Micellar polymerisation of ionic surfactants studied by conductimetry

The micellar polymerisation of ionic surfactants such as allyldodecyl-dimethylammonium bromide and 3-dodecyl-1-vinyl imidazolium iodide has been studied by conductimetry in aqueous solution. The polymerisation was carried out using two different sources of γ rays directed into solutions of surfactant above the critical micellar concentration. Conductimetry is shown to be a very good physicochemical method for analysis of these solutions. The results showed different behaviour for the two surfactants, which has highlighted a change in the structure of their aggregates which led to the assumption of an interaction between the polymers of high mass and different products of the polymerisation (oligomers, products of degradation, monomers etc.). Ultrafiltration experiments coupled with ¹H-NMR and conductivity analysis confirm these assumptions.     

An evaluation of Landsat TM spectral data and SAR-derived textural information for lithological discrimination in the Red Sea Hills,Sudan

The effectiveness of spectral and textural information in the identification of surface rock types in an arid region, the Red Sea Hills of Sudan, is evaluated using spectral information from the six Landsat TM optical bands and textural features derived from Shuttle Imaging Radar-C (SIR-C) C-band HH polarization data. An initial classification is derived from Landsat TM data alone using three classification algorithms, Gaussian maximum likelihood, a multi-layer feed-forward neural network and a Kohonen self-organizing feature map (SOM), to generate lithological maps, with classification accuracy being measured using a confusion matrix approach. The feed-forward neural net produced the highest overall classification accuracy of 57 per cent and was, therefore, selected for the second experiment, in which texture measures from SIR-C C-band HH-polarized synthetic aperture radar (SAR) data are added to selected TM spectral features. Four methods of measuring texture are employed, based on the Fourier power spectrum, grey level co-occurrence matrix (GLCM), multi-fractal measures, and the multiplicative autoregressive random field (MAR) model. The use of textural information together with a subset of the TM spectral features leads to an increase in classification accuracy to almost 70 per cent. Both the MAR model and the GLCM matrix approach perform better than Fourier and multi-fractal based methods of texture characterization.     

Associated factors to dietary intake of fruits and vegetables in Bucaramanga, Colombia

The objective of this study was to determine associated factors to the consumption of fruit and vegetables (FV) in the adult population of each socioeconomic status (SES) in Bucaramanga, Colombia. We conducted a cross-sectional in a sample of 317 people and we measured socio-demographic, economic and anthropometric variables and dietary factors related to the purchase and consumption of FV. We made a survey, a 24-Hour dietary recall and we did anthropometric measurements. Portion sizes were estimated with a standardized set of utensils and food-photography atlas. Frequencies, measures of central tendency and dispersion were established and Logistic Regression models were used for the bi and multivariate analysis. Average consumption of FV was 162.6 g/day (188.5 g in high SES and 145.7 g in low SES, p = 0.056). On average 2 servings per day of FV (2.3 servings in high SES and 1.5 in low SES, p = 0.055). The prevalence of adequate intake of FV (more than 5 servings / day) was 8.6% (8.9% in high SES and 8.4% in low SES, p = 0.896). The associated factor to consumption of FV was BMI > or =25 (OR: 0.31, CI (95%): 0.11-0.89, p = 0.030), adjusted for occupation, income, SES, and number of family members. FV consumption is low; excess weight is the only variable associated to no-consumption of five or more servings; causes: cost to the consumption of fruit and flavor in the case of vegetables.     

Gamma ray degradation of electrolytes containing alkylcarbonate solvents and a lithium salt

Lithium-ion batteries for space applications, such as satellites, are subjected to cosmic radiations, in particular, γ-irradiation. In this study, the effects of this radiation on electrolytes and their components used in the lithium-ion batteries are investigated. The conductivity and viscosity of the samples have been measured before and after the irradiation. The modifications are evaluated by spectral analyses such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR), solid phase microextraction-gas chromatography (SPME-GC) and gas chromatography-mass spectroscopy (GC-MS). The experimental results show that only the samples containing vinylene carbonate and/or the lithium salt LiPF₆ are degraded by γ-radiation.     

