Solid Condensation Research Articles

Separation of multicomponent gas mixtures

In the production of granular organo-mineral fertilizers using the fluidization technique by dehydrating heterogeneous liquids, as an energy-efficient technology, there is a need to purify the spent coolant containing solid particles, dust and a significant amount of water vapor. Solid particles up to 20 microns in size are effectively captured in cyclone devices. To further capture water vapor and fine solid particles, a scrubber is used with an additional circulation circuit involving an additional bone of water, which, upon reaching a concentration of more than 20%, is discharged back to the granulation stage. This leads to an increase in energy consumption for production in general. Condensation of vapors in a dispersion containing 5-7% (w/w) moisture in the form of water vapor at the second stage of purification will increase the level of environmental safety in production. To select an innovative method of separation of multicomponent gas dispersions accompanied by a change in the aggregate state and a rational design of the apparatus, a review of scientific articles and developments such as systematization of existing methods was carried out. Such an approach makes it possible to choose the optimal solution for the separation of gas-dust and gas-liquid flows in the conditions of the existence of a large number of types of equipment design and the level of their innovation. In addition to the rational design of the devices, great attention was also paid to the issues of energy efficiency, resource saving and ensuring the state of environmental safety at production facilities in the conducted research. Based on the results of the analysis, it is proposed to use a scheme of consecutively installed cyclones CN-11 and SK‑CN-33. It is proposed to use the ЦН-11 cyclone for the preliminary capture of highly dispersed dust, and the SK-CN‑33 for condensation and capture of water vapor and solids not caught in the previous cyclone particles.

Synthesis of 3-methyl-3-buten-1-ol by supercritical CO2 in coordination with HZSM-5-catalyzed formaldehyde-isobutene Prins reaction.

The reaction solvent and catalyst play essential roles in the Prins reaction for the synthesis of 3-methyl-3-buten-1-ol (MBO) from formaldehyde and isobutene. The reactivity of the solid base-catalyzed Prins condensation reaction by formaldehyde and isobutene in supercritical CO2 was investigated using CsH2PO4-modified HZSM-5. We found that the alkaline sites of the alkali-loaded catalyst could extract the α-H on isobutene to generate olefin carbon-negative ions, while the supercritical CO2 with weak Lewis acidity could activate formaldehyde to carbon-positive ions, which can combine more easily with carbon-negative isobutene to react, thus improving the reactivity of the reaction system.

Initiation of hnRNPA1 Low-Complexity Domain Condensation Monitored by Dynamic Light Scattering.

Biomolecular condensates (BMCs) exhibit physiological and pathological relevance in biological systems. Both liquid and solid condensates play significant roles in the spatiotemporal regulation and organization of macromolecules and their biological activities. Some pathological solid condensates, such as Lewy Bodies and other fibrillar aggregates, have been hypothesized to originate from liquid condensates. With the prevalence of BMCs having functional and dysfunctional roles, it is imperative to understand the mechanism of biomolecular condensate formation and initiation. Using the low-complexity domain (LCD) of heterogenous ribonuclear protein A1 (hnRNPA1) as our model, we monitored initial assembly events using dynamic light scattering (DLS) while modulating pH and salt conditions to perturb macromolecule and condensate properties. We observed the formation of nanometer-sized BMCs (nano-condensates) distinct from protein monomers and micron-sized condensates. We also observed that conditions that solubilize micron-sized protein condensates do not solubilize nano-condensates, indicating that the balance of forces that stabilize nano-condensates and micron-sized condensates are distinct. These findings provide insight into the forces that drive protein phase separation and potential nucleation structures of macromolecular condensation.

Harnessing endocytic pH gradients for cascaded formation of intracellular condensates to inhibit autophagy: A pathway to cancer therapy

Cancer cells rely on autophagy to degrade damaged organelles and survive in the harsh environment for progression and metastasis. Autophagy inhibition can improve the efficacy of anticancer therapy because many anticancer drugs can induce protective autophagy in cancer cells. However, current clinically available autophagy inhibitors are rare and have adverse effects with limited selectivity. This work develops an intracellular biomolecular condensate for autophagy inhibition to kill cancer without apparent side effects. A modularly designed amphiphilic peptide (PNP) can self-assemble to form toxic nanofibrous condensates successively from nanoparticles with the pH changes of the endocytic pathway. Mechanistic studies by CLSM and FRAP demonstrate that the PNP finally forms solid nanofibrous condensates in the lysosome after cell endocytosis. Bio-EM and cell transfection with adenovirus expressing mCherry-GFP-LC3B fusion protein (autophagy marker) experiments indicate the autophagy inhibition by PNP nanofibrous condensates. In vitro experiments show that PNP can significantly boost the activity of the clinical drug by 150-fold against drug-resistant lung cancer cells by inducing G2/M phase arrest of the cell cycle. Furthermore, PNPs demonstrate effective tumor targeting and permeability in vivo, inhibiting tumor growth and reducing the side effects of clinical chemotherapy drugs. Overall, this work provides a simple and feasible strategy for designing intracellular condensates to inhibit autophagy for cancer therapy.

