R a w kaolinite has been investigated as a possible starting material for low-temperature hydrothermal growth of zeolites and felspathoids. It proved to be convenient and versatile in this role, being readily transformed into a range of known and new zeolites and salt-inclusion felspathoids with a Si/AI ratio around 1 .O, some of which have novel properties. Experiments were conducted at 80" using aqueous solutions of lithium, sodium, potassium, rubidium and caesium hydroxides, sometimes in the presence of additional alkali-stable anions. Some quantitative aspects of the recrystallization reactions are discussed, as are the chemical and physical properties of representative compounds of each type synthesized.

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The imbibition of salts by sodalite and cancrinite during their hydrothermal formation from kaolinite has been studied. Isotherm contours recalling those of Langmuir's isotherm were observed in sodalite for NaCI, NaBr, NaCIO,, NaCIO,, and Na,CO,.These results have been interpreted in terms of a Donnan equilibrium, in which solid-phase activities were calculated on the experimentally justified assumption that each sodalite cage is capable of accommodating a particular number of each kind of guest molecule, which number varies with the size of the guest. The stoicheiometry, thermal stability, chemical reactivity, and crystallization kinetics of representative compounds have been discussed, and the possible importance of salt inclusion in other zeolitic materials has been noted.

Cancrinite has been synthesized in the sodalite crystallization field at 80" by addition of sodium nitrate, chromate, or molybdate. The crystals then contain these salts as guest species in place of the carbonate often found in natural cancrinites.This promotion of the formation of cancrinite was ascribed to association of anions with certain aluminosilicate species in solution, which then yielded cancrinite nuclei. As these grow into crystallites by addition of further anion-aluminosilicate complexes, the salt is incorporated into the 11 -hedral cancrinite cages and into the wide channels enclosed by these. This behaviour was studied by investigations of conditions of synthesis and by chemical and thermal analyses, i.r. measurements, X-ray powder photography, and crystal-structure determinations based on powder data.The structure determinations were made for cancrinite nitrate (R = 0-1 2) and for a basic cancrinite containing some intercalated silicate (R = 0.07). The structures were compared with one recently determined for a natural cancrinite. In addition, partial refinement of two other cancrinites rich in sodium chromate and sodium molybdate served to locate these anions.

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BACKGROUND: It remains unclear whether combination antiretroviral therapy (ART) regimens differ in their ability to fully suppress HIV replication. Here, we report the results of two cross-sectional studies that compared levels of cell-associated (CA) HIV markers between individuals receiving suppressive ART containing either a non-nucleoside reverse transcriptase inhibitor (NNRTI) or a protease inhibitor (PI).METHODS: CA HIV unspliced RNA and total HIV DNA were quantified in two cohorts (n=100, n=124) of individuals treated with triple ART regimens consisting of two nucleoside reverse transcriptase inhibitors (NRTIs) plus either a NNRTI or a PI. To compare CA HIV RNA and DNA levels between the regimens, we built multivariable models adjusting for age, gender, current and nadir CD4+ count, plasma viral load zenith, duration of virological suppression, NRTI backbone composition, low-level plasma HIV RNA detectability, and electronically-measured adherence to ART.RESULTS: In both cohorts, levels of CA HIV RNA and DNA strongly correlated (rho=0.70 and rho=0.54) and both markers were lower in NNRTI-treated than in PI-treated individuals. In the multivariable analysis, CA RNA in both cohorts remained significantly reduced in NNRTI-treated individuals (padj=0.02 in both cohorts), with a similar but weaker association between the ART regimen and total HIV DNA (padj=0.048 and padj=0.10). No differences in CA HIV RNA or DNA levels were observed between individual NNRTIs or individual PIs, but CA HIV RNA was lower in individuals treated with either nevirapine or efavirenz, compared to PI-treated individuals.CONCLUSIONS: All current classes of antiretroviral drugs only prevent infection of new cells but do not inhibit HIV RNA transcription in long-lived reservoir cells. Therefore, these differences in CA HIV RNA and DNA levels by treatment regimen suggest that NNRTIs are more potent in suppressing HIV residual replication than PIs, which may result in a smaller viral reservoir size.

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