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Creator | Title | Description | Subject | Date |
| 226 |
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Mattis, Daniel C. | Eigenstates of N excitons and one hole | We solve for the eigenstates and energy eigenvalues of N immobile Frenkel excitons (a relatively trivial proposition) and of N such excitons plus one hole (which for large N can only be done in one dimension). We also guess that a charged globule, consisting of N excitons and O(N) holes, can be stab... | Eigenstates; Frenkel excitons; Many-body problem | 1983-04 |
| 227 |
 |
Vardeny, Zeev Valentine | Photogenerated gap states in polyacetylene | We have measured the optical absorption spectrum of photogenerated gap states in polyacetylene, (CH)X . From a comparison with electroabsorption spectra the charge state of the excitations is determined. In both isomers of (CH)X locally neutral (exciton-like) states are observed. In addition a charg... | Gap state; Photoexcitation | 1983-06 |
| 228 |
 |
Vardeny, Zeev Valentine | Photo induced infrared active phonons in trans polyacetylene | We measured photogenerated ir active phonons in trans-(CH) by the photoinduced absorption technique. A correlation was found to exist with a photoinduced absorption band in which electronic transitions are involved. Our results show photoproduction of free charged defects with long lifetimes. | Photoinduced phonons; Trans polyacetylene | 1983-06 |
| 229 |
 |
Vardeny, Zeev Valentine | Photoinduced infrared activity in polyacetylene | Photoexcitation of trans - but not cis -polyacetylene, results in the appearance of strongly-ir-active local modes at 1370 and 1260 cm-1. This observation demonstrates that the photogeneration of self-localized charge carriers is unique to the trans isomer. In spite of their localization the kineti... | Photoinduced infrared activity; Photoexcitation | 1983-06 |
| 230 |
 |
Vardeny, Zeev Valentine | Picosecond photoinduced optical anisotropy in trans-(CH)x : direct measurement of soliton diffusion | Photoinduced dichroism caused by bleaching of the interband transition in trans - (CH)X was observed in the picosecond time domain. The bleaching is induced instantaneously and decays with time as t - 1 / 2 , changing to a lower power after ~ 50 ps. Although the photoinduced bleaching persists to l... | Trans-(CH)x; Soliton diffusion; Bleaching; Photoinduced dichroism | 1983-06 |
| 231 |
 |
Capecchi, Mario R. | Location and function of retroviral and SV40 sequences that enhance biochemical transformation after microinjection of DNA. | Biochemical transformation of thymidine-kinase-deficient (TK-) mouse L cells is enhanced 20 to 40 fold when microinjected plasmid DNA contains regions of the genomes of Rous sarcoma virus or simian virus 40 in addition to the complete herpes simplex virus tk gene, irrespective of the orientation and... | Animals; Base Sequence; Genes, Viral; Plasmids; Thymidine Kinase | 1983-07-01 |
| 232 |
 |
Capecchi, Mario R. | Measurement of suppressor transfer RNA activity. | Transfer RNA (tRNA) suppression of nonsense mutations in prokaryotic systems has been widely used to study the structure and function of different prokaryotic genes. Through genetic engineering techniques, it is now possible to introduce suppressor (Su+) tRNA molecules into mammalian cells. A quanti... | Animals; Cells, Cultured; Eukaryotic Cells; Genes, Viral; Mice; Orthomyxoviridae; Peptide Chain Termination, Translational; Protein Biosynthesis | 1983-08-26 |
| 233 |
 |
Vardeny, Zeev Valentine; Ehrenfreund, Eitan A. | Resonant Raman scattering from amplitude modes in trans-(CH)x and -(CD)x | The three resonantly enhanced Raman vibrations in trans-(CK)x and ~(CD)X are described in terms of amplitude modes associated with the Peierls gap. The dispersion in the Raman-line profiles is explained by inhomogeneity. A narrow distribution of the effective electron-phonon coupling constant is re... | Peierls gap | 1983-12 |
| 234 |
 |
Goller, Franz | Vorkommen und Brut des Bienenfressers (Merops apiaster) in Osttirol (Österreich) (Aves: Meropidae) | Synopsis: The first record of Bee-eater for the Eastern Tyrol is imparted by KL1MSCH (1950), three further observations are mentioned. In 1983 a breeding place was discovered near Lavant in about 650 m NN. Feeding adults were watched on the 11th and 12th of August. The breeding place is briefly desc... | Merops apiaster; Meropidae; Tyrol | 1984 |
| 235 |
 |
Williams, Clayton C. | High resolution photothermal laser probe | At frequencies near 1 GHz, the acoustic wavelength in argon gas becomes half that of visible light, making possible collinear Bragg scattering of laser light by the sound. This acousto-optic interaction has been used to detect photothermally generated acoustic power at the surface of solids. This ne... | Photothermal laser probe; Silicon wafer | 1984 |
| 236 |
 |
Coley, Phyllis D. | Guía de los arboles comunes del Parque Nacional Soberanía, Panamá | Esta es una guía con dibujos para las cincuenta especies de árboles más comunes del bosque tropical en los alrededores del Parque Soberanía, Panamá. También se incluyen siete especies de hierbas y cuatro herbáceas grandes que sobresalen en el sotobosque (bosque bajo). Aunque en el área del p... | Arboles; Arbustos | 1984 |
| 237 |
 |
Olivera, Baldomero M. | Poly(ADP-ribosylation) of DNA topoisomerase I: a nuclear response to DNA-strand interruptions | DNA in eukaryotic chromosomes is organized differently from prokaryotic DNA. It seems highly probable that mechanistic adjustments have been made in macromolecular DNA metabolism as a consequence of the chromatin structure of the eukaryotic chromosome (Igo-Kemenes et al. 1982)). This paper deals ... | Poly(ADP-ribosylation); Poly(ADP-ribose) synthetase; DNA strand interruption | 1984 |
| 238 |
 |
Vardeny, Zeev Valentine | Photoinduced absorption spectra in amorphous Si:H and Ge:H and microcrystalline Si:H | The steady state subgap photoinduced absorpotion bands in a-Ge:H and a-Si:H are interpreted in terms of two kinds of optical transitions of photoexcited carriers from traps in the gap into the bands of which one produces absorption and the other produces bleaching. The photoinduced absorption in mic... | Photoinduced absorption; Si:H; Ge:H; Amorphous silicon; Amorphous germanium; Microcrystalline silicon | 1984 |
| 239 |
 |
Vardeny, Zeev Valentine | Photoconductivity and photoinduced absorption in a-Si:F and a-Si:H | The photoconductivity (PC) and photoinduced absorption (PA) of RF glow discharge a-Si:F and a-Si:H samples is reported. The value of the room temperature PC of a-Si:F is lower by some four orders of magnitude relative to that of a-Si:H, but the PA of a-Si:F is found to be significantly higher than t... | Photoinduced absorption; a-Si:F; a-Si:H; RF glow discharge; Spin densities | 1984 |
| 240 |
 |
Olivera, Baldomero M. | Poly(ADP-ribosylation) of DNA topoisomerase I from calf thymus | We demonstrate that the activity of the major DNA topoisomerase I from calf thymus is severely inhibited after modification by purified poly(ADP-ribose) synthetase. Polymeric chains of poly(ADP-ribose) are covalently attached to DNA topoisomerase I. These observations with highly purified enzymes ... | ADP-ribosylation; Poly(ADP-ribose) synthetase | 1984 |
| 241 |
 |
Armentrout, Peter B. | Threshold behavior of endothermic reactions: C+(2P) + H2 → CH+ + H | The reaction C+(2p) + H2 → CH+ + H (1) and its deuterium analog is a model system in ion-molecule chemistry. It is of interest due to its astrophysical significance, because it is an endothermic process, and because the interaction involves several potential energy surfaces. Experimental work ha... | Endothermic reactions; Translational energy; Threshold behavior | 1984 |
| 242 |
 |
Vardeny, Zeev Valentine | Picosecond optical generation and detection of phonon waves in a-As2Te3 | Using the pump and probe technique we have observed oscillations of photoinduced transmission in thin films of a-As2Te3. The oscillations have periods of 70-240 ps, depending on sample thickness. We ascribe these to phonon propagation in the films. Thermal expansion and carrier deformation potenti... | Picosecond optical generation; a-As2Te3; Pump and probe technique | 1984 |
