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In situ operando plug flow fixed bed cell for synchrotron PXRD and XAFS investigations at high temperature, pressure, controlled gas atmosphere and ultra fast heating
Get PDFA plug flow fixed bed cell for synchrotron powder X ray diffraction PXRD and X ray absorption fine structure XAFS idoneous for the study of heterogeneous catalysts at high temperature, pressure and under gas flow is designed, constructed and demonstrated. The operating conditions up to 1000 C and 50 amp; 8197;bar are ensured by a set of mass flow controllers, pressure regulators and two infra red lamps that constitute a robust and ultra fast heating and cooling method. The performance of the system and cell for carbon dioxide hydrogenation reactions under specified temperatures, gas flows and pressures is demonstrated both for PXRD and XAFS at the P02.1 PXRD and the P64 XAFS beamlines of the Deutsches Elektronen Synchrotron DES
Protocol for depositing transparent conductive Ta doped SnO2 film by hollow cathode gas flow sputtering technology
Get PDFTransparent conductive Ta doped SnO2 SnO2 Ta thin film with low surface roughness, low resistivity, and high carrier concentration is one potential alternative of commercial transparent conductive oxides TCOs . Here, we present a protocol for fabricating tin oxide films by hollow cathode gas flow sputtering technology. We describe steps for preparing and cleaning substrate, and film deposition process on the fresh uncorroded float glass substrate. We then detail procedures for measuring the optical and electrical properties of the fil
Synthesis of Doped g C3N4 Photonic Crystals for Enhanced Light Driven Hydrogen Production from Catalytic Water Splitting
Get PDFDopants are frequently used to improve graphitic carbon nitride gCN photoactivity. As a doping source, phosphomolybdic acid PMA can activate doping sites inside the gCN lattice, resulting in 2D Mo P gCN porous material. However, the gradual loading of the PMA fraction has no systematic improvement in the Mo P gCN photoactivity. For improving the optoelectronic properties of Mo P gCN, its textural geometry is a controllable parameter that can provide enhanced photonic properties, achievable by shaping its morphology through a crystalline template structure, namely, photonic crystals PCs . Herein, a doped PC material is made of Mo P gCN and PCs and labeled as Mo P gCN PCs. The impact of PCs is highlighted in the structural, electronic, and optical performances of Mo P gCN. A well defined 3D crystalline network is evidenced by microscopic measurements scanning electron microscopy, AFM, focused ion beam . Mo P gCN PCs shows a hydrogen production rate 750 amp; 8201; amp; 956;mol amp; 8201;g amp; 8722;1 amp; 8201;h amp; 8722;1 one time higher than Mo P gCN and 6 times higher than pure gCN. The synthesis strategy proposed in this work leads simultaneously to the Mo P codoping effect provided by PMA and the slow photon effect due to the PC structure, offering a novel strategy to improve the gCN photoactivity by simultaneously applying polyoxometalates as modifiers and polystyrene opals as template
Anchoring groups for ordered and highly stable monomolecular films on naturally oxidized aluminum phosphonate versus carboxylate
No full textModification of metal oxide surfaces by self assembled monolayers SAMs is attracting growing attention. Carboxylic CA and phosphonic PA acids are most popular anchoring groups in this context, applied to create hydrophobic coatings, biosensors, and organic field effect transistors. The efficiency of these devices is crucially affected by the structural quality and stability of the SAM. In this context, we studied the effect of the preparation procedure solvent, incubation time, and temperature on the quality of PA SAMs on naturally oxidized aluminum. We demonstrate formation of PA SAMs matching structural quality of archetypical alkanethiols on gold. Next, we compare their stability with analogous CA SAMs. Our data show that PA SAMs not only exhibit much higher hydrolytic stability but are also capable to protect aluminum substrate from oxidation and degradation. Importantly, even small improvement of the PA SAMs quality, translates into enormous increase of their hydrolytic stability crucial for majority of applications. Finally, we demonstrate that the thermal stability of PA on oxidized aluminum is by amp; 8764;250 K higher than CA SAMs, and by amp; 8764;200 K higher than for thiols on gold, which makes PA SAMs an excellent candidate for organic electronics, where overheating problems and high temperature fabrication procedures are common issue
Crystallographic fragment binding studies of the Mycobacterium tuberculosis trifunctional enzyme suggest binding pockets for the tails of the acyl CoA substrates at its active sites and a potential substrate channeling path between them
Get PDFThe Mycobacterium tuberculosis trifunctional enzyme MtTFE is an amp; 945;2 amp; 946;2 tetrameric enzyme in which the amp; 945; chain harbors the 2E enoyl CoA hydratase ECH and 3S hydroxyacyl CoA dehydrogenase HAD active sites, and the amp; 946; chain provides the 3 ketoacyl CoA thiolase KAT active site. Linear, medium chain and long chain 2E enoyl CoA molecules are the preferred substrates of MtTFE. Previous crystallographic binding and modeling studies identified binding sites for the acyl CoA substrates at the three active sites, as well as the NAD binding pocket at the HAD active site. These studies also identified three additional CoA binding sites on the surface of MtTFE that are different from the active sites. It has been proposed that one of these additional sites could be of functional relevance for the substrate channeling by surface crawling of reaction intermediates between the three active sites. Here, 226 fragments were screened in a crystallographic fragment binding study of MtTFE crystals, resulting in the structures of 16 MtTFE fragment complexes. Analysis of the 121 fragment binding events shows that the ECH active site is the binding hotspot for the tested fragments, with 41 binding events. The mode of binding of the fragments bound at the active sites provides additional insight into how the long chain acyl moiety of the substrates can be accommodated at their proposed binding pockets. In addition, the 20 fragment binding events between the active sites identify potential transient binding sites of reaction intermediates relevant to the possible channeling of substrates between these active sites. These results provide a basis for further studies to understand the functional relevance of the latter binding sites and to identify substrates for which channeling is crucia
Relation Between Tensile Strut and Compressive Foam Deformation Behavior Failure Mechanisms and the Influence of Dendritic Versus Globular Grain Structure in an AlSi7Mg0.3 A356 Precision Cast Open Cell Foam
No full textOpen cell aluminum foams are gaining importance for the design of lightweight structures and as electrodes in lithium ion batteries. AlSi7Mg0.3 foams are produced by a modified investment casting process. By tuning the mold temperature, a change from the usual nearly monocrystalline dendritic to a polycrystalline globular grain structure is achieved. Tension and compression tests on single struts and foam specimens, respectively, are combined with digital image correlation, scanning electron microscopy, and phase contrast enhanced microcomputed tomography in a synchrotron facility to correlate the mechanical properties and the failure mechanisms with the microstructure. The globular foams exhibit a lower strength and a less pronounced subsequent stress drop than the dendritic foams and the deformation mechanism changes from shear band dominated failure to a layer by layer collapse, because of the lower strength and higher ductility of the globular struts. The dendritic struts have a more homogeneous microstructure, while the globular struts often contain silicon agglomerates in their central region. Accordingly, the latter struts exhibit a higher degree of scatter for the fracture strain. Thus, the arrangement of the silicon particles and the eutectic determines the mechanical properties on the strut level and thereby the failure behavior on the foam leve
PTCOG Ocular Statement Expert Summary of Current Practices and Future Developments in Ocular Proton Therapy
Get PDFAlthough rare cancers, ocular tumors are a threat to vision, quality of life, and potentially life expectancy of a patient. Ocular proton therapy OPT is a powerful tool for successfully treating this disease. The Particle Therapy Co Operative Ocular Group formulated an Evidence and Expert Based Executive Summary of Current Practices and Future Developments in OPT comparative dosimetric and clinical analysis with the different OPT systems is essential to set up planning guidelines, implement best practices, and establish benchmarks for eye preservation, vision, and quality of life measures. Contemporary prospective trials in select subsets of patients eg, tumors near the optic disc and or macula may allow for dosimetric and clinical analysis between different radiation modalities and beamline systems to evaluate differences in radiation delivery and penumbra, and resultant tumor control, normal tissue complication rates, and overall clinical cost effectiveness. To date, the combination of multimodal imaging fundus photography, ultrasound, etc , ophthalmologist assessment, and clip surgery with radiation planning have been keys to successful treatment. Increased use of three dimensional imaging computed tomography magnetic resonance imaging is anticipated although its spatial resolution might be a limiting factor eg, detection of flat diffuse tumor parts . Commercially produced ocular treatment planning systems are under development and their future use is expected to expand across OPT centers. Future continuity of OPT will depend on the following 1 maintaining and upgrading existing older dedicated low energy facilities, 2 maintaining shared, degraded beamlines at large proton therapy centers, and 3 developing adapted gantry beams of sufficient quality to maintain the clinical benefits of sharp beam conformity. Option 1 potentially offers the sharpest beams, minimizing impact on healthy tissues, whereas 2 and 3 potentially offer the advantage of substantial long term technical support and development as well as the introduction of new approaches. Significant patient throughputs and close cooperation between medical physics, ophthalmology, and radiation therapy, underpinned by mutual understanding, is crucial for a successful OPT servic
A new experiment to enable rapid systematic investigations of flux trapping dynamics for superconducting radio frequency cavity applications
Get PDFMany modern accelerators rely on superconducting radio frequency SRF cavities to accelerate particles. When these cavities are cooled to the superconducting state, a fraction of the ambient magnetic field e.g., Earth s magnetic field may be trapped in the superconductor. This trapped flux can significantly increase the power dissipation of the SRF cavities. It is, therefore, crucial to understand the underlying mechanism of how magnetic flux is trapped and what treatments and operating conditions can reduce the flux trapping efficiency. A new experiment was designed that enables a systemic investigation of flux trapping. It allows for independent control of cooldown conditions, which might have an influence on flux trapping temperature gradient across the superconductor during cooldown, cooldown rate, and ambient magnetic field. For exhaustive studies, the setup was designed for quick thermal cycling, permitting up to 300 superconducting transitions in one day. In this paper, the setup and operation is described in detail and an estimation of the measurement errors is given. Exemplary data are presented to illustrate the efficacy of the syste
R Vine Copulas for Data Driven Quantification of Descriptor Relationships in Porous Materials
Get PDFLocal variations in the 3D microstructure can control the macroscopic behavior of heterogeneous porous materials. For example, the permittivity through porous sheets or membranes is governed by local high volume pathways or bottlenecks. Due to local variations, unfeasibly large amounts of microstructure data may be needed to reliably predict such material properties directly from image data. Here it is demonstrated that a vine copula approach provides parametric models for local microstructure descriptors that compactly capture the 3D microstructure including its local variations and efficiently probe it with respect to selected, measurable properties. In contrast to common methods of complexity reduction, the proposed approach creates parametric models for the multivariate probability distribution of high dimensional descriptor vectors that inherently contain the complex, nonlinear dependencies between these descriptors. Therein, material properties are offered in physically motivated distributions of microstructure descriptors rather than as normally distributed data. Applied to porous fiber networks paper before and after unidirectional compression, it is shown that the copula based models reveal material characteristic relationships between two or more microstructure descriptors. In this way, the presented modeling approach can provide deeper insight into the microscopic origin of effective macroscopic properties of heterogeneous porous material
Metal Organic Framework Based Materials for Advanced Sodium Storage Development and Anticipation
No full textAs a pioneering battery technology, even though sodium ion batteries SIBs are safe, non amp; 64258;ammable, and capable of exhibiting better temperature endurance performance than lithium ion batteries LIBs , because of lower energy density and larger ionic size, they are not amicable for large scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal organic frameworks MOFs would o amp; 64256;er enormous opportunities for next generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for e amp; 64256;ective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipate