Biomedical subjects
John D Mathews
Publications and source records attributed to John D Mathews.
Electrical discharge from a thundercloud top to the lower ionosphere.
For over a century, numerous undocumented reports have appeared about unusual large-scale luminous phenomena above thunderclouds and, more than 80 years ago, it was suggested that an electrical discharge could bridge the gap between a thundercloud and the upper atmosphere. Since then, two classes of vertically extensive optical flashes above thunderclouds have been identified-sprites and blue jets. Sprites initiate near the base of the ionosphere, develop very rapidly downwards at speeds which can exceed 107 m s-1 (ref. 15), and assume many different geometrical forms. In contrast, blue jets develop upwards from cloud tops at speeds of the order of 105 m s-1 and are characterized by a blue conical shape. But no experimental data related to sprites or blue jets have been reported which conclusively indicate that they establish a direct path of electrical contact between a thundercloud and the lower ionosphere. Here we report a video recording of a blue jet propagating upwards from a thundercloud to an altitude of about 70 km, taken at the Arecibo Observatory, Puerto Rico. Above an altitude of 42 km-normally the upper limit for blue jets and the lower terminal altitude for sprites-the flash exhibited some features normally observed in sprites. As we observed this phenomenon above a relatively small thunderstorm cell, we speculate that it may be common and therefore represent an unaccounted for component of the global electric circuit.
Impact of single dose azithromycin on group A streptococci in the upper respiratory tract and skin of Aboriginal children.
BACKGROUND: Aboriginal children living in remote Australia experience high rates of bacterial infection such as trachoma, otitis media and streptococcal skin infection, which often progress to associated chronic diseases in later life. METHODS: In February, 1995, single dose azithromycin was given to 130 Aboriginal children with trachoma and their contacts. The impact of this program on respiratory and skin group A Streptococcus pyogenes carriage and infection was also monitored. RESULTS: Immediately before treatment 90% of children had skin sores, 38% of sores had pus and 74% of sores with pus had group A Streptococcus (GAS). Overall 57% of children had GAS skin infections. At 2 to 3 weeks and 2 and 6 months after treatment, this proportion was 10, 32 and 51%, respectively. For the upper respiratory tract GAS recovery rates were 8% before treatment and 0, 11 and 15% at the 2- to 3-week, 2-month and 6-month posttreatment visits, respectively. Multiple types occurred concurrently in individuals, particularly after treatment. Identical types were sometimes recovered simultaneously from the upper respiratory tract and skin, suggesting that the high rates of acute rheumatic fever in this population in the absence of high rates of detectable throat GAS carriage could be related to high rates of skin GAS infection. CONCLUSIONS: There is an urgent need for education, adequate housing, scabies eradication and improved hygiene to reduce skin trauma and subsequent GAS infection in this population. Clinical trials are needed to determine how these measures can best be integrated with the trachoma eradication program to maximize health outcomes.
In vivo penicillin MIC drift to extremely high resistance in Serotype 14 Streptococcus pneumoniae persistently colonizing the nasopharynx of an infant with chronic suppurative lung disease: a case study.
This is the first report of in vivo pneumococcal penicillin MIC drift from 4.0 to 16.0 mg/liter, possibly associated with alterations in the pbp1a gene. The case presented here is of an infant with early onset recurrent pneumonia and chronic bronchitis requiring repeated antibiotics.