Long-term Dispersion Research Articles

Urea modified fluorinated carbon nanotubes: unique self-dispersed characteristic in water and high tribological performance as water-based lubricant additives

UF-CNTs retaining a long-term dispersion stability in aqueous environments exhibit excellent tribological properties.

Synthesis of boron nitride microrods with fish-scale-like structures for enhanced thermal conductivity of water

Hexagonal boron nitride (h-BN) has triggered great interest in thermal management system because of its superb thermal conductivity, excellent chemical inertness and outstanding tribological behavior. However, the application of BN in water suffers from the poor dispersion stability. Herein, we develop a spray drying and pyrolysis route to directly fabricate porous BN microrods with fish-scale-like structures. BN microrods exhibit long-term dispersion stability in aqueous solution due to their high hydroxylation degrees. Although the viscosity of water was increased after adding BN microrods, the friction coefficient and wear scar diameter were reduced obviously. Moreover, thermal conductivity of BN/water fluid was improved from 0.589 to 1.117 W/m K when the content of BN was 0.1 vol%, which was higher than that of previous results. These results demonstrate that the fish-scale-like structured BN microrods have great potential and irreplaceable advantage in thermal and tribological management.

Winter movements and long-term dispersal of Steller sea lions in the Glacier Bay region of Southeast Alaska

Winter movements and long-term dispersal of Steller sea lions in the Glacier Bay region of Southeast Alaska

Indicators for evaluating uncertainties of solute concentration prediction in wetland flows

Abstract Solute transport in wetland flows is an important process to understand for agricultural practices, providing essential information to assist in decision making and regulation for both cases of agricultural water contamination and agricultural pollution. Recent study has suggested that in the application of the one-dimensional Taylor dispersion model for solute concentration distribution in wetlands, uncertainties can arise even when contaminants are initially released at the same streamwise location. In this paper, we present an analytical study of instantaneous point-source release of solute in a wetland flow dominated by bank wall effects. The movement of the solute centroid and the long-term asymptotic Taylor dispersion coefficient are determined by the Aris concentration moment method, which are required for quantifying the streamwise distribution of the mean concentration and the transverse concentration distribution profiles. It is shown that the additional longitudinal displacement serves as a key indicator revealing the uncertainties of concentration distribution caused by different lateral positions of the contaminant release. More indicators including the lateral concentration distribution and the relative difference of the concentration are analyzed in detail. With given physical parameters, simple applications are provided to illustrate the streamwise transport of the solute plume centroid and the evolution of the additional longitudinal displacement affected by the bank wall effects.

Molecular systematics and biogeography of lowland antpittas (Aves, Grallariidae): The role of vicariance and dispersal in the diversification of a widespread Neotropical lineage

We infer phylogenetic relationships, divergence times, and the diversification history of the avian Neotropical antpitta genera Hylopezus and Myrmothera (Grallariidae), based on sequence data (3,139 base pairs) from two mitochondrial (ND2 and ND3) and three nuclear nuclear introns (TGFB2, MUSK and FGB-I5) from 142 individuals of the 12 currently recognized species in Hylopezus and Myrmothera and 5 outgroup species. Phylogenetic analyses recovered 19 lineages clustered into two major clades, both distributed in Central and South America. Hylopezus nattereri, previously considered a subspecies of H. ochroleucus, was consistently recovered as the most divergent lineage within the Grallaricula/Hylopezus/Myrmothera clade. Ancestral range estimation suggested that modern lowland antpittas probably originated in the Amazonian Sedimentary basin during the middle Miocene, and that most lineages within the Hylopezus/Myrmothera clade appeared in the Plio-Pleistocene. However, the rate of diversification in the Hylopezus/Myrmothera clade appeared to have remained constant through time, with no major shifts over the 20 million years. Although the timing when most modern lineages of the Hylopezus/Myrmothera clade coincides with a period of intense landscape changes in the Neotropics (Plio-Pleistocene), the absence of any significant shifts in diversification rates over the last 20 million years challenges the view that there is a strict causal relationship between intensification of landscape changes and cladogenesis. The relative old age of the Hylopezus/Myrmothera clade coupled with an important role ascribed to dispersal for its diversification, favor an alternative scenario whereby long-term persistence and dispersal across an ever-changing landscape might explain constant rates of cladogenesis through time.

