X-ray phase-contrast imaging and tomography make use of the refraction of X-rays by the sample in image formation. This provides considerable additional information in the image compared to ...conventional X-ray imaging methods, which rely solely on X-ray absorption by the sample. Phase-contrast imaging highlights edges and internal boundaries of a sample and is thus complementary to absorption contrast, which is more sensitive to the bulk of the sample. Phase-contrast can also be used to image low-density materials, which do not absorb X-rays sufficiently to form a conventional X-ray image. In the context of materials science, X-ray phase-contrast imaging and tomography have particular value in the 2D and 3D characterization of low-density materials, the detection of cracks and voids and the analysis of composites and multiphase materials where the different components have similar X-ray attenuation coefficients. Here we review the use of phase-contrast imaging and tomography for a wide variety of materials science characterization problems using both synchrotron and laboratory sources and further demonstrate the particular benefits of phase contrast in the laboratory setting with a series of case studies.
Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk ALL subtype with high rates of relapse and poor patient outcome. Activating mutations affecting components of ...the JAK-STAT signaling pathway occur in the majority of Ph-like ALL cases. The use of JAK inhibitors represents a potential treatment option for Ph-like ALL, although we and others have shown that CRLF2-rearranged Ph-like ALL responds poorly to single-agent JAK inhibitors in the preclinical setting. Therefore, the aim of this study was to identify effective combination treatments against CRLF2-rearranged Ph-like ALL, and to elucidate the underlying mechanisms of synergy. We carried out a series of high-throughput combination drug screenings and found that ruxolitinib exerted synergy with standard-of-care drugs used in the treatment of ALL. In addition, we investigated the molecular effects of ruxolitinib on Ph-like ALL by combining mass spectrometry phosphoproteomics with gene expression analysis. Based on these findings, we conducted preclinical in vivo drug testing and demonstrated that ruxolitinib enhanced the in vivo efficacy of an induction-type regimen consisting of vincristine, dexamethasone, and L-asparaginase in 2/3 CRLF2-rearranged Ph-like ALL xenografts. Overall, our findings support evaluating the addition of ruxolitinib to conventional induction regimens for the treatment of CRLF2-rearranged Ph-like ALL.
Simple analytical expressions are derived for the spatial resolution, contrast and signal-to-noise in X-ray projection images of a generic phase edge. The obtained expressions take into account the ...maximum phase shift generated by the sample and the sharpness of the edge, as well as such parameters of the imaging set-up as the wavelength spectrum and the size of the incoherent source, the source-to-object and object-to-detector distances and the detector resolution. Different asymptotic behavior of the expressions in the cases of large and small Fresnel numbers is demonstrated. The analytical expressions are compared with the results of numerical simulations using Kirchhoff diffraction theory, as well as with experimental X-ray measurements.
Objective To examine mortality in a representative nationwide sample of homeless and marginally housed people living in shelters, rooming houses, and hotels.Design Follow-up study.Setting Canada ...1991-2001.Participants 15 100 homeless and marginally housed people enumerated in 1991 census.Main outcome measures Age specific and age standardised mortality rates, remaining life expectancies at age 25, and probabilities of survival from age 25 to 75. Data were compared with data from the poorest and richest income fifths as well as with data for the entire cohortResults Of the homeless and marginally housed people, 3280 died. Mortality rates among these people were substantially higher than rates in the poorest income fifth, with the highest rate ratios seen at younger ages. Among those who were homeless or marginally housed, the probability of survival to age 75 was 32% (95% confidence interval 30% to 34%) in men and 60% (56% to 63%) in women. Remaining life expectancy at age 25 was 42 years (42 to 43) and 52 years (50 to 53), respectively. Compared with the entire cohort, mortality rate ratios for men and women, respectively, were 11.5 (8.8 to 15.0) and 9.2 (5.5 to 15.2) for drug related deaths, 6.4 (5.3 to 7.7) and 8.2 (5.0 to 13.4) for alcohol related deaths, 4.8 (3.9 to 5.9) and 3.8 (2.7 to 5.4) for mental disorders, and 2.3 (1.8 to 3.1) and 5.6 (3.2 to 9.6) for suicide. For both sexes, the largest differences in mortality rates were for smoking related diseases, ischaemic heart disease, and respiratory diseases.Conclusions Living in shelters, rooming houses, and hotels is associated with much higher mortality than expected on the basis of low income alone. Reducing the excessively high rates of premature mortality in this population would require interventions to address deaths related to smoking, alcohol, and drugs, and mental disorders and suicide, among other causes.
This study examined barriers to colorectal cancer (CRC) screening in people living in rural areas.
We identified 2 rural counties with high rates of CRC and randomly contacted county residents by ...telephone using a published listing.
