Publications
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Rai T, Bruton P, Kall M, et al., 2019, Experience of primary care for people with HIV: a mixed-method analysis, British Journal of General Practice, Vol: 3, ISSN: 0960-1643
BackgroundAdvances in treatment have transformed HIV into a long-term condition (LTC), presenting freshchallenges for health services, HIV specialists and general practitioners (GPs).AimTo explore the experience of people living with HIV (PLHIV) regarding using their GPs.Design and settingA mixed-method analysis using data from two sources: a nationally-representative survey of PLHIVand a qualitative study with London-based PLHIV.MethodsUnivariate logistic regression for quantitative data and Framework analysis for qualitative data.ResultsThe survey had 4,422 participants; the qualitative study included 52 participants. In both studies, GPregistration and HIV status disclosure were high. Similar to general population trends, recent GP usewas associated with poor self-rated health status, co-morbidities, older age and lower socioeconomic status. Two-thirds reported a good experience with GPs; a lower proportion feltcomfortable asking HIV-related questions. Actual or perceived HIV stigma were consistentlyassociated with poor satisfaction. In the interviews, participants with additional LTCs valuedsensitive and consistent support from GPs. Some anticipated, and sometimes experienced, problems relating to HIV status, GPs’ limited experience and time to manage their complex needs. Sometimesthey took their own initiatives to facilitate coordination and communication. For PLHIV, a ‘good’ GPoffered continuity and took time to know and accept them without judgement.ConclusionWe suggest clarification of roles and provision of relevant support to build confidence in GPs andprimary care staff to care for PLHIV. As PLHIV population ages, there is a strong need to developtrusting patient/GP relationships and HIV-friendly GP practices.
Papageorgiou V, Jones K, Mindham R, et al., 2019, ‘Do I really want to do this for the rest of my life?’: a qualitative exploration of participant and study staff perspectives from the Therapy withdrawal in Recovered Dilated cardiomyopathy - Heart Failure (TRED-HF) study, Chronic Living Conference 2020
Thorpe J, Slutsky J, Baker JG, et al., 2019, Micrometeoroid events in LISA pathfinder, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 883, Pages: 1-15, ISSN: 0004-637X
The zodiacal dust complex, a population of dust and small particles that pervades the solar system, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. We present a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory. Pathfinder employed a technique known as drag-free control that achieved rejection of external disturbances, including particle impacts, using a micropropulsion system. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hr of Pathfinder data. We report a total of 54 candidates with transferred momenta ranging from 0.2 to 230 μNs. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system, including those resulting from Jupiter-family comets (JFCs), Oort Cloud comets, Halley-type comets, and asteroids. We find that our measured population is consistent with a population dominated by JFCs, with some evidence for a smaller contribution from Halley-type comets, in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.
Armano M, Audley H, Baird J, et al., 2019, Novel methods to measure the gravitational constant in space, PHYSICAL REVIEW D, Vol: 100, ISSN: 2470-0010
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Armano M, Audley H, Baird J, et al., 2019, LISA pathfinder performance confirmed in an open-loop configuration: results from the free-fall actuation mode, Physical Review Letters, Vol: 123, Pages: 111101-1-111101-7, ISSN: 0031-9007
We report on the results of the LISA Pathfinder (LPF) free-fall mode experiment, in which the control force needed to compensate the quasistatic differential force acting on two test masses is applied intermittently as a series of “impulse” forces lasting a few seconds and separated by roughly 350 s periods of true free fall. This represents an alternative to the normal LPF mode of operation in which this balancing force is applied continuously, with the advantage that the acceleration noise during free fall is measured in the absence of the actuation force, thus eliminating associated noise and force calibration errors. The differential acceleration noise measurement presented here with the free-fall mode agrees with noise measured with the continuous actuation scheme, representing an important and independent confirmation of the LPF result. An additional measurement with larger actuation forces also shows that the technique can be used to eliminate actuation noise when this is a dominant factor.
