Mathematical modeling of bioremediation of trichloroethylene in aquifers

AbstractTrichloroethylene (TCE) is a very common contaminant of groundwater. It is used as an industrial solvent and is frequently poured into the soil. There exist bacteria that can degrade TCE. In contrast with most cases of bioremediation, the bacteria that degrade TCE do not use it as a carbon source. Instead the bacteria produce an enzyme to metabolize methane. This enzyme can degrade other organics including TCE. In this paper we model in situ bioremediation of TCE in an aquifer by using two species of bacteria: one that forms biobarriers to restrict the movement of TCE and the second one to reduce TCE. The model includes flow of water, transport of TCE and the nutrients, bacterial growth and degradation of TCE. Nonstandard numerical methods are used to discretize the equations. Some results are presented

On the environmental stability of quantum chaotic ratchets

The transitory and stationary behavior of a quantum chaotic ratchet consisting of a biharmonic potential under the effect of different drivings in contact with a thermal environment is studied. For weak forcing and finite $\hbar$, we identify a strong dependence of the current on the structure of the chaotic region. Moreover, we have determined the robustness of the current against thermal fluctuations in the very weak coupling regime. In the case of strong forcing, the current is determined by the shape of a chaotic attractor. In both cases the temperature quickly stabilizes the ratchet, but in the latter it also destroys the asymmetry responsible for the current generation. Finally, applications to isomerization reactions are discussed.Comment: 6 pages, 5 figure

Clinical Outcome in Human T-Lymphotropic Virus Type 2 Carriers Following Organ Transplantation

Background: Frequent and rapid development of myelopathy has been reported in individuals with human T-lymphotropic virus type 1 (HTLV-1) infection following solid organ transplantation. There is no information regarding HTLV-2, a closely related virus that often infects injection drug users. Methods: This study includes a retrospective analysis of all consecutive organ transplants performed during the last 2 decades at a large reference transplantation unit in Spain. All participants were tested for anti-HTLV antibodies. Results: A total of 2019 individuals were tested for HTLV during the study period, including 663 potential donors and 1356 recipient candidates. Twelve (0.59%) were reactive on initial HTLV serologic screening, but only 6 (all recipients) were confirmed as positive, all for HTLV-2. Two recipients underwent liver transplantation and have remained asymptomatic despite being on tacrolimus for 4 and 8 years, respectively. Likewise, the remaining 4 HTLV-2 carriers have not developed clinical complications potentially associated with HTLV-2. Conclusions: Unlike HTLV-1 infection, HTLV-2 infection in the transplantation setting does not seem to be associated with rapid development of neurologic complications, Given the cross-seroreactivity between HTLV-1 and HTLV-2, discriminatory rapid tests are urgently needed and would reduce unnecessary organ discharge

Geopolymers: A new and smart way for a sustainable development

“Geopolymers” is a general term that describes a wide variety of inorganic and composite materials with limited restrictions on alumina and silica content. In the last decades, they have been also defined as “low-temperature aluminosilicate glasses”, “hydroceramics”, “inorganic polymer concrete” or “alkali bonded ceramics”. Recently, an updated definition has been proposed by the RILEM Technical Committee 224-AAM: “geopolymer materials are essential aluminosilicates activated with alkaline solution, excluding any other alkali-activated materials that should be classified apart” [1]

Signatures of homoclinic motion in quantum chaos

Homoclinic motion plays a key role in the organization of classical chaos in Hamiltonian systems. In this Letter, we show that it also imprints a clear signature in the corresponding quantum spectra. By numerically studying the fluctuations of the widths of wavefunctions localized along periodic orbits we reveal the existence of an oscillatory behavior, that is explained solely in terms of the primary homoclinic motion. Furthermore, our results indicate that it survives the semiclassical limit.Comment: 5 pages, 4 figure