scholarly journals Stoichiometric Ratio in Calixarene Complexes

10.5772/32984 ◽  
2012 ◽  
Author(s):  
Flor de Mara Ramrez ◽  
Irma Garca-Sos
Keyword(s):  
Stoichiometric Ratio

Void-Lattice Formation in Natural Fluorite by Electron Irradiation

1976 ◽  
Vol 34 ◽  
pp. 614-615 ◽  
Author(s):  
L.E. Murr
Keyword(s):  
Electron Microscope ◽  
Electron Irradiation ◽  
Heavy Ion ◽  
High Energy ◽  
Stoichiometric Ratio ◽  
Direct Observations ◽  
Transmission Electron ◽  
Anion Vacancies ◽  
Cation And Anion Vacancies ◽  
Lattice Formation

The production of void lattices in metals as a result of displacement damage associated with high energy and heavy ion bombardment is now well documented. More recently, Murr has shown that a void lattice can be developed in natural (colored) fluorites observed in the transmission electron microscope. These were the first observations of a void lattice in an irradiated nonmetal, and the first, direct observations of color-center aggregates. Clinard, et al. have also recently observed a void lattice (described as a high density of aligned "pores") in neutron irradiated Al2O3 and Y2O3. In this latter work, itwas pointed out that in order that a cavity be formed,a near-stoichiometric ratio of cation and anion vacancies must aggregate. It was reasoned that two other alternatives to explain the pores were cation metal colloids and highpressure anion gas bubbles.Evans has proposed that void lattices result from the presence of a pre-existing impurity lattice, and predicted that the formation of a void lattice should restrict swelling in irradiated materials because it represents a state of saturation.

Synthesis and Structural Studies of Bismuth-piroxicam Complex

2018 ◽  
Vol 69 (7) ◽  
pp. 1702-1705
Author(s):  
Ayesha Kanwal ◽  
Muhammad Imran ◽  
Zafar Iqbal ◽  
Summia Rehman ◽  
Zeeshan Danish ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Bismuth Nitrate ◽  
Stoichiometric Ratio ◽  
Structural Studies ◽  
Ambient Conditions ◽  
Analgesic Drug ◽  
Photoluminescent Property ◽  
Chemically Modified ◽  
Bismuth Complex ◽  
Luminescent Behavior

Piroxicam [4-hydroxy-2-methyl-N-2-(pyridyl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide] is an effective antiinflammatory analgesic drug. In the present work, piroxicam has been chemically modified into its bismuth complex by reacting it with bismuth nitrate at ambient conditions and optimized stoichiometric ratio. The synthesis of the complex has been monitored by TLC and characterized well by Fourier Transform Infrared (FTIR), UV-Vis, ICP, TGA, XRD and SEM. The luminescent behavior of this complex has also been studied which determined its photoluminescent property.

Nevirapine Pharmaceutical Cocrystal: Design, Development and Formulation

2019 ◽  
Vol 9 (3) ◽  
pp. 240-247
Author(s):  
Prabhakar Panzade ◽  
Priyanka Somani ◽  
Pavan Rathi
Keyword(s):  
Dosage Form ◽  
In Vitro Dissolution ◽  
Soluble Form ◽  
Ir Absorption ◽  
Stoichiometric Ratio ◽  
Design Development ◽  
Formulation Development ◽  
Scanning Calorimetry ◽  
Absorption Bands ◽  
Pharmaceutical Cocrystal

