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The bending strength of silicon nitride (Si3N4) plays a vital role in its application and is influenced by various process factors. Current experimental methods for investigating Si3N4 ceramics exhibiting low efficiency and high cost are incapable of systematically analysing the effect of process factors on the bending strength of Si3N4 ceramics and quantitatively predicting the optimum process parameters. In this study, machine learning (ML) approaches based on extreme gradient boosting (XGBoost) were applied to predict and analyse the bending strength of Si3N4 ceramics. Because the classification model of XGBoost is easily interpretable, the factors affecting the bending strength could be quantitatively evaluated. The current model can provide a suitable order of adding sintering additives to obtain excellent bending strength in Si3N4 ceramics. Although this study focuses on the bending strength of Si3N4 ceramics, the new approach reported herein is applicable for the in silico design and analysis of other ceramic materials.

The status of oxygen impurity in β-Si3N4 lattice and its impact on β-Si3N4 phonon spectrum were studied using the first principle calculation based on density functional theory. The dependence of in silico thermal conductivity of β-Si3N4 upon lattice oxygen was quantitatively addressed. This study also confirms that rare-earth La doping has a pinning effect on oxygen, which underlies, in mechanism, for the increase of thermal conductivity of β-Si3N4 ceramic by restraining oxygen diffusion inside β-Si3N4 lattice. The theoretical prediction above is consistent in trend with the reported experimental results. In addition, in silico modulus values of β-Si3N4 ceramic were also revealed declined with increasing oxygen impurity.

Wampee fruit is a popular fruit cultivar in South‐East Asia due to its high levels of nutrients and antioxidants; however, pericarp browning leads to a short storage life with great economic loss during years. The purpose of this work was to determine whether postharvest ethanol fumigation affected pericarp browning development of wampee fruit during 12 days of storage at 8 ± 0.5°C, and if so, how it is related to phenol metabolism and how it affects quality attributes and antioxidant systems during storage. After fruits were fumigated with 100, 300, 500, and 800 μl/L for 5 hr at 22 ± 0.5°C, ethanol significantly reduced the development of pericarp browning by increasing total phenolics (TP) content and decreasing the activity of polyphenol oxidase (PPO), especially in 500 μl/L ethanol treatment. Additionally, ethanol delayed the losses in fruit firmness (FF), soluble solid content (SSC), and titratable acidity (TA), retarded weight loss and accumulation of malondialdehyde (MDA) content and maintained relatively high contents of ascorbic acid (AsA), total flavonoids (TF), and total antioxidant capacity (TAC) and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). In conclusion, results demonstrated that postharvest ethanol fumigation in wampee fruit has ability to reduce pericarp browning development by regulating phenol metabolism and enhancing antioxidant systems., Ethanol fumigation reduced the development of pericarp browning; ethanol fumigation delayed the losses in firmness, the degradation of TSS, TA, and VC of wampee fruit. Ethanol fumigation maintained high contents of AsA, TF, and TAC and activities of SOD, CAT, POD in wampee fruit.

Lanthanide fluorescence nanoprobe is versatile in multicolor cell imaging, although it still faces a great challenge in improving its luminescent efficiency. Herein, we validated the feasibility of lanthanide ions co-doped gadolinium phosphate nanocrystals serving as a safe, effective and color-tunable fluorescence probe for live cell imaging. Well-crystallized hexagonal phase GdPO4 nanoparticles with multi-morphologies such as nanowires, nanorods, tetragonal nanocubes and hexagonal nanoprisms were synthesized via a typical hydrothermal method. We have systematically investigated the synthesis of different morphologies of GdPO4 nanoparticles through adjusting their processing parameters. The nanoparticles can gain a bright color-tunable photoluminescence from red, orange, yellow to green region when the GdPO4 nanoparticles are co-doped with Eu3+ and Tb3+ ions. The Tb3+ doping significantly enhances the characteristic 4f → 4f transitions of Eu3+ owing to a specific cross-relaxation process from Tb3+ to Eu3+ ions; the mechanism underlying the cross relaxation was exposited in detail. Further biological experiments in vitro proved that the prepared nanoprisms could exhibit a favourable biocompatibility with negligible toxicity. The current investigation manifests a high potential of the nanoparticles applicable to fluorescence imaging probe for live cells.

