Softening Changes Research Articles

Intermittent stepwise cooling and warming ameliorate chilling injury and improve quality in postharvest ‘Guifei’ mango fruit

Chilling injury (CI) has been a major factor restricting the commercial distribution of mango fruit. In this study, an innovative technology termed intermittent stepwise cooling and stepwise warming (ICW) was employed to investigate its effect on CI in mango fruit by evaluating ripening- and cold tolerance-related parameters. Results showed that ICW exposure maintained normal ripening in mango fruit during refrigeration at 5 °C and subsequent shelf storage at 20 °C, as manifested by increased ethylene production and respiration rate and accelerated changes in softening, color, soluble solid content, titratable acidity and chlorophyll and carotenoid contents. ICW inhibited increases in electrolyte leakage rate (ELR) and production of reactive oxygen species (O2−. And H2O2) and malondialdehyde (MDA). ICW resulted in higher activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), while promoting more accumulation of total phenolics, flavonoids, ascorbic acid and glutathione. In addition, the expressions of genes (MiICE1, MiCBF1 and MiCOR413) encoding cold-responsive factors were upregulated in response to ICW. These physio-biochemical changes conferred by ICW contributed to enhanced cold tolerance and reduced CI in mango fruit. The results indicate that ICW application could be a potential strategy for postharvest refrigeration of ‘Guifei’ mango fruit.

Interplay between H-bonding proton dynamics and Fe valence fluctuations in Fe3(PO4)2(OH)2 at high pressure

We pressure tune the hydrogen bond in Fe-O--H\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}O-P structural segments of mixed-valence barbosalite $({\mathrm{Fe}}^{2+}{\mathrm{Fe}}_{2}^{3+}){(\mathrm{P}{\mathrm{O}}_{4})}_{2}{(\mathrm{OH})}_{2}$. Infrared spectroscopy evidences changes in softening of O--H stretch modes and excessive profile broadening onset below 10 GPa. Single-crystal x-ray diffraction shows pseudosymmetrization of the original monoclinic unit cell concurs with these changes in the O--H vibrational mode. These are considered compelling indicators of proton delocalization onset below 10 GPa as hydrogen bonds are strengthened under pressure. Subsequently in the range $10\ensuremath{-}30$ GPa, Fe M\"ossbauer spectroscopy discerns ${\mathrm{Fe}}^{2+}\ensuremath{\Leftrightarrow}{\mathrm{Fe}}^{3+}$ valence fluctuations at proximate cations of the hydrogen bonds. When the original crystal potential at an ${\mathrm{Fe}}^{2+}$ site is perturbed by proton delocalization at a ligand, electron exchange is induced along ${\mathrm{Fe}}^{2+}\ensuremath{\rightarrow}L\ensuremath{\rightarrow}{\mathrm{Fe}}^{3+}$ pathways [ligand $L=\mathrm{O}$ or ${(\mathrm{OH})}^{\ensuremath{-}}$ of shared octahedral faces]. Thus, $({\mathrm{Fe}}^{2+}{\mathrm{Fe}}_{2}^{3+}){(\mathrm{P}{\mathrm{O}}_{4})}_{2}{(\mathrm{OH})}_{2}$ under pressure exemplifies the interplay between proton (THz) and electron (MHz) dynamics on two disparate timescales in the same condensed phase.

Improving the nutraceutical value of mango during ripening by postharvest irradiation with blue LEDs via enhancing of antioxidant enzyme activities

SummaryLight‐emitting diodes (LEDs) are emerging as a clean technology for improving the postharvest preservation of fruits. Mangoes were irradiated with blue LEDs (75 µmol s‐1 m−2) and then stored for 15 days. The fruit quality, including the content of antioxidant compounds and activities of antioxidant enzymes, was evaluated during storage. The treatment with blue LEDs delayed the changes associated with the senescence processes, including the changes in softening, weight loss, total soluble solids content, and titratable acidity. Treatment also caused increases in the antioxidant capacity (1.33‐fold), ascorbic acid (1.69‐fold), total phenolic (1.33‐fold), flavonoids (1.50‐fold), and carotenoids content (1.18‐fold) compared to control. At the end of storage, blue LEDs treatment maintained higher phenylalanine ammonia‐lyase (1.28‐fold), peroxidase (1.58‐fold), catalase (2.21‐fold), and ascorbate peroxidase (1.51‐fold) activities. Our findings indicate that blue LEDs might be a potential elicitor that modulates oxidative homeostasis and improves the antioxidant and nutritional status of mango by enhancing the activity of antioxidant enzymes.

