Versatile polarization interferometer

A new form of polarizing interferometer has been assembled from six calcite-glass prisms and two halfwave plates. The interferometer has the large shear and long beam path capabilities needed for the examination of large objects and is capable of providing a stable interference pattern even when the two ends of the interferometer are supported independently. Lenses can be conveniently added to the system either to facilitate alignment or to extend its useful length.

Accurate laser wavelength measurement with a precision two-beam scanning Michelson interferometer

This paper gives the details of a precision two-beam scanning Michelson interferometer, designed and perfected for accurate comparison of an unknown laser wavelength and the precisely calibrated wavelength of a reference laser. An iodine Lamb-dip stabilized He-Ne 633-nm laser (calibrated with respect to a Kr standard) is used as the reference. The design incorporates features to minimize instrumental errors and the effect of fringe shifts caused by diffraction (in the IR). It is applied to accurate measurements of a stable CO(2) laser wavelength tuned to the centers of its various transitions. Measurements are done by simultaneous fringe counting and relative fringe-phase comparison at the two wavelengths using on-line data storage and processing with an electronic digital computer. The accuracy in the 10-microm region is several parts in 10(9) and is limited by correction for diffraction fringe shifts. Because of its low-Q and broadband operating characteristics, it can be applied to rapid accurate laser wavelength measurements over the entire wavelength range permitted by its transmitting optics. In the visible range where the diffraction correction is small, the interferometer can be used to perform measurements to within several parts in 10(11). The paper gives theoretical derivation of various diffraction corrections, the design and construction of the interferometer, the alignment procedures, detailed analysis of various error sources, and data processing. It also gives the details of a previously reported accurate measurement of the speed of light using the measured wavelength of the CO(2) R(14) line and its known frequency.

Renal brush border membrane adaptation to phosphorus deprivation: effects of fasting versus low-phosphorus diet

Alimentary phosphorus deprivation due to a low-phosphorus diet (LPD) elicits a profound antiphosphaturia and an increase in sodium-dependent inorganic phosphate (Pi) uptake by renal cortical brush border membrane (BBM) vesicles. But, in alimentary phosphorus deprivation due to total fasting, high urinary excretion of Pi persists. In the present study, we determined whether low tubular reabsorption of Pi in fasting is due to a diminished capacity of the specific Pi transport system with the renal cortical luminal BBM or whether it is due to a reduced transepithelial reabsorption of Pi because of metabolic conditions occurring in proximal tubule cells during fasting. Sodium-dependent Pi transport in compared with fasted rats or rats fed a normal phosphorus diet. Sodium-dependent uptake of D-glucose was significantly lower in LPD rats, compared with fast animals or animals fed a normal diet. Thus, in contrast to LPD, fasting does nt elicit an increase in Pi transport and a decrease in D-glucose transport across the isolated renal BBM. The same differences in BBM transport of Pi were present also in thyroparathyroidectomized rats. Further experiments demonstrated that the adaptation of renal function and the renal BBM transport to LPD are overridden by a subsequent period of total fasting. Results of the present study show that fasting both prevents and reverses the renal response of rats to alimentary phosphorus deprivation. The differences in Pi excretion between fasted rats, LPD rats, and LPD rats subsequently fasted are attributed, at least in part, to specific adaptive changes in sodium-dependent Pi transport across the luminal BBM, rather than to alterations in other cellular (metabolic) components of transepithelial Pi reabsorption in the proximal tubule.

Modulated transmission spectroscopy of gaseous chemi-excited Ca and Sr monoxides

Low pressure dilute diffusion flames of the metal-oxidation (M + N(2)O) and chain reaction (M + N(2)O + CO) types have been studied in absorption by means of modulated intracavity resonance spectroscopy. The measurements obtained were comparable in sensitivity to the intracavity dye laser technique but were of lower spectral resolution. The modulation experiment which is described herein has the advantage of measuring linearly and in real time the transmission factor gamma free from adverse anomalous dispersion effects. It is therefore well suited to the determination of electronic state densities. In these measurements, theground states of CaO and SrO were not detected, but the excited (1)pi and (3)pi states absorbed measurably and as a function of CO content in the flames.

Integration over cylindrical luminous volumes using a calibrated piston source

A method is described for measuring the absolute light output from a gas or liquid in a cylindrical tube. The apparatus used is simple to build and use. The technique results in measurements of unusually high accuracy and sensitivity. The volume integration, often done with the aid of a mathematical model, is replaced by the physical measurement made by moving a calibrated luminous disk along the axis of the empty cylindrical tube.

Handedness in a Chinese population: biological, social, and pathological factors

A questionnaire survey of 4143 Chinese was conducted. Social pressure for right-handed writing and eating was effective on these two target skills but showed little indirect influence on hand use in other activities. Neither primiparous birth nor birth to older mothers affected handedness. Twinning, however, seemed to be associated with both decreased right-handedness and lower intelligence.

Laser wavelength stabilization with a passive interferometer

A control system has been devised for stabilizing the output wavelength of a laser by reference to an external passive optical element. This element, consisting of two spherical mirrors, forms an off-axis resonator that, when broadly illuminated by a laser beam, functions as a wavelength-sensitive discriminator. The stabilization control loop is closed by using a signal from this discriminator to tune the laser by moving one of its mirrors with a piezoelectric transducer. The error signal is proportional to changes in wavelength of the incident laser beam and is derived from the discriminator without deliberate frequency or amplitude modulation of the laser The optical arrangement does not return any light in the direction of the source and thus avoids wavelength pulling due to spurious reflections. Two independent helium-neon lasers operating at 6328 A were stabilized against a common reference interferometer using this system. Their relative stability was studied by heterodyning the two outputs and analyzing the beat spectrum. Each feedback loop had a gain of 60 dB at dc falling off to 46 dB at 200 c/s and to 20 dB at 2 kc/sec. The resulting wavelength stability was about Deltalambda/lambda = 2 x 10(-10). The residual instability was mainly owing to room noise occurring at frequencies above the response of the feedback loops.