A Transport Equation Theory of Electron Scattering

The use of the Boltzmann transport equation to describe electron scattering in electron microscopy and electron probe microanalysis is discussed. A method of solution is given in which the transport equation is divided into angle and energy intervals. This gives rise to a number of coupled first order differential equations. Separation into forward and backward travelling components of the electron flux distribution enables the correct boundary conditions to be imposed. Solutions are derived which take the form of matrix operators analytic in both depth and target thickness. These matrices allow derivation of other physical quantities such as X-ray or Auger electron production. Calculations using this method are fast and accurate. Results are presented showing angular distributions of backscattered electrons and the variation of the backscattered fraction with angle of incidence and atomic number. The variations of backscattered, transmitted and absorbed fractions with target thickness are presented. The theory has also been applied to the calculation of the energy distributions of backscattered electrons, energy dissipation and X-ray production as functions of depth and the Auger backscattering factor. It appears that electron scattering in thick targets is not amenable to treatment using simple models. This is because most of the features of interest are determined by a combination of medium angle scattering (\u3c 20°) and large angle scattering (20-90°). Nevertheless certain approximations within the present framework, which describe multiple scattering correctly, can give some useful insights

Dose, exposure time, and resolution in Serial X-ray Crystallography

The resolution of X-ray diffraction microscopy is limited by the maximum dose that can be delivered prior to sample damage. In the proposed Serial Crystallography method, the damage problem is addressed by distributing the total dose over many identical hydrated macromolecules running continuously in a single-file train across a continuous X-ray beam, and resolution is then limited only by the available molecular and X-ray fluxes and molecular alignment. Orientation of the diffracting molecules is achieved by laser alignment. We evaluate the incident X-ray fluence (energy/area) required to obtain a given resolution from (1) an analytical model, giving the count rate at the maximum scattering angle for a model protein, (2) explicit simulation of diffraction patterns for a GroEL-GroES protein complex, and (3) the frequency cut off of the transfer function following iterative solution of the phase problem, and reconstruction of an electron density map in the projection approximation. These calculations include counting shot noise and multiple starts of the phasing algorithm. The results indicate counting time and the number of proteins needed within the beam at any instant for a given resolution and X-ray flux. We confirm an inverse fourth power dependence of exposure time on resolution, with important implications for all coherent X-ray imaging. We find that multiple single-file protein beams will be needed for sub-nanometer resolution on current third generation synchrotrons, but not on fourth generation designs, where reconstruction of secondary protein structure at a resolution of 0.7 nm should be possible with short exposures.Comment: 19 pages, 7 figures, 1 tabl

In Situ Formed Sn1 xInx In1 ySnyOz Core Shell Nanoparticles as Electrocatalysts for CO2 Reduction to Formate

Electrochemical reduction of CO2 CO2RR driven by renewable energy has gained increasing attention for sustainable production of chemicals and fuels. Catalyst design to overcome large overpotentials and poor product selectivity remains however challenging. Sn SnOx and In InOx composites have been reported active for CO2RR with high selectivity toward formate formation. In this work, the CO2RR activity and selectivity of metal metal oxide composite nanoparticles formed by in situ reduction of bimetallic amorphous SnInOx thin films are investigated. It is shown that during CO2RR the amorphous SnInOx pre catalyst thin films are reduced in situ into Sn1 XInX In1 YSnYOz core shell nanoparticles composed of Sn rich SnIn alloy nanocores with x lt; 0.2 surrounded by InOx rich bimetallic InSnOx shells with 0.3 lt; y lt; 0.4 and z amp; 8776; 1 . The in situ formed particles catalyze the CO2RR to formate with high faradaic efficiency 80 and outstanding formate mass activity 437 A gIn Sn amp; 8722;1 amp; 8722;1.0 V vs RHE in 0.1 m KHCO3 . While extensive structural investigation during CO2RR reveals pronounced dynamics in terms of particle size, the core shell structure is observed for the different electrolysis conditions essayed, with high surface oxide contents favoring formate over hydrogen selectivit

New Recurrent Structural Aberrations in the Genome of Chronic Lymphocytic Leukemia Based on Exome-Sequencing Data

Chronic lymphocytic leukemia (CLL) is the most frequent lymphoproliferative syndrome in Western countries, and it is characterized by recurrent large genomic rearrangements. During the last decades, array techniques have expanded our knowledge about CLL's karyotypic aberrations. The advent of large sequencing databases expanded our knowledge cancer genomics to an unprecedented resolution and enabled the detection of small-scale structural aberrations in the cancer genome. In this study, we have performed exome-sequencing-based copy number aberration (CNA) and loss of heterozygosity (LOH) analysis in order to detect new recurrent structural aberrations. We describe 54 recurrent focal CNAs enriched in cancer-related pathways, and their association with gene expression and clinical evolution. Furthermore, we discovered recurrent large copy number neutral LOH events affecting key driver genes, and we recapitulate most of the large CNAs that characterize the CLL genome. These results provide "proof-of-concept" evidence supporting the existence of new genes involved in the pathogenesis of CLL

In Situ Study of Hydrogen Permeable Electrodes for Electrolytic Ammonia Synthesis Using Near Ambient Pressure XPS

