bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning of 11 α-tubulin gene sequences from the genome of Chinese hamster ovary cells
Authors: Elliott Elizabeth M. , Sarangi Farida , Henderson Graham , Ling Victor
Published: October 2017

We have analyzed the complex tubulin gene family in clonal lines of Chinese hamster ovary cells. There are approximately 16 α-tubulin genes and a similar multiplicity of β-tubulin genes. The α-tubulin genes are not closely linked to each other nor to the β-tubulin genes. A genomic library has been constructed in the vector λ charon 4A containing insert sizes of 13–20 kilobases. The library has been screened with both inter- and intra-species α-tubulin probes. Eleven α-tubulin clones with different restriction patterns have been isolated and characterized. At least seven of these clones contain the complete gene coding region. One clone appears to represent the transcribed α-tubulin gene II. The sequence of an intron from this gene is compared with that from an equivalent gene in the rat.
Microtubule polarity in taxol-treated isolated spindles
Authors: Haimo Leah T.
Published: October 2017

Spindles were isolated from Spisula oocytes in the presence or absence of taxol to determine if cell lysis procedures previously used to analyze spindle microtubule polarity may have resulted in the loss of any microtubules of a particular polarity. Electrophoretic analysis indicated that spindle preparations isolated in the presence of taxol contained considerably more tubulin than did those isolated in the absence of taxol. Although there was no corresponding increase in the birefringence of the taxol-treated isolated spindles, thereby suggesting that they did not possess a greater concentration of aligned microtubules between the poles and the equatorial plate, electron microscopy revealed that the taxol-treated isolated spindles did, in fact, contain more microtubules than did the nontaxol-treated isolated spindles. These microtubules were predominantly localized immediately around the centrioles, suggesting that assembly may have occurred during the lysis into taxol. The spindles were decorated with Chlamydomonas dynein to display microtubule polarity. The majority of microtubules, located between the chromosomes and poles, possessed a uniform polarity in both taxol- and nontaxol-treated isolated spindles. In the region of the chomosomes, however, up to 45% of the microtubules were oriented with a polarity opposite to the remainder and were intermingled among them. It is probable that microtubules with opposite polarities arise from the opposing poles and overlap in the equatorial region. The extent of overlap appears to be quite substantial and thus may be of significance during mitotic movements.
Stable intermicrotubule linkers in the isolated cytostomal apparatus of Tetramitus
Authors: Dingle Allan D. , Larson Dawn E.
Published: October 2017

Detergent lysis of Tetramitus rostratus flagellates liberates intact a "cytostomal apparatus" composed of four flagella, their basal bodies, and several striated flagellar rootlets, as well as an unusually stable array of long cytoskeletal microtubules. Cytostomal apparatuses, purified on 5–15% Ficoll gradients and negatively stained with uranyl acetate, reveal abundant arrays of intermicrotubule linkers (IMTLs). These linkers, which are irregularly spaced vertically at approximately 50-nm intervals, appear to limit intermicrotubule distances to about 120 nm. The IMTLs of Tetramitus are unusually long, unusually abundant, and unusually stable: it is speculated that they represent an exaggerated form of (and hence a means to identify) a universal component of the microtrabecular lattice of eukaryote cells.
Comparison of microtubules and microfilaments in Tipula iridescent virus-infected and uninfected cells
Authors: Seagull Robert W. , Lee Peter E. , Frosch Monica
Published: October 2017

Microfilaments and microtubules were detected in Estigmene acrea virus-infected cells using fluorescent immunochemistry and in sections by electron microscopy. Twelve hours following infection of cells with Tipula iridescent virus, large virus assembly sites developed in the cytoplasm. The majority of infected cells exhibit no detectable changes in the cytoskeleton during the initial stage of infection, when virus assembly sites are forming. Actin was localized either in cytoplasmic spikes or in patches at the cell surface. Microtubules were parallel to the long axis of elongate cells or randomly distributed in globular cells. Intermediate filaments were not detected using either immunofluorscent or electron microscopic techniques. In later stages of infection some cells exhibit a specific association between actin and the virus assembly site. The significance of this observation remains unclear since only a portion of the population exhibits this change. From this study, it does not appear that cytoskeletal elements are of importance in the formation or maintenance of the membrane-free cytoplasmic virus assembly sites.
The focal adhesions of chick retinal pigmented epithelial cells
Authors: Opas Michał
Published: October 2017

Retinal pigmented epithelial (RPE) cells obtained from the eyes of chick embryos form colonies in vitro in which cells at the periphery of the colony express an undifferentiated, well-spread morphology and develop extremely large areas of cell–substratum adhesion. These adhesions can be classified as focal on the basis of the following: (a) their black surface reflection interference image, the contrast of which is not affected by changes in either the wavelength of the incident light or the refractive index of the immersion medium; (b) their association with the termini of actin-containing microfilament bundles; and (c) their ability to be labelled with antiserum against vinculin, a protein specific for adhesions of the focal type. The focal adhesions of RPE cells comprise laterally associated individual focal contacts, the mechanism by which this association is achieved and maintained is yet unknown. Because of the unusually large size and excellent microscopical definition of their focal adhesions, I used RPE cells to investigate the role of other actin-associated proteins in adhesion complexes. One of these, nonerythroid spectrin (fodrin), a protein suggested to play a role in anchoring actin filaments to the plasma membrane, was neither concentrated in nor excluded from the focal adhesions of RPE cells. Thus, at least in this cell type, spectrin seems unlikely to serve as a link between the major actin-containing microfilament bundles and the plasma membrane in the regions of cell-to-substratum contacts.
Basket cell development in the normal and hypothyroid rat cerebellar cortex studied with a monoclonal anti-neurofilament antibody
Authors: Leclerc Nicole , Gravel Claude , Plioplys Andrius , Hawkes Richard
Published: October 2017

