EG Concentration Research Articles

Functionalized graphene sheet—Poly(vinylidene fluoride) conductive nanocomposites

AbstractPVDF nanocomposites based on functionalized graphene sheets, FGS prepared from graphite oxide, and exfoliated graphite, EG, were prepared by solution processing and compression molding. FGS remains well dispersed in the PVDF composites as evidenced by the lack of the characteristic graphite reflection in the composites. Although the α‐phase of PVDF is seen in the EG‐based composites, a mixture of α‐ and β‐phases is present in the FGS analogs. SEM and TEM imaging show smooth fractured surfaces with oriented platelets of graphite stacks and obvious debonding from the matrix in the EG‐PVDF composites. In contrast, the FGS‐PVDF composites show a wrinkled topography of relatively thin graphene sheets bonded well to the matrix. Storage modulus of the composites was increased with FGS and EG concentration. A lower percolation threshold (2 wt %) was obtained for FGS‐PVDF composites compared to EG‐PVDF composites (above 5 wt %). Lastly, the FGS‐PVDF composites show an unusual resistance/temperature behavior. The resistance decreases with temperature, indicating an NTC behavior, whereas EG‐PVDF composites show a PTC behavior (e.g., the resistance increases with temperature). We attribute the NTC behavior of the FGS based composites to the higher aspect ratio of FGS which leads to contact resistance predominating over tunneling resistance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 888–897, 2009

Crystallization and vitrification of cryoprotectants studied by Raman scattering, Brillouin scattering and THz-TDS

We examine one of the best candidates of cryoprotectant, ethylene glycol aqueous solutions by using Raman and Brillouin scattering and Terahertz time domain spectroscopy. The molecular structure can be determined by Raman scattering and the EG aqueous solutions were investigated to characterize the conformations of molecular structure. The intermediate concentrations of EG solutions easily undergo glass transitions, while the crystallization occurs in the solutions of low and high concentrations of EG. The structural configuration of EG in a crystalline phase in pure EG shows only gauche OCCO form of EG which is the lowest energy conformers, while gauche and trans forms exist in a liquid phase. The dynamical properties from gigahertz to terahertz frequency range are investigated by using Raman scattering, Brillouin scattering and terahertz time domain spectroscopy (THz-TDS). In the present frequency range, the relaxation and vibrational modes coexist. It is shown that the combination of giga to terahertz spectroscopy is a powerful tool to provide information on fast dynamics of bioprotective solutions.

Composite poly(vinyl alcohol)–poly(sulfone) membranes crosslinked by trimesoyl chloride: Characterization and dehydration of ethylene glycol–water mixtures

Composite membranes prepared from poly(vinyl alcohol) and poly(sulfone) were crosslinked with trimesoyl chloride (TMC) solutions. The degree of crosslinking, crystallinity, surface roughness and hydrophobicity of the crosslinked PVA–PSf membranes were determined from attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle measurements, respectively. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophobicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with pervaporation dehydration of ethylene glycol solutions at a range of concentrations (30–90 wt% EG) in the feed mixtures. The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. In addition, the temperature effect on the pervaporation dehydration was investigated in relation to solution–diffusion mechanisms.

52. Changes in intracellular potassium and sodium content of 2-cell mouse embryos induced by exposure to vitrification concentrations of EG and Me 2SO

52. Changes in intracellular potassium and sodium content of 2-cell mouse embryos induced by exposure to vitrification concentrations of EG and Me 2SO

Mild Tubular Damage Induces Calcium Oxalate Crystalluria in a Model of Subtle Hyperoxaluria

Environment and diet have a major role in calcium nephrolithiasis by affecting urine saturation, but this is not enough to cause lithogenesis; the crystals must adhere to the tubular epithelium (TE), but it is hard to say how environment and nutrition may be involved in this step. The hypothesis that TE damage (known to enhance crystal attachment) is lithogenic in mild hyperoxaluria was tested. Mild hyperoxaluria was induced in male Wistar rats using ethylene glycol (EG; 0.5% in water) for 21 d, and TE damage was induced by intraperitoneal administration of hexachloro-1:3-butadiene (HCBD; an industrial nephrotoxin) at 10, 25, and 50 mg/kg body wt on days 7 and 14. These EG and HCBD concentrations were chosen to span from suboptimal to very low doses as far as effects on crystalluria and TE damage are concerned. Enzymuria, proteinuria, oxaluria, crystalluria, and renal pathology were investigated. All HCBD dosages induced crystalluria in mildly hyperoxaluric rats, but no intrarenal crystals were found. EG alone induced very mild hyperoxaluria but no damage to the renal tubule observable on transmission electron microscopy, and it did not cause crystalluria or intrarenal crystals. HCBD with the concomitant administration of EG caused apoptosis of the TE at the two highest dosages after the second injection. Apoptosis did not correlate with crystalluria. A TE toxin is needed for crystallogenesis to occur in borderline metabolic conditions. It may take more than just a metabolic predisposition for calcium nephrolithiasis to occur, and the second hit could come from an environmental pollutant such as HCBD.

