¿Por qué no se presta suficiente atención a la corrosión?

In this paper, we intend to invite reflection on why insufficient attention is paid to the problems associated with the corrosion of metallic components or structures. Practical corrosion cases that we may observe in our daily life are presented as examples for different perceptions of the observed phenomena in terms of failure or poor design. We conclude that all who participate in a component´s lifetime, from the specification phase over manufacturing through the time in service, in order to achieve an economically optimized technical solution for a desired functionality, require awareness of corrosion. Some aspects for improving the awareness are identified in education, in industry, and in their interaction.En este articulo, nos proponemos invitar a la reflexión sobre por qué no se presta suficiente atención a los problemas relacionados con la corrosión de los componentes o estructuras metálicas. Los casos prácticos de corrosión que podemos observar en nuestra vida cotidiana se presentan como ejemplos de las diferentes percepciones de los fenómenos observados en cuanto a fallos o diseño deficiente. Concluimos que la conciencia de la corrosión es necesaria para todos los que participan en la vida de un componente, desde la fase de especificación, pasando por la fabricación, hasta el tiempo en servicio, para lograr una solución técnica económicamente optimizada para una funcionalidad deseada. Se identifican algunos aspectos para mejorar la conciencia en la educación, en la industria y en su interacción

Influence of surface oxide characteristics and speciation on corrosion, electrochemical properties and metal release of atomized 316L stainless steel powders

Surface oxide characteristics of powder particles are important to consider for any toxicological risk assessment based on in-vitro or in-vivo tests. This study focuses on a multi-analytical approach (X-ray photoelectron spectroscopy, Auger electron spectroscopy, scanning- and transmission electron microscopy, and different electrochemical techniques) for in-depth characterization of surface oxides of inert-gas-atomized (GA) AISI 316L stainless steel powder, compared with massive sheet and a water-atomized (WA) 316L powder. Implications of differences in surface oxide phases and their surface distribution on corrosion, electrochemical properties and metal release are systematically discussed. Cr was enriched in an inner surface layer for both GA powders, with Mn and S enriched in the outermost surface oxide. The surface oxide was 2-5 nm thick for both GA powder size fractions, amorphous for the GA powder size

Influence of surface oxide characteristics and speciation on corrosion, electrochemical properties and metal release of atomized 316L stainless steel powders

Surface oxide characteristics of powder particles are important to consider for any toxicological risk assessment based on in-vitro or in-vivo tests. This study focuses on a multi-analytical approach (X-ray photoelectron spectroscopy, Auger electron spectroscopy, scanning- and transmission electron microscopy, and different electrochemical techniques) for in-depth characterization of surface oxides of inert-gas-atomized (GA) AISI 316L stainless steel powder, compared with massive sheet and a water-atomized (WA) 316L powder. Implications of differences in surface oxide phases and their surface distribution on corrosion, electrochemical properties and metal release are systematically discussed. Cr was enriched in an inner surface layer for both GA powders, with Mn and S enriched in the outermost surface oxide. The surface oxide was 2-5 nm thick for both GA powder size fractions, amorphous for the GA powder size

Unbound states of 32Cl and the 31S(p,\gamma)32Cl reaction rate

The 31S(p,\gamma)32Cl reaction is expected to provide the dominant break-out path from the SiP cycle in novae and is important for understanding enrichments of sulfur observed in some nova ejecta. We studied the 32S(3He,t)32Cl charge-exchange reaction to determine properties of proton-unbound levels in 32Cl that have previously contributed significant uncertainties to the 31S(p,\gamma)32Cl reaction rate. Measured triton magnetic rigidities were used to determine excitation energies in 32Cl. Proton-branching ratios were obtained by detecting decay protons from unbound 32Cl states in coincidence with tritons. An improved 31S(p,\gamma)32Cl reaction rate was calculated including robust statistical and systematic uncertainties

Chemoenzymatic synthesis of glycosaminoglycans: Re-creating, re-modeling and re-designing nature's longest or most complex carbohydrate chains

Glycosaminoglycans (GAGs) are complex polysaccharides composed of hexosamine-containing disaccharide repeating units. The three most studied classes of GAGs, heparin/heparan sulfate, hyaluronan and chondroitin/dermatan sulfate, are essential macromolecules. GAGs isolated from animal and microbial sources have been utilized therapeutically, but naturally occurring GAGs are extremely heterogeneous limiting further development of these agents. These molecules pose difficult targets to construct by classical organic syntheses due to the long chain lengths and complex patterns of modification by sulfation and epimerization. Chemoenzymatic synthesis, a process that employs exquisite enzyme catalysts and various defined precursors (e.g. uridine 5′-diphosphosphate-sugar donors, sulfate donors, acceptors and oxazoline precursors), promises to deliver homogeneous GAGs. This review covers both theoretical and practical issues of GAG oligosaccharide and polysaccharide preparation as single molecular entities and in library formats. Even at this early stage of technology development, nearly monodisperse GAGs can be made with either natural or artificial structures

Chemoenzymatic synthesis of unmodified heparin oligosaccharides: cleavage of p-nitrophenyl glucuronide by alkaline and Smith degradation

A heparin oligosaccharide having a completely natural structure was successfully synthesized through a chemoenzymatic approach using an unnatural glycosyl acceptor, p -nitrophenyl glucuronide (GlcA- p NP)

Effects of glycosaminoglycan supplementation in the chondrogenic differentiation of bone marrow- and synovial- derived mesenchymal stem/stromal cells on 3D-extruded poly (ε-caprolactone) scaffolds

The lack of effective and long-term treatments for articular cartilage defects has increased the interest for innovative tissue engineering strategies. Such approaches, combining cells, biomaterial matrices and external biochemical/physical cues, hold promise for generating fully functional cartilage tissue. Herein, this study aims at exploring the use of the major cartilage glycosaminoglycans (GAGs), chondroitin sulfate (CS) and hyaluronic acid (HA), as external biochemical cues to promote the chondrogenic differentiation of human bone marrow- and synovium-derived mesenchymal stem/stromal cells (hBMSC/hSMSC) on custom-made 3 D porous poly (ε-caprolactone) (PCL) scaffolds. The culture conditions, namely the chondrogenic medium and hypoxic environment (5% O2 tension), were firstly optimized by culturing hBMSCs on PCL scaffolds without GAG supplementation. For both MSC sources, GAG supplemented media, particularly with HA, promoted significantly cartilage-like extracellular matrix (ECM) production (higher sulfated GAG amounts) and chondrogenic gene expression. Remarkably, in contrast to tissues generated using hBMSCs, the hSMSC-based constructs showed decreased expression of hypertrophic marker COL X. Histological, immunohistochemical and transmission electron microscopy (TEM) analysis confirmed the presence of typical articular cartilage ECM components (GAGs, aggrecan, collagen fibers) in all the tissue constructs produced. Overall, our results highlight the potential of integrating GAG supplementation, hSMSCs and customizable 3 D scaffolds toward the fabrication of bioengineered cartilage tissue substitutes with reduced hypertrophy.info:eu-repo/semantics/publishedVersio

Heparin and Heparan Sulfate: Analyzing Structure and Microheterogeneity [chapter]

available in PMC 2013 August 28The structural microheterogeneity of heparin and heparan sulfate is one of the major reasons for the multifunctionality exhibited by this class of molecules. In a physiological context, these molecules primarily exert their effects extracellularly by mediating key processes of cellular cross-talk and signaling leading to the modulation of a number of different biological activities including development, cell proliferation, and inflammation. This structural diversity is biosynthetically imprinted in a nontemplate-driven manner and may also be dynamically remodeled as cellular function changes. Understanding the structural information encoded in these molecules forms the basis for attempting to understand the complex biology they mediate. This chapter provides an overview of the origin of the structural microheterogeneity observed in heparin and heparan sulfate, and the orthogonal analytical methodologies that are required to help decipher this information

γ spectroscopy of states in Cl 32 relevant for the S 31 (p,γ) Cl 32 reaction rate

Background: The S31(p,γ)Cl32 reaction becomes important for sulfur production in novae if the P31(p,α)Si28 reaction rate is somewhat greater than currently accepted. The rate of the S31(p,γ)Cl32 reaction is uncertain, primarily due to the properties of resonances at Ec.m.=156 and 549 keV. Purpose: We precisely determined the excitation energies of states in Cl32 through high-resolution γ spectroscopy including the two states most important for the S31(p,γ)Cl32 reaction at nova temperatures. Method: Excited states in Cl32 were populated using the B10(Mg24,2n)Cl32 reaction with a Mg24 beam from the ATLAS facility at Argonne National Laboratory. The reaction channel of interest was selected using recoils in the Fragment Mass Analyzer, and precise level energies were determined by detecting γ rays with Gammasphere. Results: We observed γ rays from the decay of six excited states in Cl32. The excitation energies for two unbound levels at Ex=1738.1 (6) keV and 2130.5 (10) keV were determined and found to be in agreement with a previous high-precision measurement of the S32(He3,t)Cl32 reaction [1]. Conclusions: An updated S31(p,γ)Cl32 reaction rate is presented. With the excitation energies of important levels firmly established, the dominant uncertainty in the reaction rate at nova temperatures is due to the strength of the resonance corresponding to the 2131-keV state in Cl32