We have used a monoclonal antibody against an antigenic determinant of the 210-kdalton neurofilament protein to study basket cell maturation in rat cerebellar cortex. Neurofilament immunoreactivity first appears in basket cells at postnatal day 12 and mature axonal "pinceaux" are present at postnatal day 17. There are large differences in the rate of maturation from lobe to lobe which do not fully correspond to the rate of Purkinje cell differentiation. In hypothyroid rats the expression of the neurofilament antigen by basket cells is almost completely suppressed.
Immunostaining of neurofilament protein in human postmortem cortex: A sensitive and specific approach to the pattern analysis of human cortical cytoarchitecture
Authors: Majocha Ronald E. , Marotta Charles A. , Benes Francine M.
Published: October 2017

Antibodies raised against the 200 000 neurofilament protein (NFP) of rat brain have been successfully applied to the staining of human postmortem cortex using a modified immunoperoxidase procedure. Human anterior cingulate cortex which has been in formaldehyde fixative for as long as 4 years shows extensive and reliable staining of axons and, to a lesser degree, apical dendrites of cortical neurons. The immunostaining of 200 000 NFP in human cortex has revealed cytoarchitectural details not generally visible with other more conventional neuroanatomical stains, particularly when counterstaining with cresyl violet is employed. Potential applications of this approach to the pattern analysis of human cortical cytoarchitecture in both health and disease are discussed.
Does actin produce the force that moves a chromosome to the pole during anaphase?
Authors: Forer Arthur
Published: October 2017

Chromosomes move towards spindle poles because of force produced by chromosomal spindle fibres. I argue that actin is involved in producing this force. Actin is present in chromosomal spindle fibres, with consistent polarity. Physiological experiments using ultraviolet microbeam irradiations suggest that the force is due to an actin and myosin (or myosin-equivalent) system. Other physiological experiments (using inhibitors in "leaky" cells or antibodies injected into cells) that on the face of it would seem to rule out actin and myosin on closer scrutiny do not really do so at all. I argue that in vivo the "on" ends of chromosomal spindle fibre microtubules are at the kinetochores; I discuss the apparent contradiction between this conclusion and those from experiments on microtubules in vitro. From what we know of treadmilling in microtubules in vitro, the poleward movements of irradiation-induced areas of reduced birefringence (arb) can not be explained as treadmilling of microtubules: additional assumptions need to be made for arb movements toward the pole to be due to treadmilling. If arb movement does indeed represent treadmilling along chromosomal spindle fibre microtubules, treadmilling continues throughout anaphase. Thus I suggest that chromosomal spindle fibres shorten in anaphase not because polymerization is stopped at the kinetochore (the on end), as previously assumed, but rather because there is increased depolymerization at the pole (the "off" end).
Elongation of cytoplasmic processes during gametic mating: Models for actin-based motility
Authors: Detmers Patricia A.
Published: October 2017

The acrosomal processes of Thyone and Limulus sperm and the fertilization tubule of mt+ gametes of Chlamydomonas are interesting models for actin-based motility. Each is a long thin process that elongates rapidly and contains a core of actin filaments having uniform polarity: arrowheads formed by myosin subfragments point toward the base of the processes. In Limulus, directed outgrowth of the acrosomal process is achieved by a rearrangement in the packing of superhelically coiled actin filaments that form during spermatogenesis. In contrast, outgrowth of the acrosomal process in Thyone and the fertilization tubule in Chlamydomonas is accompanied by actin polymerization. Both Thyone and Chlamydomonas possess structures, the actomere and the doublet zone, respectively, that serve as microfilament organizing centers, nucleating actin polymerization and defining the polarity of the growing filaments. Alkalinization of the cytoplasm may promote polymerization of actin in Thyone, whereas an apparent rise in the intracellular Ca2+ concentration is associated with the transmission of intracellular signals during mating in Chlamydomonas. Further examination of these three actin-based motile systems should provide new insights into the assembly of the actin cytoskeleton, a process critical for many forms of nonmuscle cellular motility.
Evidence that cell surface motility in Allogromia is mediated by cytoplasmic microtubules
Authors: Bowser Samuel S. , Rieder Conly L.
Published: October 2017

We have previously shown that reticulopods of Allogromia sp. (strain NF) and Allogromia laticollaris display rapid, bidirectional saltatory transport of plasma membrane surface markers (i.e., polystyrene microspheres). Correlative video microscopic and electron microscopic methods were used to determine whether cytoskeletal components are involved in this surface transport. Such transport was observed only where the plasma membrane overlay cytoplasmic fibrils, which have been shown to be involved in organelle transport. Ultrastuctural analysis indicated that these fibrils contain microtubules and an associated flocculent fibrillar material. In studies with nonionic detergents the surface marker particles remained bound to these microtubule-containing fibrils, even after the plasma membrane had been removed. Surface transport was inhibited when reticulopods were treated with agents that induce microtubule disassembly. Together these observations provide strong evidence that surface motility in Allogromia is mediated by labile cytoplasmic microtubules.
Role of the marginal band in an invertebrate erythrocyte: evidence for a universal mechanical function
Authors: Joseph-Silverstein Jacquelyn , Cohen William D.
Published: October 2017

