ResearchPad - particle-physics https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Zinc isotope variations in archeological human teeth (Lapa do Santo, Brazil) reveal dietary transitions in childhood and no contamination from gloves]]> https://www.researchpad.co/article/elastic_article_14585 Zinc (Zn) isotope ratios of dental enamel are a promising tracer for dietary reconstruction in archeology, but its use is still in its infancy. A recent study demonstrated a high risk of Zn contamination from nitrile, and latex gloves used during chemical sample preparation. Here we assess the potential impact of the use of such gloves during enamel sampling on the Zn isotope composition of teeth from a population of early Holocene hunter gatherers from Lapa do Santo, Lagoa Santa, Minas Gerais, Brazil. We first examined the amount of Zn and its isotopic composition released from the gloves used in this study by soaking them in weak nitric acid and water. We compared Zn isotope ratios obtained from teeth that were sampled wearing nitrile, latex or no gloves. Finally, we performed a linear mixed model (LMM) to investigate post hoc the relationship between the gloves used for sampling and the Zn isotope variability in dental enamel. We found that the gloves used in this study released a similar amount of Zn compared to previous work, but only in acidic solution. Zn isotope ratios of teeth and the LMM identified no sign of significant Zn coming from the gloves when teeth were handled for enamel sampling. We hypothesize that Zn in gloves is mostly released by contact with acids. We found that the main source of Zn isotope variability in the Lapa do Santo population was related to the developmental stage of the tooth tissues sampled. We report identical results for two individuals coming from a different archeological context. Tooth enamel formed in utero and/or during the two first years of life showed higher Zn isotope ratios than enamel formed after weaning. More work is required to systematically investigate if Zn isotopes can be used as a breastfeeding tracer.

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<![CDATA[The effect of Mn2Sb2 and Mn2Sb secondary phases on magnetism in (GaMn)Sb thin films]]> https://www.researchpad.co/article/N94466bcc-ad77-4d3b-8f3f-3aceb39bbed5

In this work, a detailed study of structural, electrical and magnetic characterization of (GaMn)Sb diluted magnetic semiconductors (DMS) is presented. (GaMn)Sb thin films were grown by DC magnetron co-sputtering method as an innovative procedure to fabricate III-V DMS. The presence of unusual Mn2Sb2 and Mn2Sb secondary phases, induced by substrate temperature and deposition time, were revealed through XRD measurements. Magnetization measurements allow determining crossover between a paramagnetic-like to a ferromagnetic-like behavior controlled by secondary phases. It was found that both, the magnetic remanence and magnetic coercivity, increases with substrate temperature. Interestingly, the magnetic response is paramagnetic at lower deposition times and substrate temperatures, and XRD measurements suggest the absence of Mn2Sb and Mn2Sb2 in secondary phases. For longer deposition times or higher substrate temperature, XRD shows the presence of Mn2Sb2 and Mn2Sb phases and ferromagnetic-like behavior. The DC resistivity of our samples was characterized and the carrier density was determined by Hall measurements and, in contrast with the reported in other studies, found them to be a p-type semiconductor with carrier densities as big as one order of magnitude larger than reported values. From the ferromagnetic-like samples, evidence of an anomalous Hall-effect in the sample was found, with higher magnetic saturation and a anomalous Hall conductivity of 2380 S/cm. All the results point to a contribution of the secondary phases to the overall magnetic response of the samples used, and suggest the importance of studying the formation of secondary phases in the growth of DMS, especially, for the case of (GaMn)Sb where Mn ion can have multiple oxidation states.

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<![CDATA[Highly efficient and sensitive patient-specific quality assurance for spot-scanned proton therapy]]> https://www.researchpad.co/article/5c6f1505d5eed0c48467acb1

The purpose of this work was to develop an end-to-end patient-specific quality assurance (QA) technique for spot-scanned proton therapy that is more sensitive and efficient than traditional approaches. The patient-specific methodology relies on independently verifying the accuracy of the delivered proton fluence and the dose calculation in the heterogeneous patient volume. A Monte Carlo dose calculation engine, which was developed in-house, recalculates a planned dose distribution on the patient CT data set to verify the dose distribution represented by the treatment planning system. The plan is then delivered in a pre-treatment setting and logs of spot position and dose monitors, which are integrated into the treatment nozzle, are recorded. A computational routine compares the delivery log to the DICOM spot map used by the Monte Carlo calculation to ensure that the delivered parameters at the machine match the calculated plan. Measurements of dose planes using independent detector arrays, which historically are the standard approach to patient-specific QA, are not performed for every patient. The nozzle-integrated detectors are rigorously validated using independent detectors in regular QA intervals. The measured data are compared to the expected delivery patterns. The dose monitor reading deviations are reported in a histogram, while the spot position discrepancies are plotted vs. spot number to facilitate independent analysis of both random and systematic deviations. Action thresholds are linked to accuracy of the commissioned delivery system. Even when plan delivery is acceptable, the Monte Carlo second check system has identified dose calculation issues which would not have been illuminated using traditional, phantom-based measurement techniques. The efficiency and sensitivity of our patient-specific QA program has been improved by implementing a procedure which independently verifies patient dose calculation accuracy and plan delivery fidelity. Such an approach to QA requires holistic integration and maintenance of patient-specific and patient-independent QA.

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<![CDATA[Searching for the causal effects of body mass index in over 300 000 participants in UK Biobank, using Mendelian randomization]]> https://www.researchpad.co/article/5c5df305d5eed0c484580b50

Mendelian randomization (MR) has been used to estimate the causal effect of body mass index (BMI) on particular traits thought to be affected by BMI. However, BMI may also be a modifiable, causal risk factor for outcomes where there is no prior reason to suggest that a causal effect exists. We performed a MR phenome-wide association study (MR-pheWAS) to search for the causal effects of BMI in UK Biobank (n = 334 968), using the PHESANT open-source phenome scan tool. A subset of identified associations were followed up with a formal two-stage instrumental variable analysis in UK Biobank, to estimate the causal effect of BMI on these phenotypes. Of the 22 922 tests performed, our MR-pheWAS identified 587 associations below a stringent P value threshold corresponding to a 5% estimated false discovery rate. These included many previously identified causal effects, for instance, an adverse effect of higher BMI on risk of diabetes and hypertension. We also identified several novel effects, including protective effects of higher BMI on a set of psychosocial traits, identified initially in our preliminary MR-pheWAS in circa 115,000 UK Biobank participants and replicated in a different subset of circa 223,000 UK Biobank participants. Our comprehensive MR-pheWAS identified potential causal effects of BMI on a large and diverse set of phenotypes. This included both previously identified causal effects, and novel effects such as a protective effect of higher BMI on feelings of nervousness.

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<![CDATA[Multifractality of posture modulates multisensory perception of stand-on-ability]]> https://www.researchpad.co/article/5c6c7582d5eed0c4843cfe31

By definition, perception is a multisensory process that unfolds in time as a complex sequence of exploratory activities of the organism. In such a system perception and action are integrated, and multiple energy arrays are available simultaneously. Perception of affordances interweaves sensory and motor activities into meaningful behavior given task constraints. The present contribution offers insight into the manner in which perception and action usher the organism through competent functional apprehension of its surroundings. We propose that the tensegrity structure of the body, manifested via multifractality of exploratory bodily movements informs perception of affordances. The affordance of stand-on-ability of ground surfaces served as the experimental paradigm. Observers viewed a surface set to a discrete angle and attempted to match it haptically with a continuously adjustable surface occluded by a curtain, or felt an occluded surface set to a discrete angle then matched it visually with a continuously adjustable visible surface. The complex intertwining of perception and action was demonstrated by the interactions of multifractality of postural sway with multiple energy arrays, responses, and changing geometric task demands.

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<![CDATA[Weighted lambda superstrings applied to vaccine design]]> https://www.researchpad.co/article/5c6730d9d5eed0c484f38214

We generalize the notion of λ-superstrings, presented in a previous paper, to the notion of weighted λ-superstrings. This generalization entails an important improvement in the applications to vaccine designs, as it allows epitopes to be weighted by their immunogenicities. Motivated by these potential applications of constructing short weighted λ-superstrings to vaccine design, we approach this problem in two ways. First, we formalize the problem as a combinatorial optimization problem (in fact, as two polynomially equivalent problems) and develop an integer programming (IP) formulation for solving it optimally. Second, we describe a model that also takes into account good pairwise alignments of the obtained superstring with the input strings, and present a genetic algorithm that solves the problem approximately. We apply both algorithms to a set of 169 strings corresponding to the Nef protein taken from patiens infected with HIV-1. In the IP-based algorithm, we take the epitopes and the estimation of the immunogenicities from databases of experimental epitopes. In the genetic algorithm we take as candidate epitopes all 9-mers present in the 169 strings and estimate their immunogenicities using a public bioinformatics tool. Finally, we used several bioinformatic tools to evaluate the properties of the candidates generated by our method, which indicated that we can score high immunogenic λ-superstrings that at the same time present similar conformations to the Nef virus proteins.

