A single-image retrieval method for edge illumination X-ray phase-contrast imaging: Application and noise analysis

PurposeEdge illumination (EI) X-ray phase-contrast imaging (XPCI) has been under development at University College London in recent years, and has shown great potential for both laboratory and synchrotron applications. In this work, we propose a new acquisition and processing scheme. Contrary to existing retrieval methods for EI, which require as input two images acquired in different setup configurations, the proposed approach can retrieve an approximate map of the X-ray phase from a single image, thus significantly simplifying the acquisition procedure and reducing data collection times.MethodsThe retrieval method is analytically derived, based on the assumption of a quasi-homogeneous object, i.e. an object featuring a constant ratio between refractive index and absorption coefficient. The noise properties of the input and retrieved images are also theoretically analyzed under the developed formalism. The method is applied to experimental synchrotron images of a biological object.ResultsThe experimental results show that the method can provide high-quality images, where the “edge” signal typical of XPCI images is transformed to an “area” contrast that enables an easier interpretation of the sample geometry. Moreover, the retrieved images confirm that the method is highly stable against noise.ConclusionsWe anticipate that the developed approach will become the method of choice for a variety of applications of EI XPCI, thanks to its ability to simplify the acquisition procedure and reduce acquisitions time and dose to the sample. Future work will focus on the adaptation of the method to computed tomography and to polychromatic radiation from X-ray tubes.     

Physiological responses of Prunus cerasus to whole-plant source manipulation. Leaf gas exchange, chlorophyll fluorescence, water relations and carbohydrate concentrations.

The source-sink ratio of 1-year-old, potted sour cherry trees ( Prunus cerasus L.) was altered by whold-plant partial defoliation or continuous illumination to determine if trees were primarily sink limited and to elucidate the means whereby photosynthetic enhancement or inhibition occurs. Leaf xylem water potential was not affected by either treatment. Although stomatal conductance was reduced by 1 to 3 days of continuous illumination, internal CO₂ concentration was not significantly affected indicating that the enhanced physical limitation imposed by the stomata was of no physiological significance. Net CO₂ assimilation (A) was significantly higher 4 days after partial defoliation and lower from 1 to 4 days following continuious illumination. The increase in A in partially defoliated plants was associated with reduced leaf starch and increased surose and sorbitol concentrations. The decrease in A in continuously illuminated plants was associated with a decrease in variable fluorescence, photochemical efficiency of photosystem II (PSII) and an increase in instantaneous fluorescence, indicating that leaves were photoinhibited and that irreversible damage had occurred to PSII. In addition, leaves of continuously illuminated plants had 80% more starch and significantly less sucrose and sorbitol. These altered leaf carbohydrate concentrations indicate that the existing sink limitation may have been aggravated by continuous illumination leading to an insufficient utilization of sucrose from the leaf. Whether the altered photochemical and biochemical events occurred simultaneously and/or to the same degree to lead to the observed responses remains equivocal.     

A comparative analysis of Chrysoperla carnea catches in light- and suction-traps

ABSTRACT.

• 1 The lacewing C.carnea was caught weekly at Rothamsted in six traps, in 1973 and between 1975 and 1980. The traps were in three pairs: two light-traps in woodland, two light-traps in open fields, and two suction-traps, sampling at 12 m and 1.2 m above the ground.
• 2 Standardized trap phenologies were compared seasonally, for each year, using multivariate methods. Trap environments caused the greatest phenological difference, which was between the woodland and the other traps. The suctiontraps and the light-traps in open fields also differed. The greatest similarity was between the woodland light-traps, the next between the suction-traps, but the two light-traps in open fields were relatively dissimilar.
• 3 These results were supported by analysis of the sex-ratio of catches in each trap. We suggest an overall phenology in which the wood is important as an overwintering site for adults in autumn and as a source in spring.
• 4 Assessment of consistency over years showed no year was typical, but 1979 was markedly dissimilar from other years; 1976 was particularly similar to 1975.
• 5 The use of generalized Procrustes analysis (Gower, 1975) is recommended for similar sets of ecological data.

     

Spontaneous cardiomyopathy and nephropathy in the owl monkey (Aotus sp.) in captivity.

Clinical and pathologic data were reviewed for 72 owl monkeys that died between January 1987 and May 1990 at the Center for Reproduction and Conservation of Nonhuman Primates in Iquitos, Peru. Tissue samples from 39 animals were examined. Hypertrophic cardiac disease (51% of animals examined), dilative cardiomyopathy (26%), and nephropathy (87%) were the most common diagnoses. The incidence of all three diseases appeared to increase with time in captivity. Nephropathy was less severe in colony-born animals.     

