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Liu, Runzhan, Guoyong Mao e Ning Zhang. "Research of chemical elements and chemical bonds from the view of complex network". Foundations of Chemistry 21, n.º 2 (11 de junho de 2018): 193–206. http://dx.doi.org/10.1007/s10698-018-9318-7.
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Morawetz, Herbert. "History of Rubber Research". Rubber Chemistry and Technology 73, n.º 3 (1 de julho de 2000): 405–26. http://dx.doi.org/10.5254/1.3547599.
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Abstract After the discovery of the tapping of Hevea rubber trees in the middle of the eighteenth century and early technological applications of Hevea rubber, efforts to discover the chemical nature of rubber started with the determination of its elemental composition in 1826. Later it was shown that rubber pyrolysis yields low molecular weight chemicals with the identical elemental composition. It was long believed that these add to each other by “secondary valence bonds.” However Staudinger's work starting in 1920 proved that Hevea (H.) rubber consists of chains linked by covalent bonds. The utility of rubber increased dramatically with the discovery of vulcanization by Goodyear in 1844. However the nature of this process remained for many years controversial due to the influence of the “colloid school” of chemistry. The first observations on the nature of rubber elasticity date back to 1805, but more than a century passed before it was shown that the retractive force of stretched rubber is entropic. X-ray crystallographic studies not only provided the ultimate proof that natural rubber consists of covalently bonded chain molecules, but also gave evidence for its chemical structure. A century ago it was found that polymeric products other than H. rubber exhibited similar elastic properties. The race to produce synthetic rubbers was largely stimulated by the two World Wars. The availability of 14C labeled precursors led to the detailed description of the biosynthetic pathway by which rubber is produced in the Hevea plant.
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Li, Pei Yi, Mei Yun Zhang, Zhi Jie Wang e Chun Tao Lin. "A Research on Modification of Paper-Based Functional Polyurethane Material". Advanced Materials Research 311-313 (agosto de 2011): 1186–89. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1186.
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The methods of synthesizing polyurethane (Isophorone diisocyanate IPDI) with paper were investigated. The combination of SEM and IR analysis were used to analyze the chemical and physical characteristics and forming mechanism of the polyurethane derived from paper. The physical of base-paper material improved remarkably on the conditions of dosage of IPD 12%, reaction time 10min and temperature 60°C, facture length elevated by54.4%, folding strength raised by 12.4 times, and wet strength / dry strength was 50.54%.It was found that carbonate bond was formed between IPDI with cellulose in fibers when the paper was treated with IPDI .The treatment can change hydrogen bonds into chemical bonds and enhance the base-paper material’s physical strength. The Hydroxyl of Cellulose and －N=C=O produced the structure of amino formic acid ester, which formed as a bridge between the fibers. The hydrogen combining was transformed to chemical combining, which strengthened the intensity of single fiber and reinforce the combine of fibers. The treatment can change hydrogen bond into chemical bond and improved the paper’s physical strength, especially the wet strength.
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Abed, Heba F., Waad H. Abuwatfa e Ghaleb A. Husseini. "Redox-Responsive Drug Delivery Systems: A Chemical Perspective". Nanomaterials 12, n.º 18 (14 de setembro de 2022): 3183. http://dx.doi.org/10.3390/nano12183183.
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With the widespread global impact of cancer on humans and the extensive side effects associated with current cancer treatments, a novel, effective, and safe treatment is needed. Redox-responsive drug delivery systems (DDSs) have emerged as a potential cancer treatment with minimal side effects and enhanced site-specific targeted delivery. This paper explores the physiological and biochemical nature of tumors that allow for redox-responsive drug delivery systems and reviews recent advances in the chemical composition and design of such systems. The five main redox-responsive chemical entities that are the focus of this paper are disulfide bonds, diselenide bonds, succinimide–thioether linkages, tetrasulfide bonds, and platin conjugates. Moreover, as disulfide bonds are the most commonly used entities, the review explored disulfide-containing liposomes, polymeric micelles, and nanogels. While various systems have been devised, further research is needed to advance redox-responsive drug delivery systems for cancer treatment clinical applications.
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Wu, Shao Gui, Ya Ru Fan e Jun Zhou. "Research Progress on Preparation Methods of PMIA Fiber". Advanced Materials Research 463-464 (fevereiro de 2012): 769–72. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.769.
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PMIA is a functional fiber with superior heat-resistance, flame resistance, high temperature dimensional stability and electrical insulation. In PMIA crystal structure, there exist hydrogen bonds between two planes in the crystal and they are arranged in grid. The strong interactions between hydrogen bonds result in a very stable chemical structure of PMIA. Owing to lower internal rotation potential energy than PPTA, PMIA molecular chains are flexible structures and its elastic modulus is in the same level as other flexible macromolecules. In this paper, the structure character of molecular chain and performance of PMIA have been introduced. Additionally, the common used polymerization techniques for PMIA have been described in detail. These synthesis techniques include low-temperature solution polymerization, interfacial polymerization and emulsion polymerization.
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Santoso, Agus Muji, Bayu Guruh Binangkit, Mohamad Amin, Sutiman Bambang Sumitro, Betty Lukiati, Mumun Nurmilawati, Poppy Rahmatika Primandiri, Ida Rahmawati, S. Sulistiono e Yayoi Kodama. "Anticancer mechanism of Pisangulin angulata through in silico and development as teaching material". Biosfer 12, n.º 1 (29 de abril de 2019): 45–57. http://dx.doi.org/10.21009/biosferjpb.v12n1.45-57.
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This study aims to reveal the anticancer mechanism of the bioactive compound of Pisangulin angulata and to assess the feasibility of that results as teaching material. This research includes descriptive explorations. In the first stage, an in silico analysis was performed by molecular docking method between physalin compounds and GLI1 protein. The second steps of this study aim to develop teaching materials based research using the Analysis, Reorganizing, Piloting Class, and Evaluating (ARPE models). Feasibility test was carried out by experts and practitioners. Think Pair Share was used in the pilot project. Student motivation and misconception were recorded using SMI and CRI instrument. This study reveals that physalin B has higher activities than controls. The type of chemical bond that is formed between GLI1 amino acids residues with physalin is hydrogen bonds and hydrophobic bonds. The visualization of the types of bonds in that molecular docking between GLI1 amino acid residues and physalin has a high degree of feasibility (89) and can be used to enrich Chemistry for Biology lectures. The visualization of these chemical bonds can increase learning motivation and can improve the understanding of the concept of chemical bonds.
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Yang, Dong Bo, Xing Kai Meng, Xia Zhang e Jing Jing Tian. "Research on the Correlation between Biodiesel's Composition and Physical & Chemical Properties". Applied Mechanics and Materials 737 (março de 2015): 65–70. http://dx.doi.org/10.4028/www.scientific.net/amm.737.65.
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Biodiesel's composition has a significant effect on biodiesel’s main physical and chemical properties. Through the test and analysis of the composition and the physical & chemical properties of 5 types of biodiesel, this paper uses linear regression model and least square method to conduct a research on the correlation between biodiesel's physical and chemical properties such as density, cold filter plugging point (CFPP), cetane number and kinematic viscosity, biodiesel's FAME content and the number of double bonds in its UFAME, and establishes correlation functions for relevant indexes, providing a theoretical basis for rapid test of biodiesel’s physico-chemical performance index.
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Sari, Novieta, Suandi Sidauruk, Ruli Meiliawati e Anggi Ristiyana Puspita Sari. "The Difficulties of X Grade High School Students in Palangka Raya City Academic Year of 2018/2019 in Understanding Chemical Bond Concept using Two-Tier Multiple Choice". GAMAPROIONUKLEUS 1, n.º 2 (30 de novembro de 2020): 135–48. http://dx.doi.org/10.37304/jpmipa.v1i2.3686.
