Diffractive triangulation of radiative point sources

We describe a general method to determine the location of a point source of waves relative to a twodimensional single-crystalline active pixel detector. Based on the inherent structural sensitivity of crystalline sensor materials, characteristic detector diffraction patterns can be used to triangulate the location of a wave emitter. The principle described here can be applied to various types of waves, provided that the detector elements are suitably structured. As a prototypical practical application of the general detection principle, a digital hybrid pixel detector is used to localize a source of electrons for Kikuchi diffraction pattern measurements in the scanning electron microscope. This approach provides a promising alternative method to calibrate Kikuchi patterns for accurate measurements of microstructural crystal orientations, strains, and phase distributions

Use of Electron Back Scatter Diffraction Patterns for Determination of Crystal Symmetry Elements

The application of electron back scatter diffraction in the scanning electron microscope has been extended to the determination of crystal symmetry elements, point group and space group. The wide angular range of the patterns makes this a relatively simple task compared with equivalent analysis using electron channelling patterns, convergent beam patterns or standard x-ray methods, though the complexity of the analysis does not permit an unthinking approach. To establish the best procedure specimens from the seven crystal systems were investigated and results from the examination of the metal tin (tetragonal), and minerals zircon (ZrSiO4, tetragonal) and calcite (CaCO3 rhombohedral) are presented. The procedure entails determination of the crystal system from detection of rotation axes, determination of point group from the observed combinations of mirror planes and rotation axes, determination of Bravais lattice, and finally, determination of space group from the absences of lines due to screw axes and glide planes. Considerable computational aids were required in the latter stages of analysis and for this a computer program was written to simulate the diffraction patterns from any crystal system and Bravais lattice with line delete procedures to remove lines forbidden because of space group requirements

On-Line Analysis of Electron Back Scatter Diffraction Patterns. I. Texture Analysis of Zone Refined Polysilicon

A technique has been developed for determining crystal orientations on-line from bulk polycrystalline materials using wide angle back scatter electron diffraction patterns. The patterns were imaged on a phosphor screen and viewed using a low light level television camera. A computer generated cursor superimposed on the diffraction pattern, permitted the coordinates of zone axes to be determined. These were interpreted by the computer to yield the crystal orientation. The accuracy of the technique for absolute orientation was shown to be of the order 1° and the precision for relative orientation better than 0.5°. The technique was used to investigate texture and nearest neighbour orientation relationships in polysilicon, recrystallised using a graphite strip heater technique. It was shown that the orientations become less random as the recrystallisation front proceeded along the specimen

4D Imaging and Diffraction Dynamics of Single-Particle Phase Transition in Heterogeneous Ensembles

In this Letter, we introduce conical-scanning dark-field imaging in four-dimensional (4D) ultrafast electron microscopy to visualize single-particle dynamics of a polycrystalline ensemble undergoing phase transitions. Specifically, the ultrafast metal–insulator phase transition of vanadium dioxide is induced using laser excitation and followed by taking electron-pulsed, time-resolved images and diffraction patterns. The single-particle selectivity is achieved by identifying the origin of all constituent Bragg spots on Debye–Scherrer rings from the ensemble. Orientation mapping and dynamic scattering simulation of the electron diffraction patterns in the monoclinic and tetragonal phase during the transition confirm the observed behavior of Bragg spots change with time. We found that the threshold temperature for phase recovery increases with increasing particle sizes and we quantified the observation through a theoretical model developed for single-particle phase transitions. The reported methodology of conical scanning, orientation mapping in 4D imaging promises to be powerful for heterogeneous ensemble, as it enables imaging and diffraction at a given time with a full archive of structural information for each particle, for example, size, morphology, and orientation while minimizing radiation damage to the specimen

Real-Time Measurement of Xenon Concentration in a Binary Gas Mixture Using a Modified Ultrasonic Time-of-Flight Anesthesia Gas Flowmeter

Background: Xenon (Xe) is an anesthetic gas which may have potential as a neuroprotectant. To measure each gas in a xenon/oxygen mixture one would typically use a thermal conductivity meter and a fuel cell respectively. The speed of sound in a binary gas mixture like this is related to fractional concentration, temperature, pressure, and masses of the gases present. We assessed the feasibility of developing a novel single sterilizable device which used the time of flight of ultrasound through the gas to measure both real-time gas flow and also the concentration of Xe in O2.Method: We adapted an ultrasonic time-of-flight flow meter from a conventional anesthetic machine to also measure the real time fractional concentration of Xe in O2. A total of 5 095 readings of were taken in the range 5 % to 95 % xenon, and compared with simultaneous measurements from a commercially available thermal conductivity xenon analyser.Results: Ultrasonic measurements of Xe (%) showed agreement with thermal conductivity meter measurements but there was marked discontinuity in the central region of the measurement range. Bland-Altman analysis (95% CI): Mean Difference (Bias) 3.1 (2.9 % to 3.2 %); lower 95 % Limit of Agreement -4.6 % (-4.8 % to -4.4 %); upper 95 % Limit of Agreement 10.8 % (10.5 % to 11.0 %).Conclusions: The modified ultrasonic flow meter estimated the Xe (%) however at present the accuracy is not sufficient for clinical use. With further work it may be possible to improve the accuracy sufficiently for potential clinical use

