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  • Cooperatives  (41)
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  • Articles  (518)
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  • 1
    Publication Date: 2012-12-28
    Description: We investigate the impact of decentralised decision-making on product quality. Comparing a cooperative and an investor-owned firm suggests that members of the cooperative have an incentive to produce too much and to free-ride on quality. Whether or not cooperatives deliver higher quality products depends on the way in which the quality of the final product is determined from the quality levels of the inputs delivered (quality aggregation) as well as the number of members of the cooperative. Empirical evidence on the Austrian wine market suggests that wines produced by cooperatives tend to be of significantly lower quality, ceteris paribus .
    Keywords: D22 - Firm Behavior: Empirical Analysis, D23 - Organizational Behavior ; Transaction Costs ; Property Rights, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 2
    Publication Date: 2013-02-26
    Description: The survival of agricultural marketing co-operatives depends on their capability of satisfying and maintaining their base of farmer members. Hypotheses regarding these two success factors are developed in neoclassical economics and transaction cost economics. They are tested with a survey of 321 members of marketing co-operatives specialising in fresh fruits and vegetables. Our results show support for both perspectives. Price paid to farmers is important for their satisfaction with the co-operative. Farmers' perceptions of transaction costs are even more important.
    Keywords: D22 - Firm Behavior: Empirical Analysis, D23 - Organizational Behavior ; Transaction Costs ; Property Rights, P13 - Cooperative Enterprises, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 3
    Publication Date: 2013-02-26
    Description: This paper explores the demand and willingness to pay (WTP) for value-added services to chicken. Since the demand for such services are likely to be highly segmented and often applies only to a market niche, models based on assumptions of homogeneity among consumers are likely to be inappropriate. For this reason, this paper combines discrete and continuous mixing distributions to concurrently identify the size of the niche market and the heterogeneity among consumers within the market niche. Failing to account for the niche market nature of value-added services is shown to have implications for predictions of WTP, demand and total revenue.
    Keywords: C25 - Discrete Regression and Qualitative Choice Models, D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 4
    Publication Date: 2011-11-24
    Description: We use a stochastic dynamic programming model to simulate the market implications of alternative foot and mouth disease scenarios in the Finnish pig sector. The model considers the dynamics of animal stock adjustment and price movements when the duration of export disruptions is unknown. Explicit treatment of these issues is crucial in the economic analysis of livestock epidemics, especially if there is a risk of a prolonged export ban. Results suggest that the risk of a prolonged ban increases disease losses considerably. It also increases economic benefits from production adjustments.
    Keywords: C61 - Optimization Techniques ; Programming Models ; Dynamic Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 5
    Publication Date: 2011-11-24
    Description: Consumers' preferences for food safety characteristics are investigated with a particular focus on the existence of an embedding effect. Embedding exists if consumer valuation of food safety is insensitive to scope. We conduct between-attribute external tests for embedding in two choice experiments concerning the value of food safety attributes in minced pork and chicken breasts. We find no evidence of embedding neither when using food safety attributes that are not close substitutes and which exhibit both private and public good characteristics, nor when using food safety attributes that are closer substitutes and which have primarily private good characteristics.
    Keywords: Q10 - General, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 6
    Publication Date: 2011-11-24
    Description: This paper presents an empirical investigation of the link between intangible expenses of French wine companies and their financial performance. A flexible moment-based approach is used to analyse the impact of tangible and intangible expenses on the mean, variance and skewness of profit. Econometric evidence shows that a high level of intangible expenses has a positive impact on performance by increasing the expected profit and reducing variance risk. A lower level of intangible expenses reduces risk and mean of profit of corporations. This study provides insights on the use of intangible expenses as a risk management tool.
    Keywords: G32 - Financing Policy ; Financial Risk and Risk Management ; Capital and Ownership Structure, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 7
    Publication Date: 2011-11-24
    Description: Economists frequently use choice experiments (CEs) to evaluate demand for new attributes in food products. Using a split-sample experimental design focused on demand for pork chop attributes, we find consumer inferences regarding food safety and quality to impact estimates of marginal willingness to pay, market participation, policy appropriateness and consumer welfare effects. Our results suggest that interpretation of findings should be noted as conditional on attributes included in original analyses. A split-sample experimental approach involving multiple CE designs is described and suggested to practitioners to better consider consumer inference effects in future studies.
    Keywords: B40 - General, D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 8
    Publication Date: 2011-11-24
    Description: Geographical origin labels are important information and marketing tools and have recently become a central component of EU agricultural promotion. We consider demand in a non-EU export market for two distinct label types: country of origin (COO) and geographical indications (GIs). Additionally, two types of GIs, ‘protected designations of origin’ (PDOs) and ‘protected GIs’ (PGIs) are considered. Empirical findings indicate consumers’ willingness to pay varies with the oil's COO and is greater for GIs than for non-GIs from a given country. Weaker evidence that consumers value PDOs more than PGIs is also found.
    Keywords: C25 - Discrete Regression and Qualitative Choice Models, D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 9
    Publication Date: 2012-03-08
    Description: We determine the circumstances when the absence of public listing, often believed to be a disadvantage, makes a cooperative the unique efficient governance structure. This is established in a multi-task principal–agent model, capturing that cooperatives are not publicly listed and their CEOs have to bring the downstream enterprise to value as well as to serve upstream member interests. Not having a public listing prevents the CEO from choosing the level of the downstream activities too high. Cooperatives are uniquely efficient when the upstream marginal product multiplied with a function increasing in the strength of the chain complementarities is higher than the downstream marginal product.
    Keywords: D21 - Firm Behavior, L23 - Organization of Production, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 10
    Publication Date: 2012-03-08
    Description: Branded food manufacturers vindicate the use of excess production capacities to justify their production of retailers’ brands. We study the distributor's and food manufacturer's private label (PL) strategy for production within a framework featuring endogenous store brand quality, bargaining power, possible differences in production technology and potential capacity constraints for the branded manufacturer. Depending on the structure of capacity constraint (applying to both products or to the PL only), we find that the retailer may prefer to choose an independent firm for the production of the store brand whereas the branded manufacturer is chosen in the case of excess capacity.
    Keywords: L11 - Production, Pricing, and Market Structure ; Size Distribution of Firms, L13 - Oligopoly and Other Imperfect Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 11
    Publication Date: 2014-01-22
    Description: Water theft carried out by manipulating water meters constrains volumetric pricing in semi-arid regions. Cooperative management can reduce theft and improve incentives for efficient water use by inducing peer monitoring. Using a theoretical model, we show that theft is more likely when prices are high, punishments are weak, and cooperatives are large. We also show how cooperative membership and punishment levels are determined endogenously by constraints on monitoring. We test the model on data from Tunisia for the years 2001–2003, relying on instruments that proxy for unobservable monitoring costs. The results confirm that well-designed incentives can reduce theft, and that constraints on monitoring costs affect institutional design.
    Keywords: D82 - Asymmetric and Private Information, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q15 - Land Ownership and Tenure ; Land Reform ; Land Use ; Irrigation, Q25 - Water
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 12
    Publication Date: 2014-03-21
    Description: This is the first paper to analyze liquidity costs in agricultural futures markets based on the observed bid-ask spread (BAS) faced by market participants. The results reveal a highly liquid corn market that mostly offers order execution at minimum cost. The BAS responds negatively to volume and positively to price volatility, but also affects volume traded and price volatility. While statistically significant, these responses on a cents/bushel or a percentage basis are generally small. Liquidity costs are also virtually impervious to short-term changes in demand for spreading and trend-following trader activity, as well as differences from day-of-the-week changes in market activity. Much larger cents/bushel and percentage changes in BAS occur during commodity index trader roll periods and on USDA report release days. The roll period findings indicate a sunshine trading effect, while announcement effects identify the importance of unexpected information and adverse selection on order execution costs. Overall, our research demonstrates that the transition to electronic trading in the corn futures market has led to low and stable liquidity costs, despite the market turbulence in 2008–2009.
    Keywords: C36- Instrumental Variables (IV) Estimation, G12 - Asset Pricing ; Trading volume ; Bond Interest Rates, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 13
    Publication Date: 2014-03-21
    Description: The Minnesota Food Network is a limited liability company comprised of 52 farmers producing a variety of high-quality, sustainably produced agricultural products in southern Minnesota. The network's goal is to develop a regional food system to provide locally grown food at a price that "is fair" to both consumers and producers. This case outlines the challenges that the network faces in their efforts to expand to take advantage of a market opportunity. One of their biggest challenges is that they face high operating costs because of their disaggregated distribution system and need to purchase a distribution and storage facility and two vehicles. They will fund the purchase of a building through an angel investor. An angel investor is necessary because the network cannot sustain traditional loan payments in its current form. Students are asked to consider a number of questions pertaining to the decisions in this case outlined in the final section of the case study.