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The concept of chemical bonds is one of the concepts that students are less familiar with, so there is a need for a diagnostic test to determine students' difficulty. This study aims to describe students' difficulties in understanding the concept of chemical bonds using two-tier multiple-choice which includes the following sub: (1) stable electron configuration, (2) valence electrons, (3) ionic bonds, (4) covalent bonds, and (5) metal bonds. The subjects of this study were students of class X MIA from SMA Negeri 1 Palangka Raya, SMA Negeri 3 Palangka Raya, and SMA Negeri 4 Palangka Raya with a total number of research subjects being 335 students. Students' difficulties in understanding the concept of chemical bonds were expressed using the Tes Kemampuan Ikatan Kimia (TKIK) form two-tier multiple choice of 15 questions and interviews to confirm the students' difficulty. The test results of TKIK showed a reliability of 0.68, an item discrimination power of 0.5, and an item difficulty level of 0.41. The results showed that the difficulty of the students in understanding the concept of chemical bonds with the percentage of the most difficult to easy difficulties was in order to determine the covalent bonds of 58.7%, determined the ionic bond at 55.4%, determined the metal bond at 54.3%, determined the stable electron configuration of 35.8%, and determine the valence electrons at 35.1%.
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Pumera, Martin, e Zdeněk Sofer. "Towards stoichiometric analogues of graphene: graphane, fluorographene, graphol, graphene acid and others". Chemical Society Reviews 46, n.º 15 (2017): 4450–63. http://dx.doi.org/10.1039/c7cs00215g.
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Inaltekin, Tufan, Hakan Akcay e Mehmet Kürşat Duru. "Examination of Pre-Service Science Teachers' Model Based-Content Knowledge and Knowledge of Students’ Understanding on Chemical Bonds". International Journal of Research in Education and Science 9, n.º 1 (13 de fevereiro de 2023): 17–54. http://dx.doi.org/10.46328/ijres.3084.
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This study aims to examine pre-service science teachers' (PSTs') model-based (MB) content knowledge (CK) and knowledge of students' understanding (KSU) of chemical bonds. The participants of the study consist of 229 senior pre service science teachers. The study is a case study from qualitative research designs. The data of the study were collected by using the "Chemical Bonds Model Knowledge Test (CBMKT)". The obtained data were analyzed using the "Model Based-Content Knowledge Rubric (MB-CK Rubric)" and "Model Based-Knowledge of Students' Understanding Rubric (MB-KSU Rubric)". The findings showed that PSTs mostly have an understanding of wrong modeling and not being able to make any modeling in terms of MB-CK on chemical bonds. In addition, it has been determined that the majority of pre-service teachers have an invalid and weak level in terms of MB-KSU. These findings indicate that PSTs' professional knowledge of chemical bonds in their undergraduate education should be supported by model-based teaching.
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Jusli, Euniza, Hasanan M. Nor, Ramadhansyah Putra Jaya e Haron Zaiton. "Chemical Properties of Waste Tyre Rubber Granules". Advanced Materials Research 911 (março de 2014): 77–81. http://dx.doi.org/10.4028/www.scientific.net/amr.911.77.
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This research aims to examine the chemical properties of waste rubber tyre granules. Rubber granules were analysed by using X-ray fluorescence to establish its chemical composition. Thermogravimetry and differential thermogravimetric analyses were performed to investigate the relationship between temperature and the minerological compositions of rubber granules to determine its suitability as an aggregate replacement in concrete mix. Fourier Transform Infra-Red (FTIR) indicated that due to the stability of the structures developed in OPC samples, the reactions between the structure bonds are less at the range of 650-1500 cm-1. Scanning electron microscopy (SEM) was performed to examine the physical properties of rubber granule particles and to magnify the bonds between cement and rubber granules in a concrete mix. The results of the SEM analysis showed that carbon, zinc, magnesium, and calcium are the major components of waste tyre rubber granules.
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MOHAJERI, A., e P. DASMEH. "EVALUATING THE NATURE OF CHEMICAL BONDS BASED ON PROBABILISTIC MODELS". International Journal of Modern Physics C 18, n.º 11 (novembro de 2007): 1795–809. http://dx.doi.org/10.1142/s0129183107011753.
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A theoretical measure of the ionicity based on different mathematical concepts is presented in this research. Considering the distribution of valence electrons on each atom in a bond, we assume that the chemical properties of the atom can be expressed by means of probability. Using the introduced probability, different probabilistic models such as classical, fuzzy and information theoretical models have been employed to introduce new descriptors of bond ionicity. The ionicities were calculated for 12 heterodiatomic molecules and the bonds were classified in terms of covalency vs. ionicity. It was found that our proposed ionicity descriptors correlate well with the partial ionic character of the bonds.
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Hafis, Muhammad, e Ahmad Afif Supianto. "Mobile Game Design for Learning Chemical Bonds with Endless Run Approach". International Journal of Interactive Mobile Technologies (iJIM) 12, n.º 8 (24 de dezembro de 2018): 104. http://dx.doi.org/10.3991/ijim.v12i8.9260.
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This research focuses on the design of a mobile application game that uses endless run method to learn chemistry concept of chemical bonds, its design is analyzed thoroughly. Application-based learning is one of the method of learning that has been proven to be effective, however, previous studies focuses on the elements of serious gaming that neglects the fun elements in the game itself, disdaining the nature of a game. This research aims to discover the relevance of player happiness and fun level based when playing an educational game and its correlation with the level of learning while also focuses on understanding what hinders a player in the context of chemistry-based games. The testing planning are exposed along with a hypothesis that player happiness positively correlates with its level of learning, while the hindrance can be identified by using statistical approach.
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BOGDANOVA, Ekaterina V., Elena I. MELNIKOVA e Irina B. KOSHEVAROVA. "THE RESEARCH OF THE TYPES OF MOISTURE BONDS IN PROTEIN-CARBOHYDRATE CONCENTRATES OF CHEESE WHEY". Periódico Tchê Química 17, n.º 34 (20 de março de 2020): 33–44. http://dx.doi.org/10.52571/ptq.v17.n34.2020.51_p34_pgs_33_44.pdf.
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The purpose of the research is to improve the technology of producing cheese whey proteincarbohydrate concentrates, in terms of binding moisture with the main components. Objects of the research were natural cheese whey obtained in the production of Rossiyskii cheese and ultrafiltration cheese whey concentrates with protein dry matter percentage of 35 and 55%, produced with the use of MMS Swissflow UF industrial ultrafiltration unit with ceramic membranes. The chemical composition and Physico-chemical properties of raw materials and the finished product have been studied using standard methods. Three stages of sample dehydration have been identified. They conform to moisture release with different bonds and energy. Stage I is the production area where unbound moisture is heated and removed, and water molecules are held by weak capillary forces. Stage II is the production area for immobilized moisture removal. Stage III is the production area for chemically bound water removal, which conforms to the residual moisture after drying the sample. An increase in the least mobile water and a change in the ratio between different types of moisturebinding have been observed with an increase in the protein mass fraction in the dry matter of the samples. It has been found that the Maillard reaction occurred in cheese whey concentrates with protein dry matter percentage of 35 and 55% at the temperatures above 78 and 70 °C, respectively. The temperature range of the unbound moisture release was increasing during the drying process due to an increase of the protein content in concentrates as well as the rate of interaction between proteins and lactose leading to non-enzymatic browning of dry products. It has been established that drying cheese whey protein-carbohydrate concentrates with protein dry matter percentage of 35, and 55% is inexpedient at temperatures exciding 130 and 173 °C, respectively.
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Kristyasari, Marantika Lia, Henie Poerwandar Asmaningrum e Rizka Fauzia Hanif. "Wright-Map to Analyze Students’ Abilities on Chemical Bond Test". SHS Web of Conferences 149 (2022): 01050. http://dx.doi.org/10.1051/shsconf/202214901050.
