scholarly journals Efficient Homogeneous TEMPO-mediated Oxidation of Cellulose  in Lithium Bromide Hydrates

2021 ◽  
Author(s):  
Xiaotong Fu ◽  
Fulong Zhang ◽  
Cuihua Dong ◽  
Wenyuan Zhu ◽  
Kaifeng Xiong ◽  
...  
Keyword(s):  
Selective Oxidation ◽  
Water Solubility ◽  
Lithium Bromide ◽  
High Water ◽  
Amorphous Structure ◽  
Cellulose Oxidation ◽  
Homogeneous Oxidation ◽  
Fractionation Analysis ◽  
Ft Ir ◽  
High Degree

Abstract An appropriate cellulose-dissolving solvent is critical for the homogeneous oxidation of cellulose using TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl)-mediated system. Herein, TEMPO/NaClO/NaClO2 system in lithium bromide hydrates (LBHs) was developed for the homogeneous selective-oxidation of cellulose, which was two-stage protocol involving cellulose dissolution and homogeneous oxidation. Specifically, cellulose was firstly dissolved in LiBr⋅3.5H2O and offered the optimal pH (5.6) for the subsequent TEMPO/NaClO/NaClO2 oxidation without precipitation of the cellulose chains. Effect of reaction conditions on cellulose oxidation was investigated. The results showed that high degree of oxidation (DO) and evenly distributed carboxyl could be achieved. The particle size gradually decreased with DO, and oxidized cellulose with high water solubility and amorphous structure could be obtained. Furthermore, FT-IR, 13C NMR and fractionation analysis verified that cellulose was successfully converted and the carboxyl uniformly distributed onto the cellulose chains. This TEMPO-mediated system using LBHs as solvent presented an efficient method on the homogeneous selective oxidation of primary hydroxyl in cellulose.

FUNGITOXICITY OF CHLORINATED HYDROCARBON INSECTICIDES IN RELATION TO WATER SOLUBILITY AND VAPOR PRESSURE

1960 ◽  
Vol 38 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Lloyd T. Richardson ◽  
D. M. Miller
Keyword(s):  
Vapor Pressure ◽  
Water Solubility ◽  
High Water ◽  
Assay Method ◽  
Vapor Pressures ◽  
Response Curves ◽  
Chlorinated Hydrocarbon ◽  
High Degree ◽  
Dosage Response Curve ◽  
Bio Assay

Fungitoxicity, in terms of inhibition of mycelial growth, was demonstrated with eight chlorinated hydrocarbon insecticides by the culture plate bio-assay method. All of the dosage–response curves thus derived were bimodal rather than linear. Evidence is presented to show that the shape of these curves is governed by two physical properties of the compounds: water solubility (which was determined experimentally) and vapor pressure. The concentration of insecticide in solution governs the initial rise of each dosage–response curve which is extended to a peak because of supersaturation and is followed by a decline as normal saturation is regained. The concentration of toxicant vapor in contact with the organism governs the second rise in the curve to a level dependent on the vapor pressure of the compound. Lindane has a high degree of fungitoxicity because of its relatively high water solubility. Heptachlor, chlordane, and aldrin are also highly toxic because of their vapor pressures. DDT, methoxychlor, dieldrin, and endrin are weakly fungitoxic because of both low water solubility and low vapor pressure.

Characterization of SrBi2Nb2O9 Thin Films Prepared by Sol Gel Technique

1996 ◽  
Vol 459 ◽  
Author(s):  
E. Ching-Prado ◽  
W. Pérez ◽  
A. Reynés-Figueroa ◽  
R. S. Katiyar ◽  
D. Ravichandran ◽  
...  
Keyword(s):  
Thin Films ◽  
Raman Band ◽  
Sol Gel ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Ft Ir ◽  
Gel Technique ◽  
High Degree ◽  
First Time

