Structural Formula Research Articles

Chemical stability diagrams as a powerful tool to the synthesis of Cu2SnS3 thin films by chemical bath deposition

Cu2SnS3 films are produced by chemical bath method employing low toxicity citrate precursor taking advantage of the strong complexes formed with Cu(II) and Sn(II). The deposition conditions for Cu2SnS3 thin films were obtained through a thermodynamic analysis of the effect of tin concentration on Cu(II)–Sn(II)-Citrate complexes and Cu(II)–Sn(II)-Citrate-Thiourea system using a species distribution and potential–pH (Eh-pH) analysis. Theoretical analysis of the speciation fraction of Cu(II) and Sn(II) shown that the predominant species at pH equal to 4.5 at 90 °C are [Cu2(Cit)2OH]3− and [Sn2(Cit)2]2−. For the Cu(II)–Sn(II)-Citrate-Thiourea system at 90 °C, the Eh-pH diagrams established that binary precursors, Cu2S and SnS2, would be obtained under basic pH conditions. Subsequently, Cu2SnS3 films were synthetized at 90 °C at pH equal to 8 by keeping fixed the molar relationships complexing agent-metal and sulfur-metal. The redox potentials were measured in solution and chemical equilibrium diagrams were constructed, confirming the existence of binary precursors under reductive conditions. Characterization of structural, electronic and transport properties indicated that Cu2SnS3 fabricated by chemical bath deposition have monoclinic crystal structure, a direct band gap energy of 1.70 eV and p-type conductivity.

Mineralogy, geochemistry, and genesis of bentonites in Upper Cretaceous pyroclastics of the Bereketli member of the Reşadiye Formation, Reşadiye (Tokat), Turkey

Bentonites have been found widespread within the Bereketli member of the Cretaceous Reşadiye Formation, central Anatolia. These bentonites were hypothesized to have been formed by the in-situ alteration of parent rhyolitic, dacitic, and trachyandesitic pyroclastics in a shallow marine environment during early diagenesis shortly after deposition. Both Na- and Na-Ca-smectites were observed. The bentonites contained heulandite-clinoptilolite, kaolinite, plagioclase/K-feldspar, mica, quartz, opal-CT, calcite, and in some samples, goethite. The chemical analyses of smectite-rich clay fractions were montmorillonitic in composition. The average structural formula is: (Ca0.13Na0.40K0.05)(Al2.98Fe0.41Mg0.50Ti0.04Mn0.002)(Si7.90Al0.10)O20(OH)4. Smectite was formed from the devitrification of glass shards and dissolution of pyroclastic feldspars, and mica during early diagenesis under alkaline conditions. Certain whole-rock major and trace element signatures supported the formation of smectite from pyroclastic progenitors. The breakdown of pyroclastic hornblende and biotite was inferred from the enrichment in Fe2O3 and MgO in the clay fractions. The devitrification of glass to clay and the dissolution of K-feldspar and plagioclase contributed to the observed negative correlation of SiO2 vs. Al2O3, Fe2O3 + TiO2, and MgO as well as the negative Eu anomaly. These bentonites originated from rhyolitic to trachyandesitic pyroclastic rocks based on the Sc/Th and Co/Th, Th/U, Nd/Sm, Zr/Hf, La/Sc, Nb/Ta, Zr/Hf ratios. The variabilities of the UCC-normalized elemental results were most pronounced for the elements whose solubilities were high in the conversion of tuff to bentonite (alkali and alkaline earth elements). The variabilities seen in the UCC normalized lanthanide elements likely reflected the lanthanide contents of the non-clay minerals in the bentonite and pyroclastic parent materials. These bentonites are presently mined as important raw materials for the drilling and molding industries in Turkey.