Alternative low-populated conformations prompt phase transitions in polyalanine repeat expansions

Abnormal trinucleotide repeat expansions alter protein conformation causing malfunction and contribute to a significant number of incurable human diseases. Scarce structural insights available on disease-related homorepeat expansions hinder the design of effective therapeutics. Here, we present the dynamic structure of human PHOX2B C-terminal fragment, which contains the longest polyalanine segment known in mammals. The major α-helical conformation of the polyalanine tract is solely extended by polyalanine expansions in PHOX2B, which are responsible for most congenital central hypoventilation syndrome cases. However, polyalanine expansions in PHOX2B additionally promote nascent homorepeat conformations that trigger length-dependent phase transitions into solid condensates that capture wild-type PHOX2B. Remarkably, HSP70 and HSP90 chaperones specifically seize PHOX2B alternative conformations preventing phase transitions. The precise observation of emerging polymorphs in expanded PHOX2B postulates unbalanced phase transitions as distinct pathophysiological mechanisms in homorepeat expansion diseases, paving the way towards the search of therapeutics modulating biomolecular condensates in central hypoventilation syndrome.

Fastchem cond: equilibrium chemistry with condensation and rainout for cool planetary and stellar environments

ABSTRACT Cool astrophysical objects, such as (exo)planets, brown dwarfs, or asymptotic giant branch stars, can be strongly affected by condensation. Condensation not only directly affects the chemical composition of the gas phase by removing elements but the condensed material also influences other chemical and physical processes in these objects. This includes, for example, the formation of clouds in planetary atmospheres and brown dwarfs or the dust-driven winds of evolved stars. In this study, we introduce fastchem cond, a new version of the fastchem equilibrium chemistry code that adds a treatment of equilibrium condensation. Determining the equilibrium composition under the impact of condensation is complicated by the fact that the number of condensates that can exist in equilibrium with the gas phase is limited by a phase rule. However, this phase rule does not directly provide information as to which condensates are stable. A major advantage of fastchem cond is its ability to automatically select the set stable condensates satisfying the phase rule. Besides the normal equilibrium condensation, fastchem cond can also be used with the rainout approximation that is commonly employed in atmospheres of brown dwarfs or (exo)planets. fastchem cond is available as open-source code, released under the GNU General Public Licence 3 (GPLv3). In addition to the c++ code, fastchem cond also offers a python interface. Together with the code update, we also add about 290 liquid and solid condensate species to fastchem.

Solid-to-liquid phase transition in the dissolution of cytosolic misfolded-protein aggregates

Accumulation of protein aggregates is a hallmark of cellular aging and degenerative disorders. This could result from either increased protein misfolding and aggregation or impaired dissolution of aggregates formed under stress, the latter of which is poorly understood. In this study, we employed quantitative live-cell imaging to investigate the dynamic process of protein disaggregation in yeast. We show that protein aggregates formed upon heat stress are solid condensates, but after stress attenuation these protein aggregates first transition into a liquid-like state during their dissolution. This solid-to-liquid phase transition (SLPT) accompanies the reduction in aggregate number due to the fusion of the liquid condensates. The chaperone activity of Hsp104, a Clp/HSP100 family chaperone, is required for both SLPT and subsequent dispersal of the liquid condensates. Sse1, a yeast HSP110 chaperone, also facilitates SLPT. These results illuminate an unexpected mechanistic framework of cellular control over protein disaggregation upon stress attenuation.

