In view of their potential applications in sandwich structures, there has been increasing interest in honeycomb networks. Several different types of honeycomb systems have been proposed each exhibiting different mechanical properties. Here we propose a new hexagonal honeycomb structure composed of two different geometrical features: a re‐entrant feature which is known to generate auxetic behavior, and a non re‐entrant feature found in regular hexagonal honeycombs which leads to conventional behavior. This results in a “semi re‐entrant honeycomb” built of alternate conventional and auxetic layers. Finite element analysis and analytical modeling of these honeycombs show that they exhibit a zero Poisson ratio in one direction and a higher than normal Young's modulus in the orthogonal direction. We also show that by virtue of its zero Poisson's ratio, this honeycomb has a natural tendency to form cylindrical shaped curvatures, something which is very difficult to achieve with conventional or auxetic honeycombs.

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Dynamic consent aims to empower research partners and facilitate active participation in the research process. Used within the context of biobanking, it gives individuals access to information and control to determine how and where their biospecimens and data should be used. We present Dwarna-a web portal for 'dynamic consent' that acts as a hub connecting the different stakeholders of the Malta Biobank: biobank managers, researchers, research partners, and the general public. The portal stores research partners' consent in a blockchain to create an immutable audit trail of research partners' consent changes. Dwarna's structure also presents a solution to the European Union's General Data Protection Regulation's right to erasure-a right that is seemingly incompatible with the blockchain model. Dwarna's transparent structure increases trustworthiness in the biobanking process by giving research partners more control over which research studies they participate in, by facilitating the withdrawal of consent and by making it possible to request that the biospecimen and associated data are destroyed.

Auxetic foams have been widely studied in view of their superior properties and many useful applications and various models have been developed to help explain the auxetic behavior in such foams. One such model involves the description of auxetic foams in terms of rotating units (e.g. the joints where different cell walls meet), a mechanism, which has also been observed experimentally. In the models, the rotating units are taken, to a first approximation, to be representable through rotating rigid triangles, which correspond to the 2D projection of these rotating units and although this model has been improved significantly since it was first proposed, current models still do not fully capture all the deformations that may occur in real foams. In this work, we propose an extended model which not only allows for relative rotation of the units (joints), represented by nonequilateral triangular units, but also for differing amount of material at the joints as well as deformation of the joints themselves, a scenario that is more representative of real auxetic foams. This model shows that, by permitting deformation mechanisms other than rotation of the triangles, the predicted extent of auxeticity decreases when compared to the equivalent idealized rotating rigid triangles model, thus resulting in more plausible predictions of the Poisson's ratios. Furthermore, it is shown that in the manufacturing process, a minimum compression factor, which is dependent on the amount of materials at the joints, is required to obtain an auxetic foam from a conventional foam, as one normally observed in experimental work on foams.

Epidermal growth factor (EGF) receptor expression was estimated in 50 invasive human colorectal cancers using immunohistochemistry and the degree of expression was quantified from integrated optical density measurements on the stained sections. All tumours stained positively, but Dukes' C tumours exhibited significantly higher levels of receptor than either Dukes' A or B tumours. In addition, histologically high grade cancers expressed receptors more strongly than those of low grade. It is concluded that a high EGF receptor concentration is associated with poor prognostic factors in colorectal malignancy.

Cellular solids, in particular hexagonal honeycombs have been the subject of numerous studies in the last decades in view of their extensive use in many applications. In particular, there have been various studies aimed at expressing the mechanical properties of honeycombs in terms of the geometrical parameters used to describe the structure of such honeycombs. Despite improvements over the first established model, finite element simulations performed in this work on honeycombs having ribs with a realistic thickness-to-length ratio suggest that the mechanical properties for such systems differ from those predicted by current models, sometimes to a very significant extent. In view of this, we analyse in detail the deformed structures in an attempt to gain insight into how and the extent to which the shape of the ligaments, in particular its thickness and mode of connection affects deformation in conventional and re-entrant hexagonal honeycombs. Based on these observations, we propose a modified version of the previous analytical models that take into consideration the finite thickness of the ligaments.

The extent to which systems (materials or structures) change shape when subjected to changes in temperature is a subject of great practical importance and has been studied for many years. It is well known that miscalculations of the temperature effects in the design of objects which are subjected to significant temperature changes can lead to disastrous consequences. This led to various studies aimed at designing, analysing, manufacturing and/or testing of materials having very particular coefficients of thermal expansion [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] (including materials exhibiting negative coefficients of thermal expansion, i.e. materials which contract when heated [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]). Of particular interest are composites having pre-determined coefficients of thermal expansion which are already being used in some niche applications, although there is still an ongoing need to develop simple and non-expensive methods for achieving the same effect on any scale.Here we propose and discuss a multi-layered system constructible at any length scale from conventional materials having different mechanical and thermal properties which may be combined to form systems which exhibit pre-determined values of thermal expansion which could also be negative. In particular we show that to optimise negative thermal expansion (NTE) characteristics, the systems must be constructed based on what is illustrated in Fig. 1, i.e. by combining thin layers of stiff materials having a high positive coefficient of thermal expansion (CTE) characteristics bonded together through thicker layers of a soft material having low CTE values and, more importantly, having Poisson's ratio as high as possible, in analogy to work presented earlier [15][16][17].To simplify our discussion we discuss first the optimal requirements for one of the most basic systems operating through the mechanism we are proposing which can be tailored to exhibit NTE, i.e. the system in Fig. 1(a). As illustrated in Figs. 1(a) and 2, this system may be described as a sandwich structure made from three layers of two different materials A and B having different thicknesses, thermal and mechanical properties which are perfectly bonded together.Let us assume that this sandwich is in the form of a cuboid of overall dimensions x y z ¥ ¥ at temperature T where the z dimension is given by A B 2 , z z + A z and B z being the thicknesses of layers A and B at temperature T, respectively. Let us also assume that (i) materials A and B are isotropic; (ii) that material A is much stiffer than material B, i.e. E A ӷ E B , where E A and E B are the Young's moduli of materials A and B, respectively, and (iii) that necking effects may be ignored. Given these assumptions, if the system is subjected to a change in temperature ΔT, A construct in the form of a multi-layered system built from conventional materials having different mechanical and thermal properties is proposed. This construct can exhibit predetermined values of ...

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