Original Size Distribution Research Articles

Multi-Species Surface Reconstruction for High-Efficiency Perovskite Nanocrystal Light-Emitting Diodes.

Although colloidal perovskite nanocrystal (PNC) solution has exhibited near-unity photoluminescence quantum yield (PLQY), the luminance would be severely quenched when the PNC solution is assembled into thin films due to the agglomeration and fusion of NCs caused by the exfoliation of surface ligands and non-radiative Förster resonance energy transfer (FRET) from small to large particle sizes, which seriously affected the performances of light-emitting diodes (LEDs). Here, we used Guanidine thiocyanate (GASCN) and Sodium thiocyanate (NaSCN) to achieve effective CsPbI3 PNC surface reconstruction. Due to the strong coordination ability of these small molecules with the anions and cations on the surface of the PNCs, they can provide strong surface protection against PNC fusion during centrifugal purification process and repair the surface defects of PNCs, so that the original uniform size distribution of PNCs can be maintained and FRET between close-packed PNC films is effectively suppressed, which allows the emission characteristics of the films to be preserved. As a result, highly oriented, smooth and nearly defect-free high-quality PNC thin films are obtained, with PLQY as high as 95.1 %, far exceeding that of the original film, and corresponding LEDs exhibit a maximum external quantum efficiency of 24.5 %.

Multi‐Species Surface Reconstruction for High‐Efficiency Perovskite Nanocrystal Light‐Emitting Diodes

AbstractAlthough colloidal perovskite nanocrystal (PNC) solution has exhibited near‐unity photoluminescence quantum yield (PLQY), the luminance would be severely quenched when the PNC solution is assembled into thin films due to the agglomeration and fusion of NCs caused by the exfoliation of surface ligands and non‐radiative Förster resonance energy transfer (FRET) from small to large particle sizes, which seriously affected the performances of light‐emitting diodes (LEDs). Here, we used Guanidine thiocyanate (GASCN) and Sodium thiocyanate (NaSCN) to achieve effective CsPbI3 PNC surface reconstruction. Due to the strong coordination ability of these small molecules with the anions and cations on the surface of the PNCs, they can provide strong surface protection against PNC fusion during centrifugal purification process and repair the surface defects of PNCs, so that the original uniform size distribution of PNCs can be maintained and FRET between close‐packed PNC films is effectively suppressed, which allows the emission characteristics of the films to be preserved. As a result, highly oriented, smooth and nearly defect‐free high‐quality PNC thin films are obtained, with PLQY as high as 95.1 %, far exceeding that of the original film, and corresponding LEDs exhibit a maximum external quantum efficiency of 24.5 %.

Raincloud conditioning by thunder

AbstractThis article considers the role of thunder in the production of rain by gravitational processes. A previous numerical work has shown that a thunder event consisting of four consecutive thunderclaps can alone produce small but significant droplet growths in a lean cumulus cloud in less than 2 s. Here we consider, also numerically, the coalescence effects produced by both thunderclaps and gravity in a cumulus congestus cloud that had more than four times the liquid content of that lean cloud. Those effects are studied separately and in tandem, using the same set of assumptions. Therefore, the results presented here provide a basis for the comparison of the effectiveness of each type to produce droplet growth in thunderclouds. For thunder alone, these results show that a small number of thunderclaps can in less than 2 s produce mean size growths larger than 50%. For gravity alone, it is found that after 60 s, the longest time considered, gravitational coalescence increases the mean diameter of the original droplet size distribution by 20%. The tandem study considers the effects produced by gravitation on the droplet size distribution that resulted after the original distribution was modified by four or five thunderclaps. Significant increases are found in both cases. For four claps it was found that the mean size increased by 71% in 60 s. The corresponding growth for five claps was slightly larger than 100%. These substantial increases also show that the growths produced by the thunderclaps are not simply additive, but significantly accelerate those produced by gravitation. This acceleration implies that the droplet size growths produced by thunderclaps can substantially decrease the time required by gravitational coagulation to produce raindrops in rainclouds.

