of time-dependent differential algebraic equations (DAEs) which is solved using the DAE solver, DASPK. We provide numerical results in which we use the new software, called BACOL2D, to solve three test problems.
State transformations and ice nucleation in amorphous (semi-)solid organic aerosol
Authors: Baustian K. J. , Wise M. E. , Jensen E. J. , Schill G. P. , Freedman M. A. , Tolbert M. A.
Published: June 2013

Abstract. Amorphous (semi-)solid organic aerosol particles have the potential to serve as surfaces for heterogeneous ice nucleation in cirrus clouds. Raman spectroscopy and optical microscopy have been used in conjunction with a cold stage to examine water uptake and ice nucleation on individual amorphous (semi-)solid particles at atmospherically relevant temperatures (200–273 K). Three organic compounds considered proxies for atmospheric secondary organic aerosol (SOA) were used in this investigation: sucrose, citric acid and glucose. Internally mixed particles consisting of each organic and ammonium sulfate were also investigated. Results from water uptake experiments followed the shape of a humidity-induced glass transition (Tg(RH)) curve and were used to construct state diagrams for each organic and corresponding mixture. Experimentally derived Tg(RH) curves are in good agreement with theoretical predictions of Tg(RH) following the approach of Koop et al. (2011). A unique humidity-induced glass transition point on each state diagram, Tg'(RH), was used to quantify and compare results from this study to previous works. Values of Tg'(RH) determined for sucrose, glucose and citric acid glasses were 236, 230 and 220 K, respectively. Values of Tg'(RH) for internally mixed organic/sulfate particles were always significantly lower; 210, 207 and 215 K for sucrose/sulfate, glucose/sulfate and citric acid/sulfate, respectively. All investigated SOA proxies were observed to act as heterogeneous ice nuclei at tropospheric temperatures. Heterogeneous ice nucleation on pure organic particles occurred at Sice = 1.1–1.4 for temperatures below 235 K. Particles consisting of 1:1 organic-sulfate mixtures took up water over a greater range of conditions but were in some cases also observed to heterogeneously nucleate ice at temperatures below 202 K (Sice= 1.25–1.38). Polynomial curves were fitted to experimental water uptake data and then incorporated into the Community Aerosol Radiation Model for Atmospheres (CARMA) along with the predicted range of humidity-induced glass transition temperatures for atmospheric SOA from Koop et al. (2011). Model results suggest that organic and organic/sulfate aerosol could be glassy more than 60% of the time in the midlatitude upper troposphere and more than 40% of the time in the tropical tropopause region (TTL). At conditions favorable for ice formation (Sice > 1), particles in the TTL are expected to be glassy more than 50% of the time for temperatures below 200 K. Results from this study suggests that amorphous (semi-)solid organic particles are often present in the upper troposphere and that heterogeneous ice formation on this type of particle may play an important role in cirrus cloud formation.
Comparison of MODIS 3 km and 10 km resolution aerosol optical depth retrievals over land with airborne sunphotometer measurements during ARCTAS summer 2008
Authors: Livingston J. M. , Redemann J. , Shinozuka Y. , Johnson R. , Russell P. B. , Zhang Q. , Mattoo S. , Remer L. , Levy R. , Munchak L. , Ramachandran S.
Published: June 2013

Abstract. Airborne sunphotometer measurements acquired by the NASA Ames Airborne Tracking Sunphotometer (AATS-14) from the NASA P-3 research aircraft are used to evaluate dark-target over-land retrievals of extinction aerosol optical depth (AOD) from spatially and temporally near-coincident measurements by the Moderate Resolution Imaging Spectroradiometer (MODIS) during the summer 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. The new MODIS Collection 6 aerosol data set includes retrievals of AOD at both 10 km × 10 km and 3 km × 3 km (at nadir) resolution. In this paper we compare MODIS and AATS AOD at 553 nm in 58 10 km and 134 3 km retrieval grid cells. These AOD values were derived from data collected over Canada on four days during short time segments of five (four Aqua and one Terra) satellite overpasses of the P-3 during low altitude P-3 flight tracks. Three of the five MODIS/AATS coincidence events were dominated by smoke: one included a P-3 transect of a well-defined smoke plume in clear sky, but two were confounded by the presence of scattered clouds above smoke. The clouds limited the number of MODIS retrievals available for comparison, and led to MODIS AOD retrievals that underestimated the corresponding AATS values. This happened because the MODIS aerosol cloud mask selectively removed 0.5 km pixels containing smoke and clouds before the aerosol retrieval. The other two coincidences (one Terra and one Aqua) occurred during one P-3 flight on the same day and in the same general area, in an atmosphere characterized by a relatively low AOD (< 0.3), and spatially homogeneous regional haze from smoke outflow with no distinguishable plume. For the ensemble data set for MODIS AOD retrievals with the highest-quality flag, MODIS AOD agrees with AATS AOD within the expected MODIS over-land AOD uncertainty in 60% of the retrieval grid cells at 10 km resolution and 69% at 3 km resolution. These values improve to 65% and 74%, respectively, when the cloud-contaminated case with the strongest plume is excluded. We find that the standard MODIS dark-target over-land retrieval algorithm fails to retrieve AOD for thick smoke, not only in cloud-contaminated regions, but also in clear sky. We attribute this to deselection, by the cloud and/or bright surface masks, of 0.5 km resolution pixels that contain smoke.
Characterization of an aerodynamic lens for transmitting particles > 1 micrometer in diameter into the Aerodyne aerosol mass spectrometer
Authors: Williams L. R. , Gonzalez L. A. , Peck J. , Trimborn D. , McInnis J. , Farrar M. R. , Moore K. D. , Jayne J. T. , Robinson W. A. , Lewis D. K. , Onasch T. B. , Canagaratna M. R. , Trimborn A. , Timko M. T. , Magoon G. , Deng R. , Tang D. , de la Rosa Blanco E. , Prévôt A. S. H. , Smith K. A. , Worsnop D. R.
Published: June 2013

