Crystal Structure of the Solid Electrolyte(C5H5NH) Ag5I6 at -30{degrees}C

The crystal structure of pyridinium hexaiodopentaargentate, (C(5)H(5)NH) Ag(5)l(6), is unique among those of the halide and chalcogenide solid electrolytes in that face-sharing iodide octahedra as well as face-sharing tetrahedra and face-sharing between octahedra and tetrahedra provide the paths for silver ion transport. There are two formula units in a hexagonal cell, space group P6/mcc (D6h(2)). At -30 degrees C, the lattice constants are a = 11.97 +/- 0.02, c = 7.41 +/- 0.01 A. The structure has three sets of sites for the silver ions. At -30 degrees C two of these sets are apparently filled with the ten silver ions per unit cell, while the third set of tetrahedrally coordinated general positions is empty. Therefore, the conductivity at this temperature is limited by the thermal excitation of the silver ions into the empty tetrahedra.     

Catalytic hydration of terminal alkenes to primary alcohols

Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction between trans- PtHCl(PMe(3))(2) (where Me = CH(3)) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60 degrees C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene to n-hexanol at a rate of 6.9 +/- 0.2 turnovers per hour. Hydration of 1-dodecene to n-dodecanol occurs at a rate of 8.3 +/- 0.4 turnovers per hour at 100 degrees C. Deuterium labeling experiments with trans-PtDCl(PMe(3))(2) show that hydration involves reductive elimination of a C-H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k(1) = 9.3 +/- 0.5 x 10(-3) liters per mol per second) appears to be limitng under these conditions.     

Kyanite-Andalusite Equilibrium from 700{degrees} to 800{degrees}C

The metastable kyaniteandalusite equilibrium in the Al(2)SiO(5) system has been reversed at 700 degrees , 750 degrees , and 800 degrees C at elevated water pressures, with a variety of natural and synthetic kyanites and andalusites as starting materials. Sillimanite, the stable form of Al(2)SiO(5) under these conditions, did not appear. The value of the transition pressure at 750 degrees C is 6.6 +/- 0.4 kilobars, several kilobars below pressures given by several convergent previous determinations. The Al(2)SiO(5) pressure-temperature triple point now indicated lies far from the points found by others. The revised aluminum silicate phase diagram indicates that many rocks crystallized at lower pressures than formerly thought possible.     

Kinetics of the fe2+-mg, order-disorder reaction in anthophyllites: quantitative cooling rates

The kinetics of the Fe(2+)-Mg, order-disorder phenomenon in a highly ordered natural anthophyllite have been determined over the temperature range from 400 degrees to 720 degrees C at a pressure of 2 kilobars. At temperatures of 600 degrees C and above, equilibrium is attained by disordering as well as ordering reactions. The intracrystalline exchange is defined by a standard Gibbs free energy of 4247 +/- 54 calories per formula unit. Rate studies at 550 degrees and 500 degrees C show that equilibrium is attained by ordering but not by disordering within the same time scale and that the exchange reaction is characterized by an activation energy of approximately 55 kilocalories per formula unit. An equilibration temperature for the natural anthophyllite of 270 degrees C is determined from the termination of the ordering process owing to excessively slow reaction kinetics after approximately 10(7) years. From the rate constants of the exchange process, for different crystallization temperatures, the apparent equilibration temperature of 270 degrees C defines a maximum linear cooling rate for the rock of 1 x 10(4) degrees C per year.     

Survival of mouse embryos frozen to -196 degrees and -269 degrees C

Mouse embryos survived freezing to -196 degrees C. Survival required slow cooling (0.3 degrees to 2 degrees C per minute) and slow warming (4 degrees to 25 degrees C per minute). Depending on the specific rates used, 50 to 70 percent of more than 2500 frozen and thawed early embryos developed into blastocysts in culture after storage at -196 degrees C for up to 8 days. When approximately 1000 of the survivors, including some frozen to -269 degrees C (4 degrees K), were transferred into foster mothers, 65 percent of the recipients became pregnant. More than 40 percent of the embryos in these pregnant mice gave rise to normal, living full-term fetuses or newborn mice.     

