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Epitaxial MgO thin films have been grown on single crystal substrates of M-plane (100), A-plane (20), C-plane (0001) and R-plane (102) sapphire by laser ablation of a Mg metal target in a molecular oxygen atmosphere using 1064 nm radiation from a Nd:YAG laser. X-ray measurements indicate that the MgO grows epitaxially on all substrates, with its orientation dependent on the cut of the sapphire substrate. (110)-oriented MgO grows on M-plane sapphire, while (111)-oriented MgO films are found on both the A-plane and the C-plane sapphire. The orientation of MgO found on R-plane sapphire appears to be surface and temperature dependent. The principal growth orientation obtained on the R-plane is (100)-oriented MgO although (100) growth tilted 30° from the [11] Al2O3 direction can result. X-ray area mapping has been performed to determine the mosaicity, d value spread and strain present in the films. These data are compared with the in-plane orientation and the mismatch of the MgO and Al2O3 lattices in an attempt to relate the preferred orientation to the plane of the sapphire on which it is grown.

Thin films of YBa 2 Cu 3 O 7 (YBCO) have been grown on MgO buffer layers on LaAlO 3 and silicon substrates by laser ablation at substrate temperatures of 750°C in a 250 mTorr oxygen atmosphere. The films grown on MgO/LaAlO 3 are c -axis oriented and epitaxial, as shown by X-ray measurements. The films grown on MgO/Si have mixed a -, b -, and c -axis orientation. For YBCO/MgO/Si the presence of the MgO buffer layer cannot be detected by X-ray diffraction, suggesting a possible reaction between the Si and MgO at elevated temperatures. Pole figures show the YBCO growth on Si to be epitaxial with a significant in plane random component. Resistivity measurements indicate that the transition temperature of the YBCO/MgO/LaAlO 3 is 87 K, while the transition temperature for YBCO/MgO/Si is lower, 85 K, probably due to the poor epitaxy of the film.

We study the heavy quark potential in the SU(2) positive plaquette model using monopoles in the maximum abelian gauge, and vortices. Monopoles give a quantitative description of the string tension. Vortices approximately reproduce the entire heavy quark potential., Comment: 3 pages, latex, 2 postscript figures

We study the effect of vortices of different size on the long range heavy quark potential. Under certain simplifying assumptions, we find that the subdominant term in the potential at long range is controlled by the distribution of vortices of large size.

Measurements of the energy deposited in silicon surface-barrier detectors as a result of proton-induced nuclear reactions were carried out at the Harvard Cyclotron for protons with incident energies ranging from 50 to 158 MeV and detectors with thicknesses of 2.5, 4.2, 24.1, 100, and 200 ?m. The number of events in which a given threshold amount of energy is deposited in a 4.2 ?m detector varied with incident proton energy in a manner similar to previous measurements of the proton-induced soft-error cross section. The number of events in which at least a threshold amount of energy was deposited in the detector fell off in a near exponential manner with increasing threshold energy. The data were found to be in reasonable agreement with a computer simulation model developed in our laboratory. The model is used to illustrate how the mass spectra of the residual nuclear fragments shifts towards lower masses with increasing recoil energy. Lighter recoils have longer ranges and a greater chance of leaving a microscopically thin sensitive volume element before coming to their end of range.

Citizen efforts to secure increased funds for St. Paul Schools and teacher salaries rewarded on fourth attempt.

The seven possible monofluoro-2-phenylbenzothiazoles have been prepared. Each was prepared by potassium hexacyanoferrate(III) oxidation of the appropriately substituted thiobenzanilide. Several were also prepared via a benzyne intermediate through treatment of suitable thiobenzanilides with potassium amide and liquid ammonia.

Zwei neue, fungistatische Tetraen-Antibiotika wurden in reiner Form isoliert und Tetrine A und B genannt. Tetrin A, das kristallin erhalten wurde, hat mit groser Wahrscheinlichkeit die Summenformel C35H53NO13, Tetrin B die von C34H53NO14. Beide Antibiotika wurden zu Mycosamin hydrolysiert.

SINCE wars begin in the minds of men," as the Unesco charter L so aptly puts it, "it is in the minds of men that the defenses of peace must be constructed." One of the most promising avenues for approaching this goal is through international intercollegiate contacts. Approaches thus far used have been through exchanges of students and teachers, educational missions sent abroad, and international conferences of students and teachers. The last of these seems to be the most fruitful for near-by schools in adjoining countries. A pioneering venture of this kind is in its eighth successful year for two midwest colleges (Macalester College of St. Paul and United College of Winnipeg), and is now being considered by United States and Canadian border colleges farther west. This annual student laboratory for international problems meets in alternate years at the two colleges. The sixth annual meeting, held in November, I946, at St. Paul, dealt with national ideologies and the prospects for world order. And, naturally, the spotlight was focused on crucial problems facing the I947 session of the United Nations General Assembly. The first annual conference, in I94I, discussed "The Western Democracies in the World of Today," seeking to promote better understanding between the college students of the two countries and to analyze the common national problems in order to achieve better international co-operation. Political and economic sections studied common problems in these fields. Against a common political and cultural background, the resulting similarities and diversities of political evolution were considered: the Dominion-Empire relationship and United States political history; the nature of federalism in the two countries; and their joint political, military, and economic support for democracy in beleaguered Europe. The r8le of geography, natural resources, and economic development in Canadian-American relations of the present and future were considered. The second annual meeting, held during our full involvement in the war, re-emphasized the political and economic interdependence of the two democracies with the theme " Our Common Purpose and Interest." Successive sessions discussed the background of separate statehood of Canada and the United States, how the two could effectively co-operate in the war effort, and collaboration in the postwar era. The third annual