Association of attrition with mortality: findings from 11 waves over three decades of the Whitehall II study

BACKGROUND: Attrition, the loss of participants as a study progresses, is a considerable challenge in longitudinal studies. This study examined whether two forms of attrition, ‘withdrawal’ (formal discontinued participation) and ‘non-response’ (non-response among participants continuing in the study), have different associations with mortality and whether these associations differed across time in a multi-wave longitudinal study. METHODS: Participants were 10 012 civil servants who participated at the baseline of the Whitehall II cohort study with 11 data waves over an average follow-up of 28 years. We performed competing-risks analyses to estimate sub-distribution HRs and 95% CIs, and likelihood ratio tests to examine whether hazards differed between the two forms of attrition. We then applied linear regression to examine any trend of hazards against time. RESULTS: Attrition rate at data collections ranged between 13% and 34%. There were 495 deaths recorded from cardiovascular disease and 1367 deaths from other causes. Study participants lost due to attrition had 1.55 (95% CI 1.26 to 1.89) and 1.56 (1.39 to 1.76) times higher hazard of cardiovascular and non-cardiovascular mortality than responders, respectively. Hazards for withdrawal and non-response did not differ for either cardiovascular (p value =0.28) or non-cardiovascular mortality (p value =0.38). There was no linear trend in hazards over the 11 waves (cardiovascular mortality p value =0.11, non-cardiovascular mortality p value =0.61). CONCLUSION: Attrition can be a problem in longitudinal studies resulting in selection bias. Researchers should examine the possibility of selection bias and consider applying statistical approaches that minimise this bias

Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures

Microscopic growth processes associated with GaN/GaAs molecular beam epitaxy (MBE) are examined through the introduction of a first-order kinetic model. The model is applied to the electron cyclotron resonance microwave plasma-assisted MBE (ECR-MBE) growth of a set of delta-GaNyAs1–y/GaAs strained-layer superlattices that consist of nitrided GaAs monolayers separated by GaAs spacers, and that exhibit a strong decrease of y with increasing T over the range 540–580 °C. This y(T) dependence is quantitatively explained in terms of microscopic anion exchange, and thermally activated N surface-desorption and surface-segregation processes. N surface segregation is found to be significant during GaAs overgrowth of GaNyAs1–y layers at typical GaN ECR-MBE growth temperatures, with an estimated activation energy Es ~ 0.9 eV. The observed y(T) dependence is shown to result from a combination of N surface segregation/desorption processes

Scanning Tunneling Microscopy and Tunneling Luminescence of the Surface of GaN Films Grown by Vapor Phase Epitaxy

We report scanning tunneling microscopy (STM) images of surfaces of GaN films and the observation of luminescence from those films induced by highly spatially localized injection of electrons or holes using STM. This combination of scanning tunneling luminescence (STL) with STM for GaN surfaces and the ability to observe both morphology and luminescence in GaN is the first step to investigate possible correlations between surface morphology and optical properties.Comment: 12 pages, Revtex 3.0, submitted to Appl. Phys. Lett., three figures available from Jian Ma at [email protected]

Adverse childhood experiences and incident coronary heart disease: a counterfactual analysis in the Whitehall II prospective cohort study

Objectives: Adverse childhood experience is thought to be associated with risk of coronary heart disease, but it is not clear which experiences are cardiotoxic, and whether risk increases with the accumulation of adverse childhood experiences. Methods: Participants were 5149 adults (72.6% men) in the Whitehall II cohort study. Parental death was recorded at phase 1 (median age in years 44.3), and 13 other adverse childhood experiences at phase 5 (55.3). We applied Cox proportional hazards regression with person-time from phase 5 to examine associations of adverse childhood experiences with incident coronary heart disease. We predicted hazard ratios according to count of the experiences, and examined dose-response effect. We finally estimated reduction of coronary heart disease in a hypothetical scenario, the absence of adverse childhood experiences. Results: Among study participants, 62.9% had at least one adversity, with “financial problems” having the highest prevalence (26.1%). There were 509 first episodes of coronary heart disease during an average 12.9 years follow-up. Among 14 adverse childhood experiences in a multiply adjusted model, “parental unemployment” showed the highest hazard of coronary heart disease incidence (hazard ratio; 95% confidence interval: 1.53; 1.16 to 2.02). No dose-response effect was observed (constant for proportionality in hazard ratio: 1.05, 0.99 to 1.11). Based on the estimates of final model, in the absence of childhood adversities, we estimated a 6.0% reduction in coronary heart disease (0.94; 0.87 to 1.01), but the confidence interval includes one. Conclusion: Although individual adverse childhood experiences show some association with coronary heart disease, there is no clear relationship with the number of adverse experiences. Further research is required to quantify effects of multiple and combinations of adverse childhood experiences considering timing, duration, and severity

Compressive strength and microstructure of alkali-activated blast furnace slag/sewage sludge ash (GGBS/SSA) blends cured at room temperature

