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Catastrophic dense granular flows, such as occur in rock avalanches, debris flows and pyroclastic flows, move as fully shearing mixtures that have approximately 60 vol.% solids and tend to segregate to form coarse-grained fronts and leveed channels. Levees restrict spreading of unconfined flows and form as coarse particles that become concentrated in the top of the flow are transported to the front and then advect to the sides in the flow head. Channels from which most material has drained away down slope are commonly lined with fine-grained deposit, widely thought to remain from the tail of the waning flow. We show how segregation in experimental dense flows of carborundum or sand (300–425 μm) mixed with spherical fine ballotini (150–250 μm), on rough slopes of 27–29°, produces fine-grained channel linings that are deposited with the levees, into which they grade laterally. Maximum runout distance is attained with mixtures containing 30–40% sand, just sufficient to segregate and form levees that are adequately robust to restrict the spreading attributable to the low-friction fines. Resin impregnation and serial sectioning of deliberately arrested experimental flows shows how fines-lined levees form from the flow head; the flows create their own stable ‘conduit’ entirely from the front, which in a geophysical context can play an important mechanistic role in facilitating runout. The flow self-organization ensures that low-friction fines at the base of the segregated channel flow shear over fine-grained substrate in the channel, thus reducing frictional energy losses. We propose that in pyroclastic flows and debris flows, which have considerable mobility attributable to pore-fluid pressures, such fine-grained flow-contact zones form similarly and not only reduce frictional energy losses but also reduce flow–substrate permeability so as to enhance pore-fluid pressure retention. Thus the granular flow self-organization that produces fine-grained channel linings can be an important factor in facilitating long runout of catastrophic geophysical flows on the low slopes (few degrees) of depositional fans and aprons around mountains and volcanoes.

Electrical properties of CdTe Schottky solar cells were investigated during exposure to air. Trap states were probed and characterized using charge extraction. Mechanisms for degradation are discussed, and it is argued that degradation in this case is due to instability at the interface between CdTe and the metal electrode.

To follow a population at high risk for endometrial carcinoma after endometrial ablation, to determine if ablation alters the incidence or detection of endometrial pathology.The animal model included 33 New Zealand white rabbits. Of this cohort, 17 underwent surgical ablation of the endometrium via laparotomy, while 16 served as controls. Vaginal bleeding was assessed with monthly cotton swab examinations as well as daily observation of the subjects. All animals received unopposed estrogen for 18 months prior to necropsy.No animal in either arm of the study demonstrated vaginal bleeding. Two rabbits from the ablation group and three controls showed histologic evidence of atypical endometrial hyperplasia or adenocarcinoma (P.20). One additional animal from each group had hyperplasia without atypia.This animal model suggests that endometrial ablation does not decrease the risk of endometrial carcinoma in patients at high risk of developing endometrial pathology. Detection of hyperplasia or carcinoma in such a population may prove difficult due to the absence of traditional signs of endometrial abnormalities.

The authors describe a C++ physics development environment, called the Tecolote Framework, which allows model developers to work more efficiently and accurately. This Framework contains a variety of meshes, operators, and parallel fields, as well as an input/output (I/O) subsystem and graphics capabilities. Model developers can inherit Tecolote`s generic model interface and use the Framework`s high-level field and operator components to write parallel physics equations. New Tecolote models are easily registered with the Framework, and they can be built and called directly from the input file, which greatly expedites model installation. In the process of developing an extensible and robust framework, they have found appealing solutions to some of the serious problems they encounter when parallelizing and extending the older codes. They also discuss memory and performance issues for a large hydrodynamics application built in this Framework.

Contralateral acoustic stimulation reduces the amplitude of the transient evoked otoacoustic emission (TEOAE) in humans. The mechanism is thought to be mediated, at least in part, through the medial olivocochlear efferent system innervating the outer hair cells. To assess its usefulness as a possible clinical test, TEOAE suppression was measured in each ear of 12 subjects over a 6-week period, and these data are shown in detail for four subjects representing extremes of variability in a tinnitus and a non-tinnitus group. Intra-subject test results (n = 18) exhibited a varying extent of suppression values and the variance of each session, consisting of three tests, was not statistically different from one session to another. There was no dependence on variables such as ear (right or left), session, day of testing or their interaction. There was a significant difference in the variability between the tinnitus and the normal group.

