bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of sea ice source in aerosol sulfate loading and size distribution in the Canadian High Arctic from isotopic analysis
Authors: Seguin Alison Michelle , Norman Ann‐Lise , Barrie Leonard
Published: January 2014

The influence of frost flowers and seawater brine on ion chemistry in snow, snowpack, ice cores, and aerosols is detected when a lower sulfate to sodium ratio than in seawater is present in polar regions. This evidence can be masked when large amounts of non‐sea‐salt sulfate are present from other sources such as biogenic and anthropogenic sulfate. Frost flower δ34S values were measured for the first time in frost flower sulfates and did not differ significantly from the sea salt δ34S values of +21‰. A method using stable isotopes is introduced to determine the limit of contributions from sea salt and sea ice sources (including frost flowers and brine) on sulfate concentrations in aerosol samples from Alert, Canada. Knowledge of the range of values of δ34Snss and the SO4/Na ratio found in sea ice sources (i.e., frost flowers) is used to quantitatively constrain the contributions from frost flowers and sea salt in the Arctic aerosol mass during the onset of winter in 2007 and 2008, allowing for quantification of non‐sea‐salt sulfate amounts during times when frost flowers are present. Frost flower and/or brine influence was found predominantly in the coarse‐mode aerosols (>0.95 µm). This method to determine the contributions from sea salt and sea ice sources can be carried over to future studies with snow and ice cores.
The responses of cloudiness to the direct radiative effect of sulfate and carbonaceous aerosols
Authors: Kim Dongchul , Wang Chien , Ekman Annica M. L. , Barth Mary C. , Lee Dong‐In
Published: January 2014

This study investigates the responses of the direct radiative effect of light absorbing and scattering carbonaceous and sulfate aerosols on cloudiness and associated radiative fluxes using an interactive aerosol‐climate model coupled with a slab ocean model. We find that without including the impact of aerosols on cloud microphysics in the model (indirect effect), the direct radiative effect of aerosols alone can cause a change in cloud coverage and thus in cloud flux change which is consistent with several previous studies. More notably, our result indicates that the direct radiative effect of absorbing aerosols can cause changes in both low‐level and high‐level clouds with opposite signs. As a result, the global mean cloud radiation response to absorbing aerosols has a rather small value. The change of cloud solar radiative response (all‐sky effect minus clear‐sky effect) at the top of the atmosphere due to the existence of direct radiative effect of scattering, absorbing, and both types of aerosols is 0.72, 0.08, and 0.81 Wm−2, respectively, all are comparable in quantity to the current estimation of aerosol direct radiative forcing. The cloud response due to the longwave radiative effect is 0.09, 0.18, and 0.27 Wm−2, respectively. The global means of the radiative flux and cloud radiative responses appear to be linearly additive; however, this is definitely not the case for the zonal mean or at the regional scale.
Effects of 3‐D clouds on atmospheric transmission of solar radiation: Cloud type dependencies inferred from A‐train satellite data
Authors: Ham Seung‐Hee , Kato Seiji , Barker Howard W. , Rose Fred G. , Sun‐Mack Sunny
Published: January 2014

Three‐dimensional (3‐D) effects on broadband shortwave top of atmosphere (TOA) nadir radiance, atmospheric absorption, and surface irradiance are examined using 3‐D cloud fields obtained from one hour's worth of A‐train satellite observations and one‐dimensional (1‐D) independent column approximation (ICA) and full 3‐D radiative transfer simulations. The 3‐D minus ICA differences in TOA nadir radiance multiplied by π, atmospheric absorption, and surface downwelling irradiance, denoted as πΔI, ΔA, and ΔT, respectively, are analyzed by cloud type. At the 1 km pixel scale, πΔI, ΔA, and ΔT exhibit poor spatial correlation. Once averaged with a moving window, however, better linear relationships among πΔI, ΔA, and ΔT emerge, especially for moving windows larger than 5 km and large θ0. While cloud properties and solar geometry are shown to influence the relationships amongst πΔI, ΔA, and ΔT, once they are separated by cloud type, their linear relationships become much stronger. This suggests that ICA biases in surface irradiance and atmospheric absorption can be approximated based on ICA biases in nadir radiance as a function of cloud type.
Arctic sea ice and atmospheric circulation under the GeoMIP G1 scenario
Authors: Moore John C. , Rinke Annette , Yu Xiaoyong , Ji Duoying , Cui Xuefeng , Li Yan , Alterskjær Kari , Kristjánsson Jón Egill , Muri Helene , Boucher Olivier , Huneeus Nicolas , Kravitz Ben , Robock Alan , Niemeier Ulrike , Schulz Michael , Tilmes Simone , Watanabe Shingo , Yang Shuting
Published: January 2014

