Unified characterization of imaging sensors from visible through longwave IR The use of minimum resolvable contrast measurements enables a uniform approach to characterizing imaging sensor performance in the visible, near-IR, and shortwave IR spectral ranges. Modern reconnaissance strategies are based on gathering information from sensors that operate in several spectral bands. Besides the well-known atmospheric windows at the visible (VIS), medium-wave IR, and longwave-IR (LWIR) wavelengths, today's detectors can also operate in the 1–1.7μm window known as shortwave IR (SWIR). SWIR cameras are especially useful in the hazy or misty atmospheric conditions typical of a maritime environment. For optimum application of SWIR cameras, as well as detectors in other bands, it would be useful to have a single, uniform method of characterizing the various sensors. One way to provide such characterization is to use minimum resolvable contrast (MRC) measurements. MRC is a measure of a system's sensitivity and its ability to resolve data. It was pioneered by John Johnson in the late 1950s when he first described the probability of detecting an object as dependent on the object's effective resolution.1 This intuitive idea showed that the probability of locating a target increases with the number of resolvable cycles across that target. Johnson's analysis was initially used to assist the design of image intensifier tubes, which increase the intensity of light in optical systems where there is limited light available. Later—with the growing importance of day sight (surveillance) cameras—Johnson's work was revived by developers who used MRC measurements to assess electro- optical systems. SWIR imaging makes use of the radiation reflected by observed objects in the same way that visible imaging does. It is therefore possible to use MRC methods to characterize SWIR imaging.2 We have employed MRC measurements to determine the ability of a camera system to resolve detail contrast in the visible spectrum in relation to range and luminance. The system (optics, detector, electronics, display, and the observer's eye) captures a collimated USAF 1951 resolution test chart in front of an adjustable light source (see Figure 1). The USAF target is a widely accepted test pattern created by the US Air Force, and consists of groups of three bars with different dimensions, from large to small. The imager's resolving power is defined as the largest bar in the pattern that it cannot discern. We used a sequence of USAF targets—which had different contrast values in the bar pattern structure—to establish an MRC curve as a function of spatial frequency. We input the recorded values into visual range model (VRM) software,3 which calculated the ranges of the camera system. The output is presented as a graph that shows contrast to spatial frequency at a given luminance. Figure 1. Setup used for measuring minimum resolvable contrast (MRC). Setup used for measuring minimum resolvable contrast (MRC). 3 The targets are mounted in front of a light source with specified luminance. The outcoming light is collimated by a parabolic mirror and directed into the aperture of the camera under test. The camera is fixed on a rotatable arm to allow measurements under different angles of incidence. To take experimental MRC measurements, we used a light bulb with a temperature of 3000K as the visible light source. This temperature is considerably lower than that of our key visible light source—the Sun—which radiates with a source temperature of 5777K and emits a different spectrum (see Figure 2). Thus, to compare the amount of light in the VIS band with that in the SWIR and near-IR (NIR) bands, we evaluated correction factors for NIR and SWIR from the calculated integrals of the light distribution in the corresponding bands. We realized our measurements using the patterns taken by two different cameras (see Table 1). The first camera had one HD color sensor with a switchable optical filter, which enables VIS and NIR imaging. The second realizes simultaneous imaging on two image sensors, and thus enables recording of VIS and SWIR images. The results of the MRC values are shown in Figure 3.4 We used these values to make a range of calculations in VRM3 for a maritime atmosphere. The achievable ranges are shown in Figure 4. Figure 2. Relative spectral emittance (I) in the visible (VIS), near-IR (NIR), and shortwave IR (SWIR) wavelength bands in sunlight and under a halogen bulb. Figure 3. Measured MRC values. The diagram shows the contrast of targets of Table 1 as a function of the spatial resolution for the spectral ranges VIS, NIR, and SWIR. Notably, the spatial resolution of the SWIR sensor is three times lower than the other two. Figure 4. Calculated ranges for detection (D), recognition (R), and identification (I) in the VIS, NIR, and SWIR wavelengths based on the measured MRC data from Table Calculated ranges for detection (D), recognition (R), and identification (I) in the