Ensor S, Davies B, Rai T, et al., 2019, The effectiveness of demand creation interventions for voluntary male medical circumcision for HIV prevention in Sub-Saharan Africa; a mixed methods systematic review, Journal of the International AIDS Society, Vol: 22, Pages: 40-53, ISSN: 1758-2652
IntroductionUNAIDS has recommended that in 14 countries across sub‐Saharan Africa (SSA), 90% of men aged 10 to 29 years should be circumcised by 2021 to help reduce transmission of HIV. To achieve this target demand creation programmes have been widely implemented to increase demand for Voluntary Medical Male Circumcision (VMMC). This review explores the effectiveness of demand creation interventions and factors affecting programme implementation.MethodsWe completed a mixed methods systematic review searching Medline, Embase, Global health, psycINFO and CINAHL databases in August 2018 with no time restrictions. Demand creation interventions conducted in SSA were categorized and quantitative data about VMMC uptake was used to compare relative and absolute effectiveness of interventions. Qualitative data were summarized into themes relevant to the delivery and impact of programmes.Results and discussionEighteen of the 904 titles were included in the review. Effective interventions were identified in each demand creation category: financial incentives, counselling or education, involvement of influencers and novel information delivery. Of the 11 randomized controlled trials (RCTs), the greatest absolute impact on VMMC prevalence was seen with a complex intervention including VMMC promotion training for religious leaders (compared to control: 23% (95% CI 22.8 to 23.8) absolute increase; odds ratio (OR) 3.2 (1.4 to 7.3)). Financial incentives generally produced the largest relative effects with men up to seven‐times more likely to undergo VMMC in the intervention arm compared to control (adjusted OR 7.1 (95% CI 2.4 to 20.8), 7.1% (3.7 to 10.5) absolute increase). Qualitative findings suggest that interventions are more impactful when they are judged appropriate and acceptable by the target population; delivered by people with relevant personal experience; and addressing broader social and cultural influences through partnership with and education of community leaders.Con
Armano M, Audley H, Baird J, et al., 2019, Temperature stability in the sub-milliHertz band with LISA Pathfinder, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 486, Pages: 3368-3379, ISSN: 0035-8711
Ward H, Garnett GP, Mayer KH, et al., 2019, Maximizing the impact of HIV prevention technologies in sub‐Saharan Africa, Journal of the International AIDS Society, Vol: 22, ISSN: 1758-2652
Ward H, 2019, IMPACT OF HIV PREP ON RISK COMPENSATION AND STI EPIDEMIOLOGY - WHAT DOES THE EVIDENCE SHOW?, Publisher: BMJ PUBLISHING GROUP, Pages: A9-A10, ISSN: 1368-4973
Armano M, Audley H, Baird J, et al., 2019, LISA Pathfinder micronewton cold gas thrusters: In-flight characterization, PHYSICAL REVIEW D, Vol: 99, ISSN: 2470-0010
Ensor S, Davies B, Rai T, et al., 2019, The effectiveness of demand creation interventions for voluntary male medical circumcision for HIV prevention in Sub-Saharan Africa; a mixed methods systematic review, AIDS Impact 2019
Papageorgiou V, Crittendon E, Davies B, et al., 2019, Impact of pre-exposure prophylaxis on the risk of bacterial sexually transmitted infections among cisgender women: systematic review, AIDS Impact 2019