    Keywords: A22 - Undergraduate, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
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    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 14
    Publication Date: 2014-03-21
    Description: To successfully market new products in a social network it is essential to identify influential individuals whose product recommendations influence the consumption choices of their peers. In this study, we use spatial econometric methods to determine how individuals revise their preferences for product attributes when exposed to product recommendations from peers, and how different individuals who vary in their degree of network connectedness exert influence on the product choices of others. We find evidence that consumers look to others for guidance from peers in their preference for subjective, taste-specific parameters, but tend not to respond to peer price choices. Our spatial methods allow us to empirically determine the influence exerted by individual members on the consumption choices of other members of the social network. We find that connected members of the social network are not always the most influential in revising the consumption choices of others. Our estimates reveal that network proximity explains only 8.8% of influence.
    Keywords: D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 15
    Publication Date: 2014-04-05
    Description: Randomized controlled trials (RCTs) in the social sciences are typically not double-blind, so participants know they are "treated" and will adjust their behavior accordingly. Such effort responses complicate the assessment of impact. To gauge the potential magnitude of effort responses we implement a conventional RCT and double-blind trial in rural Tanzania, and randomly allocate modern and traditional cowpea seed varieties to a sample of farmers. Effort responses can be quantitatively important—for our case they explain the entire "treatment effect on the treated" as measured in a conventional economic RCT. Specifically, harvests are the same for people who know they received the modern seeds and for people who did not know what type of seeds they got; however, people who knew they had received the traditional seeds did much worse. Importantly, we also find that most of the behavioral response is unobserved by the analyst, or at least not readily captured using coarse, standard controls.
    Keywords: Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 16
    Publication Date: 2011-12-27
    Description: European cattle markets have recently undergone significant change. We explore the simultaneous impacts of agricultural policy reform and the occurrence of an animal health crisis on spatial interdependencies of calf prices of four major European Union markets. The markets are found to be integrated. Price shocks are rapidly absorbed. We find that the member state specific implementations of the 2003 Common Agricultural Policy reforms significantly affected prices of both the national market and of other member states. The blue tongue disease further induced structural change. Using counterfactual scenarios, we show that the decoupling of payments from production led to reduced calf prices.
    Keywords: C32 - Time-Series Models, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 17
    Publication Date: 2014-09-06
    Description: This article investigates the announcement effects of major USDA reports using intraday Chicago Board of Trade corn futures prices and trading volume from the electronic trading platform for July 2009 to May 2012. Focusing on intraday market reactions, we analyze the extent to which new information impacts and is rapidly reflected in prices. Results show that USDA reports contain substantial information for market participants. Strongest price reactions to the releases are found immediately after the market opens, and market reactions persist for approximately ten minutes. The electronic corn futures market quickly incorporates this new public information, and little evidence exists to support systematic under- or overreactions in prices. Other more subtle reactions occur in the last trading session before USDA announcements as traders adjust their market exposure in anticipation of the release.
    Keywords: D80 - General, G14 - Information and Market Efficiency ; Event Studies, Q11 - Aggregate Supply and Demand Analysis ; Prices, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 18
    Publication Date: 2014-09-06
    Description: Increases in crop yields and changing cropping patterns have placed stress on agribusiness handling and storage facilities. The objective of this research is to gain insight into the relationship between safety culture and safety performance, and to identify the determinants of safety culture in agribusinesses. The research suggests that investments in labor inputs such as increased training, consistent discipline, and recognition of safety achievements all increase safety culture. Furthermore, improvements in employee perceptions of safety culture have a positive impact on reducing employee injuries. Congress has recently funded nine centers to work on occupational health and safety research in agriculture, fisheries, and forestry.
    Keywords: J43 - Agricultural Labor Markets, L66 - Food ; Beverages ; Cosmetics ; Tobacco ; Wine and Spirits, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 19
    Publication Date: 2014-12-13
    Description: In a well-functioning futures market, the futures price at expiration equals the price of the underlying asset. This condition failed to hold in grain markets for most of 2005-2010, calling into question the ability of these markets to perform their price discovery and risk management functions. During this period, futures contracts expired up to 35% above the cash grain price. We develop a dynamic rational expectations model of commodity storage that explains how these recent convergence failures were generated by the institutional structure of the delivery system. When delivery occurs on a grain futures contract, the firm on the short side of the market provides a delivery instrument (a warehouse receipt or shipping certificate) to the firm on the long side of the market. The firm taking delivery may hold the delivery instrument indefinitely, providing it pays a daily storage rate. The futures exchange sets the maximum allowable storage rate at a fixed value. We show that non-convergence arises in equilibrium when the market price of physical grain storage exceeds the maximum storage rate on delivery instruments. We call the difference between the price of carrying physical grain and the maximum storage rate the wedge , and demonstrate theoretically and empirically that the magnitude of the non-convergence equals the expected present discounted value of a function of future wedges.
    Keywords: G13 - Contingent Pricing ; Futures Pricing, G14 - Information and Market Efficiency ; Event Studies, Q11 - Aggregate Supply and Demand Analysis ; Prices, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 20
    Publication Date: 2014-12-13
    Description: A recently developed testing procedure is used to detect and date-stamp explosive episodes ("bubbles") in corn, soybean, and wheat futures markets during 2004–2013. We find that the markets experienced price explosiveness only approximately two percent of the time and, when bubbles do occur, they are generally short-lived and small in magnitude. The correspondence between observed price spikes and bubbles is rather low, with a large portion of the price explosiveness occurring during downward price movements. Commodity index trader positions do not significantly affect the probability of a positive bubble occurring in grain futures markets, which directly contradicts the argument (the "Masters Hypothesis") that waves of index investment distorted underlying supply-and-demand relationships and led to a series of massive bubbles in agricultural futures markets. In addition, commodity index trader positions tend to reduce negative bubble occurrence, while general speculative activity as measured by Working's T reduces the probability of a positive bubble. There is some evidence that the positions of noncommercial traders have a direct effect on positive bubble occurrence, but the effect declines when accounting for the composition of other traders in the market. Overall, speculation has little effect or negative effects on price explosiveness. Finally, positive bubbles are more likely to occur in the presence of low inventories, strong exports, a weak U.S. dollar, and booming economic growth, whereas negative bubbles are more likely to occur with large inventories, weak exports, and stagnant economic growth.
    Keywords: D84 - Expectations ; Speculations, G12 - Asset Pricing ; Trading volume ; Bond Interest Rates, G13 - Contingent Pricing ; Futures Pricing, G14 - Information and Market Efficiency ; Event Studies, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q41 - Demand and Supply
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 21
    Publication Date: 2014-09-02
    Description: This article discusses the current state of contract theory and its usefulness for conceptualizing issues related to agricultural contracting. The paper will explore the limitations of existing theory for applied work, and what methodological improvements are needed to enhance the usefulness of the theory to agricultural economists. One pervasive problem is that the economic literature on contracts is rather fragmented and the various methodological strands are narrow in their focus. As such, agricultural economists should engage in methodological research to develop applied contracting models that can capture higher-order features of real-world agricultural contracts while delivering generalizable comparative statics predictions because contracting continues to expand along the entire modern food marketing channel. In the latter part of this article, a simple model is developed to illustrate how classic methodological approaches can be combined with recent developments in contract and game theory to construct applied theory models that are useful for capturing some important features of agricultural contracts.
    Keywords: D43 - Oligopoly and Other Forms of Market Imperfection, D82 - Asymmetric and Private Information, D86 - Economics of Contract: Theory, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 22
    Publication Date: 2014-09-02
    Description: Information and communications technologies have spread rapidly in developing countries. We investigate the impact of mobile phones on traders' search behavior in Niger by constructing a theoretical model of search in which traders engage in sequential search for the optimal sales price. Using a trader panel dataset spanning 2005–2007, we find empirical support for the model in that the duration of mobile phone coverage is associated with increased search activity. This effect evolves dynamically over time and is stronger for larger traders, who engage in arbitrage over longer distances. Results provide empirical evidence for the observed linkages between mobile telephony and price dispersion.
    Keywords: O10 - General, O30 - General, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 23
    Publication Date: 2014-08-02
    Description: In the past two decades, there has been an explosion of studies eliciting consumer willingness-to-pay for food attributes; however, this work has largely refrained from drawing a distinction between preferences for health, safety and quality on the one hand and consumers' subjective beliefs that the products studied possess these attributes, on the other. Using data from three experimental studies, along with structural economic models, we show that controlling for subjective beliefs can substantively alter the interpretation of results and the ultimate implications derived from a study. The results suggest the need to measure subjective beliefs in studies of consumer choice and to utilise the measures when making policy and marketing recommendations.
