Curvature wavefront sensing performance evaluation for active correction of the Large Synoptic Survey Telescope (LSST).

The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, modified Paul-Baker design, with an 8.4-meter primary mirror, a 3.4-m secondary, and a 5.0-m tertiary, along with three refractive corrector lenses to produce a flat focal plane with a field of view of 9.6 square degrees. In order to maintain image quality during operation, the deformations and rigid body motions of the three large mirrors must be actively controlled to minimize optical aberrations, which arise primarily from forces due to gravity and thermal expansion. We describe the methodology for measuring the telescope aberrations using a set of curvature wavefront sensors located in the four corners of the LSST camera focal plane. We present a comprehensive analysis of the wavefront sensing system, including the availability of reference stars, demonstrating that this system will perform to the specifications required to meet the LSST performance goals.

Men caring for wives or partners with dementia: masculinity, strain and gain.

Over the last three decades, demographic changes in the developed world have meant more older men find themselves in caregiving roles. Little research has been undertaken with male caregivers in dementia care. Although there is general consensus that men construe care differently to women, gender has seldom been treated as an independent variable that can inform supportive interventions. This study, underpinned by an assumption of the benefits of men's differential response to managing illness, sought to explore how facets of masculinity might relate to male caregivers' appraisals of strain and gain in dementia care. Seventy men, currently caring for a partner with dementia, completed questionnaires exploring their gender identity (Personal Attributes Questionnaire), gender role conflict (Gender Role Conflict Scale), and appraisals of carer strain and gain (Brief Zarit Burden Interview and Caregiving Satisfaction Scale). They were also asked to provide demographic information and, since caregiver strain is significantly affected by a care-receiver's cognitive and behavioural difficulties, to complete the revised Memory and Behaviour Problems Checklist. Carers' age and duration of caregiving was broadly representative of previous studies. A series of regression analyses revealed contrasting findings to previous studies. Gender identity did not appear important in carer's evaluations of strain or gain, and only the 'restrictive affectionate behaviour between men' subscale of gender role conflict had explanatory power in analyses with all strain and gain variables. Findings are discussed with regard to response bias and defended masculinity. Consideration is made about how men can successfully access services.

Coping with caring for someone with dementia: reviewing the literature about men.

As the demographics of the population change, men are assuming increasingly important roles as caregivers, despite caregiving often being perceived as a feminine activity. Research to date has described sex differences in caregiving and psychological outcomes. However, there appears to be little understanding of varying ways men may cope with the strains of caregiving. To this end, a systematic literature search was carried out to determine what is known about men coping with caring for someone with dementia. The search process elicited 93 articles, reviewed and categorised by their content. The majority of articles reported research and interventions with little detailed analysis of gender as a mediating variable for coping. Four articles reported finding no sex-differences in coping and burden. Of the nine articles that reported exclusively on men caregivers, only one generated quantitative data within an explicit framework of stress, appraisal and coping. Conclusions suggest that future research requires refinement and sophistication to address the role of gender in mediating appraisals of strain and coping responses to familial dementia care. The limitations of gender difference research and self-report methodologies are discussed along with their implications for interventions and suggestions for future research.

Open- and closed-loop aberration correction by use of a quadrature interferometric wave-front sensor.

Experimental results are presented for an adaptive optics system based on a quadrature Twyman-Green interferometric wave-front sensor. The system uses a circularly polarized reference beam to form two interferograms with a pi/2 phase shift. The experiments conducted used Kolmogorov phase screens to simulate atmospheric phase distortions. Strehl ratio improvements by a factor of 8, to an absolute value of 0.45, are demonstrated.

Breadboard testing of a phase-conjugate engine with an interferometric wave-front sensor and a microelectromechanical systems-based spatial light modulator.

Laboratory breadboard results of a high-speed adaptive-optics system are presented. The wave-front sensor for the adaptive-optics system is based on a quadrature interferometer, which directly measures the turbulence-induced phase aberrations. The spatial light modulator used in the phase-conjugate engine was a microelectromechanical systems-based piston-only correction device with 1024 actuators. Laboratory experiments were conducted with this system utilizing Kolmogorov phase screens to simulate atmospheric phase distortions. The adaptive-optics system achieved correction speeds in excess of 800 Hz and Strehl ratios greater than 0.5 with the Kolmogorov phase screens.