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Many fruits are harvested at the early ripening stage and left to attain an edible stage during the post-ripening process or by ethylene treatment. However, the post-ripening quality of fruit is generally inferior to the quality of fruit that ripened naturally. Sugar metabolism plays critical roles in regulating fruit flavor and stress responses. Methyl Jasmonate (MeJA) treatment modulates sugar accumulations and postharvest fruit quality. However, the regulation mechanism of MeJA on sugar metabolism and its relationship with fruit post-ripening quality are unclear. The results indicated that MeJA-treated fruit possessed higher total antioxidant, lycopene and soluble solids content and lower electrical conductivity and malondialdehyde content. Besides, the post-ripening quality of fruit was strongly related to the starch and sucrose content. Compared to the control and ethephon treatments, MeJA treatment increased the activities and transcript levels of amylase, sucrose phosphate synthase (SPS) and sucrose synthase (SUS), but decreased the activities and transcript levels of acid invertase and neutral invertase. Further analysis suggested that the sucrose content had a strongly positive correlation with the activities and transcript levels of SUS and SPS, except SlSPS2. Thus, MeJA treatment improved fruit post-ripening quality by regulating sugar metabolism.

The phenol derivatives, as one kind of hormone, are analogous to endocrine disruptors with high carcinogenicity. The photocatalytic technology is an effective approach to mitigate environmental pollution by utilizing solar energy to degrade organic pollutants. In this work, CoPt hollow nanoparticles (NPs) attached to carbon nanotubes (CNTs) are employed to catalytically decompose the p-aminothiophenol (PATP) molecules under light irradiation, which is monitored by using surface-enhanced Raman scattering spectra. The effect of temperature on the catalytic efficacy of CoPt hollow NPs is investigated. Moreover, the use of CNTs coating on CoPt NPs is found to accelerate the photocatalytic degradation rate of PATP molecules, attributed to the enhanced plasmon-exciton coupling interaction of the CoPt/CNTs hybrid configuration.

The high-temperature wear properties of the gradient microstructure formed by ultrasonic impact treatment (UIT) on the surface of low-carbon steel are investigated. The dominant wear mechanism of the sample is oxidation wear and adhesive wear as the temperature increased from 300 °C to 500 °C. The wear mechanism of the sample changed from abrasive wear to fatigue wear as the applied load increased from 15 N to 95 N. The improvement in the high-temperature wear properties is due to the gradient nanocrystallization, which is helpful for forming an oxide film during wearing. As well as due to presence of the grain boundary wetting phase transitions of cementite, which can effectively delay the crack initiation.

Chilling acclimation and methyl jasmonate (MeJA) treatments are effective ways to alleviate chilling injury (CI) in postharvest fruit and vegetables. Soluble sugars can be used as an important energy substance, as well as an osmotic adjustment substance, participating in various stress responses in plants. However, the regulation mechanism of chilling acclimation and MeJA treatments on sugar metabolism remains unclear during the fruit response to chilling stress. In this study, tomato fruits were used to study the regulation of sugar metabolism during chilling resistance induced by 0.05 mM MeJA and 2 °C chilling acclimation treatments for 12 h and recovering at 25 °C for 6 h before being stored at 2 °C for up to 20 days. The results showed that both 2 °C and MeJA significantly induced chilling tolerance in tomato fruit, which was reflected by the decreased CI and malondialdehyde content, as well as the increased fruit color change and total antioxidant capacity. In addition, we found that 2 °C and MeJA promoted starch degradation and sucrose accumulation, but inhibited the increase of glucose and fructose contents. MeJA and 2 °C treatments enhanced the transcription levels of genes encoding amylase (AM), sucrose phosphate synthase (SPS), sucrose synthase (SuS) and neutral invertase (NI), while decreased the transcription level of gene encoding acid invertase (AI) during most of the storage periods. Further correlation analysis suggested that the chilling resistance of three groups of fruit was closely associated with sucrose content (r=−0.824 in control, r=−0.964 in 2 °C-treated fruit and r=−0.838 in MeJA-treated fruit); and the sucrose content of the fruit was positively correlated with SlSPS3 (r=0.681 in control, r=0.947 in 2 °C-treated fruit and r=0.889 in MeJA-treated fruit) and negatively correlated with SlAI (r=−0.954 in control, r=−0.921 in 2 °C-treated fruit and r=−0.637 in MeJA-treated fruit). In addition, in 2 °C-treated fruit, sucrose content was also correlated with the expression of a-AM (r=0.723), while in MeJA-treated fruit sucrose content was correlated with β-AM (r=0.694). These results suggested that 2 °C and MeJA treatments were both effective measures for enhancing the chilling resistance of tomato fruit by regulating sugar metabolism.

