Modeling water purification by an aquaporin-inspired graphene-based nano-channel.

Understanding the mechanism of water and particle transport through thin-film membranes is essential to improve the water permeability and the salt rejection rate of the purification progress. In this research, mimicking from the structure and operation of the aquaporin channel, graphene-based nano-channels were designed to be used as a water filter. The effects of variation of the channel's main elements, such as the width of the bottleneck and charges attached to the channel on its efficiency, were investigated via molecular dynamics simulations. We observe that the water flow through the channel decreases by increasing the charge, while the ion rejection rate of the channel is enhanced. Moreover, we find that the geometry and shape of the bottleneck part of the channel can affect the channel water flow and its selectivity. Finally, the pressure and the flow velocity in the channel were considered by using finite element models, and the results indicate that they are high at the entrance of the channel. The outcomes of this study can be used to improve the molecular knowledge of water desalination, which might be helpful in designing more efficient membranes. Graphical abstract As the piston pushed the solution to pass through the nano-channel, positive and negative ions are remained in the first box, by sensing electric field generated from the attached charges to the bottleneck part of the channel. Atomistic structure of channel is shown in the right part of the figure and the generated electric field is shown in the left part of the figure.

Experience with low-dose valganciclovir prophylaxis in adult liver transplant recipients.

Valganciclovir (VGCV) is considered the agent of choice after organ transplant for cytomegalovirus (CMV) prophylaxis. The purpose of this retrospective study was to determine the effectiveness and safety of a low-dose regimen after liver transplant (OLT). Eighty-five patients who underwent OLT between August 2002 and August 2004 were included. All patient data for the first 12 months after transplant were collected. Patients received VGCV 450 mg once daily for 3 months posttransplant. CMV infection was based on detection of CMV virus or viral proteins in blood. CMV disease was defined by the presence of positive antigenemia/viremia and evidence of clinical symptoms and/or tissue findings. Patients were D+R+ (54%) and D-R+ (29%), D+R-(11%) and D-R-(6%). Overall, CMV infection and disease occurred in 13% (11/85). CMV infection and disease occurred in 7% and 6%, respectively. CMV infection and disease occurred in 44% (D+R-), 13% (D+R+), 4% (D-R+) patients. The mean time to onset of CMV infection and disease was 103 days (14 to 312 days). Overall, 82% of patients received antibody therapy. The most common adverse events associated with VGCV were leukopenia (16%), thrombocytopenia (4%), anemia (<1%), and neurotoxicity (<1%). Low-dose VGCV was not an effective means to prevent CMV infection in high-risk (D+R-) patients, especially those who received antibody induction. High-risk patients may require a high-dose regimen, such as 900 mg daily, and/or a longer period of prophylaxis, and/or reduction in the use of potent antibody treatments after liver transplant.

The electronic structure of liquid silver chalcogenides: a tight-binding approach.

We present a computational study of the electronic structure of the stoichiometric liquid zero-gap semiconductors [Formula: see text], [Formula: see text] and [Formula: see text]. The geometry of the fluids is described by the primitive model of charged hard spheres; the electronic structure is modelled using a tight-binding Hamiltonian. The density of states is computed considering the Madelung potential fluctuations and the topological disorder characteristic of an ionic fluid. Only the introduction of nonzero tight-binding hopping matrix elements - equivalent to the formation of chemical bonds - induces a pseudogap between the chalcogenide conduction band and the silver valence band. The Fermi level can be located in a region of a small density of states; eigenstates at [Formula: see text] are likely to exhibit disorder-induced localization.