Association between serum iron, blood lead, cadmium, mercury, selenium, manganese and low cognitive performance in old adults from National Health and Nutrition Examination Survey (NHANES): a cross-sectional study.

Cognitive decline is a public health problem for the world's ageing population. This study was to evaluate the relationships between serum Fe, blood Pb, Cd, Hg, Se and Mn and cognitive decline in elderly Americans. Data of this cross-sectional study were extracted from the National Health and Nutritional Examination Survey (NHANES 2011-2014). Cognitive performance was measured by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), Animal Fluency and Digit Symbol Substitution Test (DSST) tests. Weighted univariable and multivariate logistic regression analyses were used to assess the associations between six trace elements and low cognitive performance. Subgroup analyses based on diabetes and hypertension history were further assessed the associations. A total of 2002 adults over 60 years old were included. After adjusting covariates, elevated serum Fe levels were associated with the decreased risk of low cognitive performance, especially in the elderly without diabetes history and with hypertension history. High blood Cd levels were associated with the high odds of low cognitive performance in old adults with diabetes and hypertension history. Elevated blood Mn levels were connected with low cognitive performance in old hypertensive people. High blood Pb levels were related to the high odds of low cognitive performance, especially in the elderly without diabetes and hypertension history. High blood Se levels were linked to the decreased risk of low cognitive performance in all the elderly. Appropriate Fe, Se supplementation and Fe-, Se-rich foods intake, while reducing exposure to Pb, Cd and Mn may be beneficial for cognitive function in the elderly.

Two-Dimensional Ultrathin Silica Films.

Two-dimensional (2D) ultrathin silica films have the potential to reach technological importance in electronics and catalysis. Several well-defined 2D-silica structures have been synthesized so far. The silica bilayer represents a 2D material with SiO2 stoichiometry. It consists of precisely two layers of tetrahedral [SiO4] building blocks, corner connected via oxygen bridges, thus forming a self-saturated silicon dioxide sheet with a thickness of ∼0.5 nm. Inspired by recent successful preparations and characterizations of these 2D-silica model systems, scientists now can forge novel concepts for realistic systems, particularly by atomic-scale studies with the most powerful and advanced surface science techniques and density functional theory calculations. This Review provides a solid introduction to these recent developments, breakthroughs, and implications on ultrathin 2D-silica films, including their atomic/electronic structures, chemical modifications, atom/molecule adsorptions, and catalytic reactivity properties, which can help to stimulate further investigations and understandings of these fundamentally important 2D materials.

CsPbBr3 microarrays with tunable periodicity, optoelectronic and field emission properties using self-assembled polystyrene template and co-evaporation method.

The booming growth of all inorganic cesium lead halide perovskites in optoelectronic applications has prompted extensive research interest in the fabrication of ordered nanostructures or microarrays for enhanced device performances. However, the high cost and complexity of commercial lithographic approaches impede the facile fabrication of perovskite microarrays. Herein, CsPbBr3 microarrays with tunable periodicities have been fabricated using a self-assembled polystyrene nanosphere template and a co-evaporation method. The periodicity of CsPbBr3 microarrays is precisely manipulated by simply modifying the size of polystyrene nanospheres. These microarrays are beneficial for light harvesting, leading to better light absorption ability and prolonged photoinduced carrier lifetime. The longest average carrier lifetime of 58.3 ns is obtained for CsPbBr3 microarrays with a periodicity of 1.0 µm. More importantly, the periodic structures of CsPbBr3 microarrays result in a tunable density of emitter tips in field emission devices. Compared to compact CsPbBr3 films, a 68.2% decrease of the turn-on field is observed for CsPbBr3 microarrays when the periodicity is 150 nm. The higher density of emitter tips leads to larger local field enhancement, and hence the largest field enhancement factor of 3346.6. Finally, a good emission current stability for CsPbBr3 microarray-based field emission devices has been demonstrated.

Structural Evolution of Ga-Cu Model Catalysts for CO2 Hydrogenation Reactions.

