Role of the interface in the melt‐rheology properties of linear low‐density polyethylene/low‐density polyethylene blends: Effect of the molecular architecture of the dispersed phase

We studied the melt linear viscoelastic and elongational properties of blends consisting of a Ziegler–Natta linear low‐density polyethylene (LLDPE) and different LDPEs. The weight fraction of the LDPE used in the blends was 15%. The linear viscoelastic characterization was performed at different temperatures for all of the blends to determine the thermorheological behavior in the melt state. The blends fulfilled the time–temperature superposition but exhibited a broad linear viscoelastic response, which was further than that expected for miscible blends and even immiscible systems with a sharp interface. A rheological study of the application of the Palierne model revealed that in addition to the droplet shape relaxation, another mechanism was present at lower frequencies. We discuss the results by hypothesizing a strong interaction between the high‐molecular‐weight linear fraction of the LLDPE matrix and a fraction of molecules of the dispersed phase, which formed a thick interface with its own viscoelastic properties. A clear change in this additional mechanism was observed, depending on the dispersed minor‐phase properties, which produced an impact on the processing of the blends, and more precisely, on the values of the melt strength in the melt‐spinning experiments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Monitoring Apricot (Prunus armeniaca L.) Ripening Progression through Candidate Gene Expression Analysis

This study aimed at the monitoring of the apricot (Prunus armeniaca L.) ripening progression through the expression analysis of 25 genes related to fruit quality traits in nine cultivars with great differences in fruit color and ripening date. The level of pigment compounds, such as anthocyanins and carotenoids, is a key factor in food taste, and is responsible for the reddish blush color or orange skin and flesh color in apricot fruit, which are desirable quality traits in apricot breeding programs. The construction of multiple linear regression models to predict anthocyanins and carotenoids content from gene expression allows us to evaluate which genes have the strongest influence over fruit color, as these candidate genes are key during biosynthetic pathways or gene expression regulation, and are responsible for the final fruit phenotype. We propose the gene CHS as the main predictor for anthocyanins content, CCD4 and ZDS for carotenoids content, and LOX2 and MADS-box for the beginning and end of the ripening process in apricot fruit. All these genes could be applied as RNA markers to monitoring the ripening stage and estimate the anthocyanins and carotenoids content in apricot fruit during the ripening process.     

Data-Based Models for the Prediction of Dam Behaviour: A Review and Some Methodological Considerations

Predictive models are an important element in dam safety analysis. They provide an estimate of the dam response faced with a given load combination, which can be compared with the actual measurements to draw conclusions about dam safety. In addition to numerical finite element models, statistical models based on monitoring data have been used for decades for this purpose. In particular, the hydrostatic-season-time method is fully implemented in engineering practice, although some limitations have been pointed out. In other fields of science, powerful tools such as neural networks and support vector machines have been developed, which make use of observed data for interpreting complex systems. This paper contains a review of statistical and machine-learning data-based predictive models, which have been applied to dam safety analysis. Some aspects to take into account when developing analysis of this kind, such as the selection of the input variables, its division into training and validation sets, and the error analysis, are discussed. Most of the papers reviewed deal with one specific output variable of a given dam typology and the majority also lack enough validation data. As a consequence, although results are promising, there is a need for further validation and assessment of generalisation capability. Future research should also focus on the development of criteria for data pre-processing and model application.     

Pretest-posttest field studies on psychological restoration: a descriptive review and reflections for the future

Almost four decades ago, Attention Restoration Theory and Stress Recovery Theory postulated that nature could help people to recover from the attentional fatigue and the emotional negative outcomes coming from their daily performance. Since then, these theories have inspired a great amount of research. In this review, 19 restoration pretest-posttest field studies were selected. A systematic analysis of the papers was conducted using two rating tools to assess the quality of the studies and to detect their main strengths and weaknesses. The results allowed us to synthesise the results of this sample of studies, to reflect about the nature of the research conducted until today and to point to some issues and challenges that might be addressed in future studies.     

