Types Of Days Research Articles

Relative Importance of Reradiation, Convection, and Transpiration in Heat Transfer from Plants

For a plant of average spectral properties and average diffusion resistance (2 sec/cm), diurnal variations in the energy dissipated by reradiation, convection, and transpiration have been explicitly calculated and plotted for certain environmental conditions as measured at St. Paul, Minnesota. These conditions represent the environments of characteristic types of days and of characteristic types of leaves. In all situations reradiation is overwhelmingly the dominant mode of heat transfer.A new method for the calculation of Bowen's ratio is also presented which gives results in very good agreement with older procedures. For certain individual leaves the energy dissipated by convection is found to be greater than that dissipated by transpiration. For a crop as a whole, however, transpiration is found to be by far the most important.

Instrumental Acquisition and Performance on Fixed-Interval Reinforcement as a Function of Incentive Contrast

Four groups of rats were alternately magazine trained and bar-press trained on successive days. Two incentive-contrast groups both received 64% sucrose on magazine-training days; one group was shifted to 32% and the other to 8% sucrose reinforcement on barpress days. One control group received 32% sucrose on both types of days and a second received 8% sucrose on both. All reinforcements were on a 1-min. fixed-interval schedule. Both of the shift groups barpressed at a higher rate than their respective controls during early acquisition trials, but at a lower rate during later trials, on which asymptotic performance was approached. Interpretation of this two-phase result was suggested in terms of an increasing discrimination in the experimental Ss between magazine and barpress incentives.

The diurnal temperature variation during the polar night

AbstractIt is well known that if special types of days are considered separately, systematic diurnal temperature variations may be found to exist at polar stations even during the dark season. In the present paper it is shown that, in all probability, this phenomenon is of trivial nature and that a perfectly simple explanation of its origin is possible.

Electrical resistance of a vertical column of air over Watheroo (western Australia) and over Huancayo (Peru)

For the first time, strictly simultaneous atmospheric‐electric data on sea and land have been compared. Such comparisons make it possible, on the basis of reasonable assumptions, to compute the total resistance of a vertical air‐column of unit cross‐section at the station on land. A total of 42 complete fair‐weather days during November and December, 1928, and January and February, 1929, from the Pacific Ocean and from the Watheroo Magnetic Observatory have been utilized. The data were formed into two groups, (1) smoky days (when smoke was in the air at Watheroo) and (2) non‐smoky days (air without smoke). The computed resistance of the vertical air‐column at Watheroo has a pronounced diurnal variation with a minimum shortly before noon for both types of days. This is accounted for on the basis of two stratified horizontal layers of air, assuming that the resistivity of the upper layer is constant through the day, and that of the lower layer is giyen by the conductivity‐measurements near the ground. Half of the total resistance lies in the upper and half in the lower layer. The resistance of the lower layer varies with the resistivity; hence the effective height to which the layer extends is constant, amounting to about 1.5 km. Gish and Sherman concluded from stratosphere conductivity‐measurements that between this height and the ground in the free atmosphere almost half of the total resistance is normally encountered, in good accord with the present results.Comparison of data from Huancayo Magnetic Observatory with those from the Pacific Ocean taken during October, 1929, indicates that the total resistance at Huancayo is independent of variations in resistivity of the lower layer, thus indicating a very small thickness for the lower layer. The computed resistance for Huancayo is over three times that expected from consideration of the altitude of the station (3.3 km). This and other observed facts in atmospheric electricity at Huancayo are explainable on the assumption that a permanent bank of condensation‐nuclei exists in the air a short distance above the ground.