Design of a compact cw chemical HF/DF laser using a microwave discharge.

A compact cw chemical HF/DF laser is described. The laser system consists of a microwave discharge using a surfatron to dissociate SF6 molecules mixed with He, a reaction chamber engineered to provide a fast mixing of reacting atoms and molecules, and an optical resonator which includes a concave mirror and a blazed grating for line selection, both mounted on a rigid Invar frame. The laser oscillates on a single line single TEM00 mode over many P transitions of HF and DF with a typical intensity fluctuation of 5% and a frequency jitter of about 30 MHz.

Relationship between inflammatory hepatic disease and inflammatory bowel disease, pancreatitis, and nephritis in cats.

OBJECTIVE: To determine whether cats with inflammatory hepatic disease had concurrent inflammatory bowel disease (IBD), pancreatitis, or chronic interstitial nephritis. DESIGN: Prospective case series. SAMPLE POPULATION: 78 tissue sections of liver, intestine, pancreas, and kidney from cats that had previous necropsy examinations at the teaching hospital. PROCEDURE: We reviewed histologic sections of liver, intestine, pancreas, and kidney from cats that had previous necropsy examinations and determined the prevalence of lymphocytic portal hepatitis, cholangiohepatitis, IBD, pancreatitis, and chronic interstitial nephritis, and the relationship among them. RESULTS: 36 cats had lymphocytic portal hepatitis, 18 had cholangiohepatitis, and 24 did not have inflammatory hepatic disease. The prevalence of IBD (10/36; 28%) and pancreatitis (5/36; 14%) in cats with lymphocytic portal hepatitis was not significantly different from cats without inflammatory hepatic disease. The prevalence of IBD (15/18; 83%) and pancreatitis (9/18; 50%) was greater (P < 0.05) for cats with cholangiohepatitis, compared with cats without inflammatory hepatic disease. Thirty-nine percent of cats (7/18) with cholangiohepatitis had IBD and pancreatitis. Evidence of IBD in association with cholangiohepatitis was characterized by infiltration of lymphocytes and plasma cells into the lamina propria; however, neutrophilic infiltrates also were found in 6 of 15 (40%) cats with cholangiohepatitis. Pancreatitis was mild in all cats. CLINICAL IMPLICATIONS: Cats with a diagnosis of cholangiohepatitis should be evaluated for IBD and pancreatitis.

Clinical features of inflammatory liver disease in cats: 41 cases (1983-1993).

OBJECTIVE: To compare the clinical and clinicopathologic findings in and prognosis for cats with lymphocytic portal hepatitis (LPH) versus cats with acute or chronic cholangiohepatitis (CH). DESIGN: Retrospective study. ANIMALS: 25 cats with LPH; 16 cats with CH (7 acute, 9 chronic). PROCEDURE: Cats with LPH and CH were selected by evaluating records from liver biopsy specimens submitted to the University of Minnesota Veterinary Teaching Hospital during a 10-year period. Clinical and clinicopathologic data were retrieved. RESULTS: Cats with CH had higher segmented and band neutrophil counts, alanine aminotransferase activities, and total bilirubin concentrations than did cats with LPH. Cats with acute CH had higher segmented and band neutrophil counts and lower serum alkaline phosphatase activities and total bilirubin concentrations than did cats with chronic CH. Twelve of 14 cats with LPH or CH had coarse or nodular texture to the liver on ultrasonography, with loss of portal vein wall clarity noticed in 4 of 8 cats with LPH. Sixteen of 23 cats with LPH and 8 of 15 cats with CH survived > 1 year. Of those cats living < 1 year, all cats with LPH and 5 of 7 cats with CH had a serious concurrent illness that may have been responsible for their deaths. CLINICAL IMPLICATIONS: LPH and CH can be detected and tentatively differentiated through evaluation of clinical laboratory test results, but histologic evaluation of liver specimens is necessary for definitive differentiation. Survival time was good regardless of the type of inflammatory liver disease.

[High resolution optical spectroscopy]. / Application de la spectroscopie optique de hauterésolution à l'étude des moments quadrupolairesdes isotopes pairs radioactifs.

By means of high resolution optical spectroscopy, we can determine nuclear quadrupole moments of radioactive or stable nuclides with even atomic number in the heavy elements region. We discuss and summarize the main conditions applicable to the method.

[high resolution photoelectric Fabry-Perot spectrometer]. / Description d'un spectromètre de haute résolution Fabry-Pérot.

