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E C Peters

Publications and source records attributed to E C Peters.

14 recordsLinked to original sources
PubMed2000

Chiral monolithic columns for enantioselective capillary electrochromatography prepared by copolymerization of a monomer with quinidine functionality. 1. Optimization of polymerization conditions, porous properties, and chemistry of the stationary phase.

Monolithic columns for chiral capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine , ethylene dimethacrylate, and glycidyl methacrylate or 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as a porogenic solvent. The porous properties of the monolithic columns can easily be controlled through changes in the composition of the binary porogenic solvent. Although both thermal- and UV light-initiated polymerizations afford useful capillary columns, monoliths prepared using the former approach exhibit better chromatographic properties. The ability to control pore size independently of the polymerization mixture composition enables the preparation of monoliths with varying percentages of the chiral monomer and cross-linker, as well as the optimization of their separation properties. Very good separations of model racemate (R,S)-N-3,5-dinitrobenzoylleucine were achieved using an optimized monolithic CEC column, with high efficiencies of up to 74000 plates/m for the retained peaks.

Chromatography, Liquid↗
PubMed2000

Design of the monolithic polymers used in capillary electrochromatography columns.

Monolithic columns for capillary electrochromatography (CEC) are receiving quite remarkable attention. Both the simplicity of the in situ preparation and the large number of readily available chemistries make the monolithic separation media a vital alternative to capillary columns packed with particulate materials. This review summarizes the current state-of-the-art in this rapidly growing area of CEC with a focus on monolithic capillary columns prepared from synthetic polymers. Recent achievements in column technologies for both high-performance liquid chromatography and capillary electrophoresis are used as the starting point to highlight the influence of these well established analytical methods on the development of monolithic capillary columns for CEC. The effects of individual variables on the separation properties of monolithic capillaries are discussed in detail. The analytical potential of these columns is demonstrated with separations involving various families of compounds in different chromatographic modes.

Electrophoresis, Capillary↗
PubMed1998

Molded rigid polymer monoliths as separation media for capillary electrochromatography. 1. Fine control of porous properties and surface chemistry.

Monolithic columns for capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of butyl methacrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) in the presence of a porogenic solvent. The use of these novel macroporous monoliths eliminates the need for frits, the difficulties encountered with packed capillaries, and capillary surface functionalization. Since the porous properties of the monolithic materials can be easily tailored through changes in the composition of the ternary porogenic solvent, the effects of both pore size and the percentage of sulfonic acid monomer on the efficiency and the electroosmotic flow velocity of the capillary columns could be studied independently over a broad range. A simple increase in the content of charged functionalities within the monolith leads to an expected acceleration of the flow velocity. However, increasing the pore size leads to a substantial deterioration of the efficiency of the separation. In contrast, monoliths with increasing levels of AMPS in which the pore size remains fixed due to adjustments in the composition of the porogenic solvent show no deterioration in efficiency while maintaining the same increase in flow velocity, thus producing a significant reduction in separation time. Additionally, measurements on monoliths with constant levels of AMPS but different pore sizes suggest that flow velocity may be affected by the flow resistance within the capillary column.

Chromatography, High Pressure Liquid↗
PubMed1998

Molded rigid polymer monoliths as separation media for capillary electrochromatography. 2. Effect of chromatographic conditions on the separation.

The effect of chromatographic conditions on the performance of monolithic poly(butyl methacrylate-co-ethylene dimethacrylate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) columns in capillary electrochromatography has been studied. The flow velocity was found to be proportional to the strength of the electric field and both the pH and the composition of the mobile phase. A column efficiency of 120,000 plates/m at the optimum flow velocity of 1.5 cm/min is achieved for all the monolithic capillary columns of identical composition and porosity, regardless of their length, which varied from 30 to 120 cm. The polymeric separation medium exhibits retention and selectivity properties similar to those of typical ODS packings for reversed-phase chromatography. In addition to the "classical" use of monolithic capillary columns for the electrochromatographic separation of small molecules in reversed-phase mode, larger styrene oligomers were also separated under isocratic elution conditions. In addition, the electroosmotically driven size exclusion chromatography of polystyrene standards with molecular weights up to 10(6) has been demonstrated for the first time.