The Effect of Ergometer Cycling and Visual Foraging on Brain Function: A Pilot Study

Data Availability: All relevant data are within the manuscript and its Supporting Information files.Supporting information is available online at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0336642#sec021 .Dual-task training comprising cognitive and physical components may enhance cognitive function, and increased prefrontal cortex activation may underpin these improvements. The aim of this pilot study was to examine the effects of cycling and visual foraging on executive function (EF). Twenty-seven participants (mean age 25.44 ± 4.31 years) completed four lab-based sessions, one in which their aerobic capacity (O2max) and baseline EF scores assessed were determined, and three randomized experimental conditions: ergometer cycling (EC), visual foraging (VF) and both combined (EC + VF). Participants’ EF performance was assessed at baseline, and pre-and post- intervention using the 2-Back task (working memory), the Flanker Task (inhibitory control), and the Wisconsin Card Sorting Task (WCST; task switching). Functional near-infrared spectroscopy (fNIRS) and eye-tracking data were collected throughout each condition. Affective state was assessed via the Affect Grid. Repeated measures ANCOVAs, incorporating baseline EF task scores as covariates, revealed condition x time x covariate interactions for the Flanker task only; task performance of participants with poorer baseline scores improved more profoundly in the EC condition. Subjective arousal and prefrontal cortex (PFC) activation were higher in both cycling conditions relative to VF; hence, ergometer cycling, rather than visual foraging, might be the more impactful intervention in these regards. However, these elevations were not associated with EF enhancements; near-ceiling effects in EF task performance may explain this. The EC condition elicited greater energetic investment than the EC + VF condition; possibly because the secondary VF task distracted from the cycling exercise. PFC activation was only correlated with gaze fixations during the EC + VF condition, potentially reflecting concurrent increases in supply of, and demand for, oxygen during the combined condition.The author(s) received no specific funding for this work

Unique Structure and Dynamics of the EphA5 Ligand Binding Domain Mediate Its Binding Specificity as Revealed by X-ray Crystallography, NMR and MD Simulations

10.1371/journal.pone.0074040PLoS ONE89-POLN

Determination of the Tissue Distribution and Excretion by Accelerator Mass Spectrometry of the Nonadecapeptide 14C-Moli1901 in Beagle dogs after Intratracheal Instillation

Administration of {sup 14}C-Moli1901 (duramycin, 2622U90), a 19 amino acid polycyclic peptide by intratracheal instillation (approximately 100 {micro}g) into the left cranial lobe of the lung of beagle dogs resulted in retention of 64% of the dose in the left cranial lobe for up to 28 days. In this study, we used accelerator mass spectrometry (AMS) to quantify Moli901 following administration of only 0.045 {micro}Ci of {sup 14}C-Moli901 per dog. Limits of quantitation of AMS were 0.03 (urine) to 0.3 (feces) ng equiv. Moli1901/g. Whole blood and plasma concentrations of {sup 14}C were <5ng/ml at all times after the dose. Concentrations of {sup 14}C in whole blood and plasma declined over the first day after the dose and rose thereafter, with the rise in plasma concentrations lagging behind those in whole blood. During the first 3 days after the dose, plasma accounted for the majority of {sup 14}C in whole blood, but after that time, plasma accounted for only 25-30% of the {sup 14}C in whole blood. Tissue (left and right caudal lung lobe, liver, kidney, spleen, brain) and bile concentrations were low, always less than 0.25% the concentrations found in the left cranial lung lobe. Approximately 13% of the dose was eliminated in urine and feces in 28 days, with fecal elimination accounting for about 10% of the dose. The data presented here are consistent with that obtained in other species. Moli1901 is slowly absorbed and excreted from the lung, and it does not accumulate in other tissues. Moli1901 is currently in the clinic and has proven to be safe in single dose studies in human volunteers and cystic fibrosis patients by the inhalation route. No information on the disposition of the compound in humans is available. This study in dogs demonstrates the feasibility of obtaining that information using {sup 14}C-Moli1901 and AMS

Functional diversity can facilitate the collapse of an undesirable ecosystem state

Biodiversity may increase ecosystem resilience. However, we have limited understanding if this holds true for ecosystems that respond to gradual environmental change with abrupt shifts to an alternative state. We used a mathematical model of anoxic–oxic regime shifts and explored how trait diversity in three groups of bacteria influences resilience. We found that trait diversity did not always increase resilience: greater diversity in two of the groups increased but in one group decreased resilience of their preferred ecosystem state. We also found that simultaneous trait diversity in multiple groups often led to reduced or erased diversity effects. Overall, our results suggest that higher diversity can increase resilience but can also promote collapse when diversity occurs in a functional group that negatively influences the state it occurs in. We propose this mechanism as a potential management approach to facilitate the recovery of a desired ecosystem state