Morphological variations to a ptychographic algorithm.

Ptychography is a technique widely used in microscopy for achieving high-resolution imaging. This method relies on computational processing of images gathered from diffraction patterns produced by several partial illuminations of a sample. We numerically studied the effect of using different shapes for illuminating the aforementioned sample: convex shapes, such as circles and regular polygons, and unconnected shapes that resemble a QR code. Our results suggest that the use of unconnected shapes seems to outperform convex shapes in terms of convergence and, in some cases, accuracy.

Ptychographic reconstruction of pure quantum states.

The quantum analogue of ptychography, a powerful coherent diffractive imaging technique, is a simple method for reconstructing d-dimensional pure states. It relies on measuring partially overlapping parts of the input state in a single orthonormal basis and feeding the outcomes to an iterative phase retrieval algorithm for postprocessing. We provide a proof of concept demonstration of this method by determining pure states given by superpositions of d transverse spatial modes of an optical field. A set of n rank-r projectors, diagonal in the spatial mode basis, is used to generate n partially overlapping parts of the input, and each part is projectively measured in the Fourier transformed basis. For d up to 32, we successfully reconstructed hundreds of random states using n=5 and n=d rank-⌈d/2⌉ projectors. The extension of quantum ptychography for other types of photonic spatial modes is outlined.

Tunable entanglement distillation of spatially correlated down-converted photons.

We report on a new technique for entanglement distillation of the bipartite continuous variable state of spatially correlated photons generated in the spontaneous parametric down-conversion process (SPDC), where tunable non-Gaussian operations are implemented and the post-processed entanglement is certified in real-time using a single-photon sensitive electron multiplying CCD (EMCCD) camera. The local operations are performed using non-Gaussian filters modulated into a programmable spatial light modulator and, by using the EMCCD camera for actively recording the probability distributions of the twin-photons, one has fine control of the Schmidt number of the distilled state. We show that even simple non-Gaussian filters can be finely tuned to a ∼67% net gain of the initial entanglement generated in the SPDC process.

Experimental Minimum-Error Quantum-State Discrimination in High Dimensions.

Quantum mechanics forbids perfect discrimination among nonorthogonal states through a single shot measurement. To optimize this task, many strategies were devised that later became fundamental tools for quantum information processing. Here, we address the pioneering minimum-error (ME) measurement and give the first experimental demonstration of its application for discriminating nonorthogonal states in high dimensions. Our scheme is designed to distinguish symmetric pure states encoded in the transverse spatial modes of an optical field; the optimal measurement is performed by a projection onto the Fourier transform basis of these modes. For dimensions ranging from D=2 to D=21 and nearly 14 000 states tested, the deviations of the experimental results from the theoretical values range from 0.3% to 3.6% (getting below 2% for the vast majority), thus showing the excellent performance of our scheme. This ME measurement is a building block for high-dimensional implementations of many quantum communication protocols, including probabilistic state discrimination, dense coding with nonmaximal entanglement, and cryptographic schemes.

Preparing arbitrary pure states of spatial qudits with a single phase-only spatial light modulator.

Spatial qudits are D-dimensional (D ≥ 2) quantum systems carrying information encoded in the discretized transverse momentum and position of single photons. We present a proof-of-principle demonstration of a method for preparing arbitrary pure states of such systems by using a single phase-only spatial light modulator (SLM). The method relies on the encoding of the complex transmission function corresponding to a given spatial qudit state onto a preset diffraction order of a phase-only grating function addressed at the SLM. Fidelities of preparation above 94% were obtained with this method, which is simpler, less costly, and more efficient than those that require two SLMs for the same purpose.

Learning needs in a medical curriculum in Hong Kong.

OBJECTIVE: To survey medical graduates from the University of Hong Kong on how well they perceived their learning needs had been fulfilled by the old (before 1997) and the new (after 1997) curricula. DESIGN: Retrospective questionnaire survey. SETTING: The University of Hong Kong, Hong Kong. PARTICIPANTS: Medical graduates from the University of Hong Kong who graduated between 1997 and 2006 were invited to complete a questionnaire online or in paper form; 1997-2001 graduates were trained under the old curriculum, and 2002-2006 graduates under the new curriculum. RESULTS: The response rate was 23%. The survey showed that the graduates of both curricula felt that research skills, population health, and ophthalmology were not emphasised enough in the medical programme. In addition, some graduates of the old curriculum mentioned interpersonal skills, ethics and professionalism, and language skills, which were pinpointed in the curriculum reform in 1997. Some graduates of the new curriculum mentioned anatomy, microbiology, and diagnostic radiology. Graduates of both the old and the new curricula perceived the same top five areas as being lacking in their respective curricula, in relationship to their clinical career and personal growth, namely: business administration, law, professional English, life coaching, and humanities. A small percentage of graduates also took courses in these areas after graduation. CONCLUSIONS: The survey showed that the curriculum reform in 1997 at the University of Hong Kong had correctly pinpointed some of the learning needs. The survey also identified educational needs in the existing curriculum that need to be dealt with in the forthcoming curriculum reform in 2012.

