bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulating the physical and biological performances of poly(p‐dioxanone) by copolymerization with L‐phenylalanine
Authors: Wang Bing , Ma Chi , Xiong Zuo‐Chun , Xiong Cheng‐Dong , Zhou Hong‐Wei , Zhou Quan‐hua , Chen Dong‐Liang 
Published: May 2013

ABSTRACTThe high crystallinity, low solubility in normal solvents, and low hydrophilicity of poly(p‐dioxanone) (PPDO) are unsuitable for the expansion of its biomedical applications. In order to circumvent these problems and induce biological properties, a series of poly(ester amide)s based on p‐(dioxanone) and l‐phenylalanine were synthesized by copolymerization of p‐dioxanone with l‐phenylalanine N‐carboxyanhydride monomers. The structures of the copolymers were confirmed by 1H NMR. The crystallinity of the copolymers was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Increasing contents of phenylalanine resulted in decreased crystallinity owing to the rigid phenyl groups of phenylalanine, which disrupted the regularities of the chains, thus confining their movement. The synthesized copolymers were more soluble in chloroform than PPDO. Moreover, the copolymers were more hydrophilic and hydrolyzed more slowly than PPDO, as indicated by water angle contact measurements and in vitro hydrolysis studies. Especially, the copolymers showed inhibition on cell proliferation of L929 mouse fibroblasts by MTT assay, suggesting that the polymers might be useful in the areas where cell proliferation need to be inhabited such as adhesion prevention. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2311–2319, 2013
Enhanced stability of newly isolated trimeric l‐methionine‐N‐carbamoylase from Brevibacillus reuszeri HSN1 by covalent immobilization
Authors: Nandanwar Hemraj S. , Vohra Rakesh M. , Hoondal Gurinder S. 
Published: May 2013

AbstractNewly isolated and partially purified trimeric l‐methionine‐N‐carbamoylase from Brevibacillus reuszeri HSN1 was immobilized by covalent coupling to a well‐known support material, Eupergit® C. Approximately 80% enzyme activity yield was achieved with ≈61% binding of a soluble protein from a solution containing 5 mg/mL protein. The immobilized preparation was found to be quite unstable due to a poor multisubunit covalent interaction of trimeric enzyme. Additional cross‐linking with polyaldehyde–dextran was done to sustain the biotechnological application of immobilized enzyme. The temperature and pH optima of immobilized enzyme were increased by 10°C and 0.5 unit, respectively. The enzyme was significantly stabilized and retained ≈93% enzyme activity when incubated at 60°C for 60 Min, whereas free enzyme lost ≈50% activity. It was recycled nine times with ≈100% conversion efficiency when batch experiments were carried out at 35°C, pH 7.5, for the 180 Min cycle, using 5% N‐carbamoyl‐l‐methionine as the substrate. The half‐life of the immobilized preparation was determined as 23 cycles and is significant. Approximately 50% of enzyme activity was retained even after 5 months of storage at 4°C, whereas free enzyme lost complete enzyme activity. Hence, we could enhance the stability of l‐methionine‐N‐carbamoylase to make it a potential biocatalyst for biotechnological production of α‐amino acids.
Cross‐linked gelatin microspheres with continuously tunable degradation profiles for renal tissue regeneration
Authors: Serban Monica A. , Knight Toyin , Payne Richard G. , Basu Joydeep , Rivera Elias A. , Robbins Neil , McCoy Darell , Halberstadt Craig , Jain Deepak , Bertram Timothy A. 
Published: May 2013

AbstractCollagen and gelatin‐based biomaterials are widely used in tissue engineering applications. Various methods have been reported for the cross‐linking of these macromolecules for the purpose of delaying their biodegradation to prolong their in vivo residence (in tissue engineering applications) or tailoring their drug releasing capacity (when used as drug carriers). In this study, a carbodiimide‐based cross‐linking method, also used in the production of United States Food and Drug Administration‐approved products, was employed to obtain differentially cross‐linked gelatin beads. The colorimetric determination of the in vitro enzymatic susceptibility of the beads indicated that the resistance to degradation linearly correlated with the concentration of carbodiimide used for the cross‐linking reaction. This result was also confirmed in vivo by the histological evaluation of the residence time of orthotopically injected cell‐seeded beads. These data would indicate that the production of gelatin‐based microbeads with tunable degradation profiles might be applicable toward the development of products that catalyze regeneration of kidney and other solid organs.
Digital microfabrication of user‐defined 3D microstructures in cell‐laden hydrogels
Authors: Soman Pranav , Chung Peter H. , Zhang A. Ping , Chen Shaochen 
Published: May 2013

