Developing Consistency in Enamel Etching by CO\u3csub\u3e2\u3c/sub\u3e Laser

It has been reported that CO2 laser energy can be utilized to etch enamel. However, consistency of etching has been a significant problem. This research was designed to ascertain which exposure parameters result in consistent etching of enamel. Fourteen non.carious teeth were selected and a 2x4 gridwork was cut into the buccal surfaces creating eight discrete windows for laser exposures. Four teeth served for the initial pilot project. Two windows were lased at each combination of exposure parameters. Laser exposures were at .01, .02, .05, or .10 sec. at 2, 5, 10, or 15 Watts (W) with a model 20C Pfizer CO2 laser. A 1.0mm focal spot was used throughout. Following SEM examinations, it became clear that etching occurred only at .05 and .10 sec. at 10 and 15W. Ten teeth were used for the main project at .05 and .10 sec. exposures at 10 and 15W. Ten windows were lased for each combination of exposure parameters. SEM analysis was accomplished at 100X and 1,200X. 10/10 laser exposures at .05 sec./15W, .10 sec./10W and .10 sec./15W resulted in etched enamel. Statistical analysis showed a significant difference in etching between the .05 sec.10W group and the higher exposure parameters (p= .003). The results indicate that CO2 laser energy can consistently etch enamel at .10 sec. at 10 or 15W and at .05 sec. at 15W with a 1.0mm focal spot

Prospects for global food security: a critical appraisal of past projections and predictions

During the last half century, a number of individuals and institutions, including the Food and Agriculture Organization of the United Nations (FAO) and IFPRI, have engaged in projections of future food demand, supply, and related variables. In this brief, Alex McCalla and Cesar Revoredo compare projections with real-life outcomes. Projections forecast outcomes on the basis of certain underlying factors. If such forecasted outcomes are undesirable, changes may be made in the underlying factors so that the projections may not, in fact, come to pass. Many projections serve this precise goal. Therefore, the success of projections may not be that they match actual outcomes but that they avoid such outcomes by promoting action to change underlying variables. Unlike predictions, which are successful only if they match actual outcomes, projections that differ from actual outcomes may reflect either poor projection models or changes in underlying variables, possibly caused by the projections themselves.Food consumption., Food security.,

Determinants of the Organic Farmers' Demand for Hired Farm Labor

Labor and Human Capital,

FARM FINANCIAL STRUCTURE DECISIONS UNDER DIFFERENT INTERTEMPORAL RISK BEHAVIORAL CONSTRUCTS

An alternative unconstrained expected-utility maximization model of farm debt is developed using the location-scale parameter condition that incorporates the empirically validated hypotheses of decreasing absolute and constant relative risk aversion. Simulation-optimization results based on the old and new model versions provide interesting implications for various levels of risk aversion and initial equity investments.Risk and Uncertainty,

Farmland Control Decisions under Different Intertemporal Risk Behavioral Constructs

Simulation-optimization techniques are employed to analyze changes in farmland control arrangements as a result of using different constructs of intertemporal risk behavior. Risk behavior based on constant absolute risk aversion (CARA) and constant relative risk aversion (CRRA) mean-standard deviation functions are used to achieve this objective. Specfically, a multi-period programming framework for a representative grain farm is developed to explore farmland control decisions under these two behavioral assumptions. Our results suggest that the use of a CRRA behavioral construct in analyzing farmland control decisions produce predictions that are more consistent with observed farm behavior.Farm Management,

THE SUSTAINABLE GROWTH PARADIGM'S APPLICATION TO U.S. FARM BUSINESSES

The sustainable growth paradigm is used to analyze aggregate output decisions across U.S. agricultural productions regions. Results show that the farm sector has adapted to positive or negative sustainable growth challenges (SGC) and that, from an equilibrium point of view, SGC countercyclical measures indicate a usual tendency towards balanced growth.Production Economics,

Weather Cycles, Production Yields and Georgia's Muscadine

This paper looks at the relationship between weather, crop yield, and market price of muscadines using a dynamic panel data that spans from the 2000 to 2005 and across the state of Georgia. We use a Generalized Methods of Moments technique to estimate the impact of weather on the price of muscadines with the yield per acre as the instrumented variable. The results suggest that there is a relationship between the price and weather for muscadines, which provide important implications for the potential relevance of a weather derivative for muscadine production.muscadines, weather cycles, price, production yields, Georgia, Generalized Method of Moments, Farm Management, Risk and Uncertainty,

Evaluating Agricultural Banking Efficiency Using the Fourier Flexible Functional Form

This study applied more flexible cost functional form, Fourier Flexible Functional Form, and tested the validity of the Translog cost functional form as to estimate the cost function incorporating risk and loan's quality for banking industry. Meanwhile, the study extended four different cost efficiency measures for banking industry not only among different sized banks but also between commercial banks and agricultural banks. And thereafter, by evaluating these efficiency measures, banks will identify sources of inefficiency, which should aid banks in developing approaches to improve their operational policies, procedures, and performance.Agricultural Finance,

Gender Bias Claims in Farm Service Agency’s Lending Decisions

This study analyzes the courts’ denial of women farmers’ motion for class-action certification of their lawsuits alleging gender discrimination in Farm Service Agency (FSA) lending decisions. The plaintiffs’ claim of “commonality†of circumstances in women farmers’ dealings with FSA is tested using a four-year sampling of Georgia FSA loan applications. The econometric framework has been developed after accounting for the separability of loan approval and amount decisions, as well as endogeneity issues through instrumental variable estimation. This study’s results do not produce overwhelming evidence of gender bias in FSA loan approval decisions and in favor of the “commonality†argument among Georgia FSA farm loan applicants.class-action suit, credit risk, creditworthiness, gender discrimination, Heckman selection, instrumental variable probit, Labor and Human Capital,

Determinants and outcomes of motivation in health professions education: a systematic review based on self-determination theory

Purpose: This study aimed at conducting a systematic review in health professions education of determinants, mediators and outcomes of students’ motivation to engage in academic activities based on the self-determination theory’s perspective. Methods: A search was conducted across databases (MEDLINE, CINHAL, EMBASE, PsycINFO, and ERIC databases), hand-search of relevant journals, grey literature, and published research profile of key authors. Quantitative and qualitative studies were included if they reported research in health professions education focused on determinants, mediators, and/or outcomes of motivation from the self-determination and if meeting the quality criteria. Results: A total of 17 studies met the inclusion and quality criteria. Articles retrieved came from diverse locations and mainly from medical education and to a lesser extent from psychology and dental education. Intrapersonal (gender and personality traits) and interpersonal determinants (academic conditions and lifestyle, qualitative method of selection, feedback, and an autonomy supportive learning climate) have been reported to have a positive influence on students’ motivation to engage in academic activities. No studies were found that tested mediation effects between determinants and students’ motivation. In turn, students’ self-determined motivation has been found to be positively associated with different cognitive, affective, and behavioural outcomes. Conclusion: This study has found that generally, motivation could be enhanced by changes in the educational environment and by an early detection of students’ characteristics. Doing so may support future health practitioners’ self-determined motivation and positively influence how they process information and their emotions and how they approach their learning activities