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Geology and Chromite Deposits of the Camagüey District, Camagüey Province, Cuba

Description: From abstract: Geophysical prospecting by gravity methods has been successful in finding new deposits in the [Camaguey] district, and the present studies have brought out new information on the localization and attitudes of the known deposits that may be of assistance in planning future geophysical work.
Date: 1948
Creator: Flint, Delos E.; de Albear, Jesus Francisco & Guild, Philip White

Manganese Deposits of the Talamantes District Near Parral, Chihuahua, Mexico

Description: From abstract: The Talamantes district, 20 kilometers east of Parral in southern Chihuahua, has been the second largest producer of manganese ore in Mexico. Production, which started during World War I and has been more or less continuous since 1930, has totaled about 50,000 tons of ore with an average manganese content of 40 or 41 percent. The mines are on the Mesa de Talamantes, which is underlain by folded Cretaceous (?) limestone, overlain unconformably by gently dipping Tertiary rhyolite flows and tuff, volcanic breccia, agglomerate, and tuffaceous sandstone. Steeply dipping normal faults of northerly trend cut the rock and divide the mesa into a series of blocks.
Date: 1948
Creator: Wilson, Ivan F. & Rocha, Victor S.

Aluminous Lateritic Soil of the Republic of Haiti, W.I.

Description: From abstract: Aluminous lateritic soil containing as much as 50 percent of alumina (A120) Is found in several places in the Republic of Haiti. The largest deposits are on the Rochelois Plateau southwest of Miragoane on the Southern Peninsula. Mapping and drilling of the deposits indicate fifteen million long tons in place (dried basis). It is estimated that a minimum of 10 million long tons of this reserve is recoverable. The average chemical composition of this material is as follows: A1203, 46.8 percent; SiO2, 3.4 percent; T1O2, 2.8 percent; Fe20, 21.9 percent ; P206, 0.6 percent ; MnO5, 0.5 percent ; and loss on ignition, 24.1 percent. Other localities in which similar lateritic soil occurs are Beaumont in the Massif de la Hotte ; the vicinity of Savane Zombi in the Massif de la Selle ; and Savane Terre Rouge on the plateau northwest of Gonaives. In none of these regions were large deposits found.
Date: 1948
Creator: Goldich, Samuel S. & Bergquist, Harlan R.

Optical Calcite Deposits of the Republic of Mexico

Description: From abstract: Many small deposits of optical calcite (Iceland spar) were discovered in the States of Chihuahua, Durango, Sonora, and Sinaloa from early in 1942 to late in 1944. Exploration that began in Sonora led to the discovery of commercial deposits in the eastern part of that State, and subsequently other deposits were found and mined in southwestern and northeastern Chihuahua and in western and central Durango. The largest deposits can be reached by foot or by horse in from 1 to 3 hours from the nearest truck roads, but some of the small deposits are 1 to 3 days by horse from the nearest roads.
Date: 1948
Creator: Fries, Carl, Jr.

Manganese Deposits of Mexico

Description: From abstract: Manganese has been reported from 335 deposits in 20 of the 30 States and Territories of Mexico. The production of manganese ore prior to 1942, according to published figures, amounted to about 54,000 tons. For the year 1942 production rose to 35,000 tons, for 1943 to 70,503 tons, and for 1944 to 80,671 tons; but for 1945 it dropped to a little less than 52,000 tons, and during 1946 it continued to drop. Up to the end of 1941 Chihuahua had produced about half the manganese ore from Mexico; San Luis Potosi produced about 17 percent, and Baja California and Zacatecas each about 10 percent. In 1942 Baja California became the chief producer; Durango, Chihuahua, and Zacatecas each yielded somewhat less. During that year the ore came from 76 deposits, of which only 30 yielded more than 500 tons each.
Date: 1948
Creator: Trask, Parker D. & Cabo, José́ Rodríguez, Jr.