ABSTRACTComplex 3D interfacial arrangements of cells are found in several in vivo biosystems such as blood vasculature, renal glomeruli, and intestinal villi. Current tissue engineering techniques fail to develop suitable 3D microenvironments to evaluate the concurrent effects of complex topography and cell encapsulation. There is a need to develop new fabrication approaches that control cell density and distribution within complex 3D features. In this work, we present a dynamic projection printing process that allows rapid construction of complex 3D structures using custom‐defined computer‐aided‐design (CAD) files. Gelatin‐methacrylate (GelMA) constructs featuring user‐defined spiral, pyramid, flower, and dome micro‐geometries were fabricated with and without encapsulated cells. Encapsulated cells demonstrate good cell viability across all geometries both on the scaffold surface and internal to the structures. Cells respond to geometric cues individually as well as collectively throughout the larger‐scale patterns. Time‐lapse observations also reveal the dynamic nature of mechanical interactions between cells and micro‐geometry. When compared to conventional cell‐seeding, cell encapsulation within complex 3D patterned scaffolds provides long‐term control over proliferation, cell morphology, and geometric guidance. Overall, this biofabrication technique offers a flexible platform to evaluate cell interactions with complex 3D micro‐features, with the ability to scale‐up towards high‐throughput screening platforms. Biotechnol. Bioeng. 2013;110: 3038–3047. © 2013 Wiley Periodicals, Inc.
An age–size reaction norm yields insight into environmental interactions affecting life‐history traits: a factorial study of larval development in the malaria mosquito Anopheles gambiae sensu stricto
Authors: Phelan Conan , Rotiberg Bernard D. 
Published: May 2013

AbstractEnvironmental factors frequently act nonindependently to determine growth and development of insects. Because age and size at maturity strongly influence population dynamics, interaction effects among environmental variables complicate the task of predicting dynamics of insect populations under novel conditions. We reared larvae of the African malaria mosquito Anopheles gambiae sensu stricto (s.s.) under three factors relevant to changes in climate and land use: food level, water depth, and temperature. Each factor was held at two levels in a fully crossed design, for eight experimental treatments. Larval survival, larval development time, and adult size (wing length) were measured to indicate the importance of interaction effects upon population‐level processes. For age and size at emergence, but not survival, significant interaction effects were detected for all three factors, in addition to sex. Some of these interaction effects can be understood as consequences of how the different factors influence energy usage in the context of a nonindependent relationship between age and size. Experimentally assessing interaction effects for all potential future sets of conditions is intractable. However, considering how different factors affect energy usage within the context of an insect's evolved developmental program can provide insight into the causes of complex environmental effects on populations.
Links between wave forcing, offshore islands and a macro‐tidal headland‐bound bay beach
Authors: Thomas Tony , Phillips Michael R. , Williams Allan T. , Jenkins Rhian E. 
Published: May 2013

ABSTRACTProfiles were analysed in conjunction with wave climate to assess offshore island influences on an embayed beach at Tenby, Wales. Time series analyses showed medium and short‐term beach oscillation, with volume exchanges between zones lagging by up to six months. Dominant southerly and southwesterly waves caused sub and low tidal longshore drift from south towards north, while less frequent southeasterly waves generated counter drift. Modelled inshore breaking waves had less energy than offshore ones and the former behaved differently between the low and high tidal zones (spring tidal range of 7 · 5 m). Variations in wave direction from directly behind the islands resulted in reduced wave heights and statistical analyses agreed with wave model results. These were correlated to morphological change and it was concluded that offshore islands change wave dynamics and modify the morphology of embayed beaches in their lee. Consequently, this work provides significant new insights into offshore island influences, shoreline behaviour and especially tidal setting Copyright © 2013 John Wiley & Sons, Ltd.
The use of tetragnathid spiders as bioindicators of metal exposure at a coal ASH spill site
Authors: Otter Ryan R. , Hayden Mary , Mathews Teresa , Fortner Allison , Bailey Frank C. 
Published: May 2013