    Keywords: C91 - Laboratory, Individual Behavior, D83 - Search ; Learning ; Information and Knowledge ; Communication ; Belief, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 24
    Publication Date: 2012-05-29
    Description: Using stated preference data from Kentucky and Ohio, USA, we estimate consumer willingness-to-pay for varieties of a processed food product (blackberry jam) that are differentiated with respect to their local production labelling and a series of other value-added claims. Results show that consumers were willing to pay more for the product indicating locally produced, produced in their state or in a well-identified multi-state region. Consumers were willing to purchase organic products, although there might be some confusion as to the meaning of the organic logo. Our results also supported the notion that consumers are willing to support small family farms.
    Keywords: Q11 - Aggregate Supply and Demand Analysis ; Prices, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 25
    Publication Date: 2012-05-29
    Description: This paper studies the determinants and consequences of heterogeneous market participation among Polish dairy farmers using a unique data set on supply chain characteristics and individuals with different market relationships. It investigates factors that cause households not to participate in the market and then estimates farm orientation effects on revenues, using semi-parametric methods. The key finding is that farms maintaining commercial dairy business were better off than those who ceased milk sales. However, detailed analysis shows that this difference could be attributed to supply chain modernisation and becomes insignificant once subsistence farmers are compared to commercial farms supplying the traditional marketing channel.
    Keywords: D22 - Firm Behavior: Empirical Analysis, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
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    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 26
    Publication Date: 2013-11-22
    Description: India and China have the largest farm-household populations in the world—populations that are also among the poorest. Among the many factors that affect farm livelihoods, access to credit has been identified as a significant barrier preventing the escape from poverty. While there has been significant research on credit constraints in developing countries, there is surprisingly little information pertaining to the actual impacts of credit constraints on household well-being. The objective of this paper is to investigate the impacts of credit constraints on various factors affecting farm households, such as physical and human capital formation, agricultural inputs applications, consumption smoothing, and wage-seeking behavior using direct elicitation. This paper contributes to the literature and policy debates by comparing the effects of credit constraints in China and India as surveyed in 2008–2009. The analytical results and data demonstrate that binding credit constraints adversely affect a broad range of production and livelihood choices. We empirically show that credit constraints negatively affect food consumption, farm input applications, and health and educational attainments.
    Keywords: O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products, O17 - Formal and Informal Sectors ; Shadow Economy ; Institutional Arrangements, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 27
    Publication Date: 2013-11-22
    Description: Using a lab experiment with 351 adult non-student subjects, we investigate the impact of labels and secondary information on willingness to pay (WTP) for foods that use various ingredients and processes that have been the subject of food policy discussions. We find a distinct asymmetry of WTP sensitivity between "Contains X" and "Free of X" labels with negatively-framed secondary information. The "Free of X" label has an impact only when secondary information is provided, and the negative impact of "Contains X" is mitigated by secondary information. We also consider how the results of our study can inform the ongoing debate about mandatory food labeling regulations in the United States: if mandatory labeling is adopted, providing additional information about what the product contains would significantly lessen the negative impact on demand.
    Keywords: M31 - Marketing, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 28
    Publication Date: 2013-11-22
    Description: This study examines the risk management opportunities for fluid milk market participants in the United States through the use of milk futures contracts. We estimate the nature of basis risk from 2002–2011 using modern time-series and econometric techniques. The results of this investigation reveal that at sufficient hedging intervals, using class III manufacturing milk futures contracts to cross-hedge fluid milk has the ability to reduce risk and provide revenue stability to market participants. When used in conjunction with milk futures, prediction algorithms for the closing basis facilitate more direct management of fluid milk price risk.
    Keywords: Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q14 - Agricultural Finance, Q18 - Agricultural Policy ; Food Policy
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 29
    Publication Date: 2014-07-23
    Description: Livestock Gross Margin Insurance for Dairy Cattle (LGM-Dairy) is a risk management tool for protecting milk income over feed cost margins. In this article, we examine the assumptions underpinning the method used to determine LGM-Dairy premiums. Analysis of the milk–feed dependence structure is conducted using copula methods, a rich set of tools that allow modelers to capture nonlinearities in dependence among variables of interest. We find a significant relationship between milk and feed prices that increases with time-to-maturity and severity of negative price shocks. Extremal, or tail, dependence is the propensity of dependence to concentrate in the tails of a distribution. A common theme in financial and actuarial applications and in agricultural crop revenue insurance is that tail dependence increases the risk to the underwriter and results in higher insurance premiums. We present, to our knowledge, the first case in which tail dependence may actually reduce actuarially fair premiums for an agricultural risk insurance product. We examine hedging effectiveness with LGM-Dairy and show that, even in the absence of basis or production risk, hedging horizon plays an important role in the ability of this tool to smooth farm income over feed cost margins over time. Rating methodology that accounts for tail dependence between milk and feed prices extends the optimal hedging horizon and increases hedging effectiveness of the LGM-Dairy program.
    Keywords: G13 - Contingent Pricing ; Futures Pricing, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 30
    Publication Date: 2014-07-23
    Description: We study the effect of alleviating the information asymmetry regarding product quality that is widespread in contracts between agricultural producers and buyers in developing countries. Opportunistic buyers may underreport quality levels to farmers to reduce the price that they have to pay. In response, farmers may curb investment, thereby negatively affecting farm productivity. In an experiment, we entitle randomly selected smallholder dairy farmers in Vietnam, who are contracted by a large company, to independently verify milk testing results. Results indicate that treatment farmers use 12% more inputs, and they also increase their output significantly. Some wider research and policy implications are discussed.
    Keywords: C93 - Field Experiments, D82 - Asymmetric and Private Information, O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 31
    Publication Date: 2014-07-23
    Description: We address the question of how the strength of protection for geographical indications (GIs) affects the GI industry's promotion incentives, equilibrium market outcomes, and the distribution of welfare. Geographical indication producers engage in informative advertising by associating their true quality premium (relative to a substitute product) with a specific label emphasizing the GI's geographic origin. The extent to which the names/words of the GI label can be used and/or imitated by competing products—which depends on the strength of GI protection—determines how informative the GI promotion messages can be. Consumers’ heterogeneous preferences (vis-à-vis the GI quality premium) are modeled in a vertically differentiated framework. Both the GI industry and the substitute product industry are assumed to be competitive (with free entry). The model is calibrated and solved for alternative parameter values. Results show that producers of the GI and of the lower-quality substitute good have divergent interests: GI producers are better off with full protection, whereas the substitute good's producers prefer intermediate levels of protection (but they never prefer zero protection because they benefit indirectly if the GI producers’ incentives to promote are preserved). For consumers and aggregate welfare, the preferred level of protection depends on the model's parameters, with an intermediate level of protection being optimal in many circumstances.
    Keywords: D23 - Organizational Behavior ; Transaction Costs ; Property Rights, L15 - Information and Product Quality ; Standardization and Compatibility, M37 - Advertising, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 32
    Publication Date: 2014-07-23
    Description: Retail-price pass-through is one of the most important issues facing manufacturers of consumer packaged goods. Although retailers tend to pass higher wholesale prices through to consumers quickly and completely, they often do not pass on trade promotions. Currently, asymmetric pass-through is commonly thought to result from retailers’ exercise of market power. Alternatively, it may be because of consumer search behavior and retailers’ competitive response. We test this theory using a panel threshold asymmetric error-correction model applied to wholesale and retail scanner data for ready-to-eat cereal for a number of retailers in the Los Angeles metropolitan market. We find that consumer search behavior contributes significantly to imperfect pass-through. By allowing pass-through to depend on market power and consumer search costs, we find results that are contrary to the conventional wisdom. Namely, market power causes retail prices to fall quickly and rise slowly, whereas consumer search behavior causes retail prices to rise quickly and fall slowly—precisely the "rockets and feathers" phenomenon.
    Keywords: C35 - Discrete Regression and Qualitative Choice Models, L13 - Oligopoly and Other Imperfect Markets, L66 - Food ; Beverages ; Cosmetics ; Tobacco ; Wine and Spirits, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 33
    Publication Date: 2014-07-23
    Description: The degradation of product quality is one form of rent dissipation resulting from incomplete property rights in fisheries. Industry structure and information asymmetries can also lead to underinvestment in product quality, even when property rights are well defined. In this article we empirically examine whether the voluntary formation of a marketing cooperative was able to mitigate market failures that led to the production of inferior-quality fish. Specifically, we use a difference-in-differences estimation strategy to measure the impact that the Copper River Fishermen's Cooperative, an Alaskan salmon marketing cooperative, had on ex-vessel salmon prices and salmon quality measures. We find that the cooperative was able to improve product quality, as well as attract and sustain a higher price for its salmon. Our findings provide empirical support for many of the key tenets of cooperative theory. Specifically, we find evidence that marketing cooperatives can address existing market failures, that marketing cooperatives can have advantages in high-quality product markets, and that over time, as a result of their success, marketing cooperatives may lead to lasting producer benefits even though they become obsolete due to nonmember free-riding.
