Hasil untuk "Chemistry"

D. Dias, S. Urban, U. Roessner

Historically, natural products have been used since ancient times and in folklore for the treatment of many diseases and illnesses. Classical natural product chemistry methodologies enabled a vast array of bioactive secondary metabolites from terrestrial and marine sources to be discovered. Many of these natural products have gone on to become current drug candidates. This brief review aims to highlight historically significant bioactive marine and terrestrial natural products, their use in folklore and dereplication techniques to rapidly facilitate their discovery. Furthermore a discussion of how natural product chemistry has resulted in the identification of many drug candidates; the application of advanced hyphenated spectroscopic techniques to aid in their discovery, the future of natural product chemistry and finally adopting metabolomic profiling and dereplication approaches for the comprehensive study of natural product extracts will be discussed.

D. Thévenot, K. Toth, R. Durst et al.

Abstract Two Divisions of the International Union of Pure and Applied Chemistry (IUPAC), namely Physical Chemistry (Commission I.7 on Biophysical Chemistry formerly Steering Committee on Biophysical Chemistry) and Analytical Chemistry (Commission V.5 on Electroanalytical Chemistry) have prepared recommendations on the definition, classification and nomenclature related to electrochemical biosensors; these recommendations could, in the future, be extended to other types of biosensors. An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element. Because of their ability to be repeatedly calibrated, we recommend that a biosensor should be clearly distinguished from a bioanalytical system, which requires additional processing steps, such as reagent addition. A device which is both disposable after one measurement, i.e., single use, and unable to monitor the analyte concentration continuously or after rapid and reproducible regeneration should be designated a single use biosensor. Biosensors may be classified according to the biological specificity-conferring mechanism or, alternatively, to the mode of physico-chemical signal transduction. The biological recognition element may be based on a chemical reaction catalysed by, or on an equilibrium reaction with macromolecules that have been isolated, engineered or present in their original biological environment. In the latter cases, equilibrium is generally reached and there is no further, if any, net consumption of analyte(s) by the immobilized biocomplexing agent incorporated into the sensor. Biosensors may be further classified according to the analytes or reactions that they monitor: direct monitoring of analyte concentration or of reactions producing or consuming such analytes; alternatively, an indirect monitoring of inhibitor or activator of the biological recognition element (biochemical receptor) may be achieved. A rapid proliferation of biosensors and their diversity has led to a lack of rigour in defining their performance criteria. Although each biosensor can only truly be evaluated for a particular application, it is still useful to examine how standard protocols for performance criteria may be defined in accordance with standard IUPAC protocols or definitions. These criteria are recommended for authors, referees and educators and include calibration characteristics (sensitivity, operational and linear concentration range, detection and quantitative determination limits), selectivity, steady-state and transient response times, sample throughput, reproducibility, stability and lifetime.

M. Polanyi

P. Hodge

O. Yaghi, M. O'Keeffe, N. W. Ockwig et al.

C. Moreno-Castilla

E. Cox

R. P. Bell, R. Roy

J. Lee

Amala Paul

M. Beck

Z. Rappoport, S. Patai

J. Lehn

Sirah Diniati Nea, Nurhaeni, Dwi Juli Puspitasari et al.

The increasing environmental pollution is one of the consequences of human activities that continue to expand. The environment has limitations in coping with pollutants generated by humans, such as waste from the laundry industry. This research aims to evaluate the combined effect of zeolite produced from corn cobs and the use of microorganisms capable of degrading anionic surfactants, with the goal of reducing the concentration of anionic surfactants in laundry wastewater. The methods used include adsorption using corn cobs as adsorbents and biodegradation using surfactant-degrading bacteria. Morphological observations using Scanning Electron Microscope (SEM) indicate that the produced zeolite has a crystal structure that stacks up like clumps of cubes. X-ray Diffraction (XRD) analysis shows that zeolite synthesized with a silica extraction ratio from corn cobs and sodium aluminate of 20:20 mL has been successfully conducted. The biodegradation process of anionic surfactants in laundry wastewater using a combination of synthesized zeolite and Pseudomonas aeruginosa bacteria employing the Methylene Blue Alkyl Substance (MBAS) method has shown a decrease in concentration to 1.66 mg/L and degradation of 33.55%, especially in sample 3 with variations of 7.5 grams of corn cob zeolite and 15% microorganisms, during a 5-day experiment.

