Eradication-resolution dynamics with stochastic flare-ups

In infectious disease as well as in cancer, the ultimate outcome of the curative response, mediated by the body itself or through drug treatment, is either successful eradication or a resurgence of the disease (“flare-up” or “relapse”), depending on random fluctuations that dominate the dynamics of the system when the number of diseased cells has become very low. The presence of a low-numbers bottle-neck in the dynamics, which is unavoidable if eradication is to take place at all, renders at least one phase of the dynamics essentially stochastic. However, the eradicating agents (e.g. immune cells, drug molecules) generally remain at high numbers during the critical bottle-neck phase, sufficiently so to warrant a deterministic treatment. This leads us to consider a hybrid stochastic-deterministic approach where the infected cells are treated stochastically whereas the eradicating agents are treated deterministically. Exploiting the fact that the number of eradicating agents typically decreases monotonically during the resolution phase of the response, we derive a set of coupled first-order differential equations that describe the probability of ultimate eradication as a function of the system's state, and we consider a number of biomedical applications

Interaction of Agulhas filaments with mesoscale turbulence: a case study

The inter-ocean leakage of heat and salt from the South Indian Ocean to the South Atlantic has important consequences for the global thermohaline circulation and in particular for the strength of overturning of the Atlantic Ocean as a whole. This leakage between these two subtropical gyres takes place south of Africa. The main mechanisms are the intermittent shedding of Agulhas rings from the retroflection of the Agulhas Current and the advection of Agulhas filaments from the border of the Agulhas Current, both of which move northwestward into the South Atlantic. The subsequent behaviour and mixing of Agulhas rings has been much studied over the past years, that of Agulhas filaments not at all. We report here on fortuitous hydrographic observations of the behaviour of an Agulhas filament that interacted with a number of mesoscale features shortly after formation. This suggests that Agulhas filaments may be involved in many other circulation elements and not only the Benguela upwelling front, as was surmised previously, and may mix out in a very site-specific region

Chasing the Elderly: Can State and Local Governments Attract Recent Retirees?

Recruiting recent retirees to relocate from elsewhere has become an important economic development strategy in an increasing number of states. State governments have planned or enacted a variety of tax and fee incentives to lure retirees. The objective of this paper is to determine whether states can, in fact, influence the retirement destination of elder households using fiscal tools. To estimate the determinants of retiree location decisions we have developed an extensive data set on county attributes, and a methodology for estimating an individual-level discrete-choice model for a very large number of potential locations. Using 1990 county-to-county migration data, we estimate the effects of an array of tax and expenditures variables on the probability that a retiree locates in that county. We find that changes in tax burdens and service levels can affect location decisions. Of the fiscal variables, inheritance taxes, income taxes, and property taxes have the largest relative effects. However, very large tax reductions would be required to attract even one more retiree to the average county. Unless these tax breaks could be narrowly targeted to the group of retirees most likely to consider migrating, the revenue losses from such a program are likely to significantly outweigh the economic and fiscal benefits. Our results suggest that states should focus on marketing their amenities, rather than using fiscal policy to recruit retirees

Photometry of Proxima Centauri and Barnard's Star Using HST Fine Guidance Sensor 3: A Search for Periodic Variations

We have observed Proxima Centauri and Barnard's Star with Hubble Space Telescope Fine Guidance Sensor 3. Proxima Centauri exhibits small-amplitude, periodic photometric variations. Once several sources of systematic photometric error are corrected, we obtain 2 milli-magnitude internal photometric precision. We identify two distinct behavior modes over the past four years: higher amplitude, longer period; smaller amplitude, shorter period. Within the errors one period (P ~ 83d) is twice the other. Barnard's Star shows very weak evidence for periodicity on a timescale of approximately 130 days. If we interpret these periodic phenomena as rotational modulation of star spots, we identify three discrete spots on Proxima Cen and possibly one spot on Barnard's Star. We find that the disturbances change significantly on time scales as short as one rotation period.Comment: 39 pages, 17 figure

Interferometric Astrometry of Proxima Centauri and Barnard's Star Using Hubble Space Telescope Fine Guidance Sensor 3: Detection Limits for sub-Stellar Companions

We report on a sub-stellar companion search utilizing interferometric fringe-tracking astrometry acquired with Fine Guidance Sensor 3 (FGS 3) on the Hubble Space Telescope. Our targets were Proxima Centauri and Barnard's Star. We obtain absolute parallax values for Proxima Cen pi_{abs} = 0.7687 arcsecond and for Barnard's Star pi_{abs} = 0.5454 arcsecond. Once low-amplitude instrumental systematic errors are identified and removed, our companion detection sensitivity is less than or equal to one Jupiter mass for periods longer than 60 days for Proxima Cen. Between the astrometry and the radial velocity results we exclude all companions with M > 0.8M_{Jup} for the range of periods 1 < P < 1000 days. For Barnard's Star our companion detection sensitivity is less than or equal to one Jupiter mass for periods long er than 150 days. Our null results for Barnard's Star are consistent with those of Gatewood (1995).Comment: 35 pages, 13 figures, to appear in August 1999 A

Nox2 underpins microvascular inflammation and vascular contributions to cognitive decline

