Phase retrieval of coherent diffractive images with global optimization algorithms

Coherent diffractive imaging (CDI) or lensless microscopy has recently been of great interest as a promising alternative to electron microscopy in achieving atomic spatial resolution. Reconstruction of images in real space from a single experimental diffraction pattern in CDI is based on applying iterative phase-retrieval (IPR) algorithms, such as the hybrid input–output and the error reduction algorithms. For noisy data, these algorithms might suffer from stagnation or trapping in local minima. Generally, the different local minima have many common as well as complementary features and might provide useful information for an improved estimate of the object. Therefore, a linear combination of a number of chosen minima, termed a basis set, gives an educated initial estimate, which might accelerate the search for the global solution. In this study, a genetic algorithm (GA) is combined with an IPR algorithm to tackle the stagnation and trapping in phase-retrieval problems. The combined GA–IPR has been employed to reconstruct an irregularly shaped hole and has proven to be reliable and robust. With the concept of basis set, it is strongly believed that many effective local and global optimization frameworks can be combined in a similar manner to solve the phase problem.</jats:p

Synchrotron radiation in soil and geosciences

This special issue is the outcome of the Session SSS24 `Synchrotron radiation in soil and geosciences' that was held on 21 April 2009 in Vienna during the EGU (European Geosciences Union) General Assembly 2009, within the Soil System Sciences (SSS) program. In this special issue ten papers are presented, chosen after a selection among 19 written contributions that were received after the scientific Session at EGU

Spectroscopic investigations of Np(V/VI) redox speciation in hyperalkaline TMA-(OH, Cl) solutions

The redox chemistry of Np(V/VI) was investigated in ∼0.6M tetramethylammonium hydroxide/chloride (TMA-(OH, Cl)) solutions with 9 ≤ −log [H+] ≤ 13.5. Redox conditions were defined by the absence or presence of ClO− as oxidizing agent (Na-salt, 5×10−3M and 5×10−2M). The high total Np concentration ([Np]tot ∼ 2×10−3M) led to the precipitation of solid phases in some of the samples. The carbonate concentration (as impurity of TMA-OH) was 2-3×10−3M. UV-vis/NIR spectra obtained from the supernatant in TMA-(OH, Cl) solutions and absence of ClO− showed clear Np(V) features, identified as NpO2+, NpO2CO3− and (NpO2)x(CO3)y(OH)zx−2y−z. No NIR features were observed within 800nm ≤ λ ≤ 1300nm for samples with ClO−. XANES edge energies and features of these samples confirmed the predominance of Np(V) in the absence of ClO− and Np(VI) in the presence of ClO−, by comparison to XANES reference spectra of Np(III/IV/V/VI) prepared within the present work by in-situ electrolysis. Asimilar Np redox distribution was observed for the solid phases based on XANES and EXAFS measurements. EXAFS spectra indicative of NpVO2OH(s) and NpVIO3· xH2O(s) were obtained for samples in absence and presence of ClO−, respectively. The formation of aNa-Np(VI) phase in 5×10−2M ClO− and −log [H+] ∼ 12 was also indicated from the EXAFS, chemical analysis and SEM-EDS. These results indicate that Np(VI) aqueous species and solid compounds prevail far below the oxidation border of water in alkaline solutions and also far below the EH border calculated with the current NEA data selection [1]. These observations are further supported by correlations of literature thermodynamic data for actinides (U, Np, Pu and Am), which predict the formation of NpO2(OH)3− and NpO2(OH)42− aqueous species with stability constants (log *βº1,3 and log *βº1,4) similar to those available for U(VI

Hydrophilic 2,9-bis-triazolyl-1,10-phenanthroline ligands enable selective Am(iii) separation: a step further towards sustainable nuclear energy

The first hydrophilic, 1,10-phenanthroline derived ligands consisting of only C, H, O and N atoms for the selective extraction of Am(iii) from spent nuclear fuel are reported herein. One of these 2,9-bis-triazolyl-1,10-phenanthroline (BTrzPhen) ligands combined with a non-selective extracting agent, was found to exhibit process-suitable selectivity for Am(iii) over Eu(iii) and Cm(iii), providing a clear step forward

Neptunium and manganese biocycling in nuclear legacy sediment systems

Understanding the behaviour of the highly radiotoxic, long half-life radionuclide neptunium in the environment is important for the management of radioactively contaminated land and the safe disposal of radioactive wastes. Recent studies have identified that microbial reduction can reduce the mobility of neptunium via reduction of soluble Np(V) to poorly soluble Np(IV), with coupling to both Mn- and Fe(III)- reduction implicated in neptunyl reduction. To further explore these processes Mn(IV) as δMnO2 was added to sediment microcosms to create a sediment microcosm experiment "poised" under Mn-reducing conditions. Enhanced removal of Np(V) from solution occurred during Mn-reduction, and parallel X-ray absorption spectroscopy (XAS) studies confirmed Np(V) reduction to Np(IV) commensurate with microbially-mediated Mn-reduction. Molecular ecology analysis of the XAS systems, which contained up to 0.2 mM Np showed no significant impact of elevated Np concentrations on the microbial population. These results demonstrate the importance of Mn cycling on Np biogeochemistry, and clearly highlight new pathways to reductive immobilisation for this highly radiotoxic actinide

The CAT-ACT Beamline at ANKA: A new high energy X-ray spectroscopy facility for CATalysis and ACTinide research

A new hard X-ray beamline for CATalysis and ACTinide research has been built at the synchrotron radiation facility ANKA. The beamline design is dedicated to X-ray spectroscopy, including ‘flux hungry’ photon-in/photon-out and correlative techniques with a special infrastructure for radionuclide and catalysis research. The CAT-ACT beamline will help serve the growing need for high flux/hard X-ray spectroscopy in these communities. The design, the first spectra and the current status of this project are reported

Histone H3.3 beyond cancer: Germline mutations in Histone 3 Family 3A and 3B cause a previously unidentified neurodegenerative disorder in 46 patients

Although somatic mutations in Histone 3.3 (H3.3) are well-studied drivers of oncogenesis, the role of germline mutations remains unreported. We analyze 46 patients bearing de novo germline mutations in histone 3 family 3A (H3F3A) or H3F3B with progressive neurologic dysfunction and congenital anomalies without malignancies. Molecular modeling of all 37 variants demonstrated clear disruptions in interactions with DNA, other histones, and histone chaperone proteins. Patient histone posttranslational modifications (PTMs) analysis revealed notably aberrant local PTM patterns distinct from the somatic lysine mutations that cause global PTM dysregulation. RNA sequencing on patient cells demonstrated up-regulated gene expression related to mitosis and cell division, and cellular assays confirmed an increased proliferative capacity. A zebrafish model showed craniofacial anomalies and a defect in Foxd3-derived glia. These data suggest that the mechanism of germline mutations are distinct from cancer-associated somatic histone mutations but may converge on control of cell proliferation

Synchrotron applications to f-element research in the nuclear fuel cycle

A summary of innovative techniques using synchrotron radiation for actinide studies in nuclear research, including X-ray spectroscopy and imaging.</p