Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals.

Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing the surface structure at an atomic resolution is difficult, especially for solution ensembles of catalytic nanocrystals, which consist of heterogeneous particles with irregular shapes and surfaces. Here, we constructed 3D maps of the coordination number (CN) and generalized CN (CN_) for individual surface atoms of sub-3 nm Pt nanocrystals. Our results reveal that the synthesized Pt nanocrystals are enclosed by islands of atoms with nonuniform shapes that lead to complex surface structures, including a high ratio of low-coordination surface atoms, reduced domain size of low-index facets, and various types of exposed high-index facets. 3D maps of CN_ are directly correlated to catalytic activities assigned to individual surface atoms with distinct local coordination structures, which explains the origin of high catalytic performance of small Pt nanocrystals in important reactions such as oxygen reduction reactions and CO electro-oxidation.

Dynamic Computation Offloading Scheme for Drone-Based Surveillance Systems.

Recently, various technologies for utilizing unmanned aerial vehicles have been studied. Drones are a kind of unmanned aerial vehicle. Drone-based mobile surveillance systems can be applied for various purposes such as object recognition or object tracking. In this paper, we propose a mobility-aware dynamic computation offloading scheme, which can be used for tracking and recognizing a moving object on the drone. The purpose of the proposed scheme is to reduce the time required for recognizing and tracking a moving target object. Reducing recognition and tracking time is a very important issue because it is a very time critical job. Our dynamic computation offloading scheme considers both the dwell time of the moving target object and the network failure rate to estimate the response time accurately. Based on the simulation results, our dynamic computation offloading scheme can reduce the response time required for tracking the moving target object efficiently.

Adenine attenuates lipopolysaccharide-induced inflammatory reactions.

A nucleobase adenine is a fundamental component of nucleic acids and adenine nucleotides. Various biological roles of adenine have been discovered. It is not produced from degradation of adenine nucleotides in mammals but produced mainly during polyamine synthesis by dividing cells. Anti-inflammatory roles of adenine have been supported in IgE-mediated allergic reactions, immunological functions of lymphocytes and dextran sodium sulfate-induced colitis. However adenine effects on Toll-like receptor 4 (TLR4)-mediated inflammation by lipopolysaccharide (LPS), a cell wall component of Gram negative bacteria, is not examined. Here we investigated anti-inflammatory roles of adenine in LPS-stimulated immune cells, including a macrophage cell line RAW264.7 and bone marrow derived mast cells (BMMCs) and peritoneal cells in mice. In RAW264.7 cells stimulated with LPS, adenine inhibited production of pro-inflammatory cytokines TNF-α and IL-6 and inflammatory lipid mediators, prostaglandin E2 and leukotriene B4. Adenine impeded signaling pathways eliciting production of these inflammatory mediators. It suppressed IκB phosphorylation, nuclear translocation of nuclear factor κB (NF-κB), phosphorylation of Akt and mitogen activated protein kinases (MAPKs) JNK and ERK. Although adenine raised cellular AMP which could activate AMP-dependent protein kinase (AMPK), the enzyme activity was not enhanced. In BMMCs, adenine inhibited the LPS-induced production of TNF-α, IL-6 and IL-13 and also hindered phosphorylation of NF-κB and Akt. In peritoneal cavity, adenine suppressed the LPS-induced production of TNF-α and IL-6 by peritoneal cells in mice. These results show that adenine attenuates the LPS-induced inflammatory reactions.

Sevoflurane exposure during the neonatal period induces long-term memory impairment but not autism-like behaviors.

