Cellulose Acetate Sulfate as a Lyotropic Liquid Crystalline Polyelectrolyte: Synthesis, Properties, and Application

The optimal conditions of cellulose acetate sulfate (CAS) homogeneous synthesis with the yield of 94–98 wt.% have been determined. CAS was confirmed to have an even distribution of functional groups along the polymer chain. The polymer was characterized by an exceptionally high water solubility (up to 70 wt.%). The isothermal diagrams of its solubility in water-alcohol media have been obtained. CAS aqueous solutions stability, electrolytic, thermal, and viscous properties have been defined. The main hydrodynamic characteristics such as intrinsic viscosity, Huggins constant, and crossover concentration have been evaluated. The parameters of polymer chain thermodynamic rigidity have been calculated. The formation of liquid crystalline structures in concentrated CAS solutions has been confirmed. CAS was recommended to be used as a binder for the medicinal forms of activated carbon and carbon sorbent for water treatment, hydrophilic ointment foundation

Плазменный синтез кремний-углеродных композитов для анодов литий-ионных аккумуляторов

One of the key challenges of modern technology is the development of efficient methods for producing and storing energy. Against the backdrop of the intensive development of a new generation of alternative “green” energy, developments in the field of improving lithium-ion batteries seem relevant and promising. However, since currently used graphite-based anode materials are limited by theoretical specific capacity values (372 mAh/g), the development of new materials for application in lithium-ion battery technology is in high demand. Silicon-based materials with a high theoretical capacity of 4200 mAh/g are being considered as a promising alternative to graphite. However, the practical use of silicon anodes is difficult due to the significant volumetric expansion of silicon (~400 %) during repeated lithiation/delithiation, which leads to instability of the resulting electrode materials. Si-C nanocomposite anode materials have been proposed as a solution due to their high capacity and stability

The use of nanoparticles to improve the analytical capabilities of LIBS for solution sample analysis

Laser-induced breakdown spectroscopy (LIBS) is a diagnostic technique based on optical emission spectroscopy, suitable for rapid, in situ, and multi-element analysis of all sample types. LIBS has demonstrated its greatest potential in the analysis of solids, both conducting and nonconducting. However, when it comes to quantitative LIBS analysis of liquids, there are still some drawbacks that limit its applicability, such as poor repeatability and low sensitivity. To some extent LIBS performance may be improved if directly performing LIBS on the solution is avoided by converting the liquid into a solid phase. Another recently proposed method to resolve the difficulties in LIBS analysis of liquid samples is the application of Nanoparticle - Enhanced LIBS (NELIBS) [1,2]. The aim of the present work was to examine the effect of copper oxide nanoparticles (NPs) on the analytical capabilities of LIBS analysis of lead in aqueous solutions. The apparatus for NELIBS experiments comprises a laser source, a spectrograph (F=850 mm, grating 1800 groves/mm, F/11) coupled with a CCD, and the focusing and collecting optics, i.e. the same as used in conventional LIBS. A double pulse Q-switched Nd:YAG laser at 1064 nm, pulse duration 10 ns, pulse energy 50 mJ, interpulse delay 1 μs was used. The spectra were registered in a time-integrated mode (integration time 1 ms). A glass plate was chosen as the substrate to ensure there is no interference between NPs and the substrate. The first type of samples was prepared by drying a droplet of a Pb solution (10 μl, concentration 100 ppm) on the glass substrate. The second type was prepared by drying a droplet of the copper oxide colloidal solution on the glass, prior to the deposition of the analyte solution. Three sets of the LIBS spectra were acquired; spectra of glass with deposited CuO NPs, of glass with deposited sample solution of Pb, and of the glass with deposited NPs of CuO and the sample solution of Pb. The spectra were obtained in the 395-415 nm spectral range. Only in the third case, intense Pb lines appeared in the spectrum. Estimation of the limit of detection (LOD) for the resonance Pb line at 405.78 nm, without additional optimization of the measurement parameters, gave a value of 3.6 ppm. Regarding the fact that without the addition of the NPs layer no analyte signal was obtained, it can be concluded that the enhancement of the lead emission line intensity is caused by the presence of the NPs, i.e. by the lower plasma formation threshold and more efficient atomization of the analyte deposited on the NP layer. The main benefits of using NELIBS for the analysis of solutions lie in its simplicity, speed, the small amount of solution needed (few microliters), and the ability to analyze very dense or slurry samples.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Two family interventions to reduce BMI in low-income urban youth: A randomized trial