Marginal bands of microtubules are present in erythrocytes of all nonmammalian vertebrates and some invertebrates, in which they are thought to play a role in erythrocyte morphogenesis. Recently, marginal bands have also been implicated in maintenance of shape in vertebrate erythrocytes and platelets subjected to external mechanical forces. Here we demonstrate that marginal bands in an invertebrate ("blood clam") erythrocyte act similarly. Cells with and without marginal bands at the same temperature were prepared by (a) nocodazole or colchicine inhibition of marginal band reassembly following 0 °C disassembly, (b) taxol inhibition of marginal band disassembly at 0 °C, and (c) taxol induction of marginal band reassembly at 0 °C. As shown previously for temperture-induced marginal band reassembly in this species, taxol-induced reassembly at 0 °C occurred in association with centrioles. When erythrocytes with and without marginal bands were compared for their response to the mechanical stress of fluxing through capillary tubes, many more of those without marginal bands tended to become folded or buckled regardless of the method used to prepare them. The results provide evidence that marginal bands have a universal mechanical function in mature erythrocytes.
Nuclear RNA-associated proteins and their relationship to the nuclear matrix and related structures in HeLa cells
Authors: Bouvier Dominique , Hubert Jean , Sève Annie-Pierre , Bouteille Michel
Published: October 2017

The ultrastructure and the polypeptide composition of residual nuclear substructures including nuclear matrices, nuclear ghosts, and residual envelopes were investigated by means of electron microscopy and two-dimensional gel electrophoresis. Nuclear matrices were prepared by digesting isolated nuclei with DNase I alone, followed by high-salt extraction in 2 M NaCl. Nuclear ghosts were obtained by high-salt extraction of nuclei previously digested with DNase and RNase in MgCl2-containing buffers. To prepare residual envelopes, nuclei were first digested with RNase in the presence of EDTA, then digested with Mg2+-activated DNase I, and extracted in 2 M NaCl. The results of this comparative study support the conclusion that the intranuclear matrix is made of two distinct RNA-containing elements. One of these elements appears on ultrathin sections as a thin fibrillar network. It disappears from RNase-digested nuclei, together with numerous basic proteins, whatever the conditions of digestion. Although this element is present in extranucleolar territories, it is a major component of residual nucleoli. The second element appears as coarse-beaded fibers absent from the nucleolar areas. Its preservation in residual nuclear substructures depends on the presence of Mg2+ ions during RNase digestion of nuclei. It is enriched in two minor basic proteins of relative mass 49 000 and 70 000. The involvement of this fibrogranular element in heterogeneous nuclear RNA attachment to the nuclear matrix is discussed.
Localization of nuclear antigens during preparation of nuclear matrices in situ
Authors: Chaly Nathalie , Little Judy E. , Brown David L.
Published: October 2017

Nuclear matrix structure closely resembles the organization of nonchromatin components of nuclei in situ. However, reports on the extent to which nuclear components are reorganized during matrix isolation have produced conflicting results, and the reality of an in situ nuclear matrix is still in question. We have prepared nuclear matrices by processing cells still attached to the growth substrate through the extraction steps, thus avoiding mechanical disruption due to homogenization and centrifugation. Furthermore, the extensive residual cytoskeleton seems to keep the residual nuclei "stretched out" so that they retain many features of intact nuclei. Indirect immunofluorescence staining was used to compare the distribution of nuclear antigens in intact nuclei with their organization in nuclear matrices, as well as at each stage of nuclear matrix preparation. We have applied monoclonal antibodies P1, I1, PI1, and PI2, which had been generated against isolated matrices, as well as autoimmune sera detecting lamins, perichromin, and centromere antigens. Chromatin and RNA extraction was monitored with Hoechst 33258, ethidium bromide, and antihistone. The lamins, PI1, and, to a great extent, PI2 and centromere antigens were little affected by the extraction. The data suggest furthermore that PI1 is a fundamental nuclear matrix component and may serve in integrating peripheral and internal nuclear functions. P1 and perichromin were extensively redistributed after chromatin extraction, supporting a role for these antigens in spatial ordering of chromatin. I1 was progressively extracted at each stage of nuclear matrix preparation and was artifactually associated with matrices which had not been digested with RNase. This study demonstrates unequivocally that the organization of many nuclear matrix components in final preparations reflects their organization in situ. It does indicate, however, that some components retained in matrices are extensively redistributed during nuclear matrix preparation and that their role in nuclear organization must be evaluated in consequence.
An association between replicating adenovirus DNA and the nuclear matrix of infected HeLa cells
Authors: Younghusband H. B.
Published: October 2017