The Coalstoun porphyry copper prospect in southeast Queensland lies adjacent to the north-northwest-trending Perry fault zone near the intersection with an east-northeast-trending structural lineament. Late Permian intrusions at the prospect are dominantly porphyritic biotite + or - hornblende microtonalite and quartz microdiorite emplaced into Devonian ?-Carboniferous quartz-rich fine-grained metasediments. Three intrusive centers, each containing several distinct phases, are recognized in an area of 6 X 2.5 km. The intrusions appear to have attained shallow crustal levels as evidenced by porphyritic texture, abundance of metasedimentary xenoliths, rafts and screens, moderately developed fracturing, and the presence of numerous surrounding breccia pipes.A core of hydrothermal biotite alteration containing copper grades of 2,000 to 4,000 ppm and up to 150 ppm Mo is present in the central intrusion. The biotite zone possibly overlies a deep, relatively unaltered core and grades outward into a chlorite-carbonate alteration zone which extends out into surrounding metasediments. Small pockets of quartz-sericite-pyrite and hypogene sericite-clay alteration occur surrounding, and within, the biotite zone, and the complete hypogene alteration system is partially blanketed by supergene clay (-seriate) alteration containing enriched copper grades. Associated breccia pipes are dominantly composed of angular metasedimentary fragments and exhibit quartz-sericite-pyrite and sericite-clay alteration with sporadic tourmaline. Copper grades decrease outward from the biotite zone, whereas pyrite: chalcopyriteratios increase.Alteration in the biotite and chlorite-carbonate zones is nearly isochemical, with a minor decrease in Na 2 O/K 2 O, an increase in Rb/Sr, and increases in Cu and K 2 O in the former. Volumetrically minor quartz-sericite-pyrite and sericite-clay zones generally show decreases in MgO, CaO, Na 2 O, Ba, Cr, Ga, Sr, V, Y, Zn, and Na 2 O/K 2 O and increases in H 2 O, S, K 2 O, K/Rb, and Rb/Sr.Hydrothermal biotites commonly pseudomorph magmatic biotite and hornblende pheno-crysts, are finer grained, and are pale brown to greenish-brown compared to magmatic biotites which are orange-brown. Hydrothermal biotites contain lower TiO 2 , total Fe and FeO, Fe/Fe + Mg + Mn, and Na 2 O, and higher (A1) VI and possibly higher Fe (super 3+) /Fe (super 2+) + Fe (super 3+) than the magmatic biotites. The differences between the two biotite types are interpreted as indicating a decrease in pressure and/or temperature and increases in oxygen and sulfur fugacities in the formation of hydrothermal biotite.Initial emplacement of porphyry intrusions (possibly generated in a continental margin tectonic environment) to high crustal levels was controlled by regional fault intersections. Columns of shattered rock above the intrusions were mobilized as breccia plugs ahead of the rising stocks. Crystallization and cooling of the stocks was accompanied by retrograde boiling, fluid expulsion through the breccias, additional collapse structures, and stockworking. A high-temperature biotite zone formed with pervasive and fracture-controlled mineral deposition from high-salinity, possibly oxidizing, magmatically derived hydrothermal fluids, which introduced Cu, Mo, S, and K 2 O and initially extended toward the margins of the intrusives.Expulsion of magmatic fluids and interaction with convecting meteoric waters possibly caused deposition of quartz-sericite-pyrite and hypogene sericite-clay alteration assemblages peripheral to, and within, the biotite zone. Gradual cooling of the system initiated an inward collapse of the meteoric fluid convective cells, forming pervasive retrograde chlorite-carbonate alteration in the metasediments and outer portions of the stocks.Possibly from the Tertiary to the present, topographically controlled supergene clay (-sericite) alteration has occurred, with significant secondary copper sulfide development.

The L2 and L3 subshell fluorescence yields, ω2 and ω3, and the Coster–Kronig transition probability f23 in 88Ra and 94Pu have been deduced from conversion electron L X-ray coincidence measurements. The Chalk River [Formula: see text]-spectrometer was used to select the conversion electrons. X rays were detected in a Si(Li) counter which was calibrated for absolute X-ray detection efficiency. The results are as follows: [Formula: see text]

The nine L subshell radiative and nonradiative de-excitation probabilities, ωi and fij, have been determined for the atom Yb (Z = 70) by conversion electron–X-ray coincidence measurements. The results are in good agreement with theoretical values calculated by McGuire using a simple approximation to the Herman–Skillman potential.

