Photoredox catalysis of intramolecular cyclizations with a reusable silica-bound ruthenium complex

Photoredox catalysis with the use of a stable, reusable silica-bound chromophore was applied to the intramolecular cyclization of a series of 2-benzylidenehydrazinecarbothioamides to give 5-phenyl-1,3,4-thiadiazol-2-amines. The catalyst was readily prepared by carbodiimide-mediated coupling of commercially available amine-functionalized silica beads to a carboxylic acid functionalized ruthenium complex. The immobilized catalyst was readily removed from the reaction product by filtration and was used eight times without loss of catalytic activity. This simple, safe, and practical method is an attractive alternative to conventional procedures.

Microstructure and texture evolution during tensile deformation of symmetric/asymmetric-rolled low carbon microalloyed steel

The deformation and fracture mechanisms of a low carbon microalloyed steel processed by asymmetric rolling (AsR) and symmetric rolling (SR) were compared by microstructural and texture evolutions during uniaxial tensile deformation. A realistic microstructure-based micromechanical modeling was involved as well. AsR provides more effective grain refinement and beneficial shear textures, leading to higher ductility and extraordinary strain hardening with improved yield and ultimate tensile stresses as well as promoting the occurrence of ductile fracture. This was verified and further explained by means of the different fracture modes during quasi-static uniaxial deformation, the preferred void nucleation sites and crack propagation behavior, and the change in the dislocation density based on the kernel average misorientation (KAM) distribution. The equivalent strain/stress partitioning during tensile deformation of AsR and SR specimens was modeled based on a two-dimensional (2D) representative volume element (RVE) approach. The trend of strain/stress partitioning in the ferrite matrix agrees well with the experimental results.

Asymmetric risk and return: evidence from the Australian Stock Exchange

This paper examines volatility asymmetry in a financial market using a stochastic volatility framework. We use the MCMC method for model estimations. There is evidence of volatility asymmetry in the data. Our asymmetric stochastic volatility in mean model, which nests both asymmetric stochastic volatility (ASV) and stochastic volatility in mean models (SVM), indicates ASV sufficiently captures the risk-return relationship; therefore, augmenting it with volatility in mean does not improve its performance. ASV fits the data better and yields more accurate out-of-sample forecasts than alternatives. We also demonstrate that asymmetry mainly emanates from the systematic parts of returns. As a result, it is more pronounced at the market level and the volatility feedback effect dominates the leverage effect.

Enhanced mechanical response of an ultrafine grained Ti-6Al-4V alloy produced through warm symmetric and asymmetric rolling

An equiaxed ultrafine-grained (UFG) microstructure was successfully produced in a Ti-6Al-4V alloy with an average grain size of 110-230. nm through symmetric and asymmetric warm rolling of a martensitic starting microstructure. The UFG material displayed a combination of ultrahigh strength and ductility at room temperature. Compared with the conventional symmetric rolling, the asymmetric rolling process led to a more pronounced effect of microstructure refinement and a higher tensile ductility. The optimum mechanical response was obtained though the asymmetric rolling at 70% reduction, offering an ultimate tensile strength of 1365. MPa and a total elongation of ~23%. Apart from the magnitude of grain refinement, the inclination of basal texture component from the normal towards the rolling direction during asymmetric rolling and possible strain induced β to martensite transformation may concurrently contribute to a remarkable tensile strength-ductility balance.

Asymmetric oil shocks and external balances of major oil exporting and importing countries

This study investigates the effects of oil price shocks on three measures of oil exporters' and oil importers' external balances: total trade balance, oil trade balance and non-oil trade balance. We employ three second-generation heterogeneous linear panel models and one recently developed non-linear panel estimation technique that allows for cross-sectional dependence. With respect to 28 major oil exporting countries, an increase in oil prices leads to an improved real oil trade balance, although it is detrimental to non-oil and total trade balances. This finding might be due to the expenditure effect arising from increases in proceeds from oil exports. A decrease in oil prices is found to be beneficial for both total and oil trade balances in these oil exporting countries. Forty major oil importers seem to be increasingly shielded from positive oil shocks over the 1970s and 1980s; however, they must worry about oil price declines. A decline in oil prices has a negative impact on both total and real oil trade balances resulting from increased oil imports in emerging economies. Hence, a decline in oil prices is beneficial to oil exporters due to the quantity effect outweighing the price effect, while for oil importers a stable oil price is more desirable than a price decline. These results are important to take into account if we are to gain a full understanding on the magnitude of the trade and macroeconomic effects of oil price changes and what the policy responses should be.

Qualitative assessment of bubble behaviour for central and asymmetric injection in 2D gas-solid fluidized bed using image analysis technique and CFD modelling

Bubble characteristics such as shape, size, and trajectory control the hydrodynamics and therefore heat transfer in fluidized bed reactors. Thus understanding these characteristics is very important for the design and scaleup of fluidized beds. An earlier developed Eulerian-Eulerian two-fluid model for simulating dense gas–solid two-phase flow has been used to compare the experimental data in a pseudo-two-dimensional (2-D) bed. Bubbles are injected asymmetrically by locating the nozzle at proximity to the wall, thus presenting the effect wall has on asymmetrical injection as compared to symmetrical injection. In this work, a digital image analysis technique was developed to study the bubble behaviour in a two-dimensional bubbling bed. The high-speed photography reveals an asymmetric wake formation during detachment indicating an early onset of mixing process. The wall forces acts tangentially on thebubble and has a significant impact on the bubble shape, neck formation during detachment and its trajectory through the bed. Larger bubbles drifting away from the centre with longer paths are observed. This qualitative behaviour is well predicted by CFD modelling. Asymmetric injection can significantly influence the heat and mass transfer characteristics.