Bioavailability and translocation of platinum nanoparticles and platinum ions in rice (Oryza sativa L.): Nanoparticles biosynthesis and size-dependent transformation

Metal nanoparticles accumulation and bioavailability in plants raised much attention, specifically transformation and transportation of nanoparticles and their corresponding ions in plants are still unknown. In this work, rice seedlings were exposed to platinum nanoparticles (PtNPs) (with three sizes of 25, 50, and 70 nm) and Pt ions (with doses of 1, 2, and 5 mg/L) to investigate the influences of particle size and Pt form on bioavailability and translocation mechanism of metal nanoparticles. Results based on single particle ICP-MS (SP-ICP-MS) demonstrated the biosynthesis of PtNPs in Pt ions treated rice seedlings. The particle size ranges at 75–79.3 nm were detected in Pt ions exposed rice roots, and further migrated up to rice shoots at 21.7–44.3 nm. After exposed to PtNP-25, the particles could transfer to shoots with the original size distribution detected in roots, even with the PtNPs dose change. PtNP-50 and PtNP-70 translocated to shoots with the particle size increase. For the rice exposure with three dose levels, PtNP-70 had the highest number-based bioconcentration factors (NBCFs) in all Pt species, while Pt ions had the highest bioconcentration factors (BCFs), a range of 1.43–2.04. All PtNPs and Pt ions could be accumulated in rice plants and further transferred to shoots, and particle biosynthesis was proved through SP-ICP-MS. The finding could help us better understand the influence of particle size and form on the transformations of PtNPs in environment.

Effect of original crystal size of kaolinite on the formation of intercalation compounds of coal-measure kaolinite

Coarse crystalline (14.8–19.8 µm) and crypto crystalline (0.51–0.92 µm) coal-measure kaolinite were selected to explore the effect of original crystal sizes on intercalation. Characterization methods of SEM, XRF, XRD, FT-IR, and TG-DTG were utilized to study the original crystal size distribution, chemical composition, crystal structure changes, vibrational characteristics of functional groups, and thermal stability before and after intercalation. The test results reflected that the original crystal size significantly affects the formation of intercalated compounds. Coal-measure kaolinite intercalation compounds have been successfully prepared. Nonlinear fitting curves between the different characterization methods and the original average crystal size showed a significant positive correlation. The results showed that the intercalation effect of coarse crystalline was more significant than those of crypto crystalline, that is to say, the larger the original crystal sizes of coal-measure kaolinite, the higher the intercalation rate, the higher the grafting rate and the more pronounced the mass loss rate. Based on the theory of surface energy and surface charge of mineral particles, the electrical double layer theory which was different from the previous researchers was proposed to explain the intrinsic mechanism of the effect of original crystal size on intercalation.

STUDY ON THE EVOLUTION LAW OF PORE STRUCTURE AND MECHANICAL PROPERTIES OF MUDSTONE UNDER THE EFFECT OF WATER-ROCK CHEMISTRY

The influence of different pH and concentration of water chemical solutions on the mechanical properties of mudstone is studied. The triaxial compression test and nuclear magnetic resonance (NMR) test of mudstone are carried out, and the root cause of the deterioration of mechanical properties of mudstone during the hydration damage process is explored, combining macroscopic and microscopic. The results show that hydrolysis and chemical ion exchange are responsible for the deterioration of mudstone shear strength parameters. The essence of mudstone hydration damage is that water chemistry changes the original pore space structure and pore size distribution inside. Part of the minerals dissolve and fall off under the influence of the water chemical solution, which expands the pore size and increases the porosity. The connection force between mineral particles decreases, macroscopically, the mudstone undergoes a softening evolution from brittleness to ductility, and the shear strength parameters deteriorate. The results show that mudstone is more sensitive to acidic solution than neutral and alkaline solution. The higher the pH of the alkaline solution or the higher the concentration of the neutral solution, the more significant the deterioration of mudstone. Under the influence of hydrochemical solution, the fractal dimension of mudstone gradually tends to 2 from 3, which indicates that the process of hydration damage reduces the complexity of mudstone pore structure. On this basis, the damage variable D<sub>n</sub> defined based on the change of porosity before and after hydration damage of mudstone, to a certain extent, quantitatively reflects the law of mudstone shear strength parameters accompanied by microscopic pore structure evolution. The shear strength parameters of mudstone decrease significantly with the increase of damage variable D<sub>n</sub>. The test analyzes the root cause of the deterioration of the macroscopic mechanical properties of mudstone during the hydration damage process from a microscopic point of view, and the conclusions obtained provide a good reference for the quantitative study of the effect of water chemistry on the mechanical properties of mudstone.