We analyze simulated sea ice changes in eight different Earth System Models that have conducted experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP). The simulated response of balancing abrupt quadrupling of CO2 (abrupt4xCO2) with reduced shortwave radiation successfully moderates annually averaged Arctic temperature rise to about 1°C, with modest changes in seasonal sea ice cycle compared with the preindustrial control simulations (piControl). Changes in summer and autumn sea ice extent are spatially correlated with temperature patterns but much less in winter and spring seasons. However, there are changes of ±20% in sea ice concentration in all seasons, and these will induce changes in atmospheric circulation patterns. In summer and autumn, the models consistently simulate less sea ice relative to preindustrial simulations in the Beaufort, Chukchi, East Siberian, and Laptev Seas, and some models show increased sea ice in the Barents/Kara Seas region. Sea ice extent increases in the Greenland Sea, particularly in winter and spring and is to some extent associated with changed sea ice drift. Decreased sea ice cover in winter and spring in the Barents Sea is associated with increased cyclonic activity entering this area under G1. In comparison, the abrupt4xCO2 experiment shows almost total sea ice loss in September and strong correlation with regional temperatures in all seasons consistent with open ocean conditions. The tropospheric circulation displays a Pacific North America pattern‐like anomaly with negative phase in G1‐piControl and positive phase under abrupt4xCO2‐piControl.
A model for the dynamics of crater‐centered intrusion: Application to lunar floor‐fractured craters
Authors: Thorey Clément , Michaut Chloé
Published: January 2014

Lunar floor‐fractured craters are a class of craters modified by post‐impact mechanisms. They are defined by distinctive shallow floors that are convex or plate‐like, sometimes with a wide floor moat bordering the wall region. Radial, concentric, and polygonal floor fractures suggest an endogenous process of modification. Two mechanisms have been proposed to account for such deformations: viscous relaxation and spreading of a magma intrusion at depth below the crater. To test the second assumption and bring more constraints on the intrusion process, we develop a model for the dynamics of magma spreading below an elastic overlying layer with a crater‐like topography. As predicted in earlier more qualitative studies, the increase in lithostatic pressure at the crater wall zone prevents the intrusion from spreading laterally, leading to the thickening of the intrusion. Additionally, our model shows that the final crater floor appearance after the uplift, which can be convex or flat, with or without a circular moat bordering the wall zone, depends on the elastic thickness of the layer overlying the intrusion and on the crater size. Our model provides a simple formula to derive the elastic thickness of the overlying layer hence a minimum estimate for the intrusion depth. Finally, our model suggests that crust redistribution by cratering must have controlled magma ascent below most of these craters.
Long‐term variability of Mars' exosphere based on precise orbital analysis of Mars Global Surveyor and Mars Odyssey
Authors: Bruinsma Sean , Forbes Jeffrey M. , Marty Jean‐Charles , Zhang Xiaoli , Smith Michael D.
Published: January 2014

A long‐term perspective on Mars' exosphere variability at 405 km is provided by merging together density data derived from precise orbit determination of the Mars Global Surveyor and Mars Odyssey (MO) satellites extending from 2001 to 2010. These data are heavily weighted toward afternoon local times at high latitudes in the Southern Hemisphere. Clear long‐term solar and annual variations are well captured by empirical formulas. Residuals from the empirical fit show evidence for relative depletions in exosphere density around Mars' closest approach to Earth, which would be consistent with a scavenging mechanism that is dependent on solar wind dynamic pressure. Superimposed on this variation with Mars‐Sun distance are positive density residuals during Mars year (MY)25, MY27, and MY29 that are apparently due to elevated dust levels in Mars' middle atmosphere. However, during MY24, MY26, and MY28 there are dust level increases without any corresponding increase in exosphere density. We suspect that this inconsistency is related to a variable ability to sense the response to dust‐related effects, imposed by the high‐latitude limitations of our measurements combined with interference between the mechanisms that translate middle atmosphere heating to an exosphere response. Evidence also supports the hypothesis that winter helium bulge effects contributed to the inferred interannual density variability during the 2007–2009 solar minimum period, when the O‐He transition height likely resided near the ~405 km orbit of MO.
Outcrops on lunar crater rims: Implications for rim construction mechanisms, ejecta volumes and excavation depths
Authors: Sharpton Virgil L.
Published: January 2014

The raised rims of impact craters consist of ejecta deposited onto structurally uplifted target rocks. Although it is commonly accepted that ejecta makes up 50–75% of the total rim height, no previous measurements on well‐preserved, naturally occurring impact craters exist. Relying on data from the Lunar Reconnaissance Orbiter, I report the first direct measurements of the rim‐forming constituents from 21 lunar craters ranging in diameter from 2.2 km to 45 km. Results show that the ejecta deposit accounts for no more than ~20% of rim relief, and structural uplift is the primary mechanism of rim development in both simple and complex craters. Thick, quasi‐horizontal outcrops of coherent bedrock indicate that this uplift is the result of subsurface injection of debris or melt into the surrounding target rocks. Crater growth, at least during the latest portion of the excavation stage, therefore, proceeds mainly through injection—rather than ejection—of material. These results suggest that ejecta volumes and excavation depths may be factors of 3 to 4 less than previously considered.
Spectral description of migrating bed forms and sediment transport
Authors: Guala Michele , Singh Arvind , BadHeartBull Nicholas , Foufoula‒Georgiou Efi
Published: January 2014

