Nonlinear dynamics of sand banks and sand waves

Sand banks and sand waves are two types of sand structures that are commonly observed on an off-shore sea bed. We describe the formation of these features using the equations of the fluid motion coupled with the mass conservation law for the sediment transport. The bottom features are a result of an instability due to tide–bottom interactions. There are at least two mechanisms responsible for the growth of sand banks and sand waves. One is linear instability, and the other is nonlinear coupling between long sand banks and short sand waves. One novel feature of this work is the suggestion that the latter is more important for the generation of sand banks. We derive nonlinear amplitude equations governing the coupled dynamics of sand waves and sand banks. Based on these equations, we estimate characteristic features for sand banks and find that the estimates are consistent with measurements

Alterations in immunoglobulin levels in uninfected children born to HIV infected women

Background Immunoglobulin levels are known to be elevated in HIV infected children. However, little is known about the effect of maternal HIV infection and the maternal altered immune system on immunoglobulin levels in uninfected children. As few data are available on immunoglobulins from young healthy children, we used data from uninfected children born to hepatitis C virus (HCV) infected women as a comparison. Methods Prospective data on immunoglobulin levels were available from birth to 5 years for children enrolled in the European Collaborative Study (ECS) of children born to HIV-1 infected women and from birth to 24 months for children enrolled in the European Paediatric HCV Network (EPHN). Children born to HIV/HCV co-infected women were excluded. Smoothers (running means) illustrated patterns of immunoglobulins over age by infection status. Associations between infant and maternal factors and child log10 total IgG, IgM and IgA levels were quantified in linear regression analyses allowing for repeated measures within child. Further analyses were performed using only data of HIV exposed uninfected children to investigate associations between child immunoglobulins and maternal immunological and virological factors and anti-retroviral therapy exposure. Results 1751 HIV uninfected, 190 HIV infected children (ECS), 173 HCV uninfected and 30 HCV infected children (EPHN) were included. HIV infected children had higher levels of all immunoglobulins compared to uninfected children over all ages. HIV uninfected children had significantly higher IgG, IgM and IgA levels than HCV uninfected children upto at least 24 months, adjusting for gender, prematurity and race. Prematurity was associated with significantly lower levels of immunoglobulins upto 24 months. Children born to African women had higher IgG and IgA levels upto 24 months than those born to white women but lower IgM in the first 6 months. Among HIV uninfected children higher IgG levels were associated with elevated maternal IgG levels, as well for measurements from 18 months to 5 years of age. No significant effect of maternal CD4 count was observed. ART exposure was associated with significantly lower IgG levels at 6-24 months. Race was not associated with immunoglobulin levels in multivariable analyses in this sub-group. Conclusions These findings indicate significant alterations in immunoglobulin levels in uninfected children born to HIV infected women. This suggests that exposure to an activated maternal immune system is associated with an altered humoral response in children without antigen stimulation, and warrants further research

The role of impulse parameters in force variability

One of the principle limitations of the human motor system is the ability to produce consistent motor responses. When asked to repeatedly make the same movement, performance outcomes are characterized by a considerable amount of variability. This occurs whether variability is expressed in terms of kinetics or kinematics. Variability in performance is of considerable importance because for tasks requiring accuracy it is a critical variable in determining the skill of the performer. What has long been sought is a description of the parameter or parameters that determine the degree of variability. Two general experimental protocals were used. One protocal is to use dynamic actions and record variability in kinematic parameters such as spatial or temporal error. A second strategy was to use isometric actions and record kinetic variables such as peak force produced. What might be the important force related factors affecting variability is examined and an experimental approach to examine the influence of each of these variables is provided

