Academic literature on the topic 'Forest products – Labeling'

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Journal articles on the topic "Forest products – Labeling"

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CARBONE, MARIAH S., CLAUDIA I. CZIMCZIK, KELSEY E. McDUFFEE, and SUSAN E. TRUMBORE. "Allocation and residence time of photosynthetic products in a boreal forest using a low-level14C pulse-chase labeling technique." Global Change Biology 13, no. 2 (February 2007): 466–77. http://dx.doi.org/10.1111/j.1365-2486.2006.01300.x.

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Aguilar, Francisco X., and Zhen Cai. "Conjoint effect of environmental labeling, disclosure of forest of origin and price on consumer preferences for wood products in the US and UK." Ecological Economics 70, no. 2 (December 2010): 308–16. http://dx.doi.org/10.1016/j.ecolecon.2010.09.002.

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Tan, Qin, Kohei Imamura, Kenji Nagasaka, and Masafumi Inoue. "Effects of Eco-Label Knowledge on Chinese Consumer Preferences for Certified Wood Flooring: A Case Study in Chongqing City." Forest Products Journal 69, no. 4 (January 1, 2019): 329–36. http://dx.doi.org/10.13073/fpj-d-19-00017.

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Abstract Expanding the use of eco-labeled wood flooring in China is an important step in achieving the country's sustainable development goals. For a deep understanding of the relationship between the knowledge of the eco-label and consumer preferences for certified wood flooring in China, this study assessed consumers' purchase intention (PI) and price premium (PP) for Forest Stewardship Council (FSC)- and China Environmental Labeling (CEL)-labeled wood flooring versus nonlabeled wood flooring. A total of 367 face-to-face interviews were conducted at building material markets in Chongqing City with visitors planning to purchase wood flooring in March 2018. The results showed, first, that 21 percent of respondents knew the FSC label, and 65 percent of respondents intended to buy FSC-labeled wood flooring with a PP of 41 CNY/m2. Second, 46 percent of respondents knew the CEL label, and 81 percent of respondents intended to buy CEL-labeled wood flooring with a PP of 48 CNY/m2. Third, the knowledge of the FSC label positively affected consumers' PI and PP, but the knowledge of the CEL label only influenced PI for certified wood flooring. This study showed that the eco-label knowledge played a main role in consumer preferences for certified wood products and suggested that different strategies should be considered in promoting FSC- and CEL-labeled wood products in the Chongqing market.
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Archer, Hadley, Robert Kozak, and David Balsillie. "The impact of forest certification labelling and advertising: An exploratory assessment of consumer purchase intent in Canada." Forestry Chronicle 81, no. 2 (April 1, 2005): 229–44. http://dx.doi.org/10.5558/tfc81229-2.

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This exploratory research of four Canadian cities, conducted in 2003, compares the impact of forest certification labelling and advertising on the purchase intent of wood and paper products by end-use consumers. Telephone survey results indicate that Canadians are concerned about the environment, have positive attitudes towards certification, and are willing to alter their purchase habits to favour certified wood and paper products. Respondents indicated that labelling would more likely influence their purchase decision than advertising. They also indicated a lack of awareness regarding forest certification, and that advertising was the preferred strategy to increase general awareness among consumers. A segment of consumers was identified, representing 70% of the sample, which is highly concerned about the environment, willing to seek out certified products, and favours labelling as a source of information to assist with their purchase decisions for certified forest products. Key words: forest certification, eco-labelling, green advertising, consumer purchase intent, green consumers
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Durst, P. B., P. J. McKenzie, C. L. Brown, and S. Appanah. "Challenges facing certification and eco-labelling of forest products in developing countries." International Forestry Review 8, no. 2 (June 2006): 193–200. http://dx.doi.org/10.1505/ifor.8.2.193.

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Deng, Xiuxiu, Zheng Shi, Lixiong Zeng, Lei Lei, Xuebing Xin, Shunxiang Pei, and Wenfa Xiao. "Photosynthetic Product Allocations to the Organs of Pinus massoniana Are Not Affected by Differences in Synthesis or Temporal Variations in Translocation Rates." Forests 12, no. 4 (April 12, 2021): 471. http://dx.doi.org/10.3390/f12040471.