Early diagnosis of diseases by contrast-enhanced magnetic resonance imaging (MRI) using iron oxide superparamagnetic nanoparticles (IOSNPs) has been extensively investigated due to the good biocompatibility of modified IOSNPs. However, the low magnetic sensitivity of IOSNPs still inflicts a certain limitation on their further application. In this study, we employed first-principles calculations based on spin-polarized density functional theory (SDFT) to find the optimal dysprosium-doped scheme for improving the magnetic sensitivity of IOSNPs. Elicited from the optimal doping scheme, we synthesized a sort of ultrasmall γ-iron oxide superparamagnetic nanoparticle by a special phase transfer-coprecipitation method. The appropriately Dy-doped γ-IOSNPs coated with short-chain polyethylene glycol are small in hydrodynamic size and highly dispersed with effectively improved superparamagnetism for enhancing T2-weighted MRI relaxivity, which is well consistent with the SDFT prediction. The measured spin-spin relaxivity r2 is 123.2 s-1 mM-1, nearly double that of the pure γ-IOSNPs (67.8 s-1 mM-1) and substantially surpassing that of both clinically-approved T2 contrast agents Feridex and Resivist. The low dysprosium doping does not induce notable nanotoxicity for IOSNPs, but contributes sufficiently to their high relaxation performance instead, which endows the Dy-doped γ-IOSNPs with high potential as a better T2-weighted MRI contrast medium. Both the method and the nanomagnets reported in this study are expected to promote studies on designing and preparing high-performance MRI contrast agents as well as computational materials.

Rapid pericarp browning is the leading factor for quality deterioration and marketing decline of litchi fruit. In the present study, litchi fruit was treated with phenolic compounds, proanthocyanidin, p-coumalic acid, chlorogenic acid, apple polyphenol, and tea polyphenol, before being stored at 20°C for 10 d. Phenolic compound treatment delayed pericarp browning and weight loss, reduced respiration rate, and maintained high total acid levels and vitamin C content in litchi fruit. Subsequently, the key antioxidant characteristics were determined to evaluate the effects of phenolic compounds on the antioxidant system during pericarp browning. The phenolic compound-treated fruit exhibited higher levels of antioxidant enzymes, anthocyanins, total phenols, flavonoids, and antioxidant capacity, as well as a lower superoxide radical production rate and polyphenol oxidase and peroxide activities during whole-fruit storage than the control. Of the five treatments, proanthocyanidin application produced the most significant effects; therefore, this may be the best method for inducing antioxidant system-related factors, enhancing antioxidant capacity, and delaying pericarp browning in litchi.

Herein, hollow-structured Gd2O3:RE3+/Yb3+ (RE = Er, Ho, Tm) nanoparticles (NPs) were prepared via a urea-based chemical coprecipitation method followed by subsequent calcination and etching. Under 980 nm near-infrared (NIR) irradiation, upconversion (UC) emission gains the highest intensity of red, green and blue peaks for Gd2O3:Er3+/Yb3+, Gd2O3:Ho3+/Yb3+ and Gd2O3:Tm3+/Yb3+ NPs respectively. The corresponding fluorescence in-cell images exhibit bright visible light. The continuous color-tunable UC emission of each spectrum was investigated by increasing the concentration of the sensitizer Yb3+ ions from 0 to 20 mol% with the most intense red, green and blue emission achieved. The structure, morphology, components and magnetic property of Gd2O3:Ho3+/Yb3+ NPs were investigated intensively. The results show that the NPs possess a distinctly hollow structure and uniform spherical shape, and are well-crystallized and highly monodispersed with a mean diameter of 118 nm. Due to the designed hollow structure which is of benefit to water contact of a large number of Gd3+ on the surface, the measured T1 relaxivity of the NPs is nearly 5 times larger than the relaxivity of the commercial gadolinium diethylenetriaminepentaacetate (Gd-DTPA). The relaxation enhancement in the hollow-structured Gd2O3:RE3+/Yb3+ (RE = Er, Ho, Tm) NPs is addressed in the framework of Solomon–Bloembergen–Morgan theory. The biocompatibility studies in 293 and HeLa cells indicate that the hollow NPs have no observable cytotoxicity at a concentration up to 200 μg ml−1. All these results demonstrate that the hollow-structured nanocomposite has the potential to be developed into a safe and highly efficient magnetic resonance and fluorescence nanoprobe for in-cell molecular imaging of cancer.