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The implementation of the evaluation of learning outcomes for students allows the emergence of biases that can cause students' abilities to not be depicted properly. This study aims to determine the ability of students based on the evaluation test of chemistry learning in high school. The research subjects involved 41 students. Data analysis using Wright Map on Rasch modelling based on chemical bond indicators such as 1) the process of forming ionic and covalent bonds, 2) differences in ionic and covalent bonds from physical and chemical properties, 3) analyzing the type of chemical bonds formed, and 4) determination of the shape of the molecule. Based on the results of the Wright Map, the percentage of students' abilities as much as 2% are in the high, 78% are in the medium, and 8% are in the low and very low categories. Overall, students have difficulty analyzing the type of chemical bond formed and the shape of the molecule. By using the Wright Map, the actual abilities of students can be seen clearly and accurately. This is very helpful for teachers to classify students whose scores are still below the average so that a corrective test can be done.
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Dewi, Akmalia Mutiara, e Agus Kamaludin. "Development of Audiovisual-Based PowToon Animation Video on Chemical Bonds for Tenth Grade". Jurnal Penelitian Pendidikan IPA 8, n.º 1 (14 de janeiro de 2022): 222–29. http://dx.doi.org/10.29303/jppipa.v8i1.865.
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This research aimed to develop an audiovisual-based PowToon animation video on the subject matter of chemical bonds and analyze the quality of the audiovisual-based animated video as learning media to study chemical bonds based on the assessment of material experts, media experts, chemistry teachers, and students’ responses. This research used development research methods (R&D) with a 4D development model (Define, Design, Development, and Dissemination). However, the 4D development model was limited to the dissemination stage in this research. The product is an animated video, which is in the form of mp4, containing chemical bond materials. Based on product quality assessment by a material expert, it gained a percentage of 84.375% with very good (VG) category; from the media expert’s assessment, it obtained a percentage of 96.428% with very good (VG) category; and according to assessment by chemistry teachers of high school, it got a percentage of 98.48% in the very good (VG) category. The product was responded to positively by students with a percentage of 95%. Based on the results of assessments, the animated video can be used as an alternative media for the chemistry learning process in the classroom
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Anugrah, Daru Seto Bagus, Laura Virdy Darmalim, Muhammad Rifky Irwanto Polanen, Permono Adi Putro, Nurwarrohman Andre Sasongko, Parsaoran Siahaan e Zeno Rizqi Ramadhan. "Quantum Chemical Calculation for Intermolecular Interactions of Alginate Dimer-Water Molecules". Gels 8, n.º 11 (31 de outubro de 2022): 703. http://dx.doi.org/10.3390/gels8110703.
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The abundance of applications of alginates in aqueous surroundings created by their interactions with water is a fascinating area of research. In this paper, computational analysis was used to evaluate the conformation, hydrogen bond network, and stabilities for putative intermolecular interactions between alginate dimers and water molecules. Two structural forms of alginate (alginic acid, alg, and sodium alginate, SA) were evaluated for their interactions with water molecules. The density functional theory (DFT-D3) method at the B3LYP functional and the basis set 6-31++G** was chosen for calculating the data. Hydrogen bonds were formed in the Alg-(H2O)n complexes, while the SA-(H2O)n complexes showed an increase in Van der Walls interactions and hydrogen bonds. Moreover, in the SA-(H2O)n complexes, metal-nonmetal bonds existed between the sodium atom in SA and the oxygen atom in water (Na…O). All computational data in this study demonstrated that alginate dimers and water molecules had moderate to high levels of interaction, giving more stability to their complex structure.
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Ma, Yin, Qing Shan Li, You Bo Di e Min Zhang. "Research on Superfine Wool Surface Texture Modified in Biochemistry". Advanced Materials Research 96 (janeiro de 2010): 189–96. http://dx.doi.org/10.4028/www.scientific.net/amr.96.189.
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Superfine wool surface texture changed after the processing with biochemistry technology. Its fiber thinness and friction effect reduce, the itchy feeling caused by wool is rid of, and the contraction of carpets diminishes so that it lives up to the standard of machine washing and anti-pilling. Meanwhile, the chemical groups of fiber surface of the superfine wool changes as well, which produces a material of which the physical and chemical structure of the surface differs from the nano-interface of the original fiber. If supplemented by functional stuff and combined in the form of chemical bonds, it would equally distribute and functions everlasting, thus achieving a comprehensive effect of the superfine wool-smoothness glutinosity, brightness, as well as anti-virus. Boiled under high temperature, it is still capable of retaining all the styles prior to the dyeing with no apparent reduction of the feel.
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Yoqubov, Bekhzod B., Akhmadjon Ibadullaev, Dilnora Q. Yoqubova e Elmira U. Teshabaeva. "Prospects and Development of Research of Composite Elastomer Materials". Journal of Siberian Federal University. Chemistry 14, n.º 4 (dezembro de 2021): 464–76. http://dx.doi.org/10.17516/1998-2836-0255.
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The aim of this work is to study the effect of new modified ingredients on the complex of properties of composite elastomeric materials. It was found that the introduction of modified ingredients into the composition of elastomeric compositions enhances interfacial interaction at the «rubber-filler» interface and the formation of additional bonds between rubber macromolecules and functional groups, as a result of which an improvement in the complex of properties of the compositions is observed. The introduction of modified carbon into the composition of elastomeric compositions enhances interfacial interaction at the «rubber-filler» interface and the formation of additional bonds between rubber macromolecules and functional groups of the oligomer, as a result of which an improvement in the complex of properties of the compositions is observed. The technology of purification of mineral fillers from metal oxides has been developed. A sufficiently high degree of purification by this method is due to the fact that in the process of temperature exposure at 950 K, iron ions from the paramagnetic state (d-form Fe2O3) pass into ferromagnetic (r-form Fe3O4). Feasibility and prospects of using modified fillers, both mineral and organic, in the formulations of rubber compounds for the production of various types of rubber products
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Shabani, Amin, Xavier Colin, Gregory Marque e Carole Monchy-Leroy. "PEROXIDE CROSS-LINKING OF EPDMs HAVING HIGH FRACTIONS OF ETHYLENIC UNITS". Rubber Chemistry and Technology 87, n.º 4 (1 de dezembro de 2014): 679–702. http://dx.doi.org/10.5254/rct.14.85989.
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ABSTRACT The considerable amount of research in the literature has practically allowed the elucidation of the mechanism of peroxide cross-linking of ethylene–propylene–diene–monomer rubber (EPDM), which occurs through a radical chain reaction initiated by the thermal decomposition of the peroxide molecule. According to this radical chain reaction, all types of labile hydrocarbon bonds (i.e., allylic, methynic, and methylenic CH bonds) would be exposed to alkoxy radicals and involved in the formation of the elastomeric network. However, for high fractions of ethylenic units (typically ≥60 mol.%), simple chemical kinetics and thermochemical analyses have shown that the radical attack would essentially occur on the methylenic CH bonds. Starting from this assertion, a simplified mechanistic scheme has been proposed for the three commercial EPDMs under study. The corresponding kinetic model, derived from this new scheme by using the basic concepts of the chemical kinetics, provides access to the changes in concentration of the main reactive chemical functions (against exposure time), among which are double bonds and changes in cross-linking density. The validity of these predictions has been eventually successfully verified by five distinct analytical techniques frequently used for studying the cross-linking of rubbers.
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Rohmah, Rosyidah Syafaatur, Nikmatin Sholichah, Yunilia Nur Pratiwi e Rizki Nur Analita. "Analysis of Students’ Chemical Bonding Misconception with A Four-Tier Diagnostic Test". JTK (Jurnal Tadris Kimiya) 7, n.º 2 (31 de dezembro de 2022): 166–74. http://dx.doi.org/10.15575/jtk.v7i2.20343.