VIS, NIR, and SWIR wavelengths based on the measured MRC data from Table 1 In summary, we have described a single approach based on MRC measurements to characterize the performance of imaging sensors in the VIS, NIR, and SWIR spectral ranges. We demonstrated measurement of MRC for all three types of sensors, showing that this approach has potential for use in real-world devices. Our method would enable a reliable base from which to make a range of calculations under all kinds of atmospheric conditions. In future work, we will apply MRC methods to assess commercial camera devices and to create consistent assessment parameters for multi-camera observation platforms, such as those in submarines and tank periscopes. Airbus DS Optronics Martin Gerken is a project manager who holds responsibility for the development of a day sight zoom camera for operation in spectral ranges from VIS to SWIR. He holds a doctor's degree in nuclear physics with synchrotron radiation from the University of Hamburg. Harry Schlemmer obtained a diploma in physics from the Technical University of Hannover in 1978, and completed a PhD thesis on investigations of two-photon amplification in coupled laser systems. He was group manager for spectral analysis at Carl Zeiss, Oberkochen, from 1981 until 1992, and was later manager of the optical technology research and development department. Since 2008 he has been principal scientist for optical technology and systems design at Airbus DS Optronics. Mario Münzberg is director of the Imaging Devices Department, where he is responsible for the cross-functional development of all imaging modules and devices that are sensitive in the VIS, near-IR, SWIR, and IR spectral bands. He holds a doctor's degree in physics from the Institute of Applied Physics in Erlangen, Germany. 2. M. Gerken, H. Schlemmer, H. Haan, C. Siemens, M. Münzberg, Characterization of SWIR cameras by MRC measurements, Proc. SPIE 9071, p. 907110, 2014. doi:10.1117/12.2052928 4. M. Gerken, H. Schlemmer, M. Mnzberg, Unified characterization of imaging sensors from visible through longwave IR, Proc. SPIE 9820, p. 98200G, 2016. doi:10.1117/12.2224182
Eggs can be 'tricked' into developing into an embryo without fertilisation, but the resulting embryos, called parthenogenotes, die after a few days because key developmental processes requiring input from sperm don't happen. However, scientists from the Department of Biology & Biochemistry at the University of Bath have developed a method of injecting mouse parthenogenotes with sperm that allows them to become healthy baby mice with a success rate of up to 24 per cent. This compares to a rate of zero per cent for parthenogenotes or about two per cent for nuclear transfer cloning. The study is published today (Tuesday, 13 September, 2016) in the journal Nature Communications. Molecular embryologist Dr Tony Perry, senior author of the study, said: "This is first time that full term development has been achieved by injecting sperm into embryos. "It had been thought that only an egg cell was capable of reprogramming sperm to allow embryonic development to take place. "Our work challenges the dogma, held since early embryologists first observed mammalian eggs around 1827 and observed fertilisation 50 years later, that only an egg cell fertilised with a sperm cell can result in a live mammalian birth." The idea was the brain child of Dr Toru Suzuki in Dr Perry's team in the University of Bath's Laboratory of Mammalian Molecular Embryology, who performed the study together with team member Dr Maki Asami and colleagues from the University of Regensburg and the Fraunhofer Institute for Toxicology and Experimental Medicine in Germany. The baby mice born as a result of the technique seem completely healthy, but their DNA started out with different epigenetic marks compared with normal fertilisation. This suggests that different epigenetic pathways can lead to the same developmental destination, something not previously shown. The discovery has ethical implications for recent suggestions that human parthenogenotes could be used as a source of embryonic stem cells because they were considered inviable. It also hints that in the long-term future it could be possible to breed animals using non-egg cells and sperm. Although this is still only an idea, it could have potential future applications in human fertility treatment and for breeding endangered species. Dr Paul Colville-Nash, from the Medical Research Council (MRC) who funded the work, said: "This is an exciting piece of research which may help us to understand more about how human life begins and what controls the viability of embryos, mechanisms which may be important in fertility. It may one day even have implications for how we treat infertility, though that's probably still a long way off." More information: Suzuki, T. et al. Mice produced by mitotic reprogramming of sperm injected into haploid parthenogenotes. Nat. Commun. 7:12676, DOI: 10.1038/ncomms12676 (2016).