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Photosynthesis and the allocation of photosynthetic products are the two main factors that determine plant growth. To understand the growth and productivity of Pinus massoniana Lamb., the diurnal changes in photosynthetic rate were continuously monitored. Furthermore, the translocation and allocation of the photosynthetic products synthesized in the morning and afternoon were explored using 13C pulse labeling. The results showed that: (1) on sunny days, the diurnal variation of the net photosynthetic rate showed a “double peak” curve, with an obvious “a depression” when temperatures were highest and humidity lowest. On cloudy days, it showed an irregular “jagged” curve, which was curve consistent with the variations in photosynthetically active radiation (PAR). Meanwhile, the photosynthetic rate changed with the transient changes in environmental factors such as PAR, temperature, and humidity. (2) The mean value of the net photosynthetic rate in the morning was higher than in the afternoon, and the response of the net photosynthetic rate to environmental change (PAR, temperature, humidity, and CO2 concentration) in the morning was greater than that in the afternoon. (3) The translocation of photosynthetic products synthesized in the afternoon was faster than that in the morning. Shortly after synthesis of photosynthetic products, the translocation of products synthesized in the morning tended toward upper organs (including current-year leaves and 1-year leaves), while the translocation of products synthesized in the afternoon decreased in the upper organs. However, after 15 days of 13C pulse labeling, the allocation of the photosynthetic products synthesized in the morning and afternoon tended to be the same. These results indicate that the differences in the photosynthetic products synthesized and the temporal differences in the translocation rates did not affect the final allocation of the photosynthetic products in the various organs of the P. massoniana. These results improve our knowledge of the functional phases of P. massoniana during the diurnal cycle.
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Wingate, K. G., and P. N. McFarlane. "Chain of custody and eco-labelling of forest products: a review of the requirements of the major forest certification schemes." International Forestry Review 7, no. 4 (December 2005): 342–47. http://dx.doi.org/10.1505/ifor.2005.7.4.342.

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Stephenie, Budi Warsito, and Alan Prahutama. "Sentiment Analysis on Tokopedia Product Online Reviews Using Random Forest Method." E3S Web of Conferences 202 (2020): 16006. http://dx.doi.org/10.1051/e3sconf/202020216006.

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Tokopedia is one of the most popular e-commerce sites in Indonesia that offers consumer products from various categories. In each product section, a review feature is offered. This review feature became essential in evaluating the sellers and become one consideration for customers in making purchase consideration. Sentiment analysis of Tokopedia product reviews may provide the opportunity to look on how Tokopedia customers respond to product quality and sellers’ hospitality. In evaluating the model, the reviews were grouped as: “positive sentiment” and “negative sentiment” using the Random Forest method and 10-fold cross-validation. Data labelling was carried out automatically by calculating the sentiment score using Lexicon-Based. Visualization of the labelling results was then done using a bar graph and a word cloud on each class of sentiment in order to look up for information that is considered important and most discussed. The test results showed that the accuracy of the Random Forest Method with parameter mtry = 73 and ntree = 50 is 97.38% which leads to the conclusion that the Random Forest Method could well predict the product reviews of Tokopedia. The greater the accuracy, the better performance of the classification model.
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Turpeinen, Tuomas, Timo Lappalainen, Eija Kenttä, and Katariina Torvinen. "Detection of iron and iron-cobalt labeled cellulose nanofibrils using ICP-OES and XµCT." Nordic Pulp & Paper Research Journal 33, no. 4 (December 19, 2018): 610–17. http://dx.doi.org/10.1515/npprj-2018-0015.

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Abstract When studying the properties of cellulose nanofibrils (CNF) enriched fiber products, it is essential to be able to determine the retention and the spatial distribution of the CNF inside the end-product. That is, to determine how much and where the CNF has been attached. As the CNF and cellulose fibers share the same density and chemical composition, labeling of the CNF is required to distinguish them from each other. In this work, we have applied iron and iron-cobalt -labeling. Labeling with iron is more desirable because of the carcinogenic and toxic properties of cobalt chloride. The benefits of our labeling method are the possibility to determine the retention of the labeled nanocellulose using inductively coupled plasma optical emission spectroscopy (ICP-OES), and to define the spatial distribution using X-ray micro-computed tomographic (XμCT). With XμCT we were able to measure fairly large samples (2 cm × 5 cm × 5 cm). Our study found that the retention of iron-labeled CNF was about 95 % and that of iron-cobalt labeled CNF was 84–94 %. Labeling of CNF improves the contrast of X-ray images. Labeled CNF is attached to fiber network also in the inner structures of the sample. Furthermore, when making thick porous structures using cationic starch, there might be agglomerates in the sample that cannot be visually detected by looking the sample.
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Vara, Saritha, Manoj Kumar Karnena, Bhavya Kavitha Dwarapureddi, and Bhavannarayana Chintalapudi. "Will Single Use Products Lead to Sustainability?" International Journal of Social Ecology and Sustainable Development 10, no. 2 (April 2019): 37–52. http://dx.doi.org/10.4018/ijsesd.2019040104.

