Fabrication and magnetic properties of arrays of metallic nanowires

Arrays of ferromagnetic nickel and cobalt nanowires have been fabricated by electrochemical deposition of the metals into templates with nanometer-sized pores prepared by nuclear track etching. These systems display distinctive characteristics because of their one-dimensional microstructure. The preferred magnetization direction is perpendicular to the film plane. Enhanced coercivities as high as 680 oersteds and remnant magnetization up to 90 percent have also been observed.     

Interferometer experiment with independent local oscillators

We have operated an interferometer with independent local oscillators and without any communication link of wide bandwidth between the elements of the interferometer. This makes operation possible at very long base lines because, heretofore, construction of the communications link has been the factor limiting the separation of the elements. In our system, coherence at the two elements is maintained through the use of two highly stable, atomic oscillators. The intermediate-frequency output signals are recorded at each element on a high-speed digital tape recorder. Interference fringes are produced later by cross-correlating the two tape records in a digital computer.     

Murine leukemia virus: high-frequency activation in vitro by 5-iododeoxyuridine and 5-bromodeoxyuridine

Cells of embryos of the high leukemic mouse strain AKR can be grown in culture as virus-negative cell lines. However, these lines and clonal sublines uniformly have the capacity to initiate synthesis of murine leukemia virus. Exposure of the cells to 5-iododeoxyuridine or 5-bromodeoxyuridine induced synthesis of virus in as high as 0.1 to 0.5 percent of the cells; many of the cells were producing virus as soon as 3 days after initiation of treatment. Induction of virus by these drugs is several orders of magnitude greater than that obtained with any other treatment tested. These studies indicate that the full genome of murine leukemia virus is present in an unexpressed form in all AKR cells and provide a potentially powerful technique for activating leukemia virus genomes in other cell systems.     

Magnetic properties of lunar dust and rock samples

Determinations on 20-to 80-milligram portions of the rock samples and the -150 mesh fraction of the lunar dust show pronounced Curie points between 680 degrees and 780 degrees C. Remanent intensities of five rock fragments vary from 8.4 x 10(-5) to 0.30 X J0(-5) emu/gram. Upon demagnetization, two of the samples had only viscous magnetization and two other samples had stable magnetizations with remanent coercivities in excess of 50 oersteds. Partial thermal demagnetization suggests that these apparently stable moments may have been acquired in a magnetic field in excess of 1500 gammas. xsxs.     

Giant Magnetoresistance at Low Fields in Discontinuous NiFe-Ag Multilayer Thin Films

A series of sputtered multilayers of Ni(80)Fe(20)-Ag was prepared to examine the giant magnetoresistance effect before and after annealing. For a wide range of NiFe and Ag thicknesses, no giant magnetoresistance was observed in the unannealed films. After annealing, a large, negative magnetoresistance was observed of order 4 to 6% in applied fields of order 5 to 10 oersteds at room temperature. The appearance of giant managetoresistance is concurrent with the breakup of the NiFe layers, which is attributable to a magnetostatic interaction that favors local antiparallel alignment of the moments in adjacent layers. These structures may be of significant practical importance as sensors that require large changes in resistance at low fields, such as magnetoresistive heads used in magnetic recording systems.     

Electron nuclear double resonance spectroscopy

Precise information about the molecular structure, stereochemistry, and environment of paramagnetic species can be obtained by electron nuclear double resonance (ENDOR) spectroscopy. This technique has been applied in a wide range of disciplines to liquid-phase, single-crystal, and powder samples. In some cases-the study of defects in ionic single crystals, for instance-the volume and complexity of data obtained by ENDOR can hinder interpretation. Such difficulties have been overcome by the use of supplemental ENDOR techniques that simplify the assignment of ENDOR lines. The increased use of computers for the automation of instrumentation, the design of experiments, and the analysis of data has made possible the study of a wider range of problems. With these improvements, as well as with the increased sensitivity provided by optically detected ENDOR, it is now feasible to study polycrystalline and amorphous materials, such as thin-film semiconductors and biological samples in vivo.     

