Hasil untuk "Chemistry"

C. Hawker, K. Wooley

K. Krauskopf, D. Bird

David A. Fletcher, R. Mcmeeking, D. Parkin

Yanjiao Jiang, J. Chen, Chao Deng et al.

J. Bull, J. Mousseau, G. Pelletier et al.

W. Roth, P. Nachtigall, R. Morris et al.

J. Bobacka, A. Ivaska, A. Lewenstam

Xin Yan, Xiao Cui, Liang-Shi Li

A. Lowe

T. Helgaker, S. Coriani, P. Jørgensen et al.

N. Ng, S. Brown, A. Archibald et al.

Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models. This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.

Hanno C. Erythropel, J. Zimmerman, T. Winter et al.

Verónica Estévez, M. Villacampa, J. Menéndez

I. Beletskaya, F. Alonso, V. Tyurin

Abstract Synthetic organic chemistry experienced a significant advance in the last quarter of the 20th century with the advent of the transition-metal catalyzed cross-coupling reactions. The utility of these reactions was universally acknowledged and expressed in the Chemistry Nobel prize awarded to professors Heck, Suzuki and Negishi in 2010. In this scenario, the discovery of the Suzuki-Miyaura reaction was a landmark that occupies a privileged position because of its versatility, compatibility and pivotal contribution to diverse disciplines, including materials science and drug discovery. Despite the substantial progress attained for this reaction until 2010, there is still room for improvement, particularly, if we are concerned about the health of the Earth and aware of the paramount importance to produce substances under the guidelines of sustainable and Green Chemistry. In the present review, we summarize the efforts devoted by a wide and specialized scientific community to upgrade the Suzuki-Miyaura reaction during the post-Nobel prize period. An overview covering new catalytic systems, methods and conditions is provided, together with some applications and updated mechanistic viewpoints.

Yiyun Chen, Liang‐Qiu Lu, Da‐Gang Yu et al.

D. Pollard, J. Woodley

Jia‐Hao Xie, Yi‐Ming Hou, Zhi‐Jie Wu et al.

ABSTRACT Herein, we report a highly efficient synthesis of aliphatic nitro compounds bearing multi‐contiguous stereocenters in good yields (up to 72%) with excellent diastereo‐ and enantio‐selectivities (up to 12:1 dr, and >99% ee) by combining copper‐catalyzed asymmetric conjugate addition of dialkylzinc reagents to nitroalkenes with iridium‐catalyzed asymmetric allylic substitution reaction. Stereodivergent construction of nonadjacent stereocenters (1,3‐positions) has been achieved by combining two chiral catalysts with different enantiomers. By first introducing a chiral center at the β‐position of the nitro group, highly diastereoselective control has been achieved in iridium‐catalyzed allylic substitution reaction of prochiral nitro compounds.

P. Jöckel, A. Kerkweg, A. Pozzer et al.

Abstract. The Modular Earth Submodel System (MESSy) is an open, multi-institutional project providing a strategy for developing comprehensive Earth System Models (ESMs) with highly flexible complexity. The first version of the MESSy infrastructure and process submodels, mainly focusing on atmospheric chemistry, has been successfully coupled to an atmospheric General Circulation Model (GCM) expanding it into an Atmospheric Chemistry GCM (AC-GCM) for nudged simulations and into a Chemistry Climate Model (CCM) for climate simulations. Here, we present the second development cycle of MESSy, which comprises (1) an improved and extended infrastructure for the basemodel independent coupling of process-submodels, (2) new, highly valuable diagnostic capabilities for the evaluation with observational data and (3) an improved atmospheric chemistry setup. With the infrastructural changes, we place the headstone for further model extensions from a CCM towards a comprehensive ESM. The new diagnostic submodels will be used for regular re-evaluations of the continuously further developing model system. The updates of the chemistry setup are briefly evaluated.

Magdalena Pająk, Agnieszka Dzieniszewska, Joanna Kyzioł-Komosińska

This study investigates the adsorption of Acid Black 1 (ABk 1) dye onto natural clinoptilolite (CLIN) and synthetic NaP1 zeolites under various conditions of adsorbent dose (5, 10, 20 g/L), dye concentration (1–1000 mg/L), and contact time (5–1440 min). The adsorption data were analyzed using Freundlich and Langmuir isotherms, as well as pseudo-first-order and pseudo-second-order kinetic models. Both linear and nonlinear regression methods were applied to assess the model fit. The results showed that CLIN exhibited maximum adsorption capacities of 35.32 mg/g, 21.9 mg/g, and 9.39 mg/g at doses of 5 g/L, 10 g/L, and 20 g/L, respectively. For NaP1, the corresponding values were 28.44 mg/g, 12.46 mg/g, and 9.11 mg/g. The pseudo-first-order model described adsorption at low dye concentrations and short contact times, while the pseudo-second-order model successfully explained adsorption across all tested conditions. These findings suggest that both zeolites, particularly CLIN, are effective adsorbents for ABk 1 dye removal, presenting a valuable solution for wastewater treatment applications.

Joanna Siwek, Konrad Pierzyński, Przemysław Siwek et al.

This paper introduces a novel artificial intelligence model that integrates artificial empathy into the decision-making processes of collaborative agent systems. The existing models of collaborative behaviors, especially in swarm applications, lack the aspect of empathy, known to improve cooperation in human teams. Emphasizing both cognitive and emotional aspects of empathy, the introduced model navigates communication uncertainties and ambiguities, transforming these challenges into opportunities for learning and adaptation in dynamic environments. A significant feature of this model is its handling of imprecision through fuzzy logic, using fuzzy similarity measures in the decision process. The main objective of the presented research is to introduce a new model for improving cooperativeness in multi-agent systems with the use of cognitive empathy. Future research focus on implementing the model on physical platform and optimize the artificial empathy algorithms in the decision-making module.