Investigation on Hot Compression Precipitation and Recrystallization Behavior of 23.7Cr–2.2Ni–1.3Mo–14Mn–0.26N High‐Manganese Low‐Nickel Duplex Stainless Steel

Isothermal compression deformation studies for 23.7Cr–2.2Ni–1.3Mo–14Mn–0.26 N low‐nickel duplex stainless steel (DSS) are investigated under deformation conditions of 800–1150 °C/0.01–10 s−1. The flow curve and deformation microstructure analysis show that deformation softening changes from ferrite dynamic recrystallization (DRX) to austenite DRX, with increasing temperature from 800 and 900 °C to 1050 °C deformed at 0.01–1 s−1. The sigma (σ) precipitate formation is mainly affected by the interaction of deformation temperature and strain rate. In addition to deformation time controlled by strain rate, the refining microstructure of ferrite DRX accelerates σ precipitate formation due to the increase in diffusion channels deformed at 900 °C/0.01 s−1 and 900 °C/1 s−1. The hot deformation activation energy is calculated as 367.03 kJ mol−1, and the relationship between the critical conditions for DRX initiating and Zener–Hollomon parameters is established. The decreasing Z value contributes to deformation softening at low strain, and the DRX softening effect is enhanced deformed at 800–900 °C/0.01–0.1 s−1. Meanwhile, the modified dynamic crystallization kinetics model of tested DSS at a strain rate of 1 s−1 is established.

Learning the deformation mechanism of poly(vinylidine fluoride-co-chlorotrifluoroethylene): an insight into strain-induced microstructure evolution via molecular dynamics.

Learning the micro-mechanisms of fluorinated polymers during mechanical response is more difficult than that of common polymers due to the unique intrinsic characteristics of the fluorine element. In this paper, we applied molecular dynamics simulations to study deformation mechanisms of poly(vinylidine fluoride-co-chlorotrifluoroethylene) during uniaxial tension. We analyzed the variations of individual energy components and structural distribution curves versus strain in addition to the commonly used stress-strain curves and microstructure evolutions during stretching. The elastic limit is ɛ = 0.02, ɛ = 0.06 is the yield point, ɛ = 0.24 is the termination of the softening, necking occurs at 0.24 < ɛ < 0.5, strain hardening occurs at 0.5 < ɛ < 2.6, and ɛ = 2.6 is the damage or brake point. The elastic behavior of the material does not rely on strain rate, the obvious effect of strain rate can be seen at the yield region and strain softening region, and the stress values are not influenced by strain rates at the softening and hardening stages. Overall, total potential energy is mainly correlated with non-bonded energy, and the proportion of ΔEcoul overwhelms all the others. The energy components are ordered: ΔEcoul > ΔEvdwl > > ΔEangle > ΔEdihed > ΔEbond. The chain conformation at yield point is almost unchanged compared with the pre-stretching conformation. The chain conformations at the end of strain softening changes more obviously than that at yield point. The molecular chains maintain random coil structure before strain hardening, and switch into a stretch chain conformation gradually during strain hardening. The maximum change in bond angle during the stretching process is F-C-H, the largest change in bond length is the C-Cl bond, and the largest change in dihedral angle is H-C-C-H. The change of non-bonded interaction in the poly(VDF-co-CTFE) system is much larger than the bonding interaction, and the main factor affecting bonding interaction is the change of angles. Graphical abstract Poly(vinylidine fluoride-co-chlorotrifluoroethylene) during tensionᅟ.

Treatment with Focused Ultrasound Waves Softens the Rat Cervix During Pregnancy

Application of focused ultrasound stimulation (FUS) to the rat cervix during pregnancy has significant physiologic effects. One-millisecond-long pulses of 680-kHz ultrasound with a repetition frequency of 25 Hz, at ISPTA (spatial-peak, temporal-average intensity) of 1, 2 and 4W/cm2, were applied to the rat abdomen over the cervix. FUS produced a significant change in cervical elasticity known as softening, which is part of the ripening process, comparable to the degree seen just before delivery. Timed-pregnant Sprague-Dawley rats (n = 40) were used. During gestation, the FUS system was applied to the cervix for variable times up to 1 h. Daily measurements of cervix light-induced florescence were made to estimate changes in softening. In addition, cervical stretch estimates of softening were made of isolated cervices of control and FUS-treated rats to measure distensiblity. The ultrasound power with ISPPA (spatial-peak, pulse-average intensity) of 40 W/cm2 was considered tolerable; the U.S. Food and Drug Administration regulatory limit is 190 W/cm2 for both the body periphery and the fetus. This is the first report of alterations induced by ultrasound in the connective tissue of the cervix and suggests the therapeutic application of ultrasound for the facilitation of labor and delivery.

Elastic and anelastic relaxations accompanying magnetic ordering and spin-flop transitions in hematite, Fe2O3

