Shell Cross-sections Research Articles

Effects of thermal discharges on mortality ofMercenaria mercenaria in Barnegat bay, New Jersey

Thermal discharges from the Oyster Creek Nuclear Generating Station do not affect mortality in natural populations ofMercenaria mercenaria (Linne) in Barnegat Bay, New Jersey. The analyses of daily growth increments and disturbance bands in shell cross-sections of death assemblages of the pelecypods collected at the mouth of Oyster Creek (strongly affected by thermal discharges) and at three control sites (unaffected by thermal discharges) in the bay indicate that similar mortality patterns exist in all assemblages. This is revealed by mortality rate curves, survivorship curves, and life tables, which are nearly identical for each assemblage.

Fixed-molecule photoelectron angular distributions:K-shell cross sections of CO at fixed detection angles

Photoelectron angular distributions, doubly differential in target and detector orientation, are calculated for $K$-shell ionization of carbon and oxygen in CO at the $f$-wave shape resonance in the $\ensuremath{\sigma}(\ensuremath{\lambda}=0)$ channel (0.8-Ry kinetic energy). Dipole amplitudes are computed by the multiple-scattering formulation of inner-shell photoionization. Results are presented for several fixed-detector orientations and all possible target orientations for linearly, circularly, and naturally polarized light. Distributions are rich in structure because of the interplay of anisotropies in target and detector orientations, and serve to predict the complexity of measured distributions.

Age and growth rate determinations for the Atlantic surf clam Spisula solidissima (Bivalvia: Mactracea), based on internal growth lines in shell cross-sections

Marked and recovered surf clams, Spisula solidissima Dillwyn, from Virginia (USA) deposited one internal growth line during a period of 11/2 years, probably in response to spawning during late summer. We have used these annual growth lines to make growth curves for two samples of New Jersey (USA) clams, one from inshore (1.8 km from shore, 15 m deep), the other from offshore (17.5 km from shore, 28 m deep) waters. The offshore and inshore clams grow at approximately the same rate until Age 3 years, after which time the growth rates differ, as does the ultimate lifespan; the offshore clams grow more rapidly and attain a greater age — up to 31 years. Comparison of our growth curves with other published curves revealed a close correspondence to a curve which was based on a study of growth over a 5-year period. Curves based on external growth lines probably underestimate growth rate in early life and overestimate it in later years.

Theoretical Calculation of Relative Intensities in ESCA

Calculations of the photoionization cross-sections of atomic and molecular levels for the A1Kα and MgKα lines depending on the wave function of the final and the initial states are analysed. The ns, np and nd photoionization cross-sections of atomic shells for Z ⩽ 36 and the HF, NH3, H2O, CH4, CH3F, CH2F2, CHF3, CF4, N2, CO and C2H4 molecular levels for the YMζ line and the photoionization cross-sections of atoms for Z ⩽ 36 and the CH4, N2 and H2O molecular levels for the ZrMζ line are calculated. The theoretical cross-sections of atoms for Z ⩽ 10 for the FKα line are presented too. Photoionization cross-section calculations using Hartree-Fock-Slater potential are in better agreement with the experiment than those using orthogonalized plane waves for photo-electron wave functions.

Relative intensities in X-ray photoelectron spectra part III

Calculations for the photoionization cross-sections of atomic and molecular levels for the Al Kα and Mg Kα lines depending on the wave function of the final and the initial states are analysed. The ns, np, and nd photoionization cross-sections of atomic shells for Z ⩽ 36 and the HF, NH 3, H 2O, CH 4, CH 3F, CH 2F 2, CHF 3, CF 4, N 2, CO, and C 2H 4 molecular levels for the YMξ line and the photoionization cross-sections of atoms for Z ⩽ 36 and the CH 4, N 2, and H 2O molecular levels for the ZrMξ line are calculated. Photoionization cross-section calculations using the Hartree—Fock—Slater potential are better agreement with experiment than those using orthogonalized plane waves for photoelectron wave functions.

Study of the precritical deformation of cylindrical shells made of inorganic glass with initial geometrical imperfections on subjecting to external hydrostatic pressure

1. We have proposed a method which enables us, by considering the relative deviations of the outer and inner sides of the cross sections of cylindrical shells, to determine their average radius and thickness, together with the magnitude and distribution of the initial geometrical imperfections. 2. Under the influence of hydrostatic pressure, the initial shape of the cross section in silicate glass cylindrical shells usually undergoes a considerable rearrangement. In shells of ideal or nearly ideal initial geometry, the critical loss-of-stability shape corresponds to that predicted by the linear theory. In geometrically imperfect shells the change in the initial deflection develops in the following way: In the zones having the maximum initial deflection, the latter increases, while in the zones intermediate between those with the maximum initial geometrical imperfections a complete rearrangement of the initial equilibrium shape may occur. 3. Loss of stability of the equilibrium state in cylindrical glass shells leads to the exhaustion of their carrying capacity. 4. Until recommendations soundly based on a great deal of experimental data have been developed, the stability of smooth inorganic glass cylindrical shells having a maximum deflection of Wmax≤0.3H and H/R=0.06–0.07 may conveniently be estimated by reference to the upper critical load.

Analysenmethoden Auf der Grundlage von Kernstreuung, Kernreaktionen und Fluoreszenz

For the methods treated, the analysis of materials containing light elements stands in the foreground. For low Z targets a relative high mass resolution is reached for scattering, and the utilization of structural anisotropy of crystals allows also substrates with heavier atoms. A not too high Coulomb barrier for nuclear reactions as well as the particular large ionization cross-sections of inner shells for heavy charged particles exciting X-rays, favour light targets for research and application. The regression to phenomena of quantum polarization shows new possibilities to increase the sensitivity of X-ray fluorescence analysis.