Hydrogen permeable electrodes can be utilized for electrolytic ammonia synthesis from dinitrogen, water, and renewable electricity under ambient conditions, providing a promising route toward sustainable ammonia. The understanding of the interactions of adsorbing N and permeating H at the catalytic interface is a critical step toward the optimization of this NH3 synthesis process. In this study, we conducted a unique in situ near ambient pressure X ray photoelectron spectroscopy experiment to investigate the solid gas interface of a Ni hydrogen permeable electrode under conditions relevant for ammonia synthesis. Here, we show that the formation of a Ni oxide surface layer blocks the chemisorption of gaseous dinitrogen. However, the Ni 2p and O 1s XPS spectra reveal that electrochemically driven permeating atomic hydrogen effectively reduces the Ni surface at ambient temperature, while H2 does not. Nitrogen gas chemisorbs on the generated metallic sites, followed by hydrogenation via permeating H, as adsorbed N and NH3 are found on the Ni surface. Our findings suggest that the first hydrogenation step to NH and the NH3 desorption might be limiting under the operating conditions. The study was then extended to Fe and Ru surfaces. The formation of surface oxide and nitride species on iron blocks the H permeation and prevents the reaction to advance; while on ruthenium, the stronger Ru N bond might favor the recombination of permeating hydrogen to H2 over the hydrogenation of adsorbed nitrogen. This work provides insightful results to aid the rational design of efficient electrolytic NH3 synthesis processes based on but not limited to hydrogen permeable electrode

Dise?o, procura, construcci?n e implementaci?n de la torre de control para la nueva base aeronaval del Callao

Concebido por un equipo multidisciplinario, con diferentes visiones y experiencias para abordar los procesos de inicio y planificaci?n del proyecto ?Dise?o, procura, construcci?n e implementaci?n de la torre de control para la nueva base aeronaval del Callao?; permitiendo as? que la direcci?n de proyectos en sus diferentes fases de planeaci?n sea un proceso innovador, por medio de GISA, empresa de ingenier?a y construcci?n con una trayectoria de 20 a?os. El proyecto forma parte del megaproyecto de remodelaci?n de la base aeronaval del Callao para la Marina de Guerra del Per?. ?ste abarca la gesti?n, dise?o, procura construcci?n de una torre de control de medidas reglamentarias, implementaci?n de equipos de telecomunicaci?n de ?ltima generaci?n y capacitaci?n al personal usuario del cliente, hasta obtener la certificaci?n internacional. GISA ha establecido objetivos de eficiencia (2) alineados con la triple restricci?n, objetivos de producto (2) orientados a la conexi?n de los equipos de telecomunicaciones, as? como la obtenci?n de la certificaci?n aeron?utica internacional y satisfacci?n de stakeholders; para ello ha desarrollado los planes subsidiarios necesarios con plena conciencia de los factores pol?ticos, econ?micos, tecnol?gicos, ecol?gicos, legales y socioculturales presentes. El ?xito del proyecto posicionar? a GISA como un contratista preferente para el Estado

A snapshot of cancer-associated thromboembolic disease in 2018-2019: First data from the TESEO prospective registry

BACKGROUND: The ever-growing complexity of cancer-associated thrombosis (CAT), with new antineoplastic drugs and anticoagulants, distinctive characteristics, and decisions with low levels of evidence, justifies this registry. METHOD: TESEO is a prospective registry promoted by the Spanish Society of Medical Oncology to which 34 centers contribute cases. It seeks to provide an epidemiological description of CAT in Spain. RESULTS: Participants (N=939) with CAT diagnosed between July 2018 and December 2019 were recruited. Most subjects had advanced colon (21.4%), non-small cell lung (19.2%), and breast (11.1%) cancers, treated with dual-agent chemotherapy (28.4%), monochemotherapy (14.4%), or immune checkpoint inhibitors (3.6%). Half (51%) were unsuspected events, albeit only 57.1% were truly asymptomatic. Pulmonary embolism (PE) was recorded in 571 (58.3%); in 120/571 (21.0%), there was a concurrent deep venous thromboembolism (VTE). Most initially received low molecular weight heparin (89.7%). Suspected and unsuspected VTE had an OS rate of 9.9 (95% CI, 7.3-non-computable) and 14.4 months (95% CI, 12.6-non-computable) (p=0.00038). Six-month survival was 80.9%, 55.9%, and 55.5% for unsuspected PE, unsuspected PE admitted for another reason, and suspected PE, respectively (p<0.0001). The 12-month cumulative incidence of venous rethrombosis was 7.1% (95% CI, 4.7-10.2) in stage IV vs 3.0% (95% CI, 0.9-7.1) in stages I-III. The 12-month cumulative incidence of major/clinically relevant bleeding was 9.6% (95% CI, 6.1-14.0) in the presence of risk factors. CONCLUSION: CAT continues to be a relevant problem in the era of immunotherapy and targeted therapies. The initial TESEO data highlight the evolution of CAT, with new agents and thrombotic risk factors

Novel Mutation Hotspots within Non-Coding Regulatory Regions of the Chronic Lymphocytic Leukemia Genome

Mutations in non-coding DNA regions are increasingly recognized as cancer drivers. These mutations can modify gene expression in cis or by inducing high-order chormatin structure modifications with long-range effects. Previous analysis reported the detection of recurrent and functional non-coding DNA mutations in the chronic lymphocytic leukemia (CLL) genome, such as those in the 3' untranslated region of NOTCH1 and in the PAX5 super-enhancer. In this report, we used whole genome sequencing data produced by the International Cancer Genome Consortium in order to analyze regions with previously reported regulatory activity. This approach enabled the identification of numerous recurrently mutated regions that were frequently positioned in the proximity of genes involved in immune and oncogenic pathways. By correlating these mutations with expression of their nearest genes, we detected significant transcriptional changes in genes such as PHF2 and S1PR2. More research is needed to clarify the function of these mutations in CLL, particularly those found in intergenic regions