Droplet Helical Motion on Twisted Fibers.

We investigate herein the impact of helical structures on the motion of asymmetrical droplets along vertically twisted fibers. The droplet adopts helical motion around the bundle driven by gravity. This complex motion can be manipulated by varying the twists turns of the fibers.

Reactivity-Tuning in Frustrated Lewis Pairs: Nucleophilicity and Lewis Basicity of Sterically Hindered Phosphines.

The nucleophilicity and Lewis basicity of sterically hindered phosphines, widely used in catalysis and in frustrated Lewis pair (FLP) chemistry, have been quantified by determining the rates and equilibrium constants of their associations with reference systems (benzhydrylium and tritylium ions) of calibrated electrophilicities and Lewis acidities. These structure-reactivity investigations allow a rationalization of the Lewis acid-base interactions all along the way from covalent Lewis adducts to FLPs. Comparisons of the association of phosphines of increasing sizes (Ph P, (o-tolyl) P, and tBu P) with the triarylborane B(C F ) and with the isoelectronic tritylium ions Ar C provide detailed insights for the future fine-tuning of the reactivities of FLPs.

Structures, Lewis Acidities, Electrophilicities, and Protecting Group Abilities of Phenylfluorenylium and Tritylium Ions.

The isolation, characterization, and the first X-ray structures of a fluorenylium ion and its Lewis adducts with nitrogen- and phosphorus-centered Lewis bases are reported. Kinetics of the reactions of a series of fluorenylium ions with reference π-, σ-, and n-nucleophiles of various sizes and nucleophilicities allowed the interplay between electronic and structural parameters on the electrophilicities of these planarized tertiary carbenium ions to be elucidated. Structure-reactivity correlations and extensive comparisons of their reactivities with those of di- and triarylcarbenium ions are described.

Structure and Reactivity of Indolylmethylium Ions: Scope and Limitations in Synthetic Applications.

Eight substituted aryl(indol-3-yl)methylium tetrafluoroborates 3(a-h)-BF4 and three bis(indol-3-yl)methylium tetrafluoroborates 3(i-k)-BF4 have been synthesized and characterized by NMR spectroscopy and X-ray crystallography. Their reactions with π-nucleophiles 8(a-j) (silylated enol ethers and ketene acetals) were studied kinetically using photometric monitoring at 20 °C. The resulting second-order rate constants were found to follow the correlation log k(20 °C) = sN(N + E), in which nucleophiles are characterized by the two solvent-dependent parameters N and sN, and electrophiles are characterized by one parameter, E.

Female streetworking prostitution and HIV infection in Glasgow.

Objectives: To identify the extent of HIV infection and injecting drug use among female streetworking prostitutes in Glasgow; to estimate the size of the female streetworking prostitute population in the city; and to estimate the number of HIV positive women working as prostitutes on the streets in Glasgow.

Design: Observation and interviewing of female prostitutes over seven months in red light district; analysis of saliva samples for presence of antibodies to HIV; capture-recapture approach to estimating the size of the female streetworking prostitute population.

Setting: Glasgow.