We studied the initial stages of Ga interaction with the Cu(001) surface and environment-induced surface transformations in an attempt to elucidate the surface chemistry of the Cu-Ga catalysts recently proposed for CO2 hydrogenation to methanol. The results show that Ga readily intermixes with Cu upon deposition in vacuum. However, even traces of oxygen in the gas ambient cause Ga oxidation and the formation of two-dimensional ("monolayer") Ga oxide islands uniformly covering the Cu surface. The surface morphology and the oxidized state of Ga remain in H2 as well as in a CO2 + H2 reaction mixture at elevated pressures and temperatures (0.2 mbar, 700 K). The results indicate that the Ga-doped Cu surface under reaction conditions exposes a variety of structures including GaO x /Cu interfacial sites, which must be taken into account for elucidating the reaction mechanism.

Interaction of Hydrogen with Ceria: Hydroxylation, Reduction, and Hydride Formation on the Surface and in the Bulk.

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO2 ) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO2 (111) thin films and CeO2 powders, and theoretical calculations of CeO2 (111) surfaces with oxygen vacancies (Ov ) at the surface and in the bulk. We show that, on a stoichiometric CeO2 (111) surface, H2 dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO2-x samples, both films and powders, hydroxyls and hydrides (Ce-H) are formed on the surface as well as in the bulk, accompanied by the Ce3+ ↔ Ce4+ redox reaction. As the Ov concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H2 /CeO2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.

CORM-3 Regulates Microglia Activity, Prevents Neuronal Injury, and Improves Memory Function During Radiation-induced Brain Injury.

OBJECTIVE: This study aims to explore in detail, the mechanism of the carbon monoxide releasing molecule-3 (CORM-3) in regulating the activity of microglia (MG) in the treatment of radiation brain injury (RBI). METHODS: The brain injury models of BV2 cells and Balb/C mice were established and randomly divided into three groups: the normal control group (CON), the single radiation group (RAD), and the radiation plus CORM-3 intervention group (RAD+CORM). Immunofluorescence was used to observe the effects on activation of the MG. The expressions of inflammatory factors, such as intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS), were detected by Western blot. Neuron apoptosis and regeneration in the radiation brain injury (RBI) model were detected by neuronal nuclear antigen (NeuN)+TUNEL and NeuN+BrdU double staining. A Morris water maze was used to assess the spatial learning and memory of the mice. RESULTS: Within 48 h after radiation, CORM-3 inhibited activation of the MG, blocked the phosphorylation of P38, and increased the expression of ICAM-1 and iNOS. Therefore, CORM-3 might alleviate MG-mediated neuronal apoptosis and promote neural regeneration in the subgranular zone (SGZ) of the dentate gyrus of the hippocampus. CORM-3 could increase the swimming distance and platform-stay time of the mice in the target platform quadrant after radiation. CONCLUSION: CORM-3 could effectively improve the inflammatory response induced by activation of the MG, reduce neuronal apoptosis, promote neural regeneration, and improve the learning and memory performance of mice after radiation.

Water-Assisted Homolytic Dissociation of Propyne on a Reduced Ceria Surface.

The emergence of ceria (CeO2 ) as an efficient catalyst for the selective hydrogenation of alkynes has attracted great attention. Intensive research effort has been devoted to understanding the underlying catalytic mechanism, in particular the H2 -CeO2 interaction. Herein, we show that the adsorption of propyne (C3 H4 ) on ceria, another key aspect in the hydrogenation of propyne to propene, strongly depends on the degree of reduction of the ceria surface and hydroxylation of the surface, as well as the presence of water. The dissociation of propyne and the formation of methylacetylide (CH3 CC-) have been identified through the combination of infrared reflection absorption spectroscopy (IRAS) and DFT calculations. We demonstrate that propyne undergoes heterolytic dissociation on the reduced ceria surface by forming a methylacetylide ion on the oxygen vacancy site and transferring a proton to the nearby oxygen site (OH group), while a water molecule that competes with the chemisorbed methylacetylide at the vacancy site assists the homolytic dissociation pathway by rebounding the methylacetylide to the nearby oxygen site.

Isolating the Roles of Hydrogen Exposure and Trace Carbon Contamination on the Formation of Active Catalyst Populations for Carbon Nanotube Growth.

