ALBERT

Description: High-protein and acidogenic diets induce hypercalciuria. Foods or supplements with excess sulfur-containing amino acids increase endogenous sulfuric acid production and therefore have the potential to increase calcium excretion and alter bone metabolism. In this study, effects of an amino acid/carbohydrate supplement on bone resorption were examined during bed rest. Thirteen subjects were divided at random into two groups: a control group (Con, n = 6) and an amino acid-supplemented group (AA, n = 7) who consumed an extra 49.5 g essential amino acids and 90 g carbohydrate per day for 28 days. Urine was collected for n-telopeptide (NTX), deoxypyridinoline (DPD), calcium, and pH determinations. Bone mineral content was determined and potential renal acid load was calculated. Bone-specific alkaline phosphatase was measured in serum samples collected on day 1 (immediately before bed rest) and on day 28. Potential renal acid load was higher in the AA group than in the Con group during bed rest (P 〈 0.05). For all subjects, during bed rest urinary NTX and DPD concentrations were greater than pre-bed rest levels (P 〈 0.05). Urinary NTX and DPD tended to be higher in the AA group (P = 0.073 and P = 0.056, respectively). During bed rest, urinary calcium was greater than baseline levels (P 〈 0.05) in the AA group but not the Con group. Total bone mineral content was lower after bed rest than before bed rest in the AA group but not the Con group (P 〈 0.05). During bed rest, urinary pH decreased (P 〈 0.05), and it was lower in the AA group than the Con group. These data suggest that bone resorption increased, without changes in bone formation, in the AA group.

Description: No abstract available

Description: Treatment strategies for Space Motion Sickness were compared using the results of postflight oral debriefings. Standardized questionnaires were administered to all crewmembers immediately following Space Shuttle flights by NASA flight surgeons. Cases of Space Motion Sickness were graded as mild, moderate or severe based on published criteria, and medication effectiveness was judged based on subjective reports of symptom relief. Since October 1989, medication effectiveness is reported inflight through Private Medical Conferences with the crew. A symptom matrix was analyzed for 19 crewmembers treated with an oral combination of scopolamine and dextroamphetamine (scopdex) and 15 crewmembers treated with promethazine delivered by intramuscular (IM) or suppository routes. Scopdex has been given preflight as prophaxis for Space Motion Sickness but analysis showed delayed symptom presentation in 9 crewmembers or failed to prevent symptoms in 7. Only three crewmembers who took scopdex had no symptoms inflight. Fourteen out of 15 crewmembers treated with IM promethazine and 6 of 8 treated with promethazine suppositories after symptom development had immediate (within 12 h) symptom relief and required no additional medication. There were no cases of delayed symptom presentation in the crewmembers treated with promethazine. This response is in contrast to untreated crewmembers who typically have slow symptom resolution over 72-96 h. We conclude that promethazine is an effective treatment of Space Motion Sickness symptoms inflight. NASA policy currently recommends treating crewmembers with Space Motion Sickness after symptom development, and no longer recommends prophylaxis with scopdex due to delayed symptom development and apparent variable absorption of oral medications during early flight days.

Description: A model of Saturn's magnetic field, called Saturn Pioneer Voyager (SPV), is developed on the basis of an analysis of three sets of data: those from the Pioneer 11, the Voyager 1, and the Voyager 2 magnetometers. It is shown that the SPV model fits the data observed between 1.3 and 8.0 Saturn radii from the planet's center with a 1.13 percent weighted rms average of the percent differences between the observed and modeled fields, which is substantially better than the fits yielded by any of the previous models.

Description: Detailed photoclinometric data are presented for a variety of surface features (pits, troughs, wall valleys, and grabens) within three study areas in the western equatorial regions of Mars (Lunae, Syria, and Sinai Plana) that provide evidence for mechanical discontinuities within the shallow Martian crust in these regions. The data's relation to some of the previously proposed mechanical discontinuities within the Martian crust is discussed, and the geologic significance of these features is speculated upon.

Description: Trace element analyses of the phosphates minerals in stony-iron pallasite meteorites are used here to investigate the magmatic history of the silicate portions of pallasites. In Eagle Station and seven other pallasites, the phosphates have relatively low concentrations of REEs and are strongly enriched in heavy relative to light REE. These patterns are consistent with formation of phosphate by subsolidus reactions between metal and silicate, in which phosphate inherits the REE pattern of olivine. In Springwater and Santa Rosalia, calcium-rich phosphates have higher concentrations of REE, are enriched in light relative to heavy REE, and have negative europium anomalies. These patterns are consistent with crystallization of phosphate from a europium-depleted chondritic liquid. This is unlikely to have happened near the base of the differentiating parent-body mantle; it suggests that some pallasites may come from regions of their parent bodies much nearer the surface than the core-mantle boundary.

Description: Synthetic forsterite (Mg2SiO4) was partially evaporated in vacuum for various durations and at different temperatures. The residual charges obtained when molten Mg2SiO4 was evaporated to 12 percent of its initial mass were enriched in heavy isotopes by about 20, 30, and 15 per mil/amu for O, Mg, and Si, respectively, whereas solid forsterite evaporated to a similar residual mass fraction showed negligible fractionations. These results imply that calcium and aluminum-rich refractory inclusions in carbonaceous chondrites must have been at least partially molten in the primordial solar nebula if the observed large mass fractionation effects were caused by evaporation processes in the nebula.

Description: The duration of ice-covered lakes after the initial freezing of the early Mars is presently estimated via a climate model whose critical parameter is the existence of peak seasonal temperatures above freezing, and in which the variability of insolation is included. Under conditions in which meltwater was supplied by an ice source, it is found that water habitats could have been maintained under relatively thin ice sheets for as many as 700 million years after the onset of below-freezing global temperatures. The duration of such habitats on the early Mars therefore exceeds the upper limit of the time envisioned for the emergence of aquatic life on earth.

Description: The 21st century is likely to see the start of the manned exploration and settlement of the inner solar system. NASA's plans for this endeavor are focused upon the Space Exploration Initiative which calls for a return to the Moon, to stay, followed by manned missions to Mars. To execute these missions safely provides solar physics with both a challenge and an opportunity. As the past solar maximum has clearly demonstrated, the Sun, through the solar flare process, is capable of generating and accelerating to high energies large fluxes of protons whose cumulative dose to unprotected astronauts can be fatal. It will be the responsibility of solar physicists to develop an accurate physical description of the mechanisms of flare energy storage and release, and of particle acceleration and propagation through interplanetary space upon which to base a sound method of flare and energetic particle prediction.

Description: There is considerable evidence that Mars had liquid water early in its history and possibly at recurrent interval. It has generally been assumed that this implied that the climate was warmer as a result of a thicker CO2 atmosphere than at the present. However, recent models suggest that Mars may have had a thick atmosphere but may not have experienced mean annual temperatures above freezing. In this paper we report on models of liquid water formation and maintenance under temperatures well below freezing. Our studies are based on work in the north and south polar regions of Earth. Our results suggest that early Mars did have a thick atmosphere but precipitation and hence erosion was rare. Transient liquid water, formed under temperature extremes and maintained under thick ice covers, could account for the observed fluvial features. The main difference between the present climate and the early climate was that the total surface pressure was well above the triple point of water.