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Students had difficulty understanding the chemical bonding concept because of its complex and abstract nature. This difficulty could lead to chemical bonding misconceptions. This study aimed to investigate basic chemistry students' misconceptions of chemical bonding. This study used a descriptive research design with a four-tier diagnostic test. The research’s subjects were basic chemistry students. Chemical Bonding Diagnostic Tool (CBDT) was used as an instrument to determine students' misconceptions. The results showed that students who had misconceptions about ionic, covalent, and coordinate covalent bonding were 48.90%, 53.00%, and 37.50%, respectively. The misconception in this course is that students need to learn about ionic bonds formed by electrostatic forces between cations and anions. As a result, students cannot determine the difference in electronegativity values in ionic and covalent bonds and the number of valence electrons of each atom in a chemical bonding. Therefore, the misconception is in the moderate category.
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Fawcett, Alexander. "Advances in the catalyst- and reagent-controlled site-divergent intermolecular functionalization of C(sp3)–H bonds". Pure and Applied Chemistry 92, n.º 12 (16 de dezembro de 2020): 1987–2003. http://dx.doi.org/10.1515/pac-2020-0803.
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AbstractIntermolecular C(sp3)–H bond functionalization reactions promise to revolutionize how we synthesize organic molecules by enabling the introduction of functionality at previously inert sites. However, one of the greatest challenges in this research field is site-selectivity, wherein chosen C(sp3)–H bonds must be selectively functionalized and other C(sp3)–H bonds with similar stereoelectronic properties must remain intact. To address this problem, chemists have developed methods that rely on targeting innately more reactive C(sp3)–H bonds or on using pre-installed functional groups to direct a catalyst or reagent to a particular C(sp3)–H bond. However, such approaches invariably have limited applicability because only a handful of innately reactive C(sp3)–H bonds or those nearby certain functional groups can be functionalized with good site-selectivity. To overcome these limitations, chemists also have developed catalysts and reagents that control the site of C(sp3)–H bond functionalization and have begun to unlock the potential of these reactions to achieve the site-divergent functionalization of C(sp3)–H bonds, wherein the site of functionalization is changed by modulating the stereoelectronic properties of the catalyst or reagent. This short review will provide a summary of selected examples of catalyst- and reagent-controlled site-divergent intermolecular functionalization of C(sp3)–H bonds, the factors responsible for modulating the site selectivity of these reactions, and will identify potential areas worthy of future research in this field.
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Liu, Qi Feng. "Research on Treatment of the Micro-Polluted Reservoir Water with Ozone Oxidation". Advanced Materials Research 884-885 (janeiro de 2014): 129–33. http://dx.doi.org/10.4028/www.scientific.net/amr.884-885.129.
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Bench and pilot scale pre-oxidation treatment runs were performed on the raw water samples from micro-polluted reservoir. Bench experimental results showed that the particles with large size decreased when ozone pre-oxidation was applied, meanwhile, the organic matters with unsaturated chemical bonds decreased obviously. Pilot experimental results showed that turbidity, UV254,CODMn and total coliform could be treated efficiently by ozone pre-oxidation combined with traditional technologies, but the effectiveness of DOC removal is not obvious. Keywords: ozone oxidation; UV254; Organic matter; micro-polluted water
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Ma, Rongqing, Hongfan Hu, Xinle Li, Guoliang Mao, Yuming Song e Shixuan Xin. "Advances in Catalytic C–F Bond Activation and Transformation of Aromatic Fluorides". Catalysts 12, n.º 12 (18 de dezembro de 2022): 1665. http://dx.doi.org/10.3390/catal12121665.
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The activation and transformation of C–F bonds in fluoro-aromatics is a highly desirable process in organic chemistry. It provides synthetic methods/protocols for the generation of organic compounds possessing single or multiple C–F bonds, and effective catalytic systems for further study of the activation mode of inert chemical bonds. Due to the high polarity of the C–F bond and it having the highest bond energy in organics, C–F activation often faces considerable academic challenges. In this mini-review, the important research achievements in the activation and transformation of aromatic C–F bond, catalyzed by transition metal and metal-free systems, are presented.
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Zhao, Zhuo, Fang Fang, Junsheng Wu, Xinru Tong, Yanwen Zhou, Zhe Lv, Jian Wang e David Sawtell. "Interfacial Chemical Effects of Amorphous Zinc Oxide/Graphene". Materials 14, n.º 10 (11 de maio de 2021): 2481. http://dx.doi.org/10.3390/ma14102481.
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Research on the preparation and performance of graphene composite materials has become a hotspot due to the excellent electrical and mechanical properties of graphene. Among such composite materials, zinc oxide/graphene (ZnO/graphene) composite films are an active research topic. Therefore, in this study, we used the vacuum thermal evaporation technique at different evaporation voltages to fabricate an amorphous ZnO/graphene composite film on a flexible polyethylene terephthalate (PET). The amorphous ZnO/graphene composite film inherited the great transparency of the graphene within the visible spectrum. Moreover, its electrical properties were better than those of pure ZnO but less than those of graphene, which is not consistent with the original theoretical research (wherein the performance of the composite films was better than that of ZnO film and slightly lower than that of graphene). For example, the bulk free charge carrier concentrations of the composite films (0.13, 1.36, and 0.47 × 1018 cm−3 corresponding to composite films with thicknesses of 40, 75, and 160 nm) were remarkably lower than that of the bare graphene (964 × 1018 cm−3) and better than that of the ZnO (0.10 × 1018 cm−3). The underlying mechanism for the abnormal electrical performance was further demonstrated by X-ray photoelectron spectroscopy (XPS) detection and first-principles calculations. The analysis found that chemical bonds were formed between the oxide (O) of amorphous ZnO and the carbon (C) of graphene and that the transfer of the π electrons was restricted by C=O and C-O-C bonds. Given the above, this study further clarifies the mechanism affecting the photoelectric properties of amorphous composite films.
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Czepułkowska, W., E. Wołowiec-Korecka e L. Klimek. "The role of mechanical, chemical and physical bonds in metal-ceramic bond strength". Archives of Materials Science and Engineering 1, n.º 92 (1 de julho de 2018): 5–14. http://dx.doi.org/10.5604/01.3001.0012.5506.
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Purpose: A review regarding the mechanisms of metal-ceramic join is presented. Design/methodology/approach: The impact of the air-abrasion parameters on the mechanical bond strength of the ceramic crowns was discussed. The presence of opaque on the chemical bond was analysed. Research of the influence of the difference in the coefficient of thermal expansion values on the metal-ceramic bond was included. The methods of testing the bond strength were analysed. Findings: The metal substructure-dental ceramic bond strength is affected by all types of bond. In bond strength, 3-point bending test and shear test are mainly used. Created samples simulate the ceramic crowns veneered on one side. The role of physical bond on ceramic crowns veneered around metal substructure is unknown. Research limitations/implications: The prosthetic restorations with the ceramic surrounding whole the metal substructure are commonly used. The impact of shrinkage in the cylindrical deposition of the ceramic on metal substructure should be analysed. Practical implications: Numerical analysis and FEM simulation can be helpful in the analysis of the physical bond between the metal substructure and the dental ceramic around it. Originality/value: The impact of the type of the bond to metal-ceramic bond strength is presented, taking into account the cognitive gap in the influence of the coefficient of thermal expansion on the cylindrical placement of ceramic on the substructure.
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Leal, Wilmer, e Guillermo Restrepo. "Formal structure of periodic system of elements". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, n.º 2224 (abril de 2019): 20180581. http://dx.doi.org/10.1098/rspa.2018.0581.
