New land surface temperature retrieval algorithm for heavy aerosol loading during nighttime from Gaofen-5 satellite data.

Land surface temperature (LST) is a key variable used for studies of the water cycles and energy budgets of land-atmosphere interfaces. The Chinese Gaofen-5 (GF5) satellite, with an onboard visual and infrared multispectral imager (VIMS), is the only satellite that can capture the earth's thermal infrared information for use in the national high-resolution earth observation project of China; it can observe the earth surface at a high spatial resolution of 40 m in four thermal infrared channels and two mid-infrared channels. This article selects the optimum spectral channel combination for reducing the aerosol effect on LST retrieval with the aid of simulated data, and a new four-channel LST retrieval method from GF5 infrared data under heavy dust aerosol during nighttime is proposed. The results show that the channel combination of channels 7, 8, 9, and 10 (denoted as CC1) performed better than the combination of channels 7, 8, 11, and 12 (denoted as CC2). The root mean square errors (RMSEs) between the actual and estimated LST were 0.28 K for the CC1 group with an aerosol optical thickness (AOD) of 0.1 and 1.94 K for the CC1 group with an AOD of 1.0. The RMSEs for CC2 were 0.28 K for the group with an AOD of 0.1 and 2.54 K for the other group with an AOD of 1.0. Moreover, an error analysis for the proposed method was performed in terms of the noise equivalent temperature difference (NEΔT), the uncertainties of land surface emissivity (LSE), water vapor content (WVC) and AOD. The results show that the LST errors caused by an LSE uncertainty of 0.01, a NEΔT of 0.2 K, a WVC uncertainty of 20%, an AOD uncertainty of 0.1 were 0.31 ∼ 1.01 K, 0.4 ∼ 2.0 K, within 0.6 K, and within 0.3 K for CC1 and 0.32 ∼ 3.08 K, 0.4 ∼ 1.7 K, within 0.7 K, and within 0.3 K for CC2, respectively.

An Improved Linear Spectral Emissivity Constraint Method for Temperature and Emissivity Separation Using Hyperspectral Thermal Infrared Data.

The linear spectral emissivity constraint (LSEC) method has been proposed to separate temperature and emissivity in hyperspectral thermal infrared data with an assumption that land surface emissivity (LSE) can be described by an equal interval piecewise linear function. This paper combines a pre-estimate shape method with the LSEC method to provide an initial-shape estimation of LSE which will create a new piecewise scheme for land surface temperature (LST) and LSE separation. This new scheme is designated as the pre-estimate shape (PES)-LSEC method. Comparisons with the LSEC method using simulated data sets show that the PES-LSEC method has better performance in terms of accuracy for both LSE and LST. With an at-ground error of 0.5 K, the root-mean-square errors (RMSEs) of LST and LSE are 0.07 K and 0.0045, respectively, and with the scale factor of moisture profile 0.8 and 1.2, the RMSEs of LST are 1.11 K and 1.14 K, respectively. The RMSEs of LSE in each channel are mostly below 0.02 and 0.04, respectively, which are better than for the LSEC method. In situ experimental data are adopted to validate our method: The results show that RMSE of LST is 0.9 K and the mean value of LSE accuracy is 0.01. The PES-LSEC method with fewer segments achieves better accuracy than that of LSEC and preserves most of the crest and trough information of emissivity.

Land surface temperature retrieval from AMSR-E passive microwave data.

The land surface temperature (LST) is a key parameter for energy balance, evapotranspiration and climate change. In this study, two new methods of LST retrieval from passive microwave data are developed: one is deriving LST only using single-channel dual-polarized data based on the relationship between the emissivity and microwave polarization difference index (MPDI) (denoted as Method 1); the other one is deriving LST using the traditional multi-channel method with prior knowledge of the normalized difference vegetation index (NDVI) (denoted as Method 3). Taking Moderate Resolution Imaging Spectroradiometer (MODIS) LST products as the actual LSTs, the coefficients for these algorithms are determined. From the results for the year 2008, it is demonstrated that the root mean square errors (RMSEs) for the LST retrieval using Method 3 are the smallest and range from 2.92 K to 3.44 K, the RMSEs for the LST retrieval using traditional multi-channel method (denoted as Method 2) range from 3.07 K to 4.05 K, and the worst results come from Method 1, whose RMSEs range from 3.11 K to 4.13 K at a frequency of 89 GHz. This could be caused by the fact that the NDVI provides substantial emissivity knowledge in Method 3, and much richer vegetation could result in a more accurate emissivity estimation.

Small is Smarter: Nano MRI Contrast Agents - Advantages and Recent Achievements.

