102 research outputs found
Thermal properties of acylated low molecular weight chitosans
No full textSummary: Acylated low molecular weight chitosans (LChA) were prepared from nucleophilic acylation of chitosan using acid anhydrides of short and medium chain length (4 - 10) to study the response of applied heat as a function of acyl chain length. Thermogravimetric analysis (TGA) revealed the decomposition of LChA consisted of glucosamine and acyl-glucosamine units around 141 - 151°C to 400 - 410°C. Both TGA and differential scanning calorimetry (DSC) analyses indicated that the introduction of acyl groups disrupted the hydrogen bonding of chitosan, the effect was more prominent as the degree of substitution and chain length of LChA increased. Grafting of acyl chains lowered the kinematic viscosity of LChA as the disruption of hydrogen bonding led to decreased hydrodynamic volume. Field emission scanning electron micrographs showed that LChA with longer chains having larger particle size due to bigger occupancy volume of acyl chains during spray drying. © 2019 Chemical Society of Pakistan. All rights reserved
Analisis Bentuk Lagu Ayam Putih Pungguk Karya H Misran Rais Di Kabupaten Rokan Hilir Provinsi Riau
Get PDFThis study aims to determine the form of the song Ayam Putih Pungguk by H Misran Rais. The theory used in this study is the theory of song form according to Prier (1996), where the form of the song is divided based on the number of sentences, namely the form of a one-part song, a two-part song form and a three-part song form. The elements of song form according to Prier (1996) consist of 4 parts, namely themes, motifs, phrases, song sentences. And the elements of music according to Joseph Machlis (1984) which consists of rhythm, melody, harmony and timbre (sound color). This study uses a non-interactive qualitative method with data collection techniques, namely observation techniques by listening to the song Ayam Putih Pungguk repeatedly and then transcribing the song in the form of notation. This study also uses a documentation technique where the author searches for and collects documents and books related to the title of the study, namely the analysis of the form of the song Ayam Putih Pungguk by H misran Rais in Rokan Hilir district, Riau province. The source of this research is the scores of the song Ayam Putih Pungguk by H Misran Rais. Based on the results of the study, it can be described that the song Ayam Putih Pungguk is included in the group of three-part song forms consisting of A-B-C, has 8 phrases with 4 antecedent phrases (questioning sentences) and 4 consequent phrases (answer sentences), consisting of several song motifs from 40 bars. with a 4/4 mark and using a 2# D=do scale with an Allegro tempo which has a speed of 120
Adsorption kinetics of partially ionized fatty acids at oil/water interface of their monomeric and liposomal solution
No full textFatty acid in the partially ionized form has an astounding ability to adsorb at oil/water interface. The mechanism for adsorption of fatty acids in this condition is expected to be diffusion controlled without the presence of the adsorption barrier. Based on the existing adsorption theory, we studied the kinetics of adsorption of fatty acid at pKa environment. It was observed that both the diffusion and the kinetic (barrier) models satisfactorily described the adsorption kinetics of fatty acid monomeric solution. This behavior thus leads to a contradiction in the interpretation of results. It was observed that the contradictions could occur in the controlling mechanism, the location of the barrier, and the origination of the existence of the barrier. Herein reports the contradiction observed in the kinetics of surfactant adsorption that is often overlooked. The higher affinity of fatty acids molecule for adsorption leads to the breakdown of liposome in solution. The liposome dissociation rate constant, k, obtained from the diffusion model is increased with the increase in the liposome concentration
Interaction between C18 fatty acids and DOPE PEG2000 in Langmuir monolayers: effect of degree of unsaturation
No full textIn this study, we address the effect of the cis-double bond in 1,2dioleoyl-sn-glycero-3-phosphoethanolamide-N-[methoxy(polyethylene glycol)-2000, DOPE PEG2000 (DP), on the Langmuir monolayer of C18 fatty acids—namely, stearic acid (SA), oleic acid (L1), linoleic acid (L2), and linolenic acid (L3)—with the same head group but different degrees of saturation on their hydrocarbon chains. Negative values of Gibbs free energy of mixing (ΔGmix) were obtained throughout the investigated ranges of the unsaturated C18 fatty-acid (L1, L2 and L3) mixed systems, indicating that very strong attractions occurred between molecules in the monolayers. The bend and kink effects from the cis-double bond(s) in the hydrocarbon chain affected the membrane fluidity and molecular packing in the monolayers, which resulted in a greater interaction between unsaturated C18 fatty acids and DP. The most thermodynamically stable mole composition of unsaturated C18 fatty acids to DP was observed at 50:1; this ratio is suggested to be the best mole ratio and will be subsequently used to prepare DP–C18 fatty-acid nanoliposomes. The presence of cis-double bonds in both hydrocarbon chains of DOPE in DP also created an imperfection in the membrane structure of lipid-drug delivery systems, which is expected to enhance lipid-based systems for antibody conjugation and drug encapsulatio