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There has been intensification regarding environmental consciousness in recent decades with increased attention on generated waste. This might not be one of the most imperative of problems but surely is the one that is most instantaneously manageable. An individual may not be directly influenced by global climate change, the destruction of the rain forests, disasters like Chernobyl and Bhopal; nevertheless, the constant disposal of garbage is happening endlessly, immediate to us and is definitely under our control. One of the prime reasons for the tremendous increase in solid waste is disposable products, that are readily availability and disposed after a single use. Use of disposable products in all areas from food packing, product packing, hospitals, etc., continues to increase despite limited landfill space and dwindling natural resources. This has led to the term “throw-away society.” In the present article, the authors focus on such products which are growing in the market and highlight the environmental effects once they are discarded. In this context, their efforts are to make significant contributions that could be applied to the support of designing and environmental labeling disposable products. This is in an effort to promote production and consumption of product options which can be characterized for lowering environmental impacts.
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Dissertations / Theses on the topic "Forest products – Labeling"

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O'Brien, Kelly Ann. "Factors Affecting Consumer Valuation of Environmentally Labeled Forest Products." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/ObrienKA2001.pdf.

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Ham, Cornelis. "Green labelling : investigation into the marketing of FSC certified timber along the domestic timber value chain in South Africa." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/20835.

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Thesis (MBA)--Stellenbosch University, 2007.
ENGLISH ABSTRACT: Green consumerism is on the increase, especially in developed countries. Green labels plays a key role in informing and assuring consumers about the environmental credibility of the products that they purchase. Within the global forestry industry green label certification schemes have also had a large impact. More than 80% of the 1.3 million hectares of plantations in South Africa are certified under the Forestry Stewardship Council (FSC) green label standard. A research survey was undertaken amongst growers, processors and retailers of timber products in South Africa to assess the current FSC domestic market situation. The survey indicated that although growers and processors support FSC certification, as a way of improving the quality of forestry in South Africa, they receive very limited market benefits for FSC certified products and do not market FSC products actively. Hardware retailers were found to be unaware of FSC certification. Reports from other developing countries indicate similar trends. This raises the question if it is worth marketing FSC products to domestic consumers? The marketing of FSC certified products might not yield direct financial gains but it can help to improve the image of forestry companies and the forestry industry in general. FSC certification can be used as a way of showing corporate social responsibility towards consumers and in raising the profile of the South African forestry industry. Based on the results from the research survey a number of recommendations can be made regarding the marketing of FSC as a green label certification system in South Africa. A marketing campaign for FSC certified timber products should ideally focus on the social benefits of buying high quality timber products. This marketing message should be targeted at individual and corporate consumers. Individual consumers could be educated about the benefits of buying green label products while corporate consumers could be encouraged to use and sell FSC certified products as part of their corporate social responsibility. The promotion of FSC certification could also be boosted if it can be included in activities related to the 2010 Soccer World Cup. The different role players in the domestic timber value chain can each playa role in marketing FSC certified products. These roles differ from creating a promotional push in the timber value chain by growers, processors and retailers to a promotional pull amongst consumers by the FSC, NGO's, certification bodies, industry representatives and government. A marketing campaign for FSC products should ideally be coordinated and driven by the South African FSC National Initiative
AFRIKAANSE OPSOMMING: Groen verbruikersdruk is aan die toeneem, veral in ontwikkelde lande. Groen etikette speel 'n sleutelrol in die verskaffing van inligting en 'n versekering aan verbruikers oor die omgewingsgeloofwaardigheid van die produkte wat hulle koop. Groen sertifiseringskemas het ook 'n groot impak op die globale bosbou-industrie gehad. Meer as 80% van die 1.3 miljoen hektaar plantasies in Suid Afrika is gesertifiseer volgens die "Forestry Stewardship Council" (FSC) groen etiket standaard. 'n Navorsingsopname is onderneem onder kwekers, verwerkers en kleinhandelaars van houtprodukte in Suid Afrika. Die doel was om die huidige binnelandse marksituasie van FSC gesertifiseerde houtprodukte te ontleed. Die opname het getoon dat, alhoewel kwekers en verwerkers FSC sertifisering ondersteun as 'n manier om bosbou se kwaliteit in Suid Afrika te verbeter, hulle baie min markvoordeel uit FSC gesertifiseerde produkte kry en dat hulle nie FSC produkte aktief bemark nie. Daar is bevind dat hardeware kleinhandelaars onbewus is van FSC sertifisering. Verslae vanaf ander ontwikkelende lande dui op soortgelyke tendense. Dit laat ontstaan die vraag of dit die moeite werd is om FSC produkte aan binnelandse verbruikers te bemark? Die bemarking van FSC gesertifiseerde produkte mag dalk nie direkte finansieHe voordele inhou nie, maar kan help om die beeld van bosboumaatskappye en die bosboubedryf in die algemeen te verbeter. FSC sertifisering kan gebruik word om korporatiewe sosiale verantwoordelikheid aan verbuikers te demonstreer en om die profiel van die Suid-Afrikaanse bosbou industrie te verbeter. 'n Aantal aanbevelings, gebaseer op die resultate van die navorsingsopname, kan gemaak word oor die bemarking van FSC as 'n groen etiket sertifiseringstelsel in Suid Afrika. 'n Bemarkingsveldtog vir FSC gesertifiseerde houtprodukte behoort te fokus op die sosiale voordele van die koop van hoe kwaliteit houtprodukte. Individuele en korporatiewe verbruikers behoort geteiken te word met die bemarkingsboodskap. Individuele verbruikers kan opgelei word in die voordele van die koop van groen etiket produkte, terwyl korporatiewe verbruikers aangemoedig kan word om FSC produkte te gebruik en te verkoop as deel van hulle korporatiewe sosiale verantwoordelikheid. Die promosie van FSC sertifisering kan ook aangehelp word deur dit in te sluit by aktiwiteite wat betrekking het op die 2010 Sokker Wereldbeker. Die verskillende rolspelers in die binnelandse hout waardeketting kan elk 'n rol speel in die bemarking van FSC gesertifiseerde produkte. Hierdie rolle kan wissel vanaf die skepping van 'n promosie stootkrag in die hout waardeketting deur kwekers, verwerkers en kleinhandelaars tot die skepping van 'n promosie trekkrag onder verbruikers deur die FSC, nie-regeringsorganisasies, industriele verteenwoordigers en die regering. 'n Bemarkinsgveldtog behoort deur die Suid-Afrikaanse FSC Nasionale Inisiatief gedryf en geko6rdineer te word
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Books on the topic "Forest products – Labeling"

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Tropical wood labeling: Hearing before the Subcommittee on Commerce, Consumer Protection, and Competitiveness of the Committee on Energy and Commerce, House of Representatives, One Hundred Second Congress, second session on H.R. 2854, a bill to provide for the labeling or marking of tropical wood and tropical wood products sold in the United States, and related issues, May 13, 1992. Washington: U.S. G.P.O., 1992.

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Gladi, Hardiyanto, Lembaga Ekolabel Indonesia, and International Tropical Timber Organization, eds. Label hijau: Kompilasi pengetahuan dan pengalaman sertifikasi ekolabel di Indonesia. Bogor: Diterbitkan oleh Lembaga Ekolabel Indonesia atas kerjasama dengan ITTO (International Tropical Timber Organization), 2005.

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Morgan, Kevin, Terry Marsden, and Jonathan Murdoch. Worlds of Food. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780199271580.001.0001.

