Activation analysis for selected elements in micrometeorites and hypervelocity projectiles Annual progress report, 1 Jul. 1969 - 1 Jul. 1970

Activation analysis to identify materials for use as catcher for micrometeoroid

Canonical Transformation Approach to the Ultrafast Non-linear Optical Dynamics of Semiconductors

We develop a theory describing the effects of many-particle Coulomb correlations on the coherent ultrafast nonlinear optical response of semiconductors and metals. Our approach is based on a mapping of the nonlinear optical response of the ``bare'' system onto the linear response of a ``dressed'' system. The latter is characterized by effective time-dependent optical transition matrix elements, electron/hole dispersions, and interaction potentials, which in undoped semiconductors are determined by the single-exciton and two-exciton Green functions in the absence of optical fields. This mapping is achieved by eliminating the optically-induced charge fluctuations from the Hamiltonian using a Van Vleck canonical transformation. It takes into account all many-body contributions up to a given order in the optical fields as well as important Coulomb-induced quantum dynamics to all orders in the optical field. Our approach allows us to distinguish between optical nonlinearities of different origins and provides a physically-intuitive interpretation of their manifestations in ultrafast coherent nonlinear optical spectroscopy.Comment: 24 page

PID and PID-like controller design by pole assignment within D-stable regions

This paper presents a new PID and PID-like controller design method that permits the designer to control the desired dynamic performance of a closed-loop system by first specifying a set of desired D-stable regions in the complex plane and then running a numerical optimisation algorithm to find the controller parameters such that all the roots of the closed-loop system are within the specified regions. This method can be used for stable and unstable plants with high order degree, for plants with time delay, for controller with more than three design parameters, and for various controller configurations. It also allows a unified treatment of the controller design for both continuous and discrete systems. Examples and comparative simulation results are pro-vided to illustrate its merit

A posteriori noise estimation in variable data sets

Most physical data sets contain a stochastic contribution produced by measurement noise or other random sources along with the signal. Usually, neither the signal nor the noise are accurately known prior to the measurement so that both have to be estimated a posteriori. We have studied a procedure to estimate the standard deviation of the stochastic contribution assuming normality and independence, requiring a sufficiently well-sampled data set to yield reliable results. This procedure is based on estimating the standard deviation in a sample of weighted sums of arbitrarily sampled data points and is identical to the so-called DER_SNR algorithm for specific parameter settings. To demonstrate the applicability of our procedure, we present applications to synthetic data, high-resolution spectra, and a large sample of space-based light curves and, finally, give guidelines to apply the procedure in situation not explicitly considered here to promote its adoption in data analysis.Comment: Accepted for publication in A&

Accelerator Constraints on Neutralino Dark Matter

The constraints on neutralino dark matter \chi obtained from accelerator searches at LEP, the Fermilab Tevatron and elsewhere are reviewed, with particular emphasis on results from LEP 1.5. These imply within the context of the minimal supersymmetric extension of the Standard Model that m_\chi \ge 21.4 GeV if universality is assumed, and yield for large tan\beta a significantly stronger bound than is obtained indirectly from Tevatron limits on the gluino mass. We update this analysis with preliminary results from the first LEP 2W run, and also preview the prospects for future sparticle searches at the LHC.Comment: Presented by J. Ellis at the Workshop on the Identification of Dark Matter, Sheffield, September, 1996. 14 pages; Latex; 12 Fig

Influencia de la gestión de los bosques y las zonas de pastos en la diversidad y conservación de las mariposas diurnas y zygenas (Lepidoptera, Papilionoidea, Hesperiidae, Zygaenidae)

The distribution of butterflies and burnet moths was investigated at 38 patches in the Oettinger Forst (Bavaria, Germany) in 2001. Forty–two butterfly and four burnet moth species were recorded. They were unequally distributed over the study area. The diversity was significantly lower in the forests than in the non–forest patches. Windblows and meadows showed largely similar results but clearings had higher Shannon indices and Eveness and presented a trend to higher species numbers. The hay meadows had higher mean incidences of the 25 common species and exhibited a trend to higher numbers of individuals and species as well as higher mean Shannon indices than in the mulched meadows. The old quarries and sandpits harboured remarkable species, some of these occurring in high densities, thus underlining the conservation value of such structures in a non–target area for nature–conservation measurements.Se ha estudiado la distribución de las mariposas diurnas y zygenas en 38 parcelas de Oettinger Forst (Baviera, Alemania) en el año 2001. En total, se contabilizaron 42 especies de mariposas diurnas y cuatro de mariposas zygenas, cuya distribución en la zona de estudio resultó bastante irregular. La diversidad fue considerablemente inferior en las zonas boscosas en comparación con las zonas de pastos. En general, no parece que los windblows (áreas de un bosque donde los árboles han sido abatidos por el viento) y los prados ejerzan influencia alguna sobre las concentraciones de especies, si bien los claros presentan unos índices de Shannon y Eveness más altos y una tendencia a contar con un mayor número de especies. Los campos de heno presentan la incidencia media más alta de las 25 especies comunes y muestran una tendencia general a contar con un número superior de especies y ejemplares, así como unos índices de Shannon más elevados que los prados cubiertos de mantillo. Las antiguas canteras y arenales albergan varias especies notables, algunas de ellas en grandes densidades, lo que pone de relieve el gran valor que este tipo de estructuras desempeñan en la conservación, pese a ser zonas que no suelen tenerse en cuenta al efectuarse mediciones sobre el estado de conservación de la naturaleza