Analysis of chemical constituents of Ginseng-Douchi compound fermentation products based on UPLC-Q-TOF-MS

In this experiment, ultra high performance liquid chromatography-quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS) was used to analyze and identify chemical constituents of Ginseng-Douchi(GD) compound fermentation, and explore the conversion rules of ginsenosides and soybean isoflavones after compound fermentation. Waters Acquity UPLC BEH C_(18) column(2.1 mm×100 mm, 1.7 μm) was adopted, with 0.1% formic acid aqueous solution(A)-0.1% formic acid acetonitrile solution(B) as mobile phase for gradient elution; electrospray ion source(ESI) was used to collect data in positive and negative ion modes; according to the exact mass number, the secondary spectrum comparison of the database and the existing literature reports, Peakview 2.0/masterview 1.0 software was used to determine the common ion structure formula. Finally, a total of 133 chemical constituents were analyzed and identified from the GD. Ginseng saponins and isoflavone glycosides were significantly converted after fermentation. Among them, peak areas of prototype ginsenosides Rk_3, Rh_1, Rh_2, Rh_3, daidzin, glycitin and genistin decreased significantly; whereas peak areas of se-condary ginsenoside Rb_1, Rb_2, Rk_1, glycitein, genistein and daidzein increased significantly. In this experiment, liquid-mass spectrometry technique was used to investigate the conversion of active ingredients of GD compound fermented products after co-fermentation, so as to provide a scientific basis for elucidating pharmacodynamics material basis and quality control.

Chemical variability in vyacheslavite, U(PO4)(OH): Crystal-chemical implications for hydrous and hydroxylated U4+, Ca, and REE phosphates

Abstract Particularly interesting chemical variability in the U4+ phosphate mineral vyacheslavite from Menzenschwand (Germany) has been discovered and investigated by means of electron-diffraction and micro-chemical methods. Suggested variability comprises the elevated contents of calcium and rare-earth elements (REEs or Ln). Based on the crystal structure refinement from 3D electron diffraction data, the structural formula of Ca-rich vyacheslavite studied is U0.895Ca0.105 PO4(OH)0.790(H2O)0.210. In general, such compositional variability involving Ca2+ can be expressed as U1–x CaxPO4(OH)1–2x(H2O)2x. Based on detailed electron-probe microanalysis, regions extremely enriched in Y and Ln have been discovered, characterized by the contents up to 11 wt% of Y2O3 and ~4.5 wt% of Ln2O3. In addition to the above-mentioned substitution mechanism, substitution involving Y and Ln can be expressed as U4+ + OH– → REE3+ + H2O. Although the structure refinement has not provided direct evidence of H2O in the studied nano-fragments of vyacheslavite, the presence of H2O and its substitution at OH– sites is a reasonable and necessary charge-balancing mechanism. One H atom site was located during structure refinements; however, an additional H-site is only partially occupied and thus was not revealed from the refinement despite the high-quality data. Substitutional trends observed here suggest possible miscibility or structural relationship between vyacheslavite, rhabdophane, and ningyoite that may depend strongly on OH/H2O content, considering that all crystallize under similar paragenetic conditions.

Structure Drawing at the Heart of Teaching Chemistry.

Chemistry is all about structures. There are myriads of structural representations that are required for the students to become familiar with when learning chemistry. Structural formula, skeletal formula, Lewis and resonance structures, three-dimensional representations are just a few examples of the drawing styles that should be readily interpreted by a chemistry student. In order to gain the necessary knowledge to understand and manipulate chemical structures, students must extensively solve problems with structural illustrations and practice drawing chemical structures themselves. Here we present Zosimos, an online chemistry educational tool with comprehensive structure-drawing capabilities that allows chemistry teachers to create real chemistry quizzes, share them with their students and get immediate feedback on their learning progress. 5th grade students at Kantonsschule Zug have been learning chemistry with Zosimos since September 2019 and this article also shares insights on how to implement this learning tool in a real classroom setting.

Rational Analysis of Thimi White Clay Deposits of Bhaktapur District, Nepal

Clay deposits become one of the natural mineral sources used abundantly as cost-effective raw materials for various industrial productions in recent years that use depend mainly on their quantification done by rational analysis. The rational analysis is a reliable and optimization method for the quantitative determination of all mineralogical components and structural formulae of the clay minerals that furnishes all their properties. However, no work reports the aspect of the quantitative analysis of the clay minerals deposited in Nepal. Considering the facts, the present work targeted to carry out the rational analysis of a bulk (BC), fine (FC), and HCl-activated Thimi white clay (FCHCl) sample specimens to explore its potential uses in all industrial sectors, based on their chemical and mineralogical analysis data. Vermiculite, K-mica minerals with feldspars and quartz as assessors confirmed qualitatively in the Thimi white clay sample specimens, and their quantification of all the mineralogical components and their ionic structural formulae successfully estimated at present. The quantitative amounts of the iron-bearing vermiculite and K-mica minerals are increased with decreases of the quartz and Na-mica in the fine clay particles compared to the bulk clay sample. Acid-activated fine clay particles would apply as a suitable raw material for the quality production of white-wares on an industrial scale.

