Measurements of the Marine Reservoir Effect on Radiocarbon Ages in the Eastern Bering Sea

The marine reservoir effect is known to skew radiocarbon dating (marine samples appear "older" than terrestrial samples of equivalent age), but the magnitude of this effect is not the same in all locations. Carbon-14 age determinations from 23 paired samples of terrestrial and marine origin are presented for five areas around the northern and eastern Bering Sea. It appears statistically suitable to average the age differences for three pairs, weighted inversely by variance. Differences from within each of 14 pairs of wood charcoal vs. sea mammal residue (from St. Lawrence Island, Cape Prince of Wales, Nunivak Island, Alaska Peninsula, and Unalaska Island) yield a weighted mean of 737 ± 20 years. Somewhat more variant differences from within each of five additional pairs of wood charcoal vs. sea mammal residue (St. Lawrence Island, Unalaska Island) provide a lower weighted mean of 460 ± 41 years. Differences from within each of four pairs of wood charcoal vs. marine shell (Nunivak Island) produce a weighted mean of 459 ± 32 years. Variations in these apparent reservoir effects presumably result largely from the interplay of differential ocean water upwelling and customary faunal feeding areas, although possible effects of other species characteristics cannot be ruled out. Dating of marine samples from the Bering Sea should thus either proceed with the expectation that age determinations may not be accurate within several centuries, or be approached through experimental measurement of reservoir effect among restricted faunal species in limited areas. Overall, the effect throughout the eastern Bering Sea appears to range from about 450 to 750 years.On sait que l'effet du réservoir marin biaise la datation au radiocarbone (les échantillons marins semblent être "plus vieux" que les échantillons terrestres d'âge similaire), mais la grandeur de cet effet n'est pas la même à tous les endroits. On présente les déterminations de l'âge au carbone 14 pour 23 échantillons appariés d'origine terrestre et marine provenant de cinq zones situées aux environs de la mer de Béring septentrionale et orientale. Il semble approprié sur le plan statistique d'établir la moyenne des différences d'âge pour trois paires, pondérées inversement par la variance. Les différences provenant de chacune des 14 paires de charbon de bois comparé à des restes de mammifère marin (île Saint-Laurent, cap Prince-de-Galles, île Nunivak, péninsule d'Alaska, et île Unalaska) donnent une moyenne pondérée de 737 ± 20 ans. Des différences un peu plus variables provenant de chacune de cinq autres paires de charbon de bois comparé à des restes de mammifère marin (île Saint-Laurent, île Unalaska) donnent une moyenne pondérée plus faible de 460 ± 41 ans. Les différences entre chacune des quatre paires de charbon de bois comparé à des coquillages marins (île Nunivak) donnent une moyenne pondérée de 459 ± 32 ans. Les variations dans ces effets de réservoir apparents proviennent probablement en grande partie du jeu réciproque entre les zones de remontée différentielle des eaux océaniques et les aires d'alimentation habituelles, bien qu'on ne puisse éliminer les effets possibles de caractéristiques propres à d'autres espèces. La datation des échantillons marins de la mer de Béring devrait donc se faire soit en s'attendant à des erreurs de plusieurs siècles dans les déterminations d'âge, soit en l'abordant par le biais de mesures expérimentales portant sur l'effet de réservoir parmi un petit nombre d'espèces fauniques et à l'intérieur d'un territoire restreint. Dans l'ensemble, cet effet dans tout l'est de la mer de Béring semble aller de 450 à 750 ans

The Design, Construction, and Performance of a Magnetic Focusing, Semi-Circular, Low Energy Beta-Ray Spectrometer