Abstract

On 22 December 2008, a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Fuel Plant (TN, USA) failed, resulting in the largest coal ash spill in US history. The present study was designed to determine sediment metal concentrations at multiple site locations and to determine whether site-specific bioaccumulation of metals existed in tetragnathid spiders. Selenium and nickel were the only 2 metals to exceed the US Environmental Protection Agency sediment screening levels. Selenium concentrations in spiders were significantly higher at ash-affected sites than in those from reference sites. The ratio of methylmercury to total mercury in spiders was found to be similar to that in other organisms (65–75%), which highlights the potential use of tetragnathid spiders as an indicator species for tracing contaminant transfer between the aquatic and terrestrial ecosystems. Environ Toxicol Chem 2013;32:2065–2068. © 2013 SETAC
Comparing the effects of nanosilver size and coating variations on bioavailability, internalization, and elimination, using Lumbriculus variegatus
Authors: Coleman Jessica G. , Kennedy Alan J. , Bednar Anthony J. , Ranville James F. , Laird Jennifer G. , Harmon Ashley R. , Hayes Charolett A. , Gray Evan P. , Higgins Christopher P. , Lotufo Guilherme , Steevens Jeffery A. 
Published: May 2013

Abstract

As the production and applications of silver nanoparticles (AgNPs) increase, it is essential to characterize fate and effects in environmental systems. Nanosilver materials may settle from suspension; therefore, the authors' objective was to utilize environmentally relevant bioassays and study the impact, bioaccumulation, tissue distribution, uptake, and depuration of AgNPs on a sediment-dwelling invertebrate, Lumbriculus variegatus. Hydrodynamic diameters of uncoated 30-nm, 80-nm, and 1500-nm AgNP powders and a polyvinyl pyrrolidone (PVP) AgNP suspension were measured utilizing dynamic light scattering in freshwater media (0–280 µS/cm). Aggregation for 30 nm, 80 nm, and 1500 nm silver increased with conductivity but was minimal for PVP silver. Lumbriculus variegatus were exposed to AgNPs or silver nitrate (AgNO3) spiked into sediment (nominally 100 mg/kg) and water (PVP 30 nm and 70 nm Ag, nominally 5 mg/L). Uptake was assessed through inductively coupled plasma mass spectroscopy (ICP-MS) and hyperspectral imaging. Particle sizes were examined through field flow fractionation–ICP-MS (FFF-ICP-MS) and ICP-MS in single particle mode (SP-ICP-MS). Lumbriculus variegatus were also depurated for 6 h, 8 h, 24 h, and 48 h to determine gut clearance. Bioaccumulation factors of sediment-exposed L. variegatus were similar regardless of particle size or coatings. The FFF-ICP-MS and SP-ICP-MS detected AgNPs for up to 48 h post depuration. The present study provides information on bioaccumulation and interactions of AgNPs within biological systems. Environ Toxicol Chem 2013;32:2069–2077. © 2013 SETAC
Lethal and sublethal effects of three insecticides on two developmental stages of xenopus laevis and comparison with other amphibians
Authors: Yu Shuangying , Wages Mike R. , Cai Qingsong , Maul Jonathan D. , Cobb George P. 
Published: May 2013

Abstract

It has been suggested that Xenopus laevis is less sensitive than other amphibians to some chemicals, and therefore, that the Frog Embryo Teratogenesis Assay—Xenopus (FETAX) may have limited use in risk assessments for other amphibians. However, comparisons are based mostly on results of FETAX, which emphasizes embryos. Larval X. laevis may be more sensitive to chemicals than embryos and may serve as a better life stage in risk assessments. The present study was conducted to determine the lethal and sublethal effects of 3 insecticides (malathion, endosulfan, and α-cypermethrin) on X. laevis embryos and larvae and to compare toxicity of X. laevis with that of other amphibians. All 3 insecticides have different modes of action, and they caused mortality, malformations, and growth inhibition in both developmental stages. Compared with embryos, larvae were more sensitive to endosulfan and α-cypermethrin but not to malathion. Xenopus laevis larvae had low sensitivity to endosulfan, median sensitivity to malathion, and high sensitivity to α-cypermethrin/cypermethrin relative to other larval amphibians. Our results suggest that X. laevis larvae may generate more protective toxicity estimates in risk assessments than embryos. Xenopus laevis may have limited use in evaluating risk of organochlorine insecticides to other amphibians but may provide useful toxicity thresholds for pyrethroid and perhaps organophosphorus insecticides. Environ Toxicol Chem 2013;32:2056–2064. © 2013 SETAC
Linear contrail and contrail cirrus properties determined from satellite data
Authors: Minnis Patrick , Bedka Sarah T. , Duda David P. , Bedka Kristopher M. , Chee Thad , Ayers J. Kirk , Palikonda Rabindra , Spangenberg Douglas A. , Khlopenkov Konstantin V. , Boeke Robyn 
Published: May 2013

