Granitic Bornhardts And Associated Landform Features In Zimbabwe

A Geographical Proceedings article on Zimbabwe's GRANITIC BORNHARDTS AND ASSOCIATED LANDFORM FEATURES.Steep-sided convex domes or bomhardts are characteristic of about one third of the granitic ‘ landscapes in central and eastern Zimbabwe. These features are associated with batholith intrusions which make up a large portion, of a massive and ancient crafon that extends some 600 kilometres in a north-east to south-west direction across the country (see Figure 1). The bombardt terrain forms a distinctive although discontinuous arc on the southern margin of this craton and the adjacent mobile belts of gneissic rocks. Morphologically, the granitic domes vary from completely stripped through to debris- covered hills, and from almost perfectly symmetrical ‘whaleback1 residuals through to irregular,-sugar-loaf features

NASA research in supersonic propulsion: A decade of progress

A second generation, economically viable, and environmentally acceptable supersonic aircraft is reviewed. Engine selection, testbed experiments, and noise reduction research are described

Time-marching transonic flutter solutions including angle-of-attack effects

Transonic aeroelastic solutions based upon the transonic small perturbation potential equation were studied. Time-marching transient solutions of plunging and pitching airfoils were analyzed using a complex exponential modal identification technique, and seven alternative integration techniques for the structural equations were evaluated. The HYTRAN2 code was used to determine transonic flutter boundaries versus Mach number and angle-of-attack for NACA 64A010 and MBB A-3 airfoils. In the code, a monotone differencing method, which eliminates leading edge expansion shocks, is used to solve the potential equation. When the effect of static pitching moment upon the angle-of-attack is included, the MBB A-3 airfoil can have multiple flutter speeds at a given Mach number

Seasonal variations of glaciochemical, isotopic and stratigraphic properties in Siple Dome (Antarctica) surface snow

Six snow-pit records recovered from Siple Dome, West Antarctica, during 1994 are used to study seasonal variations in chemical (major ion and H202), isotopic (deuterium) and physical stratigraphic properties during the 1988-94 period. Comparison of δD measurements and satellite-derived brightness temperature for the Siple Dome area suggests that most seasonal SD maxima occur within ±4 weeks of each 1 January. Several other chemical species (H2O2, non-sea-salt (nss) SO4 2-, methanesulfonic acid and NO3-) show coeval peaks with SD, together providing an accurate method for identifying summer accumulation. Sea-salt-derived species generally peak during winter/spring, but episodic input is noted throughout some years. No reliable seasonal signal is identified in species with continental sources (nssCa2+ nss Mg2+), NH4 + or nssCl-. Visible strata such as large depth-hoar layers (\u3e5 cm) are associated with summer accumulation and its metamorphosis, but smaller hoar layers and crusts are more difficult to interpret. A multi-parameter approach is found to provide the most accurate dating of these snow-pit records, and is used to determine annual layer thicknesses at each site Significant spatial accumulation variability exists on an annual basis, but mean accumulation in the sampled 10 km2 grid for the 1988-94 period is fairly uniform

Influence of Collision Cascade Statistics on Pattern Formation of Ion-Sputtered Surfaces

Theoretical continuum models that describe the formation of patterns on surfaces of targets undergoing ion-beam sputtering, are based on Sigmund's formula, which describes the spatial distribution of the energy deposited by the ion. For small angles of incidence and amorphous or polycrystalline materials, this description seems to be suitable, and leads to the classic BH morphological theory [R.M. Bradley and J.M.E. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988)]. Here we study the sputtering of Cu crystals by means of numerical simulations under the binary-collision approximation. We observe significant deviations from Sigmund's energy distribution. In particular, the distribution that best fits our simulations has a minimum near the position where the ion penetrates the surface, and the decay of energy deposition with distance to ion trajectory is exponential rather than Gaussian. We provide a modified continuum theory which takes these effects into account and explores the implications of the modified energy distribution for the surface morphology. In marked contrast with BH's theory, the dependence of the sputtering yield with the angle of incidence is non-monotonous, with a maximum for non-grazing incidence angles.Comment: 12 pages, 13 figures, RevTe

Climatic impact of the A.D. 1783 Asama (Japan) Eruption was minimal: Evidence from the GISP2 Ice Core

Assessing the climatic impact of the A.D. 1783 eruption of Mt. Asama, Japan, is complicated by the concurrent eruption of Laki, Iceland. Estimates of the stratospheric loading of H2SO4 for the A.D. 1108 eruption of Asama derived from the SO42− time series in the GISP2 Greenland ice core indicate a loading of about 10.4 Tg H2SO4 with a resulting stratospheric optical depth of 0.087. Assuming sulfur emissions from the 1783 eruption were only one‐third of the 1108 event yields a H2SO4 loading value of 3.5 Tg and a stratospheric optical depth of only 0.029. These results suggest minimal climatic effects in the Northern Hemisphere from the 1783 Asama eruption, thus any volcanically‐induced cooling in the mid‐1780s is probably due to the Laki eruption

Radiative Corrections to Electron-Proton Scattering

The radiative corrections to elastic electron-proton scattering are analyzed in a hadronic model including the finite size of the nucleon. For initial electron energies above 8 GeV and large scattering angles, the proton vertex correction in this model increases by at least two percent the overall factor by which the one-photon exchange (Rosenbluth) cross section must be multiplied. The contribution of soft photon emission is calculated exactly. Comparison is made with the generally used expressions previously obtained by Mo and Tsai. Results are presented for some kinematics at high momentum transfer.Comment: 31 pages, 4 figure

Greenland ice core “signal” characteristics: An expanded view of climate change

The last millenium of Earth history is of particular interest because it documents the environmental complexities of both natural variability and anthropogenic activity. We have analyzed the major ions contained in the Greenland Ice Sheet Project 2 (GISP 2) ice core from the present to ∼674 A.D. to yield an environmental reconstruction for this period that includes a description of nitrogen and sulfur cycling, volcanic emissions, sea salt and terrestrial influences. We have adapted and extended mathematical procedures for extracting sporadic (e.g., volcanic) events, secular trends, and periodicities found in the data sets. Finally, by not assuming that periodic components (signals) were “stationary” and by utilizing evolutionary spectral analysis, we were able to reveal periodic processes in the climate system which change in frequency, “turn on,” and “turn off” with other climate transitions such as\u27that between the little ice age and the medieval warm period

The Q2Q^2 dependence of the measured asymmetry A1A_1: the test of the Bjorken sum rule

We analyse the proton and deutron data on spin dependent asymmetry $A_1(x,Q^2)$ supposing the DIS structure functions $g_1(x,Q^2)$ and $F_3(x,Q^2)$ have the similar $Q^2$-dependence. As a result, we have obtained that $\Gamma_1^p - \Gamma_1^n = 0.190 \pm 0.038$ at $Q^2= 10 GeV^2$ and $\Gamma_1^p - \Gamma_1^n = 0.165 \pm 0.026$ at $Q^2= 3 GeV^2$, what is in the best agreement with the Bjorken sum rule predictions.Comment: LaTeX, 5 pages, no figures, to be published in JETP Letter

Parton distribution functions from the precise NNLO QCD fit

We report the parton distribution functions (PDFs) determined from the NNLO QCD analysis of the world inclusive DIS data with account of the precise NNLO QCD corrections to the evolution equations kernel. The value of strong coupling constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate bosons rates calculated in the NNLO using obtained PDFs are in agreement to the latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS