Optimized imaging using non-rigid registration

The extraordinary improvements of modern imaging devices offer access to data with unprecedented information content. However, widely used image processing methodologies fall far short of exploiting the full breadth of information offered by numerous types of scanning probe, optical, and electron microscopies. In many applications, it is necessary to keep measurement intensities below a desired threshold. We propose a methodology for extracting an increased level of information by processing a series of data sets suffering, in particular, from high degree of spatial uncertainty caused by complex multiscale motion during the acquisition process. An important role is played by a nonrigid pixel-wise registration method that can cope with low signal-to-noise ratios. This is accompanied by formulating objective quality measures which replace human intervention and visual inspection in the processing chain. Scanning transmission electron microscopy of siliceous zeolite material exhibits the above-mentioned obstructions and therefore serves as orientation and a test of our procedures

High-Pressure Phase Transitions of Morphologically Distinct Zn2SnO4 Nanostructures

Many aspects of nanostructured materials at high pressures are still unexplored. We present here, high-pressure structural behavior of two Zn2SnO4 nanomaterials with inverse spinet type, one a particle with size of similar to 7 nm zero dimensional (0-D)] and the other with a chain-like one dimensional (1-D)] morphology. We performed in situ micro-Raman and synchrotron X-ray diffraction measurements and observed that the cation disordering of the O-D nanoparticle is preserved up to similar to 40 GPa, suppressing the reported martensitic phase transformation. On the other hand, an irreversible phase transition is observed from the 1-D nanomaterial into a new and dense high-pressure orthorhombic CaFe2O4-type structure at similar to 40 GPa. The pressure-treated 0-D and 1-D nanomaterials have distinct diffuse reflectance and emission properties. In particular, a heterojunction between the inverse spinet and quenchable orthorhombic phases allows the use of 1-D Zn2SnO4 nanomaterials as efficient photocatalysts as shown by the degradation of the textile pollutant methylene blue

Insights into the capping and structure of MoS2 nanotubes as revealed by aberration-corrected STEM

Aberration-corrected electron microscopy (STEM-HAADF) has been used for the first time to understand the capping, nature and structure of the MoS2 nanotubes. The MoS2 nanotubes that have been obtained have various unusual faceted caps presumably arising from the presence of topological defects. A detailed study of the capping of the nanotubes, along with identification that the MoS2 nanotubes are of the zigzag type have been carried out using both experimental and simulated STEM images. The presence of 3R-rhombohedral stacking of the MoS2 nanotubes has been identified

On the structure of Au/Pd bimetallic nanoparticles

We performed a study on bimetallic Au/Pd nanoparticles using aberration corrected electron microscopy along with molecular dynamics simulations to investigate the features of specific atomic sites at the surface, which can be related to the high catalytic activity properties of the particles. The calculations mimic the growth of nanoparticles through a cooling process from a molten solid to a crystalline structure at room temperature. We found that the final structure for the alloy particles is neither a cuboctahedral nor an icosahedral,but a complex structure that has a very rough surface and unique isolated Pd sites surrounded by Au atoms. We also found that there is predominance of three specific Pd sites at the surface, which can be directly related to the catalytic activity of the nanoparticle

Integrative conjugative elements of the ICEPan family play a potential role in Pantoea ananatis ecological diversification and antibiosis

Pantoea ananatis is a highly versatile enterobacterium isolated from diverse environmental sources. The ecological diversity of this species may be attributed, in part, to the acquisition of mobile genetic elements. One such element is an Integrative and Conjugative Element (ICE). By means of in silico analyses the ICE elements belonging to a novel family, ICEPan, were identified in the genome sequences of five P. ananatis strains and characterized. PCR screening showed that ICEPan is prevalent among P. ananatis strains isolated from different environmental sources and geographic locations. Members of the ICEPan family share a common origin with ICEs of other enterobacteria, as well as conjugative plasmids of Erwinia spp. Aside from core modules for ICEPan integration, maintenance and dissemination, the ICEPan contain extensive non-conserved islands coding for proteins that may contribute toward various phenotypes such as stress response and antibiosis, and the highly diverse ICEPan thus plays a major role in the diversification of P. ananatis. An island is furthermore integrated within an ICEPan DNA repair-encoding locus umuDC and we postulate its role in stress-induced dissemination and/or expression of the genes on this island

Particulate Emissions from a Pre-Emissions Control Era Spark-Ignition Vehicle: A Historical Benchmark

