Glasses exhibit slow crack growth under stress intensities below the fracture toughness in the presence of water vapor or liquid water. It has been observed by several authors that when an oxide ...glass with a large crack is held under a subcritical stress intensity (where no slow crack growth occurs) in room‐temperature water vapor or liquid water, upon reloading to a higher stress intensity, a finite restart time is observed prior to measurable crack extension. This phenomenon of apparent strengthening, or crack arrest, has been attributed to concepts such as corrosive dissolution of the crack tip, crack tip blunting, or water diffusion, and subsequent swelling of the material around the crack tip. Recently, a newly observed surface stress relaxation process that is aided by molecular water diffusion was used to improve the mechanical strength of glass fibers and to explain the subsurface compressive stress peak observed in ion‐exchange strengthened glasses. The same process is employed here to explain these delayed slow crack growth data. A simple mathematical model has been developed utilizing water‐assisted surface stress relaxation and fracture mechanics. Predictions of restart times using the model agreed well with published experimental data, indicating that surface stress relaxation is responsible for the anomalous delayed slow crack growth behavior.
The proteins of the hedgehog (Hh) family regulate various aspects of development. Recently, members of this family have been shown to regulate skeletal formation in vertebrates and to control both ...chondrocyte and osteoblast differentiation. In the present study, we analyzed the effect of Sonic hedgehog (Shh) on the osteoblastic and adipocytic commitment/differentiation. Recombinant N-terminal Shh (N-Shh) significantly increased the percentage of both the pluripotent mesenchymal cell lines C3H10T1/2 and ST2 and calvaria cells responding to bone morphogenetic protein 2 (BMP-2), in terms of osteoblast commitment as assessed by measuring alkaline phosphatase (ALP) activity. This synergistic effect was mediated, at least partly, through the positive modulation of the transcriptional output of BMPs via Smad signaling. Furthermore, N-Shh was found to abolish adipocytic differentiation of C3H10T1/2 cells both in the presence or absence of BMP-2. A short treatment with N-Shh was sufficient to dramatically reduce the levels of the adipocytic-related transcription factors C/EBPalpha and PPARgamma in both C3H10T1/2 and calvaria cell cultures. Given the inverse relationship between marrow adipocytes and osteoblasts with aging, agonists of the Hh signaling pathway might constitute potential drugs for preventing and/or treating osteopenic disorders.
Abstract Aims In Guadeloupe, an island in the French West Indies, diabetes has a prevalence recently reported to be 10%. Myocardial ischaemia is more frequently silent in diabetics, and needs to be ...screened for and monitored, once identified. This study aimed to evaluate the prevalence of silent myocardial ischaemia (SMI) in a diabetic population and to analyze its associated cardiovascular risk (CVR) factors. Methods This was a cross-sectional study of 147 patients with associated CVR factors, defined according to the 2004 SFC/ALFEDIAM guidelines. Exercise stress tests, myocardial performance imaging and stress echocardiography were performed. Ancova and logistic regression were used in the statistical analyses. Results The patients’ mean age was 62 years, and 53% were male. Mean duration of diabetes was 14 years. Overall, 23.1% had SMI, and these patients more frequently had a personal history of cardiovascular disease vs those without SMI. On multivariate logistic-regression analyses, the adjusted odds ratios of SMI were significantly increased in patients with a personal history of cardiovascular disease (4.36, 95% CI: 1.36–13.96; P = 0.01) and left ventricular hypertrophy (LVH) (2.46, 95% CI: 1.03–5.86; P = 0.04). Conclusion The prevalence of SMI in our Afro-Caribbean diabetic population was 23.1%. Searching for a personal history of cardiovascular disease and LVH may help to identify patients who need to be screened for SMI.
Several members of the transforming growth factor- beta (TGF- beta ) superfamily have been demonstrated to play regulatory roles in osteoblast differentiation and maturation, but the mechanisms by ...which they act on different cells at different developmental stages remain largely unknown. We studied the effects of TGF- beta 1 and bone morphogenetic protein-2 (BMP-2) on the differentiation/maturation of osteoblasts using the murine cell lines MC3T3-E1 and C3H10T1/2. BMP-2 induced or enhanced the expression of the osteoblast differentiation markers alkaline phosphatase (ALP) and osteocalcin (OC) in both cells. In contrast, TGF- beta 1 was not only unable to induce these markers, but it dramatically inhibited BMP-2-mediated OC gene expression and ALP activity. In addition, TGF- beta 1 inhibited the ability of BMP-2 to induce MC3T3-E1 mineralization. TGF- beta 1 did not sensibly modify the increase of Osf2/Cbfa1 gene expression mediated by BMP-2, thus demonstrating that the inhibitory effect of TGF- beta 1 on osteoblast differentiation/maturation mediated by BMP-2 was independent of Osf2/Cbfa1 gene expression. Finally, it is shown that TGF- beta 1 does not affect BMP-2-induced Smad1 transcriptional activity in the mesenchymal pluripotent cells studied herein. Our data indicate that in vitro BMP-2 and TGF- beta 1 exert opposite effects on osteoblast differentiation and maturation.