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From farm to fork, the conventional food chain is under enormous pressure to respond to a whole series of new challenges - food scares in rich countries, food security concerns in poor countries, and a burgeoning problem of obesity in all countries. As more and more people demand to know where their food comes from, and how it is produced, issues of place, power, and provenance assume increasing significance for producers, consumers, and regulators, challenging the corporate forces that shape the 'placeless foodscape'. Far from being confined to niche products, questions about the origins of food are also surfacing in the conventional sector, where labelling has become a major political issue. Drawing on theories of multi-level governance, three leading scholars in the field explore the geo-politics of the food chain in different spatial arenas: the World Trade Organization, where free trade principles clash with fair trade concerns in the debate about agricultural reform; the European Union, where producers are under pressure from environmentalists for a more traceable and sustainable food system; and the US, where there is a striking contradiction between the rhetoric of free markets and the reality of a heavily subsidised farming sector. To understand the local impact of these global trends, the authors explore three different regional worlds of food: the traditional world of localised quality in Tuscany, the peripheral world of commodity production in Wales, and the frontier world of agri-business in California.
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Book chapters on the topic "Forest products – Labeling"

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"What We May Have is a Failure to Communicate: Labeling Environmentally Certified Forest Products." In Labelling Strategies in Environmental Policy, 361–74. Routledge, 2017. http://dx.doi.org/10.4324/9781351154529-28.

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Hughes, Brian. "Old Enemies? July 1921–June 1922." In Defying the IRA? Liverpool University Press, 2017. http://dx.doi.org/10.5949/liverpool/9781781382974.003.0007.

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This chapter explores the year between the Truce and ceasefire between the Irish Republican Army (IRA) and the British forces in July 1921 and the outbreak of civil war in June 1922. First, it will examine non-lethal breaches of the terms of the Truce by the IRA and the reaction of Crown forces, highlighting a conflict between the political necessities of the Truce and the behaviour of local IRA units and civilians on the ground. Secondly, it will interrogate the nature of suspicion and the labelling of civilians at this time through a study of extant intelligence reports compiled by the IRA in early 1922. It will be seen that production of these files, and the IRA’s intelligence war more generally, was a product of the communities in which it was conducted and personal traits or labels that would have been well known in an everyday context were produced as evidence of suspicion. This idea will be expanded upon in the final section of the chapter as it takes a broader approach to civilian defiance and IRA punishment by dealing with the experiences of and perceptions towards specific minority groups, including Protestants, loyalists, and disbanded policemen.
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Dauvergne, Peter. "Million Dollar Pandas." In Environmentalism of the Rich. The MIT Press, 2016. http://dx.doi.org/10.7551/mitpress/9780262034951.003.0011.

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This chapter analyzes the turn within mainstream environmentalism toward business partnerships, cause marketing, professional fundraising, and the co-branding of products. The chapter further examines the role of nongovernmental organizations in setting up and running eco-labeling and eco-certification organizations. WWF, also known as the World Wildlife Fund and the World Wide Fund for Nature, is a leader in the nongovernmental embrace of business, markets, and certification as ways to conserve nature and improve environmental conditions. Certification standards, such as those of the Marine Stewardship Council and the Round Table on Responsible Soy, are creating some modest reforms to business practices. NGO-business partnerships, such as the one between WWF and Coca-Cola, are also producing some small-scale benefits. But partnering with business and relying on market solutions risks legitimizing business as usual as well as shifting responsibility for global environmental problems onto consumers, a weak global force of change compared to the forces of unsustainability.
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Bortiatynski, Jacqueline M., and Patrick G. Hatcher. "The Development of 13C Labeling and 13C NMR Spectroscopy Techniques to Study the Interaction of Pollutants with Humic Substances." In Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0007.

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Modern agricultural practices have contributed to the accumulation of herbicides, pesticides and their decomposition products in the soil. These pollutants are known to interact with soil organic matter to form covalent and/or noncovalent bonding associations. The covalent bonds are thought to result from addition or oxidative coupling reactions, some of which may be catalyzed by oxidoreductive enzymes. Noncovalent associations include such interactions as ion exchange, hydrogen bonding, protonation, charge transfer, ligand exchange, coordination through metal ions, van der Waals forces, and hydrophobic bonding. The association of pollutants with soil organic matter is an area of study that is of extreme interest for two reasons. First, dissolved organic matter present in lakes and streams is known to enhance the solubility of pollutants, which poses a real threat to the quality of fresh water supplies. Therefore, if we are to predict the movement of pollutants in the water table we need to have a mechanistic understanding of their interactions with dissolved humic materials. Second, early studies had indicated that some pollutants chemically bind to humic materials, thus reducing the risk of further transport and dispersion. If this chemical binding of the pollutants is irreversible, then this process may serve as a natural means for their detoxification. Regardless of the type of association, the first task in any mechanistic study is to characterize the reaction products structurally. In the case of noncovalent binding mechanisms, studies have focused on the physical characteristics of the process and not on the structure of the associated pollutant. Association studies are used to determine the sorption kinetics and transport of pollutants as well as their association constants. These types of studies utilize various techniques such as batch sorption, gas-purge desorption, column adsorption, and miscible displacement. All of these techniques are only capable of providing quantitative information on the amount of pollutant sorbed by a substrate. The study of the covalent binding of pollutants to humic substances has utilized 14C labeling in addition to various spectrometric techniques such as ultraviolet (UV) difference, fluorescence polarization and infrared (IR) spectroscopy.
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Conference papers on the topic "Forest products – Labeling"

