Surface modification of ultra‐high‐molecular‐weight polyethylene. I. Characterization and sintering studies

We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching with the aim of improving the performance of UHMWPE's composites with poly(ethylene terephthalate) fibers. In part I of this study, we evaluated the effects of chemical modification on the surface properties of UHMWPE with X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle measurements. The thermal properties, rheology, and sintering behavior of the modified UHMWPE were compared to those of the base material. XPS and FTIR analysis confirmed the presence of carboxyl and hydroxyl groups on the surface of the modified powders. The substitution of polar groups into the backbone of the polymer decreased its contact angles with water and hexadecane and increased its surface energy, as evidenced by contact angle measurements. The modified UHMWPE was more crystalline than the base resin and less prone to thermal degradation. Although the rheological properties were virtually identical, the modified powders sintered more readily, presumably due to their higher surface energy, which suggested enhanced processability by compression molding. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Towards children's creative museum engagement and collaborative sense-making

Abstract

In this article, we elucidate a socio-culturally framed approach to supporting children's creative museum engagement. Specifically, we focus on social activities and socio-cultural resources that can act as boundary-permeating objects in mediating children's creative engagement and collaborative sense-making regarding cultural content within, across and beyond the spatio-material context of the museum. We contend that designing and organising children's creative engagement and collaborative sense-making in ways that cultivate boundary-crossing broadens opportunities for engagement and leverages children's creative potential and expansive learning. We build our argument by starting with a theoretical introduction to the design principles that constitute the Kids, Museums, and Technology Programme. We will illuminate the design principles of the programme with empirical examples and consider how the design principles and their situated construction can help us re-imagine museum exhibitions as hybrid, boundary-permeating spaces that afford novel transformative interactions, as well as new roles and identities for both children and museums.     

HCI and Society: Towards a Typology of Universal Design Principles

The task of this article is to focus on aspects of design from a theoretical perspective that works out a general framework of techno-social design that is grounded in the notion of the participatory, cooperative, sustainable information society. The approach is normative in that it is based on the judgment that not just any information society is needed, but one that has specific qualities that this article tries to identify. Methodologically, the article works out a conceptual framework that synthesizes general social theory and human–computer interaction. Design is seen as a social process that shapes society and techno-social systems. First, a model of society that is based on the dialectical interaction of economic, political, and cultural subsystems is introduced. Then, the notion of the the participatory, cooperative, sustainable information society is introduced. This theoretical definition is then used for classifying design principles of techno-social information systems from a social theory perspective.     

On semidefinite programming bounds for graph bandwidth

In this paper, we propose two new lower bounds on graph bandwidth and cyclic bandwidth based on semidefinite programming (SDP) relaxations of the quadratic assignment problem. We compare the new bounds with two other SDP bounds reported in [A. Blum, G. Konjevod, R. Ravi, and S. Vempala, Semi-definite relaxations for minimum bandwidth and other vertex-ordering problems, Theoret. Comput. Sci. 235(1) (2000), pp. 25–42; J. Povh and F. Rendl, A copositive programming approach to graph partitioning, SIAM J. Optim. 18(1) (2007), pp. 223–241].     

Network Analysis of Gut Microbiome and Metabolome to Discover Microbiota-Linked Biomarkers in Patients Affected by Non-Small Cell Lung Cancer

Several studies in recent times have linked gut microbiome (GM) diversity to the pathogenesis of cancer and its role in disease progression through immune response, inflammation and metabolism modulation. This study focused on the use of network analysis and weighted gene co-expression network analysis (WGCNA) to identify the biological interaction between the gut ecosystem and its metabolites that could impact the immunotherapy response in non-small cell lung cancer (NSCLC) patients undergoing second-line treatment with anti-PD1. Metabolomic data were merged with operational taxonomic units (OTUs) from 16S RNA-targeted metagenomics and classified by chemometric models. The traits considered for the analyses were: (i) condition: disease or control (CTRLs), and (ii) treatment: responder (R) or non-responder (NR). Network analysis indicated that indole and its derivatives, aldehydes and alcohols could play a signaling role in GM functionality. WGCNA generated, instead, strong correlations between short-chain fatty acids (SCFAs) and a healthy GM. Furthermore, commensal bacteria such as Akkermansia muciniphila, Rikenellaceae, Bacteroides, Peptostreptococcaceae, Mogibacteriaceae and Clostridiaceae were found to be more abundant in CTRLs than in NSCLC patients. Our preliminary study demonstrates that the discovery of microbiota-linked biomarkers could provide an indication on the road towards personalized management of NSCLC patients.     

Asymptotic Distribution of Eigenvalues for Damped String Equation: Numerical Approach

In the present paper, we consider a one-parameter family of the nonself-adjoint operators, which are the dynamics generators for systems governed by the wave equations containing dissipative terms. The equations contain viscous damping terms and are equipped with the boundary conditions involving an arbitrary complex parameter. In the current engineering literature, this type of boundary condition is used to model the action of smart materials (self-sensing/self-straining actuators). In the previous research of the first writer, the aforementioned dynamics generators have been studied analytically and precise asymptotic formulas for the eigenvalues have been derived (the asymptotic when the number of the eigenvalues tends to infinity). The goal of the present paper is to demonstrate that the analytic formulas are not only important theoretically, but also extremely efficient practically. Namely, we show that the leading terms in the asymptotic formulas approximate the actual eigenvalues with excellent accuracy. To justify the results, we use two methods, i.e., the Newton method and the Tchebychev method. First, Newton’s method is applied to the characteristic equation using asymptotic formulas as initial guesses to find the eigenvalues. The convergence of Newton’s method is improved by modifying the asymptotic formula. Second, we use Tchebychev discretization to circumvent the nonlinear characteristic equation and to obtain a finite-dimensional generalized eigenvalue problem that approximates the infinite-dimensional one. Finally, to solve the generalized eigenvalue problem, we use the QT algorithm.     

Methanol diffusion in polyimides: A molecular description

In this contribution the diffusion of methanol in two commercial polyimides (6FDA-ODA and Ultem^® 1000) is investigated in detail by gravimetric analysis and in-situ, time-resolved FTIR spectroscopy. Two methods of spectral data analysis are employed, namely difference spectroscopy (DS) and least-squares curve fitting (LSCF). These approaches provided complementary information about the overall diffusivity, the interactions and the dynamics of the molecular species present in the investigated systems. Spectroscopic measurements on thin film samples (2–4 μm) allowed us to identify the interaction site(s) on the polymer backbone and to propose likely structures for the H-bonding molecular aggregates.     

Antioxidant and anti-inflammatory activity of red and white wine extracts

Two commercially available Greek wines were treated with two different extraction methods in order to obtain either the total lipid fraction or several fractions containing different classes of phenolic compounds.