Binding and Coulomb-deflection effects inL-shell Coulomb ionization by heavy charged particles. Low particle velocities

Experimental cross sections for $L$ -shell ionization by heavy charged particles, of atomic number small compared to the target atomic number and with velocities low compared to the $L$ -shell orbital velocities, can be smaller by more than an order of magnitude than the quantum-mechanical predictions in the plane-wave Born approximation (PWBA). The contribution of two effects, not contained in the PWBA, is derived. These effects are the binding of the $L$ -shell electrons to the moving particle during collision and the Coulomb deflection of the particle in the field of the target nucleus. As developed here for $L$ shells and previously for $K$ shells, the theory treats the excitation of inner shells from perturbed stationary states (PSS) and incorporates the effect of the Coulomb-distorted wave of the heavy charged projectile semiclassically. It agrees well with experimental $L$ -shell cross sections of 16 different target atoms for protons, and accounts for the isotope effect observed on various targets with protons and deuterosn of equal velocities.

Electron-impact-ionization cross sections of inner shells measured by Auger-electron spectroscopy

Electron-impact-ionization cross sections of inner shells measured by Auger-electron spectroscopy

ZnK- and PbL-shell ionization by proton andHe3-ion bombardment

Absolute cross sections and excitation functions have been measured for Zn $K$-x-ray production by proton impact and for Pb $L$-x-ray production by proton and $^{3}\mathrm{He}$-ion impact over the bombarding energy range from 1.4 to 4.4 MeV using a Si(Li) detector. The total ionization cross sections for the Zn $K$ shell and x-ray production cross sections for the Pb $L$ shell obtained are compared with the binary-encounter approximation (BEA) and the plane-wave Born approximation calculations and the agreement is found to be good. X-ray production ratios, such as $\frac{L\ensuremath{\alpha}}{L\ensuremath{\beta}}$ and $\frac{L\ensuremath{\alpha}}{L\ensuremath{\gamma}}$, for Pb are also compared with the BEA calculations. The cross-over behavior of the ${Z}_{1}$ (projectile nuclear charge) dependence of the x-ray production cross sections was studied for the Pb $L$ lines.

Pb and BiL-subshell ionization cross-section ratios versus proton bombarding energy from 0.5 to 4 MeV

Experimental ratios of $L$-subshell cross sections are given for ionization of lead and bismuth by 0.5-4-MeV-proton bombardment. The ratio of the ${L}_{\mathrm{II}}$ to ${L}_{\mathrm{I}}$ cross sections exhibits a maximum near 1.75 MeV. Individual subshell cross sections are obtained from the experimental ratios and previous total-cross-section data. These subshell ratios and cross sections are compared with the theoretical predictions of the plane-wave Born approximation using nonrelativistic hydrogenic wave functions, of the binary-encounter approximation scaled from Mg $K$-shell cross sections, and of the binary-encounter approximation scaled from cross sections obtained using $L$-shell velocity distributions. It was found that both approximations predict the trend of the data for the ${L}_{\mathrm{II}}$ and ${L}_{\mathrm{III}}$ subshells, but that only the plane-wave Born approximation gave the proper behavior for the ${L}_{\mathrm{I}}$ subshell.

Inner-Shell Ionization Cross Sections of Argon, Krypton, and Xenon by 1.5- to 5.0-MeV Protons

The radiative decay of $K$-shell vacancies of argon, krypton, and xenon, and $L$-shell vacancies of krypton and xenon, has been observed with a Si(Li) x-ray detector for thin gas targets of these atoms excited by 1.5- to 5.0-MeV protons. X-ray yields were measured as a function of target thickness under single-collision conditions, and inner-shell ionization cross sections were determined using atomic fluorescence yields. The $L$-shell ionization cross sections obtained are in good agreement with theoretical calculations in the plane-wave Born approximation. The $K$-shell cross sections show good agreement with these calculations for the argon $K$ shell, but fall above the theoretical values for krypton and xenon, the discrepancy with theory increasing with increasing atomic number. The binary-encounter model was also compared to the experimental $K$-shell ionization cross sections, and for all gases the agreement is somewhat worse. $\frac{K\ensuremath{\beta}}{K\ensuremath{\alpha}}$ relative intensities for krypton and xenon were determined, and good agreement of these values with the results of experiments using other modes of excitation is shown.

Implications of absolute age and season of death data compiled for Recent Gemma gemma

Absolute age and season of death data, obtained by observation of daily growth increments in shell cross-sections, are compiled for Recent Gemma gemma (Eulamellibranchia: Veneridae) collected from four different assemblages. When absolute age and size-frequency data are compared for the same assemblage, the resulting histograms are quite different. Part of this difference is attributed to the fact that there is no definitive, linear correlation between shell length and absolute age. The value of absolute age determinations made by counting and observing external growth increments is questioned. It is found that by observing the shell's exterior it is easy to confuse sickness or spawning patterns with winter growth patterns. Such confusion results in assigning anomalously high absolute ages for individual shells. Also, the amount of time represented by external individual riblets varies geographically. Collected Gemma are found to have died at various times of the year, but primarily in autumn. This variability in season of death indicates that the assemblages are the result of natural rather than catastrophic mortality.

A new method for measuring electron impact ionization cross sections of inner shells

Relative and absolute electron impact ionization cross sections of the K shell of C, N, O and Ne have been measured for electron energies from E P = 1.5 E K to E P = 4800 eV.