Abstract. We have designed and characterized a new inlet and aerodynamic lens for the Aerodyne aerosol mass spectrometer (AMS) that transmits particles between 80 nm and more than 3 μm in diameter. The design of the inlet and lens was optimized with computational fluid dynamics (CFD) modeling of particle trajectories. Major changes include a redesigned critical orifice holder and valve assembly, addition of a relaxation chamber behind the critical orifice, and a higher lens operating pressure. The transmission efficiency of the new inlet and lens was characterized experimentally with size-selected particles. Experimental measurements are in good agreement with the calculated transmission efficiency.
Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra
Authors: Rieger L. A. , Bourassa A. E. , Degenstein D. A.
Published: June 2013

Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) on-board the Odin satellite has now taken over a decade of limb scatter measurements that have been used to retrieve the Version 5 stratospheric aerosol extinction product. This product is retrieved using a representative particle size distribution to calculate scattering cross sections and scattering phase functions for the forward model calculations. In this work the information content of OSIRIS measurements with respect to stratospheric aerosol is systematically examined for the purpose of retrieving particle size information along with the extinction coefficient. The benefit of using measurements at different wavelengths and scattering angles in the retrieval is studied and it is found that incorporation of the 1530 nm radiance measurement is key for a robust retrieval of particle size information. It is also found that using OSIRIS measurements at different solar geometries simultaneously provides little additional benefit. Based on these results, an improved aerosol retrieval algorithm is developed that couples the retrieval of aerosol extinction and mode radius of a log-normal particle size distribution. Comparison of these results with coincident measurements from SAGE III show agreement in retrieved extinction to within approximately 10% over the bulk of the aerosol layer, which is comparable to Version 5. The retrieved particle size, when converted to Ångström coefficient, shows good qualitative agreement with SAGE II measurements made at somewhat shorter wavelengths.
Evaluating climate field reconstruction techniques using improved emulations of real-world conditions
Authors: Wang J. , Emile-Geay J. , Guillot D. , Smerdon J. E. , Rajaratnam B.
Published: June 2013

Abstract. Pseudoproxy experiments (PPEs) have become an essential framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multi-proxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. Additionally, an investigation of a real-world global multi-proxy network suggests that proxies are not exclusively indicators of local climate; rather, many are indicative of large-scale teleconnections. A suite of PPEs constructed from a millennium-length general circulation model simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least square embedded within the regularized EM algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but rather is a function of the type of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of pseudoproxy noise. Results collectively highlight the importance of designing realistic pseudoproxy networks and implementing multiple noise realizations of PPEs. The results also underscore the difficulty in finding the proper bias-variance tradeoff for jointly optimizing the spatial skill of CFRs and the fidelity of the global mean reconstructions.
On the parallelization of atmospheric inversions of CO2 surface fluxes within a variational framework
Authors: Chevallier F.
Published: June 2013

Abstract. The variational formulation of Bayes' theorem allows inferring CO2 sources and sinks from atmospheric concentrations at much higher time–space resolution than the ensemble or analytical approaches. However, it usually exhibits limited scalable parallelism. This limitation hinders global atmospheric inversions operated on decadal time scales and regional ones with kilometric spatial scales because of the computational cost of the underlying transport model that has to be run at each iteration of the variational minimization. Here, we introduce a physical parallelization (PP) of variational atmospheric inversions. In the PP, the inversion still manages a single physically and statistically consistent window, but the transport model is run in parallel overlapping sub-segments in order to massively reduce the computation wall-clock time of the inversion. For global inversions, a simplification of transport modelling is described to connect the output of all segments. We demonstrate the performance of the approach on a global inversion for CO2 with a 32 yr inversion window (1979–2010) with atmospheric measurements from 81 sites of the NOAA global cooperative air sampling network. In this case, we show that the duration of the inversion is reduced by a seven-fold factor (from months to days), while still processing the three decades consistently and with improved numerical stability.
An approach to computing direction relations between separated object groups
Authors: Yan H. , Wang Z. , Li J.
Published: June 2013

