Real-time simulations of ADF STEM probe position-integrated scattering cross-sections for single element fcc crystals in zone axis orientation using a densely connected neural network.

Quantification of annular dark field (ADF) scanning transmission electron microscopy (STEM) images in terms of composition or thickness often relies on probe-position integrated scattering cross sections (PPISCS). In order to compare experimental PPISCS with theoretically predicted ones, expensive simulations are needed for a given specimen, zone axis orientation, and a variety of microscope settings. The computation time of such simulations can be in the order of hours using a single GPU card. ADF STEM simulations can be efficiently parallelized using multiple GPUs, as the calculation of each pixel is independent of other pixels. However, most research groups do not have the necessary hardware, and, in the best-case scenario, the simulation time will only be reduced proportionally to the number of GPUs used. In this manuscript, we use a learning approach and present a densely connected neural network that is able to perform real-time ADF STEM PPISCS predictions as a function of atomic column thickness for most common face-centered cubic (fcc) crystals (i.e., Al, Cu, Pd, Ag, Pt, Au and Pb) along [100] and [111] zone axis orientations, root-mean-square displacements, and microscope parameters. The proposed architecture is parameter efficient and yields accurate predictions for the PPISCS values for a wide range of input parameters that are commonly used for aberration-corrected transmission electron microscopes.

Dynamical diffraction of high-energy electrons investigated by focal series momentum-resolved scanning transmission electron microscopy at atomic resolution.

We report a study of scattering dynamics in crystals employing momentum-resolved scanning transmission electron microscopy under varying illumination conditions. As we perform successive changes of the probe focus, multiple real-space signals are obtained in dependence of the shape of the incident electron wave. With support from extensive simulations, each signal is shown to be characterised by an optimum focus for which the contrast is maximum and which differs among different signals. For instance, a systematic focus mismatch is found between images formed by high-angle scattering, being sensitive to thickness and chemical composition, and the first moment in diffraction space, being sensitive to electric fields. It follows that a single recording at one specific probe focus is usually insufficient to characterise materials comprehensively. Most importantly, we demonstrate in experiment and simulation that the second moment µ20+µ02=〈p2〉 of the diffracted intensity exhibits a contrast maximum when the electron probe is focused at the top and bottom faces of the specimen, making the presented concept attractive for measuring local topography. Given the versatility of 〈p2〉, we furthermore present a detailed study of its large-angle convergence both analytically using the Mott scattering approach, and by dynamical simulations using the multislice algorithm including thermal diffuse scattering. Both approaches are in very good agreement and yield logarithmic divergence with increasing scattering angle.

Materials Imaging and Dynamics (MID) instrument at the European X-ray Free-Electron Laser Facility.

The Materials Imaging and Dynamics (MID) instrument at the European X-ray Free-Electron Laser (EuXFEL) facility is described. EuXFEL is the first hard X-ray free-electron laser operating in the MHz repetition range which provides novel science opportunities. The aim of MID is to enable studies of nano-structured materials, liquids, and soft- and hard-condensed matter using the bright X-ray beams generated by EuXFEL. Particular emphasis is on studies of structure and dynamics in materials by coherent scattering and imaging using hard X-rays. Commission of MID started at the end of 2018 and first experiments were performed in 2019.

Single Atom Detection from Low Contrast-to-Noise Ratio Electron Microscopy Images.

Single atom detection is of key importance to solving a wide range of scientific and technological problems. The strong interaction of electrons with matter makes transmission electron microscopy one of the most promising techniques. In particular, aberration correction using scanning transmission electron microscopy has made a significant step forward toward detecting single atoms. However, to overcome radiation damage, related to the use of high-energy electrons, the incoming electron dose should be kept low enough. This results in images exhibiting a low signal-to-noise ratio and extremely weak contrast, especially for light-element nanomaterials. To overcome this problem, a combination of physics-based model fitting and the use of a model-order selection method is proposed, enabling one to detect single atoms with high reliability.

Frozen lattice and absorptive model for high angle annular dark field scanning transmission electron microscopy: A comparison study in terms of integrated intensity and atomic column position measurement.

In this paper, both the frozen lattice (FL) and the absorptive potential (AP) approximation models are compared in terms of the integrated intensity and the precision with which atomic columns can be located from an image acquired using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). The comparison is made for atoms of Cu, Ag, and Au. The integrated intensity is computed for both an isolated atomic column and an atomic column inside an FCC structure. The precision has been computed using the so-called Cramér-Rao Lower Bound (CRLB), which provides a theoretical lower bound on the variance with which parameters can be estimated. It is shown that the AP model results into accurate measurements for the integrated intensity only for small detector ranges under relatively low angles and for small thicknesses. In terms of the attainable precision, both methods show similar results indicating picometer range precision under realistic experimental conditions.

