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In vitro toxicity of new engineered nanoparticles through their life cycle
Full text linkThe rapid development of nanotechnology has caused concerns about
nanoproducts on human health throughout their lifecycle. As part of the consortium
NEPHH (nanomaterial related environmental pollution on human health through their
life cycle, funded by EU-FP7), this project aimed to assess the potential effect of novel
polymer-silicon composites on human health from a lifecycle perspective, focusing on
in vitro toxicity of raw silica nanoparticles (SiNP) and dust nanoparticles (NP) released
from silicon-based polymer composites. The main objectives were to characterise a
group of amorphous SiNP and dust NP in water and cell culture medium; assess NP
toxicity potential in in vitro models; and establish mode of SiNP action.
The selection of SiNP of size 7-14 nm was based on their wide use in
developing polymer nanocomposites. Dust NP were generated from mechanical
processing of polymer composites made of polyamide-6 (PA6), polyurethane (PU) and
polypropylene (PP), each incorporated with SiNP or 3 other different silicon
reinforcement materials. The dispersion and size of NP in water and in cell culture
medium were characterized using dynamic light scattering, scanning electron
microscopy and transmission electron microscopy. The chemical composition of NP
was assessed by infra-red spectroscopy. NP were assessed in vitro for induction of
membrane damage, intracellular reactive oxygen species (ROS), loss of cell viability,
and cellular uptake by flow cytometry and confocal microscopy. In order to identify
potential biomarkers for toxicity prediction, miRNA array and extracellular
metabonomic assays were performed.
The size of SiNP (10-100 µg/ml) ranged from ~200-500 nm in water and ~20-
500 nm in culture medium, indicating the presence of aggregates. The infra-red
spectrum of SiNP dried from culture medium showed a slight difference as compared
with that dried from water, indicating protein adsorption. SiNP induced acute ROS
increase, cell membrane damage, and reduction in cell viability after 48 h in human lung
carcinoma epithelial A549 cells, lung fibroblast MRC-5 cells and skin HaCaT
keratinocytes. SiNP were up taken by all 3 cell types, and located in the cytosol. Six
early (<48h) SiNP responsive miRNAs were identified in A549 cells. SiNP also induced early changes in metabolites including glucose, lactate, ethanol, phenylalanine, histidine
and tyrosine. Dust NP generated from PA6 group materials were more toxic than those
from other polymer composites when assessed at 25-100 µg/ml at 72 h in A549 cells.
The results obtained from this study suggest that 1) both small and larger SiNP
aggregates are taken up into the target cells; 2) conventional cytotoxicity assays
combined with miRNA and metabonomic assays provide insight into the molecular
mechanisms of the nanotoxicity; 3) metabonomics and miRNA assays can serve as
robust tools for recognising sub-toxic dose-effect relationships; 4) the toxicity of dust
NP from polymer composites depends on polymer type but not reinforcement materials.
This study demonstrated the importance of lifecycle analysis as opposed to single stage
analysis of novel materials. Further studies need to improve study design to enable
interpretation of cytotoxicity in relation to NP size, physiochemical property and
intracellular dose, and to simulate the health effect of polymer-silicon composites under
more realistic scenarios
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Development of novel flax bio-matrix composites for non-structural and structural vehicle applications
Full text linkThe use of natural fibres (e.g. flax, hemp etc.) instead of synthetic fibres (carbon
and glass etc.) as composite reinforcements not only benefits the environment,
but also provides economical lightweight products for transports. Although there
are a few studies reported in literature on use of flax fibres, there is no
comprehensive guide on use of flax fibres with bio-resins to re-engineer bio-
composite systems that can be used in vehicle structures. The state-of-art of
the current research towards using natural fibre reinforced composites is
reviewed by the thesis. The review covers the performances of flax composites,
concentrating on the effect of matrix types and existing development methods.
The review also identifies the rational of selecting tannin resins and bio-epoxy
resins to combine with flax fibre reinforcements.
In the experimental work, mimosa tannin resin (natural phenolic resin) and pine-
oil derived supersap epoxy resin are selected to manufacture the fully
renewable flax composites. By tailoring the fibre configurations and chemical
surface treatments, the resultant composites were investigated to provide
information for engineers to understand the composite behaviours and
properties. Mechanical properties (tension, flexural, shear, impact etc.) and
physical properties (moisture, ageing etc.) were assessed through adequate
tests and analysing methods. In addition, bio-sandwich structures based on the
novel studied composites and commercial bio-foams were evaluated to study
the energy absorption which could be very important in vehicle design. Based
on the results, flax/supersap epoxy and flax/tannin composites are suitable for
possible exterior structural and interior non-structural applications, respectively.
The developed flax fibre composites with innovative bio-matrices have a
potential to prevail in modern vehicle applications, due to the competitive
performances, economic viability and environmental acceptability
In vitro toxicological assessment of amorphous silica particles in relation to their characteristics and mode of action in human skin cells
Full text linkBackground: Silica is the common name for silicon dioxide (SiO2) materials
and exists in both crystalline and amorphous forms. While crystalline silica is
known for its severe health effects, amorphous silica has been considered safe
and applied in many areas. However, some recent studies have showed
evidence of their toxicity, raising concerns about its use as nanomaterial for
biomedical applications. When nanomaterials enter the body, they are
enveloped in biological fluids rich in biomolecules, which compete for binding to
the nanomaterial. Such effect could alter their surface chemistry and therefore
affect their bio-distribution and interaction with cells.
