Background corrected measurements of optical quantities in the far-infrared spectral range.

By definition, optical quantities transmittance and reflectance can basically be determined as the ratio of two flux measurements. One measurement is performed with, and the other without, the sample under test in the optical path. However, at longer wavelengths the temperature radiation of the sample itself as well as of the applied spectrometer and detector increasingly contribute to the detected radiation budget. This leads to growing systematic errors in the determination of the transmittance and reflectance of samples with Fourier transform infrared spectrometers at longer wavelengths. We present an effective method to overcome this problem by measuring a sequence of four measurements at two different flux levels. Results obtained with this method are compared to the basic ratio method over a spectral range from 200 cm-1 to 30 cm-1 (0.9 THz to 6 THz).

Intercomparison of far-infrared transmittance measurements.

We present the results of the first systematic "round-robin" comparison of far-infrared transmittance spectra measurements, which was performed by five laboratories and piloted by Physikalisch-Technische (PTB). The transmittance spectra of four different samples were measured by the participating laboratories in the 600 cm-1 to 10 cm-1 range (16.67 µm to 1000 µm) in a blind comparison. Different types of instruments, Fourier transform infrared (FT-IR) spectrometers of Michelson type and a laser radiation-based system were used for the transmittance measurements. FT-IR spectrometers are the most popular and commonly used instruments for the spectral characterization of materials in the infrared spectral range, and are well established for quantitative measurements in the mid- and near-infrared spectral ranges. However, obtaining quantitative transmittance measurements in the far-infrared spectral range by means of these instruments is challenging, because it involves weaker radiation sources, stronger diffraction effects, significant radiation originating from the sample itself and temperature gradients inside the spectrometer that may not be given proper consideration. Therefore, this comparison was initiated to test the actual capability of and identify problems with FT-IR transmittance measurements in this spectral region. We discuss the results and the possible reasons for the observed discrepancies.

Three-element trap filter radiometer based on large active area silicon photodiodes.

This paper shows the opto-mechanical design of a new filter radiometer built at the Physikalisch-Technische Bundesanstalt, Germany, for the accurate determination of the thermodynamic temperature of high-temperature blackbodies. The filter radiometer is based on a three-element reflection-type trap detector that uses three large active area silicon photodiodes. Its spectral coverage and field of view are defined by a detachable narrow-band filter and a diamond-turned precision aperture, respectively. The temperature of the filter radiometer is stabilized using a water-streamed housing and is measured using a thin-film platinum thermometer placed onto the first photodiode element. The trap "mount" has been made as compact as possible, which, together with the large active area of the chosen photodiodes, allows a wide field of view. This work presents the design of the filter radiometer and discusses the criteria that have been considered in order for the filter radiometer to suit the application.

[Cutaneous form of sarcoidosis at the auricle]. / Kutane Manifestation einer Sarkoidose an der Ohrmuschel.

Sarkoidosis is a disease of so far unknown etiology that can affect potentially every organ. Sarcoidosis of the lung is the most common form, nevertheless in more than one third of the cases the head and neck area is affected. Manifestations of the disease can be present in lymph nodes of the neck, the middle ear, the pars petrosa of the temporal bone and in the paranasal sinuses as well as in the larynx and pharynx. We would like to present two rare manifestations of sarkoidosis of the ear lobe. The cutaneous form of sarcoidosis is characterized by a spectrum of skin changes. Aside from the physical presentation and observation of the disease progress the diagnosis is confirmed histologically. A multidisciplinary care of the affected patients is needed to diagnose the systemic extend of the disease on one side and to provide the patient with an effective therapeutic regimen that includes surgical and conservative measures on the other.

Traceability in fluorometry--Part I: Physical standards.

The inter-instrument, inter-laboratory, and long-term comparability of fluorescence data requires the correction of the measured emission and excitation spectra for the wavelength- and polarization-dependent spectral irradiance of the excitation channel at the sample position and the spectral responsivity of the emission channel employing procedures that guarantee traceability to the respective primary standards. In this respect the traceability chain of fluorometry is discussed from a radiometrist's point of view. This involves, in a first step, the realization of the spectral radiance scale, based on the blackbody radiator and electron storage ring, and the spectral responsivity scale, based on the cryogenic radiometer and their control via key comparisons of the national metrology institutes. In a second step, the characterization including state-of-the art uncertainties of the respective source and detector transfer standards such as tungsten strip lamps, integrating sphere radiators, and trap detectors used to disseminate these radiometric quantities to users of spectroscopic techniques is presented.

Traceability in fluorometry: Part II. Spectral fluorescence standards.

