Search

Thermoplastics when they become thermally conductive, have a great potential to be used in thermal management applications due to their low cost, lightweight, and flexibility. Here, synthetic graphite and graphene are used as thermally conductive fillers to fabricate Polyphenylene Sulfide-(PPS) based composite materials with high thermal conductivity. Graphene and graphite added PPS composites were manufactured by using a twin-screw exit-uder and injection molding machine. Physical, thermal, meehanical. and morphological properties of the composites were investigated by several characterization methods including thermogravimetric analysis, differential scanning calorimetry, thermomechanical analysis, scanning electron microscopy, thermal diffusivity measurement, and tensile and flexural tests, The in-plane and through-plane thermal conductivity coefficient of graphene (5 wt. %) loaded synthetic graphite (40 wt. %)/PPS composites are greatly improved to 26.45 and 5.02 W/raK, respectively compared to that of neat PPS. The outstanding in-plane thermal conductivity of graphene loaded graphite/PPS composites is attributed to the formation of an effective thermal conductive pathway due to the alignment of the layered structure of' graphene and graphite fillers in the Bow direction. [ABSTRACT FROM AUTHOR]

In this study it was aimed to improve the fire retardant performance of halogen free flame-retardant polypropylene by increasing limiting oxygen index value. Ammonium polyphosphate, pentaerythritol, and ulexite were used to improve flame retardancy of polypropylene. Ulexite powder filled (1, 2, and 4 wt%) polypropylene composites were obtained by using a twin-screw extruder and injection molding method. Thermal, mechanical, and flame retardant performances of polypropylene composites were investigated by several characterization techniques. Limiting oxygen index value was obtained higher than 45% when ulexite was added into polypropylene at 1–4 wt%. It was observed that flame retardant additives do not change the mechanical properties considerably. The effect of ulexite addition on melting and crystallization temperatures of polypropylene-based composite is not pronounced. [ABSTRACT FROM AUTHOR]

Polyurethane based materials are usually preferred due to thermal and electrical insulation, lightness, durability, ease of design and production, high compression strength and corrosion resistance in many industries such as heat insulation and automotive industry. In this study, ammonium polyphosphate and pentaerythritol was used as flame retardant additives for polyurethane based composite materials. Boron derivative, ulexite, was also added at 1, 3, and 5 wt% as a synergist to improve fire retardancy performance of polyurethane composites. It is aimed to examine thermal, mechanical, physical properties especially flammability, by adding ammonium polyphosphate, pentaerythritol, and ulexite with different weight ratios into the polyurethane. It is shown that thermal conductivity, density, compression strength, modulus and Limited Oxygen Index values increased in polyurethane based composites. Flame retardants and ulexite addition have improved flammability properties of polyurethane composites. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop composites with high thermal conductivity by employing the thermophysical properties of aluminum nitride (AlN), hexagonal boron nitride (hBN), and synthetic graphite (SG). AlN, hBN, and SG filled polyamide 6 (PA) composites were prepared using a co-rotating twin-screw extruder and injection molding. Changes in thermal, mechanical, and electrical properties of the composites were investigated. The highest in-plane and through-plane thermal conductivity values were obtained with 50 wt.% SG and 50 wt.% AlN loadings, respectively. Mechanical strength of PA decreased for all filler loadings. Electrical conductivity results showed that AlN and hBN filled PA composites behave as electrical insulators. On the contrary, SG loading led to electrically conductive PA composites. [ABSTRACT FROM AUTHOR]

