A simplified model is proposed for an easy understanding of the coarse-grained technique and for achieving a first approximation to the behavior of gases. A mole of a gas substance, within a cubic container, is repres...A simplified model is proposed for an easy understanding of the coarse-grained technique and for achieving a first approximation to the behavior of gases. A mole of a gas substance, within a cubic container, is represented by six particles symmetrically moving. The impacts of particles on container walls, the inter-particle collisions, as well as the volume of particles and the inter-particle attractive forces, obeying a Lennard-Jones curve, are taken into account. Thanks to the symmetry, the problem is reduced to the nonlinear dynamic analysis of a SDOF oscillator, which is numerically solved by a step-by-step time integration algorithm. Five applications of proposed model, on Carbon Dioxide, are presented: 1) Ideal gas in STP conditions. 2) Real gas in STP conditions. 3) Condensation for small molar volume. 4) Critical point. 5) Iso-kinetic energy curves and iso-therms in the critical point region. Results of the proposed model are compared with test data and results of the Van der Waals model for real gases.展开更多
When writing equations of chemical dissociation, students and scholars are taught two fundamental rules to balance the equation. On both sides of the equation, the types of elements and their quantity are conserved, a...When writing equations of chemical dissociation, students and scholars are taught two fundamental rules to balance the equation. On both sides of the equation, the types of elements and their quantity are conserved, as well as the global electrical charge. This paper introduces additional methods during dissociation of gaseous compounds, to precisely describe how electrical charges locally move and how bonding structures are modified. Specific rules revolving around electrons pairs displacements are developed and applied to about 150 dissociations of small gaseous molecules using atoms from the three first rows of the periodic table. Results obtained tend to demonstrate the relevance of these tools for chemists.展开更多
The mechanism of reaction of cyclic monoimides with oxiranes was established based upon kinetic studies and product analysis. It has been established that the reaction proceeds through initial formation of an adduct o...The mechanism of reaction of cyclic monoimides with oxiranes was established based upon kinetic studies and product analysis. It has been established that the reaction proceeds through initial formation of an adduct of imide and triethylamine. The crucial bond in adduct has ionic character;in non-aqueous solvents it is present as ion pair, while in water the adduct dissociate and free ions are present. The adduct enables the proton transfer from imide to oxirane. The rate determining step is reaction of imide and this adduct. Different values of entropy of transition states obtained from thermodynamic calculations suggest slightly different structure of transition state of rate determining step.展开更多
Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT)...Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT) calculations indicated that absorption peak at 238 nm was mainly due to excitation of electrons from the linear chain structure Adda of microcystin-LR. Irradiation of microcystin-LR with UV light resulted in the reduction of the 238 nm absorption peak and the appearance of a new peak at 300 nm. Density functional theory (DFT) and TDDFT calculations with a model molecule suggested that this 300 nm peak was due to tricyclo-Adda microcystin-LR, an intermediate in photochemical reactions of microcystin-LR. Analysis of the rate of this photochemical reaction showed that it was a first order reaction.展开更多
We performed density functional theory (DFT) calculations for ribonucleotides and active triphosphate metabolites of candidate drugs against Coronavirus disease 2019 (Covid-19). Frontier orbitals (highest occupied mol...We performed density functional theory (DFT) calculations for ribonucleotides and active triphosphate metabolites of candidate drugs against Coronavirus disease 2019 (Covid-19). Frontier orbitals (highest occupied molecular orbital and lowest unoccupied molecular</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">orbital) at optimized structure of each molecule were obtained. T-705RTP (active triphosphate metabolite of favipiravir) and cytidine triphosphate (CTP) have similar shapes of frontier orbitals. We also obtained similar shapes of frontier orbitals among dihydroxy GS-441524 triphosphate (GS-441524 is an active triphosphate metabolite of remdesivir) and adenosine triphosphate (ATP). From a theoretical </span><span style="font-family:Verdana;">viewpoint, we suggest T-705RTP is a CTP analogue and dihydroxy GS-441524</span><span style="font-family:Verdana;"> triphosphate is an</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">ATP analogue.展开更多
It is currently admitted that the intermolecular forces implicated in Gas Liquid Chromatography (GLC) can be expressed as a product of parameters (or descriptors) of solutes and of parameters of solvents. The present ...It is currently admitted that the intermolecular forces implicated in Gas Liquid Chromatography (GLC) can be expressed as a product of parameters (or descriptors) of solutes and of parameters of solvents. The present study is limited to those of solutes, and among them the three ones are involved in the Van der Waals forces, whereas the two ones involved in the hydrogen bonding are left aside at this stage. These three studied parameters, which we call δ, ω and ε, respectively reflect the three types of Van der Waals forces: dispersion, orientation or polarity strictly speaking, and induction-polarizability. These parameters have been experimentally obtained in previous studies for 121 Volatile Organic Compounds (VOC) via an original Multiplicative Matrix Analysis (MMA) applied to a superabundant and accurate GLC data set. Then, also in previous studies, attempts have been made to predict these parameters via a Simplified Molecular Topology procedure (SMT). Because these last published results have been somewhat disappointing, a promising new strategy of prediction is developed and detailed in the present article.展开更多
