Rapid Softening Research Articles

Rhizopus fruit Rot Caused by Rhizopus oryzae on Strawberry

Rhizopus fruit rot was observed on strawberry fruit (Fragaria x ananassa Duchesne) grown in a glass greenhouse at the Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, South Korea, from 2011 to 2013. Symptoms included water-soaking, rapid softening, and rotting. When these symptoms were left untreated, vigorous fungal growth was observed on the surface of infected fruits. Colonies on potato dextrose agar (PDA) at 30°C were white-cottony to brownish-black. Sporangia were globose, black, and 40–210 ㎛ in diameter. Sporangiophores were light-brown and 6–22 ㎛ in diameter. Sporangiospores were globose to oval, brownish, streaked, and 4–12 ㎛ in length. Columellae were light brownish gray, hemispherical, and 80– 120 ㎛ in diameter. To confirm the identity of the causal fungal pathogen, the complete internal transcribed spacer (ITS) ribosomal RNA gene region was amplified and sequenced. Based on these symptoms, mycological characteristics, pathogenicity tests on host plants, and molecular identification, the fungus was identified as Rhizopus oryzae Went & Prinsen Geerligs. This is the first report of Rhizopus fruit rot on strawberry caused by R. oryzae in Korea.

Low-cycle fatigue of Fe-20%Cr alloy processed by equal- channel angular pressing

Low-cycle fatigue properties were investigated on Fe-20%Cr ferritic stainless steel processed by equal channel angular pressing (ECAP). The Fe-20%Cr alloy bullets were processed for one to four passes via Route-Bc. The ECAPed samples were cyclically deformed at the constant plastic strain amplitude εpl of 5x10−4 at room temperature in air. After the 1-pass ECAP, low-angle grain boundaries were dominantly formed. During the low-cycle fatigue test, the 1-pass sample revealed the rapid softening which continued until fatigue fracture. Fatigue life of the 1-pass sample was shorter than that of a coarse-grained sample. After the 4-pass ECAP, the average grain size reduced down to about 1.5 μm. At initial stage of the low-cycle fatigue tests, the stress amplitude increased with increasing ECAP passes. At the samples processed for more than 2 passes, the cyclic softening was relatively moderate. It was found that fatigue life of the ECAPed Fe-20%Cr alloy excepting the 1-pass sample was improved as compared to the coarse-grained sample, even under the strain controlled fatigue condition.

Improving Storability of Fresh Strawberries with Controlled Release Chlorine Dioxide in Perforated Clamshell Packaging

Fresh strawberries have short shelf life because of rapid weight loss, softening, and decay. The objective of this research was to study the response of strawberries to ClO2 when applied to the fruit using a controlled release pad. Four experiments were conducted over 2011 to 2013. Strawberries were packed in perforated commercial clamshells, with or without ClO2 treatments, and stored at 1 and 6 °C for up to 14 days and at 10 and 20 °C for up to 7 days. The effect of ClO2 on strawberries was assessed by measuring decay incidence, weight loss, firmness, volatile composition, and stomate activity during storage. Chlorine dioxide treatments induced closing of stomata, markedly slowed weight loss and softening, and reduced decay incidence of strawberry fruit at 10 °C or lower temperatures, but not at 20 °C. Fruit flavor profiles were not affected by ClO2 treatment.

Microstructure, hardness evolution and thermal stability of binary Al-7Mg alloy processed by ECAP with intermediate annealing

A binary Al-7Mg alloy was processed by equal channel angular pressing (ECAP) at room temperature via route Bc, combined with intermediate annealing. After 6 passes, a high hardness of 218 HV is achieved. Transmission electron microscopy (TEM) observations demonstrate that ECAP leads to a significant grain refinement and ultrafine grains down to 100-200 nm are developed after 5 or 6 passes. X-ray diffraction (XRD) analysis indicates that the major part of Mg atoms are in solid solution in the deformed material, and the possible strengthening effect of Mg solute atom clusters or precipitates is neglected. The high hardness of the 6 pass-treated materials comes mainly from grain boundary strengthening, which contributes about 41% to the total strength, while dislocations and Mg solid solution contribute about 24% and 35% to the remaining strength, respectively. Also, the thermal stability of this severely deformed material was investigated by hardness measurements. The material is relatively stable when annealed at a temperature lower than 250 °C, while annealing at 300 °C leads to a rapid softening of the material.