Pristera P, Bruton J, Cooke G, et al., 2019, Perspectives on transmission, treatment and elimination of hepatitis C in HIV-positive MSM in London: a qualitative study, AIDS IMPACT 2019
Armano M, Audley H, Baird J, et al., 2019, LISA Pathfinder platform stability and drag-free performance, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 99, ISSN: 1550-2368
The science operations of the LISA Pathfinder mission have demonstrated the feasibility of sub-femto-g free fall of macroscopic test masses necessary to build a gravitational wave observatory in space such as LISA. While the main focus of interest, i.e., the optical axis or the x-axis, has been extensively studied, it is also of great importance to evaluate the stability of the spacecraft with respect to all the other degrees of freedom (d.o.f.). The current paper is dedicated to such a study: the exhaustive and quantitative evaluation of the imperfections and dynamical effects that impact the stability with respect to its local geodesic. A model of the complete closed-loop system provides a comprehensive understanding of each component of the in-loop coordinates spectral density. As will be presented, this model gives very good agreement with LISA Pathfinder flight data. It allows one to identify the noise source at the origin and the physical phenomena underlying the couplings. From this, the stability performance of the spacecraft with respect to its geodesic is extracted as a function of frequency. Close to 1 mHz, the stability of the spacecraft on the XSC, YSC and ZSC d.o.f. is shown to be of the order of 5.0×10−15 m s−2 Hz−1/2 for X, 6.0×10−14 m s−2 Hz−1/2 for Y, and 4.0×10−14 m s−2 Hz−1/2 for Z. For the angular d.o.f., the values are of the order of 3×10−12 rad s−2 Hz−1/2 for ΘSC, 5×10−13 rad s−2 Hz−1/2 for HSC, and 3×10−13 rad s−2 Hz−1/2 for ΦSC. Below 1 mHz, however, the stability performances are worsened significantly by the effect of the star tracker noise on the closed-loop system. It is worth noting that LI
Papageorgiou V, Crittendon E, Davies B, et al., 2019, PROSPERO registration: Impact of pre-exposure prophylaxis (PrEP) on the risk of bacterial sexually transmitted infections (STIs) among cisgender women: a systematic review, PROSPERO International prospective register of systematic reviews
Armano M, Audley H, Baird J, et al., 2019, Forbush Decreases and < 2 Day GCR Flux Non-recurrent Variations Studied with LISA Pathfinder, Astrophysical Journal, Vol: 874, ISSN: 0004-637X
Non-recurrent short-term variations of the galactic cosmic-ray (GCR) flux above 70 MeV n−1 were observed between 2016 February 18 and 2017 July 3 on board the European Space Agency LISA Pathfinder (LPF) mission orbiting around the Lagrange point L1 at 1.5 × 106 km from Earth. The energy dependence of three Forbush decreases is studied and reported here. A comparison of these observations with others carried out in space down to the energy of a few tens of MeV n−1 shows that the same GCR flux parameterization applies to events of different intensity during the main phase. FD observations in L1 with LPF and geomagnetic storm occurrence are also presented. Finally, the characteristics of GCR flux non-recurrent variations (peaks and depressions) of duration <2 days and their association with interplanetary structures are investigated. It is found that, most likely, plasma compression regions between subsequent corotating high-speed streams cause peaks, while heliospheric current sheet crossing causes the majority of the depressions.