This paper considers the problem of spatiotemporal bed topography evolution and sediment transport estimation in rivers with migrating bed forms of different types and sizes, in statistical equilibrium conditions. Instead of resorting to bed form classification, we propose to evaluate the evolution of multiscale bed topography as the integral of unit contributions defined through a space‒time Fourier decomposition of bed elevations. Using joint 2‒D spectra in the frequency and wave number domain, a functional relationship between the length scales and the timescales in which migrating bed forms are decomposed is proposed and developed into a dimensionless expression for scale‒dependent convection velocities. This formulation highlights the violation of Taylor's hypothesis for migrating bed forms, confirming statistically that larger bed forms travel slower as compared to smaller bed forms. This phenomenological description leads to a spectral extension of the Simons et al. (1965) formula for sediment transport to incorporate a range of multiscale migrating features. Both the scaling of convection velocities and the spectral estimate of sediment transport rate were validated through extensive bed elevation data from laboratory experiments conducted at the St. Anthony Falls Laboratory, for a range of Froude numbers 0.2<Fr<0.5, under varying discharge and bed material composition.
Semiempirical Model for Ionospheric Absorption based on the NRLMSISE‐00 atmospheric model
Authors: Pederick L. H. , Cervera M. A.
Published: January 2014

The strength of high‐frequency radio signals, when refracted by the ionosphere, can be strongly influenced by ionospheric absorption. Accurate modeling of the amount of this absorption is a vital part of many studies of radio waves propagating in the ionosphere. We have developed a new, flexible model of ionospheric absorption, the Semiempirical Model for Ionospheric Absorption based on the NRLMSISE‐00 atmospheric model (SiMIAN). This article describes the methods and formulae used by SiMIAN, a comparison of SiMIAN with an older absorption model, and validation work performed by simulating the power returned in vertical incidence soundings of the ionosphere and comparing the results with real soundings.
Evaluation of nanoparticle tracking for characterization of fibrillar protein aggregates
Authors: Yang Dennis T. , Lu Xiaomeng , Fan Yamin , Murphy Regina M.
Published: January 2014

Amyloidogenesis is the process of formation of protein aggregates with fibrillar morphology. Because amyloidogenesis is linked to neurodegenerative disease, there is interest in understanding the mechanism of fibril growth. Kinetic models of amyloidogenesis require data on the number concentration and size distribution of aggregates, but this information is difficult to obtain using conventional methods. Nanoparticle tracking analysis (NTA) is a relatively new technique that may be uniquely suited for obtaining these data. In NTA, the two‐dimensional (2‐D) trajectory of individual particles is tracked, from which the diffusion coefficient, and, hence, hydrodynamic radius is obtained. Here we examine the validity of NTA in tracking number concentration and size of DNA, as a model of a fibrillar macromolecule. We use NTA to examine three amyloidogenic materials: beta‐amyloid, transthyretin, and polyglutamine‐containing peptides. Our results are instructive in demonstrating the advantages and some limitations of single‐particle diffusion measurements for investigating aggregation in protein systems. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1236–1244, 2014
Obesity and other risk factors: The National Survey of U.S. Long‐Haul Truck Driver Health and Injury
Authors: Sieber W. Karl , Robinson Cynthia F. , Birdsey Jan , Chen Guang X. , Hitchcock Edward M. , Lincoln Jennifer E. , Nakata Akinori , Sweeney Marie H.
Published: January 2014

Background

Drivers of heavy and tractor‐trailer trucks accounted for 56% of all production and nonsupervisory employees in the truck transportation industry in 2011. There are limited data for illness and injury in long‐haul truck drivers, which prompted a targeted national survey.

Methods

Interviewers collected data during 2010 from 1,670 long‐haul truck drivers at 32 truck stops across the 48 contiguous United States that were used to compute prevalence estimates for self‐reported health conditions and risk factors.

Results

Obesity (69% vs. 31%, P < 0.01) and current smoking (51% vs. 19%, P < 0.01) were twice as prevalent in long‐haul truck drivers as in the 2010 U.S. adult working population. Sixty‐one percent reported having two or more of the risk factors: hypertension, obesity, smoking, high cholesterol, no physical activity, 6 or fewer hours of sleep per 24‐hr period.

Conclusion

Survey findings suggest a need for targeted interventions and continued surveillance for long‐haul truck drivers. Am. J. Ind. Med. 57:615–626, 2014. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
Modeling of the degradation kinetics of biodegradable scaffolds: The effects of the environmental conditions
Authors: Heljak Marcin K. , Swieszkowski Wojciech , Kurzydlowski Krzysztof Jan
Published: January 2014

The rate of hydrolytic degradation of tissue‐engineered scaffolds made from bioresorbable polyesters is dependent on several factors. Some are related to the properties of the degrading polymeric material, but others are related to the geometry of the porous structure and the operating environment. It is well known that the rate of hydrolytic degradation of a given object, porous or nonporous, is lower when it is exposed to dynamic conditions, a flowing medium, than when it operates in static conditions. The most likely reason is the more efficient removal of the acidic degradation products from the vicinity of the polymeric material when it is operating in a flowing medium. In this article, we present a new phenomenological reaction–diffusion model of aliphatic polymer degradation. The model can be used to predict the significance of various factors in in vitro degradation tests, with particular reference to the flow of the degradation medium, and the frequency of medium replacement in the case of static conditions. The developed model was used to simulate the degradation of poly(dl‐lactide‐co‐glycolide) scaffolds with different porosities subjected to static and dynamic testing conditions. The results confirm that the porosity of the scaffold had a significant influence on the degradation rate. It was shown that the combination of dynamic conditions and high porosity effectively reduced the mass loss and molecular weight loss of the degrading polymer. However, the effect of changes in the velocity of the flowing medium had a negligible effect on the rate of degradation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40280.
Independent investigation on the influences of the processing conditions on the reclamation of crosslinked isoprene rubber after the impregnation of a reclaiming reagent
Authors: Shi Jinwei , Jiang Kuan , Zou Hua , Ding Linlin , Zhang Xiaodan , Li Xiaolin , Zhang Liqun , Ren Dongyun
Published: January 2014

