ABSTRACT The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov-Gerasimenko, has been detecting individual dust particles of mass larger than 10−10 kg by means of the GIADA dust collector and ...the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes >1 mm observed by OSIRIS is consistent with a differential power index of −4, which was derived from models of 67P's trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from −2 beyond 2 au to −3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion.
A novel stereoscopic image acquisition setup and a procedure for measuring multidimensional particle size distributions (nD PSDs) during crystallization based on image analysis are presented. Images ...of crystals in suspension passing a flow through cell are generated by two cameras which are arranged in an orthogonal manner. Particles are conveyed to the flow through cell using a sampling loop, thus allowing for online monitoring. Automated image analysis provides contour data which can be used to classify crystals into different generic particle model classes. For each type of particle size data is calculated and stored. Finally, time resolved nD PSD data can be calculated. The accuracy of this novel size measurement was confirmed by comparison to measurements obtained with a Coulter Multisizer. The non-invasive nature and repeatability of experiments are shown by monitoring populations of sodium chloride and of the β polymorph of l-glutamic acid under different conditions. Finally, crystal growth of acetaminophen during cooling crystallization is shown. In addition, a virtual test bench is used to study the measurement method in silico.
•An image based setup for measuring nD particle size distributions online is shown.•Particle classification and size calculation algorithms are introduced.•Capabilities of the setup in terms of accuracy and time resolution are demonstrated.•A virtual test bench is developed and used to investigate different image analysis effects.•The setup is tested during the growth of organic crystals.
The effects of removing non-starch components on the surface microstructure, water migration and glucose diffusion rate of highland barley starch (HBS) were systematically studied to reveal the ...models that affect the digestibility of HBS. The results of scanning electron micrographs, confocal laser scanning microscopy, polarization cross and particle size distribution showed that there were two particle size ranges in highland barley flour, large (73.99–591.90 μm) and small (<73.99 μm). Partial β-glucan and proteins form a compact and continuous matrix on the surface of HBS granules; lipids can partly be adsorbed on the surface of HBS granules, while other lipids, proteins and β-glucan are scattered around HBS granules. After the removal of non-starch components, the ratio of large particles decreased and the starch granules were more exposed, especially proteins and β-glucan. The results of low-field nuclear magnetic resonance investigation showed that the water migration rate was accelerated after the removal of β-glucan, and partial free water was transformed into weakly bound water, while the opposite effect was observed for the removal of proteins and lipids. The glucose diffusion rate in vitro was unchanged after the removal of lipids, while the removal of β-glucan significantly accelerated the diffusion of glucose in vitro. This study reveals that the effective models of HBS inhibited by non-starch components is the compact matrix mainly formed by proteins and β-glucan on the surface of HBS granules. Additionally, the rate of glucose diffusion across the small intestinal wall could be considered as one of the means of constructing slowly digestible starch.
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•The continuous matrix formed by proteins and β-glucan were found on HBS granules.•Removing β-glucan accelerated water migration and glucose release of sample gels.•Removing non-starch components decreased large particle ratio (73.99–591.90 μm).•The particle size distribution of large particles changed less during digestion.•The proteins on HBS surface still block amylase after limited gastric digestion.
Abstract
The strong metal-support interaction (SMSI) has long been studied in heterogonous catalysis on account of its importance in stabilizing active metals and tuning catalytic performance. As a ...dynamic process taking place at the metal-support interface, the SMSI is closely related to the metal surface properties which are usually affected by the size of metal nanoparticles (NPs). In this work we report the discovery of a size effect on classical SMSI in Au/TiO
2
catalyst where larger Au particles are more prone to be encapsulated than smaller ones. A thermodynamic equilibrium model was established to describe this phenomenon. According to this finding, the catalytic performance of Au/TiO
2
catalyst with uneven size distribution can be improved by selectively encapsulating the large Au NPs in a hydrogenation reaction. This work not only brings in-depth understanding of the SMSI phenomenon and its formation mechanism, but also provides an alternative approach to refine catalyst performance.
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•Bio-inspired encapsulation of Iron oxide nanoparticles for cancer therapy is presented.•State-of-the-art synthetic routes and various surface architectures with biopolymers.•Advances ...on, biocompatibility, and functionalization of FeNPs for drug delivery.
Cancer cells are typified by proliferating mass of cells that grow faster than other smaller cell tissues within the body. Efforts to combat this effect through chemotherapy, radiotherapy, immunotherapy and surgery are still challenging. Magnetic Iron oxide nanoparticles (FeO-NPs) encapsulated with biopolymers as a local drug delivery system with the control via an external magnetic field has been widely used as a drug delivery system in cancer therapy, minimizing the side effects and lack of pathological site-specific action common to the conventional approaches. For the FeO-NPs to function optimally in actualizing the applications as mentioned earlier, it requires that the FeO-NPs have high magnetization values, narrow particle size distribution and a special surface encapsulation. Biopolymers used for surface functionalization offer several advantages in biomedical applications, owing to their defined primary structures, nontoxicity, biocompatibility and biodegradability. The functionalized FeO-NPs offer various possibilities, which include targeting ligands, proteins, antibodies and covalent attachment of drugs using an external magnetic field for cancer therapeutic purposes. This work discusses recent advances in the development of FeO-NPs from fabrication to applications and the state-of-the-arts synthetic routes. The work gives special attention to the biopolymer surface functionalization of FeO-NPs now and future perspective of drug delivery in oncologic disease therapy chiefly cancer cells.
