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Caltech Authors (125,769 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 54,934

1. A lunar density model consistent with topographic, gravitational, librational, and seismic data - Bills, Bruce G.; Ferrari, Alfred J.
A series of models of the lunar interior are derived from topographic, gravitational, librational, and seismic data. The librational parameters and low-degree gravity harmonics result primarily from surface height variations and only secondarily from lateral density variations. The moon departs from isostasy, even for the low-degree harmonics, with a maximum superisostatic stress of 200 bars under the major mascon basins. The mean crustal thicknesses under different physiographic regions are: mascons, 30–35 km; irregular maria, 50–60 km; and highlands, 90–110 km. A possible composition consistent with our model is an anorthositic crust, underlain by a predominantly forsterite upper mantle which grades...

2. Combined Vital Dye Labelling and Catecholamine Histofluorescence of Transplanted Ciliary Ganglion Cells - Sechrist, John; Coulombe, James N.; Bronner-Fraser, Marianne
We have utilized the carbocyanine dye, Dil, to label suspensions of dissociated ciliary ganglion cells removed from 6 to 12 day old quail embryos. Some of the cells were injected into the trunk somites of 2.5 - 3 day old chick embryos along pathways where neural crest cells migrate to form sensory and sympathetic ganglia, aortic plexuses and the adrenal medulla; the remainder of the cells were cultured to check their viability and the persistence of the Dil label. Embryos were incubated for 1 - 8 days post-injection, fixed in 4% paraformaldehyde/0.25% glutaraldehyde and processed for cryostat sectioning. DH-labelled cells were readily...

3. Theory of Air-Coupled Flexural Waves - Press, Frank; Ewing, Maurice
The theory of air‐coupled flexural waves in a floating ice sheet is derived for the case of an impulsive point source situated either in the air or in the water. It is found that new branches are introduced to the dispersion curve of flexural waves as a result of coupling to compressional waves in the atmosphere. Experimental data are briefly reviewed.

4. Sound Waves in the Atmosphere Generated by a Small Earthquake - Benioff, Hugo; Ewing, Maurice; Press, Frank
In previous papers theoretical and experimental results on the coupling of atmospheric compressional waves to various types of surface waves in the underlying earth or ocean have been presented. Recently Benioff presented a paper describing a remarkable instance of atmospheric waves received at Pasadena from the earthquake of January 24, 1951, 07-17-01, magnitude 5.6, 33° 07'N., 115° 34'W., Δ = 265 km. The microbarograph recorded a train of waves which commenced gradually at about 23:34:00 P.S.T. with periods of about 3/4 second and ended at about 23:39:00 P.S.T. with periods of about 1 sec. (Fig. 1). Benioff had noticed a...

5. Epithelial cells of Hydra are dye-coupled - Fraser, Scott E.; Bode, Hans R.
In the past decade, a strong correlation has been established between gap junctions, seen in cell ultrastructure studies, and cell coupling (ionic, metabolic or dye coupling) assayed physiologically1. In Hydra, ultrastructural analyses have indicated that the epithelial cells of both cell layers are connected extensively by gap junctions; lap junctions have also been observed between the two layers. On the basis of these results, one would expect electrical and dye coupling between epithelial cells of Hydra. However, de Laat et al. reported that these cells were neither dye- nor electrically coupled, which was unexpected as cells in another coelenterate have been...

6. Purine and pyrimidine antagonism in a pyrimidine-deficient mutant of Neurospora - Pierce, John G.; Loring, Hubert S.
The present study is concerned with the inhibition of growth of the pyrimidine-deficient Neurospora mutant, No. 1298, by the naturally occurring purine ribonucleotides and ribonucleosides. This experimentally produced strain, unlike the wild type, is unable to synthesize the pyrimidine ribonucleosides on a medium containing inorganic salts, carbohydrate, and biotin. Normal growth takes place, however, when the medium is supplemented with either cytidine or uridine or the corresponding nucleotides. It has been found that adenosine and adenosine-3-phosphate (yeast adenylic acid) inhibit the utilization of the pyrimidine compounds to a varying degree. An amount of adenine nucleoside which is sufficient to inhibit...

7. The Development of Eye Colors in Drosophila as Studied by Transplantation - Beadle, G. W.
THE present report is an attempt to summarize briefly studies of eye color development in Drosophila melano- gaster, carried out, for the most part, jointly by Dr. Boris Ephrussi of the Institut de Biologie physico-chemique, Paris, and the writer. Detailed evidence for statements made here have been or will be published elsewhere (see references at the end of this paper). Those developmental reactions leading to the formation of specific types of eye colors in Drosophila presumably constitute a very small part of the general reticulum of developmental reactions. This particular small group, which of course in reality is probably very...

8. A 100-Inch Mirror for the Solar Observatory - Hale, George E.
[no abstract]

9. High-Resolution Density Gradient Sedimentation Analysis - Britten, R. J.; Roberts, R. B.
The principle of stability for a sample layered in a density-gradient liquid column is discussed, and a method for separating ribonucleoprotein particles by means of sedimentation in the ultracentrifuge is described.

10. Complementary Strand Association between Nucleic Acids and Nucleic Acid Gels - Britten, R. J.
Nucleic acid gels can be formed as a result of the cross-linking action of ultraviolet light or of nitrous acid. Such gels form duplex combinations with complementary nucleic acid strands.

11. Nucleotide Sequence Repetition: A Rapidly Reassociating Fraction of Mouse DNA - Waring, Michael; Britten, Roy J.
The separated complemnentary strands of a minor component in mouse DNA reassociate with each other much more rapidly than do the complementary strands of other DNA's including those of the principal part of mouse DNA. This difference in capacity of the strands to reassociate can be used to effect a preparative separation of the minor component from the principal fraction. The rate constant for reassociation of the minor component, compared with those of viral and bacterial DNA's, indicates that the minor component consists of a short nucleotide sequence present in about one million copies.

12. Use of Bacteriophage φX174 Replicative from Progeny DNA as Templates for Transcription - Truffaut, Nicole; Sinsheimer, Robert L.
The synthesis of φX174-specific RNA has been studied in infected cells in which the thymine of the viral (+) strand of the parental RF*, of the complementary (−) strand of the parental RF, or of both strands of the progeny RF molecules has been replaced with 5-bromouracil (5 BU). By irradiation of such cells with UV light at a wavelength of 313 nm it was possible to affect, specifically, the 5 BU-labeled strands. When the progeny RF molecules contain thymine, irradiation has no effect upon the synthesis of viral-specific RNA, regardless of 5 BU substitution in either strand of parental...

13. Nature of the Complementary Strands Synthesized in Vitro upon the Single-Stranded Circular DNA of Bacteriophage øX174 after Ultraviolet Irradiation - Poddar, Ramendra K.; Sinsheimer, Robert L.
This paper describes experiments intended to decide whether UV lesions in DNA act as absolute blocks to chain elongation by the Escherichia coli DNA polymerase or only slow down the polymerization process. Ultraviolet (UV)-irradiated, single-stranded (SS) circular DNA of bacteriophage øX174 was used as template for the polymerase in a reaction mixture in vitro, under conditions allowing synthesis of not more than one complementary strand per template molecule. The mean length of the newly synthesized complementary strands (as determined by velocity sedimentation in alkaline CsCl gradients), as well as the over-all template activity (as measured by deoxyadenosine monophosphate [dAMP] incorporation)...

14. Genetic expression in whole cells of heterozygous replicative-form molecules of Φ174 - Merriam, Virginia; Funk, Fred; Sinsheimer, Robert L.
The role of the parental viral strand in infection with bacteriophage Φ174 has been deduced from both biophysical and biological studies. The viral strand, on entering the cell, is converted to a double-stranded replicative form (RF). This parental RF is bound to the membrane, where the viral strand appears to be physically conserved throughout infection and to be required even at late times. In starved cells, only the RF containing the parental viral strand replicates, semiconservatively. The parental viral strand is conserved in this RF, with each new complementary partner being released in turn in a progeny RF molecule. The...

15. Retinotectal Specificity: Models and Experiments in Search of a Mapping Function - Fraser, Scott E.; Hunt, R. Kevin
Embryonic development of nerve patterns has fascinated and frustrated neurobiologists for decades. The orderly connections within the central nervous system and between the central nervous system and peripheral end organs are thought to be formed by a number of different means ranging from selective cell death, through timing and mechanical guidance, to chemospecificity. A system that has gained great popularity for the study of topographic connections between sets of neurons is the retinotectal system of lower vertebrates (amphibia and fish). Although this system has hardly been cooperative in yielding conclusive evidence (Horder & Martin 1978, Hunt & Jacobson 1974), its...

16. Metalloregulation in the Sequence Specific Binding of Synthetic Molecules to DNA - Griffin, John H.; Dervan, Peter B.
The design, synthesis, and DNA binding studies of a series of bis(netropsin)s linked by homologous polyether tethers has been undertaken. DNA affinity cleaving experiments show that one compound, bis(netropsin)-3,6,9,12,15-pentaoxahepta-decanediamine-EDTA:Fe(II) (1b:Fe(II)) is positively activated for specific DNA binding in the presence of Sr^(2+) or Ba^(2+) ions. The effects of linker structure, metal ion concentration, and DNA sequence on the metalloregulated binding are reported.

17. The Origins of the DNA Binding Affinity and Specificity of Minor Groove Directed Ligands: Correlations of Thermodynamic and Structural Data - Breslauer, Kenneth J.; Ferrante, Robert; Marky, Luis A.; Dervan, Peter B.; Youngquist, R. Scott
[no abstract]

18. What is biotechnology? - Barton, Jacqueline K.
I have been given the task and opportunity of introducing chapters that describe some of the exciting new chemical advances in the field we call "biotechnology". You may notice that neither the words "chemical" nor "molecular" is incorporated into "biotechnology", but really the heart of what I think is exciting about this are is indeed chemical.

19. Synthetic Tools for Molecular Biology - Dervan, Peter B.
Chemistry has made tremendous advances over the past four decades in the broad fields of synthesis and understanding chemical reactivity. In that same time span, a series of revolutionary events occurred in biology. First came the discovery of the double helical structure of DNA in the 1950s by Watson and Crick. This discovery allowed the elucidation of the mechanisms of DNA replication -- how DNA makes copies of itself -- and DNA transcription and translation -- the processes that allow the genetic code to be read and translated into proteins. In the 1970s, the techniques that permit DNA to be...

20. Sequence Specific Recognition of Double Helical DNA. A Synthetic Approach - Dervan, P. B.
The design of synthetic sequence-specific DNA-binding molecules has advanced in recent years due, in part, to analytical techniques such as foot-printing and affinity cleaving which allow rapid and precise analyses of hundreds of potential DNA-binding sites to nucleotide resolution on sequencing gels (Dervan 1986). During the past 10 years our group has focused on the construction of molecules that bind in the minor and major groove of DNA with incrementally increasing sequence specificity as a first step toward defining the chemical principles for creating specificity at the 15-base pair level (Dervan 1986). Recent progress illustrates how the tools of chemical...

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