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Author(s): Kim, Min-cheol; Ahn, Namyoung; Cheng, Diyi; Xu, Mingjie; Pan, Xiaoqing; Kim, Suk Jun; Luo, Yanqi; Fenning, David P; Tan, Darren HS; Zhang, Minghao; Ham, So-Yeon; Jeong, Kiwan; Choi, Mansoo; Meng, Ying Shirley | Abstract: Perovskite solar cells have drawn much attention in recent years, owing to its world-record setting photovoltaic performances. Despite its promising use in tandem applications and flexible devices, its practicality is still limited by its structural instability often arising from ion migration and defect formation. While it is generally understood that ion instability is a primary cause for degradation, there is still a lack of direct evidence of structural transformation at the atomistic scale. Such an understanding is crucial to evaluate and pin-point how such instabilities are induced relative to external perturbations such as illumination or electrical bias with time, allowing researchers to devise effective strategies to mitigate them. Here, we designed an in-situ TEM setup to enable real-time observation of amorphization in double cation mixed perovskite materials under electrical biasing at 1 V. It is found that amorphization occurs along the (001) and (002) planes, which represents the observation of in-situ facet-dependent amorphization of a perovskite crystal. To reverse the degradation, the samples were heated at 50 oC and was found to recrystallize, effectively regaining its performance losses. This work is vital toward understanding fundamental ion-migration phenomena and address instability challenges of perovskite optoelectronics.

Toll-like receptor 4 (TLR4) is a lipopolysaccharide receptor that may influence tumor progression through inflammatory response and immune response. This complex process mainly occurs within cells. The correlation between TLR4 and neoplasms has been of great interest, but discrepancies remain.We analyze the literature retrieved from five databases (Web of Science, PubMed, Embase, CNKI, and Wan Fang) to assess the intensity of association using odds ratio (ORs) and 95% confidence intervals (95% CI). Meta-regression and subgroup analysis were utilized to find sources of heterogeneity. Publication bias is estimated using contour-enhanced funnel plots, Begg's test, and Egger's test, and we implemented sensitivity analysis to clarify the reliability of the outcomes. We also conducted an evaluation of the sample size using trial sequential analysis (TSA) method.We found a significant association between rs4986790 and tumors (dominant model: OR [95% CI] = 1.25 [1.11-1.42]; heterozygous model OR [95% CI] = 1.25 [1.11-1.41]; and additive model: OR [95% CI] = 1.25 [1.10-1.41]. Specifically, the rs4986790 minor allele G may increase the risk of gastric cancer (dominant model: OR [95% CI] = 1.62 [1.3-2.03]; heterozygous model: OR [95% CI] = 1.57 [1.24-1.97]; additive model: OR [95% CI] = 1.64 [1.31-2.05] and other tumors (dominant model: OR [95% CI] = 1.36 [1.17-1.57]; heterozygous model: OR [95% CI] = 1.43 [1.25-1.63]; additive model: OR [95% CI] = 1.35 [1.18-1.55]. Further subgroup analysis showed that this association are both present in Caucasian and Asian.The outcomes of our systemic review proved that the TLR4 polymorphism rs4986790 is associated with cancer, especially with gastric cancer, and this strong correlation are evident in Caucasians and Asian.

Lithium phosphorus oxynitride (LiPON) is a well-known amorphous thin film solid electrolyte that has been extensively studied in the last three decades. Despite the promises to enable Li metal anode and various cathode materials, the presence of rigid substrate and LiPON’s unique amorphous, air-sensitive characteristics set limitations to comprehensively understand its intrinsic properties for next-stage advancement and applications. This work demonstrates a different methodology to synthesize LiPON in a freestanding form that removes the substrate. The freestanding LiPON (FS-LiPON) exhibits remarkable flexibility, with controllable film thickness and large-scale production compatibility. Benefited from the freestanding form, solid-state nuclear magnetic resonance (ss-NMR) and differential scanning calorimetry (DSC) are able to attain high S/N ratio to determine the local bonding structures and glass transition temperature of LiPON. In the presence of interfacial stress and a seeding layer, FS-LiPON demonstrates a uniform and fully dense Li metal deposition without the aid of external pressure. Such a FS-LiPON film offers new opportunities for fundamental study of LiPON material and associated interfaces, and provide perspectives for interface engineering in bulk solid-state battery.