AbstractThe properties of contrail cirrus clouds are retrieved through analysis of Terra and Aqua Moderate Resolution Imaging Spectroradiometer data for 21 cases of spreading linear contrails. For these cases, contrail cirrus enhanced the linear contrail coverage by factors of 2.4–7.6 depending on the contrail mask sensitivity. In dense air traffic areas, linear contrail detection sensitivity is apparently reduced when older contrails overlap and thus is likely diminished during the afternoon. The mean optical depths and effective particle sizes of the contrail cirrus were 2–3 times and 20% greater, respectively, than the corresponding values retrieved for the adjacent linear contrails. When contrails form below, in, or above existing cirrus clouds, the column cloud optical depth is increased and particle size is decreased. Thus, even without increased cirrus coverage, contrails will affect the radiation balance. These results should be valuable for refining model characterizations of contrail cirrus needed to fully assess the climate impacts of contrails.
Deforestation causes different subregional effects on the Amazon bioclimatic equilibrium
Authors: Pires Gabrielle Ferreira , Costa Marcos Heil 
Published: May 2013

AbstractDeforestation on Amazonia and central Brazil Cerrado could change regional climate, possibly shifting forest equilibrium into a bioclimatic envelope typical of savannas. Although impacts of climate change induced by deforestation are likely to vary subregionally, the potential geographic variation of these effects and the thresholds of rainforest and Cerrado removal that will affect Amazonian bioclimatic equilibrium remain unknown. We evaluate the effects of deforestation scenarios of increasing severity on the bioclimatic equilibrium of Amazon subregions. Results indicate that subregional precipitation responds in three distinct ways to progressive deforestation: a near‐constant rate of reduction, a rapid drop for low deforestation levels, and a decrease after intermediate deforestation levels. Additionally, while inner forest regions remain inside rainforest bioclimatic envelope, outer forest regions may cross forest‐savanna bioclimatic threshold even at low deforestation levels. We argue that at least 90% of Amazonia and 40% of Cerrado should be sustained to avoid subregional bioclimatic savannization.
The Pacific Meridional Mode as a trigger for ENSO in a high‐resolution coupled model
Authors: Larson Sarah , Kirtman Ben 
Published: May 2013

AbstractThis study investigates El Niño precursors in a high‐resolution version of CCSM3.5. First, using an Empirical Orthogonal Function analysis of all non‐ENSO tropical Pacific variability, we find that the Pacific Meridional Mode (PMM) acts as an ENSO trigger 7–9 months prior to large El Niño events in the model, which is consistent with previous model and observational studies. However, because not every PMM event triggers an ENSO event, we also find that PMM appears to be an effective trigger when the western‐to‐central Pacific is preconditioned (i.e., anomalously high sea surface heights or heat content). Second, this study looks at the contribution of western Pacific variability, namely westerly wind bursts (WWBs), as well as all other non‐ENSO variability in the tropical Pacific. We find that the relative importance of low‐frequency climate variability associated with PMM dominates over other non‐ENSO variability between 15°N and 15°S, including high‐frequency atmospheric variability and WWBs, in acting as a precursor to El Niño events.
The effect of carbon‐nitrogen coupling on the reduced land carbon sink caused by tropospheric ozone
Authors: Kvalevåg Maria Malene , Myhre Gunnar 
Published: May 2013

AbstractTropospheric ozone is known to have a damaging effect on carbon uptake in the terrestrial biosphere. We show that limitations of available nitrogen for sufficient plant growth reduce the negative impact of tropospheric ozone on carbon uptake in plants, leading to a smaller indirect change in radiative forcing than previously calculated. Transient climate simulations between 1900 and 2004 where plant growth is affected by tropospheric ozone have been performed by the National Center for Atmospheric Research Community Land Model with and without a coupling to the nitrogen cycle. When the land model includes nitrogen limitation on plant growth, the negative effect from tropospheric ozone on carbon uptake in plants is reduced by up to a factor of four compared to model simulation without nitrogen limitation. Only 2–5% of the radiative forcing from CO2 between 1900 and 2004 can be attributed to the indirect effect of tropospheric ozone which is a factor of six lower than results from previous studies.
Responses of the Antioxidant System in QGY‐7701 Cells to the Cytotoxicity and Apoptosis Induced by 1‐Octyl‐3‐methylimidazolium Chloride
Authors: Jing Changqin , Li Xiaoyu , Zhang Jihong , Wang Jianji 
Published: May 2013