Asymmetric self-learning for tackling Twitter spam drift

Spam has become a critical problem on Twitter. In order to stop spammers, security companies apply blacklisting services to filter spam links. However, over 90% victims will visit a new malicious link before it is blocked by blacklists. To eliminate the limitation of blacklists, researchers have proposed a number of statistical features based mechanisms, and applied machine learning techniques to detect Twitter spam. In our labelled large dataset, we observe that the statistical properties of spam tweets vary over time, and thus the performance of existing ML based classifiers are poor. This phenomenon is referred as 'Twitter Spam Drift'. In order to tackle this problem, we carry out deep analysis of 1 million spam tweets and 1 million non-spam tweets, and propose an asymmetric self-learning (ASL) approach. The proposed ASL can discover new information of changed tweeter spam and incorporate it into classifier training process. A number of experiments are performed to evaluate the ASL approach. The results show that the ASL approach can be used to significantly improve the spam detection accuracy of using traditional ML algorithms.

Ion-tagged prolinamide organocatalysts for the direct aldol reaction on-water

A concise synthesis of two imidazolium ion-tagged prolinamide organocatalysts 3 and 4, varying in anionic component (CF3COO- and PF6 -, respectively) is presented. The latter could be classified as an ionic liquid with a melting point of 66.3 °C, and glass transition temperature of 14.5 °C. The efficiency of each catalyst was compared via a direct aldol reaction revealing a large contrast in catalytic performance, with the catalyst bearing the PF6 - anion being superior. The optimal conditions were determined to be an on-water reaction system, and substrate scoping gave a range of desired aldol products in high conversion (up to >99 %), dr (up to 98:2), and er (up to 96:4). The application of these catalysts to beta-nitrostyrene conjugate addition is also presented. Graphical Abstract: [Figure not available: see fulltext.]

The asymmetric behavior of the U.S public debt

Our main goal in this paper was to measure how e¢ cient is risk sharing between countries. In order to do so, we have used a international risk sharIn this paper we re-analyze the question of the U.S. public debt sustainability by using a quantile autoregression model. This modeling allows for testing whether the behavior of U.S. public debt is asymmetric or not. Our results provide evidence of a band of sustainability. Outside this band, the U.S. public debt is unsustainable. We also nd scal policy to be adequate in the sense that occasional episodes in which the public debt moves out of the band do not pose a threat to long run sustainability.

Central limit theorem for asymmetric kernel functionals

Asymmetric kernels are quite useful for the estimation of density functions with bounded support. Gamma kernels are designed to handle density functions whose supports are bounded from one end only, whereas beta kernels are particularly convenient for the estimation of density functions with compact support. These asymmetric kernels are nonnegative and free of boundary bias. Moreover, their shape varies according to the location of the data point, thus also changing the amount of smoothing. This paper applies the central limit theorem for degenerate U-statistics to compute the limiting distribution of a class of asymmetric kernel functionals.

The asymmetric behavior of the U.S. public debt

In this paper we re-analyze the question of the U.S. public debt sustainability by using a quantile autoregression model. This modeling allows for testing whether the behavior of U.S. public debt is asymmetric or not. Our results provide evidence of a band of sustainability. Outside this band, the U.S. public debt is unsustainable. We also find fiscal policy to be adequate in the sense that occasional episodes in which the public debt moves out of the band do not pose a threat to long run sustainability.

Equilibrium theory with asymmetric information and infinitely many states

Radner (1968) proved the existence of a competitive equilibrium for differential information economies with finitely many states. We extend this result to economies with infinitely many states of nature.

Essays on asymmetric information problems without the single-crossing property: applications to corporate finance

The objective of this dissertation is to re-examine classical issues in corporate finance, applying a new analytical tool. The single-crossing property, also called Spence-irrlees condition, is not required in the models developed here. This property has been a standard assumption in adverse selection and signaling models developed so far. The classical papers by Guesnerie and Laffont (1984) and Riley (1979) assume it. In the simplest case, for a consumer with a privately known taste, the single-crossing property states that the marginal utility of a good is monotone with respect to the taste. This assumption has an important consequence to the result of the model: the relationship between the private parameter and the quantity of the good assigned to the agent is monotone. While single crossing is a reasonable property for the utility of an ordinary consumer, this property is frequently absent in the objective function of the agents for more elaborate models. The lack of a characterization for the non-single crossing context has hindered the exploration of models that generate objective functions without this property. The first work that characterizes the optimal contract without the single-crossing property is Araújo and Moreira (2001a) and, for the competitive case, Araújo and Moreira (2001b). The main implication is that a partial separation of types may be observed. Two sets of disconnected types of agents may choose the same contract, in adverse selection problems, or signal with the same levei of signal, in signaling models.