In recent years, with the development of hydrogen energy economy, there is an increasing demand for hydrogen in the market, and hydrogen production through biomass will provide an important way to supply clean, environmentally friendly and highly efficient hydrogen. In this study, cow dung was selected as the biomass source, and the efficiency of the biomass to hydrogen reaction was explored by coupling high temperature pyrolysis and water vapor gasification. The experimental conditions of gasification temperature, water mass fraction, heating rate and feed temperature were systematically studied and optimized to determine the optimal conditions for in situ hydrogen production by gasification of cow dung. The relationship of each factor to the yield of hydrogen production by gasification of cow dung semi-coke was investigated in order to elucidate the mechanism of the hydrogen production. The experiment determined the optimal operating parameters of in situ gasification: gasification temperature 1173 K, water mass fraction 80%, heating rate 10 K/min and feed temperature 673 K. The semi-coke treatment separated high temperature pyrolysis and water vapor gasification, and reduced the influence on gasification of volatile substances such as tar extracted from pyrolysis. The increase of semi-coke preparation temperature increases the content of coke, reduces the volatile matter and improves the yield of hydrogen; the small size of semi-coke particles and large specific surface area are beneficial to the gasification reaction.

Hydrogen peroxide (H2O2) has been reported to mediate a variety of physiological and pathological processes in living systems. In this work, a biosensor for determination of H2O2 was prepared by using an HRP/Ti3C2/Nafion film-modified glassy carbon electrode (GCE). Ti3C2 nanosheets with remarkable conductivity and high specific surface area were chosen as carriers for HRP. Moreover, this biosensor modified with HRP has a specific catalytic effect on H2O2. The difference in peak current could reflect the quantitative change of H2O2. The linear range of the biosensor is 5-8000 μM, and the detection limit is 1 μM (S/N = 3). This biosensor was used to detect H2O2 in clinical serum samples of normal controls and patients with acute myocardial infarction (AMI) before and after percutaneous coronary intervention (PCI). The results showed that the difference between normal controls and patients is significant (P < 0.05), as well as the difference for patients before and after PCI (P < 0.01), but no significant difference existed between postoperative patients and normal controls. This biosensor has the advantages of simple preparation, high sensitivity, and quick detection, showing potential application in clinical diagnosis.

Crystallization by particle attachment (CPA) is a frequently occurring mechanism of colloidal crystallization that results in hierarchical morphologies1–4. CPA has been exploited to create nanomaterials with unusual properties4–6 and is implicated in the development of complex mineral textures1,7. Oriented attachment7,8—a form of CPA in which particles align along specific crystallographic directions—produces mesocrystals that diffract as single crystals do, although the constituent particles are still discernible2,9. The conventional view of CPA is that nucleation provides a supply of particles that aggregate via Brownian motion biased by attractive interparticle potentials1,9–12. However, mesocrystals often exhibit regular morphologies and uniform sizes. Although many crystal systems form mesocrystals1–9 and individual attachment events have been directly visualized10, how random attachment events lead to well defined, self-similar morphologies remains unknown, as does the role of surface-bound ligands, which are ubiquitous in nanoparticle systems3,9,11. Attempts to understand mesocrystal formation are further complicated in many systems by the presence of precursor nanoparticles with a phase distinct from that of the bulk1,13,14. Some studies propose that such particles convert before attachment15, whereas others attribute conversion to the attachment process itself16 and yet others conclude that transformation occurs after the mesocrystals exceed a characteristic size14,17. Here we investigate mesocrystal formation by iron oxides, which are important colloidal phases in natural environments18,19 and classic examples of systems forming ubiquitous precursor phases and undergoing CPA accompanied by phase transformations15,19–21. Combining in situ transmission electron microscopy (TEM) at 80 degrees Celsius with ‘freeze-and-look’ TEM, we tracked the formation of haematite (Hm) mesocrystals in the presence of oxalate (Ox), which is abundant in soils, where iron oxides are common. We find that isolated Hm particles rarely appear, but once formed, interfacial gradients at the Ox-covered surfaces drive Hm particles to nucleate repeatedly about two nanometres from the surfaces, to which they then attach, thereby generating mesocrystals. Comparison to natural and synthetic systems suggests that interface-driven pathways are widespread. Mesocrystal formation is investigated for haematite in the presence of oxalate, showing that chemical gradients at interfaces cause nucleation near surfaces rather than in the bulk, followed by particle attachment.

The high information content of proteins drives their hierarchical assembly and complex function, including the organization of inorganic nanomaterials. Peptoids offer an organic scaffold very similar to proteins, but with a wider solubility range and easily tunable side chains and functional groups to create a variety of self-assembling architectures with atomic precision. If we could harness this paradigm and understand the factors that govern how they direct nucleation and assembly of inorganic materials to design order within such materials, new dimensions of function and fundamental science would emerge. In this work, peptoid tubes and sheets were explored as platforms to assemble colloidal quantum dots (QDs) and clusters. We have successfully synthesized CdSe QDs with difunctionalized capping ligands containing both carboxylic acid and thiol groups and mixed them with maleimide containing peptoids, to create an assembly of the QDs on the peptoid surface via a covalent linkage. This conjugation was seen to be successful with peptoid tubes, sheets and CdSe QDs and clusters. The particles were seen to have a high preference for the peptoid surface but non-specific interactions with carboxylic acid groups on the peptoids limited control over QD density via maleimide conjugation. Replacing the carboxylic acid groups with methoxy ethers, however, allowed for control over QD density as a function of maleimide concentration. 1H NMR analysis demonstrated that binding of QDs to peptoids involved a subset of surface ligands bound through the carboxylate functional group, allowing the distal thiol to engage in a covalent linkage to the maleimide. Overall, we have shown the compatibility and control of CdSe-peptoid interactions via a covalent linkage with varying peptoid structures and CdSe particles to create complex hybrid structures.

On the Wasserstein space over a complete, separable, non-compact, locally compact length space, we consider the horo-functions associated to sequences of atomic measures. We show the existence of co-rays for any prescribed initial probability measure with respect to a sequence of atomic measures and show that co-rays are negative gradient curves in some sense. Some other fundamental results of this kind of functions are also obtained.

Sodium yttrium fluoride (NaYF4) is an important upconverting material with many potential uses in chemistry, materials science, and biology, which can be synthesized hydrothermally in both cubic (α...

We have synthesized unique colloidal nanoplatelets of the two-dimensional (2D) van der Waals ferromagnet CrI3 and have characterized these nanoplatelets structurally, magnetically, and by magnetic circular dichroism spectroscopy. The CrI3 nanoplatelets have lateral dimensions of ∼25 nm and thicknesses of only ∼4 nm, corresponding to just a few CrI3 monolayers. Magnetic and magneto-optical measurements demonstrate robust 2D ferromagnetic ordering with Curie temperatures similar to bulk CrI3, despite their small size. These data also show magnetization steps akin to those observed in micron-sized few-layer 2D sheets associated with concerted spin-reversal of individual CrI3 layers within few-layer van der Waals stacks. Similar data have also been obtained for CrBr3 and anion-alloyed Cr(I1–xBrx)3 nanoplatelets. These results represent the first example of lateral nanostructures of 2D van der Waals ferromagnets of any composition. The demonstration of robust ferromagnetism at nanometer lateral dimensions open...

