Spatial variations in aromatic hydrocarbon emission in a dust-rich galaxy.

Dust grains absorb half of the radiation emitted by stars throughout the history of the universe, re-emitting this energy at infrared wavelengths1-3. Polycyclic aromatic hydrocarbons (PAHs) are large organic molecules that trace millimetre-size dust grains and regulate the cooling of interstellar gas within galaxies4,5. Observations of PAH features in very distant galaxies have been difficult owing to the limited sensitivity and wavelength coverage of previous infrared telescopes6,7. Here we present James Webb Space Telescope observations that detect the 3.3 µm PAH feature in a galaxy observed less than 1.5 billion years after the Big Bang. The high equivalent width of the PAH feature indicates that star formation, rather than black hole accretion, dominates infrared emission throughout the galaxy. The light from PAH molecules, hot dust and large dust grains and stars are spatially distinct from one another, leading to order-of-magnitude variations in PAH equivalent width and ratio of PAH to total infrared luminosity across the galaxy. The spatial variations we observe suggest either a physical offset between PAHs and large dust grains or wide variations in the local ultraviolet radiation field. Our observations demonstrate that differences in emission from PAH molecules and large dust grains are a complex result of localized processes within early galaxies.

Grading Osteoarthritic Changes of the Zygapophyseal Joints from Radiographs: A Reliability Study.

OBJECTIVE: This study tested the reliability of a 5-point ordinal scale used to grade the severity of degenerative changes of zygapophyseal (Z) joints on standard radiographs. METHODS: Modifications were made to a Kellgren grading system to improve agreement for grading the severity of osteoarthritic changes in lumbar Z joints. These included adding 1 grade of no degeneration, multiple radiographic views, and structured examiner training. Thirty packets of radiographic files were obtained, which included representation of all 5 grades including no degeneration (0) and Kellgren's 4-point (1-4) joint degeneration classification criteria. Radiographs were digitized to create a radiographic atlas that was given to examiners for individual study and blinded evaluation sessions. Intrarater and interrater agreement was determined by weighted κ (κw) from the examination of 79 Z joints (25 packets). RESULTS: Using the modified scale and after training, examiners demonstrated a moderate-to-substantial level of interrater agreement (κw = 0.57, 0.60, and 0.68). Intrarater agreement was moderate (κw = 0.42 and 0.54). CONCLUSIONS: The modified Kellgren 5-point grading system provides acceptable intrarater and interrater reliability when examiners are adequately trained. This grading system may be a useful method for future investigations assessing radiographic osteoarthritis of the Z joints.

Symptomatic expansile vertebral hemangioma causing conus medullaris compression.

OBJECTIVE: To present a case of symptomatic, expansile L1 vertebral hemangioma. CLINICAL FEATURES: A 46-year-old man presented with progressive neurologic changes and insidious onset of low back pain. INTERVENTION AND OUTCOME: After a trial of 3 visits of conservative chiropractic care, no improvement was noted. Magnetic resonance imaging was obtained, revealing an expansile hemangioma with extra-osseous component compromising the conus medullaris at the level of the L1 lumbar vertebra. Neurosurgical intervention resulted in clinical improvement. CONCLUSION: Primary care physicians treating patients with low back pain should be aware of neurologic red flags requiring prompt attention. Magnetic resonance imaging is the imaging modality of choice when evaluating a neurologic abnormality presumably related to a space-occupying lesion. Although a disk herniation is the most common cause of these symptoms, clues in the history and examination must prompt physicians to expand their differential diagnosis to include a variety of other extradural masses.