Cryopreservation of rat hippocampal slices by vitrification

Although much interest has attended the cryopreservation of immature neurons for subsequent therapeutic intracerebral transplantation, there are no reports on the cryopreservation of organized adult cerebral tissue slices of potential interest for pharmaceutical drug development. We report here the first experiments on cryopreservation of mature rat transverse hippocampal slices. Freezing at 1.2 °C/min to −20 °C or below using 10 or 30% v/v glycerol or 20% v/v dimethyl sulfoxide yielded extremely poor results. Hippocampal slices were also rapidly inactivated by simple exposure to a temperature of 0 °C in artificial cerebrospinal fluid (aCSF). This effect was mitigated somewhat by 0.8 mM vitamin C, the use of a more “intracellular” version of aCSF having reduced sodium and calcium levels and higher potassium levels, and the presence of a 25% w/v mixture of dimethyl sulfoxide, formamide, and ethylene glycol (“V EG solutes”; Cryobiology 48, pp. 22–35, 2004). It was not mitigated by glycerol, aspirin, indomethacin, or mannitol addition to aCSF. When RPS-2 (Cryobiology 21, pp. 260–273, 1984) was used as a carrier solution for up to 50% w/v V EG solutes, 0 °C was more protective than 10 °C. Raising V EG concentration to 53% w/v allowed slice vitrification without injury from vitrification and rewarming per se, but was much more damaging than exposure to 50% w/v V EG. This problem was overcome by using the analogous 61% w/v VM3 vitrification solution (Cryobiology 48, pp. 157–178, 2004) containing polyvinylpyrrolidone and two extracellular “ice blockers.” With VM3, it was possible to attain a tissue K +/Na + ratio after vitrification ranging from 91 to 108% of that obtained with untreated control slices. Microscopic examination showed severe damage in frozen–thawed slices, but generally good to excellent ultrastructural and histological preservation after vitrification. Our results provide the first demonstration that both the viability and the structure of mature organized, complex neural networks can be well preserved by vitrification. These results may assist neuropsychiatric drug evaluation and development and the transplantation of integrated brain regions to correct brain disease or injury.

Solid-state polycondensation of poly(ethylene terephthalate) modified with isophthalic acid: kinetics and simulation

The kinetics for the solid-state polycondensation (SSP) of poly(ethylene terephthalate) modified with isophthalic acid at the protection of nitrogen gas was studied in the paper. A kinetic model controlled by the reversible chemical reactions and the three dimension diffusions of small molecule by-products has been established. The kinetic parameters of the SSP of PET at different temperatures, including the forward rate constants of transesterification reaction ( k 1) and esterification reaction ( k 2), the diffusion coefficients of EG ( D 1) and water ( D 2), the concentrations of EG ( g s) and water ( w s) on the surface of PET chips in SSP, and the activation energies of these kinetic parameters were obtained by experiments and solution of the model. Using the model and the kinetic parameters, the SSP of poly(ethylene terephthalate) modified with isophthalic acid can be simulated with good accuracy. In addition, the influences of nitrogen gas flow rate, the chip dimension and the carboxyl end-group concentration of the PET prepolymer on the molecular weight of PET after SSP, and the change of the EG concentration of PET chips with reaction time were also studied by simulation.