Static Grain Growth in an Austenitic Stainless Steel Subjected to Intense Plastic Straining

The post-dynamic recrystallization of an ultrafine grained 304-type austenitic stainless steel was studied during annealing at 800 and 1000°C for 7.5 to 480 minutes. The initial ultrafine grained microstructures have been developed by continuous dynamic recrystallization during isothermal multidirectional forging to a total strain of ∼4 at temperatures ranging from 500 to 800°C. The post-dynamic recrystallization involves a rapid softening at early stage of annealing followed by a sluggish decrease of hardness upon further annealing. A transient recrystallization at early annealing stage results in somewhat heterogeneous microstructures in the samples subjected to previous deformation at relatively low temperatures of 500-600°C. This structural heterogeneity disappears with increasing the annealing time. Commonly, the post-dynamic recrystallization behavior can be considered as a kind of continuous recrystallization.

Cyclic Strain Resistance, Stress Response, Fatigue Life, and Fracture Behavior of High Strength Low Alloy Steel 300 M

The focus of this technical manuscript is a record of the specific role of microstructure and test specimen orientation on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of alloy steel 300 M. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure for both longitudinal and transverse orientations. Test specimens of the longitudinal orientation showed only a marginal improvement over the transverse orientation at equivalent values of plastic strain amplitude. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by gradual softening for a large portion of fatigue life before culminating in rapid softening prior to catastrophic failure by fracture. Fracture characteristics of test specimens of this alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be a combination of both brittle and ductile mechanisms. The underlying mechanisms governing stress response, deformation characteristics, fatigue life, and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of test specimen orientation, intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude, and response stress.

Influence of microstructure on strain-controlled fatigue and fracture behavior of ultra high strength alloy steel AerMet 100

In this paper, the results of a study aimed at understanding the specific role of microstructure on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of high strength alloy steel AerMet® 100 is presented and discussed. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by stability for large portion of fatigue life before culminating in rapid softening to failure at the lower cyclic strain amplitudes and intermediate cyclic strain amplitudes and resultant enhanced cyclic fatigue life. Fracture characteristics of test specimens of this high strength alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be essentially ductile with features reminiscent of locally occurring ductile mechanisms. The intrinsic microscopic mechanisms governing stress response, deformation characteristics, fatigue life and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude and concomitant response stress.

The Role of Net Development as a Barrier to Moisture Loss in Netted Melon Fruit (Cucumis melo L.)

The transpiration rate of cuticular membrane and fissures that comprise the netting on fruits of three netted melon cultivars, Life, Andesu, and Gurandoru, were measured during fruit development. Fissures in the equatorial region first developed vertically, then became interconnected by horizontal fissures as the fruit developed. Some cracks remained along the net, even at the fruit ripening stage, regardless of cultivar. Both lignified and suberized cell wall layers in the net tissues of the cultivar Life were thinner than those of the other cultivars, probably because of the shorter developmental period of fruits in the variety. Nevertheless, net transpiration rate did not differ significantly among cultivars at the fruit ripening stage. Peroxidase (POD) activity in the skin tissues of ‘Life’ was lower than that in ‘Andesu’ and ‘Gurandoru’ throughout fruit development and was not correlated with climacteric ethylene production. Among these cultivars, significantly higher ethylene production occurred in ‘Life’ fruit at the ripening stage. This can accelerate membrane permeability of hypodermal tissues, resulting in rapid fruit softening. Our results indicate that the net tissues of netted melons can be as waterproof as cutinized membranes if suberized cell wall layers with wax depositions develop below the net fissures at the fruit ripening stage.

Heart-Specific Stiffening in Early Embryos Parallels Matrix and Myosin Expression to Optimize Beating

In development and differentiation, morphological changes often accompany mechanical changes [1], but it is unclear whether or when cells in embryos sense tissue elasticity. The earliest embryo is uniformly pliable, while adult tissues vary widely in mechanics from soft brain and stiff heart to rigid bone [2]. However, cell sensitivity to microenvironment elasticity is debated based in part on results from complex three-dimensional culture models [3]. Regenerative cardiology provides strong motivation to clarify any cell-level sensitivities to tissue elasticity because rigid postinfarct regions limit pumping by the adult heart [4]. Here, we focus on the spontaneously beating embryonic heart and sparsely cultured cardiomyocytes, including cells derived from pluripotent stem cells. Tissue elasticity, Et, increases daily for heart to 1-2 kPa by embryonic day 4 (E4), and although this is ~10-fold softer than adult heart, the beating contractions of E4 cardiomyocytes prove optimal at ~Et,E4 both in vivo and in vitro. Proteomics reveals daily increases in a small subset of proteins, namely collagen plus cardiac-specific excitation-contraction proteins. Rapid softening of the heart's matrix with collagenase or stiffening it with enzymatic crosslinking suppresses beating. Sparsely cultured E4 cardiomyocytes on collagen-coated gels likewise show maximal contraction on matrices with native E4 stiffness, highlighting cell-intrinsic mechanosensitivity. While an optimal elasticity for striation proves consistent with the mathematics of force-driven sarcomere registration, contraction wave speed is linear in Et as theorized for excitation-contraction coupled to matrix elasticity. Pluripotent stem cell-derived cardiomyocytes also prove to be mechanosensitive to matrix and thus generalize the main observation that myosin II organization and contractile function are optimally matched to the load contributed by matrix elasticity.

Effects of hot water treatment on anthracnose disease in papaya fruit and its possible mechanism

Harvested papaya fruit are perishable due to rapid ripening and softening and susceptibility to biotic or abiotic stresses. Hot water treatment (HWT) can preserve fruit quality by reducing decay. The present study investigated effects of HWT on controlling fungal pathogens of papaya fruit and the possible mechanism by which HWT induced disease resistance. HWT (54°C, 4min) of papaya fruit had a pronounced effect on reducing the carrier rate of Colletotrichum gloeosporioides (C. gloeosporioides) in fruit peel, significantly inhibited the incidence of anthracnose and stem-end rot, effectively delayed fruit softening, but slightly promoted the rate of fruit coloring. HWT reduced the anthracnose index and fruit ripeness to a certain extent and induced changes in the wax arrangement on the surface of treated fruit, causing the wax to melt. The cracks and most stomata appeared to be partially or completely plugged by the melted wax, thereby providing a mechanical barrier against wound pathogens. HWT induced the expression of CpPGIP and promptly induced the expression of CpNPR1, and then regulated the expression of the CpPR1 gene, which may enhance the resistance of the fruit to anthracnose disease and reduce the decay rate. Together, these results confirm that HWT could reduce disease incidence and induce resistance, and thus maintain postharvest quality during storage and prolong the shelf-life of papaya fruit.

Dependence of dynamic strain ageing on strain amplitudes during the low-cycle fatigue of TP347H austenitic stainless steel at 550 °C

Low-cycle fatigue (LCF) tests are carried out on TP347H stainless steel at a strain rate of 8×10−3s−1 with total strain amplitudes (Δεt/2) of ±0.4% and ±1.0%, at room temperature (RT) and 550°C. It is found that the stress responses and dislocation structures under cyclic loading strongly depend on the value of strain amplitude at 550°C. Compared with those at the same strain amplitude at RT, the material shows a rapid strain softening, and finally attains a stabilized state at Δεt/2=±0.4% and 550°C, but the one presents an anomalous behavior, i.e., first a rapid hardening to the maximum stress, followed by a reducing softening at Δεt/2=±1.0% and 550°C. More cells resulting from dislocation cross-slip and planar structures due to dynamic strain ageing (DSA) restricting cross-slip develop at low strain amplitude of ±0.4% at the first cycle. However, there are more complicated dislocation structures, such as cells, elongated cells, walls/channels and planar structures at Δεt/2=±1.0%. The observations of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) exclude the effects of martensitic transformation, creep, oxidation, and precipitations on these stress responses and microstructure evolutions, which result from DSA appearing at 550°C.

Effects of Strain Rate on Low Cycle Fatigue Behaviors of High-Strength Structural Steel

The low cycle fatigue (LCF) behavior of a high-strength structural steel was investigated in the strain rate range of 4×10−5— 0. 12 s−1 (0. 001 — 3 Hz) under constant total strain (±1%) control. The cyclic stress response at all strain rates exhibited behavior of rapid softening in the early stage of fatigue life and subsequent saturation up to failure. It was found that the stress amplitude, the plastic strain amplitude, the plastic strain energy density and the fatigue life depend mainly on the strain rate. The strain rate of 0. 012 s−1 was found as a transition point where the LCF of the steel showed different behavior from low strain rate to high strain rate. The relationship between the time to failure and strain rate was expressed well by a power law relation. The fracture surfaces of the fatigue samples were characterized by using a scanning electron microscope (SEM) and the fracture mechanisms were discussed in terms of time-dependent deformation of the steel.