Ultraviolet germicidal irradiation of melted snow and ice samples: inactivation of microorganisms and effects on insoluble microparticles

AbstractThe long-term refrigerated storage of melted snow and/or ice samples for analyses of insoluble microparticles (hereafter, microparticles) may be limited by increases in the biological particle concentration caused by microbial growth after ~1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples and determined the effects of this method on microparticles. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Microparticle concentrations and size distributions (in the range of 0.52–12.0 μm) in the samples were measured using a Coulter counter. Whereas the microparticle concentration in untreated samples increased, no obvious increase was observed over 53 d in the samples subjected to UV treatment. Microbial growth was detected in only untreated samples using a viable particle counter. In addition, the original microparticle concentrations and size distributions were unaffected by UV treatment. Our results demonstrated that the microparticle size distribution in untreated melted water samples reflects the growth, decomposition and succession of microorganisms over time and further indicate that UV irradiation is effective for long-term storage for microparticle analysis.

Effect of bimodal WC particle size and binder composition on the morphology of WC grains in WC–Co–Ni3Al cemented carbides

In addition to dispersed nanoparticles in the binder phase, the effect of Ni3Al on the growth mechanism of tungsten carbide (WC) grains is also essential for the fabrication of high-quality of cemented carbides. In this work, WC–Co–Ni3Al cemented carbides with different combinations of Co and Ni3Al binders was studied by using the original artificial bimodal WC grain size distribution. The WC particle sizes of medium 4 μm, fine 1 μm and ultrafine 0.2 μm were adopted. A series of WC–Co–Ni3Al alloys were firstly designed based on thermodynamic calculations and then liquid-sintered at 1450 °C for 1 h. Subsequently, the morphology and grain size distribution of WC grains were studied. By increasing the proportion of Ni3Al in the Co–Ni3Al composite binder phase, the solid–liquid interfacial energy increases significantly, which may provide a higher driving force for abnormal grain growth (AGG) through 2-dimension (2D) nucleation. However, the increase of Ni3Al proportion conversely greatly raises the energy barrier for the migration of W and C atoms into liquid binder phase, which finally retards the AGG of WC. Consequently, the AGG of WC decreases and the number of crystallites with blunt faces increases on WC particles with the increase of Ni3Al proportion, which can be well accounted for by the presently detected WC morphology evolution.

The characteristics of atmospheric particles and metal elements during winter in Beijing: Size distribution, source analysis, and environmental risk assessment