OBJECTIVE: To examine whether neonatal exposure to sevoflurane induces autism-like behaviors in mice. BACKGROUND: There are continuing reports regarding the potential negative effects of anesthesia on the developing brain. Recently, several studies suggest that neurotoxicity caused by anesthesia may lead to neurodevelopmental impairments. However, unlike reports focusing on learning and memory, there are only a few animal studies focusing on neurodevelopmental disorders after general anesthesia. Therefore, we have focused on autism, a representative neurodevelopmental disorder. METHODS: Neonatal mice (P6-7) were exposed to a titrated dose of sevoflurane for 6 h. Apoptosis was evaluated by assessing the expression level of cleaved (activated) caspase-3. Autism-like behaviors, general activity, anxiety level, and long-term memory were evaluated with multiple behavioral assays. RESULTS: Western blotting confirmed that neonatal exposure to sevoflurane increased the expression level of activated caspase-3, indicative of apoptosis. Mice exposed to sevoflurane also showed impaired long-term memory in fear tests. However, sevoflurane-exposed mice did not exhibit autism-like features in all of the following assays: social interaction (three-chamber test, caged social interaction), social communication (ultrasonic vocalization test), or repetitive behavior (self-grooming test, digging). There were also no differences in general activity (open field test, home cage activity) and anxiety (open field test, light-dark box) after sevoflurane exposure. CONCLUSIONS: Our results confirm previous studies that neonatal sevoflurane exposure causes neurodegeneration and long-term memory impairment in mice. However, sevoflurane did not induce autism-like features. Our study suggests that mice are more vulnerable to long-term memory deficits than autism-like behaviors after exposure to sevoflurane.

Docosahexaenoic acid-induced apoptosis is mediated by activation of mitogen-activated protein kinases in human cancer cells.

BACKGROUND: The role of omega-3 polyunsaturated fatty acids (ω3-PUFAs) in cancer prevention has been demonstrated; however, the exact molecular mechanisms underlying the anticancer activity of ω3-PUFAs are not fully understood. Here, we investigated the relationship between the anticancer action of a specific ω3-PUFA docosahexaenoic acid (DHA), and the conventional mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK) and p38 whose dysregulation has been implicated in human cancers. METHODS: MTT assays were carried out to determine cell viability of cancer cell lines (PA-1, H1299, D54MG and SiHa) from different origins. Apoptosis was confirmed by TUNEL staining, DNA fragmentation analysis and caspase activity assays. Activities of the conventional MAPKs were monitored by their phosphorylation levels using immunoblotting and immunocytochemistry analysis. Reactive oxygen species (ROS) production was measured by flow cytometry and microscopy using fluorescent probes for general ROS and mitochondrial superoxide. RESULTS: DHA treatment decreased cell viability and induced apoptotic cell death in all four studied cell lines. DHA-induced apoptosis was coupled to the activation of the conventional MAPKs, and knockdown of ERK/JNK/p38 by small interfering RNAs reduced the apoptosis induced by DHA, indicating that the pro-apoptotic effect of DHA is mediated by MAPKs activation. Further study revealed that the DHA-induced MAPKs activation and apoptosis was associated with mitochondrial ROS overproduction and malfunction, and that ROS inhibition remarkably reversed these effects of DHA. CONCLUSION: Together, these results indicate that DHA-induced MAPKs activation is dependent on its capacity to provoke mitochondrial ROS generation, and accounts for its cytotoxic effect in human cancer cells.

Small, solubilized platinum nanocrystals consist of an ordered core surrounded by mobile surface atoms.

In situ structures of Platinum (Pt) nanoparticles (NPs) can be determined with graphene liquid cell transmission electron microscopy. Atomic-scale three-dimensional structural information about their physiochemical properties in solution is critical for understanding their chemical function. We here analyze eight atomic-resolution maps of small (<3 nm) colloidal Pt NPs. Their structures are composed of an ordered crystalline core surrounded by surface atoms with comparatively high mobility. 3D reconstructions calculated from cumulative doses of 8500 and 17,000 electrons/pixel, respectively, are characterized in terms of loss of atomic densities and atomic displacements. Less than 5% of the total number of atoms are lost due to dissolution or knock-on damage in five of the structures analyzed, whereas 10-16% are lost in the remaining three. Less than 5% of the atomic positions are displaced due to the increased electron irradiation in all structures. The surface dynamics will play a critical role in the diverse catalytic function of Pt NPs and must be considered in efforts to model Pt NP function computationally.

Insights into structural defect formation in individual InP/ZnSe/ZnS quantum dots under UV oxidation.

