26 Al: measurement and applications

1987 ◽  
Vol 323 (1569) ◽  
pp. 121-143 ◽  
Keyword(s):  
Cosmic Rays ◽  
Solar Flares ◽  
Diagnostic Value ◽  
University Of Pennsylvania ◽  
Production Rates ◽  
The Earth ◽  
Crustal Abundance ◽  
The University ◽  
Very High

26 Al(r1/2 = 0.7 Ma), like 10 Be (r1/2 = 1.5 Ma), is produced by cosmic rays in the atm osphere, but its production rate is low ( ca 4 x 10 -3 that of 10 Be) and the crustal abundance o f 27 Al is high, resulting in 26 A1:27Al ratios rarely exceeding 10 ~14 . Both isotopes are also produced in surficial rocks by cosmic rays; in quartz the production rates of 26 Al and 10 Be are ca . 70 atoms g -1 a -1 and ca . 10 atoms g -1 a -1 , respectively (at sea level). Because quartz frequently contains 27 Al at less than 100 p.p.m. (by mass), the 26 Al : 27 A1 ratio resulting from this situ production can be as high as 3 x 10 -11 . In extraterrestrial m atter, where the production rates are several hundred times greater, samples containing a few percent o f 27 Al have 26 Al: 27 Al ratios of 10 -11 or larger. We describe an experim ental arrangem ent that was developed at the University of Pennsylvania for measuring 26 A1: 27 Al ratios as low as 10-15. The size requirements for samples are approximately a factor of 100000 smaller than those of decay counting, and measurement times are less than an hour, compared with weeks or months. We discuss several applications of the technique to the measurement of terrestrial as well as extraterrestrial samples. Emphasis is placed on the combined measurement of 10 Be and 26 Al and the various uses to which the ratio o f 26 Al: 10 Be in a sample can be put. In particular, we discuss the very high 26 Al: 10 Be ratios that are found in the outer few millimetres of extraterrestrial bodies, resulting from low-energy protons emitted by solar flares, and the diagnostic value of these ratios in determining the size of objects in space. The low value of the 26 A1: 10 Be ratio resulting from atmospheric production is used to prove the terrestrial origin of tektites. And finally, we discuss the manner in which the variable 26 Al: 10 Be ratio that results from in situ production in objects on the Earth ’s surface can be used to measure rates of weathering and exposure histories.

TEM Studies of Shear Bands in a Bulk Metallic Glass Based Composite

2001 ◽  
Vol 7 (S2) ◽  
pp. 1120-1121
Author(s):  
E. Pekarskaya ◽  
C.P. Kim ◽  
W.L. Johnson
Keyword(s):  
Metallic Glasses ◽  
Shear Bands ◽  
High Yield ◽  
In Situ Tem ◽  
Two Phase ◽  
University Of Illinois ◽  
Glass Forming ◽  
The University ◽  
Very High

In 1980’s the discovery of multicomponent systems with exceptional glass forming ability enabled the synthesis of metallic glasses at relatively low cooling rates, 10−1 — 102 K/s and at a larger thicknesses. Bulk metallic glasses normally have very high yield stress, σy = 0.02 · Y (Y is Young’s modulus), high elastic limit of about 2%, but fail with very little global plasticity, typically along a localized shear band at a 45 degree angle with respect to the applied stress.The material studied in the present work is a two-phase Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 alloy,prepared by in-situ processing. The alloy consists of amorphous and crystalline phases. In-situ TEM straining (tensile) experiments were performed at room temperature in JEOL 4000EX operating at 300kV. The experiments were carried out in the Center for Microanalysis of Materials in the University of Illinois at Urbana-Champaign. The goal of the study was to understand the deformation mechanisms of such composite material.

scholarly journals Revealing Histories of Exposure Using In Situ Produced 26Al and 10Be in Libyan Desert Glass

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 547-555 ◽  
Author(s):  
Jeffrey Klein ◽  
Robert Giegengack ◽  
Roy Middleton ◽  
Pankaj Sharma ◽  
J R Underwood ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Sea Level ◽  
Surface Processes ◽  
Earth Surface ◽  
Production Rates ◽  
The Past ◽  
Libyan Desert ◽  
Libyan Desert Glass