    Keywords: Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q22 - Fishery ; Aquaculture
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 34
    Publication Date: 2014-07-23
    Description: The emergence of community supported agriculture (CSA) farms has been recognized as a new way for small farms to remain competitive while engaging in their local community through direct marketing. In this study, we report on first revealed preference valuation of CSA attributes using data on share prices and CSA characteristics for the summer 2012 growing season. Using data covering 453 CSA farms in Michigan, New York, Ohio, and Pennsylvania, we develop a hedonic model based on firm-level prices to reveal consumer valuations of CSA attributes, including various types of organic certification. We also test for competition in the CSA market using a model of firm entry to evaluate whether firms appear perfectly competitive, which is a requirement when using firm-level prices in our hedonic analysis. Our results reveal a price premium of approximately 7% for USDA organic certification, although this value is heterogeneous across states. We find no premium associated with competing certified naturally grown programs. Finally, we find that CSA farms exhibit little market power and appear to act competitively even with few market entrants.
    Keywords: Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q51 - Valuation of Environmental Effects
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 35
    Publication Date: 2012-08-03
    Description: This study investigates the choice of quality by producer organisations (POs) in charge of defining product specifications for geographical indications. The model assumes that the PO chooses the quality level that maximises joint producer profits in anticipation of the competitive equilibrium that arises once quality is set. Using a fairly general variant of the vertical differentiation model and a flexible specification of production costs, we show that the PO has an incentive to supply quality in excess of the socially optimal level.
    Keywords: L15 - Information and Product Quality ; Standardization and Compatibility, L44 - Antitrust Policy and Public Enterprises, Nonprofit Institutions, and Professional Organization, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 36
    Publication Date: 2012-12-28
    Description: This paper investigates household expenditures on food away from home by type of facility. A system of expenditures at full-service restaurants, fast-food restaurants and other facilities are estimated with a multivariate sample selection procedure, for three types of households by household composition. Statistical significance of error correlations suggests endogeneity of sample selectivity and justifies estimation of the equations in a system to improve statistical efficiency. Differentiated effects of economic and demographic factors are found on expenditures at different facilities and across household types. Findings on the roles of economic and socio-demographic factors can inform marketing strategies and policy deliberations.
    Keywords: C31 - Cross-Sectional Models ; Spatial Models ; Treatment Effect Models, D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 37
    Publication Date: 2013-05-31
    Description: European Union regulation on quality food products (protected designations of origin (PDO) labelling) is expected to sustain competitiveness within the agricultural sector. This paper examines the impact of this policy on the survival of cheese firms over the period 1990–2006 in France. We show that such a policy (Appellation d'Origine Controlée) reduces exiting risk for smaller firms. However, smaller firms still have a lower survival rate compared with larger ones that cannot be compensated by the quality label effect.
    Keywords: L10 - General, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 38
    Publication Date: 2013-12-24
    Description: The investigation of hypothetical bias in choice experiments (CEs) has typically been conducted in the laboratory with only minimal field experiments. Moreover, it is common practice to provide an initial endowment (money or coupons) to respondents. In this research, we employed a between-subject CE in a supermarket with three different treatments (i.e. hypothetical, hypothetical with cheap talk script and real). With the ‘real’ treatment, we required respondents to use their own money when making a payment. The proposed incentive-compatible mechanism mimics as close as possible the everyday purchasing situation. Results confirm the presence of hypothetical bias and the mixed effectiveness of a cheap talk script.
    Keywords: D12 - Consumer Economics: Empirical Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 39
    Publication Date: 2013-12-24
    Description: Policymakers have suggested the use of taxes to raise the relative cost of buying fast food. Yet, little is known of the structure of demand for food-away-from-home (FAFH) in general. This study provides estimates of the price-elasticity of demand for four different types of FAFH using a new data set from NPD, Inc. and an econometric approach that accounts for the multiple-discrete–continuous nature of FAFH demand. We find that cross-price elasticities of demand are small, so consumers are unwilling to substitute between food-at-home and any type of FAFH or among types of FAFH. Therefore, taxing fast food may be effective in reducing the number of fast food visits and shifting consumption to at-home meals.
    Keywords: C35 - Discrete Regression and Qualitative Choice Models, D12 - Consumer Economics: Empirical Analysis, I18 - Government Policy ; Regulation ; Public Health, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 40
    Publication Date: 2013-12-24
    Description: Using experimental auctions carried out on apples in different European countries, this paper contributes to the assessment of consumer willingness to pay for the reduction of pesticides. We study several systems of good agricultural practices, possibly signalled to consumers, ranging from Integrated Pest Management certifications to organic production methods. The results show a relatively homogeneous behaviour of European consumers and reveal that improving the information on pesticide reduction may have unintended consequences. Results also suggest that taste characteristics and reference to a Protected Denomination of Origin should not be overlooked.
    Keywords: C91 - Laboratory, Individual Behavior, D12 - Consumer Economics: Empirical Analysis, Q01 - Sustainable Development, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 41
    Publication Date: 2014-03-07
    Description: This paper estimates capitalisation effects of farm attributes with a particular focus on the decoupled Single Farm Payment (SFP) on prices. The spatial analysis employs a sample of mainly small- and medium-sized Swedish farm transactions sold all across Sweden; the results from a spatial multiple-membership model suggest that decoupled SFP has no influence on farm prices. Prices are profoundly influenced by residential characteristics and accessibility to urban amenities. Spatial heterogeneity is found for both regional and local levels, and a large spatial spillover effect is found between neighbouring farms. Results are confirmed by sensitivity analyses.
    Keywords: Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, R38 - Government Policies ; Regulatory Policies
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 42
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    Journal of Biomedical Materials Research 14 (1980), S. 31-40 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Metallurgical observations of phenomena which influence the clinically successful performance of permanent implants and implant materials are reported. The effect of casting voids in cast cobalt chromium femoral stems of total hip replacements is discussed first. Pitting corrosion occurred in a retrieved stainless-steel implant type AISI 316 containing 2.7% Mo. The fractographic pattern of this device retrieved for fatigue failure shows typical characteristics of corrosion-enhanced fatigue.
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  • 43
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    Journal of Biomedical Materials Research 14 (1980), S. 11-21 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The outer and inner surfaces of six commercial endotracheal tube cuffs were characterized using scanning electron microscopy (SEM) and energy dispersive x-ray analysis. Lateral tracheal wall pressure (LWP) was measured at various steps of cuff inflation using a mock-trachea system. The surface characteristics of the cuffs were found to vary widely. The surface of the Lanz cuff was relatively smooth but showed a regular array of circular depressions 0.8 μm in diameter. Uniform spheres also 0.8 μm in diameter were distributed through the thickness of the membrane. The American Hi-Lo cuff surface was also relatively smooth but was covered widely with flakes of material which x-ray showed to be a clay-like substance containing aluminum, silica, and potassium. The Harlake cuff was covered widely with roughly spherical, 5-μm-diam particles, probably starch granules. The membrane itself was smooth even at 3,000X. The Foregger cuff had a rough surface and was covered with the same clay-like particles seen on the American cuff. The inner surface with irregular, uneven areas were surrounded by fissures. The Rusch Armored tube cuff was completely covered by a continuous 2-μm-thick chlorinated coating. The surface was highly convoluted and irregular. The three cuff membranes showing relatively smooth surfaces, Lanz, American and Harlake, also produced relatively low LWP at various points of cuff inflation. While we have no data to indicate that cuff surface smoothness correlates with tracheal morbidity, it would seem prudent to select cuffs that produce low LWP's with smooth surfaces for clinical use.
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  • 44
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    Journal of Biomedical Materials Research 14 (1980) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 45
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    Journal of Biomedical Materials Research 14 (1980), S. 55-64 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bioglass, which has a composition of sodium carbonate, calcium carbonate, phosphorous pentoxide and silica, has been shown to bond to living bone. This ability is dependent on controlled surface reactions. Investigators with 45S5 bioglass have demonstrated that the formation of a SiO2-rich layer and a calcium phosphate film on its surface in an aqueous environment is associated with the film bonding the bioglass to bone. The objects of this research were: 1To study SiO2 dependence on the formation of a silica-rich layer and calcium phosphate films on a bioglass surface in a simulated physiological solution, and2To establish a correlation between in vitro surface reactions and in vivo bonding ability.It was discovered that three types of reactions occur in a simulated physiological solution depending on bioglass composition: 1A calcium phosphate film and SiO2-rich layer form simultaneously and the reaction rate is fast for bioglasses which have a lower content of SiO2 (∼46 mol% SiO2).2A SiO2-rich layer forms first and a calcium phosphate film develops later between the aqueous environment and the SiO2-rich layer for bioglasses whose SiO2 content is between 46-55 mol %.3A calcium phosphate film does not form for glasses whose SiO2 content is more than 60 mol %.
