Biomedical subjects

J B Blake

Publications and source records attributed to J B Blake.

At least 19 recordsLinked to original sources

PubMed1998

Maps of hydrogen isotopes at low altitudes in the inner zone from SAMPEX observations.

The PET instrument aboard the SAMPEX satellite has provided us with long-term intra-calibrated observations of geomagnetically trapped protons and deuterons in the inner zone, suitable for use in constraining the low-altitude portions of radiation belt models being developed as successors to AP-8. These observations have been summarized elsewhere (Looper et al., 1996). Here we report a detection of geomagnetically-trapped tritum at energies from 14 to 35 MeV/nuc below L = 1.2, at about 1/8 the flux of deuterium previously reported at that location and at similar energy per nucleon. We also demonstrate the utility of the SAMPEX/PET observations for measuring the east-west anisotropy in the trapped particle flux at low altitudes, which is due to displacement of particle gyrocenters from the position of observation in a region of strong flux gradients. This anisotropy is implicitly ignored in omnidirectional radiation-flux models, but it can be important to mission planners considering how to distribute shielding over the surface of oriented spacecraft in low Earth orbit.

Anisotropy↗

PubMed1996

SAMPEX observations of energetic hydrogen isotopes in the inner zone.

We report observations of geomagnetically-trapped hydrogen isotopes at low altitudes, near the feet of field lines in the inner zone, made with the PET instrument aboard the SAMPEX satellite. We have mapped protons from 19 to 500 MeV, and have discovered a collocated belt of deuterons, which we have mapped from 18 to 58 MeV/nucleon. We found deuterium at about 1% of the level of the proton flux at the same energy per nucleon, and no tritium at energies of tens of MeV/nucleon with an upper limit of about 0.1% of the proton flux. Protons and deuterons showed similar time dependence, with fluxes approximately tripling from July 1992 to March 1996, and similar pitch-angle dependence. The high-L limits of the proton and deuteron belts as functions of energy were organized by rigidity, as was to be expected if these limits were set for both species by inability of particles to sustain adiabatic motion and stable trapping.

Altitude↗

PubMed1995

Observations of energetic particles with EPAC on Ulysses in polar latitudes of the heliosphere.

Measurements with the Energetic Particle Composition instrument (EPAC) aboard Ulysses show particles from near the ecliptic that were apparently accelerated by shocks associated with a corotating interaction region. The particles were detected together with the shocks and even when shocks no longer arrived at Ulysses up to -65 degrees of heliographic latitude but not beyond. Particles could have reached these latitudes along magnetic fields; such connections to the outer lower latitude heliosphere evidently do not exist above that latitude. The accelerated streams have composition similar to solar wind abundances, no dispersion, and a net inward anisotropy. The underlying composition between the recurrent stream is similar to the anomalous component of cosmic rays. The channel sensitive to high-energy protons (> 230 megaelectron volts) shows a 26-day variation of the flux superimposed on the heliospheric modulation of galactic ions.

Acceleration↗

PubMed1988

Frank Bradway Rogers 1914-1987.

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History, 20th Century↗

PubMed1986

From Surgeon General's bookshelf to National Library of Medicine: a brief history.

The National Library of Medicine originated as a few books in the office of the army's surgeon general, Joseph Lovell, between 1818 and 1836. It became the nation's largest medical library after the Civil War under the direction of John Shaw Billings and began publishing the Index-Catalogue of the Library of the Surgeon General's Office and preparing the Index Medicus. After Billings retired in 1895, the library marked time as army medical officers were rotated through as directors until modernization began under Harold Wellington Jones during World War II. during the directorship of Frank B. Rogers (1949-1963), who introduced MEDLARS, guided the move to a new building in Bethesda, and revitalized other operations, the institution received statutory authority as the National Library of Medicine within the Public Health Service (1956). By 1965, which was marked by the passage of the Medical Library Assistance Act, the library had again regained a position of world leadership.

History, 19th Century↗

PubMed1985