Experimental study of an R1234ze(E)/R134a mixture (R450A) as R134a replacement

[EN] This work presents an experimental analysis of a non-flammable R1234ze(E)/R134a mixture (R450A) as R134a drop-in replacement. While R134a has a high GWP value (1430), the R450A GWP is only 547. The experimental tests are carried out in a vapour compression plant equipped with a variable-speed compressor. The replacement suitability has been studied combining different operating conditions: evaporation temperature, condensation temperature and the use of an internal heat exchanger (IHX). The drop-in cooling capacity of R450A compared with R134a is 6% lower as average. R450A COP is even higher to those resulting with R134a (approximately 1%). The discharge temperature of R450A is lower than that of R134a, 2K as average. The IHX has a similar positive influence on the energy performance of both fluids. In conclusion, R450A can be considered as a good candidate to replace R134a.The authors thankfully acknowledge "Ministerio de Educacion, Cultura y Deporte" for supporting this work through "Becas y Contratos de Formacion de Profesorado Universitario del Programa Nacional de Formacion de Recursos Humanos de Investigacion del ejercicio 2012".Mota Babiloni, A.; Navarro Esbri, J.; Barragán Cervera, Á.; Moles Ribera, F.; Peris Pérez, B. (2015). Experimental study of an R1234ze(E)/R134a mixture (R450A) as R134a replacement. International Journal of Refrigeration. 51:52-58. doi:10.1016/j.ijrefrig.2014.12.010S52585

A global inventory of stratospheric NOy from ACE-FTS

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board the Canadian SCISAT-1 satellite (launched in August 2003) measures over 30 different atmospheric species, including six nitrogen trace gases that are needed to quantify the stratospheric NOy budget. We combine volume mixing ratio (VMR) profiles for NO, NO2, HNO3, N2O5, ClONO2, and HNO4 to determine a zonally averaged NOy climatology on monthly and 3 month combined means (December–February, March–May, June–August, and September–November) at 5° latitude spacing and on 33 pressure surfaces. Peak NOy VMR concentrations (15–20 ppbv) are situated at about 3 hPa (∼40 km) in the tropics, while they are typically lower at about 10 hPa (∼30 km) in the midlatitudes. Mean NOy VMRs are similar in both the northern and southern polar regions, with the exception of large enhancements periodically observed in the upper stratosphere and lower mesosphere. These are primarily due to enhancements of NO due to energetic particle precipitation and downward transport. Other features in the NOy budget are related to descent in the polar vortex, heterogeneous chemistry, and denitrification processes. Comparison of the ACE-FTS NOy budget is made to both the Odin and ATMOS NOy data sets, showing in both cases a good level of agreement, such that relative differences are typically better than 20%. The NOy climatological products are available through the ACE website and are a supplement to the paper. - A middle-atmosphere NOy climatology has been produced using ACE-FTS measurements; - A robust method for quality controlling the input data has been developed - Good agreement is found between ACE-FTS NOy climatology and other climatologie

Validation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)

This paper presents extensive bias determination analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45 60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about + 20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within +/- 10% (average values within +/- 6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (similar to 35-55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to -10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45-55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements

Causal and associational language in observational health research: a systematic evaluation

We estimated the degree to which language used in the high profile medical/public health/epidemiology literature implied causality using language linking exposures to outcomes and action recommendations; examined disconnects between language and recommendations; identified the most common linking phrases; and estimated how strongly linking phrases imply causality. We searched and screened for 1,170 articles from 18 high-profile journals (65 per journal) published from 2010-2019. Based on written framing and systematic guidance, three reviewers rated the degree of causality implied in abstracts and full text for exposure/outcome linking language and action recommendations. Reviewers rated the causal implication of exposure/outcome linking language as None (no causal implication) in 13.8%, Weak 34.2%, Moderate 33.2%, and Strong 18.7% of abstracts. The implied causality of action recommendations was higher than the implied causality of linking sentences for 44.5% or commensurate for 40.3% of articles. The most common linking word in abstracts was “associate” (45.7%). Reviewer’s ratings of linking word roots were highly heterogeneous; over half of reviewers rated “association” as having at least some causal implication. This research undercuts the assumption that avoiding “causal” words leads to clarity of interpretation in medical research

Injection drug use and food insecurity among HIV-hepatitis C virus co-infected individuals: associations, mechanisms, and interventions