An association between newly synthesized human adenovirus type 5 DNA and the nuclear matrix of infected HeLa cells is described. Adenovirus-infected cells were pulsed labeled with [3H]thymidine late in infection and the nuclear matrix was prepared. After a 1-min pulse more than 95% of the labeled viral DNA was matrix associated and, when compared with total cell DNA, was resistant to DNase I digestion. When the pulse is longer or is followed by a chase period, the viral DNA remains nuclear matrix associated and less nuclease sensitive than bulk cellular DNA. The resistance to nuclease digestion may result from the close association of viral DNA with the nuclear matrix or could be due to a number of viral-specific proteins which are nuclear matrix associated. It is concluded that viral DNA synthesis occurs in association with the nuclear matrix and the newly synthesized DNA remains matrix associated until it is incorporated into a mature virus particle.
Chromaffin cell cytoskeleton: its possible role in secretion
Authors: Trifaró J.-M. , Bader M.-F. , Doucet J.-P.
Published: October 2017

Cytoskeleton proteins (actin, myosin, α-actinin, spectrin, tubulin, neurofilament subunits) and their regulatory proteins (calmodulin, gelsolin) have been isolated from adrenal chromaffin cells and characterized. Their physicochemical properties have been studied and their cell localizations have been revealed by biochemical, immunocytochemical, and ulstrastructural techniques. α-Actinin and spectrin are components of chromaffin granule membranes and some of the cell actin copurifies with these secretory granules. Myosin is not detected in the granules, but is present mainly in the cytosol and close to the cell surface. Trifluoperazine, a calmodulin antagonist, blocks stimulation-induced hormone release from chromaffin cells at a step distal from Ca2+ entry. High affinity calmodulin-binding sites have also been found in chromaffin granule membranes and their calmodulin-binding proteins have been characterized. Furthermore, microinjection of calmodulin antibodies into chromaffin cells blocks hormone output in response to stimulation. In view of the above findings, the possible roles of contractile proteins and calmodulin in chromaffin cell functions are discussed.
Ultrastructural localization of cytoskeletal proteins in pancreatic secretory cells
Authors: Bendayan Moïse
Published: October 2017

Actin, myosin, and keratin immunoreactive sites have been localized with high resolution in pancreatic exocrine cells, by applying the protein A – gold technique on tissues processed at low temperature conditions. The labeling by gold particles was found at the level of the cell web and closely associated with the limiting membranes of the immature and mature secretory granules, as well as those of the "trans" cisternae of the Golgi apparatus. These results, together with those obtained in the study on the localization of secretory proteins in exocrine pancreatic cells, demonstrate that cytoskeletal proteins are present at sites where maturation and (or) concentration of the secretory proteins occur. Thus, besides the role that cytoskeletal proteins must play in the transport of the secretory granules from the Golgi to the plasma membrane, they may also be involved in the process of protein maturation and (or) concentration.
MEASUREMENTS OF THE DAYTIME ABUNDANCE OF UPPER ATMOSPHERIC SODIUM
Authors: Neo Y. P. , Shepherd G. G.
Published: October 2017

Measurements made in 1961 by Blamont and Donahue on daytime sodium emission indicated that the sodium abundance was several times larger than during twilight. If this is true, then the sodium twilight emission should be profoundly affected, but no such effect has been observed. It is, therefore, of considerable importance that the daytime abundance measurement be confirmed by an independent method. This paper reports measurements of the daytime sodium abundance made at Saskatoon (52° 08′ N., 106° 40′ W.) by observing the variation of absorption of solar radiation by the terrestrial sodium as a function of the solar elevation. The apparatus consisted basically of a low-resolution Fabry–Perot spectrometer and a sodium-vapor cell. The results suggest that the daytime abundance is about 4.6 times higher than that during twilight, but for two reasons this result must be accepted with reservation. First, the seasonal variation of daytime abundance appears to be the same as that for twilight, whereas Blamont and Donahue found them to be opposite in phase. Second, the abundance values obtained from the D1 line differ, sometimes by as much as a factor of 2, from those obtained from the D2 line. Several reasons, none of them conclusive, are offered for this inconsistency.
EFFECT OF TEMPERATURE ON THE LATTICE PARAMETERS OF SOME SILVER–PALLADIUM ALLOYS
Authors: Rao C. Nagabhushana , Rao K. Krishna
Published: October 2017

Lattice-parameter variations as a function of temperature for silver–palladium alloys of five different compositions were investigated using a high-temperature 19-cm Unicam X-ray camera. Alloys containing 63 wt. % Ag and 80 wt. % Ag show a straight-line relationship between lattice parameter and temperature.Measurements made at room temperature on specimens quenched from different temperatures, after maintaining them for different periods of time at each particular temperature, indicate no changes in the lattice-parameter values. It is suggested that the observed deviations from a straight-line relationship in the above three alloys reflect temperature-induced changes in electronic structure.
DESIGN OF A 300 000-Oe TWO-REGION SOLENOID FOR INTERMITTENT OPERATION
Authors: Stevenson Richard
Published: October 2017

This paper contains a design of an aluminum solenoid magnet system capable of producing a field of 300 000 Oe over a bore of 5.8 cm. The magnetic field is produced by a two-region solenoid operated at 15 °K and cooled by compressed helium gas. Details of the structure are described, and calculations are given for all important parts of the cooling system. The magnet is designed for a total operating time at maximum power of at least 40 minutes in a week. The low capital expense of the system makes it suitable for installation in small laboratories.
ANTENNA PATTERN RESPONSE TO ARBITRARY TIME SIGNALS
Authors: Tseng Fung-I , Cheng David K.
Published: October 2017

This paper presents a simplified method for the analytical determination of the transient and steady-state pattern characteristics of an antenna for arbitrary time signals and arbitrary aperture distributions. For uniform aperture illumination, the pattern response of an antenna for any time signal, no matter how complicated, can be found through simple shifts of the signal, and both the transient and the steady-state behavior can be determined without performing any integration. Examples are given for responses to suddenly applied excitations, to rectangular pulses, to excitations for electronic scanning, and to time signals in a pulse-compression system. For pulse signals, a steady state is not reached in any given direction, θ, if the duration of the pulse T is less than (a/c)sin θ, where a is the maximum aperture dimension and c is the velocity of light. Graphical representations for easy interpretation of the different states of pattern characteristics are included.
ELECTROMAGNETIC RADIATION FROM AN ARBITRARY SLOT ON A CONDUCTING CYLINDER COATED WITH A UNIFORM COLD PLASMA SHEATH WITH AN AXIAL STATIC MAGNETIC FIELD
Authors: Yeh C.
Published: October 2017

The expressions for the radiated fields of an arbitrary slot on a conducting cylinder coated with a cold plasma sheath with an axial static magnetic field are obtained. It is well known from the plane-wave analysis that the presence of a static magnetic field has a considerable effect on the transmission characteristics of the signal through the plasma sheath. The principal concern of this paper is to consider the effects of a static magnetic field on the radiation pattern of a plasma-coated slot antenna. Extensive numerical computations are carried out for the special case of an infinite axial slot. It is found that, if the plasma frequency is moderate, a small axial static magnetic field could change significantly the radiation patterns of the slotted antenna. Furthermore, owing to the anisotropy of the plasma medium, the radiation patterns are asymmetric.
ABSORPTION MEASUREMENTS DURING THE SOLAR ECLIPSE OF JULY 20, 1963
Authors: Vogan E. L.
Published: October 2017

Riometer data obtained from several Canadian stations during the total solar eclipse of July 20, 1963, are presented and discussed. A small increase in cosmic noise level, amounting to about 0.25 dB at 30 Mc/s, was observed at Ottawa, Cape Jones, and Churchill.
LOW-ENERGY GAMMA-RAY TRANSITIONS IN Np237 FOLLOWING α DECAY OF Am241
Authors: Wolfson J. L. , Park J. J. H.
Published: October 2017

The low-energy gamma-ray transitions in Np237 following α decay of Am241 have been studied by examination of the internal conversion spectrum at good resolution. Improved measurements of the energies and intensities of the lines due to the well-known transitions of energies 26.36, 33.21, 43.44, 55.56, 59.57, and 99.00 keV have been made. The existence of a weak transition of energy 67.52 keV has been confirmed. The existence of weak transitions of energies 27, 42.8, 70, and 76 keV, previously reported, has not been substantiated.For the 43.44-keV transition the L subshell ratios LI/LIII and LII/LIII are in disagreement as to the proportion of E2 component in the M1, E2 mixture assigned to this radiation, while the M subshell ratios are in disagreement with both L subshell ratios.The binding energies of the L, M, and N subshells in Np have been measured. All values are slightly higher than found by extrapolation from values at lower Z, though within experimental uncertainty the values are in agreement with such extrapolations.
An estimate of the mass of the 'slow bodies' emitted in p–nucleus interactions at 200 and 300 GeV
Authors: Areti H. , Hébert C. J. D. , Hébert J. , Friedländer E. M. , Cohen J. , Marcu M. , Marin A. , Nitu R. , Adamovic O. , Juric M. , Baroni G. , Liberto S. Di , Petrera S. , Romano G. , Baumann G. , Devienne R. , Bolta J. M. , Rey G. , Massué J. P. , Pfohl R. , Jacquot C. , Kaiser R. , Lory J. , Meton C. , Schune D. , Tsai-Chü  , Willot B. , Otterlund I. , Schmitt R. , Ginneken A. Van , Vincent M.-A.
Published: October 2017

Angular and multiplicity correlations in proton–nucleus interactions in emulsion are interpreted within the framework of the Energy Flux Cascade model. The average mass of the 'slow bodies' or novae emitted in the backward hemisphere is ~3.5 GeV/c2 at both energies. This result is in reasonable agreement with previous work on two-particle correlations.
Electroexcitation of 15N levels from 9.7 to 14.7 MeV
Authors: Ansaldo E. J. , Bergstrom J. C. , Caplan H. S. , Yen R.
Published: October 2017

The electromagnetic form factors of five transitions in 15N have been measured for momentum transfers between 0.48 and 1.27 fm−1. The transitions observed were identified with levels at 9.76, 10.80, 11.88, 12.50, and 14.7 MeV excitation energy. Ground state radiative widths have been extracted by a Helm model analysis.
Low temperature photoconductivity in a-ZnSe
Authors: Brodie D. E. , Lim P. K. , Shiah R. T. S.
Published: October 2017

At lower temperatures, the photoconductivity of near stoichiometric or slightly selenium-rich a-ZnSe increases with an activation energy of 0.04 eV as the temperature decreases. Slightly Zn-rich samples do not exhibit this behaviour. This paper presents a model and a possible mechanism for this effect, which involves intimate valence alternation pairs as the controlling recombination centres at low temperatures. A similar effect has been observed in tellurium-rich a-CdTe.
The systematics of the (n, 2n) cross section (the Csikai–Peto effect)
Authors: Pai H. L. , Andrews D. G.
Published: October 2017