Over the last decades, automotive industries have investigated a variety of technological developments and design strategies. The reduction of vehicle weight has been proved to be a particularly effective way to meet automobile performance requirements in the areas of fuel economy and emissions. One major option in the vehicle weight reduction strategy is the use of lightweight materials, namely the carbon fiber reinforced polymers. However, poor adhesion between carbon fibers and polymer matrix could be an important issue for carbon fiber reinforced polymers. In this study, in order to increase interfacial bonding between carbon fibers and the polymer matrix, maleic anhydride grafted polypropylene at different weight contents was used as a compatibilizer for better polymer/fiber interpenetration. Recycled chopped carbon fiber reinforced polypropylene composites with maleic anhydride grafted polypropylene were prepared with high speed thermo kinetic mixing and hot press molding techniques. Thermal properties of the composites were studied by thermal gravimetric analysis and differential scanning calorimety. Morphology of the composites was observed by scanning electron microscopy. The tensile properties of these composites were investigated. Tensile strength values of recycled chopped carbon fiber reinforced polypropylene based composites increased with increasing compatibilizer content. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate mechanical and thermal properties of linear low density polyethylene (LLDPE)-based composite prepared with different almond shells powder (AS) contents. In this paper, AS (5, 10, 20, 30, and 40 wt%) filled LLDPE composites were prepared by compounding polyethylene and AS using a corotating twin screw extruder. All specimens for mechanical tests were molded using injection molding. 40 wt% AS filling into LLDPE has led to 100% increase in flexural strength of LLDPE. AS filling into LLDPE decreased the MFI value of LLDPE. AS filling into LLDPE at low weight fractions (5 and 10%) has not affected the un-notched impact strength of LLDPE. Thermal properties of the composite were studied by thermal gravimetric analysis (TGA). From TGA analysis, it is seen that degradation of AS within LLDPE started at about 200 °C [ABSTRACT FROM AUTHOR]

Background: We are witnessing the growth of urban populations, particularly in the developing world. São Paulo, the largest city in South America, continues to grow, and this growth is dramatically effecting the environment and human health. The aim of this study was to estimate the point prevalence of chronic pain in São Paulo city dwellers and to explore the influence of aspects related to urbanicity. Methods: A two-stage cluster randomized sample included 1100 individuals of the city of Sao Paulo, representing the population proportionally in terms of gender, age and social classes in 2007. For this observational cross-sectional study, the household sample was interviewed using validated questionnaires for sociodemographic aspects, the Beck inventories for anxiety and depression, the WHOQoL-REF for quality of life, the Chalder Fatigue Scale. Musculoskeletal pain was defined as diffuse pain or pain located in the back, joints or limbs. Data regarding sleep complaints and polysomnography were obtained from the Epidemiologic Sleep Study conducted in São Paulo city in 2007. Results: The prevalence estimate of chronic musculoskeletal pain was approximately 27%, with a female/male ratio of approximately 2.6/1. The predictors were being in the age-range of 30–39 years, low socioeconomic and schooling levels, obesity, sedentarism, fatigue, non-restorative sleep, daytime sleepiness, poor sleep quality, poor life quality, anxiety and depression symptoms. Psychological wellbeing was the main discriminator between responders with chronic musculoskeletal pain and the controls, followed by depression for the participants with poor psychological wellbeing, and fatigue, for the remaining ones. Insomnia syndrome was the third-level discriminator for those with fatigue, whereas sleep quality for those without fatigue. Conclusions: Musculoskeletal pain was frequently reported by São Paulo city dwellers and its correlates with psychological and sleep aspects are suggestive of a response to urbanicity. Trial Registration: ClinicalTrials.gov [ABSTRACT FROM AUTHOR]

High density polyethylene (HDPE) has been used extensively in many sectors of the industry. The main reason for the frequent use of HDPE is its low cost, easy processing, and high performance. These sectors include household and garden products, packaging etc. In order to reduce the production cost of plastic products and to improve plastic's moldability and stability, one or more minerals are usually filled into the thermoplastics. The minerals commonly used as fillers in plastic molding compounds include calcium carbonate, talc, silica, wollastonite, clay, mica, glass beads, and alumina trihydrate. In this paper, diatomite (DA) filled HDPE composites were prepared with gelimat mixer and hot press molding technique. Thermal properties of the composites were studied by thermogravimetric analysis and dynamic mechanical analysis. The mechanical properties of the composites were determined by using universal testing machine. Morphology of the composites was investigated by scanning electron microscopy. With the addition of DA into HDPE, significant change in tensile and flexural strengths of HDPE was not observed. The loss and storage moduli increased with increasing weight fraction of DA. [ABSTRACT FROM AUTHOR]

This study aimed to determine the retest variability of quantitative fundus autofluorescence (QAF) in patients with and without age-related macular degeneration (AMD) and evaluate the predictive value of patient reliability indices on retest reliability. A total of 132 eyes from 68 patients were examined, including healthy individuals and those with various stages of AMD. Duplicate QAF imaging was conducted at baseline and 2 weeks later across six study sites. Intraclass correlation (ICC) analysis was used to evaluate the consistency of imaging, and mean opinion scores (MOS) of image quality were generated by two researchers. The contribution of MOS and other factors to retest variation was assessed using mixed-effect linear models. Additionally, a Random Forest Regressor was trained to evaluate the extent to which manual image grading of image quality could be replaced by automated assessment (inferred MOS). The results showed that ICC values were high for all QAF images, with slightly lower values in AMD-affected eyes. The average inter-day ICC was found to be 0.77 for QAF segments within the QAF8 ring and 0.74 for peripheral segments. Image quality was predicted with a mean absolute error of 0.27 on a 5-point scale, and of all evaluated reliability indices, MOS/inferred MOS proved most important. The findings suggest that QAF allows for reliable testing of autofluorescence levels at the posterior pole in patients with AMD in a multicenter, multioperator setting. Patient reliability indices could serve as eligibility criteria for clinical trials, helping identify patients with adequate retest reliability. [ABSTRACT FROM AUTHOR]

This study aimed to determine the retest variability of quantitative fundus autofluorescence (QAF) in patients with and without age-related macular degeneration (AMD) and evaluate the predictive value of patient reliability indices on retest reliability. A total of 132 eyes from 68 patients were examined, including healthy individuals and those with various stages of AMD. Duplicate QAF imaging was conducted at baseline and 2 weeks later across six study sites. Intraclass correlation (ICC) analysis was used to evaluate the consistency of imaging, and mean opinion scores (MOS) of image quality were generated by two researchers. The contribution of MOS and other factors to retest variation was assessed using mixed-effect linear models. Additionally, a Random Forest Regressor was trained to evaluate the extent to which manual image grading of image quality could be replaced by automated assessment (inferred MOS). The results showed that ICC values were high for all QAF images, with slightly lower values in AMD-affected eyes. The average inter-day ICC was found to be 0.77 for QAF segments within the QAF8 ring and 0.74 for peripheral segments. Image quality was predicted with a mean absolute error of 0.27 on a 5-point scale, and of all evaluated reliability indices, MOS/inferred MOS proved most important. The findings suggest that QAF allows for reliable testing of autofluorescence levels at the posterior pole in patients with AMD in a multicenter, multioperator setting. Patient reliability indices could serve as eligibility criteria for clinical trials, helping identify patients with adequate retest reliability. [ABSTRACT FROM AUTHOR]

Drusen are hallmarks of early and intermediate age-related macular degeneration (AMD) but their quantification remains a challenge. We compared automated drusen volume measurements between different OCT devices. We included 380 eyes from 200 individuals with bilateral intermediate (iAMD, n = 126), early (eAMD, n = 25) or no AMD (n = 49) from the MACUSTAR study. We assessed OCT scans from Cirrus (200 × 200 macular cube, 6 × 6 mm; Zeiss Meditec, CA) and Spectralis (20° × 20°, 25 B-scans; 30° × 25°, 241 B-scans; Heidelberg Engineering, Germany) devices. Sensitivity and specificity for drusen detection and differences between modalities were assessed with intra-class correlation coefficients (ICCs) and mean difference in a 5 mm diameter fovea-centered circle. Specificity was > 90% in the three modalities. In eAMD, we observed highest sensitivity in the denser Spectralis scan (68.1). The two different Spectralis modalities showed a significantly higher agreement in quantifying drusen volume in iAMD (ICC 0.993 [0.991–0.994]) than the dense Spectralis with Cirrus scan (ICC 0.807 [0.757–0.847]). Formulae for drusen volume conversion in iAMD between the two devices are provided. Automated drusen volume measures are not interchangeable between devices and softwares and need to be interpreted with the used imaging devices and software in mind. Accounting for systematic difference between methods increases comparability and conversion formulae are provided. Less dense scans did not affect drusen volume measurements in iAMD but decreased sensitivity for medium drusen in eAMD. Trial registration: ClinicalTrials.gov NCT03349801. Registered on 22 November 2017. [ABSTRACT FROM AUTHOR]

