Formation energies of low-indexed surfaces of tin dioxide terminated by nonmetals

The surface formation energies of four low-indexed surfaces, including (001), (100), (110) and (011), of tin dioxide (SnO2) terminated by nonmetals (H, N, O, F, Cl, Br, and I) have been studied with the frameworks of density functional theory. A strong dependence of relative surface stabilities on surface atoms has been presented based on the calculations. Several instructions, in particular the selection of specific precursors and morphology controlling agents, have been further illustrated as a guideline for experimentalists.

The effect of Fe doping on adsorption of CO2/N2within carbon nanotubes : a density functional theory study with dispersion corrections

An ab initio density functional theory (DFT) study with correction for dispersive interactions was performed to study the adsorption of N2 and CO2 inside an (8, 8) single-walled carbon nanotube. We find that the approach of combining DFT and van der Waals correction is very effective for describing the long-range interaction between N2/CO2 and the carbon nanotube (CNT). Surprisingly, exohedral doping of an Fe atom onto the CNT surface will only affect the adsorption energy of the quadrupolar CO2 molecule inside the CNT (20–30%), and not that of molecular N2. Our results suggest the feasibility of enhancement of CO2/N2 separation in CNT-based membranes by using exohedral doping of metal atoms.

First principle study of hydrogenation of MgB2 : an important step toward reversible hydrogen storage in the coupled LiBH4/MgH2 system

Recent experiments [F. E. Pinkerton, M. S. Meyer, G. P. Meisner, M. P. Balogh, and J. J. Vajo, J. Phys. Chem. C 111, 12881 (2007) and J. J. Vajo and G. L. Olson, Scripta Mater. 56, 829 (2007)] demonstrated that the recycling of hydrogen in the coupled LiBH4/MgH2 system is fully reversible. The rehydrogenation of MgB2 is an important step toward the reversibility. By using ab initio density functional theory calculations, we found that the activation barrier for the dissociation of H2 are 0.49 and 0.58 eV for the B and Mg-terminated MgB2(0001) surface, respectively. This implies that the dissociation kinetics of H2 on a MgB2 (0001) surface should be greatly improved compared to that in pure Mg materials. Additionally, the diffusion of dissociated H atom on the Mg-terminated MgB2(0001) surface is almost barrier-less. Our results shed light on the experimentally-observed reversibility and improved kinetics for the coupled LiBH4/MgH2 system.

Half metallicity in a zigzag double-walled nanotube nanodot : an Ab initio prediction

Ab initio density functional calculations were performed to study finite-length zigzag (7, 0) @ (16, 0) double-walled carbon nanotubes (DWCNTs) with H-termination at the open ends. We find that such a DWCNT nanodot displays a very large magnetic moment at the zigzag edges and the ground state displays symmetric anti-ferromagnetic coupling. When an external electric field is applied along the direction of tube axis, a gap is opened for one spin channel, whereas another spin channel remains metallic, i.e. half metallicity occurs. Our results suggest an important new avenue for the development of CNT-based spintronic materials with enhanced properties.

Computational study of methyl derivatives of ammonia borane for hydrogen storage

The structures and thermodynamic properties of methyl derivatives of ammonia–borane (BH3NH3, AB) have been studied with the frameworks of density functional theory and second-order Møller–Plesset perturbation theory. It is found that, with respect to pure AB, methyl ammonia–boranes show higher complexation energies and lower reaction enthalpies for the release of H2, together with a slight increment of the activation barrier. These results indicate that the methyl substitution can enhance the reversibility of the system and prevent the formation of BH3/NH3, but no enhancement of the release rate of H2 can be expected.

CO2 capture and gas separation on boron carbon nanotubes

Concern about the increasing atmospheric CO2 concentration and its impact on the environment has led to increasing attention directed toward finding advanced materials and technologies suited for efficient CO2 capture, storage and purification of clean-burning natural gas. In this letter, we have performed comprehensive theoretical investigation of CO2, N2, CH4 and H2 adsorption on B2CNTs. Our study shows that CO2 molecules can form strong interactions with B2CNTs with different charge states. However, N2, CH4 and H2 can only form very weak interactions with B2CNTs. Therefore, the study demonstrates B2CNTs could sever as promising materials for CO2 capture and gas separation.

