Single and hybrid organoclay-filled PLA nanocomposites: mechanical properties, viscoelastic behavior and fracture toughening mechanism

Poly (lactic acid) (PLA) nanocomposites based on single and hybrid organic-modified montmorillonites were previously studied in terms of their morphologi-cal, thermal and fire performance. As surfactants of the organoclays influenced thecompatibility between the nanofillers and PLA with different degrees of clay plate-lets dispersion, the present work investigated the effect of these features in themechanical properties of PLA nanocomposites. PLA nanocomposites specimenswere analyzed by dynamic-mechanical-thermal analysis, which pointed outchanges in the viscoelastic behavior of the materials by the incorporation of theorganoclays, namely the increase of the storage modulus due to polymerchains movements rest riction and reinfor cement effects associated with the disper-sion of the nanofillers. Flexural and impact testing showed that hybridorganomontmorillonites containing ester ammonium and ethoxylated amineimproved PLA's ductility, toughness and impact resistance. This behavior wasexplained by the high level of compatibility and interaction between the surfactantsand PLA chains due to the polar groups in their structures. These organoclays cau-sed a transition on PLA's fracture from brittle to ductile in a way that the toughen-ing mechanism was explained by crazing and multi-shear banding induced by theplasticized interfacial region around these organoclaysPostprint (author's final draft

Editorial Peer Reviewers' Recommendations at a General Medical Journal: Are They Reliable and Do Editors Care?

BACKGROUND: Editorial peer review is universally used but little studied. We examined the relationship between external reviewers' recommendations and the editorial outcome of manuscripts undergoing external peer-review at the Journal of General Internal Medicine (JGIM). METHODOLOGY/PRINCIPAL FINDINGS: We examined reviewer recommendations and editors' decisions at JGIM between 2004 and 2008. For manuscripts undergoing peer review, we calculated chance-corrected agreement among reviewers on recommendations to reject versus accept or revise. Using mixed effects logistic regression models, we estimated intra-class correlation coefficients (ICC) at the reviewer and manuscript level. Finally, we examined the probability of rejection in relation to reviewer agreement and disagreement. The 2264 manuscripts sent for external review during the study period received 5881 reviews provided by 2916 reviewers; 28% of reviews recommended rejection. Chance corrected agreement (kappa statistic) on rejection among reviewers was 0.11 (p<.01). In mixed effects models adjusting for study year and manuscript type, the reviewer-level ICC was 0.23 (95% confidence interval [CI], 0.19-0.29) and the manuscript-level ICC was 0.17 (95% CI, 0.12-0.22). The editors' overall rejection rate was 48%: 88% when all reviewers for a manuscript agreed on rejection (7% of manuscripts) and 20% when all reviewers agreed that the manuscript should not be rejected (48% of manuscripts) (p<0.01). CONCLUSIONS/SIGNIFICANCE: Reviewers at JGIM agreed on recommendations to reject vs. accept/revise at levels barely beyond chance, yet editors placed considerable weight on reviewers' recommendations. Efforts are needed to improve the reliability of the peer-review process while helping editors understand the limitations of reviewers' recommendations

Urban futures and the code for sustainable homes

Copyright © 2012 ICE Publishing Ltd. Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.A 6?6 ha (66 000 m2) regeneration site, commonly referred to as Luneside East, is to be turned from a run down, economically under-achieving area of Lancaster, UK, into a new, distinctive, vibrant, sustainable quarter of the city. As a result several aspects of water planning for 350 new homes and 8000 m2 of workspace needed to be considered before any infrastructure investment was undertaken. This included assessment of the future capacity requirements (i.e. inflows and outflows) for water infrastructure (i.e. mains water supply, wastewater disposal, rainwater storage and stormwater disposal) much of which will be located underground. This paper looks at the implications of various water management strategies on the Luneside East site (e.g. water-efficient appliances, greywater recycling and rainwater harvesting) in line with current policy measures that focus on technology changes alone (e.g. the code for sustainable homes). Based on these findings this paper outlines some basic implications for technological resilience discussed in the context of four ‘world views’ – that is, the urban futures scenarios considered in this special issue. Conclusions are drawn as to how far this can take engineers, planners and developers in understanding and planning for resilient water infrastructure within a development like Luneside East

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure &lt;= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

The effect of brazilian organic-modified montmorillonites on the thermal stability and fire performance of organoclay-filled PLA nanocomposites

