Low Degree Of Aggregation Research Articles

The study of the ontogenesis of crystals of the Ural type diamonds by the method of IR-spectrometry

The collection of the Ural, Anabar and Brazilian diamonds conducted research by infrared spectrometry method. It was found that a diamond with a low degree of aggregation of nitrogen defects composing the crystals of the later generation from mantle eclogite xenoliths and outer zones of the greater part of the crystals from deposits of kimberlite-lamproite type is missing or is poorly developed in the crystals of the Ural type. Conclusions about the thermal conditions of the Ural diamonds formation and their possible affinity to the specification and type of original sources.

Wearable supercapacitors based on graphene nanoplatelets/carbon nanotubes/polypyrrole composites on cotton yarns electrodes

The development of highly conductive, flexible, mechanical reinforced and chemically modified cotton yarns for electrodes of supercapacitors represents an important advance in the energy storage devices applied in wearable electronics. The production of carbon-based conductive layers as supports for chemical polymerization of active polymeric materials (such as polypyrrole) is an important strategy that associates the high electrical double-layer capacitance of the carbon derivatives (carbon nanotubes and graphene nanoplatelets) and the pseudocapacitance of the polypyrrole in truly flexible devices with improved electrochemical response—high capacitance. These properties are affected by relative concentration of graphene nanoplatelets in carbon complexes due to the variation in overall conductivity of electrodes (in consequence of low aggregation degree and available surface area) and the electrochemical properties of the resulting devices that reaches capacitance in order of 45.5 F g−1 with a capacitive retention of 70% after 2000 cycles of use. These promising results open possibilities for new systems in wearable electronics.

Embedding Carbon Dots in Superabsorbent Polymers for Additive Manufacturing.

A type of orange carbon dots (O-CDs) synthesized via an ultrasonication route with citric acid and 1,2-phenylenediamine as precursors was embedded into sodium polyacrylate (SPA) as the ink for 3D printing. Characterizations of these spherical O-CDs revealed an ultra-small size (~2 nm) and excitation-independent, but solvent dependent, emission. The O-CDs were evenly distributed with low degree of aggregation in sodium polyacrylate (SPA), which was achieved due to the property that SPA can absorb water together with O-CDs. The 3D printed photoluminescent objective with the ink revealed a great potential for high yield application of these materials for additive manufacturing. This also represents the first time, bare CDs have been reported as a photoluminescent material in 3D printing, as well as the first time SPA has been reported as a material for 3D printing.

Yttria nanopowders with low degree of aggregation by a spray precipitation method

Highly sinterable Y2O3 nano-powder with low degree of agglomeration was synthesized by using a spray precipitation technology, without the use of any additives and dispersants. Compared with the precursor made by using the dripping method (D-precursor), the precursor made by the spraying method (S-precursor) had much lower degree of hard agglomeration. So did the resultant calcined Y2O3 powder (S-Y2O3 powder) as compared with the D-Y2O3 powder. Sintering behaviors of the two powders were studied. Ceramics made from the S-Y2O3 powder (S-Y2O3 ceramics) showed much higher densification rate and final density. After vacuum sintered at 1650 °C for 5 h, relative density of the D-Y2O3 ceramics was merely 97.3%, while that of the S-Y2O3 ceramics reached 99.5%. In addition, the D-Y2O3 ceramics cannot be sintered to 98% relative density by using the vacuum sintering technique, due to the high degree of agglomeration of the D-Y2O3 powder. Moreover, the S-Y2O3 ceramic exhibited homogeneous microstructure and an in-line optical transmittance of 81.6% at 1200 nm after HIP treatment. The spray precipitation method should be applicable to synthesizing other oxide powders.