Background and Objective: The top approach to deliver poorly soluble drugs is the use of a highly soluble form. The present study was conducted to enhance the solubility and dissolution of a poorly aqueous soluble drug nevirapine via a pharmaceutical cocrystal. Another objective of the study was to check the potential of the nevirapine cocrystal in the dosage form. Methods: A neat and liquid assisted grinding method was employed to prepare nevirapine cocrystals in a 1:1 and 1:2 stoichiometric ratio of drug:coformer by screening various coformers. The prepared cocrystals were preliminary investigated for melting point and saturation solubility. The selected cocrystal was further confirmed by Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC), and Xray Powder Diffraction (XRPD). Further, the cocrystal was subjected to in vitro dissolution study and formulation development. Results: The cocrystal of Nevirapine (NVP) with Para-Amino Benzoic Acid (PABA) coformer prepared by neat grinding in 1:2 ratio exhibited greater solubility. The shifts in IR absorption bands, alterations in DSC thermogram, and distinct XRPD pattern showed the formation of the NVP-PABA cocrystal. Dissolution of NVP-PABA cocrystal enhanced by 38% in 0.1N HCl. Immediate release tablets of NVP-PABA cocrystal exhibited better drug release and less disintegration time. Conclusion: A remarkable increase in the solubility and dissolution of NVP was obtained through the cocrystal with PABA. The cocrystal also showed great potential in the dosage form which may provide future direction for other drugs.

Preliminary Studies on Non-Reactive Flow Vortex Cooling

2019 ◽  
Vol 12 (3) ◽  
pp. 262-271
Author(s):  
T.N. Rajesh ◽  
T.J.S. Jothi ◽  
T. Jayachandran
Keyword(s):  
Combustion Chamber ◽  
Inner Core ◽  
Rocket Engine ◽  
Injection Pressure ◽  
Chamber Pressure ◽  
Reactive Flow ◽  
Stoichiometric Ratio ◽  
Gaseous Oxygen ◽  
Mixture Ratio ◽  
Vortex Combustion

Background: The impulse for the propulsion of a rocket engine is obtained from the combustion of propellant mixture inside the combustion chamber and as the plume exhausts through a convergent- divergent nozzle. At stoichiometric ratio, the temperature inside the combustion chamber can be as high as 3500K. Thus, effective cooling of the thrust chamber becomes an essential criterion while designing a rocket engine. Objective: A new cooling method of thrust chambers was introduced by Chiaverni, which is termed as Vortex Combustion Cold-Wall Chamber (VCCW). The patent works on cyclone separators and confined vortex flow mechanism for providing high propellant mixing with improved degree of turbulence inside the combustion chamber, providing the required notion for studies on VCCW. The flow inside a VCCW has a complex structure characterised by axial pressure losses, swirl velocities, centrifugal force, flow reversal and strong turbulence. In order to study the flow phenomenon, both the experimental and numerical investigations are carried out. Methods: In this study, non-reactive flow analysis was conducted with real propellants like gaseous oxygen and hydrogen. The test was conducted to analyse the influence of mixture ratio and injection pressure of the propellants on the chamber pressure in a vortex combustion chamber. A vortex combustor was designed in which the oxidiser injected tangentially at the aft end near the nozzle spiraled up to the top plate and formed an inner core inside the chamber. The fuel was injected radially from injectors provided near the top plate and the propellants were mixed in the inner core. This resulted in enhanced mixing and increased residence time for the fuel. More information on the flow behaviour has been obtained by numerical analysis in Fluent. The test also investigated the sensitivity of the tangential injection pressure on the chamber pressure development. Results: All the test cases showed an increase in chamber pressure with the mixture ratio and injection pressure of the propellants. The maximum chamber pressure was found to be 3.8 bar at PC1 and 2.7 bar at PC2 when oxidiser to fuel ratio was 6.87. There was a reduction in chamber pressure of 1.1 bar and 0.7 bar at PC1 and PC2, respectively, in both the cases when hydrogen was injected. A small variation in the pressure of the propellant injected tangentially made a pronounced effect on the chamber pressure and hence vortex combustion chamber was found to be very sensitive to the tangential injection pressure. Conclusion: VCCW mechanism has been to be found to be very effective for keeping the chamber surface within the permissible limit and also reducing the payload of the space vehicle.

