Showing papers by "Rakesh K. Jain published in 1982"

Incorporating toxicology in the synthesis of industrial chemical complexes

Abstract: A systematic procedure is presented for synthesizing chemical complexes in which toxicology aspects are incorporated in addition to the economic considerations Based on previous, work by Grossmann ...

The linear, hydrodynamic stability of an interfacially perturbed, transversely isotropic, thin, planar viscoelastic film

Abstract: A dispersion equation which describes the linear, hydrodynamic stability of an interfacially perturbed, thin (O(10–100 nm)), planar, uncharged, transversely isotropic, viscoelastic film bounded by electrolytic Newtonian fluids is developed for the case in which the film interfaces are tangentially immobile. The linear viscoelastic rheology of the film is described by a Boltzmann superposition in which the stress relaxation tensor is formulated by utilizing Kelvin models. The influence of the electrical interactions of the film system on the linear dynamics is derived explicitly by integrating the normal mode electrostatic field equations. An investigation of the adjoint properties of the normal mode mechanical field relations indicates that for a certain class of films, (i) the principle of exchange of stabilities is valid, (ii) instability is nonoscillatory, and (iii) oscillatory states decay. A simplified dispersion equation for a symmetric film system is deduced, and it is shown that this equation describes squeezing and stretching eigenmodes.

Temperature Gradients and Local Perfusion in a Mammary Carcinoma

Abstract: Temperature gradients of mammary tumors in randombred Sprague-Dawley rats under normothermia, hypothermia, and hyperthermia were determined, and their experimental modifications were utilized to assess differences in perfusion rates within the neoplastic tissue. Normothermic tumors showed a circadian rhythm with zenith at midnight and nadir at midday. Differences between highest and lowest temperatures recorded during the 24-hour period reached up to 3 degrees C. Similar oscillations were observed in subcutaneous tissue without tumor. An average temperature increment of 0.5-1.0 degrees C was observed when a tumor was transferred from the subcutaneous to the abdominal location. Gradients larger than 1 degrees C were observed within the same tumor in locations only a few millimeters distance from each other. The nonuniformity in temperature within normothermic tumors was exaggerated during hyperthermia. No appreciable change in temperature gradients was seen within a normothermic tumor when tumor blood flow was doubled or reduced to one-third of the basal level. Hyperthermia increased both volume and temperature of tumor efferent blood. As expected, decrease or increase in blood flow during hyperthermia increased or decreased tumor temperature, respectively, but substantial temperature gradients up to 2 degrees C still persisted within adjacent regions. The extent of temperature changes in the tumor could not be correlated with a known change in blood supply. A pulse of cold serum into the tumor afferent artery produced a substantial reduction of tumor blood flow, but only a small depression in tumor temperatures, and a very small change in tumor temperature gradients. No appreciable modification could be brought about in tumor temperature levels and temperature gradients within the tumor by pulses of cold serum in the afferent artery during hyperthermia. After external cooling of the tumor, the time necessary to compensate for temperature depression did not correlate with either the reduction of temperature or with the thickness of the tumor tissue separating the thermistor from the cold source. The results indicate extensive anisotropy of temperature and blood distribution within growing neoplastic tissue and suggest that heat transfer by convection within the tumor is much less effective than it is commonly assumed.

Temperature distributions and thermal response in humans. I. Simulations of various modes of whole-body hyperthermia in normal subjects.

Abstract: The necessity for a mathematical model of human heat transfer as an aid in determining the clinical effectiveness of whole‐body hyperthermia technique is brought out. A 45‐compartment lumped parameter model of the human thermal system is developed. The model accounts for changes in metabolism, blood flow, and other physiological mechanisms during hyperthermia. Simulations of the model’s projected temperature distributions and responses to six clinical whole‐body techniques are investigated.

Effects of hyperthermia and hyperglycemia on the metastases formation and on survival of rat bearing W256 carcinosarcoma.

Abstract: The selective destructive effect of hyperthermia (temperatures ≥ 42°C) on a variety of malignant tumors in animals is now well documented, and there is increasing evidence that many of the findings in animal tumor systems apply to human cancer (see Milder, 1979; Jain and Gullino, 1980). Current thrust in this field is directed towards defining the place of hyperthermia in human cancer therapy, and advance in this direction depends upon determining how best to apply and control the heat, as well as understanding more about its mechanism of action. It has been suspected for a long time that the interplay of various physiological factors (e.g. cell pH, tumor blood flow and the host immune system) other than the degree of physical heat applied may determine the outcome for a tumor treated by hyperthermia in vivo. Results to date indicate that tumors fall into two zones of thermal sensitivity, 42–43°C and 45–50°C. Most human tumors are not sensitive to 42–43°C temperature range (see Dickson and Shah, 1977), and temperatures greater than 42°C for prolonged periods can cause irreversible damage to normal surrounding tissues. Also, due to physiological limitations, disseminated disease cannot be treated by whole-body hyperthermia in the higher temperature zone. Therefore, effective treatment of cancer by hyperthermia would depend on selectively heating the tumor by manipulating tumor blood flow and by using potentiators of hyperthermia.