Sorption of platinum and rhodium on carbon adsorbents from chloride solutions

Sorption recovery of platinum (II, IV) and rhodium (III) on different carbon adsorbents has been studied using fresh chloride model solutions with platinum and rhodium concentrations of 0.25–1.0 and 0.049 mmol/L, respectively. The concentration of hydrochloric acid in these solutions varied from 0.001 to 1.0 mol/L. The maximum recovery of platinum and rhodium was achieved with the carbon adsorbent based on charcoal (wood). This sorbent possesses the highest sorption ability to noble metals in medium acidic solutions (0.01–0.1 M HCl). However, the sorption from higher acid solutions (0.5–1.0 M HCl) proceeds on sufficiently high level as well (>80%). The use of thiocarbamide (10%) solutions in sulfuric acid (0.3 mol/L) as a desorption agent results in almost complete elution of rhodium (more than 95%), whereas platinum is retained in carbon adsorbent. This brings out some prospects for separation of these noble metals during their recovery from solutions of spent platinum–rhodium catalysts.     

Possibility of using low-energy nuclear transitions as benchmarks for frequency stabilization

The fundamental possibility of using low-energy nuclear transitions for obtaining highly stable frequency standards is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 3–4, December, 2007.     

Nanoporous Crystalline Material CsLiB6O10

CsLiB₆O₁₀ crystals up to 60 × 40 × 20 mm in dimensions were prepared by top-seeded solution growth, and their interaction with water was studied. The crystals were found to be subject to hydration followed by hydrolysis, during which water leaches Cs from the structural channels to yield Cs₂B₁₀O₁₆ · 8H₂O as the final product. The channel dimensions are not large enough to incorporate ethanol or acetone molecules.     

In vitro dissolution of bioactive glass S53P4 microspheres

Static and dynamic in vitro dissolution studies showed large differences for various size-fractions of non-porous, flame-sprayed commercial microspheres (45–500 µm) of bioactive glass S53P4. The smaller the spheres, the more their composition deviated from the nominal glass. The dissolution studies were carried out in simulated body fluid and tris(hydroxymethyl) aminomethane buffer for seven days. The ion concentrations in solutions were analyzed using inductively coupled plasma optical emission spectrometry, and the pH was measured as a function of time. Also, changes in the sphere size distribution and mass losses were determined. The calcium phosphate and the silica-rich layers at the sphere surfaces were investigated using scanning electron microscopy after several immersion times. The smallest (45–90 µm) spheres appeared almost inert. In contrast, typical silica-rich and calcium phosphate layers were identified at the largest spheres after three days of static and dynamic dissolutions. During the past years, bioactive glass microspheres have been added to paste-like injectable bone grafting materials, putties to enhance their molding properties. The obtained results provide a better understanding of the dissolution patterns of bioactive glass microspheres.     

Development of a Model for the Formation of Materials with a Hierarchical Pore Structure Produced under Sol–Gel Processing Conditions

We have developed a model for the formation of silica-containing synthetic functional materials with a hierarchical pore structure and a large specific surface area under self-assembly conditions of sol–gel processes. The model includes the formation of a three-dimensional core (of a cristobalite type) of sol particles consisting of joined polymorphoids in the form of n-membered rings and a continuous transition between fractal aggregate growth mechanisms, from diffusion-limited to cluster–cluster aggregation, followed by evolution culminating in spinodal decomposition. Hierarchical structures have been studied using three-dimensional simulation with Autodesk 3ds Max software.     

On the construction of invertible filter banks on the 2-sphere

The theories of signal sampling, filter banks, wavelets, and "overcomplete wavelets" are well established for the Euclidean spaces and are widely used in the processing and analysis of images. While recent advances have extended some filtering methods to spherical images, many key challenges remain. In this paper, we develop theoretical conditions for the invertibility of filter banks under continuous spherical convolution. Furthermore, we present an analogue of the Papoulis generalized sampling theorem on the 2-Sphere. We use the theoretical results to establish a general framework for the design of invertible filter banks on the sphere and demonstrate the approach with examples of self-invertible spherical wavelets and steerable pyramids. We conclude by examining the use of a self-invertible spherical steerable pyramid in a denoising experiment and discussing the computational complexity of the filtering framework.     

Microstructure and Reliability Comparison of Different Pb-Free Alloys Used for Wave Soldering and Rework

This paper describes the results of an intensive microstructural and reliability study of pin-through-hole (PTH) and surface mount technology (SMT) components which were wave solder assembled using three groups of alloys: (1) near-eutectic Sn-Ag-Cu alloys such as SAC405 and SAC305, (2) low-Ag off-eutectic Pb-free alloys with an Ag content of about 1% and lower, and (3) eutectic Sn-Cu alloys with Ni and other additives. Both primary attach and reworked solder connections using solder fountain and hand rework were studied. The PTH connector types and SMT components were wave solder assembled on a test vehicle. Accelerated thermal cycling (ATC) was conducted at 0°C to 100°C for 6000 cycles. The difference in microstructures, intermetallic formation, Cu dissolution, grain coarsening, and crack formation is shown. The influence of the microstructure after assembly and rework on Weibull plot parameters and failure modes is described for 2512 resistors. Interconnect defects such as nonuniform phase distribution and void formation are discussed. The Sn-Cu-Ni- and Sn-Cu-Ag-Bi-based alloys tested in this study are recommended as potential suitable replacements for SAC305/405 in the wave solder process; no failure was detected up to 6000 cycles at 0°C to 100°C. Although SAC405 demonstrated better barrel fill and lower rate of crack propagation during ATC, after PTH rework, both of the alternative Pb-free alloys have a much lower Cu dissolution rate and definitely outperform SAC405 in ATC. SAC405 glue and wave resistors after primary attachment and rework demonstrate higher reliability than alternative alloys. Early failures relate to alternative alloy characteristics and should be considered for some applications.     

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.