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For more than 150 years, the structure of the periodic system of the chemical elements has intensively motivated research in different areas of chemistry and physics. However, there is still no unified picture of what a periodic system is. Herein, based on the relations of order and similarity, we report a formal mathematical structure for the periodic system, which corresponds to an ordered hypergraph. It is shown that the current periodic system of chemical elements is an instance of the general structure. The definition is used to devise a tailored periodic system of polarizability of single covalent bonds, where order relationships are quantified within subsets of similar bonds and among these classes. The generalized periodic system allows envisioning periodic systems in other disciplines of science and humanities.
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Barsky, Vadim, Vitaly Gulyaev e Andriy Rudnitsky. "Composition and Structure of Coal Organic Mass. Analytical Review". Chemistry & Chemical Technology 3, n.º 4 (15 de dezembro de 2009): 315–19. http://dx.doi.org/10.23939/chcht03.04.315.
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The research works dedicated to the formation regularities of solid fuels chemical structure were analyzed. Modern conceptions of coals chemical structure, which are becoming deeper owing to tooling growth and facts accumulation, were examined by means of critical comparison of different hypothetical models of solid fuels “molecular” structure. The most general points of the respective theories were formulated, according to which “soft” influence on coal structure primary elements bonds system allows bringing its chemical potential to the maximum.
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Thanh, Le Tat. "RESEARCH OF CHEMICAL COMPONENTS OF SOME SEAWEED SPECIES IN CON CO ISLAND – QUANG TRI PROVINCE". Vietnam Journal of Science and Technology 54, n.º 2C (19 de março de 2018): 493. http://dx.doi.org/10.15625/2525-2518/54/2c/11879.
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11 samples of 8 seaweed families were collected at Con Co – Quang Tri and determined ofthe chemical compositions. The analysis results showed that these seaweed samples in Con Cocontain high content of trace elements and low content of heavy metals. Many samples havegood lipid quality to meet the requirements of safe food, as well as being good for the humanhealth (such as CC1, N9, N4, and N6 samples). Especially, some seaweed samples were foundto contain long-chain fatty acids with many double bonds presenting high bioactivity in theirlipid composition, such as C20: 4n-6 (AA) up to 22.35% (Hypnea flagelliformis Grev., sampleN6), C20: 5n-3 (EPA) 16.36 % (Grateloupia lithophila, sample N9), C22: 6n-3 (DHA) 1.07 %(Hypnea esperi, sample N2), C22: 5n-3 (DPA) 1.82% (Liagora spl., samples N4).
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Ghahri, Saman, Xinyi Chen, Antonio Pizzi, Reza Hajihassani e Antonios N. Papadopoulos. "Natural Tannins as New Cross-Linking Materials for Soy-Based Adhesives". Polymers 13, n.º 4 (16 de fevereiro de 2021): 595. http://dx.doi.org/10.3390/polym13040595.
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Human health problems and formaldehyde emission from wood-based composites are some of the major drawbacks of the traditional synthetic adhesives such as urea formaldehyde resins. There have been many attempts to decrease formaldehyde emission and replace urea formaldehyde resins with bio-based adhesives for wood-based composites. Because of some weakness in soy-based adhesive, chemicals have been used as modifiers. Modified soy-based adhesives without any formaldehyde have been successfully used to prepare wood panels. To achieve this, different synthetic cross-linking chemicals such as phenol formaldehyde resins and polyamidoamine-epichlorohydrin were used. However, in reality, what we need are totally green adhesives that use natural materials. In our previous research work, the use of tannins in combination with soy-based adhesives to make wood composites was investigated. Thus, in this research work, the feasibility of using three types of natural tannins (quebracho, mimosa and chestnut tannins) as cross-linking materials for soy adhesive was studied. The chemical bond formation and adhesion behaviors of tannin-modified soy adhesives were also investigated by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-ToF-MS) and thermo-mechanical analysis (TMA). The results showed that at ambient temperature, both ionic and covalent bonds formed between tannin constituents and amino acids; however, at higher temperature, covalent bonds are largely predominate. Based on the results obtained from the thermo-mechanical analysis, the modulus of elasticity (MOE) of soy adhesive is increased by adding tannins to its formulation. In addition, the chemical bond formation was proved by MALDI-ToF-MS.
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Setiawan, Nur Candra Eka, e Putri Ridha Ilahi. "Identification of Misconceptions in Chemical Bonding Materials Using Three Tier Diagnostic Test". Journal of Natural Science and Integration 5, n.º 1 (30 de abril de 2022): 77. http://dx.doi.org/10.24014/jnsi.v5i1.16860.
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Chemistry learning focuses on understanding concepts, thus students who get difficulty understanding the concepts of chemistry learning will experience conceptual mistakes, especially abstract concepts such as chemical bonds. Students' difficulty understanding the material of chemical bonds can occur due to misconceptions. The misconceptions will hinder the construction and assimilation of new knowledge in students and thus students will experience difficulties in learning chemistry. To address such issue, an instrument for detecting misconceptions in chemistry is necessary to find out the misconceptions that occur among learners. The identification of such emerging misconceptions in understanding the subject matter can be analyzed using a three-tier multiple-choice diagnostic test. The present study was carried out to determine the presence or absence, and the percentage of misconceptions regarding chemical bonding material using the Three Tier Test diagnostic test. Conducted through purposive sampling technique, this research-based paper is a type of qualitative research with a descriptive approach. The research instrument uses a three-tier test objective test. The data obtained was analyzed descriptively for each student's response by using students' level of understanding list. In general, the results obtained in this line of research showed that; (1) Indicator 1, student misconceptions were 91.17% (2) Indicator 2, student misconceptions were 64.14%, (3) Indicator 3, student misconceptions were 67.64%, (4) Indicator 4, student misconceptions were 76.47%. (5) Indicator 5, students' misconceptions were 63.23%. By way of conclusion, the present project argues that there were misconceptions that occured in students of SMA Negeri 1 Class X Teluk Kuantan on the chemical bonding material, with the percentage 72.53% students experiencing misconceptions, 14, 98% students do not understand the concept, and the rest 12.48% students understand the concept of chemical bonding.Keywords: misconception, diagnostic test, three tier test
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Kuang, Ge, Zhi Bin Chen, Hui Guo e Ming Hao Li. "Lithium Extraction Mechanism from α-Spodumene by Fluorine Chemical Method". Advanced Materials Research 524-527 (maio de 2012): 2011–16. http://dx.doi.org/10.4028/www.scientific.net/amr.524-527.2011.
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In order to decrease lithium extraction cost, pollution and energy. A new and efficient technology was particularly discussed in this paper, the fluorine chemical method to extract lithium from spodumene. The reaction mechanism had also been analysed by studying the crystal structure variation and reaction products. The results show that hydrofluoric acid corroded α-spodumene in low temperature, damaged the compact chemical bonds: Li-O, Al-O, Si-O, and Al-O-Si, and generated Li3AlF6 and AlF3, which can be dissolved in sulfuric acid. Our research provides theoretical guidance for the lithium extraction process from α-spodumene.
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Ibrahim, Muhammad Aidil, Nur Atikah M. Jani, Oskar Hasdinor Hassan, F. Abdullah, T. I. T. Kudin, Ab Malik Marwan Ali e Muhd Zu Azhan Yahya. "FTIR Spectrum Investigation of Thionine-Graphene Nanocomposite". Applied Mechanics and Materials 864 (abril de 2017): 42–47. http://dx.doi.org/10.4028/www.scientific.net/amm.864.42.