ABSTRACTThis study aims to evaluate the cytotoxicity and responses of the cellular antioxidant system of 1‐octyl‐3‐methylimidazolium chloride ([C8mim][Cl]) on human hepatocarcinoma QGY‐7701 cells. The results show that [C8mim][Cl] can inhibit QGY‐7701 cell growth and decrease their viabilities in a dose‐dependent manner. The results also reveal that [C8mim][Cl] exposure can induce apoptosis in the [C8mim][Cl]‐treated QGY‐7701 cells. In addition, the results of biochemical assays show that [C8mim][Cl] exposure causes overproduction of reactive oxygen species (ROS), inhibits superoxide dismutase (SOD) and catalase (CAT) activities, decreases reduced glutathione (GSH) content, and increases the cellular malondialdehyde (MDA) level. These results suggest that ROS‐mediated oxidative stress may be responsible for the apoptosis induced by [C8mim][Cl] in QGY‐7701 cells. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:330‐336, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.21495
Variability of rock texture and morphology correlated with the clay‐bearing units at Mawrth Vallis, Mars
Authors: McKeown Nancy K. , Bishop Janice L. , Silver Eli A. 
Published: May 2013

AbstractThe clay units at Mawrth Vallis have been well‐characterized in hyperspectral data; however, a similar study of high spatial resolution High Resolution Imaging Science Experiment (HiRISE) data has not been previously conducted. Here the textures of the clay units are described and related to mineralogy across the central Mawrth Vallis region. The nontronite‐bearing rocks appear tan in HiRISE COLOR data and are polygonally fractured with polygons 2–5 m across. In some cases, the fractures appear wider and/or have darker fill or the rocks are a darker brown. The montmorillonite‐bearing rocks appear blue with regular polygons 0.5–1.5 m across; sometimes, there are larger polygons surrounded by regular polygons, a square fracture pattern, or the color appears yellow or mottled blue‐yellow. Kaolinite‐rich rocks are the brightest outcrops and are nonpolygonally fractured. Regions with spectra consistent with hydrated silica or the ferrous mineral component do not have unique textures. Hydrated silica‐bearing rocks appear yellow or mottled with a regular polygonal texture or yellow with hummocky appearance with no polygons. It is also possible that dust/sand on the surface alters the montmorillonite spectrum to appear like that of hydrated silica. The ferrous component may be expressed as mottled coloring or as a bright fracture fill. The nontronite‐ and montmorillonite‐bearing units have remarkably consistent textures in this region, allowing them to be uniquely identified in the Mawrth Vallis region in nonhyperspectral data sets such as CTX and HiRISE. The morphology of the polygons in these two units suggests that their formation is likely dominated by desiccation and controlled by composition.
Lunar opposition effect as inferred from Chandrayaan‐1 M3 data
Authors: Kaydash Vadym , Pieters Carle , Shkuratov Yuriy , Korokhin Viktor 
Published: May 2013

AbstractThe shadow‐hiding and coherent backscattering enhancement mechanisms are considered to be the major contributors to the brightness opposition effect of the Moon. However, the actual proportions of the mechanisms at different phase angles still remain not well determined. In order to assess the lunar phase function across small phase angles, we utilize imaging spectrometer data acquired by the Moon Mineralogy Mapper (M3) onboard the Chandrayaan‐1 spacecraft. We calculated phase functions of apparent reflectance and color ratios in the wavelength range 541–2976 nm for several mare and highland areas. As inferred from changes in the wavelength dependence of the phase curves, the shadow‐hiding effect is a major component of the brightness opposition surge at phase angle > 2°. The coherent backscattering enhancement may contribute some to the opposition effect at phase angles < 2°. We found nonmonotonic behavior of color‐ratio phase curves that reveal the minimum at ~ 2–4°. Using lunar observations, this is the first reliable evidence of the colorimetric opposition effect found earlier for lunar samples.