Tantalum L X-ray spectra were recorded in coincidence with KLL Auger electrons emitted in the decay of 181W. The Chalk River [Formula: see text] spectrometer was used to select individual KLL peaks. The measured X-ray fluorescence yields for five different double-L vacancy states are in agreement with theoretical values derived on the assumption that for Ta, spectator vacancies have negligible effect on the de-excitation of their partners.

The design of a lens spectrometer with respect to economy in power consumption and copper weight, resolving and collecting power has been studied by small scale experiments The construction and performance of a large β-ray spectrometer is described which focuses 15 MeV electrons when its coil is energized by 50 amp at 360 volts. The coil is cooled by a flow of 12 gallons of water per minute Maximum resolution and collecting power of the spectrometer are 0 8% and 0 6% respectively The influences of spherical aberration, source and window size on the resolution of the thick lens spectrometer are discussed.

Natural silver has been irradiated for 75.3 days in a thermal neutron flux of 2.42 × 1014 cm−2 sec−1 and the complex beta-ray spectrum of the resulting activities of 249-day Ag110m and 7.5-day Ag111 have been studied with a magnetic spectrometer. From the measured ratio of the respective beta-ray intensities and using the currently accepted decay schemes of these nuclides a value of 82 ± 11 barns is obtained for the reactor neutron capture cross section of Ag110m. Possible causes of systematic error are discussed.

The high efficiencies of large volume 'coaxial' Ge(Li) detectors make them attractive for coincidence experiments. However the electric field in this configuration is not uniform and hence the charge collection times vary widely as a function of position in the detector. The resultant variations in output pulse shape limit coincidence resolving times. In our studies one 511 keV annihilation quantum (22Na source) was detected in a scintillation counter to establish the zero (start) time and its partner in the Ge(Li) detector (at 1500 V) was accepted only when a full energy pulse was registered. The stop pulse to the timesorter was generated by the leading edge of the Ge(Li) preamplifier pulse at ~ 10% (50 keV) of maximum amplitude. Scanning the detector with a 1 mm wide collimated ?-beam resulted in time distributions whose full widths at half-maximum (fwhm) were ~ 8 nsec in the coaxial region of the detector broadening to ~ 35 nsec at the closed end. The distributions are skew in shape with long approximately exponential tails having half value slopes of ~ 5 to ~ 20 nsec. Similar studies with stop pulses generated at ~ 50% of maximum amplitude show much broader time distributions. The position variation in pulse shapes due to charge collection time was confirmed from oscilloscope photographs by triggering with the scintillation counter 'start' pulse.

A mass spectrometer of the Nier type has been designed and constructed for the identification of isotopes and measurement of their relative abundances. This instrument employs a universal gas-type ion source which may readily be replaced with a furnace or filament-type ion source for use with solids. The instrument is compact and portable with the exception of service connexions and a galvanometer shelf. The electronic units designed for this instrument are described in detail. These units operate satisfactorily from unstabilized a.c. and do not require batteries. The mass spectrometer is capable of detecting isotopic components present to the extent of 1 part in 100,000 of a sample. With the present slit dimensions, the instrument was found to have a resolving power better than 1 in 130, which agrees with that calculated from the slit dimensions and the radius of curvature.

A 180 degree direction focusing mass spectrometer for isotope abundance measurements is described. In operation, the instrument has a resolution of one mass unit in 100, which is the resolution expected from the dimensions of the slits and the radius of curvature of the ion path.The precision of the instrument is sufficiently good to make possible the direct measurement of equilibrium constants for many isotopic reactions. Several reactions previously used to separate the nitrogen and the sulphur isotopes have been investigated. The equilibrium constants for the two reactions[Formula: see text]were found to be about 60% higher than those previously reported from fractionation column experiments. However, the low values previously reported can be accounted for on the basis of Cohen's theory of packed columns.

The radiations from the decay of Tm170 (127 day) have been studied by means of a lens type β-ray spectrometer, a scintillation spectrometer, short resolving time (2τ0 = 2 × 10−9 sec.) coincidence counting techniques, and a pair of lens type β-ray spectrometers placed end to end with coincidence counting of the focused radiations from a single source. A disintegration scheme is proposed which is consistent with the experimental results. Decay is found to be by negative β-ray emission; the spectrum consists of two components, one of maximum energy 968 ± 4 kev. (76%) proceeding to the ground state of Yb170 and one of maximum energy 884 ± 4 kev. (24%) to an excited state in Yb170 followed by emission of a γ ray or conversion electron to the ground state. The γ-ray transition in Yb170 is found to have an energy of 84.1 ± 0.1 kev., a half-life of (1.57 ± 0.05) × 10−9 sec, and conversion coefficients aK = 1.60 ± 0.15, aL = 4.1 ± 0.5, aM = 1.2 ± 0.2 which show that it is electric quadrupole in character. Upper limits are given for decay by K capture, 0.3%, or positive β-ray emission, 0.01%, and also for the occurrence of other γ rays.

The K–LL Auger spectrum of 94Pu239 has been examined using a high resolution π√2 β-ray spectrometer with a proportional counter detector. Seven lines have been observed in the Auger spectrum with the following energies and relative intensities.[Formula: see text]The presence of seven lines in this K–LL Auger spectrum is in disagreement with theoretical predictions based on pure j–j coupling and supports, rather, the recent theoretical treatment of Asaad and Burhop. The energies of the observed lines are in satisfactory agreement with their theoretical predictions but discrepancies exist in the relative intensities.

The K–LL Auger spectrum of 62Sm152 has been studied in the Chalk River high-resolution β-ray spectrometer with a proportional counter detector. Seven lines were observed in the Auger spectrum with the following energies and relative intensities:[Formula: see text]These measurements are compared with the theoretical predictions of Asaad and Burhop. The measured energies are ~50–60 ev higher than their predictions. Discrepancies exist in the relative intensities but these are smaller than were observed at Z = 94.

A number of magnetic dipole γ-ray transitions have been studied using a coincidence circuit of short resolving time (2τ0 = 2 × 10−9 sec), a two lens single β-ray spectrometer, a pair of lens spectrometers placed end to end with coincidence counting of the focused radiations from a single source, and a scintillation spectrometer. Lifetimes have been measured using the delayed coincidence method and where feasible conversion coefficients and K/L ratios obtained. Comparison is made with theoretical estimates of the lifetime–energy relation for M1 γ-ray transitions.The new results are as follows:[Formula: see text]

The three-component fluxgate magnetometer developed by Serson has been adapted to provide continuous correction signals to the degaussing system of the Chalk River iron-free β-ray spectrometer. Improved electronic circuitry has been developed for the magnetometer which minimizes the zero error and reduces to −4 gauss long-term drift caused by component aging. The degaussing coil arrangement used to generate uniform magnetic field components opposite to those of the earth is indicated and the current regulation system is described briefly. The method in which the magnetometer correction signal is introduced into the current regulators is shown and an example is given of the performance of this degaussing system during a magnetic storm.

Momentum ratios of some of the more intense internal conversion lines from sources of thorium radioactive deposit have been determined with accuracies of 1 to 4 parts in 105 using an iron-free β spectrometer. Accurate absolute values of the momenta were obtained from intercomparisons of these line momenta with that of the K-412 internal conversion line in 198Hg. The X-ray self-calibration method of Siegbahn is discussed in some detail and is shown to be less accurate at this time. The results are analyzed on both the 1955 and 1963 least-squares adjusted values of the fundamental constants.

A quantitative method has been developed for measuring the mean depth within a solid of those radioactive atoms which decay with the emission of monoenergetic conversion electrons. By acceleration to kev energies in a mass separator 16.8-hour Xe125 atoms were injected into metal foils, and the intense K 54.96 and K 188.4 conversion lines were then scanned in the Chalk River π√2 β-ray spectrometer. The manner in which these conversion line shapes varied with Xe125 depth was calibrated by covering the foil surfaces with known thicknesses of Al or Au; it was found that the peak heights decreased in an approximately exponential manner with increasing Xe125 depths. With this calibration, mean depths can be determined under unknown conditions; the maximum sensitivity is about 6 atom layers (15 Å) under the most favorable conditions. Examples are given of the application of the method to metal oxidation studies and to Xe125 range measurements.