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Graphene is a material that has been heavily investigated in many researches due to its beneficial characteristics such as large surface area, low manufacturing cost, high electro conductivity and incredible mechanical strength. Applying the graphene in water-based solvents however can cause agglomeration due to its hydrophobic properties. Researchers have composited the graphene with other materials in overcoming its hydrophobicity. In this research, graphene was nanocomposited with thionine to make it disperse well in water-based solvents while preserving its intrinsic properties. The nanocomposition process involves mixing of both graphene oxide with thionine and were reduced by hydrazine hydrate while reflux heating. The produced mixture was then filtered to obtain the Thionine-Graphene nanocomposite. The obtained sample was then characterized to confirm the composition of both graphene and thionine. Fourier transfer infrared spectroscopy was operated to investigate the chemical bonds and hence concluding the presence of both graphene and thionine in the sample. The preservation of the intrinsic properties of graphene was also investigated through observing the absence of functionalized graphene bonds. Post-investigation reports that the chemical bonds from both of the materials, graphene and thionine were detected confirming the successfulness of the nanocomposition.
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Tam, Justin Z., Talulla Palumbo, Julie M. Miwa e Brian Y. Chen. "Analysis of Protein-Protein Interactions for Intermolecular Bond Prediction". Molecules 27, n.º 19 (21 de setembro de 2022): 6178. http://dx.doi.org/10.3390/molecules27196178.
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Protein-protein interactions often involve a complex system of intermolecular interactions between residues and atoms at the binding site. A comprehensive exploration of these interactions can help reveal key residues involved in protein-protein recognition that are not obvious using other protein analysis techniques. This paper presents and extends DiffBond, a novel method for identifying and classifying intermolecular bonds while applying standard definitions of bonds in chemical literature to explain protein interactions. DiffBond predicted intermolecular bonds from four protein complexes: Barnase-Barstar, Rap1a-raf, SMAD2-SMAD4, and a subset of complexes formed from three-finger toxins and nAChRs. Based on validation through manual literature search and through comparison of two protein complexes from the SKEMPI dataset, DiffBond was able to identify intermolecular ionic bonds and hydrogen bonds with high precision and recall, and identify salt bridges with high precision. DiffBond predictions on bond existence were also strongly correlated with observations of Gibbs free energy change and electrostatic complementarity in mutational experiments. DiffBond can be a powerful tool for predicting and characterizing influential residues in protein-protein interactions, and its predictions can support research in mutational experiments and drug design.
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Zenil, Hector, Narsis A. Kiani, Ming-mei Shang e Jesper Tegnér. "Algorithmic Complexity and Reprogrammability of Chemical Structure Networks". Parallel Processing Letters 28, n.º 01 (março de 2018): 1850005. http://dx.doi.org/10.1142/s0129626418500056.
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Here we address the challenge of profiling causal properties and tracking the transformation of chemical compounds from an algorithmic perspective. We explore the potential of applying a computational interventional calculus based on the principles of algorithmic probability to chemical structure networks. We profile the sensitivity of the elements and covalent bonds in a chemical structure network algorithmically, asking whether reprogrammability affords information about thermodynamic and chemical processes involved in the transformation of different compound classes. We arrive at numerical results suggesting a correspondence between some physical, structural and functional properties. Our methods are capable of separating chemical classes that reflect functional and natural differences without considering any information about atomic and molecular properties. We conclude that these methods, with their links to chemoinformatics via algorithmic, probability hold promise for future research.
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Korolev, Slava, e Alexsander Lavrov. "Research and technological testing of ores with dispersed gold of the Yellow Jacket Deposit". E3S Web of Conferences 192 (2020): 02027. http://dx.doi.org/10.1051/e3sconf/202019202027.
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The article discusses the mineral and geochemical features of the yellow Jacket ore Deposit located in Clark County, Nevada. Тhe Deposit differs significantly in many mineral and geochemical features from the deposits of dispersed gold ores belonging to the so-called Karlin formation type in compacted and locally weakly metamorphosed strata of carbonate rocks, mudstones and carbonated shales (carbonated turbidites). Positive results of analyses, including those with a cupellation (gravimetric) termination, were obtained in laboratories using non-standard approaches to sample preparation. Based on the working hypothesis of finding chemically bound dispersed gold in hematite-goethite films on the surface of quartz-chalcedony particles and internal microcracks, it was proposed to use active metastable chlorine-oxygen compounds to break the chemical bonds between iron atoms and clustered dispersed gold atoms and transfer it to a solution. In the liquid phase of the ore pulp with reagents added to it , after its activation treatment, the gold content, depending on its duration and intensity, varied in the range from 1.2 to 30 mg/l( at W:T=1:1).
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Ermania Widjajantin e Rusmilawati Windari. "PEDOPHILIA AS A FORM OF SEXUAL DEVIANCE FROM A SOCIAL BONDS THEORETICAL PERSPECTIVE". IIUM Law Journal 29, (S1) (12 de maio de 2021): 177–94. http://dx.doi.org/10.31436/iiumlj.v29i(s1).641.
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Sexual crimes have seen a considerably increase in Indonesia. It not only affects women but also children. Sexual crime against children is also known as “pedophilia” and has now become a terrifying phenomenon. The escalation of sexual crime against children in Indonesia shows that there is a dire need to look into possible prevention strategies to sexual crime prevention. Considering the rapid increase of case of pedophilia in Indonesia, the government has enacted more severe punisment to the offender, that is, by imposing chemical castration under the Law No. 17 Year 2016 on the second amendment of the Law No. 23 Year 2002 on child protection. This article examines the causal factors of pedophilia by employing the social bonds theory introduced by Travis Hirschi. The primary premise of this theory states that deliquency comes up when social bonds tend to be fragile or not unavailable, or in other words, the stronger there bonds, the less likelihood of delinquency. Hirschi also mentioned four social bonds that push up socialization and conformity in society, those are: attachment, commitment, involvement, dan belief. Finally, the problems raised in this article is how does pedophilia in perspective of social bonds theory?. This article is a legal research with normative approach. It is geared to look phaedophilia as a sexual deviance in perspective of social bonds theory.
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Шматко, В. А., Т. Н. Мясоедова e Г. Э. Яловега. "Электронная структура полианилина, модифицированного солями меди и циркония". Журнал технической физики 128, n.º 5 (2020): 617. http://dx.doi.org/10.21883/os.2020.05.49319.328-19.
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The results of spectroscopic studies of the electronic structure and chemical bonds of PANI - Me composites (Me - Cu, Zr) are presented. X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, IR spectroscopy were used for research. It was established that regardless of which modifying additive polyaniline is used in composites is in partially oxidized form, however, in PANI - Zr is more oxidized than in PANI - Cu. The chemical states of nitrogen in the composites are determined; a different ratio of neutral and charged nitrogen groups is observed.
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Rey, Alicia, Arturo Espinosa Ferao e Rainer Streubel. "Quantum Chemical Calculations on CHOP Derivatives—Spanning the Chemical Space of Phosphinidenes, Phosphaketenes, Oxaphosphirenes, and COP− Isomers". Molecules 23, n.º 12 (17 de dezembro de 2018): 3341. http://dx.doi.org/10.3390/molecules23123341.
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After many decades of intense research in low-coordinate phosphorus chemistry, the advent of Na[OCP] brought new stimuli to the field of CHOP isomers and derivatives thereof. The present theoretical study at the CCSD(T)/def2-TZVPP level describes the chemical space of CHOP isomers in terms of structures and potential energy surfaces, using oxaphosphirene as the starting point, but also covering substituted derivatives and COP− isomers. Bonding properties of the P–C, P–O, and C–O bonds in all neutral and anionic isomeric species are discussed on the basis of theoretical calculations using various bond strengths descriptors such as WBI and MBO, but also the Lagrangian kinetic energy density per electron as well as relaxed force constants. Ring strain energies of the superstrained 1H-oxaphosphirene and its barely strained oxaphosphirane-3-ylidene isomer were comparatively evaluated with homodesmotic and hyperhomodesmotic reactions. Furthermore, first time calculation of the ring strain energy of an anionic ring is described for the case of oxaphosphirenide.
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Li, Yaoming, Xin Pei, Huang Zhang e Meini Yuan. "A First-Principle Study of Interactions between Magnesium and Metal-Atom-Doped Graphene". Nanomaterials 12, n.º 5 (1 de março de 2022): 834. http://dx.doi.org/10.3390/nano12050834.