This paper describes a high resolution photoelectric Fabry-Perot spectrometer for measuring optical line shifts, hyperfine structure intensities, and spectral line widths. The measurements reported were made within an accuracy of 1%. Details of the instrument construction are given.

Simple method for identifying doubly ionized uranium (U III) produced in a hollow-cathode discharge.

We have studied by emission spectroscopy the spectral properties of doubly ionized uranium, produced in a vapor generator of hollow-cathode design, as a function of the nature of a pure fill gas (helium, neon, argon, krypton, xenon) and its pressure. The spectral intensity is found to increase with increasing ionization potential of the discharge buffer gas, except in the case of helium. Based on our preliminary results, a simple and practical method for the positive identification of the complex U III spectrum is suggested.

Frequency locking of laser diode using metallic vapor optogalvanic spectrum: Ui.

The frequency of a AlGaAs diode laser has been locked to the 8118-cm(-1)(f(3)d(2)s(5)M(0)(7))-20,218-cm(-1) transition of UI at 826.20570 nm using the optogalvanic effect. A hollow cathode vapor generator has been utilized to produce a density of 10(12) atoms/cm(3) of uranium in vapor phase. The absolute frequency stability for a 10-min run was estimated to be better than 500 kHz P-P at an integration time of 1 s. This preliminary result shows that the rich optogalvanic spectrum of uranium can be efficiently used for the frequency-locking of semiconductor lasers.

Atom confinement in a laser open atomizer.

We have investigated the effects of a buffer gas (air) on the vapor plume produced in a laser open atomizer using atomic absorption spectroscopy. The absorption signal is related to the concentration of absorbing species by a modified Beer-Lambert equation in which the buffer gas pressure and temperature and the diameter of the diffusing species appear explicitly. Our experimental results show that the observed maximum of absoprtion as a function of gas pressure is well explained by the classical gas diffusion theory. Furthermore, our measurements indicate that the plume created by the laser has a conical shape.

Transverse-Flow Quasi-cw HF Chemical Laser: Design and Preliminary Performance.

A small transverse-flow HF chemical laser has been constructed using a large volume microwave plasma generator for the production of F atoms. The F atoms react with hydrogen to form the lasing HF molecules. The active medium is about 5 cm long, and the maximum average laser power was found to be 560mW for all lines. Three laser lines with wavelengths 2.61 microm, 2.64 microm, and 2.73 microm were observed. The time-varying laser transition profile closely resembles the density profile of the excited fluorine atoms in the plasma. Both profiles are greatly affected by changes in flow conditions.

Refractometer associated with the fabry-perot spectrometer.

This paper describes the principles, realization, and characteristics of a refractometer used as a reference for measuring the scanning of a high resolution, photoelectric Fabry-Perot spectrometer. The precision of the measurements on this refractometer is approximately one order of magnitude greater than that obtainable with other instruments.

Electrooptical fabry-perot spectroscopy.

A new method is described that uses an elegtronic imaging tube to record and explore Fabry-Perot fringes. The light intensity distribution of an interference pattern and the Doppler effect of a line can be observed with an exploration time of the order of 1O(-5) sec. Some important applications in the fields of spectroscopy and education are also considered.

Déformations du profil du coefficient d'absorption de la raie 5915 A UI dans un générateur de vapeur à cathode creuse pulsée.

During the development and study of a hollow cathode pulsed source of uranium vapor, we have observed that the absorption line shape changes considerably with time. This has been shown to be due to oscillatory collective displacement of the vapor in the cavity of the source.

Characterization of portal lymphocytic infiltrates in feline liver.

To better understand the relationship of portal lymphocytic infiltrates to feline inflammatory liver disease, liver sections were semiquantitatively evaluated from healthy cat and liver sections randomly selected at necropsy from clinical cases. Healthy specific pathogen-free kittens and healthy young adult cats had up to 10 lymphocytes and plasma cells per portal area. Neutrophils were infrequently seen in portal areas. Approximately one-third of sections obtained from clinical cases younger than 10 years had increased numbers of lymphocytes and plasma cells in portal areas. Seventy percent of these had a concurrent increase in neutrophils. Eighty-two percent of liver sections obtained from clinical cases older than 10 years had increased numbers of portal lymphocytes and plasma cells. Almost all of these sections had concurrent fibrosis and bile duct proliferation. These data indicate that a progressive lymphocytic portal hepatitis is a common finding in cats older than 10 years.

Histopathologic evaluation of feline inflammatory liver disease.