This study examined the particulate emissions from a pre-emissions control era vehicle operated on both leaded and unleaded fuels for the purpose of establishing a historical benchmark. A pre-control vehicle was located that had been rebuilt with factory original parts to approximate an as-new vehicle prior to 1968. The vehicle had less than 20,000 miles on the rebuilt engine and exhaust. The vehicle underwent repeated FTP-75 tests to determine its regulated emissions, including particulate mass. Additionally, measurements of the particulate size distribution were made, as well as particulate lead concentration. These tests were conducted first with UTG96 certification fuel, followed by UTG96 doped with tetraethyl lead to approximate 1968 levels. Results of these tests, including transmission electron micrographs of individual particles from both the leaded and unleaded case are presented. The FTP composite PM emissions from this vehicle averaged 40.5 mg/mile using unleaded fuel. The results from the leaded fuel tests showed that the FTP composite PM emissions increased to an average of 139.5 mg/mile. Analysis of the particulate size distribution for both cases demonstrated that the mass-based size distribution of particles for this vehicle is heavily skewed towards the nano-particle range. The leaded-fuel tests showed a significant increase in mass concentration at the <0.1 micron size compared with the unleaded-fuel test case. The leaded-fuel tests produced lead emissions of nearly 0.04 g/mi, more than a 4-order-of-magnitude difference compared with unleaded-fuel results. Analysis of the size-fractionated PM samples showed that the lead PM emissions tended to be distributed in the 0.25 micron and smaller size range

Cation and lone pair order-disorder in the polymorphic mixed metal bismuth scheelite Bi3FeMo2O12

The Bi3FeMo2O12 system is examined as a rare example of a transition metal oxide which, upon heating, undergoes a symmetry lowering and 2:1 ordering of the transition metal cations. The compound was synthesised in the tetragonal scheelite structure (S.G. #88: I41/a) by a sol-gel method and converted into the monoclinic polymorph (S.G. #15: C2/c) by calcination above 500 °C. The structure of both polymorphs was analysed using a combination of X-ray and neutron diffraction data, and the temperature-dependent phase transition between these was investigated in situ using variable temperature neutron powder diffraction and scanning transmission electron microscopy. The results show that the structural phase transition takes place at low temperature (~500 °C) and is 1st order in nature, as evident from the coexistence of both structures. The transition from tetragonal to monoclinic results in reduction of the equivalent unit cell volume. The role of the Bi3+ 6s lone pairs in the temperature-driven phase transition has been studied using neutron pair distribution function analysis. Local structure analysis via neutron total scattering revealed the Bi3+ 6s lone pairs to be stereochemically active in both structures, with short correlation lengths in the tetragonal structure and long correlation lengths in the monoclinic structure, leading to the facile phase conversion and to a more efficient packing density with highly correlated lone pairs in the monoclinic structure. Magnetization isotherms of the tetragonal structure collected at 1.8 K exhibit ferromagnetic behavior, suggesting that the interplay between the observed short-range monoclinic order, defects and surface-to-bulk effects alters the magnetic interaction, leading to short range ferromagnetic interactions, which is highly unexpected given the low temperature antiferromagnetic order observed in the monoclinic structure

Integrative conjugative elements of the ICEPan family play a potential role in Pantoea ananatis ecological diversification and antibiosis

Pantoea ananatis is a highly versatile enterobacterium isolated from diverse environmental sources. The ecological diversity of this species may be attributed, in part, to the acquisition of mobile genetic elements. One such element is an Integrative and Conjugative Element (ICE). By means of in silico analyses the ICE elements belonging to a novel family, ICEPan, were identified in the genome sequences of five P. ananatis strains and characterized. PCR screening showed that ICEPan is prevalent among P. ananatis strains isolated from different environmental sources and geographic locations. Members of the ICEPan family share a common origin with ICEs of other enterobacteria, as well as conjugative plasmids of Erwinia spp. Aside from core modules for ICEPan integration, maintenance and dissemination, the ICEPan contain extensive non-conserved islands coding for proteins that may contribute toward various phenotypes such as stress response and antibiosis, and the highly diverse ICEPan thus plays a major role in the diversification of P. ananatis. An island is furthermore integrated within an ICEPan DNA repair-encoding locus umuDC and we postulate its role in stress-induced dissemination and/or expression of the genes on this island.This study was partially supported by the University of Pretoria Postdoctoral Fellowship Fund, National Research Foundation (NRF), the Tree Protection Co-operative Programme (TPCP), the NRF/Dept. of Science and Technology Centre of Excellence in Tree Health Biotechnology (CTHB), and the THRIP support program of the Department of Trade and Industry, South Africa, the department of Life Sciences and Facility Management of ZHAW, the Swiss Federal Office for Agriculture (BLW Fire Blight Research – Achilles), and the Swiss Secretariat for Education and Research (SBF C07.0038).http://www.frontiersin.org/Microbiologyam2016Forestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog