Time to Switch to Second-line Antiretroviral Therapy in Children With Human Immunodeficiency Virus in Europe and Thailand.

Background: Data on durability of first-line antiretroviral therapy (ART) in children with human immunodeficiency virus (HIV) are limited. We assessed time to switch to second-line therapy in 16 European countries and Thailand. Methods: Children aged <18 years initiating combination ART (≥2 nucleoside reverse transcriptase inhibitors [NRTIs] plus nonnucleoside reverse transcriptase inhibitor [NNRTI] or boosted protease inhibitor [PI]) were included. Switch to second-line was defined as (i) change across drug class (PI to NNRTI or vice versa) or within PI class plus change of ≥1 NRTI; (ii) change from single to dual PI; or (iii) addition of a new drug class. Cumulative incidence of switch was calculated with death and loss to follow-up as competing risks. Results: Of 3668 children included, median age at ART initiation was 6.1 (interquartile range (IQR), 1.7-10.5) years. Initial regimens were 32% PI based, 34% nevirapine (NVP) based, and 33% efavirenz based. Median duration of follow-up was 5.4 (IQR, 2.9-8.3) years. Cumulative incidence of switch at 5 years was 21% (95% confidence interval, 20%-23%), with significant regional variations. Median time to switch was 30 (IQR, 16-58) months; two-thirds of switches were related to treatment failure. In multivariable analysis, older age, severe immunosuppression and higher viral load (VL) at ART start, and NVP-based initial regimens were associated with increased risk of switch. Conclusions: One in 5 children switched to a second-line regimen by 5 years of ART, with two-thirds failure related. Advanced HIV, older age, and NVP-based regimens were associated with increased risk of switch

Static and dynamic magnetic properties of melt-spun granular Cu100-xCox alloys

The magnetic properties of granular Cu-Co alloys produced by melt-spinning have been investigated by DC and AC susceptibility measurements. The results indicate the occurrence of blocking processes of interacting superparamagnetic particles. The effects of annealing by Joule heating at different current densities are discussed in relation to the giant magnetoresistance properties of the system

Study of magnetic properties of Joule heated granular CoxCu100-x ribbons

Granular Co-Cu alloy ( Co10Cu90) produced by melt-spinning and subsequently annealed in vacuum by DC Joule heating at different current densities have been investigated by DC and AC susceptibility measurements. High values of the heating current density lend to promote grain growth and to favore the increase of intergrain interactions strength, determining a variety of magnetic propeties from a collective fi freezing in random directions of moments of nanosized Co particles to an inhomogeneous and pl progressive blocking of moments of particles with increasing size. Meanwhile, significant changes of the giant magnetoresistance exhibited by the system were also observed. The correlation between microstructure, magnetic properties and GMR is discussed

Investigation of static and dynamic magnetic properties of Joule heated granular Co10Cu90 ribbons

The magnetic properties of a granular Co-Cu alloy (Co,,Cu,,) produced by melt-spinning and annealed by Joule heating at different DC current densities have been investigated by magnetization, DC and AC susceptibility measurements. The increase of the heating current density has been found to promote grain growth and to enhance the strength of intergrain interactions, determining a change of magnetic behavior: from a collective freezing in random directions of moments of nanosized Co particles to an inhomogeneous and progressive blocking of moments of particles with increasing size. The effects of Joule heating on microstructure and magnetic properties are discussed in relation to-the giant magnetoresistance properties exhibited by the system, which confirm the development of interparticle correlations with increasing the heating current density. (C) 1999 Elsevier Science B.V. All rights reserved