High burden of viral respiratory co-infections in a cohort of children with suspected pulmonary tuberculosis.

BACKGROUND: The presentation of pulmonary tuberculosis (PTB) in young children is often clinically indistinguishable from other common respiratory illnesses, which are frequently infections of viral aetiology. As little is known about the role of viruses in children with PTB, we investigated the prevalence of respiratory viruses in children with suspected PTB at presentation and follow-up. METHODS: In an observational cohort study, children < 13 years were routinely investigated for suspected PTB in Cape Town, South Africa between December 2015 and September 2017 and followed up for 24 weeks. Nasopharyngeal aspirates (NPAs) were tested for respiratory viruses using multiplex PCR at enrolment, week 4 and 8. RESULTS: Seventy-three children were enrolled [median age 22.0 months; (interquartile range 10.0-48.0); 56.2% male and 17.8% HIV-infected. Anti-tuberculosis treatment was initiated in 54.8%; of these 50.0% had bacteriologically confirmed TB. At enrolment, ≥1 virus were detected in 95.9% (70/73) children; most commonly human rhinovirus (HRV) (74.0%). HRV was more frequently detected in TB cases (85%) compared to ill controls (60.6%) (p = 0.02). Multiple viruses were detected in 71.2% of all children; 80% of TB cases and 60.6% of ill controls (p = 0.07). At follow-up, ≥1 respiratory virus was detected in 92.2% (47/51) at week 4, and 94.2% (49/52) at week 8. CONCLUSIONS: We found a high prevalence of viral respiratory co-infections in children investigated for PTB, irrespective of final PTB diagnosis, which remained high during follow up. Future work should include investigating the whole respiratory ecosystem in combination with pathogen- specific immune responses.

Quantum quench of Kondo correlations in optical absorption.

The interaction between a single confined spin and the spins of an electron reservoir leads to one of the most remarkable phenomena of many-body physics--the Kondo effect. Electronic transport measurements on single artificial atoms, or quantum dots, have made it possible to study the effect in great detail. Here we report optical measurements on a single semiconductor quantum dot tunnel-coupled to a degenerate electron gas which show that absorption of a single photon leads to an abrupt change in the system Hamiltonian and a quantum quench of Kondo correlations. By inferring the characteristic power-law exponents from the experimental absorption line shapes, we find a unique signature of the quench in the form of an Anderson orthogonality catastrophe, induced by a vanishing overlap between the initial and final many-body wavefunctions. We show that the power-law exponent that determines the degree of orthogonality can be tuned using an external magnetic field, which unequivocally demonstrates that the observed absorption line shape originates from Kondo correlations. Our experiments demonstrate that optical measurements on single artificial atoms offer new perspectives on many-body phenomena previously studied using transport spectroscopy only.

Clinical spectrum of disease and outcomes in children with Omicron SARS-COV-2 infection in Cape Town, South Africa.

INTRODUCTION: Children with underlying comorbidities and infants are most severely affected by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, including in low- and middle-income countries with a high prevalence of HIV and TB. We describe the clinical presentation of SARS-CoV-2 infection in children during the Omicron wave, in Cape Town, South Africa. METHODS: We analysed routine care data from a prospective cohort of children aged 0-13 years, with a positive SARS-CoV-2 real-time reverse-transcription polymerase chain reaction (rRT-PCR) or SARS-CoV-2 antigen test, admitted to Tygerberg Hospital between 1 November 2021 until 1 March 2022. Risk factors for severity of disease were assessed. RESULTS: Ninety-five children tested positive for SARS-CoV-2, of whom 87 (91.6%) were symptomatic. Clinical data were available for 86 children. The median age was 11 months (IQR 3.0-60.0), 37 (43.0%) were females, 21 (24.7%) were HIV-exposed and 7 (8.1%) were living with HIV (CLHIV). In total, 44 (51.2%) children had at least one underlying comorbidity. TB co-infection was seen in 11 children, 6 children were newly diagnosed and 5 children were already on TB treatment at the time of admission. CONCLUSION: There was no evidence of more severe disease in children living with HIV or TB.

INTRODUCTION: Les enfants et les nourrissons présentant des comorbidités sous-jacentes sont les plus gravement touchés par l'infection par le coronavirus-2 du syndrome respiratoire aigu sévère (SARS-CoV-2), y compris dans les pays à revenu faible ou intermédiaire où la prévalence du VIH et de la TB est élevée. Nous décrivons la présentation clinique de l'infection par le SARS-CoV-2 chez les enfants pendant la vague Omicron, au Cap, en Afrique du Sud. MÉTHODES: Nous avons analysé les données de soins de routine d'une cohorte prospective d'enfants âgés de 0 à 13 ans, avec un test positif de réaction en chaîne de la polymérase de transcription inverse en temps réel (rRT-PCR) ou d'antigène du SARS-CoV-2, admis à l'hôpital Tygerberg entre le 1er novembre 2021 et le 1er mars 2022. Les facteurs de risque de gravité de la maladie ont été évalués. RÉSULTATS: Quatre-vingt-quinze enfants ont été testés positifs au SARS-CoV-2, dont 87 (91,6%) étaient symptomatiques. Des données cliniques étaient disponibles pour 86 enfants. L'âge médian était de 11 mois (IQR 3,0­60,0), 37 (43,0%) étaient des filles, 21 (24,7%) étaient exposés au VIH et 7 (8,1%) vivaient avec le VIH (CLHIV). Au total, 44 (51,2%) enfants présentaient au moins une comorbidité sous-jacente. La co-infection par la TB a été observée chez 11 enfants, 6 enfants ont été nouvellement diagnostiqués et 5 enfants étaient déjà sous traitement antituberculeux au moment de l'admission. CONCLUSION: Il n'y a pas de preuve d'une maladie plus grave chez les enfants vivant avec le VIH ou la TB.

Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.

Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system.

Many-body dynamics of exciton creation in a quantum dot by optical absorption: a quantum quench towards Kondo correlations.

We study a quantum quench for a semiconductor quantum dot coupled to a fermionic reservoir, induced by the sudden creation of an exciton via optical absorption. The subsequent emergence of correlations between spin degrees of freedom of dot and reservoir, culminating in the Kondo effect, can be read off from the absorption line shape and understood in terms of the three fixed points of the single-impurity Anderson model. At low temperatures the line shape is dominated by a power-law singularity, with an exponent that depends on gate voltage and, in a universal, asymmetric fashion, on magnetic field, indicative of a tunable Anderson orthogonality catastrophe.

One-dimensional flat bands in twisted bilayer germanium selenide.

Experimental advances in the fabrication and characterization of few-layer materials stacked at a relative twist of small angle have recently shown the emergence of flat energy bands. As a consequence electron interactions become relevant, providing inroads into the physics of strongly correlated two-dimensional systems. Here, we demonstrate by combining large scale ab initio simulations with numerically exact strong correlation approaches that an effective one-dimensional system emerges upon stacking two twisted sheets of GeSe, in marked contrast to all moiré systems studied so far. This not only allows to study the necessarily collective nature of excitations in one dimension, but can also serve as a promising platform to scrutinize the crossover from two to one dimension in a controlled setup by varying the twist angle, which provides an intriguing benchmark with respect to theory. We thus establish twisted bilayer GeSe as an intriguing inroad into the strongly correlated physics of lowdimensional systems.

Extraction buffer contaminated bacterially as a cause of invalid HIV-1 viral load results on the NucliSens EasyQ system.

Shortly after starting to use the NucliSens EasyQ HIV-1 V1.1 system for HIV-1 RNA load testing, the number of invalid tests per assay run gradually increased. Within five days, approximately 50% of tests showed a total lack of amplification of the calibrator and in most cases also of the HIV-1 template. According to the manufacturer's specifications, the lysis buffer and three extraction buffers remain on the automated NucliSens easyMAG extraction system between assay runs. Therefore possible microbial contamination of these buffers was investigated, after they had been on the automated system for approximately one week. The NucliSens easyMAG extraction buffer 2 yielded bacterial growth identified as Acinetobacter baumannii. After regular decontamination of the machine's tubing system with 70% alcohol and storage of the buffers at 4 degrees C between assay runs were commenced, invalid results due to failed internal calibrator signal occurred no longer. It is likely that bacterial contamination of the buffer was the cause of assay failure, probably due to ribonuclease (RNase) activity. Bacterial contamination of PCR systems should be added to the list of potential hazards in diagnostic virology. This experience underlines the necessity of state-of-the-art assay design incorporating adequate internal controls and calibrators.

