31 research outputs found
Ontwerp kademuur Waalhaven Terminal BV
No full textNaast de behoefte aan extra haventerrein in de Waalhaven, is er ook behoefte aan kadefaciliteiten aanwezig. De functie van de afscheiding tussen het land en het water is het kunnen keren van de grond. In dit geval moet de constructie meerdere functies kunnen vervullen. Als eerste moeten op de kade overslagactiviteiten kunnen plaatsvinden, ofwel het hierop kunnen overslaan van goederen vanuit het schip op de kade of andersom. Ten tweede moeten de scheepsbelastingen opgenomen kunnen worden door deze constructie. Met behulp van het programma van eisen voor deze kademuur, waarin de benodigde afmetingen worden beschreven, en de hierboven genoemde functies zijn een aantal mogelijke oplossingen ontwikkeld in hoofdstuk 6. Bij de beschrijving is onderscheid gemaakt tussen één enkele constructie die alle functies vervult en een samengestelde constructie. Bij de beschrijving van de diverse constructies zijn per alternatief ook de bouwfase en de voor- en nadelen besproken. Ondanks de hoge kosten is, na een afweging in hoofdstuk 7, gekozen voor een uitwerking van een caissonconstructie. Zeer belangrijk bij deze afweging is de besparing van het ruimtegebruik en het niet hoeven toepassen van een bemaling in de Waalhaven. Het caisson wordt namelijk elders gebouwd en naar de haven gevaren. Het realiseren van een caissonconstructie in de Waalhaven is opgebouwd uit een aantal fasen: \u95 Het bouwen in een bouwdok buiten het Waalhavengebied, waar de constructie moet worden geplaatst. \u95 Het varen van het caisson van het bouwdok naar de Waalhaven. \u95 Ter plaatse afzinken van het caisson door het aanbrengen van ballast. \u95 Aan landzijde aanaarden tot op juiste terreinhoogte, afwerken en in gebruik nemen van de kade. Hierbij geldt dat de constructie per fase verschillend wordt belast. Bij het berekenen van de afmetingen van de constructie is elk stadium apart bekeken om na te gaan wat de meest ongunstige situatie is. In het laatste hoofdstuk zijn de conclusies en aanbevelingen voor deze deelstudie beschreven. Ondanks de grote afmetingen en een aantal beperkingen, is een kademuur uitgevoerd als caisson in dit geval een mogelijke oplossing.waterbouwHydraulic EngineeringCivil Engineering and Geoscience
Hydrolyse van ureum in een ureumfabriek effluent
No full textDocument uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Timing of Initiation of Antiretroviral Therapy and Risk of Preterm Birth in Studies of HIV-infected Pregnant Women: The Role of Selection Bias
Get PDFBackground: Women who initiate antiretroviral therapy (ART) during pregnancy are reported to have lower risk of preterm birth compared with those who enter pregnancy care already receiving ART. We hypothesize this association can be largely attributed to selection bias. Methods: We simulated a cohort of 1000 preconceptional, HIV-infected women, where half were randomly allocated to receive immediate ART and half to delay ART until their presentation for pregnancy care. Gestational age at delivery was drawn from population data unrelated to randomization group (i.e., the true effect of delayed ART was null). Outcomes of interest were preterm birth (<37 weeks), very preterm birth (<32 weeks), and extreme preterm birth (<28 weeks). We analyzed outcomes in 2 ways: (1) a prospectively enrolled clinical trial, where all women were considered (the intent-to-treat (ITT) analysis); and (2) an observational study, where women who deliver before initiating ART were excluded (the naïve analysis). We explored the impact of later ART initiation and gestational age measurement error on our findings. Results: Preconception ART initiation was not associated with preterm birth in ITT analyses. Risk ratios (RRs) for the effect of preconception ART initiation were RR = 1.10 (preterm), RR = 1.41 (very preterm), and RR = 5.01 (extreme preterm) in naïve analyses. Selection bias increased in the naïve analysis with advancing gestational age at ART initiation and with introduction of gestational age measurement error. Conclusions: Analyses of preterm birth that compare a preconception exposure to one that occurs in pregnancy are at risk of selection bias. See video abstract at, http://links.lww.com/EDE/B313
A WARNING ABOUT USING PREDICTED VALUES TO ESTIMATE DESCRIPTIVE MEASURES
Get PDFIn a recent article in the Journal, Ogburn et al. highlighted the issues with using predicted values when estimating associations or effects. While the authors cautioned against using predicted values to estimate associations or effects, they noted that predictions can be useful for descriptive purposes. In this work, we highlight the issues with using individual-level predicted values to estimate population-level descriptive parameter
Preconception ART and preterm birth: real effect or selection bias?