This study parsed the mechanism of SlMYC2 involving methyl jasmonate (MeJA)-mediated tomato fruit chilling tolerance. The data indicated that the application of MeJA significantly prevented chilling injury (CI) and inhibited the accumulation of hydrogen peroxide (H2O2) and superoxide anions (O2•−) in tomato fruit during cold storage. The accumulation of endogenous ascorbate (AsA) and glutathione (GSH) contents in fruit were enhanced by MeJA treatment resulting from increasing activities of enzymes related to AsA-GSH cycle. Meanwhile, the MeJA-treated fruit exhibited significantly higher expression levels of C-repeat-binding factor 1 (SlCBF1), cold regulated gene (SlCOR413) and inducer of SlCBF expression (SlICE1 and SlICEa), which belong to the SlICE-SlCBF-SlCOR (ICC) signaling pathway. However, the effects of MeJA were inhibited by the silence of SlMYC2. The expression levels of SlCBF1, SlCOR413, SlICE1 and SlICEa were reduced in SlMYC2-silenced fruits, and there was no significant difference in CI index and the indexes related to AsA-GSH cycle between (SlMYC2-silenced+MeJA)-treated fruit and control during most storage periods. In addition, correlation analysis indicated that the indexes involved in AsA-GSH cycle and ICC signaling pathway were closely related to the transcription of SlMYC2. Therefore, these results illustrated that SlMYC2 was involved in the regulation of ASA-GSH cycle and ICC signaling pathway mediated by MeJA during the cold tolerance of tomato fruit.

Chilling injury (CI) is a major limiting factor in the retention of the postharvest quality of chilling-sensitive vegetables and fruit stored at low temperatures. The enhanced chilling tolerance induced by methyl jasmonate (MeJA) treatment might be related to the polyamines biosynthesis. However, the molecular mechanism of polyamines biosynthesis induced by MeJA is far from clear. Here, we found that the application of 0.05 mmol L−1 MeJA enhanced the activities of arginase, arginine decarboxylase and ornithine decarboxylase, as well as the transcripts of SlARG1, SlARG2, SlADC and SlODC, promoted the accumulations of polyamines and further inhibited CI development. In addition, polyamines induced by MeJA were strongly positively correlated with the SlMYC2 expression level. Moreover, MeJA-induced polyamines biosynthesis was largely inhibited due to the silencing of SlMYC2. The (SlMYC2-silenced + MeJA)-treated fruit possessed higher incidence and index of CI than the MeJA-treated fruit. Combining these findings with results of the principal component analysis, we concluded that SlMYC2 is involved in MeJA-induced chilling tolerance in postharvest tomato fruit by regulating polyamines biosynthesis. Furthermore, the electrophoretic mobility shift and dual-luciferase reporter assays indicated that SlMYC2 could activate the transcription of SlARG1, SlARG2, SlADC and SlODC by binding directly to G/E-box elements in their promoters. From the findings, it was revealed that the targeted up-regulation of SlARG1, SlARG2, SlADC and SlODC by SlMYC2 is involved in MeJA-induced polyamines biosynthesis, which enhances chilling tolerance in tomato fruit.

The present research investigated the effect of loads on high-temperature wear behavior of carbon steel with gradient microstructure. The results demonstrated that the gradient grain refinement was obtained, with grain size ranging from 0.1 to 3 μm. An increase in the coefficient of friction and wear volume was observed with the load increased. The wear mechanism of the sample changed from oxidation wear to delamination wear, with the load increased from 15 N to 75 N. Moreover, under low loads, it was found that a continuous oxide film was formed on the gradient surface, which retained the favorable high temperature wear properties. However, under high loads, the gradient layer was completely penetrated, and the low binding strength between the oxide film and the matrix resulted in the initiation and propagation of cracks, thereby exhibiting a poor wear performance of the sample.

