Search Results - (Author, Cooperation:P. Waterman)

2018-02-28

National Academy of Sciences

0027-8424

1091-6490

Biology

Medicine

Natural Sciences in General

2012-07-06

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Apolipoproteins E/genetics ; Atherosclerosis/*etiology/*pathology ; Hematopoietic Stem Cells/cytology ; Inflammation/complications ; Mice ; Mice, Inbred C57BL ; Monocytes/cytology ; Myocardial Infarction/*complications/*pathology ; Spleen/cytology ; Stem Cells/cytology

1089-7550

AIP Digital Archive

Physics

For a conducting wire of finite length illuminated by an incident electromagnetic wave, induced surface current is represented as the sum of a driven term and resonant traveling waves, for which free-space propagation behavior is slightly modified by a perturbation m. Requiring current to vanish at the ends of the wire, both m and the resulting amplitude are obtained for normal incidence by applying Galerkin's method to the resulting trial function. In the Rayleigh limit cross sections are expressed analytically. For wires up to one-half wavelength long, we find equivalence with Tai's variational results [J. Appl. Phys. 23, 909 (1952)]. Beyond this point, the driven term goes over to the infinite cylinder current, as wire length increases. At the same time, for highly conducting wires one finds an explicit formula for m, in which ||m−1||(very-much-less-than)1; for moderate conductivity, m reduces to the attenuated propagation behavior found by Sommerfeld [J. A. Stratton, Electromagnetic Theory (McGraw-Hill, New York, 1941), pp. 524ff] for infinite-length wires.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The scattering from a thin conducting wire is computed by representing the induced current as a sum of driven and resonant terms, the latter with complex propagation constant mk perturbed from its free space value k. Using Galerkin's method, the central problem of determining m reduces to a minimization problem. For the limiting cases of highly conducting or highly absorbing wires simplifications are found. For short wires the Rayleigh cross sections are obtained; for longer wires with high absorption, accurate cross section formulas are constructed based on the unperturbed infinite wire currents. For general wire lengths and conductivities the method is computationally very simple and results are in excellent agreement with independent computations of both current and far field quantities, as well as experimental measurements. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Extinction efficiency was measured for fibrous aerosol particles arrayed on a diaphragm in a plane orthogonal to the Poynting vector of the incident radiation. Very small quantities of material can be characterized in this static fashion. Two-dimensional extinction efficiencies for a series of graphitic fibers of various resistivities are shown to agree with results of a variational theory. Particle interaction distances initiate at approximately the value of the length of the particle.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Employing self-consistency, the multiple-scattering problem is formulated for periodic arrays of particles having constitutive parameters distinct from those of the embedding material. A T-matrix description of individual particle scattering is employed, so that particles need not be spherical. Explicit analytical and numerical results are obtained for the effective complex dielectric constant ε¯ and permeability μ¯ in the quasistatic and infinitesimal lattice limits for several lattice geometries, and shown to agree with existing static computations under appropriate conditions. Random arrays are also considered briefly, and the role of single-particle resonance effects is examined. Finally, longitudinal electric and magnetic waves are predicted to exist at certain discrete frequencies where ε¯ or μ¯ vanish.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Extinction cross sections normalized to particle volume for two fibrous graphitic aerosols were measured at 0.319 cm (94 GHz) and 0.857 cm (35 GHz). Characterization of the aerosol was performed using several techniques, that is, dosimetrically, through time correlation of millimeter wavelength extinction signals with scattered radiation at much shorter wavelengths, through time correlation with a nearly colinear measurement of extinction at visible wavelengths and using a purpose-built time resolved particle collector system. Results compare well with existing detailed theory.