Experiments described in this paper show that there is the photoconductive effect of liquid, i.e. when light shines into a sort of alkali, acid or salt solution, the conductivity of the solution will increase. The mec...Experiments described in this paper show that there is the photoconductive effect of liquid, i.e. when light shines into a sort of alkali, acid or salt solution, the conductivity of the solution will increase. The mechanism of the effect is explained as follows. When hydrated ions in the solution absorb photons with their high enough energies, they will decompose to naked ions and water-molecules. The naked ions can reach an anode or a cathode more easily and faster than the hydrated ions;It is possible that when a molecule in the solution absorbs a photon with its high enough energy, it will decompose to negative and positive ions. Based on the effect, a device producing hydrogen by the solar-energy had been devised.展开更多
Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic leve...Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.展开更多
Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric...Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated.展开更多
A redshift in the wavelength of excitation spectra is experimentally measured as a function of the concentration parameter for tryptophan solutions in water. To understand the microscopic causes of this behavior, theo...A redshift in the wavelength of excitation spectra is experimentally measured as a function of the concentration parameter for tryptophan solutions in water. To understand the microscopic causes of this behavior, theoretical calculations obtained from four model clusters are carried out: (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">1</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">9</span></sub><span style="font-family:Verdana;">, (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">2</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">18</span></sub><span style="font-family:Verdana;">, (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">3</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">27</span></sub><span style="font-family:Verdana;"> and (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">4</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">36</span></sub><span style="font-family:Verdana;">, where there are interactions among 1, 2, 3 and 4 molecules of tryptophan. According to the literature, each interaction occurred with nine molecules of water to stabilize its expected zwitterionic form. In these models, the molecules of tryptophan appear at an adjacent distance among them to generate an analogous behavior when there is an experimental increase in the concentration. It is evident that </span><span style="font-family:Verdana;">the distance between adjacent molecules of tryptophan decreases as their concentration</span><span style="font-family:Verdana;"> increases. The optical properties of these clusters are obtained by studying the corresponding excited states and the molecular orbitals involved, showing charge transfers by using time-dependent density functional theory (TD-DFT) methods. The experimental spectroscopic data are obtained by using the clusters proposed, and good agreement is found by drawing a comparison with the theoretical data</span></span><span style="font-family:Verdana;">.展开更多
MoO<sub>3</sub> and 5% MoO<sub>3</sub>/ZnO were prepared by impregnation method using (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub>, 4...MoO<sub>3</sub> and 5% MoO<sub>3</sub>/ZnO were prepared by impregnation method using (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub>, 4H<sub>2</sub>O as precursor and ZnO as support. The prepared samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), infra red (FTIR) <span style="font-family:;" "="">and</span><span style="font-family:;" "=""> UV-Vis diffuse reflectance (DRS)</span><span> </span><span style="font-family:;" "="">spectroscopies and pho<span>to-electrochemistry. The XRD pattern showed that the MoO<sub>3</sub> powder treated at 700°C is a single-phase crystallizing in an orthorhombic structure with a direct optical transition </span></span><span style="font-family:;" "="">(</span><span style="font-family:;" "="">2.70 eV</span><span style="font-family:;" "="">)</span><span style="font-family:;" "="">. The hetero-junction 5% MoO<sub>3</sub>/ZnO</span><span style="font-family:;" "=""> was photo-electrochemically characterized to assess its feasibility for H<sub>2</sub> production under visible light. The capacitance potential (<i>C<sup>-</sup></i><sup>2</sup><i> f</i>(<i>E</i>)) characteristic of MoO<sub>3</sub> plotted in Na<sub>2</sub>SO<sub>4</sub>, (0.1 M) electrolyte indicates <i>n-</i>type conduction with a flat band potential of -</span><span style="font-family:;" "=""><span>0.54 V<i><sub>SCE</sub></i>. The photocatalytic activity was performed for the photoreduction of water to hydrogen under visible light illumination. The best performance occurs at pH ~ 7 with an evolved volume of 5.9 mL.</span></span>展开更多
Proteoglycans and collagen molecules are interacting with each other thereby forming various connective tissues. The sulfation pattern of proteoglycans differs depending on the kind of tissue and/or the degree of matu...Proteoglycans and collagen molecules are interacting with each other thereby forming various connective tissues. The sulfation pattern of proteoglycans differs depending on the kind of tissue and/or the degree of maturation. Tissues from Cnidaria are suitable examples for exploration of the effects in relation to the presence and the absence of sulfate groups, when studying characteristic fragments of the long proteoglycan carbohydrate chains in silico. It has been described that a non-sulfated chondroitin appears as a scaffold in early morphogenesis of all nematocyst types in Hydra. On the other hand, sulfated glucosaminoglycans play an important role in various developmental processes of Cnidaria. In order to understand this biological phenomenon on a sub-molecular level we have analysed the structures of sulfated and non-sulfated proteoglycan carbohydrate chains as well as the structure of diverse collagen molecules with computational methods including quantum chemical calculations. The strong interactions between the sulfate groups of the carbohydrates moieties in proteoglycans and positively charged regions of collagen are essential in stabilizing various Cnidaria tissues but could hinder the nematocyst formation and its proper function. The results of our quantum chemical calculations show that the sulfation pattern has a significant effect on the conformation of chondroitin structures under study.展开更多
