Polymer Composites Containing Non-Covalently Functionalized Carbon Nanotubes: A Study of Their Dispersion Characteristics and Response to AC Electric Fields

AbstractMulti-wall carbon nanotubes (MWCNT) functionalized with a hyperbranched polyethylene (HBPE) and subsequently melt compounded with an ethylene-octene copolymer (EOC8100) matrix are examined in terms of their dispersion characteristics and electric field response. It was found that, when compared with their non-functionalized counterparts, HBPE-functionalized MWCNT produce substantially more uniform composites. On the other hand, MWCNT functionalization results in a higher electrical percolation threshold. Electrification of the composite melts showed that longer insulator-to-conductor transition times should be expected as a consequence of the improved dispersion quality. The functionalization, however, did not prevent MWCNT from forming highly electrically conducting networks in the melt, or exhibiting electric field-induced percolation thresholds of less than 1wt% filler

Efficacy and Selectivity of Pre- and Post-emergence Herbicides in Chia (Salvia hispanica L.) under Mediterranean Semi-arid Conditions

In the present study, the selectivity and efficacy of several post and pre-emergence herbicides in chia (Salvia hispanica L.) were examined. Field experiments were conducted at two locations with different soil types and environmental conditions. Our results showed that the pre-emergence application of pendimethalin, oxyfluorfen and linuron reduced total weed density by 71-74%, 74-82% and 53-55%, respectively. Despite their high effectiveness, the above-mentioned herbicides had a negative effect on plant density and biomass yield. In addition, herbicides bentazon and fluazifop-p-butyl which applied post-emergence did not affect significantly plant height and biomass yield. In conclusion, the herbicides linuron, pendimethalin and oyxfluorfen do not seem to be a viable option for weed control in chia crop, whereas the post-emergence applied herbicides did not affect significantly plants’ growth. Further evaluation of chia tolerance to herbicides is needed under different application rates in order to make safe suggestions for chemical control of weeds

Pertinence of salt-related knowledge and reported behaviour on salt intake in adults : a cross-sectional study

The association between salt-related knowledge, attitude, behaviour (KAB) and actual salt consumption in Greek adults is uncertain. This study investigates the correlation between salt intake, gauged by 24-h urinary sodium excretion, with salt-related KAB. It further explores how socio-demographic factors influence these behaviors. Salt consumption was evaluated using a 24-h urinary sodium test, and compared to self-reported KAB data. Knowledge and behavior scores related to salt were computed. An overall cohort-adjusted model examined the relationship between daily salt consumption, knowledge and behavior scores, and certain covariates. Through the stratification by the cohort random effect, two models were established (Cohort I Adults; Cohort II Students) examining the same relationships of the overall cohort model. 463 Greek adults participated. The average salt intake was 9.54 g/day, nearly double the WHO recommendation. Significant differences in knowledge scores were noted based on sex, age, education, and BMI. A trend suggesting lower discretionary salt use with increased salt intake was observed (p = 0.06). However, comprehensive analysis revealed no direct correlation between salt intake and either knowledge (p = 0.562) or behavior scores (p = 0.210). The results emphasize the need for food product reforms by industry stakeholders and accelerated efforts towards reducing salt intake

Poly(vinyl alcohol) molecular bottlebrushes nucleate ice

Ice binding proteins (IBP) have evolved to limit the growth of ice but also to promote ice formation by ice-nucleating proteins (INPs). IBPs, which modulate these seemingly distinct processes, often have high sequence similarities, and molecular size/assembly is hypothesized to be a crucial determinant. There are only a few synthetic materials that reproduce INP function, and rational design of ice nucleators has not been achieved due to outstanding questions about the mechanisms of ice binding. Poly(vinyl alcohol) (PVA) is a water-soluble synthetic polymer well known to effectively block ice recrystallization, by binding to ice. Here, we report the synthesis of a polymeric ice nucleator, which mimics the dense assembly of IBPs, using confined ice-binding polymers in a high-molar-mass molecular bottlebrush. Poly(vinyl alcohol)-based molecular bottlebrushes with different side-chain densities were synthesized via a combination of ring-opening metathesis polymerization (ROMP) and reversible addition–fragmentation chain-transfer (RAFT) polymerization, using “grafting-to” and “grafting-through” approaches. The facile preparation of the PVA bottlebrushes was performed via selective hydrolysis of the acetate of the poly(vinyl acetate) (PVAc) side chains of the PVAc bottlebrush precursors. Ice-binding polymer side-chain density was shown to be crucial for nucleation activity, with less dense brushes resulting in colder nucleation than denser brushes. This bio-inspired approach provides a synthetic framework for probing heterogeneous ice nucleation and a route toward defined synthetic nucleators for biotechnological applications

The effect of materials' rheology on process energy consumption and melt thermal quality in polymer extrusion

YesPolymer extrusion is an important but an energy intensive method of processing polymeric materials. The rapid increase in demand of polymeric products has forced manufactures to rethink their processing efficiencies to manufacture good quality products with low-unit-cost. Here, analyzing the operational conditions has become a key strategy to achieve both energy and thermal efficiencies simultaneously. This study aims to explore the effects of polymers' rheology on the energy consumption and melt thermal quality (ie, a thermally homogeneous melt flow in both radial and axil directions) of extruders. Six commodity grades of polymers (LDPE, LLDPE, PP, PET, PS, and PMMA) were processed at different conditions in two types of continuous screw extruders. Total power, motor power, and melt temperature profiles were analyzed in an industrial scale single-screw extruder. Moreover, the active power (AP), mass throughput, torque, and power factor were measured in a laboratory scale twin-screw extruder. The results confirmed that the specific energy consumption for both single and twin screw extruders tends to decrease with the processing speed. However, this action deteriorates the thermal stability of the melt regardless the nature of the polymer. Rheological characterization results showed that the viscosity of LDPE and PS exhibited a normal shear thinning behavior. However, PMMA presented a shear thickening behavior at moderate-to-high shear rates, indicating the possible formation of entanglements. Overall, the findings of this work confirm that the materials' rheology has an appreciable correlation with the energy consumption in polymer extrusion and also most of the findings are in agreement with the previously reported investigations. Therefore, further research should be useful for identifying possible correlations between key process parameters and hence to further understand the processing behavior for wide range of machines, polymers, and operating conditions

Designing a consequentially based study into the online support of pre-service teachers in the UK

This paper reports on the design of a pilot doctoral study into the online support of pre-service teachers. It highlights the significance of a consequential, rather than deontological, perspective in guiding the development of a study's design. The study initially aimed to explore pre-service teachers’ perceptions and use of social media on their school placements by setting up groups on Facebook and Twitter. However, several problems occurred in relation to the recruitment of participants. It became increasingly clear that there was significance in the positionality of the researcher as an “outsider” to the research context and the potential role for gatekeepers in understanding remote research sites. An ethical framework was used to make a more comprehensive analysis of the issues at play, which helped identify ways of proceeding. A redesign of the study followed with a stronger rationale for the way consequential considerations can help address deontological concerns

American and Greek Children’s Visual Images of Scientists: Enduring or Fading Stereotypes?

This study explores American and Greek primary pupils’ visual images of scientists by means of two nonverbal data collection tasks to identify possible convergences and divergences. Specifically, it aims to investigate whether their images of scientists vary according to the data collection instrument used and to gender. To this end, 91 third-grade American (N = 46) and Greek (N = 45) pupils were examined. Data collection was conducted through a drawing task based on Chambers (1983) ‘Draw-A-Scientist-Test’ (DAST) and a picture selection task during which the children selected between 14 pairs of illustrations those that were most probable to represent scientists. Analysis focused on stereotype indicators related with scientists’ appearance and work setting. Results showed that the two groups’ performance varied significantly across the tasks used to explore their stereotypic perceptions, although the overall stereotypy was not differentiated according to participants’ ethnic group. Moreover, boys were found to use more stereotypic indicators than girls, while the picture selection task elicited more stereotypic responses than the drawing task. In general, data collected by the two instruments revealed convergences and divergences concerning the stereotypic indicators preferred. Similarities and differences between national groups point to the influence of a globalized popular culture on the one hand and of the different sociocultural contexts underlying science curricula and their implementation on the other. Implications for science education are discussed. © 2016, Springer Science+Business Media Dordrecht

Durable Clinical Benefit of Pertuzumab in a Young Patient with BRCA2 Mutation and HER2-Overexpressing Breast Cancer Involving the Brain

Patients with HER2-positive breast cancer and brain metastases have limited treatment options, and, as a result of their poor performance status and worse prognosis, they are underrepresented in clinical trials. Not surprisingly, these patients may not be fit enough to receive any active treatment and are offered supportive therapy. BRCA2 mutations are reported to be rarely associated with HER2-overexpressing advanced breast cancer and even more rarely with brain metastases at diagnosis. We report on a BRCA2-positive breast cancer patient with metastatic disease in multiple sites, including the brain, and poor performance status who exhibited an extraordinary clinical and imaging response to the novel anti-HER2 therapy pertuzumab after multiple lines of therapy including anti-HER2 targeting. To our knowledge, the clinicopathologic and therapeutic characteristics of this patient point to a unique case and an urgent need for further investigation of pertuzumab in patients with brain metastases. © 2016 Anna Koumarianou et al