Six hundred thirty-five of the 1839 eligible respondents (34.5%) between the ages of 50 and 79 years living in McDuffie and Screven counties, Georgia, agreed to complete the survey. The mean age was 62.2 years (SD, ±7.5 years); 72.4% were women, 79.4% were white, and 19.5% were African American. African-American respondents had lower CRC screening rates (50.4%) than whites (63.4%; P = .009). Significantly more African Americans compared with whites reported barriers to CRC screening. Based on logistic regression analyses, having a physician recommend CRC screening had the strongest association with having a current CRC screening, regardless of race.
Important racial differences existed between African Americans and whites regarding the barriers to CRC screening and factors impacting current screening. However, endorsement of a small set of questionnaire items--not race--had the strongest association with being current with screening. Physician recommendation for CRC screening had the strongest association with being current with CRC screening.
X-ray fluorescence microscopy (XFM) facilitates high-sensitivity quantitative imaging of trace metals at high spatial resolution over large sample areas and can be applied to a diverse range of ...biological samples. Accurate determination of elemental content from recorded spectra requires proper calibration of the XFM instrument under the relevant operating conditions. Here, we describe the manufacture, characterization, and utilization of multi-element thin-film reference foils for use in calibration of XFM measurements of biological and other specimens. We have used these internal standards to assess the two-dimensional distribution of trace metals in a thin tissue section of a rat hippocampus. The data used in this study was acquired at the XFM beamline of the Australian Synchrotron using a new 384-element array detector (Maia) and at beamline 2-ID-E at the Advanced Photon Source. Post-processing of samples by different fixation techniques was investigated, with the conclusion that differences in solvent type and sample handling can significantly alter elemental content. The present study highlights the quantitative capability, high statistical power, and versatility of the XFM technique for mapping trace metals in biological samples, e.g., brain tissue samples in order to help understand neurological processes, especially when implemented in conjunction with a high-performance detector such as Maia.
The Imaging and Medical beamline at the Australian Synchrotron achieved `first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X‐ray ...imaging and tomography studies for a range of samples. The use of a plastic‐edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X‐ray energy for the polychromatic beam.
The first monochromatic X‐ray tomography experiments conducted at the Imaging and Medical beamline of the Australian Synchrotron are reported. The sample was a phantom comprising nylon line, Al wire ...and finer Cu wire twisted together. Data sets were collected at four different X‐ray energies. In order to quantitatively account for the experimental values obtained for the Hounsfield (or CT) number, it was necessary to consider various issues including the point‐spread function for the X‐ray imaging system and harmonic contamination of the X‐ray beam. The analysis and interpretation of the data includes detailed considerations of the resolution and efficiency of the CCD detector, calculations of the X‐ray spectrum prior to monochromatization, allowance for the response of the double‐crystal Si monochromator used (via X‐ray dynamical theory), as well as a thorough assessment of the role of X‐ray phase‐contrast effects. Computer simulations relating to the tomography experiments also provide valuable insights into these important issues. It was found that a significant discrepancy between theory and experiment for the Cu wire could be largely resolved in terms of the effect of the point‐spread function. The findings of this study are important in respect of any attempts to extract quantitative information from X‐ray tomography data, across a wide range of disciplines, including materials and life sciences.
One of the most substantial challenges facing the field of injury and violence prevention is bridging the gap between scientific knowledge and its real-world application to achieve population-level ...impact. Much synergy is gained when academic and practice communities collaborate; however, a number of barriers prevent better integration of science and practice. This article presents 3 examples of academic-practitioner collaborations, their approaches to working together to address injury and violence issues, and emerging indications of the impact on integrating research and practice. The examples fall along the spectrum of engagement with nonacademic partners as coinvestigators and knowledge producers. They also highlight the benefits of academic-community partnerships and the engaged scholarship model under which Centers for Disease Control and Prevention-funded Injury Control Research Centers operate to address the research-to-practice and practice-to-research gap.
Effects of incident illumination on phase-contrast images obtained by means of free-space propagation are investigated under the "transport-of-intensity" approximation. Analytical expressions for ...image intensity distribution are derived in the cases of coherent quasi-plane and quasi-spherical incident waves, as well as for spatially incoherent and quasi-homogeneous sources and some other types of sources. Practical methods for measuring the relevant parameters of the incident radiation are discussed together with formulas allowing one to calculate the effect of these parameters on the image intensity distribution. The results are expected to be useful in quantitative in-line imaging, phase retrieval, and tomography with polychromatic and spatially partially coherent radiation. As an application we present a method for simultaneous "automatic" phase retrieval and spatial deconvolution in in-line imaging of homogeneous objects using extended polychromatic x-ray sources.
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