I Klich | PubMed Health

PubMed2002

Repulsive Casimir forces.

We discuss repulsive Casimir forces between dielectric materials with nontrivial magnetic susceptibility. It is shown that considerations based on the naive pairwise summation of van der Waals and Casimir-Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force but even the wrong sign of the force when materials with high dielectric and magnetic responses are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we suggest that the effect may be realized in known materials. The phenomenon of repulsive Casimir forces may be of importance both for experimental study and for nanomachinery applications.

Journal Article↗

PubMed2001

Trace metal and mineral speciation of remediated wastes using electron microscopy.

Electron microscopic techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalyses (EPMA), were used to evaluate metal species and mineralogical phases associated with metal-bearing contaminated soil and industrial wastes that have been solidified and stabilized with Portland cement. Metals present in the wastes included arsenic, barium, cadmium, chromium, copper, lead, nickel, and zinc. In addition, mineral alterations and weathering features that affect the durability and containment of metals in aged remediated wastes were analyzed microscopically. Physical and chemical alteration processes identified included: freeze-thaw cracking; cracking caused by the formation of expansive minerals, such as ettringite and thaumasite; carbonation; and the movement of metals from waste aggregates into the surrounding cement matrix. Preliminary results show that although the extent of degradation after 6 years is considered slight to moderate, evaluations of durability and permanence of metals containment cannot be based on leaching and bulk chemistry analyses alone. The use of electron microscopic analyses is vital in studies that evaluate trace metal and mineral species and that attempt to predict the long-term performance of metal containment in solidified and stabilized wastes.

Industrial Waste↗