Kilvington J, Day S, Ward H, 2019, Prostitution policy in Europe: A time of change?, FEMINIST REVIEW, Pages: 78-93, ISSN: 0141-7789
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Ronn M, Mc Grath-Lone L, Davies B, et al., 2019, Evaluation of the performance of nucleic acid amplification tests (NAATs) in detection of chlamydia and gonorrhoea infection in vaginal specimens relative to patient infection status: a systematic review, BMJ Open, Vol: 9, ISSN: 2044-6055
OBJECTIVE: We aimed to assess the performance of NAATs using vaginal specimens in comparison to other urogenital specimens in their ability to detect chlamydia and gonorrhea infection in women.DESIGN: Systematic review.DATA SOURCES: EMBASE and Ovid MEDLINE databases through 3 October 2017.ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We included studies that tested samples from the vagina and ≥1 other site (cervix and/or urine) with ≥2 NAATs for chlamydia and ≥2 NAATs or 1 NAAT and culture for gonorrhoea for each site.DATA EXTRACTION AND SYNTHESIS: We compared the performance of NAATs on specimens taken from the vagina to those from the cervix or urine in diagnosing chlamydia and gonorrhoea infection in women based on patient infection status (PIS). We analysed the performance using vaginal specimens compared to PIS. Performance is defined as the sensitivity of a NAAT using a specimen site and PIS status of the patient. We assessed risk of bias using modified QUADAS-2.RESULTS: Nine publications met the inclusion criteria (eight for chlamydia; six for gonorrhoea) and were narratively reviewed. Pooled summary estimates were not calculated due to the variable methodology and PIS definitions. Tests performed on vaginal specimens accomplished similar performance to cervical and urine specimens for chlamydia (range of performance estimates: vaginal 65-100%, cervical 59-97%, urine 57-100%) and gonorrhoea (vaginal 64-100%, cervical 85-100%, urine 67-94%). Vaginal specimens were estimated to have a performance >80% for chlamydia and gonorrhoea infections in all but one study.CONCLUSIONS: Performance of the NAATs for chlamydia and gonorrhea detection using vaginal specimens was similar to that of cervical and urine specimens relativeto PIS. As vaginal samples have a higher acceptability and lower cost, the study can support clinical testing guidelines by providing evidence that vaginal samples are a suitable alternative to traditional test sites.
Rai T, Bruton P, Day S, et al., 2018, From activism to secrecy: contemporary experiences of living with HIV in London in people diagnosed from 1986 to 2014, Health Expectations, Vol: 21, Pages: 1134-1141, ISSN: 1369-6513
Background:Successes in biomedicine have transformed HIV from a debilitating and frequently fatal infection to a chronic, manageable condition. Objective:To explore how the contemporary metanarrative of HIV as a chronic condition is understood by patients and how it varies depending on when they were diagnosed.Design:Qualitative interviews with fifty-two people living with HIV who were diagnosed during different phases in the history of the epidemic. Setting and participantsParticipants were recruited from two HIV clinics in London to include four “HIV generations”: generation 1 were those who had been diagnosed pre-1997 (pre-ART), generation 2 from 1997-2005 (complex ART), generation 3 from 2006-2012 (simpler ART) and generation 4 were diagnosed in the year before the study (2013-2014). Results: Participants in all HIV generations took their medication as prescribed, attended clinic appointments and were well-informed about their immunological biomarkers. While the pre-treatment generation had been engaged in community endeavours such as activism, public education and use of support groups, those more recently diagnosed had little experience of collective activities and their HIV was essentially a private matter, separate from their social identity. These strategies worked for some however those experiencing clinical or social problems related to HIV or wider issues often relied exclusively on their HIV clinic for wider support. Conclusion:The loss of public conversation around HIV, the imperative for patients to take on greater individual responsibility for HIV management and the streamlining of HIV services alongside reductions in ancillary support services may expose some people to suboptimal health outcomes.
Anderson G, Anderson J, Anderson M, et al., 2018, Experimental results from the ST7 mission on LISA Pathfinder, Physical Review D, Vol: 98, ISSN: 2470-0010
The Space Technology 7 Disturbance Reduction System (ST7-DRS) is a NASA technology demonstration payload that operated from January 2016 through July 2017 on the European Space Agency’s (ESA) LISA Pathfinder spacecraft. The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observatory targeting the source-rich millihertz band. The two primary components of ST7-DRS are a micropropulsion system based on colloidal micro-Newton thrusters (CMNTs) and a control system that simultaneously controls the attitude and position of the spacecraft and the two free-flying test masses (TMs). This paper presents our main experimental results and summarizes the overall performance of the CMNTs and control laws. We find the CMNT performance to be consistent with preflight predictions, with a measured system thrust noise on the order of 100 nN/√Hz in the 1 mHz≤f≤30 mHz band. The control system maintained the TM-spacecraft separation with an RMS error of less than 2 nm and a noise spectral density of less than 3 nm/√Hz in the same band. Thruster calibration measurements yield thrust values consistent with the performance model and ground-based thrust-stand measurements, to within a few percent. We also report a differential acceleration noise between the two test masses with a spectral density of roughly 3 fm/s2/√Hz in the 1 mHz≤f≤30 mHz band, slightly less than twice as large as the best performance reported with the baseline LISA Pathfinder configuration and below the current requirements for the Laser Interferometer Space Antenna mission.
Benjamin CM, Boudioni M, Ward H, et al., 2018, Evaluation of the 100,000 Genomes Project Consent Process and Participant Materials, 50th European-Society-of-Human-Genetics (ESHG) Conference, Publisher: NATURE PUBLISHING GROUP, Pages: 51-52, ISSN: 1018-4813
Armano M, Audley H, Baird J, et al., 2018, Precision charge control for isolated free-falling test masses: LISA pathfinder results, Physical Review D, Vol: 98, ISSN: 2470-0010
The LISA Pathfinder charge management device was responsible for neutralizing the cosmic-ray-induced electric charge that inevitably accumulated on the free-falling test masses at the heart of the experiment. We present measurements made on ground and in flight that quantify the performance of this contactless discharge system which was based on photoemission under UV illumination. In addition, a two-part simulation is described that was developed alongside the hardware. Modeling of the absorbed UV light within the Pathfinder sensor was carried out with the Geant4 software toolkit and a separate Matlab charge transfer model calculated the net photocurrent between the test masses and surrounding housing in the presence of AC and DC electric fields. We confront the results of these models with observations and draw conclusions for the design of discharge systems for future experiments like LISA that will also employ free-falling test masses.
Aghaizu A, Tosswill J, De Angelis D, et al., 2018, HIV incidence among sexual health clinic attendees in England: First estimates for black African heterosexuals using a biomarker, 2009-2013, PLoS ONE, Vol: 13, ISSN: 1932-6203
IntroductionThe HIV epidemic in England is largely concentrated among heterosexuals who are predominately black African and men who have sex with men (MSM). We present for the first time trends in annual HIV incidence for adults attending sexual health clinics, where 80% of all HIV diagnoses are made.MethodsWe identified newly diagnosed incident HIV using a recent infection testing algorithm (RITA) consisting of a biomarker (AxSYM assay, modified to determine antibody avidity), epidemiological and clinical information. We estimated HIV incidence using the WHO RITA formula for cross-sectional studies, with HIV testing data from sexual health clinics as the denominator.ResultsFrom 2009 to 2013, each year, between 9,700 and 26,000 black African heterosexuals (of between 161,000 and 231,000 heterosexuals overall) were included in analyses. For the same period, annually between 19,000 and 55,000 MSM were included. Estimates of HIV incidence among black Africans increased slightly (although non-significantly) from 0.15% (95% C.I.0.05%-0.26%) in 2009 to 0.19% (95% C.I.0.04%-0.34%) in 2013 and was 4-5-fold higher than among all heterosexuals among which it remained stable between 0.03% (95% C.I.0.02%-0.05%) and 0.05% (95% C.I.0.03%-0.07%) over the period. Among MSM incidence was highest and increased (non-significantly) from 1.24% (95%C.I 0.96–1.52%) to 1.46% (95% C.I 1.23%-1.70%) after a peak of 1.52% (95%C.I 1.30%-1.75%) in 2012.ConclusionThese are the first nationwide estimates for trends in HIV incidence among black African and heterosexual populations in England which show black Africans, alongside MSM, remain disproportionately at risk of infection. Although people attending sexual health clinics may not be representative of the general population, nearly half of black Africans and MSM had attended in the previous 5 years. Timely and accurate incidence estimates will be critical in monitoring the impact of the reconfiguration of sexual health services in England
Armano M, Audley H, Baird J, et al., 2018, Calibrating the system dynamics of LISA Pathfinder, Physical Review D, Vol: 97, ISSN: 2470-0010
LISA Pathfinder (LPF) was a European Space Agency mission with the aim to test key technologies for future space-borne gravitational-wave observatories like LISA. The main scientific goal of LPF was to demonstrate measurements of differential acceleration between free-falling test masses at the sub-femto-g level, and to understand the residual acceleration in terms of a physical model of stray forces, and displacement readout noise. A key step toward reaching the LPF goals was the correct calibration of the dynamics of LPF, which was a three-body system composed by two test-masses enclosed in a single spacecraft, and subject to control laws for system stability. In this work, we report on the calibration procedures adopted to calculate the residual differential stray force per unit mass acting on the two test-masses in their nominal positions. The physical parameters of the adopted dynamical model are presented, together with their role on LPF performance. The analysis and results of these experiments show that the dynamics of the system was accurately modeled and the dynamical parameters were stationary throughout the mission. Finally, the impact and importance of calibrating system dynamics for future space-based gravitational wave observatories is discussed.
