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An important trend in modern electronics is toward decreased size and increased reliability of electronic systems. This paper discusses a new simple structure which performs the function of a twin-T network, i.e., a null output is produced at a single frequency. This new structure has the advantage of being very small, simple to fabricate, and easy to use in conjunction with transistorized circuits. The theory of operation of the device, experimental verification of the theory, and some circuits containing the device is also discussed. The structure has been found useful to create a high-Q tuned amplifier, an oscillator, and a threshold transducer. The physical simplicity of the structure should result in a high degree of reliability and uniformity of response. It should be noted that the structure can be fabricated from semiconductor materials and is thus suited to "molecularized" or "integrated" solid state systems.

The pulsatile organ, or "accessory heart," in the tibia of Triatoma consists of a membrane which divides the femur and tibia into a series of sinuses, a pulsatile muscle which propels the haemolymph through the sinuses, and a valvular membrane, which imposes unidirectional flow on the system. A possible innervation of the muscle is described, and simple experiments involving nerve stimulation demonstrate that the pulsatile muscle is under nervous control. Using partially isolated preparations of the pulsatile organ, it has been shown that the organ responds to dopamine and serotonin, but fails to respond to acetylcholine. The pulsatile muscle therefore resembles visceral muscle rather than skeletal muscle.

Heat treatments of evaporated CdS layers in nitrogen containing HCl and traces of oxygen, and providing a transport of CdS and copper are reported. Recrystallization of areas up to several mm2 are observed. At 25°C, the treated layers show mobilities of 140 to 230 cm2/V·sec, photoconductivities of 10−3 to 2×10−1Ω−1cm−1 at 750 ft‐c (2600°K white light) with light‐to‐dark‐current ratios of 108–109 and response time (decay) of 300 μsec to 1.2 msec at 100 ft‐c. The level distribution and capture cross section for electrons is investigated using spectral distribution, light intensity, and temperature dependence of photoconductivity, thermally stimulated current and response time analyses. Levels at 0.23, 0.43, 0.67, 1.05, and 2.05 eV are observed and the latter three attributed to Cu centers. Compared to other layers and single crystals, these layers show a density of

The effects of small (

Laboratory and field experiments were conducted with helium as a ground-water tracer. Techniques were developed for the addition and extraction of helium from water. A mass spectrometer and a pressure-volume apparatus were used for helium measurements at concentrations in water ranging from 1.5 to 5.5×10−4 milligrams per liter. In the field investigation, flow was traced through a confined aquifer for a distance of 188 feet. Both laboratory and field experiments showed that helium traveled at a slightly lower velocity than chloride. The advantages of helium as a ground-water tracer are its safety, low cost, relative ease of analysis, low concentrations required, and chemical inertness. The disadvantages include the relatively large errors in analysis, difficulties of maintaining a constant recharge rate, time required to develop equilibrium conditions in unconfmed aquifers, and possible loss to the atmosphere in unconfined aquifers.

Tritium in form of tritiated water is nearly perfect ground water tracer; its disadvantage lies in its radioactive properties and effects on public health; comparison of risks and benefits; evaluation of possible public health hazards and permissible concentrations of tritium in water; it is concluded that in case of aquifer recharge with waste waters in Los Angeles County mentioned as example, proposed study by use of tritium as tracer would be justified.

A study has been made to see if hyperplastic and biochemical responses similar to those which occur in temperature-exposed rodents also occur in insectivores, protoprimates and primates. Representative insectivores included the shrewsSuncus murinus andCryptotis parva. The representative prottoprimate wasTupaia chinensis. The representative primate wasMacaca mulatta. Both shrews show a striking thermogenic response in the brown fat with respect to increased specific activity of α-glycerophosphate oxidase and succinoxidase.Suncus also showed an increase in brown fat mass following cold exposure. In both shrews cold caused the brown fat to become darker in color.Cryptotis did not show a significant increase in brown fat mass, but this may be due to the fact that the cold exposure period was only four days. Thus the shrews appear to be rodent-like with respect to effects of cold on brown fat. In the Tupaiads the ratio of brown fat to body weight is not nearly as high as in rodents nor is there a striking hyperplasia with cold exposure. Thus the brown fat would seem to be of less importance to the Tupaiads than to rodents and shrews and the Tupaiads appear to be intermediate in this respect between the insectivores and the true primates. AdultMacaca, in spite of eight months of cold exposure at about 4–6 C, showed no hyperplasia of the brown fat and no increase in oxidative enzyme levels. Thus in adult primates so far studied, the evidence indicates that brown fat does not play an important role in homeothermy as it does in rodents.

Valving concepts and functional approaches for inert gas attitude control thrustor systems providing redundancy safeguards at minimum weight, volume and power costs

The ideal ground-water tracer should correctly depict the movement of water through a porous medium without modifying the transmission characteristics of the system. Cationic materials, including radio-isotopes and certain organic dyes, are generally unsatisfactory and anionic radio-isotopes when used without stable carriers may be largely retained by adsorption. Chloride may be satisfactorly used where density effects can be avoided and dispersion of clays is not likely. Organic materials are subject to decomposition by soil microorganisms and hence their value as water tracers are limited. Tritium, when used as tritiated water, may exchange with soil bound water with a resulting reduction in velocity of the tracer front.