Abstract. Direction relations between object groups play an important role in qualitative spatial reasoning, spatial computation and spatial recognition. However, none of existing models can be used to compute direction relations between object groups. To fill this gap, an approach to computing direction relations between separated object groups is proposed in this paper, which is theoretically based on Gestalt principles and the idea of multi-directions. The approach firstly triangulates the two object groups; and then it constructs the Voronoi Diagram between the two groups using the triangular network; after this, the normal of each Vornoi edge is calculated, and the quantitative expression of the direction relations is constructed; finally, the quantitative direction relations are transformed into qualitative ones. The psychological experiments show that the proposed approach can obtain direction relations both between two single objects and between two object groups, and the results are correct from the point of view of spatial cognition.
Errors in climate model daily precipitation and temperature output: time invariance and implications for bias correction
Authors: Maurer E. P. , Das T. , Cayan D. R.
Published: June 2013

Abstract. When correcting for biases in general circulation model (GCM) output, for example when statistically downscaling for regional and local impacts studies, a common assumption is that the GCM biases can be characterized by comparing model simulations and observations for a historical period. We demonstrate some complications in this assumption, with GCM biases varying between mean and extreme values and for different sets of historical years. Daily precipitation and maximum and minimum temperature from late 20th century simulations by four GCMs over the United States were compared to gridded observations. Using random years from the historical record we select a "base" set and a 10 yr independent "projected" set. We compare differences in biases between these sets at median and extreme percentiles. On average a base set with as few as 4 randomly-selected years is often adequate to characterize the biases in daily GCM precipitation and temperature, at both median and extreme values; 12 yr provided higher confidence that bias correction would be successful. This suggests that some of the GCM bias is time invariant. When characterizing bias with a set of consecutive years, the set must be long enough to accommodate regional low frequency variability, since the bias also exhibits this variability. Newer climate models included in the Intergovernmental Panel on Climate Change fifth assessment will allow extending this study for a longer observational period and to finer scales.
A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches
Authors: Favier P. , Bertrand D. , Eckert N. , Naaim M.
Published: June 2013

Abstract. Snow avalanches are a threat to many kinds of elements (human beings, communication axes, structures, etc.) in mountain regions. For risk evaluation, the vulnerability assessment of civil engineering structures such as buildings and dwellings exposed to avalanches still needs to be improved. This paper presents an approach to determine the fragility curves associated with Reinforced Concrete (RC) structures loaded by typical avalanche pressures and provides quantitative results for different geometrical configurations. First, several mechanical limit states of the RC wall are defined using classical engineering approaches (Eurocodes – EC2), and the pressure of structure collapse is calculated from the usual yield line theory. Next, the failure probability is evaluated as a function of avalanche loading using a Monte Carlo approach, and sensitivity studies (Sobol indexes) are conducted to estimate the respective weight of the RC wall model inputs. Finally, fragility curves and relevant indicators such a their mean and fragility range are proposed for the different structure boundary conditions tested. The influence of the input distributions on the fragility curves is investigated. This shows the wider fragility range and/or the slight shift in the median that has to be considered when the possible correlation/non-Gaussian nature of the input distributions is accounted for.
The physical basis for gas transport through polar firn: a case study at Summit, Greenland
Authors: Adolph A. C. , Albert M. R.
Published: June 2013

Abstract. Compared to other natural porous materials, relatively little is known about the physical nature of polar firn. This intricate network of ice and pore space that comprises the top 60–100 m of the polar ice sheets is the framework that forms the natural archive of past climate information. Despite the many implications for ice core interpretation, direct measurements of physical properties throughout the firn column are limited. Models of gas transport through firn are used to interpret in-situ chemical data which is retrieved to analyze past atmospheric composition. These traditional models treat the firn as a "black box," with gas transport parameters tuned to match gas concentrations with depth to known atmospheric histories. Though this method has been largely successful and provided very useful insights, there are still many questions and uncertainties to be addressed. This work seeks to understand the impact of firn structure on gas transport in firn from a first principles standpoint through direct measurements of permeability, gas diffusivity and microstructure. The relationships between gas transport properties and microstructure will be characterized and compared to existing relationships for general porous media. Direct measurements of gas diffusivity are compared to diffusivities deduced from models based on firn air chemical sampling. Our comparison illuminates the primary importance of including microstructural parameters, beyond just porosity or density, in mass transport modeling, and it provides insights about the nature of gas transport throughout the firn column. Guidance is provided for development of next-generation firn air transport models.
Fault Tolerant Attitude Control for Flexible Satellite with Uncertainties and Actuator Saturation
Authors: Meng Qiang , Zhang Tao , Li Da-Chuan , Liang Jie-Mei , Liu Bo , Song Jing-Yan
Published: June 2013