Metacercariae of Austrodiplostomum compactum (Lutz, 1928) (Trematoda, Diplostomidae) infecting the eyes of Plagioscion squamosissimus (Heckel, 1840) (Perciformes, Scienidae) from Lake Catalão, Amazonas, Brazil

ABSTRACT Austrodiplostomum compactum is a digenetic trematode whith metacercariae that occur in the eyes of a wide variety of fish species. In Brazil, A. compactum metacercariae have been reported in many fish species, but there are only a few studies in the Amazon region. Due to the lack of information in the Amazon, the aim of this study was to report the occurrence of A. compactum metacercariae in the eyes of 15 specimens of Plagioscion squamosissimus from the Lake Catalão, in Amazonas, Brazil. Fishes were collected using gill nets placed randomly in the lake, euthanized in a field laboratory, and had their eyes dissected and examined under a stereomicroscope. A total of 801 metacercariae were registered infecting the eyes of the hosts with a parasitic prevalence of 100%. There was a significant positive correlation between the number of metacercariae recorded and the standard body length of fishes. No significant correlation was found between the number of metacercariae and the weight and relative condition factor (Kn) of the hosts. Values of the variance-to-mean ratio and Green's index suggested an aggregate distribution of the parasites in the hosts, with a low degree of aggregation. This is the first report of occurrence of A. compactum parasitizing a fish in the Lake Catalão.

Effect of Carbon Content on Morphology, Size and Phase of Submicron Tungsten Carbide Powders by Salt-assisted Combustion Synthesis

Abstract The diluent NaCl was introduced into the WO 3 -Mg-C-Na 2 CO 3 system to prepare submicron tungsten carbide (WC) powders via salt-assisted combustion synthesis. The products were analyzed by SEM, EDS and XRD, and the effects of C content on morphology, average particle size and phase composition of the products were studied. Results show that on basis of the m = 0.125 (the number of moles of Na 2 CO 3 ), when the number of moles of carbon in raw material increases from l =2 to 2.25 and 2.5, before leaching, the product is made up of a small number of large size particles and a large number of small size particles; after leaching, samples are composed of aggregates of submicron particles, and the sintering phenomenon between particles is very weak, indicating low degree of aggregation. Particle size distribution of leached product almost falls into the normal distribution, and the particle sizes range from 200 nm to 350 nm. Under the condition of l =2.25, a main target product is WC, and the content of by-products W 2 C is extremely few. That is, k = 2.0 (the number of moles of NaCl), m = 0.125, and l =2.25 are the process conditions for single-phase WC synthesis.

Dinámica poblacional de Metamicrocotyla macracantha (Monogenea: Microcotylidae) parásito de Mugil cephalus (Pisces: Mugilidae) en la costa central peruana

Infestation by the monogenean Metamicrocotyla macracantha was studied from 1983 to 1986 in 584 fishes (Mugil cephalits) from the central Peruvian coast. Prevalence, abundance and mean intensity of infestation were- 60.8%, 2.14 and 3.53, respectively. A total of 1 252 parasites were collected; they had an overdispersed distribution and a low degree of aggregation. Longer fishes were more heavi1y infested, but sexes did not differ. The infestation . showed no significant seasonal variations. The parasite preferred the first branchial pairo Because of an absence of drastic temperature changes, the central Peruvian coast is a favorable environment for the continuity of the tife cycle of M. macracantha

The transformation features of impurity defects in natural diamonds of various habits under high P–T conditions

The results of the investigations of the transformation of impurity defects in natural diamonds of various habits at the stage of high-temperature annealing at P = 6 GPa and T = 2200°C are presented. The studies conducted allowed us to ascertain that the transformations of Aand B-defects in diamonds of octahedral and cubic habits follow general regularities. This fact shows that most of the diamonds of cubic habit with low degree of aggregation of nitrogen centers were not really annealed over a long-term interval. Unlike octahedral diamonds, those of cubic habit are characterized by a pronounced increase in the peak of H-containing defects (3107 cm–1) after annealing.

Synthesis and Luminescent Properties of REVO4–REPO4 (RE = Y, Eu, Gd, Er, Tm, or Yb) Heteronanostructures: A Promising Class of Phosphors for Excitation from NIR to VUV

Despite presenting very similar structural properties, rare earth (RE) phosphate and vanadate solids display different spectroscopic behaviors, which makes the elaboration of REVO4–REPO4 mixed structures an interesting prospect for the design of luminescent materials with improved activity. This work describes the application of a two-step colloidal precipitation approach for the formation of REVO4–REPO4 heteronanostructures and an investigation of their luminescent properties. The growth of the phosphate phase over REVO4 particles was kinetically evaluated through spectroscopic methodologies comprising the observation of the VO43– → Eu3+ energy transfer and the absorption of vanadium(V) peroxocomplexes in solution. This confirmed an effective coating of the precursor nanoparticles. In order to obtain materials with enhanced properties, a protected annealing methodology in SiO2 was applied, leading to highly crystalline nanorods with low degree of aggregation. The final materials display efficient emissio...

