Subsequent Softening Research Articles

Can Henna Prevent Ulceration in Diabetic Feet at High Risk?

Diabetic foot infections are one of the most dreadful and costly complications of diabetes. Efforts have recently focused on preventive measures. The balance of moisture in the neuropathic foot is critical and challenging. Whilst the interdigital areas should be kept dry to prevent maceration and subsequent softening and thinning of the skin other areas of the foot should be managed for optimal moisture to avoid dry skin and resulting cracks. Oftentimes, the primary cause of infection is a breakdown of skin integrity. Several factors may cause a break in healthy skin, however some parts of the foot, notably the interdigital area, are more prone to compromise. The interdigital area, which usually provides entrance points for infectious agents, is a rather closed environment and may therefore be subject to more moisture than any other part of the foot. Excess moisture may in turn cause maceration which increases the likelyhood of skin breakdown and microbial colonisation and invasion. Indeed, it has been shown that the skin in interdigital areas of the diabetic patients has higher PH levels which promotes susceptibility to candidal infections [1]. Many products have been developed for the protection of skin integrity. Topical henna is an extract of the lawsonia plant. Some experimental and clinical studies have reported antibacterial and antifungal effectiveness and wound healing activity of this product [2–4]. Henna is an easily accessible, inexpensive product which, to our best knowledge, has not been studied so far in the diabetic foot at risk. The henna extract may be prepared by mixing 1 gr of powdered leaves to 10 mL of distilled water which will subsequently be applied to the interdigital space. It is then kept wrapped with a dressing for 4–6 hours before it is washed. This procedure will provide a long-term barrier against moisture in the problematic interdigital area (1 to 3 months) and thus will not require frequent application. Henna may also improve wound healing in fissures and cracks in diabetic feet. As prevention is of paramount importance, studies should focus more on intensive preventive strategies that are promising in maintaining healthy skin. In this context, henna could be a valuable, inexpensive, and readily accessible product that does not require frequent application to maintain skin integrity in the interdigital area.

Macro versus micro-scale constitutive models in simulating proportional and nonproportional cyclic and ratcheting responses of stainless steel 304

A recent study by Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] demonstrated that some of the nonproportional ratcheting responses under stress-controlled loading histories cannot be simulated reasonably by two recent cyclic plasticity models. Two major drawbacks of the models identified were: (i) the stainless steel 304 demonstrated cyclic hardening under strain-controlled loading whereas cyclic softening under stress-controlled loading, which depends on the strain-range and which the existing models cannot describe; (ii) the change in biaxial ratcheting responses due to the change in the degree of nonproportionality were not simulated well by the models. Motivated by these findings, two modified cyclic plasticity models are evaluated in predicting a broad set of cyclic and ratcheting response of stainless steel 304. The experimental responses used in evaluating the modified models included both proportional (uniaxial) and nonproportional (biaxial) loading responses from Hassan and Kyriakides [Hassan, T., Kyriakides, S., 1994a. Ratcheting of cyclically hardening and softening materials. Part I: uniaxial behavior. Int. J. Plasticity, 10, 149–184; Hassan, T., Kyriakides, S., 1994b. Ratcheting of cyclically hardening and softening materials. Part II: multiaxial behavior. Int. J. Plasticity, 10, 185–212.] and Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] The first model studied is a macro-scale, phenomenological, constitutive model originally proposed by Chaboche et al. [Chaboche, J.L., Dang-Van, K., Cordier, G., 1979. Modelization of the strain memory effect on the cyclic hardening of 316 stainless steel. In: Proceedings of the Fifth International Conference on SMiRT, Div. L, Berlin, Germany, L11/3.]. This model was systematically modified for incorporating strain-range dependent cyclic hardening–softening, and proportional and nonproportional loading memory parameters. The second model evaluated is a polycrystalline model originally proposed by Cailletaud [Cailletaud, G., 1992. A micromechanical approach to inelastic behavior of metals. Int. J. Plasticity, 8, 55–73.] based on crystalline slip mechanisms. These two models are scrutinized against simulating hysteresis loop shape, cyclic hardening–softening, cross-effect, cyclic relaxation, subsequent cyclic softening and finally a broad set of ratcheting responses under uniaxial and biaxial loading histories. The modeling features which improved simulations for these responses are elaborated in the paper. In addition, a novel technique for simulating both the monotonic and cyclic responses with one set of model parameters is developed and validated.