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In this study, the interactions of magnesium (Mg) atom and Mg(001) surface with different metal-atom-doped graphene were investigated using a density functional theory (DFT) method. For the interactions of magnesium with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene, it was found that the magnesium atoms were physisorbed into the hollow sites of the intrinsic graphene with only the smallest interaction energy (approximately −1.900 eV). However, the magnesium atoms tended to be chemisorbed on the doped graphene, which exhibited larger interaction energies and charge transfers. Additionally, the Zn-doped graphene displayed the largest interaction energy with the Mg atom (approximately −3.833 eV). For the interactions of Mg(001) with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene (intrinsic and doped graphene/Mg interface), doped atoms interacted with a Mg layer to make graphene wrinkle, resulting in a higher specific surface area and better stability. Mg–C chemical bonds were formed at the Al-, Zn-, and Zr-doped interface, and Mg–Mn chemical bonds were formed at the Mn-doped interface. This study provided the fundamental research for future research into doped atoms on graphene reinforced magnesium matrix composites.
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Kwun, Young, Abaid Virk, Waqas Nazeer, M. Rehman e Shin Kang. "On the Multiplicative Degree-Based Topological Indices of Silicon-Carbon Si2C3-I[p,q] and Si2C3-II[p,q]". Symmetry 10, n.º 8 (3 de agosto de 2018): 320. http://dx.doi.org/10.3390/sym10080320.
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The application of graph theory in chemical and molecular structure research has far exceeded people’s expectations, and it has recently grown exponentially. In the molecular graph, atoms are represented by vertices and bonds by edges. Topological indices help us to predict many physico-chemical properties of the concerned molecular compound. In this article, we compute Generalized first and multiplicative Zagreb indices, the multiplicative version of the atomic bond connectivity index, and the Generalized multiplicative Geometric Arithmetic index for silicon-carbon Si2C3−I[p,q] and Si2C3−II[p,q] second.
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Anandari, Risma Nila, Siti Khaizatul Minnah, Vidya Utami Widadni, Dona Safira e Fatchiyah Fatchiyah. "In-Silico Analysis of Procyanidin Type-A Extracted From Cinnamon for Diabetes Mellitus Type 2 Treatment". JSMARTech 2, n.º 3 (1 de outubro de 2021): 92–95. http://dx.doi.org/10.21776/ub.jsmartech.2021.002.03.92.
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Type 2 diabetes mellitus (T2DM) is the most common disease in developing countries. People with type-2 diabetes are at high risk of complications leading to disability and premature death. Procyanidin compounds in cinnamon have an insulin-like activity that can regulate normal blood sugar levels. This research aimed to investigate the interaction between α-glucosidase and α-amylase with procyanidin A and their potential for diabetes treatment therapy. Data mining receptor was downloaded from RCSB PDB and ligands from PubChem. Drug likeness properties were evaluated using SwissADME, while toxicity analysis was assessed using metatox. Molecular docking between α-glucosidase and α-amylase with procyanidin A was performed using HEX 8.0.0 and was visualized by Discovery Studio. Procyanidin A showed interaction with α-glucosidase by non-bonds interaction, including hydrogen, hydrostatic and hydrophobic bonds, while procyanidin A and α-amylase formed hydrogen and hydrophobic bonds. Procyanidin A is an alternative treatment for T2DM with a variety of supportive chemical bonds. Procyanidin A has an excellent ability to inhibit activity α-glucosidase and α-amylase in the process of breaking down glucose in the intestines.
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Hassanain, Waleed A., e Emad L. Izake. "Toward Label-Free SERS Detection of Proteins through Their Disulfide Bond Structure". SLAS DISCOVERY: Advancing the Science of Drug Discovery 25, n.º 1 (19 de setembro de 2019): 87–94. http://dx.doi.org/10.1177/2472555219875102.
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The molecular structure of many proteins contains disulfide bonds between their cysteine residues. In this work we demonstrate the utilization of the disulfide bond structure of proteins for their label-free determination by surface-enhanced Raman spectroscopy (SERS). The new approach for label-free SERS detection of proteins is demonstrated for human insulin. The protein was selectively extracted from spiked plasma samples using target-specific functionalized nanomaterial. Enzyme-linked immune assay (ELISA) was used to detect insulin in the blood plasma and cross-validate the SERS method. The disulfide bonds in the molecular structure of the protein were chemically reduced and used for their chemisorption onto the gold-coated copper oxide substrate in a unified orientation at a very short distance from the hotspots. The oriented chemisorption of the protein caused significant enhancement to the signal intensity of its Raman vibration modes. This is attributed to the strong short-range electromagnetic and chemical enhancement effects that are experienced by the immobilized protein. Using this approach, label-free and reproducible SERS detection of insulin, down to 10 zM (relative standard deviation [RSD] = 5.52%), was achieved. Sixty-five percent of proteins contain disulfide bonds in their molecular structure. Therefore, the new label-free SERS detection method has strong potential for the determination of ultralow concentrations of proteins at pathology labs and in biology research.
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Seyyedi, Behnam, Mohammad Edrisi, Maryam Seyyedi e Gholamreza Mahdavinia. "A new single step synthesis of copper phthalocyanine green using microwave irradiation effects in functionalisation of C−H bonds in aromatic rings". Pigment & Resin Technology 43, n.º 3 (29 de abril de 2014): 113–17. http://dx.doi.org/10.1108/prt-04-2013-0029.
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Purpose – The paper introduces a new method for single step synthesis of copper phthalocyanine green pigment using microwave irradiation to activate C−H bonds on the aromatic rings that are possible by creation of chlorine radicals. The aims of this study are to investigate the possibility of high-efficiency product reaction, removing acidic wastewater, time optimization, and maximizing number of chlorine on aromatic rings. Design/methodology/approach – The paper presents a new synthesis technique, which does not have the problems of the conventional methods. Microwave irradiation is used as a chemical reaction initiator by creation of chlorine radicals in saturated aqueous solution of sodium chloride and C−H bond activation on aromatic rings. The approach yields to a high quality of product, uniform particle size distribution, high efficiency and an environmental friendly procedure. Findings – The paper introduces the use of suitable materials and water solvents in chemical reactions under microwave radiation at low temperatures. This shows that the microwave irradiation activates C−H bonds on aromatic rings and creates chlorine radicals at the same time, which results in relatively fast reaction of synthesis copper phthalocyanine green. Research limitations/implications – The ammonium molybdate catalyst, which is used in this method, should be weighed carefully. The effects of transition metals on chemical reactions in the presence of microwave irradiation can also be chlorinated other unsaturated bonds. Practical implications – The method develops a simple and practical solution to improve the synthesis of phthalocyanine green pigment. Originality/value – The synthesis method of copper phthalocyanine green pigment is novel. CuPhcCl16 has numerous applications in industrial.
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Kijaszek, Wojciech, Waldemar Oleszkiewicz, Adrian Zakrzewski, Sergiusz Patela e Marek Tłaczała. "Investigation of optical properties of silicon oxynitride films deposited by RF PECVD method". Materials Science-Poland 34, n.º 4 (1 de dezembro de 2016): 868–71. http://dx.doi.org/10.1515/msp-2016-0111.
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AbstractIn this study, the authors deposited silicon oxynitride films by Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF PECVD) method. The research explores the relationship between the deposition process parameters and the optical properties of the deposited SiOxNy films. The optical constants of SiOxNy films were measured and calculated by spectroscopic ellipsometry method. Additionally, the authors investigated the possibility of controlling the deposited film composition by the flow ratio of different gaseous precursors: ammonia (NH3), diluted silane (2%SiH4/98%N2), nitrous oxide (N2O) and nitrogen (N2). The gas mixture introduced to the working chamber during the growth of the film has the influence on the Si–O and Si–N bonds formation and the ratio between these bonds determines the refractive index of the deposited film.