Sma-and mad-related protein 7 (SMAD7) can affect tumor progression by closing transforming growth factor-beta intracellular signaling channels. Despite the extensive research on the correlation between SMAD7 polymorphisms and colorectal cancer (CRC), the conclusions of studies are still contradictory. We conducted a study focusing on the association of SMAD7 polymorphisms rs4939827, rs4464148, and rs12953717 with CRC.We searched through 5 databases for articles and used odd ratios (ORs) and 95% confidence intervals (CIs) to discuss the correlation of SMAD7 polymorphisms with CRC risk. The heterogeneity will be appraised by subgroup analysis and meta-regression. Contour-enhanced funnel plot, Begg test and Egger test were utilized to estimate publication bias, and the sensitivity analysis illustrates the reliability of the outcomes. We performed False-positive report probability and trial sequential analysis methods to verify results. We also used public databases for bioinformatics analysis.We conclusively included 34 studies totaling 173251 subjects in this study. The minor allele (C) of rs4939827 is a protective factor of CRC (dominant, OR/[95% CI] = 0.89/[0.83-0.97]; recessive, OR/[95% CI] = 0.89/[0.83-0.96]; homozygous, OR/[95% CI] = 0.84/[0.76-0.93]; heterozygous, OR/[95% CI] = 0.91/[0.85-0.97]; additive, OR/[95% CI] = 0.91/[0.87-0.96]). the T allele of rs12953717 (recessive, OR/[95% CI] = 1.22/[1.15-1.28]; homozygous, OR/[95% CI] = 1.25/[1.13-1.38]; additive, OR/[95% CI] = 1.11/[1.05-1.17]) and the C allele of rs4464148 (heterozygous, OR/[95% CI] = 1.13/[1.04-1.24]) can enhance the risk of CRC.Rs4939827 (TC) can decrease the susceptibility to CRC. However, the rs4464148 (TC) and rs12953717 (CT) variants were connected with an enhanced risk of CRC.

Rational design and synthesis of materials, determination of environmental conditions at the time of mineral formation, and definition of mechanisms in biomineralizing systems all require an understanding of the effect of multiple factors on modulating crystallization pathways. In this study, we investigate the influence of temperature, oxalate additive, aging time, and addition of seed crystals on hematite (α-Fe2O3, Hm) crystallization from a two-line ferrihydrite (Fe2O3·xH2O, Fh) suspension. We also investigate the effect of temperature on the aging of spindle-shaped Hm mesocrystals, which we synthesize through the addition of sodium oxalate. The results show that Hm mesocrystals form in a temperature window of 45 °C−130 °C. Temperatures ≥ 140 °C favor formation of rhombohedral Hm, suggesting classical monomer-by-monomer growth dominates, whereas crystallization by particle attachment (CPA) is dominant between 45 and 90 °C, while the two processes compete in the intermediate temperature range. Aging of mesocrystals in the original solution at 90 °C or 180 °C leads to a slow morphological evolution towards rhombohedral crystals due to Ostwald ripening. Finally, by utilizing rhombohedral Hm and rod-shaped goethite as substrates on which to assemble the mesocrystals, we demonstrate formation of complex heterogeneous structures.

In situ liquid phase scanning/ transmission electron microscopy (LP-S/TEM), enables direct observation of particle formation and evolution in the hydrated liquid state. Though powerful, this technique has significant technical limitations, which need to be carefully addressed in order to obtain reliable quantitative data. In this paper, we highlight several common challenges seen in LP-TEM, including electron-beam induced particle dissolution and motion, particle-membrane adhesion, contamination, and triggering of reactions. We describe our efforts to address these challenges by modifying solution and interface chemistry, maintaining solution flow, performing systematic post in situ analyses on the samples and applying controlled heating.

Alloy-based nanostructure anodes have the privilege of alleviating the challenges of large volume expansion and improving the cycling stability and rate performance for high energy lithium- and sodium-ion batteries (LIBs and SIBs). Yet, they face the dilemma of worsening the parasitic reactions at the electrode-electrolyte interface and low packing density for the fabrication of practical electrodes. Here, pomegranate Sb@C yolk-shell microspheres were developed as a high-performance anode for LIBs and SIBs with controlled interfacial properties and enhanced packing density. Although the same yolk-shell nanostructure (primary particle size, porosity) and three-dimensional architecture alleviated the volume change induced stress and swelling in both batteries, the SIBs show 99% capacity retention over 200 cycles, much better than the 78% capacity retention of the LIBs. The comparative electrochemical study and X-ray photoelectron spectroscopy characterization revealed that the different SEIs, besides the distinct phase transition mechanism, played a critical role in the divergent cycling performance.