In order to investigate the pollution characteristics of size-segregated particles and metal elements (MEs) after the Chinese Air Pollution Prevention Action Plan was released in 2013, an intensive field campaign was conducted in the suburban area of Chaoyang District, Beijing in winter 2016. The size distributions of particle mass concentrations were bimodal, with the first peak in the fine fraction (0.4–2.1 µm) and the second peak in the coarse fraction (3.3–5.8 µm). Moreover, the proportion of fine particles increased and the proportion of coarse particles decreased as the pollution level was more elevated. It was found that the composition of coarse particles is as important as that of fine particles when pollution of aerosol metals in the atmosphere in 2016 were compared to 2013. In addition, according to the size distribution characteristics, 23 MEs were divided into three groups: (a) Fe, Co, Sr, Al, Ti, Ba, and U, which concentrated in coarse mode; (b) Zn, As, Cd, Tl, and Pb, which concentrated in fine mode; and (c) Na, K, Be, V, Cr, Mn, Ni, Cu, Mo, Ag, and Sn, showing bimodal distribution. Under clean air, slight pollution and moderate pollution conditions, most elements maintained their original size distributions, while under severe pollution, the unimodal distributions of most MEs became bimodal distributions. The factors analysis combined with size distributions indicated that Na, Zn, Mo, Ag, Cd, and Tl, showing the moderate to severe contamination on environment, were significantly influenced by diffuse regional emissions or anthropogenic source emissions (vehicle exhaust emissions and combustion process). The environmental risk assessment revealed that the heavy metal loading in the atmospheric particles collected had a high potential for ecological risk to the environment during sampling period because of the high contribution of Cd, Tl, Zn and Pb.

Effect of turbulent kinetic energy dissipation rate on the prediction of droplet size distribution in stirred tanks

In this work the capabilities of Two Fluid Model simulations coupled with a Population Balance Model solved with the Quadrature Method of Moments in predicting the turbulent kinetic energy dissipation rate and the droplet size distribution in a dilute liquid-liquid stirred tank are investigated. For a strict evaluation of the numerical and modelling approximations, original two-phase flow fields and droplet size distributions are collected by Particle Image Velocimetry and a laser diffraction technique, respectively. The spatial discretization requirements for achieving grid independent and reliable predictions of the turbulent variables already observed in RANS-based simulations of single-phase stirred tanks are confirmed also for the investigated dilute two-phase system, for which the effect of the dispersed phase on the continuous liquid is negligible. Besides, better prediction of the droplet size distribution is apparently obtained with poorly predicted turbulent kinetic energy dissipation rate, showing that the usually adopted parameters of the breakup kernel have been tuned for coarse grids. A way to derive grid independent breakup kernel parameters and a correction based on the spatial distribution of turbulent dissipation rate are proposed to account for the underestimation of the turbulent variables in the RANS simulation of industrial scale equipment.

Impact of chloride intrusion on the pore structure of recycled aggregate concrete based on the recycled aggregate porous interface

This study presents the experimental results of pore structure change in recycled aggregate concrete (RAC) with a 100% replacement ratio subjected to chloride intrusion, comprehensively considered with dry-wet cycles, flexural loading, and temperature. The pore structure of the mortar was determined by mercury intrusion porosimetry, and the scanning electron microscope used to observe the apparent morphology of old and new mortar. The changes in the chemical composition of specimens after chloride intrusion were measured by X-ray diffraction. The results showed that Cl- intrusion led to the formation of a large number of new pores in the original pores that were smaller than the original pore size. The range of the original pore size distribution was also reduced. The increase in temperature increased the rate of dissolution and migration of products between the pores and promoted changes in the pore structure. A large number of connected micro-cracks were generated between the pores under flexural load conditions, which provided additional space for product recrystallization and reshaped the original crack space. The changes in the characteristics of pore structure of old mortar were generally more extensive than those of new mortar after Cl− intrusion. Based on the experimental results, a model for RA dual partition-interface pore network is proposed by considering the old mortar, new mortar, old-new mortar interface, and old aggregate-old mortar interface to analyze the mechanism of change of pore structure.

Grain-size end-members and environmentally sensitive grain-size components: A comparative study in the mud shelf depocenters off southern Brazil

The current study aims to do a comparative analysis of the results obtained with two End-Member (EM) grain-size modeling techniques (AnalySize and BasEMMA) and the Environmental Sensitive Grain-Size (ESGS) modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf. The methods were compared using grain-size data from the south Brazilian shelf, and the results are discussed here. It is the first time that the concept of ESGS, in its present form, is utilized outside China. The results show that despite its relative ease of use, the ESGS is not fully comparable to the EM analyses, and only two grain-size ESGS classes were recognized as analogous to EMs. The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques. A comparative analysis between the two EM techniques revealed advantages in the BasEMMA, especially in the better correlation of the end-members with the original grain size distribution. The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred.