InP/ZnSe/ZnS quantum dots (QDs) stand as promising candidates for advancing QD-organic light-emitting diodes (QLED), but low emission efficiency due to their susceptibility to oxidation impedes applications. Structural defects play important roles in the emission efficiency degradation of QDs, but the formation mechanism of defects in oxidized QDs has been less investigated. Here, we investigated the impact of diverse structural defects formation on individual QDs and propagation during UV-facilitated oxidation using high-resolution (scanning) transmission electron microscopy. UV-facilitated oxidation of the QDs alters shell morphology by the formation of surface oxides, leaving ZnSe surfaces poorly passivated. Further oxidation leads to the formation of structural defects, such as dislocations, and induces strain at the oxide-QD interfaces, facilitating In diffusion from the QD core. These changes in the QD structures result in emission quenching. This study provides insight into the formation of structural defects through photo-oxidation, and their effects on emission properties of QDs.

Facile one-pot synthesis of biomass-derived activated carbon as an interlayer material for a BAC/PE/Al2O3 dual coated separator in Li-S batteries.

Lithium-sulfur batteries (LSB) are an attractive alternative electrochemical energy storage device compared to conventional lithium-ion batteries due to their higher theoretical capacity and energy density. Despite these advantages, it is still difficult to commercialize LSB because of poor electrochemical performance caused by the dissolution of soluble lithium polysulfides (LiPS). To solve these critical issues, a multi-functional separator was prepared using biomass-derived activated carbon (BAC) and a ceramic layer on the polyethylene (PE) separator. For this purpose, BAC was synthesized by a facile one-pot synthesis method by a specifically designed furnace using various forms of milk waste. The multi-functional separator suppresses the effect of LiPS dissolution and increases the Li+ diffusion kinetics. BAC was able to absorb the LiPS shuttle, as confirmed by UV-vis measurements and X-ray photoelectron spectroscopy (XPS). LSB cells assembled using this multi-functional separator show a higher discharge capacity of 1092.5 mA h g-1 at 0.1 C-rate, while commercial PE separators deliver a specific capacity of 811.8 mA h g-1. These novel separators were also able to suppress lithium dendrites during cycling. This work offers a novel and simple approach for streamlining the synthesis process of BAC and applying it to LSB, aiding in the development of sustainable energy sources.

Complex ligand adsorption on 3D atomic surfaces of synthesized nanoparticles investigated by machine-learning accelerated ab initio calculation.

Nanoparticle surfaces are passivated by surface-bound ligands, and their adsorption on synthesized nanoparticles is complicated because of the intricate and low-symmetry surface structures. Thus, it is challenging to precisely investigate ligand adsorption on synthesized nanoparticles. Here, we applied machine-learning-accelerated ab initio calculation to experimentally resolved 3D atomic structures of Pt nanoparticles to analyze the complex adsorption behavior of polyvinylpyrrolidone (PVP) ligands on synthesized nanoparticles. Different angular configurations of large-sized ligands are thoroughly investigated to understand the adsorption behavior on various surface-exposed atoms with intrinsic low-symmetry. It is revealed that the ligand binding energy (Eads) of the large-sized ligand shows a weak positive relationship with the generalized coordination number . This is because the strong positive relationship of short-range direct bonding (Ebind) is attenuated by the negative relationship of long-range van der Waals interaction (EvdW). In addition, it is demonstrated that the PVP ligands prefer to adsorb where the long-range vdW interaction with the surrounding surface structure is maximized. Our results highlight the significant contribution of vdW interactions and the importance of the local geometry of surface atoms to the adsorption behavior of large-sized ligands on synthesized nanoparticle surfaces.

Method for 3D atomic structure determination of multi-element nanoparticles with graphene liquid-cell TEM.

