Showing papers by "State University of New York System published in 1977"

Electrostatic Potentials at Membrane-Solution Interfaces

Abstract: Publisher Summary This chapter discusses electrostatic potentials at membrane solution interfaces. Lipids in the membranes of all cells and subcellular organelles are arranged in the form of a bilayer with the hydrocarbon tails sequestered away from the water and the polar head groups exposed to the aqueous environment. About 10%–20% of the lipids in the membranes of many cells and organelles bear a net negative charge, whereas positively charged lipids are extremely rare. The concentration of monovalent cations at the surface of the bilayer will be an order of magnitude higher than the concentration of these ions in the bulk aqueous phase. The surface potential produced by charged lipids is dependent on the salt concentration in the bulk aqueous phase and a seminal paper. The absence of proteins, polysaccharides, and other macromolecules present in biological membranes can be considered an advantage to test how well the theory of the diffuse double layer describes the electrostatic potential produced by charges on lipids. The chapter describes hydrophobic adsorption of charged molecules to bilayer membranes, the electrostatic potential produced by molecular dipoles at membrane-solution interfaces, and the electrostatic boundary potential produced by charges located in the interior of the membrane, a few angstroms from the interface. Few examples of the possible biological significance of these electrostatic surface potentials are also described.

Androgenetic origin of hydatidiform mole

Abstract: CLASSIC hydatidiform mole is the product of an abnormal pregnancy with grossly swollen chorionic villi, but without an embryo, cord or amniotic membrane. Histologically, the villi are characterised by advanced hyperplasia and anaplasia of the trophoblast, oedema of the stroma and the absence of foetal capillaries1. A malignant change to invasive mole or choriocarcinoma is frequent. The karyotype of the mole is predominantly, if not exclusively, 46,XX. We have made a cytogenetic study of the origin of hydatidiform mole and found that it receives only paternal chromosomes and is therefore androgenetic in origin.

The composition of the atmosphere at the surface of Mars

Abstract: The current status is summarized of investigations of the composition of the Martian atmosphere, in which use was made of the mass spectrometers that function as the analytical component of the molecular analysis experiments on the two Viking landers. The following points seem well established: N2, Ar-40, Ne, Kr, Xe, and the primordial isotope of Ar are present. The present atmosphere of Mars represents only a small fraction of the total amount of volatiles outgassed by the planet, so that high surface pressure and abundant water may have been present. The noble gases in the Martian atmosphere exhibit a relative abundance pattern similar to that in the earth's atmosphere and (except for Xe) to that in the primordial component of meteorites. The existence of a 'planetary component' is thus proven, supporting the arguments of those who favor a fractionation of noble gases prior to the formation of the planets. In spite of these similarities, the isotopic ratios of nitrogen, argon, and xenon indicate that the histories of the Martian and the earth's atmospheres have been very different.

The Photographic Determination of Group Size, Composition, and Stability of Coastal Porpoises (Tursiops truncatus)

Abstract: During a 21-month study, 53 individual bottle-nosed porpoises were recognized by photographs of their dorsal fins. They traveled in small subgroups (mean size = 15) composed of a stable core of five animals plus other individuals that varied greatly from sighting to sighting.

Mars and Earth: Origin and Abundance of Volatiles

Abstract: Mars, like Earth, may have received its volatiles in the final stages of accretion, as a veneer of volatile-rich material similar to C3V carbonaceous chondrites. The high (40)Ar/(36)Ar ratio and low (36)Ar abundance on Mars, compared to data for other differentiated planets, suggest that Mars is depleted in volatiles relative to Earth-by a factor of 1.7 for K and 14 other moderately volatile elements and by a factor of 35 for (36)Ar and 15 other highly volatile elements. Using these two scaling factors, we have predicted martian abundances of 31 elements from terrestrial abundances. Comparison with the observed (36)Ar abundance suggests that outgassing on Mars has been about four times less complete than on Earth. Various predictions of the model can be checked against observation. The initial abundance of N, prior to escape, was about ten times the present value of 0.62 ppb, in good agreement with an independent estimate based on the observed enhancement in the martian (15)N/(14)N ratio (78,79). The initial water content corresponds to a 9-m layer, close to the value of >/=13 m inferred from the lack of an (18)O/(16)O fractionation (75). The predicted crustal Cl/S ratio of 0.23 agrees exactly with the value measured for martian dust (67); we estimate the thickness of this dust layer to be about 70 m. The predicted surface abundance of carbon, 290 g/cm(2), is 70 times greater than the atmospheric CO(2) value, but the CaCO(3) content inferred for martian dust (67) could account for at least one-quarter of the predicted value. The past atmospheric pressure, prior to formation of carbonates, could have been as high as 140 mbar, and possibly even 500 mbar. Finally, the predicted (129)Xe/(132)Xe ratio of 2.96 agrees fairly well with the observed value of 2.5(+2)(-1) (85). From the limited data available thus far, a curious dichotomy seems to be emerging among differentiated planets in the inner solar system. Two large planets (Earth and Venus) are fairly rich in volatiles, whereas three small planets (Mars, the moon, and the eucrite parent body-presumably the asteroid 4 Vesta) are poorer in volatiles by at least an order of magnitude. None of the obvious mechanisms seems capable of explaining this trend, and so we can only speculate that the same mechanism that stunted the growth of the smaller bodies prevented them from collecting their share of volatiles. But why then did the parent bodies of the chondrites and shergottites fare so much better? One of the driving forces behind the exploration of the solar system has always been the realization that these studies can provide essential clues to the intricate network of puzzles associated with the origin of life and its prevalence in the universe. In our own immediate neighborhood, Mars has always seemed to be the planet most likely to harbor extraterrestrial life, so the environment we have found in the vicinity of the two Viking landers is rather disappointing in this context. But the perspective we have gained through the present investigation suggests that this is not a necessary condition for planets at the distance of Mars from a solar-type central star. In other words, if it turns out that Mars is completely devoid of life, this does not mean that the zones around stars in which habitable planets can exist are much narrower than has been thought (114). Suppose Mars had been a larger planet-the size of Earth or Venus-and therefore had accumulated a thicker veneer and had also developed global tectonic activity on the scale exhibited by Earth. A much larger volatile reservoir would now be available, there would be repeated opportunities for tapping that reservoir, and the increased gravitational field would limit escape from the upper atmosphere. Such a planet could have produced and maintained a much thicker atmosphere, which should have permitted at least an intermittently clement climate to exist. How different would such a planet be from the present Mars? Could a stable, warm climate be maintained? It seems conceivable that an increase in the size of Mars might have compensated for its greater distance from the sun and that the life zone around our star would have been enlarged accordingly.

