Performance of horn-coupled transition edge sensors for L- and S-band optical detection on the SAFARI instrument

We describe the geometry, architecture, dark- and optical performance of ultra-low-noise transition edge sensors as THz detectors for the SAFARI instrument. The TESs are fabricated from superconducting Mo/Au bilayers coupled to impedance-matched superconducting ß-phase Ta thin-film absorbers. The detectors have phonon-limited dark noise equivalent powers of order 0.5 - 1.0 aW/$\sqrt{Hz}$ and saturation powers of order 20 - 40 fW. The low temperature test configuration incorporating micro-machined backshorts is also described, and construction and typical performance characteristics for the optical load are shown. We report preliminary measurements of the optical performance of these TESs for two SAFARI bands; L-band at 110 - 210 µm and S-band 34 - 60 µm .European Space AgencyThis is the final version of the article. It first appeared from SPIE via http://dx.doi.org/10.1117/12.223274

Learning from interaction: models and applications

A large proportion of Machine Learning (ML) research focuses on designing algorithms that require minimal input from the human. However, ML algo- rithms are now widely used in various areas of engineering to design and build systems that interact with the human user and thus need to “learn” from this interaction. In this work, we concentrate on algorithms that learn from user interaction. A significant part of the dissertation is devoted to learning in the bandit setting. We propose a general framework for handling dependencies across arms, based on the new assumption that the mean-reward function is drawn from a Gaussian Process. Additionally, we propose an alternative method for arm selection using Thompson sampling and we apply the new algorithms to a grammar learning problem. In the remainder of the dissertation, we consider content-based image re- trieval in the case when the user is unable to specify the required content through tags or other image properties and so the system must extract infor- mation from the user through limited feedback. We present a novel Bayesian approach that uses latent random variables to model the systems imperfect knowledge about the users expected response to the images. An impor- tant aspect of the algorithm is the incorporation of an explicit exploration- exploitation strategy in the image sampling process. A second aspect of our algorithm is the way in which its knowledge of the target image is updated given user feedback. We considered a few algorithms to do so: variational Bayes, Gibbs sampling and a simple uniform update. We show in experi- ments that the simple uniform update performs best. The reason is because, unlike the uniform update, both variational Bayes and Gibbs sampling tend to focus on a small set of images aggressively

Optical Characterisation of a Camera module Developed for Ultra-low NEP TES Detector Arrays at FIR Wavelengths

Here we report on the optical design and on the spectral-spatial characterisation of a small 16 pixel camera. The prototype uses TES detectors with NEPs ~10-16 W/Hz0.5 which have been fabricated with near identical optical coupling structures to mimic their much lower NEP counterparts (~10-19 W/Hz0.5). This modification, which is achieved through changing only the pixel thermal conductance, G, has allowed us to perform spectral/spatial cryogenic testing using a 100mK ADR to view room temperature thermal sources. The measurements show a flat spectral response across the waveband and minimal side lobe structure in the antenna patterns down to 30dB

Intentstreams: Smart parallel search streams for branching exploratory search

The user's understanding of information needs and the information available in the data collection can evolve during an exploratory search session. Search systems tailored for well-defined narrow search tasks may be suboptimal for exploratory search where the user can sequentially refine the expressions of her information needs and explore alternative search directions. A major challenge for exploratory search systems design is how to support such behavior and expose the user to relevant yet novel information that can be difficult to discover by using conventional query formulation techniques. We introduce IntentStreams, a system for exploratory search that provides interactive query refinement mechanisms and parallel visualization of search streams. The system models each search stream via an intent model allowing rapid user feedback. The user interface allows swift initiation of alternative and parallel search streams by direct manipulation that does not require typing. A study with 13 participants shows that IntentStreams provides better support for branching behavior compared to a conventional search system

Optical requirements and modelling of coupling devices for the SAFARI instrument on SPICA

The next generation of space missions targeting far-infrared bands will require large-format arrays of extremely low-noise detectors. The development of Transition Edge Sensors (TES) array technology seems to be a viable solution for future mm-wave to Far-Infrared (FIR) space applications where low noise and high sensitivity is required. In this paper we concentrate on a key element for a high sensitivity TES detector array, that of the optical coupling between the incoming electromagnetic field and the phonon system of the suspended membrane. An intermediate solution between free space coupling and a single moded horn is where over-moded light pipes are used to concentrate energy onto multi-moded absorbers. We present a comparison of modelling techniques to analyse the optical efficiency of such light pipes and their interaction with the front end optics and detector cavity

\u3ci\u3ePhotosystem II Subunit S\u3c/i\u3e overexpression increases the efficiency of water use in a field-grown crop

Insufficient water availability for crop production is a mounting barrier to achieving the 70% increase in food production that will be needed by 2050. One solution is to develop crops that require less water per unit mass of production. Water vapor transpires from leaves through stomata, which also facilitate the influx of CO2 during photosynthetic assimilation. Here, we hypothesize that Photosystem II Subunit S (PsbS) expression affects a chloroplastderived signal for stomatal opening in response to light, which can be used to improve wateruse efficiency. Transgenic tobacco plants with a range of PsbS expression, from undetectable to 3.7 times wild-type are generated. Plants with increased PsbS expression show less stomatal opening in response to light, resulting in a 25% reduction in water loss per CO2 assimilated under field conditions. Since the role of PsbS is universal across higher plants, this manipulation should be effective across all crops

Add-on treatment with nebulized hypertonic saline in a child with plastic bronchitis after the Glenn procedure

Plastic bronchitis (PB), although a rare cause of airway obstruction, has mortality rates up to 50% in children after Fontan-type cardiac surgery. We present the case of an 18-month-old female patient with PB following pneumonia. At 6 months of age, the patient underwent the Glenn procedure due to functionally univentricular heart. Fiberoptic bronchoscopy revealed complete blockage of the left bronchus by mucoid casts. Pharmacotherapy consisted of glucocorticosteroids, azithromycin, and enalapril maleate. The child also received nebulized 3% NaCl solution, which proved to be beneficial. In children submitted to Fontan-type procedures, physicians must be alert for PB, which can be triggered by respiratory tract infection