Aim and objectives: As part of the EU-funded NANODRUG network
programme, the aim of this project was the in vitro toxicity assessment of
commercially-sourced fumed and colloidal amorphous silica particles in relation
to their physico-chemical properties and potential application as carriers for
drug delivery. The objectives were 1) characterization of silica particles
hydrodynamic (Hd) size and dispersity in different cell culture media; 2) in vitro
toxicological assessment of silica particles in human skin cells; 3) delineation of
toxicity mechanisms in relation to their size; 4) assessment of the influence of
Foetal Bovine Serum (FBS) on particle Hd size and toxicity; and 5) contributing
to the overall objective of the NANODRUG programme - development of safe
nanodrugs for skin application - through collaborations with different partners. ...[cont.
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Nano-sized particles emission during drilling and low velocity impact of silica-based thermoplastic nanocomposites
Full text linkDuring the past decade, polymer nanocomposites have emerged as a novel and
rapidly developing class of materials and attracted considerable investment in research
and development worldwide. Driven by the certainty that by the integration
of low nano ller amounts, existing material properties can be improved and moreover
new material properties can be developed. Despite the clear bene t and
therefore, increasing research, production and utilisation of nanomaterials, little
is known about how nanocomposites will perform over their whole life cycle, especially
in the usage and end of life phase. Under the in uence of environmental
factors such as ultraviolet light, moisture, temperature and mechanical actions,
nano-sized particles can be potentially released from nanocomposites and thus
may have negative e ects on the human health and the environment.
Within the scope of this work an extensive literature review has been conducted
in which polymer nanocomposites are brie y introduced and release scenarios of
engineered nano-sized particles from nanocomposites during their life cycle are discussed.
In the experimental part of this work silica based polypropylene, polyamide
and polyurethane composites were manufactured and particle exposure mechanism
during mechanical processing and testing were monitored and analysed. A series of
comprehensive physical characterisation techniques were utilised to assess particle
size distribution, shape, and concentration in di erent mediums, once emitted by
the solid composite materials.
It was observed that during drilling of PA6 composites, the airborne particle emission rates were 10 times higher than those for the PP based composites. However,
the characterisation of deposited particles showed exactly the opposite behaviour,
were the total number of particles emitted by the PP based composites was 10-100
times higher than those of the PA6 based composites. To the best of our knowledge,
this is the rst time such work has been reported in the literature.
Further, the addition of secondary ller into a polymer/glass- bre composites
changed the micro-mechanism during crash testing and therefore controlled the
energy absorption characteristics of the composites. However, it was shown that
once subjected to higher impact energies the geometric particle size of the released
particles increased from approx. 25 nm for the 530 J to approx. 60 nm for the
1560 J impact. Additionally, the tensile modulus increased by 0.31 GPa and the
speci c energy absorbed during impact test increased from 20.7 kJ to 22.6 kJ by
using nano-SiO2 alternative to micro-SiO2 particles in PP/glass- bre matrix. Even
though a respective enhancement in mechanical properties were observed by using
nano llers over micro llers, no signi cant di erence in particle emission during
impact test were measured.
Further, it could be shown that during drilling and testing, nano-sized particles
were released from all materials studied, regardless of whether they had nanoparticles
integrated or not. In one particular case, the neat polymer matrix generated
more nano-sized particles during drilling than the exfoliated PA6/nanoclay
nanocomposite. Hence, the addition of nanoclay can have bene cial impact in
terms of controlled particle release. However, in general the addition of nano llers
increased the particle emission rates during drilling and impact testing of the
nanocomposites. Further, the emitted nano-sized particles were not all free engineered
pristine nanoparticles but also hybrid particles consisting of matrix/nano ller
material. A signi cant set of data was obtained during this study and hence the
outcomes sets an excellent foundation for risk assessment and life cycle analysis of
silica based polypropylene, polyamide and polyurethane nanocomposites
Cardiac exposure in left-sided breast cancer patients undergoing deep inspiratory breath hold radiation therapy
Full text linkBackground: Left- sided breast cancer (BC) patients undergoing post-operative radiation therapy (PRT) may have higher risk of late cardiovascular toxicity, which may be reduced by hearth-sparing RT techniques. This study evaluated dosimetric parameters of the deep inspiration breath hold (DIBH) compared to free breathing (FB) RT. We analysed factors impacting on doses to the heart and cardiac substructures and sought anatomic factors allowing patient selection for DIBH. Methods: The study group included 67 left-sided BC patients who underwent RT after breast-conserving surgery or mastectomy. Patients treated with DIBH were trained to hold their breath. Computed tomography (CT) scans were performed in both FB and DIBH patients. Plans were generated using 3-dimensional (3D) conformal RT. The dosimetric variables were obtained from dose-volume histograms, and the anatomical variables were derived from the CT scans. The variables in the two groups were compared by t-test, the U test, and the chi-squared test. Correlation analysis was performed using Pearson's correlation coefficient. Receiver operating characteristic curves were used to analyze the efficacy of the predictors. Results: Compared to the FB, DIBH allowed for a mean dose reduction to the heart, left anterior descending coronary artery (LAD), left ventricle (LV), and right ventricle (RV) by 30.0%, 38.7%, 39.3%, and 34.7%, respectively. DIBH markedly increased the heart height (HH), heart chest wall distance (HCWD), the mean distance between the ipsilateral lung and breast (DBIB), and decreased the heart-chest wall length (HCWL) (P<0.05). The different value of HH, DBIB, HCWL, and HCWD between DIBH and FB were 1.31, 1.95, -0.67, and 0.22 cm, respectively (all P<0.05)..HH was an independent predictor of the mean dose to the heart, LAD, LV, and RV, with the area under the curve values of 0.818, 0.725, 0.821, and 0.820, respectively. Conclusions: DIBH significantly reduced the dose to the entire heart and its substructures in left-sided BC patients undergoing post-operative RT..HH predicts the mean dose to the heart and its substructures. These results may inform patient selection for DIBH
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