In this study, the reclamation of sulfur (S)‐cured isoprene rubber (IR) was investigated independently after the impregnation process of the reclaiming reagent diphenyl disulfide (DD) into the crosslinked IR matrix with supercritical carbon dioxide (scCO2) as the transmission medium. According to the mass uptake of DD into IR and scanning electron microscopy–energy‐dispersive X‐ray spectrometry measurements, DD was highly impregnated and homogeneously dispersed in the network under 12 MPa at 80°C for 11 h in scCO2. During the impregnation process, almost no reclaiming reaction occurred. Then, through three different reclaiming methods, a mechanochemical method, a chemical method with oxygen, and a chemical method without oxygen, the influences of the shear force, reclaiming atmosphere, reaction time, and amounts of reclaiming reagent on the reclamation with crosslinked IR with pre‐impregnated DD were independently investigated and compared with those of the reaction without pre‐impregnated DD. The sol fraction of the reclaimed rubber and molecular weight of the sol were measured. The results show that the reclaiming speed greatly depended on the amount of reclaiming reagent and that the reclaiming reaction was dramatically accelerated when the reclaiming reagents were pre‐impregnated into the crosslinked IR under the same processing conditions. This indicated that the impregnation time of the reclaiming reagent into the crosslinked network constituted a large proportion of the reclaiming time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40298.
Mass production of carbon nanotube‐reinforced polyacrylonitrile fine composite fibers
Authors: Weng Baicheng , Xu Fenghua , Lozano Karen
Published: January 2014

A facile and large‐scale production method of polyacrylonitrile (PAN) fibers and carboxyl functionalized carbon nanotube reinforced PAN composite fibers was demonstrated by the use of Forcespinning® technology. The developed polymeric fibers and carbon nanotube‐reinforced composite fibers were subsequently carbonized to obtain carbon fiber systems. Analysis of the fiber diameter, homogeneity, alignment of carbon nanotube and bead formation was conducted with scanning electron microscopy. Thermogravimetric analysis, electrical, and mechanical characterization were also conducted. Raman and FTIR analyses of the developed fiber systems indicate interactions between carbon nanotubes and the carbonized PAN fibers through π–π stacking. The carbonized carbon nanotube‐reinforced PAN composite fibers possess promising applications in energy storage applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40302.
The effect of polyethylene crystallinity and polarity on thermal stability and controlled release of essential oils in antimicrobial films
Authors: Efrati Roni , Natan Michal , Pelah Avishay , Haberer Anina , Banin Ehud , Dotan Ana , Ophir Amos
Published: January 2014

Antimicrobial packaging can preserve and increase shelf life of free preservatives food products. Active materials present in the packaging material can migrate, in a controlled manner, to the food surface, avoiding bacterial and fungal proliferation and keeping the food product edible for longer periods of time. Essential oils (EO) are natural antimicrobial agents that can be released to the headspace with no direct contact between the package and the food. To minimize loses of EO during high heat melt processing, a three stages process was implemented and tested. Antimicrobial films were prepared by melt mixing a variety of polyethylene copolymers in the presence of organo‐modified montmorillonite nano clay (NC) and thymol, an EO present in oregano and thyme. A controlled EO desorption from films can be achieved by changing the polymer crystallinity and polarity. As the crystallinity increased, the thermal stability of the EO during the extrusion process improved. The addition of NC affects the structure and homogeneity of the crystals. The combination of high polymer crystallinity and chemical affinity between EO and NC increased the thermal stability of the EO during film processing, enabling to control the desorption rate. The effect of multilayer structure based on varied densities and polarities was also studied. Increasing the polarity of the outer layers in multilayered film reduced the EO desorption rate as a result of chemical interactions between the polymer and the EO. The final antimicrobial activity of the films was also found to be dependent on the EO partitioning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40309.
Effect of the compatibilizer, on the engineering properties of TPV based on Hypalon® and PP prepared by dynamic vulcanization
Authors: Mandal Asis K. , Chakraborty Debabrata , Siddhanta Samir K.
Published: January 2014

Elastomeric Chlorosulfonated polyethylene (Hypalon®) and thermoplastic Polypropylene (PP) based thermoplastic vulcanizates (TPVs) were prepared in presence of different doses of compatibilizer, maleic anhydride grafted PP (PP‐g‐MA) by employing dynamic vulcanization technique. The effect of incorporation in different proportions of compatibilizer on mechanical, spectral, morphological, thermal, and rheological properties of such TPVs was studied and the same were compared to that of virgin PP and amongst themselves. The mechanical analysis of the prepared TPVs exhibited significant improvements in stress at 25% modulus, ultimate tensile strength (UTS), and hardness values. FTIR studies revealed that a chemical interaction had taken place between Hypalon® and functionalized compatibilizer during the process of dynamic vulcanization which led to an enhancement of interfacial adhesion between them. The two‐phase morphologies were clearly observed by scanning electron microscopic studies. The Tg values of Hypalon® was modified in the TPVs as exhibited by differential scanning calorimetric studies. TGA studies indicated the increase in thermal stability of all TPVs with respect to the elastomeric Hypalon®. Rheological properties showed that the compatibilizer reduces the melt viscosity of TPVs and thus facilitates the processibility of such TPVs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40312.
Orthogonal surface functionalization through bioactive vapor‐based polymer coatings
Authors: Deng Xiaopei , Lahann Joerg
Published: January 2014

