A rapid and efficient method for plasmid transformation of Klebsiella pneumoniae M5a1 and Escherichia coli K12 has been developed. The method, which uses a freeze-thaw cycle in the presence of CaCl2 to facilitate DNA uptake, is substantially more efficient for K. pneumoniae M5a1 than the conventional transformation procedure for E. coli. The simplicity and speed of the method makes it very attr...

R. P. Goodrich and co-workers, 1989 have reported that red blood cells (RBCs) can be preserved in the dry state by addition of mixtures of hydroxyethyl starch (HES) and glucose (59,60). In this thesis work we tried to investigate the effect of HES alone on the viability, functionality and oxidative state of red blood cells after freeze thaw stress. Here we prepared eight formulations having var...

Results: The experiment results indicate that the type of recycled aggregate and its replacement ratio have significant effects on the freezethaw performance. The cubic compressive strength of recycled aggregate concrete is overall slightly lower than that of normal concrete. After 100 freeze-thaw cycles, the compressive strength decreases and the reduction extent increases with increasing repl...

The effects of freeze/thaw (F/T) cycling on the structure of dry Nafion® membranes were investigated using positron annihilation lifetime spectroscopy (PALS). The method correlates the lifetime and relative intensity of positrons (anti-electrons) annihilating in the open-volume voids of the membrane with void size and void volume fraction. The results, though still preliminary, show freeze/thaw...

an experimental program was carried out to investigate the behavior of steel, fiber reinforced concrete (sfrc) under abrasion and cycles of freeze and them. compression and flexural tests were also performed in order to reach a comprehensive conclusion of the response. in total, over 200 specimens were tested the test variables included two concrete strength., (i. e., 28 mpa as normal strength ...

Polyphenoloxidase (PPO), protease activities, melanosis and exudate loss of pre-cooked Pacific white shrimp (Litopenaeus vannamei) subjected to multiple freeze-thaw cycles (1, 3 and 5 cycles) using different thawing methods were studied. PPO and protease activities increased as freeze-thaw cycles increased (p < 0.05). Thawing using running tap water resulted in the higher increases in both PPO ...

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...

This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, meth...

Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and ...

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...