Nanomechanical characterization of alumina coatings grown on FeCrAl alloy by thermal oxidation.

This work studies the feasibility of using repetitive-nano-impact tests with a cube-corner tip and low loads for obtaining quantitative fracture toughness values in thin and brittle coatings. For this purpose, it will be assumed that the impacts are able to produce a cracking, similar to the pattern developed for the classical fracture toughness tests in bulk materials, and therefore, from the crack developed in the repetitive impacts it will be possible to evaluate the suitability of the classical indentation models (Anstins and Laugier) for measuring fracture toughness. However, the length of this crack has to be lower than 10% of the total coating thickness to avoid substrate contributions. For this reason, and in order to ensure a small plastic region localized at the origin of the crack tip, low load values (or small distance between the indenter tip and the surface) have to be used. In order to demonstrate the validity of this technique, repetitive-nano-impact will be done in a fine and dense oxide layer (α-Al2O3), which has been developed on the top of oxide dispersion strengthened (ODS) FeCrAl alloys (PM 2000) by thermal oxidation at elevated temperatures. Moreover, it will be shown how it is possible to know with each new impact the crack geometry evolution from Palmqvist crack to half-penny crack, being able to study the proper evolution of the different values of fracture toughness in terms of both indentation models and as a function of the strain rate, ε̇, decreasing. Thereby, fracture toughness values for α-Al2O3 layer decrease from ~4.40MPam , for high ϵ̇ value (10(3)s(-1)), to ~3.21MPam, for quasi-static ϵ̇ value (10(-3)s(-1)). On the other hand, ϵ̇ a new process to obtain fracture toughness values will be analysed, when the classical indentation models are not met. These values are typically found in the literature for bulk α-Al2O3, demonstrating the use of repetitive-nano-impact tests which not only provide qualitative information about fracture resistance of the materials but it also can be used to obtain quantitative information as fracture toughness values in the case of brittle materials.

Denosumab increases sublesional bone mass in osteoporotic individuals with recent spinal cord injury.

UNLABELLED: Osteoporosis is a frequent complication related to spinal cord injury (SCI), and data on osteoporosis treatment after SCI is scarce. Treatment with denosumab increases lumbar and femoral BMD and decreases bone turnover markers in individuals with recent SCI. This drug may be a promising therapeutic option in SCI-related osteoporosis. INTRODUCTION: Osteoporosis development is a frequent complication related to SCI, especially at the sublesional level. Nevertheless, data on osteoporosis treatment after SCI is scarce, particularly short term after injury, when the highest bone loss is produced. The aim of this study was to analyze the efficacy of denosumab in the treatment of SCI-related osteoporosis. METHODS: Fourteen individuals aged 39 ± 15 years with osteoporosis secondary to recent SCI (mean injury duration 15 ± 4 months) were treated with denosumab for 12 months. Bone turnover markers (BTMs) (PINP, bone ALP, sCTx), 25-hydroxyvitamin D (25OHD) levels and bone mineral density (BMD) at the lumbar spine (LS), total hip (TH), and femoral neck (FN) were assessed at baseline and at 12 months. All participants received calcium and vitamin D supplementation. RESULTS: At 12 months, SCI denosumab-treated participants showed a significant increase in BMD at TH (+2.4 ± 3.6 %, p = 0.042), FN (+3 ± 3.6 %, p = 0.006), and LS (+7.8 ± 3.7 %, p < 0.001) compared to baseline values. Denosumab treatment was associated with significant decreases in BTMs (bone ALP -42 %, p < 0.001; PINP -58 %, p < 0.001, sCTx -57 %, p = 0.002) at 12 months. BMD evolution was not related to BTM changes or 25OHD serum levels. No skeletal fractures or serious adverse events were observed during follow-up. CONCLUSIONS: Treatment with denosumab increases lumbar and femoral BMD and decreases bone turnover markers in individuals with recent SCI. This drug may be a promising therapeutic option in SCI-related osteoporosis.

Fatigue behavior of Ti6Al4V and 316 LVM blasted with ceramic particles of interest for medical devices.

