Multi-species sensing using multi-mode absorption spectroscopy with mid-infrared interband cascade lasers.

The application of an interband cascade laser, ICL, to multi-mode absorption spectroscopy, MUMAS, in the mid-infrared region is reported. Measurements of individual mode linewidths of the ICL, derived from the pressure dependence of lineshapes in MUMAS signatures of single, isolated, lines in the spectrum of HCl, were found to be in the range 10-80 MHz. Multi-line spectra of methane were recorded using spectrally limited bandwidths, of approximate width 27 cm-1, defined by an interference filter, and consist of approximately 80 modes at spectral locations spanning the 100 cm-1 bandwidth of the ICL output. Calibration of the methane pressures derived from MUMAS data using a capacitance manometer provided measurements with an uncertainty of 1.1 %. Multi-species sensing is demonstrated by the simultaneous detection of methane, acetylene and formaldehyde in a gas mixture. Individual partial pressures of the three gases are derived from best fits of model MUMAS signatures to the data with an experimental error of 10 %. Using an ICL, with an inter-mode interval of ~10 GHz, MUMAS spectra were recorded at pressures in the range 1-10 mbar, and, based on the data, a potential minimum detection limit of the order of 100 ppmv is estimated for MUMAS at atmospheric pressure using an inter-mode interval of 80 GHz.

Mid-infrared multi-mode absorption spectroscopy using interband cascade lasers for multi-species sensing.

An interband cascade laser (ICL) operating at 3.7 µm has been used to perform multimode absorption spectroscopy, MUMAS, at scan rates up to 10 kHz. Line widths of individual modes in the range 10-80 MHz were derived from isolated lines in the MUMAS signatures of HCl. MUMAS data for methane covering a spectral range of 30 nm yielded a detection level of 30 µbar·m for 1 s measurement time at 100 Hz. Simultaneous detection of methane, acetylene, and formaldehyde in a gas mixture containing all three species is reported.

Rapid passage signals induced by chirped quantum cascade laser radiation: K state dependent-delay effects in the nu2 band of NH3.

In this Letter, a 10 microm quantum cascade laser operating in the intrapulse mode is used observe rapid passage (RP) effects within a 40 cm single-pass gas cell containing low pressures of NH(3). The laser tuning range allows the rotational states J=2 with K=0, 1, and 2 to be probed. We show that the RP structures change as a function of optical density and that the magnitude of the delay in the switch from absorption to emission as a function of increased gas pressure is dependent upon the initial value of K. These measurements are qualitatively well modeled using the Maxwell-Bloch equations.

Diagnosis of microthrombocytosis and immune-mediated thrombocytopenia in dogs with thrombocytopenia: 68 cases (1987-1989).

The mean platelet volume (MPV) was evaluated in 68 dogs with thrombocytopenia attributable to various causes. Platelet size was high or low in some dogs. The most clinically useful observation was that low MPV (microthrombocytosis) was a specific indicator of immune-mediated thrombocytopenia (IMT) in these thrombocytopenic dogs. All but one case of microthrombocytosis (MPV less than 5.4 fl) was found in dogs with IMT. Microthrombocytosis was detected in 17 of 31 dogs with IMT and appeared at the onset of the disease. Macrothrombocytosis (MPV greater than 9.4 fl) indicated active thrombopoiesis, but was not unique to any disease category. Macrothrombocytosis was detected in 18 of 31 dogs with IMT, 3 of 17 dogs with disseminated intravascular coagulation, and 3 of 9 dogs with primary bone-marrow disease.

Early Language Milestone Scale and language screening of young children.

The purpose of this project was to evaluate the use of the Early Language Milestone Scale (ELM) in screening language skills in young children. In this study, 657 children from birth to 36 months of age were evaluated with the ELM. The overall failure rate was 8%. Children who failed the ELM screening were evaluated with the Sequenced Inventory of Communication Development (SICD) that was used as the "gold standard" for diagnosing language disorders. In the 12-month age and younger group, there was poor agreement between the ELM Scale and the SICD. For infants 13 to 24 months of age, there was moderately good agreement between the SICD and a second ELM that was administered 1 to 2 weeks after the initial screening. In the 25- to 36-month age group, there was excellent agreement between the SICD and a rescreen ELM. The agreement between the two instruments indicated that the rescreen ELM correctly classified 79% of the 13- to 24-month-old infants and 89% of the 25- to 36-month-old toddlers.

New technology in infant hearing screening.

Early identification of hearing loss is critical in enhancing auditory and language skills in the hearing-impaired infant. Various strategies for infant hearing screening are discussed. The current status of technology for screening, including auditory brainstem response audiometry, is also discussed.

Impedance screening. An integral part of hearing screening.

Rationale is presented for including tympanometry as an integral part of all hearing screening programs. Impedance screening will yield more accurate screening results in the identification of middle ear disease than traditional hearing testing or otoscopic examination. Medical complications often result from unidentified otitis media which also contributes to speech, language, and educational delays in children. Although additional research information is needed on the significance of early identification of children with otitis media, it is argued that tympanometry will foster such research efforts, while providing improved identification and potential management of middle ear disease in screening programs.

Aural rehabilitation in noise induced hearing loss.

The patient with noise induced hearing loss presents complex aural rehabilitative problems. Such patients are not generally good candidates for "traditional" aural rehabilitation involving speech reading therapy and auditory training. Instead aural rehabilitation efforts involve individual evaluation of the communication handicap, non-medical relief for tinnitus, possible hearing aid use with carefully selected amplification and earmold, and counseling on hearing and listening.

The controversial relationship between loudness discomfort levels and acoustic reflex thresholds.

Controversy presently exists concerning the relationship between loudness discomfort levels (LDL's) and acoustic reflex thresholds (ART's). In this study, LDL's and ART's were obtained for two groups of ten normal-hearing adult subjects and one group of ten adult subjects with bilateral sensorineural hearing losses. The procedure involved obtaining LDL's and ART's under earphones and under sound field conditions for four different acoustic stimuli: pure tones, warble tones, spondaic words, and speech spectrum noise. One group of normal-hearing subjects and the hard-of-hearing group of subjects were given "too loud, uncomfortably loud, or annoyingly loud" LDL instructions while a second group of normal hearing subjects were instructed to respond when a sound "first starts to become uncomfortable." Results indicated that LDL's, irregardless of instructional pattern, were reported at consistently higher sound pressure levels than the ART's, for all groups of subjects. The magnitude of the differences between the LDL's and ART's varied according to LDL instrucitons, type of test stimulus, hearing sensitivity of the subjects (normal hearing or hard-of-hearing) and transducer used for stimulus presentation. The results of this study demonstrate that ART's correlate too poorly with the LDL to permit ART's to be used as an objective measure of loudness discomfort.