Determining oxygen relaxations at an interface: A comparative study between transmission electron microscopy techniques.

Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO3-La0.67Sr0.33MnO3 (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording.

Three-dimensional atomic models from a single projection using Z-contrast imaging: verification by electron tomography and opportunities.

In order to fully exploit structure-property relations of nanomaterials, three-dimensional (3D) characterization at the atomic scale is often required. In recent years, the resolution of electron tomography has reached the atomic scale. However, such tomography typically requires several projection images demanding substantial electron dose. A newly developed alternative circumvents this by counting the number of atoms across a single projection. These atom counts can be used to create an initial atomic model with which an energy minimization can be applied to obtain a relaxed 3D reconstruction of the nanoparticle. Here, we compare, at the atomic scale, this single projection reconstruction approach with tomography and find an excellent agreement. This new approach allows for the characterization of beam-sensitive materials or where the acquisition of a tilt series is impossible. As an example, the utility is illustrated by the 3D atomic scale characterization of a nanodumbbell on an in situ heating holder of limited tilt range.

How precise can atoms of a nanocluster be located in 3D using a tilt series of scanning transmission electron microscopy images?

In this paper, we investigate how precise atoms of a small nanocluster can ultimately be located in three dimensions (3D) from a tilt series of images acquired using annular dark field (ADF) scanning transmission electron microscopy (STEM). Therefore, we derive an expression for the statistical precision with which the 3D atomic position coordinates can be estimated in a quantitative analysis. Evaluating this statistical precision as a function of the microscope settings also allows us to derive the optimal experimental design. In this manner, the optimal angular tilt range, required electron dose, optimal detector angles, and number of projection images can be determined.

Depth sectioning combined with atom-counting in HAADF STEM to retrieve the 3D atomic structure.

Aberration correction in scanning transmission electron microscopy (STEM) has greatly improved the lateral and depth resolution. When using depth sectioning, a technique during which a series of images is recorded at different defocus values, single impurity atoms can be visualised in three dimensions. In this paper, we investigate new possibilities emerging when combining depth sectioning and precise atom-counting in order to reconstruct nanosized particles in three dimensions. Although the depth resolution does not allow one to precisely locate each atom within an atomic column, it will be shown that the depth location of an atomic column as a whole can be measured precisely. In this manner, the morphology of a nanoparticle can be reconstructed in three dimensions. This will be demonstrated using simulations and experimental data of a gold nanorod.

Progress and new advances in simulating electron microscopy datasets using MULTEM.

A new version of the open source program MULTEM is presented here. It includes a graphical user interface, tapering truncation of the atomic potential, CPU multithreading functionality, single/double precision calculations, scanning transmission electron microscopy (STEM) simulations using experimental detector sensitivities, imaging STEM (ISTEM) simulations, energy filtered transmission electron microscopy (EFTEM) simulations, STEM electron energy loss spectroscopy (EELS) simulations along with other improvements in the algorithms. We also present a mixed channeling approach for the calculation of inelastic excitations, which allows one to considerably speed up time consuming EFTEM/STEM-EELS calculations.

Supervivencia y estado neurológico de la parada cardiaca extrahospitalaria en edad pediátrica en Andalucía / Survival and neurological status after out-of-hospital cardiac arrest in the pediatric population in Andalusia

OBJETIVO: No existe demasiada información sobre la evolución y estado neurológico a largo plazo de los pacientes en edad pediátrica que sobreviven a una parada cardiaca extrahospitalaria. Nuestro objetivo es describir la supervivencia y estado neurológico de estos pacientes a largo plazo. DISEÑO: Estudio observacional retrospectivo. Basado en el Registro Andaluz de Parada Cardiaca Extrahospitalaria. ÁMBITO: Atención Prehospitalaria. PACIENTES: Entre 0 y 15 años atendidos entre enero de 2008 y diciembre de 2012 por Parada Cardiaca Extrahospitalaria. Intervenciones: Seguimiento de pacientes. Variables: Se incluyen variables de la atención prehospitalaria, hospitalaria y del seguimiento al año y un seguimiento específico de los supervivientes en junio de 2014. RESULTADOS: Se incluyeron en el registro un total de 5069 pacientes de los que 125(2.5%) tenían 15 o menos años. La parada fue presenciada en el 52.8% de los casos y hubo reanimación previa en 65.6%. El ritmo inicial fue desfibrilable en 7 (5.2%) casos. Un 48.8% de los pacientes llegó al hospital aunque un 20% lo hizo en situación de reanimación en curso. De los 9 (7.2%) pacientes que sobrevivieron al alta hospitalaria, 5 de ellos lo hicieron con recuperación ad integrum y 4 con grave deterioro neurológico. Los 5 pacientes con recuperación completa mantuvieron su situación a largo plazo. Los 4 pacientes restantes, aunque con discreta mejoría, se mantuvieron en situación de discapacidad neurológica. CONCLUSIONES: La supervivencia de la parada cardiaca extrahospitalaria en edad pediátrica es baja. El pronóstico a largo plazo de los pacientes con buena recuperación neurológica desde el inicio se mantiene, aunque la mejoría en el resto es mínima