Intermittent pneumatic compression in patients with ESRD. A systematic review

Introduction: Patients with end‐stage renal disease (ESRD) experience frequent hemodialysis (HD) complications. Intradialytic hypotension (IDH) is a common complication presenting in approximately between 20 and 50% of HD sessions. Available interventions such as volume replacement or vasoactive medications are associated with significant side effects. Intermittent pneumatic compression (IPC) has been proposed as a feasible intervention for the prevention of IDH, treatment of peripheral arterial disease and venous ulcers. These devices apply intermittent pressure to the legs improving arterial blood flow, mobilization of pooled blood with an increase in venous return increasing the effective circulatory volume. Our goal was to identify the published clinical evidence on whether IPC has a circulatory benefit and is it well‐tolerated among patients receiving HD. Methods: We conducted a systematic review to identify studies assessing the efficacy and safety of IPC in patients with ESRD. Our primary outcome was IDH. Secondary outcomes such as HD comfort, ultrafiltration volume, and physical activity were collected. No restrictions where used and we included all observational and interventional studies. Two reviewers performed screening and study quality assessment. Findings: We included seven studies. Out of the seven studies, five addressed IDH, and the rest were included for secondary outcomes such as physical capacity and HD comfort. In one randomized crossover trial comparing exercise against IPC, 21 patients were randomized to 3 different arms (no intervention, cycling, IPC) a decrease in the rates of IDH with IPC was described (43%, 38%, and 24% respectively P = 0.014). The smaller studies corroborated these results. All studies where at high risk of bias. Discussion: IPC might offer significant benefits for patients undergoing HD not limited to prevention of IDH but also improvement of hemodialysis comfort and physical capacity. However, our results should be interpreted in the context of its limitations.     

Wind-gust Compensation Algorithm based on High-gain Residual Observer to Control a Quadrotor Aircraft: Real-time Verification Task at Fixed Point

Wind is considered a strong disturbance for quadrotor aircrafts (UAV) when an outdoor task at a fixed point is carried out. The effect of wind produces a distortion on the attitude of the vehicle which is reflected on undesired longitudinal movements. This paper addresses a real-time implementation and design of a robust embedded control-observer based on a type high-gain observer algorithm for on-line estimation and compensation of external disturbances produced by wind gusts on an autonomous quadrotor aircraft. A real-time experimental implementation of embedded Residual High Gain algorithm control is proposed in order to eliminate the effects of real perturbations in the hover position of the UAV. A Lyapunov function was used to practical stability analysis the system. Also numerical simulations were carried out to estimate wind behavior by the use of Drydel mathematical wind model. The main contribution of this work is the implementation of a Residual High Gain Observer in an outdoor real-time experiment in presence of real wind gusts perturbations. The proposed embedded algorithm control improves the stabilization of an UAV in the presence of real wind gusts with average of 8 m/s. The proposed algorithm improved the UAV behavior as shown by the GPS position experimental results, decreasing the wind effect on the translational movement of the aircraft.

     

Viscoelastic properties and textural characterisation of high methoxyl pectin of hawthorn (Crataegus pubescens) in a gelling system

The viscoelastic behaviour and texture profile of gels composed of the high methoxyl pectin in hawthorn (HMPH) were studied, and these gels were compared with commercial citrus gels (HMPC). The values of G′ (elastic component) for the HMPH and HMPC gels (1% pectin and pH 3.0) were 2567 and 1177 Pa, respectively, and the values of G″ (viscous component) were 494 and 253, respectively. Because G′ > G″, both of these gels exhibit viscoelastic solid behaviour with predominant elastic characteristics. The viscoelastic behaviours of the gels were analysed using the Burger model. The texture analysis demonstrated that the hardness of the HMPH gels was almost 10‐fold higher than that of the HMPC gels. In addition, the gumminess and chewiness of the HMPH gels were 31.2‐ and 46.1‐fold higher than those of the HMPC gels, respectively. These results could likely contribute to the utilisation of HMPH pectins.     

Bacteremia due to glucose non-fermenting gram-negative bacilli in patients with hematological neoplasias and solid tumors

Twenty-six patients with hematological or solid tumors who developed bacteremia caused by Stenotrophomonas maltophilia (n = 10), Pseudomonas putida (n = 6), Sphingomonas paucimobilis complex (n = 4) or Alcaligenes xylosoxidans (n = 6) in the period between 1993 and 1995 were studied. Seventeen patients were neutropenic during the infection, and 13 were undergoing bone marrow or peripheral blood stem cell transplantation. Twenty-three patients had catheter-related infections; only 3 of the 26 patients developed septic complications (all due to Stenotrophomonas maltophilia). Twenty patients were cured following catheter removal, either as primary measure (n = 8) or salvage measure (n = 12). Four responded to antibiotic therapy only, and two died of septic complications. Such infections in hematological and oncological patients have increased in this hospital from no cases in 1975 to 11 cases in 1995.