Cell wall disassembly during papaya softening: Role of ethylene in changes in composition, pectin-derived oligomers (PDOs) production and wall hydrolases

Cell wall disassembly in ripening climacteric fruit is a highly complex process where ethylene plays a crucial role. Ethylene inhibitors can be used to explore the changes in the cell wall matrix and cross-linked polysaccharides in ethylene-regulated processes. The results of applying the ethylene receptor blocking inhibitor 1-methylcyclopropene (1-MCP) and the ethylene-releasing compound ethephon (2-chloroethylphosphonic acid) indicate that softening of ‘Maradol’ papaya fruit is dependent on ethylene. When fruit were induced to ripen extensively by exposure to a high dose of ethephon, 1-MCP inhibited the subsequent softening dramatically, but when inhibition of the ethylene response was caused by application of 1-MCP, subsequent fruit treatment with ethephon promoted extensive loss of galactose from the water-soluble polysaccharides, but this was not accompanied by fruit softening. The cell wall changes accompanying normal fruit softening were pectin solubilization and polyuronide depolymerization and these processes occurred simultaneously. Polygalacturonase likely is responsible for the ripening-associated changes in ‘Maradol’ papaya fruit texture and pectin polymer integrity. An increase in extractable fruit polygalacturonase follows the increased presence of pectin-derived oligosaccharides.

Modulation of host cell mechanics by Trypanosoma cruzi

To investigate the effects of Trypanosoma cruzi on the mechanical properties of infected host cells, cytoskeletal stiffness and remodeling dynamics were measured in parasite-infected fibroblasts. We find that cell stiffness decreases in a time-dependent fashion in T. cruzi-infected human foreskin fibroblasts without a significant change in the dynamics of cytoskeletal remodeling. In contrast, cells exposed to T. cruzi secreted/released components become significantly stiffer within 2 h of exposure and exhibit increased remodeling dynamics. These findings represent the first direct mechanical data to suggest a physical picture in which an intact, stiff, and rapidly remodeling cytoskeleton facilitates early stages of T. cruzi invasion and parasite retention, followed by subsequent softening and disassembly of the cytoskeleton to accommodate intracellular replication of parasites. We further suggest that these changes occur through protein kinase A and inhibition of the Rho/Rho kinase signaling pathway. In the context of tissue infection, changes in host cell mechanics could adversely affect the function of the infected organs, and may play an important role on the pathophysiology of Chagas' disease.

Effect of initial microstructure on plastic flow behaviour during isothermal forging of Ti–10V–2Fe–3Al

The plastic flow behaviour and microstructural development during isothermal forging was determined for near beta alloy Ti–10V–2Fe–3Al. Two different initial microstructures were employed: (i) a beta forged billet with a large prior beta grain size with Widmanstätten alpha platelets; and (ii) an alpha–beta forged billet with prior globular primary alpha. The beta forged condition exhibited a peak stress followed by intense flow softening, which is attributed to the break up of the Widmanstätten alpha platelets. Evidence suggests that peak hardening at low strains is due to dislocation pile-ups at alpha platelet/subgrain beta interfaces and subsequent flow softening is attributed to the transmission of beta phase through the alpha platelets. A strain rate ‘jump’ test investigation provided sufficient evidence to suggest that there is a transition from dislocation dominant deformation mechanisms at high strains rates to diffusional dominant deformation at low strain rates in Ti–10V–2Fe–3Al during forging.

