7,459 research outputs found
The site of ribonucleic acid synthesis in the isolated nucleus
There is still controversy concerning the primary site of RNA synthesis in the cell.(1) When tissues are radioautographed after administration of radioactive inorganic phosphorus or radioactive RNA(2) precursors such as tritiated uridine or cytidine, it is commonly observed that radioactivity appears in the nucleus first and in the cytoplasm later. It has furthermore been shown that isolated nuclei of both animal(3) and plant(4) material are able to synthesize RNA in vitro but that enucleated cytoplasm is unable to carry on such synthesis.(5) Although the problem of whether or not RNA is synthesized in both nucleus and cytoplasm is not completely understood,(6-8) there is increasing cytological evidence that a substantial portion of the cytoplasmic RNA is synthesized in the nucleus (9-17) and subsequently migrates to the cytoplasm
Review of \u3ci\u3eFishes of the Central United States\u3c/i\u3e by Joseph R. Tomelleri and Mark E. Eberle.
The second, enlarged edition is a timely and necessary revision of the comfortable first edition classic. Tomelleri and Eberle remain true to their initial intent of providing accurate yet readable species accounts and detailed illustrations of Great Plains fishes. Format and style are especially suited for nontechnical audiences (anglers, naturalists, fish enthusiasts), whereas detailed life history accounts, summaries of conservation threats, and an extensive bibliography serve as handy references for natural resource managers and researchers.
Upon first review, the Revised and Expanded label may seem suspect: this second edition has 34 fewer total pages. However, revision of taxonomy and addition of species accounts are quickly noticed and appreciated. Two families elevated since 1990 are added along with revised family and genera names. Notable additions are made to Cyprinidae, Ictaluridae, and Percidae. Among cyprinids, several genera (e.g., Hybognathus, Macrhybopsis, Dionda) are expanded or added, five new species accounts appear, and illustrations increase from 27 to 71
The impact of space and space-related activities on a local economy. a case study of boulder, colorado. part i- the input-output analysis
Impact of space and space-related activities on industry and general economy of Boulder, Colorad
The susceptibility and excitation spectrum of (VO)PO in ladder and dimer chain models
We present numerical results for the magnetic susceptibility of a Heisenberg
antiferromagnetic spin ladder, as a function of temperature and the spin-spin
interaction strengths and . These are contrasted with new
bulk limit results for the dimer chain. A fit to the experimental
susceptibility of the candidate spin-ladder compound vanadyl pyrophosphate,
(VO)PO, gives the parameters meV and meV. With these values we predict a singlet-triplet energy gap of
meV, and give a numerical estimate of the ladder triplet
dispersion relation . In contrast, a fit to the dimer chain model
leads to meV and meV, which predicts a gap of meV.Comment: 16 pages, 6 figures available upon request, RevTex 3.0, preprint
ORNL-CCIP-94-04 / RAL-94-02
Crystal Structure and Magnetism of the Linear-Chain Copper Oxides Sr5Pb3-xBixCuO12
The title quasi-1D copper oxides (0=< x =<0.4) were investigated by neutron
diffraction and magnetic susceptibility studies. Polyhedral CuO4 units in the
compounds were found to comprise linear-chains at inter-chain distance of
approximately 10 A. The parent chain compound (x = 0), however, shows less
anisotropic magnetic behavior above 2 K, although it is of substantially
antiferromagnetic (mu_{eff}= 1.85 mu_{B} and Theta_{W} = -46.4 K) spin-chain
system. A magnetic cusp gradually appears at about 100 K in T vs chi with the
Bi substitution. The cusp (x = 0.4) is fairly characterized by and therefore
suggests the spin gap nature at Delta/k_{B} ~ 80 K. The chain compounds hold
electrically insulating in the composition range.Comment: To be published in PR
Different time scales in plasmonically enhanced high-order harmonic generation
We investigate high-order-harmonic generation in inhomogeneous media for reduced dimensionality models. We perform a phase-space analysis, in which we identify specific features caused by the field inhomogeneity. We compute high-order-harmonic spectra using the numerical solution of the time-dependent Schrödinger equation, and provide an interpretation in terms of classical electron trajectories. We show that the dynamics of the system can be described by the interplay of high-frequency and slow-frequency oscillations, which are given by Mathieu's equations. The latter oscillations lead to an increase in the cutoff energy, and, for small values of the inhomogeneity parameter, take place over many driving-field cycles. In this case, the two processes can be decoupled and the oscillations can be described analytically
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