Search results for " graded"

Development of polymeric functionally graded scaffolds: a brief review.

2016

Over recent years, there has been a growing interest in multilayer scaffolds fabrication approaches. In fact, functionally graded scaffolds (FGSs) provide biological and mechanical functions potentially similar to those of native tissues. Based on the final application of the scaffold, there are different properties (physical, mechanical, biochemical, etc.) which need to gradually change in space. Therefore, a number of different technologies have been investigated, and often combined, to customize each region of the scaffolds as much as possible, aiming at achieving the best regenerative performance. In general, FGSs can be categorized as bilayered or multilayered, depending on the number…

Spark Plasma Sintering tool design for preparing alumina-based Functionally Graded Materials

2016

Abstract A way to produce Functionally Graded Materials (FGM) is by means of Spark Plasma Sintering (SPS) and specifically designated tools. These new tools permit a current density modulation and therefore a temperature variation along the z-axis. The key feature relies on a varying die section. FEM modelling has given the suitable range of die dimensions between the top and the bottom to obtain a given temperature gradient (around 300 °C) out of roughly a 15 mm height. Experiments conducted in different configurations (with or without samples) and the measurement of the associated thermal gradient led to improvements of the mould (in particular the introduction of a counter-piston). By th…

Graded Poisson structures on the algebra of differential forms

1995

We study the graded Poisson structures defined on Ω(M), the graded algebra of differential forms on a smooth manifoldM, such that the exterior derivative is a Poisson derivation. We show that they are the odd Poisson structures previously studied by Koszul, that arise from Poisson structures onM. Analogously, we characterize all the graded symplectic forms on ΩM) for which the exterior derivative is a Hamiltomian graded vector field. Finally, we determine the topological obstructions to the possibility of obtaining all odd symplectic forms with this property as the image by the pullback of an automorphism of Ω(M) of a graded symplectic form of degree 1 with respect to which the exterior der…

Bi-layer PCL/PLA scaffold prepared by melt for interface tissue engineering

2017

The development of porous multilayer devices allow controlling chemical, physical and mechanical properties by tuning the properties of each single layer. For instance, this feature is of main concern for the production of porous devices designed to regenerate diseased zones at the interface of tissue presenting intrinsic anisotropic structures that gradually change from one tissue to another. In this context, synthetic biodegradable polymers commonly used biomedical applications include polylactic acid (PLA) and polycaprolactone (PCL). In this work, a novel bi-layered multiphasic scaffold (BLS) is presented. It is composed by a PLA-layer presenting pore size in the range of 90-110 μm while…

Gradings on the algebra of upper triangular matrices of size three

2013

Abstract Let UT 3 ( F ) be the algebra of 3 × 3 upper triangular matrices over a field F . On UT 3 ( F ) , up to isomorphism, there are at most five non-trivial elementary gradings and we study the graded polynomial identities for such gradings. In case F is of characteristic zero we give a complete description of the space of multilinear graded identities in the language of Young diagrams through the representation theory of a Young subgroup of S n . We finally compute the multiplicities in the graded cocharacter sequence for every elementary G -grading on UT 3 ( F ) .

Photocurrent Spectroscopy Applied to the Characterization of Compositionally and Structurally Graded Materials: from Thin Films to Nanostructures

2010

GRADED IDENTITIES FOR THE ALGEBRA OF n×n UPPER TRIANGULAR MATRICES OVER AN INFINITE FIELD

2003

We consider the algebra Un(K) of n×n upper triangular matrices over an infinite field K equipped with its usual ℤn-grading. We describe a basis of the ideal of the graded polynomial identities for this algebra.

A facile and eco-friendly route to fabricate poly(Lactic acid) scaffolds with graded pore size

2016

Over the recent years, functionally graded scaffolds (FGS) gaineda crucial role for manufacturing of devices for tissue engineering. The importance of this new field of biomaterials research is due to the necessity to develop implants capable of mimicking the complex functionality of the various tissues, including a continuous change from one structure or composition to another. In this latter context, one topic of main interest concerns the design of appropriate scaffolds for bone-cartilage interface tissue. In this study, three-layered scaffolds with graded pore size were achieved by melt mixing poly(lactic acid) (PLA), sodium chloride (NaCl) and polyethylene glycol (PEG). Pore size distr…

Cocharacters of group graded algebras and multiplicities bounded by one

2017

Let G be a finite group and A a G-graded algebra over a field F of characteristic zero. We characterize the (Formula presented.)-ideals (Formula presented.) of graded identities of A such that the multiplicities (Formula presented.) in the graded cocharacter of A are bounded by one. We do so by exhibiting a set of identities of the (Formula presented.)-ideal. As a consequence we characterize the varieties of G-graded algebras whose lattice of subvarieties is distributive.

Polynomial identities for the Jordan algebra of upper triangular matrices of order 2

2012

Abstract The associative algebras U T n ( K ) of the upper triangular matrices of order n play an important role in PI theory. Recently it was suggested that the Jordan algebra U J 2 ( K ) obtained by U T 2 ( K ) has an extremal behaviour with respect to its codimension growth. In this paper we study the polynomial identities of U J 2 ( K ) . We describe a basis of the identities of U J 2 ( K ) when the field K is infinite and of characteristic different from 2 and from 3. Moreover we give a description of all possible gradings on U J 2 ( K ) by the cyclic group Z 2 of order 2, and in each of the three gradings we find bases of the corresponding graded identities. Note that in the graded ca…