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Koski, Oona. "UPM Raflatac: Labeling a smarter future with forest based products." In 5th European Congress of Conservation Biology. Jyväskylä: Jyvaskyla University Open Science Centre, 2018. http://dx.doi.org/10.17011/conference/eccb2018/109070.

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Wasley, Louise C., Andrew J. Dorner, and Randal C. Kaufman. "SYNTHESIS. PROCESSING AND SECRETION OF HUMAN FACTOR VIII IN MAMMALIAN CELLS: REQUIREMENT FOR VON WILLEBRAND FACTOR." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643874.

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In the plasma factor VIII exists as a complex with von Willebrand factor (vWF). The cloning of the cDNA for factor VIII has provided the ability to develop mammalian cell lines which express high levels of factor VIII by using appropriatate expression plasmids and DNA cotransformation with selectable markers. We have studied the synthesis, processing, and secretion of factor VIII expressed in baby hamster kidney cells and in Chinese hamster ovary cells by 35S-methionine pulse and chase labeling and analysis by immunoprecipitation with specific antibodies which recognize the light and heavy chains of factor VIII. In both mammalian cell lines, factor VIII is synthesized as a primary translation product of 230 kDa. A significant amount remains within the endoplasmic reticulum in a stable complex with a glucose regulated protein of 78 kDa. The remainder traverses into the Golgi compartment where it is cleaved to the heavy and light chain forms. Very shortly thereafter the mature factor VIII appears in the conditioned media as the mature heavy and light chain species. Very little single chain factor VIII is secreted into the conditioned media. The accumulation of factor VIII in the conditioned media requires the presence of vWF factor. In the absence of vWF, the factor VIII appears as unassociated heavy and light chains which are rapidly degraded. Bovine, porcine, or human 3WF all effectively stabilize human factor VIII expressed in these rodent cell lines. These results suggest the presence of vWF promotes factor VIII chain association which stabilizes the factor VIII to proteolysis.
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Chen, Kok Hao, and Jong Hyun Choi. "Nanoparticle-Aptamer: An Effective Growth Inhibitor for Human Cancer Cells." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11966.