The longitudinal surface plasmon resonance of light-irradiated gold nanorods (Au NRs) is generated to enhance the local electric fields of Au NR-based nano-dumbbells (NDs), tailored specifically by coating mesoporous silica at two poles of Au NRs and embedding photosensitizer indocyanine green (ICG) into the mesopores. The assembled NDs possess a superior uniformity and water dispersity with a strong plasmonic absorption around 800 nm. Time-domain finite-difference calculations indicate that the enhanced local electric field of NDs is predominantly distributed in the dumbbells at two poles of Au NRs, which improves the photonic performance of ICG significantly. Illuminated by an 800 nm laser, the fabricated NDs demonstrate an enhanced combination of photothermal and photodynamic effects in comparison to either Au NRs or ICG alone. Synergistic damaging of photothermal and photodynamic combination to nasopharyngeal carcinoma cells has been corroborated experimentally, thus causing substantial cell death under a lower incident near-infrared laser power. This study concludes that the plasmonic NDs combined synergistically with efficient photothermal and photodynamic effects are highly promising in cancer therapy.

The structural stability and electronic and magnetic properties of stoichiometric (Gd2O3)n clusters with n = 1–10 were investigated using spin-polarized density functional theory through the broken-symmetry approach. Size-induced changes in the point symmetry of these clusters were observed. A large coordination number led to elongation of Gd–O bonding. Either adding an electron to or removing an electron from the ground state of a neutral cluster brought significant changes in the van der Waals volume for clusters n = 1–3. Binding energy increased with cluster size. However, the highest occupied molecular orbital–lowest unoccupied molecular orbital gap, ionization, and electron affinity fluctuated when n increased from 1 to 10. Natural population analysis and partial density of states revealed that the Gd-4f orbital hardly participated in bonding and that the Gd-5d/6s/6p orbitals were hybrid with the O-2p orbitals. The competition between Ruderman–Kittel–Kasuya–Yosida-type and superexchange-type interact...

Manipulation of upconversion (UC) emission is of particular importance for multiplexed bioimaging. Here, we precisely manipulate the UC color output by utilizing the phonon-assisted energy back transfer (EBT) process in ultra-small (sub-10 nm) Gd2O3:Yb(3+)/Er(3+) UC nanoparticles (UCNPs). We synthesized the Gd2O3:Yb(3+)/Er(3+) UCNPs by adopting the laser ablation in liquid (LAL) technique. The synthesized Gd2O3:Yb(3+)/Er(3+) UCNPs are small spherical and monoclinic structures. Continuous color-tunable (from green to red) UC fluorescence emission is achieved by increasing the concentration of Yb(3+) ions from 0 to 15 mol%. A phonon-assisted energy back transfer (EBT) process from Er(3+) ((4)S3/2 → (4)I13/2) to nearby Yb(3+) ((2)F7/2 → (2)F5/2), which can significantly enhance red emission at 672 nm and decrease green emission, is responsible for the color-tunable UC emission by increasing the Yb(3+) concentration in Gd2O3:Yb(3+)/Er(3+) UC nanoparticles.

In this study, four bi-modal core-shelled contrast agents of SiO2(FITC)@Gd2O(CO3)2·H2O with varying shell thicknesses but the same cores have been prepared via a two-step wet chemistry method. The four samples were quite close to sphericity and their averaged diameters were 127, 140, 148.7 and 174.0 nm. The composition of their shells was also examined. As the shell thickness increased, the fluorescence intensity halved but the longitudinal relaxivity remained high (28, 29, 27, 24 mM−1 s−1). The measured relaxivities of the samples were more than 5.8 times higher than the relaxivity of Gd-DTPA-BMA in a 0.55 T MR (magnetic resonance) system. The levels of cytotoxicity were tested on four cell lines (293, HeLa, HFL1, MCF-7) and the results indicated that the samples were safe. The intracellular fluorescence in HeLa cells was clearly observed using laser confocal microscopy. These results showed that this material had potential for application in MR-fluorescence bi-modal imaging.