Cobalt chromite obtained by thermal decomposition of oxalate coordination compounds

Cobalt chromites (CoCr2O4) powders have been synthesized via thermal decomposition of oxalate precursor compounds (NH4)4[CoCr2(C2O4)4(OH)4]·7H2O (I) and (NH4)12[CoCr2(C2O4)8(OH)4]·(NH4)2C2O4·12H2O (II). The oxalate precursors have been characterized by infrared (IR) and ultraviolet–visible spectroscopy (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis. The structure, morphology and magnetic properties of CoCr2O4 powders have been investigated by XRD, SEM, IR and Raman spectroscopy (RS), UV–vis and magnetic measurements. XRD patterns confirmed the formation of spinel-type cobalt chromite, with average crystallite sizes calculated from XRD patterns of 38nm and 58nm, for spinel chromites from precursors I and II, respectively. SEM micrographs revealed particle sizes between 30 and 130nm, with a low degree of aggregation of primary nanocrystallites. Both CoCr2O4 powders presented ferrimagnetic ordering below the Currie temperature (Tc) and a phase transition at Ts~20K attributed to the onset of long-range spiral magnetic order.

Novel solvothermal approach to hydrophilic nanoparticles of late transition elements and its evaluation by nanoparticle tracking analysis

Solvothermal treatment of late transition metal acetylacetonates in a novel medium composed either of pure acetophenone or acetophenone mixtures with amino alcohols offers a general approach to uniform hydrophilic metal nanoparticles with high crystallinity and low degree of aggregation. Both pure metal and mixed-metal particles can be accesses by this approach. The produced materials have been characterized by SEM-EDS, TEM, FTIR in the solid state and by Nanoparticle Tracking Analysis in solutions. The chemical mechanisms of the reactions producing nanoparticles has been followed by NMR. Carrying out the process in pure acetophenone produces palladium metal, copper metal with minor impurity of Cu2O, and NiO. The synthesis starting from the mixtures of Pd and Ni acetylacetonates with up to 20 mol% of Pd, renders in minor yield the palladium-based metal alloy along with nickel oxide as the major phase. Even the synthesis starting from a mixed solution of Cu(acac)2 and Ni(acac)2 produces oxides as major products. The situation is improved when aminoalcohols such as 2-aminoethanol or 2-dimethylamino propanol are added to the synthesis medium. The particles in this case contain metallic elements and pairs of individual metals (not metal alloys) when produced from mixed precursor solutions.

Low-agglomerated yttria nanopowders via decomposition of sulfate-doped precursor with transient morphology

The fabrication peculiarities of low-agglomerated yttria (Y2O3) nanopowders via thermal decomposition of sulfate-doped precursor with transient morphology were studied. It was determined that Y2(OH)5(NO3)x(CO2)y(SO4)z·nH2O (n=1-2) crystalline precursor underwent fragmentation and decomposition into isolated quasi-spherical Y2O3 particles upon calcination. Effect was connected with minimizing the free energy of the plate-like crystallites via reducing the contact surface until to the moment of spheroidization and attainment of isolation that occurred at T=1100 °C. Residual sulfate ions slowed down the surface diffusion during heat treatment thus retaining quasy-spherical morphology and low aggregation degree of Y2O3 nanopowders. Sulfate-doped yttria nanopowders with medium particle size of 53±13 nm possessed improved sinterability in comparison with undoped ones arising from finer particle size, narrower particle distribution and lower agglomeration degree.

“Balanced aggregation – “snow man” shaped or tripod-like (fumed) particles that allow for better fixation on toner resin surfaces”

The aggregates for two types of fumed silica are compared with each other and with colloidal silica similar to one used as a spacer additive for toner. These examples of fumed silica differ in that one is made up of very large (sub-micron) sized primary particles with a low degree of aggregation while the second fumed silica example has a much higher, balanced, degree of aggregation. The aggregates of both forms of fumed silica disperse on a toner surface to result in effective particle diameters larger than the colloidal silica particle. Also, because of their fractal morphology, these dispersed aggregates are more likely to remain fixed on the toner surface as compared to the colloidalbased additives.

