doi: 10.1038/335598a0pmid: N/A
Encyclopedia of Human Evolution and Prehistory.Edited by Ian Tattersall Eric Delson John Van Couvering Garland:1988. Pp.603. $87.50.
Peebles, P. J. E.; Silk, Joseph
doi: 10.1038/335601a0pmid: N/A
Modern theories of the origin of large-scale structure depend on a variety of stimulating new ideas about the physics of the early Universe. In the absence of clean observational tests one can obtain figures of merit for the theories by counting and weighing the plausibility of each of those basic elements that are not substantially supported by observation or mature fundamental theory. A survey of the speculative elements of the leading rival theories illustrates the exciting and highly uncertain state of research in the physics of the early Universe.
Vogel, Jonathan; Hinrichs, Steven H.; Reynolds, R. Kay; Luciw, Paul A.; Jay, Gilbert
doi: 10.1038/335606a0pmid: 2845275
When the human immunodeficiency virus transactivating gene under the control of the viral regulatory region is introduced into the germline of mice, skin lesions are induced that resemble Kaposi's sarcoma seen in AIDS. Our findings indicate that HIV could play a direct part in causing cancer.
Lasko, Paul F.; Ashburner, Michael
doi: 10.1038/335611a0pmid: 3140040
The vasa gene product of Drosophila melanogaster is required only in the female germ line. Progeny of females homozygous for vasa mutations lack posterior structures and pole cells. Isolation and characterization of vasa genomic and complementary DNA clones show that the transcript is abundant in the female germ line and early embryos only. The predicted amino acid sequence is very similar to those of the translation initiation factor eIF-4A and the human nuclear antigen p68.
Villasenor, J. D.; Bracewell, R. N.
doi: 10.1038/335617a0pmid: N/A
We recently reported a method of optical phase measurement1 that involves the creation of a Hartley transform2 plane, which is constructed by the superposition of two Fourier transforms3, one of which was rotated spatially by 180° and shifted in phase by 90°. Because the Hartley transform, unlike the Fourier transform, is entirely real, it is able to extract more information when a phase-insensitive detector (for example, an optical detector) is used. In particular, the Hartley intensity encodes the location of the centroid of a source, whereas the intensity distribution of a Fraunhofer diffraction pattern does not change when the source shifts because source location is hidden in the phase information. Through the Hartley transform one gains access to the Fourier phase by amplitude measurements only. We have now extended this technique to the microwave range, and have also demonstrated how to obtain an image of an isophase source without using a phase-sensitive detector.
Heap, M. P.; Chen, S. L.; Kramlich, J. C.; McCarthy, J. M.; Pershing, D. W.
doi: 10.1038/335620a0pmid: N/A
The combustion of coal and heavy oil produces significant quantities of NOx (NO + NO2), which ultimately participates in photochemical smog and acid rain. Combustion modification schemes, such as staged combustion1 and reburning2, or downstream injection of selective reducing agents, particularlarly ammonia3 and urea4, can significantly reduce NOx emissions, but their effectiveness may be limited by operating constraints. Perry and Siebers5 described a selective reduction process using cyanuric acid, reported to be effective over a broad temperature range. Here we report new data that indicate that the same reductions can be achieved without stainless steel to activate the reaction mechanism, if the process is combined with reburning or staged combustion (or slightly fuel-rich operation in internal combustion) to produce carefully controlled stoichiometry. The NOx reductions that can be achieved with cyanuric acid and other –NH- and –CN-containing compounds at relatively low temperatures exceed those possible with either combustion modifications or selective reduction techniques alone or in normal combination.
Fisher, Nicholas S.; Cochran, J. Kirk; Krishnaswami, S.; Livingston, Hugh D.
doi: 10.1038/335622a0pmid: N/A
The vertical flux of long-lived radionuclides, and of metals in general, in marine systems has been linked to the flux of particulate matter1,2. Various forms of particulate matter have been shown to be capable of transporting radionuclides in the sea, with greatest interest in recent years focusing on debris of biological origin3. Here we calculate the degree to which radionuclide flux out of the euphotic zone can be attributed to sinking biodetritus deriving ultimately from phytoplankton. We use experimentally determined concentration factors in phytoplankton, dissolved radionuclide concentrations in surface waters and new production estimates for specific ocean regions. Our predictions of radionuclide fluxes are generally comparable with sediment-trap measurements of radionuclide fluxes in these waters, suggesting that the downward flux from open ocean surface waters of particle-reactive radionuclides is governed principally by sinking biogenic debris.
Showing 41 to 50 of 62 Articles