99Tc- and 239Pu-Doped Glass Leaching Experiments: Residual Alteration Rate and Radionuclide Behavior

The long-term behavior of high-level nuclear glass subjected to alpha/beta radiation by long-life radionuclides must be investigated with respect to geological disposal. This study focuses on the effects of alpha and beta radiations on the chemical reactivity of R7T7 glass with pure water, mainly on the residual alteration rate regime. Glass specimens doped with 0.85 wt% ²³⁹PuO₂ (α emitter) and 0.24 wt% ⁹⁹TcO₂ (β emitter) that simulate alpha and beta dose rate corresponding to long-term disposal conditions are leached under static conditions in argon atmosphere at 90°C, in initially pure water and at a high surface-area-to-volume ratio (S/V = 20/cm). The alteration rate is monitored by the release of glass alteration tracer elements (B, Na, and Li). Radiation effects on the leached glass and its gel network are characterized by SEM and TEM analyses. Plutonium and technetium releases are also measured by radiometry, and their chemical oxidation state is assessed by measuring the pH and reduction–oxidation potential of the leachates. The results do not highlight any significant effect of alpha/beta radiation on the residual alteration of these doped glasses. These observations are consistent with solid characterizations, which show that a protective layer can be formed under such irradiation fields. Under our experimental conditions (Eh~380 mV/SHE, pH_90°C = 8–8.6), very low concentrations of soluble plutonium are measured in the leachate, indicating strong plutonium retention, whereas technetium performs as a soluble element and is not retained in the altered layer.     

Gender and Ethnicity Differences in Freshmen Engineering Student Attitudes: A Cross‐Institutional Study*

We examine the attitudes of entering freshman engineering students and how they change over the course of the first year at 17 institutions. In addition to better understanding these attitudes and the changes that occur, we explore how these changes potentially affect such issues as “first term probation” and attrition from engineering programs. Particular attention is directed at isolating differences due to gender and ethnicity. Thirteen different student attitudes were captured using the Pittsburgh Freshman Engineering Attitude Survey© (PFEAS) at the beginning of the first semester (pre) and at either the end of the first semester or first academic year (post). Definite gender differences were found on the pre‐survey for five of the attitude measures. For all but one of these measures, female engineering students' initial attitudes were more negative than those of male students. Across the sample of institutions, female students consistently began their engineering studies with a lower confidence in background knowledge about engineering, their abilities to succeed in engineering, and their perceptions of how engineers contribute to society than did their male counterparts. However, those same female students were more comfortable with their study habits than were the male students. The post questionnaire data indicated that differences for three of these five attitude measures persisted. Most important, female engineering students continued to maintain a lower confidence in their abilities to succeed in engineering as compared to male engineering students. When the PFEAS data were mapped into EC 2000 outcomes, comparable cross‐institutional gender differences were observed that paralleled those found for the attitudinal measures. Because the number of minority students was relatively small, significant cross‐institutional differences between each minority cohort studied (African American, Asian Pacific, and Hispanic) and the majority cohort, similar cross‐institutional patterns could not be observed. However, possible trends were found between African American and majority students' attitudes for certain measures, while other attitudinal measures were found to be significant when Hispanic students were compared to majority students. Significant attitudinal differences between Asian Pacific and majority students were similar to those found between female and male engineering students. By knowing how attitudinal measures differ among gender and ethnic cohorts, and understanding how those differences relate to attrition from engineering programs, we can then developed more informed programmatic initiatives that can impact these attitude in a positive manner. As a result, we may be able to reduce engineering attrition, especially by underrepresented student cohorts.     