ABSTRACTThin films of SrBi2Nb2O9 (SBN) with thicknesses of 0.1, 0.2, and 0.4 μ were grown by Sol-gel technique on silicon, and annealed at 650°C. The SBN films were investigated by Raman scatering for the first time. Raman spectra in some of the samples present bands around 60, 167, 196, 222, 302, 451, 560, 771, 837, and 863 cm−1, which correspond to the SBN formation. The study indicates that the films are inhomogeneous, and only in samples with thicknesses 0.4 μ the SBN material was found in some places. The prominent Raman band around 870 cm−1, which is the A1g mode of the orthorhombic symmetry, is assigned to the symmetric stretching of the NbO6 octahedrals. The frequency of this band is found to shift in different places in the same sample, as well as from sample to sample. The frequency shifts and the width of the Raman bands are discussed in term of ions in non-equilibrium positions. FT-IR spectra reveal a sharp peak at 1260 cm−1, and two broad bands around 995 and 772 cm−1. The bandwidths of the latter two bands are believed to be associated with the presence of a high degree of defects in the films. The experimental results of the SBN films are compared with those obtained in SBT (T=Ta) films. X-ray diffraction and SEM techniques are also used for the structural characterization.

A Fluorescence Quenching Analysis of the Binding of Fluoroquinolones to Humic Acid

2017 ◽  
Vol 71 (11) ◽  
pp. 2512-2518 ◽  
Author(s):  
Ryan P. Ferrie ◽  
Gregory E. Hewitt ◽  
Bruce D. Anderson
Keyword(s):  
Humic Acid ◽  
Fluorescence Quenching ◽  
Water Solubility ◽  
Binding Constants ◽  
High Water ◽  
Static Quenching ◽  
Temperature Range ◽  
Equilibrium Binding ◽  
Quenching Analysis ◽  
High Water Solubility

Fluorescence quenching was used to investigate the interaction of six fluoroquinolones with humic acid. Static quenching was observed for the binding of ciprofloxacin, enoxacin, fleroxacin, levofloxacin, norfloxacin, and ofloxacin to humic acid. The equilibrium binding constants were found from Stern–Volmer plots of the data. The quenching experiments were repeated over a temperature range of 25–45 ℃ and van’t Hoff plots were generated. From these linear plots, thermodynamic values were calculated for Δ H, Δ G, and Δ S for each of the fluoroquinolones. The equilibrium binding constants were found to be <1 for all the antibiotics studied. The calculated ΔH values were all negative and ranged from −9.5 to −27.6 kJ/mol. The high water solubility of the antibiotics and low ΔH of binding suggests that the antibiotics will be transported easily through the environment. Finally, whether the fluoroquinolones are in a protonated, deprotonated, or partially protonated state is found to correlate to the strength of binding to humic acid.

Novel tetrazole PtII and PdII complexes with enhanced water solubility: synthesis, structural characterization and evaluation of antiproliferative activity

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Tatiyana V. Serebryanskaya ◽  
Alexander S. Lyakhov ◽  
Ludmila S. Ivashkevich ◽  
Yuri V. Grigoriev ◽  
Andreii S. Kritchenkov ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Performance ◽  
Water Solubility ◽  
Thermal Analyses ◽  
High Water ◽  
Acetonitrile Solution ◽  
X Ray ◽  
Molecular And Crystal Structures ◽  
Tetrazole Derivatives ◽  
High Water Solubility

AbstractNovel platinum(II) and palladium(II) chlorido complexes with tetrazole derivatives 1-(2-hydroxyethyl)tetrazole (het) and 1-[tris(hydroxymethyl)methyl]tetrazole (thm), viz. cis-[Pt(het)2Cl2], trans-[Pt(het)2Cl2], trans-[Pt(thm)2Cl2], trans-[Pd(het)2Cl2], and trans-[Pd(thm)2Cl2], were synthesized. The compounds were characterized by elemental and high-resolution electrospray ionization (HRESI) mass spectrometry, high-performance liquid chromatography (HPLC), 1H, 13C and 195Pt nuclear magnetic resonance (NMR) spectroscopy, thermal analyses, and Infrared (IR) spectroscopy. Molecular and crystal structures of trans-[PdL2Cl2] and trans-[PtL2Cl2] (L = het, thm) were established by single-crystal X-ray analysis. The complex cis-[Pt(het)2Cl2] was found to undergo cis–to–trans isomerization upon heating in acetonitrile solution and in the solid state. The synthesized complexes show rather high water solubility lying in the range of 2–10 mg/L.