A study of continuous vector representations for theorem proving

Abstract Applying machine learning to mathematical terms and formulas requires a suitable representation of formulas that is adequate for AI methods. In this paper, we develop an encoding that allows for logical properties to be preserved and is additionally reversible. This means that the tree shape of a formula including all symbols can be reconstructed from the dense vector representation. We do that by training two decoders: one that extracts the top symbol of the tree and one that extracts embedding vectors of subtrees. The syntactic and semantic logical properties that we aim to preserve include both structural formula properties, applicability of natural deduction steps and even more complex operations like unifiability. We propose datasets that can be used to train these syntactic and semantic properties. We evaluate the viability of the developed encoding across the proposed datasets as well as for the practical theorem proving problem of premise selection in the Mizar corpus.

Simulating the ghost: quantum dynamics of the solvated electron

The nature of the bulk hydrated electron has been a challenge for both experiment and theory due to its short lifetime and high reactivity, and the need for a high-level of electronic structure theory to achieve predictive accuracy. The lack of a classical atomistic structural formula makes it exceedingly difficult to model the solvated electron using conventional empirical force fields, which describe the system in terms of interactions between point particles associated with atomic nuclei. Here we overcome this problem using a machine-learning model, that is sufficiently flexible to describe the effect of the excess electron on the structure of the surrounding water, without including the electron in the model explicitly. The resulting potential is not only able to reproduce the stable cavity structure but also recovers the correct localization dynamics that follow the injection of an electron in neat water. The machine learning model achieves the accuracy of the state-of-the-art correlated wave function method it is trained on. It is sufficiently inexpensive to afford a full quantum statistical and dynamical description and allows us to achieve accurate determination of the structure, diffusion mechanisms, and vibrational spectroscopy of the solvated electron.

On the structural formula of smectites: a review and new data on the influence of exchangeable cations.

The understanding of the structural formula of smectite minerals is basic to predicting their physicochemical properties, which depend on the location of the cation substitutions within their 2:1 layer. This implies knowing the correct distribution and structural positions of the cations, which allows assigning the source of the layer charge of the tetrahedral or octahedral sheet, determining the total number of octahedral cations and, consequently, knowing the type of smectite. However, sometimes the structural formula obtained is not accurate. A key reason for the complexity of obtaining the correct structural formula is the presence of different exchangeable cations, especially Mg. Most smectites, to some extent, contain Mg2+ that can be on both octahedral and interlayer positions. This indeterminacy can lead to errors when constructing the structural formula. To estimate the correct position of the Mg2+ ions, that is their distribution over the octahedral and interlayer positions, it is necessary to substitute the interlayer Mg2+ and work with samples saturated with a known cation (homoionic samples). Seven smectites of the dioctahedral and trioctahedral types were homoionized with Ca2+, substituting the natural exchangeable cations. Several differences were found between the formulae obtained for the natural and Ca2+ homoionic samples. Both layer and interlayer charges increased, and the calculated numbers of octahedral cations in the homoionic samples were closer to four and six in the dioctahedral and trioctahedral smectites, respectively, with respect to the values calculated in the non-homoionic samples. This change was not limited to the octahedral sheet and interlayer, because the tetrahedral content also changed. For both dioctahedral and trioctahedral samples, the structural formulae improved considerably after homoionization of the samples, although higher accuracy was obtained the more magnesic and trioctahedral the smectites were. Additionally, the changes in the structural formulae sometimes resulted in changing the classification of the smectite.

Structure modeling of mining machinery systems for production of raw peat materials

This work describes systems of mining machines for peat extraction, particularly, the systems that exploit environment-friendly technologies. An algorithm for schematic structure modeling of modular mining machinery systems was introduced and analyzed. Based on the analysis, an algorithm for assessing energy consumption of an entire machinery system on the basis of its structure was described. As an example, structural schemes of four modular mining machinery systems were assessed. These structural formulae were also used for structuring mining machinery systems by the energy efficiency criterion. Effectiveness value of mining machinery system is suggested to be assessed by energy efficiency coefficient. The results of the analysis and assessed models proved the viability of mining machinery systems for open-cast peat winning that combine the modules of extraction, processing, transfer, and others organized by applying devised structural formulae and energy efficiency criterion.