Limited understanding of the factors influencing the yield of carbon nanotubes (CNTs) relative to the number of catalyst particles remains an important barrier to their large-scale production with high quality, and to tailoring CNT properties for applications. This lack of understanding is evident in the frequent use of Edisonian approaches to give high-yield CNT growth, and in the sometimes-confusing influence of trace residues on the reactor walls. In order to create conditions wherein CNT yield is reproducible and to enable large-scale and reliable CNT synthesis, it is imperative to understand-fundamentally-how these common practices impact catalytic activity and thus CNT number density. Herein, we use ambient pressure-X-ray photoelectron spectroscopy (AP-XPS) to reveal the influence of carbon and hydrogen on the coupling between catalyst reduction and CNT nucleation, from an iron catalyst film. We observe a positive correlation between the degree of catalyst reduction and the density of vertically aligned CNTs (forests), verifying that effective catalyst reduction is critical to CNT nucleation and to the resulting CNT growth yield. We demonstrate that the extent of catalyst reduction is the reason for low CNT number density and for lack of self-organization, lift-off, and growth of CNT forests. We also show that hydrocarbon byproducts from consecutive growths can facilitate catalyst reduction and increase CNT number density significantly. These findings suggest that common practices used in the field-such as reactor preconditioning-aid in the reduction of the catalyst population, thus improving CNT number density and enabling the growth of dense forests. Our results also motivate future work using AP-XPS and complementary metrology tools to optimize CNT growth conditions according to the catalyst chemical state.

Immobilization of single argon atoms in nano-cages of two-dimensional zeolite model systems.

The confinement of noble gases on nanostructured surfaces, in contrast to bulk materials, at non-cryogenic temperatures represents a formidable challenge. In this work, individual Ar atoms are trapped at 300 K in nano-cages consisting of (alumino)silicate hexagonal prisms forming a two-dimensional array on a planar surface. The trapping of Ar atoms is detected in situ using synchrotron-based ambient pressure X-ray photoelectron spectroscopy. The atoms remain in the cages upon heating to 400 K. The trapping and release of Ar is studied combining surface science methods and density functional theory calculations. While the frameworks stay intact with the inclusion of Ar atoms, the permeability of gasses (for example, CO) through them is significantly affected, making these structures also interesting candidates for tunable atomic and molecular sieves. These findings enable the study of individually confined noble gas atoms using surface science methods, opening up new opportunities for fundamental research.

Probing the effect of the Pt-Ni-Pt(111) bimetallic surface electronic structures on the ammonia decomposition reaction.

We report a detailed investigation of elementary catalytic decomposition of ammonia on the Pt-Ni-Pt(111) bimetallic surface using in situ near ambient pressure X-ray photoelectron spectroscopy. Under the near ambient pressure (0.6 mbar) reaction conditions, a different dehydrogenation pathway with a reduced activation energy barrier for recombinative nitrogen desorption on the Pt-Ni-Pt(111) bimetallic surface is observed. The unique surface catalytic activity is correlated with the downward shift of the Pt 5d band states induced by the Ni subsurface atoms via charge redistribution of the topmost Pt layer. Our results provide a practical understanding of the unique chemistry of bimetallic catalysts for facile ammonia decomposition under realistic reaction conditions.

Reversible Tuning of Interfacial and Intramolecular Charge Transfer in Individual MnPc Molecules.

The reversible selective hydrogenation and dehydrogenation of individual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics.

Tuning the electronic properties of ZnO nanowire field effect transistors via surface functionalization.

Using in situ field effect transistor (FET) characterization combined with the molecular beam epitaxy technique, we demonstrate a significant depletion of electron charge carriers in single zinc oxide (ZnO) nanowire through the surface modification with molybdenum trioxide (MoO3) and 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HATCN) layers. The electron mobility of ZnO nanowire was found to sharply decrease after the surface modification with MoO3; in contrast, the electron mobility significantly increased after functionalization with HATCN layers. Such depletion of n-type conduction originates from the interfacial charge transfer, corroborated by in situ photoelectron spectroscopy studies. The air exposure effect on MoO(3-) and HATCN-coated ZnO nanowire devices was also investigated.

Energy level realignment in weakly interacting donor-acceptor binary molecular networks.

