Controlling spin relaxation in hexagonal BN-encapsulated graphene with a transverse electric field.

We experimentally study the electronic spin transport in hexagonal BN encapsulated single layer graphene nonlocal spin valves. The use of top and bottom gates allows us to control the carrier density and the electric field independently. The spin relaxation times in our devices range up to 2 ns with spin relaxation lengths exceeding 12 µm even at room temperature. We obtain that the ratio of the spin relaxation time for spins pointing out-of-plane to spins in-plane is τ(⊥)/τ(||) ≈ 0.75 for zero applied perpendicular electric field. By tuning the electric field, this anisotropy changes to ≈ 0.65 at 0.7 V/nm, in agreement with an electric field tunable in-plane Rashba spin-orbit coupling.

The use of a Ga+ focused ion beam to modify graphene for device applications.

In this work, we clarify the features of the lateral damage of line defects in single layer graphene. The line defects were produced through well-controlled etching of graphene using a Ga(+) focused ion beam. The lateral damage length was obtained from both the integrated intensity of the disorder induced Raman D band and the minimum ion fluence. Also, the line defects were characterized by polarized Raman spectroscopy. It was found that graphene is resilient under the etching conditions since the intensity of the defect induced Raman D peak exhibits a dependence on the direction of the lines relative to the crystalline lattice and also on the direction of the laser polarization relative to the lines. In addition, electrical measurements of the modified graphene were performed. Different ion fluences were used in order to obtain a completely insulating defect line in graphene, which was determined experimentally by means of charge injection and electric force microscopy measurements. These studies demonstrate that a Ga+ ion column combined with Raman spectroscopy is a powerful technique to produce and understand well-defined periodic arrays of defects in graphene, opening possibilities for better control of nanocarbon devices.

Testing of visual acuity in young children: an evaluation of some commonly used methods.

In a comparative study of screening tests for visual acuity in young children, two groups of children were presented with three different tests. In the younger group (three to five years) three single opto-type tests were compared: Sheridan's five and seven letter matching test, the Fooks test and the E card test. The Sheridan test gave the best results and the E card test was found to be unsuitable for this age-group. The Fooks is an attractive test but was less sensitive in the detection of defects than the Sheridan test. In the older group (five to seven years) a single opto-type test, the Sheridan-Gardiner test, was compared with the E chart and the Snellen chart. The Sheridan-Gardiner test was found to have limitations in the detection of defects, including amblyopia, therefore results obtained by this method should not be considered to be directly comparable with those of the Snellen chart. The E chart gave good results in the detection of defects and there was less lateral confusion than had been expected. It has disadvantages, but there is still a place for its use in the screening of normal school-age children. The Snellen chart was the most effective test in the detection of defects, but not all the children were able to co-operate in its use. It is concluded that where it is possible to use the Snellen chart it should always be the method of choice.

A PAP - puncao-aspiracao pulmonar para o diagnostico bacteriologico das pneumonias agudas das criancas. / Pulmonary puncture-aspiration (PPA) in the bacteriological diagnosis of acute pneumonia in children

Os autores apresentam o resultado do emprego da PAP (Puncao-aspiracao-pulmonar) para o diagnostico bacteriologico das pneumonias agudas na crianca, em 13 pacientes com quadro clinico e radiologico de pneumonia aguda, admitidos no HINSG, Vitoria-ES, no periodo de 20/4 a 17/9/71. Dos 13 casos, a bacteriologia (bacterioscopia ao Gram) foi positiva em 9 e negativa em quatro casos. Na cultura foram isolados Staphylococcus aureus em cinco casos, Escherichia coli em um caso, associacao de germes em tres casos e resultado negativo em quatro casos. Dada a simplicidade da tecnica e as minimas complicacoes observadas (dois casos de discreta hemoptise e um caso de pequeno pneumotorax), os AA concluem tratar-se de um procedimento util para o diagnostico das pneumonias agudas na infancia