Grit blasting is used as a cost-effective method to increase the surface roughness of metallic biomaterials, as Ti6Al4V and 316 LVM, to enhance the osteointegration, fixation and stability of implants. Samples of these two alloys were blasted by using alumina and zirconia particles, yielding rough (up to Ra~8µm) and nearly smooth (up to Ra~1µm) surfaces, respectively. In this work, we investigate the sub-surface induced microstructural effects and its correlation with the mechanical properties, with special emphasis in the fatigue behavior. Blasting with zirconia particles increases the fatigue resistance whereas the opposite effect is observed using alumina ones. As in a conventional shot penning process, the use of rounded zirconia particles for blasting led to the development of residual compressive stresses at the surface layer, without zones of stress concentrators. Alumina particles are harder and have an angular shape, which confers a higher capability to abrade the surface, but also a high rate of breaking down on impact. The higher roughness and the presence of a high amount of embedded alumina particles make the blasted alloy prone to crack nucleation. Interestingly, the beneficial or detrimental role of blasting is more intense for the Ti6Al4V alloy than for the 316 steel. It is proposed that this behavior is related to their different strain hardening exponents and the higher mass fraction of particles contaminating the surface. The low value of this exponent for the Ti6Al4V alloy justifies the expected low sub-surface hardening during the severe plastic deformation, enhancing its capability to soft during cyclic loading.

Potential of FeAlCr intermetallics reinforced with nanoparticles as new biomaterials for medical devices.

Novel FeAlCr oxide dispersion strengthened intermetallics that are processed by powder metallurgy have been developed as potential biomaterials. The alloys exhibit a small grain size and a fine dispersion of yttria provides the material with a high yield strength and depending on the alloy composition good ductility (up to 5%). The biocompatibility of the alloy was assessed in comparison with commercial alumina. Saos-2 osteoblast-like cells were either challenged with mechanically alloyed particles, or seeded onto solid samples. Viability and proliferation of cells were substantially unaffected by the presence of a high concentration of particles (1 mg/mL). Solid samples of novel FeAlCr intermetallic have shown a good biocompatibility in vitro, often approaching the behavior of materials well known for their biological acceptance (e.g. alumina). It has been found that osteoblasts are able to produce ALP, a specific marker of cells with bone-forming activity. In this respect, ALUSI alloys hold the promise to be suitable substrate for bone integration. The finding of no cytotoxic effect in the presence of the alloy particles is a reliable proof of the absence of acute toxicity of the material.

Evaluating associations between Mediterranean diet adherence indexes and biomarkers of diet and disease.

OBJECTIVE: We examined associations between two Mediterranean diet (MD) adherence indexes (the MD index, MDI, and the MD score, MDS) and several blood biomarkers of diet and disease. SUBJECTS: We studied 328 individuals from Catalonia (Northeastern Spain), ages 18-75, who provided fasting blood samples, a subset of the 2346 individuals as part of a larger representative and random sample from the 1992-1993 Catalan Nutritional Survey. DESIGN AND METHOD: Diet was measured using 24-h recalls. Biomarkers studied were plasma levels of beta-carotene, alpha-tocopherol, retinol, vitamins B12, C and folates as well as serum total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides. Multivariate linear regression was used to analyse associations of the nutrient biomarkers with the dietary pattern indexes, adjusting for potential confounders. RESULTS AND CONCLUSIONS: Subjects with higher MD adherence, as measured by the two dietary indexes, had significantly higher plasma concentrations of beta-carotene, folates, vitamin C, alpha-tocopherol and HDL cholesterol. The most highly significant relationship was that between folates and the adherence to the MD Pattern, as determined by both indexes. These research findings suggest the potential usefulness of biomarkers as complementary tools for assessing adherence to a dietary pattern. This type of data not only informs the development of robust dietary adherence indexes, but it also provides specific clues about the potential physiological mechanisms that explain the beneficial effects of the MD pattern on chronic disease risk.

Evaluation of mechanical properties and biological response of an alumina-forming Ni-free ferritic alloy.

PM 2000 is a Ni-free oxide dispersion strengthened Fe-20Cr-5Al alloy able to develop a fine, dense and tightly adherent alpha-alumina scale during high-temperature oxidation. Despite the high temperature involved during thermal oxidation (1100 degrees C), microstructural changes in the candidate material, a hot rolled product, hardly occurs. Consequently, the good mechanical properties of the as-received material are not significantly affected. Moreover, due to the high compressive residual stresses at the alumina scale, an increase in the fatigue limit from 500 to 530 MPa is observed. Such stresses also account for the high capability of the coating/metal system to withstand more than 1% tensile deformation without cracking. The biocompatibility of the alloy was assessed in comparison to commercial alumina. Saos-2 osteoblast-like cells were either challenged with PM 2000 particles, or seeded onto PM 2000 (with and without scale) solid samples. Viability, growth, and ALP release from cells were assessed after 3 or 7 days, while mineralization was checked at 18 days. This study has demonstrated that PM 2000 with and without scale are capable of supporting in vitro growth and function of osteoblast-like cells over a period of 18 days. Results from this study suggest that the resulting alumina/alloy system combines the good mechanical properties of the alloy with the superior biocompatibility of the alpha-alumina, for which there is very good clinical experience.

Effects of polyethylene and alpha-alumina particles on IL-6 expression and secretion in primary cultures of human osteoblastic cells.

