Role Of Experimental Conditions Research Articles

Kinetics of free fatty acids esterification in waste frying oil using novel carbon-based acid heterogeneous catalyst derived from Amazonian Açaí seeds – Role of experimental conditions on a simpler pseudo first-order reaction mechanism

This study reports the kinetics of free fatty acids esterification in waste frying oil, based on a simpler non-conventional pseudo first-order homogeneous reaction mechanism using a highly-efficient acid heterogeneous catalyst derived from seeds of Açaí (Euterpe oleracea Mart.), subjected to changes in temperature, catalyst dosage, MeOH:Oil ratio, and stirring speed. Statistical analyses revealed significant effects all four conditions (p < .05) on the reaction's apparent rate constant (k1) over their different pre-defined levels. Reaction mechanism was inferred to be fundamentally acid ionic exchanges with the oil/water film on catalyst's surface, neglecting kinetically controlled liquid-to-liquid splitting and autocatalyzed esterification.

Chitosan Nanoparticles as Potential Nano-Sorbent for Removal of Toxic Environmental Pollutants.

Adsorption is the most widely used technique for advanced wastewater treatment. The preparation and application of natural renewable and environmentally friendly materials makes this process easier and more profitable. Chitosan is often used as an effective biomaterial in the adsorption world because of its numerous functional applications. Chitosan is one of the most suitable and functionally flexible adsorbents because it contains hydroxyl (-OH) and amine (-NH2) groups. The adsorption capacity and selectivity of chitosan can be further improved by introducing additional functions into its basic structure. Owing to its unique surface properties and adsorption ability of chitosan, the development and application of chitosan nanomaterials has gained significant attention. Here, recent research on chitosan nanoparticles is critically reviewed by comparing various methods for their synthesis with particular emphasis on the role of experimental conditions, limitations, and applications in water and wastewater treatment. The recovery of pollutants using magnetic nanoparticles is an important treatment process that has contributed to additional development and sustainable growth. The application of such nanoparticles in the recovery metals, which demonstrates a "close loop technology" in the current scenarios, is also presented in this review.

Role of Mechanochemistry in Solid Form Selection and Identification of the Drug Praziquantel

Identification of all possible polymorphs for a pharmaceutical compound is vital for the better formulation of medicine with desired properties. This study demonstrates the application of a mechanochemical approach to reveal new polymorphs of a drug and the potential of variable amounts of solvent in liquid-assisted grinding for solid form screening. Without solvent and by varying the amount of solvent added, we found two new polymorphs and an amorphous form, which were not reported previously. The finding portrays the advantage of the mechanochemical approach as a means of the polymorph screening strategy. While the focus here was on praziquantel, a similar approach is applicable to other pharmaceutical systems. This study also contributed to reinvestigate the solid-state behavior of the chiral praziquantel system, including the melt phase diagram and the role of experimental conditions on its phase behavior.

Heterocyclic-2-thione derivatives of group 10–12 metals: Coordination versatility, activation of C S (thione) bonds and biochemical potential

Heterocyclic thione derivatives of group 10–12 metals (Ni-Pt, Cu-Au, Zn-Hg) are reviewed in this article. A survey of relatively recent coordination compounds of these metals are described with selective heterocyclic thiones, namely, pyridine-2-thione, pyrimidine-2-thione, purine-6-thione, 2-thiouracil, 2,4-dithiouracil, 2,4,6-trimercaptotriazine, N-substituted imidazolidine-2-thiones, 1, 3-thiazolidine-2-thione, 1-methyl-imidazoline-2-thione, benzo-1, 3-imidazoline-2-thione, benzo-1, 3-oxazoline-2-thione, benzo-1,3-thiazoline-2-thione (bztztH) and some other thio-ligands. The article attempts to bring together the formation of coordination compounds of different nuclearity, namely, mononuclear, homo- and hetero-bridged di-nuclear, clusters and coordination polymers. The role of experimental conditions, where investigated, is also highlighted. In addition, some new aspects of synthetic chemsitry involving copper mediated activation and rupture of CS (thione) bonds and their transformations are described. The last part deals with the bio-activity of metal complexes and it represents an important aspect of applications. The main focus is to cover relatively recent and novel coordination chemistry, though some earlier examples might appear as a part of revealing the overall trend of a metal in terms of its coordination fexibility. In short, this review coveres more recent structurally characterized coordination molecules of group 10–12 elements, attempts to cover reaction chemistry under ambient conditions, including the activation of CS (thione) bonds encountered with copper, and finally provide the bio-activity status of the title metals

Solvent-free preparation of hierarchical 4A zeolite monoliths: Role of experimental conditions

A series of novel self-supporting hierarchically porous zeolite monoliths with micropores and macropores were successfully prepared using polymethyl methacrylate (PMMA) microbeads as sacrificial template via solvent-free strategy. The effects of several synthesis parameters, such as Na/Al molar ratio, H2O/metakaolin (MK) mass ratio, MK/PMMA mass ratio and curing time on the structure and morphology of hierarchical zeolite monoliths were systematically investigated. Multiple techniques, including SEM, XRD, FTIR, XRF, BET, MIP and TG-DTG were used to test the properties of resultant products. The experimental results show that hierarchical 4A zeolite monoliths could be obtained at Na/Al molar ratio of 1.2:1, H2O/MK mass ratio of 1.1:1, MK/PMMA mass ratio of 50/50, curing temperature of 70 °C for 24 h and calcination temperature of 550 °C for 2 h. The SiO2/Al2O3 molar ratio and BET specific surface area were found to be 1.92 and 57.67 m2/g, respectively. The diameter of macropore pores were mainly in the range of 840–4130 nm.

Electrochemical scaling of stainless steel in artificial seawater: Role of experimental conditions on CaCO3 and Mg(OH)2 formation

In seawater, during the application of cathodic protection, a scale layer forms on the metal surface. As function of its chemical composition and compactness, it can improve the metal protection against corrosion by reducing the oxygen diffusion. The present investigation focuses on the electrochemical scaling of stainless steel in artificial seawater. Formed scales were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. It was found that the formed scales are mainly CaCO3 aragonite. The brucite (Mg(OH)2) was identified, as a component of the scale layer, only for a high temperature and a more cathodic potential. It was also shown that, unlike other substrates, stainless steel promotes the precipitation of brucite. If the experimental conditions favoured its formation, the scaling process starts with brucite deposition. The growth of CaCO3 nucleuses, developed on interstice, recovers after brucite layer.

Stabilization of Liposomes by Polyelectrolytes: Mechanism of Interaction and Role of Experimental Conditions

Abstractζ‐potential measurements on LUVs allow to evidence the influence of pH, ionic salt concentration, and polyelectrolyte charge on the interaction between polyelectrolyte (chitosan and hyaluronan) and zwitterionic lipid membrane. First, chitosan adsorption is studied: adsorption is independent on the chitosan molecular weight and corresponds to a maximum degree of decoration of 40% in surface coverage. From the dependence with pH and independence with MW, it is concluded that electrostatic interactions are responsible of chitosan adsorption which occurs flat on the external surface of the liposomes. The vesicles become positively charged in the presence of around two repeat units of chitosan added per lipid accessible polar head in acid medium down to pH = 7.2. Direct optical microscopy observations of GUVs shows a stabilization of the composite liposomes under different external stresses (pH and salt shocks) which confirms the strong electrostatic interaction between the chitosan and the lipid membrane. It is also demonstrated that the liposomes are stabilized by chitosan adsorption in a very wide range of pH (2.0 &lt; pH &lt; 12.0).Then, hyaluronan (HA), a negatively charged polyelectrolyte, is added to vesicles; the vesicles turn rapidly negatively charged in presence of adsorbed HA Finally, we demonstrated that hyaluronan adsorbs on positively charged chitosan‐decorated liposomes at pH &lt; 7.0 leading to charge inversion in the liposome decorated by the chitosan‐hyaluronan bilayer. Our results demonstrate the adsorption of positive and/or negative polyelectrolyte at the surface of lipidic vesicles as well as their role on vesicle stabilization and charge control.

Biphasic synthesis of fatty acids stabilized silver nanoparticles: Role of experimental conditions on particle size

Synthesis of silver nanoparticles stabilized by stearic, palmitic and lauric acids is reported. Three reducing agents, which are moderate strong to mild, formaldehyde, triethanolamine and dimethylformamide, are used. The synthesized nanoparticles are dispersible in non-polar solvents such as benzene and toluene. The IR spectra showed the existence of adsorbed fatty acids. The toluene solution of these nanoparticles exhibited a surface plasmon resonance in the range 420–432 nm. It is shown that the silver nanoparticles have an enhanced stability with increasing chain length of the fatty acid. The size of the nanoparticles is greatly influenced by the experimental conditions such as temperature and concentration. The nanoparticles are characterized by UV–vis, FTIR, XRD, AFM and TEM techniques.

Critical assessment of size exclusion chromatography

Size exclusion chromatography (SEC) of synthetic polymers is assessed from the point of view of its both strong and weak points, advantages and drawbacks. Basic information on the SEC retention mechanism arc presented together with the complexity of SEC systems and processes. Present stand of SEC instrumentation is outlined and the role of experimental conditions is described. The need of further development of SEC and of standardization of experimental conditions is demonstrated. The enthalpic interactions, leading to adsorption and enthalpic partition phenomena in the SEC columns are described. It is shown that the latter should be suppressed to obtain reliable SEC results. Alternatively, enthalpic interactions can be deliberately combined with the entropic partition (exclusion) basic SEC retention mechanism either to allow separation of complex polymers exhibiting multiple distributions in their molecular characteristics or to increase selectivity of separation.