Pufall EL, Kall M, Shahmanesh M, et al., 2018, Sexualized drug use ('chemsex') and high-risk sexual behaviours in HIV-positive men who have sex with men, HIV Medicine, Vol: 19, Pages: 261-270, ISSN: 1464-2662
OBJECTIVES: The incidence of sexually transmitted infections (STIs) and HIV infection remains high in gay, bisexual, and other men who have sex with men (MSM) in the UK, and sexualized drug use ("chemsex") and injecting drug use ("slamsex") may play a part in this. We aimed to characterize HIV-positive MSM engaging in chemsex/slamsex and to assess the associations with self-reported STI diagnoses and sexual behaviours. METHODS: Data from a 2014 survey of people attending HIV clinics in England and Wales were linked to clinical data from national HIV surveillance records and weighted to be nationally representative. Multivariable logistic regression assessed the associations of chemsex and slamsex with self-reported unprotected anal intercourse (UAI), serodiscordant UAI (sdUAI) (i.e. UAI with an HIV-negative or unknown HIV status partner), sdUAI with a detectable viral load (>50 HIV-1 RNA copies/mL), hepatitis C, and bacterial STIs. RESULTS: In the previous year, 29.5% of 392 sexually active participants engaged in chemsex, and 10.1% in slamsex. Chemsex was significantly associated with increased odds of UAI [adjusted odds ratio (AOR) 5.73; P < 0.001], sdUAI (AOR 2.34; P < 0.05), sdUAI with a detectable viral load (AOR 3.86; P < 0.01), hepatitis C (AOR 6.58; P < 0.01), and bacterial STI diagnosis (AOR 2.65; P < 0.01). Slamsex was associated with increased odds of UAI (AOR 6.11; P < 0.05), hepatitis C (AOR 9.39; P < 0.001), and bacterial STI diagnosis (AOR 6.11; P < 0.001). CONCLUSIONS: Three in ten sexually active HIV-positive MSM engaged in chemsex in the past year, which was positively associated with self-reported depression/anxiety, smoking, nonsexual drug use, risky sexual behaviours, STIs, and hepatitis C. Chemsex may therefore play a role in the ongoing HIV and STI epidemics in the UK.