Determination of activities and condensation temperatures of GaO1.5 and InO1.5 in anorthite-diopside eutectic melts by Knudsen Effusion Mass Spectrometry

The group 13 elements Ga and In are overabundant in bulk silicate Earth (BSE) when compared to lithophile elements of similar 50% nebular condensation temperature Tc50. To understand whether evaporation from silicate melts provides a more accurate description of volatility during the later stages of planetary accretion, namely, at higher temperatures and oxygen fugacities than in the solar nebula, knowledge of the activities of GaO1.5 and InO1.5 in silicate melts and their stable gaseous species are required. To this end, we doped anorthite-diopside (An-Di) eutectic glasses with ∼1000 and ∼10,000 ppm of Ga and In and determined their equilibrium partial pressures above the silicate liquid by Knudsen Effusion Mass Spectrometry (KEMS) using Ir cells at 1550–1740 K over the log(fO2) range ΔIW+1.5 to ΔIW+2.5 (IW = iron-wüstite buffer). We detect Ga0 and In0 as the dominant vapour species and determine activity coefficients of γ(GaO1.5) = 0.036(6) at 1700 K and of γ(InO1.5) = 0.017(12) at 1674 K. Using these activity coefficients, we calculate partial pressures of Ga and In, together with those of similarly volatile elements, K and Zn and show that their relative volatilities from An-Di eutectic melts are in the in order Ga > K ∼ In > Zn, different from those predicted from their Tc50 under nebular conditions but in line with their relative abundances in the BSE. This substantiates the view that the abundances of volatiles in BSE, such as Ga and In, may have been set by evaporation from silicate melts under oxidising conditions at later stages of planetary accretion. Moreover, chondrules likely never underwent significant evaporation during melting and their volatile-depleted nature is likely inherited from the earliest solid condensates.

Evaluation of per- and polyfluoroalkyl substances (PFAS) in leachate, gas condensate, stormwater and groundwater at landfills

Per- and polyfluoroalkyl substances (PFAS), found in many consumer products, are commonly disposed of in landfills at the end of their service lives. To identify landfill liquids that should be prioritized for treatment, this study aimed to evaluate PFAS levels in different aqueous samples from landfills and identify relationships between PFAS and landfill characteristics. Twenty-six PFAS including 11 perfluoroalkyl carboxylic acids (PFCAs), 7 perfluoroalkyl sulfonates (PFSAs), and 8 perfluoroalkyl acid precursors (PFAA-precursors) were measured in municipal solid waste (MSW) leachate, construction and demolition debris (CDD) leachate, municipal solid waste incineration (MSWI) ash leachate, gas condensate, stormwater, and groundwater from landfills. Based on the median, results show that PFAS levels in MSW leachate were the highest (10,000 ng L−1), CDD leachate were intermediate (6200 ng L−1), and MSWI ash leachate were the lowest (1300 ng L−1) among the leachates evaluated. PFAS levels in gas condensate (7000 ng L−1) were similar to MSW leachate. PFAS in stormwater and groundwater were low (medians were less than 500 ng L−1). Dominant subgroups included PFCAs and PFAA-precursors in all leachates. PFSAs were also found in CDD leachate, PFAA-precursors in gas condensate, and PFCAs in stormwater and groundwater. Landfill characteristics significantly correlated with ∑26PFAS included waste proportions (percentage of MSWI ash in landfill, |rs| = 0.22), operational status (active or not, |rs| = 0.27) and rainfall (30-d cumulative rainfall, |rs| = 0.39). The results from this study can be used to prioritize which landfills and which reservoir of liquids (and corresponding subgroup of PFAS) to target for PFAS management.

Increase in wear resistance of tribo-couplers due to ion-plasma coating

Problem. Determination of the impact on the wear resistance of the tribosurface (IPP) of the TiN-Cr2N system by the method of solid matter condensation under ion bombardment conditions. Goal. The goal is studying of the effect on the wear resistance of the tribosurface of the TiN-Cr2N system by the method of solid substance condensation under ion bombardment conditions. Methodology. The choice of the composition for ion-plasma pavement for tribocouplers laboratory tests were carried out on the SMC-2 friction machine. The wear test samples were subjected to ion-plasma coatings such as МоN, ТіN and TiN-Cr2N. Results. As a result of laboratory tests it was found that ion-plasma coating of TiN-Cr2N improves the wear resistance of the tribocouplers by about 2.0 times. Furthermore, the wear of the samples with the ion plasma coating TiN and MoN at all loads is less than of the samples after quenching by high frequency but higher than when using the coating TiN-Cr2N. Originality. The coating of the TiN-Cr2N system increases the wear resistance of the tested samples (tribocompounds) due to the presence of titanium nitride and contributes to the increase in corrosion resistance due to the presence of chromium. Practical value. The obtained results of laboratory tests make it possible to predict an increase in the wear resistance of tribocombinations in real conditions of their operation (especially with limited lubrication or without it at all).