Reactive chemical vapor deposition (CVD) polymerization provides a substrate‐independent platform for effective functionalization of virtually any solid substrates, flat, or curved, even with complex geometries. This article reviews bioactive surface functionalization strategies based on CVD polymerization and highlights commonly used surface chemistries. These reactions include alkyne–azide “click” chemistry, reactions of active esters with amine, aldehydes/ketones with hydrazides and alkoxyamines, thiols with alkenes and alkynes and surface‐initiated atom transfer radical polymerization. The resulting biofunctional surface coatings can facilitate orthogonal immobilization of more than one type of ligand on a substrate. CVD polymer coatings with nanoscale thicknesses are widely applicable in biomedical applications and can be easily integrated into micro‐ and nanodevice fabrication. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40315.
Isothermal crystallization kinetics of poly(lactic acid)/synthetic mica nanocomposites
Authors: Souza Diego H. S. , Andrade Cristina T. , Dias Marcos L.
Published: January 2014

The isothermal crystallization kinetics of PLA/fluoromica nanocomposites was studied. Three types of synthetic mica at three concentrations (2.5, 5.0, and 7.5 wt % mica) were used and the effect of these micas on the crystallization and thermal properties of PLA was investigated by differential scanning calorimetry (DSC). The Avrami and Hoffman‐Weeks equations were used to describe the isothermal crystallization kinetics and melting behavior. Addition of these micas to the PLA matrix increased the crystallization rate, and this effect depended on the mica type and concentration. While the nonmodified Somasif ME‐100 exerted the smallest effect, the effect observed for the organically modified Somasif MPE was the most pronounced. The lower half‐time of crystallization t1/2 was around 3 min for the PLA/Somasif MPE nanocomposites containing 7.5 wt % of filler at 90°C, which is about 16 min below that found for neat PLA. The equilibrium melting temperature (
) of PLA were estimated for these systems, showing an increase in the composites and an increase with increasing loading, except for PLA/Somasif MPE, in which the increase of the mica content decreased
about 5°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40322.
Homogenization of natural rubber network induced by nanoclay
Authors: Nie Yijing , Qu Liangliang , Huang Guangsu , Wang Xiaoan , Weng Gengsheng , Wu Jinrong
Published: January 2014

Vulcanization gives birth to the nonuniformity of rubber network, the identification of which is the basis of improvement of performance of rubber products. We established a visco‐hyperelastic constitutive equation to reveal the quantitative distribution of the inhomogeneous network phases according to a three‐phase model. The cross‐linked network was assumed to be composed of the cross‐linking cluster, the low network chain density domain and the fluid‐like mass. The incorporation of clay with high specific surface area induced the effective uniformity of network structure by decreasing the content of the cross‐linking cluster and increasing that of the low network chain density domain. These structural variations were responsible for excellent mechanical properties and strong strain‐induced crystallization ability probed by the in situ synchrotron wide‐angle X‐ray diffraction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40324.
Antibacterial and antifungal dressings obtained by photochemical deposition of silver nanoparticles
Authors: Paladini Federica , De Simone Serena , Sannino Alessandro , Pollini Mauro
Published: January 2014

The antimicrobial activity of silver against a wide spectrum of bacteria, fungi and viruses is known since antiquity. Silver has been used as topical antimicrobial agent in the treatment of wounds since many years and advanced silver‐based dressings have been designed so far. The aim of this study was the development of low‐cost antibacterial and antifungal dressings through the surface modification of conventional cotton gauzes. Different percentages of silver were deposited on textile substrates by adopting an innovative silver deposition technique based on the photochemical deposition of silver nanoparticles. The uniformity of the coating and the distribution of the silver clusters on the surface were evaluated by scanning electron microscopy (SEM). The amount of silver was quantified by thermogravimetric analysis (TGA) and the presence of metallic silver nanoparticles was also assesses through UV–Vis–NIR with integrating sphere and energy dispersive X‐ray spectroscopy EDX. The effectiveness of the silver treated textile was verified on different microorganisms, namely Escherichia coli, Staphylococcus aureus, Pseudomonas p43 and Candida albicans derived from a clinical isolate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40326.
Tough hyperbranched epoxy/poly(amido‐amine) modified bentonite thermosetting nanocomposites
Authors: De Bibekananda , Karak Niranjan
Published: January 2014

A tough and highly flexible hyperbranched epoxy and poly(amido‐amine) modified bentonite based thermosetting nanocomposite was demonstrated. The FTIR, XRD, and TGA analyses confirmed the modification of bentonite. The formation of partially exfoliated structure of the nanocomposite with good physicochemical interactions among the hyperbranched epoxy, poly(amido‐amine) hardener and modified clay was investigated by the FTIR, XRD, SEM, and TEM analyses. Significant improvements of 750% toughness, 300% elongation at break, 50% tensile strength, 300% modulus, and 250% adhesive strength of the pristine epoxy were achieved by the formation of nanocomposites with 3 wt % of modified clay. The experimental modulus values of the nanocomposites were compared with three theoretical models to account the interactions between filler and matrix. Thus, the studied epoxy nanocomposite has great potential to be used as an advanced epoxy thermoset. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40327.
Characterization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biosynthesized by mixed microbial consortia fed fermented dairy manure
Authors: Wei Liqing , Guho Nicholas M. , Coats Erik R. , McDonald Armando G.
Published: January 2014

The bioplastic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), was isolated from a bioreactor using mixed microbial consortia fed volatile fatty acids (VFA), from fermented dairy manure, as the carbon source. The molar fraction of 3‐hydroxyvalerate (3HV) amounted to 0.33 mol mol−1 for two isolated PHBV samples as determined by GC‐MS and 1H‐NMR spectroscopy. The chemical, thermal, and mechanical properties were determined. The PHBVs had relatively high Mw (∼790,000 g mol−1). Only a single glass transition temperature (Tg) and melting point (Tm) were observed. Isolated PHBVs exhibited good flexibility and elongation to break as compared with commercial PHBVs with lower HV. The diad and triad sequence distributions of the monomeric units were determined by 13C‐NMR spectroscopy and followed Bernoullian statistics suggesting that the PHBVs were random. The PHBV sequence distribution was also characterized by electrospray ionization‐mass spectrometry (ESI‐MSn) after partial alkaline hydrolysis to oligomers showing a random 3HV distribution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40333.
Crosslinked PVA nanofibers reinforced with cellulose nanocrystals: Water interactions and thermomechanical properties
Authors: Peresin Maria Soledad , Vesterinen Arja‐Helena , Habibi Youssef , Johansson Leena‐Sisko , Pawlak Joel J. , Nevzorov Alexander A. , Rojas Orlando J.
Published: January 2014

Acid‐catalyzed vapor phase esterification with maleic anhydride was used to improve the integrity and thermo‐mechanical properties of fiber webs based on poly(vinyl alcohol), PVA. The fibers were produced by electrospinning PVA from aqueous dispersions containing cellulose nanocrystals (CNCs). The effect of esterification and CNC loading on the structure and solvent resistance of the electrospun fibers was investigated. Chemical characterization of the fibers (FTIR, NMR) indicated the formation of ester bonds between hydroxyl groups belonging to neighboring molecules. Thermomechanical properties after chemical modification were analyzed using thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. An 80% improvement in the ultimate strength was achieved for CNC‐loaded, crosslinked PVA fiber webs measured at 90% air relative humidity. Besides the ultra‐high surface area, the composite PVA fiber webs were water resistant and presented excellent mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40334.
Influence of the degree of crosslinking on the stringiness of crosslinked polyacrylic pressure‐sensitive adhesives
Authors: Ito Keiko , Shitajima Kohei , Karyu Nozomi , Fujii Syuji , Nakamura Yoshinobu , Urahama Yoshiaki
Published: January 2014

The stringiness of crosslinked polyacrylic pressure‐sensitive adhesive (PSA) was observed during 90° peeling under the constant peel load. The random copolymer of butyl acrylate with 5 wt % acrylic acid crosslinked by N,N,N′,N′‐tetraglycidyl‐m‐xylenediamine was used as PSA. All observed stringiness upon peeling was sawtooth‐shaped, but it could be classified into three types dependent on the degree of crosslinking. The typical sawtooth‐shaped stringiness with interfacial failure was observed at the relatively higher crosslinker content ranging from 0.008 to 0.016 chemical equivalents (Eq.), where the PSA has high cohesive strength and low interfacial adhesion. The frame formed at the front end of stringiness at the content ranging from 0.002 to 0.004 Eq. Sufficient interfacial adhesion and deformability generate large internal deformation of the PSA layer. Internal deformation occurred preferentially over peeling as a result of front frame formation. The mode of peeling was changed from cohesive failure to interfacial failure in this range of crosslinker content. The sawtooth‐shaped with cohesive failure was observed at the lower content ranging from 0 to 0.001 Eq. The PSA has high interfacial adhesion and low cohesive strength, and thus exhibited cohesive failure. The PSA after peeling remained in the shape of belts. It was found that the shape of stringiness is strongly dependent on the balance between the interfacial adhesion and the cohesive strength of PSA. When the sawtooth‐shaped stringiness with frame formed, the peeling rate was lowest. This means the peel strength should be the maximum in this shape of stringiness. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40336.
Synthetic small intestinal scaffolds for improved studies of intestinal differentiation
Authors: Costello Cait M. , Hongpeng Jia , Shaffiey Shahab , Yu Jiajie , Jain Nina K. , Hackam David , March John C.
Published: January 2014

