Tuning the polarized quantum phonon transmission in graphene nanoribbons.

We propose systems that allow a tuning of the phonon transmission function T(ω) in graphene nanoribbons by using C(13) isotope barriers, antidot structures, and distinct boundary conditions. Phonon modes are obtained by an interatomic fifth-nearest neighbor force-constant model (5NNFCM) and T(ω) is calculated using the non-equilibrium Green's function formalism. We show that by imposing partial fixed boundary conditions it is possible to restrict contributions of the in-plane phonon modes to T(ω) at low energy. On the contrary, the transmission functions of out-of-plane phonon modes can be diminished by proper antidot or isotope arrangements. In particular, we show that a periodic array of them leads to sharp dips in the transmission function at certain frequencies [Formula: see text] which can be pre-defined as desired by controlling their relative distance and size. With this, we demonstrated that by adequate engineering it is possible to govern the magnitude of the ballistic transmission functions [Formula: see text] in graphene nanoribbons. We discuss the implications of these results in the design of controlled thermal transport at the nanoscale as well as in the enhancement of thermo-electric features of graphene-based materials.

Detection of HIV-1 infection in blood donors during the immunological window period using the nucleic acid-amplification technology.

Individual nucleic acid-amplification testing (NAT) was recently recommended by Brazilian legislation and has been implemented at some blood banks in the city of São Paulo, Brazil, in an attempt to reduce the transfusion transmission of human immunodeficiency virus (HIV) and hepatitis C viruses. This screening test can identify donations made during the immunological window period before seroconversion. The impact of this technology in our blood donors and transfusion routine was studied. In all, 47 866 donations were tested from March 2004 until November 2005, according to Brazilian legislation, using two approved enzyme immunoassays for HIV antibodies and individual NAT. Supplemental tests included Western blot, p24 antigen detection and quantitative PCR-HIV-1. Among the donors screened, two (one first-time and one repeat donor) were non-reactive in enzyme immunoassays, with negative confirmatory p24 antigen and Western blot, but positive for HIV-1 NAT. Although serological analysis for HIV is a primary tool for diagnostic testing, the addition of NAT allowed for identification and prevention of component transfusion from two HIV-positive blood donations during an 18-month period. The screening of donors reduced the immunological window period, permitting the identification of very early stage HIV infections. In addition, this report also emphasized the fact that the risk of HIV transmission is not limited to the first-time donors.

[Meningitis and other neurological complications in infectious endocarditis]. / Meningite e outras complicações neurológicas na endocardite infecciosa.

PURPOSE: To study the localization, etiological agents and the respective prognosis in patients with infective endocarditis with or without neurological complications, with emphasis on the association of endocarditis and meningitis. METHODS: 222 patients with clinical, echocardiographic and laboratory diagnosis of infective endocarditis were treated at Instituto Dante Pazzanese de Cardiologia from 1985 to 1990. They were classified in two groups: group A-116 patients without neurological complications, ages 4 months-76 (mean 30) years old and 66.3% males. group B-56 patients with neurological complication, ages 1-71 (mean 31) years old and 46.4% males. A third group, group C, comprised 17 patients, ages 8-51 (mean 23.7) years old and 9 patients (52.9%) male, assisted at Hospital Emilio Ribas, which is specialized at infectious diseases, which presented meningitis as the unique manifestation of neurological complication associated to the diagnosis of infective endocarditis (IE). In all patients the diagnosis of IE was based on the presence of at least two of three essential findings: echocardiogram with vegetations or valvar dysfunctions, positive hemocultures and the compatible clinical picture. For the comparative analysis among the groups was employed through the chi-square test corrected according to Yates. RESULTS: No differences of sex and age of the patients were found among the three groups. Predominated the Staphylococcus aureus as etiological agent. The localization of cardiac lesions was similar in the three groups, except for the tricuspid valve affected in 16.3% of patients of group A and 2.3% of group B. There was a greater association of the structures on the left side of the heart with IE of group B (p < 0.05). Group B and C showed a general mortality rate greater than group A (p < 0.001). CONCLUSION: Meningitis and other neurological complications showed interrelationship between the presence of "Staphylococcus aureus" as etiological agent of endocarditis and the association with infection of the left heart side.