Three essays on HIV/AIDS related issues in Southern Africa

For many years, the number of HIV/AIDS-related deaths in developing countries has been increasing at such an alarming rate that it is no longer whether it will be an epidemic, but rather how severe the epidemic will be. This study addresses three important aspects of the epidemic, including effects as well as causes. The first paper identifies the potential effects of HIV on labor market participation, which affects economic outcomes. Using Heckman selection models and Demographic and Health Survey data from Lesotho, Malawi, Swaziland, and Zimbabwe, results show a significant negative association between being HIV positive and currently working, as well as having worked in the past 12 months, for men and women. The second paper measures the spillover effects of fostering to help inform welfare policies. Linear probability models with fixed effects are estimated using data from the Cape Area Panel Study to quantify the effects of orphan fostering on the school enrollment, employment, and health status of young adults living in households which foster orphans. Results indicate that young adults from higher wealth quintile households which foster orphans have a higher probability of being enrolled in school. The third paper highlights the role played by parental investment in influencing concurrent sexual partners, a risk factor affecting the rate of HIV transmission, which can help make HIV prevention campaigns more effective. Results from multinomial logistic regressions on data from the Cape Area Panel Study show that financial support from fathers significantly decreased the probability of sexual concurrency among Black and Colored males, 11% of whom reported having been in sexually concurrent relationships. The findings have important implications for the macroeconomic stability and future growth of the countries under investigation. The first paper suggests a need for employment protection for HIV positive individuals and their households. The second paper indicates that further research into subsidies for families taking on orphans is warranted. The third paper recommends health education programs on the risks of sexual concurrency for young adults. By providing empirical evidence, HIV policies can be made more effective, thereby mitigating any negative impacts on vulnerable individuals and families

Improved Coherence in Optically-Defined Niobium Trilayer Junction Qubits

Niobium offers the benefit of increased operating temperatures and frequencies for Josephson junctions, which are the core component of superconducting devices. However existing niobium processes are limited by more complicated fabrication methods and higher losses than now-standard aluminum junctions. Combining recent trilayer fabrication advancements, methods to remove lossy dielectrics and modern superconducting qubit design, we revisit niobium trilayer junctions and fabricate all-niobium transmons using only optical lithography. We characterize devices in the microwave domain, measuring coherence times up to $62~\mu$s and an average qubit quality factor above $10^5$: much closer to state-of-the-art aluminum-junction devices. We find the higher superconducting gap energy also results in reduced quasiparticle sensitivity above $0.16~$K, where aluminum junction performance deteriorates. Our low-loss junction process is readily applied to standard optical-based foundry processes, opening new avenues for direct integration and scalability, and paves the way for higher-temperature and higher-frequency quantum devices

Structural study in Highly Compressed BiFeO3 Epitaxial Thin Films on YAlO3

We report a study on the thermodynamic stability and structure analysis of the epitaxial BiFeO3 (BFO) thin films grown on YAlO3 (YAO) substrate. First we observe a phase transition of MC-MA-T occurs in thin sample (<60 nm) with an utter tetragonal-like phase (denoted as MII here) with a large c/a ratio (~1.23). Specifically, MII phase transition process refers to the structural evolution from a monoclinic MC structure at room temperature to a monoclinic MA at higher temperature (150oC) and eventually to a presence of nearly tetragonal structure above 275oC. This phase transition is further confirmed by the piezoforce microscopy measurement, which shows the rotation of polarization axis during the phase transition. A systematic study on structural evolution with thickness to elucidate the impact of strain state is performed. We note that the YAO substrate can serve as a felicitous base for growing T-like BFO because this phase stably exists in very thick film. Thick BFO films grown on YAO substrate exhibit a typical "morphotropic-phase-boundary"-like feature with coexisting multiple phases (MII, MI, and R) and a periodic stripe-like topography. A discrepancy of arrayed stripe morphology in different direction on YAO substrate due to the anisotropic strain suggests a possibility to tune the MPB-like region. Our study provides more insights to understand the strain mediated phase co-existence in multiferroic BFO system.Comment: 18 pages, 6 figures, submitted to Journal of Applied Physic

Autonomous error correction of a single logical qubit using two transmons

Large-scale quantum computers will inevitably need quantum error correction to protect information against decoherence. Traditional error correction typically requires many qubits, along with high-efficiency error syndrome measurement and real-time feedback. Autonomous quantum error correction (AQEC) instead uses steady-state bath engineering to perform the correction in a hardware-efficient manner. We realize an AQEC scheme, implemented with only two transmon qubits in a 2D scalable architecture, that actively corrects single-photon loss and passively suppresses low-frequency dephasing using six microwave drives. Compared to uncorrected encoding, factors of 2.0, 5.1, and 1.4 improvements are experimentally witnessed for the logical zero, one, and superposition states. Our results show the potential of implementing hardware-efficient AQEC to enhance the reliability of a transmon-based quantum information processor