The need for the traceable characterization of fluorescence instruments is emphasized from a chemist's point of view, focusing on spectral fluorescence standards for the determination of the wavelength- and polarization-dependent relative spectral responsivity and relative spectral irradiance of fluorescence measuring systems, respectively. In a first step, major sources of error of fluorescence measurements and instrument calibration are revealed to underline the importance of this issue and to illustrate advantages and disadvantages of physical and chemical transfer standards for generation of spectral correction curves. Secondly, examples for sets of traceable chemical emission and excitation standards are shown that cover a broad spectral region and simple procedures for the determination of corrected emission spectra with acceptable uncertainties are presented. With proper consideration of the respective measurement principle and geometry, these dye-based characterization procedures can be not only applied to spectrofluorometers but also to other types of fluorescence measuring systems and even to Raman spectrometers.

[Necrotizing mucosal ulcers cause by anaerobic bacteria. Fusiform bacterial and spirochete infections]. / Nekrotisierende Schleimhautulzera durch Anaerobier. Fusospirochätosen.

Vincent's angina (Plaut-Vincent) is the most prominent disease caused by coinciding infections from fusibacteria and spirochaeta both belonging to obligate anaerobic bacteria. A possible symbiotic infection of both anaerobics may become manifest on the mucous membranes of the oral cavity and the oropharynx beside the tonsillas. The clinical outcome may be different and pose difficulties in the differential diagnosis. We report the case of a 29 year old female patient with necrotizing ulcera of the soft palate suspicious for stomatitis ulceromembranacea. In case necrotizing inflammations of the oral cavity area were to be found infections due to anaerobic bacteria should be considered mostly occurring as mixed infections. The correct identification by cultivation turns out to be difficult in that it requires special conditions. Furthermore, reliable detection of these bacteria necessitates careful collection and transport of patients specimens. In case of Fusospirochaetosis (Fusotreponematose) a specimen should be prepared for microscopic examination beside setting up a special culture. This is because the staining is the most suitable procedure for bacteril identification to support the clinical diagnosis of stomatitis ulceromembranacea.

High-current hollow-cathode source as a radiant intensity standard in the 40-125-nm wavelength range.

The radiant intensity of VUV emission lines of a high-current hollow-cathode source has been determined for the 40-125-nm spectral range. The source is operated at a constant current of 1 A with an aluminum cathode. Different rare gases are alternatively used as the buffer gas at pressures of ~100 Pa. The radiant intensity has been determined by comparison with the calculable spectral radiant flux of the electron storage ring BESSY. Radiant intensities of the emission lines are in the 7-1400-µW/sr range. The long-term reproducibility of the radiant intensity of the source is within ±10% (2σ value). The systematic uncertainty of the radiometric calibration is better than 9% (√32σ value).

[Therapy with nasal CPAP (continuous positive airway pressure) in patients with obstructive sleep apnea syndrome (OSAS). II: Side-effects of nCPAP therapy. Effect on long-term acceptance]. / Therapie mit nasalem CPAP (continuous positive airway pressure) bei Patienten mit Obstruktivem Schlafapnoe Syndrom (OSAS). Teil II: Nebenwirkungen der nCPAP-Therapie. Einfluss auf die Langzeitakzeptanz.

BACKGROUND: nCPAP is a well established method for the management of OSAS. The aim of this study was to evaluate long-term side effects and complications of nCPAP therapy and their influence on the patients compliance with treatment. PATIENTS AND METHODS: Forty-one patients with OSAS were interviewed by questionnaire to elucidate the problems and adverse effects of their nCPAP therapy. The patients were divided into responders and non-responders. Non-responding OSAS patients were using their nCPAP devices less then 5 hours each night by definition. RESULTS: The number of side effects and type of complication during nCPAP therapy were the same in both the responding and non-responding groups. The most frequently reported problems were a tender region on the bridge of the nose and discomfort associated with a dry nasal mucosa. Although nCPAP treatment was initially accepted by most patients, adverse effects and other difficulties decreased patient compliance, with time, in many cases. CONCLUSIONS: Despite there being no difference between responders and non-responders with respect to the number and severity of complications, it should not be presumed that these side effects do not influence long-term patient compliance with nCPAP therapy. Patients who suffer from symptoms of OSAS tend to accept these adverse effects, while those who do not feel limited by their disease are less persistent in their use of this treatment modality. Identification and elimination of the problems associated with the use of nCPAP equipment may increase longterm patient compliance. Close monitoring in the outpatient department combined with intermittent inpatient assessment in the sleep laboratory will also help to improve acceptance of nCPAP therapy.

[Therapy with nasal CPAP (continuous positive airway pressure) in patients with obstructive sleep apnea syndrome (OSAS). I: Long-term acceptance of nasal CPAP]. / Therapie mit nasalem CPAP (continuous positive airway pressure) bei Patienten mit Obstruktivem Schlafapnoe Syndrom (OSAS). Teil I: Langzeitakzeptanz von nasalem CPAP.

