Search results for "stearic acid"
showing 10 items of 31 documents
Influence of cyclopropene fatty acids (Baobab seed oil) feeding on the in vitro Δ9 desaturation of stearic acid in rat liver microsomes
1993
Abstract Δ9 desaturation of [1−14C] stearic acid to oleic acid was studied in liver microsomes of rats fed either fresh Baobab seed oil, containing cyclopropene fatty acids (malvalic acid and sterculic acids), or heated Baobab oil, containing only minor amounts of these acids. This was compared with rats fed a control oil mixture or a fat-free diet. Up to 50 nmol of substrate, Δ9 desaturation rate was the same in rats fed the three fat diets. From 50 to 150 nmol, the desaturation rates were practically constant in rats fed fresh Baobab seed oil. It increased in heated oil-fed rats at the same rate as in the control group, but more slowly than in the fat-free diet group. Fatty acid compositi…
Production of vegetable oil-based biofuels—Thermochemical behavior of fatty acid sodium salts during pyrolysis
2009
Abstract To develop an advanced pyrolysis process for various biomass-derived feedstocks and improve product quality and yield, in-depth investigations into the reaction mechanisms are needed. This paper reports on pyrolysis experiments (Py-GC/MSD and FID) with model compounds including the sodium salts of stearic (C18), oleic (C18:1), and linoleic (C18:2) acids principally obtained from alkaline hydrolysis of vegetable oils. Of the parameters studied – temperature (450–750 °C), time (20 s and 80 s), and the degree of unsaturation (i.e., saturated and mono- and dienoic C18-hydrocarbon chains) – the latter had the most significant effect on the formation of volatile compounds detected in pyr…
Control of CaCO3 Crystallization by Demixing of Monolayers
2006
In this paper we describe how to template a demixed monolayer into a spatially patterned inorganic replica. For this purpose a new amphiphilic monomer was synthesized which can be polymerized both in solution and in the monolayer of a Langmuir-Blodgett (LB) trough. Since it inhibits the crystallization of CaCO3, it can be used--in combination with stearic acid (nucleation-promotor)--to control CaCO3 crystals formed under the monolayer. Investigations of the two-component monolayer (Langmuir isotherms and AFM measurements of transferred films) show--in the biphasic region--demixing in solid analogue stearic acid domains and the liquid analogue phase of the monomer. Crystallization of CaCO3 s…
Water repellency as conditioned by particle size and drying in hydrophobized sand
2013
The effects of particle size and soil moisture on water repellency (WR) from hydrophobized sand are studied in this research. Quartz sand samples were separated into three sieve fractions: 0.5–2 mm (coarse sand, CS), 0.25–0.5 mm (medium sand, MS), and 0.05–0.25 mm (fine sand, FS). WR of sand was induced using different concentrations of stearic acid (SA; 0.5, 1, 5, 10, 20 and 30 g kg− 1). Moist samples have been exposed to two types of drying: air-drying at standard laboratory conditions and oven-drying at 50 °C. Change in moisture content, and water repellency has been monitored every 24 h for 10 days. After 1 day of drying, SA concentrations ≥ 10 g kg− 1 caused extreme WR in oven-dry samp…
Cytotoxic Glial Swelling by Arachidonic Acid
1994
Arachidonic acid (AA, 20:4) is a major constituent of membrane phospholipids in brain tissue. Normally, the free fatty acid is present only in a small amount, but it accumulates under adverse conditions, such as ischemia or brain injury [1,9]. The release of free fatty acid involves activation of phospholipases and breakdown of membrane phospholipids. AA in particular is considered to mediate pathological processes. The polyunsaturated compound is a precursor of prostaglandins, leukotrienes, and oxygen-derived free radicals [11]. In cerebral ischemia concentrations of free AA of up to 0.5 mM/kg have been found in brain tissue [9].
The influence of counterions and hydrophobic moieties on the thermostability of Langmuir-Blodgett multilayers
1994
Abstract Langmuir-Blodgett (LB) multilayers with various counterions and different organic moieties (one- and two-chain fatty acids, polymeric acid) are prepared to investigate on line temperature-dependent structural changes and desorption by small-angle X-ray scattering (SAXS), interference-enhanced reflection and Nomarsky microscopy. On temperature increase a sequence of phase transitions can be observed. A crystalline LB film melts to a fluid phase and eventually desorbs either from droplets or from a homogeneous film. The phase sequence depends on the counterion: nickel stearate and magnesium stearate melt while the layered structure is conserved; SAXS measurements reveal a continuous,…
Mechanisms of Glial Swelling by Arachidonic Acid
1994
The effect of arachidonic acid (AA, 20:4) was analyzed in vitro by employment of C6 glioma cells and astrocytes from primary culture. The cells were suspended in an incubation chamber under continuous control of pH, pO2, and temperature. Cell swelling was quantified by flow cytometry. After a control period, the suspension was added with AA at concentrations of 0.01 to 1.0 mM. Administration of AA induced an immediate, dose dependent swelling in C6 glioma cells or astrocytes. AA-concentrations of 0.01 mM led to an increase of the glial cell volume to 103.0 ± 1.0% of control, 0.1 mM to 110.0 ± 1.5%, and l.0 mM to 118.8 ± 1.5% within 10 min. The swelling response to linoleic acid (18 : 2) was…
Platelet and Plasmatic Lipidic Profile as Potential Marker of Bipolar Disorders: Preliminary Findings
2017
IntroductionAlthough the diagnosis of bipolar disorder is currently based on clinical criteria, preliminary studies showed that palmitic and arachidonic acid levels are able to discriminate adult patients with major depressive disorder (MDD) from those with bipolar disorder (BD).ObjectivesTo replicate and to expand previous findings by investigating the relation between mood disorders and platelet and plasmatic fatty levels.AimsTo compare the lipidic profile of individuals with different mood disorder (MDD vs. BD) and to investigate the relation with specific clinical features (duration of illness, attempted suicide, psychotic symptoms).MethodsPotential participants were recruited from the …
Identification of drying oils used in pictorial works of art by liquid chromatography of the 2-nitrophenylhydrazides derivatives of fatty acids.
2004
A new HPLC-UV-Vis method for identification of drying oils from binding media or protective film used in pictorial works of art prior to conservation or restoration is proposed. Chromophore derivatization of fatty acids released by hydrolysis of structural drying oils is studied. The derivatization reagent selected was 2-nitrophenylhydrazine with 1-ethyl-3-(3-dimethyl animopropyl)carbodiimide hydrochloride/pyridine as catalyst. This reaction was carried out using microwave heating. Mobile phase was methanol/water/n-propanol/acetic acid (80:14:5:1) running in isocratic mode. Absorbance was measured at 400nm. In these conditions, hydrazides of myristic, palmitic, oleic, and stearic acids were…
Determination of the Absolute Density of Fe3+ and Ni2+ Ions in Langmuir-Blodgett Films
1996
By means of the Langmuir–Blodgett (LB) technique, mono- and multilayers of Ni2+ and Fe3+ containing fatty acid salts are transferred onto silicon wafers. After thermal treatment, oxidic layers can be produced. The absolute amounts of Fe3+ and Ni2+ ions per monolayer of LB film were measured and calculated by three different methods. In the case of nickel, the amount expected from theory and preparation conditions was obtained experimentally. In contrast, about twice the number of Fe3+ ions as expected is transferred. An explanation can be given by the presence of hydroxide groups bound to iron. The mean film thickness of the oxidic layers after thermal treatment was estimated where the thic…