Identification of a β-galactosidase fruit pulp-specific promoter and its use in silencing constructs to reduce fruit softening in papaya

β-Galactosidases have been proposed as key hydrolytic enzymes involved in cell wall degradation and rapid softening during postharvest processing and storage of papaya. To genetically improve the shelf life of papaya, we identified a softening-related β-Gal gene in fruit pulp at the 50% pericarp yellowing stage and isolated a novel β-Gal promoter region. An online database search predicted that the core promoter motifs and cis-acting elements in the isolated sequence were related to phytohormones, particularly to ethylene and stress responsiveness. GUS staining revealed different patterns of transient GUS expression in papaya organs driven by the putative promoter, with the highest level in the fruit pulp followed by the embryo and the root. Further, such expression was wound inducible in vascular tissues. Co-transformation of the two T-DNAs was performed, mediated by Agrobacterium tumefaciens harboring a plant expression vector with the fruit pulp-specific promoter and an inverted repeat β-Gal cassette in one T-DNA and marker genes in the other T-DNA. A total of 24 regenerated plantlets were obtained, one of which was identified to be co-transformed using GUS staining, PCR assay and Southern blotting. Keywords : β-Gal, Carica papaya, fruit softening, gene silencing, marker-free transgenic plants, two-T-DNA transformation African Journal of Biotechnology Vol. 12(18), pp. 2427-2436

FORCED-AIR COOLING REDUCES 1-MCP APPLICATION DURATION ON PLUMS (PRUNUS SALICINA LINDL.) WITHOUT REDUCING EFFECTIVENESS

FORCED-AIR COOLING REDUCES 1-MCP APPLICATION DURATION ON PLUMS (PRUNUS SALICINA LINDL.) WITHOUT REDUCING EFFECTIVENESS

Hypersensitive Ethylene Signaling and ZMdPG1 Expression Lead to Fruit Softening and Dehiscence

‘Taishanzaoxia’ fruit rapid softening and dehiscence during ripening stage and this process is very sensitive to endogenous ethylene. In this study, we cloned five ethylene signal transcription factors (ZMdEIL1, ZMdEIL2, ZMdEIL3, ZMdERF1 and ZMdERF2) and one functional gene, ZMdPG1, encoding polygalacturonase that could loose the cell connection which associated with fruit firmness decrease and fruit dehiscence to illustrate the reasons for this specific fruit phenotypic and physiological changes. Expression analysis showed that ZMdERF1 and ZMdEIL2 transcription were more abundant in ‘Taishanzaoxia’ softening fruit and dehiscent fruit and their expression was inhibited by an ethylene inhibitor 1-methylcyclopropene. Therefore, ZMdERF1 and ZMdEIL2 expression were responses to endogenous ethylene and associated with fruit softening and dehiscence. ZMdPG1 expression was induced when fruit softening and dehiscence but this induction can be blocked by 1-MCP, indicating that ZMdPG1 was essential for fruit softening and dehiscence and its expression was mediated by the endogenously occurred ethylene. ZMdPG1 overexpression in Arabidopsis led to silique early dehiscence while suppressing ZMdPG1 expression by antisense ZMdPG1 prevented silique naturally opening. The result also suggested that ZMdPG1 related with the connection between cells that contributed to fruit softening and dehiscence. ZMdERF1 was more closely related with ethylene signaling but it was not directly regulated the ZMdPG1, which might be regulated by the synergic pattern of ethylene transcription factors because of both the ZMdERF1 and ZMdERF2 could interact with ZMdEIL2.

Shear bands evolution in ultrafine-grained aluminium under cyclic loading

The microstructural response and deformation mechanisms under cyclic and monotonic loading were investigated in a commercially pure Al subjected to grain refinement by cryorolling. A fatigue dependent shear banding and grain coarsening was detected and it was shown that pre-existing shear bands induced by cryorolling play a vital role in this regard. A rapid initial cyclic softening dominated by activation of pre-existing shear bands is replaced by a more gradual cyclic softening dominated by grain coarsening within these shear bands.

Cell wall structures leading to cultivar differences in softening rates develop early during apple (Malus x domestica) fruit growth

BackgroundThere is a paucity of information regarding development of fruit tissue microstructure and changes in the cell walls during fruit growth, and how these developmental processes differ between cultivars with contrasting softening behaviour. In this study we compare two apple cultivars that show different softening rates during fruit development and ripening. We investigate whether these different softening behaviours manifest themselves late during ethylene-induced softening in the ripening phase, or early during fruit expansion and maturation.Results‘Scifresh’ (slow softening) and ‘Royal Gala’ (rapid softening) apples show differences in cortical microstructure and cell adhesion as early as the cell expansion phase. ‘Scifresh’ apples showed reduced loss of firmness and greater dry matter accumulation compared with ‘Royal Gala’ during early fruit development, suggesting differences in resource allocation that influence tissue structural properties. Tricellular junctions in ‘Scifresh’ were rich in highly-esterified pectin, contributing to stronger cell adhesion and an increased resistance to the development of large airspaces during cell expansion. Consequently, mature fruit of ‘Scifresh’ showed larger, more angular shaped cells than ‘Royal Gala’, with less airspaces and denser tissue. Stronger cell adhesion in ripe ‘Scifresh’ resulted in tissue fracture by cell rupture rather than by cell-to-cell-separation as seen in ‘Royal Gala’. CDTA-soluble pectin differed in both cultivars during development, implicating its involvement in cell adhesion. Low pectin methylesterase activity during early stages of fruit development coupled with the lack of immuno-detectable PG was associated with increased cell adhesion in ‘Scifresh’.ConclusionsOur results indicate that cell wall structures leading to differences in softening rates of apple fruit develop early during fruit growth and well before the induction of the ripening process.

