The influence of the ion content of whey on the pH-activity profile of the β-galactosidase from Aspergillus oryzae

The pH-dependence of the reaction kinetics of lactase (β-galactosidase) from Aspergillus oryzae in different reaction media is presented in terms of a two-parameter model. The lactase from A. oryzae seems to have replaced the A. niger lactase on the market owing to a better activity/price ratio and may be utilised for lactose hydrolysis in acid as well as in neutral milk products. Its pH optimum is around pH 4.5. However, in the neutral pH-range its activity depended strongly on the salt content of the substrate solution. For example, its activity in whey (pH 6.5) fell to only 30% of its expected activity in a pure lactose solution at the same pH. The whey effect was the same for both soluble and immobilised lactase. The two parameter kinetic model, which included a term for competitive product inhibition gave excellent agreement with experimental data, and may thus be useful for the prediction of reactor performance with this enzyme.     

Low Temperature Water–Gas Shift/Methanol Steam Reforming: Alkali Doping to Facilitate the Scission of Formate and Methoxy C–H Bonds over Pt/ceria Catalyst

Doping Pt/ceria catalysts with the Group 1 alkali metals was found to lead to an important weakening of the C–H bond of formate and methoxy species. This was demonstrated by a shift to lower wavenumbers of the formate and methoxy ν(CH) vibrational modes by DRIFTS spectroscopy. Li and Na-doped Pt/ceria catalysts were tested relative to the undoped catalyst for low temperature water–gas shift and methanol steam reforming using a fixed bed reactor and exhibited higher catalytic activity. Steaming of formate and methoxy species pre-adsorbed on the catalyst surface during in-situ DRIFTS spectroscopy suggested that the species were more reactive for dehydrogenation steps in the catalytic cycle for the Li and Na-doped catalysts relative to undoped Pt/ceria. However, with increasing atomic number over the series of alkali-doped catalysts, the stability of a fraction of the carbonate species was found to increase. This was observed during TPD-MS measurements of the adsorbed CO₂ probe molecule by a systematic increase of a high temperature peak for a fraction of the CO₂ desorbed. This result indicates that alkali-doping is an optimization problem—that is, while improving the dehydrogenation rates of methoxy and formate species, the carbonate intermediate stability increases, making it difficult to liberate the CO₂. Infrared spectroscopy results of CO adsorbed on Pt and ceria suggest that the alkali dopant is located on, and electronically modifies, both the Pt and ceria components. The results not only lend further support to the role that methoxy and formate species play as intermediates in the catalytic mechanisms, but also provide a path forward for improving rates by means other than resorting to higher noble metal loadings.     

Comparing problem formulations for coupled sets of components

This paper presents several formulations and comparative test results for problems involving the general paradigm of coupled sets of components (CSoC). This paradigm is general enough to include systems of systems (SoS) under any of the various definitions, as well as multidisciplinary design optimization (MDO). It is assumed that a CSoC involves a (potentially inactive) coordinating component, or “Central Authority”, and one or more, potentially interacting, subordinate components. The formulations differ in the amount of control given to the CA versus the autonomy granted to the subordinate components. In this generality, satisfaction of equilibrium conditions replaces the optimality condition in defining a solution. A solution still requires feasibility of all constraints. The desirability of a particular equilibrium point depends on the specific problem being studied and the component algorithms used to obtain that equilibrium. These concepts are illustrated using comparative test results for several of the formulations on a NASA-generated, public domain, aircraft conceptual design problem.     

The investigation of contact performance of oxide reinforced copper composite via mechanical alloying

In this study, the electrical performance of ODS Cu-based contact materials produced by mechanical alloying (MA) was investigated. Cu-based powder mixtures that contain various oxides at different proportions were milled by the high energy planetary ball mill for 5 h. Mechanically alloyed powder mixtures containing ZnO, Al₂O₃ and Y₂O₃ at the ratios of 1, 2, 4 and 6 wt.% were pressed and sintered at 800 °C in vacuum environment. These compacts were then forged axially at the ratio of 75% at 650 °C so as to increase the density. At the first step, electrical conductivity experiments were applied to these samples to determine the best conductivity. Results showed that, reinforced Cu samples containing 4% oxides exhibited the best. At the second step, contact count experiments were made with these samples for determining contact performance for the counts of 3000, 6000 and 9000 turn on/off. The samples of 4 wt.% ZnO, 4 wt.% Al₂O₃, 4 wt.% Y₂O₃ reinforced Cu materials, respectively, exhibited both the best conductivity and the best contact performances.     

Thin layer drying kinetics of Gundelia tournefortii L.

The literature surveyed revealed that the drying kinetics of Gundelia tournefortii has not been investigated. In this study, mathematical modeling of the thin layer drying kinetics of G. tournefortii is investigated for both the microwave and open sun drying conditions. Five different microwave power levels ranging from 90 to 800 W were used for the microwave drying. Solar radiation for the open sun drying varied from 350 to 1100 W/m². Drying took place in the falling rate period. Increasing the microwave power caused a significant decrease in drying time. The experimental moisture loss data were fitted to the 14 thin layer drying models. Among the models proposed, the Midilli model precisely represented the microwave drying behavior of G. tournefortii with the coefficient of determination higher than 0.996 and mean square of deviation (χ²), root mean square error (RMSE) and mean bias error (MBE) lower than 1.82 × 10^?4, 12 × 10^?3 and 1.4 × 10^?4, respectively for all the microwave drying conditions studied. Values of drying constant (k) were in the range of 0.0098–0.2943 min^?1 and the effective moisture diffusivities (D_eff) of G. tournefortii ranged from 5.5 × 10^?8 to 3.5 × 10^?7 m²/s. The values of k and D_eff increased with the increase of microwave power level. The logarithmic model was found to best describe the open sun drying kinetics of G. tournefortii. The effective diffusivity of G. tournefortii under the sun drying condition was determined as 2.48 × 10^?10 m²/s.     

An analysis of silver candlesticks from a casting point of view： originals, copies, forgeries

Collecting silver artefacts has traditionally been a very popular hobby.Silver is addictive,therefore the number of potential collectors and investors appears to grow each year.Unfortunately,increases in the interest and buying potentials resulted in a number of forgeries manufactured and introduced to the open antique market.The items such as early silver candlesticks dictate a very high price,for many high quality fakes show very good appearances and matching similarities with originals.Such copies are tr...     

The production of graphene nano layers by using milling—exfoliation hybrid process

Even though high quality graphene can be produced through chemical exfoliation of Graphite or Expanded graphite (EG), the amount of acquired products is limited. Graphite powders were subjected to a pre-milling process with prevailing shear stress in order to increase the amount of products. Therefore, separation of hexagonal layers through pre-separation process was targeted. The milled powders were firstly mixed in the saturated acid mixture containing H₂SO₄ and HNO₃, and then heated to 950°C. At the end of process, the distance between layers was expanded and the structure called as expanded graphite was obtained. Separation of layers and formation of graphene were provided by stirring expanded graphite within a chemical solvent for a while. The obtained samples were examined by using X-ray analysis, electron microscopy analysis, and Raman spectroscopy analysis. Despite the fact that there is a production method for graphene by chemical exfoliation, addition of the milling into steps of this process is an unusual step. Although a great amount of amorphous structures occurred in the structure at the end of milling process in this study, there were still graphitic structures preserving its hexagonality in the sample even if just a little. Most of amorphous carbon was removed from the structure as a result of applying further steps of process to milled graphite. A great part of graphitic structures apart from amorphous carbon structures were transformed into graphene. Even though amorphous carbon structures and defects were still found in the product, the obtained graphenes were relatively qualified and of high amount.     

Low Temperature Water–Gas Shift: Alkali Doping to Facilitate Formate C–H Bond Cleaving over Pt/Ceria Catalysts—An Optimization Problem

Doping Pt/ceria catalysts with alkali metals was found to lead to an important weakening of the formate C–H bond, as demonstrated by a shift to lower wavenumbers of the ν(CH) vibrational mode. However, with high alkalinity (∼2.5%Na or equimolar amounts of K, Rb, or Cs), a tradeoff was observed such that while the formate became more reactive, the stability of the carbonate species, which arises from the formate decomposition, was found to increase. This was observed by TPD-MS measurements of the adsorbed CO₂ probe molecule. Increasing the amount of alkali to levels that were too high also led to lower catalyst BET surface area, the blocking of the Pt surface sites as observed in infrared measurements, and also a shift to higher temperature of the surface shell reduction step of ceria during TPR. When the alkalinity was too high, the CO conversion rate during water–gas shift decreased in comparison with the undoped Pt/ceria catalyst. However, at lower levels of alkali, the abovementioned inhibiting factors on the water–gas shift rate were alleviated such that the weakening of the formate C–H bond could be utilized to improve the overall turnover efficiency during the water–gas shift cycle. This was demonstrated at 0.5%Na (or equimolar equivalent levels of K) doping levels. Not only was the formate turnover rate found to increase significantly during both transient and steady state DRIFTS tests, but this effect was accompanied by a notable increase in the CO conversion rate during low temperature water–gas shift.     

Encountering the Urban Crisis: The Gezi Event and the Politics of Urban Design

This article addresses an experimental urban design studio conducted in Bilkent University in Ankara, which problematized the protests that initially started in Gezi Park in Istanbul and shook Turkey in the summer of 2013. As will be argued in detail below, we claim that the Gezi event represents an urban crisis. The particular event was the rapid escalation of a small protest against the destruction of a public space into a nationwide anti-government insurrection. But it also represented a larger urban crisis: the increasing influence of neoliberalism on the city, as the protests were the outcome of a period marked by zealous commodification of urban space. In both instances, such urban conflicts have to be addressed by urban designers, since they produce the renewal projects that gentrify urban spaces and, at the same time, seek possible alternatives for a better urban environment.