Measurements of the K-LL Auger lines were made to test the nonrelativistic theory of Asaad and Bishop (1958) at the lowest value of the atomic number. The source material, xenon-133, was prepared by neutron irradiation of natural xenon for six days in the NRU Reactor. The energies snd relative intensities are summarized in tabular form; some results are similar to those found previously. Others seemed to indicate two additional satellite lines. The absolute coefficient for K-LL Auger yield can be deduced from the data. (L.N.N.)

A search has been made for delayed γ rays with 1 second [Formula: see text] minutes following 10.5-MeV proton bombardment of 18 natural metallic targets. The five activities observed are: (1) 139Ce, Eγ = 754.5 ± 1.3 keV, [Formula: see text] second; (2) 141Nd, Eγ = 756.8 ± 1.3 keV, [Formula: see text] second; (3) 161Ho, Eγ = 211 ± 2 keV, [Formula: see text] second; (4) 163Ho, Eγ = 299 ± 2 keV, [Formula: see text] second; and (5) a γ ray of 122 ± 2 keV, [Formula: see text] second which is tentatively assigned to 179Ta. All transitions have been measured using a Ge(Li) γ-ray detector. The internal conversion electrons of the transitions in 139Ce and 141Nd were also studied using an orange β-ray spectrometer. Rotational transition energies in 158Dy, 164Er, 168Yb, and 174Hf were measured in conjunction with the internal conversion studies and are reported in an Appendix.

A logarithmic radiation meter is described using as detector, a photomultiplier and scintillation phosphor. A one‐tube feedback circuit varies the voltage applied to the photomultiplier so as to hold its anode current constant for different incident radiation intensities. The voltage applied to the photomultiplier is then a nearly logarithmic measure of the radiation intensity over a range of 104. Circuit details and experimental results are given of a battery‐operated portable model and an ac operated model which incorporates means for correcting the slight compression towards one end of the scale found in the portable model.

A detailed study of the disintegration scheme of Pr144 has been carried out using lens spectrometers, scintillation spectrometers, and fast coincidence techniques. The 2293 kev β-component (1.3%) studied in coincidence with γ 691 has a predominantly first forbidden unique shape and the β–γ directional correlation is strongly anisotropic. The results indicate a probable spin-sequence 0−(β)2+(γ)0+, but the accuracy is not sufficient to exclude completely a 1− assignment for the Pr144 ground state. The β 803 component (1.0%) observed in coincidence with γ 2181 has an allowed shape and the β–γ directional correlation is isotropic. The shape of the total β-spectrum was studied in a double lens spectrometer having good anti-scattering properties using sources of Ce144 oxide sublimed onto 200 μg/cm2 Al leaf. Subtraction of a unique (Bij) shape 2293 kev 1.3% component and an allowed shape 803 kev 1.0% component yields the ground state β-spectrum. Analyses were made using the electronic functions of Zerianova which assume uniform charge distribution with ρ = 1.2 A1/3 10−13 cm as well as the point charge functions of Rose with ρ = 1.41 A1/3 10−13 cm. The observed spectrum shape can be explained on 0− to 0+ selection rules only by the axial vector interaction. Limits on the permissible tensor or pseudoscalar admixtures with the axial vector are discussed. No acceptable fit is possible with tensor, pseudoscalar, or any TP admixture (interfering or not) using Rose and Osborn's pseudoscalar formalism.

Mass spectrometer investigations have been made of rare gas fission products extracted from uranium irradiated with thermal neutrons. The irradiated uranium rods were allowed to stand for various periods of time after irradiation to permit the decay of most fission product chains to stable isotopes. Four stable isotopes of xenon were found having mass numbers 131, 132, 134, and 136, and three stable isotopes of krypton with mass numbers 83, 84, and 86. Kr86, the most abundant of the latter group, is probably formed directly in fission. In addition a long lived krypton with mass 85 was discovered which is isomeric with a 4.0 hr. Kr85 reported previously.The relative abundances of these isotopes which are related directly to fission yields of the corresponding mass chains have been determined with an accuracy of 1% or better. The mass numbers of these fission chains can now be identified with certainty by comparing mass spectrometer abundance data with known yield values of the active chain members. Finally, the half-life of krypton 85 was determined by comparing its concentration to that of a stable isotope over a period of time.