A comprehensive investigation on the formation mechanism of gold nanoparticles (AuNPs) in colloidal mixture obtained from the reduction of chloroauric acid (HAuCl4) solution using a single reducing agent (sodium citra...A comprehensive investigation on the formation mechanism of gold nanoparticles (AuNPs) in colloidal mixture obtained from the reduction of chloroauric acid (HAuCl4) solution using a single reducing agent (sodium citrate;process-I), (tannic acid;process-II), and a combination of two reducing agents (sodium citrate plus tannic acid;process-III) is reported. The growth steps at different time intervals during synthesis of colloidal AuNPs were monitored in situ and ex situ using various methods for all the three processes. The measurement of changes in the surface plasmon band position of colloidal AuNPs, along with dynamic light scattering results gave important information for the first assessing of particle size, shape and distribution. Besides, the size and morphological changes at different stages during different processes were also analyzed by transmission electron microscopy. The final Au particles of processes-I & II exhibited different shapes (spherical and nanowires) with particle size and nano wire diameter of 12 nm and 17 nm, respectively. Nevertheless, combination of two reductants (process-III) surprisingly leads to drastically reduced size (ca. 3 nm) with spherical morphology compared to their parent solutions with either of single reducing agent. This result clearly indicates that the combination of reductants has a significant influence on the particle size, morphology and formation mechanism.展开更多
The technique of supported liquid membranes was used to achieve the facilitated transport of Cr(III) ions, using tow amphiphilic carriers, the methyl cholate and resorcinarene. For prepared SLMs, toluene as organic ph...The technique of supported liquid membranes was used to achieve the facilitated transport of Cr(III) ions, using tow amphiphilic carriers, the methyl cholate and resorcinarene. For prepared SLMs, toluene as organic phase and film of polyvinylidene difluoride, as hydrophobic polymer support with 100 μm in thickness and 0.45 μm as the diameter of the pores. The macroscopic parameters (P and J0) on the transport of these ions were determined for different medium temperatures. For these different environments, the prepared SLMs were highly permeable and a clear evolution of these parameters was observed. The parameter J0 depended on the temperature according to the Arrhenius equation. The activation parameters, Ea, ΔH≠ and ΔS≠, for the transition state on the reaction of complex formation (ST) , were determined. To explain these results for this phenomenon, and achieve a better extraction of the substrate, a model based on the substrate complexation by the carrier and the diffusion of the formed complex (ST) was developed. The experimental results verify this model and determine the microscopic parameters (Kass and D*). These studies show that these parameters Kass and D* are specific to facilitated transport of Cr(III) ions by each of the carriers and they are changing significantly with temperature.展开更多
Purpose: Tenofovir disoproxil fumarate (TEN) and emtricitabine (EMT) are both second generation ant-retroviral drugs used in the “treatment” of HIV/AIDS. The aim of this study is to establish the physic-chemical pro...Purpose: Tenofovir disoproxil fumarate (TEN) and emtricitabine (EMT) are both second generation ant-retroviral drugs used in the “treatment” of HIV/AIDS. The aim of this study is to establish the physic-chemical properties of their reaction with chloranilic acid in different solvent systems and to justify the chemical basis for simultaneous quantitative determination of these drugs in their combined formulation. Method: TEN and EMT were individually isolated from their single formulations and purified by chromatography to obtain secondary standard. Purity of the isolates were tested for by comparison with literature values. Stock solution of chloranilic acid (CA) [3.0 × 10﹣3 M] was prepared in the following solvents of different polarities: ethanol, acetonitrile, ethylacetate, chloroform and hexane. Equal volumes of CA and TEN [3.0 × 10﹣2 M] and EMT [3.0 × 10﹣2 M] dissolved in different solvents were mixed whereby colored products were observed. Absorption maxima were determined. Calibration curves were generated and validated. Quantitative simultaneous determination of TEN and EMT was determined by standard protocol. Stoichiometric relationships between the drugs and CA were established. Equilibrium constants were determined at different temperatures from which the Gibb’s free energies were calculated. Arrhenius equation was used to calculate the enthalpy, entropy was similarly calculated. Results: Absorption maxima of CA in different solvents are as follows: Ethanol 310 nm;Acetonitrile 330 nm;Ethyl acetate 340 nm;Chloroform 350 nm and hexane 310 nm. The complex of CA and TEN in the different solvents are: Alcohol 525 nm, Acetonitrile 500 nm;Ethyl acetate 505 nm;Chloroform 510 nm and hexane 515 nm. For EMT complex absorption maxima are: Alcohol 510 nm;Acetonitrile 515 nm’ Ethyl acetate 520 nm’ Chloroform 505 nm and hexane 530 nm. Simultaneous quantitative recovery values for TEN are: Ethanol;97.89% ± 1.21;Acetonitrile 101.17 V 1.51%;Ethyl acetate 96.55% ± 0.71%;Chloroform 99.11% ± 0.34% and hexane 98.03% ± 0.15%. For EMT the values are also: Ethanol: 98.92% ± 1.45%;Acetonitrile 100.471 ± 13;Ethyl acetate 97.06% ± 0.87%;Chloroform 99.31% ± 0.94% and Hexane 99.97% ± 1.63%. Stoichiometry of complexation showed a 1:1 ratio for both drugs. Equilibrium constants for TEN were highest in acetonitrile and least for Ethanol while for EMT, equilibrium constant was least for acetonitrile and highest in chloroform. Gibb’s free energy for TEN was least in ethanol and highest in acetonitrile. Gibb’s free energy for EMT was least in acetonitrile and highest in chloroform. Enthalpy for TEN was least in chloroform and highest in hexane. Similarly, the enthalpy for EMT was highest in chloroform and lowest in hexane. Conclusion: These results shows that solvent polarity influence charge transfer complexes in a non consistent fashion. The structure of the donor might have contributed to thermodynamics of complexation since orbital overlap may vary from solvent to solvent. For quantitative analysis hexane appears to be the most suitable solvent because it has the highest molar absorptivity and higher enthalpy of interactions. Molecules that can donate electrons and their stereochemistry could contribute to intensity of absorption maxima of the electronic transitions.展开更多
In this study, we used potentiometric titration to investigate the interaction of the saprophytic fungus Trametes villosa in an aqueous environment. The study of this biological complex system allowed us to observe th...In this study, we used potentiometric titration to investigate the interaction of the saprophytic fungus Trametes villosa in an aqueous environment. The study of this biological complex system allowed us to observe the evolution of out-ofequilibrium hydrogen ion potential states after systematic perturbations. The responses of the complex system to perturbations were interpreted from relations that provided qualitative response patterns for mycelium in agreement with their basic structural and organizational characteristics. We consider this to be a transdisciplinary example of the behavior of general systems with thermodynamic properties of great ecological relevance, being specifically related to the negentropic properties of heterogeneous systems.展开更多