Glass surfaces exhibit faster relaxation than the bulk at a constant temperature in the presence of either a liquid water or water vapor atmosphere. Permanent bending of glass fibers at temperatures ...lower than their glass transition temperatures in an atmosphere containing water vapor or in liquid water was attributed to and analyzed in terms of surface stress relaxation and the resulting surface residual stress. It was found that the fiber bending kinetics are controlled by water diffusion into the glass surface and that glasses with a faster transition crack velocity from region I (linear relation between logarithm of crack velocity and stress intensity factor) to the fatigue limit exhibited a faster rate of surface stress relaxation. It was suggested that this surface stress relaxation and resulting residual stress is the cause of various strengthening phenomena of glasses such as static fatigue limit and coaxing.
► Permanent bending kinetics of glass fibers were analyzed in terms of surfaces stress relaxation and residual stress. ► The fiber bending kinetics were found to be controlled by water diffusion into the glass surface. ► The surface stress relaxation and the resultant residual stress can be used for strengthening of glasses. ► This strengthening process can be used for thin specimens as well as for alkali-free glasses.
In the presence of water vapor, oxide glasses exhibit faster surface stress relaxation than bulk stress relaxation at a temperature below the glass transition temperature. When surface stress ...relaxation takes place in a glass under an applied stress, surface residual stress can develop upon the release of the applied stress. This phenomenon can be explored by studying the permanent bending of a fiber that is observed when a fiber is heat-treated in air under a bending load, and subsequently released from the bending load. Simple and accurate methods to evaluate the residual curvature in a bent fiber from two-point bending treatments were developed and applied to the bending of SiO2 glass optical fibers.
► Two point bending test is useful in evaluation of surface stress relaxation and resultant residual stress, which is affected by moisture. ► Radius of curvature of permanently bent fiber can be related to residual stress. ► Simple and accurate methods of evaluating the radius of curvature of two-point bent fiber were demonstrated.
To prevent surface damage, roughening, and wear of foil bearings during startup and shutdown conditions when speeds become insufficient to provide hydrodynamic air films, plasma-sprayed solid ...lubricant PS304 has been used as a journal coating. With increasing demands for operational bearing temperature, Rene 41 is one candidate material that may be considered as a replacement for current Inconel X-750 foil materials. In this study, the tribological behavior of plasma-sprayed PS304 coatings, as well as potentially smoother HVOF-sprayed PS304 coatings, was characterized against Rene 41 and Inconel X-750 counterfaces in thrust-washer tests. Tribological behavior of Rene 41 against plasma- and HVOF-sprayed PS304 coatings, and uncoated 13-8 stainless steel, at 538
°C was found to be equivalent to the high-temperature behavior of Inconel X-750 against the same surfaces. Typical wear factors found for the coatings were in 1.5–3
×
10
−4
mm
3/N
m range, while the coefficients of friction were generally about 0.4.
ABSTRACT
We assessed whether re-nutrition and weight gain have an influence on comorbid depression and anxiety in patients hospitalised for chronic eating disorders (ED). Seventy-five inpatients ...agreed to participate by completing the Eating Attitudes Test (EAT- 40), the Beck Depression Inventory (BDI-13), and the State-Trait Anxiety Inventory (STAI-Y) before, during and after three months of treatment. Patients suffering from either anorexia nervosa or bulimia nervosa successfully regained weight during treatment. This weight gain was accompanied by statistically significant reductions in ED symptoms. Anxiety and, to a lesser extent, depressive symptoms diminished, but remained at pathological levels, with between diagnostic subtype differences. Improvement of depressive (r=0.77) and anxiety (r=0.64) levels were significantly (p<0.001) and positively correlated with the reduction of eating attitudes (EAT). These results are discussed in the context of re-orienting the therapeutic strategies aimed at reducing emotional suffering in patients with ED.
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