A novel fault tolerant control scheme, using model-based control and time delay control theories, is proposed for flexible satellites with uncertainties and actuator saturation and the stability condition of the scheme is analysed. The moment–of-inertia uncertainty, actuator faults uncertainty, space environment disturbances and the actuator saturation are analysed. The computable control torques, including the space environmental torques, reaction wheel dynamics and the known flexible appendage dynamics, are formulated using the model-based control. The unknown flexible satellite dynamics is estimated according to its one-step previous value and employed to update the control command; this greatly reduces the conservativeness and enhances the pointing accuracy. Numerical simulations under different conditions demonstrate the advantages of the novel proposed controller compared to the conventional PD controller and a simplified fault tolerant controller.
3D Flapping Trajectory of a Micro-Air-Vehicle and its Application to Unsteady Flow Simulation
Authors: Yang Lung-Jieh , Hsiao Fu-Yuen , Tang Wen-Tzu , Huang I-Cheng
Published: June 2013

A three-dimensional (3D) trajectory detection framework using two high-speed cameras for the flapping flexible wing of a micro-air-vehicle (MAV) is presented. This MAV, which is called the “Golden Snitch”, has a successful flight record of 8 minutes. We embed the flexible wingskin with a nine light emitting diode (LED) array as the light enhancing marker and capsulate it with parylene (poly-para-xylylene) as the protection layer. We confirm an oblique figure of eight trajectory of this MAV's wing with time-varying coordinate data. The corresponding aerofoil of the main wings' profiles was subjected to the time-varying coordinate data, yielding a resolution of a 1/70 wing beating cycle of 15Hz flapping. The trajectory information is first demonstrated as the moving boundaries of an unsteady flow simulation around a flapping flexible wing.
Modelling Hospital Materials Management Processes
Authors: Iannone Raffaele , Lambiase Alfredo , Miranda Salvatore , Riemma Stefano , Sarno Debora
Published: June 2013

Materials management is an important issue for healthcare systems because it influences clinical and financial outcomes. Before selecting, adapting and implementing leading or optimized practices, a good understanding of processes and activities has to be developed.

In real applications, the information flows and business strategies involved are different from hospital to hospital, depending on context, culture and available resources; it is therefore difficult to find a comprehensive and exhaustive description of processes, even more so a clear formalization of them.

The objective of this paper is twofold. First, it proposes an integrated and detailed analysis and description model for hospital materials management data and tasks, which is able to tackle information from patient requirements to usage, from replenishment requests to supplying and handling activities. The model takes account of medical risk reduction, traceability and streamlined processes perspectives. Second, the paper translates this information into a business process model and mathematical formalization.

The study provides a useful guide to the various relevant technology-related, management and business issues, laying the foundations of an efficient reengineering of the supply chain to reduce healthcare costs and improve the quality of care.
An Overview of QT Interval Assessment in Safety Pharmacology
Authors: Guillaume Philippe , Goineau Sonia , Froget Guillaume
Published: June 2013

Medicinal products that prolong cardiac repolarization, as assessed in terms of prolongation of the QT interval of the electrocardiogram, may trigger torsade de pointe, a potentially fatal arrhythmia. The lethality of this risk necessitates a detailed preclinical evaluation before initiating clinical trials. The strategy for assessing the potential of new chemical entities to cause QT interval prolongation involves two complementary approaches. An in vivo test provides information on the potential of the agent to prolong the QT interval under near‐physiological conditions. The results are mostly descriptive, providing little insight into the mechanisms of action. In vitro experiments provide more mechanistic data, although the test procedure is far removed from the clinical situation. While both approaches have reasonable predictive value, the results may depend largely on the experimental conditions employed. Discussed in this unit are experimental issues that should be considered when testing agents for their potential to cause arrhythmias, as well as general strategies for understanding the problems associated with this cardiovascular risk. Curr. Protoc. Pharmacol. 61:10.7.1‐10.7.14 © 2013 by John Wiley & Sons, Inc.
Multilevel‐statistical reformulation of citation‐based university rankings: The Leiden ranking 2011/2012
Authors: Bornmann Lutz , Mutz Rüdiger , Daniel Hans‐Dieter
Published: June 2013