OBJECTIVE: Little is known about the evolution and long-term neurological status of pediatric patients who survive out-of-hospital cardiac arrest. Our aim is to describe long-term survival and neurological status. DESIGN: Retrospective observational study, based on the Andalusian Register of out-of-hospital Cardiac Arrest. SETTING: Pre-hospital Care. PATIENTS: The study included patients aged 0-15 years between January 2008 and December 2012. Interventions: Patients follow up. Variables: Prehospital and hospital care variables were analyzed and one-year follow-up was performed, along with a specific follow-up of survivors in June 2014. RESULTS: Of 5069 patients included in the register, 125 (2.5%) were aged less or equal15 years. Cardiac arrest was witnessed in 52.8% of cases and resuscitation was performed in 65.6%. The initial rhythm was shockable in 7 (5.2%) cases. Nearly half (48.8%) the patients reached the hospital alive, of whom 20% did so while receiving resuscitation maneuvers. Only 9 (7.2%) patients survived to hospital discharge; 5 showed ad integrum recovery and 4 showed significant neurological impairment. The 5 patients with complete recovery continued their long-term situation. The remaining 4 patients, although slight improvement, were maintained in situation of neurological disability. CONCLUSIONS: Survival after out-of-hospital cardiac arrest in pediatric patients was low. The long-term prognosis of survivors with good neurological recovery remains, although improvement in the rest was minimal

Survival and neurological status after out-of-hospital cardiac arrest in the pediatric population in Andalusia.

OBJECTIVE: Little is known about the evolution and long-term neurological status of pediatric patients who survive out-of-hospital cardiac arrest. Our aim is to describe long-term survival and neurological status. DESIGN: Retrospective observational study, based on the Andalusian Register of out-of-hospital Cardiac Arrest. SETTING: Pre-hospital Care. PATIENTS: The study included patients aged 0-15 years between January 2008 and December 2012. INTERVENTIONS: Patients follow up. VARIABLES: Prehospital and hospital care variables were analyzed and one-year follow-up was performed, along with a specific follow-up of survivors in June 2014. RESULTS: Of 5069 patients included in the register, 125 (2.5%) were aged ≤15 years. Cardiac arrest was witnessed in 52.8% of cases and resuscitation was performed in 65.6%. The initial rhythm was shockable in 7 (5.2%) cases. Nearly half (48.8%) the patients reached the hospital alive, of whom 20% did so while receiving resuscitation maneuvers. Only 9 (7.2%) patients survived to hospital discharge; 5 showed ad integrum recovery and 4 showed significant neurological impairment. The 5 patients with complete recovery continued their long-term situation. The remaining 4 patients, although slight improvement, were maintained in situation of neurological disability. CONCLUSIONS: Survival after out-of-hospital cardiac arrest in pediatric patients was low. The long-term prognosis of survivors with good neurological recovery remains, although improvement in the rest was minimal.

MULTEM: A new multislice program to perform accurate and fast electron diffraction and imaging simulations using Graphics Processing Units with CUDA.

The main features and the GPU implementation of the MULTEM program are presented and described. This new program performs accurate and fast multislice simulations by including higher order expansion of the multislice solution of the high energy Schrödinger equation, the correct subslicing of the three-dimensional potential and top-bottom surfaces. The program implements different kinds of simulation for CTEM, STEM, ED, PED, CBED, ADF-TEM and ABF-HC with proper treatment of the spatial and temporal incoherences. The multislice approach described here treats the specimen as amorphous material which allows a straightforward implementation of the frozen phonon approximation. The generalized transmission function for each slice is calculated when is needed and then discarded. This allows us to perform large simulations that can include millions of atoms and keep the computer memory requirements to a reasonable level.

A complete comparison of simulated electron diffraction patterns using different parameterizations of the electron scattering factors.