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Alkorta, Ibon, José Elguero e Antonio Frontera. "Not Only Hydrogen Bonds: Other Noncovalent Interactions". Crystals 10, n.º 3 (6 de março de 2020): 180. http://dx.doi.org/10.3390/cryst10030180.
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In this review, we provide a consistent description of noncovalent interactions, covering most groups of the Periodic Table. Different types of bonds are discussed using their trivial names. Moreover, the new name “Spodium bonds” is proposed for group 12 since noncovalent interactions involving this group of elements as electron acceptors have not yet been named. Excluding hydrogen bonds, the following noncovalent interactions will be discussed: alkali, alkaline earth, regium, spodium, triel, tetrel, pnictogen, chalcogen, halogen, and aerogen, which almost covers the Periodic Table entirely. Other interactions, such as orthogonal interactions and π-π stacking, will also be considered. Research and applications of σ-hole and π-hole interactions involving the p-block element is growing exponentially. The important applications include supramolecular chemistry, crystal engineering, catalysis, enzymatic chemistry molecular machines, membrane ion transport, etc. Despite the fact that this review is not intended to be comprehensive, a number of representative works for each type of interaction is provided. The possibility of modeling the dissociation energies of the complexes using different models (HSAB, ECW, Alkorta-Legon) was analyzed. Finally, the extension of Cahn-Ingold-Prelog priority rules to noncovalent is proposed.
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Yang, Hui, Tian He e Xixi Yan. "Adhesion strategies for heterogeneous soft materials—A review". Engineering Research Express 4, n.º 1 (14 de janeiro de 2022): 012001. http://dx.doi.org/10.1088/2631-8695/ac342e.
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Abstract Adhesion is a long-term research topic of great importance attracting plenty of attention. In past few years, many remarkable advances have been made in the field of heterogeneous soft material adhesion, considerably boosting the functional diversity and viability of heterogeneous soft material assemblies. This review focuses on the status quo of this field with attention leaning towards recently active and outstanding bioinspiration and biomimetic areas. First, the fundamental mechanisms of adhesion, including chemical bonds, topological entanglement, and gradient connections, are introduced. Then influence factors on adhesion strength are derived from the adhesion mechanisms. The influence factors are classified into two categories: physical factors, including interface geometry (interface stress singularity for macroscopic and interface roughness for microscopic) and mismatch of material properties, and chemical factors, including chemical complementarities and ambient conditions. Abundant examples from recent representative research efforts are provided to demonstrate how these factors are tuned to enable or improve an adhesion. As a fabrication process dealing with multiple material interfaces, additive manufacturing (AM) is discussed separately emphasizing on its space and time discretization nature. After that, several adhesion enhancement strategies are presented, among them is one synergistically integrating covalent bonds, noncovalent complexes, polymer chains/networks, and nanoparticles. Finally, based on the current research status, it is proposed that general methodologies for adhesion strategy selection and simulation models capable of accurately predicting adhesion strength are greatly needed. Heterogeneous material adhesion is also expected to acquire insights and impetuses from fields like cell differentiation and tissue development.
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Kamaluddin, Agus. "Chemo-entrepreneurship Modelling on Chemical Bonding Materials as an Effort to Grow Entrepreneurial Spirit of Students with Hearing Impairment in (Islamic) Senior High School". International Journal of Chemistry Education Research 2, n.º 1 (19 de fevereiro de 2018): 34–44. http://dx.doi.org/10.20885/ijcer.v2i1.10085.
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ABSTRACT: This research aims to develop MEc Bond learning media (Magnetic Educhem Bonding) for students with hearing impairment in (Islamic) senior high school based on chemo-entrepreneurship modeling. This research uses the development model by Borg & Gall that includes the identification of potentials and problems, product selection, literature review, planning, developing initial product draft, initial field trials and product revisions, and it ends with major field trials and product revision. The subjects of this research include material experts, media experts, disability experts, senior high school chemistry teachers and students. The data of this research are taken by using several instruments:interview guide, product quality assessment sheet, and student response sheet. The interview result is analyzed by using descriptive technique, assessment result of product quality is analyzed by using categorical descriptive quantitative technique, and student's response is analyzed by using percentage technique. The results of this research has been developed with the input from the validation specialist and chemistry teachers. Learning media which is developed has best quality, according to the assessment of chemistry teachers in (Islamic) senior high school, with the ideality percentage of 91.02%. In general, students with hearing impairment might respond positively which gets the ideality percentage of 86% to the MEc Bond learning media which makes the material chemical bonds easier to be understood and fun. In addition, the media is desperately necessary for studying chemical bonding in class and it can foster entrepreneurial spirit for the students in the form of making learning media ofchemical bonds.
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Kamaluddin, Agus. "Chemo-entrepreneurship Modelling on Chemical Bonding Materials as an Effort to Grow Entrepreneurial Spirit of Students with Hearing Impairment in (Islamic) Senior High School". International Journal of Chemistry Education Research 2, n.º 1 (19 de fevereiro de 2018): 34–44. http://dx.doi.org/10.20885/ijcer.vol2.iss1.art6.
Texto completo da fonteResumo:
ABSTRACT: This research aims to develop MEc Bond learning media (Magnetic Educhem Bonding) for students with hearing impairment in (Islamic) senior high school based on chemo-entrepreneurship modeling. This research uses the development model by Borg & Gall that includes the identification of potentials and problems, product selection, literature review, planning, developing initial product draft, initial field trials and product revisions, and it ends with major field trials and product revision. The subjects of this research include material experts, media experts, disability experts, senior high school chemistry teachers and students. The data of this research are taken by using several instruments:interview guide, product quality assessment sheet, and student response sheet. The interview result is analyzed by using descriptive technique, assessment result of product quality is analyzed by using categorical descriptive quantitative technique, and student's response is analyzed by using percentage technique. The results of this research has been developed with the input from the validation specialist and chemistry teachers. Learning media which is developed has best quality, according to the assessment of chemistry teachers in (Islamic) senior high school, with the ideality percentage of 91.02%. In general, students with hearing impairment might respond positively which gets the ideality percentage of 86% to the MEc Bond learning media which makes the material chemical bonds easier to be understood and fun. In addition, the media is desperately necessary for studying chemical bonding in class and it can foster entrepreneurial spirit for the students in the form of making learning media ofchemical bonds.
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Cong, Qiao, Xing Yuan e Jiao Qu. "A review on the removal of antibiotics by carbon nanotubes". Water Science and Technology 68, n.º 8 (1 de outubro de 2013): 1679–87. http://dx.doi.org/10.2166/wst.2013.420.
Texto completo da fonteResumo:
Increasing concerns have been raised regarding the potential risks of antibiotics to human and ecological health due to their extensive use. Carbon nanotubes (CNTs) have drawn special research attention because of their unique properties and potential applications as a kind of adsorbents. This review summarizes the currently available research on the adsorption of antibiotics on CNTs, and will provide useful information for CNT application and risk assessment. Four different models, the Freundlich model (FM), Langmuir model (LM), Polanyi–Mane model (PMM), and Dubinin–Ashtakhov model (DAM), are often used to fit the adsorption isotherms. Because different mechanisms may act simultaneously, including electrostatic interactions, hydrophobic interactions, π–π bonds, and hydrogen bonds, the prediction of organic chemical adsorption on CNTs is not straightforward. Properties of CNTs, such as specific surface area, adsorption sites, and oxygen content, may influence the adsorption of antibiotics on CNTs. Adsorption heterogeneity and hysteresis are two features of antibiotic–CNT interactions. In addition, CNTs with adsorbed antibiotics may have potential risks for human health. So, further research examining how to reduce such risks is needed.