Aghaizu A, Ward H, McOwan A, et al., 2018, Preventive and risk behaviours among MSM recently infected with HIV: results of a pilot cross-sectional survey in England, Publisher: WILEY, Pages: S59-S59, ISSN: 1464-2662
Bruton PJ, Rai T, Day S, et al., 2018, Patient perspectives on the HIV continuum of care in London: a qualitative study of people diagnosed between 1986 and 2014, BMJ Open, Vol: 8, ISSN: 2044-6055
Objectives: To describe the experiences of the HIV treatment cascade of diagnosis, engagement with care and initiation of treatment, from the perspective of patients; we explored whether this differed according to the year of their diagnosis, for example whether they had experienced HIV care in the pre-treatment era.Design: Qualitative interview study with framework analysisSetting: Two large HIV adult outpatient clinics in central London. Participants: 52 HIV positive individuals, 41 men, 11 women, purposively sampled to include people who had been diagnosed at different stages in the history of the epidemic classified as four ‘generations’: pre-1996 (pre-ART), 1997 to 2005 (complex ARTs), 2006 to 2012 (simpler ARTs), 2013 onwards (recent diagnoses).Results: Some important differences were identified; for earlier generations, the visible illness and deaths from AIDS made it harder to engage with care following diagnosis. Subsequent decisions about starting treatment were deeply influenced by the fear of severe side-effects from early antiretroviral therapy (ART). However, despite improvements in ART and life expectancy over the epidemic we found a striking similarity across participants’ accounts of the key stages of the care continuum, regardless of when they were diagnosed. Diagnosis was a major traumatic life event for almost everyone, fear of testing positive or having low self-perceived risk affected the timing of testing and diagnosis, engaging with care was facilitated by a flexible approach from services/clinicians and initiating treatment was a major life decision. Conclusion: We found patients’ experiences are influenced by when they were diagnosed, with earliest cohorts facing substantial challenges. However, being diagnosed with HIV and starting treatment continue to be significant life-altering events even in the era of effective, simple treatments. Despite the advances of biomedical treatment services should continue to recogn
Armano M, Audley H, Baird J, et al., 2018, Characteristics and energy dependence of recurrent galactic cosmic-ray Flux depressions and of a Forbush decrease with LISA Pathfinder, Astrophysical Journal, Vol: 854, ISSN: 0004-637X
Galactic cosmic-ray (GCR) energy spectra observed in the inner heliosphere are modulated by the solar activity, the solar polarity and structures of solar and interplanetary origin. A high counting rate particle detector (PD) aboard LISA Pathfinder, meant for subsystems diagnostics, was devoted to the measurement of GCR and solar energetic particle integral fluxes above 70 MeV n−1 up to 6500 counts s−1. PD data were gathered with a sampling time of 15 s. Characteristics and energy dependence of GCR flux recurrent depressions and of a Forbush decrease dated 2016 August 2 are reported here. The capability of interplanetary missions, carrying PDs for instrument performance purposes, in monitoring the passage of interplanetary coronal mass ejections is also discussed.
Armano M, Audley H, Baird J, et al., 2018, Beyond the required LISA free-fall performance: new LISA pathfinder results down to 20 μHz, Physical Review Letters, Vol: 120, ISSN: 0031-9007
In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20 μHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05) fm s^{-2}/sqrt[Hz] above 2 mHz and (6±1)×10 fm s^{-2}/sqrt[Hz] at 20 μHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.
Armano M, Audley H, Baird J, et al., 2018, Measuring the Galactic Cosmic Ray Flux with the LISA Pathfinder Radiation Monitor, Astroparticle Physics, Vol: 98, Pages: 28-37, ISSN: 0927-6505
Test mass charging caused by cosmic rays will be a significant source ofacceleration noise for space-based gravitational wave detectors like LISA.Operating between December 2015 and July 2017, the technology demonstrationmission LISA Pathfinder included a bespoke monitor to help characterise therelationship between test mass charging and the local radiation environment.The radiation monitor made in situ measurements of the cosmic ray flux whilealso providing information about its energy spectrum. We describe the monitorand present measurements which show a gradual 40% increase in count ratecoinciding with the declining phase of the solar cycle. Modulations of up to10% were also observed with periods of 13 and 26 days that are associated withco-rotating interaction regions and heliospheric current sheet crossings. Thesevariations in the flux above the monitor detection threshold (approximately 70MeV) are shown to be coherent with measurements made by the IREM monitoron-board the Earth orbiting INTEGRAL spacecraft. Finally we use the measureddeposited energy spectra, in combination with a GEANT4 model, to estimate thegalactic cosmic ray differential energy spectrum over the course of themission.
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