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<![CDATA[Ecologically relevant biomarkers reveal that chronic effects of nitrate depend on sex and life stage in the invasive fish Gambusia holbrooki]]> https://www.researchpad.co/article/5c58d619d5eed0c484031602

Agricultural intensification and shifts in precipitation regimes due to global climate change are expected to increase nutrient concentrations in aquatic ecosystems. However, the direct effects of nutrients widely present in wastewaters, such as nitrate, are poorly studied. Here, we use multiple indicators of fish health to experimentally test the effects of three ecologically relevant nitrate concentrations (<10, 50 and 250 mg NO3-/l) on wild-collected mosquitofish (Gambusia holbrooki), a species widely introduced for mosquito biocontrol in often eutrophic waters. Overall, biomarkers (histopathology, feeding assays, growth and caloric content and stable isotopes as indicators of energy content) did not detect overt signs of serious disease in juveniles, males or females of mosquitofish. However, males reduced food intake at the highest nitrate concentration compared to the controls and females. Similarly, juveniles reduced energy reserves without significant changes in growth or food intake. Calorimetry was positively associated with the number of perivisceral fat cells in juveniles, and the growth rate of females was negatively associated with δ15N signature in muscle. This study shows that females are more tolerant to nitrate than males and juveniles and illustrates the advantages of combing short- and long-term biomarkers in environmental risk assessment, including when testing for the adequacy of legal thresholds for pollutants.

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<![CDATA[Dorset Pre-Inuit and Beothuk foodways in Newfoundland, ca. AD 500-1829]]> https://www.researchpad.co/article/5c3d0114d5eed0c4840381ce

Archaeological research on the Canadian island of Newfoundland increasingly demonstrates that the island’s subarctic climate and paucity of terrestrial food resources did not restrict past Pre-Inuit (Dorset) and Native American (Beothuk) hunter-gatherer populations to a single subsistence pattern. This study first sought to characterize hunter-gatherer diets over the past 1500 years; and second, to assess the impact of European colonization on Beothuk lifeways by comparing the bone chemistry of Beothuk skeletal remains before and after the intensification of European settlement in the early 18th century. We employed radiocarbon dating and stable carbon and nitrogen isotope ratio analysis of bulk bone collagen from both Dorset (n = 9) and Beothuk (n = 13) cultures, including a naturally mummified 17th century Beothuk individual. Carbon and nitrogen isotope analysis of 108 faunal samples from Dorset and Beothuk archaeological sites around the island were used as a dietary baseline for the humans. We combined our results with previously published isotope data and radiocarbon dates from Dorset (n = 12) and Beothuk (n = 18) individuals and conducted a palaeodietary analysis using Bayesian modelling, cluster analysis and comparative statistical tests. Dorset diets featured more marine protein than those of the Beothuk, and the diets of Beothuk after the 18th century featured less high trophic level marine protein than those of individuals predating the 18th century. Despite inhabiting the same island, Dorset and Beothuk cultures employed markedly different dietary strategies, consistent with interpretations of other archaeological data. Significantly, European colonization had a profound effect on Beothuk lifeways, as in response to the increasing European presence on the coast, the Beothuk relied more extensively on the limited resources of the island’s boreal forests and rivers.

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<![CDATA[Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line]]> https://www.researchpad.co/article/5c3e4f51d5eed0c484d740e5

The aim of our work is to provide the up-to-now missing information on the Siemens Artiste FFF 7 MV beam line using a Monte-Carlo model fit to the realistic dosimetric measurements at the linear accelerator in clinical use at our department. The main Siemens Artiste 6MV and FFF 7MV beams were simulated using the Geant4 toolkit. The simulations were compared with the measurements with an ionization chamber in a water phantom to verify the validation of simulation and tuning the primary electron parameters. Hereafter, other parameters such as surface dose, spectrum, electron contamination, symmetry, flatness/unflatness, slope, and characteristic off-axis changes were discussed for both Flat and FFF mode. The mean electron energy for the FFF beam was 8.8 MeV and 7.5 MeV for Flat 6 MV, the spread energy and spot size of the selected Gaussian distribution source were 0.4 MeV and 1mm, respectively. The dose rate of the FFF beam was 2.8 (2.96) times higher than for the flattened beam for a field size of 10×10 (20×20) cm2. The electron contamination has significant contribution to the surface dose especially for the flattened beam. The penumbra, surface dose and the mean energy of photons decrease by removing the flattening filter. Finally, the results show that off-axis changes have no strong effect on the mean energy of FFF beams, while this effect was more considerable for the flattened beam.