Effect of dietary esterified glucomannan on performance, serum biochemistry and haematology in broilers exposed to aflatoxin

The amelioration of aflatoxicosis in broiler chickens was examined by feeding two concentrations of yeast component (esterified glucomannan; EG). EG, incorporated into the diet at 0.5 and 1 g/kg, was evaluated for its ability to reduce the detrimental effects of 2 mg total aflatoxin (AF; 82.72% AFB<sub>1</sub>, 5.50% AFB<sub>2</sub>, 10.20% AFG<sub>1</sub> and 1.58% AFG<sub>2</sub>) in diet on growing broiler chicks from 1 to 21 d of age. A total of 240 male broiler chicks (Ross-308) were divided into 6 treatment groups [control, AF, EG (0.5 g/kg), AF plus EG (0.5 g/kg), EG (1 g/kg), and AF plus EG (1 g/kg)]. Compared to the control, AF treatment significantly decreased body weight gain from week 2 onwards. AF treatment also caused significant decreases in serum total protein, albumin, total cholesterol, triglyceride, glucose, inorganic phosphorus, creatinine levels and alanine-aminotransferase (ALAT) activity but increased the aspartate-aminotransferase (ASAT) activity. Red blood cell, haematocrit, haemoglobin, thrombocyte, and lymphocyte counts and tibial crude ash levels were significantly reduced by AF treatment, while significant increases were seen in heterophil counts. The addition of EG (1 g/kg) to an AF-containing diet significantly improved the adverse effects of AF on haematological parameters, total protein, albumin values and ASAT activity. EG (1 g/kg) also partially improved body weight gains (59%) and the other biochemical parameters influenced by AF treatment. The addition of EG (both 0.5 and 1 g/kg) to the AF-free diet did not cause any considerable changes in the investigated values. These results clearly indicated that EG (1 g/kg) addition effectively diminished the adverse effects of AF on the investigated values. Also, the higher dietary concentration of EG (1 g/kg) was found more effective than the lower concentration (0.5 g/kg) against the adverse effects of AF on the variables investigated in this study.  

Ethylene glycol: an estimate of tolerable levels of exposure based on a review of animal and human data.

Upon ingestion ethylene glycol (EG, monoethylene glycol) is rapidly absorbed from the gastrointestinal tract, and depending on the severity of exposure signs of toxicity may progress through three stages. Neurological effects characterize the first step consisting of central nervous depression (intoxication, lethargy, seizures, and coma). The second stage, usually 12-24 h after ingestion, is characterized by metabolic acidosis due to the accumulation of acidic metabolites of EG, primarily glycolic acid (GA), contributing to the ensuing osmolal and anion gaps. Stage 3, generally 24-72 h after ingestion, is determined mainly by oxalic acid excretion, nephropathy, and eventual renal failure. Because the toxicity of EG is mediated principally through its metabolites, adequate analytical methods are essential to provide the information necessary for diagnosis and therapeutic management. The severe metabolic acidosis and multiple organ failure caused by ingestion of high doses of EG is a medical emergency that usually requires immediate measures to support respiration, correct the electrolyte imbalance, and initiate hemodialysis. Since metabolic acidosis is not specific to EG, whenever EG intoxication is suspected, every effort should be made to determine EG as well as its major metabolite GA in plasma to confirm the diagnosis and to institute special treatment without delay. A number of specific and sensitive analytical methods (GC, GC-MS, or HPLC) are available for this purpose. Due to the rapid metabolism of EG, the plasma concentration of GA may be higher than that of EG already upon admission. As toxicity is largely a consequence of metabolism of EG to GA and oxalic acid, the simultaneous quantification of EG and GA is important. Formation of calcium oxalate monohydrate in the urine may be a useful indicator of developing oxalate nephrosis although urine crystals can result without renal injury. The pathways involved in the metabolism of EG are qualitatively similar in humans and laboratory animals, although quantitative differences have been reported. Comparison between species is difficult, however, because the information on humans is derived mainly from acute poisoning cases whereas the effects of repeated exposures have been investigated in animal experiments. Based on published data the minimum human lethal dose of EG has been estimated at approx. 100 ml for a 70-kg adult or 1.6 g/kg body weight (calculation of dose in ml/kg to mg/kg based in EG density=1.11 g/l). However, human data from case reports are generally insufficient for the determination of a clear dose-response relationship and quantification of threshold doses for systemic toxicity, in particular renal effects, is limited. As toxicity is largely a consequence of metabolism of EG to GA, it is important to note that no signs of renal injury have developed at initial plasma glycolate concentrations of up to 10.1 mM (76.7 mg/dl). Plasma EG levels of 3.2 mM (20 mg/dl) are considered the threshold of toxicity for systemic exposure, if therapeutic strategy is based on the EG concentration alone.

