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Siegert and Weijer presented evidence indicating the existence of spiral waves of cell migration induced by cyclic adenosine monophosphate (cAMP) in hemispherical aggregates (mounds) of Dictyostelium cells [Current Biol. 5, 937 (1995)]. Here I report experimental evidence of the eccentric motion of the spiral core in single mounds of the wild-type strain NC-4. I observed two types of motion of the spiral core. One type is a core shift, in which a spiral core initially situated at the center of a circular mound moves toward the circular boundary of the mound. Another type is a continuous drift of a spiral core along the circular boundary. To obtain some insights into the mechanism of the motion of the spiral cores, I perform a numerical simulation of spiral waves in two-dimensional excitable media with a circular boundary.

Novel second harmonic generation (SHG) was observed from the crystalline powder of the ion-pair charge-transfer (CT) complexes consisting of 1-methyl-4-(4-nitrostyryl)pyridinium as an acceptor and tetraphenylborate as a donor. The second harmonic light intensity dramatically decreased upon excitation of a CT band due to the photoinduced electron transfer from tetraphenylborate to styrylpyridinium moiety. These results strongly suggested that the CT transition in the ion-pair complexes would cause SHG. The crystalline structure of an ion-pair CT complex of 1-methyl-4-(4-cyanostyryl)pyridinium tetraphenylborate which also exhibited strong SHG was investigated to elucidate the mechanism of the SHG in the ion-pair CT complex system.

We present a model of limit cycle oscillators for collective oscillations in intracellular calcium concentration in cell communities. A phase-dependent discrete coupling between nearest neighbors is introduced into the model on the basis of the experimental observation that intercellular transmission of calcium or calcium mobilizing messenger is effected by gap junction and gap junctional permeability is affected by intracellular calcium concentration. The spatial phase pattern of several clusters in which oscillations are in phase is found with the phase-dependent discrete coupling.

C 13 H 20 O 5 cristallise dans P1 avec a=7,535, b=9,472, c=10,927 A, α=104,631, β=103,430, γ=109,130°, Z=2; affinement jusqu'a R=0,045. La structure cristalline a une conformation symetrique C 1 comme une «selle»: l'angle d'intersection entre les 2 liaisons doubles est de 148,3° et l'atome oxygene du carbonyl est en dehors des 2 plans des liaisons doubles

C7H5C102, Mr = 156.6, monoclinic, P21/c, a = 8.476 (2), b = 12.241 (2), c = 8.170 (2) A, /3 -- 126.47 °, V= 681.7 A 3, z = 4, Dx = 1.525 g cm -3, A(Cu Ka) = 1.54184 A, /z = 44.63 cm-~, F(000) = 320, T = 293 K, R -- 0.046 for 833 reflections with I > 3tr(I). The hydroxylic proton forms a bifurcated hydrogen bond with carbonyl O atoms, one branch intramolecular and the other intermolecular. The latter intermolecular branches form a hydrogen- bonded dimer, which is roughly planar. Introduction. The structures of tropolone and some tropolone derivatives have been studied. It has been shown that 5,isopropyltropolone (Berg, Karlasson, (P~.tti & Wiehager, 1976) as well as tropolone manouchi & Sasada, 1973) forms a bifurcated hydrogen bond with the carbonyl O atoms, one branch being intramolecular and other intermolecu- lar. On the other hand, 4-isopropyltropone does not form a dimer, but O...O hydrogen bonds of 2.8 A link the molecules in a chain (Derry & Hamor, 1972). Very recently, we have measured the electronic spectra of the isolated 3-chlorotropolone (Tsuji, Sekiya, Nishimura, Mori & Takeshita, 1991) and 3-bromotropolone (Sekiya, Sasaki, Nishimura, Mori & Takeshita, 1990). The observation of tunnel splitting provides conclusive evidence for the de- localization of the proton. We have found that the hydroxylic proton is delocalized in 3-chlorotro- polone, whereas the proton is localized in 3- bromotropolone. It has been suggested that the localization of the hydroxylic proton strongly depends on the planarity of the molecule. In order to examine the effect of the substitution of a C1 atom on the molecular and crystal structure, an X-ray

25,27-Bis(ethoxycarbonylmethoxy)-26,28-bis(2-pyridylmethoxy)-5,11,17,23-tetra-tert-butylcalix[4]arene with a 1,3-alternate conformation (1,3-alternate-2) has been synthesized. Dynamic 1H NMR spectroscopy has established that the conformation is immobilized (i.e., the oxygen-through-the-annulus rotation is inhibited). The single crystal was grown from acetonitrile and analysed by X-ray crystallography. It was found that the structural characteristics of a 1,3-alternate conformation are (i) the four phenyl rings are more or less parallel to each other, the dihedral angles between the four phenyl rings and the mean plane of the four methylene groups being 93.5, 100.4, 101.4 and 106.1°, (ii) the ArCH2Ar bond angles are more expanded than those for other conformations and (iii) 1,3-alternate-2 in solution adopts C2 symmetry whereas in the solid state it is less symmetrical because of the unsymmetrical orientation of the ester and the pyridyl substituents. This is a rare example of the X-ray crystallographic analysis of 1,3-alternate calix[4]arenes.

The asymmetric 4a and symmetric conformers 4b of a trimethoxy[2.2.1]metacyclophane were isolated and the structures were established by 1H NMR spectroscopy and X-ray crystallography. The trihydroxy[2.2.1]-5 and dihydroxy(methoxy)[2.2.1]metacyclophane 6 were obtained by demethylation of isomers 4a and 4b, respectively. Treatment of compound 5 with ethyl bromoacetate afforded only the tris(ethoxycarbonylmethoxy)[2.2.1]metacyclophane 7. On the other hand the bis(ethoxycarbonylmethoxy)(methoxy)[2.2.1]-8 and ethoxycarbonylmethoxy(hydroxy)(methoxy)[2.2.1]metacyclophane 9 were obtained from compound 6. It was found that compounds 4a and 7 assume a ‘2,1-alternate’ conformation, whereas, on the other hand, compounds 4b, 6, 8 and 9 have a ‘2,2-alternate’ conformation. In the case of compound 5 both ‘2,1-alternate’ and ‘2,2-alternate’ conformers were detected by 1H NMR spectroscopy. The chiralities of compounds 4a and 9 were confirmed by their 1H NMR spectrum in the presence of Pirkle's reagent.

The structure of saponified product of Wittmann’s trimeric condensates of phenylmalonyl dichloride is revised from 4-hydroxy-3,6,7-triphenyl-p-tropoquinone to 5H-3,5,7-triphenylfuro[3,2-b]pyran-2,6-dione based on the chemical and X-ray crystallographic results.

Treatment of [{RhCl(CO)2}2] with 5 equivalents of PhCH2SCH2PPh2(btmp) gave the mononuclear Vaska-type complex trans-[RhCl(CO)(btmp-P)2], whereas the reaction with 2 equivalents of btmp afforded not the expected face-to-face complex [Rh2Cl2(CO)2(µ-btmp)2] but the chloro-bridged complex [Rh2(µ-Cl)(CO)2(µ-btmp)2][RhCl2(CO)2]. The tetraphenylborate salt analogue [Rh2(µ-Cl)(CO)2(µ-btmp)2]BPh4 was obtained from the reaction of an ethanolic solution of [RhCl2(CO)2]– with 1 equivalent of btmp and NaBPh4. Treatment of [NBun4][RhCl2(CO)2] with 1 equivalent of btmp afforded the carbonyl-bridged dinuclear complex [Rh2Cl2(µ-CO)(µ-btmp)2], while the above reaction performed in the presence of hydrochloric acid gave the novel dinuclear rhodium(II) complex [Rh2Cl4(CO)2(µ-btmp)2](5). Complex (5) was also obtained from the reaction of an ethanolic solution of [RhCl2(CO)2]–and 1 equivalent of btmp. Crystals of (5) are monoclinic, space group C2/c, with a= 14.064(3), b= 19.364(4), c= 16.930(5)A, β= 116.67(2)°, and Z= 4; final R= 0.036 for 3 529 observed reflections. The structure shows that there is a metal–metal bond [Rh–Rh 2.733(3)A] and the two µ-btmp ligands are co-ordinated to rhodium atoms cis to each other with a head-to-tail arrangement. The relationships among the synthesized complexes are discussed.

金沢大学大学教育開発・支援センター, Spatiotemporal patterns of chemical wave propagation in the assemblies of nine cation-exchange beads loaded with the catalyst ferroin of Belousov-Zhabotinsky reaction are reported. The beads are immersed in the reaction mixture, on which periodic chemical waves are emerged. In the bead assemblies, abrupt changes of initiation site and direction of the periodic chemical waves were observed. In some cases, it was observed that transient oscillation cessations and the following rotating spiral wave occur. © 1997 American Institute of Physics.

Finding the means to efficiently summarize electroencephalographic data has been a long-standing problem in electrophysiology. A popular approach is identification of component modes on the basis of the time-varying spectrum of multichannel EEG recordings—in other words, a space/frequency/time atomic decomposition of the time-varying EEG spectrum. Previous work has been limited to only two of these dimensions. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) have been used to create space/time decompositions; suffering an inherent lack of uniqueness that is overcome only by imposing constraints of orthogonality or independence of atoms. Conventional frequency/time decompositions ignore the spatial aspects of the EEG. Framing of the data being as a three-way array indexed by channel, frequency, and time allows the application of a unique decomposition that is known as Parallel Factor Analysis (PARAFAC). Each atom is the tri-linear decomposition into a spatial, spectral, and temporal signature. We applied this decomposition to the EEG recordings of five subjects during the resting state and during mental arithmetic. Common to all subjects were two atoms with spectral signatures whose peaks were in the theta and alpha range. These signatures were modulated by physiological state, increasing during the resting stage for alpha and during mental arithmetic for theta. Furthermore, we describe a new method (Source Spectra Imaging or SSI) to estimate the location of electric current sources from the EEG spectrum. The topography of the theta atom is frontal and the maximum of the corresponding SSI solution is in the anterior frontal cortex. The topography of the alpha atom is occipital with maximum of the SSI solution in the visual cortex. We show that the proposed decomposition can be used to search for activity with a given spectral and topographic profile in new recordings, and that the method may be useful for artifact recognition and removal.

C7H5C102, Mr = 156.6, monoclinic, P21/c, a = 8.476 (2), b = 12.241 (2), c = 8.170 (2) A, /3 -- 126.47 °, V= 681.7 A 3, z = 4, Dx = 1.525 g cm -3, A(Cu Ka) = 1.54184 A, /z = 44.63 cm-~, F(000) = 320, T = 293 K, R -- 0.046 for 833 reflections with I > 3tr(I). The hydroxylic proton forms a bifurcated hydrogen bond with carbonyl O atoms, one branch intramolecular and the other intermolecular. The latter intermolecular branches form a hydrogen- bonded dimer, which is roughly planar. Introduction. The structures of tropolone and some tropolone derivatives have been studied. It has been shown that 5,isopropyltropolone (Berg, Karlasson, (P~.tti & Wiehager, 1976) as well as tropolone manouchi & Sasada, 1973) forms a bifurcated hydrogen bond with the carbonyl O atoms, one branch being intramolecular and other intermolecu- lar. On the other hand, 4-isopropyltropone does not form a dimer, but O...O hydrogen bonds of 2.8 A link the molecules in a chain (Derry & Hamor, 1972). Very recently, we have measured the electronic spectra of the isolated 3-chlorotropolone (Tsuji, Sekiya, Nishimura, Mori & Takeshita, 1991) and 3-bromotropolone (Sekiya, Sasaki, Nishimura, Mori & Takeshita, 1990). The observation of tunnel splitting provides conclusive evidence for the de- localization of the proton. We have found that the hydroxylic proton is delocalized in 3-chlorotro- polone, whereas the proton is localized in 3- bromotropolone. It has been suggested that the localization of the hydroxylic proton strongly depends on the planarity of the molecule. In order to examine the effect of the substitution of a C1 atom on the molecular and crystal structure, an X-ray

C 13 H 20 O 5 cristallise dans P1 avec a=7,535, b=9,472, c=10,927 A, α=104,631, β=103,430, γ=109,130°, Z=2; affinement jusqu'a R=0,045. La structure cristalline a une conformation symetrique C 1 comme une «selle»: l'angle d'intersection entre les 2 liaisons doubles est de 148,3° et l'atome oxygene du carbonyl est en dehors des 2 plans des liaisons doubles

A new experimental system of coupled chemical oscillators is presented. Three cation‐exchange beads loaded with ferroin are spatially distributed in triangular forms and immersed in the Belousov–Zabotinsky reaction mixture. The cation‐exchange beads were in no contact with each other. The cation‐exchange bead was used as a chemical oscillator. Spontaneous switching between two out‐of‐phase oscillation was observed.

25,27-Bis(ethoxycarbonylmethoxy)-26,28-bis(2-pyridylmethoxy)-5,11,17,23-tetra-tert-butylcalix[4]arene with a 1,3-alternate conformation (1,3-alternate-2) has been synthesized. Dynamic 1H NMR spectroscopy has established that the conformation is immobilized (i.e., the oxygen-through-the-annulus rotation is inhibited). The single crystal was grown from acetonitrile and analysed by X-ray crystallography. It was found that the structural characteristics of a 1,3-alternate conformation are (i) the four phenyl rings are more or less parallel to each other, the dihedral angles between the four phenyl rings and the mean plane of the four methylene groups being 93.5, 100.4, 101.4 and 106.1°, (ii) the ArCH2Ar bond angles are more expanded than those for other conformations and (iii) 1,3-alternate-2 in solution adopts C2 symmetry whereas in the solid state it is less symmetrical because of the unsymmetrical orientation of the ester and the pyridyl substituents. This is a rare example of the X-ray crystallographic analysis of 1,3-alternate calix[4]arenes.

The asymmetric 4a and symmetric conformers 4b of a trimethoxy[2.2.1]metacyclophane were isolated and the structures were established by 1H NMR spectroscopy and X-ray crystallography. The trihydroxy[2.2.1]-5 and dihydroxy(methoxy)[2.2.1]metacyclophane 6 were obtained by demethylation of isomers 4a and 4b, respectively. Treatment of compound 5 with ethyl bromoacetate afforded only the tris(ethoxycarbonylmethoxy)[2.2.1]metacyclophane 7. On the other hand the bis(ethoxycarbonylmethoxy)(methoxy)[2.2.1]-8 and ethoxycarbonylmethoxy(hydroxy)(methoxy)[2.2.1]metacyclophane 9 were obtained from compound 6. It was found that compounds 4a and 7 assume a ‘2,1-alternate’ conformation, whereas, on the other hand, compounds 4b, 6, 8 and 9 have a ‘2,2-alternate’ conformation. In the case of compound 5 both ‘2,1-alternate’ and ‘2,2-alternate’ conformers were detected by 1H NMR spectroscopy. The chiralities of compounds 4a and 9 were confirmed by their 1H NMR spectrum in the presence of Pirkle's reagent.

Two conformers, (5A) and (5B), of trimethoxy[2.2.1]metacyclophane have been separated and characterized by 1H NMR spectroscopy, X-ray crystallography, and demethylation.

The Ar(3P2,0)+NH3 reaction has been studied by optical emission spectroscopy. Experiments have been performed by using a flowing afterglow apparatus and a new low‐pressure apparatus. In the latter experiment the Ar(3P2,0) atoms generated by a microwave discharge were expanded into a high vacuum chamber through an orifice. Essentially the same results have been obtained from the two experimental systems. The NH(c 1Π–a 1Δ) emission as well as the NH(A 3Π–X 3∑−) emission was observed. The emission intensity ratio INH(c)/INH(A) was measured to be 0.31±0.03. The vibrational population ratio P(v’=1)/P(v’=0) for the NH(A 3Π) state was determined to be 0.35±0.05, while the effective rotational temperatures for the NH(A 3Π,v’=0) and NH(c 1Π,v’=0) states were estimated to be 2000±300 K and 1050±70 K, respectively. The observed vibrational and rotational distributions of the NH(A 3Π) state and the rotational distribution of the NH(c 1Π) state were much colder than those predicted from a simple statistical theory. Th...