BACKGROUND: Our primary aim was to evaluate the effects of 2 family-based obesity management interventions compared with a control group on BMI in low-income adolescents with overweight or obesity. METHODS: In this randomized clinical trial, 360 urban-residing youth and a parent were randomly assigned to 1 of 2 behaviorally distinct family interventions or an education-only control group. Eligible children were entering the sixth grade with a BMI $85th percentile. Interventions were 3 years in length; data were collected annually for 3 years. Effects of the interventions on BMI slope (primary outcome) over 3 years and a set of secondary outcomes were assessed. RESULTS: Participants were primarily African American (77%), had a family income of,25 000 per year, and obese at enrollment (68%). BMI increased over time in all study groups, with group increases ranging from 0.95 to 1.08. In an intent-to-treat analysis, no significant differences were found in adjusted BMI slopes between either of the family-based interventions and the control group (P = .35). No differences were found between the experimental and control groups on secondary outcomes of diet, physical activity, sleep, perceived stress, or cardiometabolic factors. No evidence of effect modification of the study arms by sex, race and/or ethnicity, household income, baseline levels of child and parent obesity, or exposure to a school fitness program were found. CONCLUSIONS: In this low-income, adolescent population, neither of the family-based interventions improved BMI or health-related secondary outcomes. Future interventions should more fully address poverty and other social issues contributing to childhood obesity

ANALYSIS OF WORK AND OPERATION OF ROTOR-TILTING DRUM-TYPE FURNACE

Analysis of works is carried out and characteristics of operation of a rotor-tilting drum-type furnace are given. Technological process of melting of black and nonferrous alloys in a rotor-tilting furnace is considered

INFLUENCE OF COOLING SPEED ON CRACKS FORMATION OF IRON-BORON-CARBON ALLOYS

The investigation of heterogeneity of the boron-containing alloy structure with the aim of determination of the cooling speed influence on fragility is carried out in this work

Synthesis of colloidal CuInSe

This work presents a low-cost, non-vacuum, and facile process for fabrication of CuInSe2 (CIS) nanoparticles using electrical discharge treatment of mixture of copper, indium, and selenium powders between two tungsten electrodes immersed in pure ethanol. The synthesized particles were characterized by UV-Vis-NIR absorption, X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Raman spectroscopy, transmission and scanning electron microscopy (TEM and SEM). TEM images exhibited that the final product is mainly composed of a large amount of primary nanoparticles typically 10–40 nm in diameter. The band gap energy value of the nanoparticles was estimated to be around 1.2 eV. The XRD pattern of the as-prepared samples besides the main peaks of chalcopyrite tetragonal CIS showed the diffraction peaks which could be attributed to intermediate phases. To omit the intermediate phases and reach to pure CIS nanoparticles the as-prepared in electrical discharge samples were annealed in vacuum at the temperature of 700 °C during 90 min. The XRD and SEM analysis results of annealed samples clearly indicated that chalcopyrite CuInSe2 particles with good crystallinity and near stoichiometric atomic composition were obtained. The composition and crystalline structure of the product was also confirmed by the room-temperature Raman spectrum showing an intense peak at 172 cm-1 corresponding to the A1 phonon mode of tetragonal CuInSe2 chalcopyrite

Time-spatial resolved LIBS of atomic and molecular carbon in laser ablation plasma

For elucidation a possibility to use molecular emission spectra in LIBS analysis of carbon containing materials time and space resolved spectra of laser ablation plasma from graphite were studied. Laser plasma was produced on a rotated graphite target by fundamental harmonic of YAG: Nd3+ laser (Lotis TII) in air at atmospheric pressure. The optical emission spectra were analyzed using a GSM850 Lotis TII monochromator/spectrograph equipped with a CCD detector. The atomic and molecular spectra in the region of emission of molecules C2 (λ = 516,52 nm) and CN (λ = 421,16 nm) were registered by photomultiplier placed behind the interference filter to record the intensity of the selected plasma emission line. The temporal and spatial characteristics of the plasma spectra with special attention to molecular carbon including molecules СN and С2 were analyzed. It was found that the time range of dominance of the C2 and CN emission is related to the stage of the plasma decay (10–20 μs after the action of the laser pulse, depending on the conditions for plasma creating). The atomic emission spectra of the plasma were used to estimate the concentration of electrons and the electron temperature of the plasma. The vibrational temperature of the carbon plasma was determined from the molecular spectrum of the radical СN ((∆ν = 0, -1). The plasma electron concentration and electron temperature as well as vibrational temperature were determined in different zones of the expanding plasma and at different values of laser power densities (2,2·108 ÷ 3,7·108 W/cm2 ) used in experiments. The electron temperature varied in the range 9700 – 10300 K, the electron concentration was estimated to be in the range from 0,8·1018 cm-3 to 8,0·1018 cm-3 , the vibrational temperature of the plasma was 4560 - 7350 K depending on the experimental conditions (laser power density, spatial zone of the plasma plume).VIII International School and Conference on Photonics and HEMMAGINERO workshop : PHOTONICA2021 : book of abstracts; August 23-27, 2021; Belgrad