\ua9 The Author(s) 2022. Chronic microvascular inflammation and oxidative stress are inter-related mechanisms underpinning white matter disease and vascular cognitive impairment (VCI). A proposed mediator is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (Nox2), a major source of reactive oxygen species (ROS) in the brain. To assess the role of Nox2 in VCI, we studied a tractable model with white matter pathology and cognitive impairment induced by bilateral carotid artery stenosis (BCAS). Mice with genetic deletion of Nox2 (Nox2 KO) were compared to wild-type (WT) following BCAS. Sustained BCAS over 12 weeks in WT mice induced Nox2 expression, indices of microvascular inflammation and oxidative damage, along with white matter pathology culminating in a marked cognitive impairment, which were all protected by Nox2 genetic deletion. Neurovascular coupling was impaired in WT mice post-BCAS and restored in Nox2 KO mice. Increased vascular expression of chemoattractant mediators, cell-adhesion molecules and endothelial activation factors in WT mice post-BCAS were ameliorated by Nox2 deficiency. The clinical relevance was confirmed by increased vascular Nox2 and indices of microvascular inflammation in human post-mortem subjects with cerebral vascular disease. Our results support Nox2 activity as a critical determinant of VCI, whose targeting may be of therapeutic benefit in cerebral vascular disease

A cross sectional survey of sociodemographic characteristics, primary care health needs and living conditions of asylum-seekers living in a Greek reception centre

Background In 2019, a migrant camp on the Greek island of Samos designed for 650 people was home to a growing population of over 5500. We aimed to quantitatively describe living conditions and health needs in the camp. Methods A questionnaire was designed with reference to international humanitarian standards, following a consultative process with the asylum-seeker population. Domains assessed included demographics, living conditions, safety/vulnerability, and health. The questionnaire was piloted and then conducted in June 2019 on a sample of asylum seekers. Results Five hundred participants, predominantly from Afghanistan and the Democratic Republic of Congo (DRC). Of these, 79.4% lived in tents. Respondents cared for a total of 570 children; 20.6% of women were pregnant, 35.4% had experienced violence, 83% psychological distress, 71% skin disease, 66% diarrhoea and vomiting, and 64% respiratory disease. Accommodation, sanitation, and nutrition fell below internationally recognised standards, and poor access to water was significantly associated (p < 0.001) with respiratory disease, diarrhoea and vomiting, skin disease ,and psychological distress. Conclusions Living conditions in the Samos camp fall below basic humanitarian standards and are associated with poor health status. Further research is imperative to analyse and monitor the diverse, varying needs of asylum-seekers and inform policies to improve conditions

The Distance To The Hyades Cluster Based On Hubble Space Telescope Fine Guidance Sensor Parallaxes

Trigonometric parallax observations made with the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) 3 of seven Hyades members in six fields of view have been analyzed along with their proper motions to determine the distance to the cluster. Knowledge of the convergent point and mean proper motion of the Hyades is critical to the derivation of the distance to the center of the cluster. Depending on the choice of the proper-motion system, the derived cluster center distance varies by 9%. Adopting a reference distance of 46.1 pc or m - M = 3.32, which is derived from the ground-based parallaxes in the General Catalogue of Trigonometric Stellar Parallaxes (1995 edition), the FK5/PPM proper-motion system yields a distance 4% larger, while the Hanson system yields a distance 2% smaller. The HST FGS parallaxes reported here yield either a 14% or 5% larger distance, depending on the choice of the proper-motion system. Orbital parallaxes (Torres et al.) yield an average distance 4% larger than the reference distance. The variation in the distance derived from the HST data illustrates the importance of the proper-motion system and the individual proper motions to the derivation of the distance to the Hyades center; therefore, a full utilization of the HST FGS parallaxes awaits the establishment of an accurate and consistent proper-motion system.NASA HST GTO, HF-1042.01-93A, HF-1046.01-93A, NAS526555Astronom

Adherence and Risk Behaviour in Patients with HIV Infection Receiving Antiretroviral Therapy in Bangkok

It could be postulated that due to lifestyle factors, patients with poor antiretroviral therapy (ART) adherence may also have risky sexual behaviour potentially leading to HIV transmission. There are limited data regarding unprotected sex risk and ART adherence in resource limited settings and our study set out to investigate these in an HIV clinic in Bangkok. Patients completed an anonymous questionnaire regarding their relationship details, ART adherence, sexual behaviour, alcohol and drug use and HIV transmission beliefs. Laboratory findings and medical history were also collected. Unprotected sex risk (USR) was defined as inconsistent condom use with a partner of negative or unknown HIV status. Five hundred and twelve patients completed the questionnaire. Fifty seven per cent of patients reported having taken ARV >95% of the time in the last month and 58% had been sexually active in the previous 30 days. Only 27 patients (5%) were classified as having USR in our cohort. Multivariate analysis showed USR was associated with female gender (OR 2.9, 95% CI 1.2-7.0, p0.02) but not with adherence, age, type or number of partners, recreational drug or alcohol use nor beliefs about HIV transmission whilst taking ART. Levels of USR in this resource limited setting were reassuringly low and not associated with poor ART adherence; as all USR patients had undetectable viral loads onward HIV transmission risk is likely to be low but not negligible. Nonetheless condom negotiation techniques, particularly in women, may be useful in this group