High resolution Fourier interferometer-spectrophotopolarimeter

A high-resolution Fourier interferometer-spectrophotopolarimeter is provided using a single linear polarizer-analyzer the transmission axis azimuth of which is positioned successively in the three orientations of 0 deg, 45 deg, and 90 deg, in front of a detector; four flat mirrors, three of which are switchable to either of two positions to direct an incoming beam from an interferometer to the polarizer-analyzer around a sample cell transmitted through a medium in a cell and reflected by medium in the cell; and four fixed focussing lenses, all located in a sample chamber attached at the exit side of the interferometer. This arrangement can provide the distribution of energy and complete polarization state across the spectrum of the reference light entering from the interferometer; the same light after a fixed-angle reflection from the sample cell containing a medium to be analyzed; and the same light after direct transmission through the same sample cell, with the spectral resolution provided by the interferometer

Minimization search method for data inversion

Technique has been developed for determining values of selected subsets of independent variables in mathematical formulations. Required computation time increases with first power of the number of variables. This is in contrast with classical minimization methods for which computational time increases with third power of the number of variables

Developments in spectrophotometry I: An instrument for high-resolution measurements of optical intensity and polarization

Device has resolution required to analyze polarization of the spectra of unknown gases, liquids, or solids (or a mixture of these phases). Such resolution has not been available on conventional instruments

Frequency-scanning particle size spectrometer

A particle size spectrometer having a fixed field of view within the forward light scattering cone at an angle theta sub s between approximately 100 and 200 minutes of arc (preferably at 150 minutes), a spectral range extending approximately from 0.2 to 4.0 inverse micrometers, and a spectral resolution between about 0.1 and 0.2 inverse micrometers (preferably toward the lower end of this range of spectral resolution), is employed to determine the distribution of particle sizes, independently of the chemical composition of the particles, from measurements of incident light, at each frequency, sigma (=1/lambda), and scattered light, I(sigma)

Interferometer for measurement of optical polarization

Standard two-beam interferometer with polarizers in each beam and an analyzer at the recombined focal point provides greater accuracy and higher resolution than any other known method for measuring variation of polarization within a spectral line and in the surrounding continuum

Relations between the elements of the phase matrix for scattering

The process of scattering of radiation is usually characterized by a 4 × 4 transformation matrix which relates the radiation field vector incident on the scatterer to the scattered field vector. The nine relations between the 16 elements of this phase matrix for scattering are derived explicitly for the three most commonly used representations of the intensity vector, viz., Wolf's coherency matrix formalism, Chandrasekhar's and Stokes's representations. The invariance of these relations under the action of any optical train containing one or more elements characterized by their Jones representation is demonstrated. These relations should be useful in the theory of polarization optics. The same relations are also shown to hold after rotation of the axes of reference for the electric vectors in the incident and scattered beams. Since such a transformation is required in the formulation of the theory of radiative transfer, the relations derived here may find use in multiple scattering problems as well

An interferometric approach to the measurement of optical polarization

After discussing the desirability of determining the variation of polarization with frequency in planetary spectra, the possibility of measuring the intensity and state of polarization of optical radiation by means of the high resolution Fourier spectroscopic method is discussed. In the proposed experimental arrangement a two-beam interferometer is used with a polarizer in each beam. After recombination the emergent radiation is analyzed with a linear polarizer. It is shown that the interferograms obtained in this way contain information about the four Stokes parameters of the incident radiation. The polarizers introduce an asymmetry in the interferograms requiring full (exponential) transforms for retrieval of the desired data. The effects of the finite range of path difference and the variation of its zero point with frequency are considered, and evaluation of the corresponding phase error with a proper choice of the polarizer settings is discussed. The formalism also takes into account the residual polarization introduced by the beam splitter, and the differential transmission of the two beams. Generally, three independent interferograms are needed for determining the phase error and the four Stokes parameters. Some simple arrangements are described in which the two beams are either both linearly or both circularly polarized. It is hoped that instruments based on the principle described here will be built by workers in the field

On the solution H<SUB>1</SUB>(&#956;) of Ambarzumian-Chandrasekhar H-equation

It is shown in a simple manner why the H-equation admits two solutions and how they are related to each other. A justification for rejecting the solution H1(&#956;) is given without referring to the auxiliary equation for the source function

Effect of absorption on scattering by planetary atmospheres

Discrepancies between observed and theoretical values of intensity and polarization of light scattered by planetary atmospheres are usually attributed to Mie scattering by aerosols. It is shown that absorption by molecules or aerosols or both is another important contributor to such deviations

Epinephrine reduces cerebral perfusion during cardiopulmonary resuscitation

OBJECTIVE: Epinephrine has been the primary drug for cardiopulmonary resuscitation (CPR) for more than a century. The therapeutic rationale was to restore threshold levels of myocardial and cerebral blood flows by its alpha1 (alpha1) and alpha2 (alpha2)-adrenergic agonist vasopressor actions. On the basis of coincidental observations on changes in microvascular flow in the cerebral cortex, we hypothesized that epinephrine selectively decreases microvascular flow. DESIGN: Randomized prospective animal study. SETTING: University-affiliated research laboratory. SUBJECTS: Domestic pigs. INTERVENTIONS: Four groups of five male domestic pigs weighing 40 +/- 3 kg were investigated. After induction of anesthesia, endotracheal intubation was followed by mechanical ventilation. A frontoparietal bilateral craniotomy was created. Ventricular fibrillation was induced and untreated for 3 minutes before the start of precordial compression, mechanical ventilation, and attempted defibrillation. Animals were randomized to receive central venous injections during CPR of 1) placebo, 2) epinephrine, 3) epinephrine in which both alpha1- and beta (beta)-adrenergic effects were blocked by previous administration of prazosin and propranolol, and 4) epinephrine in which both alpha2- and beta-adrenergic effects were blocked by previous administration of yohimbine and propranolol. MEASUREMENTS AND MAIN RESULTS: Cerebral cortical microcirculatory blood flow (MBF) was measured with orthogonal polarization spectral imaging. Cerebral cortical carbon dioxide and oxygen tensions (Pbco2 and Pbo2) were concurrently measured using miniature tissue optical sensors. Each animal was resuscitated. No differences in the number of electrical shocks for defibrillation or in the duration of CPR preceding return of spontaneous circulation were observed. Yet when epinephrine induced increases in arterial pressure, it significantly decreased Pbo2 tension and increased Pbco2 tension. Epinephrine therefore significantly decreased MBF and increased indicators of cerebral ischemia. Reduced MBF and magnified brain tissue ischemia during and after cardiopulmonary resuscitation were traced to the alpha1-adrenergic agonist action of epinephrine. When the alpha2 effects of epinephrine were blocked, reduced MBF and tissue ischemia persisted. No differences in cardiac output, end tidal Pco2, arterial Po2 and Pco2, and brain temperature were observed before inducing cardiac arrest and following return of spontaneous circulation. CONCLUSIONS: In this model, epinephrine through its alpha1-agonist action had adverse effects on cerebral microvascular blood flow such as to increase the severity of cerebral ischemia during CPR