We study rays and co-rays in the Wasserstein space $$P_p({\mathcal {X}})$$ ( $$p > 1$$ ) whose ambient space $${\mathcal {X}}$$ is a complete, separable, non-compact, locally compact length space. We show that rays in the Wasserstein space can be represented as probability measures concentrated on the set of rays in the ambient space. We show the existence of co-rays for any prescribed initial probability measure. We introduce Busemann functions on the Wasserstein space and show that co-rays are negative gradient lines in some sense.

Sodium yttrium fluoride (NaYF4) is an upconverting material with many potential uses in chemistry, materials science, and biology that can be synthesized hydrothermally in both cubic (α) and hexagonal (β) crystallographic polymorphs. Understanding the mechanisms underlying the phase conversion between the cubic and hexagonal polymorphs is of great interest to help inform future efforts to synthesize atomically-precise quantum materials with well-defined sizes and morphologies. In this work, we use a combination of analytical transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), powder X-ray diffraction (XRD), in situ liquid cell TEM, atom probe tomography (APT), and extended x-ray absorption fine structure (EXAFS) measurements to show evidence suggesting that the hexagonal NaYF4 nanowires form through a non-classical crystal growth mechanism involving the formation and subsequent oriented attachment of mesocrystals consisting of cubic (α) plase units. EXAFS spectroscopy also suggests that substitutional Yb3+ point defects within NaYF4 are distributed evenly throughout the crystal lattice without clustering, and also that they may exhibit selective substitution into one of the two possible trivalent yttrium sites in the unit cell for hydrothermally synthesized NaYF4.

Sodium yttrium fluoride (NaYF4) is an upconverting material with many potential uses in chemistry, materials science, and biology that can be synthesized hydrothermally in both cubic (α) and hexagonal (β) crystallographic polymorphs. Understanding the mechanisms underlying the phase conversion between the cubic and hexagonal polymorphs is of great interest to help inform future efforts to synthesize atomically-precise quantum materials with well-defined sizes and morphologies. In this work, we use a combination of analytical transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), powder X-ray diffraction (XRD), in situ liquid cell TEM, atom probe tomography (APT), and extended x-ray absorption fine structure (EXAFS) measurements to show evidence suggesting that the hexagonal NaYF4 nanowires form through a non-classical crystal growth mechanism involving the formation and subsequent oriented attachment of mesocrystals consisting of cubic (α) plase units. EXAFS spectroscopy also suggests that substitutional Yb3+ point defects within NaYF4 are distributed evenly throughout the crystal lattice without clustering, and also that they may exhibit selective substitution into one of the two possible trivalent yttrium sites in the unit cell for hydrothermally synthesized NaYF4.

Because they provide lower cost but comparable activity to precious platinum (Pt)-based catalysts, nonprecious iron (Fe)-based materials, such as Fe/Fe3C and Fe–N–C, have gained considerable attention as electrocatalysts for the oxygen reduction reaction (ORR). However, their practical application is hindered by their poor stability, which is attributed to the defective protection of extremely unstable Fe nanoparticles. Here, we introduce a synthesis strategy for a stable Fe-based electrocatalyst, which was realized by defect-free encapsulation of Fe nanoparticles using a two-dimensional (2D) phenazine-based fused aromatic porous organic network (Aza-PON). The resulting Fe@Aza-PON catalyst showed electrocatalytic activity (half-wave potential, 0.839 V; Tafel slope, 60 mV decade–1) comparable to commercial Pt on activated carbon (Pt/C, 0.826 V and 90 mV decade–1). More importantly, the Fe@Aza-PON displayed outstanding stability (zero current loss even after 100 000 cycles) and tolerance against contaminati...