| 243 |
 |
Bastiani, Michael | Pathfinding by neuronal growth cones in grasshopper embryo: III. Selective affinity of the G growth cone for the P cells within the A/P fascicle | The growth cone of the G neuron selectively fasciculates upon specific axon bundles in a stereotypic sequence as it navigates through the developing central nervous system of the grasshopper embryo. It turns and extends anteriorly in the contralateral neuropil of the second thoracic ganglion at a s... | Axon; Filopodia; Neuropil | 1984 |
| 244 |
 |
Mattis, Daniel C. | What is the effective mass of an exciton? | In the effective-mass approximation, the mass M* of an exciton is just the sum of the electron and hole masses, me*+ mh*. However, the effective-mass approximation is invalid if the forces are strong. Here we derive a plausible formula for the n th bound state of the exciton: Mn*= (me* + mh*) / (... | Kinetic; Energy; Electron | 1984 |
| 245 |
 |
Bastiani, Michael | Pathfinding by neuronal growth cones in grasshopper embryos: IV. The effects of ablating the A and P axons upon the behavior of the G growth cone | In the companion paper (Bastiani, M. J., J. A. Raper, and C. S. Goodman (1984) J. Neurosci. 4: 2311-2328), we show that as the G growth cone reaches its choice point and turns anteriorly on the A/P fascicle, its filopodia demonstrate selective affinity for the A/P fascicle as compared to the other a... | Labeled pathway; Anterior extension; Fascicle | 1984 |
| 246 |
 |
Beckerle, Mary C. | Microinjected fluorescent polystyrene beads exhibit saltatory motion in tissue culture cells | Microinjected 0.26-um fluorescent, carboxylated microspheres were found to display classical saltatory motion in tissue culture cells . The movement of a given particle was characterized by a discontinuous velocity distribution and was unaffected by the activity of adjacent particles. | Organelles; Microscopy; Proteins | 1984 |
| 247 |
 |
Wu, Yong-Shi | Massless fermions and Kaluza-Klein theory with torsion | A pure Kaluza-Klein theory contains no massless fermion in four-dimensional theory. We investigate the effect of introducing torsion on the internal manifold and find that there are massless fermions. The hope is that given an isometry group the representation to which these fermions belong is fixe... | Massless fermions; Four-dimensional theory; Torsion | 1984 |
| 248 |
 |
Davidson, Diane W. | Granivory in a desert ecosystem: experimental evidence for indirect facilitation of ants by rodents | Two major groups of desert granivores, ants and rodents, coexist as permanent residents of local desert habitats in southwestern North America. At our Sonoran Desert study site, both of the major taxa exhibited short-term increase in density when the other taxon was experimentally removed. Over the... | Ants; Arizona; Desert annuals; Facilitation; Granivory; Indirect mutualism; Rodents; Seed predation; Sonoran Desert | 1984 |
| 249 |
 |
Mattis, Daniel C. | Three-body bound states on a lattice | The theory of three-body bound states for particles moving on a lattice and interacting with attractive two-body pointlike potentials is presented. The applications are to bosons, fermions (no three-body bound states are found), and magnons. When a three-body bound state forms in three dimensions, i... | Particle; Fermions; Ferromagnet | 1984 |
| 250 |
 |
Ailion, David Charles | Molecular reorientations in the ordered phases of KCN and NaCN studied by NMR | We have measured 13C and 23Na NMR spin-lattice relaxation times as a function of temperature in KCN and NaCN in order to study the head-to-tail reorientations of the CN- molecules in the two low-temperature ordered phases. We have combined our data with those of dielectric-response and ionic-thermal... | Spin; Interactions; Fluctuations | 1984 |