Biodegradable polymers-based nanoparticles to enhance the antifungal efficacy of fluconazole against Candida albicans

2021 ◽  
Vol 22 ◽  
Author(s):  
Noha Saleh ◽  
Soha Elshaer ◽  
Germeen Girgis
Keyword(s):  
Candida Albicans ◽  
Antifungal Activity ◽  
Encapsulation Efficiency ◽  
Water Solubility ◽  
In Vitro Release ◽  
Double Emulsion ◽  
Dilution Method ◽  
Ft Ir ◽  
Antifungal Efficacy

Background: Fluconazole (FLZ), a potent antifungal medication, is characterized by poor water solubility that reduced its antifungal efficacy. Objective: This study aimed to prepare FLZ-loaded polymeric nanoparticles (NPs) by using different polymers and techniques as a mean of enhancing the antifungal activity of FLZ. Methods: NP1, NP2, and NP3 were prepared by the double emulsion/solvent evaporation method using PLGA, PCL, and PLA, respectively. The ionotropic pre-gelation technique was applied to prepare an alginate/chitosan-based formulation (NP4). Particle size, zeta potential, encapsulation efficiency, and loading capacity were characterized. FT-IR spectra of FLZ, the polymers, and the prepared NPs were estimated. NP4 was selected for further in-vitro release evaluation. The broth dilution method was used to assess the antifungal activity of NP4 using a resistant clinical isolate of Candida albicans. Results: The double emulsion method produced smaller-sized particles (<390 nm) but with much lower encapsulation efficiency (< 12%). Alternatively, the ionic gelation method resulted in nanosized particles with a markedly higher encapsulation efficiency of about 40%. The FT-IR spectroscopy confirmed the loading of the FLZ molecules in the polymeric network of the prepared NPs. The release profile of NP4 showed a burst initial release followed by a controlled pattern up to 24 hours with a higher percent released relative to the free FLZ suspension. NP4 was able to reduce the value of MIC of FLZ by 20 times. Conclusion: The antifungal activity of FLZ against C. albicans was enhanced markedly via its loading in the alginate/chitosan-based polymeric matrix of NP4.

scholarly journals Optimization and Modeling of an Emulsion Polymerization Reactor

2021 ◽  
Author(s):  
Narges Ghadi
Keyword(s):  
Emulsion Polymerization ◽  
Water Solubility ◽  
Monomer Conversion ◽  
High Water ◽  
Oscillatory Behavior ◽  
Operating Conditions ◽  
Polymer Properties ◽  
Continuous Polymerization ◽  
Simulation Results ◽  
The Impact

A mathematical model was developed to simulate emulsion polymerization in batch, semi-batch and continuous reactors for monomers with high water solubility and significant desorption such as vinyl acetate. The effects of operating conditions such as initiator and emulsifier concentration as well as reactor temperature have been studied. The simulation results revealed the sensitivity of polymer properties and monomer conversion to variation of these operating conditions. Furthermore, the impact of monomer soluble impurities on reduction of monomer conversion has been investigated. In order to control polymer molecular weight, application of chain transfer agents such as t-nonyl mercaptan was suggested. Generally, the simulation results fitted well [with] experimental data from the literature. Several optimizing policies were considered to enhance the reaction operation for better product quality. During continuous polymerization, the reactor demonstrates oscillatory behavior throughout the operation. A new reactor train configuration was consistent with the aim of damping the oscillations and producing high-quality latex.

scholarly journals CCN activity of organic aerosols observed downwind of urban emissions during CARES