Effect of the Duration of Meteorological Data Collection on the Prospective Assessment of Long-Term Atmospheric Dispersion Factors.

Assessing the environmental dispersion of radioactive effluents from a nuclear facility under normal operation is a prerequisite in applying for the construction permit and operation license of the facility. In Korea, the Nuclear Safety and Security Commission requires at least 1- and 2-year periods of site-specific meteorological data to assess the atmospheric dispersion of the effluents from a nuclear reactor facility for a construction permit and operating license, respectively. In this study, we investigated if an extended period of meteorological data would be certainly preferable for the prospective assessment of dispersion of the atmospheric effluents under current data handling approaches. For test estimation, the meteorological data collected in the Kori nuclear power plant site in 2001 to 2008 were utilized. We suggest that the accumulated meteorological data be reflected in assessing the atmospheric dispersion in the form of individual annual data rather than the averaged data over the whole period.

Quantifying airborne dispersal routes of pathogens over continents to safeguard global wheat supply.

Infectious crop diseases spreading over large agricultural areas pose a threat to food security. Aggressive strains of the obligate pathogenic fungus Puccinia graminis f.sp. tritici (Pgt), causing the crop disease wheat stem rust, have been detected in East Africa and the Middle East, where they lead to substantial economic losses and threaten livelihoods of farmers. The majority of commercially grown wheat cultivars worldwide are susceptible to these emerging strains, which pose a risk to global wheat production, because the fungal spores transmitting the disease can be wind-dispersed over regions and even continents 1-11 . Targeted surveillance and control requires knowledge about airborne dispersal of pathogens, but the complex nature of long-distance dispersal poses significant challenges for quantitative research 12-14 . We combine international field surveys, global meteorological data, a Lagrangian dispersion model and high-performance computational resources to simulate a set of disease outbreak scenarios, tracing billions of stochastic trajectories of fungal spores over dynamically changing host and environmental landscapes for more than a decade. This provides the first quantitative assessment of spore transmission frequencies and amounts amongst all wheat producing countries in Southern/East Africa, the Middle East and Central/South Asia. We identify zones of high air-borne connectivity that geographically correspond with previously postulated wheat rust epidemiological zones (characterized by endemic disease and free movement of inoculum) 10,15 , and regions with genetic similarities in related pathogen populations 16,17 . We quantify the circumstances (routes, timing, outbreak sizes) under which virulent pathogen strains such as 'Ug99' 5,6 pose a threat from long-distance dispersal out of East Africa to the large wheat producing areas in Pakistan and India. Long-term mean spore dispersal trends (predominant direction, frequencies, amounts) are summarized for all countries in the domain (Supplementary Data). Our mechanistic modelling framework can be applied to other geographic areas, adapted for other pathogens and used to provide risk assessments in real-time 3 .

Between housing and deep forest: Long-term population biology and dispersal of suburban Smooth snakes (Coronella austriaca)

We investigated the characteristics of a small smooth snake population in central Germany after it experienced a rapid loss of habitat between 1955 and 1990. We hypothesised that local smooth snakes might demonstrate abnormalities in population characteristics such as age of maturity, growth rates, sex-ratio, reproduction, movement behaviour or in population density, indicating degradation. To address this issue, we analysed data of a 17-year visual encounter survey (VES) accompanied by mark-recapture methods and complemented by a short-term radiotelemetry study of nine adult snakes. We then compared the population and behavioural characteristics with those from other European smooth snake populations. Our results indicated a healthy population despite the severe habitat loss. The population was characterised by a balanced sex-ratio and large litter sizes. Gender specific differences in migration behaviour and home ranges were typical for this species. However, the home ranges were unusually small which agrees with the noticeably high population density and the short time periods tracked. Although adult migration to adjacent habitats was never detected, some migration to and from other suburban sites likely occurred, evidenced annually by the high rate of first-captures of previously unregistered adults. Our results suggested that even a very small area could be sufficient for the survival and maintenance of a viable population of smooth snakes if the habitat provides a high abundance of essential microhabitats. Comparing our population variables with those from other studies help (1) to reduce potential threats at a regional level and (2) to define specific conservation actions for the population.

