Investigating Dielectric Properties of Sintered Polymers for Rapid Manufacturing

Selective Laser Sintering (SLS) of polymers is the leading technology in the growing field of Rapid Manufacturing. High Speed Sintering (HSS) is a process that offers the potential to reduce costs and processing times and thus open significant new markets for Rapid Manufactured parts. Much academic research has been performed with respect to mechanical properties of Rapid Manufactured parts, however the area of electrical properties has received little attention to date. Electrical properties are obviously important in applications that will involve embedding of circuits with Rapid Manufactured 3D objects. However electrical properties are also important for a wide variety of electrical products where Rapid Manufactured parts can be used as housings etc. This paper focuses on the dielectric properties of parts made by SLS and HSS and compares properties with those for conventionally processed polymers. Dielectric strength results show that SLS parts are comparable with injection moulded parts, while HSS parts are inferior to SLS parts. Dielectric constant and dissipation factor results show that HSS parts are comparable with injection moulded parts, whilst SLS parts have superior properties. The presence of porosity (SLS and HSS) and the presence of carbon (HSS) are suggested as reasons behind the variation in dielectric properties when compared with injection moulded parts.Mechanical Engineerin

Degree of Cajal-Retzius cell mislocalisation correlates with the severity of structural brain defects in mouse models of dystroglycanopathy

The secondary dystroglycanopathies are characterized by the hypoglycosylation of alpha dystroglycan, and are associated with mutations in at least 18 genes that act on the glycosylation of this cell surface receptor rather than the Dag1 gene itself. At the severe end of the disease spectrum, there are substantial structural brain defects, the most striking of which is often cobblestone lissencephaly. The aim of this study was to determine the gene‐specific aspects of the dystroglycanopathy brain phenotype through a detailed investigation of the structural brain defects present at birth in three mouse models of dystroglycanopathy—the FKRPKD, which has an 80% reduction in Fkrp transcript levels; the Pomgnt1null, which carries a deletion of exons 7–16 of the Pomgnt1 gene; and the Largemyd mouse, which carries a deletion of exons 5–7 of the Large gene. We show a rostrocaudal and mediolateral gradient in the severity of brain lesions in FKRPKD, and to a lesser extent Pomgnt1null mice. Furthermore, the mislocalization of Cajal–Retzius cells is correlated with the gradient of these lesions and the severity of the brain phenotype in these models. Overall these observations implicate gene‐specific differences in the pathogenesis of brain lesions in this group of disorders

Tadalafil in patients with chronic obstructive pulmonary disease:a randomised, double-blind, parallel-group, placebo-controlled trial

SummaryBackgroundPhosphodiesterase-5 (PDE5) inhibitors improve exercise capacity and quality of life in patients with idiopathic pulmonary arterial hypertension. However, whether such beneficial effects take place in selected populations with chronic obstructive pulmonary disease (COPD) remains uncertain. We aimed to assess the effects of tadalafil—a PDE5 inhibitor—on exercise capacity and quality of life in patients with COPD and mild pulmonary hypertension.MethodsWe did a randomised, double-blind, parallel-group, placebo-controlled trial at three centres in Scotland, UK, between Sept 1, 2010, and Sept 1, 2012. Patients with moderate to severe COPD were randomly assigned (1:1), via centralised randomisation with a computer-generated sequence and block sizes of four, to receive daily tadalafil 10 mg or placebo for 12 weeks. Patients, study investigators, outcome assessors, and those administering drugs were masked to group allocation. The primary endpoint was the mean placebo-corrected difference between the baseline and final 6 min walk distance after 12 weeks. We measured change in quality of life at baseline, 8 weeks, and 12 weeks, with standardised questionnaires. Analysis was per protocol and by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01197469.Findings120 patients were randomly assigned to receive tadalafil (n=60) or placebo (n=60), of whom 56 (93%) versus 57 (95%) completed the study. At 12 weeks the difference in 6 min walking distance between the tadalafil and placebo groups was 0·5 m (95% CI −11·6 to 12·5; p=0·937). We recorded no statistically significant changes in quality of life (between-group difference on the St George's Respiratory Questionnaire −2·64 [95% CI −6·43 to 1·15]; Research and Development version 1 short-form-36 4·08 [–1·35 to 9·52]; Minnesota Living with Heart Failure questionnaire −2·31 [–7·06 to 2·45]). 19 (32%) of 60 patients in the treatment group had dyspepsia; the severity of dyspepsia ranged from mild to severe, with four (21%) of 19 patients needing a proton-pump inhibitor. Five (8%) of 60 participants had dyspepsia in the placebo group. Headache was noted in 17 (28%) patients in the treatment group versus 5 (8%) in the placebo group, but was mild in all patients. Two (3%) patients in the treatment group had facial flushing, which resulted in one withdrawal. Other withdrawals within the tadalafil group happened after a transient ischaemic attack and two deaths (ruptured abdominal aortic aneurysm and pneumonia).InterpretationTadalafil does not improve exercise capacity or quality of life despite exerting pulmonary vasodilation.FundingChief Scientist Office for Scotland