Kyanite-Sillimanite Equilibrium at 750{degrees}C

Reversal of the kyanite-sillimanite inversion has been accomplished hydrothermally at 750 degrees C. The inversion pressure at 750 degrees C is 8.1 +/- 0.4 kilobars. The calculated pressuretemperature slope at this point is 17.7+/- 1.0 bars per degree celsius. Geologically, this result seems more plausible than previous estimates of the location of the boundary. When combined with other work on the relative stability of andalusite, the data indicate that andalulsite cannot be stable at a pressure greater than 4.2 kilobars.     

The silica-alumina system: stable and metastable equilibria at 1.0 atmosphere

Diffusion couples, consisting of sapphire and fused silica, which were annealed in the temperature range from 1678 degrees to 2003 degrees C and analyzed by electron beam microprobe, have provided data on the stable phase equilibrium of the silica-alumina system. Under stable equilibrium conditions, the intermediate compound of this system, mullite (3Al(2)O(3) . 2SiO(2)), melts incongruently at 1828 degrees +/- 10 degrees C and its solid solution field extends from 70.5 to 74.0 percent (by weight) alumina. The stable phase diagram is a composite of the two binary eutectic diagrams: silica-mullite in the absence of alumina and silica-alumina in the absence of mullite. Under metastable conditions, mullite melts congruently at approximately 1890 degrees +/- 10 degrees C and its solid solution field extends to approximately 83.2 percent (by weight) alumina.     

Kaolinite Synthesis at 25{degrees}C

The addition of quercetin, an organic flavone (C(15)H(10)O(7)), to aqueous solutions containing silica and aluminum and adjusted to final pH's from 6.5 to 8.5 produced a 1 : 1 alumninosilicate precipitate which, after 6 to 16 months of aging in solution at 25 degrees C, contained as much as 5 percent well-formed kaolinite plates. Similar solutions containing no organic material produced relatively amorphous precipitates with the same composition and stability (standard free energy of formation = -897+/-1 kilocalories per mole) but with substantially smaller amounts of crystaline material even after 2 years of aging.     

Temporal variability of the Atlantic meridional overturning circulation at 26.5 degrees N

The vigor of Atlantic meridional overturning circulation (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5 degrees N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 +/- 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10(6) cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv.     

Crystal Structure of Benzene II at 25 Kilobars

Crystals of a high-pressure form of benzene (benzene 11) were grown in the diamond-anvil pressure cell at elevated temperature and pressure from the transition of solid I to solid II. X-ray precession data were obtained from a single-crystal in the high-pressure cell. At 21 degrees C and about 25 kilobars, benzene II crystallizes in the monoclinic system with a = 5.417 +/- 0.005 angstroms (S.D.), b = 5.376 +/- 0.019 angstroms, c = 7.532 +/- 0.007 angstroms, beta = 110.00 degrees +/- 0.08 degrees , space group P2(1)/ c, Pc= 1.26 grams per cubic centimeter. The crystal structure was solved by generating all possible molecular packing configurations and calculating structure factors, reliability factors, and packing energies for each configuration. This procedure produced a unique solution for the molecular packing of benzene II.     

Potassium-Argon Ages and Spreading Rates on the Mid-Atlantic Ridge at 45{degrees} North

Potassium-argon dates obtained from extrusives collected on a traverse across the Mid-Atlantic Ridge at 45 degrees N are consistent with the hypothesis of ocean-floor spreading. The dates suggest a spreading rate in the range of 2.6 to 3.2 centimeters per year near the axis of the ridge; the rate agrees with that computed from fission-track dating of basalt glasses. Additional data for a basalt collected 62 kilometers west of the axis gives a spreading rate of 0.8 centimeter per year, which is similar to the rate inferred from magnetic anomaly patterns in the area. Reasons for the difference in calculated spreading rates are discussed.     