Pitfalls with rapid HIV antibody testing in HIV-infected children in the Western Cape, South Africa.

BACKGROUND: Rapid HIV antibody tests are commonly used for HIV diagnosis in the developing world. These tests are generally reported as sensitive, despite paucity of evaluations in paediatric populations. OBJECTIVES: We tested specimens of paediatric patients, known to be HIV-infected, to detect any false negative tests and determine associations with such an outcome. STUDY DESIGN: One hundred and fifty-three specimens, from 109 patients, recorded to be HIV-infected by standard testing, were tested on the Capillustrade mark HIV-1/HIV-2 test (Trinity Biotech, Ireland); 150 specimens also had sufficient volume to be tested on Abbott Determinetrade mark HIV1/2 assay (Abbott GmbH, Wiesbaden, Germany). Treatment information, CD4 counts and HIV-1 viral load measurements were obtained from patient files and laboratory databases. RESULTS: Twenty-one of 153 specimens tested negative on the Capillus (sensitivity 86.3%). False negative results by Capillus were associated with antiretroviral treatment (ART) (p=0.0018) and lower HIV-1 viral load (p=0.013). Serial dilutions of some of the specimens indicated that both rapid tests, and the Capillus in particular, became negative at lower dilutions than an HIV enzyme immunoassay (EIA). CONCLUSIONS: The Capillus test had an unexpectedly low sensitivity in a South African population of HIV-infected children that had access to antiretroviral treatment, posing a risk of false negative HIV testing.

Origin of the low critical observing temperature of the quantum anomalous Hall effect in V-doped (Bi, Sb)2Te3 film.

The experimental realization of the quantum anomalous Hall (QAH) effect in magnetically-doped (Bi, Sb)2Te3 films stands out as a landmark of modern condensed matter physics. However, ultra-low temperatures down to few tens of mK are needed to reach the quantization of Hall resistance, which is two orders of magnitude lower than the ferromagnetic phase transition temperature of the films. Here, we systematically study the band structure of V-doped (Bi, Sb)2Te3 thin films by angle-resolved photoemission spectroscopy (ARPES) and show unambiguously that the bulk valence band (BVB) maximum lies higher in energy than the surface state Dirac point. Our results demonstrate clear evidence that localization of BVB carriers plays an active role and can account for the temperature discrepancy.

Acute hepatitis C in the Netherlands: characteristics of the epidemic in 2014.

Within the Dutch Acute HCV in HIV Study, a surveillance system was initiated to estimate the incidence of hepatitis C virus (HCV) infections in 2014. Following the Dutch HIV treatment guidelines, HIV-positive men having sex with men (MSM) in 19 participating centers were screened. Ninety-nine acute HCV infections were reported, which resulted in a mean incidence of 11 per 1000 patient-years of follow-up. Unfortunately, the HCV epidemic among Dutch HIV-positive MSM is not coming to a halt.

Theory of Floquet band formation and local pseudospin textures in pump-probe photoemission of graphene.

Ultrafast materials science promises optical control of physical properties of solids. Continuous-wave circularly polarized laser driving was predicted to induce a light-matter coupled state with an energy gap and a quantum Hall effect, coined Floquet topological insulator. Whereas the envisioned Floquet topological insulator requires high-frequency pumping to obtain well-separated Floquet bands, a follow-up question regards the creation of Floquet-like states in graphene with realistic low-frequency laser pulses. Here we predict that short optical pulses attainable in experiments can lead to local spectral gaps and novel pseudospin textures in graphene. Pump-probe photoemission spectroscopy can track these states by measuring sizeable energy gaps and Floquet band formation on femtosecond time scales. Analysing band crossings and pseudospin textures near the Dirac points, we identify new states with optically induced nontrivial changes of sublattice mixing that leads to Berry curvature corrections of electrical transport and magnetization.

A handful of questions. Supporting parental decision making.

Advances in healthcare have improved the survival rates of children with serious health problems. Parents, relieved that their child is alive, often face the challenge of caring for a child with a chronic illness and must make healthcare decisions that have life-long consequences. Supporting parents through the decision-making process is a complex challenge for the advanced practice nurse. This article offers an original and dynamic decision-making assessment tool to help the advanced practice nurse provide effective evaluation and appropriate support for the parents. This "Handful of Questions" was created using a patient-oriented decision-making model by Pierce and the work of other decision-making researchers. The literature reviewed includes the topics of surrogate parental decision making and an examination of the relationship between the decision-maker and healthcare providers.

