769 research outputs found

    Using the TIMS to estimate evapotranspiration from a forest

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    The main goals were: (1) to characterize the evapotranspiration (Et) of two forested watersheds using direct measurement techniques, and (2) to evaluate if remotely sensed surface temperatures could be used to estimate Et from the same watersheds. Two independent approaches for estimating the Et from watersheds were used. The first was derived using the Penman-Monteith Equation. This model requires the direct measurement of the microclimate of the site as well as biological measurements, i.e., stomatal conductance to water vapor and the leaf area of the stand. The primary limitation of this approach is that the measurement of stomatal conductance is time consuming, and in large trees, access to the foliage is difficult so the sample must be limited to the small number of trees. In the study, the sample was limited to the trees which could be measured from a single tower in each stand

    A Mariotte-based verification system for heat-based sap flow sensors

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    Determination of the accuracy of commonly used techniques for measuring sap flux density in trees often presents a challenge. We therefore designed and built a verification system for heat-based sap flow sensors typically used at stem level. In the laboratory, a Mariotte's bottle device was used to maintain a constant flow rate of water through freshly cut stem segments of American beech (Fagus grandifolia Ehrh.). This verification system was used to determine the accuracy of three heat-based sap flux density techniques: heat pulse velocity, thermal dissipation and heat field deformation. All three techniques substantially underestimated sap flux density when compared against gravimetric measurements. On average the actual sap flux density was underestimated by 35% using heat pulse velocity, 46% using heat field deformation and 60% using thermal dissipation. These differences were consistent across sap flux densities ranging from 5 to 80 cm(3) cm(-2) h(-1). Field measurements supported the relative sensor performance observed in the laboratory. Applying a sensor-specific correction factor based on the laboratory test to the field data produced similar estimates of sap flux density from all three techniques. We concluded that a species-specific calibration is therefore necessary when using any of these techniques to insure that accurate estimates of sap flux density are obtained, at least until a physical basis for error correction can be proposed

    Expression Of The Proto-oncogene C-fos Following Electrical Kindling In The Rat

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    Kindling is an example of permanent change in brain function that results from repeated elicitation of epileptiform neural activity. The molecular/genetic mechanisms by which kindling is produced and maintained are just beginning to be addressed. Recently two proto-oncogenes, c-fos and c-Ha-ras, have been identified as possible mediators of intracellular signal transduction and may mediate the kindling process. Additionally, c-fos, has been proposed as the gene responsible for turning on molecular events that might underlie the long-term neural changes that occur during kindling. The objective of the present study was to: (i) further investigate the enhancement of c-fos and c-Ha-ras levels following kindled seizures and (ii) investigate the role of c-fos in the plastic changes underlying kindling.;In this study, male hooded rats, were electrically kindled and the resulting c-fos and c-Ha-ras gene expression was quantified using Northern blot analysis. The results indicated that: (i) c-fos was constitutively expressed in forebrain and cerebellum, (ii) basal levels of c-fos were equivalent in naive and in fully kindled rats that has been seizure free for 3 weeks, (iii) an amygdala-pyriform kindled seizure massively and transiently increased c-fos levels, (iv) kindled seizure enhancement of c-fos was observed throughout forebrain and cerebellum, (v) enhancement of AD duration corresponded to enhanced c-fos levels, (vi) enhanced c-fos levels were observed in the amygdala-pyriform contralateral to the kindled site, and the enhancement did not depend on the occurrence of Ad in the contralateral amygdala-pyriform, (vii) electrical stimulations not resulting in AD increased c-fos levels, (viii) c-fos levels were increased by control stimulation, (ix) c-fos induction was partially refractory, (x) PTZ caused c-fos induction independent of a motor convulsion, and (xi) kindled seizures did not alter the expression of c-Ha-ras.;The most parsimonious explanation that accounts for the observations made in this study is that c-fos was expressed simply as a consequence of neural activity and not exclusively due to the specific neural activity (afterdischarge) required for kindling

    Partners in Haiti

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    In this article, a group of Purdue Students describes their service-learning experience in Haiti. They highlight what they learned about Haitian culture, the country’s need for agricultural and economic sustainability, and how Purdue students contribute to meet these needs. Maggie Del Ponte is a senior in biological engineering, Rachel Stowers is a sophomore in agricultural economics, Montana Campbell and Kelli Teskey are seniors in animal sciences, and Christa Cheatham is a junior in animal sciences
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