Binding of lead and copper(II) cations to hemicelluloses of rye bran

1986 ◽  
Vol 51 (10) ◽  
pp. 2250-2258 ◽  
Author(s):  
Rudolf Kohn ◽  
Zdena Hromádková ◽  
Anna Ebringerová
Keyword(s):  
Uronic Acid ◽  
Equilibrium Solution ◽  
Glucuronic Acid ◽  
The Other ◽  
Carboxyl Groups ◽  
Stoichiometric Ratio ◽  
Molar Ratios ◽  
Free Ions ◽  
Uronic Acid Content ◽  
The Relationship

Several fractions of acid hemicelluloses isolated from rye bran were characterized by molar ratios of saccharides (D-Xyl, L-Ara, D-Glc, D-Gal) and 4-O-methyl-D-glucuronic acid and protein content. Binding of Pb2+ and Cu2+ ions to these acid polysaccharides was considered according to function (M)b = f([M2+]f), expressing the relationship between the amount of metal (M)b bound to 1 g of the substance and the concentration of free ions [M2+]f in the equilibrium solution and according to the association degree β of these cations with carboxyl groups of uronic acid at a stoichiometric ratio of both components in the system under investigation. Acid hemicelluloses contained only a very small portion of uronic acid ((COOH) 0.05-0.18 mmol g-1); the model polysaccharide, 4-O-methyl-D-glucurono-D-xylan of beech, was substantially richer in uronic acid content ((COOH) 0.73 mmol g-1). Consequently, the amount of lead and copper bound to acid hemicelluloses is very small ((M)b 0.017-0.025 mmol g-1) at [M2+]f = 0.10 mmol l-1. On the other hand, much greater amount of cations ((M)f 0.09-0.10 mmol g-1) was bound to the glucuronoxylan. The association degree β was like with the majority of samples (β = 0.31-0.38). The amount of lead and copper(II) bound to acid hemicelluloses from rye bran is several times lower than that bound to dietary fiber isolated from vegetables (cabbage, carrot), rich in pectic substances.

Investigation of the products of carbothermal reduction of yttrium oxide by the hydrolysis method

1984 ◽  
Vol 49 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Bohumil Hájek ◽  
Pavel Karen ◽  
Vlastimil Brožek
Keyword(s):  
Yttrium Oxide ◽  
Carbothermal Reduction ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Method ◽  
Sample Decomposition ◽  
Products Of Reaction ◽  
Hydrolysis Of ◽  
Lower Carbon

For the investigation of the products of reaction of yttrium oxide with carbon mixed in various proportions, the chemical and X-ray diffraction methods of analysis were combined with the gas chromatographic analysis of the mixture of hydrocarbons and hydrogen formed on the sample decomposition with water. The carboreduction of Y2O3 was examined at relatively low temperatures, convenient for obtaining the reaction intermediates in higher yields. At 1 600 °C and pressures of 10-3 Pa the reduction of a mixture of Y2O3 with carbon in a stoichiometric ratio of 1 : 7 yields YC2 in equilibrium with 20% of Y2OC phase. At lower carbon contents (down to the Y2O3 : C ratio of 1 : 2) tha fraction of the Y2OC phase increases up to approximately 30%. In addition to Y2O3, the reaction mixture contains also Y2C, Y2OC and a phase giving propyne on hydrolysis. The presence of traces of C3 hydrocarbons and small amounts of methane in the product of hydrolysis of the carbide sample prepared by the carbothermal reduction of the oxide can be explained in terms of the occurrence of the Y15C19 phase, probably substituted in part by oxygen, and of the Y2OC phase. The results are compared with those obtained previously for the Sc2O3 + C system.

Facile fabrication of Tl4HgI6 nanostructures as a novel antibacterial and antibiofilm agent and photocatalyst in degradation of organic pollutants

2021 ◽  
Author(s):  
Maryam Karami ◽  
Mojgan Ghanbari ◽  
Hassan Abbas Alshamsi ◽  
Somaye Rashki ◽  
Masoud Salavati-Niasari
Keyword(s):  
Organic Pollutants ◽  
Stoichiometric Ratio ◽  
Facile Fabrication ◽  
The Impact

In the present study, Tl4HgI6 nanostructures have been successfully fabricated through a simple precipitation route. The impact of TlI stoichiometric ratio to HgI2, and kind of surfactants was explored on...

scholarly journals Nutrient and Stoichiometric Characteristics of Aggregates in a Sloping Farmland Area under Different Tillage Practices

