Field Studies of the Archean in Grand Canyon

The oldest rocks of Arizona which form the precipitous walls of the inner or granite gorge of the Grand Canyon have never received the intensive study that has been given to their counterparts over the great northeastern plains of Canada, in the mountains of Scandinavia or on the rolling expanses of Finland. The metamorphosed rocks standing in places on end under the wedge of the Grand Canyon series of sediments (Algonkian) and elsewhere under the mantle of Paleozoic sediments are known as the Vishnu schist. To J.W. Powell these were known as the “Grand Canyon schists” of tentative “Eozoic” age. C.D. Walcott who proposed the term Vishnu from the occurrence beneath Vishnu temple in the Grand Canyon classified them as “bedded, sedimentary, unconformable, pre-Unkar (Lower Grand Canyon series) strata.

Economic geology of portions of Del Norte and Siskiyou counties, northwesternmost California

The mineral deposits discussed in this report were studied in connection with a program of research in the geology of the western Siskiyou Mountains carried out under the supervision of Professor J. P. Buwalda. Most of the deposits are not being exploited at present and many have not been worked in over a decade. Some occurrences have potential economic value, depending upon market and possible improvements in transportation. The study has been made, however, not from the standpoint of a mining engineer interested in future production, reserves, ownership, etc., but rather from the scientific aspect in regard to geological setting and genesis

Field Studies of the Archean in Grand Canyon

The oldest rocks of Arizona which form the precipitous walls of the inner or granite gorge of the Grand Canyon have never received the intensive study that has been given to their counterparts over the great northeastern plains of Canada, in the mountains of Scandinavia or on the rolling expanses of Finland. The metamorphosed rocks standing in places on end under the wedge of the Grand Canyon series of sediments (Algonkian) and elsewhere under the mantle of Paleozoic sediments are known as the Vishnu schist. To J.W. Powell these were known as the “Grand Canyon schists” of tentative “Eozoic” age. C.D. Walcott who proposed the term Vishnu from the occurrence beneath Vishnu temple in the Grand Canyon classified them as “bedded, sedimentary, unconformable, pre-Unkar (Lower Grand Canyon series) strata.

Merychippus Isonesus (Cope) from the Later Tertiary of the Crooked River Basin, Oregon

Although Tertiary deposits, presumed to be the correlative of the Mascall and Rattlesnake formations of the John Day basin, are known to occur in the Crooked River basin south of the Ochoco Mountains in central Oregon, no vertebrate fossils of diagnostic value have been obtained from these beds. Merriam and Sinclair record the finding of a caniniform premolar of a merycoidodont in Mascall beds exposed on the divide between Camp Creek and the Crooked River. Recently R. W. Chaney has reviewed the evidence on which is based the recognition of the Mascall horizon in the Crooked River region. In the course of palreontological investigations conducted in central Oregon under the leadership of Dr. Chester Stock, an upper tooth of Merychippus was collected in deposits, regarded as Mascall in age, along the Crooked River between Post and Paulina. In view of the opportunity to compare the stage of evolution of this specimen with that represented by the dentition of the merychippine forms from the type Mascall, a description seems desirable. The writer wishes to acknowledge the guidance of Dr. Stock during the progress of this study

Demonstration of Low Emittance in the Cornell Energy Recovery Linac Injector Prototype

We present a detailed study of the six-dimensional phase space of the electron beam produced by the Cornell Energy Recovery Linac Photoinjector, a high-brightness, high repetition rate (1.3 GHz) DC photoemission source designed to drive a hard x-ray energy recovery linac (ERL). A complete simulation model of the injector has been constructed, verified by measurement, and optimized. Both the horizontal and vertical 2D transverse phase spaces, as well as the time-resolved (sliced) horizontal phase space, were simulated and directly measured at the end of the injector for 19 pC and 77 pC bunches at roughly 8 MeV. These bunch charges were chosen because they correspond to 25 mA and 100 mA average current if operating at the full 1.3 GHz repetition rate. The resulting 90% normalized transverse emittances for 19 (77) pC/bunch were 0.23 +/- 0.02 (0.51 +/- 0.04) microns in the horizontal plane, and 0.14 +/- 0.01 (0.29 +/- 0.02) microns in the vertical plane, respectively. These emittances were measured with a corresponding bunch length of 2.1 +/- 0.1 (3.0 +/- 0.2) ps, respectively. In each case the rms momentum spread was determined to be on the order of 1e-3. Excellent overall agreement between measurement and simulation has been demonstrated. Using the emittances and bunch length measured at 19 pC/bunch, we estimate the electron beam quality in a 1.3 GHz, 5 GeV hard x-ray ERL to be at least a factor of 20 times better than that of existing storage rings when the rms energy spread of each device is considered. These results represent a milestone for the field of high-brightness, high-current photoinjectors.Comment: Physical Review Special Topics - Accelerators and Beams 16, 073401 (2013

Photocathode Behavior During High Current Running in the Cornell ERL Photoinjector

The Cornell University Energy Recovery Linac (ERL) photoinjector has recently demonstrated operation at 20 mA for approximately 8 hours, utilizing a multialkali photocathode deposited on a Si substrate. We describe the recipe for photocathode deposition, and will detail the parameters of the run. Post-run analysis of the photocathode indicates the presence of significant damage to the substrate, perhaps due to ion back-bombardment from the residual beamline gas. While the exact cause of the substrate damage remains unknown, we describe multiple surface characterization techniques (X-ray fluorescence spectroscopy, X-ray diffraction, atomic force and scanning electron microscopy) used to study the interesting morphological and crystallographic features of the photocathode surface after its use for high current beam production. Finally, we present a simple model of crystal damage due to ion back-bombardment, which agrees qualitatively with the distribution of damage on the substrate surface.Comment: 20 pages, 15 figure

Förster energy transfer between neighbouring chromophores in C-phycocyanin trimers

The excitation-energy transfer in C-phycocyanin (C-PC) trimers and monomers isolated from phycobilisomes of Mastigocladus laminosus has been studied by polarization femtosecond laser spectroscopy. Excitation with 70-fs pulses at 615 nm gave rise to a 500-fs energy-transfer process that was observed only in trimeric preparations. The rate of the process is in agreement with earlier calculated Förster energy transfer rates between neighbouring α-84 and β-84 chromophores of different monomeric subunits. This process is most clearly seen in the anisotropy decay kinetics. As a result of femtosecond excitation-energy transfer, the anisotropy relaxes from 0.4 to 0.23. The final anisotropy value is in fair agreement with the results of calculations based on the crystal structure and spectroscopic data of C-PC trimers. Our results support the conclusion that Förster energy transfer can occur between excitonically coupled chromophores