Quantification of the relative ellipsoid zone reflectivity (rEZR) might be a structural surrogate parameter for an early disease progression in the context of age-related macular degeneration (AMD). Within the European multicenter, cross-sectional MACUSTAR study, we have devised an automatic approach to determine the mean rEZR [arbitrary units, AU] at two independent visits in SD-OCT volume scans in study participants. Linear mixed-effects models were applied to analyze the association of AMD stage and AMD associated high-risk features including presence of pigmentary abnormalities, reticular pseudodrusen (RPD), volume of the retinal-pigment-epithelial–drusenoid-complex (RPEDC) with the rEZR. Intra-class correlation coefficients (ICC) were determined for rEZR reliability analysis. Within the overall study cohort (301 participants), we could observe decreased rEZR values (coefficient estimate ± standard error) of − 8.05 ± 2.44 AU (p = 0.0011) in the intermediate and of − 22.35 ± 3.28 AU (p < 0.0001) in the late AMD group. RPD presence was significantly associated with the rEZR in iAMD eyes (− 6.49 ± 3.14 AU; p = 0.0403), while there was a good ICC of 0.846 (95% confidence interval: 0.809; 0.876) in the overall study cohort. This study showed an association of rEZR with increasing disease severity and the presence of iAMD high-risk features. Further studies are necessary to evaluate the rEZR's value as a novel biomarker for AMD and disease progression. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effect of various filler materials such as talc, glass bead (GB), and bentonite on sound insulation efficiency of polypropylene (PP). In order to evaluate sound insulation properties of PP-based composites sound transmission loss (STL) was determined. Polypropylene based-composite granules were produced by using twin-screw extruder. Some test specimens were obtained by injection molding process. bentonite filled PP composite exhibited the highest STL values for 100, 200, 400, 500, and 800 Hz. While talc and bentonite loadings at 40 wt% into PP increased the flexural strength of PP, GB loading decreased the flexural strength of PP. Izod notched and unnotched impact strength of PP decreased by loading talc, bentonite, and GB into PP. [ABSTRACT FROM AUTHOR]

Human leucocyte antigen ( HLA) DQB1*0602 allele, a well-known genetic risk factor for narcolepsy, has been associated with sleep parameters in healthy subjects. We aimed to assess the association of this allele with daytime sleepiness and altered sleep electroencephalogram characteristics in the general population and in patients with obstructive sleep apnoea syndrome ( OSAS). Eight hundred and ninety-four individuals from the Epidemiologic Study of Sleep were genotyped for the HLA DQB1*0602 allele. Full-night polysomnography was performed, and daytime sleepiness was analysed according to the Epworth Sleepiness Scale. HLA - DQB1*0602 allele-positive and -negative subjects in the general population, as well as in patients with OSAS, exhibited similar sleep parameters and levels of daytime sleepiness. However, spectral analysis showed that allele-positive individuals with OSAS exhibited higher theta power during sleep Stage 1 ( P < 0.05) in occipital derivations, and lower delta power during sleep Stages 1 and 2 ( P < 0.01) compared with individuals negative for the allele, even after correction for potential confounders as age, sex, body mass index and European ancestry. No significant differences in the electroencephalogram variables were found in individuals without OSAS. The data highlight the HLA- DQB1*0602 as a potential genetic factor influencing sleep physiology in individuals diagnosed with OSAS. [ABSTRACT FROM AUTHOR]