A coincidence circuit for use with anthracene or stilbene scintillation counters is described. Its resolving time lies in the 10−9 sec. range, in agreement with theoretical estimates of the minimum possible resolving time with these scintillation counters. Examples are given of the use of the circuit in the measurement of short gamma-ray half-lives and, in conjunction with beta-ray spectrometers, in the determination of the details of radioactive disintegration schemes. The new results given in these examples are as follows:[Formula: see text]

The energies of the Hg199 50-, 158-, and 208-keV, and Hg198 676-and 1088-keV transitions have been measured. This has been done by comparing the momenta of the internal conversion lines of each transition with three conversion lines of the Hg198 412-keV transition, the energy of which has been previously measured with high accuracy. The comparison was made using the Chalk River π√2 β-ray spectrometer. From the momentum comparisons the following transition energies were obtained: Hg199, 49.828 ± 0.004, 158.370 ± 0.006, and 208.198 ± 0.007 keV; Hg198, 675.878 ± 0.018 and 1087.69 ± 0.03 keV.

Internal conversion measurement studies of the 14.6 min 101Mo β decay have led to the discovery of the following low-energy transitions in 101Tc: 6.281 ± 0.007 (75.4 ± 9%), 9.317 ± 0.010 (97 ± 1%), and 15.606 ± 0.015 keV (1.9 + 0.3%). From relative L-subshell intensities, the 6.281 and 9.317 keV transitions are found to be M1 with E2 admixtures of 0.010 ± 0.005% and 0.021 + 0.006% respectively; the weak 15.606 keV transition is E2 in character. These transitions establish excited states in 101Tc at 9.317 ± 0.010 and 15.601 ± 0.009 keV. The measured multipolarities together with decay scheme considerations lead to Jπ values of 9/2 +, 7/2 +, and 5/2 + for the ground state, the 9.317, and the 15.601 keV states respectively. Since these transitions were not observed in earlier studies of the β decay of 101Mo, quoted decay energies have been 15.6 keV too low. The measured K-conversion coefficient of the 80.926 keV transition shows that it is M1 with an E2 component of

The properties of the γ-ray transitions in 171Tm, following beta decay of 7.5 h 171Er, have been studied using an iron-free π√2 beta spectrometer and Ge(Li) detectors, singly and in coincidence. The multipolarities of 8 lower-energy γ transitions have been established from a study of L- or M-subshell-internal-conversion lines. The measured K-line intensities of 20 higher-energy transitions yield K conversion coefficients and hence additional multipolarity assignments. Gamma-ray energy measurements, together with an extensive series of gamma–gamma coincidence experiments, have been used to establish the role of 59 (out of 65) γ transitions in the 171Tm level scheme. Sixteen excited states are identified at energies of 5.025 (3/2+), 116.6 (5/2+), 129.0 (7/2+), 326.7* (9/2+), 424.8 (7/2−), 635.4 (7/2+), 675.7 (3/2+), 737.2 (5/2+), 822.3* (7/2+), 912.8 (5/2+), 998.6 (7/2+), 1225.5* (3/2, 5/2, or 7/2+), 1284.7* (5/2+), 1296.3*, 1391.2*, and 1400.5* (5/2+) keV. The asterisks indicate levels which are new or at variance with those proposed by some other workers. The coincidence data does not support a level at 861 keV proposed by two other groups of workers on the basis of energy sums. Nilsson orbital assignments are proposed and discussed for 12 levels.

The periodic Anderson model for a lattice of magnetic ions as applied to the description of intermediate valence in rare‐earth compounds is investigated within the coherent potential approximation.

A delayed γ activity, Eγ = 122.2 ± 0.2 keV, t1/2 = 18.82 ± 0.09 s, is observed following 10 MeV proton bombardment of targets of natural Zr and of natural Hf in which Zr is present as a contaminant. The present results taken together with other recently published data show that this activity arises from 90Zr(p,n)90Nbm. The tentative assignment of this 122 keV γ activity to 179Ta, which we proposed in an earlier publication, is withdrawn.