Sequence determinants and solution conditions underlying liquid to solid phase transition.

Life consists of numberless functional biomolecules that exist in various states. Besides well-dissolved phases, biomolecules especially proteins and nucleic acids can form liquid droplets through liquid-liquid phase separation (LLPS). Stronger interactions promote a solid-like state of biomolecular condensates, which are also formerly referred to as detergent-insoluble aggregates. Solid-like condensates exist in vivo physiologically and pathologically, and their formation has not been fully understood. Recently, more and more research has proven that liquid to solid phase transition (LST) is an essential way to form solid condensates. In this review, we summarized the regions in the sequence that have different impacts on phase transition and emphasized that the LST is affected by its sequence characteristics. Moreover, increasing evidence unveiled that LST is affected by various solution conditions. We discussed solution conditions like protein concentration, pH, ATP, ions, and small molecules in a solution. Methods have been established to study these solid phase components. Here, we summarized low-throughput experimental techniques and high-throughput omics methods in the study of the LST.

Diverse oxygen isotopic compositions among cometary vapor-phase condensates

Filamentary enstatite crystals, formed by gas–solid condensation in the solar nebula, are found in chondritic porous interplanetary dust particles of probable cometary origin. We measured the oxygen isotopic composition of four filamentary enstatite grains, two whiskers (1.8 μm and 2.3 μm in length) and two ribbons (3.4 μm and 6.1 μm in length), from the giant cluster interplanetary dust particle U2-20 GCP using NanoSIMS ion imaging. These grains represent both the 16O-rich solar (δ17,18O ≈-70‰) and 16O-poor planetary (δ17,18O ≈0‰) isotope reservoirs. Our measurements provide evidence for very early vaporization of dust-poor and dust-rich regions of the solar nebula, followed by condensation and outward transport of crystalline dust to the comet-forming region very far from the Sun. Similar processes are likely responsible for the crystalline silicates observed in the outer regions of protoplanetary disks elsewhere in the Galaxy.

Thermodynamic factor and vacuum crystallization

Sucrose crystallization depends on various thermal phenomena, which makes them an important scientific issue for the sugar industry. However, the rationale and theory of sucrose crystallization still remain understudied. Among the least described problems is the effect of time and temperature on the condensation rate of sucrose molecules on crystallization nuclei in a supersaturated sugar solution. This article introduces a physical and mathematical heat transfer model for this process, as well as its numerical analysis.
 The research featured a supersaturated sugar solution during sucrose crystallization and focused on the condensation of sucrose molecules on crystallization nuclei. The study involved the method of physical and mathematical modeling of molecular mass transfer, which was subjected to a numerical analysis.
 While crystallizing in a vacuum boiling pan, a metastable solution went through an exothermal reaction. In a supersaturated solution, this reaction triggered a transient crystallization of solid phase molecules and a thermal release from the crystallization nuclei into the liquid phase. This exogenous heat reached 39.24 kJ/kg and affected the mass transfer kinetics. As a result, the temperature rose sharply from 80 to 86 °C.
 The research revealed the effect of temperature and time on the condensation of solids dissolved during crystalline sugar production. The model involved the endogenous heat factor. The numerical experiment proved that the model reflected the actual process of sucrose crystallization. The obtained correlations can solve a number of problems that the modern sugar industry faces.

Forming Planets Around Stars With Non-Solar Elemental Composition

Context. Stars in the solar neighbourhood have refractory element ratios slightly different from that of the Sun. It is unclear how much the condensation of solids and thus the composition of planets forming around these stars is affected. Aims. We aim to understand the impact of changing the ratios of the refractory elements Mg, Si, and Fe within the range observed in solar-type stars within 150 pc of the Sun on the composition of planets forming around them. Methods. We use the GGchem code to simulate the condensation of solids in protoplanetary disks with a minimum mass solar nebula around main sequence G-type stars in the solar neighbourhood. We extract the stellar elemental composition from the Hypatia Database. Results. We find that a lower Mg/Si ratio shifts the condensation sequence from forsterite (Mg2SiO4) and SiO to enstatite (MgSiO3) and quartz (SiO2); a lower Fe/S ratio leads to the formation of FeS and FeS2 and few or no Fe-bearing silicates. Ratios of refractory elements translate directly from the gas phase to the condensed phase for T < 1000 K. However, ratios with respect to volatile elements (e.g. oxygen and sulphur) in the condensates – the building blocks of planets – differ from the original stellar composition. Conclusions. Our study shows that the composition of planets crucially depends on the abundances of the stellar system under investigation. Our results can have important implications for planet interiors, which depend strongly on the degree of oxidation and the sulphur abundance.

Aberrant Phase Separation of FUS Leads to Lysosome Sequestering and Acidification.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that leads to the death of upper and lower motor neurons. While most cases of ALS are sporadic, some of the familial forms of the disease are caused by mutations in the gene encoding for the RNA-binding protein FUS. Under physiological conditions, FUS readily phase separates into liquid-like droplets in vivo and in vitro. ALS-associated mutations interfere with this process and often result in solid-like aggregates rather than fluid condensates. Yet, whether cells recognize and triage aberrant condensates remains poorly understood, posing a major barrier to the development of novel ALS treatments. Using a combination of ALS-associated FUS mutations, optogenetic manipulation of FUS condensation, chemically induced stress, and pH-sensitive reporters of organelle acidity, we systematically characterized the cause-effect relationship between the material state of FUS condensates and the sequestering of lysosomes. From our data, we can derive three conclusions. First, regardless of whether we use wild-type or mutant FUS, expression levels (i.e., high concentrations) play a dominant role in determining the fraction of cells having soluble or aggregated FUS. Second, chemically induced FUS aggregates recruit LAMP1-positive structures. Third, mature, acidic lysosomes accumulate only at FUS aggregates but not at liquid-condensates. Together, our data suggest that lysosome-degradation machinery actively distinguishes between fluid and solid condensates. Unraveling these aberrant interactions and testing strategies to manipulate the autophagosome-lysosome axis provides valuable clues for disease intervention.

Modelling the influence of gaseous products of explosive detonation on the processes of crack treatment while rock blasting

Purpose is mathematical modeling of fracturing as well as influence of gaseous products of explosive detonation on the changes in rock strength. Methods. Mathematical model, using foundations of Griffith theory, has been developed. To explain conditions of bridge formation while exploding lead azide charges, a two-stage description of solid particle condensation at a crack surface and inside it has been applied using the smoothed particle hydrodynamics. The analysis, involved electronic microscope, has helped verified the results experimentally. Findings. The effect of rock mass disturbance, resulting from explosive destruction, is manifested maximally right after the action. Subsequently, it decreases owing to the gradual relaxation of the formed defects. Therefore, an urgent problem is to develop ways slowing down strength restore of the blasted rock mass fragments. The process of rock fragment strength restoring may be prevented by microparticles getting into the microcrack cavities together with the detonation products. The research simulates their action. The data correlate to the simulation results confirming potential influence of the blasted rock on the dynamics of changes in the strength characteristics of the rock mass. Various compositions of charges with shells made of inert solid additions have been applied which solid particles can avoid the process of microcrack closure. Originality. For the first time, the possibility of deposition formation within rock micro- and macrocracks has been proposed and supported mathematically. Practical implications. Strength properties of the finished product and the energy consumption during impulse loading as well as subsequent mechanical processing of nonmetallic building materials depend on the strength properties of rock mass fragments. Hence, the ability to control the strength restore has a great practical value. Moreover, it can be implemented during the blasting operations.

Shape and porosity of refractory inclusions in CV3 chondrites: A micro‐computed tomography (µCT) study

AbstractRefractory calcium‐aluminum‐rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs) in chondritic meteorites are the earliest solids of our solar system, bearing the information of nebular condensation as well as accretion and asteroidal shock and metasomatism processes. While the compositions of refractory inclusions have been intensely studied for ~50 years, their physical properties such as shape and porosity are poorly constrained. Here, we present a microcomputed tomography (µCT) study on 16 refractory inclusions of condensate origin in five CV3 chondrites. We find that they are prolate or triaxial in shape with very rough morphologies. The CAIs have nodular textures and are thought to form by agglomerating individual nodules via collision‐induced bouncing and/or fragmentation, where the nodules were grown by gas–solid reactions during condensation. On the parent body, refractory inclusions from the CVR meteorite Leoville experienced intense shocks that led to the flattening of their shapes and lowering of their porosities. High‐temperature metasomatism in CVOxA meteorites and low‐temperature metasomatism in CVOxB meteorites do not seem to have large effects on the porosities of their refractory inclusions, which have similar ranges and pore‐size distributions. Instead, we infer that their pores are mostly inherited from the gas–solid condensation and subsequent agglomeration processes. The porosities of CAIs are higher than those of AOAs, which is mainly due to the high‐temperature sintering process of AOAs.

