Showing papers by "Waseda University published in 1979"

Raman spectra of polypeptides containing L‐histidine residues and tautomerism of imidazole side chain

Abstract: Raman spectra were measured for poly(L-histidine) in H2O, poly(L-histidine-d2 and -d3) in D2O, L-histidine in H2O, L-histidine-d3 (and d4) in D2O, and 4-methylimidazole in H2O with various pH (or pD) values. The Raman scattering peaks observed for these samples were ascribed to the neutral and positively charged imidazole groups on the basis of the spectral changes due to the pH variation and to the deuterium substitution of the imino protons. The vibrational modes of these peaks were deduced from the normal coordinate analysis made on the positively charged and neutral 4-ethylimidazoles. The Raman scattering peaks from the imidazole groups in the neutral form clearly indicate that these imidazole groups exist in the equilibrium between the two tautomeric forms, the 1-N protonated from (tautomer I) and the 3-N protonated one (tautomer II). For example, the breathing vibration of the 1-N protonated form is observed at 1282 cm−1 for L-histidine and at 1304 cm−1 for 4-methylimidazole, while the breathing vibration of the 3-N protonated form is observed at 1260 cm−1 for L-histidine and 4-methylimidazole. From the temperature dependence of the relative intensities of the tautomer I peak to that of the tautomer II, it was concluded that the tautomer I is energetically more stable than the tautomer II, and the ΔH value is 1.0 ± 0.3 kcal/mol for L-histidine and 0.4 ± 0.1 kcal/mol for 4-methylimidazole. Poly(L-histidine) with the neutral imidazole side chains shows the amide I peak at 1672 cm−1, indicating that the sample assumes the antiparallel pleated-sheet structure. Poly(L-Ala75L-His25) and poly(L-Ala50L-His50) were found to take the α-helical and β-form conformations, respectively.

Ratio of diffusion coefficient to mobility for electrons in liquid argon

Abstract: The ratio of the diffusion coefficient $D$ to the mobility $\ensuremath{\mu}$ for electrons has been measured in liquid argon by using a modified Townsend apparatus. The measured ratio $\frac{\mathrm{eD}}{\ensuremath{\mu}}$ monotonically increases from \ensuremath{\sim}0.1 to \ensuremath{\sim}0.4 eV with an increase in the electric field from \ensuremath{\sim}2 to \ensuremath{\sim}10 kV/cm. The ratio $\frac{\mathrm{eD}}{\ensuremath{\mu}}$ is smaller than that in gaseous argon at the same value of $\frac{E}{N}$, where $N$ is the atomic density. The mean momentum-transfer cross section $〈\ensuremath{\sigma}〉$ is estimated as a function of $〈\ensuremath{\epsilon}〉$ on the assumption $〈\ensuremath{\epsilon}〉=\frac{3eD}{2\ensuremath{\mu}}$, where $〈\ensuremath{\epsilon}〉$ is the mean electron agitation energy. Thus the $〈\ensuremath{\sigma}〉$ obtained is nearly constant (3\ensuremath{\sim}4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$) for $〈\ensuremath{\epsilon}〉$ from 0.15 to 0.6 eV. This value of $〈\ensuremath{\sigma}〉$ is almost the same as that estimated from the low-field mobility of electrons in liquid argon. This result is consistent with both Derenzo's experiment and Lekner's theory. It is concluded that there is no Ramsauer minimum at about 0.4 eV of $〈\ensuremath{\epsilon}〉$, where the minimum exists in gaseous argon.

Skipping motion of the surface scattering of ion beams

Abstract: We propose a new motion of the ion near the surface of a solid due to the surface potential of the dynamical polarization of the valence-electron cloud induced by the moving ion itself Under some appropriate conditions the outgoing ions are forced to be drawn once again to the surface by this potential and go through with skipping motions Computer simulation shows that a large number of ions are trapped in the skipping motions

An Improved Method Fòr Extraction, Partial Purification, Separation and Isolation of Chlorophyll from Spinach Leaves

Abstract: Powdered sugar column chromatographic separation and isolation of chlorophyll were studied. A wet column was employed using a Pharmacia R25 chromatographic tube connected, through a UV monitor, to a fraction collector. Chlorophyll extracted from spinach leaves with acetone was selectively precipitated with dioxane and water, and then was washed with 80% (v/v) aqueous methanol. Use of the further purified chlorophyll as a starting material for chromatographic separation and isolation of chlorophyll, made column chromatographic procedures become extremely effective and easier. Thin-layer chromatographic and high-performance liquid chromatographic tests revealed that chlorophyll preparations in this study did not contain any other photosynthetic pigments and their degradation products.

Magnetoelectric Effect of Fe 3 O 4 at 77 K. I. Crystal Symmetry

Abstract: Magnetoelectric effect of the low temperature phase of magnetite was measured at 77 K. It was confirmed that the magnetic crystal symmetry at 77 K is triclinic but the breaking of the mirror symmetry parallel to the (1\bar10) plane is very small. Dispersion of the magnetoelectric effect was observed with the relaxation time of approximately 2 µs. Magnitude of magnetoelectric susceptibility depends on the direction of the applied electric field. Both phenomena were attributed to the dispersion and the anisotropy of the electric susceptibility. The structure of the low temperature phase was discussed briefly in connection with the model proposed by Mizoguchi (J. Phys. Soc. Jpn. 44 (1978) 1512).

Phase Transition in Sr 2 Nb 2 O 7 at 215°C

Abstract: A new phase transition in Sr 2 Nb 2 O 7 was found at 215°C in addition to the already known phase transitions. The elastic compliance coefficients, the electromechanical coupling factor and the dielectric constant of an Sr 2 Nb 2 O 7 single crystal show anomaly around 215°C.

Hysteresis of Contraction‐Extension Cycle of Glycerinated Vorticella

Abstract: SYNOPSIS. The helical coiling state of a glycerinated stalk in the family Vorticellidae had been regarded, without any evidence, as a reversible and completely equilibrated mechano-chemical system regulated by the external free Ca2+ concentration. Our present detailed observations of many individual stalks of glycerinated Vorticella convallaria revealed that the contraction-extension cycle of the helical stalks caused by increasing and decreasing free Ca2+ concentrations in the medium represents a kind of hysteresis. This phenomenon was observed in extensively glycerinated Vorticella in a medium of very low or physiological ionic strength, as well as in briefly glycerinated ciliates. With regard to the configurational change in various parts of a glycerinated stalk during the contraction-extension cycle, it was found that the initial bending of the stalk caused by increasing free Ca2+ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca2+ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca2+ concentration takes place simultaneously throughout the entire stalk. The Ca2+ threshold for complete reextension of the part of the stalk near the rootlet was found to be much higher than that near the zooid.

Preparation of montmorillonite-nylon complexes and their thermal properties

Abstract: Montmorillonite-aminocaproic acid complexes (monomer complexes) were prepared by the intercalation of 6-aminocaproic acid to various homoionic (Na+, Ca2+, Mg2+, Co2+, and Cu2+) montmorillonites. Infrared spectra of the monomer complexes indicated that the interaction between the exchangeable cations and the 6-aminocaproic acid increased in the following order: Na-, Ca-, and Mg- < Co- < Cu-montmorillonite-aminocaproic acid complex. Montmorillonite-nylon complexes (polymer complexes) were prepared by thermal treatment of the monomer complexes, which was confirmed by X-ray powder diffraction and infrared spectroscopy the results of which indicated the condensation of 6-aminocaproic acid in the interlayer space. Thermal degradation of montmorillonite-nylon complexes was studied by thermogravimetry. It was found that the thermal stability of the polymer complexes increased in the following order: Cu- < Co- < Na- < Mg- < Ca-montmorillonite-nylon complex. It was suggested that the difference in thermal stability depended upon the length of the polymer chain which might be influenced by the interaction between the exchangeable cations and the 6-aminocaproic acid. The activation energy for the thermal degradation of each montmorillonite-nylon complex was obtained, and the value for Cu-montmorillonite-nylon complex was smaller than that for the other cation-exchanged montmorillonite-nylon complexes.

Heteroepitaxial InSb Films Grown by Molecular Beam Epitaxy

Abstract: Films of InSb are heteroepitaxially grown on GaAs substrates by MBE. In spite of a large lattice mismatch, single-crystalline films with a fairly flat surface are obtained. Experimental data on electrical properties of these films suggest that dislocation scattering represents a significant mobility limiting process above 230 K. From in-depth profiles of the electron concentration and mobility, it is found that the layer within about 1.5 μm from the interface is inferior in crystallinity. Les films de SbIn ont ete crǔs a la maniere heteroepitaxique sur le substratum de AsGa au moyen de MBE. Malgre la presence d'une grande discontinuite de reseau, les films monocristallins a la surface assez plate ont ete obtenus. Les donnees experimentales sur les proprietes electriques de ces films suggerent que la diffusion par dislocation represente le procede limitant une mobilite significative, superieur a 230 K. D'apres le profils a la profondeur de la concentration de electron et de la mobilite, il se trouve que la couche dans 1,5 μm environ a partir de l'interface est inferieure a la cristallinite.

