The influence of the freeze-thawing process on the size and lamellarity of multilamellar PEG-lipid liposomes prepared from a mixture of egg yolk phosphatidilcholine (EggPC) and distearoyl phosphatidylethanolamine polyethyleneglycol (DSPE-PEG) 2000 was investigated. Trapped volume measurement, quasielastic light scattering (QELS) and freeze-fracture electron microscopy were used to estimate the ...

background: freezing is a common way and one of the best methods of seafood preservation for long periods of time; however, the freeze thawing process may influence the quality of food. objectives: oxidation and denaturation of proteins, sublimation and recrystallization of ice crystals can cause changes in the quality of the frozen products. this study was aimed to evaluate the effect of three...

BACKGROUND: Freezing is a common way and one of the best methods of seafood preservation for long periods of time; however, the freeze thawing process may influence the quality of food. OBJECTIVES: Oxidation and denaturation of proteins, sublimation and recrystallization of ice crystals can cause changes in the quality of the frozen products. This study was aimed to evaluate the effect of three...

OBJECTIVE To study the resistance of human spermatozoa to cryoinjury in repeated cycles of thaw-refreezing by using the fast liquid nitrogen vapor method. MATERIALS AND METHODS Semen specimens were obtained from sixteen normal and oligozoospermic individuals who required disposal at the sperm bank. Five of them had testicular cancer. Specimens were thawed and an aliquot was removed for analys...

In this study, the development and characterization of novel polymer blends based on chitosan-poly (vinyl alcohol) and physically cross-linked by freeze-thaw method for possible use in a variety of biomedical application is reported. The present investigation deals with designing savlon-loaded blend hydrogels (coined as cryogels) of poly (vinyl alcohol) (PVA) and chitosan by repeated freeze-tha...

Freeze-thaw cycles are one of the greatest threats to concrete durability. Lately, protection against this threat excites scientists’ attention. Air-entraining admixtures have been widely used to produce freeze-thaw resistant at concretes. The use of airentraining agents (AEAs) enhances not only freeze-thaw endurance but also the properties of fresh concrete such as segregation, bleeding and fl...

OBJECTIVES To assess the reliability of intradiscal pressure measurement during in vitro biomechanical testing. In particular, the variability of measurements will be assessed for repeated measures by considering the effect of specimens and of freezing/thawing cycles. METHODS Thirty-six functional units from 8 porcine spines (S1: T7-T8, S2: T9-T10, S3: T12-T11, S4: T14-T13, S5: L1-L2 and S6: ...

To evaluate the effects of sequential, repetitive freezing on their in-vitro development, mouse embryos at the eight- to 16-cell stage were subjected to one of five treatments. They were (i) cultured as unfrozen controls, (ii) frozen once and cultured, (iii) subjected to two consecutive freeze-thaw cycles, (iv) frozen and thawed, and then cultured for 18-30 h before being frozen a second time, ...

Introduction: Methanogens are obligate anaerobes that use molecular hydrogen as an energy source and carbon dioxide as a carbon source to produce methane. They are classified as Archaea and are found in many extreme environments, including hydrothermal vents, volcanoes, and also the human microflora. The current Martian atmosphere is low in pressure, very dry (hyper-arid), and high in radiation...

BACKGROUND Paraoxonase (PON1) enzymatic activity assays are used to characterize sensitivity to organophosphates and oxidative stress. Length of sample storage, temperature and other factors may influence variability of PON1 measurements, especially in longitudinal studies. METHODS Effects of assay temperature, storage duration up to 7 y (-80 degrees C), freeze-thaw cycles, the type of specim...