We report a class of multi-functional core–shell nanoarchitectures, consisting of silica nanospheres as the core and Gd2O3:Dy3+ nanocrystals as the ultra-thin shell, that enable unique multi-color living cell imaging and remarkable in vivo magnetic resonance imaging. These types of targeted cell imaging nanoarchitectures can be used as a variety of fluorescence nanoprobes due to the multi-color emissions of the Gd2O3:Dy3+ nanophosphor. We also proposed a strategy of modulating core–shell structure design to achieve an enhanced magnetic resonance contrast ability of Gd2O3 nanoagents, and the classical Solomon–Bloembergen–Morgan theory was applied to explicate the mechanism underlying the enhancement. The as-synthesized ligand-free nanomaterial possesses a suitable particle size for cellular uptake as well as avoiding penetrating the blood–brain barrier with good water-solubility, stability, dispersibility and uniformity. The extremely low cytotoxicity and favorable biocompatibility obtained from in vitro and in vivo bioassays of the as-designed nanoparticles indicate their excellent potential as a candidate for functioning as a targeted nanoprobe.

Yingying Shen,1,2,* Yuanzhi Shao,3,* Haoqiang He,1 Yunpu Tan,4 Xiumei Tian,2 Fukang Xie,2 Li Li11Imaging Diagnostic and Interventional Center, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China; 2Department of Histology and Embryology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China; 3Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou, Guangdong, China; 4Department of Gastrointestinal Surgery, Sun Yat-sen University, Guangzhou, Guangdong, China *These authors contributed equally to this workAbstract: We investigated the tracking potential of a magnetic resonance imaging (MRI) probe made of gadolinium-doped mesoporous silica MCM-41 (Gd2O3@MCM-41) nanoparticles for transplanted bone mesenchymal stem cells (MSCs) and neural stem cells (NSCs) in vivo. The nanoparticles, synthesized using a one-step synthetic method, possess hexagonal mesoporous structures with appropriate assembly of nanoscale Gd2O3 clusters. They show little cytotoxicity against proliferation and have a lower effect on the inherent differentiation potential of these labeled stem cells. The tracking of labeled NSCs in murine brains was dynamically determined with a clinical 3T MRI system for at least 14 days. The migration of labeled NSCs identified by MRI corresponded to the results of immunofluorescence imaging. Our study confirms that Gd2O3@MCM-41 particles can serve as an ideal vector for long-term MRI tracking of MSCs and NSCs in vivo.Keywords: nanoparticles, gadolinium, magnetic resonance imaging, stem cells

Introduction . Rambutan (Nephelium lappaceum L.) is a kind of tropical fruit with high commercial value in international trade. However, harvested rambutan fruits suffer from a short shelf life and show rapid postharvest deterioration problems due to spintern browning and flesh decay. Materials and methods . Rambutan fruit (cv. ‘Baoyan 5’) were harvested in 2009 and 2010. Changes in some chemical components and the physiology of fruits were investigated at different storage temperatures (25 °C and 10 °C) and with different packing materials (regular low-density polyethylene and anti-moisture polyethylene bags). Results and discussion . Changes in the development of the browning index, and contents of total soluble solids, titratable acidity and vitamin C greatly decreased during low temperature storage (10 °C); moreover, low temperature storage (10 °C) could maintain a significantly higher level of superoxide dismutase activity and lower values of malondialdehyde and cell membrane permeability. The effects of packing material were different according to the different storage temperatures. At 10 °C, the beneficial effects of anti-moisture polyethylene bags on fruit quality and physiology were observed. However, at 25 °C, fruit packed with regular low-density polyethylene proved to be of better quality than those packed with anti-moisture polyethylene bags. Conclusion . The overall results suggest that packing with anti-moisture polyethylene bags and storage at 10 °C were the most suitable conditions to maintain quality and to extend the storage life of rambutan fruit.

