Tensile Response of Adhesively Bonded Composite-to-composite Single-lap Joints in the Presence of Bond Deficiency

This paper studies the quasi-static tensile response of adhesively bonded composite-to-composite single-lap joints in the presence of weak and kissing bonds, as an attempt for characterisation of bond deficiencies likely to occur in polymer composite bonded repair. Cytec FM®94 adhesive film (0.25 mm nominal thickness) was used for all joints to bond two 2mm-thickness carbon fibre polymer composite laminates manufactured from unidirectional Hexcel M21/T800S pre-pregs. Peel-ply surface treatment was used for all joints. The bonds were deteriorated via five methods: pre-curing the centre of bond area prior to the cure of the bond edges, increasing the curing temperature rate, reducing the curing time, and embedding PTFE films over the centre of the bond. For the last method, the studies were carried out by embedding PTFE films on one and two sides of the adhesive film. The bond deterioration was followed by non-destructive inspections using ultrasound C-scanning. The ultimate failure load of the joints with defected bonds (i.e. weak and kissing bonds) was measured and compared to that of the joints with no defect (i.e. good bonds). It was found that rapid curing and short-time curing reduces more than 50% of the load carrying capacity of the single-lap joins in tension while the joints with weak bonds introduced by pre-curing of a large area of the bond (>60%) can take up more than 65% of the ultimate load of the joint with good bond. Also, optical microscopy of the bond surfaces after failure showed changes in failure type for the rapid and short-time cure, strongly correlated with their significant failure load reduction

Promoter methylation analysis of WNT/β-catenin pathway regulators and its association with expression of DNMT1 enzyme in colorectal cancer

Background: Aberrant DNA methylation as the most important reason making epigenetic silencing of genes is a main mechanism of gene inactivation in patients with colorectal cancer. In this study, we decided to identify promoter methylation status of ten genes encoding WNT negative regulators, and measure the expression of DNMT1 enzyme in colorectal cancer samples. Results: Aberrant methylation of APC gene was statistically significant associated with age over 50 (p = 0.017), DDK3 with male (p < 0.0001), SFRP4, WIF1, and WNT5a with increasing tumor stage (p = 0.004, p = 0.029, and p = 0.004), SFRP4 and WIF1 with tumor differentiation (p = 0.009 and p = 0.031) and SFRP2 and SFRP5 with histological type (p = 0.001 and p = 0.025). The increasing number of methylated genes correlated with the expression levels of the DNMT1 mRNA. Conclusions: The rate of gene promoter methylation of WNT pathway regulators is high in colorectal cancer cells. Hyper-methylation is associated with increased expression of the DNMT1 enzyme. © 2014 Mansour Samaei et al.; licensee BioMed Central

Atom Transfer and Single-Adatom Contacts

The point contact of a tunnel tip approaching towards Ag(111) and Cu(111) surfaces is investigated with a low temperature scanning tunneling microscope. A sharp jump-to-contact, random in nature, is observed in the conductance. After point contact, the tip-apex atom is transferred to the surface, indicating that a one-atom contact is formed during the approach. In sharp contrast, the conductance over single silver and copper adatoms exhibits a smooth and reproducible transition from tunneling to contact regime. Numerical simulations show that this is a consequence of the additional dipolar bonding between the homoepitaxial adatom and the surface atoms.Comment: 4 pages, 4 figure

Failure of Scattering Interference in the Pseudogap State of Cuprate Superconductors

We calculate scattering interference patterns for various electronic states proposed for the pseudogap regime of the cuprate superconductors. The scattering interference models all produce patterns whose wavelength changes as a function of energy, in contradiction to the energy-independent wavelength seen by scanning tunneling microscopy (STM) experiments in the pseudogap state. This suggests that the patterns seen in STM local density of states measurements are not due to scattering interference, but are rather the result of some form of ordering.Comment: To be submitted to Phys. Rev.

Cd3As2 is Centrosymmetric

This is a revised version of a manuscript that was originally posted here in February of 2014. It has been accepted at the journal Inorganic Chemistry after reviews that included those of two crystallographers who made sure all the t's were crossed and the i's were dotted. The old work (from 1968) that said that Cd3As2 was noncentrosymmetric was mistaken, with the authors of that study making a type of error that in the 1980s became infamous in crystallography. As a result of the increased scrutiny of the issue of centrosymmetricity of the 1980's, there are now much better analysis tools to resolve the issue fully, and its important to understand that not just our crystals are centrosymmetric, even the old guy's crystals were centrosymmetric (and by implication everyone's are). There is no shame in having made that error back in the day and those authors would not find the current centrosymmetric result controversial; their paper is excellent in all other aspects. This manuscript describes how the structure is determined, explains the structure schematically, calculates the electronic structure based on the correct centrosymmetric crystal structure, and gives the structural details that should be used for future analysis and modeling.Comment: Accepted by ACS Inorganic Chemistr

Markov Chain Modelling-Based Approach to Reserve Electric Vehicles in Parking Lots for Distribution System Energy Management

Integration of renewable energy resources in distribution networks with intermittent behaviour increases the challenge of power balance in transmission systems. To mitigate the undesired impacts, transmission operator involves distribution operators to get local contribution from their flexible resources. In this paper, we address the flexibility offered by some electric car sharing agents which can serve some reserve capacity to distribution system. A Markov Chain modelling based approach is proposed to support system operator to properly estimate the number of electric vehicles required to be booked in advance as reserve. Underestimation would result in imperfect demand correction, and overestimation would imply extra costs. Using a realistic case under a near future scenario of high PV integration and EV accommodation, we demonstrate the contribution of our approach to this problem of planning or scheduling. Obtained results quantifies the performance of the proposed method in terms of average energy difference based on number of EVs. The results can be used as a basis to decide the appropriate number of EV reservations

Adaptive control of sub-populations in evolutionary dynamic optimization

Multi-population methods are highly effective in solving dynamic optimization problems. Three factors affect this significantly: the exclusion mechanisms to avoid the convergence to the same peak by multiple sub-populations, the resource allocation mechanism which assigns the computational resources to the sub-populations, and the control mechanisms to adaptively adjust the number of sub-populations by considering the number of optima and available computational resources. In the existing exclusion mechanisms, when the distance (i.e. the distance between their best found positions) between two sub-populations becomes less than a predefined threshold, the inferior one will be removed/reinitialized. However, this leads to incapability of algorithms in covering peaks/optima that are closer than the threshold. Moreover, despite the importance of resource allocation due to the limited available computational resources between environmental changes, it has not been well studied in the literature. Finally, the number of sub-populations should be adapted to the number of optima. However, in most existing adaptive multi-population methods, there is no predefined upper bound for generating sub-populations. Consequently, in problems with large numbers of peaks, they can generate too many subpopulations sharing limited computational resources. In this paper, a multi-population framework is proposed to address the aforementioned issues by using three adaptive approaches: subpopulation generation, double-layer exclusion, and computational resource allocation. The experimental results demonstrate the superiority of the proposed framework over several peer approaches in solving various benchmark problems

Crust-mantle interaction inferred from the petrology and Sr-Nd-Pb isotope geochemistry of Eocene arc lavas from the Kahrizak Mountains, north-Central Iran

The Eocene volcanic rocks from the Kahrizak Mountains in north-central Iran are part of the Urumieh-Dokhtar magmatic arc, which runs parallel to the Main Zagros Thrust segment of the Neo-Tethys suture. These volcanic rocks, similar to those from eastern Pontides and northern Anatolia, Turkey, were mainly produced during the Eocene magmatic flare-up associated with the Arabia-Eurasia convergence. The rock suite includes basalt, trachyandesite/andesite and trachydacite/rhyolite lavas and pyroclastic deposits that evolved compositionally from calc-alkalic to shoshonitic. Their normalized trace element concentration patterns are moderately enriched in light rare earth element and depleted in high field-strength elements (HFSE; e.g., Nb, Ta, Ti). They have narrow ranges of initial Pb isotopic ratios and ^(143)Nd/^(144)Nd_i, but highly variable ^(87)Sr/^(86)Sr_i. The new analyses indicate that the parental magmas of the volcanic rocks were derived from a mantle source that had been enriched by fluids released from a subducted oceanic slab. The fluids introduced significant amounts of large ion lithophile elements, but negligible HFSE to the source. The parental magmas underwent fractional crystallization and assimilation of upper crustal materials to produce the range of volcanic rocks. Integration of new analyses with regional data suggests that the Eocene volcanic rocks from north-central Iran, together with ~coeval volcanic rocks in eastern Pontides and northern Anatolia, were most probably derived from a lithospheric mantle source that had been previously metasomatized by fluids derived from a subducted slab before and during the Arabia-Eurasia collision