CHEN Meng-han, Amel Mohamed, XU Ying-shu, YANG Zi-fan, JIA Hong-bing*

"Rubber blending was an effective way to develop new rubber materials that could achieve better properties than those of single components. The properties of blend could be precisely controlled by using different types of rubbers. However, most blends tended to phase separation, which led to deterioration in mechanical properties. Graphene oxide (GO) could be used as a novel compatibilizer to improve compatibility between rubbers［1-2］. 　In this work, GO was added to the blends of carboxylated nitrile butadiene rubber (XNBR) and styrene-butadiene rub-ber (SBR). The XNBR/SBR blend with different blend ratios were designed, and the effect of GO on the mechanical properties of GO/XNBR/SBR blended systems was analyzed in detail by a combination of molecular dynamics (MD) simulations and experiments. The formulation of rubber compounds was XNBR/SBR 100 phr (in mass, the same below), GO 0 or 3.0 phr, antideteriorant 4010 NA 2.0 phr, zinc oxide 2.0 phr, stearic acid 2.4 phr, accelerator CZ 2.2 phr and sulfur 1.5 phr. The mass ratios of XNBR/SBR were 25/75, 50/50 and 75/25, respectively. 　Through MD simulation, the number of hydrogen bonds of GO/XNBR/SBR blends was shown in Fig 1. The results showed that plenty of hydrogen bonds existed in GO/XNBR/SBR blends, and both the total number of hydrogen bonds and the number of interfacial hydrogen bonds increased with increasing XNBR content, indicating that the interfacial interaction of GO/XNBR/SBR blends was enhanced. After adding 75 phr of XNBR, the number of hydrogen bonds was the highest［3］. ■ Fig 1 Number of hydrogen bonds of GO/XNBR/SBR blends 　Tensile strength of XNBR/SBR and GO/XNBR/SBR blends were shown in Fig 2. It could be seen that the tensile strength of XNBR/SBR blend increased gradually with the growing of XNBR content, mainly due to the higher strength of XNBR compared to SBR. The higher the proportion of XNBR rubber was, the better the mechanical properties of the blends were. Compared to that of XNBR/SBR blend, the tensile strength of GO/XNBR/SBR blend increased by 86% when adding XNBR of 75 phr. The strong interfacial interactions, such as hydrogen bonds, may lead to a remarkable increase in the mechanical properties of the blend. ■ Fig 2 Tensile strength of XNBR/SBR and GO/XNBR/SBR blends"

Tagui Nagano, Akira Matsumoto, Ryotaro Yoshizaki et al.

Catalytic asymmetric cyanation of ketones is a straightforward method to construct tetrasubstituted chiral carbon centers, but for acylsilanes this method has been limited to enzymatic approaches. Here, non-enzymatic catalytic asymmetric cyanation of acylsilanes is accomplished using a chiral Lewis base as an enantioselective catalyst.

Cheng-Jung Yang, Sin-Syuan Wu

The 3D printers integrated with fused filament fabrication (FFF) are highly valued worldwide because of their properties, which include fast proofing, compatibility with various materials, and low printing cost. The competitiveness of FFF can be enhanced by improving printing quality. However, due to the increasing sustainability issues worldwide, there is an urgent need to lower energy consumption. In this study, we focused on fan rate, printing speed, nozzle temperature, build plate temperature, and layer thickness as factors that directly impact the dimensional accuracy, carbon dioxide emissions, and printing cost of FFF printers. Several single-objective and multiobjective optimization tasks were performed using the Taguchi method and desirability approach to implement sustainable manufacturing decisions. In single-objective optimization, the inner width, outer width, material cost, and labor cost were most easily affected by the layer thickness. The outer length, carbon dioxide emissions, and electricity cost were significantly affected by the build plate temperature. In multiobjective optimization, a different set of printing parameters can be used to optimize dimensional accuracy, carbon dioxide emissions, material cost, labor cost, and electricity cost. This study helps users to obtain optimal solutions under different optimization requirements to cope with diverse manufacturing characteristics.