We present the results of measurements of 26Al and 10Be produced in situ in 12 samples of Libyan Desert Glass by cosmic rays during the last ten million years. Based on the variability of the concentrations of 10Be and of the 26Al/10Be ratios we measured, we conclude that individual fragments of glass have experienced different exposure histories, implying several major redistributions of the glass within the past 106 years. The 26Al and 10Be concentrations are inconsistent with the theoretical estimates of the rates of in situ production. We estimate minimum production rates of 70 atoms g-1 yr-1 and 10 atoms g-1 yr-1 for 26Al and 10Be, respectively, produced in quartz at sea level between 60–90° latitude. Despite the present uncertainty in the rates of production, we feel that these results show clearly the effectiveness of in situ produced 26Al and 10Be in studying earth-surface processes.

scholarly journals 6. Space Observations of Solar System Objects

1985 ◽  
Vol 19 (1) ◽  
pp. 642-643
Author(s):  
J. Caldwell
Keyword(s):  
Solar System ◽  
Phase Angle ◽  
Spatial Resolution ◽  
Spectral Range ◽  
High Spatial Resolution ◽  
The Earth ◽  
Solar System Objects ◽  
Very High Spatial Resolution ◽  
Very High

Solar system objects may be studied in space by two general techniques. Everyone is familiar with the exciting aspects of deep space probes: very high spatial resolution; in situ measurements of particles and fields; in situ chemistry studies by mass spectrographs and gas chromatographs; unique phase angle and occultation opportunities. However, the Solar system can also be studied to great advantage by observatories in orbit around the Earth. The broader spectral range available above the terrestrial atmosphere is as important for planetary studies as it is for investigations of more distant astronomical targets. Both techniques will be discussed in this brief report.

Un fragment de stèle inédit de Dendara

2018 ◽  
Vol 104 (2) ◽  
pp. 217-227
Author(s):  
Jérémie Florès
Keyword(s):  
University Of Pennsylvania ◽  
Economic Role ◽  
Intermediate Period ◽  
Archaeological Data ◽  
Poor State ◽  
Registration Number ◽  
First Intermediate Period ◽  
The University

This article studies a fragment of a stele found by Clarence Stanley Fisher in 1915 at Dendara necropolis and most probably left in situ. Nevertheless, based on a photograph kept in the archives of the University of Pennsylvania Museum of Archaeology and Anthropology, it has been pointed out that the artefact, also known under the registration number D 628, presents a cut biography and a very damaged decorated scene. Despite its poor state of preservation, two themes have been recognized in the hieroglyphic text. The first is about the management of a grain silo, the second concerns the economic role of the owner for the funerary cult of his father. In addition to a phraseological analysis based on the terms mḫr/mẖr and šnwt, taking into account different information such as archaeological data, allowed an identification of the stele owner. It appears that he was a middle-ranking official who lived during the First Intermediate Period.

Production of New and Revised A.A.V.S.O. Charts

1979 ◽  
Vol 46 ◽  
pp. 368
Author(s):  
Clinton B. Ford
Keyword(s):  
Variable Star ◽  
Standard Form ◽  
Original Data ◽  
University Of Pennsylvania ◽  
Standard Format ◽  
Additional Information ◽  
The Gift ◽  
The University

A “new charts program” for the Americal Association of Variable Star Observers was instigated in 1966 via the gift to the Association of the complete variable star observing records, charts, photographs, etc. of the late Prof. Charles P. Olivier of the University of Pennsylvania (USA). Adequate material covering about 60 variables, not previously charted by the AAVSO, was included in this original data, and was suitably charted in reproducible standard format.Since 1966, much additional information has been assembled from other sources, three Catalogs have been issued which list the new or revised charts produced, and which specify how copies of same may be obtained. The latest such Catalog is dated June 1978, and lists 670 different charts covering a total of 611 variables none of which was charted in reproducible standard form previous to 1966.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

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