Search

This article examines a selection of paintings by Guido Reni (1575–1642) and his studio that display comparable stylistic, compositional, and technical characteristics, all of which have been ascri...

We report on an opto-mechanical metal mirror design for highly dynamic, diffraction-limited focus shifting. Here, the mechanical geometry of the membrane is of crucial interest as it must provide sufficient optical performance to allow for diffraction limited focussing and have a high mechanical eigenfrequency to provide dynamic motions. The approach is the analytical consideration of the plate theory and provides the basis for a parameterized finite element model. By means of an finite element analysis (FEA), essential steps for the optimization of the mirror design with respect to a wide range of optical power and a high operating frequency are shown. To verify the results of the FE analysis, the deformed surface is decomposed into Zernike coefficients. An analysis of the point spread function is performed to evaluate the optical performance. For dynamic evaluation a modal and a harmonic vibration analysis are conducted. The opto-mechanical design allows a biconical deformation of the mirror surface, enabling the generation of a diffraction-limited spot diameter in the adjustment range of ±1.2 dpt. The surface shape error in this range is 53 nm. The dynamic analysis shows the first excited eigenfrequency at 21.6 kHz and a diffraction-limited operation frequency at 9.5 kHz. This paper provides an alternative design approach for highly dynamic beam oscillation in the Z direction, forming a complement to highly dynamic X-Y scanning systems.

The measured fiber coupling efficiency (FCE) in atmospheric laser communication is not fully explored. We experimentally study the FCE for tip-tilt aberrations. Finally, we explain the FCE with the tip-tilt phase response.

A primiparous woman in her late 30s at 28+1 weeks’ gestation presented with a 3-day history of abdominal pain, loss of appetite, nausea and vomiting and was diagnosed with starvation ketoacidosis. A routine admission swab returned positive for COVID-19. She had been diagnosed with acrorenal syndrome from birth. Three days post admission, she deteriorated rapidly into respiratory failure requiring intubation and ventilation. She was treated with dexamethasone, prophylactic enoxaparin, a course of piperacillin/tazobactam followed by meropenem and fluconazole and 8 cycles of proning. An emergency caesarean section was performed on day 12 of hospital admission at 29+5 weeks’ gestation to improve maternal oxygenation and ventilation. The baby had deformities consistent with acrorenal syndrome but no evidence of COVID-19. She spent 23 days in the intensive care unit. Our case describes an unusual presentation of COVID-19, the challenges in managing critically ill pregnant patients along with a rare background history of acrorenal syndrome.

Though long anticipated, adaptive optical (AO) pre-compensation is now experiencing a surge in interest thanks to technological advances and the identification of a real-world application with the advent of satellite laser communication as a viable alternative to radio-frequency. Here, we present an overview of our activities to date in pre-compensation, from the development of our AO system in laboratory experiments using artificial turbulence [1], to the integration into a transportable "AO-box" and testing in first proof-of-principle experiments over horizontal links using real turbulence [2] to the verification in horizontal tests of pre-compensation under large point-ahead-angles beyond the estimated isoplanatic range [3]. We describe the concept and realization of our experimental setup which provides simultaneous bidirectional correction of the incoming beam (post-compensation) and outgoing beam (pre-compensation). We then detail the transfer of this setup into two optical terminals representing a "ground terminal" and "satellite terminal". We describe the results of the horizontal measurement campaigns which have been undertaken to date in which a 7.1 dB increase in the received intensity was demonstrated under a small PAA over 0.5 km and in which a decline in the received laser power over increasingly large point-ahead-angle was demonstrated over a 1.0 km test range. We conclude with the current outlook for pre-compensation technology and indicate future planned experiments.

In the development of laser communication networks, atmospheric turbulence remains an obstacle in the efficiency optimisation of bidirectional optical links. Post-compensation of the downlink signal through adaptive optics (AO) has been verified as a method of increasing the efficiency of satellite-to-ground optical links, however, similar efficiencies have yet to be achieved in the opposite direction (uplink) largely due to the shower curtain effect and the consequent impossibility of conducting post-compensation over the smaller receiver aperture at the satellite terminal. Pre-compensation is anticipated to be a promising method of increasing the efficiency in uplink communications for Earth-to- GEO optical feederlinks, by pre-distorting the uplink wavefront prior to propagation through the atmosphere using measurements of the downlink. Here, we present the recent modifications to our current experimental setup and initial results of a pre-compensation experiment conducted over a 1 km horizontal path. The experiment aimed to investigate pre-compensation under a point-ahead-angle for the special case of a focussed uplink beam. Two optical terminals were developed, a “ground terminal breadboard” (GTB) consisting of a commercially available 30 cm reflective telescope in combination with an AO-box [3] capable of simultaneous post-and pre-compensation and a “satellite terminal breadboard” (STB) with separate transmission and receiving apertures for measurement of the uplink beam under a point-ahead-angle (PAA). We present a first look at and discussion of the experimental results which show that AO pre-compensation increased the measured intensity of the uplink beam over the receiving aperture of the STB for a PAA of up to 0.27 mrad.