Classical antiferromagnet on a hyperkagome lattice

Motivated by recent experiments on Na_4Ir_3O_8 [Y. Okamoto, M. Nohara, H. Aruga-Katori, and H. Takagi, arXiv:0705.2821 (unpublished)], we study the classical antiferromagnet on a frustrated three-dimensional lattice obtained by selectively removing one of four sites in each tetrahedron of the pyrochlore lattice. This ``hyperkagome'' lattice consists of corner-sharing triangles. We present the results of large-N mean field theory and Monte Carlo computations on O(N) classical spin models. It is found that the classical ground states are highly degenerate. Nonetheless a nematic order emerges at low temperatures in the Heisenberg model (N=3) via ``order by disorder'', representing the dominance of coplanar spin configurations. Implications for ongoing experiments are discussed.Comment: 4 pages, 6 figures, published versio

Core-level photoemission spectroscopy of nitrogen bonding in GaNxAs1–x alloys

The nitrogen bonding configurations in GaNxAs1–x alloys grown by molecular beam epitaxy with 0.07=0.03, the nitrogen is found to exist in a single bonding configuration – the Ga–N bond; no interstitial nitrogen complexes are present. The amount of nitrogen in the alloys is estimated from the XPS using the N 1s photoelectron and Ga LMM Auger lines and is found to be in agreement with the composition determined by x-ray diffraction

LiV2O4: evidence for two-stage screening

LiV2O4, a frustrated mixed valent metal (d^1 d^2), is argued to undergo two spin-screening processes. The first quenches the effective spin to produce the spin 1/2 behavior seen below room temperature[1], while the second produces the heavy fermi liquid character seen at low temperatures[2]. We present here a preliminary discussion of a t-J model with strong Hund's coupling of the strongly correlated d-electrons. Valence fluctuations of the Hubbard operators (S = {1/2} 1) combined with the frustration of the underlying corner-shared tetrahedral vanadium lattice are the essential components of our model.Comment: 5 pages, 1 figure, accepted for proceedings of SCES'2001 Physica B, minor change

Dependence of the Electroluminescence on the Spacer Layer Growth Temperature of Multilayer Quantum-Dot Laser Structures

Electroluminescence (EL) measurements have been performed on a set of In(Ga)As-GaAs quantum-dot (QD) structures with varying spacer layer growth temperature. At room temperature and low injection current, a superlinear dependence of the integrated EL intensity (IEL) on the injection current is observed. This superlinearity decreases as the spacer layer growth temperature increases and is attributed to a reduction in the amount of nonradiative recombination. Temperature-dependent IEL measurements show a reduction of the IEL with increasing temperature. Two thermally activated quenching processes, with activation energies of ˜ 157 meV and ˜ 320 meV, are deduced and these are attributed to the loss of electrons and holes from the QD ground state to the GaAs barriers. Our results demonstrate that growing the GaAs barriers at higher temperatures improves their quality, thereby increasing the radiative efficiency of the QD emission

The regenerative supply chain: a framework for developing circular economy indicators

This is the final version. Available on open access from Taylor & Francis via the DOI in this recordThere are widely differing experiences and practices in the development of indicators to monitor, report and communicate progress towards the implementation of the circular economy (CE). We present a framework for developing CE indicators which link to the core goals, principles and building blocks of a CE. To do this we utilise the Ellen MacArthur Foundation butterfly model as a coherent systems overview of key material stocks and flows, and representation of relationships between inputs, outputs, recovery processes, emissions, energy and value loops in physical and financial measures which constitute the CE supply chain. Based on nine multinational organisations and four cases of leading companies engaged with CE activity, we address the types of indicators being used and make recommendations for indicators to reflect key goals and principles of CE. Our research on the development and expansion of circular practices leads to the question of what new opportunities and challenges CE raises for such companies in terms of competitive business advantage and resultant requirements for supply chain redesign and indicator development, over and above pre-existing closed-loop production.This work was supported by Engineering and Physical Sciences Research Council [grant number EP/P008941/1 Modelling supply chain optimisation i]