bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rocky Mountain National Park reduced nitrogen source apportionment
Authors: Thompson Tammy M. , Rodriguez Marco A. , Barna Michael G. , Gebhart Kristi A. , Hand Jennifer L. , Day Derek E. , Malm William C. , Benedict Katherine B. , Collett Jeffrey L. , Schichtel Bret A. 
Published: April 2015

AbstractExcess wet and dry deposition of nitrogen‐containing compounds are a concern at a number of national parks. The Rocky Mountain Atmospheric Nitrogen and Sulfur Study Part II (RoMANS II) campaign was conducted from November 2008 to November 2009 to characterize the composition of reactive nitrogen and sulfur deposited in Rocky Mountain National Park (RMNP). RoMANS II identified reduced nitrogen as the major contributor to reactive nitrogen deposition in RMNP, making up over 50% of the total. Motivated by this finding, the particulate source apportionment technology within the Comprehensive Air Quality Model with extensions was used here to estimate source apportionment of reduced nitrogen concentrations at RMNP. Source apportionment results suggest that approximately 40% of reduced nitrogen deposition to RMNP comes from ammonia sources within Colorado. However, the model evaluation also suggests that this number could be underrepresenting ammonia sources in eastern Colorado due to the difficulty of capturing upslope airflow on the eastern side of the Continental Divide with meteorological models. Emissions from California, the western model boundary, and the Snake River Valley in Idaho, the next three most influential sources, contribute approximately 15%, 8%, and 7%, respectively, to total reduced nitrogen measured in RMNP. Within Colorado, about 61%, 26%, and 13% of the total Colorado contribution comes from sources to the east of the Continental Divide, sources to the west of the Continental Divide, and from the park itself.
Trace element anomaly in fault rock induced by coseismic hydrothermal reactions reproduced in laboratory friction experiments
Authors: Tanikawa Wataru , Ishikawa Tsuyoshi , Honda Go , Hirono Tetsuro , Tadai Osamu 
Published: April 2015

AbstractFriction experiments at high velocities (0.1 to 0.4 m/s) at room temperature under high pore fluid pressures (2 or 5 MPa) and trace element analyses of the run products were carried out on simulated fault gouge derived from the Chelungpu fault, Taiwan. The friction coefficient decreased to ~0.1 during sliding, and the slip surface temperature reached 300°C by 6 m of slip displacement. The slip caused a small, but distinct decrease of Li in the deformed gouge when the slip surface temperature exceeded 300°C. The observed Li depletion agreed with calculated results, indicating that it resulted from a hydrothermal reaction at a high temperature produced by short‐duration (up to 40 s) frictional heating. The geochemical data suggest a small fluid/rock ratio and low reaction temperature in the simulated fault, which is explained by higher normal stress or repeated earthquakes which elevated fluid‐rock ratios in the natural fault.
Geometrical Dependence of the Highest Occupied Molecular Orbital in Bicyclic Systems: π‐Facial Stereoselectivity of Bicyclic and Tricyclic Olefins
Authors: Tsuji Motonori 
Published: April 2015

AbstractSterically unbiased bicyclic and tricyclic olefins were reacted with electrophiles to assess the π‐facial stereoselectivity. The stereochemical preference of the reactions of these olefins with electrophiles is attributed to the HOMO, which is derived from the interaction between a higher‐lying π orbital and particular lower‐lying σ orbitals. The selectivity of electrophilic reactions of these olefinic molecules is thought to be controlled by two types of HOMO, which are formed by a combination of different orbitals, depending on the geometrical conditions. A novel interpretation of orbital interactions enabled us to account for the facial selectivity in a unified manner.
Hydrolytic degradation of biodegradable polyesters under simulated environmental conditions
Authors: Muthuraj Rajendran , Misra Manjusri , Mohanty A.K. 
Published: April 2015

ABSTRACTIn this study, the durability of poly(butylene succinate) (PBS), poly(butylene adipate‐co‐terephthalate) (PBAT), and PBS/PBAT blend was assessed by exposure to 50°C and 90% relative humidity for a duration of up to 30 days. Due to the easy hydrolysis of esters, the mechanical properties of PBS and PBAT were significantly affected with increasing conditioning time. The PBS, PBAT, and PBS/PBAT showed an increase in modulus as well as a decrease in tensile strength and elongation at break with increased exposure time. Furthermore, the impact strength of PBAT remains unaffected up to 30 days of exposure. However, it was clearly observed that the fracture mode of PBS/PBAT changed from ductile to brittle after being exposed to high heat and humid conditions. This may be attributed to the hydrolysis products of PBS accelerating the degradation of PBAT in the PBS/PBAT blend. The differential scanning calorimetry results suggested that the crystallinity of the samples increased after being exposed to elevated temperature and humidity. This phenomenon was attributed to the induced crystallization from low molecular weight polymer chains that occurred during hydrolysis. Therefore, low molecular weight polymer chains are often favored to the crystallinity enhancement. The increase in crystallinity eventually increased the modulus of the conditioned samples. The enhanced crystallinity was further confirmed by polarizing optical microscopy analysis. Moreover, the hydrolysis of the polyesters was evaluated by scanning electron microscopy, rheology, and Fourier transform infrared spectroscopy analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 42189.
Effect of clay type on dispersion and barrier properties of hydrophobically modified poly(vinyl alcohol)–bentonite nanocomposites
Authors: Johansson Caisa , Clegg Francis 
Published: April 2015

ABSTRACTThe oxygen and water vapor permeability at high relative humidity was studied for composite films formed by incorporation of three different bentonites (MMT) into an ethylene‐modified, water‐soluble poly(vinyl alcohol), EPVOH. The oxygen permeability decreased linearly with an increased addition of hydrophilic MMTs. X‐ray diffraction and Fourier transform infrared spectroscopy suggested a homogeneous distribution in the thickness direction with disordered and probably exfoliated structures for hydrophilic MMTs. In contrast, organophilic modified clay showed an intercalated structure with the clay preferentially located at the lower film surface, a combination which was however efficient in reducing the water vapor‐ and oxygen permeabilities at low addition levels. Composite films of EPVOH and Na+‐exchanged MMT resulted in high resistance to dissolution in water, which was ascribed to strong interactions between the components resulting from matching polarities. Annealing the films at 120°C resulted in enhanced resistance to water dissolution and a further reduction in oxygen permeability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42229.
Effects of molecular weight and grafted maleic anhydride of functionalized polylactic acid used in reactive compatibilized binary and ternary blends of polylactic acid and thermoplastic cassava starch
Authors: Detyothin Sukeewan , Selke Susan E. M. , Narayan Ramani , Rubino Maria , Auras Rafael A. 
Published: April 2015

ABSTRACTPolylactic acid (PLA) was reactively functionalized with maleic anhydride (MA) and 2,5‐bis(tert‐butylperoxy)−2,5‐dimethylhexane (Luperox 101 or L101) using a twin screw extruder (TSE). The effects of functionality (grafted MA level) and/or number average molecular weight of functionalized PLA (PLA‐g‐MA) as the reactive polymer pairs (binary blends) and reactive compatibilizer (ternary blends) were investigated. Due to the dominant side reaction during melt free radical grafting, polymer degradation or chain scission, PLA‐g‐MA having a higher grafted MA had lower molecular weights and intrinsic viscosity as well as broader molecular weight distribution values. The thermal, physical, mechanical, and morphological properties of binary blends produced by using the TSE and injection molding at a ratio of 70 wt % PLA‐g‐MA and 30 wt % thermoplastic cassava starch (TPCS) were analyzed. The reactive blends having grafted MA more than 0.4 wt % had poor tensile strength and elongation at break. Similar trends in morphology and tensile properties were observed in the reactive ternary blends. The use of PLA‐g‐MA strongly impacted the elongation at break but not the modulus or tensile strength. An increase of PLA‐g‐MA's number average molecular weight (
or Mn) improved the tensile properties of the blends. The reactive ternary blend having 0.1 wt % grafted MA on PLA and PLA‐g‐MA basis and PLA‐g‐MA's Mn of 45 kDa offered the highest elongation at break. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42230.
Genipin‐cross‐linked chitosan‐based hydrogels: Reaction kinetics and structure‐related characteristics
Authors: Dimida Simona , Demitri Christian , De Benedictis Vincenzo M. , Scalera Francesca , Gervaso Francesca , Sannino Alessandro 
Published: April 2015

