31 research outputs found
IDENTIFICATION AND QUANTIFICATION OF QUINONES IN ENVIRONMENTAL SAMPLES
No full textQuinones represent an important class of compounds, widely recognized redox-reactive organic substances in natural organic matter (NOM). Despite their critical importance in biogeochemical cycles, degradation of pollutants, and greenhouse gas (GHG) emission, their precise structure and abundance in environmental samples have puzzled environmental geochemists for decades due to the complexity of environmental samples. To tackle the grand challenge of identifying and quantifying quinones, this study aimed to: 1. Develop a chemical tagging method for quinone identification; 2. Identify quinones in complex environmental samples by integrating chemical tagging with metabolomic analysis; 3. Screen and isolate quinones through coupling chromatography separation with redox reactivity screening; and 4. Establish a method for quantifying the total quinone concentrations in environmental samples. A selective chemical tagging method for quinones was developed by using Michael addition reactions with cysteine (Cys) and cysteine-containing peptides (CCPs), and validated by UV and mass spectra (MS) analysis using model quinones. Quinones in biochars were identified by coupling chemical tagging with Cys and/or CCPs to metabolomic analysis based on high-performance liquid chromatography-high resolution tandem mass spectrometry (HPLC-HRMS/MS) analysis. Total quinones in water extraction of environmental samples were measured by integrating specific tagging with non-aromatic CCPs with size exclusionary chromatography (SEC) analysis. Analysis of Swiss biochar shows a diverse pool of quinones (390 candidates) tagged with Cys or CCPs. Benzoquinone and methyl-p-benzoquinone were confirmed, and additional high-confidence candidates include C7H6O5, C11H10O3, C12H12O3, and C12H12O4. Redox reactivity screening-based chromatography separation isolated new quinones with two quinone functional groups, i.e., doxorubicin derivatives. From quinone quantification analysis, pyrogenic carbon from wildfires showed three times higher quinone concentration (1 – 14 μM) and reactivity than background soils. In summary, this study developed innovative methodologies for identifying quinones and quantifying their concentrations in complex environmental media. These methods identified the chemical structures of quinones in complex biochar extracts, and novel quinones were isolated. Future investigations using the methods developed herein may replace the enigmatic black box of redox-reactive NOM with compounds characterized by their structures and concentrations
A Narrative Review of Personal Protective Equipment Uses in Coronavirus Disease 2019 and Its Disposable Practices
No full textSince severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for causing coronavirus disease 2019 (COVID-19), is transmitted through close contact and droplets, people, especially those at risk of infection, must follow preventive measures in the community and healthcare settings. Healthcare personnel (HCP) must appropriately select and use personal protective equipment (PPE) with sensible donning and doffing and disposal practices. A narrative review of the existing literature was conducted, in which articles from Scopus, PubMed, Google Scholar, ScienceDirect, and Web of Science were collected. The primary findings of the retained articles were reviewed according to official recommendations on PPE use. The World Health Organization (WHO), US Centers for Disease Control and Prevention (CDC), and European Center for Disease Control and Prevention (ECDC) recommend standard precautions for contact transmission, respiratory transmission, and droplet precautions among HCPs caring for patients with COVID-19. Indeed, healthcare workers working in high-risk areas, as well as the public, when social distancing cannot be assured, must wear PPE such as face mask and protective eyewear to prevent the transmission of SARS-CoV-2 infection. Due to the increased use of PPE, the potentially infectious waste stream has been rapidly increasing, requiring safe and adequate solid waste management. The proper use of PPE and management of waste generated from COVID-19 care centers can reduce the risk of COVID-19 infection. These measures should be implemented to counter the rapid spread and any long-term impacts of the current pandemic
The effects of size and surface-coating of CuO-nanoparticles on extractable Cu and enzyme activities in soil
No full textThe application of nano-enabled agricultural chemicals introduces metal oxide nanoparticles (NPs) into agricultural soils, with CuO-NPs as one of the most common. Because CuO-NPs can dissolve to release Cu ions, they often display different environmental impacts. As such, it is essential to comprehensively examine the Cu bioavailability of CuO-NPs in soil and its impacts on soil enzyme activities, which are critical for soil health. This research examined how variations in CuO-NP size (10, 40, and 80 nm), surface coatings (polyvinylpyrrolidone and polyacrylic acid), and concentrations (100, 250, and 500 mg/kg) influenced the extractable Cu in soil and their impacts on selected soil enzymes (acid phosphatase and dehydrogenase). Main indicators were quantified after a 30-day incubation period. The bioactive Cu related to CuO-NPs as determined via CaCl2 and DTPA extractions indicated that 10 nm CuO-NPs had the highest extractable Cu across all incubation times. Besides, polyvinylpyrrolidone and polyacrylic acid coating had little impact on extractable Cu compared to uncoated ones. Unlike CuSO₄, extractable Cu concentrations in CuO-NPs spiked soil increased over time. CuO-NPs dissolution was negatively correlated with soil pH. CuO-NPs after 24 h short-term exposure significantly inhibited both enzyme activities across all tested concentrations, with smaller NPs showing greater effect. However, reduced toxicity to enzyme activities was observed after 30 days. A strong negative correlation was observed between CuO dissolution and enzyme activities after 1 and 30 days, indicating Cu ions are the main toxicity source. This study elucidates that CuO-NP size, concentration, surface coating, and exposure duration collectively impact the interactions of CuO-NPs with soil enzymes, providing critical insights into the sustainable use of nanotechnology in agriculture
Would There Be Surplus Grains for Biofuels? An Assessment of Agro-economic Factors and Biofuel Production Potential at the Global Level
No full textPaper removed for editing by author 10/19/11.biofuel, land resources, productivity increase, food supply, Crop Production/Industries, Resource /Energy Economics and Policy, Q0, Q42, Q18,
