The Silicon Tracking System (STS) is the main tracking detector of the upcoming fixed-target Compressed Baryonic Matter (CBM) experiment which aims to explore the phase diagram of the strongly ...interacting matter in a region of high net baryonic densities and moderate temperatures. The STS will be used for the reconstruction of tracks of charged particles and determination of their momenta. The system comprises 8 tracking stations located 30 cm downstream the target and will be mounted with 300 mum thick double-sided silicon microstrip sensors in three different sizes. In this paper, the Quality Assurance (QA) procedures for the STS sensors are overviewed highlighting the automated QA testing procedure for a single strip defect identification.
Zr-based metal–organic frameworks (Zr-MOF) UiO-66 and UiO-67 catalyze thioether oxidation in nonprotic solvents with unprecedentedly high selectivity toward corresponding sulfones (96–99% at ca. 50% ...sulfide conversion with only 1 equiv of H2O2). The reaction mechanism has been investigated using test substrates, kinetic, adsorption, isotopic (18O) labeling, and spectroscopic tools. The following facts point out a nucleophilic character of the peroxo species responsible for the superior formation of sulfones: (1) nucleophilic parameter XNu = 0.92 in the oxidation of thianthrene 5-oxide and its decrease upon addition of acid; (2) sulfone to sulfoxide ratio of 24 in the competitive oxidation of methyl phenyl sulfoxide and p-Br-methyl phenyl sulfide; (3) significantly lower initial rates of methyl phenyl sulfide oxidation relative to methyl phenyl sulfoxide (k S/k SO = 0.05); and (4) positive slope ρ = +0.42 of the Hammett plot for competitive oxidation of p-substituted aryl methyl sulfoxides. Nucleophilic activation of H2O2 on Zr-MOF is also manifested by their capability of catalyzing epoxidation of electron-deficient CC bonds in α,β-unsaturated ketones accompanied by oxidation of acetonitrile solvent. Kinetic modeling on methyl phenyl sulfoxide oxidation coupled with adsorption studies supports a mechanism that involves the interaction of H2O2 with Zr sites with the formation of a nucleophilic oxidizing species and release of water followed by oxygen atom transfer from the nucleophilic oxidant to sulfoxide that competes with water for Zr sites. The nucleophilic peroxo species coexists with an electrophilic one, ZrOOH, capable of oxygen atom transfer to nucleophilic sulfides. The predominance of nucleophilic activation of H2O2 over electrophilic one is, most likely, ensured by the presence of weak basic sites in Zr-MOFs identified by FTIR spectroscopy of adsorbed CDCl3 and quantified by adsorption of isobutyric acid.
Probes sensitive to mechanical stress are in demand for the analysis of pressure distribution in materials, and the design of pressure sensors based on metal-organic frameworks (MOFs) is highly ...promising due to their structural tunability. We report a new pressure-sensing material, which is based on the UiO-66 framework with trace amounts of a spin probe (0.03 wt%) encapsulated in cavities. To obtain this material, we developed an approach for encapsulation of stable nitroxide radical TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) into the micropores of UiO-66 during its solvothermal synthesis. Pressure read-out using electron paramagnetic resonance (EPR) spectroscopy allows monitoring the degradation of the defected MOF structure upon pressurization, where full collapse of pores occurs at as low a pressure as 0.13 GPa. The developed methodology can be used
in
and
ex situ
and provides sensitive tools for non-destructive mapping of pressure effects in various materials.
The metal-organic framework UiO-66 with embedded nitroxide radicals represents a new strategy for the design of MOF-nitroxide-based pressure sensors with non-invasive EPR detection.
The results of studies of the structure, phase composition, and mechanical and chemical properties of aluminosilicate, magnesia-quartz, and glass-ceramic proppants (RosProp, BorProp, ForeRCP, Wauli, ...etc.) are reported. It is shown that glass-ceramic proppants outperform ceramic analogs because a highly efficient method of dispersing a melt jet into droplets is used to spherize the particles and because of the structural features manifested in the formation of a homogeneous dense material represented by microcrystals with pyroxene composition.
The effect of modifying components, including Al
2
O
3
, SiO
2
, B
2
O
3
, and CaO, on the melting of basalt and crystallization of basalt glasses intended for continuous manufacture of fiber was ...investigated. It was ascertained that the introduction of complex aluminum- and boron-containing modifiers effects a 15 – 20% greater strength and, at the same time, stable technological properties of basalt glass.