The steadily improving experimental possibilities in instrumental resolution as in sensitivity and quantization of the data recording put increasingly higher demands on the precision of the scattering factors, which are the key ingredients for electron diffraction or high-resolution imaging simulation. In the present study, we will systematically investigate the accuracy of fitting of the main parameterizations of the electron scattering factor for the calculation of electron diffraction intensities. It is shown that the main parameterizations of the electron scattering factor are consistent to calculate electron diffraction intensities for thin specimens and low angle scattering. Parameterizations of the electron scattering factor with the correct asymptotic behavior (Lobato and Dyck [5], Kirkland [4], and Weickenmeier and Kohl [2]) produce similar results for both the undisplaced lattice model and the frozen phonon model, except for certain thicknesses and reflections.

Descripción y resultados iniciales del registro andaluz de parada cardiaca extrahospitalaria / Description of cases in the Andalusian registry of out-of-hospital cardiac arrest and initial results

OBJETIVOS: La incidencia y los resultados en la parada cardiaca extrahospitalaria muestran gran variabilidad entre países o regiones. Nuestro objetivo es describir los procedimientos y resultados de un registro continuo de ámbito regional. MÉTODO: Descripción y análisis de un registro continuo de casos de parada cardiaca extrahospitalaria atendidos por un sistema de emergencias médicas (SEM). Periodo: enero- 2008/diciembre-2010. Se realiza análisis descriptivo y de los factores asociados con el alta hospitalaria con buen estado neurológico (CPC1-2). RESULTADOS: Se registraron 8.889 pacientes y se realizó reanimación en 3.054 (34,4%): 2.103 (71%) hombres y 857 (29%) mujeres. La media de edad fue 60,1 (DE 17,8) años (hombres: 59, DE = 17,8; mujeres: 63, DE = 19,4). En un tercio de las llamadas el motivo no fue inconsciencia. El 30% de las paradas no fueron presenciadas. La hora del colapso se recogió en el 83,7% de los casos. El ritmo inicial fue desfibrilable en el 19,3%. Hubo reanimación previa por testigos en el 12,8%. El 29% de los pacientes llegó con pulso al hospital, que alcanzó el 56,7% cuando el ritmo inicial era desfibrilable. El 9,1% recibieron el alta con CPC1-2. Los factores asociados con CPC1-2 al alta fueron: lugar de parada "no domicilio" (OR: 2,06; IC: 1,22-3,47), parada presenciada (OR: 2,14; IC: 1,12-4,14), ritmo inicial desfibrilable (OR: 7,04; IC: 4,31-11,5), desfibrilación previa a la llegada del equipo de emergencias (EE) (OR: 2,33; IC: 1,09-4,98) y etiología cardiaca (OR: 2,30; IC: 1,27-4,14). CONCLUSIONES: La automatización en la inclusión de pacientes favorece una alta exhaustividad y minimiza sesgos de inclusión. La fase previa a la llegada de los EE es un aspecto clave en la supervivencia con estado neurológico CPC1-2 y un área de mejora para los SEM

BACKGROUND AND OBJECTIVE: The incidence of out-of-hospital cardiac arrest and response outcomes are highly variable between countries or geographic regions. We aimed to describe procedures and outcomes in these cases based on data from a regional registry. METHODS: Description and analysis of registered cases of out-of-hospital cardiac arrest treated by an emergency response service from January 2008 to December 2010. Descriptive statistics were analyzed; we also explored factors associated with a satisfactory cerebral performance category (CPC) of 1 or 2 on discharge. RESULTS: Records were obtained for 8889 patients, of whom 3054 (34.4%) were resuscitated; 2,103 (71.04%) of the patients were men and 857 (29%) women. The mean (SD) age was 60.1 (17.8) years (men, 59 [17.8] years; women, 63 (19.4) years. In a third of the calls, the patient had not lost consciousness. In 30%, no witnesses were present at the time of cardiac arrest, and in 83.7% the time of collapse was recorded. A shockable heart rhythm was detected at the start of resuscitation in 19.3%. Witnesses had previously attempted resuscitation of 12.8%. Pulse was present on arrival at the hospital in 56.7% of the patients with a shockable heart rhythm on start of resuscitation. Discharge with a CPC1-2 was possible in 9.1%. Factors associated with a CPC1-2 were cardiac arrest outside the home (odds ratio [OR], 2.056; 95% CI, 1.218-3.472), witnessed event (OR, 2.137; 95% CI, 1.117-4.138), initial shockable heart rhythm (OR, 7.040; 95% CI, 4.313-11.490), defibrillation prior to arrival of first emergency responders (OR, 2.330; 95% CI, 1.091-4.976), and cardiac etiology (OR, 2.295; 95% CI, 1.270-4.145). CONCLUSIONS: Automatic registry of cases facilitates inclusion of all patients and minimizes bias. Factors during the period prior to the arrival of first emergency responders are key to survival in CPC1-2 status and are an aspect to target for improvement

Improved multislice calculations for including higher-order Laue zones effects.