Ice adhesion of an aqueous solution including a surfactant with stirring on cooling wall: ethylene glycol—a silane coupling agent aqueous solution

Ice adhesion to the cooling wall directly hinders continuous ice formation or system performance due to the increase of flow and thermal resistance. In order to obtain the basic characteristics of two- or three-component aqueous solutions with EG, SCA and water on freezing, the influence of component ratio and supercooling degree on those solutions was investigated through a batch type freezing process of the solutions. Moreover, the strength of ice adhesion was shown to vary by stirring power. Ice adhesion was suppressed when (1) the solution including the additive SCA at comparatively high concentration; (2) the solution had high initial concentration of EG or SCA; (3) the brine temperature was higher; (4) the supercooling degree was comparatively small in the lower concentrations. No ice adhesion occurred at the stirring power below 30 W. Furthermore, particle size of the ice slurry was smaller in higher concentrations.

Foam-mat drying of cowpea ( Vigna unguiculata ) using glyceryl monostearate and egg albumin as foaming agents

Foam-mat drying of cowpea using glyceryl monostearate (GMS) and egg albumin (EG) as foaming agents was investigated. GMS and EG were incorporated into cowpea paste (22%, 25% and 28% total solids) at 2.5, 5.0, 7.5, 10.0, 12.5 and 15% (w/w), and whipped for 3, 6, 9, 12, 15, 18 and 21 min, maintaining 15, 25 and 35 °C foaming temperatures. Foam density was measured and expressed in g/cm3. Cowpea foams were dried at 60 °C (Twb, wet bulb temperature 35 °C) for 48 min. Sensory attributes of akara produced from fresh and reconstituted pastes were evaluated. Generally, foam density decreased with increased concentrations of GMS and EG in cowpea paste. Foam density decreased with decrease in total solids of cowpea paste. Minimum foam densities were obtained in cowpea foams with GMS and EG after 9 and 21 min of whipping, respectively. EG-stabilized foams were unstable for drying. Sensory evaluation showed no significant difference (P>0.05, 0.01) in the quality attributes of akara produced from fresh and reconstituted GMS-stabilized cowpea powders.

The measurement of oestrone-3-glucuronide in urine by non-competitive idiometric assay

We report a novel non-competitive idiometric assay for the measurement of oestrone-3-glucuronide (EG) in diluted urine. The method is based on the use of two types of anti-idiotypic antibody, the β-type and α-type, that recognize different epitopes within the hypervariable region of the primary anti-EG antibody (Ab 1). The β-type anti-idiotypic antibody is analyte sensitive and competes with the analyte for an epitope of the primary antibody at the binding site. On the other hand, the α-type is analyte insensitive, but does not bind the Ab 1 in the presence of the β-type due to epitope proximity. In the present format, reaction mixtures containing the europium labelled Ab 1 are reacted sequentially with EG standards or diluted urine samples, with the β-type anti-idiotypic antibody and biotinylated α-type anti-idiotypic antibody on immobilized streptavidin coated microtiter plates. After 1 h incubation, the fluorescence of europium is measured by a time-resolved fluorescence and is proportional to the concentration of EG over a range of 0–10 nmol/l. The method demonstrates good sensitivity, precision and comparability with an alternative competitive fluorescent immunoassay. The idiometric assay for EG may be applied for the monitoring of ovarian function in women and is suitable for dipstick technology.

Nucleation and Growth of Ice Crystals in Concentrated Solutions of Ethylene Glycol

