Multipoint monitoring of amplitude, frequency, and phase of vibrations using concatenated modal interferometers.

Concatenated modal interferometers-based multipoint monitoring system for detection of amplitude, frequency, and phase of mechanical vibrations is proposed and demonstrated. The sensor probes are fabricated using identical photonic crystal fiber (PCF) sections and integrated along a single fiber channel to act as a compact and efficient sensing system. Each identical probe acts as a modal interferometer to generate a stable interference spectrum over the source spectrum. In the presence of an external dynamic field about each probe, the probes respond independently, producing a resultant signal superposition of each interferometer response signal. By analyzing the resultant signals using computational techniques, the vibration parameters applied to each interferometer are realized. The sensing system has an operation range of 1 Hz-1 kHz with a sensitivity of 51.5 pm/V. Such a sensing system would find wide applications at industrial, infrastructural, and medical fronts for monitoring various dynamic physical phenomena.

Human immunodeficiency virus (HIV) infection in a child presenting as acute disseminated encephalomyelitis.

Acute disseminated encephalomyelitis is an extremely rare occurrence in human immunodeficiency virus (HIV) infection. We describe an 8-year-old male child who presented with weakness of both lower limbs for 10 days and focal convulsions for 2 days. The child had left, upper motor neuron facial palsy, lower limb hypotonia, and exaggerated deep tendon reflexes. Enzyme-linked immunosorbent assay antibodies for HIV tested positive and the CD4 count was 109 cells/µL. The magnetic resonance imaging (MRI, brain) revealed extensive confluent hyperintensities (on T2-weighted images) in left parietal, right temporal, and right occipital regions of the white matter, and similar signals were seen in right lentiform nucleus and right posterior thalami, suggesting acute disseminated encephalomyelitis. There was transient improvement with intravenous methyl prednisolone. The patient succumbed to the illness. Perinatally transmitted pediatric HIV infection presenting with acute disseminated encephalomyelitis has not yet been reported in the medical literature.