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<![CDATA[Implementation and assessment of the black body bias correction in quantitative neutron imaging]]> https://www.researchpad.co/article/5c390ba1d5eed0c48491d96e

We describe in this paper the experimental procedure, the data treatment and the quantification of the black body correction: an experimental approach to compensate for scattering and systematic biases in quantitative neutron imaging based on experimental data. The correction algorithm is based on two steps; estimation of the scattering component and correction using an enhanced normalization formula. The method incorporates correction terms into the image normalization procedure, which usually only includes open beam and dark current images (open beam correction). Our aim is to show its efficiency and reproducibility: we detail the data treatment procedures and quantitatively investigate the effect of the correction. Its implementation is included within the open source CT reconstruction software MuhRec. The performance of the proposed algorithm is demonstrated using simulated and experimental CT datasets acquired at the ICON and NEUTRA beamlines at the Paul Scherrer Institut.

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<![CDATA[cellSTORM—Cost-effective super-resolution on a cellphone using dSTORM]]> https://www.researchpad.co/article/5c3fa5b7d5eed0c484ca7b36

High optical resolution in microscopy usually goes along with costly hardware components, such as lenses, mechanical setups and cameras. Several studies proved that Single Molecular Localization Microscopy can be made affordable, relying on off-the-shelf optical components and industry grade CMOS cameras. Recent technological advantages have yielded consumer-grade camera devices with surprisingly good performance. The camera sensors of smartphones have benefited of this development. Combined with computing power smartphones provide a fantastic opportunity for “imaging on a budget”. Here we show that a consumer cellphone is capable of optical super-resolution imaging by (direct) Stochastic Optical Reconstruction Microscopy (dSTORM), achieving optical resolution better than 80 nm. In addition to the use of standard reconstruction algorithms, we used a trained image-to-image generative adversarial network (GAN) to reconstruct video sequences under conditions where traditional algorithms provide sub-optimal localization performance directly on the smartphone. We believe that “cellSTORM” paves the way to make super-resolution microscopy not only affordable but available due to the ubiquity of cellphone cameras.

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<![CDATA[Dual isotopic evidence for nitrate sources and active biological transformation in the Northern South China Sea in summer]]> https://www.researchpad.co/article/5c3667a8d5eed0c4841a5f49

Nitrate (NO3-) concentrations and their dual isotopic compositions (δ15N-NO3- and δ18O-NO3-) were measured to constrain N sources and their cyclic processes in summer using samples from the water column of the northern South China Sea (NSCS). Our data revealed that higher NO3- concentrations and δ15N-NO3- values were observed in the upper waters of the coastal areas near the Pearl River Estuary (PRE). The Bayesian stable isotope mixing model was used to calculated the proportion of nitrate sources, the results indicated that the nitrate in the upper waters of the coastal areas near PRE were mainly influenced by manure and sewage (63%), atmospheric deposition (19%), soil organic nitrogen (12%) and reduced N fertilizer (6%). For the upper waters of the outer areas, low NO3- concentrations and δ15N-NO3- values, but high δ18O-NO3- values, reflected that NO3- was mainly influenced by Kuroshio water intrusion (60%), atmospheric deposition (32%) and nitrogen fixation/nitrification (8%). Complex processes were found in bottom waters. Nitrification and phytoplankton assimilation may be responsible for the higher nitrate concentrations and δ15N-NO3- values. Our study, therefore, utilizes the nitrate dual isotope to help illustrate the spatial variations in nitrate sources and complex nitrogen cycles in the NSCS.

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<![CDATA[The study of degradation mechanisms of glyco-engineered plant produced anti-rabies monoclonal antibodies E559 and 62-71-3]]> https://www.researchpad.co/article/5c25455ed5eed0c48442c5ec