Decoration of gold nanoparticles with thiolated pH-responsive polymeric (PEG-b-p(2-dimethylamio ethyl methacrylate-co-itaconic acid) shell: A novel platform for targeting of anticancer agent

The aim of this study was to design and develop a new pH-responsive nano-platform for controlled and targeted delivery of anticancer drugs. Engineering of pH-responsive nanocarriers was prepared via decoration of gold nanoparticles (NPs) by thiolated (methoxy-poly(ethylene glycol)-b-poly((2-dimethylamino) ethyl methacrylate-co-itaconic acid) (mPEG-b-p(DMAEMA-co-IA) copolymer and fully characterized by various techniques and subsequently used for loading and targeted delivery of anticancer agent, methotrexate (MTX). By conjugation of MTX with the amino groups of polymeric shell of gold NPs (with the high loading capacity of 31%), since MTX is also the target ligand of folate receptors, the targeted performance of NPs examined through the cell uptake study. The results indicated that MTX-loaded NPs showed 1.3 times more cell internalization than MTX free NPs. Cell cytotoxicity studies pointed out ~1.5 and 3 times higher cell cytotoxicity after 24h for MTX-loaded nanoparticles than MTX in MTT assay and cell cycle arrest experiments, respectively. Additionally, mPEG was used as the outer shell of NPs which caused the long-term dispersibility of the NPs even under high ionic strength. The in-vitro pH-triggered drug release of MTX showed that MTX released more than three times in simulated cancerous tissue (40°C, pH5.3) than physiologic condition (37°C, pH7.4) during 48h. The results of various experiments determined that the developed smart nanocarrier proposed as a promising nanocarrier for active and passive targeting of anionic anti-cancer agents such as MTX.

Long-term dispersion and availability of metals from submarine mine tailing disposal in a fjord in Arctic Norway.

Mining of Cu took place in Kvalsund in the Arctic part of Norway in the 1970s, and mine tailings were discharged to the inner part of the fjord, Repparfjorden. Metal speciation analysis was used to assess the historical dispersion of metals as well as their potential bioavailability from the area of the mine tailing disposal. It was revealed that the dispersion of Ba, Cr, Ni, Pb and Zn from the mine tailings has been limited. Dispersion of Cu to the outer fjord has, however, occurred; the amounts released and dispersed from the mine tailing disposal area quantified to be 2.5-10t, less than 5% of Cu in the original mine tailings. An estimated 80-390t of Cu still remains in the disposal area from the surface to a depth of 16cm. Metal partitioning showed that 56-95% of the Cu is bound in the potential bioavailable fractions (exchangeable, reducible and oxidisable) of the sediments, totalling approximately 70-340t, with potential for continuous release to the pore water and re-precipitation in over- and underlying sediments. Surface sediments in the deposit area were affected by elevated Cu concentrations just above the probable effect level according to the Norwegian sediment quality criteria, with 50-80% Cu bound in the exchangeable, reducible and oxidisable fractions, potentially available for release to the water column and/or for uptake in benthic organisms.

Experimental investigation on the stability and abrasive action of cerium oxide nanoparticles dispersed diesel

Ceria nanoparticle is a well-known fuel borne additive for reducing the particulate emissions from diesel engines. Main challenges in the use of ceria nanoparticles are the lack of long-term dispersion stability in diesel and their effect on lubricity of diesel. The present work mainly focuses on synthesis of stable ceria nanoparticle diesel suspension and study on their lubricity. Ceria nanoparticles were synthesized by co-precipitation method and nano fluids were prepared by two-step method. The optimum concentration of oleic acid (surfactant) was determined based on critical micelle concentration studies and concentration of ceria nanoparticle in diesel was varied from 5 to 25 ppm. Long term dispersion stability studies using Dynamic light scattering system and Turbidity meter shows 10 ppm as an optimum concentration of ceria nanoparticle in diesel for maximum stability. Tribological properties of modified diesel were studied by a standard pin on disk apparatus. The wear rate was found to be reduced for all the nano additive concentrations in diesel and was least for 15 ppm. Based on studies conducted, 10 ppm is reported as an optimum concentration of nanoparticle in diesel having both enhanced stability and lubricity as compared to other concentrations of ceria nanoparticles in diesel.