During non-classical growth of nanostructures via assembly of primary nuclei, nucleation and assembly are assumed to be distinct processes: nanoparticles nucleate randomly and aggregate to form extended structures through Brownian motion in the presence of long-range attractive interactions. Here we investigate the relationship between these two processes by using in situ AFM, in situ, ex situ and cryo TEM and UV-Vis spectroscopy to observe growth of colloidal gold and simulations to develop a mechanistic model of the process. Our results reveal an inexorable link between nucleation and assembly with nuclei forming almost exclusively within a ∼1 nm interfacial region of existing particles. The new particles immediately close the gap either through a diffusive jump or via growth of a neck between the seed and new particle, generating aggregates exhibiting features commonly attributed to oriented attachment of independently nucleated particles. The results demonstrate that creation of initial particle interfaces leads to local environments that redirect growth towards non-classical processes.

1,4,8,9-Naphthalene diimides (NDIs) with strong electron accepting ability and high stability are excellent building blocks for semiconductor polymers. However, 1,8-naphthalene monoimide (NMI) with similar structure and energy levels as that of NDI has never been used to construct conjugated polymers because of synthetic difficulty. Herein, 3,6-dibromo-NMI (DBNMI) with bulky alkyl groups was obtained effectively in a four-step synthesis, and three donor-acceptor (D-A) type conjugated polymers based on NMI were firstly prepared. These polymers have strong absorption in the range of 300–600 nm, low LUMO level of 3.68 eV, and moderate bandgaps of 2.18 eV. Space charge limiting current measurements indicate these polymers are typical electron transporting materials, and the highest electron mobility is up to 5.8 × 10−3 cm2 V−1 s−1, which is close to the star acceptor based on NDI (N2200, 5.0 × 10−3 cm2 V−1 s−1). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

A microscopic study of dissolution process of nanocrystals, an opposite while functioning cooperatively with growth in many cases, is an essential issue in variety aspects of research on nanocrystals. In this work, an in situ study of the dynamic dissolution process of palladium nanocrystals by liquid cell transmission electron microscope (TEM) is presented. The effective critical size (Rcritical) for monodispersed nanocrystals is determined to be about 5nm in the experimental condition of this article. When the size of nanocrystal is above Rcritical, the dissolution rate (dr/dt) is nearly a constant. For the nanocrystal sizing below Rcritical, the dissolution rate (dr/dt) increases with the decrease of the nanocrystal radius r, indicating that high equilibrium solubility must be taken into account in the dissolution rate of small nanocrystals in solution. It is found that the aggregation kinetics and confinement effect between adjacent nanocrystals have effects on the dissolution rate during the reaction, and it has been analyzed in details and discussed in terms of the underlying physics involved. Lastly, the effects of electron beam-water interaction and the iron (III) agents on the oxidative etching are also compared.

Sodium yttrium fluoride (NaYF4) is an upconverting material with many potential uses in chemistry, materials science, and biology that can be synthesized hydrothermally in both cubic (α) and hexagonal (β) crystallographic polymorphs. Understanding the mechanisms underlying the phase conversion between the cubic and hexagonal polymorphs is of great interest to help inform future efforts to synthesize atomically-precise quantum materials with well-defined sizes and morphologies. In this work, we use a combination of analytical and cryogenic transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), powder X-ray diffraction (XRD), in situ liquid cell TEM, atom probe tomography (APT), and extended x-ray absorption fine structure (EXAFS) measurements to show evidence suggesting that the hexagonal NaYF4 nanowires form through a non-classical crystal growth mechanism involving oriented attachment of grains of the cubic (α) phase. EXAFS spectroscopy also suggests that substitutional Yb3+ point defects within NaYF4 are distributed evenly throughout the crystal lattice without clustering, and also that they selectively substitute into one of the two possible trivalent yttrium sites in the unit cell.

