Chemical Dynamics (United States)

The article presents the results of comprehensive studies of the current state of terrestrial and aquatic ecosystems in southeastern Yakutia, with the Ust-Maisky District of the Republic of Sakha (Yakutia) as the case study. The soil cover of the study area is characterized by vertical zonality with a predominance of permafrost Leptosols and Podzols, and high heavy metal concentrations, exceeding health standards, including elements of the first hazard class: mercury, zinc, and lead. The surface waters of watercourses surveyed in this area feature a low total dissolved solids content, neutral to weakly alkaline pH, and a predominance of bicarbonates, calcium, and magnesium in their ionic composition. Iron, copper, aluminum, and mercury levels in the water exceeded maximum permissible concentrations for fishery waterbodies, not only due to the natural features of the area but also under the mining impact. Industry-generated water in the tailings dumps at the villages of Allah-Yun and Zvezdochka contained elevated levels of lead, mercury, and cadmium. Analysis of bottom sediments revealed local accumulation of manganese, zinc, lead, and cobalt in natural watercourses, as well as mercury in man-made water bodies. In this context, the zooplankton community was found to be inhibited. In general, this area requires long-term monitoring to assess the pollution sources and their impact on the ecosystems. Particular attention should be given to abandoned hydraulic engineering facilities in the villages of Allah- Yun and Zvezdochka, with a recommendation to include them in the State Register of Accumulated Environmental Damage in order to develop measures to reduce environmental risks.

در این پژوهش، ابتدا طراحی و محاسبه مدار آنتن برای مشعل ICP به منظور تطبیق امپدانس اولیه انجام شده است. بر این اساس، امپدانس القایی مدار آنتن برای هر دو رژیم اتمسفری و خلأ به ترتیب حدود 36 و 50 اهم، بسیار بزرگ‌تر از مقاومت اهمی مدار که به ترتیب حدود 08/0 و 05/0 اهم بوده است. این مرحله از محاسبه مدار آنتن برای رسیدن به حالت سازگاری کلی بین منبع RF و محیط مدار آنتن است. در مرحله دوم، حین تشکیل پلاسما با توجه به تغییرات آن و یونیزه شدن گاز، شرایط دقیق‌تر سازگاری امپدانس به‌وسیله دستگاه تطبیق امپدانس به‌صورت خودکار انجام می͏گیرد. در مولدهای پلاسمایی جفت شده القائی، شرایط بهینه به پارامترهای کاری، نظیر فشار گاز، توان اعمال شده و هندسه مشعل وابسته است. مشخصات دستگاه مذکور با بسامد کاری MHz 56/13 و بیشینه توان kW 2 (در رژیم خلأ تا W 400 و در رژیم اتمسفری تا W 1800) است. دیگر دستاورد این پژوهش بهینه͏سازی مشعل در گستره وسیعی از پارامترهای فیزیکی است. رفتار افزایشی جریان برحسب افزایش توان الکتریکی و همچنمین ثابت ماندن تقریبی امپدانس (در رژیم اتمسفری) یا کاهش امپدانس (در رژیم خلأ) در گستره وسیع پارامترهای فیزیکی، نشانه شرایط بهینه است. در بازه توان ورودی از 200 تا 1800 وات به مشعل ICP اتمسفری، امپدانس مدار در گستره 8/0 تا 2/1 اهم تغییر می͏کند. در این حالت، تطبیق امپدانسی بین منبع و پلاسما به­گونه͏ایی است که جریان الکتریکی متناسب با توان، رفتار افزایشی داشته و شرایط تخلیه الکتریکی در مد مطلوب H قرار دارد. در رژیم خلأ، رفتار امپدانس با توان الکتریکی در حال تغییر بوده و در فشار mbar 1 و توان 350 وات، بیشینه جریان حدود 43 آمپر و امپدانس 19/0 اهم و شرایط کاری در حالت بهینه قرار دارد. دستاورد دیگر این پژوهش، راستی͏آزمایی مقدار تخمینی بزرگ مقیاس رسانش پلاسما 1-Ω 77/44 در مقایسه با مقدار کوچک مقیاس محاسبه شده 1-Ω 40 بوده و حاکی از سازگاری نتایج تجربی با نتایج نظری است.