Physicochemical properties of acylated low molecular weight chitosans
No full textHydrophobically modified chitosans are developing progressively in drug delivery system due to their ability to encapsulate drugs with the amphiphilic architecture. In this study, low molecular weight chitosans were acylated with hexanoyl (LCh-C6), octanoyl (LCh-C8) and decanoyl (LCh-C10) groups to study their physicochemical properties for the potential as drug carriers. Both fourier transform-infrared (FT-IR) and 1H NMR (Nuclear Magnetic Resonance) analyses confirmed the successful acylation of alkyl chains onto chitosan backbone. LCh-C6, LCh-C8 and LCh-C10 showed the similar value of critical aggregation concentration around 40 µg L−1. The average particle size of LCh-C6, LCh-C8 and LCh-C10 obtained by dynamic light scattering measurement was compared to by mean of transmission electron microscopy. Acylated low molecular weight chitosans (LChA) showed higher encapsulation efficiency and drug loading toward hydrophobic salicylic acid as compared to hydrophilic caffeine, as well as exhibited higher increment in particle size due to possible inner volume expansion. Both long alkyl chains and high degree of substitution contributed to better drug encapsulation of LChA
Flow Behavior of Oleic Acid Liposomes in Sucrose Ester Glycolipid Oil‐in‐Water Emulsions
No full textRheological and physicochemical characterization of alpha-tocopherol loaded lipid nanoparticles in thermoresponsive gel for topical application
No full textFeatures of a thermoresponsive gel is advantageous in topical application. Lipid nanoparticles is incorporated as a carrier for hydrophobic active ingredient which is not stable in the aqueous gel system. In this work, a thermoresponsive gel mixture consists of carboxymethyl cellulose (CMC) and iota-carrageenan (ι-C) was prepared. Nanostructured lipid carriers (NLC) made of fatty acids and lecithin was incorporated into the gel formulation as a carrier for alpha-tocopherol. Temperature effect on rheological behavior of the prepared gel mixture was investigated. The NLC was evaluated for its mean particle size, zeta potential, morphology, encapsulation efficiency and in vitro drug release. Physicochemical characterization showed that alpha-tocopherol loaded NLC being stored at 4 ˚C was stable for 1 month and encapsulation efficiency of alpha-tocopherol was more than 90 % for all formulations due to its hydrophobicity to stay in the lipid matrix. In vitro release studies proved that NLC was able to provide slow release of loaded alpha-tocopherol. On the other hand, the phase transition from gel-like to liquid-like of the formulated gel mixture was proven to be activated by temperature changes. The rheological gelling point of the gel mixture was represented by the crossover point of storage modulus, G’ and loss modulus, G’’ which was obtained in the vicinity of body temperature 37 ˚C. This property is useful in topical application for its better spreadability on skin upon usage and hence better penetration for the alpha-tocopherol loaded NLC across skin barrier. Prolong release of alpha-tocopherol with enhanced stability is favored as alpha-tocopherol is commonly known for its potent antioxidant activities. These results suggested that gel mixture of CMC and ι-C is a good candidate to be developed as a thermoresponsive gel while lipid nanoparticles is a promising carrier system for alpha-tocopherol in topical use.</jats:p
Effect of sodium dodecyl sulphate and polyoxyethylene dodecyl ether on the rheological behaviour and stability of natural rubber latex
No full textSurfactants are important class of material used in latexes to impart stability at the solid/liquid interface. Ionic surfactants and nonionic surfactants are known to provide elec- trostatic and steric stabilisation. In this study, two surfactants having chain length of twelve hydrocarbons were added to the natural rubber latex (NRL) respectively to determine its zeta potential values, adsorption isotherm and rheological properties. Previous study has shown that optimum stability was observed when the alkyl chain of surfactant contains twelve car- bon atoms. The zeta potential magnitude of NRL in the presence of sodium dodecyl sulphate increased as the surfactant concentration increases, while polyoxyethylene dodecyl ether did not show a significant change in zeta potential. The isotherms were of Langmuir Type 1, the amount of surfactant adsorbed per unit area at the plateau region was 6.0 × 10-6 mol m-2 for sodium dodecyl sulphate and 2.1 × 10-6 mol m-2 for polyoxyethylene dodecyl ether. The elastic modulus and relative viscosity of the NRL suspensions increased significantly in the presence of sodium dodecyl sulphate and also with polyoxyethylene dodecyl ether as compared to the NRL system due to stronger colloidal forces. The maximum packing volume fractions of the NRL stabilised with sodium dodecyl sulphate and polyoxyethylene dodecyl ether were found to be lower than NRL itself
Thermoresponsive Gel Mixture Carboxymethyl Cellulose and iota-Carrageenan for Topical Delivery of Hydroquinone
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