On the Formation of Copper Linear Atomic Suspended Chains

We report high resolution transmission electron microscopy and classical molecular dynamics simulation results of mechanically stretching copper nanowires conducting to linear atomic suspended chains (LACs) formation. In contrast with some previous experimental and theoretical work in literature that stated that the formation of LACs for copper should not exist our results showed the existence of LAC for the [111], [110], and [100] crystallographic directions, being thus the sequence of most probable occurence.Comment: 4 pages, 3 figure

Nonequilibrium molecular dynamics simulation of rapid directional solidification

We present the results of non-equilibrium molecular dynamics simulations for the growth of a solid binary alloy from its liquid phase. The regime of high pulling velocities, $V$, for which there is a progressive transition from solute segregation to solute trapping, is considered. In the segregation regime, we recover the exponential form of the concentration profile within the liquid phase. Solute trapping is shown to settle in progressively as $V$ is increased and our results are in good agreement with the theoretical predictions of Aziz [J. Appl. Phys. {\bf 53}, 1158 (1981)]. In addition, the fluid advection velocity is shown to remain directly proportional to $V$, even at the highest velocities considered here ($V\simeq10$ms$^{-1}$).Comment: Submitted to Phys. Rev.

Feasibility, drug safety, and effectiveness of etiological treatment programs for Chagas disease in Honduras, Guatemala, and Bolivia: 10-year experience of Médecins Sans Frontières

BACKGROUND: Chagas disease (American trypanosomiasis) is a zoonotic or anthropozoonotic disease caused by the parasite Trypanosoma cruzi. Predominantly affecting populations in poor areas of Latin America, medical care for this neglected disease is often lacking. Médecins Sans Frontières/Doctors Without Borders (MSF) has provided diagnostic and treatment services for Chagas disease since 1999. This report describes 10 years of field experience in four MSF programs in Honduras, Guatemala, and Bolivia, focusing on feasibility protocols, safety of drug therapy, and treatment effectiveness. METHODOLOGY: From 1999 to 2008, MSF provided free diagnosis, etiological treatment, and follow-up care for patients <18 years of age seropositive for T. cruzi in Yoro, Honduras (1999-2002); Olopa, Guatemala (2003-2006); Entre Ríos, Bolivia (2002-2006); and Sucre, Bolivia (2005-2008). Essential program components guaranteeing feasibility of implementation were information, education, and communication (IEC) at the community and family level; vector control; health staff training; screening and diagnosis; treatment and compliance, including family-based strategies for early detection of adverse events; and logistics. Chagas disease diagnosis was confirmed by testing blood samples using two different diagnostic tests. T. cruzi-positive patients were treated with benznidazole as first-line treatment, with appropriate counseling, consent, and active participation from parents or guardians for daily administration of the drug, early detection of adverse events, and treatment withdrawal, when necessary. Weekly follow-up was conducted, with adverse events recorded to assess drug safety. Evaluations of serological conversion were carried out to measure treatment effectiveness. Vector control, entomological surveillance, and health education activities were carried out in all projects with close interaction with national and regional programs. RESULTS: Total numbers of children and adolescents tested for T. cruzi in Yoro, Olopa, Entre Ríos, and Sucre were 24,471, 8,927, 7,613, and 19,400, respectively. Of these, 232 (0.9%), 124 (1.4%), 1,475 (19.4%), and 1,145 (5.9%) patients, respectively, were diagnosed as seropositive. Patients were treated with benznidazole, and early findings of seroconversion varied widely between the Central and South American programs: 87.1% and 58.1% at 18 months post-treatment in Yoro and Olopa, respectively; 5.4% by up to 60 months in Entre Ríos; and 0% at an average of 18 months in Sucre. Benznidazole-related adverse events were observed in 50.2% and 50.8% of all patients treated in Yoro and Olopa, respectively, and 25.6% and 37.9% of patients in Entre Ríos and Sucre, respectively. Most adverse events were mild and manageable. No deaths occurred in the treatment population. CONCLUSIONS: These results demonstrate the feasibility of implementing Chagas disease diagnosis and treatment programs in resource-limited settings, including remote rural areas, while addressing the limitations associated with drug-related adverse events. The variability in apparent treatment effectiveness may reflect differences in patient and parasite populations, and illustrates the limitations of current treatments and measures of efficacy. New treatments with improved safety profiles, pediatric formulations of existing and new drugs, and a faster, reliable test of cure are all urgently needed

Indication Of Unusual Pentagonal Structures In Atomic-size Cu Namwires

A study of the structural and quantum conductance properties of atomic-size copper nanowires generated by mechanical stretching was presented. The time-resolved electron microscopy observations and molecular dynamics simulations were used to derive the atomistic evolution. The quantum transport behavior was analyzed by means of conductance measurements and theoretical calculations. The formation of an unusual and highly pentagonal Cu nanowires with a diameter of ∼0.45 nm and ∼4.5 conductance quanta was also shown.93121261031-126103-4Agraït, N., Yeyati, A.L., Van Ruitenbeek, J.M., (2003) Phys. Rep., 377, p. 81Gulseren, O., Ercolessi, F., Tosatti, E., (1998) Phys. Rev. Lett., 80, p. 3775Kondo, Y., Takayanagi, K., (2000) Science, 289, p. 606Oshima, Y., Onga, A., Takayanagi, K., (2003) Phys. Rev. Lett., 91, p. 205503Ohnishi, H., Kondo, Y., Takayanagi, K., (1998) Nature (London), 395, p. 780Yanson, A.I., (1998) Nature (London), 395, p. 783Rodrigues, V., Fuhrer, T., Ugarte, D., (2000) Phys. Rev. Lett., 85, p. 4124Rego, L.G.C., Rocha, A.R., Rodrigues, V., Ugarte, D., (2003) Phys. Rev. B, 67, p. 045412Rodrigues, V., (2002) Phys. Rev. B, 65, p. 153402Krans, J.M., (1995) Nature (London), 375, p. 767Kondo, Y., Takayanagi, K., (1997) Phys. Rev. Lett., 79, p. 3455Rodrigues, V., Ugarte, D., (2003) Nanowires and Nanobelts, 1, p. 177. , edited by Z. L. Wang Kluwer, DordrechtRodrigues, V., Bettini, J., Silva, P.C., Ugarte, D., (2003) Phys. Rev. Lett., 91, p. 096801Marks, L.D., (1994) Rep. Prog. Phys., 57, p. 603Urban, J., (1998) Cryst. Res. Technol., 33, p. 1009Lisiecki, I., (2000) Phys. Rev. B, 61, p. 4968Emberly, E.G., Kirczenow, G., (1998) Phys. Rev. B, 58, p. 10911(1999) Phys. Rev. B, 60, p. 6028Reinhard, D., (1997) Phys. Rev. Lett., 79, p. 1459Sen, P., (2002) Phys. Rev. B, 65, p. 235433Cleri, F., Rosato, V., (1993) Phys. Rev. B, 48, p. 22Tomànek, D., Aligia, A.A., Balseiro, C.A., (1985) Phys. Rev. B, 32, p. 5051Coura, P.Z., (2004) Nano Lett., 4, p. 1187EPAPS Document No. E-PRLTAO-93-010436, E-PRLTAO-93-010436. , http://www.aip.org/pubservs/epaps.html)orfromftp.aip.orginthedirectory/ epaps, Figure 4 snapshot of a Cu nanowire being elongated along the [110] axis. A direct link to this document may be found in the online article's HTML reference section. The document may also be reached via the EPAPS homepage See the EPAPS homepage for more informatio