Formulation of a new single crystal law for modeling the cyclic softening

The present paper proposes to modify the single crystal law [Hoc, T., Forest, S., 2001. Polycrystal modelling of IF-TI steel under complex loading path. Int. J. Plast. 27, 65–85] used in polycrystalline model developed by [Pilvin, P., 1990. Approches multiéchelles pour la prévision du comportement anélastique des métaux. Ph.D. Thesis, Université Pierre et Marie Curie; Cailletaud, G., 1992. A micromechanical approach to inelastic behavior of metals. Int. J. Plast. 8, 55–73], in order to account for the cyclic softening observed in some metallic materials during fully reversed low-cycle fatigue tests under total strain control. Experimental observations [Mayama, T., Sasaki, K., 2006. Investigation of subsequent viscoplastic deformation of austenitic stainless steel subjected to cyclic preloading. Int. J. Plast. 22, 374–390] show that the cyclic softening is partially due to a rearrangement of dislocations in hard and soft zones within the grains during cyclic straining. We propose thus to modify the initial single crystal law by including a composite model of hard and soft zones on each slip system within a grain. The softening is modeled through the evolution of soft zones. The model is applied to a FCC polycrystal. The self-consistent scheme is used in order to obtain the polycrystalline macroscopic behavior. The results show that the new model correctly describes an initial cyclic hardening, a subsequent cyclic softening and finally a stabilized state.

Microstructural Evaluation of Friction Stir Processed AZ31B-H24 Magnesium Alloy

The microstructural characteristics in an AZ31B-H24 magnesium alloy after friction stir processing (FSP) were examined. The effects of FSP parameters including forge force and traverse speed on the microstructure were evaluated. It was observed that the grain size increased from about 4 μm in the base metal to about 8 μm at the centre of the stir zone after FSP. The aspect ratio of the grains decreased towards the centre of the stir zone. The changes in the grain size and shape resulted in a drop in micro-indentation hardness from 75 HV in the base metal to about 55 HV at the centre of the stir zone. Increasing the forge force or decreasing the traverse speed increased the grain size due to a greater heat input. It was also observed that the annealing effects (recrystallization and subsequent softening) of FSP were less pronounced with increasing distance horizontally or vertically from the pin tool due to the presence of temperature gradient. Furthermore, the Hall-Petch type relationships between the microhardness and the grain size were found to be valid after FSP.

Microstructural Evaluation of Friction Stir Processed AZ31B-H24 Magnesium Alloy

The microstructural characteristics in an AZ31B-H24 magnesium alloy after friction stir processing (FSP) were examined. The effects of FSP parameters including forge force and traverse speed on the microstructure were evaluated. It was observed that the grain size increased from about 4 μm in the base metal to about 8 μm at the centre of the stir zone after FSP. The aspect ratio of the grains decreased towards the centre of the stir zone. The changes in the grain size and shape resulted in a drop in micro-indentation hardness from 75 HV in the base metal to about 55 HV at the centre of the stir zone. Increasing the forge force or decreasing the traverse speed increased the grain size due to a greater heat input. It was also observed that the annealing effects (recrystallization and subsequent softening) of FSP were less pronounced with increasing distance horizontally or vertically from the pin tool due to the presence of temperature gradient. Furthermore, the Hall-Petch type relationships between the microhardness and the grain size were found to be valid after FSP.

Ethylene regulation of fruit softening and cell wall disassembly in Charentais melon

Cell wall disassembly in ripening fruit is highly complex, involving the dismantling of multiple polysaccharide networks by diverse families of wall-modifying proteins. While it has been reported in several species that multiple members of each such family are expressed in the same fruit tissue, it is not clear whether this reflects functional redundancy, with protein isozymes from a single enzyme class performing similar roles and contributing equally to wall degradation, or whether they have discrete functions, with some isoforms playing a predominant role. Experiments reported here sought to distinguish between cell wall-related processes in ripening melon that were softening-associated and softening-independent. Cell wall polysaccharide depolymerization and the expression of wall metabolism-related genes were examined in transgenic melon (Cucumis melo var. cantalupensis Naud.) fruit with suppressed expression of the 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene and fruits treated with ethylene and 1-methylcyclopropene (1-MCP). Softening was completely inhibited in the transgenic fruit but was restored by treatment with exogenous ethylene. Moreover, post-harvest application of 1-MCP after the onset of ripening completely halted subsequent softening, suggesting that melon fruit softening is ethylene-dependent. Size exclusion chromatography of cell wall polysaccharides, from the transgenic fruits, with or without exogenous ethylene, indicated that the depolymerization of both pectins and xyloglucans was also ethylene dependent. However, northern analyses of a diverse range of cell wall-related genes, including those for polygalacturonases, xyloglucan endotransglucosylase/hydrolases, expansin, and beta-galactosidases, identified specific genes within single families that could be categorized as ethylene-dependent, ethylene-independent, or partially ethylene-dependent. These results support the hypothesis that while individual cell wall-modifying proteins from each family contribute to cell wall disassembly that accompanies fruit softening, other closely related family members are regulated in an ethylene-independent manner and apparently do not directly participate in fruit softening.