Electronic Resource

0021-9673

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0031-9422

Rutaceae ; Z. coriaceum ; Zanthoxylum spinosum ; alkaloids ; benzophenanthridines ; chemical taxonomy. ; dihydrobenzophenanthridines

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

0031-9422

3',4'-methylenedioxy-7-methoxyflavone. ; Leguminosae ; Millettia hemsleyana ; Papilionoidae ; chalcones ; dihydrochalcones ; dihydroisomilletenone methyl ether ; dihydromilletenone methyl ether ; lanceolatin-B ; milletenone ; pongaflavone

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

1420-9071

Aeollanthus buchnerianus ; Lamiaceae ; dodecanoic acids ; abietane diterpenes ; antifungal and antibacterial bioactivity

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract Using bioassay guided isolation, three novel 12 carbon polyoxygenated fatty acids and a novel abietane diterpene have been isolated from the the chloroform extract of aerial parts ofAeollanthus buchnerianus (Lamiaceae). Rigorous spectroscopic methods were used for compound identification. (Z,Z)-8ζ-acetoxy-5ζ-hydroxydodeca-2,6-dienoic acid and (Z,Z)-5ζ,8ζ-dihydroxydodeca-2,6-dienoic acid inhibited the spore germination ofCladosporium cucumerinum (both with Minimum Inhibitory Dose (MID) values of 1 μg) andAspergillus niger (MID 5 and 25 μg respectively). Further, they also reduced the hyphal growth ofPythium ultimum. (Z)-5ζ-hydroxy-6ζ,7ζ,8ζ-triacetoxydodeca-2-dienoic acid exhibited short term inhibition of the growth ofCladosporium cucumerinum. The novel abietane diterpenoid, (rel)-14α-acetoxyabiet-7-en-18-oic acid inhibited the growth of the gram positive bacteriaBacillus subtilis, staphylococcus aureus andStreptomyces scabies (MIC values 80, 20 and 20 μg ml−1 respectively).

Electronic Resource

1438-1168

Springer Online Journal Archives 1860-2000

Geosciences

Zusammenfassung Der Longwood Igneous Complex liegt au der Südküste der der Südinsel Neuseelands. Er ist 32 km lang und 12 km breit und ist Teil eines Nord-Süd verlaufenden Gesteinsgürtels paläozoischer vulkanischer, vulkano-klastischer und intrusiver Gesteine. Der Komplex beinhaltet geschichtete Gabbros (Pahia Layered Series) gemeinsam mit Dioriten, Trondjhemiten und Granitoiden. Bedeutende Platinanomalien in Bachsedimenten, die aus einem ca. 10 x 1 km großen Gebiet mit Plagioklas-reichen, Olivin-führenden Kumulat-Gesteinen stammen, wurden von Sigma Resources lokalisiert. Platin- und Palladiumsulfide, -arsenide und -Legierungen wurden in Seifenlager-stätten, in diesem Gebiet nachgewiesen. Insgesamt wurden 1500 Unzen Platin während der historischen Bergbautätigkeit auf Gold in diesen Lagerstätten als Nebenprodukt gewonnen. PGE-Mineralisation (bis 3.0 ppm Pt und 3.3 ppm Pd) in Geschieben und bedeutende Pt-Bodenanomalien (max. 0.47 ppm Pt) wurden in diesem Gebiet entdeckt. Die mineralisierten Troktolit- und Olivin-Gabbro-Gerölle und benachbarte Aufschlüsse zeigen weitgehende Ähnlichkeit mit der Anorthosit-Troktolit-Olivin-GabbroAbfolge der Banded Series des Stillwater Komplexes. Die mineralisierten leukokraten Gesteine führen Plagioklas und Olivin als Kumulusphasen sowie untergeordnet Klinopyroxene, primäre Amphibole und geringe Mengen (〈 0.5 %) an Sulfiden. Als Sulfide kommen Magnetkies, Kupferkies, Pyrit und sekundäre Kupfersulfide vor. Die Ähnlichkeit dieser Mineralisation und ihrer Nebengesteine mit dem JM Reef des Stillwater Komplexes und der AP und PV Mineralisation in der Penikat Intrusion läßt die Pahia Layered Series als geeignetes Gebiet für die Entdeckung großer stratiformer PGE-Lagerstätten erscheinen.

