Time-dependent angularly averaged inverse transport

This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain

High Temperature Limit of the N=2 N= 2 IIA Matrix Model

The high temperature limit of a system of two D-0 branes is investigated. The partition function can be expressed as a power series in $\beta$ (inverse temperature). The leading term in the high temperature expression of the partition function and effective potential is calculated {\em exactly}. Physical quantities like the mean square separation can also be exactly determined in the high temperature limit. We comment on SU(3) IIB matrix model and the difficulties to study it.Comment: Lattice 2000 (Gravity and Matrix Models

Inverse Transport Theory of Photoacoustics

We consider the reconstruction of optical parameters in a domain of interest from photoacoustic data. Photoacoustic tomography (PAT) radiates high frequency electromagnetic waves into the domain and measures acoustic signals emitted by the resulting thermal expansion. Acoustic signals are then used to construct the deposited thermal energy map. The latter depends on the constitutive optical parameters in a nontrivial manner. In this paper, we develop and use an inverse transport theory with internal measurements to extract information on the optical coefficients from knowledge of the deposited thermal energy map. We consider the multi-measurement setting in which many electromagnetic radiation patterns are used to probe the domain of interest. By developing an expansion of the measurement operator into singular components, we show that the spatial variations of the intrinsic attenuation and the scattering coefficients may be reconstructed. We also reconstruct coefficients describing anisotropic scattering of photons, such as the anisotropy coefficient $g(x)$ in a Henyey-Greenstein phase function model. Finally, we derive stability estimates for the reconstructions

Wageningen koploper in viskweek

Honden, koeien, paarden, varkens én vissen. Wageningen UR staat bij het grote publiek bekend als landbouwuniversiteit, maar dit kennisinstituut voor Life Sciences is wereldwijd ook vooraanstaand in de viskweek. Sietze Leenstra (62) is al 32 jaar werkzaam bij De Haar Vissen, het ‘natte lab’ van de WUR. In dit artikel een portret van deze expert op het gebied van kweekvis en zijn werkomgeving

Dynamics of parametric fluctuations induced by quasiparticle tunneling in superconducting flux qubits

We present experiments on the dynamics of a two-state parametric fluctuator in a superconducting flux qubit. In spectroscopic measurements, the fluctuator manifests itself as a doublet line. When the qubit is excited in resonance with one of the two doublet lines, the correlation of readout results exhibits an exponential time decay which provides a measure of the fluctuator transition rate. The rate increases with temperature in the interval 40 to 158 mK. Based on the magnitude of the transition rate and the doublet line splitting we conclude that the fluctuation is induced by quasiparticle tunneling. These results demonstrate the importance of considering quasiparticles as a source of decoherence in flux qubits.Comment: 12 pages, including supplementary informatio

An inceptisol formed in calcareous loess on the 'Dast-i-Esan Top' plain in North Afghanistan. Fabric, mineral and trace element analysis.

The calcixerollic xerochrept described has a low bulk density (1.1 g/cm3) which is attributed to faunal activity. The average mineral composition was 25% quartz, 20% CaCO3, 15% feldspars, 15% micas, 15% chlorites, 2-3% other minerals and 10% amorphous material and there was a clear relationship between minerals and particle size fractions. Trace element contents were 0.6, 11.0, 23.2, 49.1; 19.4, 75.9, 18.7 and 525 mg/kg for V, Cr, Co, Ni, Cu, Zn, Sr and Ba, respectively. Sr and Ba contents were related to carbonate redistribution. (Abstract retrieved from CAB Abstracts by CABI’s permission

Radiation- and Phonon-Bottleneck-Induced Tunneling in the Fe8 Single-Molecule Magnet

We measure magnetization changes in a single crystal of the single-molecule magnet Fe8 when exposed to intense, short (<20 $\mu$s) pulses of microwave radiation resonant with the m = 10 to 9 transition. We find that radiation induces a phonon bottleneck in the system with a time scale of ~5 $\mu$s. The phonon bottleneck, in turn, drives the spin dynamics, allowing observation of thermally assisted resonant tunneling between spin states at the 100-ns time scale. Detailed numerical simulations quantitatively reproduce the data and yield a spin-phonon relaxation time of T1 ~ 40 ns.Comment: 6 RevTeX pages, including 4 EPS figures, version accepted for publicatio