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  • 46
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    Journal of Biomedical Materials Research 14 (1980), S. 93-106 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Methods by which in vitro heterogeneous phase degradation rates of the poly(n-alkyl α-cyanoacrylates) have been directly obtained are described. The data indicate that the rates of degradation in aqueous buffer solutions depend not only upon pH of the medium and length of the monomer alkyl side chain, but also critically upon polymer particle specific surface, particle size, polymer molecular weight, and molecular weight distribution. A modification of the currently held theory of degradation of these polymers is required, and postulated.
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  • 47
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    Journal of Biomedical Materials Research 14 (1980), S. 23-29 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Three-dimensional finite element analysis (FEA) has been used to determine the implant-bone interface characteristics of bioglass dental implants. The results of the FEA were verified by comparison with the results of mechanical testing performed on animal implant specimens. The results of the study showed that the assumption of a discontinuous change of elastic properties at the bone-implant interface was a poor assumption for the bioglass implants. Interface elastic moduli of 354.0, 155.0, and 47.0 MPa for conditions of 25, 50, and 100% tissue attachment were determined for the bioglass implants.
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  • 48
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    Journal of Biomedical Materials Research 14 (1980), S. 1-10 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Contact angle studies have been carried out on plasma protein layers adsorbed on selected polymer surfaces under buffered saline at 37°, in an attempt to demonstrate directly a recent suggestion that the interfacial free energy between such protein layers and surrounding liquid phase should be zero at equilibrium. Although an initial contact angle of 180° was always obtained, the angle decayed slowly to a stationary value which varied for any one drop on each polymer surface. The stationary values could be reasonably correlated with the reversible work of adhesion predicted for each polymer/protein combination, suggesting that protein desorption from the solid surface is a dominant event in the contact angle decay process. It is concluded that the data bear more relevance to the protein layer/polymer interface than to the protein layer/solution interface, and that the contact angle technique is not a suitable technique for studying the latter on biomaterials.
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  • 49
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    Journal of Biomedical Materials Research 14 (1980), S. 83-90 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Distributions of Ca-to-Ca distances have been obtained from the crystal structure of hydroxyapatite for all biologically significant planes. Most frequently, calcium ions are separated by about 4, 6.3, 7.9, and 9.0 to 9.6 Å. Frequent occurrence of distances at 10.4, 11.8, and 12.6 Å result from a Ca ion in one repeating unit being paired with a Ca in another unit cell.
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  • 50
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Individuals who suffer extensive loss of skin, commonly in fires, are acutely ill, in danger of succumbing either to massive infection or to severe fluid loss. Patients who survive these early threats must often cope with problems of rehabilitation arising from deep, disfiguring scars and crippling contractures. In this report we describe the physiocochemical, biochemical, and mechanical considerations that form the basis for two-stage design of a membrane useful as an experimental wound closure. Stage 1 of the design, applicable to short-term acute use, calls for a membrane which displaces efficiently air pockets from a carefully prepared woundbed, free of weak boundary layers, and maintains the moisture flux through the wound at an optimal level. Optimization of the surface energy modulus of elasticity, energy to fracture and moisture permeability of the membrane are among the essential attributes of Stage 1 design. Stage 2 of the design, applicable to long-term, chronic use, focuses on a nonantigenic membrane which performs as a biodegradable template for synthesis of neodermal tissue. A survey of candidate materials suggests reasons for selection of a porous, crosslinked collagen - glycosaminoglycan coprecipitate as the chemical basis of an evolving design which was initiated 10 years ago. Over the past several years a set of membranes has been iteratively designed on this basis and has been used to cover satisfactorily large experimental fullthickness skin wounds in guinea pigs. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. Several rules relating the molecular structure and morphology of these membranes to cellular response of adjacent tissue have also been derived. This report is the first in a series which details the methodology of preparation and the record of performance.
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    Journal of Biomedical Materials Research 14 (1980), S. 177-180 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    Journal of Biomedical Materials Research 14 (1980), S. 181-181 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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  • 53
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    Journal of Biomedical Materials Research 14 (1980), S. 211-224 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Several kinds of polyamide microcapsules containing mammalian hemolysate were prepared by making use of the interfacial polycondensation reaction between diamines and terephthaloyl dichloride and their blood compatibility in terms of platelet adhesion was examined aiming at their ultimate clinical use as artificial red blood cells. It was found that rabbit platelets adhere onto the hemolysate-loaded microcapsules in the presence of the plasma, while no platelet adhesion takes place in the absence of the plasma. This was interpreted as indicating an important role of plasma components in platelet adhesion. Moreover, platelet adhesion was observed to be facilitated by negative charges on the surface of the hemolysate-loaded microcapsules; the more negatively the surface was charged, the more easily the platelets adhered onto the surface. Finally, the present method of assessing platelet adhesion suggested the possibility of its use for the kinetic study of platelet adhesion since it allowed us to make numerical evaluation of platelet adhesion as a function of time.
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    Journal of Biomedical Materials Research 14 (1980), S. 251-268 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The thrombogenicity of five suture materials - polypropylene (Prolene), polyester (Mersilene), polyglactin 910 (Vicryl), nylon (Ethilon), and silk - was examined in vivo by scanning electron microscopy. The most blood-compatible material appeared to be Prolene. A rather satisfactory antithrombogenciity was shown by Mersilene, in comparison with which Ethilon and Vicryl provided less thromboresistance. The possible connection between the chemical changes which occur during the hydrolysis of Vicryl and its blood compatibility is discussed. Of the tested materials, silk proved to be the most thrombogenic. This study shows that the thrombogenicity of a suture material could be easily and conveniently tested in an experimental model by scanning electron microscopy, thus enabling the first choice of a suitable suture for the cardiovascular surgery, before one continues with other more sophisticated methods for the evaluation of thromboresistance.
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    Journal of Biomedical Materials Research 14 (1980), S. 289-309 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: It is known that tissues surrounding the site of an implanted prosthetic alloy are exposed to increased concentrations of the metals comprising the alloy. However, the exact identity and concentration of such metallic products are usually unknown, thus limiting the possibilities for quantifying any observed toxicological response to the metals. This report describes some of the effects of increased concentrations (7.5-30 μg/ml; 1-5 × 10-4M) of cobalt (as CoCl2·6H2O) and of nickel (as NiCl2·6H2O) on the growth and morphology of cultured mouse fibroblasts. Ultrafiltration experiments indicated that much of the total Co or Ni present in cell culture medium could become bound to macromolecular serum components of the medium. Morphological changes and depressions in the cell growth rate were found to result from high concentrations (15-30 μg/ml) of either Co or Ni. However, lower concentrations of nickel may have produced some stimulation of cell growth, whereas all concentrations of Co studied were found to depress the rate of cell growth. The growth rate of actively proliferating fibroblasts was quite sensitive to variations in the concentration of either cobalt or nickel. Increased concentrations of cobalt or nickel, therefore, might also affect the normal reconstructive activity of fibroblasts in vivo.
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    Journal of Biomedical Materials Research 14 (1980), S. 329-338 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In vitro and in vivo experiments were performed on polyglycolic acid and plain catgut sutures to study the effects of bacteria on their rate of degradation. Experiments with Strep, mites, E. coli and Staph. albus in culture showed that the polyglycolic acid sutures degraded faster in broth controls than in a broth containing bacteria as measured by the loss in breaking strength. No difference was observed with the catgut. Polyglycolic acid sutures in subcutaneous sites in rats inoculated with Staph. albus again degrade slower than in similar wounds which were not deliberately infected. With high bacterial counts, the catgut showed the reverse trend although no differences were noted at lower counts.
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    Journal of Biomedical Materials Research 14 (1980) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 58
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    Journal of Biomedical Materials Research 14 (1980), S. 359-371 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Two types of fracture toughness specimen, the tapered cleavage (TC) and single edge notch (SEN), are compared. Their reproducibility, accuracy, and ease of preparation are investigated. The fracture toughness of four types of acrylic resin, heat cured, autopolymerized, injection molded, and high impact resistant, has been determined by one or both of the above methods. High impact acrylic proved too ductile for either of the specimens to be used to assess K1c; however, these deviations from brittle behavior were revealed by the tests and some insight into impact resistance was gained. The SEN specimens proved capable of distinguishing between the fracture toughness characteristics of the four types of denture base acrylics and proved easy to fabricate. The TC specimens proved difficult to fabricate requiring specialized equipment; however, once made, the specimens revealed more of the fracture process than did the SEN specimens.