Rabies is an ancient and neglected zoonotic disease caused by the rabies virus, a neurotropic RNA virus that belongs to the Rhabdoviridae family, genus Lyssavirus. It remains an important public health problem as there are cost and health concerns imposed by the current human post exposure prophylaxis therapy. The use of monoclonal antibodies (mAbs) is therefore an attractive alternative. Rabies mostly affects people that reside in resource-limited areas where there are occasional failures in the cold-chain. These environmental changes may upset the stability of the mAbs. This study focused on mAbs 62-71-3 and E559; their structures, responses to freeze/thaw (F/T) and exposure to reactive oxygen species were therefore studied with the aid of a wide range of biophysical and in silico techniques in order to elucidate their stability and identify aggregation prone regions. E559 was found to be less stable than 62-71-3. The complementarity determining regions (CDR) contributed the most to its instability, more specifically: peptides 99EIWD102 and 92ATSPYT97 found in CDR3, Trp33 found in CDR1 and the oxidised Met34. The constant region “158SWNSGALTGHTFPAVL175” was also flagged by the special aggregation propensity (SAP) tool and F/T experiments to be highly prone to aggregation. The E559 peptides “4LQESGSVL11 from the heavy chain and 4LTQSPSSL11 from the light chain, were also highly affected by F/T. These residues may serve as good candidates for mutation, in the aim to bring forward more stable therapeutic antibodies, thus paving a way to a more safe and efficacious antibody-based cocktail treatment against rabies.

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<![CDATA[QTM: Computational package using MPI protocol for Quantum Trajectories Method]]> https://www.researchpad.co/article/5c1813c5d5eed0c484775c4a

The Quantum Trajectories Method (QTM) is one of the frequently used methods for studying open quantum systems. The main idea of this method is the evolution of wave functions which describe the system (as functions of time). Then, so-called quantum jumps are applied at a randomly selected point in time. The obtained system state is called as a trajectory. After averaging many single trajectories, we obtain the approximation of the behavior of a quantum system. This fact also allows us to use parallel computation methods. In the article, we discuss the QTM package which is supported by the MPI technology. Using MPI allowed utilizing the parallel computing for calculating the trajectories and averaging them—as the effect of these actions, the time taken by calculations is shorter. In spite of using the C++ programming language, the presented solution is easy to utilize and does not need any advanced programming techniques. At the same time, it offers a higher performance than other packages realizing the QTM. It is especially important in the case of harder computational tasks, and the use of MPI allows improving the performance of particular problems which can be solved in the field of open quantum systems.

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<![CDATA[Filter paper-based spin column method for cost-efficient DNA or RNA purification]]> https://www.researchpad.co/article/5c141ee9d5eed0c484d28cb3

We describe herein a method of recharging used commercial spin columns or assembling homemade spin columns using filter paper as binding material for cost-effective, low throughput nucleic acid purification. The efficiency of filter paper-based spin columns was evaluated for purification of nucleic acids from various sources. Following protocols of commercial kits, we found filter paper to be a useful binding material for purification of nucleic acids, including plant genomic DNA, plant total RNA, PCR products, and DNA from agarose gels. However, filter paper has a weak binding affinity to plasmid DNA in tested miniprep protocols. Protocols for the use of filter paper recharged spin columns or homemade spin columns for low throughput purification of plant genomic DNA and total RNA with unused commercial kit buffers or less expensive homemade buffers are presented.

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<![CDATA[Tribological and antioxidation properties study of two N-containing borate ester derivatives as additive in rapeseed oil]]> https://www.researchpad.co/article/5c181382d5eed0c4847751f2

Two kinds of phenol- and N- containing borate ester, BTEB and BMEB have good hydrolysis stability due to the B-N coordination bond. The PB value improved by 60.7% and 67.6% respectively at 0.5wt% BTEB, BMEB in rapeseed oil. Their antiwear effect increases with the increase of adding content, and BMEB is better than BTEB. The friction-reducing effect of BTEB is better than BMEB. All additives formed a protective film which containing BOx, FeOx and other organic nitrogen compounds. The better capacities of BMEB may due to the complex boundary lubricating film which contain ferrous sulfate, ferrous sulfide. All additives possessed good antioxidation effect, and it increased the oxidation activation energy than rapeseed oil by 51.15% and 78.82% respectively at 0.25wt%.

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<![CDATA[An Analysis of Precipitation Isotope Distributions across Namibia Using Historical Data]]> https://www.researchpad.co/article/5989d9feab0ee8fa60b72f0b