Para-aryl-dithiols (PADTs, HS-(C6H4)n-SH, n = 1, 2, and 3) have been used extensively in molecular electronics, surface-enhanced Raman spectroscopy (SERS), and quantum electron tunneling between two gold or silver nanoparticles (AuNPs and AgNPs). One popular belief is that these dithiols cross-link noble metal nanoparticles (NPs) as monolayer dithiolate spacers. Reported herein is our finding that PADTs predominantly exist as monothiolate forms on AuNPs or AgNPs. No PADT-induced NP cross-linking was observed regardless of the NP/PADT concentration ratios. Moreover, only one PADT thiol can be deprotonated even when PADTs are treated with concentrated NaOH or AgNO3 solutions. In contrast, 1,4-benzenedimethanethiol (HS-CH2-(C6H4)1-CH2-SH) and alkyl dithiol 1,2-ethanedithiol can be dithiolated on AuNPs and AgNPs, and in excess NaOH and AgNO3 solutions. This study should be of broad importance for plasmonic NP research given the popularity of PADTs in molecular electronics and SERS applications.

We review our developed visualization method of charge transfer (CT) for chemical enhancement mechanism on surface-enhanced Raman scattering (SERS) and tip-enhanced Raman spectroscopy (TERS). Firstly, we describe our visualization method of charge difference density, which provides direct visual evidence for photoinduced CT. And then, using the visualization method of CT, we interpreted the mechanism of SERS and TERS. Photoinduced charge transfer in the processes of SERS and TERS can be clearly seen. Our visualization method provides a visual and easy understanding way for the mechanism of SERS and TERS. Copyright (C) 2014 John Wiley & Sons, Ltd.

When stacking with various underlying layers in the microelectronics devices, titanium nitride electrode films are not only desired to meet the critical requirements for high conductivity and low surface roughness, but also to be deposited over a wide processing window. In this work, a negative substrate bias was introduced as an additional power for the reactive sputtering of titanium nitride films. Upon systematically adjusting the substrate bias, working pressure and substrate temperature, the evolution of film properties was studied in detail in terms of resistivity, growth rate, crystal structure, surface morphology and composition. It was shown that an optimized substrate bias is beneficial for film densification and grain reorientation. As a result, titanium nitride films with superior-performance (resistivity ≤ 53.2 μΩ·cm and surface roughness ≤0.66 nm) can be grown over a wide working pressure range of 0.3–1.1 Pa and substrate temperature range from room temperature to 350 °C.

Ferroelectricity in calcium doped hafnium oxide (Ca:HfO2) thin films has been experimentally proved for the first time in this work. All films prepared by chemical solution deposition exhibited smooth and crack-free surfaces, which were observed using an atomic force microscope. After 104 field cycling, a maximum remanent polarization of 10.5 μC/cm2 was achieved in HfO2 films with 4.8 mol. % Ca content. Meanwhile, the breakdown of the film occurred after 7 × 106 electric cycles. A phase transition from the monoclinic phase to cubic/orthorhombic phases was observed with increasing Ca concentration. We suggest the change in oxygen vacancy concentration as the origin of phase evolution, which was confirmed by X-ray photoelectron spectroscopy analysis. These results open a new pathway for realizing ferroelectricity in HfO2-based films.

Edible canna is a productive starch source in some tropical and semitropical regions. In these regions, water deficit stress is one of factors that limit the crop yield. In the present study, we investigated seven physiological indexes and photosynthetic responses of three edible canna (Canna edulis Ker.) cultivars (‘PLRF’, ‘Xingyu-1’, and ‘Xingyu-2’) under 35 days drought stress. Our results indicated that drought treatment caused visible wilting symptoms in all cultivars, especially in ‘Xingyu-1’. Coupled with the increase of wilting symptoms, relative water content (RWC) and chlorophyll content decreased progressively, malondialdehyde (MDA) content gradually increased, and key antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities increased first and then decreased in all three cultivars. The effect of water stress was more pronounced in ‘Xingyu-1’ than in ‘PLRF’ and ‘Xingyu-2’, and in lower leaves than in upper leaves. In addition, 35 days drought stress also significantly reduced the photosynthetic capacity. Consistent with antioxidant parameters, photosynthetic changes of ‘Xingyu-2’ were less than those of the other cultivars under water deficit stress. Drought stress caused a significant increase of water use efficiency (WUE) in ‘Xingyu-2’, but little in ‘PLRF’, and obvious decrease in ‘Xingyu-1’. These results indicated that ‘Xingyu-2’ was more tolerant to drought stress than ‘PLRF’ and ‘Xingyu-1’ by maintaining lower lipid peroxidation and higher antioxidant enzyme activities.