Summary The Longwood Igneous Complex is situated at the southern tip of the South Island of New Zealand. The Complex is 32 km long and up to 12 km wide and is part of a more extensive north-trending belt of late Paleozoic volcanic, volcaniclastic and intrusive rocks. The complex is comprised of an extensive series of layered gabbros (Pahia Layered Series) together with diorites, trondjhemite and granitoids. Exploration by Sigma Resources has located significant platinum-in-drainage anomalies which are derived from a 10 km x 1 km area of largely plagioclase-rich, olivinebearing cumulate rocks within the Pahia Layered series. Grains of platinum and palladium sulphide, arsenide and alloy minerals have been identified in placer deposits derived from this area. A total of 1,500 ounces of platinum was reported to have been recovered as a by-product of historic placer gold mining of these deposits. Platinumgroup element mineralisation in float rocks (up to 3.0 ppm Pt and 3.3 ppm Pd) and significant platinum-in-soil anomalies (peak value 0.47 ppm Pt) have been found within this area. The mineralised troctolite and olivine-gabbro float and adjacent exposures are broadly similar to the anorthosite-troctolite-olivine gabbro zones within the Banded Series of the Stillwater Complex. The mineralised rocks are leucocratic plagioclaseolivine adcumulates with minor clinopyroxene oikocrysts, primary amphibole and sparse (〈0.5%) sulphide. Sulphide minerals are pyrrhotite, chalcopyrite, pyrite and secondary copper sulphides. The similarity of this mineralisation style and its host rocks to the JM Reef of the Stillwater Complex and AP and PV mineralisation of the Penikat Intrusion highlights the excellent potential for discovery of a large stratiform platinumgroup element deposit in the Pahia Layered Series.

Electronic Resource

1432-1939

Springer Online Journal Archives 1860-2000

Biology

Summary The relative susceptibility of thirty-tree species to feeding by the coccid, Icerya seychellarum, (from a previous atoll survey) were correlated with four morphological characters (leaf lamina and midrib thicknesses, density of hairs on leaf underside and presence of waxy upper leaf surface) and the concentrations of six mineral elements (N, P, K, Ca, Mg and Na) and three measures of chemical defense (total phenols, condensed tannins and alkaloids). For twenty-two species four phenological variables, from a separate two year study, were also correlated with susceptibility. Lamina thickness, presence of dense hairs and the concentrations of alkaloids or condensed tannins were significantly correlated with host susceptibility. The ideal host has thick, evergreen and hairless leaves. Some host species with high concentrations of secondary chemicals were also highly susceptible and a new hypothesis suggests that stylet manoeuvrability enables a coccid to avoid these substances in thick, but not thin, leaves. Experimental ‘seeding’ of crawlers on to eleven host species showed marked differences in susceptibility in different stages of the life-cycle: presence of dense hairs appeared to deter settlement whilst thick lamina enhanced coccid survival.

Electronic Resource

1432-1939

Tannin ; Protein precipitation ; Phenolics ; Feeding-deterrents

Springer Online Journal Archives 1860-2000

Biology

Summary A series of seventeen plant extracts rich in phenolic materials, including condensed and hydrolysable tannins, have been subjected to a series of chemical analyses in an attempt to gather ecologically significant information about their structure. Procedures investigated were (i) the Folin-Denis and Hagerman and Butler methods for quantifying total phenolics, (ii) the vanillin and proanthocyanidin methods for quantifying condensed tannins, (iii) the iodate and nitrous acid methods for hydrolysable tannins. It was found that the techniques for total phenolics correlated well, the Hagerman and Butler method giving higher estimates where solutions were particularly phenol rich. By contrast there was considerable discrepancy between the methods examined for condensed tannins. This is probably due primarily to the very different chemical reactions that form the basis of these procedures and also to the fact that the extract dependent products of the proanthocyanidin method vary in their A 1 1 values. During the study of condensed tannins methods for estimating their contribution to total phenolics and for measuring their average polymer length were examined. In both cases different procedures produced very variable results. Available methods for hydrolysable tannins were found not to be generally applicable across all extracts thought to contain this type of tannin on the basis of chromatographic analysis. An attempt to produce a quantitative spectrophotometric assay for hydrolysable tannins based on changes in reactivity to ferric chloride due to hydrolysis is described. This proved to be of limited sensitivity but may have some merit for estimating levels in hydrolysable tannins in phenol-rich plant extracts that also contain condensed tannins. It is concluded that whilst the overall level of phenolics in extracts can be estimated with some confidence the information imparted by more specific assays is very dependent on the procedures employed, particularly when dealing with extracts from taxonomically highly diverse sources.