Zidovudine with nevirapine for the prevention of HIV mother-to-child transmission reduces nevirapine resistance in mothers from the Western Cape, South Africa.

In the Western Cape province of South Africa, an intensified regimen for the prevention-of-mother-to-child-transmission-of-HIV consisting of zidovudine (AZT) from 34 weeks of pregnancy plus single dose (sd) nevirapine (NVP) during labor was instituted in 2004. The newborn baby receives a single dose of NVP and AZT for 7 days. Similar strategies in Thailand and Africa have been shown to be more effective in reducing transmission than NVP alone. The use of sd NVP only for the prevention-of-mother-to-child-transmission-of-HIV has a high risk of inducing resistance (25-69%) with an average of 35.7% by a recent meta-analysis and has been shown to adversely affect non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy when initiated within 6 months. In this study the prevalence of resistance to NVP and AZT in mothers who had received the intensified regimen was measured. Specimens collected from mothers were genotyped by in-house PCR and sequencing. In specimens obtained within 60 days of delivery, acquired NVP resistance mutations were detected in 13 of 76 patients (17.1%, 95% confidence interval: 8.7-25.6%), which appears to be lower than in studies with sd NVP alone (37.5%, 95% confidence interval: 23.0-50.6%).

Histochemical differentiation between nitric oxide synthase-related and -unrelated diaphorase activity in the rat olfactory bulb.

The widely used NADPH-diaphorase reaction for demonstrating neuronal nitric oxide synthase is not as specific as previously thought, as it visualizes both a nitric oxide synthase-related activity and a nitric oxide synthase-unrelated diaphorase. In the present study, we used the rat olfactory bulb as a model to characterize the NADPH-diaphorase activity of neuronal nitric oxide synthase histochemically in comparison with neuronal nitric oxide-unrelated diaphorase activity. The NADPH-diaphorase activity of nitric oxide synthase peaked at pH 8 and at Triton X-100 concentrations of 1-2.5%. It was stable in an acidic environment but was reduced in the presence of Triton X-100 and was inactivated by the flavoprotein inhibitor, diphenyleneiodonium. It preferred beta-NADPH as the co-substrate to alpha-NADPH and alpha-NADH. In contrast, nitric oxide synthase-unrelated diaphorase peaked at pH 10, displayed a Triton X-100 optimum at a concentration of 1%, was unstable in an acidic environment and used beta-NADPH, alpha-NADPH and alpha-NADH to similar extents. Differences in the characteristics between neuronal nitric oxide synthase-related and nitric oxide synthase-unrelated NADPH-diaphorase can be used to increase the specificity of the histochemical nitric oxide synthase marker reaction.

Red cell distribution at microvascular bifurcations.

The distribution of red cell and blood volume flow was studied at 65 arteriolar bifurcations in the rat mesentery. Hematocrit and flow velocity were measured simultaneously in all three vessel segments constituting a bifurcation. Blood flow distribution was manipulated by irreversibly occluding downstream side branches of one of the daughter vessels. The dependence of fractional red cell volume flow on fractional blood flow was described using a three-parameter (X0, B, A) logit function. The critical volume flow fraction below which only plasma enters a downstream branch (X0), the nonlinearity of the relation between red cell and blood volume flow (B), and the asymmetry of that relation which is described by the parameter A decrease with increasing diameter of the vessel feeding the bifurcation. At diameters above 30 microns, phase separation is very limited. In addition, the nonlinearity parameter B decreases with decreasing hematocrit in the feeding vessel. The asymmetry parameter A strongly depends on the diameter ratio between the two daughter branches: For a given fractional blood flow, the smaller branch receives more red cells than the larger branch. Using a model for plasma skimming based on the assumption of a planar separating surface, the shape of the radial hematocrit profile in the feeding vessel has been calculated. The model predicts a decrease in local hematocrit from the vessel axis toward the wall with a distinct marginal zone free from cell centers. With increasing vessel diameter the hematocrit profile becomes more blunted while the width of the marginal zone increases.