Background: In Canada, 20% of individuals living with HIV are estimated to be co-infected with hepatitis C virus (HCV). In addition to the high prevalence of injection drug use (IDU), the characteristics of individuals living with HIV-HCV co-infection reflect socioeconomic and sociodemographic vulnerability. Central to the concept of food insecurity (FI), a social determinant of health, is the focus on uncertain or inadequate food access due to limited financial resources. The existing evidence has documented high prevalences of FI, particularly severe FI, among individuals living with HIV. Furthermore, FI is associated with lower CD4 cell counts, incomplete HIV viral load suppression, and sub-optimal HIV treatment adherence. These consequences of FI motivate studies that focus on identifying modifiable risk factors for FI with the goal of informing interventions to reduce FI. However, given the differences between those living with HIV mono-infection and HIV-HCV co-infection and the context-specific nature of FI risk factors, the generalizability of findings from HIV-related studies that do not consider HCV co-infection is unclear. Therefore, novel research is needed to further our understanding of the relationship between IDU, a highly prevalent behaviour in this vulnerable subset of the HIV-positive population, and FI. Objectives: The overall aim of this doctoral thesis was to examine associations, mechanisms, and interventions related to IDU and FI, particularly severe FI, in a population of HIV-HCV co-infected individuals in Canada. Specifically, this dissertation addressed the following objectives using longitudinal cohort data from individuals living with HIV-HCV co-infection: 1. To examine the relationship between IDU and FI. 2. To examine whether unemployment is a mediator in the mechanism linking IDU and severe FI. 3. To examine whether a substance use intervention, methadone maintenance treatment, is associated with a lower risk of severe FI.Contexte: Au Canada, on estime que 20% des personnes vivant avec le VIH sont co-infectées par le virus de l'hépatite C (VHC). En plus d'une forte prévalence de consommation de drogues injectables, on retrouve chez les personnes co-infectées par le VIH et le VHC des caractéristiques reflétant d'importantes vulnérabilités socioéconomiques et sociodémographiques. L'accès incertain ou inadéquat à la nourriture en raison de ressources financières limitées est central au concept d'insécurité alimentaire (IA), un déterminant social de la santé. Des données probantes démontrent des prévalences élevées d'IA et plus particulièrement un degré grave (ou sévère) d'IA chez les personnes vivant avec le VIH. En plus, l'IA est associée à une diminution du nombre de cellules CD4, à une suppression incomplète de la charge virale du VIH et à une observance sous-optimale du traitement anti-VIH. Ces conséquences ont mené à des études sur l'identification des facteurs de risque modifiables de l'IA afin d'éclairer le travail d'intervention visant à réduire l'IA. Toutefois, étant donné les différences entre les personnes vivant avec la mono-infection par le VIH et celles vivant avec la co-infection VIH-VHC, et la nature contextuelle des facteurs de risque de l'IA, la généralisabilité des résultats des études liées au VIH qui ne tiennent pas compte de la co-infection par le VHC n'est pas claire. Par conséquent, une recherche innovante est nécessaire pour mieux comprendre la relation entre la consommation des drogues injectables, un comportement très répandu dans ce sous-ensemble vulnérable de la population séropositive, et l'IA. Objectifs: L'objectif global de cette thèse de doctorat était d'examiner les associations, les mécanismes et les interventions liés à la consommation de drogues injectables et à l'IA, plus particulièrement l'IA sévère, dans une population de personnes co-infectées par le VIH et le VHC au Canada. Plus précisément, cette thèse, qui se fonde sur des données de cohortes longitudinales provenant de personnes vivant avec une co-infection VIH-VHC, porte sur les objectifs suivants: 1. Examiner la relation entre la consommation de drogues injectables et l'IA. 2. Examiner si le chômage est un médiateur du mécanisme liant la consommation de drogues injectables à l'IA sévère. 3. Examiner si un programme de traitement à la méthadone est associé à un moindre risque de l'IA sévère

Estimation of time of HIV seroconversion using a modified CD4 depletion model.