Neutron Deficient Isotopes of Tellurium and Antimony

Description: While investigating the relative yields for the many reactions resulting from the irradiation of antimony with 200-Mev deuterons in the Berkeley 184-inch cyclotron several previously unreported isotopes of tellurium and antimony were encountered. The tellurium fraction when followed on a thin mica window counter could be resolved into half-life periods of 2.5 hrs, 6.0 days and a small amount of a long-lived component. The 2.5 hour period has not been further characterized with respect to mass number or mode of decay other than to note that the radiation is predominantly electrons. The 6.0-day period is accompanied by positrons which were shown to be due to a 3.5 minute antimony daughter which is undoubtedly the same activity assigned to Sb{sup 118} by Risser, Lark-Horowitz and Smith. The positron energy was found to be 3.1 {+-} 0.2 Mev by absorption in berylllum and from the end point of the energy distribution curve taken with a low-resolution beta-ray spectrometer. Gamma activity is also present with this period. The 6.0-day tellurium showed a high abundance of x-rays, little or no conversion electrons and some gamma-ray activity which could be due to the 3.5 minute antimony daughter. The tellurium fraction contained another component of 4.5-day half-life which could not be observed in the decay curve because of its low abundance but which was detected by means of its 39-hour antimony daughter. The 39-hour antimony showed x-rays of tin (critical absorption with cadmiium, silver and palladium), no detectable hard radiation or electrons and is apparently identical with an activity recently assigned to Sb{sup 119} by Coleman and Pool.
Date: January 1, 1948
Creator: Lindner, M. & Perlman, I.

The Estimation of Heats of Formation

Description: The procedure for estimation of heats of formation of compounds is illustrated by discussion of compounds of several of the elements of the actinide series. The procedure is particularly suited for lanthanide and actinide elements because of the similarity of the ionic radii and types of bonding.
Date: February 2, 1948
Creator: Brewer, Leo

Excitation Curves of C12(p,pn)C11 and B11(p,n)C11 up to 32 MeV.

Description: The reaction C{sup 12} (p,pn)C{sup 11} which has been studied by McMillan, Chubb and Miller for energies up to 100 Mev is an example of a reaction whose high energy behavior cannot be explained by a compound nucleus process. The purpose of the study was to investigate this reaction at the high resolution possible with the Berkeley linear accelerator near the excitation threshold. The excitation curve was obtained by stacking specially molded polystyrene (composition C{sub n}H{sub n}) foils of high uniformity and bombarding them in the proton beam. The resultant activity was then counted on a Geiger counter in standard geometry. The resultant curve is shown in Figure 1. An immediately evident feature is the sharp threshold of the reaction. The second derivative curve, illustrated in Figure 2, of the excitation shows an RMS width of 270 kV, the theoretical straggling width due to the foils of 170 kv, and the remaining width in accordance with the energy spread of approximately {+-} 100 kv half width of the linear accelerator. The data therefore are compatible with a sharp threshold for this reaction. This curve, incidentally, furnishes independent evidence as to the energy homogeneity of the linear accelerator beam.
Date: April 20, 1948
Creator: Phillips, Robert & Panofsky, Wolfgang K.H.

The Half-Lives of Aluminum25 and Aluminum26

Description: The availability of separated isotopes of Mg makes it easy to determine the half life of Al{sup 26}, a member of the Wigner series which has long been suspected to have a half life of approximately 7 seconds, but which has not been confirmed because of the masking 7 second activity of Al{sup 26}. Mg{sup 24}, Mg{sup 25} and Mg{sup 26} (in the form of MgO) have been bombarded with protons from the Berkeley Linear Accelerator, with the following results: (1) Mg{sup 24} yields an activity of approximately 23 seconds half life, presumably due to Na{sup 21} from the reaction Mg{sup 24}(p,a)Na{sup 21}; (2) the Mg{sup 25} yields an activity of approximately 8 seconds half life, which they assign to the reaction Mg{sup 25}(p,n)Al{sup 25}; and (3) The Mg{sup 26} yields an activity of approximately 6 seconds half life, assigned to Al{sup 26} according to a similar reaction. It seems probable therefore that the 7 seconds half life normally given for Al{sup 26} is a mixture of these two activities.
Date: April 24, 1948
Creator: Bradner, Hugh & Gow, J.D.

THE RELATION OF BACKSCATTERING TO SELF-ABSORPTION

Description: The effects of backscattering upon self-absorption correction curves are demonstrated. Data are given for the backscattering powers of several substances for the beta radiations from C{sup 14}, and for se1f-absorption of samples of barium carbonate and wax, containing C{sup 14}, mounted on aluminum.
Date: January 1, 1948
Creator: Yankwich, Peter E. & Weigl, John.