International audience; The efficient assembly of nanoparticles by oriented attachment (OA) mechanism has attracted more and more attention. However, the morphological and structural coupling during the OA processes is not fully understood. Here, we propose the OA mechanism during the layer-based δ-MnO2 transformation to tunnel-based α-MnO2 using powder X-ray diffraction, X-ray atomic pair distribution function and transmission electron microscopy. It is suggested staged three-dimensional OA processes play a vital role in both morphological and concurrent structural evolution of δ-MnO2 into α-MnO2. In the initial stage of the evolution, the δ-MnO2 nanodots are found to spontaneously self-assemble into long nanosheet via OA process along a-b plane driven by hydrogen bonding through edge sites. Meanwhile, the Mn(IV) in the [MnO6] octahedral layers are reduced to Mn(III)/Mn(II) by H2O with the release of O2 and oxygen vacancies generation in the δ-MnO2 structure. The newly formed Mn(III) which migrates from layers to above/below the vacancies coordinate with three hydroxide oxygen. Therefore, the adjacent long nanosheets attach with each other driven by hydrogen bonding between hydroxide oxygen which coordinated with interlayer Mn(III) and form primary nanorods through face-to-face OA mechanism along c-axis. Concomitantly, the bonding of [Mn(III)O6] octahedra in interlayer of long nanosheets with adjacent [MnO6] octahedral layers were facilitated to construct the new 2  2 tunnel α-MnO2. These findings provide insight not only on mechanism of transformation of layer-based nanoparticles to tunnel-based nanoparticles but also on the efficient controlled synthesis and design of nanomaterials through different structures and morphologies.

We demonstrate that silanization can control the adhesion of nanostructures to the SiN windows compatible with liquid-cell transmission electron microscopy (LC-TEM). Formation of an (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayer on a SiN window, producing a surface decorated with amino groups, permits strong adhesion of Au nanoparticles to the window. Many of these nanoparticles remain static, undergoing minimal translation or rotation during LC-TEM up to high electron beam current densities due to the strong interaction between the APTES amino group and Au. We then use this technique to perform a direct comparative LC-TEM study on the behavior of ligand and nonligand-coated Au nanoparticles in a Au growth solution. While the ligand coated nanoparticles remain consistent even under high electron beam current densities, the naked nanoparticles acted as sites for secondary Au nucleation. These nucleated particles decorated the parent nanoparticle surface, forming consecutive monolayer assemblies of ∼2 nm diameter nanoparticles, which sinter into the parent particle when the electron beam was shut off. This method for facile immobilization of nanostructures for LC-TEM study will permit more sophisticated and controlled in situ experiments into the properties of solid-liquid interfaces in the future.

Because they provide lower cost but comparable activity to precious platinum (Pt)-based catalysts, nonprecious iron (Fe)-based materials, such as Fe/Fe

Oxidative etching has widely prevailed in the synthesis of a crystal and played a critical role in determining the final growth behavior. In this Letter, we report an in situ microscopic study on the oxidative etching of palladium cubic nanocrystals by liquid cell scanning transmission electron microscopy. The etching was realized with oxidative radiation reactants from electron-water interaction in the presence of Br(-) ions. Dissolution dynamics of monodispersed and aggregated nanocrystals were both investigated and compared. Analyses on the dissolution kinetics of nanocrystals and the diffusion kinetics of the dissolved agents were carried out based on the scanning transmission electron microscopy characterizations. The results presented here pave a way toward the quantitative understanding of the oxidative etching reaction and its application in the functionally orientated fabrication of nanocrystals with certain sizes, structures, and morphologies.

Density-functional theory calculations were performed to investigate CO adsorption and oxidation on V2O5 nanotubes formed by rolling V2O5 (010) layers. CO adsorbs on both the inside and outside walls of V2O5 nanotubes by physisorption and chemisorption modes. The bidentate carbonate can form from CO chemisorption and decompose to CO2 on V2O5 nanotubes. CO oxidation into CO2 by the lattice oxygen, i.e., decomposition of carbonate, on the inside wall of V2O5 nanotubes requires less (0.21 vs 0.40 and 0.43 eV) and releases more energy (−0.17 vs −0.02 and −0.03 eV) than that on the V2O5 (010) single layer and the outside wall of V2O5 nanotubes. Our study shows that lattice oxygen of V2O5 participates in CO oxidation, and the confined environment is beneficial to CO2 formation.