Long-Term Polarization Mode Dispersion Evolution and Accelerated Aging in Old Optical Cables

Today’s optical networks are composed of thousands of kilometers of aging optical cables. Many of these cables are located in harsh environments, which contribute to induced birefringence of the fibers and a corresponding increase of polarization mode dispersion (PMD). This letter introduces derived statistics from the longest-known running evaluation of a PMD measuring campaign and an investigation into how higher optical power affects these aging systems. Results indicate strong seasonal dependence of PMD on temperature for an optical cable test bed exposed to atmospheric changes, leading to a 16% increase of a mean PMD value in summer. This fluctuation causes bit error rate limits to be exceeded for 10 and 40 Gbps non-return-to-zero signals, which is a critical issue for applications where high reliability is required. Moreover, due to the high optical power load within old optical infrastructures, a more than 0.15 dB increase of relative loss per year in tested routes, compared with reference routes, has been observed.

Polyacrylonitrile-grafted reduced graphene oxide hybrid: An all-round and efficient hole-extraction material for organic and inorganic-organic hybrid photovoltaics

In this research, we demonstrate that aliphatic polyacrylonitrile-grafted reduced graphene oxide (PRGO) hybrid can function efficiently as an all-round hole-extraction layer (HEL) in organic and organic-inorganic hybrid perovskite photovoltaic devices (OPVs and PePVs). The hybrid-structure PRGO was developed by facile and scalable in-situ radiation-induced reduction and graft polymerization with polymerizable styryl-functionalized graphene oxide and acrylonitrile. The newly developed PRGO exhibits long-term dispersion stability of six months even up to the high concentration of 10mg/ml. It also shows a full-cover uniform thin-film morphology, good electrical conductivity (0.87S/cm), high work function (4.87eV), and excellent weather stability. Moreover, the incorporation of PRGO (as a HEL) into the OPVs and PePVs results in greater efficiency than chemically-converted graphene nanoflakes references, and device durability superior to poly(ethylenedioxythiophene):poly(styrene sulfonate)-based ones with comparable power conversion efficiencies. Noticeably, our finding demonstrates that the hybrid-structure PRGO provides an all-round and efficient hole-extraction material for use in various conjugated-polymer and perovskite-based PV systems.

Improvement in clinical trial disclosures and analysts’ forecast accuracy: evidence from the pharmaceutical industry

This paper examines whether financial analysts use the information contained in clinical trial disclosures to improve their forecast accuracy for pharmaceutical companies. Findings indicate that the improved clinical trial disclosures due to a quasi-regulation issued by the International Committee of Medical Journal Editors (ICMJE) significantly reduce analysts’ long-term forecast error. In addition, a propensity-score matching analysis provides additional strong evidence that issuance of the 2005 ICMJE’s regulation is accompanied by an average 45 % decrease in long-term forecast error, and a more than 50 % decrease in long-term forecast dispersion. This study contributes to the accounting literature regarding nonfinancial disclosures by providing the first insights into financial analysts’ use of clinical trial disclosures in their forecasts of future earnings. In addition, because the major event examined in this study is a quasi-regulation issued by the ICMJE, we provide additional insights on the effectiveness of industry-initiated regulations (or quasi-regulations) on nonfinancial disclosure practice.

Iris alterations after DSAEK

Abstract Objective To evaluate a series of case that developed iris changes after performing Descemet's stripping automated endothelial keratoplasty (DSAEK). Methods Retrospective study of eyes that developed iris abnormalities, such as pupil ovalisation, iris atrophy, iridocorneal synechiae, mydriatic pupil, and pigmentary changes after performing DSAEK in a tertiary hospital. Results In a series of the first 32 DSAEK procedures performed, new single or mixed iris alterations were observed in 12 eyes (37.5%). Iris-corneal synechiae were observed in 7 eyes, corectopias in 9 eyes, iris atrophy in 3 cases, and one case developed an areflexic mydriatic pupil. Long-term pigment dispersion at the edge of the lenticule was observed in 12 eyes. The alterations occurred after three months from the surgery. In the evaluation of the associated factors, malignant glaucoma had occurred in 1 case, 2 eyes had required a second surgery, one case by re-DSAEK, and the other one by removing the intraocular lens due to lens opacification. Two cases had a shallow anterior chamber. No relationship was found between the thickness of the peripheral lenticule and the presence of synechiae. Conclusion Iris changes regarding DSAEK are possible. A discussion is presented on the relationship between increased intraocular pressure due to air in anterior chamber and its relationship with ischemia and secondary alterations in the iris.

Area use and movements of the white croaker (Genyonemus lineatus) in the Los Angeles and Long Beach Harbors

Understanding the movements of fish in relation to areas of contaminated and urbanized habitats is crucial to fisheries management and habitat remediation. In this study, the movements of white croaker in the Los Angeles and Long Beach Harbors were examined using both active and passive acoustic telemetry tracking. Daily area use for 20 fish actively tracked over multiple days averaged 94,720 ± 78,720 m2 (±SD), with daily activity spaces shifting over periods of up to 1 month. Long-term dispersal (up to 7 months) of 93 passively tracked white croaker followed significantly non-random patterns, with 55 individuals (59.1%) making inter-regional Harbor movements. Inter-regional movements took an average of 4.7 ± 4.1 weeks to complete. Dispersal was significantly faster than what was predicted by an individual-based random walk model generated from short-term white croaker movements recorded during active tracking within the Harbor. Longer-term dispersal is likely the result of intentional movements between patches of favorable habitat rather than random daily shifts in activity spaces, indicating that white croaker deliberately utilize different areas within the Harbor and over the course of a year utilize much of the favorable Harbor habitat.

Preparation of lipophilic graphene oxide derivates via a concise route and its mechanical reinforcement in thermoplastic polyurethane

A facile, effective and environmental friendly route was presented to prepare lipophilic graphene oxide (GO) derivates via the esterification reaction of the carboxylate salt of GO and 1-bromohexadecane in the presence of a phase-transfer reagent in water. The resultant long alkyl chains modified graphene oxide sheets (GO-HD) show the long-term and stable dispersion capability in many organic solvents. Successful grafting of long alkyl chains onto GO surfaces was confirmed through FTIR, XPS, TGA, UV–vis spectrum techniques. Moreover, we utilized the GO-HD as a reinforcing filler to prepare GO-HD/thermoplastic polyurethane (TPU) nanocomposites through solution casting method. The uniform distribution and good interfacial adhesion are expected for the GO-HD based nanocomposites due to the good compatibility between long alkyl chains of GO-HD fillers and TPU chains. Notably, tensile mechanical tests demonstrated that the GO-HD/TPU nanocomposites at low filler contents (≤2 wt%) exhibit higher modulus, ultimate tensile strength without compromising the intrinsic extensibility of TPU matrix as compared with the GO/TPU nanocomposites with same filler content. Further, in situ tensile-micro Raman spectroscopy tests were employed to monitor the load transfer process at a microscopic level, and revealed the improved load transfer efficiency in the GO-HD/TPU nanocomposites.

A novel dual-responsive core-crosslinked magnetic-gold nanogel for triggered drug release

A facial approach was reported to prepare a novel dual-responsive core-crosslinked nanogel and investigated for the triggered methotrexate (MTX) release. Nanogels with core-shell architecture were synthesized by decoration of Au/Fe3O4 core/shell NPs using poly(ethylene glycol)-b-poly((N,N-dimethylamino)ethyl methacrylate-co-2-hydroxyethyl methacrylate)-maleic acid (PEG-b-P(DMAEMA-co-HEMA)-MA) for crosslinking and autoreduction processes. The second block containing amino groups and maleate groups as the inner shell was used for the reduction of HAuCl4 (auric cation) in the presence of Fe3O4 NPs and as a crosslinker agent, respectively. Furthermore, to improve the long-term dispersibility of the nanogels, poly(ethylene glycol) was preferred as outer shell even under high ionic strength. After that, NIPAAm was polymerized from the vinyl double bonds for fabricating the thermo and pH-responsive core-crosslinked nanogels. MTX (an anti-cancer agent) was successfully loaded (the loading capacity of 37%) into the nanogels by both ionic interaction and entrapment in polymeric network in the inner shell. The triggered MTX release ability of the synthesized nanocarriers was proved through the comparison of in-vitro drug release at simulated physiological condition and tumor tissue environment. MTT assay showed that MTX-loaded nanocarriers revealed high antitumor activity in MCF7 cell line after incubation following 24 and 48h. It was concluded that the developed nanogels have many promising qualities as an efficient carrier for the targeted MTX delivery to cancer tissues.

Alteraciones iridianas tras Queratoplastia endotelial automatizada con stripping de la Descemet

ObjectiveTo evaluate a series of case that developed iris changes after performing Descemet's stripping automated endothelial keratoplasty (DSAEK). MethodsRetrospective study of eyes that developed iris abnormalities, such as pupil ovalisation, iris atrophy, iridocorneal synechiae, mydriatic pupil, and pigmentary changes after performing DSAEK in a tertiary hospital. ResultsIn a series of the first 32 DSAEK procedures performed, new single or mixed iris alterations were observed in 12 eyes (37.5%). Iris-corneal synechiae were observed in 7 eyes, corectopias in 9 eyes, iris atrophy in 3 cases, and one case developed an areflexic mydriatic pupil. Long-term pigment dispersion at the edge of the lenticule was observed in 12 eyes. The alterations occurred after three months from the surgery. In the evaluation of the associated factors, malignant glaucoma had occurred in 1 case, 2 eyes had required a second surgery, one case by re-DSAEK, and the other one by removing the intraocular lens due to lens opacification. Two cases had a shallow anterior chamber. No relationship was found between the thickness of the peripheral lenticule and the presence of synechiae. ConclusionIris changes regarding DSAEK are possible. A discussion is presented on the relationship between increased intraocular pressure due to air in anterior chamber and its relationship with ischaemia and secondary alterations in the iris.

Biocompatible multilayer capsules engineered with a graphene oxide derivative: synthesis, characterization and cellular uptake.

Graphene-based capsules have strong potential for a number of applications, including drug/gene delivery, tissue engineering, sensors, catalysis and reactors. The ability to integrate graphene into carrier systems with three-dimensional (3D) geometry may open new perspectives both for fundamental tests of graphene mechanics and for novel (bio)technological applications. However, the assembly of 3D complexes from graphene or its derivatives is challenging because of its poor stability under biological conditions. In this work, we attempted to integrate a layer of graphene oxide derivative into the shell of biodegradable capsules by exploiting a facile layer-by-layer (LbL) protocol. As a first step we optimized the LbL protocol to obtain colloidal suspensions of isolated capsules embedding the graphene oxide derivative. As a following step, we investigated in detail the morphological properties of the hybrid capsules, and how the graphene oxide derivative layer influences the porosity and the robustness of the multilayer composite shells. Finally, we verified the uptake of the capsules modified with the GO derivative by two cell lines and studied their intracellular localization and biocompatibility. As compared to pristine capsules, the graphene-modified capsules possess reduced porosity, reduced shell thickness and a higher stability against osmotic pressure. They show remarkable biocompatibility towards the tested cells and long-term colloidal stability and dispersion. By combining the excellent mechanical properties of a graphene oxide derivative with the high versatility of the LbL method, robust and flexible biocompatible polymeric capsules with novel characteristics have been fabricated.