Electronic Resource

1432-1939

Tannin ; Protein precipitation phenolics ; Feeding-deterrents

Springer Online Journal Archives 1860-2000

Biology

Summary A series of seventeen taxonomically diverse plant extracts rich in phenolic materials, including condensed and hydrolysable tannins, have been subjected to a series of biochemical analyses in an attempt to gather ecologically significant information about their interaction with proteins and amino acids. Methods employed were (i) protein-precipitation, using bovine serum albumin as substrate, followed by computation of specific activities of the tannins present in the extracts, and (ii) the inhibition of cellulase activity by tannin extracts bound to the cellulose substrate and free in solution. Both techniques revealed that all extracts contained tannin material. However, attempts to relate the results of the two procedures and in turn to relate them to information reported previously on the chemical properties of these extracts revealed that there was little correlation between any of the chemical or biochemical properties examined. From this analysis it would seem that whilst the analytical procedures available for studying tannins may generate ecologically useful information it is at present impossible, at least where plant material that is taxonomically diverse is being examined, to extrapolate from one type of measure to anticipate what would be observed from another type of measure. In addition to the above three other observations arose from this study. First, it appears to be generally true that there is not an absolute positive correlation between the level of protein precipitation and the incorporation of tannin in the tannin-protein precipitate. As relative protein concentration increases the proportion of tannin bound in the precipitate decreases, leading to less stable precipitates. Second, it is confirmed that some basic amino acids will precipitate with tannins, a phenomenon that could potentially influence amino acid balance in the diet. Third, complexation between tannin and protein absorbed on a cellulose substrate is able to interfere with the digestion of that cellulose by cellulase enzymes. Cellulose masking of this type may potentially effect the efficiency of cellulolytic activity in the rumen and if so suggests another subtle variation in the potential antifeedant properties of tannins.

Electronic Resource

1573-5052

Africa ; Cameroun ; Douala-Edea ; Drainage ; Gradient ; Phosphorus ; Rain-forest

Springer Online Journal Archives 1860-2000

Biology

Abstract All living trees (≥30 cm gbh) were enumerated in 104 80×80 m plots arranged along four transects in the Douala-Edea Forest Reserve Cameroun, a system of low-lying ancient coastal sand dunes interspersed by numerous streams and swamps. The extent of permanent and seasonal swamps was recorded for each plot. Two hundred thirty taxa were recognized of which 63% were identified to species. Mean tree density was 376 ha−1, basal area 31.0 m2 ha−1 and number of species per plot 39. The Olacaceae were the most abundant family in terms of basal area, but the Euphorbiaceae the most frequently represented. The most abundant species wasCoula edulis (Olacaceae). Twenty-two plots had most of their area permanently or seasonally swamped. Percentage sand, silt and clay ranged between 32–100, 0–64, 0–21% respectively. The ranges for other variables recorded were: pH (2.7–5.4), organic carbon (1.5–12.4%), available phosphorus (7–90 ppm) and potassium (28–188 ppm), and nitrogen (ammonium 4–40 ppm, nitrate 1–12 ppm). Classification of the plots on the basis of six soil variables provided three large distinct groups: swamp plots and non-swamp plots, the latter divided into plots of low and high available soil phosphorus. Swamp plots were distinguished by high abundances ofProtomegabaria stapfiana andLibrevillea klainei, though correspondence ordination of plots in these groups showedP. stapfiana associated with more clayey soils andLibrevillea klainei (andGluema ivorensis) on the very sandy soils. Direct gradient analysis highlighted several species associated with these lower phosphorus soils. Available soil phosphorus is not as low at Douala-Edea as in parts of Korup, and the association of these Douala-Edea soils with the Caesalpinioideae is correspondingly weaker.

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