ABSTRACTThe main aim of this work is the synthesis and characterization of cross‐linked chitosan systems. Chitosan hydrogels can be prepared by physical or chemical cross‐linking of polymer chains. Chemical cross‐linking, leading to the creation of hydrogel networks possessing improved mechanical properties and chemical stability, can be achieved using either synthetic agents or natural‐based agents. In this work, the cross‐linker Genipin, a naturally derived compound, was selected because of the lower acute toxicity compared to many other commonly used synthetic cross‐linking reagents. In particular, the chemical stabilization of chitosan through genipin cross‐linking molecules was performed and characterized by calorimetric analyses (differential scanning calorimetry), swelling measurements in different pHs, and ionic strength. The reaction kinetics was carried out by means of rheological measurements, and both the activation energy (Ea) and the reaction order (m) were calculated. The hydrogel analyses were carried out at different concentrations of genipin (GN1 and GN2). The results were used to evaluate the possibility to use the chemical cross‐linked chitosan–genipin hydrogel for biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42256.
Hydrogen peroxide sensing properties of PVA/TiO2/I2 nanocomposite‐based free standing membranes
Authors: Grover Rakhi , Nanda Omita , Gupta Nidhi , Saxena Kanchan 
Published: April 2015

ABSTRACTThe nanocomposite of titanium‐di‐oxide (TiO2)/iodine (I2) in polyvinyl alcohol (PVA) matrix has been explored to be used in hydrogen peroxide (H2O2) sensing applications for the first time. The proposed nanocomposite can be easily casted in the form of thin film on glass substrates as well as free standing membranes. These nanocomposite films and membranes exhibit reduced resistance values and easily observable colour changes in the presence of H2O2. The films also exhibit significant quenching in photoluminescence emission properties upon H2O2 exposure. These sensor responses have been attributed to redox reactions at nanocomposite films and H2O2 interface. This study indicates an easy to fabricate, flexible and environmental friendly sensing platform for H2O2. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42257.
Controllable Synthesis of Bandgap‐Tunable CuSxSe1−x Nanoplate Alloys
Authors: Xu Jun , Yang Xia , Yang Qing‐Dan , Huang Xing , Tang Yongbing , Zhang Wenjun , Lee Chun‐Sing 
Published: April 2015

AbstractComposition engineering is an important approach for modulating the physical properties of alloyed semiconductors. In this work, ternary CuSxSe1−x nanoplates over the entire composition range of 0≤x≤1 have been controllably synthesized by means of a simple aqueous solution method at low temperature (90 °C). Reaction of Cu2+ cations with polysulfide/‐selenide ((SnSem)2−) anions rather than independent Sn2− and Sem2− anions is responsible for the low‐temperature and rapid synthesis of CuSxSe1−x alloys, and leads to higher S/Se ratios in the alloys than that in reactants owing to different dissociation energies of the Se−Se and the S−S bonds. The lattice parameters ‘a’ and ‘c’ of the hexagonal CuSxSe1−x alloys decrease linearly, whereas the direct bandgaps increase quadratically along with the S content. Direct bandgaps of the alloys can be tuned over a wide range from 1.64 to 2.19 eV. Raman peaks of the S−Se stretching mode are observed, thus further confirming formation of the alloyed CuSxSe1−x phase.
Redox‐Mediated Synthesis of a Fe3O4–MnO2 Nanocomposite for Dye Adsorption and Pseudocapacitance
Authors: Sahoo Ramkrishna , Pradhan Mukul , Roy Anindita , Dutta Soumen , Ray Chaiti , Negishi Yuichi , Pal Anjali , Pal Tarasankar 
Published: April 2015

AbstractA logically chosen redox reaction of submerged Fe0 in an aqueous KMnO4 solution has been reported. The template‐free reaction conditions produced gram amounts of a hierarchical flowerlike Fe3O4–MnO2 nanocomposite. More precisely, freshly prepared Fe0 nanoparticles were prepared from air‐free hot water under submerged conditions using a door magnet. The black Fe0 particles were oxidized in water quantitatively by KMnO4 in the solution phase and the nanocomposite was prepared. The material has been used as a dye adsorbent and the representative cationic dye uptake, recovery, and recycling of the dye becomes easy owing to the ferromagnetic properties and surface negative charge of the material. The nanocomposite also showed a higher specific capacitance (327 F g−1 at 10 mV s−1) than the reported values of pure MnO2 and Fe3O4. The material exhibited a high energy density as well as a high power density, and remained stable even after a large number of charge–discharge cycles.
Linker length and flexibility induces new cellobiohydrolase activity of PoCel6A from Penicillium oxalicum
Authors: Gao Le , Wang Lushan , Jiang Xukai , Qu Yinbo 
Published: April 2015

AbstractIn a previous study, a novel cellobiohydrolase, PoCel6A, with new enzymatic activity against p‐nitrophenyl‐β‐D‐cellobioside (pNPC), was purified from Penicillium oxalicum. The cellulose‐binding module and catalytic domain of PoCel6A showed a high degree of sequence similarity with other fungal Cel6As. However, PoCel6A had 11 more amino acids in the linker region than other Cel6As. To evaluate the relationship between the longer linker of PoCel6A and its enzymatic activity, 11 amino acids were deleted from the linker region of PoCel6A. The shortened PoCel6A linker nullified the enzymatic activity against pNPC but dramatically increased the enzyme's capacity for crystalline cellulose degradation. The shortened linker segment appeared to have no effect on the secondary structural conformation of PoCel6A. Another variant (PoCel6A‐6pro) with six consecutive proline residues in the interdomain linker had a higher rigid linker, and no enzymatic activity was observed against soluble and insoluble substrate. The flexibility of the linker had an important function in the formation of active cellulase. The length and flexibility of the linker is clearly able to modify the function of PoCel6A and induce new characteristics of Cel6A.
Spatial and temporal control of cell aggregation efficiently directs human pluripotent stem cells towards neural commitment
Authors: Miranda Cláudia C. , Fernandes Tiago G. , Pascoal Jorge F. , Haupt Simone , Brüstle Oliver , Cabral Joaquim M.S. , Diogo Maria Margarida 
Published: April 2015

Abstract3D suspension culture is generally considered a promising method to achieve efficient expansion and controlled differentiation of human pluripotent stem cells (hPSCs). In this work, we focused on developing an integrated culture platform for expansion and neural commitment of hPSCs into neural precursors using 3D suspension conditions and chemically‐defined culture media. We evaluated different inoculation methodologies for hPSC expansion as 3D aggregates and characterized the resulting cultures in terms of aggregate size distribution. It was demonstrated that upon single‐cell inoculation, after four days of culture, 3D aggregates were composed of homogenous populations of hPSC and were characterized by an average diameter of 139 ± 26 μm, which was determined to be the optimal size to initiate neural commitment. Temporal analysis revealed that upon neural specification it is possible to maximize the percentage of neural precursor cells expressing the neural markers Sox1 and Pax6 after nine days of culture. These results highlight our ability to define a robust method for production of hPSC‐derived neural precursors that minimizes processing steps and that constitutes a promising alternative to the traditional planar adherent culture system due to a high potential for scaling‐up.
Ca2+‐independent sortase‐A exhibits high selective protein ligation activity in the cytoplasm of Escherichia coli
Authors: Hirakawa Hidehiko , Ishikawa Suguru , Nagamune Teruyuki 
Published: April 2015

AbstractA Staphylococcus aureus transpeptidase, sortase A (SrtA), which catalyzes a peptide ligation with high substrate specificity, is a useful tool to site‐specifically attach proteinaceous/peptidic functional molecules to target proteins. However, its strong Ca2+ dependency makes SrtA difficult for use under low Ca2+ concentrations and in the presence of Ca2+‐binding substances. To overcome this problem, we designed a SrtA mutant that Ca2+‐independently demonstrates a high catalytic activity. The heptamutant (P94R/E105K/E108A/D160N/D165A/K190E/K196T), which resulted from a combination of known mutations at the Ca2+‐binding site and around the substrate‐binding site, successfully catalyzed a selective protein‐protein ligation in the cytoplasm of Escherichia coli. Selective protein modification in living cells is a promising approach for investigating cellular events and regulating cell functions. This SrtA mutant may prove to be a versatile tool for adding new functionalities to proteins of interest by incorporating functional proteins and chemically modified peptides in living cells, which usually retain low Ca2+ concentrations.
One‐step generation of triple knockout CHO cell lines using CRISPR/Cas9 and fluorescent enrichment
Authors: Grav Lise Marie , Lee Jae Seong , Gerling Signe , Kallehauge Thomas Beuchert , Hansen Anders Holmgaard , Kol Stefan , Lee Gyun Min , Pedersen Lasse Ebdrup , Kildegaard Helene Faustrup 
Published: April 2015