Correlated isotopic and chemical evidence for condensation origins of olivine in comet 81P/Wild 2 and in AOAs from CV and CO chondrites

Magnesium stable isotope ratios and minor element abundances of five olivine particles from comet 81P/Wild 2 were examined by secondary ion mass spectrometry (SIMS). Wild 2 olivine particles exhibit only small variations in δ25Mg values from –1.0 +0.4/–0.5‰ to 0.6 +0.5/–0.6‰ (2σ). This variation can be simply explained by mass-dependent fractionation from Mg isotopic compositions of the Earth and bulk meteorites, suggesting that Wild 2 olivine particles formed in the chondritic reservoir with respect to Mg isotope compositions. We also determined minor element abundances, and O and Mg isotope ratios of olivine grains in amoeboid olivine aggregates (AOAs) from Kaba (CV3.1) and DOM 08006 (CO3.01) carbonaceous chondrites. Our new SIMS minor element data reveal uniform, low FeO contents of ∼0.05 wt% among AOA olivines from DOM 08006, suggesting that AOAs formed at more reducing environments in the solar nebula than previously thought. Furthermore, the SIMS-derived FeO contents of the AOA olivines are consistently lower than those obtained by electron microprobe analyses (∼1 wt% FeO), indicating possible fluorescence from surrounding matrix materials and/or Fe,Ni-metals in AOAs during electron microprobe analyses. For Mg isotopes, AOA olivines show more negative mass-dependent fractionation (–3.8 ± 0.5‰ ≤ δ25Mg ≤ –0.2 ± 0.3‰; 2σ) relative to Wild 2 olivines. Further, these Mg isotope variations are correlated with their host AOA textures. Large negative Mg isotope fractionations in olivine are often observed in pore-rich AOAs, while those in compact AOAs tend to have near-chondritic Mg isotopic compositions. These observations indicate that pore-rich AOAs preserved their gas–solid condensation histories, while compact AOAs experienced thermal processing in the solar nebula after their condensation and aggregation. Importantly, one 16O-rich Wild 2 LIME olivine particle (T77/F50) shows negative Mg isotope fractionation (δ25Mg = –0.8 ± 0.4‰, δ26Mg = –1.4 ± 0.9‰; 2σ) relative to bulk chondrites. Minor element abundances of T77/F50 are in excellent agreement with those of olivines from pore-rich AOAs in DOM 08006. The observed similarity in O and Mg isotopes, and minor element abundances suggest that T77/F50 formed in an environment similar to AOAs, probably near the proto-Sun, and then was transported to the Kuiper belt, where comet 81P/Wild 2 likely accreted.

Tin telluride quantum dot thin films: Size dependent structural, optical and electrical properties

In the current study, efforts have been made to acquire tin telluride quantum dot (QD) thin films that work at room temperature and in the region of visible and near-infrared (NIR). SnTe ingot and thin films were formed using the solid solution and inert gas condensation (IGC) techniques respectively. A cubic polymorph structure was identified using XRD for the prepared SnTe ingot, while grazing incident in-plane X-ray diffraction (GIIXD) and HR-TEM electron diffraction was used for identifying the thin films. The average particle size was found to increase from 2.3 to 9.6 nm with increasing film thickness from 5 to 25 nm. The optical gap of thin film QDs is wider than those of bulk samples; this is attributable to the quantum confinement effect. As a result of quantum confinement, SnTe thin films have optical gap values in the visible and NIR region (2–0.85 eV) instead of being in the infrared region (0.19 eV) of their bulk materials counterpart. The electronic transition was described by studying various important optical parameters such as optical conductivity (σop), interband transition strength (JCV), and surface and volume energy loss functions (SELF, VELF). Electrical conductivity shows a degenerate semiconductor performance. I–V characteristic show symmetric nonlinear behavior for 10 and 15 nm film thickness.

Evidence of presolar SiC in the Allende Curious Marie calcium aluminum rich inclusion.

Calcium aluminum rich inclusions (CAIs) are one of the first solids to have condensed in the solar nebula, while presolar grains formed in various evolved stellar environments. It is generally accepted that CAIs formed close to the Sun at temperatures above 1500 K, where presolar grains could not survive, and were then transported to other regions of the nebula where the accretion of planetesimals took place. In this context, a commonly held view is that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. Here we demonstrate, based on noble gas isotopic signatures, that presolar SiC have been incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent body processing. This finding provides new clues on the conditions in the nascent solar system at the condensation of first solids.