Hydration of macromolecules

Frozen protein and nucleic acid solutions at -35 degrees C show relatively narrow (100 milligauss) proton nuclear magnetic resonance signals which are assignable to water that is sufficiently mobile to reduce the dipolar broadening normally associated with solids. Hydration was found to be 0.3 to 0.5 gram of water per gram of protein. Nucleic acids are three to five times as hydrated as proteins. Conformational changes in solution produce detectable changes in linewidth or amount of "bound" water, or both. The very fact that the water signals can be observed by high resolution nuclear magnetic resonance suggests that it is not "ice-like" in any literal sense, although it is clearly less mobile than liquid water at the same temperature. A simple model is described which considers both surface hydration and trapped water.     

Paleomagnetic study of antarctic deep-sea cores

The magnetic inclinations and inten sities of about 650 samples from seven deepsea cores taken in the Antarctic were measured on a spinner magnetometer. This series of measurements provided a magnetic stratigraphy, based on zones of normally or reversally polar ized specimens for each core, which was then correlated with the magnetic stra tigraphy of Cox et al. (1). One core (V16-134) gave a continuous record of the paleomagnetic field back to about 3.5 million years. When selected samples were subject ed to alternatingfield demagnetization, most were found to have an unstable component that was removed by fields of 150 oersteds; all samples from two cores were partially demagnetized in a field of 150 oersteds. The average inclination in these two cores was then in good agreement with the average inclination of the ambient field for the latitude of the core site. It was also found that the intensities of the samples decreased at the points of reversal; this finding is to be expected if, as has been postulated by the dynamo theory, the intensity of the dipole field decreases to zero and builds again with opposite polarity. We believe that the magnetiza tion of the cores results from the pres ence of detrital magnetite, although other magnetic minerals also may be present. Four faunal zones (, X, , and ) have been recognized in these Antarctic cores on the basis of upward sequential disappearance of Radiolaria. The faunal boundaries and reversals consistently have the same relations to one another, indicating that they are both timedependent phenomena. Using previously determined times of reversal, one may date the following events in the cores: 1) Radiolarian faunal boundaries:-X, 2 million years; X-, 0.7 million years; -, 0.4 to 0.5 million years. These dates are in good agreement with ages previously extrapolated from radio metric dates. 2) Initiation of Antarctic diatom ooze deposition, approximately 2.0 mil-lion years ago. 3) First occurrence of ice- rafted detritus, approximately 2.5 million years ago. One can also calculate rates of sedi mentation, which vary in the cores studied from 1.1 to about 8.0 millimeters per 1000 years. Sedimentation rates for the Indian Ocean cores are higher than for the Bellingshausen Sea cores. The near coincidence of faunal changes and reversals in the cores suggests but does not prove a causal relation. We conclude from this study that paleomagnetic stratigraphy is a unique method for correlating and dating deep sea cores, and that future work with such cores may provide a complete or nearly complete record of the history of the earth's magnetic field beyond 4 million years.     

Behavior of vervet monkeys and other cercopithecines. New data show structural uniformities in the gestures of semiarboreal and terrestrial cercopithecines

A comparison of the communicative gestures of vervets with those of other cercopithecines reveals both similarities and differences. Examples have been given of gestures (i) exhibited by all cercopithecines, (ii) rare or absent in vervets and common in several other species, (iii) demonstrated by vervets and a few other cercopithecines, and (iv) common in vervets and rare or absent in other members of the subfamily. Vervets, baboons, and rhesus monkeys have approximately the same number of visual signals in their behavioral repertoires-46, 42, and 49, respectively. Patas monkeys seem to have a smaller repertoire. Fifty-nine percent of the vervet patterns have also been described for rhesus monkeys, 63 percent for baboons, and 54 percent for patas. In cercopithecines, visual communicative patterns seem to be evolutionarily one of the most stable forms of behavior, in structural terms. Some of the greatest differences in communicative gestures are differences in the temporal aspects. In species of this subfamily, vocal patterns seem to vary more than visual signals. Greater structural differences in communicative gestures may be found in the Cercopithecinae when systematic field studies are made of some of the forest-dwelling species, about which we know very little.     