We investigated the growth of two-dimensional (2D) palladium dendritic nanostructures (DNSs) using in situ liquid-cell transmission electron microscopy (TEM). Detailed in situ and ex situ high-resolution scanning TEM (S/TEM) characterization and fractal dimension analyses reveal that the diffusion-limited aggregation and direct atomic deposition are responsible for the growth of palladium dendritic nanostructures.

We proposed a highly reproducible method that enables atomic resolution transmission electron microscopy investigations of the dynamics of nanoparticles in liquids. An ultrathin liquid layer was established as a result of formation of bubbles that was initiated and tuned by beam radiation. The migration, aggregation and rotation of palladium nanoparticles were observed.

To study the molecular mechanism of cyclooxygenase-2 (COX-2), one of effective ingredient of brucine, in inducing non-small cell lung cancer cell apoptosis.COX-2 promoter, transcription factor deletion mutants and COX-2 mRNA 3'-UTR-containing report plasmids were transfected with Renillia to non-small cell lung cancer A549 cell, in order to detect the activity of report gene luciferase and minimum cis-acting element of COX-2 promoter inhibited by brucine. The influence of brucine on IkappaB phosphorylation and the nuclear translocation of p65 were detected by immunoblotting assay.Brucine significantly suppressed LPS-induced COX-2 promoter activation, but revealed minor impact on COX-2 mRNA stability. NF-kappaB in the vicinity of COX-2 promoter-262 was an important cis-acting element of brucine for inhibiting the activity of COX-2 promoter. Brucine was found to inhibit the phosphorylation of IkappaBalpha as well as the nuclear translocation of p65.Brucine can improve A549 cells apoptosis by inhibiting the activity of NF-kappaB and the subsequent COX-2 gene expression.

OBJECTIVE To study the molecular mechanism of cyclooxygenase-2 (COX-2), one of effective ingredient of brucine, in inducing non-small cell lung cancer cell apoptosis. METHOD COX-2 promoter, transcription factor deletion mutants and COX-2 mRNA 3'-UTR-containing report plasmids were transfected with Renillia to non-small cell lung cancer A549 cell, in order to detect the activity of report gene luciferase and minimum cis-acting element of COX-2 promoter inhibited by brucine. The influence of brucine on IkappaB phosphorylation and the nuclear translocation of p65 were detected by immunoblotting assay. RESULT Brucine significantly suppressed LPS-induced COX-2 promoter activation, but revealed minor impact on COX-2 mRNA stability. NF-kappaB in the vicinity of COX-2 promoter-262 was an important cis-acting element of brucine for inhibiting the activity of COX-2 promoter. Brucine was found to inhibit the phosphorylation of IkappaBalpha as well as the nuclear translocation of p65. CONCLUSION Brucine can improve A549 cells apoptosis by inhibiting the activity of NF-kappaB and the subsequent COX-2 gene expression.

Helicopter trim models are nonlinear equations with lots of variables in fact, and the state of each variable is quite hard to determine. Itpsilas quite difficult to solve such nonlinear equations in numerical compute field so far. Combining the traditional numerical algorithmspsila (such as quasi-Newton Method) quick convergent ability, and the genetic algorithmpsilas advantages such as global convergency and mass searing. Developing a new hybrid genetic algorithm which can converge quickly in large scale. The following examples verified the algorithmpsilas feasibility and high efficiency, so it develops a new approach for triming helicopter. meanwhile, makes a successful attempt in how to combine the traditional mathematical method with the modern intelligent evaluation algorithm effectively.

Text categorization is a crucial task of increasing importance. Our work focuses on the study of Chinese text categorization on the basis of Boosting model. We chose the People's Daily news from TREC5 as our benchmark datasets. A minor modification to AdaBoost algorithm (Freund and Schapire, 1996, 2000) was applied for this hypothesis. By way of using the F1 measure for its final evaluation, the results of the Boosting model (AdaBoost.MH) is proved to be effective and outperforms most of other algorithms reported for Chinese text categorization.