AbstractThe CRISPR/Cas9 genome editing technology has previously been shown to be a highly efficient tool for generating gene disruptions in CHO cells. In this study we further demonstrate the applicability and efficiency of CRISPR/Cas9 genome editing by disrupting FUT8, BAK and BAX simultaneously in a multiplexing setup in CHO cells. To isolate Cas9‐expressing cells from transfected cell pools, GFP was linked to the Cas9 nuclease via a 2A peptide. With this method, the average indel frequencies generated at the three genomic loci were increased from 11% before enrichment to 68% after enrichment. Despite the high number of genome editing events in the enriched cell pools, no significant off‐target effects were observed from off‐target prediction followed by deep sequencing. Single cell sorting of enriched multiplexed cells and deep sequencing of 97 clones revealed the presence of four single, 23 double and 34 triple gene‐disrupted cell lines. Further characterization of selected potential triple knockout clones confirmed the removal of Bak and Bax protein and disrupted fucosylation activity as expected. The knockout cell lines showed improved resistance to apoptosis compared to wild‐type CHO‐S cells. Taken together, multiplexing with CRISPR/Cas9 can accelerate genome engineering efforts in CHO cells even further.
Sensitive and precise HPLC method with back‐extraction clean‐up step for the determination of sildenafil in rat plasma and its application to a pharmacokinetic study
Authors: Strach Beata , Wyska Elżbieta , Pociecha Krzysztof , Krupa Anna , Jachowicz Renata 
Published: April 2015

AbstractA sensitive HPLC method was developed and validated for the determination of sildenafil concentrations in rat plasma (200 μL) using a liquid–liquid extraction procedure and paroxetine as an internal standard. In order to eliminate interferences and improve the peak shape, a back‐extraction into an acidic solution was utilized. Chromatographic separation was achieved on a cyanopropyl bonded‐phase column with a mobile phase composed of 50 m m potassium dihydrogen phosphate buffer (pH 4.5) and acetonitrile (75:25, v/v), pumped at the flow rate of 1 mL/min. A UV detector was set at 230 nm. A calibration curve was constructed within a concentration range from 10 to 1500 ng/mL. The limit of detection was 5 ng/mL. The inter‐ and intra‐day precisions of the assay were in the ranges 2.91–7.33 and 2.61–6.18%, respectively, and the accuracies for inter‐ and intra‐day runs were within 0.14–3.92 and 0.44–2.96%, respectively. The recovery of sildenafil was 85.22 ± 4.54%. Tests confirmed the stability of sildenafil in plasma during three freeze–thaw cycles and during long‐term storage at −20 and −80°C for up to 2 months. The proposed method was successfully applied to a pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.
Direct Staudinger–Phosphonite Reaction Provides Methylphosphonamidates as Inhibitors of CE4 De‐N‐acetylases
Authors: Ariyakumaran Rishikesh , Pokrovskaya Varvara , Little Dustin J. , Howell P. Lynne , Nitz Mark 
Published: April 2015

AbstractDe‐N‐acetylases of β‐(1→6)‐D‐N‐acetylglucosamine polymers (PNAG) and β‐(1→4)‐D‐N‐acetylglucosamine residues in peptidoglycan are attractive targets for antimicrobial agents. PNAG de‐N‐acetylases are necessary for biofilm formation in numerous pathogenic bacteria. Peptidoglycan de‐N‐acetylation facilitates bacterial evasion of innate immune defenses. To target these enzymes, transition‐state analogue inhibitors containing a methylphosphonamidate have been synthesized through a direct Staudinger–phosphonite reaction. The inhibitors were tested on purified PgaB, a PNAG de‐N‐acetylase from Escherichia coli, and PgdA, a peptidoglycan de‐N‐acetylase from Streptococcus pneumonia. Herein, we describe the most potent inhibitor of peptidoglycan de‐N‐acetylases reported to date (Ki=80 μM). The minimal inhibition of PgaB observed provides insight into key structural and functional differences in these enzymes that will need to be considered during the development of future inhibitors.