Dispersion forces between two metal objects have been measured at distances varying from 132 to 670 nm. Precautions had to be taken to eliminate electrostatic forces arising from differences in Volta potential. The distance between the metallic objects was determined by measuring the capacitance formed by the test objects. To compare experiment and theory van der Waals forces between chromium objects have been calculated numerically on the basis of the Lifshitz theory. It is shown that when the dielectric constant of chromium is described by the free electron gas model and when an absorption band is taken into account excellent agreement with experiment is obtained. In addition the validity of a number of approximate equations for calculating the force is tested.

In vitro double-integrating-sphere optical properties of tissues between 630 and 1064 nm Beek, J.F.; Blokland, P.; Posthumus, P.; Aalders, M.C.G.; Pickering, J.W.; Sterenborg, H.J.C.M.; van Gemert, M.J.C. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract. The optical properties (absorption and scattering coefficients and the scattering anisotropy factor) were measured in vitro for cartilage, liver, lung, muscle, myocardium, skin, and tumour (colon adenocarcinoma CC 531) at 630, 632.8, 790, 850 and 1064 nm. Rabbits, rats, piglets, goats, and dogs were used to obtain the tissues. A double-integrating-sphere setup with an intervening sample was used to determine the reflectance, and the diffuse and collimated transmittances of the sample. The inverse adding-doubling algorithm was used to determine the optical properties from the measurements. The overall results were comparable to those available in the literature, although only limited data are available at 790-850 nm. The results were reproducible for a specific sample at a specific wavelength. However, when comparing the results of different samples of the same tissue or different lasers with approximately the same wavelength (e.g. argon dye laser at 630 nm and HeNe laser at 632.8 nm) variations are large. We believe these variations in optical properties should be explained by biological variations of the tissues. In conclusion, we report on an extensive set of in vitro absorption and scattering properties of tissues measured with the same equipment and software, and by the same group. Although the accuracy of the method requires further improvement, it is highly likely that the other existing data in the literature have a similar level of accuracy.

The three transport equation optical properties, the absorption coefficient, the scattering coefficient, and the average cosine of the scattering angle, or anisotropy factor have been measured (at 632.8 nm) for canine myocardium after it is heated in a water bath at room temperature and at 37-75 degrees C for 1000 s. The measurement system was a double integrating sphere with collimated light and utilized the adding-doubling solution to the equation of radiative transfer. The absorption coefficient (room temperature control, 2.0 +/- 0.4 cm(-1)) began to increase and the anisotropy factor (room temperature control, 0.93 +/- 0.02) to decrease at above 45 degrees C. At 75 degrees C the changes were significant at the p < 0.0005 level (absorption, 4.5 +/- 1.3 cm(-1); anisotropy, 0.78 +/- 0.05). There was no significant change in the scattering coefficient (room temperature controls, 161 +/- 33 cm(-1)).

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