Postinflammatory changes of the diaphragmatic stomata

Numerous investigations concerning the fine morphology of diaphragmatic stomata have been performed, but its ultrastructural changes in experimental conditions remain unclear. The present study demonstrates the peritoneal side of the diaphragm in adult Wistar rats by transmission electron microscopy. Ten experimental animals were observed 5 and 8 days after Pseudomonas aeuriginosa instillation (PI) into the peritoneal cavity. A control group of 6 rats showed flat mesothelial covering on basal lamina (BL) and connective tissue layer, as well as cubic mesothelial cells, single stomata over underlying lymphatic lacunae (LL). Five days after PI the mesothelial cells had more numerous microvilli, microvesicles, vacuoles, lysosomes and a lesser number of specialized contacts. The multiplication of the extravasal cells and larger intercellular spaces lead to thickenings of the connective tissue around LL. LL were larger and located in close proximity of the mesothelium. Intercellular spaces in the mesothelial layer and different types of contacts between mesothelial cells and endothelial protrusions of LL (with common BL or without BL) were encountered. Eight days after PI the mesothelium, endothelium of LL, their BL and surrounding connective tissue were interrupted and structurally modified to form typical new channels--stomata. The larger portion of the channels were formed of mesothelial cells, while the endothelial cells participated in the submesothelial part. LL were more numerous than in the previous period, and were arranged in groups. LL increased their vertical (50.59 microm) and horizontal (155.57 microm) diameter, as compared with control animals (respectively 12.37 microm and 74.08 microm). Neighbouring LL were separated by thin or thick septae. Peristomatal mesothelial cells or more rarely endothelium formed valve- or bridge-like structures. Valves on the opposite side of LL were observed. Groups of electron-dense bodies characterized some tall endothelial cells of LL. Cubic mesothelium, endothelium of the LL, both BL, the cell connections that formed new stomata, LL and surrounding connective tissue underwent rapid and parallel changes after PI. Among these elements of the lymphatic regions mentioned above, the mesothelium and endothelium of LL had a main role in experimental conditions.

Involvement of two different mechanisms in trigeminal ganglion-evoked vasodilatation in the cat lower lip: role of experimental conditions

The present study was designed to examine the vasodilator mechanisms elicited by electrical stimulation of trigeminal ganglion (TG) in cat lower lip of the cats. When vago-sympathectomized cats were fixed into a stereotaxic frame by means of ear-bars, etc., the lip blood flow (LBF) increase evoked by lingual nerve (LN) stimulation (parasympathetic reflex response) was almost abolished in 15 out of 34 animals, but unaffected in the other 19. With the animal in the stereotaxic frame, electrical stimulation at sites within the TG evoked an LBF increase whether or not the LN stimulation-induced reflex response was intact. However, hexamethonium abolished the TG stimulation-induced LBF increase in animals whose brainstem parasympathetic reflex was intact, but reduced it by only 50% in animals whose reflex was impaired. This difference was seen in all experiments in which the electrode site was within the TG proper, regardless of its exact position. Although the underlying mechanism is unclear, these data suggest that when the TG is stimulated the LBF increase is entirely mediated via the parasympathetic reflex mechanism in animals whose brainstem reflex is intact, and that an antidromic vasodilatation occurs only in animals whose brainstem parasympathetic reflex is impaired.

Role of experimental conditions in determining differences in exploratory behavior of prenatally stressed rats.

The effect of prenatal stress was determined on exploration in situations that induce different levels of fear. Dams (12) were stressed by noise and light thrice weekly on an unpredictable basis throughout pregnancy, and 12 controls were left undisturbed. The time spent by different groups of their adult offspring of both sexes in exploration was assessed during 4 min in a plus maze; large, well-lit open field (1), and open field (2) after prior exposure to a small, dark holebox. Prenatal stress resulted in a significant reduction in the number of arm entries in the plus maze and amount of time spent in the open arms. Locomotion and rearing were also reduced in Open Field 1 and 2, but these activities and hole poking were unchanged in the holebox. It is concluded that prenatal stress renders the animal more fearful to a novel, intimidating environment, which may be expressed as a suppression of exploratory activity.

Role of experimental conditions and of thin foil ageing on the high temperature deformation microstructure of β-CuZn

Role of experimental conditions and of thin foil ageing on the high temperature deformation microstructure of β-CuZn

Anodic oxide film on antimony : I. Role of experimental conditions and growth kinetics in acid media

Anodic oxide film on antimony : I. Role of experimental conditions and growth kinetics in acid media