A SIMPLIFIED MODEL FOR PREDICTING DAILY TRANSMISSION LOSSES IN A STREAM CHANNEL1

ABSTRACT: A simplified approach for modeling transmission losses in a stream is presented. A theory relating seepage from a channel with the depth of flow is simplified to a one-parameter relationship. A power relationship is then utilized for the stage-discharge relationship, which is coupled with the seepage relationship. This combined equation is integrated over the channel reach to arrive at a general model for seepage loss through the reach, with one parameter needing calibration. An example is provided showing the development of the relationship and the calibration technique for the parameter. The results are shown, emphasizing the use of the model for simulation of channel transmission losses at low and moderate flow conditions.     

Ventilation efficiency

Research indicates that ventilating systems can be designed for higher ventilation efficiency in the zone of occupation than systems designed for complete mixing. Expressions for ventilation efficiency are derived using a two-box theoretic model. These definitions of ventilation efficiency can be used for practical measurements, and also seem to be valid for multibox schemes. Measurements reviewed show that diagonal schemes are the most efficient. Short-circuiting schemes, with warm air supply along the ceiling and high wall exhaust, produce very low efficiencies. The mathematical model predicts high efficiencies using diffuse air supply directly to the zone of occupation, if the air is not used heating.     

欧洲地表酸化水体恢复--未来展望

到目前为止,有关欧洲地表酸化水体大范围化学恢复的文献层出不穷,而有关生物恢复的报道并不多见.建立在现今欧洲排放减少计划之上的模型研究表明,化学恢复仍将继续.而影响恢复进程的诸多不确定性因素主要包括:未来生态系统内氮的可能行为和气候变化的影响.下列4个与气候变化相关的因子可能对未来恢复进程产生影响:①海水盐分入侵事件爆发频率和强度增加;②干旱发生频率和强度上升;③有机碳交换周期加快;④硝化作用增强.目前降低水体酸化程度的国际性协作是成功的,但是未来还有大量问题需要解决,也会遇到许多困难.对未来硫、氮排放减少后以及气候变化背景下酸化地表水体的水化学和水生生物变化需要继续监测.     

东非十足类螃蟹迈纳新胀蟹对红树林海底落叶的清理

本文通过在东非进行的一系列野外和实验室试验,研究了丰富的红树林十足类螃蟹迈纳新胀蟹(Neosarmatium meinerti)对落叶的清理.在地势高的海榄雌(Avicennia meinerti)潮间带,螃蟹掩埋了所有红树林林区海底的落叶,而且会在2小时内平均消耗其中的67%.     

Visual fields in Flamingos: chick-feeding versus filter-feeding

In birds, the position and extent of the region of binocular vision appears to be determined by feeding ecology. Of prime importance is the degree to which vision is used for the precise control of bill position when pecking or lunging at prey. In birds that do not require such precision (probe and filter-feeders), the bill falls outside the binocular field, which extends above and behind the head, thus providing comprehensive visual coverage. Flamingos Phoenicopteridae are highly specialised filter-feeders. They employ a unique technique that does not require accurate bill positioning in which the inverted head is placed between the feet. Feeding flamingos often walk forwards with the head pointing “backwards”. Here we show that in Lesser Flamingos Phoeniconaias minor visual fields are in fact the same as those of birds that feed by precision pecking and that feeding flamingos are blind in the direction of their walking. We suggest that this is due to the requirement for accurate bill placement when flamingos feed their chicks with “crop-milk”, and possibly when building their nest. We propose that chick-feeding may be the ultimate determinant of visual field topography in birds, not feeding ecology.     

Initiale Aktivität und Willkürverhalten bei Tieren

Initiation as a basic property of behavioral activity is functionally analyzed and discussed at the level of voluntary behavior. Fixed action patterns often are not released by stimuli but are generated by the animal itself through brain processes of the Darwinian type. Analogous to mutations, behavioral “subroutines” are brought up by chance and are subjected to selection either by the change in the situation (trial and the elimination of error) or by mental activity suppressing inappropriate behavior even before it is executed.Initiation improves the chance of survival. It is a prerequisite of goal-oriented behavior, an essential constituent of operant conditioning and presumably the first step in the evolution of thought. According to I. Kant a person is free if, by following his own directive, he does what has to be done. This definition meets the two central criteria of initiation: the independence of releasing stimuli and the adaptive value of the behavior generated.