Pupillometry, a bioengineering overview

The pupillary control system is examined using a microprocessor based integrative pupillometer. The real time software functions of the microprocessor include: data collection, stimulus generation and area to diameter conversion. Results of an analysis of linear and nonlinear phenomena are presented

Nonextensive hydrodynamics for relativistic heavy-ion collisions

The nonextensive one-dimensional version of a hydrodynamical model for multiparticle production processes is proposed and discussed. It is based on nonextensive statistics assumed in the form proposed by Tsallis and characterized by a nonextensivity parameter $q$. In this formulation the parameter $q$ characterizes some specific form of local equilibrium which is characteristic for the nonextensive thermodynamics and which replaces the usual local thermal equilibrium assumption of the usual hydrodynamical models. We argue that there is correspondence between the perfect nonextensive hydrodynamics and the usual dissipative hydrodynamics. It leads to simple expression for dissipative entropy current and allows for predictions for the ratio of bulk and shear viscosities to entropy density, $\zeta/s$ and $\eta/s$, to be made.Comment: Final version accepted for publication in Phys. Rev.

Maternal HIV viral load testing during pregnancy and postpartum care in Gauteng Province, South Africa

Background. Pregnant and breastfeeding women living with HIV (WLHIV) are a target population for elimination of mother-to-child transmission of HIV (eMTCT). However, there are limited data on maternal virological responses during pregnancy and the postpartum period in South Africa (SA).Objectives. To review compliance of viral load (VL) testing with national guidelines and suppression rates during pregnancy and up to 9  months postpartum among WLHIV delivering in four tertiary hospitals in Gauteng Province, SA.Methods. All women who had a point-of-care HIV VL test using Xpert HIV-1 VL (Cepheid, USA) at delivery in four tertiary obstetric units in Gauteng between June 2018 and February 2020 were included. HIV VL tests of eligible women performed up to 9 months before and after delivery were extracted from the National Health Laboratory Service’s Corporate Data Warehouse. Proportions of women delivering who had antenatal and postpartum VL tests performed and their suppression rates were determined and expressed as percentages.Results. Of 4 989 eligible WLHIV (median age 31.1 years), 917 (18.4%) had a VL performed during the antenatal period; of these, 335 (36.5%) had a VL ≥50 copies/mL and 165 (18.0%) a VL ≥1 000 copies/mL. At delivery, 1 911 women (38.3%) had a VL ≥50 copies/mL and 1 028 (20.6%) a VL ≥1 000 copies/mL. Among 627 women (12.6%) with a VL test postpartum, 234 (37.3%) had a VL ≥50 copies/mL and 93 (14.8%) a VL ≥1 000 copies/mL. Overall, having a VL test performed during the antenatal period was associated with viral suppression at delivery and receiving a VL test postpartum (p<0.001). Women with a VL ≥50 copies/mL at delivery were more likely to be younger and to remain virally unsuppressed postpartum (p<0.001) compared with women with a VL <50 copies/mL.Conclusions. Fewer than 5% of WLHIV with a VL at the time of delivery received VL monitoring during the antenatal and postpartum periods in accordance with national guidelines. More than 80% of WLHIV delivering had no evidence of VL monitoring during the antenatal period, and they were more likely than women who received monitoring during the antenatal period to be virally unsuppressed at delivery and to receive no VL monitoring postpartum. Women with a high VL at delivery were likely to remain virally unsuppressed postpartum. These results emphasise the need for closer monitoring of and rapid reaction to high maternal VLs during pregnancy, at delivery and postpartum for attainment of eMTCT

Analysis of the thermomechanical inconsistency of some extended hydrodynamic models at high Knudsen number

There are some hydrodynamic equations that, while their parent kinetic equation satisfies fundamental mechanical properties, appear themselves to violate mechanical or thermodynamic properties. This article aims to shed some light on the source of this problem. Starting with diffusive volume hydrodynamic models, the microscopic temporal and spatial scales are first separated at the kinetic level from the macroscopic scales at the hydrodynamic level. Then we consider Klimontovich’s spatial stochastic version of the Boltzmann kinetic equation, and show that, for small local Knudsen numbers, the stochastic term vanishes and the kinetic equation becomes the Boltzmann equation. The collision integral dominates in the small local Knudsen number regime, which is associated with the exact traditional continuum limit. We find a sub-domain of the continuum range which the conventional Knudsen number classification does not account for appropriately. In this sub-domain, it is possible to obtain a fully mechanically-consistent volume (or mass) diffusion model that satisfies the second law of thermodynamics on the grounds of extended non-local-equilibrium thermodynamics