Ice formation in concentrated solutions of ethylene glycol (EG; 48 to 53 wt%) was studied after various thermal histories. To characterize the rate of ice nucleation as a function of temperature (to - 150°C), the solutions were cooled at a constant rate to the nadir temperature and then warmed to a storage temperature ( T s) at which ice formation was studied under isothermal conditions using differential scanning calorimetry (DSC) and cryomicroscopy. The DSC data were analyzed using the Johnson-Mehl-Avrami (JMA) model of isothermal transformation. The model contains two parameters: a kinetic constant K and a reaction-order parameter n. The kinetic constant was used to quantify the relative stability of the amorphous vs frozen state and rates of ice nucleation and growth in highly supercooled solutions of EG. Our theoretical analysis suggests that the kinetic constant is proportional to the diffusion coefficient D of water molecules and to the 2 3 power of the concentration of ice nuclei that form in a solution prior to storage at T s. Experimentally, the kinetic constant is shown to be the product of two values, the first of which is dependent on the nadir temperature and the second on storage temperature. Increases in the kinetic constant corresponding to two nucleation events occurred with decreasing nadir temperature. During cooling the second ice nucleation event began at a temperature approximately 20°C lower than that at which the first nucleation event was completed. For example, in solutions containing 50 to 51.5 wt% EG, the first nucleation event occurred at temperatures between -80 and -100°C and the second nucleation event occurred at temperatures between 120 and - 135°C, which is in the vicinity of the glass formation temperature ( T g). Cryomicroscopic measurements of the spherulite concentration confirmed the appearance of the first and second nucleation events in EG solutions. DSC studies showed that the total amount of nucleation increased approximately 20-fold if the concentration of EG was decreased from 51 to 48 wt%. Only about 10% of this increase was associated with the first nucleation event and the remainder was the result of the second nucleation event. Furthermore, the proportion of nucleation attributable to the first and second nucleation events was dependent on the EG concentration. At concentrations ⩾51 wt% EG, the majority of ice nuclei formed during the first nucleation event. However, in a 48 wt% EG solution the kinetic constant measured after cooling to T n ⩾ -100°C, when only the first nucleation event occurred, was about 16 times smaller than that measured after cooling to T n = - 150°C, when both the first and second nucleation events occurred. For this reason, the second nucleation event is the principal cause of the decrease in stability of the amorphous state in EG solutions in which the concentration is decreased from 51 to 48 wt%. Therefore, the minimum concentration of cryoprotectant needed for vitrification at a given cooling and warming rate can be substantially reduced if the rate of ice nucleation can be decreased. Addition of bovine serum albumin (BSA) decreased the value of the kinetic constant determined for concentrated solutions of EG; however, the effect of BSA was small in comparison to that which could be effected by a small increase in the concentration of EG. For example, the decrease in the nucleation parameter, which was affected by addition of 6 g of BSA to 100 g of a 48 wt% EG solution, could also be achieved by increasing the EG concentration by 0.4 wt%.

A mathematical model for a continuous esterification process with recycle between terephthalic acid and ethylene glycol

AbstractA new mathematical model for a continuous recycle esterification process has been derived by basically the same procedure as the continuous process of a cascade type, reported earlier, which includes material and heat balances. Such a model can give extensive information about the optimum design of a new plant through the predictions of oligomer characteristics (concentrations of carboxyl and hydroxyl end groups, number average molecular weight, number average degree of polymerization, esterification and saponification degree, DEG content, melting point of oligomer, etc.), distillate properties (concentrations of EG and water in the vapor phase), heat transfer area, mass flow rate of heating medium, amount of heat supplied by heating medium, enthalpy moving with recycle, and amount of heat removed from each reactor. © 1992 John Wiley & Sons, Inc.

Depolymerization of poly(ethylene terephthalate) resin under pressure

AbstractThe process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of depolymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the depolymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of higher molecular weight of oligomers rather than monomer, dimer, and trimer.

RTA removal of E-beam-induced damage in GaAs-AlGaAs heterostructures as determined by magnetotransport characterization

Measurement was made of the effect of electron energy on the 2D EG transport properties of high electron mobility transistor (HEMT) structures at low temperatures. The structures were grown by molecular beam epitaxy (MBE) with a 2D EG approximately 850A below the surface. A Cambridge EBMF 10.5 was used for electron irradiation with electron energies between 2.5 and 20 keV. The HEMTs were fabricated into Hall bars, and damage was assessed by changes in the 2D EG concentrations as determined from Shubnikov-de Haas oscillations and changes in the mobility as determined from the zero magnetic-field resistivity. For electron energies from 5.0 to 12.5 keV, the electron dose produced a degradation of the Hall mobility. No damage was observed for electron energies outside this range; this result is attributed to the penetration depth and damage distribution. The effect of performing RTA on all samples simultaneously at 450° C for 30 sec was to remove damage and in some cases restore the sample to its original mobility.

Electron-beam-induced damage study in GaAs-AlGaAs heterostructures as determined by magnetotransport characterization

The effect of electron energy on the two-dimensional electron gas (2D EG) transport properties of high-electron-mobility transistor (HEMT) structures at low temperatures is measured. The structures were grown by molecular beam epitaxy (MBE) with a 2D EG approximately 850 AA below the surface. The HEMTs were fabricated into Hall bars, and damage was assessed by changes in the 2D EG concentrations as determined from Schubnikov-de Haas oscillations and changes in the mobility as determined from the zero magnetic-field resistivity. For electron energies from 5.0 to 12.5 keV, the electron dose produced a degradation of the Hall mobility. No damage was observed for electron energies outside this range; this result is attributed to the penetration depth and damage distribution. >

Vinyl chloride-induced DNA adducts I: Quantitative determination of N2,3-ethenoguanine based on electrophore labeling