In vitro intestinal models can provide new insights into small intestinal function, including cellular growth and proliferation mechanisms, drug absorption capabilities, and host‐microbial interactions. These models are typically formed with cells cultured on 2D scaffolds or transwell inserts, but it is widely understood that epithelial cells cultured in 3D environments exhibit different phenotypes that are more reflective of native tissue. Our focus was to develop a porous, synthetic 3D tissue scaffold with villous features that could support the culture of epithelial cell types to mimic the natural microenvironment of the small intestine. We demonstrated that our scaffold could support the co‐culture of Caco‐2 cells with a mucus‐producing cell line, HT29‐MTX, as well as small intestinal crypts from mice for extended periods. By recreating the surface topography with accurately sized intestinal villi, we enable cellular differentiation along the villous axis in a similar manner to native intestines. In addition, we show that the biochemical microenvironments of the intestine can be further simulated via a combination of apical and basolateral feeding of intestinal cell types cultured on the 3D models. Biotechnol. Bioeng. 2014;111: 1222–1232. © 2014 Wiley Periodicals, Inc.
Psychological care of caregivers, nurses and physicians: a study of a new approach
Authors: Abeni Maurizio S. , Magni Margherita , Conte Martina , Mangiacavalli Silvia , Pochintesta Lara , Vicenzi Gaia , Ferretti Virginia V. , Pompa Alessandra , Cocito Federica , Klersy Catherine , Corso Alessandro
Published: January 2014

There is much evidence demonstrating that psychosocial interventions in caregivers and oncological staff produce an improvement in their patients' quality of life. The aim of this explorative study was to evaluate the effect of a new approach in promoting more functional ways to face stressful situations in the constellation of people around patients: caregivers, physicians and nurses. Thirty‐four subjects were divided into three groups: 10 caregivers, 11 physicians, and 13 nurses. A “Balint Group” method modified according to a mindfulness technique was used as the intervention. Three assessment tools were administered to the participants at baseline, during, and after completion of the study: the Response Evaluation Measure (REM‐71), the Satisfaction Profile (SAT‐P), and the Group Climate Questionnaire (GCQ). Mean values of defense mechanisms determined by the REM‐71 were compared with those of the standard population. At baseline, we observed a prevalence of immature defenses in the three groups, with mean values above those in the standard population. After the psychological intervention, a tendency to normalization of the mean values was observed, indicating the development of more adaptive ways of using defense mechanisms and the effectiveness of the intervention. Group climate, assessed through the GCQ, showed an increase in the “Engagement” factor and a decline in the “Conflict” factor in all groups. This study suggests that group treatment focused on changing personal responses to stressful situations can induce more adaptive strategies enabling caregivers, hematologists, and nurses to help patients better and thereby improve their quality of life.
Cholangiocyte senescence by way of N-ras activation is a characteristic of primary sclerosing cholangitis
Authors: Tabibian James H. , O'Hara Steven P. , Splinter Patrick L. , Trussoni Christy E. , LaRusso Nicholas F.
Published: January 2014

Primary sclerosing cholangitis (PSC) is an incurable cholangiopathy of unknown etiopathogenesis. Here we tested the hypothesis that cholangiocyte senescence is a pathophysiologically important phenotype in PSC. We assessed markers of cellular senescence and senescence-associated secretory phenotype (SASP) in livers of patients with PSC, primary biliary cirrhosis, hepatitis C, and in normals by fluorescent in situ hybridization (FISH) and immunofluorescence microscopy (IFM). We tested whether endogenous and exogenous biliary constituents affect senescence and SASP in cultured human cholangiocytes. We determined in coculture whether senescent cholangiocytes induce senescence in bystander cholangiocytes. Finally, we explored signaling mechanisms involved in cholangiocyte senescence and SASP. In vivo, PSC cholangiocytes expressed significantly more senescence-associated p16INK4a and γH2A.x compared to the other three conditions; expression of profibroinflammatory SASP components (i.e., IL-6, IL-8, CCL2, PAI-1) was also highest in PSC cholangiocytes. In vitro, several biologically relevant endogenous (e.g., cholestane 3,5,6 oxysterol) and exogenous (e.g., lipopolysaccharide) molecules normally present in bile induced cholangiocyte senescence and SASP. Furthermore, experimentally induced senescent human cholangiocytes caused senescence in bystander cholangiocytes. N-Ras, a known inducer of senescence, was increased in PSC cholangiocytes and in experimentally induced senescent cultured cholangiocytes; inhibition of Ras abrogated experimentally induced senescence and SASP. Conclusion: Cholangiocyte senescence induced by biliary constituents by way of N-Ras activation is an important pathogenic mechanism in PSC. Pharmacologic inhibition of N-Ras with a resultant reduction in cholangiocyte senescence and SASP is a new therapeutic approach for PSC. (Hepatology 2014;59:2263–2275)
To Transfuse or Not to Transfuse in Upper Gastrointestinal Hemorrhage? That Is the Question
Authors: Rockey Don C.
Published: January 2014

Abstract

Background:

The hemoglobin threshold for transfusion of red cells in patients with acute gastrointestinal bleeding is controversial. We compared the efficacy and safety of a restrictive transfusion strategy with those of a liberal transfusion strategy.

Methods:

We enrolled 921 patients with severe acute upper gastrointestinal bleeding and randomly assigned 461 of them to a restrictive strategy (transfusion when the hemoglobin level fell below 7 g per deciliter) and 460 to a liberal strategy (transfusion when the hemoglobin fell below 9 g per deciliter). Randomization was stratified according to the presence or absence of liver cirrhosis.