Many challenges for advanced sensitive and noninvasive clinical diagnostic imaging remain unmatched. In particular, the great potential of magnetic nano-probes is intensively discussed to further improve the performance of magnetic resonance imaging (MRI), especially for cancer diagnosis. Based on recent achievements, here the concepts of magnetic nanoparticle-based MRI contrast agents and tumor-specific imaging probes are critically summarized. Advances in their synthesis, biocompatible chemical and biofunctional surface modifications, and current strategies for further developing them into multimodality imaging probes are discussed. In addition, how engineered versus unintended surface coatings such as protein coronas affect the biocompatibility and performance of MRI nano-probes is also considered. To stimulate progress in the field, future strategies and relevant challenges that still need to be resolved in the field conclude this review.

Land surface reflectance retrieval from hyperspectral data collected by an unmanned aerial vehicle over the Baotou test site.

To evaluate the in-flight performance of a new hyperspectral sensor onboard an unmanned aerial vehicle (UAV-HYPER), a comprehensive field campaign was conducted over the Baotou test site in China on 3 September 2011. Several portable reference reflectance targets were deployed across the test site. The radiometric performance of the UAV-HYPER sensor was assessed in terms of signal-to-noise ratio (SNR) and the calibration accuracy. The SNR of the different bands of the UAV-HYPER sensor was estimated to be between approximately 5 and 120 over the homogeneous targets, and the linear response of the apparent reflectance ranged from approximately 0.05 to 0.45. The uniform and non-uniform Lambertian land surface reflectance was retrieved and validated using in situ measurements, with root mean square error (RMSE) of approximately 0.01-0.07 and relative RMSE of approximately 5%-12%. There were small discrepancies between the retrieved uniform and non-uniform Lambertian land surface reflectance over the homogeneous targets and under low aerosol optical depth (AOD) conditions (AOD = 0.18). However, these discrepancies must be taken into account when adjacent pixels had large land surface reflectance contrast and under high AOD conditions (e.g. AOD = 1.0).

Self-assembly cationic nanoparticles based on cholesterol-grafted bioreducible poly(amidoamine) for siRNA delivery.

In this study, a series of bioreducible poly(amidoamine)s grafting different percentages of cholesterol (rPAA-Ch14: 14%, rPAA-Ch29: 29%, rPAA-Ch57: 57% and rPAA-Ch87: 87%) was synthesized and used for siRNA delivery. These amphiphilic polymers were able to self-assemble into cationic nanoparticles in aqueous solution at low concentrations. The nanoparticle formation was evidenced via cryo-transmission electron microscope (Cryo-TEM) and dynamic light scattering analysis. The average hydrodynamic size of rPAA-Ch blank nanoparticles was about 80-160 nm with zeta potential of 50-60 mV. Also, the effects of different percentages of cholesterol grafted onto rPAA on physicochemical characteristics, in vitro cytotoxicity, cellular uptake, VEGF gene silencing efficacy and translocation mechanism of rPAA-Ch/siRNA complexes were investigated. The results showed that rPAA-Ch57 polymer was not only able to form stable nanocomplexes and possess high cell uptake, but also to exhibit the best in vitro VEGF gene silencing efficacy and the best in vivo tumor growth inhibition effect when it was formulated with VEGF-siRNA. Moreover, the observations of confocal laser scanning microscope (CLSM) and the study of cholesterol competitive inhibition demonstrated that endosomal/lysosomal escape and cytoplasmic dissociation of rPAA-Ch57/siRNA complexes were dependent on the "proton sponge effect" and disulfide cleavage, following internalization with cholesterol-related endocytosis pathway and subsequent transportion into endosomes/lysosomes. These findings indicated that the rPAA-Ch57 polymer should be a promising and potent carrier for siRNA delivery.

A comparative study of three ternary complexes prepared in different mixing orders of siRNA/redox-responsive hyperbranched poly (amido amine)/hyaluronic acid.

In this study, a novel redox-responsive hyperbranched poly(amido amine) (named PCD) was synthesized and used as a cationic polymer to form a ternary complex with small interfering RNA (siRNA) and hyaluronic acid (HA) for siRNA delivery. Here, it is hypothesized that different mixing orders result in different assembly structures, which may affect the siRNA delivery efficiency. To investigate the effects of mixing orders on siRNA delivery efficiency in two human breast cancer cell lines, three ternary complexes with different mixing orders of siRNA/PCD/HA were prepared and characterized: mixing order I (initially prepared siRNA/PCD binary complex further coated by negatively charged HA), mixing order II ( initially prepared HA/PCD binary complex further incubated with siRNA), and mixing order III ( initially prepared siRNA/HA mixture further electrostatically compacted by positively charged PCD). With an optimized siRNA/PCD/HA charge ratio of 1/20/16, the particle sizes and zeta potentials of these ternary complexes were 124.8 nm and 27.3 mV (mixing order I), 147.5 nm and 29.9 mV (mixing order II), and 128.8 nm and 19.4 mV (mixing order III). Also, the effects on stability, cellular uptake, and gene silencing efficiency of siRNA formulated in ternary complexes with different mixing orders were investigated. The results showed that mixing orders I and III displayed better siRNA transfection and protection than mixing order II in human breast cancer MCF-7 and MDA-MB-231 cells. More interesting, at the siRNA/PCD/HA charge ratio of 1/20/16, the gene silencing effects on vascular endothelial growth factor expression in MDA-MB- 231 cells were as follows: mixing order III > mixing order I > mixing order II. Based on these results, a likely explanation for the difference in functionality dependent on mixing orders is the formation of different assembly structures. These results may help future optimization of siRNA ternary complexes for achieving better delivery efficiencies, especially for target-specific siRNA delivery to cells with HA receptor overexpression.

Surface engineering of gold nanoparticles for in vitro siRNA delivery.

Cellular uptake, endosomal/lysosomal escape, and the effective dissociation from the carrier are a series of hurdles for specific genes to be delivered both in vitro and in vivo. To construct siRNA delivery systems, poly(allylamine hydrochloride) (PAH) and siRNA were alternately assembled on the surface of 11.8 ± 0.9 nm Au nanoparticles (GNP), stabilized by denatured bovine serum albumin, by the ionic layer-by-layer (LbL) self-assembly method. By manipulating the outmost PAH layer, GNP-PAH vectors with different surface electric potentials were prepared. Then, the surface potential-dependent cytotoxicity of the resultant GNP-PAH particles was evaluated via sulforhodamine B (SRB) assay, while the surface potential-dependent cellular uptake efficiency was quantitatively analyzed by using the flow cytometry method based on carboxyfluorescein (FAM)-labeled siRNA. It was revealed that the GNP-PAH particles with surface potential of +25 mV exhibited the optimal cellular uptake efficiency and cytotoxicity for human breast cancer MCF-7 cells. Following these results, two more positively charged polyelectrolytes with different protonating abilities in comparison with PAH, i.e., polyethylenimine (PEI), and poly(diallyl dimethyl ammonium chloride) (PDDA), were chosen to fabricate similarly structured vectors. Confocal fluorescence microscopy studies indicated that siRNA delivered by GNP-PAH and GNP-PEI systems was better released than that delivered by the GNP-PDDA system. Further flow cytometric assays based on immunofluorescence staining of the epidermal growth factor receptor (EGFR) revealed that EGFR siRNA delivered by GNP-PAH and GNP-PEI exhibited similar down-regulation effects on EGFR expression in MCF-7 cells. The following dual fluorescence flow cytometry assays by co-staining phosphatidylserine and DNA suggested the EGFR siRNA delivered by GNP-PAH exhibited an improved silencing effect in comparison with that delivered by the commercial transfection reagent Lipofectamine 2000.

Self-assembly nanomicelles based on cationic mPEG-PLA-b-Polyarginine(R15) triblock copolymer for siRNA delivery.

Due to the absence of safe and effective carriers for in vivo delivery, the applications of small interference RNA (siRNA) in clinic for therapeutic purposes have been limited. In this study, a biodegradable amphiphilic tri-block copolymer (mPEG(2000)-PLA(3000)-b-R(15)) composed of monomethoxy poly(ethylene glycol), poly(d,l-lactide) and polyarginine was synthesized and further self-assembled to cationic polymeric nanomicelles for in vivo siRNA delivery, with an average diameter of 54.30 ± 3.48 nm and a zeta potential of approximately 34.8 ± 1.77 mV. The chemical structures of the copolymers were well characterized by (1)H NMR spectroscopy and FT-IR spectra. In vitro cytotoxicity and hemolysis assays demonstrated that the polymeric nanomicelles showed greater cell viability and haemocompatibility than those of polyethyleneimine (PEI) or R(15) peptide. In vitro experiments demonstrated that EGFR targeted siRNA formulated in micelleplexes exhibited approximately 65% inhibition of EGFR expression on MCF-7 cells in a sequence-specific manner, which was comparable to Lipofectamine™ 2000. The results of intravenous administration showed Micelleplex/EGFR-siRNA significantly inhibited tumor growth in nude mice xenografted MCF-7 tumors, with a remarkable inhibition of EGFR expression. Furthermore, no positive activation of the innate immune responses and no significant body weight loss was observed during treatment suggested that this polymeric micelle delivery system is non-toxic. In conclusion, the present nanomicelles based on cationic mPEG(2000)-PLA(3000)-b-R(15) copolymer would be a safe and efficient nanocarrier for in vivo delivery of therapeutic siRNA.