Capillary isotachophoresis as a promising technique for the study of ionic surfactant micellization

Capillary isotachophoresis was investigated as a complementary technique to the determination of the major electrochemical parameters of ionic micelles, including critical micellar concentration, charge ratio, electrophoretic mobility and parameters of the micellization equation. The leading electrolyte parameters (mainly leading ion concentration, solvent composition and counterion nature) can readily be selected so as to promote and control micellization of the surfactant to be studied in the migration conditions. Then, the determination of the step height and length of the micelle zone give a direct access to micelle mobility and charge ratio. In addition, it was found that, when a given amount of surfactant is injected together with a ca. 2–4-fold amount of a reference mobility marker with a mobility in between those of the free and micellized forms of the surfactant, the micelle zone length is markedly decreased, while that of the marker is increased. This phenomenon was described as a pollution of the marker zone by the free and micellized forms of surfactant, and theoretically interpreted. The straightforward experimental measurement of the level of this pollution provides an additional relationship between most of the micelle parameters.     

Immunocytochemical localization of lingual lipase in serous cells of the developing rat tongue

The ontogeny of the rat lingual serous and mucous glands was explored by light and electron immune microscopy using the peroxidase-antiperoxidase and streptavidin-gold techniques. Tissues from fetal and neonatal rats from day 18 of gestation through 4 wk after birth were fixed and embedded in paraffin or Epon for light and transmission electron microscopy, respectively. Electron microscopy revealed that the only cells containing lingual lipase were the developing serous cells; secretory granules containing lingual lipase of varying degrees of maturity were seen. Mucous cells did not show immunospecific staining in rats of any age. The neonatal “mixed” lingual glands secrete lingual lipase from serous components immediately after birth to aid in fat digestion.     

Multi-resolution and temporal characterization of land-use classes in a Mediterranean wetland with land-cover fractions

Four different methods for analysing land-use and land-cover fractions at multiple scales, namely composite operator, t-test, Dutilleul’s modified t-test and ternary diagrams of physical models for process pathways, were applied to sets of multi-resolution images in order to evaluate the usefulness of coarse-resolution satellite data (e.g. the Moderate Resolution Imaging Spectroradiometer; MODIS) in obtaining similar results to those obtainable with moderate-resolution satellite data (e.g. Landsat). A spectral-mixture model based on three endmembers (soil, vegetation and water) was used to determine the land-cover fractions of the main land-use classes of a wetland in southeast Spain. The land-use map was produced by applying the unsupervised k-means classification method to the moderate-resolution image. Spatial and temporal changes in the mixture fractions at multiple resolutions and their corresponding land-cover fraction maps were assessed. Three different t-tests (paired-samples, independent-samples and Dutilleul’s modified t-tests) were used to evaluate the effects of pixel aggregation on land-cover fractions and land-use maps in terms of surface-area estimations. Ternary plots of land-use classes characterized by land-cover fractions were used to visualize environmental processes pathways describing temporal changes in the landscape. The results obtained with moderate- and coarse-resolution data were not significantly different from each other. Land-use and land-cover surface-area estimations were not significantly different between Landsat moderate-resolution (30 m) and Landsat resampled coarse-resolution (300 m) data. Spatial autocorrelation had an important effect when comparing Landsat moderate-resolution (30 m) with MODIS coarse-resolution (250 m) data. In order to minimize these effects Dutilleul’s modified t-test was applied for the comparison of Landsat with MODIS image data. However, this test did not reveal significant differences between both datasets, whereas with the ordinary t-test, significant differences were found, which suggest the existence of a bias by spatial autocorrelation that must be taken into account for up-scaling or down-scaling of remote-sensing data. The results suggest the possibility of using coarse-resolution images (MODIS) to characterize environmental changes with a similar accuracy to those of moderate-resolution images (Landsat), as long as potential spatial autocorrelation effects are taken into account. This finding indicates that a substantial reduction in the costs of conducting wetland management and monitoring tasks can be achieved by using free or low-cost coarse-resolution satellite images.