Polaron band formation in the Holstein model

We present numerical exact results for the polaronic band structure of the Holstein molecular crystal model in one and two dimensions. The use of direct Lanczos diagonalization technique, preserving the full dynamics and quantum nature of phonons, allows us to analyze in detail the renormalization of both quasiparticle bandwidth and dispersion by the electron-phonon interaction. For the two-dimensional case some of our exact data are compared with the results obtained in the framework of a recently developed finite cluster strong-coupling perturbation theory.Comment: 10 pages (LaTeX), 6 figures (ps), submitted to Phys. Rev.

Shape of a liquid front upon dewetting

We examine the profile of a liquid front of a film that is dewetting a solid substrate. Since volume is conserved, the material that once covered the substrate is accumulated in a rim close to the three phase contact line. Theoretically, such a profile of a Newtonian liquid resembles an exponentially decaying harmonic oscillation that relaxes into the prepared film thickness. For the first time, we were able to observe this behavior experimentally. A non-Newtonian liquid - a polymer melt - however, behaves differently. Here, viscoelastic properties come into play. We will demonstrate that by analyzing the shape of the rim profile. On a nm scale, we gain access to the rheology of a non-Newtonian liquid.Comment: 4 pages, 4 figure

Quality and turnaround times of viral load monitoring under prevention of mother-to-child transmission of HIV Option B+ in six South African districts with a high antenatal HIV burden

Background. Barriers to monitoring maternal HIV viral load (VL) and achieving 90% viral suppression during pregnancy and breastfeeding still need to be understood in South Africa (SA).Objectives. To measure quality of VL care and turnaround times (TATs) for returning VL results to women enrolled in the prevention of mother-to-child transmission of HIV (PMTCT) programme in primary healthcare facilities.Methods. Data were obtained from a 2018 cross-sectional evaluation of the PMTCT Option B+ programme in six SA districts with high antenatal and infant HIV prevalence. Quality of VL care was measured as the proportion of clients reporting that results were explained to them. TATs for VL results were calculated using dates abstracted from four to five randomly selected facility-based client records to report overall facility ‘short TAT’ (≥80% of records with TAT ≤7 days). Logistical regression and logit-based risk difference statistics were used.Results. Achieving overall short TAT was uncommon. Only 50% of facilities in one rural district, zero in one urban metro district and 9 - 38% in other districts had short TAT. The significant difference between districts was influenced by the duration of keeping results in facilities after receipt from the laboratory. Expected quality of VL care received ranged between 66% and 85%. Client-related factors significantly associated with low quality of care, observed in two urban districts and one rural district, included lower education, recent initiation of antiretroviral treatment and experiencing barriers to clinic visits. Experiencing clinic visit barriers was also negatively associated with short TATs.Conclusions. We demonstrate above-average quality of care and delayed return of results to PMTCT clients. Context-specific interventions are needed to shorten TATs

Random division of an interval

The well-known relation between random division of an interval and the Poisson process is interpreted as a Laplace transformation. With the use of this interpretation a number of (in part known) results is derived very easily

Eliminating Vertical Transmission of HIV in South Africa: Establishing a Baseline for the Global Alliance to End AIDS in Children

To gain a detailed overview of vertical transmission in South Africa, we describe insights from the triangulation of data sources used to monitor the national HIV program. HIV PCR results from the National Health Laboratory Service (NHLS) were analysed from the National Institute of Communicable Diseases (NICD) data warehouse to describe HIV testing coverage and positivity among children <2 years old from 2017–2021. NICD data were compared and triangulated with the District Health Information System (DHIS) and the Thembisa 4.6 model. For 2021, Thembisa estimates a third of children living with HIV go undiagnosed, with NICD and DHIS data indicating low HIV testing coverage at 6 months (49%) and 18 months (33%) of age, respectively. As immunisation coverage is reported at 84% and 66% at these time points, better integration of HIV testing services within the Expanded Programme for Immunization is likely to yield improved case findings. Thembisa projects a gradual decrease in vertical transmission to 450 cases per 100,000 live births by 2030. Unless major advances and strengthening of maternal and child health services, including HIV prevention, diagnosis, and care, can be achieved, the goal to end AIDS in children by 2030 in South Africa is unlikely to be realised