Condition of self-duality for SU(2) gauge fields on Euclidean four-dimensional space

Abstract: The condition of self-duality for a SU(2) gauge field on Euclidean four-dimensional flat space is integrated once to obtain Laplace-like equations for three real variables or for variables one real and one complex. A special case of the latter reduces to the Corrigan-Fairlie-Wilczek-'t Hooft Ansatz.

Semantic-context effects on word recognition: Influence of varying the proportion of items presented in an appropriate context

Abstract: Several recent experiments have shown that an appropriate semantic context facilitates word recognition. Lexical (word/nonword) decisions about a word such as "nurse" are faster when it follows a related word such as "doctor". The present experiment examines the consequence of varying the proportion of semantically related adjacent words. The effect of semantic context is found to depend on the overall proportion of related word pairs. More facilitation occurs when there is a greater proportion of related word pairs. This finding contradicts theories of word recognition which account for context effects solely by postulating transient increases in the aecessibility of only those words semantically related to the particular preceding stimuli encountered by the observer. An adequate theory must include an account of strategic or adaptive processes in which the past usefulness of contextual information modulates its influence in the word recognition process.

Elasticity of coesite

Abstract: The single-crystal elastic constants of SiO2, coesite (monoclinic, C2/c), have been determined from Brillouin scattering measurements on a 100-μm crystal. The elastic constants inferred from acoustic velocities for 80 different propagation directions are (in units of Mbar) c11 = 1.608, c22 = 2.304, c33 = 2.316, c44 = 0.678, c55 = 0.733, c66 = 0.588, c12 = 0.821, c13 = 1.029, c15 = −0.362, c23 = 0.356, c25 = 0.026, c35 = −0.393, and c46 = 0.099. This experimental technique provides a method of determining single-crystal elastic properties for materials such as high-pressure phases that are not available in sufficiently large sizes for ultrasonic measurements.

Nitrogen fixation, distribution, and production of Oscillatoria (Trichodesmium) spp. in the western Sargasso and Caribbean Seas1

Abstract: Measurements of Oscillatoria spp. standing crop, primary production, and N2 fixation were made at 46 stations on three cruises to the Caribbean and western Sargasso Seas. Oscillatoria is a major component of the Caribbean Sea plankton, comprising 60% of the total chlorophyll a in the upper 50 m and about 20% of the primary production. Through N2 fixation it contributes an average of 1.3 mg N m−2 d−1 to the Caribbean Sea, and this may be a major input of nitrogen to this area. Oscillatoria appears to be of relatively little importance in the western Sargasso Sea.

Recent excitement in the DNA replication problem.

Abstract: It is now possible to reproduce most of the reactions involved in DNA replication using prokaryotic enzymes in vitro. Such systems have revealed that DNA replication is a complex process depending on a relatively large number of proteins, and that nucleoside triphosphate hydrolysis energy is used at several discrete steps. Much of the complexity of DNA replication may arise from the need for extreme copying fidelity.

The effect of grazing by the detritivore Orchestia grillus on Spartina litter and its associated microbial community.

Abstract: Orchestia grillus efficiently feeds upon microorganisms attached to ingested Spartina alterniflora litter, but does not digest litter itself. Microorganisms respond to Orchestia grazing with increased metabolic activity, reflected in accelerated decomposition of the nitrogen fraction of litter and increased microbial biomass. Increased microbial activity may be partly a function of ammonia excretion and higher diffusion rate due to animal movement, but mainly it is a direct response to grazing. Microbial biomass increases with grazing because the pool of available nitrogen becomes larger. A model postulating interactions between Orchestria, Spartina litter and attached microorganisms is presented.