A semi-circular beta-ray spectrometer (Fig. 1) has been constructed for operation between 2 and 120 kev electron energy. This instrument was designed to supplement the ring- focusing beta-ray spectrometer whose lower limit is approximately 25 kev. The 180° spectrometer has an electron trajectory radius of 12 cm. The field is produced by two iron free coils spaced to give a nearly homogeneous field (with some second order focusing) in the region of the electron trajectories . The field current is supplied by a one kw motor- generator set. Stabilization is obtained to 2 parts in 10, 000 with a rotating electro- mechanical unit and an electronic servo system. Source and Geiger counter window dimensions for a standard resolution of 0 .8% are 0.1 cm x 4 cm. With a 10 μ.g/cm^2 formvar window, transmission is assured down to 2 kev electron energy. A recording potentiometer traces the counting rate vs. electron energy. Several examples of chart recordings are reproduced to illustrate the performance of the semi- circular beta-ray spectrometer

Our Knowledge of the Atomic Constants F, N, m, and h in 1947, and of Other Constants Derivable Therefrom

The present paper aims to deal only with a limited portion of the subject, the evaluation of the so-called atomic constants: e the electronic charge, m the electronic mass, and h Planck's constant of action together with certain auxiliary constants intimately associated with them. A number of useful physical constants which can be computed from the above data will also be evaluated

A Point Focusing Monochromator for the Study of Low-Angle X-Ray Diffraction: Determining the Size Distributions of Carbon Blacks and a Precision Determination of the Size of Dow Latex Particles

A point focusing x-ray monochromator was designed and constructed for low angle scattering studies. The anastigmatic point focus is achieved by means of two cylindrically bent quartz crystals whose focal circles are mutually perpendicular. The beam, emanating from the copper target of an x-ray tube, is reflected in succession, first from the crystal defining the horizontal focal circle and, second from the crystal defining the vertical focal circle following which it comes to a mono chromatic point focus of wavelength 1.537 A (Cu Ko(1). The sample to be studied is placed between the second crystal and the point focus, and the scattered beam is detected by means of a photographic plate placed at the point focus, at right angles to the undeviated beam, the latter being suppressed by means of an absorber. Mathematical analysis, in which a ray was traced through the two crystal system, revealed correctly the shape and size of the point focus, and the possibility of reducing the latter in size by stopping down the beam emerging from the target. The instrument and its lining up procedure is described in detail, particularly the latter since the orientation of the two crystals relative to each other and the x-ray tube involve twelve degrees of freedom. Suggestions for improving the intensity of the instrument are made . These consist of (1) substitution of topaz crystals for quartz, (2) use of helium atmosphere instead of air to surround the x-ray beam (3) reorientation of the x-ray tube to permit smaller angles of emergence of the beam. As a trial run for the instrument, the scattering patterns of two kinds of carbon black (good scatterers) were obtained from which the average particle sizes and size distributions were calculated

Measurement of High-Energy Gamma-Rays with a Photographic Bent Crystal Spectrograph

It has been shown by one of the authors and his coworkers that it is possible to determine accurately the wavelengths of gamma rays with quantum energies up to 1.3 Mev by direct crystal diffraction methods using the Mark I 2-meter bent crystal spectrograph at the California Institute of Technology. They were able to record and to measure with a precision of one part in 10^3 the two gamma rays at 1.17 and 1.33 Mev which are emitted by a Co^(60) source

A Point Focusing X-Ray Monochromator for the Study of Low Angle Diffraction

A point focusing x‐ray monochromator was designed and constructed for low angle scattering studies. The anastigmatic point focus is achieved by means of two cylindrically bent quartz crystals whose focal circles are mutually perpendicular. The beam, emanating from the copper target of an x‐ray tube, is reflected in succession, first from the crystal defining the horizontal focal circle, and second from the crystal defining the vertical focal circle following which it comes to a monochromatic point focus of wavelength 1.537A (CuKα_1). The sample to be studied is placed between the second crystal and the point focus, and the scattered beam is detected by means of a photographic film placed at the point focus, at right angles to the undeviated beam, the latter being suppressed by means of an absorber, or allowed to pass through a hole in the film. Mathematical analysis, in which a ray was traced through the two‐crystal system, revealed correctly the shape and size of the point focus, and the possibility of reducing the latter in size by stopping down the beam emerging from the target