Adaptive optical pre-compensation is seen as crucial for free-space laser communication in order to overcome the influence of atmospheric turbulence, particularly with respect to Earth-to-GEO feederlinks. This paper presents an experimental investigation into adaptive optical pre-compensation under large point-ahead-angles. We detail the design and realization of a free-space laser communication experiment over a 1.0 km horizontal path using a divergent beacon beam and a focussed signal beam, propagating in opposite directions. We describe the design and development of our experimental setup and measurement campaign using real turbulence. The median isoplanatic angle was calculated to be 0.16 mrad, while an increase in the received optical power through pre-compensation could be demonstrated for point-ahead-angles in the range of 0.13 mrad to 0.27 mrad.

Objective The aim of this study is to improve rates of day of surgery admission (DOSA) for all suitable elective thoracic surgery patients. Design Lean Six Sigma (LSS) methods were used to enable improvements to both the operational process and the organizational working of the department over a period of 19 months. Setting A national thoracic surgery department in a large teaching hospital in Ireland. Participants Thoracic surgery staff, patients and quality improvement staff at the hospital. Intervention(s) LSS methods were employed to identify and remove the non-value-add in the patient’s journey and achieve higher levels of DOSA. A pre-surgery checklist and Thoracic Planning Meeting were introduced to support a multidisciplinary approach to enhanced recovery after surgery (ERAS), reduce rework, improve list efficiency and optimize bed management. Main Outcome Measure(s) To achieve DOSA for all suitable elective thoracic surgery patients in line with the National Key Performance Indicator of 75%. A secondary outcome would be to further decrease overall length of stay by 1 day. Results Over a 19 month period, DOSA has increased from 10 to 75%. Duplication of preoperative tests reduced from 83 to

Objective The aim of this study is to improve rates of day of surgery admission (DOSA) for all suitable elective thoracic surgery patients. Design Lean Six Sigma (LSS) methods were used to enable improvements to both the operational process and the organizational working of the department over a period of 19 months. Setting A national thoracic surgery department in a large teaching hospital in Ireland. Participants Thoracic surgery staff, patients and quality improvement staff at the hospital. Intervention(s) LSS methods were employed to identify and remove the non-value-add in the patient’s journey and achieve higher levels of DOSA. A pre-surgery checklist and Thoracic Planning Meeting were introduced to support a multidisciplinary approach to enhanced recovery after surgery (ERAS), reduce rework, improve list efficiency and optimize bed management. Main Outcome Measure(s) To achieve DOSA for all suitable elective thoracic surgery patients in line with the National Key Performance Indicator of 75%. A secondary outcome would be to further decrease overall length of stay by 1 day. Results Over a 19 month period, DOSA has increased from 10 to 75%. Duplication of preoperative tests reduced from 83 to Conclusions Using LSS methods to improve both operational process efficiency and organizational clinical processes led to the successful achievement of increasing rates of DOSA in line with national targets.

This paper describes an opto-mechanical concept of a deformable metal mirror membrane, which can shift the focus position over a large range by use of a single actuator. The core element of the mirror is a diamond turned tulip-shaped membrane, the design is optimized to correct astigmatic aberrations which arise from the use of a curved mirror under a deflection angle. For this purpose, the target mirror surface is biconic. The manufactured mirror was tested with a maximum central deflection of 28 µm and, when used in combination with a 200 mm focal lens, is capable of producing a focus shift of up to 17.9 mm with a resulting wavefront aberration of 238.7 nm RMS error .

It is anticipated that ground-to-geostationary orbit (GEO) laser communication will benefit from pre-compensation of atmospheric turbulence for laser beam propagation through the atmosphere. Theoretical simulations and laboratory experiments have determined its feasibility; extensive free-space experimental validation has, however, yet to be fulfilled. Therefore, we designed and implemented an adaptive optical (AO)-box which pre-compensates an outgoing laser beam (uplink) using the measurements of an incoming beam (downlink). The setup was designed to approximate the baseline scenario over a horizontal test range of 0.5 km and consisted of a ground terminal with the AO-box and a simplified approximation of a satellite terminal. Our results confirmed that we could focus the uplink beam on the satellite terminal using AO under a point-ahead angle of 28 μrad. Furthermore, we demonstrated a considerable increase in the intensity received at the satellite. These results are further testimony to AO pre-compensation being a viable technique to enhance Earth-to-GEO optical communication.

Successful eLearning is predicated on the application of pedagogies appropriate to online education that respond to the capabilities and needs of the learners. Typically, designing and assembling personalized learning objects that respond to the pedagogical needs of a variety of different learners is an expensive and time-consuming process requiring both domain and educational expertise. Educators have the domain expertise and formal or informal pedagogical knowledge to create quality learning objects. However, they lack the tools and often the specific knowledge of online pedagogical approaches that make it time efficient for them to do so. This paper describes the motivation behind, the workflow supported by and the evaluation of the LO Generator, a tool that offers personalized support and scaffolding for users, who are not necessarily content creation or pedagogical experts, in assembling pedagogically sound personalized learning objects.

Activity-based personalized eLearning involves delivering to a learner a learning experience that is tailored to their individual needs. Traditionally, these needs have been met through the personalized selection of content that fits the learner's preferences. However, by coupling this approach with the possibilities of interactive services a more engaging form of personalized education may be realized. This paper describes the design principles for producing activity-based personalized distance learning offerings.