Design of a blood-freezing system for leukemia research

Leukemia research involves the use of cryogenic freezing and storage equipment. In a program being carried out at the National Cancer Institute (NCI), bone marrow (white blood cells) was frozen using a standard cryogenic biological freezer. With this system, it is difficult to maintain the desired rate of freezing and repeatability from sample to sample. A freezing system was developed that satisfies the requirements for a repeatable, constant freezing rate. The system was delivered to NIC and is now operational. This report describes the design of the major subsystems, the analyses, the operating procedure, and final system test results

System for and method of freezing biological tissue

Biological tissue is frozen while a polyethylene bag placed in abutting relationship against opposed walls of a pair of heaters. The bag and tissue are cooled with refrigerating gas at a time programmed rate at least equal to the maximum cooling rate needed at any time during the freezing process. The temperature of the bag, and hence of the tissue, is compared with a time programmed desired value for the tissue temperature to derive an error indication. The heater is activated in response to the error indication so that the temperature of the tissue follows the desired value for the time programmed tissue temperature. The tissue is heated to compensate for excessive cooling of the tissue as a result of the cooling by the refrigerating gas. In response to the error signal, the heater is deactivated while the latent heat of fusion is being removed from the tissue while the tissue is changing phase from liquid to solid

Liquid density and critical properties of hydrocarbons estimated from molecular structure

The paper provides new correlations for the estimation of the relative liquid density and critical parameters of hydrocarbons. The correlations employ molecular descriptors from computer simulation of molecular mechanics, which proved valuable in our previous work. High precision is achieved, without the use of unduly complex descriptors and rules, as a result of improved methodology. The new methodology includes a limit upon the functionality of the property database and its predesign by expanding the range and improving the distribution of the repeating structural features in the selected compounds.A compilation of estimated data for the liquid density and critical properties of some hydrocarbons of industrial importance for which no values have been available before is provided

Supercritical Extraction of Carotenoids from Rosa canina L. Hips and their Formulation with β-Cyclodextrin

The purpose of this research was to preliminary assess the suitability of a new method for the preparation of a solid formulation in form of powder composed by β-cyclodextrin and the supercritical extract of Rosa canina hips. The method implies the extraction of carotenoids, in particular β-carotene, from freeze dried fruits of R. canina with supercritical CO2 at 70 °C and 300 bar, in the presence of varying quantity of ethanol as entrainer. The obtained supercritical solution is then expanded at ambient conditions into an aqueous solution of β-cyclodextrin to favour the interaction between β-cyclodextrin and the lipophilic components of the extract. β-carotene solubility (mole fraction) in supercritical CO2 or in supercritical CO2/ethanol mixtures were in the order of 1 10−7. The β-carotene extracted from R. canina fruits (nearly 10 μg/g of dry matrix), interacts almost quantitatively with β-cyclodextrin affording a solid phase, which presents a low apparent solubility in water. Finally the interaction with β-cyclodextrin results in a higher concentration of the β-carotene trans- form relative to the cis- form in the extracted product when collected in an aqueous solution of β-cyclodextrin with respect to the extract in n-hexane