This paper considers how parents engage with a large, internationally supported childhood pneumococcal vaccine trial in The Gambia. Current analysis and professional reflection on public engagement is strongly shaped by the imperatives of public health and research institutions, and is thus couched in terms of acceptance and refusal, and ‘informed consent’. In contrast Gambian parents’ perspectives on the trial are couched in conceptual and experiential terms that are linked to their wider dilemmas of raising infants amidst the hazards of globally connected village life. Ethnographic research reveals how for most parents, longer-term experiences of the organization managing the research (the UK Medical Research Council Laboratories in The Gambia) as a health-providing institution override their reflection on trial-specific aims. A decision to participate in the trial involves a perceived balance of benefit and danger – in the extreme, of free medical treatment, versus one’s child being drained of blood for sale to Europe. Social relations (especially gender relations) shape this calculus and study participation. This case suggests how the idea of ‘public engagement with science’ in a globalized context might be recast, with implications for debates in biomedical ethics, and the sustainability of public participation in medical research.

To determine the relationships between clinical and brain function in persons with a familial risk for Alzheimer's disease, the authors assessed subjective and objective cognitive abilities, mood state, and cerebral glucose metabolism (using positron emission tomography) in 43 persons with age-associated memory impairment, with and without first-degree relatives with a clinical diagnosis of Alzheimer's disease. Subjective complaints of memory loss, mood state ratings, and objective memory measures were similar in persons with a family history of Alzheimer's disease (n = 29) compared to those without such a history (n = 14). Metabolic ratios in the frontal regions correlated with a decrease in a specific type of subjective memory complaint (mnemonics usage; p < .001) and some mood state ratings. These results indicate that parietal and temporal hypometabolism is not evident in persons with mild age-related memory complaints, even when such subjects have a familial risk for Alzheimer's disease. Moreover, self-reports of mnemonics usage may be sensitive indicators of decreased frontal lobe function. Longitudinal study will determine whether such clinical and metabolic measures will predict eventual disease progression.

The introduction of organic substituents into sol-gel materials can often result in networks that collapse during drying to afford non-porous xerogels. This can prove useful if non-porous coatings or membranes are the ultimate objectives. Collapse of porosity is also manifested in bridged polysilsesquioxanes with flexible bridging groups. Alkylene-bridged polysilsesquioxanes are hybrid xerogels whose organic bridging group is an integral constituent of the network polymer that can be systematically varied to probe the influence of its length on the xerogels' porosity and morphology. Our previous studies have shown that hexylene-bridged polysilsesquioxane xerogels prepared from 1, 6-bis(triethoxysilyl)hexane under acidic conditions are nonporous while the pentylene-bridged polysilsesquioxanes prepared under the same conditions are porous. We also discovered that the more reactive 1, 6-bis(trimethoxysilyl)hexane monomer could polymerize under acidic conditions to afford porous xerogels. Here, we have extended our study of bis(trimethoxysilyl)alkanes to include the heptylene (C7), octylene (C8), nonylene(C9) and decylene (C10) bridges so as to ascertain at what bridging group length the porosity collapses. The morphology of the resulting xerogels was characterized by nitrogen sorption porosimetry and electron microscopy. Solid state NMR was used to structurally characterize the materials.

Aging of silica gels before drying is known to result in significant changes in xerogel morphology, porosity and properties. In this study, the influence of aging gels on the porosity and morphology of alkylene-bridged polysilsesquioxane xerogels was examined. Gels of hexylene-, heptylene, octylene, nonylene, and decylene-bridged polysilsesquioxanes were prepared by the sol-gel polymerization of the respective bis(trimethoxysilyl)alkane monomers under acidic or basic conditions in methanol and in tetrahydrofuran. The gels were aged 3, 7, 14, 28, 35, 42, 49, and 56 days before drying to afford xerogels. The xerogels were characterized by nitrogen sorption porosimetry. Xerogels prepared in THF were non-porous. Those prepared and aged under basic conditions in methanol or tetrahydrofuran exhibited coarsening of porosity with aging time. With the exception of the hexylene-bridged gels, those prepared and aged in acidic methanol showed little change with aging. The surface area of the hexylene-bridged xerogels nearly tripled with aging times of up to several weeks, then decreased, for the gels aged for more than two weeks, to around 100 meters squared per gram.

In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, solubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300–350°C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.

Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane 1 and 1,4-bis(triethoxysilyl)butane 2 were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed with the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possiblity of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.

The first representatives of novel materials that contain five- and six-coordinate anionie silicon are reported. Linear (or cyclic) ionomers incorporating pentacovalent siliconate were synthesized by condensation of 1,2,4,5-tetrahydroxybenzene (THB) with alkyl and aryl trialkoxysilylanes. Network ionomers that incorporate pentacovalent siliconates were formed from THB and alkyl and aryl bistrialkoxysilanes. In addition, network ionomers with hexacoordinate silicon result from condensation of TEOS and THB. Spectroscopie evidence is presented to verify the identity of the novel structural features of these materials.

Two series of logarithmic expansion systems are described, with × 1·6 as the rate of increase in numbers of new monotypic genera correlated with a rate of × 2·0 for increase in total numbers of species. These series are discussed in relation to current numbers for monotypic genera, total genera, and total species in 36 of the largest 45 families of flowering plants.

A system of twelve stages of expansion from one primary monotypic genus is described and elaborated, using as two correlated parameters the rate of x 1·5 for the number of new monotypic genera arising (rGi) when the rate of X 2·0 is taken for the increase in generic size or numbers of species within any one genus (rSz). Too much stress should not be read into the precision of the positions indicated for known numerical data; an approximate fitting is all that can be reasonably expected even if these theoretical expansions are something like the historical truth.

A Summary of the facts with numerical details omitted can be given as follows. In the diatoms—

1. Species-lifetimes have been alternatively short or long.

2. The main ratios of shorts to longs, or evanescents to permanents, e/p, are 3:1 for Centrales, 10:6 for Fragilariaceæ, 7:9 for allogamous Pennales. These ratios or nearest approaches to these ratios occur in the above three groups, (a) in each group as a whole; (b) in species-arising in each group per geological subperiod; and (c) in heterogeneous genera in each genus as a whole and in each genus per subperiod. A derivative 1:3 ratio also occurs in some pennate genera. There are some significant and understandable exceptions.