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    Journal of Biomedical Materials Research 14 (1980), S. 427-434 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The amount of methyl methacrylate monomer present in bone tissue immediately adjacent to implanted bone cement that has polymerized in vivo has been determined. Poly(methyl methacrylate) was implanted into the distal femoral condyle of the dog and allowed to polymerize. At various times following polymerization, samples were removed and sections adjacent to the cement were cut and subjected to homogenization followed by liquid gas chromatographic determination of the amount of methyl methacrylate monomer present. The highest concentration of methyl methacrylate monomer present in bone tissue was 0.140% in the 1000 μm of bone tissue adjacent to bone cement immediately after polymerization of the cement. The concentration was very similar (0.137%) 1 hr after cement polymerization, but dropped off rapidly following that with no free methyl methacrylate monomer present in bone tissue adjacent to cement after 4 hr following cement polymerization.
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  • 60
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    Journal of Biomedical Materials Research 14 (1980), S. 447-454 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An evaluation of the biophysical changes of methylcholanthrene induced tumor (M4) in laboratory animals receiving four different alloplastic implants was conducted. The implants are silicone, polyether urethane, poly(methyl methacrylate), and bioglass. The tumor was allowed to grow to a large size in 28 days and then removed by shelling it from the surrounding tissue. Three different analytic volumetric measurements were carried; size in cm3, volume in milliliters and weight in grams. Statistical analysis on the three different analytic measurements did not disclose any significant differences in tumor growth potential between the control and the experimental groups. We conclude that in this study we were unable to demonstrate any tumor “facilitation” effect by any of the implantable polymers used. Therefore, there is no contraindication in using the polymers to reconstruct defects produced by cancer ablative procedures.
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    Journal of Biomedical Materials Research 14 (1980), S. 467-476 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Thrombin adsorbed onto Cuprophane or poly(vinyl chloride) (PVC) was shown to be inactive with respect to amidase activity. Desorbed thrombin from these two artificial surfaces showed only low amidase activity. However, in the presence of albumin, the surface-bound thrombin appeared to exhibit increased amidase activity. This apparent activity may be due to the action of thrombin displaced from the surfaces by albumin. Thrombin bound to Cuprophane or PVC was shown to be capable of reacting with antithrombin III (AT III) only in the presence of heparin. On the other hand, AT III bound to Cuprophane or PVC was unable to react with thrombin in either the absence or presence of heparin. Fibrin formation on or at surfaces was demonstrated by phase contrast microscopy when Cuprophane or PVC pretreated with thrombin and carefully rinsed was incubated in a fibrinogen solution. This fibrin formation is time dependent and likely is the result of direct interaction of adsorbed thrombin with fibrinogen in solution. Glass, Cuprophane, and PVC pretreated with thrombin were shown to attract more platelets than respective untreated surfaces. The enhancing effect of adsorbed thrombin on platelet adhesion was similar to the enhancing effect of adsorbed fibrinogen. Thrombin adsorbed onto PVC and crosslinked by glutaraldehyde treatment was shown to be antigenically active with a 125I-labeled monospecific antithrombin IgG produced in rabbits. No other plasma proteins adsorbed singly or from plasma or serum onto PVC reacted significantly with the antithrombin IgG preparation. The possible significance of these observations is discussed.
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    Journal of Biomedical Materials Research 14 (1980), S. 435-446 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The effect of thermal coefficient of expansion (α) mismatch on porcelain-metal bonding is frequently referred to in the dental literature. Thermally induced stresses may develop at metal-porcelain system interfaces due to differences in the coefficients of thermal expansion of the porcelains, metals, and metal oxides. The objective of this research is to characterize alloy and porcelain expansion behavior as a first step in developing a more specific definition of thermal compatibility. It is clear from comparisons of porcelain data and alloy data that the porcelain has expansion characteristics which are quite different from those of the alloys. The overall differences in values between these alloys and porcelains constitute a mismatch. First run dilatometric heating measurements for porcelain yield large differences between ΔL/L and α values as compared to cooling measurements. For a comparison of alloy and porcelain expansion characteristics, data should be obtained at several temperatures up to the glass transition temperature (Tg) of the porcelain.
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    Journal of Biomedical Materials Research 14 (1980), S. 455-466 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This short report concentrates on a close look at the immunological status of experimental animals which were implanted with a known dose of tumor and polymer implant. The implanted polymers used represented the most common biocompatible materials employed in current surgery. The immunological studies all were done in vitro on the cellular level. The studies suggested that there is a noticeable change of the immune system when inorganic biocompatible polymers are used in experimental animals.
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    Journal of Biomedical Materials Research 14 (1980), S. 487-497 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The linear, crosslinked amylose-succinate hemostatic agent, IP760, has been evaluated for its interaction with aminoglycosidic antibiotics. The highly structured polymer appears to act as a cationic exchange resin which binds the basic aminoglycosides. Binding of these agents to IP760 is reversed by increased pH and/or increased ionic strength. Dialysis experiments demonstrated that 85 and 90% of the bound gentamicin was released at pH 7.5 and 8.0, respectively, over a period of 36 hr. Formation of the IP760-antibiotic complexes suggests potential medicinal use for hemostasis and slow release of the antibiotic for prophylaxis of postsurgical contamination or infection.
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    Journal of Biomedical Materials Research 14 (1980), S. 477-485 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A series of membranes was prepared by air-drying the thin layers of N-acyl- and N-arylidene-chitosan gels. Their flow rates of water and permeabilities of various compounds were examined. N-Acylchitosan membranes were stable in both dilute acid and alkali, but N-arylidene-chitosan membranes were unstable in dilute acid. N-Acetylchitosan membranes were stable in formic acid at room temperature for up to 7 hr. The flow rates of water through N-acetylchitosan membranes were 10.0-23.6 × 10-3 ml/cm2 min under a pressure of 3 kg/cm2, and were unchanged by the membrane thickness (12-60 μm). The increase of carbon numbers for N-acyl groups caused a slight decrease in the flow rates, and the flow rates were decreased by partial O-acetylation of N-acetylchitosan membranes. The flow rate of water through chitosan membranes (thickness 30-35 μm) was 7.1 × 10-4 ml/cm2 min, which was decreased by an increase in the membranes thickness. Low-molecular-weight compounds (MW 〈 2900) passed through these membranes, but high molecular-weight compounds (MW 〉 13,000) did not pass through.
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    Journal of Biomedical Materials Research 14 (1980), S. 529-531 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 14 (1980), S. 499-509 
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    Notes: Kinetics of platelet adhesion from suspension to various substrates leads to Langmuir isotherm types of curves, both for suspensions in which the platelets were isolated by means of gel filtration as well as by centrifuging and washing. The level of platelet adhesion increases with increasing surface tension of the substrate. These results cannot be explained on the basis of the theoretical transport model of Ruckenstein et al. The plot of the platelet adhesion at equilibrium vs. γsv brings the observations in yet closer agreement with thermodynamic predictions based on free energy calculations than was found previously for the adhesion of platelets after short contact times between platelet suspension and substrate.
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    Journal of Biomedical Materials Research 14 (1980), S. 537-543 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Biomedical Materials Research 14 (1980), S. 533-535 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: A highly reproducible seeded crystal growth method has been used to study enamel mineralization in the presence of traces of fluoride ion. The resulting increased rate of remineralization over a range of calcium phosphate supersaturation may be attributed to the formation of surface fluorapatite.
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    Journal of Biomedical Materials Research 14 (1980), S. 545-545 
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    Journal of Biomedical Materials Research 14 (1980), S. 511-528 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Several methods are compared for preparing collagen-glycosaminoglycan (GAG) membranes of high or low porosity. Collagen-GAG membranes have been used to cover satisfactorily large experimental full-thickness skin wounds in guinea pigs over the past few years. Methods studies as means for controlling pore size are confined to purely physical processes which do not require use of additives or chemical reagents to form the porous membrane. We find that membranes, initially swollen in distilled water or saline, shrink linearly to no less than 94% of original dimension after freeze drying; to 75% after critical point drying (from CO2, following water-ethanol exchange); and to 41% of original dimension following air drying from the swollen state. Scanning electron microscopic study of the pore structure resulting from each drying procedure confirms our major conclusion: A carefully designed freeze drying process, two variants of which are described in detail, yields membranes with the highest mean pore size, as measured by quantitative stereological procedures. Critical point drying gave significantly more shrinkage and a lower mean pore size than either one of the two freeze drying procedures used.
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    Journal of Biomedical Materials Research 14 (1980), S. 567-586 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: Repair or replacement of the damaged anterior cruciate ligament (ACL) is a significant clinical problem. A design utilizing ultrahigh-molecular-weight polyethylene (UHMWPE) was developed and marketed by an orthopaedic device manufacturer. Mechanical failure rates of greater than 10%/year postoperatively raised the issue of the adequacy of UHMWPE in that design. A study has been made to estimate the forces in the human anterior cruciate ligament for young, middle age, and older patients and to thus derive the minimum materials requirements for a now withdrawn prosthetic anterior cruciate ligament (PACL) design. It is concluded that UHMWPE does not possess adequate yield, creep, or fatigue properties to meet the design. Furthermore, consideration of the varying requirements on the PACL, due to differences in age and activity levels of patients, suggest that a band-type design offers a better possibility of achieving adequate materials performance in the ACL prosthetic replacement.