Since the 1990s, with the heightened competition and the strong growth of the international higher education market, an increasing number of rankings have been created that measure the scientific performance of an institution based on data. The Leiden Ranking 2011/2012 (LR) was published early in 2012. Starting from Goldstein and Spiegelhalter's (1996) recommendations for conducting quantitative comparisons among institutions, in this study we undertook a reformulation of the LR by means of multilevel regression models. First, with our models we replicated the ranking results; second, the reanalysis of the LR data showed that only 5% of the PPtop10% total variation is attributable to differences between universities. Beyond that, about 80% of the variation between universities can be explained by differences among countries. If covariates are included in the model the differences among most of the universities become meaningless. Our findings have implications for conducting university rankings in general and for the LR in particular. For example, with Goldstein‐adjusted confidence intervals, it is possible to interpret the significance of differences among universities meaningfully: Rank differences among universities should be interpreted as meaningful only if their confidence intervals do not overlap.
Exploring methods to improve access to Music resources by aligning library Data with Linked Data: A report of methodologies and preliminary findings
Authors: Gracy Karen F. , Zeng Marcia Lei , Skirvin Laurence
Published: June 2013

As a part of a research project aiming to connect library data to the unfamiliar data sets available in the Linked Data (LD) community's CKAN Data Hub (thedatahub.org), this project collected, analyzed, and mapped properties used in describing and accessing music recordings, scores, and music‐related information used by selected music LD data sets, library catalogs, and various digital collections created by libraries and other cultural institutions. This article reviews current efforts to connect music data through the Semantic Web, with an emphasis on the Music Ontology (MO) and ontology alignment approaches; it also presents a framework for understanding the life cycle of a musical work, focusing on the central activities of composition, performance, and use. The project studied metadata structures and properties of 11 music‐related LD data sets and mapped them to the descriptions commonly used in the library cataloging records for sound recordings and musical scores (including MARC records and their extended schema.org markup), and records from 20 collections of digitized music recordings and scores (featuring a variety of metadata structures). The analysis resulted in a set of crosswalks and a unified crosswalk that aligns these properties. The paper reports on detailed methodologies used and discusses research findings and issues. Topics of particular concern include (a) the challenges of mapping between the overgeneralized descriptions found in library data and the specialized, music‐oriented properties present in the LD data sets; (b) the hidden information and access points in library data; and (c) the potential benefits of enriching library data through the mapping of properties found in library catalogs to similar properties used by LD data sets.
Nitrogen‐Rich Porous Adsorbents for CO2 Capture and Storage
Authors: Li Pei‐Zhou , Zhao Yanli
Published: June 2013

The construction of physical or chemical adsorbents for CO2 capture and sequestration (CCS) is a vital technology in the interim period on the way towards a sustainable low‐carbon future. The search for efficient materials to satisfy the increasing demand for CCS has become extremely important. Porous materials, including porous silica, porous carbons, and newly developed metal–organic frameworks and porous organic polymers, possessing regular and well‐defined porous geometry and having a high surface area and pore volume, have been widely studied for separations on laboratory scale. On account of the dipole–quadrupole interactions between the polarizable CO2 molecule and the accessible nitrogen site, the investigations have indicated that the incorporation of accessible nitrogen‐donor groups into the pore walls of porous materials can improve the affinity to CO2 and increase the CO2 uptake capacity and selectivity. The CO2‐adsorption process based on solid nitrogen‐rich porous adsorbents does generally not require heating of a large amount of water (60–70 wt %) for regeneration, while such a heating approach cannot be avoided in the regeneration of amine‐based solution absorption processes. Thus, nitrogen‐rich porous adsorbents show good regeneration properties without sacrificing high separation efficiency. As such, nitrogen‐rich porous materials as highly promising CO2 adsorbents have been broadly fabricated and intensively investigated. This Focus Review highlights recent significant advances in nitrogen‐rich porous materials for CCS.
Synthesis of Phenanthridinones from N‐Methoxybenzamides and Aryltriethoxysilanes through RhIII‐Catalyzed CH and NH Bond Activation
Authors: Senthilkumar Natarajan , Parthasarathy Kanniyappan , Gandeepan Parthasarathy , Cheng Chien‐Hong
Published: June 2013

An efficient method for the one‐pot synthesis of substituted phenanthridinone derivatives from N‐methoxybenzamides and aryltriethoxysilanes through rhodium‐catalyzed dual CH bond activation and annulation reactions is described. A double‐cycle mechanism is proposed to account for this catalytic reaction. In addition, isotope‐labeling studies were performed to understand the intimate mechanism of the reaction.
Metabolic costs of amino acid and protein production in Escherichia coli
Authors: Kaleta Christoph , Schäuble Sascha , Rinas Ursula , Schuster Stefan
Published: June 2013

