An investigation of vegetation and other earth resource/feature parameters using LANDSAT and other remote sensing data. A: LANDSAT. B: Remote sensing of volcanic emissions

There are no author-identified significant results in this report

Evidence of volcanic ash at a K-T boundary section: Ocean drilling program hole 690 C, Maud Rise, Weddell Sea off East Antarctica

Rare vitric volcanogenic ash but more abundant clay minerals considered volcanogenic in origin are associated with an expanded and essentially complete K-T boundary sequence from Ocean Drilling Project (ODP) Hole 690 C on Maud Rise in the Weddell Sea off East Antarctica. Results at this writing are preliminary and are still based to some extent on shipboard descriptions. Further shore-based studies are in progress. It would appear, however, that the presence of volcanic ash and altered ash in the Danian section beginning at the biostratigraphically and paleomagnetically determined K-T boundary on Maud Rise can be cited as evidence of significant volcanic activity within the South Atlantic-Indian Ocean sector of the Southern Ocean coincident with the time of biotic crises at the end of the Maestrichtian. This is a postulated time of tectonic and volcanic activity within this Southern Hemisphere region, including possible initiation of the Reunion hot spot and a peak in explosive volcanism on Walvis Ridge (1) among other events. A causal relationship with the biotic crisis is possible and volcanism should be given serious consideration as a testable working hypothesis to explain these extinctions

Willmore minimizers with prescribed isoperimetric ratio

Motivated by a simple model for elastic cell membranes, we minimize the Willmore functional among two-dimensional spheres embedded in R^3 with prescribed isoperimetric ratio

PHOTOCHEMISTRY OF PHYCOBILIPROTEINS

Native PEC from the cyanobacterium, Mastigocladus laminosus, and its isolated α-subunit show photoreversibly photochromic reactions with difference-maxima around 502 and 570 nm in the spectral region of the α-84 phycoviolobilin chromophore. (b) Native PEC and its β-subunit show little if any reversible photochemistry in the 600–620 nm region, where the phycocyanobilin chromophores on the β-subunit absorb maximally, (c) Reversible photochemistry is retained in ureadenatured PEC at pH = 7.0 or pH ≤ 3. The difference maxima are shifted to 510 and 600 nm, and the amplitudes are decreased. An irreversible absorbance increase occurs around 670 nm (pH ≤ 3). (d) The amplitude of the reversible photoreaction difference spectrum is maximum in the presence of 4–5 M urea or 1 M KSCN, conditions known to dissociate phycobiliprotein aggregates into monomers. At the same time, the phycocyanobilin chromophore(s) are bleached irreversibly, (e) The amplitude becomes very small in high aggregates, e.g. in phycobilisomes. (f) In a reciprocal manner, the phototransformation of native PEC leads to a reversible shift of its aggregation equilibrium between trimer and monomer. The latter is favored by orange, the former by green light, (g) It is concluded that the phycoviolobilin chromophore of PEC is responsible for reversible photochemistry in PEC, and that there is not only an influence of aggregation state on photochemistry, but also vice versa an effect of the status of the chromophore on aggregation state. This could constitute a primary signal in the putative function as sensory pigment, either directly, or indirectly via the release of other polypeptides, via photodynamic effects, or the like

Multiband theory of quantum-dot quantum wells: Dark excitons, bright excitons, and charge separation in heteronanostructures

Electron, hole, and exciton states of multishell CdS/HgS/CdS quantum-dot quantum well nanocrystals are determined by use of a multiband theory that includes valence-band mixing, modeled with a 6-band Luttinger-Kohn Hamiltonian, and nonparabolicity of the conduction band. The multiband theory correctly describes the recently observed dark-exciton ground state and the lowest, optically active, bright-exciton states. Charge separation in pair states is identified. Previous single-band theories could not describe these states or account for charge separation.Comment: 10 pages of ReVTex, 6 ps figures, submitted to Phys. Rev.

