Raman-scattering study of the phonon dispersion in twisted bi-layer graphene

Bi-layer graphene with a twist angle \theta\ between the layers generates a superlattice structure known as Moir\'{e} pattern. This superlattice provides a \theta-dependent q wavevector that activates phonons in the interior of the Brillouin zone. Here we show that this superlattice-induced Raman scattering can be used to probe the phonon dispersion in twisted bi-layer graphene (tBLG). The effect reported here is different from the broadly studied double-resonance in graphene-related materials in many aspects, and despite the absence of stacking order in tBLG, layer breathing vibrations (namely ZO' phonons) are observed.Comment: 18 pages, 4 figures, research articl

Costs Associated with Malaria in Pregnancy in the Brazilian Amazon, a Low Endemic Area Where Plasmodium vivax Predominates.

BACKGROUND: Information on costs associated with malaria in pregnancy (MiP) in low transmission areas where Plasmodium vivax predominates is so far missing. This study estimates health system and patient costs of MiP in the Brazilian Amazon. METHODS/PRINCIPAL FINDINGS: Between January 2011 and March 2012 patient costs for the treatment of MiP were collected through an exit survey at a tertiary referral hospital and at a primary health care centre in the Manaus metropolitan area, Amazonas state. Pregnant and post-partum women diagnosed with malaria were interviewed after an outpatient consultation or at discharge after admission. Seventy-three interviews were included in the analysis. Ninety-six percent of episodes were due to P. vivax and 4% to Plasmodium falciparum. In 2010, the total median costs from the patient perspective were estimated at US $45.91 and US$216.29 for an outpatient consultation and an admission, respectively. When multiple P. vivax infections during the same pregnancy were considered, patient costs increased up to US $335.85, representing the costs of an admission plus an outpatient consultation. Provider direct and overhead cost data were obtained from several sources. The provider cost associated with an outpatient case, which includes several consultations at the tertiary hospital was US$103.51 for a P. vivax malaria episode and US $83.59 for a P. falciparum malaria episode. The cost of an inpatient day and average admission of 3 days was US$118.51 and US $355.53, respectively. Total provider costs for the diagnosis and treatment of all malaria cases reported in pregnant women in Manaus in 2010 (N = 364) were US$17,038.50, of which 92.4% (US$ 15,741.14) due to P. vivax infection. CONCLUSION: Despite being an area of low risk malaria transmission, MiP is responsible for a significant economic burden in Manaus. Especially when multiple infections are considered, costs associated with P. vivax are higher than costs associated with P. falciparum. The information generated may help health policy decisions for the current control and future elimination of malaria in the area

Cell death induced by the application of alternating magnetic fields to nanoparticle-loaded dendritic cells

In this work, the capability of primary, monocyte-derived dendritic cells (DCs) to uptake iron oxide magnetic nanoparticles (MNPs) is assessed and a strategy to induce selective cell death in these MNP-loaded DCs using external alternating magnetic fields (AMFs) is reported. No significant decrease in the cell viability of MNP-loaded DCs, compared to the control samples, was observed after five days of culture. The amount of MNPs incorporated into the cytoplasm was measured by magnetometry, which confirmed that 1 to 5 pg of the particles were uploaded per cell. The intracellular distribution of these MNPs, assessed by transmission electron microscopy, was found to be primarily inside the endosomic structures. These cells were then subjected to an AMF for 30 min, and the viability of the blank DCs (i.e., without MNPs), which were used as control samples, remained essentially unaffected. However, a remarkable decrease of viability from approximately 90% to 2-5% of DCs previously loaded with MNPs was observed after the same 30 min exposure to an AMF. The same results were obtained using MNPs having either positive (NH2+) or negative (COOH-) surface functional groups. In spite of the massive cell death induced by application of AMF to MNP-loaded DCs, the amount of incorporated magnetic particles did not raise the temperature of the cell culture. Clear morphological changes at the cell structure after magnetic field application were observed using scanning electron microscopy. Therefore, local damage produced by the MNPs could be the main mechanism for the selective cell death of MNP-loaded DCs under an AMF. Based on the ability of these cells to evade the reticuloendothelial system, these complexes combined with an AMF should be considered as a potentially powerful tool for tumour therapy.Comment: In Press. 33 pages, 11 figure

Transformación de arsénico por bacterias aisladas de sedimentos enriquecidos con el metaloide

Las bacterias presentes en ambientes contaminados con arsénico son capaces de resistir esta presión ambiental y adaptarse mediante mecanismos de resistencia, lo que involucra, entre otros, la oxidación y/o reducción del metaloide. El objetivo del presente trabajo fue investigar las propiedades redox en bacterias tolerantes a arsénico, aisladas de sedimentos naturales.  Los sedimentos se obtuvieron del río Camarones(I región, Chile). Las muestras se incubaron en medio mineral durante 7 días, a temperatura ambiente. Diluciones apropiadas fueron sembradas en agar R2A se incubaron a 25 ºC, hasta 7 días. Los niveles de tolerancia para cada metal se determinaron mediante dilución seriada en placa. La propiedad de oxidar o reducir arsénico se investigó mediante nitrato de plata. Los resultados muestran la presencia de bacterias resistentes a arsenito y arseniato, con niveles de tolerancia > 8mM. El 36,84% de las cepas aisladas de sedimentos ricos en arsénico presentaron actividades reductoras(>50%). En cambio, en bacterias aisladas de sedimentoscon bajas concentraciones del metaloide, la actividad reductora varió entre un 10% y 25%. Se puede concluir que la presencia de arsénico selecciona bacterias con la capacidad de tolerar concentraciones altas de arsénico a través de la transformación de As(V) en As(III)