Influence of Md-ACS1 allelotype and harvest season within an apple germplasm collection on fruit softening during cold air storage

Previous studies have demonstrated a relationship between Md-ACS1 allelotype and apple fruit softening at ambient temperatures. The present study was undertaken to further examine the influence of this allelotype ( -1/1, -1/2 or -2/2) and its interaction with harvest season (early or late) on changes in internal ethylene concentrations (IEC) and fruit softening during cold air storage. This was carried out by describing natural differences found among old apple cultivars/species and modern commercial cultivars. For late maturing cultivars, Md-ACS1-1/1 was firmer at harvest than Md-ACS1-2/2 with the heterozygote intermediate. However harvest firmness showed no differences among for the early season Md-ACS1 allelotypes. The Md-ACS1-2/2 allelotype had a slower rate of postharvest IEC increase and flesh softening compared with Md-ACS1-1/1 and -1/2 allelotypes, and late maturing cultivars had a slower rate of fruit softening than early maturing cultivars, which was independent of postharvest IEC. All three late season allelotypes and early season Md-ACS1-2/2 were firmer after storage than early season Md-ACS1-1/1 and -1/2 allelotypes, reflecting differences in both harvest firmness and softening rates . While cultivar variation in final firmness could be explained partially through Md-ACS1-mediated postharvest ethylene increases and subsequent softening, much more variation was accounted for by their differences in harvest firmness. These results are discussed in relation to strategies for breeding cultivars with superior flesh textures that are maintained during storage.

相互干渉亀裂進展解析の高度化―岩盤内の均質化亀裂進展（第３報）―

Analysis of the pure mode I crack propagation (KII = 0) from tips of compressible joints in rock is improved by a minute computation of internal stresses in the joints, which takes a compressibility of joint and a dilatational overall sliding on joint surface into consideration. The Stress Compensation-Displacement Discontinuity Method (SC-DDM) is successfully applied to evaluate not only the internal stresses but also the stress intensity factors (KI, KII) at tips of propagating open cracks. It is firstly confirmed that the open crack propagates, describing a smooth curve, to the direction of the maximum compressive pressure applied at infinity. Subsequently the critical applied pressure to realize the critical state of KI = KIC is presented as a function of the crack elongation, and it is clarified, as a significant effect of interactive crack propagation, that the critical pressure has a maximum, and that the maximum critical pressure decreases with decreasing the joint spacing. Thus it is discussed that the quasi-brittle crack propagation in rock consists of a toughening process and a subsequent softening process, and that the maximum critical pressure appears at the transition from the toughening to the softening. Moreover, it is discussed the present improved method is a promising scheme available for the positive analysis of the critical pressure-crack elongation curve and the prediction of the strength characteristics of rock, including the delayed fracture, the effect of confining pressure and so on.

In situ neutron diffraction study of the low cycle fatigue of the α−γ duplex stainless steel

In duplex stainless steels, significant thermal stresses are generated during the cooling from the homogenization temperature due to different thermal expansion coefficients of the austenitic and ferritic phases. The results of the in situ neutron diffraction examination of the evolution of the internal stresses during the low cycle fatigue in the SAF 2507 duplex stainless steel are reported. Stress response of both constituent components resulting from the load sharing between austenitic and ferritic grains was measured. It was found that the initial thermal residual stresses were relaxed rapidly at the beginning of the cyclic loading. Whereas initial hardening was identified in both phases, the subsequent fatigue softening was fully attributed to the austenitic phase.