La falacia del Estado social en Colombia

This document carries out a normative and jurisprudential analysis on the model of the Social State of Law and Social Rights introduced by the 1991 Constitution, to validate its development. The main goal is to contrast the normative design with the reality of Colombian society to consider whether the social purposes of the state are met or if, on the contrary, the Social State of Law is a legal discourse and not a reality. To achieve such goal, the emergence and evolution of the concept of Social State of Law and its application in Colombian constitutionalism are taken into account; The study of social rights is carried out in conceptual and quantitative terms with satisfaction/deficiency indicators to identify the effectiveness degree those rights that allow the progress or setbacks of the Social State of Law to be concluded. The contrast among constitutional norms, jurisprudential rules and empirical data on the effectiveness of social rights lead us to the conclusion that in 30 years of legitimacy of the Colombian Constitution 1991-2021, the Social Rule of Law in our country is a fallacy that needs to be transformed into reality by social actors to undertake the programmatic content of the constitution. To fulfill social needs, there are legalpolitical instruments such as the National Development Plan and the Multi-Year Budgets, which meet public policy to procure the improvement and quality of life of Colombians and show that the Social State of Law is not a simple constitutional formula.

Crystal–chemical and diffraction analyses of Maya blue suggesting a different provenance of the palygorskite found in Aztec pigments*

Maya blue is a pigment found in different archaeological sites of different cultures from Mesoamerica, and also in colonial buildings in Mexico and Cuba. The pigment is made from a thermally treated mixture of indigo and palygorskite. Pigment samples from Aztec and non‐Aztec archaeological sites as well as reference Yucatecan palygorskites were studied in this paper to assess their differences. The characterization of the samples was carried out by a combination of a crystal–chemical‐point analyses using electron microscopy to obtain the structural formulae of the palygorskite crystals, and studied using high‐resolution X‐ray diffraction. The data show evidence that the palygorskite used by non‐Aztec cultures, such as the Maya, is compatible with palygorskite from known sources in the Yucatan Peninsula, while the palygorskite used by the Aztec culture is different in its structure and has an origin that is still unknown.

Synthesis, Characterization, and Biological Studies of In Vitro Antibacterial, and Cytotoxic Activities of Norfloxacin Based Square Pyramidal Copper(II) Complexes

The substantial increase in copper-containing complexes' research to treat bacterial infections encouraged us to synthesize fluoroquinolone drug norfloxacin (NFLH) based copper complexes. In this work, we presented the synthesis of mixed ligand Cu complexes with the basic structural formula [Cu(NFL)(A1)Cl], where An is isatin-based ligands. The characterization of compounds by Mass, FT-IR, UV-Vis spectroscopy, magnetic measurement, and conductivity measurement revealed the neutral nature and square pyramidal geometry of all the copper compounds. The biological screening of compounds displayed the potent bacteriostatic activity of copper compounds compare with the standard drug against four medically significant pathogens. The in vitro cytotoxic activity of copper compounds was checked on artemia cyst. The biological studies data are promising for their application as medicinally important compounds for future perspective.

Thermal rearrangements during liquid–vapor phase pyrolysis polycondensation of polysilane to high-functional polycarbosilane: spectral and thermal studies

Thermally induced Kumada rearrangement of –Si–Si– linear chains in polysilanes to –Si–C– chain was conducted in the liquid–vapor phase, followed by isothermal treatments at 410, 460 °C and pressure of 15 kgf cm−2 leading to polycarbosilane(PCS) with higher silane (–Si–H) content in the range 0.46–0.58 mass%. Molecular and thermal changes during the oligomer to polymer transformation were investigated, applying spectral and thermal techniques. FTIR, Raman, and 1H, 13C, and 29Si-NMR analytical results established the chemical structural formula, –Si–Si–, –Si–C–, –Si–H bonding networks, and evolution of –Si–H functionality in as-synthesized polycarbosilane during the thermal transformations. FTIR and 29Si-NMR studies followed the increase in silane content (–Si–H). Raman data revealed the formation and disappearance of –Si–Si– functional group as the transformation progresses. Average molecular mass increased proportionally with polymerization reaction time. Thermogravimetric studies at 1400 °C confirmed a polymer to ceramic conversion (ceramic yield) of as-synthesized PCS increased with the increase in mass average molecular mass and found to be as high as 88% mass. The formation of a high purity green β-SiC powder on heat treatment at 1500 °C confirmed the high molecular polycarbosilane.