Recently, nitric oxide (NO) has been implicated as an epigenetic factor in keloids, a scarring disease occurring primarily in dark skinned people who have relatively high amounts of pigment melanin. In this work, we t...Recently, nitric oxide (NO) has been implicated as an epigenetic factor in keloids, a scarring disease occurring primarily in dark skinned people who have relatively high amounts of pigment melanin. In this work, we tested whether a melanin-mediated redox reaction involving adsorbed NO and O2 can couple NO oxidation with O2 reduction to form reactive oxygen species (ROS) or reactive nitrogen species (RNS) in vitro at pH 7.4. We measured the formation of reactive species that oxidize dihydrorhodamine123 (DHR) to fluorescent rhodamine123 in the presence and absence of sepia melanin. In separate experiments, we monitored NO concentration with 4,5-diaminofluorescein (DAF) by measuring the highly fluorescent NO-adduct, DAF-2T. We attempted to detect peroxynitrite with 5 μM 3-methyl-1,2-cyclopentanedione (MCP), a selective scavenger of peroxynitrite (IC50 = 3.6 μM for ONOO- vs. 63.8 μM and >> 100 μM for NO and O2- respectively). However, MCP itself oxidized DHR. We found that in the absence of NO, melanin itself oxidizes DHR, with no loss of DAF-fluorescence (i.e. no net consumption of NO). In the presence of NO, there was a ~ 57% loss of DAF fluorescence, indicating that NOx is formed at the expense of NO. The data provided good fit (r2 = 0.94) to a Langmuir adsorption isotherm, with pseudo first order rate k' = 8.2 × 107) s-1 and adsorption coefficient Kad = 4.04 M-1. Both of these parameters are consistent with a facile chemisorption reaction between NO and O2 on the melanin surface. Possible reactions are a) NO and O2- → ONOO- and/or b) 2NO + O2 → 2NO2. The latter reaction is disfavored in solution but is significantly accelerated on the melanin surface via an entropy effect.展开更多
<i><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">arica papaya</span><...<i><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">arica papaya</span></span></i><span style="font-family:Verdana;"> leaf extracts from four different extraction methods (cold-water</span><span style="font-family:Verdana;">, hot-water, sonication and supercritical fluid), were characterized using physico-chemical analysis. Sonication extraction showed the highest percentage yield of crude extracts (6.76%) and the lowest from the supercritical fluid extraction (1.83%). The Infrared (IR) spectrum of cold-water extract demonstrated the most similarity of functional group to </span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin. Likewise, the thermal analysis indicated that cold-water extract gave a quite similar Endothermic peak to </span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin with the obtained value</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> was 137</span><span style="font-family:Verdana;">°</span><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> and onset value </span></span><span style="font-family:Verdana;">which</span><span style="font-family:Verdana;"> was 118</span><span style="font-family:Verdana;">°</span><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">. The liquid chromatography (LC) profile indicated that only the cold-water extract exhibited 0.203 ppm of </span></span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin.</span>展开更多
Recently, the worldwide supply of rare earth element (REE) resources will be severely restricted. On the other hand, coal fly ash particles emitted from coal-fired electric power plants contain relatively high concent...Recently, the worldwide supply of rare earth element (REE) resources will be severely restricted. On the other hand, coal fly ash particles emitted from coal-fired electric power plants contain relatively high concentrations of REEs. The contents of REEs in coal fly ash are regularly several hundreds of ppmw. In order to extract and recover REEs from coal fly ash particles, as a first step, we have investigated their dissolution behavior in a dilute H2SO4 solvent. The REE content of coal fly ash specimens has been precisely determined, and their presence in the ash component of the original coal and their enrichment in coal fly ash particles during coal combustion have been suggested. REEs in coal fly ash dissolve gradually in H2SO4 over time, and this implies two types of occurrences of the REEs in coal fly ash particles. By applying the unreacted core model to the dissolution behavior of REEs in a H2SO4 solvent, we can explain both types of occurrences.展开更多
Many of the technology and computational chemistry applications are used to study drugs and their biological effects. Flutab®drug contains Paracetamol, Diphenhydramine and Pseudoephedrine. Ab-initio calculatio...Many of the technology and computational chemistry applications are used to study drugs and their biological effects. Flutab®drug contains Paracetamol, Diphenhydramine and Pseudoephedrine. Ab-initio calculations were performed at DFT/B3LYP and HF methods with three basis sets, namely, STO-3G, 3-21G, and 6-31G(d) in order to calculate the dipole moments of the three constituents of Flutab®drug. The Diphenhydramine compound was found to be the most stable constituent, with the lowest value of dipole moment.展开更多
文摘A simplified model is proposed for an easy understanding of the coarse-grained technique and for achieving a first approximation to the behavior of gases. A mole of a gas substance, within a cubic container, is represented by six particles symmetrically moving. The impacts of particles on container walls, the inter-particle collisions, as well as the volume of particles and the inter-particle attractive forces, obeying a Lennard-Jones curve, are taken into account. Thanks to the symmetry, the problem is reduced to the nonlinear dynamic analysis of a SDOF oscillator, which is numerically solved by a step-by-step time integration algorithm. Five applications of proposed model, on Carbon Dioxide, are presented: 1) Ideal gas in STP conditions. 2) Real gas in STP conditions. 3) Condensation for small molar volume. 4) Critical point. 5) Iso-kinetic energy curves and iso-therms in the critical point region. Results of the proposed model are compared with test data and results of the Van der Waals model for real gases.
文摘When writing equations of chemical dissociation, students and scholars are taught two fundamental rules to balance the equation. On both sides of the equation, the types of elements and their quantity are conserved, as well as the global electrical charge. This paper introduces additional methods during dissociation of gaseous compounds, to precisely describe how electrical charges locally move and how bonding structures are modified. Specific rules revolving around electrons pairs displacements are developed and applied to about 150 dissociations of small gaseous molecules using atoms from the three first rows of the periodic table. Results obtained tend to demonstrate the relevance of these tools for chemists.
文摘The mechanism of reaction of cyclic monoimides with oxiranes was established based upon kinetic studies and product analysis. It has been established that the reaction proceeds through initial formation of an adduct of imide and triethylamine. The crucial bond in adduct has ionic character;in non-aqueous solvents it is present as ion pair, while in water the adduct dissociate and free ions are present. The adduct enables the proton transfer from imide to oxirane. The rate determining step is reaction of imide and this adduct. Different values of entropy of transition states obtained from thermodynamic calculations suggest slightly different structure of transition state of rate determining step.
文摘Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT) calculations indicated that absorption peak at 238 nm was mainly due to excitation of electrons from the linear chain structure Adda of microcystin-LR. Irradiation of microcystin-LR with UV light resulted in the reduction of the 238 nm absorption peak and the appearance of a new peak at 300 nm. Density functional theory (DFT) and TDDFT calculations with a model molecule suggested that this 300 nm peak was due to tricyclo-Adda microcystin-LR, an intermediate in photochemical reactions of microcystin-LR. Analysis of the rate of this photochemical reaction showed that it was a first order reaction.
文摘We performed density functional theory (DFT) calculations for ribonucleotides and active triphosphate metabolites of candidate drugs against Coronavirus disease 2019 (Covid-19). Frontier orbitals (highest occupied molecular orbital and lowest unoccupied molecular</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">orbital) at optimized structure of each molecule were obtained. T-705RTP (active triphosphate metabolite of favipiravir) and cytidine triphosphate (CTP) have similar shapes of frontier orbitals. We also obtained similar shapes of frontier orbitals among dihydroxy GS-441524 triphosphate (GS-441524 is an active triphosphate metabolite of remdesivir) and adenosine triphosphate (ATP). From a theoretical </span><span style="font-family:Verdana;">viewpoint, we suggest T-705RTP is a CTP analogue and dihydroxy GS-441524</span><span style="font-family:Verdana;"> triphosphate is an</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">ATP analogue.
文摘It is currently admitted that the intermolecular forces implicated in Gas Liquid Chromatography (GLC) can be expressed as a product of parameters (or descriptors) of solutes and of parameters of solvents. The present study is limited to those of solutes, and among them the three ones are involved in the Van der Waals forces, whereas the two ones involved in the hydrogen bonding are left aside at this stage. These three studied parameters, which we call δ, ω and ε, respectively reflect the three types of Van der Waals forces: dispersion, orientation or polarity strictly speaking, and induction-polarizability. These parameters have been experimentally obtained in previous studies for 121 Volatile Organic Compounds (VOC) via an original Multiplicative Matrix Analysis (MMA) applied to a superabundant and accurate GLC data set. Then, also in previous studies, attempts have been made to predict these parameters via a Simplified Molecular Topology procedure (SMT). Because these last published results have been somewhat disappointing, a promising new strategy of prediction is developed and detailed in the present article.
文摘Experiments described in this paper show that there is the photoconductive effect of liquid, i.e. when light shines into a sort of alkali, acid or salt solution, the conductivity of the solution will increase. The mechanism of the effect is explained as follows. When hydrated ions in the solution absorb photons with their high enough energies, they will decompose to naked ions and water-molecules. The naked ions can reach an anode or a cathode more easily and faster than the hydrated ions;It is possible that when a molecule in the solution absorbs a photon with its high enough energy, it will decompose to negative and positive ions. Based on the effect, a device producing hydrogen by the solar-energy had been devised.