BACKGROUND: Nocturnal ventilation with nCPAP has been established as the safest and most efficient nonsurgical treatment for OSAS. Long-term results, however, are determined by the patients' compliance with therapy. The aim of this study was the objective measurement of long-term acceptability of nCPAP therapy in all patients receiving this treatment in our sleep laboratory between January 1990 and March 1995. METHODS: We prospectively investigated 41 patients (36 male, 5 female) with moderate to severe OSAS who received nCPAP therapy. Mean time of follow-up was 20.6 months, ranging from 1.2 to 53.5 months. Therapy was indicated when OSAS was confirmed by cardiorespiratory polygraphy and either (1) the patient complained of daytime sleepiness or (2) the patient possessed an apnea-hypopnea index greater than 30/h or when the mean oxygen desaturation was below 80% regardless of the presenting symptoms. The compliance with treatment was defined as a mean rate of use of over 5 hours per night calculated from the time counter on the nCPAP machine. RESULTS: 33 patients (88.5%) have continued using nCPAP until the present time but only 24 patients (59%) met our criteria for long-term acceptance and this group was identified as responders. We found no significant differences in age, body mass index, apnea-hypopnea index, and nCPAP-pressure between responders and non-responders. CONCLUSION: Although nCPAP is the safest treatment for OSAS, there is still a large group of patients with moderate to severe OSAS who are not efficiently treated with nCPAP because of the low long-term acceptability of this therapy. With respect to this group of patients, surgical approaches have to be considered as an alternative therapy.

Radiometric calibration of the telescope and ultraviolet spectrometer SUMER on SOHO.

The prelaunch spectral-sensitivity calibration of the solar spectrometer SUMER (Solar Ultraviolet Measurements of Emitted Radiation) is described. SUMER is part of the payload of the Solar and Heliospheric Observatory (SOHO), which begins its scientific mission in 1996. The instrument consists of a telescope and a spectrometer capable of taking spatially and spectrally highly resolved images of the Sun in a spectral range from 50 to 161 nm. The pointing capabilities, the dynamic range, and the sensitivity of the instrument allow measurements both on the solar disk and above the limb as great as two solar radii. To determine plasma temperatures and densities in the solar atmosphere, the instrument needs an absolute spectral-sensitivity calibration. Here we describe the prelaunch calibration of the full instrument, which utilizes a radiometric transfer-standard source. The transfer standard was based on a high-current hollow-cathode discharge source. It had been calibrated in the laboratory for vacuum UV radiometry of the Physikalisch-Technische Bundesanstalt by use of the calculable spectral photon flux of the Berlin electron storage ring for synchrotron radiation (BESSY)-a primary radiometric source standard.

Radiometric characterization of a Penning discharge in the vacuum ultraviolet.

We present a Penning discharge as a possible radiometric transfer standard source in the vacuum UV, primarily in the spectral region below 20 nm. Following the concept of Finley et al., we have designed a Penning source using NdFeB permanent magnets. Emphasis was put on simple operation, quick electrode exchangeability, and easy source readjustment. The radiant intensities of the emission lines from different ionization stages of both buffer gas atoms and atoms sputtered from the cathodes have been studied in various discharge conditions. For selected Al and buffer gas emission lines we determined the absolute radiant intensities by a comparison with the calculable spectral radiant power of the Berlin Electron Storage Ring. A comparison with data from our hollow-cathode transfer standard source is given.

Radiometric calibration of SUMER: refinement of the laboratory results under operational conditions on SOHO.

The radiometric calibration of the solar telescope and spectrometer SUMER was carried out in the laboratory before delivery of the instrument for integration into the SOHO (Solar and Heliospheric Observatory) spacecraft. Although this effort led to a reasonable coverage of the wavelength range from 53.70 to 146.96 nm, uncalibrated portions of the sensitivity curves remained before SUMER became operational in early 1996. Thereafter it was possible to perform extrapolations and interpolations of the calibration curves of detector A to shorter, longer, and intermediate wavelengths by using emission line pairs with known intensity ratios. The spectra of the stars alpha and rho Leonis were also observed on the KBr (potassium bromide) photocathode and the bare microchannel plate (MCP) in the range from 120 to 158 nm. In addition, the sensitivity ratios of the KBr photocathode to the bare MCP were determined for many solar lines as well as the H i Lyman and the thermal continua. The results have been found to be consistent with published laboratory data. The uncertainty is +/-15% (1 varsigma) in the wavelength range from 54 to 125 nm.

Radiometric calibration of the vacuum-ultraviolet spectrograph SUMER on the SOHO spacecraft with the B detector.