Benzene Derivatives↗
PubMed1997

Molded rigid polymer monoliths as separation media for capillary electrochromatography.

Rigid, monolithic capillary columns for reversed-phase electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of ethylene dimethacrylate, butyl methacrylate, and 2-acrylamido-2-methyl-1-propanesulfonic acid in the presence of a porogenic solvent. The composition of the specifically designed ternary porogenic solvent allows fine control of the porous properties of the monolithic material over a broad range. While the electroosmotic flow through these capillary columns increases with both increasing pore size of the monolith and content of charged functionalities, better chromatographic properties have been observed for monoliths with larger surface area and hydrophobicity. Using this technique, monolithic capillary columns with an efficiency higher than 120000 plates/m have been easily obtained.

Chromatography, High Pressure Liquid↗
PubMed1993

Epidemic misuse.

Explore the source record for details and available documents.

Animals↗
PubMed1989

Origins of cerebral palsy.

Analyses were undertaken to determine the causes of cerebral palsy in a prospective study of 43,437 full-term children. Presumed causes were found for about 71% of the 34 quadriplegic and 40% of the 116 nonquadriplegic patients with cerebral palsy. Risk estimates based on predictive models, adjusted for multiple factors, suggest that 53% of the quadriplegic patients with cerebral palsy could be attributed to congenital disorders, 14% to birth asphyxia, and 8% to other identified disorders. Thirty-five percent of the nonquadriplegic patients with cerebral palsy could be attributed to congenital disorders and 6% to other disorders. In the victims of cerebral palsy, characteristic consequences of birth asphyxia were more often the result of nonasphyxial disorders. These included meconium in the amniotic fluid, low 10-minute Apgar scores, neonatal apnea spells, seizures, persisting neurologic abnormalities, and slow head growth after birth.

Aged↗
PubMed1987

Antenatal hypoxia and low IQ values.

We undertook analyses to determine if fetal, intrapartum, and neonatal hypoxia are important causes of low IQ values. We analyzed prospectively collected pregnancy, perinatal, and subsequent developmental data for 19,117 children. As expected, sociohereditary and demographic factors had a large influence on IQ scores. Taking these latter influences into consideration, nothing that happened during labor, delivery, or the neonatal period affected subsequent IQ values. The same was true for early pregnancy disorders that can produce acute fetal hypoxia. By contrast, antenatal disorders and conditions that can produce subacute or chronic fetal hypoxia correlated with low IQ values. These antenatal disorders and conditions were maternal gestational anemia, relative gestational hypotension, hypertension, multiple births, and fetal growth retardation. All of these findings were the same whether neurologic abnormalities were absent or present, suggesting that the same factors were sometimes involved in the genesis of cognitive impairments and neurologic abnormalities.

Child↗
PubMed1986

Calicoblastic neoplasms in Acropora palmata, with a review of reports on anomalies of growth and form in corals.

Colonies of the elkhorn coral (Acropora palmata), possessing raised, whitened, irregularly shaped skeletal protuberances, were discovered at Carysfort Reef and Grecian Rocks, Key Largo National Marine Sanctuary, Key Largo, FL. These lesions exhibited relatively rapid growth and spread along the branches, as polyps were overlaid by coenosteal skeletal material. Histopathological examinations of the soft tissues surrounding and extending into the skeletal masses revealed proliferation of gastrovascular canals and associated calicoblastic epidermis, with loss of normal polyp structures and zooxanthellae. The slightly atypical tumor calicoblasts were cuboidal to columnar, resembling those found in the rapidly growing apical tips. Stable carbon isotope ratios of skeletal samples revealed that the tumor skeleton was isotopically lighter than the skeleton in the normal or apical track regions, indicative of higher tissue metabolic rates and lack of carbon isotope fractionation by zooxanthellae. This condition appears to be a neoplasm of the coral, and it is proposed that it be classified "calicoblastic epithelioma." Several different types of abnormal skeletal deposition, possibly the result of neoplastic processes, have been reported to occur in stony corals and are here reviewed.