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Semiconductor nanocrystals have unique optical properties due to quantum confinement effects, and a variety of promising approaches have been devised to interface the nanomaterials with biomolecules for bioimaging and therapeutic applications. Such bio-interface can be facilitated via a DNA template for nanoparticles as oligonucleotides can mediate the aqueous-phase nucleation and capping of semiconductor nanocrystals.[1,2] Here, we report a novel scheme of synthesizing fluorescent nanocrystal quantum dots (NQDs) using DNA aptamers and the use of this biotic/abiotic nanoparticle system for growth inhibition of MCF-7 human breast cancer cells for the first time. Particularly, we used two DNA sequences for this purpose, which have been developed as anti-cancer agents: 5-GGT GGT GGT GGT TGT GGT GGT GGT GG-3 (also called, AGRO) and 5-(GT)15-3.[3–5] This study may ultimately form the basis of unique nanoparticle-based therapeutics with the additional ability to optically report molecular recognition. Figure 1a shows the photoluminescence (PL) spectra of GT- and AGRO-passivated PbS QD that fluoresce in the near IR, centered at approximately 980 nm. A typical synthesis procedure involves rapid addition of sodium sulfide in the mixture solution of DNA and Pb acetate at a molar ratio of 2:4:1. The resulting nanocrystals are washed to remove unreacted DNA and ions by adding mixture solution of NaCl and isopropanol, followed by centrifugation. The precipitated nanocrystals are collected and re-suspended in aqueous solution by mild sonication. Optical absorption measurements reveal that approximately 90 and 77% of GT and AGRO DNA is removed after the washing process. The particle size distribution in Figure 1b suggests that the GT sequence-capped PbS particles are primarily in 3–5 nm diameter range. These nanocrystals can be easily incorporated with mammalian cells and remain highly fluorescent in sub-cellular environments. Figure 1c serially presents an optical image of a MCF-7 cell and a PL image of the AGRO-capped QD incorporated with the cell. Figure 1. (a) Normalized fluorescence spectra of PbS QD synthesized with GT and AGRO sequences, which were previously developed as anti-cancer agents. The DNA-capped QD fluoresce in the near IR centered at ∼980 nm. (b) TEM image of GT-templated nanocrystals ranging 3–5 nm in diameter. (c) Optical image of an MCF-7 human breast cancer cell after a 12-hour exposure to aptamer-capped QD. (d) PL image of AGRO-QD incorporated with the cell, indicating that these nanocrystals remain highly fluorescent in sub-cellular environments. One immediate concern for interfacing inorganic nanocrystals with cells and tissue for labeling or therapeutics is their cytotoxicity. The nanoparticle cytotoxicity is primarily determined by material composition and surface chemistry, and QD are potentially toxic by generating reactive oxygen species or by leaching heavy metal ions when decomposed.[6] We examined the toxicity of aptamer-passivated nanocrystals with NIH-3T3 mouse fibroblast cells. The cells were exposed to PbS nanocrystals for 2 days before a standard MTT assay as shown in Figure 2, where there is no apparent cytotoxicity at these doses. In contrast, Pb acetate exerts statistically significant toxicity. This observation suggests a stable surface passivation by the DNA aptamers and the absence of appreciable Pb2+ leaching. Figure 2. Viability of 3T3 mouse fibroblast cells after a 2-day exposure to DNA aptamer-capped nanocrystals. There is no apparent dose-dependent toxicity, whereas a statistically significant reduction in cell viability is observed with Pb ions. Note that Pb acetate at 133 μM is equivalent to the Pb2+ amount that was used for PbS nanocrystal synthesis at maximum concentration. Error bars are standard deviations of independent experiments. *Statistically different from control (p<0.005). Finally, we examined if these cyto-compatible nanoparticle-aptamers remained therapeutically active for cancer cell growth inhibition. The MTT assay results in Figure 3a show significantly decreased growth of breast cancer cells incorporated with AGRO, GT, and the corresponding templated nanocrystals, as anticipated. In contrast, 5-(GC)15-3 and the QDs synthesized with the same sequence, which were used as negative controls along with zero-dose control cells, did not alter cell viability significantly. Here, we define the growth inhibition efficacy as (100 − cell viability) per DNA of a sample, because the DNA concentration is significantly decreased during the particle washing. The nanoparticle-aptamers demonstrate 3–4 times greater therapeutic activities compared to the corresponding aptamer drugs (Figure 3b). We speculate that when a nanoparticle-aptamer is internalized by the cancer cells, it forms an intracellular complex with nucleolin and nuclear factor-κB (NF-κB) essential modulator, thereby inhibiting NF-κB activation that would cause transcription of proliferation and anti-apoptotic genes.[7] The nanoparticle-aptamers may more effectively block the pathways for creating anti-apoptotic genes or facilitate the cellular delivery of aptamers via nanoparticle uptake. Our additional investigation indicates that the same DNA capping chemistry can be utilized to produce aptamer-mediated Fe3O4 nanocrystals, which may be potentially useful in MRI and therapeutics, considering their magnetic properties and biocompatibility. In summary, the nanoparticle-based therapeutic schemes developed here should be valuable in developing a multifunctional drug delivery and imaging agent for biological systems. Figure 3. Anti-proliferation of MCF-7 human breast cancer cells with aptamer-passivated nanocrystals. (a) Viability of MCF-7 cells exposed to AGRO and GT sequences, and AGRO-/GT-capped QD for 7 days. The DNA concentration was 10 uM, while the particles were incubated with cells at 75 nM. (b) Growth inhibition efficacy is defined as (100 − cell viability) per DNA to correct the DNA concentration after particle washing.
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