Substituent Effects on the Spin-Transition Temperature in Complexes with Tris(pyrazolyl) Ligands

Summary.  Iron (II) complexes with substituted tris(pyrazolyl) ligands, which exhibit a thermally driven transition from a low-spin state at low temperatures to a high-spin state at elevated temperatures, have been studied by M?ssbauer spectroscopy and magnetic susceptibility measurements. From the observed spectra the molar high-spin fraction and the transition temperature have been extracted. All substituents, except for bromine, lead to a decrease of the transition temperature. Density functional calculations have been carried out to compare the experimentally observed shifts of the transition temperature with those derived from theory. Corresponding author. E-mail: paulsen@physik.uni-luebeck.de Received June 26, 2002; accepted July 22, 2002     

Using the Exterior Matrix Method to find eigenfrequencies when the governing equations are systems of first-order equations

In this paper, we will apply the Exterior Matrix Method to the case where the governing equations for one piece of the structure is a system of 4 first-order equations. This generalizes a result when the governing equation was a single fourth-order equation. Ironically, the governing equations do not have to be solved in order to find the corresponding exterior matrix, and the exterior matrices can be used to find the eigenfrequencies of the system, even if there are dissipative joints added to the system. We will first look at the well-understood example of Euler–Bernoulli beams to illustrate the concept, and then move on to the more difficult inclined cable problem.     

Mössbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]·2H2O

The structure of the light-induced metastable state SII of Na₂[Fe(CN)₅NO]·2H₂O was investigated by transmission Mössbauer spectroscopy (TMS) in the temperature range between 85 and 135 K, nuclear inelastic scattering (NIS) at 98 K using synchrotron radiation and density functional theory (DFT) calculations. The DFT and TMS results strongly support the view that the NO group in SII takes a side-on molecular orientation and, further, is dynamically displaced from one eclipsed, via a staggered, to a second eclipsed orientation. The population conditions for generating SII are optimal for measurements by TMS, yet they are modest for accumulating NIS spectra. Optimization of population conditions for NIS measurements is discussed and new NIS experiments on SII are proposed.     

Dark-field scanning in situ spectroscopy platform for broadband imaging of resected tissue

A dark-field geometry spectral imaging system is presented to raster scan thick tissue samples in situ in 1.5 cm square sections, recovering full spectra from each 100 μm diameter pixel. This spot size provides adequate resolution for wide field scanning, while also facilitating scatter imaging without requiring sophisticated light-tissue transport modeling. The system is demonstrated showing accurate estimation of localized scatter parameters and the potential to recover absorption-based contrast from broadband reflectance data measured from 480 nm up to 750 nm in tissue phantoms. Results obtained from xenograft pancreas tumors show the ability to quantitatively image changes in localized scatter response in this fast-imaging geometry. The polychromatic raster scan design allows the rapid scanning necessary for use in surgical/clinical applications where timely decisions are required about tissue pathology.