2021 ◽  
Vol 13 (2) ◽  
pp. 890
Author(s):  
Jie Zhang ◽  
Yaojun Liu ◽  
Taihui Zheng ◽  
Xiaomin Zhao ◽  
Hongguang Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Size Distribution ◽  
Soil Aggregates ◽  
Soil Aggregate ◽  
Elemental Content ◽  
Stoichiometric Ratio ◽  
Longitudinal Ridge ◽  
Stoichiometric Ratios ◽  
Sloping Farmland ◽  
Ridge Tillage

Sloping farmland is prevalent in hilly red soil areas of South China. Improper tillage patterns induce decreased soil organic matter, soil aggregate breakdown, and nutrient imbalance, thereby restricting crop production. However, the stoichiometric characteristics could reflect the nutrient availability which was mostly studied on bulk soil. The stoichiometric characteristics of soil aggregates with multiple functions in farmlands has rarely been studied. The study was to reveal the impact of tillage patterns on the size distribution, nutrient levels, and stoichiometric ratios of soil aggregates after 20 years’ cultivation. Soil samples of 0–20 cm and 20–40 cm from five tillage patterns, bare-land control (BL), longitudinal-ridge tillage (LR), conventional tillage + straw mulching (CS), cross-ridge tillage (CR), and longitudinal-ridge tillage + hedgerows (LH) were collected. The elemental content (C, N and P) and soil aggregate size distribution were determined, and the stoichiometric ratios were subsequently calculated. Through our analysis and study, it was found that the nutrient content of >2 mm soil aggregates in all plots was the highest. In the hedgerow plots, >2 mm water-stable soil aggregate content was increased. Therefore, LH plots have the highest content of organic matter and nutrients. After 20 years of cultivation, stoichiometric ratio of each plot showed different changes on soil aggregates at different levels. the C:N, C:P, and N:P ratios are lower than the national average of cultivated land. Among of them, the stoichiometric ratio in the LH plot is closer to the mean and showed better water-stable aggregate enhancement. Therefore, longitudinal-ridge tillage + hedgerows can be recommended as a cultivation measure. This study provides a reference for determining appropriate tillage measures, balancing nutrient ratios, and implementing rational fertilization.

scholarly journals Preparation of Nanoparticle Porous-Structured BiVO4 Photoanodes by a New Two-Step Electrochemical Deposition Method for Water Splitting

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 136
Author(s):  
SocMan Ho-Kimura ◽  
Wasusate Soontornchaiyakul ◽  
Yuichi Yamaguchi ◽  
Akihiko Kudo
Keyword(s):  
Water Splitting ◽  
Electrochemical Deposition ◽  
Synthesis Method ◽  
Stoichiometric Ratio ◽  
Deposition Method ◽  
Hydrogen Electrode ◽  
Faradaic Efficiency ◽  
Xrd Pattern ◽  
Conversion Reaction ◽  
Electrochemical Deposition Method

In the synthesis method of a BiVO4 photoanode via BiOI flakes, a BiOI film is formed by electrochemical deposition in Step 1, and a vanadium (V) source solution is placed by drop-casting on the BiOI film in Step 2. Following this, BiVO4 particles are converted from the BiOI–(V species) precursors by annealing. However, it is challenging to evenly distribute vanadium species among the BiOI flakes. As a result, the conversion reaction to form BiVO4 does not proceed simultaneously and uniformly. To address this limitation, in Step 2, we developed a new electrochemical deposition method that allowed the even distribution of V2O5 among Bi–O–I flakes to enhance the conversion reaction uniformly. Furthermore, when lactic acid was added to the electrodeposition bath solution, BiVO4 crystals with an increased (040) peak intensity of the X-ray diffractometer (XRD) pattern were obtained. The photocurrent of the BiVO4 photoanode was 2.2 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) under solar simulated light of 100 mW/cm2 illumination. The Faradaic efficiency of oxygen evolution was close to 100%. In addition, overall water splitting was performed using a Ru/SrTiO3:Rh–BiVO4 photocatalyst sheet prepared by the BiVO4 synthesis method. The corresponding hydrogen and oxygen were produced in a 2:1 stoichiometric ratio under visible light irradiation.

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