Three-dimensional quasiclassical trajectory calculations have been performed for the C( 3 P) + HI/DI→CH (X 2 Π)/CD (X 2 Π) + I reactions by using LEPS potential energy surfaces. The experimental vibrational distribution of the product CH has been compared with the calculated one. It has been qualitatively suggested that the potential energy surface for the C + HI reaction is highly attractive, and that the smaller product vibrational energy disposal, 〈ƒ ν 〉, relative to those of the reactions of Cl, F, and O with HI is due to secondary encounters on its surface. This conclusion has been also supported by the calculated isotope effect on the product vibrational energy disposal for the C + HI/DI reactions.

The vibrational and rotational energy disposal for ND(A) from the CD + NO reaction was measured in a flowing afterglow. The initial vibrational and rotational distributions of ND(A) were obtained from a spectral simulation. The initial vibrational distribution was (0.51 ± 0.05) ν′ = 0 : (0.26 ± 0.05) ν′ = 1 : (0.16 ± 0.05) ν′ = 2 : (0.07 ± 0.05) ν′ = 3 . The rotational temperatures in ν′ = 0, 1, 2 and 3 levels were 4500 ± 500, 4000 ± 500, 4000 ± 500 and 4000 ± 500 K, respectively. The fractions of the available energy deposited into the vibration, 〈 f v 〉 and rotation, 〈 f R 〉, were 0.21 and 0.36, respectively. The results for ND(A) were compared with those for NH(A) from the CH + NO reaction reported previously and the reaction dynamics was discussed on the basis of the observed isotope effect on the energy state distributions. The kinetic isotope effect k H / k D in the CH, CD + NO reactions was measured to be 1.84 ± 0.23. The experimental result was compared with a theoretical calculation using transition-state theory.

Thermal energy reactions of C+(2P) and C(1D,1S) with CH3OH, C2H5OH, n-C3H7OH and i-C3H7OH to give CH(X2Π) radicals have been investigated by observing laser-induced fluorescence (LIF) spectra of CH(A—X) in a flowing afterglow. In the hydride ion abstraction by C+(2P), only CH3OH exhibited the CH(A—X) LIF spectrum with a vibrational distribution of 1.0 : 0.62 for v″ = 0 and 1, respectively. On the other hand, the CH(A—X) LIF spectra exclusively from v″ = 0 were observed in the reactions of C(1D,1S) with all alcohols studied. By isotopic substitution for CH3OH it was shown that the CH(X) radicals arise from the selective attack on the methyl site in the reactions of C+(2P) and C(1D,1S) with methanol.

Vibrational distributions of CH(X/sup 2/)PI) radicals produced from ion-molecule reactions between C/sup +/(/sup 2/P) ions and ethylene, ethane, propylene, and propane have been studied in a flowing afterglow by a laser-induced fluorescence. The initial vibrational population ratios of CH(X:nu'' = 1/nu'' = 0) were similar (0.54-0.60) for all reactions. They were compared with statistical prior distributions for the three-body model in which polyatomic product ions were treated as atomic ions.

The CH(X/sup 2/PI,nu''=0) radicals were prepared from the C(/sup 1/D) + H/sub 2/ reaction by using a flowing afterglow apparatus. Strong NH(A/sup 3/PI-X/sup 3/..sigma../sup -/) chemiluminescence was observed from the reaction CH(X/sup 2/PI,nu''=0) + NO ..-->.. NH(A/sup 3/PI,nu''=0,1) + CO. The vibrational and rotational distributions of NH(A) are more excited than the prior ones, suggesting that the reaction proceeds via a direct four-center mechanism. 24 references, 3 figures, 1 table.

Vertical arrangement of the alkyl side arm in the crystal structure of KSCN complex of N-heptylmonoaza-18-crown-6 is well-consonant with the effective side-arm participation in N-pivot lariat ether complexes and supports the lack of ‘biscrown effect’ for bis(monoaza-18-crown-6)s.

Upon UV-light irradiation with a high-pressure mercury lamp, methyl 2,4-dioxopentanoate in a mixture of benzene and cyclohexane afforded a crystalline head-to-head[2+2]cyclodimer. Its structure was elucidated by a single-crystal X-ray analysis, as well as 1H and 13C NMR spectroscopy. Ethyl 2,4-dioxopentanoate also gave a cyclodimer.