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    Journal of Biomedical Materials Research 14 (1980), S. 547-556 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Notes: The polarization resistance and anodic polarization curves of three amalgam types were determined in saline solution. Corrosion currents were determined by extrapolation of anodic Tafel slopes. A good correlation was found between corrosion currents and reciprocal polarization resistances, according to Ic = 0.02/PR.
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    Journal of Biomedical Materials Research 14 (1980), S. 557-566 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The mechanical properties of the hydrogel membrane of poly(methyl methacrylate-N-vinylpyrrolidone) were studied for the purpose of making soft contact lenses for extended wear. The dependence of tensile fracture energy, flexibility, and recovery from deformation on the water content and thickness of the hydrogel membrane was studied. Reducing the thickness of a lens was found to exert a more advantageous effect than increasing its water content on maximizing the tensile fracture energy under the condition of an adequate supply of oxygen to the cornea through the contact lens. As long as its water content is controlled between 63 and 78%, the contact lens made of poly(methyl methacrylate-N-vinylpyrrolidone) has the flexibility on the same order as that of conventional soft contact lenses of poly(2-hydroxyethyl methacrylate). The rate of recovery from deformation increases with water content, and the residual elongation is negligible in the range of water content over about 70%. It is concluded that practical requirements for use of these contact lenses, determined by these three mechanical properties, can be satisfied at the same time if the water content of the contact lens is adjusted at about 70%.
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    Journal of Biomedical Materials Research 14 (1980), S. 587-595 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A study was conducted which examined the influence of electropolishing on the corrosion resistance of a cold rolled 316L stainless steel. Test specimens were surface prepared to a final mechanical finish of wetted 600 grit SiC paper, prior to electropolishing. An o—H3PO4/Glycerol/H2O electropolishing solution was employed for times of 15, 20, and 25 min. Control specimens were surface prepared only to the final mechanical finish. Anodic polarization tests were performed in a deaerated Ringer's solution (37°C) which was acidified to pH 1, with HCl. The electropolished specimens demonstrated increased corrosion resistance, when compared to the control specimens. This was evidenced for the former by more anodic corrosion and breakdown potentials, and the absence of a dissolution peak which was observed for the control specimens at the initial polarization potentials. Surface hardness measurements indicated that this increase in corrosion resistance was produced, in part, by the removal of the cold worked surface layer produced by the mechanical finish. In terms of increasing corrosion resistance, no optimum electropolishing time was found within the 15-25 min treatment period.
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    Journal of Biomedical Materials Research 14 (1980), S. 597-605 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: When ground to a suitable form, flexural strength of single crystal alumina (Al2O3) decreases to as low as one third the strength of the intact crystal. This flexural strength decrease is, however, recovered by chemical etching at a high temperature to eliminate surface defects caused by grinding. By using this strength recovery treatment, various types of single crystal implants with fine structure were able to be designed. Four kinds of single crystal bone screws and single crystal dental implants of screw and anchor type were designed. Flexural strength and impact strength of the implants were measured.
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    Journal of Biomedical Materials Research 14 (1980), S. 619-630 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The reactions of covalently immobilized heparin, abbreviated as I-Hep, with thrombin or Factor Xa were investigated both in the presence and absence of antithrombin III, AT III. Although I-Hep was able to bind to thrombin, the complex formation of thrombin and I-Hep did not affect the thrombin activity when measured by using a small artificial substrate, a peptide-MCA. Similarly, Factor Xa bound to I-Hep, but the activity of Factor Xa was not decreased in the absence of AT III, when a peptide-MCA was used for Factor Xa assay. Thrombin bound to I-Hep in much larger amounts than Factor Xa. Thrombin and Factor Xa were instantaneously inhibited by AT III in the presence of soluble heparin. However, when I-Hep was used instead of soluble heparin, instantaneous inhibition was not observed. When a natural, high-molecular-weight substrate was used for assay, the results were dependent on the structure of the immobilization carrier. Heparin immobilized on Sepharose 4B or Poly HEMA showed considerable prolongation of plasma recalcification time. However, heparin immobilized on the surface of PVA fiber did not prolong plasma recalcification time.
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    Journal of Biomedical Materials Research 14 (1980), S. 631-638 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An in vivo model has been designed to study the acute response of exposed or unexposed dental pulp to the topical application of various biomaterials. This model permits sequential microscopic observations of the microvascular system of dental pulp before and after application of pulp capping agents, cementing agents, or cavity liners. The use of this experimental model provides useful information related to the tolerability of dental pulp to various biomaterials used in dentistry. Furthermore, this model serves as a useful supplement to more traditional long term methods for evaluating the biocompatability of dental materials.
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    Journal of Biomedical Materials Research 14 (1980), S. 607-618 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A direct physicochemical bond between alkali-rich bioglass or glass ceramic (45 S 5 A and B, Hench) or alkali-poor glass ceramic (KG S, Brömer) and bone has been well documented. Since long-term studies have revealed the interface to be subjected to remodeling of the bone and to increased focal disintegration of the implant, glass ceramics of reduced solubility have been developed by lowering the Na2O content and adding Al2O3, Ta2O5, TiO2, and Sb2O3. Implants of glass ceramic KG S and different compositions with reduced solubility have been studied histologically 14, 29, or 30, 60, 119, and 245 days after implantation in the femur of male Sprague-Dawley rats. Implants of KG S are anchored at an interface with bone connection, which is known to provide for application of considerable shear and tensile strengths; whereas, at the interface of ceramics of reduced solubility, soft tissue, chondroid and osteoid are mainly observed. The dynamics of the events at the interface indicate a disturbance of the transformation of chondroid cells into osteoblasts and of the mineralization of osteold. This disturbance of pathophysiologic processes during bone healing or bone regeneration is discussed.
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    Notes: Interfaces were formed between acrylic bone cement and three commonly used surgical alloys (316L SS, Co—Cr—Mo, and Ti—6A1—4V), in an attempt to further define cementation parameters of acrylic bone cement for use in orthopaedic surgery. Metal/cement interfaces were made at three distinct times during the setting cycle of the cement and were cured for 1 hr, 1 day, and 1 week. The metals were prepared with roughly polished or finely polished prepassivated surfaces. Tensile bond strengths and residual cement on metal coverage data indicated that, for each metal system, interfaces created prior to and at the onset of the dough stage formed superior interfaces for implanation compared to those formed late in the dough stage. Furthermore, electropolishing plus prepassivation offered a more efficient bonding surface than mechanical polishing.
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    Journal of Biomedical Materials Research 14 (1980), S. 653-663 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The effect of 16 pure metals on the in vitro growth of a form of dental caries producing Streptococcus mutans was studied under both aerobic and anaerobic conditions. Cobalt and copper were consistently observed to be inhibitory. With less consistency nickel, titanium, iron, and vanadium also exhibited ability to inhibit growth of the organism. Bacteriostasis apparently is contingent upon the presence of a corrosion process. The bacteriostatic agent is of uncertain identity and could be a corrosion product or a process secondary to the occurrence of corrosion. Concentrations of metals after 6 days of electrochemical dissolution in the growth medium were measured via electron microprobe analysis and compared with the amount of inhibition which resulted. Threshold concentrations above which growth did not occur were identified. As measured by threshold concentrations, wide variability between metals exists in the ability to inhibit the growth, with cobalt being particularly effective at small concentrations. This implies a sensitivity on the part of the organism that is different for different metals. The threshold concentration varied between aerobic and anaerobic conditions. Streptococcus mutans appeared more resistant to the effects of the metals under anaerobic conditions even though little difference in the amount of corrosion was detected.
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    Journal of Biomedical Materials Research 14 (1980), S. 665-687 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Graft copolymer systems have frequently been suggested for biomedical applications. Since the properties of polymers are altered by the grafting process, thorough characterization is critical, particularly for the surface region of these copolymers. This review briefly discusses the grafting process and then describes characterization procedures for graft copolymers. Gravimetric characterization, thermodynamic measurements, surface chemistry analysis, and surface topographical analysis are considered in detail. Also, the relevance of materials characterization for predicting and understanding the biocompatibility response is discussed. Most of the analytical techniques described are applicable to all biomaterials and should be considered for the routine characterization of materials which will be interfaced with biological systems.
