Liquid Glycerol Research Articles

Glassy dynamics under superhigh pressure

Nearly all glass-forming liquids feature, along with the structural alpha-relaxation process, a faster secondary process (beta relaxation), whose nature belongs to the great mysteries of glass physics. However, for some of these liquids, no well-pronounced secondary relaxation is observed. A prominent example is the archetypical glass-forming liquid glycerol. In the present work, by performing dielectric spectroscopy under superhigh pressures up to 6 GPa, we show that in glycerol a significant secondary relaxation peak appears in the dielectric loss at P>3 GPa. We identify this beta relaxation to be of Johari-Goldstein type and discuss its relation to the excess wing. We provide evidence for a smooth but significant increase in glass-transition temperature and fragility on increasing pressure.

Use of crude glycerol, a biodiesel coproduct, in diets for lactating sows1,2

An experiment was conducted to evaluate the effect of dietary crude glycerol in lactating sow diets on sow and litter performance under heat stress conditions. Mixed parity (range = 0 to 13) sows (n = 345; 253 +/- 24 kg of BW) were assigned randomly within gestation housing location and parity to 1 of 4 dietary treatments. Treatments consisted of a corn-soybean-based control diet (CON) and 3, 6, or 9% glycerol added at the expense of corn and soybean meal. Liquid crude glycerol was incorporated in the complete diet at the time of mixing. Dietary treatments were imposed on d 109 of gestation (2.25 kg/d) when sows were moved into farrowing rooms. Heat index during lactation in farrowing rooms exceeded 25 degrees C for all sows. At farrowing, sows were allowed ad libitum access to feed throughout lactation. Dietary treatment tended (P = 0.08) to influence ADFI of sows (CON = 6.04 kg/d; 3% = 6.21 kg/d; 6% = 5.69 kg/d; 9% = 6.00 kg/d; pooled SE = 0.18). Up to 9% crude glycerol in the diet had no effect on sow BW and backfat loss, weaning-to-estrus interval, preweaning mortality of piglets, and ADG of piglets. Increasing dietary glycerol linearly reduced (P = 0.10) litter size at weaning (CON = 9.50; 3% = 9.60; 6% = 9.36; 9% = 9.39; pooled SE = 0.08). Daily water consumption was not affected by dietary treatment. Crude glycerol did not affect respiration rates or rectal body temperatures, indicating no efficacy in reducing heat stress of sows. Plasma glycerol concentrations increased linearly (P < 0.05) as dietary crude glycerol increased (CON = 1.21 microM; 3% = 1.69 microM; 6% = 7.21 microM; 9% = 29.04 microM; pooled SE = 1.58), but plasma glucose concentrations were not affected. Crude protein content of the milk of sows was not affected (P = 0.16) by dietary treatment. Dry matter (P = 0.07) and crude fat (P = 0.09) content of the milk of the sows tended to increase linearly (DM basis: CON = 17.84%; 3% = 18.43%; 6% = 18.98%; 9% = 18.48%; pooled SE = 0.34; crude fat: CON = 4.78%; 3% = 4.91%; 6% = 5.50%; 9% = 5.24%; pooled SE = 0.30), whereas milk ash concentration tended (P = 0.09) to decrease linearly with increasing dietary glycerol (CON = 0.77%; 3% = 0.79%; 6% = 0.74%; 9% = 0.74%; pooled SE = 0.02). Increasing dietary crude glycerol linearly increased (P < 0.05) lactose concentration in the milk of sows (CON = 5.16%; 3% = 5.30%; 6% = 5.43%; 9% = 5.46%; pooled SE = 0.10). Results from this study indicate that lactating sows fed diets containing up to 9% crude glycerol perform similarly to sows fed a standard corn-soybean meal diet.

Modification of hydrophobic/hydrophilic properties of Vulcan XC72 carbon powder by grafting of trifluoromethylphenyl and phenylsulfonic acid groups

Carbon supports (glassy carbon and Vulcan XC72 powder) were modified by electrochemical and spontaneous grafting of phenylsulfonic acid (PSA) or trifluoromethylphenyl (TFMP) groups via diazonium ion reduction. The effectiveness of the grafting was confirmed electrochemically, by XPS measurements and elemental analyses. The hydrophobic or hydrophilic character of carbon surfaces was evidenced by measuring the contact angles of drops of different liquids (water, ethylene glycol and glycerol) in heptane. The surface energy was calculated and it was found, for example, that spontaneous grafting of a glassy carbon surface by PSA groups led to an increase by a factor 20 of the surface energy compared with an unmodified glassy carbon surface. The study of the grafting of such groups on XC72 carbon powder indicated that a very low grafting ratio (in wt%) led to a significant change in the macroscopic properties of the powder. Thermogravimetric analysis coupled with mass spectroscopy measurements (TGA-MS) showed that these grafted layers were thermally stable even in the presence of dispersed platinum nanoparticles. It was shown by cyclic voltammetry that the carbon substrate modification did not affect the electrochemical behavior of platinum catalyst, since the same active surface area was determined on Pt-XC72, Pt-PSA-XC72 and Pt-TFMP-XC72 catalysts.

Reactive Vaporization of Crude Glycerol in a Fluidized Bed Reactor

Crude glycerol is a coproduct of the trans-esterification of vegetable oil and animal fat to biodiesel that contains as much as 5% salt. Processing the glycerol to value added products often requires an expensive distillation step. In this work, we propose a new process in which crude liquid glycerol is fed directly to a fluidized bed, vaporizes, and then reacts to form acrolein over a tungsten doped zirconia catalyst. Salt in the crude glycerol crystallizes and accumulates in the fluid bed. In a commercial process, the salt crystals will be subject to significant mechanical stresses that will cause them to attrit. The attrited powder will be elutriated from the bed and collected by filters. The focus of this work has been to evaluate the effect of salt on catalyst activity as well as its attrition resistance. Thus far, there is little evidence of salt crystallization or migration to the interior of the catalyst particles—after more than 1 day of continuous operation, catalyst activity remained unchanged. Tests on a standard air jet mill suggest that the mechanical stresses typical of a fluidized bed will be sufficient to attrit the salt and thus minimize its accumulation in the reactor with time.

A novel circuit overrides Adr 1p control during expression ofSaccharomyces cerevisiae2-trans-enoyl-ACP reductase Etr 1p of mitochondrial type 2 fatty acid synthase

The significance of the chronicled role of the yeast transcription factor Adr1p in regulating ETR1 was examined in wild type and isogenic adr1Δ mutant cells. An ETR1-lacZ reporter construct was used to verify Adr1p-dependent gene expression. On solid glycerol medium containing X-gal, wild-type cells expressing the reporter turned blue, whereas the adr1Δ mutants remained white. β-Galactosidase activity measurements following 24-h cell growth in liquid glycerol medium revealed a 6.5-fold greater expression level of the reporter gene in the wild type compared with the adr1Δ mutant. In contrast, immunoblotting showed that Etr1p abundance was essentially indistinguishable between the two strains whereas Cta1p, whose expression depends on Adr1p, was present in the wild-type cells, but not in the mutants. Moreover, enzyme assays conducted on transformed wild-type and adr1Δ mutant cells expressing a plasmid-borne ETR1 tethered behind the native promoter revealed similar levels of reductase activity, and the lipoic acid content in the two parental strains was equivalent. Hence, while Adr1p influenced the transcription levels of ETR1, it did not alter the abundance of Etr1p, the level of reductase activity, or the cellular amount of lipoic acid. The results point toward a potentially novel layer of control for maintaining physiological levels of lipoic acid.

Effect of Ascitic Media Formed by Glycerin on the Prevention of Peritoneal Adhesions

Aim: We aimed to investigate whether or not artificial ascites media formed using glycerin are effective in the prevention of intraperitoneal adhesions. Methods: Thirty-six Wistar albino male rats were used in the study. The rats were divided into 3 groups as follows. Group I: control group; group II (isotonic group): 3 ml of 0.9% NaCl was injected into the peritoneal cavity, and group III (glycerin group): 0.5 ml of liquid glycerin and 3 ml of 0.9% NaCl was injected into the peritoneal cavity. Results: There were serious adhesions in the control group. Adhesion rates were lower in the isotonic group compared with the control group, but the difference was not statistically significant (p > 0.05). When adhesion rates of the glycerin group were compared with the control and isotonic groups, significant differences were found, especially between the glycerin and control groups (p < 0.05). Conclusions: According to the results of our study, the use of isotonic solution and liquid glycerin decreases postoperative adhesions. We suggest that glycerin was more effective as it has the chemical ability to draw water to its media. As such, the formation of adhesions may be decreased by increasing the amount of physiological liquid inside the abdomen.

Collisions of DCl with a Solution Covered with Hydrophobic and Hydrophilic Ions: Tetrahexylammonium Bromide in Glycerol

Gas-liquid scattering experiments are used to investigate interfacial interactions of gaseous DCl with liquid glycerol containing 0.03 M tetrahexylammonium bromide (THABr), an ionic surfactant composed of hydrophobic THA(+) and hydrophilic Br(-) ions. Surface tension and argon scattering measurements indicate that the surface of this solution is dominated by the hexyl chains of the THA(+) ion. The hydrocarbon character of the surface is further explored by comparing Ar and DCl scattering from the THABr solution and liquid squalane. We find that the addition of THABr to glycerol alters the reactivity of DCl in two ways: DCl molecules that land on the surface are more likely to desorb when THA(+) and Br(-) are present and are less likely to dissolve, but they are also more likely to undergo rapid, interfacial DCl --> HCl exchange. Similar trends are observed when THA(+) ions are replaced by Na(+) ions in a 2.7 M NaBr solution, even though THA(+) interacts weakly with glycerol OH groups and Na(+) binds strongly to them. These observations suggest that the THA(+) hexyl chains do not physically block DCl entry and that interfacial cation-OH bonding is not essential for promoting rapid D --> H exchange when Br(-)-OH bonding also occurs. The use of THABr confirms that ions in the top few monolayers, and not those deeper in solution, control DCl entry and rapid D --> H exchange.

Direct Coupling of High-Performance Thin-Layer Chromatography with UV Spectroscopy and IR-MALDI Orthogonal TOF MS for the Analysis of Cyanobacterial Toxins

Cyanobacteria are pathogenic prokaryotes and known for producing a high variety of cyclic hepatotoxic peptides in fresh and brackish water. Prominent members of these toxins are microcystin LR (MC LR) and nodularin (Nod), which are under suspicion to cause cancer. Various analytical methods have been reported for the detection of these cyclopeptides, and these are mainly based on liquid chromatography combined with mass spectrometric techniques. Here, we introduce a new approach based on the direct coupling of high-performance thin-layer chromatography (HPTLC) with infrared matrix-assisted laser desorption/ionization orthogonal time-of-flight mass spectrometry (IR-MALDI-o-TOF MS) using the liquid matrix glycerol. The analysis of the cyclopeptides involves the application of three complementary methods: (i) HPTLC separation of MC LR and Nod, (ii) their detection and quantification by UV spectroscopy at lambda = 232 nm, and (iii) direct identification of separated analytes on the HPTLC plate by IR-MALDI-o-TOF MS. Calibration curves exhibited a linear relationship of amount of analyte applied for HPTLC and UV absorption (R(2) > 0.99). The limits of detection were 5 ng for UV spectroscopy and 3 ng for mass spectrometric analysis of individual peptides. This novel protocol greatly improves the sensitive determination of toxins from pathogenic cyanobacteria in complex water samples. It was successfully applied to the detection and quantification of MC LR and Nod in a spiked, processed environmental water sample.

Optical Generation of Gigahertz-Frequency Shear Acoustic Waves in Liquid Glycerol

Picosecond laser ultrasonic techniques for acoustic wave generation and detection have been employed to probe shear acoustic waves in liquid glycerol at gigahertz frequencies. The experimental approach uses a unique laser pulse shaping technique and a crystallographically canted metal layer to generate frequency-tunable transverse acoustic waves, and uses time-domain coherent Brillouin scattering to detect the waves after they propagate through a liquid layer and into a solid substrate. A linear frequency dependence is found for both the shear speed and attenuation rate in glycerol.

Reactive uptake studies of NO3 and N2O5 on alkenoic acid, alkanoate, and polyalcohol substrates to probe nighttime aerosol chemistry

Heterogeneous reactions between NO3 and N2O5 and diethyl sebacate (DES), glycerol, oleic acid (OA), linoleic acid (LA), and conjugated linoleic acid (CLA) were studied to understand better nighttime aerosol chemistry. The reactive uptake coefficient of NO3 on the liquid alkenoic acids (OA, LA, and CLA) was found to be >0.07, which is higher than previous results for unsaturated organics, including alkenoic acids. This reaction could potentially be an important loss process of particle-phase unsaturated organic compounds in the atmosphere and in laboratory secondary organic aerosol studies. The reactive uptake coefficient of N2O5 on liquid glycerol was also found to be relatively large with a value of (3.2-8.5)x10(-4), suggesting that N2O5 heterogeneous reactions with alcohols may also be atmospherically relevant. For all measurements with OA, CLA, and DES, the reactive uptake coefficients decreased significantly upon freezing. One possible explanation is that the liquid reaction is due to both a surface reaction and a bulk reaction and that the freezing process significantly decreases the importance of any bulk reactions. NO3 reactive uptake coefficients for liquid-phase compounds decreased in magnitude in the order: alkenoic acids>DES>glycerol. This is different compared to previous gas-phase studies and the difference may be due to the large viscosity of glycerol compared to the other organic compounds studied. N2O5 reactive uptake coefficients for liquid-phase compounds decreased in magnitude in the order: glycerol>LA>DES congruent with OA congruent with CLA.

Exposure and temperature dependences of contact angle of liquid crystals on photoaligning surface

AbstractWe report on first studies of wetting of liquid crystal on photoaligning surface. We observed strong light-induced variations of a contact angle of a liquid LC 5CB on a photoaligning surface of fluoro-polyvinyl-cinnamate (PVCN-F) and we connected these variations with changes of PVCN-F polarity. We also present drastic changes of the contact angle of a nematic liquid crystal (MLC-6080) on the PVCN-F surface in a vicinity of temperature anchoring transition of liquid crystal from homeotropic orientation to planar one. We did not find any peculiarities in temperature dependence of the contact angle of isotropic liquid (glycerol) on PVCN-F and of nematic liquid crystal on pure glass in the same temperature range. It allows us to suggest that rearrangement of LC molecules and flexible fragments in the LC-polymer interface are responsible for the change of surface tensions both of LC and polymer and the observed jump of the contact angle.

Molecular dynamics simulation of nanoconfined glycerol

We present results from molecular dynamics simulations of liquid glycerol confined in a realistic model of a cylindrical silica nanopore. The influence of the hydrophilic surface and the geometrical confinement on the structure, hydrogen-bond lifetime, rotational and translational molecular dynamics are analysed. Layering and dynamical heterogeneities are induced by confinement. These features share some similarities with previous observations in simpler van der Waals glass-forming liquids. In addition, the specificity of glycerol as an associated liquid shows up in confinement by the formation of interfacial hydrogen bonds and some modifications of the in-pore hydrogen-bonding network. Confinement is also seen to influence the relaxation dynamics and the glassy behaviour in the supercooled state. These phenomena revealed by molecular simulation are important inputs for a better understanding of the many recent experimental results on confined glycerol and more generally for the possible manipulation of associated liquids in porous or fluidic devices.