Scattering of a Dirac particle with charge Ze by a fixed magnetic monopole

Abstract: The helicity-flip and helicity-nonflip scattering amplitudes of a Dirac particle with spin 1/2 and charge $Ze$ by a fixed magnetic monopole field are calculated. To make the Hamiltonian meaningful an infinitesimal extra magnetic moment is added to the charged particle. The sign of this extra term has measurable consequences. The differential cross section, which is independent of the sign of $Ze$, is tabulated. The helicity-flip amplitude vanishes at all angles for incoming beam helicity = +1 if $Zegg0$, and for incoming beam helicity = -1 if $Zegl0$.

An introductory guide to effective operators in nuclei

Abstract: In this tutorial-style article we discuss the time-independent perturbation formalism of Brandow for effective interactions and operators in a nonrigorous, intuitive way. The simple example of a 2\ifmmode\times\else\texttimes\fi{}2 matrix is used to introduce the basic concepts, for instance the notion of folded diagrams. The same example is used subsequently in a discussion of the branch points arising from "level crossings" and the associated convergence difficulties with the perturbation series. Numerical calculations of the effective interaction and the effective charge are then reviewed, focussing, for the most part, on the ($1s0d$) shell. Whenever possible, simple physical models are used to illustrate the results. A fairly comprehensive summary of the calculations to date is given, and we attempt to synthesize and draw conclusions.

The revised 56-item CRPBI as a research instrument: Reliability and factor structure.

Abstract: The utility of the revised 56-item Child's Report of Parental Behavior Inventory (CRPBI), an instrument less cumbersome than the 260-item original, was examined. Study I found the instrument to be highly reliable at 1-week and 5-week retest intervals. Study II found the factor structure of the revision similar to that of the original, with Factor III somewhat less stable than the other two factors. It was concluded that, in general, the 56-item CRPBI appeared to stand up well as a research instrument.

Experimental study of pyroxene-liquid interaction in quartz-normative basalt 15597.

Abstract: Equilibrium and controlled cooling rate experiments on a synthetic analog of Apollo 15 quartz normative basalt 15597 are reported. While the partitioning of the major elements Ca, Mg, and Fe between pyroxene and liquid is rate independent, the K sub D parameter for Fe/Mg, which is calculated for low-Ca pyroxene, is temperature dependent. It is suggested that chemical trends observed in lunar pyroxenes are a consequence of three rate processes. The processes are (1) rate-dependent suppression of crystallization of other phases until lower temperature alters liquid composition and, therefore, the composition of the pyroxene that crystallizes; (2) the efficiency of fractional crystallization and the extent of crystal zoning are rate dependent; and (3) the partitioning of Al2O3, TiO2, and Cr2O3 between pyroxene and liquid depends on cooling rate.

Incentive Effects in Prospective Remembering

Abstract: Summary Prospective remembering involves the remembering of information which has implications for actions to be performed in the future. In this study, the effects of level of incentive and structure of remembering task—habitual vs. episodic—upon prospective remembering were investigated. Forty-eight male and female university students were asked to mail post cards to the E on specified dates. S s in the high incentive condition mailed cards fewer days late and remembered more often than S s in the low incentive condition. S s in the high incentive condition also were more likely to use an external cue strategy than a cognitive strategy to facilitate remembering. It is concluded that motivation ought to be regarded as a critical variable in the theoretical analysis of prospective remembering.

On the Phenetic Approach to Vertebrate Classification

Abstract: I consider the general subject of phenetic classification to possess two major subdivisions. The first is the matter of definition: what is meant by phenetic classification? The second is the matter of motivation: on what grounds do pheneticists advocate their particular methods for constructing classifications? The question of motivation can be looked at in two ways. First, what principles are involked by pheneticists in selecting the methods which they advocate; and second, what drawbacks do pheneticists ascribe to the methods of classification proposed by other schools of taxonomy? The definition of phenetic taxonomy is necessarily purely a matter of convention, and I shall therefore consider it only in enough detail to avoid ambiguity. The motivations of phenetic taxonomy are of much greater importance, for they touch on the long-standing debate among taxonomists of the phenetic, phylogenetic, and evolutionary schools concerning the proper basis upon which to select classificatory methods. This debate has been perpetuated at least in part by the tendency of some reviewers (for example, Mayr, 1974; Sokal, 1975) to criticize the principles of other schools of taxonomy on a superficial, terminological level. I shall devote most of my discussion to attempts to elucidate what appear to me to be the most fundamental principles of phenetic taxonomy and to obviate the purely terminological aspects of the debate through an evaluation of both phenetic and non-phenetic taxonomic methods on the basis of these principles.

Two-Dimensional Ising Model as an Exactly Solvable Relativistic Quantum Field Theory: Explicit Formulas for n -Point Functions

Abstract: For both T > T/sub c/ and T < T/sub c/, we report exact expressions for the n-spin correlation function of the two-dimensional Ising model suitable for studying large separations between spins. In particular, the scaling limit of these correlation functions can be shown to exist and yields n-point Schwinger functions of some relativistic quantum field theories.