956 research outputs found
The Stress-Corrosion Cracking of Austentic Stainless Steels in Aqueous Chloride Solution
The stress-corrosion cracking of 18-8 type steels in hot concentrated magnesium chloride solutionshas been studied. There is an induction period, of which the processes are substantially unaffected hvv stress, followed by a period of rapid crack propagation - as shown by measurements of the electrode potential, the mechanical properties and
the extension of direct-loaded wire specimens. The indu-ction period is shortened by increase of applied stress and of temperature, and by cold-work on a fully softened material; it may he indefinitely lengthened by cathodic protection of the metal. Crack propagation is normally at rates of 1-4 mm./hr. ; it is not greatly influenced by increase of applied stress, is somewhat accelerated by increase of temperature, and may be slowed down or stopped
cntirely by cathodic protection
Nitrate and Vitamin A Interrelationship in Sheep
Several researchers have demonstrated that dietary nitrate reduced liver stores of vitamin A in ruminants. However, it has not been shown whether the effect is due to a more rapid depletion of existing vitamin A stores or to a lowered depatic deposition of the vitamin. Two experiments were conducted to determine the effect of nitrate on plasma vitamin A, hepatic vitamin A and performance of lambs during a growing period (experiment 1) and vitamin A depletion and repletion periods (experiment 2)
Urea-Nitrate Interrelations in Sheep Under Feedlot Conditions
Three experiments were conducted to determine if measurable urea-nitrate interrelationships exist in sheep under feedlot conditions, and the extent of nitrogen utilization from urea and nitrate by sheep fed rations containing suboptimum quantities of protein. Dietary conditions imposed provided for the simultaneous adaptation of lambs to urea and sodium nitrate (experiment 1); an exposure to sodium nitrate without prior adaptation after lambs has been brought to a full feed on a ration containing urea (experiment 2); and the use of soybean meal, urea and sodium nitrate independently as protein supplements to rations providing suboptimum levels of crude protein (experiment 3)
Reproduction provoquée chez les poissons : théorie et pratique
Version anglaise disponible dans la Bibliothèque numĂ©rique du CRDI : Theory and practice of induced breeding in fishVersion espagnole disponible dans la Bibliothèque numĂ©rique du CRDI : TeorĂa y práctica de la reproducciĂłn inducida en los pecesVersion arabe dans la bibliothèqueVersion chinoise dans la bibliothèqu
Theory and practice of induced breeding in fish
French version available in IDRC Digital Library: Reproduction provoquĂ©e chez les poissons : thĂ©orie et pratiqueSpanish version available in IDRC Digital Library: TeorĂa y práctica de la reproducciĂłn inducida en los pecesArabic version available in IDRC Digital LibraryChinese version available in IDRC Digital Librar
Translating aboveground cosmic-ray neutron intensity to high-frequency soil moisture profiles at sub-kilometer scale
Above-ground cosmic-ray neutron measurements provide an opportunity to infer soil moisture at the subkilometer scale. Initial efforts to assimilate those measurements have shown promise. This study expands such analysis by investigating (1) how the information from aboveground cosmic-ray neutrons can constrain the soil moisture at distinct depths simulated by a land surface model, and (2) how changes in data availability (in terms of retrieval frequency) impact the dynamics of simulated soil moisture profiles. We employ ensemble data assimilation techniques in a “nearly-identical twin” experiment applied at semi-arid shrubland, rainfed agricultural field, and mixed forest biomes in the USA. The performance of the Noah land surface model is compared with and without assimilation of observations at hourly intervals, as well as every 2 days. Synthetic observations of aboveground cosmic-ray neutrons better constrain the soil moisture simulated by Noah in root-zone soil layers (0–100 cm), despite the limited measurement depth of the sensor (estimated to be 12–20 cm). The ability of Noah to reproduce a “true” soil moisture profile is remarkably good, regardless of the frequency of observations at the semi-arid site. However, soil moisture profiles are better constrained when assimilating synthetic cosmic-ray neutron observations hourly rather than every 2 days at the cropland and mixed forest sites. This indicates potential benefits for hydrometeorological modeling when soil moisture measurements are available at a relatively high frequency. Moreover, differences in summertime meteorological forcing between the semi-arid site and the other two sites may indicate a possible controlling factor to soil moisture dynamics in addition to differences in soil and vegetation properties
Translating aboveground cosmic-ray neutron intensity to high-frequency soil moisture profiles at sub-kilometer scale
Above-ground cosmic-ray neutron measurements provide an opportunity to infer soil moisture at the subkilometer scale. Initial efforts to assimilate those measurements have shown promise. This study expands such analysis by investigating (1) how the information from aboveground cosmic-ray neutrons can constrain the soil moisture at distinct depths simulated by a land surface model, and (2) how changes in data availability (in terms of retrieval frequency) impact the dynamics of simulated soil moisture profiles. We employ ensemble data assimilation techniques in a “nearly-identical twin” experiment applied at semi-arid shrubland, rainfed agricultural field, and mixed forest biomes in the USA. The performance of the Noah land surface model is compared with and without assimilation of observations at hourly intervals, as well as every 2 days. Synthetic observations of aboveground cosmic-ray neutrons better constrain the soil moisture simulated by Noah in root-zone soil layers (0–100 cm), despite the limited measurement depth of the sensor (estimated to be 12–20 cm). The ability of Noah to reproduce a “true” soil moisture profile is remarkably good, regardless of the frequency of observations at the semi-arid site. However, soil moisture profiles are better constrained when assimilating synthetic cosmic-ray neutron observations hourly rather than every 2 days at the cropland and mixed forest sites. This indicates potential benefits for hydrometeorological modeling when soil moisture measurements are available at a relatively high frequency. Moreover, differences in summertime meteorological forcing between the semi-arid site and the other two sites may indicate a possible controlling factor to soil moisture dynamics in addition to differences in soil and vegetation properties
Changes in self-schema structure in cognitive therapy for major depressive disorder: a randomized clinical trial.
Negative cognitive structure (particularly for interpersonal content) has been shown in some research to persist past a current episode of depression and potentially to be a stable marker of vulnerability for depression (D. J. A. Dozois, 2007; D. J. A. Dozois & K. S. Dobson, 2001a). Given that cognitive therapy (CT) is highly effective for treating the acute phase of a depressive episode and that this treatment also reduces the risk of relapse and recurrence, it is possible that CT may alter these stable cognitive structures. In the current study, patients were randomly assigned to CT+ pharmacotherapy (n = 21) or to pharmacotherapy alone (n = 21). Both groups evidenced significant and similar reductions in level of depression (as measured with the Beck Depression Inventory-II and the Hamilton Rating Scale for Depression), as well as automatic thoughts and dysfunctional attitudes. However, group differences were found on cognitive organization in favor of individuals who received the combination of CT+ pharmacotherapy. The implications of these results for understanding mechanisms of change in therapy and the prophylactic nature of CT are discussed
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