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Green Synthesis nanopartikel Tembaga Menggunakan Reduktor Alami Ekstrak Daun Gambir (Uncaria Roxb Extract) dan aktivitas antibakterinya
Full text linkSUMMARY
Nanotechnology and nanomaterials have become a focus of increasing interest to a number of researchers in recent years, because nanometer-sized materials have a number of chemical and physical properties that are superior to bulk materials. The main thing that makes nanoparticles different from similar materials in their large size is the surface properties that can be modified in terms of optical, magnetic, electronic and mechanical properties as well as their small size with a greater ratio between surface area and volume.
Many researches related to the synthesis of nanoparticles have been carried out. However, there are still some weaknesses that are found among them are the high production costs and the use of chemicals that are harmful to users and the environment. Therefore, it is necessary to develop a synthesis method that is more environmentally friendly by using natural reducing agents that are safe (non-toxic), cheap and easy to obtain. In addition, this method requires a relatively short contact time compared to other methods.
In this study, copper nanoparticles were synthesized using natural reducing agents from gambier leaf extract with variations in copper precursor anions and reaction times and antibacterial activity. Gambier leaf extract acts as a reducing agent and capping agent. The reason for choosing gambier leaves is that the availability is quite abundant and easy to obtain, considering that West Sumatra is the largest gambier producing area (80%) in Indonesia. The choice of copper as a precursor metal is due to its potential applications in various fields, including as a material for conductors, catalysts, detectors, optical sensors, and antimicrobial agents. In addition, the synthesis process is very easy, the costs used are relatively cheap and affordable and the availability is sufficient. The development of the copper metal synthesis method to produce nanoparticles is directed to produce NpCu in the size of 1-100 nm.
From previous literature studies, it has not been found that the use of gambier leaf extract as a copper metal reducer in the synthesis of NpCu and its characteristics and application as antibacterial. Starting from the literature search, the authors are interested in further researching the method of copper nanoparticle synthesis with gambier leaf extract and its antibacterial activity on gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria.
In this study, three types of precursors were used, CuSO4, Cu(NO3)2 and CuCl2. Based on the research results obtained information on the potential of gambier leaf extract in reducing copper to NpCu. The formation of NpCu colloids is visually indicated by a color change from light brown to dark brown. The results of measurements with a UV-Vis spectrophotometer formed an absorption peak at a wavelength of 405-427 nm which is a specific wavelength of the formation of NpCu based on the Surface Plasmon Resonance (SPR) phenomenon. The results of the X-Ray Diffraction (XRD) analysis showed the results of NpCu with a Face Centered Cubic (FCC) crystal structure through the formation of 3 peaks in the 43.28 ° (111), 50.40 ° (200) and 74.81 ° (220) areas. The results of FTIR analysis showed that there was a vibration of Cu-O bonds which assumed interaction between Cu ions and polyphenol compounds at wave numbers 623 cm-1 for CuSO4, 615 cm-1 for Cu(NO3) 2 and 610 cm-1 for CuCl2 precursors. Transmission Electron Microscope (TEM) shows the synthesized NpCu is spherical. The results obtained by using the CuSO4 NpCu precursor formed tended to be more evenly distributed than the Cu(NO3)2 and CuCl2 precursors with particle size diameters of 15 nm, 28 nm and 25 nm, respectively. The size and morphology of these copper nanoparticles are influenced by the type of precursor anions used. The higher the polarity, the solubility and the anion charge, the more stable and the smaller the NpCu particle size. Based on the characterization results, it can be concluded that with better NpCu produced from CuSO4 precursors compared to the other 2 precursors Cu (NO3)2 and CuCl2. The precursors for CuSO4, Cu(NO3)2 and CuCl2 were 13.8 mm, 12.6 mm and 11.9 mm respectively and gram negative Escherichia coli with inhibition zone areas of 11.8 mm, 10.8 mm and 10.5 mm. This shows that NpCu has the potential as a strong category antibacterial agent. From the research conducted, the author has succeeded in discovering the potential of gambier leaf extract as a reducing agent and capping agent in synthesis. Copper nanoparticles are powdered with a size of 15 - 28 nm, a round and stable shape of the three precursors (CuSO4, Cu(NO3)2 and CuCl2). The resulting NpCu has been shown to act as a strong antibacterial agent with the formation of an inhibition zone of 11-13 mm. Advantage
UPAYA PENINGKATAN MOTIVASI DAN HASIL BELAJAR MELALUI PENDEKATAN KOOPERATIF MODEL COURSE REVIEW HORAY SISWA KELAS XII.2 PADA MATA PELAJARAN ANALISIS INSTRUMEN
Full text linkUV Vis Spectrophotometry is one of the learning materials that are difficult for students to understand because of the abstract concept. This difficulty in understanding can affect the further development of student knowledge. This research describes the learning process through a cooperative approach to the Course Review Horay model. The method used is a class action research method on one of the research subjects 17 students of class XII.2 SMK SMTI Padang. The research objectives were achieved with instruments in the form of learning descriptions, class observations, interviews, diagnostic tests and final tests. The results showed that the learning process at each stage went well. The understanding of students in the concept understanding category has increased classical completeness from 68.75% to 93.25%. Student responses to the application of a cooperative approach to the course review horay model are very positive. Suggestions put forward that this method can be used to visualize abstract photometric or spectrophotometric concepts and can minimize misconceptions. Giving examples in everyday life can improve students' understanding, and motivate students to follow the learning process
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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