Animals↗
PubMed1984

Mental development of children whose mothers smoked during pregnancy.

Data were analyzed from a large prospective study to try to determine whether or not women's smoking during pregnancy affects their children's mental development. Many confounding variables were controlled by multiple regression analysis and by intrapair comparisons of siblings whose mothers had smoked during one but not in the other of the two pregnancies. Hyperactivity, short attention span, and lower scores on spelling and reading tests were more frequent for children whose mothers had smoked throughout pregnancy. The cognitive abnormalities were mild, with achievement test scores only 2 to 4% lower in children whose mothers had smoked during pregnancy. The behavioral abnormalities in children of smokers were associated with elevated neonatal hemoglobin levels and low birth weights, suggesting that fetal hypoxemia possibly may contribute to the genesis of behavioral abnormalities.

Attention↗
PubMed1982

Working during pregnancy: effects on the fetus.

In order to determine whether pregnancy outcome was altered when women were employed outside their homes, 7,722 pregnancies were analyzed. Gestations were not shortened but newborns of women who worked in the third trimester weighed 150 to 400 gm less than newborns of mothers who remained at home. The growth retardation was greatest when women were underweight pregravid and had a low pregnancy weight gain, when they were hypertensive, or when the work required standing. The growth retardation remained after the data were stratified by race, socioeconomic status, and other maternal factors that commonly influence fetal growth. The frequency of large placental infarcts progressively increased when women continued stand-up work into late gestation. Such infarcts reached a peak of 250/1,000 births after the 37th week of gestation in stand-up workers. Low uteroplacental blood flow is a likely explanation for both the fetal growth retardation and the large placental infarcts.

Birth Weight↗
PubMed1980

Causes and consequences of premature rupture of fetal membranes.

Data from 6613 pregnancies that ended before term were analysed to determine whether amniotic-fluid infections are a cause as well as a consequence of premature rupture of the fetal membranes. Amniotic-fluid infections seem to be a cause of such ruptures because the infections were 2-3 fold more common when the fetal membranes ruptured just before labour started than when they ruptured just after the onset of labour. There was no relation between the frequency of premature rupture and the number of coital acts in the month before delivery but at every gestational age the proportion of fetuses and neonates who died with amniotic-fluid infections was greater when coitus had occurred in the month before delivery. This was because the infections associated with coitus were more severe. Low Apgar scores and neonatal hyperbilirubinaemia were 60% more frequent when preterm delivery was due to premature rupture of the membranes than when it was due to other causes. This was mainly the result of the high frequency of amniotic-fluid infections associated with the premature membrane ruptures.

Amniotic Fluid↗
PubMed1978

Amniotic fluid infections with intact membranes leading to perinatal death: a prospective study.

The pathogenesis of fatal amniotic fluid infections was analyzed in a large prospective study that included more than 1,000 medical, demographic, hereditary, and postmortem variables. The disorder was the most frequent cause of death in the study, with an overall perinatal mortality of 6.17 per 1,000 births. The mortality progressively declined after mid-gestation when antimicrobial activity normally appears in the amniotic fluid. A second peak of the fatal infections, after 37 weeks' gestation, was found mainly in the poor and undernourished. Maternal gestational weight gains were suboptimal and the involved neonates had a pattern of growth retardation characteristic of undernutrition. Maternal pregnancy weight gains were positively correlated with the number of prenatal clinic visits. Mother's race, socioeconomic status, age, short stature, and number of prior unsuccessful pregnancies lost their positive association with the fatal infections when mothers made more than nine clinic visits.

Amniotic Fluid↗