Cell wall disassembly and post-harvest deterioration of ‘sweetheart’ sweet cherry fruit: involvement of enzymic and non-enzymic factors

Sweet cherries are very perishable, owing to rapid softening rates associated to significant deterioration of fruit. Ripening-related firmness loss is generally attributed to enzyme-catalysed modifications in cell wall composition and structure, but some experimental evidence suggests that non-enzymic mechanisms may be also involved in the process. In this study, ‘Sweet Heart’ cherries were picked at commercial maturity and kept at 0 oC during 15 or 30 days, followed by up to 3 days at 20 oC to simulate commercial shelf life. Cell wall materials were extracted, fractionated and analysed, and some cell wall-modifying enzyme activities were assessed for a possible role on firmness loss and overall deterioration of fruit. Radical scavenging activity (RSA) and both reduced and oxidised ascorbate contents were also analysed in each case. Regression analysis revealed that firmness was associated to reduced ascorbate and RSA, in turn inversely correlated to decay and weight loss. Higher firmness levels were found for fruit displaying higher RSA and yields of the cell wall fractions containing covalently-bound pectins and hemicelluloses, while decay correlated inversely with RSA and reduced ascorbate content. Polygalacturonase (PG) and pectate lyase (PL) activities were related to solubilisation of cell wall pectins and inversely to reduced ascorbate, but not to firmness-contributing cell wall fractions, which correlated rather to enzyme activities acting on pectin side-chains that

Bending Deformability and Fracture Behavior of Heat-Treated 3-ply Cu/Al/Cu Clad Plates

The effect of heat treatment on the bending deformability and fracture behavior of roll-bonded Cu/Al/Cu clad plates were investigated. As-rolled clad plate and that annealed at 200OC exhibited the initial high load maintained for a short period and then a rapid drop of the load. The rapid softening promotes the continued localized bending once bending occurs because the work hardening due to the localized bending is negligible, leading to the localized fracture. Cu/Al/Cu clad metal annealed at 300OC, up to 450OC, initial load for bending decreased remarkably due to recovery/recrystallization, but work hardening occurred for an extended period before gradual softening took place. The initial extensive work hardening in the localized bent region tends to distribute the bending deformation uniformly, leading to the rather uniform bending. For annealed clad plates at high temperatures, the periodic cracks perpendicular to the interface were observed in the intermetallic layer and the localized slip developed both in Cu and Al emanating from the open cracks in the intermetallic layer. The localized slip marking was more evident in Cu than in Al, reflecting the lower stacking fault energy in Cu.

Composition and temperature-induced structural changes in lead–tellurite glasses on different length scales

Processes occurring at macroscopic and microscopic length scales across the glass transition (Tg) in lead–tellurite glass (PbO)x(TeO2)1−x (x = 0.1–0.3) are investigated using Brillouin and Raman spectroscopy, respectively. For all the samples, the temperature dependence of the longitudinal acoustic (LA) mode is found to exhibit a universal scaling below Tg and a rapid softening above Tg. The lower value of elastic modulus at a higher concentration of network modifier PbO, estimated from Brillouin data, arises due to loss of network rigidity. From quantitative analysis of the reduced Raman spectra, several modes are found to exhibit anomalous changes across Tg. Instead of the expected anharmonic behaviour, several modes exhibit hardening, suggesting stiffening of the stretching force constants with temperature, the effect being more pronounced in glasses with higher x. In addition, incorporation of PbO in the glass is also found to narrow down the bond-length distribution, as evident from the sharpening of the Raman bands. The stiffening of the force constants of molecular units at a microscopic length scale and the decrease of elastic constant attributed to loss of network rigidity on a macroscopic length scale appear to be opposite. These different behaviours at two length scales are understood on the basis of a microscopic model involving TeOn and PbO units in the structure.