Influence of thyroid hormone on the development of preoptic-hypothalamic monoaminergic neurons in tadpoles of Bufo bufo japonicus

Abstract: The effect of thyroid hormone on the development of diencephalic monoaminergic neurons was studied in tadpoles of Bufo bufo japonicus. Monoamine-containing neurons in the preoptic recess organ (PRO) appeared later than those in the paraventricular organ (PVO) and nucleus infundibularis dorsalis (NID). After deprivation of thyroidal primordium no fluorescent neurons developed in the PRO. Development of monoaminergic neurons in the PVO and NID was not affected by thyroidectomy. Thyroxine treatment brought about the fluorescent neurons in the PRO of the thyroidectomized tadpoles. Fluorescent terminals in the median eminence became conspicuous around the capillaries which penetrated to the median eminence, when the tadpoles reached late prometamorphic stage. In the median eminence of thyroidectomized tadpoles, the monoaminergic axon terminals did not develop. Thyroxine induced both the fluorescent terminals and the capillary penetration in the median eminence of the thyroidectomized tadpoles. In the tadpoles hypophysectomized at tail-bud stage, thyroxine induced neither the fluorescent terminals nor the capillaries in the median eminence.

Elastic Pion-Deuteron Scattering and Dibaryon Resonances

Abstract: We show that effects of dibaryon resonances can be clearly seen in the data on the differential cross section of red elastic scattering. Giving the formulation of the Glauber model with the resonance formation term in red direct channel in detail and analyzing all the data presently available by this model, we find that at least two resonances are needed in red direct channel in order to explain the data. One of them may be 'F, (2. 25 GeV) state of two nucleons which was found at Argonne and the other has mass value around ~.5GeV. The data are not enough to determine the spin-parity of the latter but ()' seems somewhat preferable. The branching ratios of the resonances into red system are also given.

Magnetoelectric Effect of Fe 3 O 4 at 77 K. II. Electric Field Dependence of Magnetic Anisotropy

Abstract: Anisotropy and external magnetic field dependence of the magnetoelectric effect in Fe 3 O 4 was measured at 77 K and analysed. It was concluded that a tilting of the magnetization due to a change in the magnetic anisotropy, by the application of the electric field, is a dominant mechanism, though a possibility of a non-tilting mechanism was not excluded. The main part of the magnetic anisotropy accompanied by electric polarization, which has mirror symmetry parallel to the b plane, was analysed by spherical harmonics up to the fourth order and eight constants were determined. This polarization dependent part was much smaller than the total magnetic anisotropy energy. Direction of the spontaneous electric polarization was estimated as -15° from [111] or +19° from [11\bar2] within the b plane.

A neural network model for the development of direction selectivity in the visual cortex

Abstract: A neural network model is proposed to explain the development of direction selectivity of cortical cells. The model is constructed under the following three hypotheses that are very plausible from recent neurophysiological findings. (1) Direction selectivity is developed by modifiable inhibitory synapses. (2) It results not from the direct convergence of many excitatory inputs from LGN cells but from cortical neural networks. (3) Direction-selective mechanism is independent of orientation-selective mechanism.--The model was simulated on a computer for a few kinds of inhibitory connections and initial conditions. The results were consistent with neurophysiological facts not only for normal cats but for cats reared in an abnormal visual environment.

Electrogyration of a Nonenantiomorphic Crystal, Ferroelectric K H 2 P O 4

Abstract: Temperature dependence of the quadratic electrogyration coefficient ${\ensuremath{\pi}}_{13}$ of a nonenantimorphic crystal, ferroelectric K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$, was successfully measured by using our general method. ${\ensuremath{\pi}}_{13}$ exhibits an unusual temperature dependence near the transition point. This behavior is primarily similar to that of the electrostrictive coefficient ${Q}_{13}$ of K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$. But it reveals the electronic contribution which must be of special interest for elucidating the transition mechanism of the crystal.

Birefringence of CaCO3 and Electronic Polarizabilities of the Constituent Ions

Abstract: The birefringence of CaCO 3 is discussed taking account of dipole interaction among the Ca ++ and CO 3 - -ions. The electronic rolarizabilities of the CO 3 - -ions are obtained as α 1 =3.18 ×10 -24 cm 3 and α 2 =4.20 ×10 -24 cm 3 in the direction parallel and perpendicular to the optical axes respectively for n e =1.486 and n 0 =1.658. The bond polarizabilities of C-O can be obtained as α // =1.74 ×10 -24 cm 3 and α ⊥ = 1.06 ×10 -24 cm 3 in the directions parallel and perpendicular to the direction of the line connecting C and O respectively with anisotropic ratio α // /α ⊥ =1.64.

Theory of Formamide and Its Related Compounds by INDO-CI Method

Abstract: To calculate the optical absorption of formamide and its related compounds, the INDO method for valence-shell electrons is extended to include the change in valence-state electron configurations. All the molecular integrals are parametrized as functions of electron densities. The singlet states of those amides are then determined with a due account of CI, including all the singly-excited and the simultaneous doubly-excited configurations. It is thus shown for formamide that the lowest four transitions can be assigned as n -π * , NV 1 , n '-π * and NV 2 , and that the calculated absorption agrees with the observation. It is also shown from the calculation on related compounds that the methyl substitution of hydrogen atom(s) exerts a considerable influence on NV 1 - and NV 2 -transition, and that the calculated directions of NV 1 -transition moment are in a satisfactory agreement with the observed ones.