Some sulfides of gold and silver: Composition,mineral mineral assemblage,and conditions of formation

Characteristic mineral assemblage and special features of the composition of Au and Ag sulfides of gold-silver deposits have been established. The forms of the occurrence of Au and Ag in the minerals of the early and last stages have been analyzed. The conditions for the formation of uytenbogaardtite and petrovskaite in supergene and low-temperature hydrothermal processes have been considered. A thermodynamic model explaining their genesis in the oxidation zones is presented.     

An Open Grid Services Architecture Primer

To expand the use of distributed computer infrastructures as well as facilitate grid interoperability, OGSA has developed standards and specifications that address a range of scenarios, including high-throughput computing, federated data management, and service mobility.     

Aspects of cell calculations in deterministic reactor core analysis

Τhe capability of achieving optimum utilization of the deterministic neutronic codes is very important, since, although elaborate tools, they are still widely used for nuclear reactor core analyses, due to specific advantages that they present compared to Monte Carlo codes. The user of a deterministic neutronic code system has to make some significant physical assumptions if correct results are to be obtained. A decisive first step at which such assumptions are required is the one-dimensional cell calculations, which provide the neutronic properties of the homogenized core cells and collapse the cross sections into user-defined energy groups. One of the most crucial determinations required at the above stage and significantly influencing the subsequent three-dimensional calculations of reactivity, concerns the transverse leakages, associated to each one-dimensional, user-defined core cell. For the appropriate definition of the transverse leakages several parameters concerning the core configuration must be taken into account. Moreover, the suitability of the assumptions made for the transverse cell leakages, depends on earlier user decisions, such as those made for the core partition into homogeneous cells. In the present work, the sensitivity of the calculated core reactivity to the determined leakages of the individual cells constituting the core, is studied. Moreover, appropriate assumptions concerning the transverse leakages in the one-dimensional cell calculations are searched out. The study is performed examining also the influence of the core size and the reflector existence, while the effect of the decisions made for the core partition into homogenous cells is investigated. In addition, the effect of broadened moderator channels formed within the core (e.g. by removing fuel plates to create space for control rod hosting) is also examined. Since the study required a large number of conceptual core configurations, experimental data could not be available for comparison. For this purpose, corresponding reactivity results obtained by detailed geometry/high statistics Monte Carlo calculations, performed by the well documented neutronic code TRIPOLI, were utilized. It was concluded that the assumptions made for the transverse leakages in the one-dimensional cell calculations affect significantly the core reactivity computation. Small modifications in the parameters which determine the transverse cell leakages can induce k_eff modifications of the order of 10³ pcm. Significant factors for the suitability of the adopted assumptions were also shown to be the core size and the inclusion of several components, such as reflector or internal irradiation channels.     

Hydrogen Lean-DeNOx as an Alternative to the Ammonia and Hydrocarbon Selective Catalytic Reduction (SCR)

The present article consists a critical up-to-date review of the research conducted so far on the selective catalytic reduction of NO_x with hydrogen under lean-burn conditions as an alternative technology to the existing NH₃- and HC-SCR. Noble Metal based catalysts are described in detail with emphasis on the analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the support chemical composition and the preparation method and structure of the catalysts on the reaction mechanism is also discussed. Finally, the effects of various reaction parameters on the catalysts activity, selectivity and stability with reaction time are discussed in detail.     

Comparison of total intravenous, balanced inhalational and combined intravenous-inhalational anaesthesia for tympanoplasty, septorhinoplasty and adenotonsillectomy

The induction of complex bilateral leg muscle activation combined with coordinated stepping movements is demonstrated in patients with complete paraplegia. This was achieved by partially unloading patients who were on a moving treadmill. In comparison to healthy subjects, the paraplegic patients displayed a less dynamic mode of muscle activation. In all other respects leg muscle electromyographic activity was modulated in a similar manner to that in healthy subjects. However, the level of electromyographic activity in the gastrocnemius (the main antigravity muscle during gait) was considerably lower in the patients. During the course of a daily locomotor training program, the amplitude of gastrocnemius electromyographic activity increased significantly during the stance phase, while inappropriate tibialis anterior activation decreased. Incompletely paraplegic patients benefited from the training with respect to performance of unsupported stepping movements on solid ground. In about half of completely paraplegic patients with low muscle tone, no beneficial effect of the training was seen. This may be due to an inhibitory effect on spinal neuronal activity by drugs patients were taking (e.g., prazosin, clonidine, cannabinoids). In this study intrathecal application of clonidine drastically reduced, while epinephrine enhanced locomotor muscle electromyographic activity. The results of this study promise to be significant in the treatment of paraplegic patients.     

Role of the Anion on the Transport and Structure of Organic Mixed Conductors

Organic mixed conductors are increasingly employed in electrochemical devices operating in aqueous solutions that leverage simultaneous transport of ions and electrons. Indeed, their mode of operation relies on changing their doping (oxidation) state by the migration of ions to compensate for electronic charges. Nevertheless, the structural and morphological changes that organic mixed conductors experience when ions and water penetrate the material are not fully understood. Through a combination of electrochemical, gravimetric, and structural characterization, the effects of water and anions with a hydrophilic conjugated polymer are elucidated. Using a series of sodium‐ion aqueous salts of varying anion size, hydration shells, and acidity, the links between the nature of the anion and the transport and structural properties of the polymer are systematically studied. Upon doping, ions intercalate in the crystallites, permanently modifying the lattice spacings, and residual water swells the film. The polymer, however, maintains electrochemical reversibility. The performance of electrochemical transistors reveals that doping with larger, less hydrated, anions increases their transconductance but decreases switching speed. This study highlights the complexity of electrolyte‐mixed conductor interactions and advances materials design, emphasizing the coupled role of polymer and electrolyte (solvent and ion) in device performance.     

On the Role of Contact Resistance and Electrode Modification in Organic Electrochemical Transistors

Contact resistance is renowned for its unfavorable impact on transistor performance. Despite its notoriety, the nature of contact resistance in organic electrochemical transistors (OECTs) remains unclear. Here, by investigating the role of contact resistance in n‐type OECTs, the first demonstration of source/drain‐electrode surface modification for achieving state‐of‐the‐art n‐type OECTs is reported. Specifically, thiol‐based self‐assembled monolayers (SAMs), 4‐methylbenzenethiol (MBT) and pentafluorobenzenethiol (PFBT), are used to investigate contact resistance in n‐type accumulation‐mode OECTs made from the hydrophilic copolymer P‐90, where the deliberate functionalization of the gold source/drain electrodes decreases and increases the energetic mismatch at the electrode/semiconductor interface, respectively. Although MBT treatment is found to increase the transconductance three‐fold, contact resistance is not found to be the dominant factor governing OECT performance. Additional morphology and surface energy investigations show that increased performance comes from SAM‐enhanced source/drain electrode surface energy, which improves wetting, semiconductor/metal interface quality, and semiconductor morphology at the electrode and channel. Overall, contact resistance in n‐type OECTs is investigated, whilst identifying source/drain electrode treatment as a useful device engineering strategy for achieving state of the art n‐type OECTs.     

The Effect of Alkyl Spacers on the Mixed Ionic-Electronic Conduction Properties of N-Type Polymers

Conjugated polymers with mixed ionic and electronic transport are essential for developing the complexity and function of electrochemical devices. Current n-type materials have a narrow scope and low performance compared with their p-type counterparts, requiring new molecular design strategies. This work presents two naphthalene diimide-bithiophene (NDI-T2) copolymers functionalized with hybrid alkyl-glycol side chains, where the naphthalene diimide unit is segregated from the ethylene glycol (EG) units within the side chain by an alkyl spacer. Introduction of hydrophobic propyl and hexyl spacers is investigated as a strategy to minimize detrimental swelling close to the conjugated backbone and balance the mixed conduction properties of n-type materials in aqueous electrolytes. It is found that both polymers functionalized with alkyl spacers outperform their analogue bearing EG-only side chains in organic electrochemical transistors (OECTs). The presence of the alkyl spacers also leads to remarkable stability in OECTs, with no decrease in the ON current after 2 h of operation. Through this versatile side chain modification, this work provides a greater understanding of the structure-property relationships required for n-type OECT materials operating in aqueous media.     

Flexible Organic Photovoltaic Cells with In Situ Nonthermal Photoreduction of Spin‐Coated Graphene Oxide Electrodes

The first reduction methodology, compatible with flexible, temperature‐sensitive substrates, for the production of reduced spin‐coated graphene oxide (GO) electrodes is reported. It is based on the use of a laser beam for the in situ, non‐thermal, reduction of spin‐coated GO films on flexible substrates over a large area. The photoreduction process is one‐step, facile, and is rapidly carried out at room temperature in air without affecting the integrity of the graphene lattice or the flexibility of the underlying substrate. Conductive graphene films with a sheet resistance of as low as 700 Ω sq^?1 and transmittance of 44% can be obtained, much higher than can be achieved for flexible layers reduced by chemical means. As a proof of concept of our technique, laser‐reduced GO (LrGO) films are utilized as transparent electrodes in flexible, bulk heterojunction, organic photovoltaic (OPV) devices, replacing the traditional ITO. The devices displayed a power‐conversion efficiency of 1.1%, which is the highest reported so far for OPV device incorporating reduced GO as the transparent electrode. The in situ non‐thermal photoreduction of spin‐coated GO films creates a new way to produce flexible functional graphene electrodes for a variety of electronic applications in a process that carries substantial promise for industrial implementation.