We report a convenient approach to prepare ultrasmall Fe3O4 nanoparticles (NPs) functionalized with an arginylglycylaspartic acid (RGD) peptide for in vitro and in vivo magnetic resonance (MR) imaging of gliomas. In our work, stable sodium citrate-stabilized Fe3O4 NPs were prepared by a solvothermal route. Then, the carboxylated Fe3O4 NPs stabilized with sodium citrate were conjugated with polyethylene glycol (PEG)-linked RGD. The formed ultrasmall RGD-functionalized nanoprobe (Fe3O4-PEG-RGD) was fully characterized using different techniques. We show that these Fe3O4-PEG-RGD particles with a size of 2.7 nm are water-dispersible, stable, cytocompatible and hemocompatible in a given concentration range, and display targeting specificity to glioma cells overexpressing αvβ3 integrin in vitro. With the relatively high r1 relaxivity (r1 = 1.4 mM(-1) s(-1)), the Fe3O4-PEG-RGD particles can be used as an efficient nanoprobe for targeted T1-weighted positive MR imaging of glioma cells in vitro and the xenografted tumor model in vivo via an active RGD-mediated targeting pathway. The developed RGD-functionalized Fe3O4 NPs may hold great promise to be used as a nanoprobe for targeted T1-weighted MR imaging of different αvβ3 integrin-overexpressing cancer cells or biological systems.

Abstract. This study investigates the seasonal variation, molecular distribution and stable carbon isotopic composition of diacids, oxocarboxylic acids and α-dicarbonyls to better understand the sources and formation processes of fine aerosols (PM 2.5 ) in Beijing. The concentrations of total dicarboxylic acids varied from 110 to 2580 ng m −3 , whereas oxoacids (9.50-353 ng m −3 ) and dicarbonyls (1.50-85.9 ng m −3 ) were less abundant. Oxalic acid was found to be the most abundant individual species, followed by succinic acid or occasionally by terephthalic acid (tPh), a plastic waste burning tracer. Ambient concentrations of phthalic acid (37.9 ± 27.3 ng m −3 ) and tPh (48.7 ± 51.1 ng m −3 ) were larger in winter than in other seasons, illustrating that fossil fuel combustion and plastic waste incineration contribute more to wintertime aerosols. The year-round mass concentration ratios of malonic acid to succinic acid (C 3 / C 4 ) were relatively low by comparison with those in other urban aerosols and remote marine aerosols. The values were less than or equal to unity in Beijing, implying that the degree of photochemical formation of diacids in Beijing is insignificant. Moreover, strong correlation coefficients of major oxocarboxylic acids and α-dicarbonyls with nss-K + suggest that biomass burning contributes significantly to these organic acids and related precursors. The mean δ 13 C value of succinic acid is the highest among all species, with values of −17.1 ± 3.9 ‰ (winter) and −17.1 ± 2.0 ‰ (spring), while malonic acid is more enriched in 13 C than others in autumn (−17.6 ± 4.6 ‰) and summer (−18.7 ± 4.0 ‰). The δ 13 C values of major species in Beijing aerosols are generally lower than those in the western North Pacific atmosphere, the downwind region, which indicates that stable carbon isotopic compositions of diacids depend on their precursor sources in Beijing. Therefore, our study demonstrates that in addition to photochemical oxidation, high abundances of diacids, oxocarboxylic acids and α-dicarbonyls in Beijing are largely associated with anthropogenic primary emissions, such as biomass burning, fossil fuel combustion and plastic waste burning.

The high performance and increased tumor-targeting accumulation of magnetic nanocrystals (MNCs) are the most important considerations in cancer targeted magnetic hyperthermia (TMH). To achieve these goals, our study was firstly done using well-established fluorescence/magnetic Mn-Zn ferrite MNCs (core size: 14 nm) as multi-modal imaging contrast agents and highly-efficient "heat generators", which were coated with a biocompatible PEG-phospholipid (DSPE-PEG2000) and further modified by a cyclic tripeptide of arginine-glycine-aspartic acid (RGD). By using a mouse model bearing breast carcinoma (4T1), we then systematically compared PEGylated MNCs (MNCs@PEG)- and RGD-PEGylated MNCs (MNCs@RGD)-mediated tumor targeting abilities by intravenous administration. The MNCs@PEG-based passive targeting could successfully accumulate at the tumor due to the enhanced permeability and retention (EPR) effects, but the non-targeted localization might make the MNCs@PEG "leaking" from larger pores of tumor fenestrated vascular networks. Our designed MNCs@RGD, simultaneously functionalized with PEG and RGD ligands, might promote a synergistic effect including efficient tumor vasculature active targeting and EPR-mediated passive targeting, improving total MNC concentration and retention time in tumor tissues. By combining fluorescence/magnetic resonance (MR)/thermal multi-modal imaging-guided diagnostics and continuous TMH treatment under an alternating current magnetic field (ACMF, 2.58 kA m(-1), 390 kHz), the tumor surface could be heated to approximately 43-44 °C based on the MNC-mediated repeated injections. Sufficient temperature elevation induced the apoptosis of tumor cells, and inhibited the tumor angiogenesis. Compared with MNCs@PEG, the active MNCs@RGD-based tumor targeting MR image was significantly more efficient due to both the higher and long-lasting tumor accumulation, but its antitumor efficacy was not obviously improved in the TMH treatments. To achieve a singularly promising tumor TMH therapy, a greatly increased MNC content in tumor was needed. This insight indicated that not only the tumor vasculature targeting, but also the active tumor cells targeting of MNCs should receive considerable attention in future clinical TMH therapy application.

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Fast kinetics and time-dependent yields of the hydrated electron (e(-)(aq)) in pure water under conditions of high temperature and pressure up to the supercritical region were investigated by picosecond and nanosecond pulse radiolysis experiments. More significant decays at short times followed by plateau components at longer times were observed with increasing temperature, suggesting faster spur reaction processes. In supercritical water, it was also found that the e(-)(aq) yields strongly depend on the pressure (density). Comparison of these measurements with Monte-Carlo computer simulations allowed us to identify spur reactions of e(-)(aq) that occur predominantly at high temperatures and also to provide new key information on certain spur model parameters. In particular, the experimental time-dependent e(-)(aq) yields were best reproduced if the electron thermalization distance decreases with increasing temperature. This "shrinkage" of spur sizes at high temperatures was attributed to an increase in the scattering cross sections of subexcitation electrons, likely originating from a decrease in the degree of structural order of water molecules as the temperature is increased.

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The East Asian Monsoon (EAM) exhibits a significant variability on timescales ranging from tectonic to centennial as inferred from loess, speleothem and marine records. However, the relative contributions and plausible driving forces of the monsoon variability at different timescales remain controversial. Here, we spectrally explore time series of loess grain size and speleothem δ 18 O records and decompose the two proxies into intrinsic components using the empirical mode decomposition method. Spectral results of these two proxies display clear glacial and orbital periodicities corresponding to ice volume and solar cycles, and evident millennial signals which are in pace with Heinrich rhythm and Dansgaard-Oeschger (DO) cycles. Five intrinsic components are parsed out from loess grain size and six intrinsic components from speleothem δ 18 O records. Combined signals are correlated further with possible driving factors including the ice volume, insolation and North Atlantic cooling from a linear point of view. The relative contributions of components differ significantly between loess grain size and speleothem δ 18 O records. Coexistence of glacial and orbital components in the loess grain size implies that both ice volume and insolation have distinctive impacts on the winter monsoon variability, in contrast to the predominant precessional impact on the speleothem δ 18 O variability. Moreover, the millennial components are evident in loess grain size and speleothem δ 18 O records with variances of 13 and 17 %, respectively. A comparison of the millennial-scale signals of these two proxies reveals that abrupt changes in the winter and summer monsoons over the last 260 kyr share common features and similar driving forces linked to highlatitude Northern Hemisphere climate.Published by Copernicus Publications on behalf of the European Geosciences Union.

Micro-light emitting diodes (Micro-LEDs) based on III-nitride semiconductors have become a research hotspot in the field of high-resolution display due to its unique advantages. However, the edge effect caused by inductively coupled plasma (ICP) dry etching in Micro-LEDs become significant with respect to the decreased chip size, resulting in a great reduction in device performance. In this article, sector-shaped GaN-based blue Micro-LEDs are designed and fabricated. Additionally, the device performance of different size Micro-LEDs with passivation are investigated with respect to those without passivation. Several methods have been applied to minimize the etching damage near the edge, including acid-base wet etching and SiO2 passivation layer growth. The room temperature photoluminescence (PL) results demonstrate that the light emission intensity of Micro-LEDs can be significantly enhanced by optimized passivation process. PL mapping images show that the overall luminescence of properly passivated Micro-LEDs is enhanced, the uniformity is improved, and the effective luminescence area is increased. The recombination lifetime of carriers in Micro-LEDs are increased by the usage of passivation process, which proves the reduction in non-radiative recombination centers in Micro-LEDs and improved luminescence efficiency. As a result, the internal quantum efficiency (IQE) is improved from 14.9% to 37.6% for 10 μm Micro-LEDs, and from 18.3% to 26.9% for 5 μm Micro-LEDs.