IntroductionSeveral methods have been proposed to estimate the time of HIV seroconversion, including those based on CD4 cell depletion models. However, previous models have failed to consider the heterogeneity that exists in CD4 trajectories among different sub-populations. Our objective was to estimate the time from HIV seroconversion relative to the HIV diagnosis date in a population-based cohort of people living with HIV (PLWH) in the province of British Columbia, Canada.MethodsWe used linked administrative and clinical data from the British Columbia Seek and Treat for Optimal Prevention of HIV/AIDS (STOP HIV/AIDS) cohort, which contains longitudinal individual-level data on all PLWH ever diagnosed in the province. Eligible participants were aged ≥18 years and diagnosed with HIV between 1989 and 2013. The outcome was pre-antiretroviral treatment CD4 cell count measurements assessed every six months. Models were stratified by age and stage of HIV infection at diagnosis. Several explanatory variables were considered including longitudinal viral load measurements. Longitudinal CD4, square root transformed, was modeled via a non-linear mixed effects model; time was modeled using an exponential decay function. We assumed a Gaussian distribution (identity link), an AR(1) correlation structure, and a random intercept and slope for the longitudinal viral load measurements. Due to the population variation in CD4 count among uninfected individuals, we assumed 500 to 1500 cells/mm3 as the normal range when estimating the time of HIV seroconversion.ResultsLongitudinal data on 1,253 individuals were analysed: 80% male, 33% White, and the median age at diagnosis was 38 years (25th-75th percentile [Q1-Q3], 31 to 45). CD4 decay differed by stage of infection at diagnosis and age, with those ≥50 years in Stages 1 and 2 experiencing a faster decline in CD4 over time. The median duration of infection from seroconversion until HIV diagnosis was 6.9 (Q1-Q3, 3.9 to 10.1) years.ConclusionsConsidering the heterogeneity that exists in individual CD4 cell trajectories in a population, we presented a methodology that only relies on routinely collected HIV-related data, which can be further extended to estimate other epidemic measures

The impact of lookback windows on the prevalence and incidence of chronic diseases among people living with HIV: an exploration in administrative health data in Canada

Background We described the impact of different lengths of lookback window (LW), a retrospective time period to observe diagnoses in administrative data, on the prevalence and incidence of eight chronic diseases. Methods Our study populations included people living with HIV (N = 5151) and 1:5 age-sex-matched HIV-negative individuals (N = 25,755) in British Columbia, Canada, with complete follow-up between 1996 and 2012. We measured period prevalence and incidence of diseases in 2012 using LWs ranging from 1 to 16 years. Cases were deemed prevalent if identified in 2012 or within a defined LW, and incident if newly identified in 2012 with no previous cases detected within a defined LW. Chronic disease cases were ascertained using published case-finding algorithms applied to population-based provincial administrative health datasets. Results Overall, using cases identified by the full 16-year LW as the reference, LWs ≥8 years and ≥ 4 years reduced the proportion of misclassified prevalent and incidence cases of most diseases to < 20%, respectively. The impact of LWs varied across diseases and populations. Conclusions This study underscored the importance of carefully choosing LWs and demonstrated data-driven approaches that may inform these choices. To improve comparability of prevalence and incidence estimates across different settings, we recommend transparent reporting of the rationale and limitations of chosen LWs.Medicine, Faculty ofOther UBCMedicine, Department ofPopulation and Public Health (SPPH), School ofReviewedFacultyResearcherOthe

Assessing the Impact of Food Insecurity on HIV Medication Adherence in the Context of an Integrated Care Facility for People Living with HIV in Vancouver, Canada

Objective Food insecurity, or self-reports of inadequate food access due to limited financial resources, remains prevalent among people living with HIV (PLHIV). We examined the impact of food insecurity on combination antiretroviral therapy (cART) adherence within an integrated care facility that provides services to PLHIV, including two meals per day. Design Adjusted odds ratios (aOR) were estimated by generalized estimating equations, quantifying the relationship between food insecurity (exposure) and cART adherence (outcome) with multivariable logistic regression. Setting We drew on survey data collected between February 2014-March 2016 from the Dr. Peter Centre Study based in Vancouver, Canada. Participants This study included 116 PLHIV at baseline, with 99 participants completing a 12-month follow-up interview. The median age was 46 years (IQR: 39-52) at baseline, and 82% (n=95) were biologically male at birth. Results At baseline, 74% (n=86) of participants were food insecure (≥ 2 affirmative responses on Health Canada’s Household Food Security Survey Module) and 67% (n=78) were adherent to cART ≥ 95% of the time. In the adjusted regression analysis, food insecurity was associated with suboptimal cART adherence (aOR=0.47, 95% confidence interval = 0.24-0.93). Conclusions While food provision may reduce some health-related harms, there remains a relationship between this prevalent experience and suboptimal cART adherence in this integrated care facility. Future studies that elucidate strategies to mitigate food insecurity and its affects on cART adherence among PLHIV in this setting and in other similar environments are necessary