A sensitive assay for quantitative determination of the vinyl chloride (VC)-induced cyclic DNA adduct N2,3-ethenoguanine (EG) was developed. The method is based on the detection of EG as its di-pentafluorobenzyl derivative (3,5-PFB2-EG). This compound exhibited good gas chromatographic properties and was detected with high sensitivity by gas chromatography with electron capture detection (limit of detection 300 amol/microliters injected solution) or with negative ion chemical ionization mass spectrometry monitoring the [M-181]-fragment ion at m/z 354 (GC-NICI-MS, limit of detection 190 amol/microliters injected solution). EG, its 13C-labeled analog [13C4]-EG and 3,5-PFB2-EG were synthesized and characterized by UV and fluorescence spectrophotometry, 1H- and 13C-NMR spectroscopy and mass spectrometry. The standards were used to optimize the isolation of EG and its derivatization with pentafluorobenzyl bromide (electrophore labeling) at fmol quantities. DNA solutions were spiked with EG, the DNA was depurinated by mild acid hydrolysis, and EG was isolated from the hydrolysates by low-pressure strong cation exchange chromatography with subsequent C18 solid-phase extraction. The extracted EG was electrophore labeled and 3,5-PFB2-EG was detected using GC-NICI-MS. [13C4]EG served as internal standard. 3,5-PFB2-EG was quantitated relative to its 13C-labeled analog by measuring the ion ratio m/z 354/358. The limit of detection for the complete method was 60 fmol EG/mumols guanine. The method was applied to liver DNA from young Sprague-Dawley rats exposed to 600 p.p.m. VC from day 10 through day 14 after birth. The EG concentration in these samples was 1.8 +/- 0.3 pmol/mumols guanine.

Vinyl chloride-induced DNA adducts II: Formating and persistence of 7-(2'oxoethyl)guanine and N2 ,3 ethenoguanine in rat tissue DNA

The formation and persistence of the DNA adducts 7-(2'-oxoethyl)guanine (OEG) and N2,3-ethenoguanine (EG) were investigated in preweanling Sprague-Dawley rats exposed to vinyl chloride (VC). Lactating female CD rats with 10 day old pups were exposed to 600 p.p.m. VC by inhalation for 5 days, 4 h/day. Groups of rats were killed immediately and 3, 7 and 14 days after exposure. The concentrations of OEG and EG were measured in liver, lung, kidney, brain and spleen. HPLC with fluorescence detection was used for OEG detection, and gas chromatography-negative ion chemical ionization mass spectrometry was used for EG detection. In tissues of neonatal rats, the concentrations of both DNA adducts, expressed as pmol/mumols unmodified guanine, were highest in liver (OEG 162 +/- 36, EG 1.81 +/- 0.25), followed by kidney (OEG 29 +/- 1, EG 0.31 +/- 0.02), and lung (OEG 20 +/- 7, EG 0.21 +/- 0.08). No adducts were found in brain or spleen. DNA adducts were detected only in liver (OEG 43 +/- 7, EG 0.47 +/- 0.14) and lung (OEG 20 +/- 5, EG 0.27 +/- 0.03) of the dams. The ratio between EG and OEG was approximately 1:100 in all tissues immediately after exposure. In the liver of the preweanling rats, this ratio increased to 1:14 1 week after exposure, reflecting a greater persistence of EG. A half-life of 62 h was calculated for OEG, and the estimated half-life for EG was greater than 30 days. In view of the slow loss of EG and its high efficiency for causing base-pair mismatch, these results suggest that EG may be an important DNA adduct in VC-induced carcinogenesis.

Colloid stability of silver iodide in water-ethylene glycol mixtures

This paper treats the stability of silver iodide sols in water-ethylene glycol (EG) mixtures. Rates of coagulation, obtained by a stopped-flow technique are analyzed in combination with data on surface charge, conductivity, and density. To some extent, bulk solution properties are reflected in the stability. For instance, indications of contraction, with a maximum at a molar ratio water/EG ≈2 recur in the rates of fast coagulation. It is impossible to describe the transition from water to EG through the variation of the bulk dielectric permittivityonly, because drastic alterations occur also in the Stern layer. Especially its change in thickness and the increasing specific counterion adsorption with increasing EG content are important stability-determining factors. Particularly at high EG concentrations, the outerHelmholtz plane may not be considered as a smeared-out equipotential plane. The mosaic-like potential pattern of this layer suggests the necessity to reconsider the dynamics of particle interactions.