Microstructural length-scale effects in the nanoindentation behavior of thin gold films

Nanoindentation experiments have been conducted on thin gold films of varying thickness and grain size in an effort to study the effects of microstructural length scales on indentation plasticity. We show that the deformation of epitaxial and coarse-grained films is characterized by Hertzian elastic loading, followed by discrete displacement bursts and subsequent softening with increasing depth of indentation. In contrast, the loading response of fine-grained films is continuous, and characterized by elastic–plastic behavior from the earliest stages of indentation, and gradual hardening with increasing indentation depth. We argue that these different behaviors are closely related to the mechanisms of plasticity initiation. Homogeneous dislocation nucleation at theoretical shear stresses is required for indentation into dislocation-free, single-crystalline volumes while grain boundaries provide a ready source for dislocations in fine-grained films. This picture of indentation plasticity is additionally supported by observations of grain boundary proximity effects on the critical load at which plasticity commences.

Monitoring of firmness evolution of peaches during storage by combining acoustic and impact methods

Firmness is a very important quality property in peach. The storage of peach affects its subsequent softening process and shelf life. The temperature and duration of storage mainly influence the firmness of stored fruit, and monitoring the evolution of fruits enables producers to manage its commercial life. The objective of the present study was to use non-destructive acoustic and impact tests to estimate firmness of peaches and to elucidate the influence of storage temperature and of time on the softening process of peach. Continuous and classification models based on variables obtained from non-destructive methods were developed. Parameters obtained from non-destructive methods were compared to destructive reference tests. The maximum force in ball compression correlated well with the maximum acceleration from impact test ( r 2 = 0.75), and with a band magnitude parameter from acoustic test ( r 2 = −0.71). Combining impact and acoustic parameters, the multiple correlation coefficient increases up to 0.91 (adjusted R 2 = 0.82) in the prediction of the maximum force in ball compression. Classification models based on both non-destructive parameters and sorting peaches into two classes of firmness, showed scores of well classified higher than 90%.

Effect of Strain Rate on the Subsequent Softening and Precipitation Kinetics in a Nb-Microalloyed Steel

The influence of strain rate on the subsequent softening kinetics has been investigated for a Nb-containing steel using stress relaxation. It was found that strain induced precipitation during static recrystallisation was enhanced with an increase in strain rate, resulting in an obvious plateau in the stress relaxation curve and a marked retarded softening. At the higher strain rate, since dynamic precipitation is suppressed during deformation, more solute Nb is left for the subsequent strain induced precipitation after deformation. The stress relaxation data were supported by grain size measurements and TEM observations. A significant influence of strain rate on the recrystallised grain size was not observed for longer annealing times after deformation, indicating that strain induced precipitation lost its retarding effect due to coarsening of precipitates. Clearly, care should be taken when extrapolating softening kinetics measured after deformation at low strain rates to softening kinetics at industrial rolling conditions.

Apple (Malus domestica) softening in the postharvest coolchain: Effects of delayed cooling and shelf‐life temperatures

‘Royal Gala’ and ‘Cox's Orange Pippin’ apples (Malus domestica) soften rapidly after harvest, resulting in poor fruit quality after extended periods of storage and transportation. This study sought to characterise the effects of delayed cooling, intermittent warming, and exposure to shelf‐life temperatures on softening of these cultivars during postharvest handling. Rapid cooling of freshly harvested fruit to cold‐storage temperatures delayed the onset of rapid softening and improved the firmness market life of both cultivars. Fruit transferred temporarily from 0.5–3°C to ambient temperatures (10–20°C) were softer once returned to 0.5–3°C, an effect exacerbated by increased temperature and duration of the break in the coolchain. Storage temperature and duration did not affect subsequent softening rates of either cultivar at 20°C. Softening rates, derived from constant temperature treatments, were able to describe softening in fruit treated with stepwise changes in temperature, indicating that rate of softening at a given temperature was not affected by prior exposure to temperatures between 0.5 and 20°C. Results from this research could be used to develop models that estimate softening of both cultivars during postharvest handling.