Research Progress Meeting for March 11,1948

Description: The linear accelerator is again in operation after a shutdown fore repairs and minor changes. Radiofrequency checks of the instrument were made while the Van de Graaff was open. The vacuum of the system is now very good, the base pressure being 1.7 x 10{sup -6} mm Hg with a rate of rise of 800 s/{micro}s. Some preliminary results have been obtained on the activation of carbon with protons. The experiments were done using 10 mil, 50 mg/cm{sup 2} polystyrene discs. The activation curve obtained is shown. The break shown in the curve was found on two separate runs and it yet unexplained. In another experiment a proton induced activity in nickel was found. This had a 3.3 second half-life. Positive mesons have been detected on plates exposed in the 184-inch cyclotron with an arrangement shown schematically. The beam ws allowed to strike a 1/16 inch carbon target, and the mesons, which are bent around by the magnetic field, were detected with photographic plaes placed beneath the circulating beam. A series of experiments were done in which the plates were placed at distances varying from 1-1/2 to 3/4 inch from the beam between 1/4 inch plates of copper. The plates obtained at 1 inch and 3/4 inch were so blackened as to be unusable. From the plates secuired at 1-1/4 inch Lattes has found a total of 30 positive meson tracks, of which 20 end in the emulsion. Eight of these were found to give rise to seconaries, none of which stopped in the emulsion. This work was done with 50 micron plates and will be extended using 100 micron plates. The data will be further analyzed to see if all of the positive mesons and in secondaries. The number of positive mesons produced seems to be comparable to the ...
Date: March 11, 1948
Creator: Wakerling, R.K.

Research Progress Meeting of February 19, 1948

Description: Much of the cloud chamber work has been directed toward obtaining the angular distribution of protons bombarded by deuterons from the 184-inch cyclotron. The observations have been restricted to those protons arising from neutrons of energy greater than 65 Mev. The cloud chamber used for this work is of 16-inch diruneter and employs a magnetic field of 14000 gauss. The chamber is filled with hydrogen at a pressure of 1/2 atmosphere; the vapor used is water and alchohol. Nearly 800 proton tracks were measured and calculated before analysis of the data indicated that the measuring procedure should be revised. They gave the angular and energy distributions shown in Figures 1 and 2. The discrepencies between the theoretical and experimental energy distribution of the neutrons shows that serious errors were being made. As a first check of possible sources of error, random parts of the data were remeasured. They indicated that errors in the measurements of the angles were being made that gave a mean deviation of about {+-} 2{sup o} in the beam angle and {+-} 4{sup o} in the dip angle. These errors were largest at large scatter angles. In addition, a more serious error occured in the measurements of the curvature. The mean deviation was as large as 15 percent, with many tracks having errors of 50 to 100 percent in the measured curvature. These errors were dUd to the fact that an adequate measuring technique had not been developed, that the original measuring apparatus and projector were difficult to operate, and that the cloud chamber technique had not been perfected. A systematic analysis of the errors and difficulties involved in the experiment made it evident that revisions in the technique were necessary. In view of the inaccuracy of the original measurements it is not possible to make ...
Date: February 19, 1948
Creator: Wakerling, R.K.

The Fission of Thorium with Alpha Particles

Description: The fission distribution of fission of thorium with alpha particle of average energy 37.5 Mev has been measured by the chemical method. The distribution found shows that the characteristic dip in the fission yield mass spectrum has been raised to within a factor of two of the peaks compared to a factor of 600 in slow neutron fission of U{sup 235}. The raise in the deip has caused a corresponding lowering in fission yield of these elements at the peaks. The cross section for fission of thorium with 37.5 Mev alphas was found to be about 0.6 barn, and the threshold for fission was found to be 23 to 24 Mev.
Date: April 15, 1948
Creator: Newton, Amos S.