Cobalt-doped cadmium selenide colloidal nanowires

Co2+-doped CdSe colloidal nanowires with tunable size and dopant concentration have been prepared by a solution–liquid–solid (SLS) approach for the first time. These doped nanowires exhibit anomalous photoluminescence temperature dependence in comparison with undoped nanowires.

The HealthyTexts study : A randomized controlled trial to improve skin cancer prevention behaviors among young people

Several randomized trials have found behavior change programs delivered via text messaging to be efficacious to improve preventive health behaviors such as physical activity and stopping smoking; however few have assessed its value in skin cancer prevention or early detection. The HealthyTexts study enrolled 678 participants 18–42 years, and assigned them to receive 21 text messages about skin cancer prevention, skin self-examination or physical activity(attention control) over the course of one year. Baseline data have been collected and outcomes will be assessed at three months and twelve months post intervention. The trial aims to increase the mean overall sun protection habits index score from 2.3 to 2.7 with a standard deviation of 0.5 (effect size of 0.5) and the proportion of people who conduct a whole-body skin self-examination by an absolute 10%. This paper describes the study design and participants' baseline characteristics. In addition, participants' goals for their health, and strategies they apply to achieve those goals are summarized.

The role of V2O5 on the dehydrogenation and hydrogenation in magnesium hydride : An ab initio study

Ab initio density functional theory calculations are performed to study the experimentally observed catalytic role of V2O5 in the recycling of hydrogen in magnesium hydride. We find that the Mg–H bond length becomes elongated when MgH2 clusters are positioned on single, two, and three coordinated oxygen sites (O1, O2, and O3) on the V2O5(001) surface. Molecular hydrogen is predicted to spontaneously form at the hole site on the V2O5(001) surface. Additionally, the activation barrier for the dissociation of hydrogen on V-doped Mg(0001) surface is 0.20 eV, which is only 1/5 of that on pure Mg(0001) surface. Our results indicate that oxygen sites on the V2O5(001)surface and the V dopant in Mg may be important facilitators for dehydrogenation and rehydrogenation, respectively. The understanding gained here will aid in the rational design and development of Mg-based hydrogen storage materials.

Electrical property and characterization of nano-SnO2/wollastonite composite materials

Nano-tin oxide was deposited on the surface of wollastonite using the mixed solution including stannic chloride pentahydrate precursor and wollastonite by a hydrolysis precipitation process. The antistatic properties of the wollastonite materials under different calcined conditions and composite materials (nano-SnO2/wollastonite, SW) were measured by rubber sheeter and four-point probe (FPP) sheet resistance measurement. Effects of hydrolysis temperature and time, calcination temperature and time, pH value and nano-SnO2 coating amount on the resistivity of SW powders were studied, and the optimum experimental conditions were obtained. The microstructure and surface properties of wollastonite, precipitate and SW were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), specific surface area analyzer (BET), thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier translation infrared spectroscopy (FTIR) respectively. The results showed that the nano-SnO2/wollastonite composite materials under optimum preparation conditions showed better antistatic properties, the resistivity of which was reduced from 1.068 × 104 Ω cm to 2.533 × 103 Ω cm. From TG and XRD analysis, the possible mechanism for coating of SnO2 nanoparticles on the surface of wollastonite was proposed. The infrared spectrum indicated that there were a large number of the hydroxyl groups on the surface of wollastonite. This is beneficial to the heterogeneous nucleation reaction. Through morphology, EDS and XPS analysis, the surface of wollastonite fiber was coated with a layer of 10–15 nm thickness of tin oxide grains the distribution of which was uniform.

In vitro models for investigating keratinocyte responses to ultraviolet B radiation

This thesis describes the use of 2- and 3-dimensional cell-based models for studying how skin cells respond to ultraviolet radiation. These methods were used to investigate skin damage and repair after exposure to radiation in the context of skin cancer development. Interactions between different skin cell types were demonstrated as being significant in protecting against ultraviolet radiation-induced skin damage. This has important implications in understanding how skin cancers occur, as well as in the development of new strategies to prevent and treat them.

