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The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope. The IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38micron with spectral resolutions, R \~90 and 600, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the pre-launch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data reduction pipeline has been developed at the Spitzer Science Center., Accepted in ApJ Sup. Spitzer Special Issue, 6 pages, 4 figures

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC., Comment: 7 pages, 3 figures. Accepted for publication in the ApJS. A higher resolution version is at http://cfa-www.harvard.edu/irac/publications

Some parameters of the electromyographic power spectrum of the paraspinal muscles were recorded and analyzed with regard to their ability to discriminate between normal controls and patients with back pain classified as "avoiders" or "confronters" by their responses to the Pain Behavior Checklist. In terms of the activity of the multifidus muscle, the avoider group displayed spectral changes towards lower frequencies, reduced variability in the density spectrum, and higher values of estimated initial frequencies. Measures of the activity of the iliocostalis lumborum did not contribute in any significant way to these group differences. Based on these findings, and on the available literature concerning the histology and physiology of paraspinal muscles, it is proposed that the observed characteristics of the avoider group may be due to a reduced ratio of slow twitch to fast twitch muscle fibers in the multifidus.

The present study examined the relative accuracy and precision of MR and CT procedures for determining the CSA of individual muscles from the human thigh. Serial AN, CT and MR cross-sections were obtained from three cadaveric lower limbs. The MR measurements provided accurate and precise values for the CSAs of most thigh muscles, generally within +/- 7.5% of the AN standard. In contrast, CT tended systematically to overestimate the AN CSA by 10-20%. Retest procedures indicated that highly reliable measurements could be obtained from both MR and CT images. However, subjective interpretations of boundaries between closely apposed muscle bellies, particularly for muscles with more than one head, were necessary for resolving entities in the imaging records and this decreased the relative accuracy of MR and CT measures. Interestingly, MR records demonstrated an incomplete septum between vastus lateralis and vastus intermedius more prominently than AN cross-sections. The novel cross-validation procedures used in this study also highlighted several system-based errors in the MR records that, if undetected and left uncorrected, would have seriously biased the morphometric data obtained with this technique. In general, MR provides high resolution images of the human thigh muscles which may be used to obtain valid measures of the CSA of these structures.

Spatial studies of the emission line regions in planetary nebulae (PN) can provide insight into the physical and chemical environments across the nebulae. In a collaborative effort by the coauthors, a K-band Fabry-Perot etalon has been coupled with an advanced 256 × 256 InSb focal plane array at the Wyoming Infrared Observatory 2.3m telescope. This system permits us to obtain spatially resolved, 0.24″/pixel, moderate spectral resolution (R ≈ 800), flux-density IR emission line images of astronomical sources. We obtained continuum-subtracted images of Br γ, HeI 2.06 μm, the 2-μm UIR features, and the 3.3 μm PAH dust feature in the PN NGC 6572, NGC 7027, and NGC 7662. One objective was to determine the spatial morphology of two unidentified emission lines, UIR1−2.199 μm, and UIR2−2.287 μm (Geballe et al. 1991). These UIR lines appear in the spectra of many PN (Hora et al. 1997) and in the Orion Nebula (Luhman & Rieke 1996). Geballe et al. suggested that the UIR lines are most likely forbidden transitions and showed that the parent ion ionization potential is ≈ 30–40 eV, while the ionization potential for the ions themselves is 40–60 eV. Here we directly compare the distribution of the UIR emitters to that of the gas (H+,He+) and dust (PAHs).

High spatial spectral resolution IR images of the Galactic center in the Br-gamma recombination line of hydrogen were taken. A coherent filament of gas extending from north of IRS 1, curving around IRS 16/Sgr A complex, and continuing to the southwest, is seen. Nine stellar sources have associated Br-gamma emission. The total Br-gamma line flux in the filament is approximately 3 x 10 exp -15 W/sq m. The distribution and kinematics of the northern arm suggest orbital motion; the observations are accordingly fit with elliptical orbits in the field of a central point of mass.

As part of a program of high spatial resolution imaging of gravitationally lensed sources in the visible and IR, images of 2237 + 030 were obtained in the Gunn r and infrared J, H, K, and 3.3 micron filters. The results of the photometry of the four bright quasar components provide evidence of extinction through the lens and a determination of the extinction law in the galaxy is made. The energy distribution shows evidence of a sharp decrease of the spectral index at wavelengths longer than a rest wavelength of 1 micron. Assuming that microlensing amplification in the IR is of similar strength as in the visible, the data constrain the suggested microlensing event of August-September 1988 to a time scale of 100 days.

The dynamic pattern of scapulohumeral rhythm and the scapular instantaneous center of rotation were studied in 20 healthy young male subjects. The most common pattern of scapulohumeral rhythm was characterized by three separate phases, with the greatest relative amount of scapular rotation occurring between 80 and 140 degrees of arm abduction. The scapular instantaneous center of rotation was observed to be located initially at, or near, the medial root of the scapular spine, and gradually migrated toward the region of the acromioclavicular joint as arm abduction progressed. A biomechanical model of the shoulder girdle was proposed by correlating the results from the present study with the electrical activity of the scapular rotators. This model is useful in demonstrating the true dynamic function of the muscles acting on the scapula as well as the mechanical efficiency of upward scapular rotation during arm abduction.

Observations were made from the dissection of 156 digital joints (thumbs excluded). In all joints fibrocollagenous menisci projected into the articular cavity from a ring-like structure based on the joint capsule. These meniscal structures separated the articulating cartilage surfaces at the margins of the joint. Histological examination confirmed a fibrocartilaginous nature of the tissue which demonstrated positive staining for proteoglycans and collagen fibers. Although generally similar in form, these meniscal structures varied in extent when compared between joint groups. The greatest amount and articular contribution was noted in metacarpophalangeal joints with least being found distally.

In 20 healthy, young adult male subjects, the muscular activity of the upper, middle and lower trapezius and the lower digitations of the serratus anterior were studied electromyographically during arm abduction in the plane of the scapula. The patterns of electrical activity of the trapezius and lower serratus anterior muscles were observed to increase progressively during abduction of the arm; however, a plateau phase was demonstrated in all four of the muscle parts studied. Despite the presence of considerable individual variability, common trends were observed in muscular activity patterns. It is believed that the patterns of muscle activity may be closely related to mechanical factors such as scapulohumeral rhythm and a migrating scapular Instantaneous Centre of Rotation (ICR) during arm elevation.

Brain sectioning has been improved through gelatin embedding so that more than forty precisely oriented serial sections can be obtained from a single brain. Since the embedding gelatin requires no fixation, it can be removed from the sections prior to staining by simple warming. The reduction of Berlin blue dye commonly observed after staining by the Mulligan method has been found to be at least partly due to light in the UV to near UV range. Dye reduction is significantly inhibited by postfixation in 25% acetic acid.

Infrared images of the BN-KL region in Orion obtained with the Univ. of Rochester IR Array Camera on the Mees 0.6-m (2.5“/pixel) and the Kitt Peak 1.3-m telescopes (1”/pixel) are presented. These images demonstrate the utility of small telescopes for infrared studies of star formation regions.

A medium-resolution spectrum of Saturn in the 7.5-13.5 micron range is presented. The observed low brightness temperature between 9 and 11 microns of about 100-105 K rules out gaseous NH3 as the dominant absorber in this spectral range. Absorption features due to PH3 may be present around 10 microns and cloud particles could be an important source of opacity in this wavelength range. There are strong indications of a temperature inversion in the upper atmosphere, including high brightness temperature in the 7.7-micron CH4 band, and possible emission from C2H6 around 12 microns.