Hydration rate of obsidian

The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.     

Glacial-holocene transition in deep-sea carbonates: selective dissolution and the stable isotope signal

The oxygen and carbon isotopic signals of planktonic Foraminifera from closely spaced samples from two box cores taken in the western equatorial Pacific change through the glacial-to-Holocene transition as a result of several factors, one of which is the Holocene dissolution pulse starting about 12,000 years ago and reaching full force shortly after. The onset of dissolution comes shortly after the maximum rate of deglaciation but well before the maximum drop in fertility in upper waters. The effect of dissolution is 20 to 30 percent of the amplitude of isotopic change in Globigerinoides sacculifer, at the depth of the present lysocline.     

High efficiency DNA-mediated transformation of primate cells

Tissue culture cells from several mammalian species, including three primate lines, were transfected with recombinant vectors carrying Escherichia coli xanthine-guanine phosphoribosyltransferase or Tn5 aminoglycoside phosphotransferase dominant selectable markers. Human HeLa and SV40-transformed xeroderma pigmentosum cells exhibited stable transformation frequencies of at least 10(-3) (0.1 percent). CV-1, an African green monkey kidney cell line, could be stably transformed with the exceptionally high frequency of 6 X 10(-2) (6 percent).     

Isotope separation by thermal diffusion in liquid metal

Isotopic enrichment of several percent has been obtained in liquid lithium metal by applying a temperature gradient over a single-stage separation column. For other metals the method should have the highest eficiency, if these have low melting points and are liquids over a wide temperature range.     

Subsurface valleys and geoarcheology of the eastern sahara revealed by shuttle radar

The shuttle imaging radar (SIR-A) carried on the space shuttle Columbia in November 1981 penetrated the extremely dry Selima Sand Sheet, dunes, and drift sand of the eastern Sahara, revealing previously unknown buried valleys, geologic structures, and possible Stone Age occupation sites. Radar responses from bedrock and gravel surfaces beneath windblown sand several centimeters to possibly meters thick delineate sand- and alluvium-filled valleys, some nearly as wide as the Nile Valley and perhaps as old as middle Tertiary. The now-vanished major river systems that carved these large valleys probably accomplished most of the erosional stripping of this extraordinarily flat, hyperarid region. Underfit and incised dry wadis, many superimposed on the large valleys, represent erosion by intermittent running water, probably during Quaternary pluvials. Stone Age artifacts associated with soils in the alluvium suggest that areas near the wadis may have been sites of early human occupation. The presence of old drainage networks beneath the sand sheet provides a geologic explanation for the locations of many playas and present-day oases which have been centers of episodic human habitation. Radar penetration of dry sand and soils varies with the wavelength of the incident signals (24 centimeters for the SIR-A system), incidence angle, and the electrical properties of the materials, which are largely determined by moisture content. The calculated depth of radar penetration of dry sand and granules, based on laboratory measurements of the electrical properties of samples from the Selima Sand Sheet, is at least 5 meters. Recent (September 1982) field studies in Egypt verified SIR-A signal penetration depths of at least 1 meter in the Selima Sand Sheet and in drift sand and 2 or more meters in sand dunes.     

Mariner 9 ultraviolet spectrometer experiment: stellar observations

Photoelectric spectra have been obtained for a number of early-type stars in the 1100- to 2000-angstrom region with the Mariner 9 ultraviolet spectrometer. The resonance lines of H I, Si IV, and C IV are easily identified, as are features due to C II, C III, Si III, Fe II, N IV. The absolute energy distribution derived from the data lie about 20 percent below those of OAO-2 in the 1200- to 2000-angstrom region.     

