Summary We demonstrate simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. Subject to the assumptions explicitly stated in the derivation, the algorithm solves the twin‐image problem of in‐line holography and is capable of analysing data obtained using X‐ray microscopy, electron microscopy, neutron microscopy or visible‐light microscopy, especially as they relate to defocus and point projection methods. Our simple, robust, non‐iterative and computationally efficient method is applied to data obtained using an X‐ray phase contrast ultramicroscope.

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In-line phase contrast enables weakly absorbing specimens to be imaged successfully with x-rays, and greatly enhances the visibility of fine scale structure in more strongly absorbing specimens. This type of phase contrast requires a spatially coherent beam, a condition that can be met by a microfocus x-ray source. We have developed an x-ray microscope, based on such a source, which is capable of high resolution phase-contrast imaging and tomography. Phase retrieval enables quantitative information to be recovered from phase-contrast microscope images of homogeneous samples of known composition and density, and improves the quality of tomographic reconstructions.

SummaryWe outline a new approach to X-ray projection microscopy in a scanning electron microscope (SEM), which exploits phase contrast to boost the quality and information content of images. These developments have been made possible by the combination of a high-brightness field-emission gun (FEG)-based SEM, direct detection CCD technology and new phase retrieval algorithms. Using this approach we have been able to obtain spatial resolution of < 0.2 µ m and have demonstrated novel features such as: (i) phase-contrast enhanced visibility of high spatial frequency image features (e.g. edges and boundaries) over a wide energy range; (ii) energy-resolved imaging to simultaneously produce multiple quasi-monochromatic images using broad-band polychromatic illumination; (iii) easy implementation of microtomography; (iv) rapid and robust phase/amplitude-retrieval algorithms to enable new real-time and quantitative modes of microscopic imaging. These algorithms can also be applied successfully to recover object-plane information from intermediate-field images, unlocking the potentially greater contrast and resolution of the intermediatefield regime. Widespread applications are envisaged for fields such as materials science, biological and biomedical research and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to projection microscopy using other sources of radiation, such as visible light and electrons.

The electronic properties of thin, nanometer scale GaAs quantum well tubes embedded inside the AlGaAs shell of a GaAs core-multishell nanowire are investigated using optical spectroscopies. Using numerical simulations to model cylindrically and hexagonally symmetric systems, we correlate these electronic properties with structural characterization by aberration-corrected scanning transmission electron microscopy of nanowire cross sections. These tubular quantum wells exhibit extremely high quantum efficiency and intense emission for extremely low submicrowatt excitation powers in both photoluminescence and photoluminescence excitation measurements. Numerical calculations of the confined eigenstates suggest that the electrons and holes in their ground states are confined to extremely localized one-dimensional filaments at the corners of the hexagonal structure which extend along the length of the nanowire.

Internet research is successful at accessing hidden populations of illicit drugs users, when appropriately targeted and provides unprecedented opportunities for research across a wide range of topics within the addictions field. Findings are unlikely to be generalisable to the general public, but appropriate for describing target populations.

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Abstract:Purpose: To examine the influence of an acute dose of sodium bicarbonate (NaHCO3) on buffering capacity and performance during a repeated sprint ability (RSA) protocol. Methods: Eleven (mean ± SD: age 24.6 ± 6.1y; mass 74.9 ± 5.7kg; height 177.2 ± 6.7cm) participated in the study, undertaking four test sessions. On the first visit to the laboratory, each participant ingested 300 mg.kg-1 of NaHCO3 (in 450ml of flavoured water) and blood samples were obtained at regular intervals to determine the individual times peak pH and HCO3-response time. During the subsequent visits, participants ingested either 300mg.kg-1 of NaHCO3, or 270 mg.kg-1 BM of NaCI or no drink followed by a RSA cycling protocol (10 x 6s sprints with 60s recovery), which commenced at each individuals pre-determined ingestion peak pH response time. Blood samples were obtained pre-exercise, and after the 1st, 5th and 10th sprint to determine the blood pH, HCO3-and lactate (La-) responses. Results: The total work completed during the repeated sprint protocol was higher (P < 0.05) in the NaHCO3 condition (69.8 ± 11.7kJ) compared with both the control (59.6±12.2 kJ) and placebo (63.0±8.3 kJ) conditions. Peak power output (PPO) was similar (P > 0.05) between the three conditions. Relative to the control and placebo conditions, NaHCO3 ingestion induced higher (P < 0.05) blood pH and HCO3-concentrations pre-exercise and during the bouts, and higher lactate concentrations (P < 0.05) following the final sprint. Conclusion: The results from the present study suggest that NaHCO3-improves the total amount of work completed during RSA through enhanced buffering capacity. Results:The total work completed during the repeated sprint protocol was higher (P < 0.05) in the NaHCO 3 condition (69.8 ± 11.7kJ) compared with both the control (59.6±12.2 kJ) and placebo (63.0±8.3 kJ) conditions. Peak power output (PPO) was similar (P > 0.05) between the three conditions. Relative to the control and placebo conditions, NaHCO 3 ingestion induced higher (P < 0.05) blood pH and HCO 3 -concentrations pre-exercise and during the bouts, and higher lactate concentrations (P < 0.05) following the final sprint. Conclusion: The results from the present study suggest that NaHCO 3 -improves the total amount of work completed during RSA through enhanced buffering capacity.