Numerical model of light propagation through Fabry-Perot etalons composed of interfaces with non-planar surface topography

We present a model that calculates optical fields reflected and transmitted by a Fabry-Perot (FP) etalon composed of interfaces with non-planar surface topography. The model uses the Rayleigh-Rice theory, which predicts the fields reflected and transmitted by a single interface, to account for the non-planar surface topography of each interface. The Rayleigh-Rice theory is evaluated iteratively to account for all round trips that light can take within the FP etalon. The model predictions can then be used to compute Interferometer transfer function (ITF)s, by performing wavelength or angle resolved simulations enabling predictions of the bandwidth, peak transmissivity, and sensitivity of FP etalons. The model was validated against the Pseudospectral time-domain (PSTD) method, which resulted in good agreement. Since the model accuracy is expected to reduce as the Root mean square (RMS) of the topographic map increases, the error in the model’s predictions was studied as a function of topographic map RMS. Finally, application of the model was exemplified by predicting the impact of roughness on ITFs and computing the changes in FP etalon transmissivity as cavity thickness is modulated by an ultrasonic wave

Changes in Creep Behaviour and Microstructure of Model Mozzarella Cheese During Working

The effect of shear work input on the microstructure, fat particle size and creep behavior of model Mozzarella type cheeses was studied. Cheese samples were prepared in a twin screw cooker at 70 °C by mixing protein and fat phases together with different amounts of shear work input. Major changes in cheese structure were observed while working at 150 rpm and 250 rpm screw speeds. Confocal microstructures plus macroscopic observations showed systematic changes in structure with increased shear work inputs with unmixed buttery liquid observed at kg−1, typical Mozzarella type microstructures (elongated fat-serum channels) at 6–15 kJ kg−1 and homogeneously distributed, small size fat droplets at \u3e58 kJ kg−1. At very high shear work inputs, \u3e 75 kJ kg−1, striations or anisotropy in the microstructures had disappeared and small micro-cracks were evident. A 4-element Burger\u27s model was found adequate for fitting the creep data of model cheese at 70 °C but a 6-element model was required at 20 °C. As shear work input increased retarded compliance decreased and zero shear viscosity increased indicating the more elastic behavior of the cheeses with higher shear work input. Changes in the protein matrix appear to be the main reason for increased elastic behavior

Implementing Non-Projective Measurements via Linear Optics: an Approach Based on Optimal Quantum State Discrimination

We discuss the problem of implementing generalized measurements (POVMs) with linear optics, either based upon a static linear array or including conditional dynamics. In our approach, a given POVM shall be identified as a solution to an optimization problem for a chosen cost function. We formulate a general principle: the implementation is only possible if a linear-optics circuit exists for which the quantum mechanical optimum (minimum) is still attainable after dephasing the corresponding quantum states. The general principle enables us, for instance, to derive a set of necessary conditions for the linear-optics implementation of the POVM that realizes the quantum mechanically optimal unambiguous discrimination of two pure nonorthogonal states. This extends our previous results on projection measurements and the exact discrimination of orthogonal states.Comment: final published versio

Effect of Shear Work Input on Steady Shear Rheology and Melt Functionality of Model Mozzarella Cheeses

Model Mozzarella cheeses with varied amounts of shear work input were prepared by working molten cheese mass at 70 °C in a twin screw cooker. Rheology and melt functionality were found to be strongly dependent on total shear work input. A non-linear increase in consistency coefficient (K from power law model) and apparent viscosity and decrease in flow behaviour index (n from power law model) were observed with increasing amounts of accumulated shear work, indicating work thickening behaviour. An exponential work thickening equation is proposed to describe this behaviour. Excessively worked cheese samples exhibited liquid exudation, poor melting and poor stretch. Nonfat cheese exhibited similar but smaller changes after excessive shear work input. We concluded that the dominant contributor to the changes in properties with increased shear work was shear induced structural changes to the protein matrix. A good correlation was found between the steady shear rheological properties and the melting properties of the cheeses

Strain Hardening and Anisotropy During Tensile Testing of Sheared Model Mozzarella Cheeses