Reply to Letter to the Editor : Is HPV-18 present in human breast cancer cell lines

2 page(s

A method for detecting gravitational waves coincident with gamma ray bursts

The mechanism for gamma ray bursters and the detection of gravitational waves (GWs) are two outstanding problems facing modern physics. Many models of gamma ray bursters predict copious GW emission, so the assumption of an association between GWs and GRBs may be testable with existing bar GW detector data. We consider Weber bar data streams in the vicinity of known GRB times and present calculations of the expected signal after co-addition of 1000 GW/GRBs that have been shifted to a common zero time. Our calculations are based on assumptions concerning the GW spectrum and the redshift distribution of GW/GRB sources which are consistent with current GW/GRB models. We discuss further possibilities of GW detection associated with GRBs in light of future bar detector improvements and suggest that co-addition of data from several improved bar detectors may result in detection of GWs (if the GW/GRB assumption is correct) on a time scale comparable with the LIGO projects.Comment: Accepted by MNRAS. 9 pages, 6 ps figures, MNRAS style. Proof corrections made, accepted versio

Epilepsy and Neurodevelopmental Outcomes in Children With Etiologically Diagnosed Central Nervous System Infections: A Retrospective Cohort Study

Background: Central nervous system (CNS) infection in childhood can lead to neurological sequelae, including epilepsy, and neurodevelopmental disorders, such as attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). This study investigated the association of etiologically diagnosed childhood brain infections with the subsequent risks of epilepsy and neurodevelopmental disorders.Objectives: We retrospectively analyzed the data of children aged &lt;18 years who had definite brain infections with positive cerebrospinal fluid cultures from January 1, 2005, to December 31, 2017. These patients were followed to evaluate the risks of epilepsy and neurodevelopmental disease (ADHD and ASD) after brain infections (group 1) in comparison with the risks in those without brain infections (group 2).Results: A total of 145 patients with an average age of 41.2 months were included in group 1. Enterovirus accounted for the majority of infections, followed by group B Streptococcus, S. pneumoniae, and herpes simplex virus. A total of 292 patients with an average age of 44.8 months were included in group 2. The 12-year risk of epilepsy in group 1 was 10.7 (95% confidence interval [CI], 2.30–49; p &lt; 0.01). Compared with group 2 (reference), the risk of ASD in the age interval of 2–5 years in group 1 was 21.3 (95% CI, 1.33–341.4; p = 0.03). The incidence of ADHD in group 1 was not significantly higher than that in group 2.Conclusions: This study identified the common etiological causes of brain infections in Taiwanese children. The highest-risk neurodevelopmental sequelae associated with brain infections was epilepsy. Children who had a diagnosis of brain infection (specially Enterovirus) should be followed since they are at greater risk of developing epilepsy and ASD

On the efficacy of anthracene isomers for triplet transmission from CdSe nanocrystals

The effect of isomeric substitutions on the transmitter for triplet energy transfer (TET) between nanocrystal (NC) donor and molecular acceptor is investigated. Each isomeric acceptor is expected to bind in a unique orientation with respect to the NC donor. We see that this orbital overlap drastically affects the transmission of triplets. Here, two functional groups, the carboxylic acid and dithiocarbamate, were varied between the 1-, 2- and 9-positions of the anthracene ring to give three ACA and three ADTC isomers. These six anthracene isomers served as transmitters for triplets between CdSe NC sensitizers and 9,10-diphenylanthracene annihilators for photon upconversion. The photon upconversion quantum yield (QY) is the highest for 9-ACA (12%), lowest for 9-ADTC (0.1%), around 3% for both 1-ACA and 1-ADTC, and about 1% for the 2-isomers. These trends in QYs are reflected in the rates of TET given by ultrafast transient absorption spectroscopy where a maximum of 3.8 × 107 s−1 for 9-ACA was measured. Molecular excited state energy levels were measured both in solution and polymer hosts to correlate structure to TET. This work confirms that anthracene excited states levels are very sensitive to molecular substitution, which in combination with orbital overlap, critically affect Dexter-based TET.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Managing the Double Burden: Pregnancy and Labor-Intensive Time Use in Rural China, Mexico, and Tanzania

Labor-intensive work is often a way of life for women in rural areas of developing countries. However, physical exertion may result in poor health outcomes for mother and infant if continued through pregnancy. Using longitudinal data from China, Mexico and Tanzania, we examine the relationship between pregnancy and four time use outcomes, measured as hours spent in the last week on: 1) housework, 2) care giving, 3) agricultural work, and 4) self-employed or non-agricultural work outside the home. An individual fixed effects approach is adopted to overcome potential time invariant woman-level endogeneity of pregnancy status. With a few exceptions, we do not find significantly different time use patterns between pregnant and non-pregnant women. The assumption that women decrease labor intensive work in developing countries during pregnancy needs revisiting, and may have implications for both women’s livelihood programming and assistance during childbearing periods