School problems among left-behind children of labor migrant parents: a study in Vietnam.

BACKGROUND: Many studies have shown the effects of parental migration on the psychological and daily life of left-behind children (LBC) of labor migrant parents, but the results on school-related problems of LBC remain inconsistent. Additionally, there is a dearth of research on the factors affecting school problems among LBC, especially in the socio-cultural context of Vietnam. The purpose of this study was to confirm the school problems encountered by LBC in comparison with non-left-behind children (non-LBC). The study also aimed to examine variables of bonding of caregivers with children and resilience of children affecting school problems of LBC. PARTICIPANTS AND PROCEDURE: The convenient sampling approach was used in the study. The study sample included 792 Vietnamese school students (Mage = 12.65, SD = 1.60), with 439 children of labor migrant parents and a control group of 353 children of non-migrant parents. The School Problem Questionnaire, Parental Bonding Instrument and the Resilience Scale were employed in this study. RESULTS: There was no difference in school problems between the LBC and non-LBC groups. Resilience by goal planning (RGP), resilience by affect control (RAC), and resilience by family support (RFS) were identified as protective variables for children to overcome difficulties encountered in schools, with regression coefficients of -.21, -.33 and -.20, respectively. Meanwhile, bonding of caregivers with children by control (BCCo), and resilience by positive thinking (RPT) were found to be factors that increase school problems among LBC with the same regression coefficient of .12. CONCLUSIONS: Activities to support LBC should pay attention to improving resilience, namely affect control, goal planning, and promoting the role of caregivers for LBC.

Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and methylglyoxal have the potential to produce significant organic aerosol mass and therefore could potentially impact chemical, optical and/or cloud-forming properties of aerosols, especially if the products partition to the aerosol surface.

Evaluation of transforming activity of cellular DNAs from different origins by NIH3T3 transfection test.

The NIH3T3 cell transfection test, as first described by Cooper, has been optimized, then used to examine the transforming activity of genomic DNA extracted from eucaryotic cell lines commonly used for preparing vaccines or biopharmaceuticals. Accurate assessment of technical parameters of the test has led to improvement in reproducibility, while the demonstration of dose-effect relationships has allowed the definition of applications and limits for quantitative use. We have performed the direct assessment of transforming activity of cellular DNAs from cell lines widely used in biotechnology. In particular, we have shown that genomic DNA extracted from Vero, CHO or MRC5 cells, as well as from human or murine lymphoid cells, has no detectable transforming activity on NIH3T3 cells. Lastly, it has been demonstrated that acidic pH conditions are sufficient to destroy the major part--if not all--of the transforming activity of positive control DNAs.

Use of sulfonation method to determine DNA contamination of cell cultured monoclonal antibodies produced for human therapeutics.

In the past few years, culture of transformed mammalian cells has been widely used to produce natural or recombinant molecules, as monoclonal antibodies (MAb) and cytokines. For therapeutic use, the cellular DNA level must be determined. A number of techniques have been developed to measure the DNA content, based on sequential extraction blotting and hybridization with a labeled DNA probe. The sulphonate marker has been recently introduced by PBS-Orgenics; it allows the determination of picograms (pg) quantities of purified DNA. However, it is not simple to measure in complex biological samples especially when a large amount of protein is present. In considering the following points: 1. Precautions in handling the samples at different steps of preparation; 2. Modifications of the original technique 3. Concentration of samples expected at very low level, we are able to dose up to 2 pg of contaminant DNA per mg of MAb with a satisfactory reproducibility and reliability. This level is required not only to qualify final MAb but also to evaluate the efficiency of the purification process. Efforts are being made to achieve a better sensitivity.