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We should welcome books of healthy propaganda, but let's recognize them as just that and not make them the mainstay of our children's reading diets. (CH)

Glycerylphosphorylcholine diesterase ( l -3-glycerylphosphorylcholine glycerophosphohydrolase, EC 3.1.4.2) has been studied with respect to metal ion involvement. The effects of a number of metal-binding agents have been investigated by preincubation and instantaneous inhibition techniques. A high degree of selectivity of the metal-binding agent has been observed, with EDTA showing the greatest amount of inhibition. Structural analogs of EDTA have however, been found to be as effective as EDTA. The inhibition produced by EDDA has been determined to be competitive inhibition with respect to substrate. Heat and urea potentiate the inhibition seen with EDTA. Zn 2+ ions have been found to alleviate the EDTA-produced instantaneous inhibition and were observed to produce noncompetitive inhibition with respect to GPC. Dialysis against 0.01 m EDTA, pH 7.1, and water has been found to completely inactivate the enzyme, whereas addition of several cations to the EDTA-dialyzed enzyme were observed to bring about restoration of activity. Of 26 cations tested, Zn 2+ and Sr 2+ reactivated the diesterase 100% and 109%, respectively. Zn 2+ ions, when titrated with the enzyme obtained after dialysis with EDTA and water were found to restore the activity in a sigmoidal manner. The binding constant for Zn 2+ was calculated to be approximately 3 × 10 −6 m . The substrate, glycerylphosphorylcholine, was observed to reverse the instantaneous inhibition produced by EDTA, possibly by protecting the metal from the EDTA. These observations suggest that GPC diesterase may be a metalloenzyme, and a mechanism is proposed which suggests the inclusion of two molecules of Zn 2+ per molecule of enzyme.

A simple hot wire anemometer is described which is made from a combination of straight platinum wires for the measurement of wind direction. The instrument is based on a particular combination of straight platinum wires and a `quadrant sensing' element consisting of a thin mica sheet supplied with a grid of platinum wires on either side, and has conventional electronic circuitry; the output voltage is proportional to V cos , where V is the wind speed and the wind direction. By using three sets of sensing elements orthogonally oriented in space, the three orthogonal components of wind velocity are obtained directly in the form of three analogue voltages.

A description is given of a very simple light weight and inexpensive radiosonde which measures rapid changes in relative humidity and temperature. The temperature is measured using a very thin platinum wire, the resistance of which is determined by the temperature and controls the frequency of a voltage controlled oscillator constituting a frequency-modulated subcarrier in the telemetry system. Sensitivity is typically 30 Hz degC−1 for a 10 μm wire. The sensor responds to changes in temperature up to some 60 Hz. The action of the humidity sensor is based on the relationship between mass and oscillation frequency of a piezoelectric resonator. Using two quartz crystal oscillators, paired in such a way as to give a beat frequency which is virtually independent of temperature, information about the humidity is obtained by measuring the beat frequency from the two crystal oscillators when one of the crystals is covered with a very thin hygroscopic film, the other crystal being insensitive to humidity. The crystal oscillator which is not sensitive to humidity is used as the radio carrier frequency generator for the telemetry system. Sensitivity is typically 10 Hz per percentage relative humidity and the element responds to changes in humidity up to some 50 Hz.

Copia digital : Biblioteca de Castilla-La Mancha, 2015 Mención de responsabilidad tomada de la carta de remisión Caja de escritura: 27 x 17 cm Tiene 3 h. en bl. Lám. intercaladas en p. 11, 41, 55, 85, 91, 111, 136 Contiene: en el principio va una carta de remisión original, de 2 h. y autógrafa, dirigida al Cardenal Lorenzana, por cuyo encargo fue hecha la obra

Sign.: A-N12, O6 Error tip. de sign. en N6 consta 6N Antep.

In this experiment, students determine the relative rates of oxidation by adding quantities of several different alcohols to a solution of chromium(VI) in dilute sulfuric acid and visually monitoring the course of the reaction.

The instrument makes use of two simple crystal-controlled oscillators having nearly identical temperature/frequency characteristics. One of the quartz plates is covered with a very thin hygroscopic film and exposed to the atmosphere. The difference in frequency of the two oscillators is a function of humidity. Typical results are 6.5 Hz per % change in humidity at room temperature. The hygrometer resolves changes in humity down to 4/100%, the time constant of the sensor being better than 1/50s.

Seventy-five patients with repeatedly positive standard serologic reactions for syphilis were given the Treponema pallidum immobilization (TPI) test. No included person had a history or physical findings suggesting infection, and no patients referred as having contact with syphilis or discovered to have an infected consort were accepted. Twentythree of the series were Caucasian and varied widely in socioeconomic background. In 39% of these the results of the TPI test were negative and were classified as probable false-positive reactions. Fifty-two of the patients were Negroid and thought to be a relatively homogeneous social and economic group. All had positive reactions to the TPI test. This striking difference is consistent with the accepted epidemiology of syphilis. The authors emphasize the importance of the background and habits of patients in interpretation of the results of serologic tests for syphilis.