Students' perceptions of learning outcomes from group-based, problem-based teaching and learning activities.

OBJECTIVE: A study aimed at exploring the variation in perceptions of learning outcomes reported by undergraduate nursing students enrolled in a problem-based learning subject in a pre-registration Bachelor of Nursing course (BN). METHOD: Students were asked to respond to four open-ended questions which focussed on their learning outcomes in the different teaching/learning modalities of the subject. Data were analysed in two phases using a modified phenomenographic analysis. In the first phase a set of categories of description were developed from the student responses to questions related to the learning modalities. In the second phase the individual responses were classified in terms of the categories. Finally, correlations between the learning modalities were identified. In this paper the approach to analysis, the process of category identification and the correlations between the learning modalities will be described and the implications for further research and teaching will be discussed. RESULTS: The findings indicated that there were two distinct groups of student responses. Inward focussed students who described outcomes in terms of their own learning and students whose focus was outward i.e. describing learning in terms of patient care and how learning relates to that care. Another important result shows the relationship between the learning modalities and outcomes. From the students' perspective, the most sophisticated outcomes of the lectures and laboratories were ideas and skills to be used and applied in clinical settings. Whereas, the group-based activities in which clinical problems were presented to the students in the form of Situation Improvement Packages (SIPS) focussed their attention on the clinical setting which constituted a preparation for the realities of clinical practice. CONCLUSION: The findings from this study indicate that students perceive their learning in the group based teaching/learning modality (SIPS) as effective in focussing them on the reality of their role in the clinical practice environment while lectures and laboratories provided the skills and knowledge required for this setting.

Microgeographic population genetic structure in the northern water snake, Nerodia sipedon sipedon detected using microsatellite DNA loci.

We describe the isolation and genetic characterization of eight microsatellite DNA loci from the northern water snake, Nerodia sipedon sipedon and use these loci to analyse levels of genetic differentiation between local (< 2 km apart) populations of these snakes in Ontario. These loci are variable, with expected heterozygosities ranging from 0.28 to 0.91, and can correctly exclude nonsires in parentage analyses with a high probability (0.998). Population analyses reveal significant deviation from expected heterozygosity levels for one population, probably a result of a null allele(s) at a single locus and small but significant levels of genetic differentiation among all three populations. This demonstrates that microgeographic genetic structure exists in this species, possibly due to limited dispersal.

Relations between perceptions of the teaching environment and approaches to teaching.

BACKGROUND: Previous research has established substantial relations between students' approaches to study in higher education and their perceptions of the learning environment. More recently, there has been a growing body of research into teachers' approaches to teaching and conceptions of teaching. There has, however, been little research into their perceptions of the teaching context. AIMS: This study aimed to develop an inventory of university teachers' perceptions of their teaching environment (PTE) and how those perceptions related to their approaches to teaching. SAMPLES: The interview sample comprised 13 teachers of first year university physics and chemistry courses in two Australian universities, and the survey sample comprised 46 teachers from several Australian universities. METHODS: In the qualitative study teachers were interviewed about the things they thought affected their teaching. The interviews were content analysed, and an inventory was produced. In the quantitative study, the results of the administration of the Approaches to Teaching Inventory and the PTE were analysed by correlational, factor and cluster analyses. RESULTS: This exploratory study found systematic relations between the perceptions and approaches. The relations observed suggest that the adoption of a conceptual change and student focused approach to teaching is associated with perceptions that the teacher has control over what is taught and how it is taught, as well as perceptions that the department values teaching and that class size is not too large. CONCLUSIONS: The paper concludes by arguing that if we are to improve the quality of teaching and learning in higher education we will need to take account of the perceptions teachers have of their teaching context.

Fluctuations in plasma pyrroline-5-carboxylate concentrations during feeding and fasting.

Pyrroline-5-carboxylate (P5C) is the oxidized metabolite of proline. In cultured cells redox-sensitive metabolic pathways are influenced by these two amino acids. To determine whether plasma P5C levels fluctuate enough physiologically to regulate such pathways in vivo, we measured venous plasma P5C concentrations hourly for 48 h in five normal subjects while eating and in four subjects while fasting. Two fed subjects had one or more plasma P5C excursions per day exceeding 10 times the baseline level; the other fed subjects had lesser variations. These patterns suggest a relationship of plasma P5C peaks to meals. This relationship is supported by the finding of no significant P5C elevations above baseline levels in four subjects during fasting for 24 h. Despite the changes in plasma P5C concentrations, those of proline and other metabolically related amino acids were constant. The variation among subjects in the degree of plasma P5C fluctuation could not be explained by differences in total protein and caloric intake or body weight. Among plasma constituents, the large peak to basal plasma P5C excursions in some of the normal subjects we studied are matched only by those of peptide hormones.