We study in silico the influence of host tissue inhomogeneity on tumor cell proliferation and diffusion by simulating the mobility of a tumor on percolation clusters with different homogeneities of surrounding tissues. The proliferation and diffusion of a tumor in an inhomogeneous tissue could be characterized in the framework of the percolation theory, which displays similar thresholds (0.54, 0.44, and 0.37, respectively) for tumor proliferation and diffusion in three kinds of lattices with 4, 6, and 8 connecting near neighbors. Our study reveals the existence of a critical transition concerning the survival and diffusion of tumor cells with leaping metastatic diffusion movement in the host tissues. Tumor cells usually flow in the direction of greater pressure variation during their diffusing and infiltrating to a further location in the host tissue. Some specific sites suitable for tumor invasion were observed on the percolation cluster and around these specific sites a tumor can develop into scattered tumors linked by some advantage tunnels that facilitate tumor invasion. We also investigate the manner that tissue inhomogeneity surrounding a tumor may influence the velocity of tumor diffusion and invasion. Our simulation suggested that invasion of a tumor is controlled by the homogeneity of the tumor microenvironment, which is basically consistent with the experimental report by Riching et al. as well as our clinical observation of medical imaging. Both simulation and clinical observation proved that tumor diffusion and invasion into the surrounding host tissue is positively correlated with the homogeneity of the tissue.

Pure tetragonal phase, uniform and well-crystallized sodium gadolinium molybdate (NaGd(MoO4)2) nanocrystals with diverse morphologies, e.g. nanocylinders, nanocubes and square nanoplates have been selectively synthesized via oleic acid-mediated hydrothermal method. The phase, structure, morphology and composition of the as-synthesized products are studied. Contents of both sodium molybdate and oleic acid of the precursor solutions are found to affect the morphologies of the products significantly and oleic acid plays a key role in the morphology-controlled synthesis of NaGd(MoO4)2 nanocrystals with diverse morphologies. Growth mechanism of NaGd(MoO4)2 nanocrystals is proposed based on time-dependent morphology evolution and X-ray diffraction analysis. Morphology-dependent down-shifting photoluminescence properties of NaGd(MoO4)2: Eu3+ nanocrystals and upconversion photoluminescence properties of NaGd(MoO4)2: Yb3+/Er3+ and Yb3+/Tm3+ nanoplates are investigated in detail. Charge transfer band in the down-shifting excitation spectra shows a slight blue-shift and the luminescence intensities and lifetimes of Eu3+ are decreased gradually with the morphology of the nanocrystals varying from nanocubes to thin square nanoplates. Upconversion energy transfer mechanisms of NaGd(MoO4)2: Yb3+/Er3+, Yb3+/Tm3+ nanoplates are proposed based on the energy level scheme and power dependence of upconversion emissions. Thermometric properties of NaGd(MoO4)2: Yb3+/Er3+ nanoplates are investigated and the maximum sensitivity is determined to be 0.01333 K−1 at 285 K.

Real-time reverse transcriptase (RT)-PCR using SYBR GreenI was applied to quantify sucrose phosphate synthase (SPS) mRNA expression at different storage days during the natural ripening (with no treatment), inhibited ripening with ethylene absorbent and accelerated ripening by treatment with propylene of banana fruit. The results showed that expression level of SPS mRNA were significantly different between 3 kinds of ripening fruit. Expression of SPS mRNA in fruit treated with propylene was dramatically promoted, the peak of SPS mRNA expression in these fruits appeared 16 days earlier than that in fruit with natural ripening. On the contrary, when fruit applied with ethylene absorbent, SPS mRNA expression was remarkably inhibited, the amount of SPS mRNA expression were significantly lower than that in naturally ripened fruit. These results indicated that the expression level of SPS mRNA of banana fruit can be impacted by regulating ethylene evolution, and that close relationships may exist between SPS mRNA expression and SPS activity, fruit softening, respiration rate, and ethylene production during ripening of banana fruit.