Generalized-positioning for mixed-frequency of mixed-GNSS and its preliminary applications

Modernized GPS and GLONASS, together with new GNSS systems, BeiDou and Galileo, offer code and phase ranging signals in three or more carriers. Traditionally, dual-frequency code and/or phase GPS measurements are linearly combined to eliminate effects of ionosphere delays in various positioning and analysis. This typical treatment method has imitations in processing signals at three or more frequencies from more than one system and can be hardly adapted itself to cope with the booming of various receivers with a broad variety of singles. In this contribution, a generalized-positioning model that the navigation system independent and the carrier number unrelated is promoted, which is suitable for both single- and multi-sites data processing. For the synchronization of different signals, uncalibrated signal delays (USD) are more generally defined to compensate the signal specific offsets in code and phase signals respectively. In addition, the ionospheric delays are included in the parameterization with an elaborate consideration. Based on the analysis of the algebraic structures, this generalized-positioning model is further refined with a set of proper constrains to regularize the datum deficiency of the observation equation system. With this new model, uncalibrated signal delays (USD) and ionospheric delays are derived for both GPS and BeiDou with a large dada set. Numerical results demonstrate that, with a limited number of stations, the uncalibrated code delays (UCD) are determinate to a precision of about 0.1 ns for GPS and 0.4 ns for BeiDou signals, while the uncalibrated phase delays (UPD) for L1 and L2 are generated with 37 stations evenly distributed in China for GPS with a consistency of about 0.3 cycle. Extra experiments concerning the performance of this novel model in point positioning with mixed-frequencies of mixed-constellations is analyzed, in which the USD parameters are fixed with our generated values. The results are evaluated in terms of both positioning accuracy and convergence time.

Predicate encryption for multi-inner-products

Predicate encryption is a new primitive that supports flexible control over access to encrypted data. We study predicate encryption systems, evaluating a wide class of predicates. Our systems are more expressive than the existing attribute-hiding systems in the sense that the proposed constructions support not only all existing predicate evaluations but also arbitrary conjunctions and disjunctions of comparison and subset queries. Toward our goal, we propose encryption schemes supporting multi-inner-product predicate and provide formal security analysis. We show how to apply the proposed schemes to achieve all those predicate evaluations.

Insights into the mechanism of the reaction between ttrachloro-p-bnzoquinone and hydrogen peroxide and their implications in the catalytic role of water molecules in producing the hydroxyl radial

Detailed mechanisms for the formation of hydroxyl or alkoxyl radicals in the reactions between tetrachloro-p-benzoquinone (TCBQ) and organic hydroperoxides are crucial for better understanding the potential carcinogenicity of polyhalogenated quinones. Herein, the mechanism of the reaction between TCBQ and H2O2 has been systematically investigated at the B3LYP/6-311++G** level of theory in the presence of different numbers of water molecules. We report that the whole reaction can easily take place with the assistance of explicit water molecules. Namely, an initial intermediate is formed first. After that, a nucleophilic attack of H2O2 onto TCBQ occurs, which results in the formation of a second intermediate that contains an OOH group. Subsequently, this second intermediate decomposes homolytically through cleavage of the O-O bond to produce a hydroxyl radical. Energy analyses suggest that the nucleophilic attack is the rate-determining step in the whole reaction. The participation of explicit water molecules promotes the reaction significantly, which can be used to explain the experimental phenomena. In addition, the effects of F, Br, and CH3 substituents on this reaction have also been studied.

Metabolomics coupled with proteomics advancing drug discovery toward more agile development of targeted combination therapies

To enhance the therapeutic efficacy and reduce the adverse effects of traditional Chinese medicine, practitioners often prescribe combinations of plant species and/or minerals, called formulae. Unfortunately, the working mechanisms of most of these compounds are difficult to determine and thus remain unknown. In an attempt to address the benefits of formulae based on current biomedical approaches, we analyzed the components of Yinchenhao Tang, a classical formula that has been shown to be clinically effective for treating hepatic injury syndrome. The three principal components of Yinchenhao Tang are Artemisia annua L., Gardenia jasminoids Ellis, and Rheum Palmatum L., whose major active ingredients are 6,7-dimethylesculetin (D), geniposide (G), and rhein (R), respectively. To determine the mechanisms underlying the efficacy of this formula, we conducted a systematic analysis of the therapeutic effects of the DGR compound using immunohistochemistry, biochemistry, metabolomics, and proteomics. Here, we report that the DGR combination exerts a more robust therapeutic effect than any one or two of the three individual compounds by hitting multiple targets in a rat model of hepatic injury. Thus, DGR synergistically causes intensified dynamic changes in metabolic biomarkers, regulates molecular networks through target proteins, has a synergistic/additive effect, and activates both intrinsic and extrinsic pathways.