While exploring photoisomerization of azobenzyl thiols (ABT) adsorbed on Au(111), through joint scanning tunneling microscopy (STM) and tip-enhanced Raman scattering (TERS) studies, the reversible photoisomerization of one molecule is captured in TERS trajectories. The unique signature of single molecule isomerization is observed in the form of anticorrelated flip-flops between two distinct spectra with two discrete, on- and off-levels. The apparently heterogeneously photocatalyzed reaction is assigned to cis-trans isomerization of an outlier, which is chemisorbed on the silver tip of the STM. Otherwise, the ensemble of ABT molecules that lie flat on Au(111) remain strongly coupled to the surface, excluding the possibility of photoisomerization or detection through TERS.

ObjectiveTo describe a community-based HIV testing programme.Design and settingAn intervention of HIV voluntary testing conducted in non-medical settings in four French cities.ParticipantsMen who have sex with men (MSM).InterventionCounselling and rapid HIV testing staffed by trained personnel from an HIV/AIDS community-based organisation.Primary and secondary outcome measuresThe population that has taken hold of the intervention and the satisfaction of participants. Data were collected on demographics, HIV testing history, sexual practices and satisfaction with the testing programme.Results532 MSM were tested between February 2009 and June 2010, of whom 49 (9%) were tested two or more times. 468 MSM (88%) had casual male partners in the previous 6 months, and 152 (35%) reported having unprotected anal intercourse with risky casual partners (HIV infected or HIV serostatus unknown). 159 men (30%) had not been tested in the previous 2 years, and 50 (31%) of whom had unprotected anal intercourse with risky casual partners. Among the 15 patients who tested positive (2.8%), 12 (80%) received confirmation and were linked to care (median CD4 cell count =550/mm3). Satisfaction was high: 92% reported being ‘very satisfied’ with their experience. Steps of counselling and testing procedure were respected by testers and difficulties in handling tests were rare.ConclusionsThis community-based HIV testing programme reached high-risk MSM, of whom a substantial proportion had not been tested lately. This novel service supplements pre-existing HIV testing services and increases access to HIV testing in high-risk groups.

We report 102 new redshifts and magnitudes for a sample of galaxies to RF ~ 15.5 mag in a 2.17 deg x 2.17 deg region centered on the galaxy IC 4296, the most luminous member of the A3565 cluster. Up to the limiting magnitude we find 29 cluster members, and measure a velocity dispersion of 228 km/s. The estimated total mass for this system is ~ 3.0 x h**-1 10**13 Msun (where h = H0/100 km/s/Mpc), and its dynamical properties are quite typical of poor clusters presenting X-ray emission. We also find that galaxies with absorption lines are more concentrated towards the center of the cluster, while systems with emission lines are mainly located in the outer parts. The small velocity dispersion of the cluster, coupled to the known presence of an interacting pair of galaxies, and the large extent of the brightest cluster galaxy, could indicate that galaxy formation through mergers may still be underway in this system. The surveyed region also contains galaxies belonging to the Shapley Concentration cluster A3560. Within 30 arc min of the cluster center, we detect 32 galaxies, for which we measure a velocity dispersion of 588 km/s and a mass of ~2 x h**-1 10**14 Msun. However, because our sample is restricted to galaxies brighter than M*, these values should be considered only as rough estimates.Comment: 33 pages, including 6 tables and 9 postscript figures. Uses AAS Latex macros. Postscript file and ASCII versions of Tables 4 and 6 are available at http://www.dan.on.br/other_surveys/a3565.html. Scheduled for September 1999 issue of The Astronomical Journa

The ability to develop, use, and refine models of experimental systems is a nationally recognized learning outcome for undergraduate physics lab courses. However, no assessments of students' model-based reasoning exist for upper-division labs. This study is the first step toward development of modeling assessments for optics and electronics labs. We interviewed 35 lab instructors about the ways they incorporate modeling in their courses, and we used their self-reported learning goals and activity designs to identify test contexts and objectives that are likely relevant across many institutional settings. The study design was informed by the Modeling Framework for Experimental Physics, which conceptualizes modeling as consisting of multiple subtasks: making measurements, constructing system models, comparing data to predictions, proposing causes for discrepancies, and enacting revisions to models or apparatus. We found that each modeling subtask was identified by multiple instructors as an important learning outcome for their course. Based on these results, we argue that test objectives should include probing students' competence with most modeling subtasks, and test items should be designed to elicit students' justifications for choosing particular modeling pathways. In addition to discussing these and other implications for assessment, we also identify future areas of research related to the role of modeling in optics and electronics labs. *