10 research outputs found
Thermal behaviour of highly stereoregular syndiotactic polypropene from homogeneous catalysts (Part I)
No full textThermal characterization was carried out on highly stereoregular and regioregular syndiotactic polypropene (sPP) obtained with isopropylidene(cyclopentadienyl)(9‐fluorenyl)zirconium dichloride and methylaluminoxane. The influence of molecular weight and syndiotacticity degree on the thermodynamic melting point (T°m) of sPP were separately investigated by examining samples with a fully syndiotactic pentads content (rrrr) ranging from ca. 81% to ca. 94% and with an weight‐average molecular weight (M̄w) ranging from 9,6 · 104 to 17,3 · 104. Upon excluding any influence of the molecular weight, the correlation between the rrrr pentads content and the T°m of the samples led to the extrapolation of the thermodynamic melting point for a fully syndiotactic polypropene
Syndiotactic polypropylene after drawing: The effect of stretching polymer chains on magic angle spinning NMR
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Neural precursor cells rescue symptoms of Rett syndrome by activation of the Interferon γ pathway.
No full textThe beneficial effects of Neural Precursor Cell (NPC) transplantation in several neurological disorders are well established and they are generally mediated by the secretion of immunomodulatory and neurotrophic molecules. We therefore investigated whether Rett syndrome (RTT), that represents the first cause of severe intellectual disability in girls, might benefit from NPC-based therapy. Using in vitro co-cultures, we demonstrate that, by sensing the pathological context, NPC-secreted factors induce the recovery of morphological and synaptic defects typical of Mecp2 deficient neurons. In vivo, we prove that intracerebral transplantation of NPCs in RTT mice significantly ameliorates neurological functions. To uncover the molecular mechanisms underpinning the mediated benefic effects, we analyzed the transcriptional profile of the cerebellum of transplanted animals, disclosing the possible involvement of the Interferon γ (IFNγ) pathway. Accordingly, we report the capacity of IFNγ to rescue synaptic defects, as well as motor and cognitive alterations in Mecp2 deficient models, thereby suggesting this molecular pathway as a potential therapeutic target for RTT. [Abstract copyright: © 2024. The Author(s).
CETGI : an assessment tool for global concurrent engineering : executive summary
No full textIndustrial globalisation and the increased complexity of products promote new
product development (NPD) by distributed teams. These teams facilitate the transfer
of designs to manufacturing facilities, the adaptation of products to local markets and
the access to engineering design talents. However, there are many industrial
experiences of under performing distributed teams, such as the development of the
Ford Mondeo which ran a year late and cost £4 billion. This Engineering Doctorate
project CETGI (Concurrent Engineering and Teamwork across Global Industries)
aimed to investigate and advise companies on the enabling practices of global
concurrent engineering (GCE). An assessment tool for GCE was developed,
embedding its enabling practices in a knowledge base and providing structured advice
to manufacturing companies of electro-mechanical products.
Preliminary investigation was conducted towards the development of the CETGI tool:
literature review on GCE; a benchmark study of nine current concurrent engineering
assessment tools; a comparative analysis of NPD practices in the UK and the USA; a
survey of NPD practices of global companies developing products in the UK; and
thirteen case studies of GCE projects. The CETGI tool was then developed, consisting
of an assessment process involving multifunctional teams and executives. CETGI is
different to previous tools because of its knowledge base of GCE practices and its
three analytical algorithms: the first, aggregates the individual answers; the second,
provides a customised list of prioritised actions; and the third, generates maturity
charts, providing a performance perspective and supporting benchmarking. Another
novel feature of CETGI is the Internet enabled software application that supports its
assessment process. The latter software is a multi-participant decision-making support
system. The CETGI tool has been applied to three first tier supplier companies, two
from the automotive industry and one from the transport industry aimed at fine-tuning
and validating the tool. The work focused on evaluating the reliability of the
questionnaire (constructed on the knowledge base) and establishing the validity and
the industrial usefulness of the CETGI tool. On average, the NPD executives
considered 90% of the suggested actions appropriate, selected 70% of the actions for
implementation and implemented 51% of the selected actions (based on a post-assessment
review at one company). The actions were estimated to reduce time-to-market
and product-unit costs by the NPD executives and they rated CETGI highest
in terms of promoting global product development, followed by providing an overall
picture of the current product development process.
Further research opportunities have been identified such as using the CETGI tool to
assess other business areas apart from GCE. This would require investigating best
practices in these areas and embedding the results in specific knowledge bases. The
assessment method, the structure of the knowledge base and the analytical algorithms
would remain the same
Determination of 1‐butene distribution in LLDPE by DSC analysis after thermal fractionated crystallization
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Synthesis of conducting graphite-like nanometer wires via soluble precursors
No full textGraphite - like conducting materials were
encapsulated in the channels of new mesoporous MCM-
41 materials with typical channel diameters of 30-40 Ä.
Acrylonitrile was introduced into the hosts via vapor
transport, then polymerized with external radical
initiators, K2S2O8 and HNaSOß. The polymers in the host
cavities were further pyrolyzed at different temperatures
under vacuum or nitrogen atmosphere. The properties of
the polymer systems were studied while encapsulated or
after dissolution of the host. The crystallinity of the hosts
is intact after insertion of the polymer (even after
pyrolysis at 800°C). The formation of conducting
graphite - like materials inside the hosts was
demonstrated with Raman and UV spectra. The nitrogen
to carbon ratio of the pyrolyzed polymers depends on the
pyrolysis temperature and the polymer environment.
Most interestingly, the normalized AC absorption of
pyrolyzed polyacrylonitrile in MCM-41 (at 800°C) is
comparable to graphite