The influence of a static external electric field on surface-enhanced Raman scattering is investigated by calculating the Raman spectra and excited state properties of pyridine–Au20 complex with the density functional theory and time-dependent density functional theory method. The external electric field with orientation parallel (positive) or antiparallel (negative) to the permanent dipole moment is respectively applied on the complex. This field slightly changes the equilibrium geometry and polarizabilities, which results in shifted vibration frequencies and selectively enhanced Raman intensities. The changes of charge transfer (CT) excited states in response to the electric field are visualized by employing the charge difference densities. Further, the energy of charge transfer transition is tuned by electric field to be resonant or not with the incident light, leading to the Raman intensities are enhanced or not enhanced. At the same time, the intensities of vibration modes are sensitive to the orientation of the field. The positive electric field enhances the totally symmetric ring breathing mode (~1009 cm−1) but suppresses the trigonal ring breathing mode (~1051 cm−1). On the contrary, the mode at 1051 cm−1 is more enhanced than the mode at 1009 cm−1 when the negative electric field is applied on the complex. The Raman spectra could be modulated by tuning the strength and direction of the electric field. Copyright © 2013 John Wiley & Sons, Ltd.

The physiological responses of three edible canna cultivars (Canna edulis ker. cv. ‘PLRF’, ‘Xingyu-1’, and ‘Xingyu-2’) to continuous drought stress for 35 days were investigated by characterizing the water saturation deficit (WSD), relative electrical conductivity (REC), superoxidative radical content (SRC), ascorbic acid (AsA) content, glutathione (GSH) content and protein content. It was observed that WSD, REC, SRC progressively increased in the upper leaves of three cultivars under both control and drought treatments. The content changes of AsA, GSH and water soluble protein were lower in ‘Xingyu-2’ than in ‘Xingyu-1’ and ‘PLRF’, in upper leaves than in lower leaves. Compared with control, drought stress aggravated these physiological changes in all three cultivars. The correlation analysis showed that there were significant correlations between indexes except for protein content, which significantly correlated only with SRC. These indicated that drought stress directly led to water loss, and then the REC increased, while the GSH and AsA played major roles in removing the SRC. These results revealed that ‘Xingyu-2’ was more tolerant to drought stress than ‘PLRF’ and ‘Xingyu-1’ and the lower leaves were more sensitive than the upper leaves. The present study not only provides new insights into mechanisms of acclimation and tolerance to drought stress in edible canna but also provides clues for improving drought tolerance of edible canna through breeding or genetic engineering.

In this study, malondialdehyde (MDA), relative conductivity (RC), superoxide anion (O2·−), hydrogen peroxide (H2O2), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) as well as ascorbic acid (AsA), glutation (GSH) and carotenoid (Car) were analyzed in plants under drought condition to investigate the enzymatic and non-enzymatic antioxidant defense mechanisms of leaves and petals, respectively. Two different drought resistance marigold cultivars (Tagetes erecta L. cv. Chokdee and Tagetes erecta L. cv. Discovery) treated with 6-day drought stress were used at early flowering stage. Results indicated that drought treatment increased MDA, RC, O2·− and H2O2 contents in the two cultivars, especially in drought-sensitive cultivar ‘Discovery’. In contrast, ‘Chokdee’ had higher level antioxidative enzyme activities and more non-enzymatic antioxidants than those in ‘Discovery’. SOD, POD, CAT, APX activities and non-enzymatic antioxidants (GSH and AsA) in the leaves and petals were increased at the beginning treatment, and decreased later. The activity of CAT in leaves and petals, APX in petals and AsA in petals on day 6 after treatment were lower than those in control, while Car in the two cultivars decreased consistently during drought stress treatment. In addition, all the antioxidant enzyme activities in the leaves were higher than those in petals, but AsA and GSH were accumulated at lower levels in leaves than those in petals of the both cultivars. Furthermore, significant linear relationships were found between antioxidative enzymes and reactive oxygen species (ROS), as well as in non-enzymatic antioxidants and ROS. In conclusion, drought tolerance of ‘Chokdee’ was correlated with eliminating the O2·− and H2O2 and maintaining lower lipid peroxidation as well as higher membrane stability by increasing activities of antioxidative enzymes and the amount of non-enzymatic antioxidants. Furthermore, different drought response mechanisms were involved in leaves and petals of marigold under drought stress.