Successful paediatric HIV treatment in rural primary care in Africa

<p>Objective: Clinical outcomes of HIV-infected children on antiretroviral treatment (ART) in a decentralised, nurse/counsellor-led programme.</p> <p>Design: Clinical cohort.</p> <p>Setting: KwaZulu-Natal, South Africa.</p> <p>Patients: HIV-infected children aged <= 15 years on ART, June 2004-2008.</p> <p>Main outcome measures: Survival according to baseline characteristics including age, WHO clinical stage, haemoglobin and CD4%, was assessed in Kaplan-Meier analyses. Hazard ratios for mortality were estimated using Cox proportional hazards regression and changes in laboratory parameters and weight-for-age z scores after 6-12 months' treatment were calculated.</p> <p>Results: 477 HIV-infected children began ART at a median age of 74 months (range 4-180), median CD4 count (CD4%) of 433 cells/mm(3) (17%) and median HIV viral load of log 4.2 copies/ml; 105 (22%) were on treatment for tuberculosis and 317 (76.6%) were WHO stage 3/4. There were significant increases after ART initiation in CD4% (17% vs 22%; p<0.001), haemoglobin (9.9 vs 11.7 g/l; p <= 0.001) and albumin (30 vs 36 g/l; p <= 0.001). 32 (6.7%) children died over 732 child-years of follow-up (43.7 deaths/1000 child-years; 95% CI 32.7 to 58.2), 17 (53.1%) within 90 days of treatment initiation; median age of death was 84 (IQR 10-181) months. Children with baseline haemoglobin <= 8 g/l were more likely to die (adjusted HR 4.5; 95% CI 1.6 to 12.3), as were those aged <18 months compared with >60 months (adjusted HR 3.2; 95% CI 1.2 to 9.1).</p> <p>Conclusions Good clinical outcomes in HIV-infected children on ART are possible in a rural, decentralised service. Few young children are on ART, highlighting the urgent need to identify HIV-exposed infants.</p&gt

An Analysis of Kinetic Response Variability

Studies evaluating variability of force as a function of absolute force generated are synthesized. Inconsistencies in reported estimates of this relationship are viewed as a function of experimental constraints imposed. Typically, within-subject force variability increases at a negative accelerating rate with equal increments in force produced. Current pulse-step and impulse variability models are unable to accommodate this description, although the notion of efficiency is suggested as a useful construct to explain the description outlined

Who’s afraid of the Five Star Movement? Why Italy leaving the euro remains unlikely regardless of what happens on Sunday

Several observers have raised the possibility that should Italy’s constitutional referendum result in a No vote, it could leave the door open for Beppe Grillo’s Five Star Movement (M5S) to win power at the next Italian election. As James L. Newell writes, there has been particular concern over this prospect due to the Five Star Movement’s commitment to hold a referendum on Italy’s membership of the euro. However, he argues that the chances of the M5S leading Italy out of the euro remain extremely unlikely, regardless of the result on Sunday

Systematic derivation of a rotationally covariant extension of the 2-dimensional Newell-Whitehead-Segel equation

An extension of the Newell-Whitehead-Segel amplitude equation covariant under abritrary rotations is derived systematically by the renormalization group method.Comment: 8 pages, to appear in Phys. Rev. Letters, March 18, 199

Italy’s referendum: don’t expect shockwaves after Sunday

Italy’s constitutional referendum, due to be held on Sunday, has been widely dubbed as offering a stage for a third ‘popular revolt’ against the establishment, following Brexit and the election of Donald Trump. Matteo Salvini, the leader of the right-wing populist Northern League, on receiving the news of Trump’s election, was heard to exclaim: “Now it’s our turn!

Examining Whether Social Factors Affect Listeners Sensitivity to Talker-Specific Information During Their Online Perception of Spoken Words

McLennan and Luce (2005) found no significant cost associated with changing which talker produced a particular word from the first block of trials to the second (no talker effects) when participants responded relatively quickly (easy lexical decision), and that talker effects emerged when participants responded relatively slowly (hard lexical decision). In a lexical decision task, participants hear words and nonwords and reaction times to correct responses are measured. In the current study, we examined whether social factors would lead to talker effects in an easy lexical decision task. In Experiment 1, participants were told that they have a chance to be part of a desirable high achieving group if they performed with high accuracy. Based on previous time-course findings, we predicted that talker effects would emerge in the current experiment, given that participants\u27 attention to accuracy was expected to slow processing. Participants on the contrary sped up. We successfully demonstrated that group belonging is a sufficiently strong prime to alter the way participants perform in this task. In Experiment 2, participants (all males) were told that they would have the opportunity to meet the two talkers (one male and one female) they would hear during the experiment at the end. Moreover, participants were given some (fabricated) background information about the talkers, including mention that the female is attractive and the male is unattractive. Based on previous findings in social psychology, we predicted that the male participants would attend more to the female\u27s voice than to the male\u27s voice. We demonstrated that the female serves as a more effective prime for words later spoken by both the same female talker, and also by the male talker. Examining the relationship between social factors and talker effects should lead to improved models of spoken word recognition, and provide important new insights into how listeners perceive spoken words in various social context

Italy’s general election was no electoral revolution

Italy’s general election on 25 September produced a victory for Giorgia Meloni’s Fratelli d’Italia. James L. Newell writes that while the result has provoked warnings about a return to fascism, it largely reflected a redistribution of support among parties on the right. There are nevertheless real concerns about the potential for democratic backsliding should the new government choose to reform Italy’s political system