The effect of two biomaterials, polyethylene and alpha-alumina, on interleukin-6 (IL-6) secretion and expression has been studied in human osteoblasts in primary culture. Human osteoblastic cells were derived from fresh trabecular bone explants removed during total knee arthroplasty. On reaching confluence, cells were subcultured in 6 well plates; the resulting subcultures were incubated until confluence and polyethylene or alpha-alumina particles were added to some while the rest were left as controls. The IL-6 mRNA levels were assessed by reverse transcription (RT) followed by polymerase chain reaction (PCR). IL-6 secretion was measured in the conditioned medium. The IL-6 expression was higher in the presence of both biomaterials. Maximum expression occurred in response to a dose of 50 mg particles well with both biomaterials and was greater after polyethylene particle addition than after alpha-alumina particle addition at this dose. The maximum IL-6 secretion elicited by alpha-alumina was produced at 10 mg particles well while maximum response with polyethylene required 50 mg well. At a dose of 10 mg/well, alpha-alumina particles induced more secretion than 10 mg of polyethylene particles. Nevertheless, at a dose of 50 mg/well maximum secretion was produced with polyethylene particles. In conclusion and in our experimental conditions, polyethylene as well as alpha-alumina increased both the expression and the secretion of IL-6 in human osteoblastic cells in primary culture and stimulation from polyethylene appears stronger than that from alpha-alumina at the same dose.

Effect of substrate roughness on the corrosion behaviour of the Al2O3/MA 956 system.

This paper presents the influence of substrate roughness on the corrosion behaviour of the Al2O3/MA 956 system. An alumina layer of thickness 1-5 microm was generated of the MA956 alloy by thermal oxidation at 1100 degrees C using different exposure times. This Al2O3/MA 956 system with a polished substrate has shown excellent corrosion behaviour in a physiological fluid, due to the fact that the alpha-Al2O3 layer formed is dense, continuous and firmly adhered to the substrate, irrespective of the scale thickness. This good adherence allows it to withstand potentials above 1.7 V. Specimens with rough finish substrate and treatment times above 10 h present spallation of the alumina layer at the crests of the roughness profile. In this case a mixed corrosion behaviour between an alumina coated material and one with a passive layer is observed. In both types of specimens, rough and smooth, once the passivation layer is broken the repassivation capacity of the substrate is ensured due to the high chromium content of the alloy, under oxygenation conditions.

Subtypes of ataques de nervios: the influence of coexisting psychiatric diagnosis.

The current study assesses the relationship between presenting symptomatology of the self-labeled Hispanic popular diagnosis of ataques de nervios and the specific co-morbid psychiatric diagnoses. Hispanic subjects seeking treatment at an anxiety disorders clinic (n = 156) were assessed with a specially designed self-report instrument for both traditional ataque de nervios and panic symptoms, and with structured or semistructured psychiatric interviews for Axis-I disorders. This report focuses on 102 subjects with ataque de nervios who also met criteria for panic disorder, other anxiety disorders, or an affective disorder. Distinct ataque symptom patterns correlated with co-existing panic disorder, affective disorders, or other anxiety disorders. Individuals with both ataque and panic disorder reported the most asphyxia, fear of dying, and increased fear during their ataques. People with ataques who also met criteria for affective disorder reported the most anger, screaming, becoming aggressive, and breaking things during ataques. Ataque positive subjects with other anxiety disorders were less salient for both panic-like and emotional-anger symptoms. The findings suggest that (a) ataque de nervios is a popular label referring to several distinct patterns of loss of emotional control, (b) the type of loss of emotional control is influenced by the associated psychiatric disorder, and (c) ataque symptom patterns may be a useful clinical marker for detecting psychiatric disorders. Further study is needed to examine the relationship between ataque de nervios and psychiatric disorders, as well as the relationship to cultural, demographic, environmental, and personality factors.

[Seasonal affective disorder and light therapy]. / Trastorno afectivo estacional y terapia lumínica.

Seasonal affective disorders (SAD) represents a subgroup of major depression with a regular occurrence of symptoms in autumn and winter and full remission in spring and summer. Light therapy or phototherapy has become the standard treatment of this type of depression. The phototherapy is affective therapy for depressive symptoms of SAD. However, the action mechanism of light therapy is uncertain. Finally, new lines of the investigation of light therapy are aforementioned.

Electrochemical impedance spectroscopy of preoxidized MA 956 superalloy during in vitro experiments.

Preoxidation treatment of MA 956 superalloy at 1100 degrees C produces a fine and tightly adherent alpha-alumina layer at the surface, which provides the alloy with an excellent barrier against a great variety of aggressive environments. In this work the protective capacity of the alumina/alloy system is evaluated in a physiological medium by means of electrochemical impedance spectroscopy. The electrochemical response of the material is modelled by equivalent circuits which provide the most relevant corrosion and protection parameters applicable to MA 956 in both preoxidized and as-received conditions (passivated state). The high protective capacity of preoxidized MA 956 superalloy holds for long-term tests, which indicates that the corrosion phenomena, if any, would be characterized by very slow kinetics. The corrosion resistance of the preoxidized material is at least two orders of magnitude higher than that of the non-treated alloy.

Antigenic relationships between chloroplast and cytosolic fructose-1,6-bisphosphatases.

Cytosolic fructose-1,6-biphosphatases (FBPase, EC 3.1.3.11) from pea (Pisum sativum L. cv Lincoln) and spinach (Spinacia oleracea L. cv Winter Giant) did not cross-react by double immunodiffusion and western blotting with either of the antisera raised against the chloroplast enzyme of both species; similarly, pea and spinach chloroplast FBPases did not react with the spinach cytosolic FBPase antiserum. On the other hand, spinach and pea chloroplast FBPases showed strong cross-reactions against the antisera to chloroplast FBPases, in the same way that the pea and spinach cytosolic enzymes displayed good cross-reactions against the antiserum to spinach cytosolic FBPase. Crude extracts from spinach and pea leaves, as well as the corresponding purified chloroplast enzymes, showed by western blotting only one band (44 and 43 kD, respectively) in reaction with either of the antisera against the chloroplast enzymes. A unique fraction of molecular mass 38 kD appeared when either of the crude extracts or the purified spinach cytosolic FBPase were analyzed against the spinach cytosolic FBPase antiserum. These molecular sizes are in accordance with those reported for the subunits of the photosynthetic and gluconeogenic FBPases. Chloroplast and cytosolic FBPases underwent increasing inactivation when increasing concentrations of chloroplast or cytosolic anti-FBPase immunoglobulin G (IgG), respectively, were added to the reaction mixture. However, inactivations were not observed when the photosynthetic enzyme was incubated with the IgG to cytosolic FBPase, or vice versa. Quantitative results obtained by enzyme-linked immunosorbent assays (ELISA) showed 77% common antigenic determinants between the two chloroplast enzymes when tested against the spinach photosynthetic FBPase antiserum, which shifted to 64% when assayed against the pea antiserum. In contrast, common antigenic determinats between the spinach cytosolic FBPase and the two chloroplast enzymes were less than 10% when the ELISA test was carried out with either of the photosynthetic FBPase antisera, and only 5% when the assay was performed with the antiserum to the spinach cytosolic FBPase. These results were supported by sequencing data: the deduced amino acid sequence of a chloroplast FBPase clone isolated from a pea cDNA library indicated a 39,253 molecular weight protein, with a homology of 85% with the spinach chloroplast FBPase but only 48.5% with the cytosolic enzyme from spinach.

Cloning, structure and expression of a pea cDNA clone coding for a photosynthetic fructose-1,6-bisphosphatase with some features different from those of the leaf chloroplast enzyme.

A positive clone against pea (Pisum sativum L.) chloroplast fructose-1,6-bisphosphatase (FBPase; EC 3.1.3.11) antibodies was obtained from a copy DNA (cDNA) library in lambda gt11. The insert was 1261 nucleotides long, and had an open reading frame of 1143 base pairs with coding capability for the whole FBPase subunit and a fragment of a putative processing peptide. An additional 115 base pairs corresponding to a 3'-untranslated region coding for an mRNA poly(A)+ tail were also found in the clone. The deduced sequence for the FBPase subunit was a 357-amino-acid protein of molecular mass 39,253 daltons (Da), showing 82-88% absolute homology with four chloroplastic FBPases sequenced earlier. The 3.1-kilobase (kb) KpnI-SacI fragment of the lambda gt11 derivative was subcloned between the KpnI-SacI restriction sites of pTZ18R to yield plasmid pAMC100. Lysates of Escherichia coli (pAMC100) showed FBPase activity; this was purified as a 170-kDa protein which, upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, displayed a 44-kDa band. As occurs with native FBPases, this indicates a homotetrameric structure for the expressed FBPase. When assayed under excess Mg2+ (10 mM), the expressed enzyme had a higher affinity for the substrate than the native pea leaf FBPase; this parameter appears to be substantiated by a tenfold higher specific activity than that of the native enzyme. However, when activated with dithiothreitol plus saturating concentrations of pea thioredoxin (Td) f, both FBPase had similar activities, with a 4:1 Td f-FBPase stoichiometry. In contrast to the native pea chloroplast FBPase, the E. coli-expressed enzyme did not react with the monoclonal antibody GR-PB5.(ABSTRACT TRUNCATED AT 250 WORDS)