Willmore Surfaces of Constant Moebius Curvature

We study Willmore surfaces of constant Moebius curvature $K$ in $S^4$. It is proved that such a surface in $S^3$ must be part of a minimal surface in $R^3$ or the Clifford torus. Another result in this paper is that an isotropic surface (hence also Willmore) in $S^4$ of constant $K$ could only be part of a complex curve in $C^2\cong R^4$ or the Veronese 2-sphere in $S^4$. It is conjectured that they are the only examples possible. The main ingredients of the proofs are over-determined systems and isoparametric functions.Comment: 16 pages. Mistakes occured in the proof to the main theorem (Thm 3.6) has been correcte

TWO DIFFERENT TYPES OF PHOTOCHEMISTRY IN PHYCOERYTHROCYANIN α-SUBUNIT

The photochemical activities of phycoerythrocyanin α-subunits from Mastigocladus laminosus separated by isoelectric focusing were tested by irradiating at 500, 550, 577 and 600 nm. Two types of photoreversible photochromic responses have been characterized by absorption and absorption difference spectroscopy. Type I is the well-known absorption shift from 571 to 506 nm. Type II is a new response characterized by a line-broadening of the 570 nm absorption

Gauge invariant grid discretization of Schr\"odinger equation

Using the Wilson formulation of lattice gauge theories, a gauge invariant grid discretization of a one-particle Hamiltonian in the presence of an external electromagnetic field is proposed. This Hamiltonian is compared both with that obtained by a straightforward discretization of the continuous Hamiltonian by means of balanced difference methods, and with a tight-binding Hamiltonian. The proposed Hamiltonian and the balanced difference one are used to compute the energy spectrum of a charged particle in a two-dimensional parabolic potential in the presence of a perpendicular, constant magnetic field. With this example we point out how a "naive" discretization gives rise to an explicit breaking of the gauge invariance and to large errors in the computed eigenvalues and corresponding probability densities; in particular, the error on the eigenfunctions may lead to very poor estimates of the mean values of some relevant physical quantities on the corresponding states. On the contrary, the proposed discretized Hamiltonian allows a reliable computation of both the energy spectrum and the probability densities.Comment: 7 pages, 4 figures, discussion about tight-binding Hamiltonians adde

Differential Dynamic Microscopy of Bacterial Motility

We demonstrate 'differential dynamic microscopy' (DDM) for the fast, high throughput characterization of the dynamics of active particles. Specifically, we characterize the swimming speed distribution and the fraction of motile cells in suspensions of Escherichia coli bacteria. By averaging over ~10^4 cells, our results are highly accurate compared to conventional tracking. The diffusivity of non-motile cells is enhanced by an amount proportional to the concentration of motile cells.Comment: 4 pages, 4 figures. In this updated version we have added simulations to support our interpretation, and changed the model for the swimming speed probability distribution from log-normal to a Schulz distribution. Neither modification significantly changes our conclusion

Application of advanced technologies to small, short-haul aircraft

The results of a preliminary design study which investigates the use of selected advanced technologies to achieve low cost design for small (50-passenger), short haul (50 to 1000 mile) transports are reported. The largest single item in the cost of manufacturing an airplane of this type is labor. A careful examination of advanced technology to airframe structure was performed since one of the most labor-intensive parts of the airplane is structures. Also, preliminary investigation of advanced aerodynamics flight controls, ride control and gust load alleviation systems, aircraft systems and turbo-prop propulsion systems was performed. The most beneficial advanced technology examined was bonded aluminum primary structure. The use of this structure in large wing panels and body sections resulted in a greatly reduced number of parts and fasteners and therefore, labor hours. The resultant cost of assembled airplane structure was reduced by 40% and the total airplane manufacturing cost by 16% - a major cost reduction. With further development, test verification and optimization appreciable weight saving is also achievable. Other advanced technology items which showed significant gains are as follows: (1) advanced turboprop-reduced block fuel by 15.30% depending on range; (2) configuration revisions (vee-tail)-empennage cost reduction of 25%; (3) leading-edge flap addition-weight reduction of 2500 pounds