The Solar Ultraviolet Measurement of Emitted Radiation (SUMER) vacuum-ultraviolet spectrograph was calibrated in the laboratory before the integration of the instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft in 1995. During the scientific operation of the SOHO it has been possible to track the radiometric calibration of the SUMER spectrograph since March 1996 by a strategy that employs various methods to update the calibration status and improve the coverage of the spectral calibration curve. The results for the A Detector were published previously [Appl. Opt. 36, 6416 (1997)]. During three years of operation in space, the B detector was used for two and one-half years. We describe the characteristics of the B detector and present results of the tracking and refinement of the spectral calibration curves with it. Observations of the spectra of the stars alpha and rho Leonis permit an extrapolation of the calibration curves in the range from 125 to 149.0 nm. Using a solar coronal spectrum observed above the solar disk, we can extrapolate the calibration curves by measuring emission line pairs with well-known intensity ratios. The sensitivity ratio of the two photocathode areas can be obtained by registration of many emission lines in the entire spectral range on both KBr-coated and bare parts of the detector's active surface. The results are found to be consistent with the published calibration performed in the laboratory in the wavelength range from 53 to 124 nm. We can extrapolate the calibration outside this range to 147 nm with a relative uncertainty of ?30% (1varsigma) for wavelengths longer than 125 nm and to 46.5 nm with 50% uncertainty for the short-wavelength range below 53 nm.

Radiometric Calibration Tracking of the Vacuum-Ultraviolet Spectrometer SUMER During the First Year of the SOHO Mission.

Detailed radiometric calibration tracking of the vacuum-ultravioletspectrometer SUMER (from solar ultraviolet measurements of emittedradiation) was performed during the first year of the Solar andHeliospheric Observatory (SOHO) mission and will continue. Inview of the flight history of many previous solar UV instruments, thestability of calibration of the extreme-ultraviolet instruments on SOHOhas been a major concern. Results obtained during the first year ofoperation show that excellent radiometric stability has been achievedwith SUMER. These results were accomplished by stringentcleanliness and contamination-control procedures during all phases ofthe project. We describe the strategy and results of the in-flightcalibration tracking program performed with SUMER.

Intercalibration of SUMER and CDS on SOHO. II. SUMER Detectors A and B and CDS NIS.

Results of an intercalibration between the extreme-ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) are reported. The results of the joint observing program Intercal_01 are described, and intercalibration results up to July 2000 of both SUMER detectors A and B and of the CDS Normal Incidence Spectrometer (NIS) are presented. The instruments simultaneously observed radiance of emission lines at the center of the Sun, and three lines have been chosen for intercomparison: He i 584 A, Mg x 609 A, and Mg x 624 A. Initially the same area was observed by both instruments, but, after restrictions were imposed by the scanning mechanism of SUMER in November 1996, the instruments viewed areas of different sizes. Nevertheless, the temporal correlation between the two instruments remained good through June 1998, when contact with the SOHO spacecraft was lost. Until then the CDS instrument measured (33 ? 5)% and (38 ? 7)% (?1varsigma) higher intensity than SUMER in the He i 584-A line on average for detectors A and B, respectively. Data from SUMER detector B agreed well for Mg x 609 A and Mg x 624 A with the CDS intensities, showing offsets of (2 ? 10)% and (9 ? 15)%, much less than the data of detector A with offsets of (7 ? 8)% and (16 ? 7)% for the two lines, respectively, relative to CDS. Finally, the intercalibration measurements after the loss and recovery of the SOHO spacecraft are analyzed. The data for observations from November 1998 to July 2000 are compared, and it is shown that, although the responses of the instruments have changed, the CDS and the SUMER still perform well, and their temporal correlation is good.

Intercalibration of SUMER and CDS on SOHO. I. SUMER detector A and CDS NIS.

The results of an intercalibration between the extreme ultraviolet spectrometers Coronal Diagnostic Spectrometer (CDS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO) are presented. During the joint observing program Intercal_01, CDS and SUMER were pointed at the same locations in quiet Sun areas and observed in the same wavelength bands located around the spectral lines He i 584 A, Mg x 609 A, and Mg x 624 A. The data sets analyzed here consist of raster images recorded by the CDS normal-incidence spectrometer and SUMER detector A and span the time from March 1996 to August 1996. Effects of the different spatial and spectral resolutions of both instruments have been investigated and taken into account in the analysis. We find that CDS measures generally a 30% higher intensity than SUMER in the He i 584-A line, while it measures 9% and 17% higher intensities in Mg x 609 A and Mg x 624 A, respectively. Both instruments show very good temporal correlation and stability, indicating that solar variations dominate over changes in instrumental sensitivity. Our analysis also provides in-flight estimates of the CDS spatial point-spread functions.