Extraction and analysis of chemical constituents from mangosteen pericarp

In order to improve the utilization efficiency of mangosteen pericarp and make rational use of its active components, the antibacterial, anti-inflammatory and anti-tumor active components, molecular formula, structural formula, physical and chemical properties and action mechanism of mangosteen pericarp were analyzed The results showed that the active components of mangosteen shell also had antioxidant activity, anti-ultraviolet radiation effect, cardiovascular disease improvement effect, neuroprotective effect and intestinal disease protection effect. Among the extraction methods of active components from mangosteen shell, supercritical fluid extraction and vegetable oil assisted extraction have the characteristics of green nature, environmental protection and energy saving, and have broad market prospects in the development and utilization of mangosteen pericarp.

Alluaudite-Group Phosphate and Arsenate Minerals

ABSTRACT A systematic study of alluaudite, hagendorfite, and varulite was done using single-crystal X-ray diffraction, powder diffraction, and electron probe microanalysis of samples from 12 separate localities. The crystal structures of the representative alluaudite and hagendorfite samples were refined to R1 indices of 3.7 and 1.8%, respectively, using a Siemens P4 automated four-circle diffractometer equipped with a graphite monochromator and MoKα X-radiation. These samples and several others were analyzed with an electron microprobe to study variations in chemical composition. For the single-crystal analyses, the resulting unit formulae are (Na0.11□0.89)(Na0.59Mn0.27Ca0.14)Mn1.00(Fe3+1.64Al0.24Mg0.13)(PO4)3 for alluaudite, (Na0.79□0.21)(Na0.81Mn2+0.19)(Mn0.70Fe2+0.30)(Fe2+1.72Mg0.27Al0.01)(PO4)3 for hagendorfite, and (Na0.84□0.16)(Na0.71Ca0.23□0.06)Mn1.00(Fe3+0.89Fe2+0.68Mn0.42Mg0.01)(PO4)3 for varulite. Originally, a nomenclature scheme was proposed for the alluaudite-group minerals that was based on sequentially distributing the cations in the cell according to increasing polyhedron size, matching that size with increasing ionic radii of the cations. For alluaudite, the structural formula was written as X(2)4X(1)4M(1)4M(2)8(PO4)12, with the sites ordered in decreasing size of the discrete polyhedra. Later, the formula [A(2)A(2)'A(2)”2][A(1)A(1)'A(1)”2]M(1)M(2)2(PO4)3 was proposed, which takes into account the distinct crystallographic sites in the channels of the structure. More recently there has been a revision to the nomenclature of the group. The simplified structural formula for the alluaudite-type is now A(2)'A(1)M(1)M(2)2(TO4)3; the new nomenclature scheme has been adopted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC), based on the contents of the M(1) and M(2) octahedral sites, and the results are reviewed here. Compounds belonging to the alluaudite structural family have been the focus of synthetic mineral studies for decades owing to the open-framework architecture and their unique physical properties. Improvements in synthesis methods have allowed researchers to substitute a wide range of elements into the alluaudite structure.

Using metavisualization to revise an explanatory model regarding a chemical reaction between ions

The objective of this work was to evaluate the implementation of a metavisual strategy for students to revise and self-regulate concepts arising in a study of a chemical reaction between ions. For this purpose, two chemistry education undergraduate students at a Brazilian public university carried out an investigative activity, involving metavisual steps, to revise explanatory models at the submicro level. Students were given a problem, namely a reaction between ions drawn from a real-life situation and were provided with clay to construct an explanatory model of the submicro level for the initial and final stages of the reaction. The students were asked to compare their clay model with an example of a scientifically correct figure of the submicro level of the reaction generated by the researchers. At this stage students were given the option to reconstruct their model. Data were captured via photographs of the clay models and students’ verbal discussions as they proceeded through the activity. The findings reveal evidence of self-regulation of mental models at the submicro level, from the interaction of prior knowledge, chemical diagrams and discussions and reflections by the pair of students. Difficulties regarding chemical formulae were also observed in relation to the symbolic level. Finally, there are implications for teaching chemistry, since teachers in training need to experience metavisual strategies for future application in their classrooms.

METAPHORICAL COMPARISONS WITH THE COLOR STANDARD (BASED ON THE MATERIAL OF RUSSIAN LITERARY DISCOURSE)

Modern linguistic studies of cultural manifestations of different ethnic groups that found their place in the language prove that language affects how a person perceives the world around him or her. The language creates a naive picture of the world, which is based on popular wisdom and knowledge of cultural ethnic or universal human norms and traditions. This picture has its own unique laws, different from the scientific picture of the world, dictates its own categories of space and time, as well as color and function. This article presents a linguoculturological analysis of metaphorical comparisons with a color standard to identify regular metaphorization models, the frequency of choice of a particular comparison agent, which indicates a subject of thought that does not have a conventional color meaning in the language. This study focuses on metaphoric coloratives in Russian fiction of the 20th century. The metaphorical comparisons-coloratives were selected by continuous sampling in the amount of 275 units, while the analysis covered lexemes-agents. The results show that the main colors of figurative comparisons-coloratives of the literary discourse were yellow, red, white, black, brown, gray, green, and blue. A classification of reference color agents is compiled, containing seven semantic groups, which can be correlated with both agents and references comparison, which allows using the formula of the semantic comparison structure. As a result, the quantitative indicators of formulas for different coloratives were obtained, with phytomorphs being the most frequent standards of red, yellow, brown, blue, and green. The second place belongs to reamorphs, which are rich, but not the only source of black standards. Naturmorphs are in the third place; these are the suppliers of agents of black, as well as yellow and gray. They are followed by gluttomorphs, which are the leading white standards. Zoomorphs are uniformly present in almost all colors except brown and blue. A small number of anthropomorphs agents are red standards, and hemo­morphs agents are green standards.

Intellectual Capital and Performance Among Listed Non-Financial Firms in West Africa

The purpose of this study is to examine the impact of intellectual capital on the performance of listed non-financial firms in West Africa. The study used the Value Added Intellectual Coefficient (VAIC™) to measure intellectual capital performance while return on asset measures profitability. We used the panel-corrected standard error regression on the data from 2007 to 2018 to assess the nexus while controlling for some firm-specific and country-specific factors. The findings indicate that structural capital efficiency is a major driver of profitability. On the contrary, human capital efficiency and capital employed efficiency do not have a significant impact on profitability among non-financial firms. Intellectual capital has an inverted U-shaped nexus with performance. This differs from the findings in the financial sector which emphasize human capital. In the non-financial sector, structural capital like production infrastructure, production processes, formulas, databases and designs play a significant role in driving performance. The study adds to various voices calling for the inclusion of intellectual capital valuation and metrics in all corporate analysis.

ОЦЕНКА ИЗМЕНЕНИЯ ОСНОВНЫХ ФИЛЬТРАЦИОННЫХ ПОКАЗАТЕЛЕЙ ТОРФА В ПРОЦЕССЕ ЕГО ОСУШЕНИЯ

The research subject reflects one of the special conditions for the construction of reclamation systems on peatlands – this is a significant change in many of their parameters, including filtration indicators of the peat deposit – due to precipitation and compaction of peat in the process during its drainage. This research work is of a scientific and methodological nature and represents the development of a new calculation method. The ultimate aim of the research is to develop a calculation method that improves the accuracy and reliability of the existing methods for assessing the changing water-physical properties of peat due to its drainage – due to the greatest coverage and consideration of specific conditions and design factors. The introductory part describes both the current state of the issue and the relevance of the existing problem. The main part of the content contains the structure, mathematical basis and calculation formulas of the proposed method of calculation – for predicting the reduction of filtration coefficients and water loss of drained peat. A specifi c example of the calculation of the results of the practical use of the developed methodology is considered and given. The final part provides an analysis of the research results, the main conclusions and recommendations for the practical use of this technique.