Mercury: results on mass, radius, ionosphere, and atmosphere from mariner 10 dual-frequency radio signals

Analysis of the radio-tracking data from Mariner 10 yields 6,023,600 +/- 600 for the ratio of the mass of the sun to that of Mercury, in very good agreement with values determined earlier from radar data alone. Occultation measurements yielded values for the radius of Mercury of 2440 +/- 2 and 2438 +/- 2 kilometers at laditudes of 2 degrees N and 68 degrees N, respectively, again in close agreement with the average equatorial radius of 2439 +/- 1 kilometers determined from radar data. The mean density of 5.44 grams per cubic centimeter deduced for Mercury from Mariner 10 data thus virtually coincides with the prior determination. No evidence of either an ionosphere or an atmosphere was found, with the data yielding upper bounds on the electron density of about 1500 and 4000 electrons per cubic centimeter on the dayside and nightside, respectively, and an inferred upper bound on the surface pressure of 10(-8) millibar.     

Magnetic Anomalies over the Mid-Atlantic Ridge near 27{degrees}N

Ten magnetic profiles across the mid-Atlantic ridge near 27 degrees N show trends that are parallel to the ridge axis and symmetrical about the ridge axis. The configuration of magnetic bodies that could account for the pattern supports the Vine and Matthews hypothesis for the origin of magnetic anomalies over oceanic ridges. A polarity-reversal time scale inferred from models for sea-floor spreading in the Pacific-Antarctic ridge and radiometrically dated reversals of the geomagnetic field indicates a spreading rate of 1.25 centimeters per year during the last 6 million years and a rate of 1.65 centimeters per year between 6 and 10 million years ago. A similar analysis of more limited data over the mid-Atlantic ridge near 22 degrees N also indicates a change in the spreading rate. Here a rate of 1.4 centimeters per year appears to have been in effect during the last 5 million years; between 5 and 9 million years ago, an increased rate of 1.7 centimeters per year is indicated. The time of occurrence and relative magnitude of these changes in the spreading rate, about 5 to 6 million years ago and 18 to 27 percent, respectively, accords with the spreading rate change implied for the Juan de Fuca ridge in the northeast Pacific.     

Oxygen isotope ratios in trees reflect mean annual temperature and humidity

Values of the oxygen isotope ratios (delta(18)O) in tree-ring cellulose closely reflect the delta(18)O values in atmospheric precipitation and hence mean annual temperature. The change in delta(18)O in cellulose is 0.41 per mil per degree Celsius for selected near-coastal stations. The values of delta(18)O in precipitation and cellulose also change with altitude, as demonstrated for Mount Rainier, Washington. A temperature lapse rate of 5.2 degrees +/- 0.5 degrees C per 1000 meters calculated from cellulose delta(18)O values agrees with the accepted mean annual lapse rate of 5 degrees C per 1000 meters for this region. Cellulose delta(18)O values and delta(18)O values of carbon dioxide equilibrated with leaf water differ by a fixed 16 per mil.     

Melting of tin teliuride at high pressures

The melting curve of tintelluride (Sn(0.496)Te(0.504) was determined by differential thermal analysis at pressures between 5 and 40 kilobars. Near 844 degrees +/-4 degrees C and 12.0+/-1.0 kb, the liquid and two solid polymorphscoexist.     

Water and carbon in rusty lunar rock 66095

Lunar rock 66095 contains a hydrated iron oxide and has an unusual amount of water for a lunar rock (140 to 750 parts per million), 90 percent of which is released below 690 degrees C. The deltaof water released at these low temperatures varies from -75 to -140 per mil relative to standard mean ocean water (SMOW). The small amount of water released between 690 degrees and 1300 degrees C has a delta of about -175 +/-25 per mil SMOW. These delta values are not unusual for terrestrial water. The delta(18)O of water extracted from 110 degrees to 400 degrees C has a value of +5+/- I per mil SMOW, similar to the value for lunar silicates from rock 66095 and different from the value of -4 to -22 per mil found for samples of terrestrial rust including samples of rusted meteoritic iron. The amount of carbon varies from 11 to 59 parts per million with a delta(13)C from -20 to -30 per mil relative to Pee Dee belemnite. Only very small amounts of reduced species (such as hydrogen, carbon monoxide, and methane) were found, in contrast to the analyses of other lunar rocks. Although it is possible that most of the water in the iron oxide (goethite) may be terrestrial in origin or may have exchanged with terrestrial water during sample return and handling, evidence presented herein suggests that this did not happen and that some lunar water may have a deltaD that is indistinguishable from that of terrestrial water.     