Determining the 3D atomic structures of multi-element nanoparticles in their native liquid environment is crucial to understanding their physicochemical properties. Graphene liquid cell (GLC) TEM offers a platform to directly investigate nanoparticles in their solution phase. Moreover, exploiting high-resolution TEM images of single rotating nanoparticles in GLCs, 3D atomic structures of nanoparticles are reconstructed by a method called "Brownian one-particle reconstruction". We here introduce a 3D atomic structure determination method for multi-element nanoparticle systems. The method, which is based on low-pass filtration and initial 3D model generation customized for different types of multi-element systems, enables reconstruction of high-resolution 3D Coulomb density maps for ordered and disordered multi-element systems and classification of the heteroatom type. Using high-resolution image datasets obtained from TEM simulations of PbSe, CdSe, and FePt nanoparticles that are structurally relaxed with first-principles calculations in the graphene liquid cell, we show that the types and positions of the constituent atoms are precisely determined with root mean square displacement values less than 24 pm. Our study suggests that it is possible to investigate the 3D atomic structures of synthesized multi-element nanoparticles in liquid phase.

Enhancing the reliability of head nodes in underwater sensor networks.

Underwater environments are quite different from terrestrial environments in terms of the communication media and operating conditions associated with those environments. In underwater sensor networks, the probability of node failure is high because sensor nodes are deployed in harsher environments than ground-based networks. The sensor nodes are surrounded by salt water and moved around by waves and currents. Many studies have focused on underwater communication environments in an effort to improve the data transmission throughput. In this paper, we present a checkpointing scheme for the head nodes to quickly recover from a head node failure. Experimental results show that the proposed scheme enhances the reliability of the networks and makes them more efficient in terms of energy consumption and the recovery latency compared to the previous scheme without checkpointing.

Omega-3-polyunsaturated fatty acids suppress pancreatic cancer cell growth in vitro and in vivo via downregulation of Wnt/Beta-catenin signaling.

BACKGROUND/AIMS: ω3-polyunsaturated fatty acids (ω3- PUFAs) are known to possess anticancer properties. However, the relationship between ω3-PUFAs and ß-catenin, one of the key components of the Wnt signaling pathway, in human pancreatic cancer remains poorly characterized. METHODS: Human pancreatic cancer cells (SW1990 and PANC-1) were exposed to two ω3-PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), to investigate the relationship between ω3-PUFAs and the Wnt/ß-catenin signaling pathway in vitro. Mouse pancreatic cancer (PANC02) cells were implanted into fat-1 transgenic mice, which express ω3 desaturases and result in elevated levels of ω3-PUFAs endogenously. The tumor size, levels of Wnt/ß-catenin signaling molecules and apoptosis levels were analyzed to examine the influence of ω3-PUFAs in vivo. RESULTS: DHA and EPA significantly inhibited cell growth and increased cell death in pancreatic cancer cells. DHA also reduced ß-catenin expression, T cell factor/lymphoid-enhancing factor reporter activity and induced ß-catenin/Axin/GSK-3ß complex formation, a known precursor to ß-catenin degradation. Furthermore, Wnt3a, a natural canonical Wnt pathway ligand, reversed DHA-induced growth inhibition in PANC-1 cells. Immunohistochemical analysis showed aberrant upregulation and increased nuclear staining of ß-catenin in tumor tissues from pancreatic cancer patients. However, ß-catenin levels in tumor tissues from fat-1 transgenic mice were reduced with a significant increase in apoptosis compared with those from control mice. CONCLUSION: ω3-PUFAs may be an effective therapy for the chemoprevention and treatment of human pancreatic cancer. and IAP.

SINGLE: Atomic-resolution structure identification of nanocrystals by graphene liquid cell EM.

Analysis of the three-dimensional (3D) structures of nanocrystals with solution-phase transmission electron microscopy is beginning to reveal their unique physiochemical properties. We developed a "one-particle Brownian 3D reconstruction method" based on imaging of ensembles of colloidal nanocrystals using graphene liquid cell electron microscopy. Projection images of differently rotated nanocrystals are acquired using a direct electron detector with high temporal (<2.5 ms) resolution and analyzed to obtain an ensemble of 3D reconstructions. Here, we introduce computational methods required for successful atomic-resolution 3D reconstruction: (i) tracking of the individual particles throughout the time series, (ii) subtraction of the interfering background of the graphene liquid cell, (iii) identification and rejection of low-quality images, and (iv) tailored strategies for 2D/3D alignment and averaging that differ from those used in biological cryo-electron microscopy. Our developments are made available through the open-source software package SINGLE.