文摘Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.
文摘Oxidation kinetics of fluorene (Fl) and its halogenated derivatives, namely, 2,7-dichlorofluorene (Fl-Cl), 2,7-dibromofluorene (Fl-Br) and 2,7-diiodofluorene (Fl-I), by permanganate ion in both perchloric and sulfuric acid media have been investigated using conventional spectrophotometric technique. In both acidic media, the reactions manifested first order kineticsin [permanganate] and less than unit order each in [reductants] and [acid]. Increasing ionic strength had no effect on the oxidation rates. Oxidation rates of fluorenes in perchloric acid were higher than those in sulfuric acid and the order of the oxidation rates was: Fl > Fl-I > Fl-Br > Fl-Cl. Final oxidation products were identified by GC/MS and FT-IR analyses in all cases as 9H-fluorenone derivatives. Reaction constants as well as activation parameters of the second order rate constants were also evaluated.
文摘A redshift in the wavelength of excitation spectra is experimentally measured as a function of the concentration parameter for tryptophan solutions in water. To understand the microscopic causes of this behavior, theoretical calculations obtained from four model clusters are carried out: (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">1</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">9</span></sub><span style="font-family:Verdana;">, (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">2</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">18</span></sub><span style="font-family:Verdana;">, (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">3</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">27</span></sub><span style="font-family:Verdana;"> and (</span></span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Trp</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">4</span></sub> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> (</span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">H</span></i><sub><span style="font-family:Verdana;">2</span></sub><i><span style="font-family:Verdana;">O</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:""><span style="font-family:Verdana;">)</span><sub><span style="font-family:Verdana;">36</span></sub><span style="font-family:Verdana;">, where there are interactions among 1, 2, 3 and 4 molecules of tryptophan. According to the literature, each interaction occurred with nine molecules of water to stabilize its expected zwitterionic form. In these models, the molecules of tryptophan appear at an adjacent distance among them to generate an analogous behavior when there is an experimental increase in the concentration. It is evident that </span><span style="font-family:Verdana;">the distance between adjacent molecules of tryptophan decreases as their concentration</span><span style="font-family:Verdana;"> increases. The optical properties of these clusters are obtained by studying the corresponding excited states and the molecular orbitals involved, showing charge transfers by using time-dependent density functional theory (TD-DFT) methods. The experimental spectroscopic data are obtained by using the clusters proposed, and good agreement is found by drawing a comparison with the theoretical data</span></span><span style="font-family:Verdana;">.
文摘MoO<sub>3</sub> and 5% MoO<sub>3</sub>/ZnO were prepared by impregnation method using (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub>, 4H<sub>2</sub>O as precursor and ZnO as support. The prepared samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), infra red (FTIR) <span style="font-family:;" "="">and</span><span style="font-family:;" "=""> UV-Vis diffuse reflectance (DRS)</span><span> </span><span style="font-family:;" "="">spectroscopies and pho<span>to-electrochemistry. The XRD pattern showed that the MoO<sub>3</sub> powder treated at 700°C is a single-phase crystallizing in an orthorhombic structure with a direct optical transition </span></span><span style="font-family:;" "="">(</span><span style="font-family:;" "="">2.70 eV</span><span style="font-family:;" "="">)</span><span style="font-family:;" "="">. The hetero-junction 5% MoO<sub>3</sub>/ZnO</span><span style="font-family:;" "=""> was photo-electrochemically characterized to assess its feasibility for H<sub>2</sub> production under visible light. The capacitance potential (<i>C<sup>-</sup></i><sup>2</sup><i> f</i>(<i>E</i>)) characteristic of MoO<sub>3</sub> plotted in Na<sub>2</sub>SO<sub>4</sub>, (0.1 M) electrolyte indicates <i>n-</i>type conduction with a flat band potential of -</span><span style="font-family:;" "=""><span>0.54 V<i><sub>SCE</sub></i>. The photocatalytic activity was performed for the photoreduction of water to hydrogen under visible light illumination. The best performance occurs at pH ~ 7 with an evolved volume of 5.9 mL.</span></span>
基金Elements of the project are financed by the European Commission’s Framework Program 7(BIO-NMR-00007)-Bio-NMR grant:Jellyfish protein NMR(BIO-NMR-00007)-IEP.
文摘Proteoglycans and collagen molecules are interacting with each other thereby forming various connective tissues. The sulfation pattern of proteoglycans differs depending on the kind of tissue and/or the degree of maturation. Tissues from Cnidaria are suitable examples for exploration of the effects in relation to the presence and the absence of sulfate groups, when studying characteristic fragments of the long proteoglycan carbohydrate chains in silico. It has been described that a non-sulfated chondroitin appears as a scaffold in early morphogenesis of all nematocyst types in Hydra. On the other hand, sulfated glucosaminoglycans play an important role in various developmental processes of Cnidaria. In order to understand this biological phenomenon on a sub-molecular level we have analysed the structures of sulfated and non-sulfated proteoglycan carbohydrate chains as well as the structure of diverse collagen molecules with computational methods including quantum chemical calculations. The strong interactions between the sulfate groups of the carbohydrates moieties in proteoglycans and positively charged regions of collagen are essential in stabilizing various Cnidaria tissues but could hinder the nematocyst formation and its proper function. The results of our quantum chemical calculations show that the sulfation pattern has a significant effect on the conformation of chondroitin structures under study.
