Vapor Species Over Te Precious Metal Minerals

This paper reports on two developments of interest to extractive metallurgists: how the knowledge of the vapors over tellurium minerals can be used to develop better processing methods and how graphite furnace atomic absorption, used at moderate temperatures, can be used to characterize the vapors over ore minerals. Elemental tellurium, Ag₂Te, and AuTe₂ were studied from 250°C through 1050°C. The vapors over these solids were analyzed in-situ by placing the solids directly into the graphite furnace of an atomic absorption spectrophotometer and adjusting the temperature accordingly. Atomic Ag, Au, and Te and molecular Te were analyzed in the vapor above the solids. Using absorbance versus temperature data, Clausius-Clapeyron plots were made to determine how the solids were changing.     

Optimizing NFV placement for distributing micro-data centers in cellular networks

With the popularity of mobile devices, the next generation of mobile networks has faced several challenges. Different applications have been emerged, with different requirements. Offering an infrastructure that meets different types of applications with specific requirements is one of these issues. In addition, due to user mobility, the traffic generated by the mobile devices in a specific location is not constant, making it difficult to reach the optimal resource allocation. In this context, network function virtualization (NFV) can be used to deploy the telecommunication stacks as virtual functions running on commodity hardware to meet users’ requirements such as performance and availability. However, the deployment of virtual functions can be a complex task. To select the best placement strategy that reduces the resource usage, at the same time keeps the performance and availability of network functions is a complex task, already proven to be an NP-hard problem. Therefore, in this paper, we formulate the NFV placement as a multi-objective problem, where the risk associated with the placement and energy consumption are taken into consideration. We propose the usage of two optimization algorithms, NSGA-II and GDE3, to solve this problem. These algorithms were taken into consideration because both work with multi-objective problems and present good performance. We consider a triathlon circuit scenario based on real data from the Ironman route as an use case to evaluate and compare the algorithms. The results show that GDE3 is able to attend both objectives (minimize failure and minimize energy consumption), while the NSGA-II prioritizes energy consumption.

     

Application of a thermostable Baeyer–Villiger monooxygenase for the synthesis of branched polyester precursors

BACKGROUND

It is widely accepted that the poor thermostability of Baeyer–Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5‐trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ?‐caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi‐enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co‐factor regeneration.

RESULTS

Using reaction engineering, the reaction rate and product formation of the regio‐isomeric branched lactones were improved and the use of co‐solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water‐immiscible organic solvent. A maximum volumetric productivity, or space–time‐yield, of 1.20 g L^‐1 h^‐1 was achieved with continuous feeding of substrate using methanol as co‐solvent, while a maximum product concentration of 11.6 g L^‐1 was achieved with toluene acting as a second phase and substrate reservoir.

CONCLUSION

These improvements in key process metrics therefore demonstrate progress towards the up‐scaled Baeyer–Villiger monooxygenase‐biocatalyzed synthesis of the target building blocks for polymer application. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

     

Availability analysis of design configurations to compose virtual performance-optimized data center systems in next-generation cloud data centers

Next-generation cloud data centers are based on software-defined data center infrastructures that promote flexibility, automation, optimization, and scalability. The Redfish standard and the Intel Rack Scale Design technology enable software-defined infrastructure and disaggregate bare-metal compute, storage, and networking resources into virtual pools to dynamically compose resources and create virtual performance-optimized data centers (vPODs) tailored to workload-specific demands. This article proposes four chassis design configurations based on Distributed Management Task Force's Redfish industry standard applied to compose vPOD systems, namely, a fully shared design, partially shared homogeneous design, partially shared heterogeneous design, and not shared design; their main difference is based on the used hardware disaggregation level. Furthermore, we propose models that combine reliability block diagram and stochastic Petri net modeling approaches to represent the complexity of the relationship between the pool of disaggregated hardware resources and their power and cooling sources in a vPOD. These four proposed design configurations were analyzed and compared in terms of availability and component's sensitivity indexes by scaling their configurations considering different data center infrastructure. From the obtained results, we can state that, in general, when one increases the hardware disaggregation, availability is improved. However, after a given point, the availability level of the fully shared, partially shared homogeneous, and partially shared heterogeneous configurations remain almost equal, while the not shared configuration is still able to improve its availability.     

DCAV: A software system to evaluate next-generation cloud data center availability through a friendly graphical interface

To assess the availability of different data center configurations, understand the main root causes of data center failures and represent its low-level details, such as subsystem's behavior and their interconnections, we have proposed, in previous works, a set of stochastic models to represent different data center architectures (considering three subsystems: power, cooling, and IT) based on the TIA-942 standard. In this paper, we propose the Data Center Availability (DCAV), a web-based software system to allow data center operators to evaluate the availability of their data center infrastructure through a friendly interface, without need of understanding the technical details of the stochastic models. DCAV offers an easy step-by-step interface to create and configure a data center model. The main goal of the DCAV system is to abstract low-level details and modeling complexities, becoming the data center availability analysis a simple and less time-consuming task.     

High‐Performance Solution‐Processable Poly(p‐phenylene vinylene)s for Air‐Stable Organic Field‐Effect Transistors

The influence of the substitution pattern (unsymmetrical or symmetrical), the nature of the side chain (linear or branched), and the processing of several solution processable alkoxy‐substituted poly(p‐phenylene vinylene)s (PPVs) on the charge‐carrier mobility in organic field‐effect transistors (OFETs) is investigated. We have found the highest mobilities in a class of symmetrically substituted PPVs with linear alkyl chains (e.g., R¹, R² = n‐C₁₁H₂₃, R³ = n‐C₁₈H₃₇). We have shown that the mobility of these PPVs can be improved significantly up to values of 10^–2 cm² V^–1 s^–1 by annealing at 110 °C. In addition, these devices display an excellent stability in air and dark conditions. No change in the electrical performance is observed, even after storage for thirty days in humid air.     

Enzymatic Synthesis of Enantiopure α‐ and β‐Amino Acids by Phenylalanine Aminomutase‐Catalysed Amination of Cinnamic Acid Derivatives

The phenylalanine aminomutase (PAM) from Taxus chinensis catalyses the conversion of α‐phenylalanine to β‐phenylalanine, an important step in the biosynthesis of the N‐benzoyl phenylisoserinoyl side‐chain of the anticancer drug taxol. Mechanistic studies on PAM have suggested that (E)‐cinnamic acid is an intermediate in the mutase reaction and that it can be released from the enzyme's active site. Here we describe a novel synthetic strategy that is based on the finding that ring‐substituted (E)‐cinnamic acids can serve as a substrate in PAM‐catalysed ammonia addition reactions for the biocatalytic production of several important β‐amino acids. The enzyme has a broad substrate range and a high enantioselectivity with cinnamic acid derivatives; this allows the synthesis of several non‐natural aromatic α‐ and β‐amino acids in excellent enantiomeric excess (ee >99 %). The internal 5‐methylene‐3,5‐dihydroimidazol‐4‐one (MIO) cofactor is essential for the PAM‐catalysed amination reactions. The regioselectivity of amination reactions was influenced by the nature of the ring substituent.     

Synthesis of poly[(silanylene)thiophene]s

Poly[(silanylene)thiopene]s, copolymers with alternating thiophene, 2,2-bithiophene, or 2,2:5,5-terthiophene and mono-, di-, or tetrasilanylene units, were prepared by condensation of the dilithium salts of the thiophenes or the bis(2-thienyl)silanes with ,-dichlorosilanes in diethylether. The polymers were characterized with¹H,¹³C, and²⁹Si NMR, UV, IR, GPC, TGA, and elemental analyses. UV absorption maxima of these polymers all show a red shift with increasing length of the polymer backbone, suggesting that conjugation occurs through the combined -Si and -thiophene backbone.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.