Sustainability indicators for livestock farming. A review

Intensive livestock farming has raised issues about environmental impacts and food security during the past 20 years. As a consequence, there is a strong social demand for sustainable livestock systems. Sustainable livestock systems should indeed be environmentally friendly, economically viable for farmers, and socially acceptable, notably for animal welfare. For that goal, many sustainability indicators and methods have been developed at the farm level. The main challenge is using a transparent selection process to avoid assessment subjectivity. Here, we review typologies of sustainability indicators. We set guidelines for selecting indicators in a data-driven context, by reviewing selection criteria and discussing methodological issues. A case study is presented. The selected set of indicators mainly includes (1) environmental indicators focusing on farmer practices; (2) quantitative economic indicators; and (3) quantitative social indicators with a low degree of aggregation. The selection of indicators should consider (1) contextualization to determine purpose, scales, and stakeholders involved in the assessment; (2) the comparison of indicators based on various criteria, mainly data availability; and (3) the selection of a minimal, consistent, and sufficient set of indicators. Finally, we discuss the following issues: topics for which no indicators are measurable from available data should explicitly be mentioned in the results. A combination of means-based indicators could be used to assess a theme, but redundancy must be avoided. The unit used to express indicators influences the results and has therefore to be taken into account during interpretation. To compare farms from indicators, the influence of the structure on indicator values has to be carefully studied.

Continuous synthesis of surface-modified nanoparticles in supercritical methanol: A facile approach to control dispersibility

Surface-modified cerium oxide (CeO2) nanoparticles, dispersible in either a hydrophilic or a hydrophobic medium, are synthesized continuously in supercritical methanol using methoxy polyethylene glycol (PEG350, H(OCH2CH2)nOCH3, MW=350g/mol) or α,ω-Bis(2-carboxymethyl)polyethylene glycol (PEG600, HOOCCH2(OCH2CH2)nOCH2COOH, MW=600g/mol) as a surface modifier. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the surface modifiers inhibit the growth of the particles, resulting in smaller size particles (20–25nm) as compared to unmodified particles (35nm) synthesized in supercritical methanol or unmodified particles (91nm) synthesized in supercritical water. At a high concentration of PEG600 (0.3M), surface-modified particles with a size of 3–4nm and a low degree of aggregation are produced. An X-ray diffraction analysis reveals that the PEG-modified nanoparticles retain the CeO2 phase. Fourier transform infrared spectroscopy and a thermal gravimetric analysis indicate that the amount of modifier attached to the surface of the nanoparticles is 6.88%, when 0.3M of PEG350 is used, and 4.49%, when 0.3M of PEG600 is used. A long-term stability test (40days) revealed that the PEG350-modified CeO2 nanoparticles have good dispersibility in a hydrophobic medium (oil), while PEG600-modified CeO2 nanoparticles have good dispersibility in a hydrophilic medium (water). This indicates that the nanoparticle dispersibility in either a hydrophilic or hydrophobic medium can be controlled by adjusting the end-group functionality and chain length of the modifiers.

Novel aqueous nano-scaled formulations of oleic acid stabilized hydrophobic superparamagnetic iron oxide nanocrystals

Background: Novel aqueous nano-scaled formulations were developed for hydrophobic oleic acid stabilized monodisperse superparamagnetic magnetite nanocrystals.Methods: In the study, single and mixed lipid amphiphiles based on Cremophor RH-40 (Crem-RH-40), Solutol HS-15 (Sol-HS-15), Phospholipon-100H (PL-100H) and sucrose ester M-1695 (SE-M-1695) were employed at varying concentrations. Isotonicity and physiological pH adjustments were achieved by using 5% w/v mannitol in 10 mM pH 7.4 phosphate buffer. Mannitol also served as lyoprotectant for the freeze drying of selected formulation. The developed formulations were characterized by photon correlation spectroscopy (PCS) and asymmetric flow field flow fractionation methods for their size and size distributions and morphologies were examined by transmission electron microscopy (TEM). Moreover, the potential magnetic resonance imaging (MRI) contrast agent application of a selected formulation was investigated by 1H-NMR relaxometric measurements.Results: The results showed that stable formulations of the nanocrystals with hydrodynamic diameters generally below 100 nm were obtained. Among the developed formulations, the one prepared with 0.75% Crem-RH-40, 0.5% PL-100H and 0.25% SE-M-1695 had a mean hydrodynamic diameter of ~64 nm and zeta potential of −20 mV. This formulation exhibited low degree of aggregation, high level of incorporation of magnetite nanocrystals and very good stability profile over a period of 6 months. In addition, it showed transverse and longitudinal relaxivities of 221.8 and 32.1 s−1·mM−1, respectively with r2/r1 ratio of 6.9.Conclusion: This study revealed that mixed lipid-based amphiphiles allow stable aqueous formulations of the normally challenging hydrophobic magnetite nanocrystals with potential in vivo MRI contrast applications.