The Csikai–Peto effect has been re-evaluated by a statistical-model calculation method. Agreement and disagreement of the theory with the Csikai–Peto effect are analyzed in the light of the possible underlying mechanism, which in some aspects is close to that of prompt fission neutron emission. Future work related to the subject is proposed.
A Bremmer series for radial wave equations
Authors: Couch W. E. , Torrence R. J.
Published: October 2017

The Bremmer series solution of the one-dimensional Helmholtz equation with variable velocity is generalized to obtain a similar series for the radial wave equation with a spherically symmetric velocity function. Since the leading term of Bremmer's series is the one-dimensional WKB approximation, we obtain an approximation for the radial wave equation analogous to the WKB approximation.
Importance of the nucleon Fermi motion in the pion–nucleus elastic scattering
Authors: Nakano K. , Wu Chi-Shiang
Published: October 2017

The importance of the nucleon Fermi motion in π–nucleus elastic scattering is investigated in the framework of the multiple scattering theory. Conventional factorization approximations on the π–nucleus scattering amplitude are compared with calculations that take into account the nucleon Fermi motion by using π–12C as an example. The importance of a careful treatment of the Fermi motion in low energy scattering will be stressed.
Stimulated surface ionization of alkali by superthermal alkali beams
Authors: Hsieh Y. F. , Helbing R. K. B. , Pol V.
Published: October 2017

Stimulated surface ionization has recently been found as a novelty effect. It comprises the fact that atoms adsorbed on a surface may be stimulated into surface ionization by impinging superthermal neutrals. This is the first more or less systematic study to show that this effect is common among the alkali species. The yield is studied as a function of incident energy for all alkali pairs employing a polycrystalline tungsten surface. It is found to follow an Eα power law, with α typically about 1.5 (ranging from 1.0 to 2.9).
Macroscopic theory of dielectric solids. I. The model of molecular optics
Authors: Sipe J. E.
Published: October 2017

An improved derivation is given of the macroscopic electrodynamic equations for dielectric solids of finite size composed of molecules with a given polarizability, α = α(ω), interacting only via the retarded dipole–dipole coupling. We present a derivation of the constitutive relations for both crystalline and amorphous solids, which is not based on an expansion in powers of α, and in which the radiative reaction forces are carefully taken into account. The spatially varying density and pair correlation function of an amorphous solid, defined with the help of spatial averaging procedures, are shown to satisfy an integral 'counting' relation, which puts a condition on any physically consistent model of an amorphous solid. In the absence of dissipative damping, a medium is shown to be characterized by a real, in general spatially varying, dielectric constant. For solids of uniform density, crystalline or amorphous, we obtain the standard result that inside such a medium light propagates without scattering. For amorphous solids with varying density, the theory forms the basis of the macroscopic theory of light scattering from density in-homogeneities.
De nouvelles équations intégrales pour l'étude de la radiation électromagnétique dans les enceintes
Authors: Darling Byron T. , Imbeau Jacques A.
Published: October 2017

For stationary solutions of Maxwell's equations in the interior of a closed surface, we derive two new vectorial integral equations. They consist of integrals over the surface that the values of the fields on the surface must satisfy. These integral equations have two advantages over integral equations with singular kernels obtained by taking the limiting form of the equations of Stratton and Chu as the point of observation approaches the surface. In our integral equations the kernel is regular, and the point of observation may be taken anywhere inside, outside, or on the surface. The new method of solution of Maxwell's equations for boundary value problems independent of the time which we propose, is analogous to that which we proposed previously for the boundary value problem of Helmholtz's equation.
Electron–phonon interaction in P-, As-, and Sb-doped germanium in the intermediate concentration region
Authors: Radhakrishnan V. , Sharma P. C.
Published: October 2017

The electron–phonon scattering, in the analysis of low temperature thermal conductivity of n-type germanium, is studied in the intermediate donor concentration region. At low concentrations, below metal–insulator transition, the donor electrons are bound to the impurity atoms, and at high concentrations they are free in conduction band. The properties in the intermediate concentration are explained by Mikoshiba's "inhomogeneity model". According to this model, the electrons are in a mixed state both in non-metallic and metallic state. The electron concentrations in the non-metallic and metallic regions are calculated for each sample and the theory of both bound electron–phonon scattering and free electron–phonon scattering are applied. This theory of mixed electron–phonon scattering explains the thermal conductivity results of P-, As-, and Sb-doped germanium samples between 1 and 20 K for intermediate donor concentrations from 1.1 × 1017 to 5.6 × 1017 cm−3. The values of density-of-states effective mass are kept constant (= 0.22) without variation with temperature. The values of shear and dilatation-deformation potential constants are obtained from our calculations. The values of shear-deformation potential for the electrons in the bound region are found to be between 14 and 16 eV, while the values of dilatation-deformation potential are between 1 and 3.5 eV for the electrons in the conduction band and these values are in agreement with the experimentally measured values.
Les perturbations dans l'état B2Π de NS : interactions avec les états B′2Σ+, b4Σ− et a4Π
Authors: Jenouvrier A. , Pascat B.
Published: October 2017

