Determination of the safety factor of cement stone based on numerical modeling of the stress-strain state of the near-wellbore zone, taking into account the change in the elastic-strength properties of cement during its hardening and under the influence of an acid reagent

The results of laboratory studies of the elastic-strength properties of cement stone samples depending on the hardening time and the effect of an acid reagent, and approximated dependences of the change in the elastic modulus, Poisson's ratio and strength properties, depending on the time characteristics for two types of plugging materials are presented. A finite element scheme of the nearwellbore zone has been developed, taking into account the cement stone and the production casing. The results of numerical modeling of the stress-strain state of columns with a diameter of 146 and 178 mm, cement stone and reservoir rocks near the well based on an elastic model are presented. The analysis of the stress field for the occurrence of zones of destruction in the cement stone using the Coulomb-Mohr criterion is carried out. It is shown that, depending on the time of hardening and the effect of an acidic reagent, cement does not collapse and retains a sufficient safety factor. Keywords: cement stone; plugging material; elastic-strength properties; near-wellbore zone; numerical model; finite element method; stress-strain state; safety factor.

Isolation and selection of amylase-producing microbes isolated from ragi tape and cassava tape available on the markets

Amylase has an important role in biotechnology development and occupies an important position in the world enzyme market, as a biocatalyst in various industrial fields. This study has the goal to find microbial isolates that have the ability to produce amylase enzymes. The study was conducted in two stages, namely: 1) Isolation and selection of microbes that can produce amylase enzymes using starch as substrate, was incubated for 4-7 days at 30°C. Microbial isolates that can produce amylase enzymes are characterized by the presence of clear zones around the colony after the addition of an iodine solution of 1% in the overgrown media of microbes, 2) Test the activity of amylase enzymes using a dinitrosalicylic acid reagent test. The activity of the amylase enzyme is determined by measurement using a spectrophotometer at a wavelength of 540 nm. The sample used comprised of 7 types of ragi tape and 2 samples from cassava tape that has been fermented for 5-7 days. The results obtained in the first stage were 65 microbial isolates, 16 of which had clear zones, consisting of 7 isolates from ragi tape samples and 9 isolates from cassava tape samples. In the enzyme activity test, there are several isolates that have the potential to produce amylase enzymes, these include R5I4 (0.897 ± 0.018 U/mL), R2I5.1 (0.814 ± 0.011 U/mL), R5I3 (0.727 ± 0,042 U/mL) (derived from cassava ragi tape samples) and T2I2.2 (0.812 ± 0.013 U/mL), T2I6.1 (0.817 ± 0.010 U/mL), T2I2.1 (0.735 ± 0.023 U/mL), T1I4 (0.755 ± 0.020 U/mL) (derived from cassava tape samples). The isolate with the highest enzyme activity is the R5I4 which has the value enzyme activity of 0.897 ± 0.018 U/mL and with a fairly high or moderate category, while the lowest enzyme activity is the T1I1.1 isolate of 0.284 ± 0.020 U/mL.

Identification of white jewelry alloy based on silver and platinum for testing purposes

The procedure for the identification of white jewelry alloys based on precious metals, in particular, silver, platinum and platinum group metals with different contents of alloying components, by testing on an assay stone and by the method of X-ray fluorescence analysis has been considered. The methodology for assessing the compliance of silver and platinum fineness in white jewelry alloys of different component composition with the requirements of regulatory documents and the procedure for their identification has been improved. It has been established that the silver fineness in precious alloys of the AgCu, AgZnCu system, determined using the potassium dichromate reagent on the test stone, depends on the manifestation of the contrast of the qualitative reaction from the standard sample (assay needle). It has been proven that for testing silver alloys containing palladium, the "Acid reagent for gold 750" is effective, which works to determine the qualitative and approximate content of silver in alloys. It was determined that the reagent "Ferrous-cyanide potassium" is very sensitive to changes in the alloy composition of silver alloys and makes it possible to establish the silver content with an accuracy of 5 %. The presence in silver alloys of such impurities as zinc, cadmium, nickel, gold, palladium and others increases the error in determining the fineness of silver and forms a different color and shade. It has been proven that testing of silver alloys on an assay stone with silver nitrate is effective only for the СрМ system. The presence of zinc in 925 sterling silver alloys visually increases the color intensity of the sediment, which indicates a higher overestimated fineness. It has been found that the identification of the content of precious alloys based on platinum for the presence of ligature components is carried out with a potassium iodide reagent at t=120 °C by the color and shade of the sediment. The procedure for using potassium iodide during testing of precious platinum-based alloys has been optimized