Formation of gold nanoparticles and their aggregates in a liquid at magnetron deposition

The influence of magnetron deposition conditions on the size of Au nanoparticles and their aggregates obtained by condensation in a neutral liquid is studied experimentally. A model is suggested in which the nanoparticles and aggregates form in a thin subsurface layer, which becomes oversaturated by atoms and resulting nanoparticles when the liquid flows through a localized deposition zone. The process stops when the products leave this zone because of stirring. The size of nanoparticles and aggregates depends on the particle flux density and exposure time in the deposition zone. The final size of nanoparticles depends on the exposure time only slightly, while that of aggregates significantly depends on the exposure time. This allows one to prepare a concentrated solution of almost monodisperse nanoparticles with a low degree of aggregation by properly selecting deposition conditions and multiply passing the liquid through the deposition zone.

Self-Assembly of Organophilic Nanoparticles in a Polymer Matrix: Depletion Interactions

The dispersion of nanoparticles in a polymer matrix has been proven a challenge. A recent experiment reveals that it can be controlled by the relative size of nanoparticle/matrix polymer instead of their compatibility. Dissipative particle dynamics simulations are thus employed to investigate self-assembly of organophilic nanoparticles and dispersion of organophobic nanoparticles. The degree of aggregation in terms of the mean aggregation number is evaluated to explore the aggregation kinetics of nanocubes and nanoplatelets. The influence of the length of the matrix polymer on the aggregation behavior is studied as well. It is found that the depletion attraction plays the major role for the aggregation of organophilic nanoparticles. Large nanoplatelets prefer clustering, while small nanoplatelets tend to disperse because the depletion attraction grows with the face area of nanoparticles. On the other hand, the slow aggregation kinetics, hindered by the energy barrier associated with depletion interactions and low nanoparticle diffusivity, is responsible for the low degree of aggregation for organophobic nanoparticles.

Solution behaviours and adsorption characteristics of sodium lignosulfonate under different pH conditions

Solution behaviors and adsorption characteristics of sodium lignosulfonate (NaLS) were studied under different pH conditions. The changes of Mw and particle size of NaSL with solution pH were detected by laser light scattering (LLS). Film thickness was determined with a spectroscopic ellipsometer, and surface roughness was measured by atomic force microscopy (AFMaSL was changed from compact to loose. When the NaSL with loose structure and low degree of aggregation was adsorbed on a solid substrate, the adsorption thickness and the surface roughness decreased correspondingly.

Mechanical Properties and Network Structure of Wheat Gluten Foams

This Article reports the influence of the protein network structure on the mechanical properties of foams produced from commercial wheat gluten using freeze-drying. Foams were produced from alkaline aqueous solutions at various gluten concentrations with or without glycerol, modified with bacterial cellulose nanosized fibers, or both. The results showed that 20 wt % glycerol was sufficient for plasticization, yielding foams with low modulus and high strain recovery. It was found that when fibers were mixed into the foams, a small but insignificant increase in elastic modulus was achieved, and the foam structure became more homogeneous. SEM indicated that the compatibility between the fibers and the matrix was good, with fibers acting as bridges in the cell walls. IR spectroscopy and SE-HPLC revealed a relatively low degree of aggregation, which was highest in the presence of glycerol. Confocal laser scanning microscopy revealed distinct differences in HMW-glutenin subunits and gliadin distributions for all of the different samples.