Escherichia coli is the most popular microorganism for the production of recombinant proteins and is gaining increasing importance for the production of low‐molecular weight compounds such as amino acids. The metabolic cost associated with the production of amino acids and (recombinant) proteins from glucose, glycerol and acetate was determined using three different computational techniques to identify those amino acids that put the highest burden on the biosynthetic machinery of E. coli. Comparing the costs of individual amino acids, we find that methionine is the most expensive amino acid in terms of consumed mol of ATP per molecule produced, while leucine is the most expensive amino acid when taking into account the cellular abundances of amino acids. Moreover, we show that the biosynthesis of a large number of amino acids from glucose and particularly from glycerol provides a surplus of energy, which can be used to balance the high energetic cost of amino acid polymerization.
Ascorbic acid synthesis and metabolism in maize are subject to complex and genotype‐dependent feedback regulation during endosperm development
Authors: Sanahuja Georgina , Farré Gemma , Bassie Ludovic , Zhu Changfu , Christou Paul , Capell Teresa
Published: June 2013

L‐ascorbic acid (vitamin C) is an antioxidant and electron donor whose metabolism in plants is under strict feedback control. The factors that influence L‐ascorbic acid accumulation in staple crops are only partially understood. One way to gain insight into the regulation of L‐ascorbic acid metabolism is to investigate the endogenous pathways in various genetic backgrounds and characterize their interactions with transgenes encoding relevant enzymes. In an initial step, we investigated the developmental profile of L‐ascorbic acid accumulation in the endosperm of three diverse maize genotypes and a transgenic line expressing rice dehydroascorbate reductase, which enhances L‐ascorbic acid recycling. We determined the transcript levels of all the key genes in the L‐ascorbic acid metabolic pathways as well as the specific levels of ascorbic acid and dehydroascorbate. L‐ascorbic acid levels were high 20 days after pollination and declined thereafter. We found significant genotype‐dependent variations in the transcript levels of some genes, with particular complexity in the ascorbic acid recycling pathway. Our data will help to elucidate the complex mechanisms underlying the regulation of L‐ascorbic acid metabolism in plants, particularly the impact of genetic background on the strict regulation of ascorbic acid metabolism in endosperm cells.
Enzymatic activity preservation and protection through entrapment within degradable hydrogels
Authors: Mariani Angela M. , Natoli Mary E. , Kofinas Peter
Published: June 2013

This work aims to develop a repeatable enzyme entrapment method that preserves activity within an amicable environment while resisting activity reduction in the presence of environmental challenges. Advances in such methods have wide potential use in biosensor applications. In this work β‐galactosidase (lactase) enzyme was entrapped within hydrogel matrices of acrylamide (ACR) crosslinked with N,N′‐methylenebisacrylamide (BIS, non‐degradable) or poly(ethylene glycol) diacrylate (PEGDA, degradable) to create “biogels.” Diffusivity studies of control, enzyme free, hydrogel constructs showed near‐Fickian swelling behavior in PBS regardless of crosslinker type or density. As expected, the swelling rate, Ks, decreased when increasing the crosslink density from 78.6 to 14.7 min−1 over a range of 1–20 mol% PEGDA indicating that diffusivity into the matrix is dependent on crosslink density. Fabricated biogels were evaluated for maintained enzyme activity in the 7 and 8 pH range. PEGDA crosslinked gels consistently showed improved enzymatic activity retention as compared to BIS crosslinked gels. As PEGDA crosslink density increased from 5 to 10 mol%, enzymatic activity retention post‐initial entrapment increased. Higher PEGDA crosslink densities between 15% and 40% decreased enzymatic activity due to assumed steric hindrance of the entrapped enzyme and also decreased substrate and product diffusion. Increased enzymatic stability was observed in 40 mol% PEGDA crosslinked gels. The biogels were pH challenged to 8.0 and stability, measured as retention of activity, was observed to be 91%. Free, non‐entrapped, solution based enzyme conversion only retained 23% activity under the same pH challenge conditions. No significant loss of active enzyme was determined to elute out of the biogels during storage in PBS or during biogel wash and recycling. This entrapment method illustrates the potential to sterically hinder and diffusively impede enzymes from performing their function. Degradation of the network crosslinks can then potentially enable the reactivation of the enzyme at a site and time dictated by the user. Biotechnol. Bioeng. 2013;110: 2994–3002. © 2013 Wiley Periodicals, Inc.
High‐Solid‐Content Emulsions of PVC: Scale‐Down of an Industrial Process for Enhanced Understanding of Particle Formation Part 2: Preliminary Analysis of Seed Production
Authors: McKenna T. F. L. , Pascal T. , Lys T.
Published: June 2013

A scale‐down study of an industrial reactor for the production of polyvinyl chloride (PVC) via an emulsion polymerization process was performed in order to understand the source of batch‐to‐batch variations in product quality. In Part 2 of this series of three papers, it is demonstrated that a large excess of base is required to control the particle size distribution of the seed process. Although differences exist between the critical micelle concentration and the surface area occupied by a surfactant molecule for linear and branched isomers of the surfactant sodium dodecyl benzene sulfonate, the characteristics of the molecules from different suppliers were reasonably similar.
Bright Mono‐aqua Europium Complexes Based on Triazacyclononane That Bind Anions Reversibly and Permeate Cells Efficiently
Authors: Butler Stephen J. , McMahon Brian K. , Pal Robert , Parker David , Walton James W.
Published: June 2013