Results:

A total of 225 patients assigned to the restrictive strategy (51%), as compared with 65 assigned to the liberal strategy (15%), did not receive transfusions (P < 0.001). The probability of survival at 6 weeks was higher in the restrictive-strategy group than in the liberal-strategy group (95% vs. 91%; hazard ratio for death with restrictive strategy, 0.55; 95% confidence interval [CI], 0.33 to 0.92; P = 0.02). Further bleeding occurred in 10% of the patients in the restrictive-strategy group as compared with 16% of the patients in the liberal-strategy group (P = 0.01), and adverse events occurred in 40% as compared with 48% (P = 0.02). The probability of survival was slightly higher with the restrictive strategy than with the liberal strategy in the subgroup of patients who had bleeding associated with a peptic ulcer (hazard ratio, 0.70; 95% CI, 0.26 to 1.25) and was significantly higher in the subgroup of patients with cirrhosis and Child–Pugh class A or B disease (hazard ratio, 0.30; 95% CI, 0.11 to 0.85), but not in those with cirrhosis and Child–Pugh class C disease (hazard ratio, 1.04; 95% CI, 0.45 to 2.37). Within the first 5 days, the portal-pressure gradient increased significantly in patients assigned to the liberal strategy (P = 0.03) but not in those assigned to the restrictive strategy.

Conclusions:

As compared with a liberal transfusion strategy, a restrictive strategy significantly improved outcomes in patients with acute upper gastrointestinal bleeding.
Interaction of DHPG‐LTD and synaptic‐LTD at senescent CA3‐CA1 hippocampal synapses
Authors: Kumar Ashok , Foster Thomas C.
Published: January 2014

The susceptibility, but not the magnitude, of long‐term depression (LTD) induced by hippocampal CA3‐CA1 synaptic activity (synaptic‐LTD) increases with advanced age. In contrast, the magnitude of LTD induced by pharmacological activation of CA3‐CA1 group I metabotropic glutamate receptors (mGluRs) increases during aging. This study examined the signaling pathways involved in induction of LTD and the interaction between paired‐pulse low frequency stimulation‐induced synaptic‐LTD and group I mGluR selective agonist, (RS)‐3,5‐dihydroxyphenylglycine (DHPG, 100 µM)‐induced DHPG‐LTD in hippocampal slices obtained from aged (22–24 months) male Fischer 344 rats. Prior induction of synaptic‐LTD did not affect induction of DHPG‐LTD; however, prior induction of the DHPG‐LTD occluded synaptic‐LTD suggesting that expression of DHPG‐LTD may incorporate synaptic‐LTD mechanisms. Application of individual antagonist for the group I mGluR (AIDA), the N‐methyl‐d‐aspartate receptor (NMDAR) (AP‐5), or L‐type voltage‐dependent Ca2+ channel (VDCC) (nifedipine) failed to block synaptic‐LTD and any two antagonists severely impaired synaptic‐LTD induction, indicating that activation of any two mechanisms is sufficient to induce synaptic‐LTD in aged animals. For DHPG‐LTD, AIDA blocked DHPG‐LTD and individually applied NMDAR or VDCC attenuated but did not block DHPG‐LTD, indicating that the magnitude of DHPG‐LTD depends on all three mechanisms. © 2014 Wiley Periodicals, Inc.
Performance of visual inspection with acetic acid and human papillomavirus testing for detection of high‐grade cervical lesions in HIV positive and HIV negative Tanzanian women
Authors: Dartell Myassa Arkam , Rasch Vibeke , Iftner Thomas , Kahesa Crispin , Mwaiselage Julius D. , Junge Jette , Gernow Anne , Ejlersen Sussi Funch , Munk Christian , Kjaer Susanne Kruger
Published: January 2014

The aim of this cross sectional study was to assess type distribution of human papillomavirus (HPV) among HIV positive and HIV negative women who underwent cervical cancer screening, and to examine the ability of visual inspection with acetic acid (VIA), the standard detection method in Tanzania, and HPV‐testing to detect cytologically diagnosed high grade lesions or cancer (HSIL+). Women from different areas in Tanzania were invited by public announcement to cervical cancer screening organized by Ocean Road Cancer Institute (Dar‐es‐Salaam). A total of 3,767 women were enrolled. Women underwent gynecological examination with collection of cervical cells for conventional cytological examination, and swab for HPV‐DNA detection (Hybrid‐Capture2) and genotyping (LiPAv2 test). Subsequently VIA was performed. The participants were also tested for HIV. HPV16, HPV52 and HPV18 were the three most common HR HPV types among women with HSIL+ cytology with prevalences of 42.9, 35.7 and 28.6%, respectively, in HIV positive women which was higher than among HIV negative women (30.2, 21.9 and 16.7%). A total of 4.5% of the women were VIA positive, and VIA showed a low sensitivity compared to HPV‐testing for detection of HSIL+. The sensitivity of VIA varied with staff VIA experience, HIV status and age. Vaccines including HPV16, HPV52 and HPV18 will likely reduce the number of HSIL+ cases independently of HIV status. The frequency of HSIL+ was high among HIV positive women, emphasizing the importance of establishing a screening program which also reaches HIV positive women. Our results highlight the importance of continuous training of staff performing VIA, and also point to the need for other screening methods such as HPV‐testing at low cost.