For the 22-year solar cycle oscillation there is no external time dependent source. A nonlinear oscillation, the solar cycle must be generated internally, and Babcock-Leighton models apply an artificial nonlinear sour...For the 22-year solar cycle oscillation there is no external time dependent source. A nonlinear oscillation, the solar cycle must be generated internally, and Babcock-Leighton models apply an artificial nonlinear source term that can simulate the observations—which leaves open the question of the actual source mechanism for the solar cycle. Addressing this question, we propose to take guidance from the wave mechanism that generates the 2-year Quasi-biennial Oscillation (QBO) in the Earth atmosphere. Upward propagating gravity waves, eastward and westward, deposit momentum to generate the observed zonal wind oscillation. On the Sun, helioseismology has provided a thorough understanding of the acoustic p-waves, which propagate down into the convective envelope guided by the increasing temperature and related propagation velocity. Near the tachocline with low turbulent viscosity, the waves propagating eastward and westward can produce an axisymmetric 22-year oscillation of the zonal flow velocities that can generate the magnetic solar dynamo. Following the Earth model, waves in opposite directions can generate in the Sun wind and magnetic field oscillations in opposite directions, the proposition of a potential solar cycle mechanism.展开更多
Objective: To study the effects of starting antiretroviral treatment (ART) prior the age of two years on the growth (height and weight) of HIV-infected children. Methodology: This was a retrospective cohort study. HIV...Objective: To study the effects of starting antiretroviral treatment (ART) prior the age of two years on the growth (height and weight) of HIV-infected children. Methodology: This was a retrospective cohort study. HIV-infected children on ART aged less than 15 years were divided into two groups Group 1 (G1) comprising children who started ART prior 2 years and Group (G2) those put on treatment thereafter. Main Measures: Percentage of children with growth retardation measured by Height for Age (H/A) and Weight for Age (W/A) Results: In total, we included 90 subjects. The median age was 10 years with a slight female predominance (51.2%). Most children were asymptomatic at the time of the study (96.6%), compliant with treatment (81%), 54.8% of children were on cotrimoxazole, 33% knew their status. At initiation, underweight was predominant in group 1 compared to group 2 (52% versus 29.5%;p = 0.015). Conversely, stunted growth predominated in G2 compared to G1 but without significant difference (38% versus 50%;p = 0.147). At the time of our study (median age of 10 years), catch-up height and weight predominated in G1 compared to G2;only a small proportion remained below −2SD (4% versus 18.2%;p = 0.015 and 9% versus 29.5%;p = 0.006 respectively for underweight and stunted growth). Conclusion and Global Health Implications: Growth retardation was common at ART initiation. Catch-up in height was more evident in the early treatment group. Initiation of ART before the age of 2 years rather influences children’s height than weight. The result of this study further emphasizes the need of early ART and closed clinical monitoring to better assess the impact of ART in areas with high rates of undernutrition.展开更多
文摘For the 22-year solar cycle oscillation there is no external time dependent source. A nonlinear oscillation, the solar cycle must be generated internally, and Babcock-Leighton models apply an artificial nonlinear source term that can simulate the observations—which leaves open the question of the actual source mechanism for the solar cycle. Addressing this question, we propose to take guidance from the wave mechanism that generates the 2-year Quasi-biennial Oscillation (QBO) in the Earth atmosphere. Upward propagating gravity waves, eastward and westward, deposit momentum to generate the observed zonal wind oscillation. On the Sun, helioseismology has provided a thorough understanding of the acoustic p-waves, which propagate down into the convective envelope guided by the increasing temperature and related propagation velocity. Near the tachocline with low turbulent viscosity, the waves propagating eastward and westward can produce an axisymmetric 22-year oscillation of the zonal flow velocities that can generate the magnetic solar dynamo. Following the Earth model, waves in opposite directions can generate in the Sun wind and magnetic field oscillations in opposite directions, the proposition of a potential solar cycle mechanism.
文摘Objective: To study the effects of starting antiretroviral treatment (ART) prior the age of two years on the growth (height and weight) of HIV-infected children. Methodology: This was a retrospective cohort study. HIV-infected children on ART aged less than 15 years were divided into two groups Group 1 (G1) comprising children who started ART prior 2 years and Group (G2) those put on treatment thereafter. Main Measures: Percentage of children with growth retardation measured by Height for Age (H/A) and Weight for Age (W/A) Results: In total, we included 90 subjects. The median age was 10 years with a slight female predominance (51.2%). Most children were asymptomatic at the time of the study (96.6%), compliant with treatment (81%), 54.8% of children were on cotrimoxazole, 33% knew their status. At initiation, underweight was predominant in group 1 compared to group 2 (52% versus 29.5%;p = 0.015). Conversely, stunted growth predominated in G2 compared to G1 but without significant difference (38% versus 50%;p = 0.147). At the time of our study (median age of 10 years), catch-up height and weight predominated in G1 compared to G2;only a small proportion remained below −2SD (4% versus 18.2%;p = 0.015 and 9% versus 29.5%;p = 0.006 respectively for underweight and stunted growth). Conclusion and Global Health Implications: Growth retardation was common at ART initiation. Catch-up in height was more evident in the early treatment group. Initiation of ART before the age of 2 years rather influences children’s height than weight. The result of this study further emphasizes the need of early ART and closed clinical monitoring to better assess the impact of ART in areas with high rates of undernutrition.