Stabilizer combination with varying concentrations of kappa-carrageenan (KCG) was employed to reduce hardness, control overrun and improve the overall sensory attributes. A stabilizer combination of ...guar gum and locus bean gum was used with varying levels of kappa-carrageenan to maintain the total stabilizer concentration in the ice cream mix at 0.15% (w/w). Ice creams having 4% (w/w) and 10% w/w protein prepared with commercial stabilizer and emulsifier blend were served as positive and negative controls, respectively. All the ice cream mix samples showed pseudoplastic behaviour. Increasing the KCG level (0–0.12% w/w) in ice cream mix resulted in decreased flow behaviour index (0.80–0.43) and increased consistency coefficient (0.23–4.21 Pa.sn). Instrumental hardness values decreased and overrun increased significantly (p < 0.05) with KCG addition. Samples containing lower levels of KCG (0.03% w/w) had higher melting rates. All ice cream mix samples have shown bi-modal droplet distributions. Sensorial attributes were also altered with variation in the KCG level. The sample containing 0.12% (w/w) KCG was most preferred by the sensory panellists.
•High protein ice cream (10% w/w protein) prepared by varying concentrations of KCG.•KCG increased consistency coefficient of high protein buffalo milk ice cream mix.•Overrun increased & hardness decreased with an increase in KCG concentration.•KCG affected the fat globule size distribution and melting rate of ice creams.
•The influence of an alternating magnetic field on the CaCO3 fouling is studied.•The fouling induction period can be prolonged by the alternating magnetic field.•The growth of CaCO3 is inhibited and ...smaller size calcite crystals are formed.•An evaluation index is introduced to define the fouling inhibition effect.•The fouling inhibition characteristics presented a multi-extremum feature.
Experiments were performed to investigate the influence of an alternating magnetic field with different magnetic induction intensities on the calcium carbonate (CaCO3) fouling of a heat transfer surface. Experimental results indicated that the alternating magnetic field could effectively inhibit the fouling deposition on the heat transfer surface by prolonging the fouling induction period and slowing down the growth rate of CaCO3 fouling. Moreover, the fouling inhibition characteristics of the alternating magnetic field presented a multi-extremum feature. The fouling inhibition effectiveness depended on the selection of operating parameters in the alternating magnetic field. The most significant period was 300 Gs in this work, during which the fouling inhibition rate was 91.57%. Meanwhile, the fouling induction period increased by 132.3% and the growth rate decreased by 38.8% compared with the blank test. According to the scanning electron microscopy and particle size distribution, the morphology of CaCO3 particles exhibited changes with the alternating magnetic field. The smaller crystal size and terrace-ledge-kink growth were two reasons that impeded CaCO3 fouling from adhering easily on the heat transfer surface. This work can provide a sound theoretical guidance for future alternating magnetic field system design and application in fouling inhibition.
The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit ...on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.
•The result of various range of Pt particle size was compared with the constant size.•PDF was used to randomly distribute Pt particles of different sizes to get a real CL.•Numerical result for ...non-uniform Pt particles is consistent with experimental result.
Platinum (Pt) nanoparticles are used as an electrocatalyst in polymer electrolyte membrane (PEM) fuel cells. Visualization data of PEM fuel cell catalysts have shown that the size of Pt particles in the catalyst layer (CL) varies locally from several nanometers to tens of nanometers, owing to the agglomeration and degradation of Pt particles. Although many computational-fluid-dynamics-based PEM fuel cell modeling and simulation studies have been conducted, the majority of them have used the average value of the size of Pt particles owing to the complexity involved in considering the nonuniformity of the Pt particle size in the CL. In this study, we present a new approach to fuel cell CL modeling in PEM fuel cell simulations; the approach involves the consideration of various Pt particle size distributions. In the approach, a probability density function is used to randomly distribute Pt particles with different sizes in a computational domain under the assumption that the Pt particle size distribution follows a normal distribution curve. A sufficient number of grids, typically more than several million grid points, are used to obtain a Pt particle size distribution similar to that in a real CL. The new approach was applied to a comprehensive multiscale PEM fuel cell model and full three-dimensional fuel cell simulations were performed for different CL designs, Pt catalyst degradation levels, and operating conditions. Numerical simulation results clearly showed the significant effect of a nonuniform Pt particle size distribution on multidimensional contours of species concentration, temperature, and current density as well as the overall cell performance.
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