A series of five europium(III) complexes has been prepared from heptadentate N5O2 ligands that possess a brightness of more than 10 mM−1 cm−1 in water, following excitation over the range λ=330–355 nm. Binding of several oxy anions has been assessed by emission spectral titrimetric analysis, with the binding of simple carboxylates, lactate and citrate involving a common ligation mode following displacement of the coordinated water. Selectivity for bicarbonate allows the rapid determination of this anion in human serum, with Kd=37 mM (295 K). The complexes are internalised quickly into mammalian cells and exhibit a mitochondrial localisation at early time points, migrating after a few hours to reveal a predominant lysosomal distribution. Herein, we report the synthesis and complexation behaviour of strongly emissive europium (III) complexes that bind oxy‐anions in aqueous media with an affinity and selectivity profile that is distinctively different from previously studied systems.
A Molecular Toolkit for the Functionalization of Titanium‐Based Biomaterials That Selectively Control Integrin‐Mediated Cell Adhesion
Authors: Rechenmacher Florian , Neubauer Stefanie , Mas‐Moruno Carlos , Dorfner Petra M. , Polleux Julien , Guasch Judith , Conings Bert , Boyen Hans‐Gerd , Bochen Alexander , Sobahi Tariq R. , Burgkart Rainer , Spatz Joachim P. , Fässler Reinhard , Kessler Horst
Published: June 2013

We present a click chemistry‐based molecular toolkit for the biofunctionalization of materials to selectively control integrin‐mediated cell adhesion. To this end, α5β1‐selective RGD peptidomimetics were covalently immobilized on Ti‐based materials, and the capacity to promote the selective binding of α5β1 was evaluated using a solid‐phase integrin binding assay. This functionalization strategy yielded surfaces with a nine‐fold increased affinity for α5β1, in comparison to control samples, and total selectivity against the binding of the closely related integrin αvβ3. Moreover, our methodology allowed the screening of several phosphonic acid containing anchoring units to find the best spacer–anchor moiety required for establishing an efficient binding to titanium and to promote selective integrin binding. The integrin subtype specificity of these biofunctionalized surfaces was further examined in vitro by inducing selective adhesion of genetically modified fibroblasts, which express exclusively the α5β1 integrin. The versatility of our molecular toolkit was proven by shifting the cellular specificity of the materials from α5β1‐ to αvβ3‐expressing fibroblasts by using an αvβ3‐selective peptidomimetic as coating molecule. The results shown here represent the first functionalization of Ti‐based materials with α5β1‐ or αvβ3‐selective peptidomimetics that allow an unprecedented control to discriminate between α5β1‐ and αvβ3‐mediated adhesions. The role of these two integrins in different biological events is still a matter of debate and is frequently discussed in literature. Thus, such bioactive titanium surfaces will be of great relevance for the study of integrin‐mediated cell adhesion and the development of new biomaterials targeting specific cell types.
ChemInform Abstract: Click Chemistry with 2‐Ethynyl‐4,5,6,7‐tetrahydroindoles: Towards Functionalized Tetrahydroindole—Triazole Ensembles.
Authors: Sobenina Lyubov N. , Tomilin Denis N. , Ushakov Igor A. , Mikhaleva Albina I. , Ma J. Sh. , Yang G. , Trofimov Boris A.
Published: June 2013

1,3‐Dipolar cycloaddition of the azide anion with internal alkynes of type (I) bearing an acyl or ester moiety offers a direct synthesis of the target scaffolds under very mild conditions.
Characterisation of petrologic end members of oil sands from the athabasca region, Alberta, Canada
Authors: Osacky M. , Geramian M. , Dyar M. D. , Sklute E. C. , Valter M. , Ivey D. G. , Liu Q. , Etsell T. H.
Published: June 2013

The aim of this study was to perform mineral and chemical characterisation of the four petrologic end members of Alberta oil sands in order to better understand the mineralogical and geochemical factors affecting bitumen extraction. X‐ray diffraction (XRD) results revealed that the petrologic end members contain a variable amount of quartz, clay minerals, carbonates, K‐feldspar, TiO2minerals and pyrite and the Fe‐containing phases were also observed in Mössbauer spectra. Scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX) analysis also showed the presence of Fe–Ti oxide minerals. Mössbauer results also indicated the presence of lepidocrocite in the fine fractions in amounts below the detection limit of XRD. Interstratified illite–smectite was found only in clay‐rich petrologic end members. Calcite and dolomite were primarily concentrated in the fine fractions of marine petrologic end members. Conversely, siderite was found mainly in the coarse fraction of estuarine petrologic end members.