The chemical and phase compositions and the properties of metallurgical dust were studied and its structure and granulometric composition were determined. The physicochemical processes occurring ...during heat-treatment of the dust in the temperature interval 20 – 1200°C were studied. The main directions for reprocessing of the investigated dust for purposes of obtaining useful products are proposed on the basis of the performed studies.
The developed mathematical model was applied for study of fluid dynamics in a rotational bioreactor for bone tissue engineering by
in vitro
technology. The research goal is finding an optimal mode ...for rotation ensuring proper cyclic loading from fluid upon the cell-seeded biomaterial. The basis for developing a mathematical model of a bioreactor was a design of rotational type biological reactor used in medical research; the liquid flow is generated through viscosity mechanism due to surface rotation. Mathematical description of flow in a reactor cavity was performed with Navier—Stokes equations. It was assumed that flow regime in the boundary layer is laminar. Numerical algorithm was accomplished using a fluid flow solver “Fluent” in the code package ANSYS-12. Four variants of generating the rotational motion in the reactor cavity were considered. A series of parametric computations was performed for the rotation frequency
f
in the range 0.05 ≤
f
≤ 0.25 Hz. The paper offers visualization of velocity fields in the vertical plane. The distributions for shear stress and pressure in the working zone of reactor were calculated and analyzed. Simulations demonstrated that a method of fluid rotation by driving the outer cylinder with an offset axis is the best for arranging a cyclic pressure and cyclic shear stress on the biological material.
The results of an investigation of glasses and glass ceramic materials synthesized in the system R
2
O(Na
2
O, K
2
O)–MgO–CaO–Al
2
O
3
–SiO
2
using granitoid screenings from the Mikashevichskoe ...deposit are reported. Glass ceramic materials which in terms of the performance characteristics can be used as proppants in the oil and gas industry were obtained.
The technology using for the replacement of damaged tissues the own cells of the patient, which are placed in a three-dimensional frame - scaffold, is promising for solving the problem of the bone ...tissue regeneration. A new biological reactor of the rotational type, in which the scaffold tissue rotates in a medium for cultivating the cells, was designed for the development of this technique. A numerical algorithm based on the ANSYS program was developed, which enables one to estimate in a new bioreactor the level of the mechanical load on the cells, which affects their pro-perties. The algorithm enables the computation of the values of the shear stress and static pressure acting on the scaf-fold surface. The computations have shown that the necessary shear stress is reached in the proposed rotational biore-actor on the outer side of the inner cylinder (0.002−0.1 Pa) in the range of rotation frequencies 0.083 <
f
< 0.233 Hz. At the same time, computational results have revealed the presence of an inhomogeneity in the mechanical action distribution along the scaffold tissue, which is due to the appearance of two Taylor vortices with opposite rotation directions in the gap between the cylinders. The experiments on the flow field visualization inside the rotational bio-logical reactor have shown a qualitative agreement of the flow character with computational results. The proposed numerical algorithm may simulate with sufficient accuracy the fluid flow in a real system. The obtained dependencies can be used in practice for creating an optimal microenvironment of the cells cultivated in the biological reactor.
The catalytic performance of Zr‐abtc and MIP‐200 metal–organic frameworks consisting of 8‐connected Zr6 clusters and tetratopic linkers was investigated in H2O2‐based selective oxidations and ...compared with that of 12‐coordinated UiO‐66 and UiO‐67. Zr‐abtc demonstrated advantages in both substrate conversion and product selectivity for epoxidation of electron‐deficient C=C bonds in α,β‐unsaturated ketones. The significant predominance of 1,2‐epoxide in carvone epoxidation, coupled with high sulfone selectivity in thioether oxidation, points to a nucleophilic oxidation mechanism over Zr‐abtc. The superior catalytic performance in the epoxidation of unsaturated ketones correlates with a larger amount of weak basic sites in Zr‐abtc. Electrophilic activation of H2O2 can also be realized, as evidenced by the high activity of Zr‐abtc in epoxidation of the electron‐rich C=C bond in caryophyllene. XRD and FTIR studies confirmed the retention of the Zr‐abtc structure after the catalysis. The low activity of MIP‐200 in H2O2‐based oxidations is most likely related to its specific hydrophilicity, which disfavors adsorption of organic substrates and H2O2.
An eight‐connected metal–organic framework Zr‐abtc catalyzes a range of H2O2‐based selective oxidations. The significant predominance of 1,2‐epoxide in the epoxidation of carvone and high sulfone selectivity in thioether oxidation point to a nucleophilic oxidation mechanism. With highly reactive alkenes, such as caryophyllene, electrophilic oxidation can also be realized.