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    Journal of Biomedical Materials Research 14 (1980), S. 689-703 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Failure behavior of a polyolefin elastomer which is a candidate material for blood pump applications has been studied under uniaxial and equibiaxial test conditions. Both static and dynamic (fatigue) testing were performed to study four aspects of material failure behavior as suggested by a cumulative damage failure model. Results from testing a standard formulation butyl rubber are presented for comparison. Our results show that the uniaxial failure behavior under static loads for the butyl rubber is superior to that of the polyolefin rubber at high loads but that the polyolefin is superior at low loads. Under fatigue loading conditions, the failure times for both rubbers decrease with increasing test frequency. The observed frequency dependence lies between that predicted by the cumulative damage model and that predicted by a cycle dependent fatigue model. The distribution of failure times for the polyolefin rubber is broader than that for the butyl rubber. For both uniaxial and equibiaxial testing, the distribution of failure times changes in going from the static testing to dynamic testing. This is true for both rubbers.
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  • 86
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    Journal of Biomedical Materials Research 14 (1980), S. 705-712 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to investigate whether the immune system is involved in the degradation of hydroxylapatite as implant material the adsorption behavior of several serum proteins to hydroxylapatite was studied and compared with the adsorption to other calcium phosphate compounds (Ca3(PO4)2, CaHPO4), calcium carbonate, aluminium oxide, and zinc oxide. It was found that complement factors, C4 and C3, and α2-HS-glycoprotein adsorbed to the calcium phosphate compounds, but not to the other materials. IgG and albumin were adsorbed to all investigated compounds. These results suggest that the complement factors are directly adsorbed on the surface of the calcium phosphate compounds. Therefore, the activation of complement, if any, proceeds by the classical pathway. The binding of complement factors to the calcium phosphate salts investigated points to a more specific involvement of the immunosystem in the degradation process of calcium phosphate implants.
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  • 87
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    Journal of Biomedical Materials Research 14 (1980), S. 723-730 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Pyrophosphate labeled with 99Tc was evaluated as an indicator of the calcification which occurs after implantation of polymeric materials in rats. Poly(2-hydroxyethyl methacrylate), both porous and homogeneous, had been implanted. 99Tc pyrophosphate was applied intravenously to rats in intervals from 14 days to 15 months. Scintigraphy, x-ray examination, and histology were carried out. The ratio of specific activity in the capsule around the implant to specific activity in the reference tissue was determined. The cumulation of activity was parallel with the development of calcification as revealed by histology. The method can be used not only in the screening test of new polymeric materials, but also in a quantitative determination of the degree of calcification in general.
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  • 88
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    Journal of Biomedical Materials Research 14 (1980), S. 713-721 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Dense (97-99.9%) hydroxylapatite ceramics were implanted in muscle and bone tissue of rats. The aim of this study was to compare apatite implant material made of commercially available powder with laboratory powder prepared in a painstaking manner. Biocompatibility, biostability, and adherence to bone were evaluated. In muscle tissue the implants were found to be encapsulated with a very thin connective tissue layer. Implantation in excavated bone tissue resulted with new bone directly deposited against the implant surface, irrespective of the type of hydroxylapatite used. When the implants were protruding from the bone surface, bone appeared to grow up to the edge of the protruding part of the implant. A very strong bonding developed; push-out tests indicated that the bone fractured but never at the interface. Histologic studies proved that a sleeve of newly formed bone closely encased the implant, regardless of shape. It was concluded that dense apatite ceramics are fully compatible with the tibia of the rat and that no degradation of the implant material occurred for intervals of up to 6 months after implantation. The very strong bonding without mechanical retention indicated continuity between artificial hydroxylapatite and natural bone. No difference was found between the biological behavior of the hydroxylapatites prepared from commercial or laboratory starting powders.
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  • 89
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    Journal of Biomedical Materials Research 14 (1980), S. 743-751 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Polymer-coated, activated charcoal granules have found considerable use for the direct detoxification of blood in cases of uraemia and drug overdose. Although polymer coating materials are presently selected for their biocompatibility, more selective polymers could be used to increase the adsorption capacity for specific drugs and toxins. To gain an understanding of the fundamental factors influencing these adsorbent systems, we have investigated a possible selective coating material, nylon 6 and studied its influence on adsorption rates of simple model compounds when applied as a thin coat to activated charcoal granules. Thermodynamic studies have shown that phenolic compounds interact with the polymer by a hydrogen bonding mechanism, whereas nonphenolic compounds probably bind less strongly due to Van der Waals type interactions. Kinetic studies have shown that the selectivity of charcoal granules for phenolic compounds was increased by coating the granules with a thin layer of nylon 6. The increase in selectivity is probably a result of the different binding mechanism between solute and the polymer. These studies have shown that possible selective coatings may be evaluated more effectively on the basis of simple preliminary drug-plastics interaction studies.
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  • 90
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    Journal of Biomedical Materials Research 14 (1980), S. 731-742 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Under certain circumstances, e.g., when treating “denture sore mouth” or after the provision of immediate dentures, dentures may be lined with soft rubberlike materials which have Young's moduli within the range ≃105 N m-2. Measurement of the compression modulus Ec of such soft liners is described and Gent and Lindley's method of calculating Young's modulus E was evaluated. It was established that the Young's modulus may be calculated using: Ec = E(1 + 2kS2), where k = 1 for soft rubbers, and for disks S is a shape factor and = radius/2 × thickness. It is also shown that Young's modulus is a linear function of log(rate of strain) for both tension and compression measurements. When gellation has occurred subsequent to mixing there is an increase in Young's modulus due to loss of ethanol. When immersed in brine the elastic modulus remains approximately constant from a day to a week or longer.
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  • 91
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    Journal of Biomedical Materials Research 14 (1980), S. 765-776 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A highly sensitive method to localize aluminum oxide or polyethylene wear particles in biological tissues is presented. Using the scanning electron microscope (SEM) with a special cathodoluminescence detector system, small amounts of these foreign materials can be visualized in simple frozen sections by their bright luminescence, even at low magnifications (200X). At higher magnifications, a differentiation of free as well as phagocytized aluminum oxide and polyethylene particles can be made due to their different behavior in light emission. In addition, aluminum oxide such as other metals can be identified by x-ray microprobe analysis. This combination of SEM with microprobe analysis and with the highly sensitive cathodoluminescence mode enables to detect and identify wear products from all the materials, commonly used in manufacturing artificial joint replacements.
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  • 92
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    Journal of Biomedical Materials Research 14 (1980), S. 753-764 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Glutaraldehyde is commonly used to control physical and biological properties of collagen structure by means of intramolecular and/or intermolecular crosslinking of collagen molecules. Solubility, antigenicity, and biodegradation of naturally occurring or reconstituted collagenous matrices are effectively reduced by glutaraldehyde treatment. Adverse biological reactions to glutaraldehyde have been limited to infrequent contact dermatitis and to biocidal effects which are exploited in chemical sterilization media. In the present study of glutaraldehyde-tanned collagen sponge, the presence of glutaraldehyde was correlated with cytotoxic effects upon fibroblasts in tissue culture and foreign body giant cell reaction to bioimplants of the sponge. Fibroblast growth in tissue culture is 99% inhibited at media concentrations of 3.0 ppm glutaraldehyde. Extracts of glutaraldehyde collagen sponge in aqueous media at pH 7 and 4.5 yielded 6 μg and 65 μg glutaraldehyde per gram of collagen sponge, respectively. The yield increased tenfold at pH 4.5. Observations indicate that leaching of the glutaraldehyde from glutaraldehyde-tanned collagen sponge is sufficient to produce potentially adverse cellular effects both in vivo and in vitro.
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  • 93
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    Journal of Biomedical Materials Research 14 (1980), S. 777-788 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In a clinical evaluation of marginal deterioration, 475 amalgram restorations were equally distributed in a 6 × 4 × 2 × 3 factorial design, based on alloy, operator, tooth, and number of restored surfaces. All factors except the last had a statistically significant effect after 6, 12 and 18 months. There were no consistent two-way interactions over time.
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  • 94
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    Journal of Biomedical Materials Research 14 (1980), S. 803-811 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this excellent and analytical article, the immediate past President of the Society for Biomaterials reviews some of the most salient aspects of the Biomaterials scientists' work. His observations and comments are significant and crystallize current thought succinctly and with intelligence. - Ed.
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  • 95
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    Journal of Biomedical Materials Research 14 (1980), S. 789-801 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Morris Hepatoma experimental tumor in ACI rats is treated with small anodal direct current via an implantable power pack unit. There was major retardation in tumor growth when the treatment was started early. There was enhancement of tumor growth when the treatment was started early and then was discontinued. There was no statistical difference in growth control of the experimental tumor when the electrotherapy was given after the half-life of the tumor was achieved. This last point will be the most important to the clinician scientist, for it simulates the clinical situation that faces the treating physician.
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    Journal of Biomedical Materials Research 14 (1980), S. 813-815 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    Journal of Biomedical Materials Research 14 (1980), S. 817-823 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    Journal of Biomedical Materials Research 15 (1981) 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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    Journal of Biomedical Materials Research 14 (1980), S. 825-825 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Journal of Biomedical Materials Research 15 (1981), S. iii 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
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