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Yin, L.

Publications and source records attributed to Yin, L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Structures of cyano-biphenyl liquid crystals

The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

Chu, Yuan-Chao↗
NASA NTRS1978

Trace element partitioning between ionic crystal and liquid

The partitioning of trace elements between ionic crystals and the melt has been correlated with lattice energy of the host. The solid-liquid partition coefficient has been expressed in terms of the difference in relative ionic radius of the trace element and the homogeneous and heterogeneous strain of the host lattice. Predictions based on this model appear to be in general agreement with data for alkali nitrates and for rare-earth elements in natural garnet phenocrysts.

Tsang, T.↗
NASA NTRS1976

On the ion-bombardment reduction mechanism

Recent laboratory studies of solar-wind reduction mechanisms on the lunar surface are discussed, emphasizing the effects of the electronic configurations of transition metals and the effects of covalent bonding. A series of experiments is described which involved argon ion bombardment of extremely thin targets consisting of simple halides and cyanides of first-row transition metals. Experimental results are summarized which imply that the cyanides generally have much higher reduction efficiencies than the halides. It is suggested that although reduction and sputtering take place concurrently under ion bombardment, they may actually be two independent processes.

Yin, L.↗
NASA NTRS1975

ESCA studies on solar-wind reduction mechanisms

In a continuing study of solar-wind darkening on the lunar surface, ESCA techniques have been used to examine surface reduction and optical darkening by ion bombardment. Experimental results on transition metal fluorides have shown that ion-bombardment reduction is (a) accompanied by the loss of anion species, (b) relatively independent of the incident ion mass, and (c) not simply related to physical sputtering itself. The reduction mechanism may be more chemical in nature and the rate may be determined primarily by the transition metal ion

Yin, L.↗
NASA NTRS1974

The role of horizontal transport as evaluated from the Apollo 15 and 16 orbital experiments

Despite the large amount of accumulated data there is still considerable debate about the role of various processes in the formation of the lunar surface. One of the processes frequently discussed is that of horizontal transport and how it affected surface chemistry and surface features. The orbital experiments flown on Apollo 15 and 16 enable us to consider the extent of horizontal transport. In particular, the X-ray experiment because of its low penetration depth permits us to make at least crude estimates of the extent of horizontal transport.

Adler, I.↗
NASA NTRS1973

Apollo 15 and 16 results of the integrated geochemical experiment.

A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface. The observations involved measurements of secondary (fluorescent) X-rays, gamma rays and alpha particle emissions. A large scale compositional map of over 20% of the lunar surface was obtained for the first time. It was possible to demonstrate significant chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the moon's hidden side.

Adler, I.↗
NASA NTRS1973

Results of the Apollo 15 and 16 X-ray experiment

Except for some minor modifications the Apollo 16 X-ray fluorescence experiment was similar to that flown aboard Apollo 15. The Apollo 16 provided data for a number of features not previously covered such as Mare Cognitum, Mare Nubium, Ptolemaeus, Descartes, Mendeleev, and other areas. Many data points were obtained by the X-ray experiments, so that comparisons could be drawn between Apollo 15 and 16 flights. The agreement was generally within about 10%. Al/Si concentration ratios ranged from 0.38% in Mare Cognitum to 0.67% in the Descartes area highlands. A comparison of the Apollo 16 data Al/Si values with optical albedo values along the ground tracks showed the same positive correlation as in the Apollo 15 flight. A reexamination of the detector and collimator geometries showed that the spatial resolution was better by almost a factor of two than the initial estimates.

Adler, I.↗
NASA NTRS1972

L-S coupling interpretation of high-resolution LMM Auger spectra of Cu and Zn.

High-resolution LMM Auger spectra of Cu and Zn obtained by X-ray excitation are shown to contain fine structures which have not been reported previously. An attempt has been made to classify these fine structures in terms of pure L-S coupling of the final vacancies of the atom. The agreement between the calculated and the observed energy separations of the fine-structure lines is good within the accuracy of the Hartree-Fock approximation.

Yin, L.↗
NASA NTRS1972

Apollo 16 geochemical X-ray fluorescence experiment - Preliminary report.

Mapping of the lunar surface with respect to magnesium, aluminum, and silicon as aluminum/silicon and magnesium/silicon intensity ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide new data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The aluminum/silicon and magnesium/silicon concentration ratios correspond to those for anorthositic gabbros through gabbroic anorthosites or feldspathic basalts. The X-ray results suggest the occurrence of this premare crust or material similar to it at the Descartes landing site.

Adler, I.↗
NASA NTRS1972

Apollo 16 geochemical X-ray fluorescence experiment: Preliminary report

The lunar surface was mapped with respect to Mg, Al, and Si, as Al/Si and Mg/Si ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The Al/Si and Mg/Si chemical ratios correspond to that for anorthositic gabbro through gabbroic anorthosites or feldspathic basalts. The X-ray results suggest the occurrence of this premare crust or material similar to it as the Descartes landing site.

Adler, I.↗
NASA NTRS1972

Apollo 16 geochemical X-ray fluorescene experiment: Preliminary report

The lunar surface was mapped with respect to Mg, Al and Si as Al/Si and Mg/Si ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The Al/Si and Mg/Si chemical ratios correspond to those for anorthositic gabbro through gabbroic anorthosites or feldspathic basalts. The X-ray results suggest the occurrence of this premare crust, or material similar to it, at the Descartes landing site.

Adler, I.↗
NASA NTRS1972

The Apollo 15 X-ray fluorescence experiment

The CSM spectrometric data on the lunar surface with respect to its chemical composition are presented for Al, Mg, and Si as Al/Si and Mg/Si ratios for the various features overflow by the spacecraft. The lunar surface measurements involved observations of the intensity and characteristic energy distribution of the secondary or fluorescent X-rays produced by the interaction of solar X-rays with the lunar surface. The results showed that the highlands and maria are chemically different, with the highlands having considerably more Al and less Mg than the maria. The mare-highland contact is quite sharp and puts a limit on the amount of horizontal transport of material. The X-ray data suggest that the dominant rock type of the lunar highlands is a plagioclase-rich pyroxene bearing rock, probably anorthositic gabbro or feldspathic basalt. Thus the moon appears to have a widespread differentiated crust (the highlands) systematically richer in Al and lower in Mg than the maria. This crust is pre-mare and may represent the first major internal differentiation of the moon.

Adler, I.↗
NASA NTRS1972

Apollo 15 geochemical X-ray fluorescence experiment - Preliminary report.

Although only part of the information from the X-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.

Adler, I.↗
NASA NTRS1972

X-ray fluorescence experiment

The preliminary results from the Sco X-1 and Cyg X-1 obtained from the Apollo 15 X-ray detector data are presented along with preliminary results of the X-ray fluorescence spectrometric data of the lunar surface composition. The production of the characteristic X-rays following the interaction of solar X-rays with the lunar surface is described along with the X-ray spectrometer. Preliminary analyses of the astronomical X-ray observation and the X-ray fluorescence data are presented.

Adler, I.↗