23rd International Symposium on Shiftwork and Working Time: Towards a Global Consensus

ABSTRACT

The Working Time Society (WTS), and the International Commission on Occupational Health (ICOH) Scientific Committee on Shiftwork and Working Time, are twin organisations focused on conducting research, and informing practice, regarding the impact of work hours in general, and shiftwork in particular, on the efficiency, productivity, safety, well-being, health, and biological rhythms, of employees. Every 2–3 years since 1969, the WTS and ICOH have conducted a series of international symposia in Europe, Asia, Australia, North America, and South America. The purpose of these symposia is to provide a forum for the exchange of knowledge, and the discussion of contested issues, with researchers, employee representatives, regulators, and employers. The most recent symposium in this series – the 23rd International Symposium on Shiftwork and Working Time, entitled “Toward a Global Consensus” – was held on 19–23 June 2017, at Yulara, Australia, near Uluru. Since 2004, Chronobiology International has released a special issue after each symposium, and that tradition continues with a special issue that includes 17 contributions based on a selection of the 128 papers that were presented at the most recent symposium. Here, we provide an overview of the papers that comprise the special issue, and we briefly comment on the implications of the findings for shiftworkers and their employers.     

Are diel vertical migrations of European perch (Perca fluviatilis L.) early juveniles under direct control of light intensity? Evidence from a large field experiment

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Phase-shifts of apparent circadian rhythms due to west and east transmeridian flights or to corresponding night-shift sleep displacements

Phase movements of apparent circadian rhythms during 2 wk of forward or backward displacement of the sleep-wake cycle were investigated in four experimental series in a subject. The 7-hr delay or advance of sleep due to a westward or an eastward transmeridian flight was duplicated by corresponding sleep displacements during experimental night shifts. Sudden phase advances (or delays) by several hours were observed in the rhythms of continuously recorded rectal temperature and urinary excretion rates (4-hr collection intervals) of adrenaline, noradrenaline and aldosterone the first day after sleep-wake displacement. The desired 7-hr phase-shifts were reached more quickly and completely when the phase was delayed than when it was advanced. In addition, the best-fitting period of these rhythms became shorter than 24 hr when the phase was delayed, and longer than 24 hr when it was advanced. The apparent rhythms of urine flow and electrolyte excretions (potassium, sodium, zinc) were much weaker and their phase movements more irregular than those of hormonal excretion. It is concluded that the sudden phase-shifts resulted from the immediate adaptation of the exogenous components of the rhythms to the demands of the displaced sleep-wake patterns (masking effects) and that the true phase-shifts of the endogenous components followed more slowly and gradually.     

Carbon balance and source‐sink metabolic changes in winter wheat exposed to high night‐time temperature

Carbon loss under high night‐time temperature (HNT) leads to significant reduction in wheat yield. Growth chamber studies were carried out using six winter wheat genotypes, to unravel postheading HNT (23°C)–induced alterations in carbon balance, source‐sink metabolic changes, yield, and yield‐related traits compared with control (15°C) conditions. Four of the six tested genotypes recorded a significant increase in night respiration after 4 days of HNT exposure, with all the cultivars regulating carbon loss and demonstrating different degree of acclimation to extended HNT exposure. Metabolite profiling indicated carbohydrate metabolism in spikes and activation of the TriCarboxylic Acid (TCA) cycle in leaves as important pathways operating under HNT exposure. A significant increase in sugars, sugar‐alcohols, and phosphate in spikes of the tolerant genotype (Tascosa) indicated osmolytes and membrane protective mechanisms acting against HNT damage. Enhanced night respiration under HNT resulted in higher accumulation of TCA cycle intermediates like isocitrate and fumarate in leaves of the susceptible genotype (TX86A5606). Lower grain number due to lesser productive spikes and reduced grain weight due to shorter grain‐filling duration determined HNT‐induced yield loss in winter wheat. Traits and mechanisms identified will help catalyze the development of physiological and metabolic markers for breeding HNT‐tolerant wheat.     

A laboratory experiment to determine the dispersal response of Atlantic salmon (Salmo salar) fry to street light intensity

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湘黄种鸡露天散养时光照程序制定办法研究

湘黄种鸡露天散养时,合理的光照以提高产合格种蛋率是露天散养的重要技术之一。本研究采用人工光照与自然光照结合办法,对4个批次7 400套种鸡进行了研究观察,并与对应的同日龄全自然光照专业户鸡群比较,得出散养种鸡制定出合理的光照程序可使产合格蛋率提高21.93%。