Mature green “Baxi” banana (Musa spp. AAA Group, Cavendish) fruits were harvested at 60% and 80% maturity stages. In order to evaluate the effects of harvesting at different maturity stages on storage quality and changes in sucrose-metabolizing enzymes, fruit firmness, disease index, contents of starch, and total soluble sugars were determined, and enzyme activities associated with sucrose metabolism was investigated under natural and accelerated (treated with ethylene) ripening conditions. In fruit treated with ethylene, changes in flesh firmness, total sugar content, starch content, disease index, and activity of sucrose phosphate synthase (SPS), sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) were accelerated dramatically compared with untreated fruit with both 60% and 80% maturity. When fruit ripened under natural conditions, the changes in firmness, disease index, starch content, total sugar content, SPS activity, SS, AI, and NI activity in fruit with 80% maturity were significantly faster than those in fruit with 60% maturity. On the contrary, when fruit ripened under accelerated conditions, no significant differences in firmness, sugar, starch, disease index, SPS, SS, AI, and NI were observed between fruit harvested at 60% or 80% maturity. It is suggested that storage quality and sucrose-metabolizing enzymes of banana fruit stored under natural conditions are related to harvest maturity stage; storage quality of fruit with lower harvest maturity is better than fruit with higher maturity. However, when fruit ripening is accelerated by ethylene, the harvest maturity stage has no influence on storage quality and changes in sucrose-metabolizing enzymes.

We have synthesized an efficient and highly sensitive nanoamplifier composed of gadolinium-doped silica nanoparticles and gold nanoparticles (AuNPs). Magnetic resonance imaging (MRI) in vitro and in vivo assays revealed enhancement of signal sensitivity, which may be explained by electron transfer between water and gadolinium-doped nanoparticles, apparent in the presence of gold. In vitro and in vivo evaluation demonstrated nanoamplifier incurred minimal cytotoxicity and immunotoxicity, increased stability, and gradual excretion patterns. Tumor targeted properties were preliminarily determined when the nanoamplifier was injected into mouse models of colon cancer liver metastasis. Furthermore, although AuNPs departed from the nanoamplifiers in specific mice tissues, optical and magnetic resonance imaging was efficient, especially in metastatic tumors. These assays validate our nanoamplifier as an effective MRI signal enhancer with sensitive cancer diagnosis potential.

The feasibility of the gadolinium-doped mesoporous silica nanocomposite Gd2O3@MCM-41 as a safe, effective MRI nanoprobe has been validated in the current investigation systematically from atomistic and molecular modeling to its synthesis and characterization on in vivo MR imaging and biocompatibility. The first-principles calculation indicates that it is nearly impossible for toxic Gd ions to dissociate freely from silica. The biocompatibility studies confirm that the nanocomposite is lack of any potential toxicity; the biodistribution studies reveal a greater accumulation of the nanocomposite in liver, spleen, lung and tumor than in kidney, heart and brain; the excretion studies show that the nanocomposite can be cleared nearly 50% via the hepatobiliary transport mechanism after 1.5 months of injection. A larger water proton relaxivity r1 and a better T1-weighted phantom MR imaging capability were detected in the nanocomposite than in the commercially available gadolinium diethylenetriaminepentaacetate. The results demonstrate that the nanocomposite is superior to the commercial counterpart in terms of contrast enhancement with a satisfactory biocompatibility, and it has a high potential to be developed into a safe and effective targeted probe for in vivo molecular imaging of cancer.

Substituted barium ferrite BaFe11−x−yCo0.5Ti0.5Ni x ZnyO19−r powders were prepared using a coprecipitation method and investigated by X-ray diffraction (XRD) and57Fe Mossbauer spectroscopy. The results show that the as-prepared magnetic powders possess the typical hexagonal structure and demonstrate both a good dispersibility and a narrow particle size distribution. The hyperfine fields for all sites decrease slightly asx (ory) increases. The Ni2+ ions prefer to occupy the 2a and 12k sites, and Zn2+ ions occupy the 4fIV site.

Investigation on magnetocaloric effects, magnetic entropy, Curie temperature, and specific heat of nanocomposite binary gadolinium alloys Gd–Tb, Gd–Zn, and Gd–Y has been carried out with an applied magnetic field of 1 T and in a temperature range of 233–313 K. Compared with the respective bulk alloys, the as‐prepared nanocomposite alloys were found to have higher specific heat and lower Curie temperature. The nanocomposite Gd–Y alloy exhibited distinctive enhancement of both magnetocaloric effect and magnetic entropy over that of the bulk alloy. The finding is of importance for developing new materials for magnetic refrigeration at room temperature. A discussion concerning the enhanced magnetic entropy in nanometer superparamagnetic systems is presented in detail.