Vectorial Control of the Spin-Orbit Interaction in Suspended InAs Nanowires.

Semiconductor nanowires featuring strong spin-orbit interactions (SOI), represent a promising platform for a broad range of novel technologies, such as spintronic applications or topological quantum computation. However, experimental studies into the nature and the orientation of the SOI vector in these wires remain limited despite being of upmost importance. Typical devices feature the nanowires placed on top of a substrate which modifies the SOI vector and spoils the intrinsic symmetries of the system. In this work, we report experimental results on suspended InAs nanowires, in which the wire symmetries are fully preserved and clearly visible in transport measurements. Using a vectorial magnet, the nontrivial evolution of weak antilocalization (WAL) is tracked through all 3D space, and both the spin-orbit length l SO and coherence length lφ are determined as a function of the magnetic field magnitude and direction. Studying the angular maps of the WAL signal, we demonstrate that the average SOI within the nanowire is isotropic and that our findings are consistent with a semiclassical quasi-1D model of WAL adapted to include the geometrical constraints of the nanostructure. Moreover, by acting on properly designed side gates, we apply an external electric field introducing an additional vectorial Rashba spin-orbit component whose strength can be controlled by external means. These results give important hints on the intrinsic nature of suspended nanowire and can be interesting for the field of spintronics as well as for the manipulation of Majorana bound states in devices based on hybrid semiconductors.

Single-Dose Universal Hepatitis A Immunization in Argentina: Low Viral Circulation and High Persistence of Protective Antibodies Up to 4 Years.

BACKGROUND: Single-dose hepatitis A virus (HAV) vaccination was implemented in all Argentinean children aged 12 months in 2005. Between 2005 and 2011, a dramatic decline was observed in HAV infection rates, fulminant hepatitis, and liver transplantation. This study assessed current viral circulation and estimated protective antibody persistence 4 years after vaccination. METHODS: Prevalence of prevaccination anti-HAV antibodies in 12-month-old children was evaluated as an indirect estimation of viral circulation (Group A). Seroprevalence was also measured in 5-year-old children who received 1 dose of HAV vaccine at 1 year of age (Group B). Blood samples were tested for immunoglobulin (Ig)G anti-HAV antibodies (seroprotection = ≥10 mIU/mL). All Group A-positive samples were tested for IgM anti-HAV antibodies to identify recent infections. Logistic regression analysis was done to evaluate associations between demographic and socioeconomic variables and seroprotection. RESULTS: Of 433 children from Group A, 29.5% (95% confidence interval [CI], 25.2-33.8) were positive for IgG anti-HAV antibodies with a geometric mean concentration (GMC) of 6.17 mIU/mL (95% CI, 5.33-7.15 mIU/mL); all IgM anti-HAV were negative. From 1139 in Group B, 93% (95% CI, 91.7-94.6) maintained seroprotection with a GMC of 97.96 mIU/mL (95% CI, 89.21-107.57 mIU/mL). Kindergarten attendance was associated with seroprotection in Group B (odds ratio [OR], 2.0; 95% CI, 1.26-3.3). In contrast, high maternal educational level was associated with a lack of seroprotection in this group (OR, .26; 95% CI, .09-.8). CONCLUSIONS: Single-dose, universal hepatitis A immunization in infants resulted in low HAV circulation and persistent immunologic protection up to 4 years in Argentina. Variables associated with presence or absence of seroprotection in vaccinated children could be related to differences in hygiene habits in settings with residual viral circulation.

Maternal immunization in Argentina: A storyline from the prospective of a middle income country.

The importance of vaccination during pregnancy lies not only in directly protecting vaccinated women, but also by indirectly protecting small infants during the first few months of life. Vaccination against the flu and whooping cough is a priority within the comprehensive care strategy for pregnant women and small infants in Argentina, in the context of transitioning from child vaccination to family vaccination. In 2011, the flu vaccine was included in the National Immunization Schedule (NIS) as mandatory and free of charge, with the aim of decreasing complications and death due to influenza in the at-risk population in Argentina. The national vaccination coverage attained in pregnant women in the past 4 years (2011-2014) has been satisfactory; 88% coverage was attained in the year this program was introduced to the schedule. In the following years, coverage was maintained at greater than 95%. In February 2012, Argentina became the first country in Latin America to have universal vaccination strategy for pregnant women against whooping cough. This recommendation was implemented throughout the country by vaccination with the diphtheria toxoid, tetanus toxoid, and acellular pertussis (Tdap) vaccine starting at 20 weeks of pregnancy, with the aim of decreasing morbimortality due to whooping cough in infants under 6 months of age. The vaccine was incorporated into the NIS in 2014. More than 1,200,000 doses were applied in this period. Both vaccines showed a suitable safety profile and no serious events were reported. Argentina is an example of a middle-income country that has been able to implement a successful strategy for primary prevention through vaccines, making it a health policy.

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures.

Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies. Here we report a new class of heterostructures comprising a single-layer (or bilayer) graphene in close proximity to a quantum well created in GaAs and supporting a high-mobility two-dimensional electron gas. In our devices, graphene is naturally hole-doped, thereby allowing for the investigation of electron-hole interactions. We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects, and find that the Coulomb drag resistivity significantly increases for temperatures <5-10 K. The low-temperature data follow a logarithmic law, therefore displaying a notable departure from the ordinary quadratic temperature dependence expected in a weakly correlated Fermi-liquid. This anomalous behaviour is consistent with the onset of strong interlayer correlations. Our heterostructures represent a new platform for the creation of coherent circuits and topologically protected quantum bits.

Anomalous charge tunneling in fractional quantum Hall edge states at a filling factor ν=5/2.

We explain effective charge anomalies recently observed for fractional quantum Hall edge states at ν=5/2 [M. Dolev, Y. Gross, Y. C. Chung, M. Heiblum, V. Umansky, and D. Mahalu, Phys. Rev. B 81, 161303(R) (2010)]. The experimental data of differential conductance and excess noise are fitted, using the anti-Pfaffian model, by properly taking into account renormalizations of the Luttinger parameters induced by the coupling of the system with an intrinsic 1/f noise. We demonstrate that a peculiar agglomerate excitation with charge e/2, double the expected e/4 charge, dominates the transport properties at low energies.