A new method for including higher-order Laue zones (HOLZs) effects in an efficient way in electron scattering simulations has been developed and tested by detail calculations. The calculated results by the conventional multislice (CMS) method and the improved conventional multislice (ICMS) method using a large dynamical aperture to avoid numerical errors are compared with accurate results. We have found that the zero-order Laue zones (ZOLZs) reflection cannot be properly described only using the projected potential in the whole unit cell; in general, we need to subslice the electrostatic potential inside the unit cell. It is shown that the ICMS method has higher accuracy than the CMS method for the calculation of the ZOLZ, HOLZ and Pseudo-HOLZ reflections. Hence, ICMS method allows to use a larger slice thickness than the CMS method and reduces the calculation time.

Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions.

The structural evolution and dynamics of silver nanodrops Ag(2869) (4.4 nm in diameter) under rapid cooling conditions have been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modelled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique are used to reveal the structural transition in the process of solidification. It is shown that Ag nanoparticles evolve into different nanostructures under different cooling processes. At a cooling rate of 1.5625 × 10(13) K s(-1) the nanoparticles preserve an amorphous-like structure containing a large amount of 1551 and 1541 pairs which correspond to icosahedral symmetry. For a lower cooling rate (1.5625 × 10(12) K s(-1)), the nanoparticles transform into a crystal-like structure consisting mainly of 1421 and 1422 pairs which correspond to the face centred cubic and hexagonal close packed structures, respectively. The variations of the electronic density of states for the differently cooled nanoparticles are small, but in correspondence with the structural changes.

Frecuencia de los grupos sanguíneos ABO y factor Rho(D) en la población de origen aymara de la primera región / Frequency of ABO and Rhഠ D blood groups in the aymara stock population in the first region

La frecuencia de los grupos sanguíneos ABO y el factor Rhഠ presentan una gran variabilidad en los grupos étnicos a nivel mundial. Se estudiaron mil nueve individuos de ambos sexos procedentes del altiplano de la Primera Región, de los cuales, seiscientos noventa y seis son de padres aymara y trescientos trece mestizos, con uno de los progenitores de origen aymara. Se tomó una muestra de sangre a cada individuo, por punción venosa y para la determinación de antígenos ABO y factor Rhഠ, se utilizaron el método en tubo y sueros clasificadores, además para el sistema ABO, se usó el método inverso. Los resultados obtenidos en el grupo aymara fueron: Grupo 0 Rhഠ + :95 por ciento. Grupo 0 Rhഠ (-) Du (-): 0,1 por ciento. Grupo A Rhഠ + 3,6 por ciento y Grupo B Rhഠ + : 1,3 por ciento. En el grupo mestizo, en estudio, los resultados fueron: Grupo 0 Rhഠ + :68 por ciento. Grupo A Rhഠ + :20,1 por ciento. Grupo B Rhഠ + : 11 por ciento, Grupo AB Rhഠ + : 0,6 por ciento y Grupo AB Rhഠ (-) Du (-): 0,3 por ciento. De los resultados obtenidos se concluye que en la población aymara el grupo 0 Rhഠ + presenta una elevada frecuencia.

Enteroparasitosis en manipuladores de alimentos de la ciudad de Arica, I Región, Chile / Enteroparasitosis in food mamipulators of Arica City, I Region, Chile

Durante mayo a agosto de 1983 se estudiaron 180 manipuladores de alimentos de 52 establecimientos comerciales de la ciudad de Arica, realizando a cada uno de ellos, un examen coproparasitológico seriado. 108 (60%0 presentaron infección por parásitos o comensales intestinales. La especie de mayor prevalencia fue ENDOLIMAX NANA (42,2%). Entre los patógenos se encontró GIARDIA LAMBLIA (9,4%), ENTAMOEBA HISTOLYTICA (5%) y los helmintos HYMENOLEPIS NANA (1,1%) y TRICHURIS TRICHIURA (0,6%). Con respecto al tipo de establecimientos, la mayor tasa de infección fue encontrada en los individuos provenientes de panaderías (77,8%) y fuentes de soda (63%)