Expression regulation and function of Pref-1 during adipogenesis of human mesenchymal stem cells (MSCs).

Preadipocyte Factor 1 (Pref-1), also known as Delta-like Protein 1 (DLK-1) is an epidermal growth factor-like domain-containing trans-membrane protein that is involved in adipogenesis and cell fate decision. Its function in adipogenesis is reported inconsistently based on different cellular model systems. Here, by using human mesenchymal stem cells (MSCs), we show that Pref-1 is modulated by both dexamethasone and 3-isobutyl-1methylxanthine (IBMX), two components of the adipogenic induction mixture during the adipogenesis in vitro. IBMX induces the expression of Pref-1 in a time- and dose-dependent manner through cyclic AMP and cyclic GMP independent pathway and attenuates adipocyte differentiation by down-regulating PPARgamma (peroxisome proliferator activated receptor gamma) expression. Dexamethasone, on the other hand, is capable of subduing the inhibitory effect of IBMX-induced Pref-1 and initiating the adipogenesis by up-regulating PPARgamma expression. Moreover, the treatment of IBMX or dexamethasone alone fails to develop MSCs into mature adipocytes, however, treating cells with both IBMX and dexamethasone leads to a complete adipocyte differentiation as evaluated by lipid-droplet formation. Taken together, our study demonstrates that IBMX accelerates accumulation of lipid in MSCs only under the circumstance that the negative effect of Pref-1 induced by IBMX on the adipogenesis is overcome by dexamethasone.

Downregulation of APE1/Ref-1 is involved in the senescence of mesenchymal stem cells.

The senescence of human mesenchymal stem cells (hMSCs) causes disruption of tissue and organ maintenance, and is thus an obstacle to stem cell-based therapies for disease. Although some researchers have studied changes in the characteristics of hMSCs (decreases in differentiation ability and self-renewal), comparing young and old ages, the mechanisms of stem cell senescence have not yet been defined. In this study, we developed a growth curve for human bone marrow derived MSCs (hBMSCs) which changes into a hyperbolic state after passage number 7. Senescence associated beta-galactosidase (SA beta-gal) staining of hBMSCs showed 10% in passage 9 and 45% in passage 11. We detected an increase in endogenous superoxide levels during senescence that correlated with senescence markers (SA beta-gal, hyperbolic growth curve). Interestingly, even though endogenous superoxide increased in a replicative senescence model, the expression of APE1/Ref-1, which is sensitive to intracellular redox state, decreased. These effects were confirmed in a stress-induced senescence model by exogenous treatment with H(2)O(2). This change is related to the p53 activity that negatively regulates APE1/Ref-1. p21 expression levels, which represent p53 activity, were transiently increased in passage 9, meaning that they correlated with the expression of APE1/Ref-1. Overexpression of APE1/Ref-1 suppressed superoxide production and decreased SA beta-gal in hBMSCs. In conclusion, intracellular superoxide accumulation appears to be the main cause of the senescence of hBMSCs, and overexpression of APE1/Ref-1 can rescue cells from the senescence phenotype. Maintaining characteristics of hBMSCs by regulating intracellular reactive oxygen species production can contribute to tissue regeneration and to improved cell therapy.

A smart checkpointing scheme for improving the reliability of clustering routing protocols.

In wireless sensor networks, system architectures and applications are designed to consider both resource constraints and scalability, because such networks are composed of numerous sensor nodes with various sensors and actuators, small memories, low-power microprocessors, radio modules, and batteries. Clustering routing protocols based on data aggregation schemes aimed at minimizing packet numbers have been proposed to meet these requirements. In clustering routing protocols, the cluster head plays an important role. The cluster head collects data from its member nodes and aggregates the collected data. To improve reliability and reduce recovery latency, we propose a checkpointing scheme for the cluster head. In the proposed scheme, backup nodes monitor and checkpoint the current state of the cluster head periodically. We also derive the checkpointing interval that maximizes reliability while using the same amount of energy consumed by clustering routing protocols that operate without checkpointing. Experimental comparisons with existing non-checkpointing schemes show that our scheme reduces both energy consumption and recovery latency.