文摘A comprehensive investigation on the formation mechanism of gold nanoparticles (AuNPs) in colloidal mixture obtained from the reduction of chloroauric acid (HAuCl4) solution using a single reducing agent (sodium citrate;process-I), (tannic acid;process-II), and a combination of two reducing agents (sodium citrate plus tannic acid;process-III) is reported. The growth steps at different time intervals during synthesis of colloidal AuNPs were monitored in situ and ex situ using various methods for all the three processes. The measurement of changes in the surface plasmon band position of colloidal AuNPs, along with dynamic light scattering results gave important information for the first assessing of particle size, shape and distribution. Besides, the size and morphological changes at different stages during different processes were also analyzed by transmission electron microscopy. The final Au particles of processes-I & II exhibited different shapes (spherical and nanowires) with particle size and nano wire diameter of 12 nm and 17 nm, respectively. Nevertheless, combination of two reductants (process-III) surprisingly leads to drastically reduced size (ca. 3 nm) with spherical morphology compared to their parent solutions with either of single reducing agent. This result clearly indicates that the combination of reductants has a significant influence on the particle size, morphology and formation mechanism.
基金All authors thank the Agence Universitaire de la Fran-cophonie(AUF)for financial support(PCSI 59113PS 014)Professor Jean-François Verchère from the University of Rouen(France)for his advice,fruitful dis-cussions,strong encouragement and exemplary coopera-tion.
文摘The technique of supported liquid membranes was used to achieve the facilitated transport of Cr(III) ions, using tow amphiphilic carriers, the methyl cholate and resorcinarene. For prepared SLMs, toluene as organic phase and film of polyvinylidene difluoride, as hydrophobic polymer support with 100 μm in thickness and 0.45 μm as the diameter of the pores. The macroscopic parameters (P and J0) on the transport of these ions were determined for different medium temperatures. For these different environments, the prepared SLMs were highly permeable and a clear evolution of these parameters was observed. The parameter J0 depended on the temperature according to the Arrhenius equation. The activation parameters, Ea, ΔH≠ and ΔS≠, for the transition state on the reaction of complex formation (ST) , were determined. To explain these results for this phenomenon, and achieve a better extraction of the substrate, a model based on the substrate complexation by the carrier and the diffusion of the formed complex (ST) was developed. The experimental results verify this model and determine the microscopic parameters (Kass and D*). These studies show that these parameters Kass and D* are specific to facilitated transport of Cr(III) ions by each of the carriers and they are changing significantly with temperature.
文摘Purpose: Tenofovir disoproxil fumarate (TEN) and emtricitabine (EMT) are both second generation ant-retroviral drugs used in the “treatment” of HIV/AIDS. The aim of this study is to establish the physic-chemical properties of their reaction with chloranilic acid in different solvent systems and to justify the chemical basis for simultaneous quantitative determination of these drugs in their combined formulation. Method: TEN and EMT were individually isolated from their single formulations and purified by chromatography to obtain secondary standard. Purity of the isolates were tested for by comparison with literature values. Stock solution of chloranilic acid (CA) [3.0 × 10﹣3 M] was prepared in the following solvents of different polarities: ethanol, acetonitrile, ethylacetate, chloroform and hexane. Equal volumes of CA and TEN [3.0 × 10﹣2 M] and EMT [3.0 × 10﹣2 M] dissolved in different solvents were mixed whereby colored products were observed. Absorption maxima were determined. Calibration curves were generated and validated. Quantitative simultaneous determination of TEN and EMT was determined by standard protocol. Stoichiometric relationships between the drugs and CA were established. Equilibrium constants were determined at different temperatures from which the Gibb’s free energies were calculated. Arrhenius equation was used to calculate the enthalpy, entropy was similarly calculated. Results: Absorption maxima of CA in different solvents are as follows: Ethanol 310 nm;Acetonitrile 330 nm;Ethyl acetate 340 nm;Chloroform 350 nm and hexane 310 nm. The complex of CA and TEN in the different solvents are: Alcohol 525 nm, Acetonitrile 500 nm;Ethyl acetate 505 nm;Chloroform 510 nm and hexane 515 nm. For EMT complex absorption maxima are: Alcohol 510 nm;Acetonitrile 515 nm’ Ethyl acetate 520 nm’ Chloroform 505 nm and hexane 530 nm. Simultaneous quantitative recovery values for TEN are: Ethanol;97.89% ± 1.21;Acetonitrile 101.17 V 1.51%;Ethyl acetate 96.55% ± 0.71%;Chloroform 99.11% ± 0.34% and hexane 98.03% ± 0.15%. For EMT the values are also: Ethanol: 98.92% ± 1.45%;Acetonitrile 100.471 ± 13;Ethyl acetate 97.06% ± 0.87%;Chloroform 99.31% ± 0.94% and Hexane 99.97% ± 1.63%. Stoichiometry of complexation showed a 1:1 ratio for both drugs. Equilibrium constants for TEN were highest in acetonitrile and least for Ethanol while for EMT, equilibrium constant was least for acetonitrile and highest in chloroform. Gibb’s free energy for TEN was least in ethanol and highest in acetonitrile. Gibb’s free energy for EMT was least in acetonitrile and highest in chloroform. Enthalpy for TEN was least in chloroform and highest in hexane. Similarly, the enthalpy for EMT was highest in chloroform and lowest in hexane. Conclusion: These results shows that solvent polarity influence charge transfer complexes in a non consistent fashion. The structure of the donor might have contributed to thermodynamics of complexation since orbital overlap may vary from solvent to solvent. For quantitative analysis hexane appears to be the most suitable solvent because it has the highest molar absorptivity and higher enthalpy of interactions. Molecules that can donate electrons and their stereochemistry could contribute to intensity of absorption maxima of the electronic transitions.