To better define the histopathologic features of feline inflammatory liver disease, we studied feline liver biopsies evaluated at the University of Minnesota Veterinary Teaching Hospital over a 10-year period. Of 175 liver sections examined, 45 had portal inflammatory infiltrates. Of these, 60% had infiltrates consisting of lymphocytes and plasma cells, 24% had infiltrates consisting of neutrophils, and 16% had mixed infiltrates consisting of neutrophils, lymphocytes, and plasma cells. Lymphocytic-plasmacytic portal infiltrates were characterized by various degrees of bile duct proliferation and fibrosis without evidence of bile duct infiltration or periportal necrosis. Sections with portal neutrophilic infiltrates were characterized by bile duct infiltration, bile duct epithelial degeneration, periportal necrosis, and infiltration of neutrophils into adjacent lobules. We propose that hepatitis characterized by portal lymphocyte and plasma cell infiltration be termed lymphocytic portal hepatitis and that hepatitis characterized by cholangitis and portal neutrophilic infiltrates with or without lymphocytes and plasma cells be termed cholangiohepatitis.

Méthode de comptage photonique et spectrométre Fabry-Pérot pour relever le profil d'une raie spectrale.

Nous décrivons une méthode pour relever le profil d'une raie spectrale à l'aide d'un dispositif de comptage photonique et d'un spectromètre Fabry-Pérot. Cette méthode a été appliqué au cas où l'intensité lumineuse effective au maximum d'une raie spectrale est inférieure à 1'intensité du mouvement proper d'un photomultiplicateur.

Ultraviolet optogalvanic laser spectroscopy of iron for reference wavelengths.

We present a preliminary study of a UV optogalvanic spectrum obtained by using a see-through iron hollow cathode and a tunable pulsed laser in the 240-260-nm range. The hollow cathode used and described is a homemade device that can be run in static- or dynamic-flow gas regimes. Spectra have been recorded with argon and neon buffer gases, and many classified Fe I lines have been identified. The accuracy of the measured wave numbers is limited at present to 0.05 cm(-1) by the spectral width of the UV laser. This iron optogalvanic spectrum is proposed for reference-wavelength calibration in UV laser spectroscopy, and an application to the study of Ba(+) Rydberg levels is reported. Possibilities for future developments of such a device are analyzed.

Méthode d'echantillonnage des fonctions déterministes en spectroscopie: application à un spectromètre multicanal par comptage photonique.

The sampling theorem for deterministic functions is used to locate the center of gravity of a spectral line obtained by photon counting with a multichannel spectrometer. The sampling step and the width of the channels have been evaluated to locate the line with maximum accuracy. Our analysis and experimental results give the requirements needed of a photon counting multichannel Fabry-Perot spectrometer to improve the accuracy of measurement of the spectral interval between two lines.

Ionization and excitation of uranium in a hollow-cathode lamp.

The influence of different carrier gases (Ne, Ar, Kr, Xe), their pressure, and discharge current on the excitation and ionization of uranium atoms in a vapor generator of hollow-cathode design has been investigated by monitoring emission line intensities. From our measurements of line intensities as a function of the carrier gas we obtain an indication of the role of Penning collisions on the excitation of radiative levels in U II.

Utilisation d'une ligne de microphotodiodes en spectrographie Fabry-Perot.

A self-scanned photodiode array has been used to detect the image from a Fabry-Perot spectrograph, the recording being a cut along a diameter of the interference pattern. A microcomputer plus a 12-bit analogto- digital converter are employed to store numerically the data as a central logic system and to eliminate the fixed pattern noise of the array. From the spatial photosensibility distribution, we can restore the profile of the light distribution at the sampled points. Using the Shannon interpolation method on these ideal samples, we can thus pinpoint precisely the maxima of the fringes and linearize the spectra. Theoretical and experimental comparisons with photographic plates pointed out an improvement in the SNR for the photodiode system and open up interesting and useful applications to Fabry-Perot spectrography.

Etude par absorption d'un faisceau laser d' une vapeur d' (238)U ((5)L(0)(6)) obtenue à l' aide d'une lampe à cathode creuse.

The density of U atoms in the (5)L(0)(6) ground state present in a vapor of this element from a hollow cathode lamp has been measured using laser absorption spectroscopy. The influence of the carrier gases (Ar, Kr, Xe) on the density, the absorption coefficient profiles, and on the ratio of U atoms to the dissipated electrical power has been investigated. It has been found that, in our range of operating conditions, the xenon gas is the most efficient. With xenon, a density of 2.2 x 10(12) cm(-3) ground-state U atoms is obtained when the lamp dissipates 40 W of electrical power.