2013 ◽  
Vol 13 (4) ◽  
pp. 9355-9399 ◽  
Author(s):  
F. Mei ◽  
A. Setyan ◽  
Q. Zhang ◽  
J. Wang
Keyword(s):  
Chemical Composition ◽  
Water Solubility ◽  
Volume Fraction ◽  
Field Studies ◽  
High Water ◽  
Carbonaceous Aerosols ◽  
Mass Spectral ◽  
Least Squares Fit ◽  
The Relationship ◽  
Aerosol Chemical Composition

Abstract. During the Carbonaceous Aerosols and Radiative Effects Study (CARES), activation fraction of size-resolved aerosol particles and aerosol chemical composition were characterized at the T1 site (~60 km downwind of Sacramento, California) from 10 June to 28 June 2010. The hygroscopicity of CCN-active particles (κCCN) with diameter from 100 to 171 nm, derived from the size-resolved activated fraction, varied from 0.10 to 0.21, with an average of 0.15, which was substantially lower than that proposed for continental sites in earlier studies. The low κCCN value was due to the high organic volume fraction, averaged over 80% at the T1 site. The derived κCCN exhibited little diurnal variation, consistent with the relatively constant organic volume fraction observed. At any time, over 90% of the size selected particles with diameter between 100 and 171 nm were CCN active, suggesting most particles within this size range were aged background particles. Due to the large organic volume fraction, organic hygroscopicity (κorg) strongly impacted particle hygroscopicity and therefore calculated CCN concentration. For vast majority of the cases, an increase of κorg from 0.03 to 0.18, which are within the typical range, doubled the calculated CCN concentration. Organic hygroscopicity was derived from κCCN and aerosol chemical composition, and its variations with the fraction of total organic mass spectral signal at m/z 44 (f44) and O : C were compared to results from previous studies. Overall, the relationships between κorg and f44 are quite consistent for organic aerosol (OA) observed during field studies and those formed in smog chamber. Compared to the relationship between κorg and f44, the relationship between κorg and O : C exhibits more significant differences among different studies, suggesting κorg may be better parameterized using f44. A least squares fit yielded κorg = 2.04 (± 0.07) × f44 − 0.11 (± 0.01) with the Pearson R2 value of 0.71. One possible explanation for the stronger correlation between κorg and f44 is that the m/z 44 signal (mostly contributed by the CO2+ ion) is more closely related to organic acids, which may dominate the overall κorg due to their relatively high water solubility and hygroscopicity.

An Assessment of Olmesartan Medoxomil Tablet by Inclusion Complex Technique

2021 ◽  
pp. 193-197
Author(s):  
Deepak Sarangi ◽  
Subhashree Mallick ◽  
Anjum Ara ◽  
Sanjeeb Kumar Sahoo ◽  
Rabinarayan Rana
Keyword(s):  
Inclusion Complex ◽  
Water Solubility ◽  
Olmesartan Medoxomil ◽  
Complexing Agents ◽  
Complexing Agent ◽  
Angiotensin Ii Receptor ◽  
Current Effort ◽  
Ir Studies ◽  
Beta Cyclodextrin ◽  
Ft Ir

Olmesartan Medoxomil is an AT1 subtype selected angiotensin-II receptor antagonist approved for the treatment of hypertension. It has low water solubility, so the current effort is being made to enhance the solubility of the Olmesartan by inclusion complex and to incorporate them into tablets by direct compression. Complexing agent like Beta cyclodextrin and polyvinyalpyrrolidone has been used for complexation method. FT-IR studies have shown that there is no link between drugs and complexing agents. Among all methods, the inclusion complex (OLBCD 3) containing the drug: Beta cyclodextrin in a 1: 3 ratio showed rapid drug release (87.41% within 30 minutes) and post compression parameters are within limits. All the values obtained from pre compression and post compression parameters meets the legal requirements for tablets. Stability studies of batch no OLBCD 3 shows no significant change. Therefore, it can be concluded that the structure was stable.

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