Sumei Gao, Longxiang Xu, Chaowu Jin

In this paper, the structural characteristics of electromagnetic suspension (EMS) inertial stabilizers are analyzed firstly, and then a mechanical analysis of a single mass block and double mass block is carried out. The relationship model between the inertial anti-rolling mass block and inertial force transmitted to the ship is established. The inertial force is determined by the number of coil turns, coil current, mass block, mass of the ship, electromagnet current, rate of change of the electromagnet current, air gap between the electromagnet and inertial mass block, and rotational angular speed. Through theoretical analysis, it is found that the response speed of inertia force is directly related to the electromagnetic coil current, the voltage at both ends of the electromagnetic coil, the coil resistance and the air gap. It is concluded that the response speed of the inertia force can be controlled by controlling the coil current, adjusting the voltage at both ends of the coil and adjusting the air gap. The inductance of the electromagnetic coil will also increase the nonlinearity of the inertial anti-roll system. On the basis of theoretical analysis, a digital simulation of EMS inertial stabilizer is carried out by MATLAB and ANSYS MAXWELL2D. Finally, a single mass block system of EMS inertial stabilizer is designed and tested. During the test, a 1.5 V sinusoidal excitation voltage is added to the electromagnetic coil after the mass block is suspended stably, and the maximum acceleration values of the inertial anti-rolling mass block and hull are 10.29 m/s² and 1.27 m/s². Finally, the theoretical analysis results, digital simulation results and experimental results are analyzed, which verifies the correctness of the acceleration and inertia force performance analysis of the EMS inertial stabilizer.

France, Lydéric, Brouillet, Florian, Lang, Sarah

Carbonatites are unusual C-rich alkaline magmas that have been reported throughout the geological record. Nevertheless, there is only one currently active carbonatite system on Earth: Oldoinyo Lengai stratovolcano in northern Tanzania (God’s mountain in Maasai culture). Present-day Lengai carbonatites are natrocarbonatites, peculiar Na-rich carbonatites that, under atmospheric conditions, alter and leach to compositions similar to the more common Ca-carbonatites within weeks, preventing any long-term geological record of such Na-rich magmas. It follows that the oldest report of natrocarbonatites at Oldoinyo Lengai dates to the 19th century. Here, by using samples from the Lengai I cone (${>}$11 ka), we show that immiscible silicate–carbonatite melts were already present at reservoir conditions at that time. Measurements of three-phase (carbonatite $+$ silicate $+$ gas) melt inclusions from Lengai I highlight that their chemical compositions were similar to those of immiscible melts recently present in the reservoir. Alkaline carbonatites in melt inclusions from both Lengai I and historical explosive eruptions are enriched in Ca relative to those historically effused at the surface and likely record higher equilibrium temperatures (${>}$1100 °C). We also report chemical maps that qualitatively document elemental partitioning between immiscible silicate–carbonatite melts. We show that at the melt inclusions’ entrapment conditions Si, Fe, K, Na, and Cl are compatible with the silicate phase when C, Ca, P, Sr, Ba, and F are compatible with the carbonate phase.

Lixia Ren, Min Wang, Shuanhu Wang et al.

Abstract Organic lead halide perovskites have attracted extensive interest for potential use in next‐generation photovoltaic devices due to the demonstrated high power conversion efficiency, low materials cost, and low fabrication cost. Besides, the electromechanical properties have also been explored in detail to expand the application potential. Here, we report the reversible photoelectric modulation (including photoresponse and photoresistance modulation, by near 6%) in methylammonium lead triiodide (MAPbI3) film under an external electric bias (only 0.06 V µm‐1), which stems from the strain response induced by the competition of electrical biasing and light exposure. In addition, accompanied by the use of bias and light, the lattice is found to be deformed in MAPbI3 film. This result does not only shed light on the lattice deformation from external factors but also highlights the dramatic electron/photon‐lattice coupling in perovskite films.