Effective carbon incorporation inMgB2 by combining mechanical milling and the glycerin treatment of boron powder

A combined process of a mechanical ball milling and liquid glycerin(C3H8O3) treatment of boron (B) powder has been conducted to enhance the superconducting properties ofMgB2. Theindividual aims of the mechanical milling and the glycerin treatment were to reduce the grain size ofthe MgB2 and to achieve homogeneous carbon (C) incorporation into theMgB2, respectively. Four kinds of B powders of as-received, glycerin treated, 2 h milled and 2 h milled+ glycerin treatedwere prepared. MgB2 bulks were fabricated by an in situ process using the prepared B powders. According to ourexperimental results, the mechanical ball milling was effective for grain refinement, and a latticedisorder was easily achieved by glycerin addition. It was found that the critical current density(Jc) values were enhanced in the samples with milled B or glycerin-treated B only. In theMgB2 bulk prepared with both milled and glycerin-treated B, theJc was furtherincreased to 1.27 × 104 A cm−2 at 5 K and 8 T due to a higher grain boundary density and a greater C substitution. Theupper critical field and irreversibility field were also further enhanced by a combinedtreatment process of the B powder.

마그네슘과 글리세린 처리한 붕소 분말로 합성한 Mg(B1-xCx)2의 초전도 특성

Carbon was known to be one of effective additives which can improve the flux pinning of <TEX>$MgB_2$</TEX> at high magnetic fields. In this study, glycerin <TEX>$(C_3H_8O_3)$</TEX> was selected as a chemical carbon source for the improvement of critical current density of <TEX>$MgB_2$</TEX>. In order to replace some of boron atoms by carbon atoms, the boron powder was heat-treated with liquid glycerin. The glycerin-treated boron powder was mixed with an appropriate amount of magnesium powder to <TEX>$MgB_2$</TEX> composition and the powder pallets were heat treated at <TEX>$650^{\circ}C\;and\;900^{\circ}C$</TEX> for 30 min in a flowing argon gas. It was found that the superconducting transition temperature <TEX>$(T_c)$</TEX> of <TEX>$Mg(B_{1-x}C_x)_2$</TEX> prepared using glycerin-treated boron powder was 36.6 K, which is slightly smaller than <TEX>$T_c$</TEX>(37.1 K) of undoped <TEX>$MgB_2$</TEX>. The critical current density <TEX>$(J_c)$</TEX> of <TEX>$Mg(B_{1-x}C_x)_2$</TEX> was higher than that of undoped <TEX>$MgB_2$</TEX> and the <TEX>$T_c$</TEX> improvement effect was more remarkable at higher magnetic fields. The <TEX>$T_c$</TEX>, decrease and <TEX>$J_c$</TEX> increase associated with the glycerin treatment for boron powder was explained in terms of the carbon substitution to boron site.

Infrared laser wavelength dependence of particles ablated from glycerol

Particles were generated from glycerol that was irradiated at atmospheric pressure using a mid-infrared optical parametric oscillator at wavelengths between 2.6 and 3.8 μm. The size distribution and quantity of ejected particles with diameters larger than 300 nm were measured using an aerodynamic particle sizer. At a given fluence, the particle concentration roughly tracked the infrared absorption spectrum of liquid glycerol. The threshold fluence for particle formation varied between 1000 and 5000 J/m 2 throughout the measured wavelength range and the minimum fluence corresponds to the IR absorption maxima of glycerol. The mean particle size roughly tracks the inverse of the IR absorption and smaller particles are observed at the greatest IR absorption. The material ejection mechanism is interpreted as an explosive boiling process in the stress confinement regime.

Photoisomerization of cyanine derivatives in 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol: Influence of specific interactions

Photoisomerization of two cyanine derivatives, 3,3(')-diethyloxadicarbocyanine iodide (DODCI) and merocyanine 540 (MC 540), has been investigated in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol (93 wt % glycerol +7 wt % water) by measuring fluorescence lifetimes and quantum yields. The aim of this work is to understand how the rates of photoisomerization of DODCI and MC 540 are influenced by specific solute-solvent interactions besides the viscosity of the medium. For DODCI, it has been observed that the nonradiative rate constants, which represent the rates of photoisomerization, are almost identical in the ionic liquid and aqueous glycerol at given temperature, indicating that viscosity is the sole parameter that governs the rate of photoisomerization. In contrast, the photoisomerization rate constants of MC 540 have been found to be a factor of 2 higher in aqueous glycerol compared to the ionic liquid. The observed behavior is due to the zwitterionic character of MC 540, a consequence of which, the twisted state gets stabilized by the solute-solvent hydrogen bonding interactions in aqueous glycerol, thus lowering the barrier for isomerization.