In the present work, ground granulated blast furnace slag (GGBS) and sewage sludge ash (SSA) blends were assessed for the production of alkali-activated pastes and mortars. Percentages of SSA to substitute GGBS ranged from 0–30 wt.% and sodium concentrations of 6–10 mol.kg-1 were used for the activating solutions. Pastes and mortars were cured at 20 ºC for up to 90 days. Raw materials were characterised by granulometric analysis, XRF, XRD, FTIR and SEM techniques. The replacement percentage of GGBS by SSA and the sodium hydroxide concentration of the alkaline activator were optimised to produce mortar with compressive strengths close to 30 MPa after 28 curing days at room temperature. Best results were obtained in samples blended with 20 wt.% SSA activated with 6 mol.kg-1 NaOH solutions which, according to the XRD, FTIR and microscopic results, contained higher amounts of (N,C)-A-S-H gel. The potential use of SSA for the development of alternative cementitious materials at room temperature has been demonstrated

Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer

[EN] This paper aimed to evaluate the long-term compressive strength development of the sewage sludge ash/metakaolin (SSA/MK)¿based geopolymer. SSA/MK¿based geopolymeric mortars and pastes were produced at 25ºC with different SSA contents (0 - 30 wt.%). Compressive strength tests were run within the 3-720 curing days range. A physicochemical characterisation (X-ray diffraction and scanning electron microscopy) was performed in geopolymeric pastes. All the geopolymeric mortars presented a compressive strength gain with curing time. The mortars with all the SSA evaluated contents (10, 20, 30 wt.%) developed a compressive strength over 40 MPa after 720 curing days at 25ºC. The maximum compressive strength of the mortars with SSA was approximately 61 MPa (10 wt.% of SSA), similarly to the reference mortar (100% MK-based geopolymer). The microstructure analyses showed that the SSA/MK¿based geopolymer presented a dense microstructure with N-A-S-H gel formation.This study was financed partly by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Su-perior -Brasil (CAPES) -(Finance Code 001 and CAPES/DGU n. 266/12), and the National Council of Scientific and Technological Development -Bra-sil (CNPq) -(n. 14/2013, process 478057/2013-0 and 309015/2015-4). The authors would like to thank Programa Institucional de Internacionalizacao - CAPES -PrInt. The authors acknowledge the Scanning Electron Microscopy Service of FEIS/UN-ESP, Servico Municipal Autonomo de Agua e Es-goto (SEMAE) from the Sao Jose do Rio Preto city -SP, Brazil and Diatom Mineracao Ltda. The authors would like to thank Programa Institucional de Internacionalizacao CAPES -PrInt.Istuque, D.; Soriano Martinez, L.; Borrachero Rosado, MV.; Paya Bernabeu, JJ.; Akasaki, JL.; Melges, JLP.; Tashima, MM. (2021). Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer. Materiales de Construcción. 71(343):1-10. https://doi.org/10.3989/mc.2021.13220S1107134

Pozzolanic reactivity studies on a miomass-derived waste from sugar cane production: sugar cane straw ash (SCSA)

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021%2Facssuschemeng.6b00770.”Biomass has gained in importance as an energy source in recent years. One of the crops that presents interesting opportunities with regard to biomass is sugar cane. In Brazil, sugar cane production is increasing for alcohol and sugar manufacture. Some by-products, such as sugar cane straw, also are obtained during harvesting. Due the calorific value of the sugar cane straw, its use as biomass is increasing. After the straw is burned to produce energy, an ash is obtained: sugar cane straw ash (SCSA). This waste needs an appropriate destination and, since the recent publication of successful studies using biomass derived-ashes as pozzolanic material, the present study aimed to assess the pozzolanic reactivity of sugar cane straw ash. The pozzolanic activity was assessed using a new and simple recently proposed method: evaluation of the electrical conductivity of calcium hydroxide (CH) and pozzolan suspensions, in which solid CH is initially present. These results were compared to those of two other well-established techniques: Fourier transformed infrared spectroscopy and thermogravimetric analysis. The evaluation by all three techniques is similar and shows that sugar cane straw ash is a good pozzolanic material: high lime fixation values for CH:SCSA mixes were determined by thermogravimetric analysis and unsaturation respect to CH in 3.5:6.5 CH:SCSA suspension was achieved at 60ºC. According to this behaviour, a bright future for SCSA as a replacement for Portland cement is expected.We thank CNPq (processo no. 401724/2013-1) and the "Ministerio de Education, Cultura y Deporte" of Spain ("Cooperacion Interuniversitaria" program with Brazil PHB-2011-0016-PC). Thanks are also due to the Electron Microscopy Service of the Universitat Politecnica de ValenciaMoraes, J.; Melges, JLP.; Akasaki, JL.; Tashima, MM.; Soriano Martínez, L.; Monzó Balbuena, JM.; Borrachero Rosado, MV.... (2016). Pozzolanic reactivity studies on a miomass-derived waste from sugar cane production: sugar cane straw ash (SCSA). ACS Sustainable Chemistry and Engineering. 4(8):4273-4279. https://doi.org/10.1021/acssuschemeng.6b00770S427342794

Electronic dielectric constants of insulators by the polarization method

We discuss a non-perturbative, technically straightforward, easy-to-use, and computationally affordable method, based on polarization theory, for the calculation of the electronic dielectric constant of insulating solids at the first principles level. We apply the method to GaAs, AlAs, InN, SiC, ZnO, GaN, AlN, BeO, LiF, PbTiO$_3$, and CaTiO$_3$. The predicted \einf's agree well with those given by Density Functional Perturbation Theory (the reference theoretical treatment), and they are generally within less than 10 % of experiment.Comment: RevTeX 4 pages, 2 ps figure