Global precipitation isoscapes based on the Global Network for Isotopes in Precipitation (GNIP) network are an important toolset that aid our understanding of global hydrologic cycles. Although the GNIP database is instrumental in developing global isoscapes, data coverage in some regions of hydrological interest (e.g., drylands) is low or non-existent thus the accuracy and relevance of global isoscapes to these regions is debatable. Capitalizing on existing literature isotope data, we generated rainfall isoscapes for Namibia (dryland) using the cokriging method and compared it to a globally fitted isoscape (GFI) downscaled to country level. Results showed weak correlation between observed and predicted isotope values in the GFI model (r2 < 0.20) while the cokriging isoscape showed stronger correlation (r2 = 0.67). The general trend of the local cokriging isoscape is consistent with synoptic weather systems (i.e., influences from Atlantic Ocean maritime vapour, Indian Ocean maritime vapour, Zaire Air Boundary, the Intertropical Convergence Zone and Tropical Temperate Troughs) and topography affecting the region. However, because we used the unweighted approach in this method, due to data scarcity, the absolute values could be improved in future studies. A comparison of local meteoric water lines (LMWL) constructed from the cokriging and GFI suggested that the GFI model still reflects the global average even when downscaled. The cokriging LMWL was however more consistent with expectations for an arid environment. The results indicate that although not ideal, for data deficient regions such as many drylands, the unweighted cokriging approach using historical local data can be an alternative approach to modelling rainfall isoscapes that are more relevant to the local conditions compared to using downscaled global isoscapes.

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<![CDATA[Spectral X-Ray CT Image Reconstruction with a Combination of Energy-Integrating and Photon-Counting Detectors]]> https://www.researchpad.co/article/5989da06ab0ee8fa60b76070

The purpose of this paper is to develop an algorithm for hybrid spectral computed tomography (CT) which combines energy-integrating and photon-counting detectors. While the energy-integrating scan is global, the photon-counting scan can have a local field of view (FOV). The algorithm synthesizes both spectral data and energy-integrating data. Low rank and sparsity prior is used for spectral CT reconstruction. An initial estimation is obtained from the projection data based on physical principles of x-ray interaction with the matter, which provides a more accurate Taylor expansion than previous work and can guarantee the convergence of the algorithm. Numerical simulation with clinical CT images are performed. The proposed algorithm produces very good spectral features outside the FOV when no K-edge material exists. Exterior reconstruction of K-edge material can be partially achieved.

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<![CDATA[Instrument design and protocol for the study of light controlled processes in aquatic organisms, and its application to examine the effect of infrared light on zebrafish]]> https://www.researchpad.co/article/5989db53ab0ee8fa60bdca5b

The acquisition of reliable data strongly depends on experimental design. When studying the effects of light on processes such as behaviour and physiology it is crucial to maintain all environmental conditions constant apart from the one under study. Furthermore, the precise values of the environmental factors applied during the experiment should be known. Although seemingly obvious, these conditions are often not met when the effects of light are being studied. Here, we document and discuss the wavelengths and light intensities of natural and artificial light sources. We present standardised experimental protocols together with building plans of a custom made instrument designed to accurately control light and temperature for experiments using fresh water or marine species. Infrared light is commonly used for recording behaviour and in electrophysiological experiments although the properties of fish photoreceptors potentially allow detection into the far red. As an example of our experimental procedure we have applied our protocol and instrument to specifically test the impact of infrared light (840 nm) on the zebrafish circadian clock, which controls many aspects of behaviour, physiology and metabolism. We demonstrate that infrared light does not influence the zebrafish circadian clock. Our results help to provide a solid framework for the future study of light dependent processes in aquatic organisms.

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<![CDATA[Using Stable Isotopes to Infer the Impacts of Habitat Change on the Diets and Vertical Stratification of Frugivorous Bats in Madagascar]]> https://www.researchpad.co/article/5989da04ab0ee8fa60b75157

Human-modified habitats are expanding rapidly; many tropical countries have highly fragmented and degraded forests. Preserving biodiversity in these areas involves protecting species–like frugivorous bats–that are important to forest regeneration. Fruit bats provide critical ecosystem services including seed dispersal, but studies of how their diets are affected by habitat change have often been rather localized. This study used stable isotope analyses (δ15N and δ13C measurement) to examine how two fruit bat species in Madagascar, Pteropus rufus (n = 138) and Eidolon dupreanum (n = 52) are impacted by habitat change across a large spatial scale. Limited data for Rousettus madagascariensis are also presented. Our results indicated that the three species had broadly overlapping diets. Differences in diet were nonetheless detectable between P. rufus and E. dupreanum, and these diets shifted when they co-occurred, suggesting resource partitioning across habitats and vertical strata within the canopy to avoid competition. Changes in diet were correlated with a decrease in forest cover, though at a larger spatial scale in P. rufus than in E. dupreanum. These results suggest fruit bat species exhibit differing responses to habitat change, highlight the threats fruit bats face from habitat change, and clarify the spatial scales at which conservation efforts could be implemented.

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