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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Speleothems As Proxy For The Carbon Isotope Composition Of Atmospheric Co2, M. Baskaran, R. V. Krishnamurthy
Speleothems As Proxy For The Carbon Isotope Composition Of Atmospheric Co2, M. Baskaran, R. V. Krishnamurthy
Environmental Science and Geology Faculty Research Publications
We have measured the stable isotope ratios of carbon in a suite of recent cave deposits (<200 >years) from the San Saba County, Texas, USA. The methodology for dating these deposits using excess 210Pb was recently established [Baskaran and Iliffe, 1993]. The carbon isotope ratios of these samples, spanning the time period ∼1800–1990 AD, reflect the carbon isotope ratio of atmospheric CO2 for the same period. The pathways by which the δ13C of atmospheric CO2 is imprinted on these speleothems can be explained using a model developed by Cerling (1984). The results suggest that the …200>
Atmospheric Depositional Fluxes Of 7Be And 210Pb At Galveston And College Station, Texas, M. Baskaran, Charles H. Coleman, Peter H. Santschi
Atmospheric Depositional Fluxes Of 7Be And 210Pb At Galveston And College Station, Texas, M. Baskaran, Charles H. Coleman, Peter H. Santschi
Environmental Science and Geology Faculty Research Publications
The bulk depositional fluxes of 210Pb and 7Be were measured at a coastal (Galveston) and an inland (College Station) station for about 3 years, between 1989 and 1991. The annual depositional fluxes of 7Be and 210Pb at Galveston during this period varied by a factor of about 2.5, between 8.9 and 23.2 disintegrations per minute (dpm) cm−2 yr−1, with a mean of 14.7 dpm cm−2 yr−1 for 7Be, and 0.67 and 1.71 dpm cm−2 yr−1, with a mean of 1.03 dpm cm−2 yr−1 for 210 …
K-Shell Ionization Of Atoms By Electron And Positron Impact, S. P. Khare, Vandana Saksena, J. M. Wadehra
K-Shell Ionization Of Atoms By Electron And Positron Impact, S. P. Khare, Vandana Saksena, J. M. Wadehra
Physics and Astronomy Faculty Research Publications
In the plane-wave Born approximation (PWBA), scaling relations for K-shell generalized oscillator strengths and energy-loss cross sections of atoms are given. The total K-shell ionization cross sections, obtained at high impact energy, are used to obtain the Bethe collisional parameter cK for atoms ranging from carbon to gold. These values of cK are, in general, significantly different from those obtained previously with the help of Fano plots at relatively low impact energies. Furthermore, using Hippler’s modification of the PWBA [Phys. Lett. A 144, 81 (1990)], total K-shell ionization cross sections of various atoms by …
Age Determination Of Recent Cave Deposits Using Excess 210Pb - A New Technique, M. Baskaran, Thomas M. Iliffe
Age Determination Of Recent Cave Deposits Using Excess 210Pb - A New Technique, M. Baskaran, Thomas M. Iliffe
Environmental Science and Geology Faculty Research Publications
Cave deposits have been widely used as proxy recorders in deciphering palaeoclimate during the last glacial/interglacial maxima (∼ 120 ka) [Harmon et al., 1975; Atkinson et al., 1978; Goede and Harmon, 1983; Ayliffe and Veeh, 1989]. Palaeoclimatic studies of cave deposits for the past 1–1000 yr time scale require a precise dating technique, that until now has been lacking. Due to the multiple sources of carbon in speleothems, 14C dates obtained for recently deposited calcite are highly variable and thus, 14C dating techniques are not suitable to obtain speleothem ages for the past 1–1000 years.
Here, we show …
Optimal Control And Differential Games With Measures, E. N. Barron, R. Jensen, J. L. Menaldi
Optimal Control And Differential Games With Measures, E. N. Barron, R. Jensen, J. L. Menaldi
Mathematics Faculty Research Publications
We consider control problems with trajectories which involve ordinary measureable control functions and controls which are measures. The payoff involves a running cost in time and a running cost against the control measures. In the optimal control problem we are trying to minimize this payoff with both controls. In the differential game problem we are trying to minimize the cost with the ordinary controls assuming that the measure controls are chosen to maximize the cost. We will characterize the value functions in both cases using viscosity solution theory by deriving the Bellman and Isaacs equations.
Regularizing Effect For Integro-Differential Parabolic Equations, Maria Giovanna Garroni, José Luis Menaldi
Regularizing Effect For Integro-Differential Parabolic Equations, Maria Giovanna Garroni, José Luis Menaldi
Mathematics Faculty Research Publications
No abstract provided.
Generalized Lame-Clapeyron Solution For A One-Phase Source Stefan Problem, José Luis Menaldi, Domingo Alberto Tarzia
Generalized Lame-Clapeyron Solution For A One-Phase Source Stefan Problem, José Luis Menaldi, Domingo Alberto Tarzia
Mathematics Faculty Research Publications
In this paper we obtain a generalized Lamé-Clapeyron solution for a one-phase Stefan problem with a particular type of sources. Necessary and sufficient conditions are given in order to characterize the source term which provides a unique solution. Some estimates on the free boundary and the temperature are presented. In particular, asymptotic expansions are given for small Stefan number and source.
Ext In The Nineties, Robert R. Bruner
Ext In The Nineties, Robert R. Bruner
Mathematics Faculty Research Publications
We describe a package of programs to calculate minimal resolutions, chain maps, and null homotopies in the category of modules over a connected algebra overe Z_2 and in the category of unstable modules over the mod 2 Steenrod algebra. They are available for free distribution and intended for use as an Adams spectral sequence 'pocket calculator'. We provide a sample of the results obtained from them.