The new approach is more sensitive than existing tools and could help researchers detect illnesses at a much earlier stage. Doctors may also be able to check how well a patient is responding to a treatment by monitoring changes occurring in cells. A team led by the University of Edinburgh's MRC Centre for Inflammation Research has developed probes that light up specific targets inside a cell. Scientists tested the probes using fungal cells, but the same technique could easily be used to look at cells from patient samples. The probes are made up of a short molecule called a peptide - which recognises the target that researchers are trying to detect - attached to a new type of fluorescent tag. Researchers can track this tag using microscopes to see where the target is being produced by the cell. Because the new probes are more sensitive than existing probes, researchers will be able to quantify exactly how much of the target is being produced by each cell. This will enable them to detect tiny changes in the molecular make-up of tissues that could be the early warning sign of a disease. Tracking these changes over time could also offer clues about how well a patient is responding to treatment. The researchers say that one day their approach could help to improve patient scans so that diseases could be picked up faster using clinical imaging, such as PET scans. The study in the journal Nature Communications was funded by the Medical Research Council. Dr Marc Vendrell, a Lecturer in Biomedical Imaging at the MRC Centre for Inflammation Research, said: "Peptides are a powerful tool for spotting small signs of disease but until now we did not have a good way of tracking them. With this new technology, we can make probes to detect diseases with more accuracy and at earlier stages." More information: Lorena Mendive-Tapia et al. Spacer-free BODIPY fluorogens in antimicrobial peptides for direct imaging of fungal infection in human tissue, Nature Communications (2016). DOI: 10.1038/ncomms10940
Magnesium - a nutrient found in many foods - helps control how cells keep their own form of time to cope with the natural environmental cycle of day and night. The discovery in cells is expected to be linked to whole body clocks which influence daily cycles - or circadian rhythms - of sleeping and waking, hormone release, body temperature and other important bodily functions in people. The surprising discovery may aid the development of chronotherapy - treatment scheduled according to time of day - in people, and the development of new crop varieties with increased yields or adjustable harvesting seasons. Experiments in three major types of biological organisms - human cells, algae, and fungi - found in each case that levels of magnesium in cells rise and fall in a daily cycle. Scientists found that this oscillation was critical to sustain the 24-hour clock in cells. They were surprised to discover that it also had an enormous impact on metabolism in cells - how fast cells can convert nutrients into energy - throughout the course of a day. Researchers at the University of Edinburgh and the MRC Laboratory for Molecular Biology in Cambridge used molecular analysis to find that concentrations of magnesium rose and fell in a 24-hour cycle in all cell types, and that this impacts on the cells' internal clocks. Further tests showed that magnesium levels were linked to the cells' ability to burn energy. It was already known that magnesium is essential to help living things convert food into fuel, but scientists were surprised to discover that it also controls when this biological function takes place, and how efficiently. Their study, published in Nature, was supported by the Royal Society, the Medical Research Council and the Wellcome Trust. Dr Gerben van Ooijen, of the University of Edinburgh's School of Biological Sciences, who led the study, said: "Internal clocks are fundamental to all living things. They influence many aspects of health and disease in our own bodies, but equally in crop plants and micro-organisms. It is now essential to find out how these fundamentally novel observations translate to whole tissue or organisms, to make us better equipped to influence them in complex organisms for future medical and agricultural purposes." The study's other senior author, Dr John O'Neill of the MRC Laboratory of Molecular Biology in Cambridge, said: "Although the clinical relevance of magnesium in various tissues is beginning to garner more attention, how magnesium regulates our body's internal clock and metabolism has simply not been considered before. The new discovery could lead to a whole range of benefits spanning human health to agricultural productivity." Explore further: Ancient body clock discovered that helps to keep all living things on time
Prentice A.M.,London School of Hygiene and Tropical Medicine |
Ward K.A.,MRC Human Nutrition Research |
Goldberg G.R.,MRC Human Nutrition Research |
Jarjou L.M.,MRC |
And 4 more authors.
American Journal of Clinical Nutrition
An analysis of early growth patterns in children from 54 resource-poor countries in Africa and Southeast Asia shows a rapid falloff in the height-for-age z score during the first 2 y of life and no recovery until $5 y of age. This finding has focused attention on the period 29 to 24 mo as a window of opportunity for interventions against stunting and has garnered considerable political backing for investment targeted at the first 1000 d. These important initiatives should not be undermined, but the objective of this study was to counteract the growing impression that interventions outside of this period cannot be effective. We illustrate our arguments using longitudinal data from the Consortium of Health Oriented Research in Transitioning collaboration (Brazil, Guatemala, India, Philippines, and South Africa) and our own cross-sectional and longitudinal growth data from rural Gambia. We show that substantial height catch-up occurs between 24 mo and midchildhood and again between midchildhood and adulthood, even in the absence of any interventions. Longitudinal growth data from rural Gambia also illustrate that an extended pubertal growth phase allows very considerable height recovery, especially in girls during adolescence. In light of the critical importance of maternal stature to her children's health, our arguments are a reminder of the importance of the more comprehensive UNICEF/Sub-Committee on Nutrition Through the Life-Cycle approach. In particular, we argue that adolescence represents an additional window of opportunity during which substantial life cycle and intergenerational effects can be accrued. The regulation of such growth is complex and may be affected by nutritional interventions imposed many years previously. © 2013 American Society for Nutrition. Source