Understanding the effect of intermolecular and molecule-substrate interactions on molecular electronic states is key to revealing the energy level alignment mechanism at organic-organic heterojunctions or organic-inorganic interfaces. In this paper, we investigate the energy level alignment mechanism in weakly interacting donor-acceptor binary molecular superstructures, comprising copper hexadecafluorophthalocyanine (F16CuPc) intermixed with copper phthalocyanine (CuPc), or manganese phthalocynine (MnPc) on graphite. The molecular electronic structures have been systematically studied by in situ ultraviolet photoelectron spectroscopy (UPS) and low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) experiments and corroborated by density functional theory (DFT) calculations. As demonstrated by the UPS and LT-STM/STS measurements, the observed unusual energy level realignment (i.e., a large downward shift in donor HOMO level and a corresponding small upward shift in acceptor HOMO level) in the CuPc-F16CuPc binary superstructures originates from the balance between intermolecular and molecule-substrate interactions. The enhanced intermolecular interactions through the hydrogen bonding between neighboring CuPc and F16CuPc can stabilize the binary superstructures and modify the local molecular electronic states. The obvious molecular energy level shift was explained by gap-state-mediated interfacial charge transfer.

Correlation between the changes in ambulatory electroencephalography findings and epilepsy recurrence after medication withdrawal among the population in southern China.

Patients suffering from epilepsy need long-term medication. However, after the epilepsy is completely under control, the recurrence rate is high once the drug dose is reduced gradually. The present study investigated the possible correlation between the changes shown by ambulatory electroencephalography (EEG) and epilepsy recurrence after medication withdrawal, and assessed the value of ambulatory EEG findings in predicting the recurrence of epilepsy after medication withdrawal, in 265 patients from Southern China followed up for 5 years. Anticonvulsants were withdrawn until onset had been controlled thoroughly for over 3 years and ambulatory EEG detected no abnormalities. Ambulatory EEG was performed at least once per year, and findings at the first visit, during treatment, and before and after medication withdrawal were compared and analyzed. There were 47 patients with recurrent epilepsy in this study. Patients with normal ambulatory EEG findings at the first visit and during treatment had lower recurrence rate (about 8.1%) compared to patients with epileptic waves (25.0%), and patients with focal epileptic waves in the temporal, occipital, frontal, and parietal lobes, or in multiple areas was even higher. Patients with epileptic waves also showed higher clinical recurrence rate during the follow-up period. Abnormal ambulatory EEG findings are an important indicator of epileptic recurrence, and is of great value in predicting the recurrence of epilepsy after medication withdrawal.

Tissue culture-induced somaclonal variation of decreased pollen viability in torenia (Torenia fournieri Lind.).

BACKGROUND: Phenotypic and genotypic variations, collectively called somaclonal variations, are induced during tissue culture. RESULTS: We studied the phenotypic variation in pollen viability of regenerants of torenia after subculturing for one to nine generations. We found that pollen viability of regenerants continuously decreased with increasing subculture time. High concentrations of plant growth regulators applied to the Murashige and Skoog (MS) medium also resulted in diminished pollen viability. Furthermore, antibiotic application during gene transformation also decreased pollen viability of the transformants. However, the process of long-term culture did not significantly change pollen viability. The mean methylation level of regenerants showed a 0.28% to 3.95% decrease in seedlings subcultured in vitro for nine generations. Moreover, when the ninth subcultured regenerants with reduced pollen vibility were recovered in soil to get seeds, the pollen viability of seed-derive plants was similar to that of the wild type. CONCLUSIONS: The results show that plant growth regulators, antibiotics, and the number of subculture generations influence somaclonal variations in torenia. The somaclonal variations in torenia may results from epigenetic changes.

Preparation of supercapacitor electrodes through selection of graphene surface functionalities.

In order to investigate the effect of graphene surface chemistry on the electrochemical performance of graphene/polyaniline composites as supercapacitor electrodes, graphene oxide (G-O), chemically reduced G-O (RG-O), nitrogen-doped RG-O (N-RG-O), and amine-modified RG-O (NH(2)-RG-O) were selected as carriers and loaded with about 9 wt % of polyaniline (PANi). The surface chemistry of these materials was analyzed by FTIR, NEXAFS, and XPS, and the type of surface chemistry was found to be important for growth of PANi that influences the magnitude of increase of specific capacitance. The NH(2)-RG-O/PANi composite exhibited the largest increase in capacitance with a value as high as 500 F g(-1) and good cyclability with no loss of capacitance over 680 cycles, much better than that of RG-O/PANi, N-RG-O/PANi, and G-O/PANi when measured in a three-electrode system. A NH(2)-RG-O/PANi//N-RG-O supercapacitor cell has a capacitance of 79 F g(-1), and the corresponding specific capacitance for NH(2)-RG-O/PANi is 395 F g(-1). This research highlights the importance of introducing -NH(2) to RG-O to achieve highly stable cycling performance and high capacitance values.