The Fission of thorium with Alpha Particles

Description: Soon after the discovery of fission, Meitner, Bretscher and Cook found differences in the decay of various chemical fractions separated from uranium irradiated with slow neutrons and thorium irradiated with fast neutrons respectively and suggested that a difference existed in the distribution of fission products in the two cases. In 1940, Turner suggested that the distribution in various modes of fission should be investigated. The fact that elements such as tin, cadmium, palladium, and silver were found in fast neutron and deuteron fission of uranium and thorium before they were found in slow neutron fission of uranium suggested that the middle region of the distribution was raised as the energy of the incident particle was increased. Since the compound nucleus formed in the fission of thorium with alpha particles is U{sup 236}, the same compound nucleus formed in the fission of U{sup 235} with neutrons, it is of interest to study the fission of thorium with alphas and compare the resulting distribution of fission products with that found with uranium with slow and thorium with fast neutrons. Any difference between the various results where the same compound nucleus is formed must be due to differences in energy content and possible differences in distribution of the nucleons in the compound nucleus at the time of fission.
Date: October 15, 1948
Creator: Newton, Amos S.

The Distribution of Radioactivity in the Mouse Following Administration of Dibenzanthracene Labeled in the 9 and 10 Positions with Carbon Fourteen

Description: Dibenzanthracene, labeled in the 9 and 10 positions with carbon fourteen has been administered to mice intravenously and by stomach tube as an aqueous colloid, and intraperitoneally, subcutaneously, and by stomach tube in tricaprylin solution. The distribution of radioactivity in the mice at various time intervals after administration of the carcinogen has been determined. The radioactivity is rapidly eliminated, largely through the feces, and ordinarily very little is absorbed. The distribution and rate of elimination depends upon the mode of administration. There is an appreciable quantity of radioactivity in tumors produced several months after a single subcutaneous injection of dibenzanthracene. There appear to be no detectable effects from the radiation of the labeled carcinogen.
Date: January 30, 1948
Creator: Heidelberger, Charles & Jones, Hardin, B.

Production of Mesons by the 184-inch Berkeley Cyclotron

Description: The authors have observed tracks which they believe to be due to mesons in photographic plates placed near a target bombarded by 380 Mev alpha particles. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. The mass has been determined by measuring the bending in the magnetic field and the range in emulsion. From the first 50 meson tracks measured they find a mass of 313 {+-} 16 electron masses. It is highly probable that these mesons are the heavy mesons described by Lattes, Occhialini, and Powell.
Date: January 1, 1948
Creator: Gardner, Eugene & Lattes, C.M.G.

Production of Mesons by the 184-inch Berkeley Cyclotron Part I. Experimental Arrangement

Description: The authors have observed traks which they believe to be due to mesons in photographic plates placed near a ta5rget bombarded by 380 Mev alpha particles. The plates used were Ilford Nuclear Research Plates, type C.2. the identification of the particles responsible for the tracks was first made on the basis of the appearance of the tracks; they show the same type of scattering and variation of grain density with residual range found in cosmic ray meson tracks and about two-thirds of them produce observable stars at the end of their range. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. Carbon, beryllium, copper, and uranium have been used so far as target materials, and all are found to give mesons. When a carbon target was bombarded with 300 Mev alpha particles, mesons were found but with reduced yield.
Date: April 1, 1948
Creator: Gardner, Eugene & Lattes, C.M.G.

The Production of Thin Be Foils

Description: A procedure for making Be foils between 10{sup -5} cm. and 10{sup -3} cm. thick, and with diameters up to an inch and a half is described, and methods of mounting these foils are indicated.The problem of making thin Be foils was presented in connection with focusing the proton beam in the Berkeley Linear Accelerator, and although the foils are not now used in the accelerator, they have proved to be quite useful as thin targets, target supports, thin windows, etc. The Be was evaporated in vacuum and deposited on a metal collector plate. The problems encountered were: (1) obtaining reproducible quantities of evaporated Be; (2) stripping of Be from the collector plates; (3) preventing curl of the foils when they were stripped; and (4) mounting the foils.
Date: March 18, 1948
Creator: Bradner, Hugh

Products of High-Energy Deuteron and Helium Ion Bombardments of Copper

Description: The identity and relative yields of about twenty of the radioisotopes produced by the bombardment of natural copper with 190 Mev deuterons and 380 Mev helium ions have been determined. Two previously unreported isotopes were detected: Zn{sup 62}, decaying by orbital electron capture with a 9.5-hour half-life, and Fe{sup 52}, decaying by positron emission with a 7.8-hour half-life.
Date: March 1, 1948
Creator: Miller, D.R.; Thompson, R.C. & Cunningham, B.B.