The emission bands of the B2Π–X2Π transition of 14N32S and 15N32S have been reanalysed in the spectral range 2500–5650 Å. The B2Π state, observed up to ν = 12, shows strong perturbations caused by interactions with the b4Σ− and a4Π valence states and with the B′2Σ+ state. The study of the two molecules allows the vibrational numbering and gives approximate constants of the different states from the positions of the observed perturbations and the isotopic displacements.
Approximate solutions to the half-space integral transport equation near a plane boundary
Authors: Milgram Michael S.
Published: October 2017

A set of functions spanning the solution space of the integral transport equation near a boundary in semi-infinite plane geometry is obtained and used to reduce the problem to that of a system of linear algebraic equations. Expressions for the boundary angular flux are obtained by matrix multiplication, and the theory is extended to adjacent half-space problems by matching the angular flux at the boundary. Thus a unified theory is obtained for well-behaved arbitrary sources in semi-infinite plane geometry. Numerical results are given for both Milne's problem and the problem of constant production in adjacent half-spaces, and albedo problems in semi-infinite geometry. The solutions for the flux density are best near the boundary, and for the angular flux are best for angles near the plane of the boundary; it is conjectured that the theory will prove most useful when extended to arrays of finite slabs.
Precise atomic masses and mass differences for mercury
Authors: Kozier K. S. , Sharma K. S. , Barber R. C. , Barnard J. W. , Ellis R. J. , Derenchuk V. P. , Duckworth H. E.
Published: October 2017

The 1.00 m radius high resolution mass spectrometer at the University of Manitoba ("Manitoba II") has been used to determine both atomic masses and atomic mass differences for all the naturally occurring isotopes of Hg with a precision superior to existing values. The mass difference data are in excellent agreement with recently tabulated values, while the atomic masses themselves differ significantly.
Comments on "About the equivalence of Abraham's and Minkowski's electrodynamics"
Authors: Novak Miroslav M.
Published: October 2017

It is shown that a recent claim, regarding the Abraham–Minkowski problem, is doubtful and may be valid, at most, in the high frequency domain.
Temperature dependence of the electro-optic Kerr effect for liquids at 632.8 nm
Authors: Rujimethabhas M. , Crossley J.
Published: October 2017

Kerr constants have been measured at 632.8 nm for the non-polar liquids benzene, p-xylene, and mesitylene and the polar liquids chlorobenzene and toluene from just above their freezing points up to room temperature. The temperature dependence of the molar Kerr constants, mK, have been determined for all of the liquids. For the non-polar liquids, the second molecular hyperpolarizability could be obtained from the linear plots of mK against T−1. Such plots for the polar liquids are non-linear but curves have a similar shape.
Observation of new lines in the microwave spectrum of ortho-H2 pairs in solid hydrogen
Authors: Statt B. W. , Hardy W. N. , Jochemsen R.
Published: October 2017

New microwave absorption spectra of ortho pairs in low ortho concentration samples of solid hydrogen are reported. Three excited state transitions which fix the position of the 10 Γ level for both types of nearest neighbour pairs are reported, and compared with the theoretical predictions of Harris, Berlinsky, and Hardy and Luryi and Van Kranendonk. Several new lines from the out-of-plane configuration are reported which confirm previous assignments. In contrast, two new lines from the next nearest neighbour spectrum support a reassignment of transitions for this configuration. A fit to this data determines several of the anisotropic potential parameters for next nearest neighbours. The improvements in the microwave spectrometer essential to obtaining the new results are also described. Finally, we compare our results to the most recent theoretical potential parameters of Schaefer and Meyer. A long standing discrepancy between theoretical and experimental values for the phonon renormalizationof Γ appears to be resolved by use of the new potential which has a substantial (~10%) non-quadrupolar contribution to ε4(R).
Line broadening mechanisms of the ortho-H2 pair spectrum
Authors: Statt B. W. , Hardy W. N.
Published: October 2017

Three broadening mechanisms for the ortho pair spectrum in solid hydrogen are investigated. First, theoretical predictions of the phonon induced lifetime broadening are presented. Next a theory is developed which gives the inhomogeneous broadening due to the presence of ortho molecules surrounding the pairs. An unexpected result is that certain lines remain unbroadened, at least to within the approximations made. Strain effects due to isotopic mass defect impurities are also considered. These predictions are then compared with experimental results. No temperature dependence of the lineshapes is observed, setting an upper limit on the phonon broadening contribution to the linewidth. This limit is an order of magnitude lower than the theory predicts. The predictions of the ortho broadening theory, on the other hand, are in good agreement with experiment. Samples doped with isotopic impurities are also investigated.
Microwave absorption by ortho-H2 pairs in solid hydrogen: temperature and density dependence of the frequencies
Authors: Jochemsen R. , Statt B. W. , Hardy W. N.
Published: October 2017

The energy levels of an ortho-hydrogen pair in solid para-hydrogen are mainly determined by the electric quadrupole–quadrupole interaction between the ortho molecules which has an R−5 dependence. The frequencies of the observed absorption lines should therefore shift as a function of temperature due to thermal expansion. The experimental result for this shift, however, is a factor of 2 to 3 larger than that expected from thermal expansion calculated from specific heat data. We have also pressurized the sample at constant temperature with helium gas up to ≈0.4 bar, and obtained a confirmation of the R−5 dependence.
An isospin-mixed triplet in 44Ti
Authors: Dixon W. R. , Storey R. S. , Simpson J. J.
Published: October 2017