The Front Cover shows that the self-reaction of the carbene species CHF, a main product from unimolecular dissociation of CH2F2, creates reactive radical species not considered in the literature. This chemistry is relevant to the flammability of CH2F2, a key parameter for determining the safe use of this commercial refrigerant. The relevant details of this combined experimental–theory–modeling study can be found in the Research Article by R. Sivaramakrishnan, R. S. Tranter and co-workers (DOI: 10.1002/cphc.202400362). Cover design by Argonne National Laboratory.

Maria Antonieta Antonacci possui graduação em História pela Universidade Federal do Rio Grande do Sul, além de ser mestra em História Econômica pela Universidade de São Paulo e pós-doutora em Antropologia Social pela École des Hautes Études en Sciences Sociales (EHESS),da França. Atualmente é professora associada da Pontifícia Universidade Católica de São Paulo demonstrando maestria em História da África, Culturas Africanas, Afro-Brasileiras e também em História do Brasil. É imprescindível citar que em 2003, quando promulgada a Leinº10.639, de 9 de janeiro de 2003,que estabelece a obrigatoriedade do ensino de História e Cultura Africana e Afro-brasileira nas escolas do Brasil, Antonacci posicionou-se veementemente contra o ensino, no curso de História da PUC-SP, de uma História Africana conta da sob a ótica de historiadores europeus.

Solid oxide fuel cells (SOFCs) are attractive devices for power generation because they can operate under a variety of fuels, including H2, hydrocarbon fuels, biogas, and syngas (CO + H2). Syngas is an important fuel since it is a major product of reforming hydrocarbon logistics fuels (i.e. JP-8, JP10, S8, etc.). However, the mechanism of electrochemical oxidation of CO in SOFCs is still not well understood. This is due, in part, to the difficulty in probing CO consumption and product formation under operating conditions in real time. Herein, the operando methods Fourier transform infrared emission spectra (FTIRES) of the SOFC headspace together with thermal imaging data of the Ni-YSZ anode surface to provide data relevant to understanding these reaction mechanisms. The studies are carried out on anode-supported SOFCs (Ni-YSZ/GDC-LSC button cells) operating on simulated syngas mixtures. The contamination and subsequent degradation of SOFC operation at operational temperatures of 600° C to 800° C, in the presence of sulfur concentrations below 30 ppm, is followed using potentiostatic spectroelectrochemistry, chronocoulometry, electrochemical impedance spectroscopy, and operando optical methodologies to provide a comprehensive picture of the processes occurring in the fuel oxidation. Together, the data obtained indicate that sulfur contaminants 1) competitively inhibit formation of carbon over CO catalytic and electrocatalytic sites, and 2) induce changes of the Ni-YSZ anode permanently perturbing their catalytic and electrocatalytic function.

HighlightsReduced graphene oxide (rGO) in electrode can weaken the light scattering of plasmonic Ag nanoparticles and promote the hot electrons transfer from Ag nanoparticles to Ti substrate.A route synergizing rGO with plasmonic Ag on TiO2 for plasmonic solar water splitting was provided.

Two mechanical extraction techniques were used for the extraction of environmentaly interesting elements from coal fly ash: shaking, in which the extraction process lasted from 6 to 24 hours, and ultrasonic sonication during 15 to 60 minutes, with water as extractant. The concentration of anions in fly ash extracts were determined by ion chromatography, while atomic absorption spectrometry was used for determination of: As, Pb, Cd, Ni, Cr, Zn, Cu, Fe, Mn and Al. The ultrasonic sonication yielded slightly higher amounts of extracted anions and Pb, Al, Mn and Fe, while shaking-assisted extraction was more efficient for the Cr, As, Zn and Ni ions. The changes in pH value, particle size distribution in colloid, zeta potential and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of fly ash particles in contact with water and different processes (adsorption, ion exchange, flocculation) that occur in environmental conditions. Principal Component Analysis were used for assessing the effect of observed process parameters. Essential from a practical point of view is a quantitative evaluation of these elements leachable from coal fly ash to surface waters in environmental conditions and contamination of the environment.