'Operation Enduring Nightmare'? : a strategic critique of the military intervention in Afghanistan from October 2001-October 2008
No full textIncludes abstract.Includes bibliographical references.In October 2011, the war in Afghanistan reached its ignominious ten year anniversary. As the conflict rolls on relentlessly, observers from across all disciplines, and indeed the general public themselves, have attempted to identify why the intervention, which began as Operation Enduring Freedom, has instead become an ‘Enduring Nightmare’. This dissertation attempts to provide empirical reasoning to this question by means of a literature review of the established strategic critiques of the intervention between the years of October 2001 and October 2008
Modelling of Hydroabrasive Erosion in Pelton Turbine Injector
No full textSand particle-led erosion in the turbine parts of hydropower projects (excluding storage type projects) based on Himalaya-originated Rivers is one of the key operational challenges for concerned hydropower stations. Researchers have made multiple attempts to understand the nature of erosion and its combating technique by using numerical and experimental modelling techniques. This study relates to numerical and experimental modelling of sand particle-led erosion in the injector of the most preferred high head turbine, i.e., the Pelton turbine, followed by a comparative analysis of both techniques. This article attempts to compare erosion qualitatively and quantitatively, thus adding to the current state of the art of turbine erosion modelling. The results direct that the erosion-prone area is the needle seat in the nozzle and the region between the needle tip and nozzle exit in the needle, similar to findings reported by authors performing field setting research. The innovative aspect of the study is that by mapping the shape of the initial and eroded needle, mass lost in the erosion-prone area (as indicated by numerical erosion modelling) is calculated and compared against numerical modelling results. With the Oka erosion model employed for numerical modelling, the error in computation is about 31%. The nature of erosion in a partially open injector reveals that erosion in the needle increases with the nozzle’s partial opening. Nozzle erosion spreads away from the needle seat to the whole nozzle body. As commonly understood, the erosion of turbine parts gives rise to mechanical vibrations (especially in rotating parts) and energy loss. Numerical modelling results of injector erosion’s effect on jet energy are also presented. With uniformly spread erosion of 0.5 mm in both the needle and nozzle, loss in jet energy is 5.63%
Urban Road Transportation Externalities: Costs and Choice of Policy Instruments
No full textUrban transportation externalities are a key development challenge. Based on the existing literature, the authors illustrate the magnitudes of various external costs, review response policies, and measure and discuss their selection, particularly focusing on the context of developing countries. They find that regulatory policy instruments aimed at reducing local air pollution have been introduced in most countries in the world. On the other hand, fiscal policy instruments aimed at reducing congestion or greenhouse gas emissions are limited mainly to industrialized economies. Although traditional fiscal instruments, such as fuel taxes and subsidies, are normally introduced for other purposes, they can also help to reduce externalities. Land-use or urban planning, and infrastructure investment, could also contribute to reducing externalities; but they are expensive and play a small role in already developed megacities. The main factors that influence the choice of policy instruments include economic efficiency, equity, country or city specific priority, and institutional capacity for implementation. Multiple policy options need to be used simultaneously to reduce effectively the different externalities arising from urban road transportation because most policy options are not mutually exclusive. Copyright The Author 2010. Published by Oxford University Press on behalf of the International Bank for Reconstruction and Development / <sc>the world bank</sc>. All rights reserved. For permissions, please e-mail: [email protected], Oxford University Press.
Semi-supervised regression using diffusion on graphs
No full textIndexación ScopusIn real-world machine learning applications, unlabeled training data are readily available, but labeled data are expensive and hard to obtain. Therefore, semi-supervised learning algorithms have gathered much attention. Previous studies in this area mainly focused on a semi-supervised classification problem, whereas semi-supervised regression has received less attention. In this paper, we proposed a novel semi-supervised regression algorithm using heat diffusion with a boundary-condition that guarantees a closed-form solution. Experiments from artificial and real datasets from business, biomedical, physical, and social domain show that the boundary-based heat diffusion method can effectively outperform the top state of the art methods. © 2021 The Author(s)https://www-sciencedirect-com.recursosbiblioteca.unab.cl/science/article/pii/S1568494621001113?via%3Dihu
Effect Of Company Size On Manager's Perception
No full textThe purpose of this study is to explore the effect of a company’s size on its manager’s perception towards changes in market needs and manufacturing flexibility. To serve the purpose,a questionnaire was designed by considering different types of manufacturing flexibility and changes occurring in market needs. The collected data were then analyzed to verify the proposed hypotheses. The results showed that a company’s size significantly influence manager’s perception towards manufacturing flexibility and market requirements. For instance,reliability is given higher priority by managers of micro and small enterprises in comparison with managers of medium and large enterprises. Similarly, routine flexibility is found to be significantly more important to managers of micro and small enterprises, while production facility flexibility is considered more important by managers of medium and large enterprises. Furthermore, the results showed that there is a positive relationship between changes in market requirements and manufacturing flexibility, showing that manufacturing flexibility is governed by changes in market requirements. This research was conducted with managers at various companies in the energy sector; so the results may not be applicable to other industries.© 2014 The author(s). The article is published under the terms of the Creative Commons Attribution-Non-Commercial-NoDerivs license (https://creativecommons.org/licenses/by-nc-nd/3.0/).fi=vertaisarvioitu|en=peerReviewed