Intermolecular charge transfer (ICT) enhanced resonance Raman scattering of charge transfer complex is investigated experimentally and theoretically. The evidence for intermolecular charge transfer on resonance electronic transition is visualized with charge difference density. The resonant Raman spectra reveal that the intensity of Raman peaks are strongly enhanced on the order of 104, by comparing with the normal Raman scattering spectrum. ICT complexes can be used in fluorescence-, photoluminescence-, and electrochemistry-based techniques for sensing target molecules. These strong charge-transfer Raman peaks would enable discrimination of important target molecules from interferants that is normal Raman scattering for the isolated target molecules.

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) spectra of the 1,4-benzenedithiol molecule in the junction of two Au3 clusters have been calculated using density functional theory (DFT) and time-dependent DFT method. In order to investigate the contribution of charge transfer (CT) enhancement, the wavelengths of incident light are chosen to be at resonance with four representative excited states, which correspond to CT in four different forms. Compared with SERS spectrum, SERRS spectra are enhanced enormously with distinct enhancement factors, which can be attributed to CT resonance in different forms.

The absorption spectra of dianionic tetrocyanoethylene and dicationic tetrathiafulvalene chillers have been studied theoretically with the time-dependent density functional theory and the recently proposed Coulomb-attenuated model. The nature of the excited states was further explored by means of the two-dimensional (2D) site (transition density matrix) and three-dimensional (3D) cube (transition density and charge difference density) representations. By use of the 3D transition density and charge difference density, we visualized the orientation of transition dipole moment and also explained charge-transfer characteristics occurring in the dianionic/dicationic pi-dimers system. It is found that for the dianionic/dicationic pi-dimers system there exist two kinds of charge-transfer patterns for the mainly excited states, the intermolecular charge transfer and the mixture of intramolecular charge transfer coupled with intermolecular charge transfer. Meanwhile, the coupling effect of excition and the oscillation of electron-hole pairs between the monomers have been revealed with 2-D site representation of transition density matrix, which also indicates the electron-hole coherence upon photon excitation.

We investigate surface-enhanced Raman scattering (SERS) spectra of pyridine-Ag(n) (n = 2-8) complexes by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. In simulated normal Raman scattering (NRS) spectra, profiles of pyridine-Ag(n) (n = 2-8) complexes are analogical with that of isolated pyridine. Nevertheless, calculated pre-SERS spectra are strongly dependent on electronic transition states of new complexes. Wavelengths at 335 nm, 394.8 nm, 316.9 nm and 342.6 nm, which are nearly resonant with pure charge transfer excitation states, are adopted as incident light when simulating pre-SERS spectra for pyridine-Ag(n) (n = 2-8) complexes, respectively. We obtain enhancement factors from 10(3) to 10(5) in pre-SERS spectra compared with corresponding NRS spectra. The obvious increase in Raman intensities mainly result from charge transfer resonance Raman enhancement. A charge difference densities (CDDs) methodology is adopted in describing chemical enhancement mechanism. This methodology aims at visualizing charge transfer from Ag(n) (n = 2-8) clusters to pyridine on resonant electronic transition, which is one of the most direct evidences for chemical enhancement mechanism.

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag(2)-PATP and PATP-Au(2)) and the two junctions (Ag(2)-PATP-Au(2) and Au(2)-PATP-Ag(2)) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 10(2). We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S(1) electronic transition energy of complexes and junctions. Ag(2)-PATP-Au(2) and Au(2)-PATP-Ag(2) junctions yield higher Raman intensities than those of Ag(2)-PATP and PATP-Au(2) complexes, especially for b(2) modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.