Get PDFIn a recent systematic review and meta-analysis, Uthman and colleagues 1 examined the relation between timing of antiretroviral therapy (ART) initiation and adverse pregnancy outcomes. The researchers noted that women continuing preconception ART had a modestly higher risk of preterm birth (ie, birth before 37 weeks) compared with those initiating ART in pregnancy (RR 1·20, 95% CI 1·01–1·44)
17-Hydroxyprogesterone caproate (17OHP-C) coverage among eligible women delivering at 2 North Carolina hospitals in 2012 and 2013: A retrospective cohort study
Get PDFBackground Although a weekly injection of 17-hydroxyprogestone caproate is recommended for preventing recurrent preterm birth, clinical experience in North Carolina suggested that many eligible patients were not receiving the intervention. Objective Our study sought to assess how well practices delivering at 2 major hospitals were doing in providing access to 17-hydroxyprogesterone caproate treatment for eligible patients. Study Design This retrospective cohort analysis studied all deliveries occurring between January 1, 2012, and December 31, 2013, at 2 large hospitals in North Carolina. Women were included if they had a singleton pregnancy and history of a prior spontaneous preterm birth. We extracted demographic, payer, and medical information on each pregnancy, including whether women had been offered, accepted, and received 17-hydroxyprogesterone caproate. Our outcome of 17-hydroxyprogesterone caproate coverage was defined as documentation of ≥1 injection of the drug. Results Over the 2-year study period, 1216 women with history of a prior preterm birth delivered at the 2 study hospitals, of which 627 were eligible for 17-hydroxyprogesterone caproate eligible after medical record review. Only 296 of the 627 eligible women (47%; 95% confidence interval, 43-51%) received ≥1 dose of the drug. In multivariable analysis, hospital of delivery, later presentation for prenatal care, fewer prenatal visits, later gestation of prior preterm birth, and having had a term delivery immediately before the index pregnancy were all associated with failed coverage. Among those women who were "covered," the median number of 17-hydroxyprogesterone caproate injections was 9 (interquartile range, 4-15), with 84 of 296 charts (28%) not having complete information on the number of doses. Conclusion Even under our liberal definition of coverage, less than half of eligible women received 17-hydroxyprogesterone caproate in this sample. Low overall use suggests that there is opportunity for improvement. Quality improvement strategies, including population-based measurement of 17-hydroxyprogesterone caproate coverage, are needed to fully implement this evidence-based intervention to decrease preterm birth
Adherence to antiretroviral therapy during and after pregnancy in low-, middle and high income countries: a systematic review and meta-analysis
No full textTo estimate ART adherence rates during pregnancy and postpartum in high-, middle- and low-income countries. MEDLINE, EMBASE, SCI Web of Science, NLM Gateway and Google scholar databases were searched. We included all studies reporting adherence rates as a primary or secondary outcome among HIV-infected pregnant women. Two independent reviewers extracted data on adherence and study characteristics. A random-effects model was used to pool adherence rates; sensitivity, heterogeneity, and publication bias were assessed. Of 72 eligible articles, 51studies involving 20,153 HIV-infected pregnant women were included. Most studies were from United States (n=14, 27%) followed by Kenya (n=6, 12%), South Africa (n=5, 10%), and Zambia (n=5, 10%). The threshold defining good adherence to ART varied across studies (>80%, >90%, >95%, 100%). The pooled proportion of women with adequate adherence levels was higher during the antepartum (75.7%, 95% CI 71.5-79.7%) than during postpartum (53.0%, 95% 32.8% to 72.7%) (p=0.005). Selected reported barriers for non-adherence included physical, economic and emotional stresses, depression (especially post-delivery), alcohol or drug use, and ART dosing frequency or pill burden. Our findings indicate that only 73.5% of pregnant women achieved optimal ART adherence. Reaching adequate ART adherence levels was a challenge in pregnancy, but especially during the postpartum period. Further research to investigate specific barriers and interventions to address them are urgently needed globally.
Integrating cervical cancer prevention in HIV/AIDS treatment and care programmes
Get PDFPeckham and Hann’s call for integrating cervical cancer prevention as part of broader sexual and reproductive health prevention services is especially relevant to sub-Saharan Africa where both cervical cancer and sexually transmitted infections, especially HIV/AIDS, are widely prevalent
Implementation of 'see-and-treat' cervical cancer prevention services linked to HIV care in Zambia
Get PDFGreater than 80% of the world's new cases and deaths due to cervical cancer occur in the
developing world. No more than 5% of women in these settings are screened for cervical
cancer even once in their lifetimes. Earlier attempts to establish population-based cervical
cancer prevention programs using cytology screening in resource-limited settings have
inevitably fallen short or failed. Although many of the reasons for failure can be attributed
to lack of resources and trained manpower, the multiple visit requirements of cytology-based
screening programs jeopardizes success and sustainability
Missing Outcome Data in Epidemiologic Studies
Get PDFMissing data are pandemic and a central problem for epidemiology. Missing data reduce precision and can cause notable bias. There remain too few simple published examples detailing types of missing data and illustrating their possible impact on results. Here we take an example randomized trial that was not subject to missing data and induce missing data to illustrate 4 scenarios in which outcomes are 1) missing completely at random, 2) missing at random with positivity, 3) missing at random without positivity, and 4) missing not at random. We demonstrate that accounting for missing data is generally a better strategy than ignoring missing data, which unfortunately remains a standard approach in epidemiology
