Spectrophotometric study of a hafnium-hematein chelate

A spectrophotometric study of an analytically useful hafnium chelate of hematein is presented. The stoichiometry, the formation constant, the optimal pH range and the free energy of formation of the chelate are described. Beer's law is obtained in the range 3–25 μg of hafnium(IV).The red-brown chelate, of probable formula HfO[hematein]₂, can be used for the colorimetric determination of hafnium in the presence of zirconium, if the molar concentrations of both metals are the same. The molar absorptivity of the hafnium chelate is 5.8·10⁴ 1 mole^-1 cm^-1 at 520 nm and pH 2.0 at room temperature.     

Two-photon spectroscopy of dipole-forbidden transitions

We have investigated the applicability of CNDO/S-type methods for the calculation of optical spectra of molecules with the special implication that the calculations should not only describe the intense, dipole-allowed transitions which dominate the one-photon absorption spectrum but also those transitions which are one-photon forbidden in first-order approximation. We show that such a method is well suited to predict dipole allowed and dipole forbidden transitions at a similar level of accuracy if double excited configurations are taken into account. In spite of the lack of perfect pairing in NDO methods there are still two types of states which exhibit a different sensitivity towards correlation effects. Therefore, the approximation by which we describe the R-dependence of the Coulomb repulsion gains much more importance than in cases where mainly dipole allowed transitions are of interest. These findings confirm results obtained earlier from theories for which the pairing theorem is valid. The calculated data show an excellent stability with respect to further increase of the number of configurations if at least about 200 energy selected configurations are taken into account.     

PHOTOCHEMICAL DAMAGE TO DNA TREATED WITH CHLORPROMAZINE AND NEAR UV RADIATION UNDER AEROBIC AND ANAEROBIC CONDITIONS

Double stranded salmon sperm DNA in a chlorpromazine (CPZ) solution is damaged when irradiated with near UV light. The damage of irradiated DNA can be estimated by measuring the increase in extinction at 260 nm following incubation at 60°C of the DNA with formaldehyde. Moreover, DNA irradiated in the presence of CPZ or kept in the dark separate quite differently in an aqueous polymer two-phase system. DNA irradiated in the presence of CPZ seemed to be susceptible to digestion by endonuclease S1, while the endonuclease of Neurospora crassa could not digest this DNA. Irradiation under aerobic conditions seemed to be less disastrous for DNA than under anaerobic conditions.     

Determination of the nonlinear optical susceptibility χ(2) of surface layers by sum and difference frequency generation in reflection and transmission

The theoretical investigation of sum and difference frequency generation in thin surface layers with rotational symmetry leads to formulas which connect the generated light intensities to the surface second order nonlinear susceptibility tensor. A maximum of seven tensor components can be determined in the case of lowest symmetry. Measurements in transmission should be especially useful since they allow easy variation of both polarization and angle of incidence. On the other hand, large signal enhancements are expected for total internal reflection geometries. A consistent set of ⁽²⁾ tensor components for a thin layer of rhodamine-6G adsorbed on fused silica is found based on data from reflection and transmission measurements.     

Simultaneous diffusion of ions and ion pairs across liquid membranes

The flux of tetrabutylammonium nitrate (Bu₄ NNO₃) across a liquid membrane of n-heptyl cyanide varies with the salt concentrations in dilute solution, but with the concentration squared in more concentrated solution. The results are consistent with a mechanism which includes parallel diffusion of ions and ion pairs. This type of behavior, which will be common in homogeneous membranes of low dielectric constant, is a form of facilitated diffusion in which the salt acts as its own carrier.     

Correction of peripheral blood mononuclear cell cytosolic protein for hemoglobin contamination

Pharmacodynamic (PD) analysis requires accurate and precise quantification of enzyme activity targeted by anticancer agents in surrogate cells like peripheral blood mononuclear cells (PBMCs). Enzyme activity is normally reported per mass unit of protein input. However, high and fluctuating hemoglobin (Hb) contamination strongly influences the protein content of PBMC cytosolic lysate. We present the development and validation of a spectrophotometrical Hb quantification method to correct for this contamination. The applicability of Hb correction was demonstrated by determination of the dihydropyrimidine dehydrogenase enzyme activity in PBMC cytosolic lysates.     

Model for coherent transmittance calculation for polymer dispersed liquid crystal films

This paper analyses the methods of calculating the coherent (direct) transmittance of polymer dispersed liquid crystal (PDLC) films which are polymer-based films with embedded liquid crystal droplets. By comparison with experimental data it is shown that at a high concentration of LC droplets, Beer's law, which is frequently used, leads to large errors in calculations of the transmittance of PDLC films. To calculate coherent transmittance, it is expedient to use the interference approximation which takes into account the interference of waves scattered by individual LC droplets and leads to much more accurate results.     

Wärmeeffekte bei Deformation

Zusammenfassung Aus kalorimetrischen Messungen bei stufenweiser Deformation von Weichkautschukproben und gleichzeitiger Kenntnis der mechanischen Arbeit pro Stufe folgt, daß die von der kinetisch-statistischen Theorie vorausgesetzte Bedingung, die Innere Energie hänge nicht von der Dehnung ab, eine Idealisierung darstellt, die man im tatsächlichen Verhalten selbst bei von der Theorie als geeignet angesehenen Fällen selten oder vielleicht überhaupt nicht verifiziert findet.