Rhenium-osmium isotope systematics of carbonaceous chondrites

Rhenium and osmium concentrations and Os isotopic compositions of eight carbonaceous chondrites, one LL3 ordinary chondrite, and two iron meteorites were determined by resonance ionization mass spectrometry. Iron meteorite (187)Re/(186)Os and (l87)Os/(l86)Os ratios plot on the previously determined iron meteorite isochron, but most chondrite data plot 1 to 2 percent above this meteorite isochron. This suggests either that irons have significantly younger Re-Os closure ages than chondrites or that chondrites were formed from precursor materials with different chemical histories from the precursors of irons. Some samples of Semarkona (LL3) and Murray (C2M) meteorites plot 4 to 6 percent above the iron meteorite isochron, well above the field delineated by other chondrites. Murray may have lost Re by aqueous leaching during its preterrestrial history. Semarkona could have experienced a similar loss of Re, but only slight aqueous alteration is evident in the meteorite. Therefore, the isotopic composition of Semarkona could reflect assembly of isotopically heterogeneous components subsequent to 4.55 billion years ago or Os isotopic heterogeneities in the primordial solar nebula.     

若干杂交稻亲本的配合力分析

选用福建农林大学作物遗传育种研究所育成的长穗颈不育系协青早eA(1)、协青早eA(2)、龙特浦eA(1)、龙特浦eA(2)、D297 eA(1)、D297 eA(2)及不育系协青早A、龙特浦A、D297A与恢复系R669、蜀恢527、明恢63为材料,组配成一套半双列杂交F1材料。分析了18个主要农艺及产量性状的一般配合力(gca)和特殊配合力(sca)。结果表明,杂种性状主要受亲本gca作用,同时,sca效应也起着重要作用。18个性状中,有16性状组合间遗传差异达显著或极显著水平,同一亲本不同性状或同一性状不同亲本之间gca表现较大差异,无明显规律;不同eui基因型杂交稻sca值差异依组合及性状的不同而变化,未表现出规律性。     

四川省区试小麦的戊聚糖含量分析

采用Douglas法对2004~2005年度四川小麦区试的各参试品系进行了全麦粉的戊聚糖含量及SDS沉降值的测定。结果表明,各参试材料间的戊聚糖含量差距较大,SDS沉降值偏低,戊聚糖含量与SDS值并无直接的相关性。本研究中筛选出了具有较高戊聚糖含量的参试品系,可为高戊聚糖小麦育种提供优良亲本资源。     

How low can you go? Physical production mechanism of elephant infrasonic vocalizations

Elephants can communicate using sounds below the range of human hearing ("infrasounds" below 20 hertz). It is commonly speculated that these vocalizations are produced in the larynx, either by neurally controlled muscle twitching (as in cat purring) or by flow-induced self-sustained vibrations of the vocal folds (as in human speech and song). We used direct high-speed video observations of an excised elephant larynx to demonstrate flow-induced self-sustained vocal fold vibration in the absence of any neural signals, thus excluding the need for any "purring" mechanism. The observed physical principles of voice production apply to a wide variety of mammals, extending across a remarkably large range of fundamental frequencies and body sizes, spanning more than five orders of magnitude.     

EUVE Observations of Jupiter During the Impact of Comet Shoemaker-Levy 9

The Extreme Ultraviolet Explorer (EUVE) satellite conducted extensive observations of the jovian system before, during, and after the impact of the fragments of comet Shoemaker-Levy 9 in July 1994. About 2 to 4 hours after the impacts of several of the larger fragments, the brightness of the neutral helium (He I) resonance line at 58.4 nanometers temporarily increased by a factor of about 10. The transient 58.4-nanometer brightenings are most simply explained by resonant scattering of sunlight from the widespread high-altitude remnants of the larger impact plumes. Other possible sources of emission, such as electron impact excitation of He or radiative recombination of He(+), may contribute to the observed signal.