Inheritance and expression of fruit texture melting, non-melting and stony hard in peach

Fruit ethylene production and flesh firmness were measured in F 1 and F 2 offsprings from a cross of a non-melting cultivar ‘Nishiki’ and a stony hard cultivar ‘Yumyeong’ of peach ( Prunus persicaBatsch). Fruits from genotypes that showed no natural ethylene production were treated with 1000 ppm ethylene and subsequent flesh softening was observed. Genotypes of melting and non-melting in stony hard fruits could be distinguished by the degree of softening following exogenous ethylene treatment. The stony hard trait was inherited independently of the melting flesh/non-melting flesh trait and was epistatic to this trait.

Re‐assessing 21st century risk: 21st century trends in risk management — board level decisions set the agenda

There are a number of trends clearly detectable in the UK markets that have the potential to change radically the approach of major and medium sized companies to insurance. Although some of these have been caused by the substantial increases in premiums triggered by the recent hard market, there are clear signs that these trends are becoming institutionalized, and are thus likely to continue despite any subsequent softening of the market.

Instability and localization of deformation in lower crust granulites, Minas fault zone, Nova Scotia, Canada

Abstract Blocks of granulite from within the megabreccia at Clarke Head, Nova Scotia, Canada contain extremely well preserved mylonitic and ultramylonitic textures developed in mineral assemblages for which thermobarometic calculations have indicated temperatures and pressures between 700–860 °C and 750–950 MPa. Deformation within these rocks is characterized by localization at several discrete length scales associated with the development of new microstructures comprising finer-grained material. Mylonitized granulite exhibits dislocation creep microstructures, with development of intense S-C fabrics and shear bands during the transition to ultramylonite. Dynamically recrystallization of plagioclase can be followed through progressive grain size reduction to about 5 μm, but there remain extensive zones with grains less than 1 μm in diameter. Localization of the these finest-grained ultramylonites occurs by transient frictional events associated with the introduction of partial igneous melts and formation of pseudotachylyte which produces abrupt decreases in grain size that cannot arise during dislocation mediated grain size reduction. The heterogeneous response of these rocks demonstrates the importance of considering characteristic length scales when assigning evidence from the rock record (e.g. palaeopiezometry) to bulk behaviour of the lithosphere. Associated with the localization of strain and subsequent strain softening is the observation that microstructures formed during the event that initiated the instability can be an obliterated by ductile flow. In instances where critical components of the microstructural evolution are known to have been largely overprinted, it becomes possible to reconcile contradictions in the rock record, such as production of ultra-fine-grained superplastic aggregates in what otherwise appears to be a dominantly dislocation creep regime.

Topography of the crust–mantle interface under the Western Superior craton from gravity data

The Moho undulations beneath the western part of the Archean Superior Province have been investigated with a three-dimensional gravity inversion algorithm for a single interface of constant density contrast. Inversion of the complete gravity data set produces unreal effects in the solution due to the ambiguity in the possible sources of some crustal gravity anomalies. To avoid these effects a censored gravity data set was used instead. The inversion results are consistent with reflection and refraction seismic data from the region and, therefore, provide a basis for the lateral correlation of the Moho topography between parallel seismic lines. The results indicate the existence of a major linear east–west-trending rise of the Moho below the metasedimentary English River subprovince, which is paralleled by crustal roots below the granite–greenstone Uchi and Wabigoon subprovinces. This correlation between the subprovincial structure at the surface and deep Moho undulations suggests that the topography of the crust–mantle boundary is related to the tectonic evolution of the Western Superior belts. Although certain features of the crust–mantle boundary are likely inherited from the accretionary and collisional stages of the Western Superior craton, gravity-driven processes triggered by subsequent magmatism and crustal softening may have played a role in both the preservation of those features, as well as in the development of new ones.