Competitive Adsorption between a Polymer and Solvents onto Silica

In polymer nanocomposites, particle-polymer interactions play a key role both in the processing and in the final properties of the obtained materials. Specifically, for silica, because of the surface polarity, surface modification is commonly used to improve the compatibility with apolar polymer matrices in order to prevent agglomeration. In this work, a new way to investigate the polymer-silica affinity and determine dispersibility parameters (HDP) of silica particles in the 3D Hansen space using a solvent approach is proposed. These parameters are estimated from the assessment of the stability of suspensions in a set of organic solvents. Based on the respective locations of the solvent, polymer, and silica representative points in the 3D Hansen space, the adsorption of a given polymer in solution in a given solvent can be predicted. This is shown with the industrial precipitated silica Zeosil 1165MP in combination with polystyrene and polybutadiene. It is shown that silanization of the silica particles decreases the adsorption of polystyrene, even though because of this surface treatment, silica comes closer to polystyrene in the Hansen space. This counter-intuitive effect is rationalized based on the consideration of an adsorption parameter χ_S computed from the relative locations of the solvent, polymer, and particles in the 3D Hansen space. Basically, this parameter is related to the respective distances of the solvent and polymer representative points to that of the particle in the Hansen space.

Über die schweren Kerne in der primären kosmischen Strahlung

The present paper describes the results of an investigation on heavy nuclei (Z > 2) of the primary cosmic radiation. The measurements were made in 40 stripped emulsions flown over Sardinia (λ~40°) in a height of about 27 km for 7 hours. The energy of the nuclei was deduced from their multiple Coulomb scattering, and, if they fragmentated, from the opening angles of their secondary products. For the determination of the charge number Ζ the measurement of the δ-ray density was sufficient, all particles having energies/nucleon ≥ 1,3 GeV. The result is thus independent of possible influences of spurious scattering.

The charge spectrum under an average of 32 g/cm2 of residual material shows that the number of nuclei with 3 ≤ Z ≤ 5 is approximately equal to that of nuclei with 6 ≤ Z ≤ 9. This is in agreement with the charge spectrum found by Dainton, Fowler, and Kent, but at variance with the results of Bradt and Peters. The magnitude of the correction to be applied for the scanning loss of Li-nuclei is discussed. The correction factor used by Dainton et al. appears to be too high. With regard to the influence of the residual material it is shown that the calculated intensity of the Li-, Be-, and B-nuclei at the top of the atmosphere will be strongly affected by the uncertainty of the probabilities pk i for fragmentation. The fragmentation probabilities found in this work are in good agreement with those obtained by Bradt and Peters and by Gottstein, they are, however, somewhat smaller than those measured by Noon, Kaplon, and Ritson. The values of the mean free paths in emulsion can be represented by a formula for the cross-sections given by Peters et al.

The energy spectrum agrees with that deduced by Kaplon et al. from measurements of the latitude-effect. It was found that because of spurious scattering cell lengths of at least 4 mm are required in order to measure energies > 4 GeV/nucleon. A spectrum similar to that found by Dainton et al. is obtained, if one confines the scattering measurements on cells which are not long enough. The flux of nuclei Z ≥ 6 at the top of the atmosphere is somewhat smaller than measured by other authors at λ = 41°.

Polymorphism of natural fatty acid liquid crystalline phases

We study the phase behavior in water of a mixture of natural long chain fatty acids (FAM) in association with ethylenediamine (EDA) and report a rich polymorphism depending on the composition. At a fixed EDA/FAM molar ratio, we observe upon dilution a succession of organized phases going from a lamellar phase to a hexagonal phase and, finally, to cylindrical micelles. The phase structure is established using polarizing microscopy, SAXS, and SANS. Interestingly, in the lamellar phase domain, we observe the presence of defects upon dilution, which SAXS shows to correspond to intrabilayer correlations. NMR and FF-TEM techniques suggest that these defects are related to an increase in the spontaneous curvature of the molecule monolayers in the lamellae. ATR-FTIR spectroscopy was also used to investigate the degree of ionization within these assemblies. The successive morphological transitions are discussed with regards to possible molecular mechanisms, in which the interaction between the acid surfactant and the amine counterion plays the leading role.

Should we pursue patients who fail to attend colorectal clinics? A 9-year study

INTRODUCTION

No uniform protocol exists on how to deal with patients who fail to attend colorectal clinics. Our aim was to identify whether the tendency to 'failure to attend' (FTA) in the colorectal clinic was associated with FTA in other clinics and also whether FTA patients have serious pathology.

PATIENTS AND METHODS

This was a retrospective study of a prospectively recorded list of FTA patients, in colorectal urgent or two-week wait clinics from 1996-2004.

RESULTS

A total of 151 patients, who failed to attend their first appointment, were included in the study. Of these, 61 (40.4%) were colorectal referrals, 76 (50.3%) were general surgical referrals, and for 14 (9.3%) case notes were not available. There were 59 FTA episodes in 61 colorectal patients associated with 59 FTA episodes in other clinics (Pearson correlation: r = 0.411; P = 0.01, two-tailed, SPSS v.12). Of 58 colorectal outcomes, five (8.6%) colorectal cancers (CRC) were diagnosed, 23 (39.6%) were persistent non-attendees, 16 (27.5%) had benign colorectal pathology, two (3.4%) benign non-colorectal outcomes and 12 (20.6%) normal outcomes.

CONCLUSIONS

Tendency to FTA is habitual. Care needs to be exercised in the management of FTAs to avoid delayed presentation of colorectal cancer.

Disclosure patterns and decision making preferences in BRCA 1/2 mutation carriers with young adult and minor children

1015

Background: Genetic testing of minors for adult-onset diseases has generally been discouraged. Yet, limited data suggests that many BRCA mutation carriers discuss their test results with their minor children. How parents make the decision to share this information and the effects on their health, their child and the family remains unknown. Methods: We sought to evaluate disclosure patterns and decision making practices among BRCA1/2 mutation carriers with children under the age of 25. 42 parents (with 86 children) completed a semi-structured telephone interview regarding communication of their genetic test results to their children. Chi-squared tests to assess associations between parent/child characteristics and disclosure were computed using robust variance estimates to account for clustering by family unit. Results: 55% of parents discussed hereditary risk of cancer and/or their genetic test results with at least one child. Factors associated with disclosure included older child age (p<0.001), female parent gender (p=0.049), parent history of prophylactic surgery (mastectomy: p = 0.021, oophorectomy: p<0.001) and education limited to high school (p=0.085). Child gender and parent’s history of cancer were not significantly associated with disclosure. Most participants reported themselves (45%) or their spouse (40%) as the most important person in the decision to disclose. Reports of physician (14%) and genetic counselor (21%) involvement were low. Conclusions: Parental decisions to disclose BRCA test results to children are complex and may reflect differences in perceptions of genetic disease. Further research is needed to understand parental motivations for disclosure and to define a role for health care professionals to improve counseling and recommendations regarding the risks and benefits of early communication of genetic risk to children.

No significant financial relationships to disclose.