OBTAINING HUMATE-CONTAINING NEW COMPOSITE PRODUCTS

The influence of various factors on the process of interaction in the systems "sodium humate-mixture of phosphoric and nitric acids" and "phosphorite-mixture of acids-sodium humate" has been investigated. The influence of the ratios of the initial components, the amount of sodium humate introduced, the rate of the acid reagent, the temperature and duration of the reaction on the interaction process in the systems under study was studied, and the optimal process conditions were determined. The methods of chemical and physicochemical analysis revealed that as a result of interaction in the studied heterogeneous systems, ammonium humate, sodium acid phosphates, as well as sodium and ammonium nitrates are formed. Based on the studies carried out, it was found that the introduction of sodium humate prevents the inhibition of the decomposition of phosphate raw materials and the retrogradation of P2O5, i.e. the sparingly soluble calcium hydrogen phosphate formed as a result of the interaction of the initial components under the influence of sodium humate transforms into a readily soluble dihydrogen phosphate. A basic technological scheme for obtaining new types of humate-containing composite products has been developed. A basic technological scheme for obtaining new types of humate-containing products has been developed, which allows obtaining two types of products: fertilizers and compositions. When sodium humate interacts with an acidic reagent, the finished product is a humate composition, and if phosphorite is added to the system, a humate-phosphate fertilizer. The resulting products have a high content of P2O5, nitrogen and humic substances.

The role of the 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid reagent in determining the thorium ion (IV)

The aim is to develop a method for the amperometric determination of thorium (IV) ion with 2,7-dinitroso-1,8-dihydroxynaphthalene-3,6-disulfoxyl reagent. Methods of amperometric determination of thorium by solution of 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid on different acid-base properties of background electrolytes and buffer mixtures are considered. The half-wave potential of new reagent was found by logarithmic analysis equal 0.72 V at pH 2.82, which once again indicates on the irreversibility of the process of electrooxidation of the studied organic reagent in used acid-base medias. The conditions for amperometric titration of thorium are optimized, and the influence of outside accompanying metals on the shape of curves and the results of its determination are investigated.

PHARMACOGNOSTICAL, PHYSICOCHEMICAL AND PHYTOCEMICAL STUDY OF Glycyrrhiza Glabra Linn.

Introduction - Glycyrrhiza glabra Linn. is a perennial herb of family Leguminoseae, used very extensively in Ayurveda classics. It is having property of aphrodisiac, trichogenous, expectorant, haemostatic, intellect promoting etc. Objective – Objective of this study to examine the Pharmacognastical and Phytochemical properties of Glycyrrhiza glabra Linn. Material and Method – Dry sample of Glycyrrhiza was collected from Market. The qualitative microscopy, phytochemical screening, physicochemical evolution and TLC studies were carried out according to the standard procedure recommended by API and other standards. Result –The sample is having sweetish taste, faint and characteristic odour, externally dark brown in colour and internally golden yellow. Cork, Phellogen and Phelloderm, Secondary phloem, Cambium, Secondary xylem, Medullary rays and Pith are present in microscopic examinations, from outer to inner side. Cork (in surface view), Tangentially cut medullary ray cells, Fragment of vessel, Calcium Oxalate Crystals, Starch, Mucilage were seen in powder microscopy. pH value of test sample was 5.73. Water Soluble Extractive value (25.0064%) was more than Alcohol Soluble Extractive value (12.7398 %). Total ash value of test sample was 6.131 %. Acid insoluble ash value was 0.79 %, Water soluble ash value was 1.819 %. In TLC, Rf values were found 0.23, 0.58, 0.71 after derivatization with vanillin – Sulphuric acid reagent. Car-bohydrate, alkaloid, amino acid, tannin, protein, saponin, glycosides, flavonoids and tannin were present in the sample. Conclusion - test sample of Glycyrhiza complies all standard when matches with the reference standard book. It suggests that test sample is authentic and without any impurities and adulteration.

Full-color fluorescent carbon quantum dots

Quantum dots have innate advantages as the key component of optoelectronic devices. For white light–emitting diodes (WLEDs), the modulation of the spectrum and color of the device often involves various quantum dots of different emission wavelengths. Here, we fabricate a series of carbon quantum dots (CQDs) through a scalable acid reagent engineering strategy. The growing electron-withdrawing groups on the surface of CQDs that originated from acid reagents boost their photoluminescence wavelength red shift and raise their particle sizes, elucidating the quantum size effect. These CQDs emit bright and remarkably stable full-color fluorescence ranging from blue to red light and even white light. Full-color emissive polymer films and all types of high–color rendering index WLEDs are synthesized by mixing multiple kinds of CQDs in appropriate ratios. The universal electron-donating/withdrawing group engineering approach for synthesizing tunable emissive CQDs will facilitate the progress of carbon-based luminescent materials for manufacturing forward-looking films and devices.