Hematite, Fe2O3, provides in principle a model system for multiferroic (ferromagnetic/ferroelastic) behavior at low levels of strain coupling. The elastic and anelastic behavior associated with magnetic phase transitions in a natural polycrystalline sample have therefore been studied by resonant ultrasound spectroscopy (RUS) in the temperature range from 11 to 1072 K. Small changes in softening and attenuation are interpreted in terms of weak but significant coupling of symmetry-breaking and non-symmetry-breaking strains with magnetic order parameters in the structural sequence . The transition at TN = 946 ± 1 K is an example of a multiferroic transition which has both ferromagnetic (from canting of antiferromagnetically ordered spin moments) and ferroelastic (rhombohedral → monoclinic) character. By analogy with the improper ferroelastic transition in Pb3(PO4)2, W and W′ ferroelastic twin walls which are also 60° and 120° magnetic domain walls should develop. These have been tentatively identified from microstructures reported in the literature. The very low attenuation in the stability field of the C2/c structure in the polycrystalline sample used in the present study, in comparison with the strong acoustic dissipation reported for single crystal samples, implies, however, that the individual grains each consist of a single ferroelastic domain or that the twin walls are strongly pinned by grain boundaries. This absence of attenuation allows an intrinsic loss mechanism associated with the transition point to be seen and interpreted in terms of local coupling of shear strains with fluctuations which have relaxation times in the vicinity of ∼10−8 s. The first order (Morin) transition occurs through a temperature interval of coexisting phases but the absence of an acoustic loss peak suggests that the relaxation time for interface motion is short in comparison with the time scale of the applied stress (at ∼0.1–1 MHz). Below the Morin transition a pattern of attenuation which resembles that seen below ferroelastic transitions has been found, even though the ideal low temperature structure cannot contain ferroelastic twins. This loss behavior is tentatively ascribed to the presence of local ferromagnetically ordered defect regions which are coupled locally to shear strains.

Evolution of Spin-Wave Excitations in Ferromagnetic Metallic Manganites

Neutron scattering results are presented for spin-wave excitations of three ferromagnetic metallic A1-xA'xMnO3 manganites (where A and A' are rare- and alkaline-earth-metal ions), which when combined with previous work elucidate the systematics of the interactions as a function of carrier concentration x, on-site disorder, and strength of the lattice distortion. The long-wavelength spin dynamics show only a very weak dependence across the series. The ratio of fourth to first neighbor exchange (J4/J1) that controls the zone boundary magnon softening changes systematically with x, but does not depend on the other parameters. None of the prevailing models can account for these behaviors.

Effect of heat treatment on changes in softening, pectic substances and activities of polygalacturonase, pectinesterase and β-galactosidase of ripening mango

Summary The relationship between softening, pectic substances, polygalacturonase (EC 3.2.1.15), pectinesterase (EC 3.1.1.11) and β-galactosidase (EC 3.2.1.23) during ripening of heated and non-heated mango (Mangifira indica L.) fruits cv. Nam Dokmai was investigated. Fruit softening was accompanied by a progressive increase in water-soluble and ammonium oxalate-soluble pectin and a progressive decrease in alkali-soluble pectin. Polygalacturonase and β-galactosidase activities increased while pectinesterase activity decreased continuously during softening. Heating fruits for 3 days at 38 °C resulted in an increase in softening, ammonium oxalate-soluble pectin and activity of β-galactosidase, and a decrease in alkali-soluble pectin and activities of polygalacturonase and pectinesterase, while heating had no pronounced effect on water-soluble pectin. Softening of ripening mango fruits was more closely related to changes in β-galactosidase activity than to polygalacturonase and pectinesterase activities. The possibility that softening of Nam Dokmai fruits is affected by mechanisms other than involvement of only polyglacturonase and solubilization of the polygalacturonide backbone of the pectin is discussed.

Nonlinear Magnetic Response of Superconducting Flux Arrays with Random Pinning

The static nonlinear magnetic response of randomly pinned flux-line lattice in a type-II superconductor has been investigated using variational replica-symmetry-broken method. A peak in the curve of susceptibility as a function of external magnetic field is found. When the magnetic field is low, there is a softening in the susceptibility as an effect of pinning potential with nonzero correlation length. At some critical magnetic field, the softening changes into hardening. After reaching the maximum in hardening, the susceptibility decreases to its value of pure states with the increase of magnetic field.

Pectin Changes in the Ripening of Irradiated and Stored Strawberries

SUMMARY: Strawberries of the “Red Gauntlet” variety picked at two different stages of maturation were irradiated with a 60Co source at 200 krads. After irradiation the fruits were stored in a refrigerated cell at a temperature varying from 0 to 3°C and at a R.H. between 85‐90%. During the storage a part of the control berries was irradiated at different times to find out differences in irradiation response at successive stages of ripeness in storage conditions. The effects of irradiation on the pectic substances, pectinmethylesterase activity and anthocyanin content were investigated. In addition, changes in softening and extent of fungal growth were followed. A different response of strawberries irradiated at two different stages of ripeness was found. The different ripeness in storage conditions also influences the radiation response of the strawberries. The possible practical applications of these findings are discussed.

LXXVII.A critical study of the hardness behaviour of duralumin

Synopsis The peculiar hardening and softening changes which occur in heat-treated duralumin have been investigated by means of Meyer (ball-test) analysis. A true “precipitation” process has thus been made evident in certain heat-treatments of duralumin; but, in addition, this alloy is shown to be capable of a different type of behaviour. The hardening at temperatures between 15° C. and approximately 200° C. after quenching is of this latter type, which in some ways resembles a mild strain-hardening process. X-ray and cold-rolling tests have also been made, and the age-hardening process has been discussed.