Vertical Wind Effect on Slope and Shape Parameters of Gamma Drop Size Distribution

AbstractApproximate equations for slope Λ and shape μ parameters of the gamma raindrop size distribution (DSD) are derived from theoretical considerations on the basis of the reflectivity-weighted mean terminal velocity VT and Doppler spectral width σp of the raindrop echoes. These approximate equations are then corrected to reduce the error by using the long-term ground-based disdrometer measurements. We applied these equations on the VHF-radar measurements (i.e., reflectivity-weighted mean fall velocity and Doppler spectral width) to estimate μ and Λ aloft. The effects of the vertical wind velocity on the VHF radar-estimated μ–Λ and σp–VT values are investigated. The result shows that there is a tendency for the μ and Λ values to increase with an increase of the upward wind velocity. In addition, the terminal velocity and the spread of the DSD estimated from the precipitation echoes are strongly related to the vertical air velocity. The stronger the upward vertical air velocity is, the larger the terminal velocity and the smaller the spread of the DSD will be. The dependence of the estimated μ and Λ values on the vertical wind velocity is very likely caused by the updraft that can support and carry away the smaller raindrops in the original drop size distribution in the radar volume. Consequently, the DSDs aloft are truncated and the corresponding μ and Λ values estimated from the radar returns tend to be larger. To confirm this assertion, we intentionally truncate disdrometer-measured DSDs at small drop size end and calculate corresponding μ and Λ values. The results show that the distribution patterns of the μ–Λ scatter diagrams of the truncated DSDs bear strong resemblance to those of the radar observations, both of which are very different from those obtained on the ground.

Extraction of monomer-cluster association rate constants from water nucleation data measured at extreme supersaturations

We utilize recently reported data for water nucleation in the uniform postnozzle flow of pulsed Laval expansions to derive water monomer association rates with clusters. The nucleation experiments are carried out at flow temperatures of 87.0 K and 47.5 K and supersaturations of lnS ∼ 41 and 104, respectively. The cluster size distributions are measured at different nucleation times by mass spectrometry coupled with soft single-photon ionization at 13.8 eV. The soft ionization method ensures that the original cluster size distributions are largely preserved upon ionization. We compare our experimental data with predictions by a kinetic model using rate coefficients from a previous ab initio calculation with a master equation approach. The prediction and our experimental data differ, in particular, at the temperature of 87.0 K. Assuming cluster evaporation to be negligible, we derive association rate coefficients between monomer and clusters purely based on our experimental data. The derived dimerization rate lies 2-3 orders of magnitude below the gas kinetic collision limit and agrees with the aforementioned ab initio calculation. Other than the dimerization rate, however, the derived rate coefficients between monomer and cluster j (j ≥ 3) are on the same order of magnitude as the kinetic collision limit. A kinetic model based on these results confirms that coagulation is indeed negligible in our experiments. We further present a detailed analysis of the uncertainties in our experiments and methodology for rate derivation and specify the dependency of the derived rates on uncertainties in monomer and cluster concentrations.

Development and magnetic properties of loess-derived forest soils along a precipitation gradient in northern Iran