Recent changes in atmospheric carbon monoxide

Measurements of carbon monoxide (CO) in air samples collected from 27 locations between 71 degrees N and 41 degrees S show that atmospheric levels of this gas have decreased worldwide over the past 2 to 5 years. During this period, CO decreased at nearly a constant rate in the high northern latitudes. In contrast, in the tropics an abrupt decrease occurred beginning at the end of 1991. In the Northern Hemisphere, CO decreased at a spatially and temporally averaged rate of 7.3 (+/-0.9) parts per billion per year (6.1 percent per year) from June 1990 to June 1993, whereas in the Southern Hemisphere, CO decreased 4.2 (+/-0.5) parts per billion per year (7.0 percent per year). This recent change is opposite a long-term trend of a 1 to 2 percent per year increase inferred from measurements made in the Northern Hemisphere during the past 30 years.     

Footwall refrigeration along a detachment fault: implications for the thermal evolution of core complexes

Oxygen isotope compositions of epidote and quartz from chloritic breccias that underlie the detachment fault in the metamorphic core complex of the Whipple Mountains yielded quartz-epidote fractionations that range from 4.1 to 6.4 per mil and increase systematically toward the fault. These fractionations give mean temperatures that decrease from approximately 432 degrees C at 50 meters below the fault to approximately 350 degrees C at 12 meters below the fault. This extreme thermal gradient of 82 degrees C over 38 meters (2160 degrees C per kilometer) is best explained by advective heat extraction by means of circulating surface-derived fluids. Models of lithospheric extension consider only conductive cooling resulting from tectonic denudation and thus require revision to include fluid-induced fault-zone refrigeration.     

Nitrogen fixation at 92 degrees C by a hydrothermal vent archaeon

A methanogenic archaeon isolated from deep-sea hydrothermal vent fluid was found to reduce N(2) to NH(3) at up to 92 degrees C, which is 28 degrees C higher than the current upper temperature limit of biological nitrogen fixation. The 16S ribosomal RNA gene of the hyperthermophilic nitrogen fixer, designated FS406-22, was 99% similar to that of non-nitrogen fixing Methanocaldococcus jannaschii DSM 2661. At its optimal growth temperature of 90 degrees C, FS406-22 incorporated (15)N(2) and expressed nifH messenger RNA. This increase in the temperature limit of nitrogen fixation could reveal a broader range of conditions for life in the subseafloor biosphere and other nitrogen-limited ecosystems than previously estimated.     

Cooling of Tropical Brazil (5{degrees}C) During the Last Glacial Maximum

A 30,000-year paleotemperature record derived from noble gases dissolved in carbon-14-dated ground water indicates that the climate in lowland Brazil (Piaui Province, 7 degrees S, 41.5 degrees W; altitude, 400 meters) was 5.4 degrees +/- 0.6 degrees C cooler during the last glacial maximum than today. This result suggests a rather uniform cooling of the Americas between 40 degrees S and 40 degrees N. A 5.4 degrees C cooling of tropical South America is consistent with pollen records, snow line reconstructions, and strontium/calcium ratios and delta(18)O coral records but is inconsistent with the sea-surface temperature reconstruction of CLIMAP (Climate: Long-Range Investigation, Mapping and Prediction). On the basis of these results, it appears that the tropical Americas are characterized by a temperature sensitivity comparable to that found in higher latitudes.