We studied the tensile fracture properties of model Mozzarella cheeses with varying amounts of shear work input (3.3–73.7 kJ/kg). After manufacture, cheeses were elongated by manual rolling at 65°C followed by tensile testing at 21°C on dumbbell-shaped samples cut both parallel and perpendicular to the rolling direction. Strain hardening parameters were estimated from stress–strain curves using 3 different methods. Fracture stress and strain for longitudinal samples did not vary significantly with shear work input up to 26.3 kJ/kg and then decreased dramatically at 58.2 kJ/kg. Longitudinal samples with shear work input \u3c30 kJ/kg demonstrated significant strain hardening by all 3 estimation methods. At shear work inputs \u3c30 kJ/kg, strong anisotropy was observed in both fracture stress and strain. After a shear work input of 58.2 kJ/kg, anisotropy and strain hardening were absent. Perpendicular samples did not show strain hardening at any level of shear work input. Although the distortion of the fat drops in the cheese structure associated with the elongation could account for some of the anisotropy observed, the presence of anisotropy in the elongated nonfat samples reflected that shear work and rolling also aligned the protein structure

Editorial: From Pedagogic Research to Embedded E-Learning

This Special Issue of Reflecting Education arises from the work of the PREEL project (From Pedagogic Research to Embedded e-Learning) at the Institute of Education from 2006-2008. This project was one of nine HEA/JISC (Higher Education Academy and Joint Information Systems Committee) Pilot Pathfinder Projects and followed on from our involvement in the Pilot Benchmarking of e-Learning Programme. In the benchmarking exercise we identified a lack of coordination between research and practice in e-learning at the IoE as one of our crucial weaknesses, and so our Pilot Pathfinder project concentrated on this theme of building links between e-learning research and practice

Increasing the Q-factor of Fabry-Perot etalons using focused Bessel beam illumination

Sensing and filtering applications often require Fabry-Perot (FP) etalons with an Interferometer Transfer Function (ITF) having high visibility, narrow Full Width at Half Maximum (FWHM), and high sensitivity. For the ITF to have these characteristics, the illumination beam must be matched to the modes of the FP cavity. This is challenging when a small illumination element size is needed, as typical focused beams are not matched to the FP cavity modes. Bessel beams are a potential alternative as their structure resembles the FP cavity modes while possessing a focused core. To study the feasibility of using Bessel beam illumination, in this Letter, ITFs of an FP etalon were measured using Bessel and Gaussian illumination beams. A Bessel beam with core size of 28 µm provided an ITF with visibility 3.0 times higher, a FWHM 0.3 times narrower, and a sensitivity 2.2 times higher than a Gaussian beam with waist 32 µm. The results show that Bessel beam illumination can provide ITFs similar to that of collimated beam illumination while also having with a focused core.</p

Error tolerance and tradeoffs in loss- and failure-tolerant quantum computing schemes

Qubit loss and gate failure are significant problems for the development of scalable quantum computing. Recently, various schemes have been proposed for tolerating qubit loss and gate failure. These include schemes based on cluster and parity states. We show that by designing such schemes specifically to tolerate these error types we cause an exponential blowout in depolarizing noise. We discuss several examples and propose techniques for minimizing this problem. In general, this introduces a tradeoff with other undesirable effects. In some cases this is physical resource requirements, while in others it is noise rates

Measurement Techniques for Steady Shear Viscosity of Mozzarella-Type Cheeses at High Shear Rates and High Temperature

While measuring steady shear viscosity of Mozzarella-type cheeses in a rotational rheometer at 70 °C, three main difficulties were encountered; wall slip, structural failure during measurement and viscoelastic time dependent effects. Serrated plates were the most successful surface modification at eliminating wall slip. However, even with serrated plates shear banding occurred at higher shear rates. Because of the viscoelastic nature of the cheeses, a time dependent viscous response occurred at shear rates \u3c1 \u3es−1, requiring longer times to attain steady shear conditions. Prolonged continuous shearing altered the structure of the molten cheeses. The effects of structural change were greatly reduced by minimising the total accumulated strain exerted on the sample during flow curve determination. These techniques enabled successful measurement of steady shear viscosity of molten Mozzarella-type cheeses at 70 °C at shear rates up to 250 s−1