A microprocessor-based one dimensional optical data processor for spatial frequency analysis

A high degree of accuracy was obtained in measuring the spatial frequency spectrum of known samples using an optical data processor based on a microprocessor, which reliably collected intensity versus angle data. Stray light control, system alignment, and angle measurement problems were addressed and solved. The capabilities of the instrument were extended by the addition of appropriate optics to allow the use of different wavelengths of laser radiation and by increasing the travel limits of the rotating arm to + or - 160 degrees. The acquisition, storage, and plotting of data by the computer permits the researcher a free hand in data manipulation such as subtracting background scattering from a diffraction pattern. Tests conducted to verify the operation of the processor using a 25 mm diameter pinhole, a 39.37 line pairs per mm series of multiple slits, and a microscope slide coated with 1.091 mm diameter polystyrene latex spheres are described

Magnetic activity on AB Doradus: Temporal evolution of starspots and differential rotation from 1988 to 1994

Surface brightness maps for the young K0 dwarf AB Doradus are reconstructed from archival data sets for epochs spanning 1988 to 1994. By using the signal-to-noise enhancement technique of Least-Squares Deconvolution, our results show a greatly increased resolution of spot features than obtained in previously published surface brightness reconstructions. These images show that for the exception of epoch 1988.96, the starspot distributions are dominated by a long-lived polar cap, and short-lived low to high latitude features. The fragmented polar cap at epoch 1988.96 could indicate a change in the nature of the dynamo in the star. For the first time we measure differential rotation for epochs with sufficient phase coverage (1992.05, 1993.89, 1994.87). These measurements show variations on a timescale of at least one year, with the strongest surface differential rotation ever measured for AB Dor occurring in 1994.86. In conjunction with previous investigations, our results represent the first long-term analysis of the temporal evolution of differential rotation on active stars.Comment: accepted by MNRAS 18 pages 18 figure

Aerosol seeding systems for the NSWC wind tunnels

Four types of laskin nozzles which are used to generate the primary aerosol mist are illustrated. This mist may be used directly as laser doppler velocimeters (LDV) particles. However, in general, a wide range of particle size exists at this stage and requires the use of some type of mono-dispersion refinement technique. These nozzles rely on the shearing action of high speed air near a column of seeding liquid. Typically, olive oil or dioctyl phthalate (DOP) is used, but within the past year solid polystyrene particles in an alcohol suspension have been used with great success. Air, at a typical pressure of five psig, is supplied to the top of the nozzle which is merely a hollow tube. This air issues radially from one or more small jets located near the collar close to the bottom of the tube. When the collar is submerged in the seeding liquid, the hollow columns located in the collar become filled with liquid. The air from the jet shears the liquid into the fine mist

Scedosporium prolificans Septic Arthritis

Scedosporium prolificans is an emerging fungal pathogen that can cause significant morbidity, and even mortality, in both immunocompromised and immunocompetent patients. Approximately 10% of patients affected by this rare fungal pathogen present with septic osteomyelitis or arthritis. Overall, the rate of mortality is close to 50%, and several patients with orthopedic infections have required amputations.1 Our patient is a 59-year-old woman, with a history of rheumatoid arthritis requiring immunosuppressants, who presented with a 5-month history of right wrist pain and swelling. She described an oscillating course of swelling, erythema, and pain involving the dorsal aspect of her wrist that did not show sustained response to antibiotics or a radiocarpal joint steroid injection given by other providers. On initial examination, she was afebrile with dorsal wrist swelling. There was no erythema, but wrist mobility was limited. She had tenderness throughout the wrist, but no fluctuance or drainage. All initial laboratory work was normal. Right wrist X-ray showed severe osteopenia with some mild evidence of cortical erosion. Despite the normal laboratory values, her presenting findings of swelling, radiographic erosions, and immunocompromised state prompted concern for atypical septic arthritis. The patient subsequently underwent wrist exploration for tissue and culture harvest. In addition to extensive wrist synovectomy, the proximal pole of the scaphoid, lunate, triquetrum, capitate, hamate, and metacarpal bases all showed evidence of necrosis that required debridement. One week later, her fluid aspirate and bone cultures unexpectedly grew an unidentified fungal species, and she was taken back to the operating room for further debridement and placement of a voriconazole-impregnated cement spacer. The culture grew pan-resistant Scedosporium prolificans, and based on recommendations from Rheumatology and Infectious Disease, the patient was started on a 6-week course of intravenous micafungin, and immunosuppressive medications were stopped. She returned to the operating room for debridement and serial treatments with polyhexamethylene biguanide (PHMB) irrigation until intraoperative tissue cultures showed no growth. PHMB is an antiseptic medication that has been described as a local adjunct to the treatment of resistant fungal infections.2–4 After successful eradication of her infection, she underwent wrist reconstruction and fusion with a double-barrel free fibula osteocutaneous flap. She is now 18 months out from her reconstruction, has healed uneventfully, and has a functional, painless upper extremity

UV Spectroscopy of AB Doradus with the Hubble Space Telescope. Impulsive flares and bimodal profiles of the CIV 1549 line in a young star

We observed AB Doradus, a young and active late type star (K0 - K2 IV-V, P= 0.514 d) with the Goddard High Resolution Spectrograph of the post-COSTAR Hubble Space Telescope with the time and spectral resolutions of 27 s and 15 km, respectively. The wavelength band (1531 - 1565 A) included the strong CIV doublet (1548.202 and 1550.774, formed in the transition region at 100 000 K). The mean quiescent CIV flux state was close to the saturated value and 100 times the solar one. The line profile (after removing the rotational and instrumental profiles) is bimodal consisting of two Gaussians, narrow (FWHM = 70 km/s) and broad (FWHM =330km/s). This bimodality is probably due to two separate broadening mechanisms and velocity fields at the coronal base. It is possible that TR transient events (random multiple velocities), with a large surface coverage, give rise to the broadening of the narrow component,while true microflaring is responsible for the broad one. The transition region was observed to flare frequently on different time scales and magnitudes. The largest impulsive flare seen in the CIV 1549 emission reached in less than one minute the peak differential emission measure (10**51.2 cm-3) and returned exponentially in 5 minutes to the 7 times lower quiescent level.The 3 min average line profile of the flare was blue-shifted (-190 km/s) and broadened (FWHM = 800 km/s). This impulsive flare could have been due to a chromospheric heating and subsequent evaporation by an electron beam, accelerated (by reconnection) at the apex of a coronal loop.Comment: to be published in AJ (April 98), 3 tables and 7 figures as separate PS-files, print Table 2 as a landscap