Ultra-low timing jitter, Ti:Al2O3 synchronisation for stimulated Raman scattering and pump-probe microscopy

This is the final version. Available from SPIE via the DOI in this recordSignificance: Stimulated Raman scattering and pump-probe microscopy are implementations of multiphoton microscopy that acquire high-resolution, label-free images of live samples encoded with molecular contrast. Most commercial multiphoton microscopes cannot access these techniques since they require sample illumination by two temporally synchronised ultrafast modelocked pulse trains. Here, we present a compact and robust way of synchronising an additional Ti:Sapphire laser with a conventional single beam multiphoton microscope to realise an instrument that can acquire images with enhanced molecular specificity. Aim: A passive optical synchronisation scheme for a pair of commercially available, unmodified modelocked Ti:Sapphire lasers was developed. The suitability of this synchronisation scheme for advanced biomedical microscopy was investigated. Approach: A pair of modelocked Ti:Sapphire lasers were aligned in master-slave configuration. 5% of the master laser output was used to seed the modelocking in the slave laser cavity. The timing jitter of the master and slave pulse trains was characterised using an optical autocorrelator. The synchronised output of both lasers was coupled into a laser scanning microscope and used to acquire spectral focussing stimulated Raman scattering and pump-probe microscopy images from biological and non-biological samples. Results: A timing jitter between the modelocked pulse trains of 0.74 fs was recorded. Spectral focussing stimulated Raman scattering allowed spectral discrimination of polystyrene and polymethyl methacrylate beads. Pump-probe microscopy was used to record excited state lifetime curves from haemoglobin in intact red blood cells. Conclusion: This work demonstrates a simple and robust method of upgrading single beam multiphoton microscopes with an additional ultrafast laser. The resulting dual-beam instrument can be used to acquire label-free images of sample structure and composition with high biochemical specificity.Biotechnology & Biological Sciences Research Council (BBSRC)Wellcome Trus

Systematic Evaluation of the Teaching Qualities of Obstetrics and Gynecology Faculty: Reliability and Validity of the SETQ Tools

BACKGROUND: The importance of effective clinical teaching for the quality of future patient care is globally understood. Due to recent changes in graduate medical education, new tools are needed to provide faculty with reliable and individualized feedback on their teaching qualities. This study validates two instruments underlying the System for Evaluation of Teaching Qualities (SETQ) aimed at measuring and improving the teaching qualities of obstetrics and gynecology faculty. METHODS AND FINDINGS: This cross-sectional multi-center questionnaire study was set in seven general teaching hospitals and two academic medical centers in the Netherlands. Seventy-seven residents and 114 faculty were invited to complete the SETQ instruments in the duration of one month from September 2008 to September 2009. To assess reliability and validity of the instruments, we used exploratory factor analysis, inter-item correlation, reliability coefficient alpha and inter-scale correlations. We also compared composite scales from factor analysis to global ratings. Finally, the number of residents' evaluations needed per faculty for reliable assessments was calculated. A total of 613 evaluations were completed by 66 residents (85.7% response rate). 99 faculty (86.8% response rate) participated in self-evaluation. Factor analysis yielded five scales with high reliability (Cronbach's alpha for residents' and faculty): learning climate (0.86 and 0.75), professional attitude (0.89 and 0.81), communication of learning goals (0.89 and 0.82), evaluation of residents (0.87 and 0.79) and feedback (0.87 and 0.86). Item-total, inter-scale and scale-global rating correlation coefficients were significant (P<0.01). Four to six residents' evaluations are needed per faculty (reliability coefficient 0.60-0.80). CONCLUSIONS: Both SETQ instruments were found reliable and valid for evaluating teaching qualities of obstetrics and gynecology faculty. Future research should examine improvement of teaching qualities when using SETQ