文摘In this study, we used potentiometric titration to investigate the interaction of the saprophytic fungus Trametes villosa in an aqueous environment. The study of this biological complex system allowed us to observe the evolution of out-ofequilibrium hydrogen ion potential states after systematic perturbations. The responses of the complex system to perturbations were interpreted from relations that provided qualitative response patterns for mycelium in agreement with their basic structural and organizational characteristics. We consider this to be a transdisciplinary example of the behavior of general systems with thermodynamic properties of great ecological relevance, being specifically related to the negentropic properties of heterogeneous systems.
文摘Recently, nitric oxide (NO) has been implicated as an epigenetic factor in keloids, a scarring disease occurring primarily in dark skinned people who have relatively high amounts of pigment melanin. In this work, we tested whether a melanin-mediated redox reaction involving adsorbed NO and O2 can couple NO oxidation with O2 reduction to form reactive oxygen species (ROS) or reactive nitrogen species (RNS) in vitro at pH 7.4. We measured the formation of reactive species that oxidize dihydrorhodamine123 (DHR) to fluorescent rhodamine123 in the presence and absence of sepia melanin. In separate experiments, we monitored NO concentration with 4,5-diaminofluorescein (DAF) by measuring the highly fluorescent NO-adduct, DAF-2T. We attempted to detect peroxynitrite with 5 μM 3-methyl-1,2-cyclopentanedione (MCP), a selective scavenger of peroxynitrite (IC50 = 3.6 μM for ONOO- vs. 63.8 μM and >> 100 μM for NO and O2- respectively). However, MCP itself oxidized DHR. We found that in the absence of NO, melanin itself oxidizes DHR, with no loss of DAF-fluorescence (i.e. no net consumption of NO). In the presence of NO, there was a ~ 57% loss of DAF fluorescence, indicating that NOx is formed at the expense of NO. The data provided good fit (r2 = 0.94) to a Langmuir adsorption isotherm, with pseudo first order rate k' = 8.2 × 107) s-1 and adsorption coefficient Kad = 4.04 M-1. Both of these parameters are consistent with a facile chemisorption reaction between NO and O2 on the melanin surface. Possible reactions are a) NO and O2- → ONOO- and/or b) 2NO + O2 → 2NO2. The latter reaction is disfavored in solution but is significantly accelerated on the melanin surface via an entropy effect.
文摘<i><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">arica papaya</span></span></i><span style="font-family:Verdana;"> leaf extracts from four different extraction methods (cold-water</span><span style="font-family:Verdana;">, hot-water, sonication and supercritical fluid), were characterized using physico-chemical analysis. Sonication extraction showed the highest percentage yield of crude extracts (6.76%) and the lowest from the supercritical fluid extraction (1.83%). The Infrared (IR) spectrum of cold-water extract demonstrated the most similarity of functional group to </span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin. Likewise, the thermal analysis indicated that cold-water extract gave a quite similar Endothermic peak to </span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin with the obtained value</span><span style="font-family:Verdana;"> which</span><span style="font-family:Verdana;"> was 137</span><span style="font-family:Verdana;">°</span><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;"> and onset value </span></span><span style="font-family:Verdana;">which</span><span style="font-family:Verdana;"> was 118</span><span style="font-family:Verdana;">°</span><span style="font-family:;" "=""><span style="font-family:Verdana;">C</span><span style="font-family:Verdana;">. The liquid chromatography (LC) profile indicated that only the cold-water extract exhibited 0.203 ppm of </span></span><span style="font-family:Verdana;">q</span><span style="font-family:Verdana;">uercetin.</span>
文摘Recently, the worldwide supply of rare earth element (REE) resources will be severely restricted. On the other hand, coal fly ash particles emitted from coal-fired electric power plants contain relatively high concentrations of REEs. The contents of REEs in coal fly ash are regularly several hundreds of ppmw. In order to extract and recover REEs from coal fly ash particles, as a first step, we have investigated their dissolution behavior in a dilute H2SO4 solvent. The REE content of coal fly ash specimens has been precisely determined, and their presence in the ash component of the original coal and their enrichment in coal fly ash particles during coal combustion have been suggested. REEs in coal fly ash dissolve gradually in H2SO4 over time, and this implies two types of occurrences of the REEs in coal fly ash particles. By applying the unreacted core model to the dissolution behavior of REEs in a H2SO4 solvent, we can explain both types of occurrences.
文摘Many of the technology and computational chemistry applications are used to study drugs and their biological effects. Flutab®drug contains Paracetamol, Diphenhydramine and Pseudoephedrine. Ab-initio calculations were performed at DFT/B3LYP and HF methods with three basis sets, namely, STO-3G, 3-21G, and 6-31G(d) in order to calculate the dipole moments of the three constituents of Flutab®drug. The Diphenhydramine compound was found to be the most stable constituent, with the lowest value of dipole moment.