Three levels in 44Ti at energies of 9215 ± 2, 9227 ± 2, and 9239 ± 2 keV have been studied in the 40Ca(α,γ) reaction. Gamma-ray branching ratios, angular distributions, and transition strengths have been measured for each level. Proton decay strengths have also been determined. Each level is assigned Jπ = 2+. The level at 9227 keV must be predominantly T = 1 because of its strong M1 decays, while the other two levels are believed to be predominantly T = 0 because of their stronger E2 transitions to the ground state. Treating the three levels as an isospin-mixed triplet gives a consistent interpretation for all the experimental data, and allows quantitative estimates to be made of the amount of isospin mixing and of the magnitude of the isovector matrix elements.
A bag model derivation from the principle of gauge invariance
Authors: Ragiadakos Christos
Published: October 2017

From a direct generalization of the Lagrangians of gauge theories we derive the MIT bag model Lagrangian. An additional free quark sector is derived which may disappear after the proper quantization of the bag Lagrangian. When the gauge symmetry is spontaneously broken via a Higgs mechanism, we show that the fields can be liberated. The realistic [Formula: see text] gauge model (Weinberg–Salam model with chromodynamics) is explicitly studied.
Electron–phonon coupling constant and critical temperature of binary and ternary superconducting alloys of V, Nb, Mo, and Ta
Authors: Chatterjee Parsathi
Published: October 2017

A modified version of the theory of Gaspari and Gyorffy for calculating the electron–phonon coupling constant, λ, for binary substitutional alloys has been used in conjunction with McMillan's expression as modified by Dynes for the superconducting transition temperature, Tc, to obtain λ and Tc for the substitutional alloys NbTa, NbV, VMo, VTa, and TaMo. The theory has been further extended via the Average T-matrix Approximation to calculate λ and Tc for the ternary alloy, NbTaMo, having the same body-centered cubic structure as its components. The calculations of λ are based on self-consistent APW or KRR band structure data for the transition elements V, Nb, Mo, and Ta, obtained by using either Xα or the Hedin–Lundqvist version of the [Formula: see text] exchange approximation to calculate the potentials. The results thus obtained at different concentrations agree favourably with experiments for NbTa, NbV, VMo, and VTa. For TaMo and NbTaMo, for which experimental data on Tc are not yet available, we predict that they are fairly good superconductors.
Ondes électromagnétiques de surface : application à la spectroscopie Raman
Authors: Levy Yves
Published: October 2017

We describe the properties of the surface electromagnetic modes which occur in a wave-like manner, along the interface separating two dielectric semi-infinite media. We recall the different methods for using the surface waves as probes of surfaces and interfaces. We show how the surface waves can be used in ultra-thin film Raman spectroscopy.
Channeling measurements of interstitial trapping in Al – 0.07 at% Cr crystals
Authors: Swanson M. L. , Howe L. M. , Quenneville A. F. , Dimitrov C.
Published: October 2017

The channneling method has been used to study the trapping of Al self-interstitials by Cr atoms in an Al – 0.07 at% Cr crystal. Al–Cr [Formula: see text] mixed dumbbell interstitials were created by this trapping during irradiation with 1 MeV He+ ions at 50 or 70 K. The mixed dumbbell configuration was stable up to 200 K. No evidence could be obtained for a change in this trapping configuration between 50 and 70 K.
Comments on "The Abraham force: comments on two recent experiments"
Authors: Graham G. M. , Lahoz D. G.
Published: October 2017

Lorrain's criticisms of our recent report are rejected. A trivial mathematical error in his analysis of our "μ-factor" experiment is pointed out which invalidates his argument.
A deuterium nuclear magnetic resonance study of chain disorder in lamellar potassium palmitate: the effect of long and short chain guests
Authors: Beckmann P. A. , Burnell E. E. , Heldman M. A. , Northey K. R. , Higgs T. P.
Published: October 2017

The deuterium magnetic resonance spectra of lamellar phases of host perdeuterated potassium palmitate mixed with varying amounts of guest protiated potassium octanoate and behenate and 86.3 mol% D2O are reported. At higher temperatures, the short chain guests give rise to more fluidity and the long chain guests give rise to less fluidity towards the end of the host chain. At low temperatures there are changes in the interaction between the polar head group and the water which depend on sample composition. The transition from the lamellar phase to the low temperature gel phase is investigated and in some cases the gel phase is found to be a complicated many-phase region, at least for the water. The spectral results are presented in detail but compact and empirical methods of analysis are also investigated.
Giant dipole resonance in 4He
Authors: Bevelacqua J. J.
Published: October 2017

The 4He giant dipole resonance is calculated with the generalized R-matrix method of Lane and Robson. The model treats the center of mass correctly and includes noncentral components in the nucleon–nucleon interaction via the Sussex interaction. The 4He(γ,p)3H and 4He(γ,n)3He cross sections are sensitive to the 4He level spectrum, but are in reasonable agreement with the photonuclear data for level schemes which agree with the spectrum suggested by Fiarman and Meyerhof (FM). Other spectra which bracket the FM levels lead to poorer photonuclear cross sections. R-matrix model results also lead to a (γ,p)/(γ,n) cross section ratio which is about unity.