Power dissipated measurement of an ultrasonic generator in a viscous medium by flowmetric method

A new flowmetric method of the power dissipated by an ultrasound generator in an aqueous medium has been developed in previous works and described in a preceding paper [V. Mancier, D. Leclercq, Ultrasonics Sonochemistry 14 (2007) 99–106]. The works presented here are an enlargement of this method to a high viscosity liquid (glycerol) for which the classical calorimetric measurements are rather difficult. As expected, it is shown that the dissipated power increases with the medium viscosity. It was also found that this flowmetric method gives good results for various quantities of liquid and positioning of the sonotrode in the tank. Moreover, the important variation of viscosity due to the heating of the liquid during experiments does not disturb flow measurements.

Chemical, biological and microbiological evaluation of cyclodextrin finished polyamide inguinal meshes

This study describes the use of cyclodextrins (CDs) as a finishing agent of polyamide (PA) fibers used in order to obtain inguinal meshes with improved antibiotic delivery properties. The finishing process involved polymerization between citric acid and CDs, which yielded a cross-linked polymer that physically adhered to the surface of PA fibers. This permanent functionalization was characterized by evaluating the damping property with a polar liquid (glycerol) via the drop contact angle method for various rates of modification of the fabrics. The biological and microbiological effects of the PA, which were functionalized with hydroxypropylated derivate of γ-CD (HP-γ-CDs) and charged with ciprofloxacin (CFX), were evaluated by cell culture assays. We observed a good adhesion and proliferation of fibroblastic cells (NIH3T3) after 3 and 6 days and no detectable toxicity of the modified substrate. The in vitro antibacterial activity of the HP-γ-CD grafted PA fabrics charged with CFX against the bacteria Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli was greatly superior to that of the virgin sample within a 24 h batch experiment in human blood plasma medium. In conclusion, these results from our study offer an insight into the efficient performance of CDs as drug delivery systems for multiple applications in the fields of biomaterials and medical textiles.

Nematic Pancakes Revisited

The spontaneous spreading of the 5CB nematic liquid crystal on solid substrates has been extensively studied in the last years both at the microscopic(1-4) and macroscopic(5-6) scales. The remarkable feature at the microscopic scale is the presence of a discontinuity in the thickness profile of the films. On the other hand, the spreading dynamics of macroscopic drops is quite specific. The drop first spreads like a simple liquid, and then progressively faster, while a remarkable bell-shaped profile develops at the bottom.(5-6) How the behaviors at the various scales are linked is an open question. Any answer requires reconsidering these wetting experiments deeper into the context of nematic films. More specifically, the anchoring of molecules at the interfaces(7-8) and the competition between nematic elasticity(9) and anchoring(10) must be discussed quantitatively. For the thinnest films, the problem proves to be more complex than expected and contradictory data are found in the literature. Therefore, we decided to complete our previous studies with further experiments using another compound of the cyanobiphenyls series, the 6CB in the nematic phase, and also on liquid substrates, water and glycerol. These new data confirm that the description of the thinnest nematic films is not yet fully understood.

Confinement induces both higher free volume and lower molecular mobility in glycerol

We report measurements of the local free volume and mobility of a glass-forming liquid (glycerol) confined in a mesoporous silica glass. The lower molecular mobility in confinement, measured by neutron scattering spectroscopy, is accompanied by a higher mean free volume size between molecules, measured by positron annihilation lifetime spectroscopy. The confined liquid appears to be perturbed to such an extent that the normally observed free volume/mobility relationship is reversed. This study shows that these effects originate locally at a molecular level.