Helium has always been a bit of an outsider on the Periodic Table. Its two isotopes, helium-3 and helium-4, remain liquid down to absolute zero and have the lowest liquefaction temperature among the gases. These features can be traced to the high zero-point energy relative to their attractive potential. In two dimensions, helium4 will form a liquid and become superfluid at temperatures that dep...

soil colloid particles influence soil chemical and physical properties by their surface electrical charge. with respect to the importance of this issue from both agricultural and environmental points of view, charging behavior of a kaolinite sample was studied in the ph range of 4 to 10 and at three background electrolyte concentrations, including 0.005, 0.05, 0.5 m nacl, by potentiometric titr...