In order to investigate the development of forest soils formed on loess, six representative modern soil pedons were selected along a precipitation gradient extending from eastern Golestan (mean annual precipitation, MAP = 500 mm) to eastern Mazandaran Provinces (MAP = 800 mm). Physiochemical, micromorphological and magnetic properties, as well as clay mineralogy of soils were studied using standard methods. Soils are mainly classified as Alfisols and Mollisols. Downward decalcification and the subsequent clay illuviation were the main criteria of soil development in all study areas. Pedogenic magnetic susceptibility of pedons studied varied systematically across the precipitation gradient in Northern Iran, increasing from 14.66 × 10−8 m3 kg−1 at the eastern part to 83.75 × 10−8 m3 kg−1 at the western margin of this transect. The frequencydependent magnetic susceptibility showed an increasing trend with rainfall as well. The micromorphological study of soils indicated that there is a positive relationship between climate gradient (increasing rainfall) and the micromorphological index of soil development (MISECA). The area and thickness of clay coatings showed an increasing trend with rainfall. Grain size analysis indicates that pedogenic processes are responsible for changing original grain size distribution of loess in our soils. The correlation achieved among modern soil properties and precipitation could be applied to the buried paleosols in the whole study area to refer degree of paleosol development and to reconstruct the paleoclimate.

Fuzzifier Selection in Fuzzy C-Means from Cluster Size Distribution Perspective

Fuzzy c-means (FCM) is a well-known and widely applied fuzzy clustering method. Although there have been considerable studies which focused on the selection of better fuzzifier values in FCM, there is still not one widely accepted criterion. Also, in practical applications, the distributions of many data sets are not uniform. Hence, it is necessary to understand the impact of cluster size distribution on the selection of fuzzifier value. In this paper, the coefficient of variation (CV) is used to measure the variation of cluster sizes in a data set, and the difference of coefficient of variation (DCV) is the change of variation in cluster sizes after FCM clustering. Then, considering that the fuzzifier value with which FCM clustering produces minor change in cluster variation is better, a criterion for fuzzifier selection in FCM is presented from cluster size distribution perspective, followed by a fuzzifier selection algorithm called CSD-m (cluster size distribution for fuzzifier selection) algorithm. Also, we developed an indicator called Influence Coefficient of Fuzzifier ($\mathit{ICF}$) to measure the influence of fuzzifier values on FCM clustering results. Finally, experimental results on 8 synthetic data sets and 4 real-world data sets illustrate the effectiveness of the proposed criterion and CSD-m algorithm. The results also demonstrate that the widely used fuzzifier value $m=2$ is not optimal for many data sets with large variation in cluster sizes. Based on the relationship between ${\mathit{CV}_{0}}$ and $\mathit{ICF}$, we further found that there is a linear correlation between the extent of fuzzifier value influence and the original cluster size distributions.

Use of the Single Particle Soot Photometer (SP2) as a pre-filter for ice nucleation measurements: effect of particle mixing state and determination of SP2 conditions to fully vaporize refractory black carbon

Abstract. Ice nucleation is a fundamental atmospheric process that impacts precipitation, cloud lifetimes, and climate. Challenges remain to identify and quantify the compositions and sources of ice-nucleating particles (INPs). Assessment of the role of black carbon (BC) as an INP is particularly important due to its anthropogenic sources and abundance at upper-tropospheric cloud levels. The role of BC as an INP, however, is unclear. This is, in part, driven by a lack of techniques that directly determine the contribution of refractory BC (rBC) to INP concentrations. One previously developed technique to measure this contribution uses the Single Particle Soot Photometer (SP2) as a pre-filter to an online ice-nucleating particle counter. In this technique, rBC particles are selectively heated to their vaporization temperature in the SP2 cavity by a 1064 nm laser. From previous work, however, it is unclear under what SP2 conditions, if any, the original rBC particles were fully vaporized. Furthermore, previous work also left questions about the effect of the SP2 laser on the ice-nucleating properties of several INP proxies and their mixtures with rBC. To answer these questions, we sampled the exhaust of an SP2 with a Scanning Mobility Particle Sizer and a Continuous Flow Diffusion Chamber. Using Aquadag® as an rBC proxy, the effect of several SP2 instrument parameters on the size distribution and physical properties of particles in rBC SP2 exhaust were explored. We found that a high SP2 laser power (930 nW∕(220 nm PSL)) is required to fully vaporize a ∼ 0.76 fg rBC particle. We also found that the exhaust particle size distribution is minimally affected by the SP2 sheath-to-sample ratio; the size of the original rBC particle, however, greatly influences the size distribution of the SP2 exhaust. The effect of the SP2 laser on the ice nucleation efficiency of Snomax®, NX-illite, and Suwannee River Fulvic Acid was studied; these particles acted as proxies for biological, illite-rich mineral dust, and brown carbon INPs, respectively. The original size distribution and ice nucleation efficiency of all non-rBC proxies were unaffected by the SP2 laser. Furthermore, the ice nucleation efficiencies of all proxies were not affected when externally mixed with rBC. These proxies, however, always show a reduction in ice-nucleating ability when internally mixed with rBC. We end this work with recommendations for users who wish to use the SP2 as a pre-filter to remove large rBC particles from an aerosol stream.

Crystal Growth of Layered Silicate Grafted with Organic Groups on Monodisperse Spherical Silica Particles

AbstractControl of the structure and morphology of clay crystals presents a challenge in the synthesis of materials for adsorption and catalysis. In the present study, direct crystallization of a phyllosilicate grafted with organosilyl (methylsilyl and phenylsilyl) groups on the surface of monodisperse spherical silica particles (2.6 μm) is reported. Methyl- and phenyltriethoxysilanes were allowed to react hydrothermally in a Teflon-lined autoclave with silica, MgCl2, and LiF in the presence of urea for 2 or 4 days. X-ray diffraction patterns revealed that the fine platy particles formed were a trioctahedral hectorite-like layered silicate. Greater temperature (150°C) was required to achieve homogeneous coverage of the original spherical silica particles with the hectorite-like particles. The diameter of the initial silica grains increased slightly to 3.0 μm after the hydrothermal reactions, while the original spherical shape and size distribution were maintained. Solid-state 29Si nuclear magnetic resonance analyses confirmed that the presence of resonances attributed to the RSi(OMg)(OSi)2 and RSi(OMg)(OH)(OSi) (R = methyl or phenyl) environments of the silicon proved the formation of covalent bonds between phyllosilicate sheets and the organic moieties. The crystallinity of the layered silicates increased when the reactions ran for a longer time (4 days).

Fractal Analysis of In Situ Host Rock Nepheline Syenite Xenoliths in a Micro-Shonkinite Dyke (The Elchuru Alkaline Complex, SE India)

Formation of the fragments of the wall-rock during dyking is one of the important manifestations of instantaneous magmatic events. This process is well documented at shallower depths of Earth’s crust but not at deeper levels. In this paper the in situ xenoliths of host rock nepheline syenite within a micro-shonkinite dyke emplaced at mid-crustal depths is described and the fractal theory applied to evaluate origin of the xenoliths. The nepheline syenite xenoliths are angular to oval shaped and sub-millimetre to ~50 cm long. The xenoliths are matrix supported with clasts and matrix being in equal proportions. Partly detached wall-rock fragments indicate incipient xenolith formation, which suggested that the model fragmentation processes is solely due to dyke emplacement. Fractal analytical techniques including clast size distribution, boundary roughness fractal dimension and clast circularity was carried out. The fractal data suggests that hydraulic (tensile) fracturing is the main process of host rock brecciation. However, the clast size and shape are further affected by postfragmentation processes including shear and thermal fracturing, and chemical erosion. The study demonstrates that dyking in an isotropic medium produces fractal size distributions of host rock xenoliths; however, post-fragmentation processes modify original fractal size distributions.

Measuring and predicting pore size distribution of freeze-dried solutions

ABSTRACTIn this work, a novel procedure is presented for the measurement and prediction of pore size distribution of freeze-dried solutions in vials. A method based on segmentation is proposed for determining the size of the pores left by ice crystals, using images obtained by scanning electron microscopy. The original ice crystal size distribution is also predicted using a mathematical model based on balance equations. The model predictions and the results of the segmentation technique show a fairly good agreement. The proposed procedure could be used to efficiently estimate the resistance to mass transfer during drying and hence optimize the freeze-drying process.