Critical differences in 3D atomic structure of individual ligand-protected nanocrystals in solution.

Precise three-dimensional (3D) atomic structure determination of individual nanocrystals is a prerequisite for understanding and predicting their physical properties. Nanocrystals from the same synthesis batch display what are often presumed to be small but possibly important differences in size, lattice distortions, and defects, which can only be understood by structural characterization with high spatial 3D resolution. We solved the structures of individual colloidal platinum nanocrystals by developing atomic-resolution 3D liquid-cell electron microscopy to reveal critical intrinsic heterogeneity of ligand-protected platinum nanocrystals in solution, including structural degeneracies, lattice parameter deviations, internal defects, and strain. These differences in structure lead to substantial contributions to free energies, consequential enough that they must be considered in any discussion of fundamental nanocrystal properties or applications.

A pilot study using machine learning methods about factors influencing prognosis of dental implants.

PURPOSE: This study tried to find the most significant factors predicting implant prognosis using machine learning methods. MATERIALS AND METHODS: The data used in this study was based on a systematic search of chart files at Seoul National University Bundang Hospital for one year. In this period, oral and maxillofacial surgeons inserted 667 implants in 198 patients after consultation with a prosthodontist. The traditional statistical methods were inappropriate in this study, which analyzed the data of a small sample size to find a factor affecting the prognosis. The machine learning methods were used in this study, since these methods have analyzing power for a small sample size and are able to find a new factor that has been unknown to have an effect on the result. A decision tree model and a support vector machine were used for the analysis. RESULTS: The results identified mesio-distal position of the inserted implant as the most significant factor determining its prognosis. Both of the machine learning methods, the decision tree model and support vector machine, yielded the similar results. CONCLUSION: Dental clinicians should be careful in locating implants in the patient's mouths, especially mesio-distally, to minimize the negative complications against implant survival.

ω3-polyunsaturated fatty acids induce cell death through apoptosis and autophagy in glioblastoma cells: In vitro and in vivo.

Among brain tumors, glioblastoma (GBM) is the most aggressive type and is associated with the lowest patient survival rate. Numerous lines of evidence have established that omega-3-polyunsaturated fatty acids (ω3-PUFAs) have potential for the prevention and therapy of several types of cancers. Docosahexaenoic acid (DHA), an ω3-PUFA, was reported to inhibit growth and induce apoptotic and autophagic cell death in several cancer cell lines; however, its effects on GBM cells are still unknown. in the present study, we examined the cytotoxic effect of DHA on the GBM cell lines, D54MG, U87MG, U251MG and GL261. Treatment of GBM cells with DHA induced PARP cleavage, increased the population of sub-G1 cells, and increased the number of TUNEL-positive cells, which are all indicative of apoptosis. Furthermore, treatment of GBM cells with DHA resulted in a significant increase in autophagic activity, as revealed by increased LC3-II levels, GFP-LC3 puncta, and autophagic flux activation, accompanied by activation of 5'-AMP-activated protein kinase (AMPK) and decreases in phosphorylated Akt (p-AktSer473) levels and mTOR activity. In vivo, endogenous expression of Caenorhabditis elegans ω3-desaturase, which converts ω6-PUFAs to ω3-PUFAs, in fat-1 transgenic mice yielded a significant decrease in tumor volume following subcutaneous injection of mouse glioma cells (GL261), when compared with wild-type mice. TUNEL-positive cell numbers and LC3-II levels were elevated in tumor tissue from the fat-1 transgenic mice compared with tumor tissue from the wild-type mice. In addition, p-Akt levels were decreased and p-AMPK levels were increased in tumor tissue from the fat-1 transgenic mice. These results indicate that ω3-PUFAs induce cell death through apoptosis and autophagy in GBM cells; thus, it may be possible to use ω3-PUFAs as chemopreventive and therapeutic agents for GBM.