The relative amount of toluene insoluble organics was higher in the fine fractions of marine petrologic end members.
Effect of Water Quality on Phytoplankton Structure in Oxbow Lakes under Anthropogenic and Non‐Anthropogenic Impacts
Authors: Wilk‐Woźniak Elżbieta , Ligęza Sławomir , Shubert Elliot
Published: June 2013

In this study, we present the effects of environmental factors on phytoplankton in two different oxbow lakes formed from the Vistula River. One of these lakes is under extreme anthropogenic pressure, i.e. impacted by industrial and municipal effluents and characterized by high water temperature and high concentrations of ions. The other oxbow lake is located in a natural forest with some its abiotic factors lower compared to the first oxbow lake. There were significant changes among environmental parameters, which influenced significant differences between the phytoplankton populations. The dominant algae of the impacted oxbow were small centric diatoms, which are able to rapidly absorb nutrients and have a rapid turnover. The results demonstrated that human impacted lake was a habitat, where species with a broad range of ecological requirements survive. However, these habitats are also more vulnerable for the entry and colonization of invasive algal species. In the forest oxbow lake, without human impact, heterogeneity of water quality parameters resulted in different specific habitats. Oxbow lakes are important as biodiversity hotspots for rare and/or endemic species.
Aluminum and Cadmium Forms in Stressed Rhizosphere Soil and Their Bioavailability to Two Hordeum vulgare L. Varieties
Authors: Guo Tian‐Rong , Sun Lifu , Han Li , Qiu Muqing
Published: June 2013

The effects of aluminum (Al) and cadmium (Cd) single and combinational treatments on two barley varieties differing in Al tolerance were examined in terms of chemical forms of Al and Cd in the rhizosphere soil and their plant availability. Our results showed that acidic‐soluble inorganic Al, humic acidic Al, and residue Cd were the predominant form(s) of Al and Cd in the rhizosphere soil of both barley varieties. The contents of different Al and Cd forms, especially for the exchangeable form, as well as Al and Cd contents in plants significantly increased under stress treatments. Meanwhile, stress treatments significantly reduced grain yield. In comparison with the single metal treatments, combinational stress increased the contents of exchangeable Al and Fe–Mn‐oxide‐bound Cd, but showed a decrease or no effect on the other forms. As a result, combinational stress led to a higher Al but a lower Cd accumulation in plants, and more reduction in grain yield. Increase in the contents of bioavailable Al and Cd forms in the stressed rhizosphere soil and in the concentrations of Al or Cd in plant parts was higher in the Al sensitive variety.
EXAFS studies of nanostructured Finemet‐type alloys
Authors: Swilem Y.
Published: June 2013

The nanostructure of nanocrystalline Fe66Cr8Cu1Nb3Si13B9 alloys has been studied using extended X‐ray absorption fine structure (EXAFS) and analyzed by the cumulant method. Application of the cumulant method enables us to determine the nearest‐neighbor interatomic distance and the coordination number for chromium and copper atoms, and thus we are able to obtain detailed knowledge about the role of both Cr and Cu in the structure of nanocrystals at various stages of crystallization. A detailed analysis of the distribution of alloying elements in the grains and grain boundaries reveals the accumulation of Cr in the surrounding of Fe(Si) nanocrystals. The presence of Cr in the surroundings of Fe(Si) can influence the content's arrangement of the nanograins, allowing diffusion of Si atoms in the grain boundaries. Simulated X‐ray absorption spectra of the model produced by FEFF9.05 and the proposed Cu clustering of 19 atoms with average cluster size of about 0.4 nm show a good resemblance to the experimental data of the Cu k‐edge.
Quality of service analysis and resource allocation scheme for Long‐Term Evolution network
Authors: Sallabi Farag , Shuaib Khaled
Published: June 2013

In this paper, we analyze the quality of service (QoS) framework supported by the Long‐Term Evolution standard and model the behavior of a finite‐state downlink wireless fading channel based on the configurations and system parameters provided by the 3GPP Long‐Term Evolution and provide experimental results. The model can be used to provide realistic physical layer input to evaluate the performance of algorithms at the upper layers. For example, the medium access control layer will use this data to test the performance of scheduling, admission control, power control, and so on. The QoS requirements at the physical layer, the data link layer, and the cross‐layer modeling are stated. Then, we present a QoS‐based call admission control algorithm that considers admission of calls for future start‐up as well as the immediate and hand‐off calls with a certain priority admission scheme. Analytical study based on two‐dimensional Markov chain is also provided. We then use a stochastic discrete event simulator to evaluate the performance of the call admission control algorithm. The results obtained for look‐ahead admission are compelling and indicate the usefulness of making advance resource reservations. Copyright © 2013 John Wiley & Sons, Ltd.