To investigate the influence of chemical compositions of organoclays on the thermal stability and fire behavior of PLA nanocomposites, 2, 6 and 8 wt% of single and hybrid Brazilian organically-modified montmorillonites (OMt), containing ammonium and phosphonium based surfactant - di-(hydrogenated tallow) dimethyl ammonium chloride (HTA), trihexyl tetradecyl phosphonium chloride (TDP), di(alkyl ester) dimethyl ammonium chloride (EA) and ethoxylated tallow amine (ETA) - were added to PLA using a melt-compounding process. It was noticed that the addition of OMt and melt-compounding contributed to a decrease of the initial decomposition temperature and average molecular mass of PLA, assessed by thermogravimetric analysis (TGA) and gel permeation chromatography (GPC), respectively. Moreover, PLA nanocomposites with single OMt (TDP and HTA) showed lower thermal stability than those with hybrid OMt. PLA nanocomposites with hybrid OMt containing EA and ETA displayed higher fire-reaction performance under cone calorimeter test. Comparing with neat PLA, these nanocomposites registered a peak heat release rate (pHRR) reduction of 29% and 38%, and a fire index grow rate (FIGRA) reduction of 32% and 37%, respectively, as well as the absence of melt dripping during combustion. The enhancement of the fire-reaction behavior was related to the nanoparticles high degree of dispersion and compatibility between PLA and nanoparticles, characterized in a previous work (Alves et al., 2019), which contributed to the formation of an effective protective layer on the condensed phase during combustio

Single and hybrid organoclay‐filled PLA

Poly (lactic acid) (PLA) nanocomposites based on single and hybrid organic-modified montmorillonites were previously studied in terms of their morphologi-cal, thermal and fire performance. As surfactants of the organoclays influenced thecompatibility between the nanofillers and PLA with different degrees of clay plate-lets dispersion, the present work investigated the effect of these features in themechanical properties of PLA nanocomposites. PLA nanocomposites specimenswere analyzed by dynamic-mechanical-thermal analysis, which pointed outchanges in the viscoelastic behavior of the materials by the incorporation of theorganoclays, namely the increase of the storage modulus due to polymerchains movements rest riction and reinfor cement effects associated with the disper-sion of the nanofillers. Flexural and impact testing showed that hybridorganomontmorillonites containing ester ammonium and ethoxylated amineimproved PLA's ductility, toughness and impact resistance. This behavior wasexplained by the high level of compatibility and interaction between the surfactantsand PLA chains due to the polar groups in their structures. These organoclays cau-sed a transition on PLA's fracture from brittle to ductile in a way that the toughen-ing mechanism was explained by crazing and multi-shear banding induced by theplasticized interfacial region around these organoclaysPostprint (author's final draft

Influence of chemical composition of Brazilian organoclays on the morphological, structural and thermal properties of PLA-organoclay nanocomposites

The effects of adding different Brazilian organoclays, containing di-(hydrogenated tallow) dimethyl ammonium chloride (HTA), trihexyl tetradecyl phosphonium chloride (TDP), di(alkyl ester) dimethyl ammonium chloride (EA) and ethoxylated tallow amine (ETA), on the structure and properties of poly(lactic acid) (PLA) nanocomposites, are presented. Single and hybrid organo-modified montmorillonites (OMt and HOMt, respectively) were used to prepare nanocomposites by melt mixing in a twin screw extruder. The structural and morphological properties of the nanocomposites were evaluated using wide-angle X-ray diffraction and transmission electron microscopy. The thermal behavior was studied by differential scanning calorimetry. Fourier-transform infrared spectroscopy was used to investigate the interactions between the different organoclays and PLA. Additionally, commercial organoclays (Cloisite 30B and Cloisite 20A) were used and compared with the Brazilian organoclays. It was verified that the structure and properties of the nanocomposites highly depended on chemical composition. Comparatively, HOMt containing EA and ETA presented better compatibility with PLA, showing the best level of clay dispersion. Differential scanning calorimetry showed a dependence on the nanocomposite thermal behavior with the dispersion level of the organoclays. In general, the presence of OMt and HOMt reduced the glass transition temperature of PLA and its cold crystallization temperature, and increased its crystallinity, which was related to an effective heterogeneous crystal nucleation promoted by the organocla

Perfilhamento como característica mitigadora dos prejuízos ocasionados ao milho pela desfolha do colmo principal

O objetivo deste trabalho foi verificar se os perfilhos podem mitigar os prejuízos ocasionados pela desfolha do colmo principal em milho. Os experimentos foram implantados em Lages, SC, em 20/10/2006 e 31/10/2008. O delineamento experimental utilizado foi o de blocos ao acaso, com parcelas subdivididas. Na parcela principal, foram testados dois destinos dos perfilhos: manutenção até a colheita e remoção quando o colmo principal apresentava nove folhas expandidas (V9). Nas subparcelas, avaliaram-se quatro épocas de desfolha do colmo principal: V9, V15 (quinze folhas expandidas), VT (pendoamento) e folhas preservadas até a colheita. Avaliou-se o híbrido P30F53, à densidade de 55 mil plantas por hectare. Determinaram-se: a produtividade total, a do colmo principal e a dos perfilhos. As desfolhas realizadas em V15 e VT diminuíram a produtividade, em comparação ao tratamento sem desfolha, independentemente do destino dos perfilhos. Quando o milho foi desfolhado em V15 e VT, a produtividade total das parcelas em que os perfilhos foram mantidos foi maior do que daquelas em que eles foram removidos. Isto indica que os perfilhos foram benéficos ao colmo principal do milho, quando houve restrições à produção de carboidrato oriundas da perda de área foliar próximo do florescimento