Crystal structures and growth mechanism for ultrathin films of ionic compound materials: FeO(111) on Pt(111)

The growth and atomic structures of epitaxial iron-oxide films on Pt(111) were studied with scanning tunneling microscopy and high-resolution low-energy electron diffraction. During the initial layer-by-layer growth of FeO(111) four different structures are formed as the coverage increases to 2.5 monolayers, then a three-dimensional growth of Fe3O4(111) islands begins. The structural transformations demonstrate that the relaxations within the FeO(111) films and the Stranski-Krastanov growth mode are induced by electrostatic surface energies, which dominate the energetics of thin film systems made up of ionic compound materials

Combined surface science and density functional theory approach towards water ordered structures formation on magnetite

Three different adsorbed water species were distinguished on Fe-terminated Fe3O4 multilayer films using thermal desorption spectroscopy (TDS), and ultraviolet photoelectron spectroscopy (UPS) measured under adsorption-desorption equilibrium conditions [1]. By means of density functional theory (DFT) calculations, the first species (-water) were confirmed to correspond to dissociative water adsorption with the resulting hydroxyl (OH) groups of water on the surface iron (Fe) sites, and the hydrogen (H) atoms adsorbed onto surface oxygen (O) sites. The DFT results for the -water structure are consistent with the two OH-stretch lines observed by infrared-reflection-absorption-spectroscopy (IRAS) [2], and the UPS study [1]. The DFT calculations confirm the subsequent formation of dimeric water structures (-water) formed by H-bonded molecular water to the surface OH-groups on surface-Fe, and the H on the surface-O sites, respectively, as suggested by IRAS [2] and low energy electron diffraction (LEED) experiments [1]. The DFT results reveal that formation of the -water overlayer structure results from the diffusion of the mobile H-atoms from the initially molecular adsorbed water molecules on iron sites followed by formation of a transition structure with the H-atom adsorbed on nearest-neighboring oxygen sites, diffusing over the surface to adsorb on-top onto the next O-sites. This result is consistent with the proposed second-order kinetics of the recombinative adsorption process [1]. 1. Y. Joseph et. al., J. Phys. Chem. B 104, 3224 (2000). 2. U. Leist et al., Phys. Chem. Chem. Phys. 5, 2435 (2003)

Surface structure and water adsorption on Fe₃O₄(111): Spin-density functional theory and on-site Coulomb interactions

The surface structure of magnetite Fe3O4(111) in contact with oxygen and water is investigated using spin density functional theory plus on-site Coulomb interactions. The present results unravels apparent contradictions in the experimental data regarding the equilibrium stoichiometry of the bare surface termination. Both for 298 K and 1200 K, the equilibrium structure is terminated by 1/4 monolayer (ML) of iron (Fe) on top of a full oxygen layer, consistent with an earlier low-energy electron diffraction analysis. Nontheless, the calculated negative slope of the surface energies vs oxygen partial pressure shows that a 1/2 ML Fe termination would become stable under oxygen poor conditions at high temperatures, in agreement to interpretation of scanning tunneling microscopy experiments. Initial water adsorption is dissociative and saturates when all Fe sites are occupied by OH groups while the H atoms bind to surface oxygen. Further water bridges the OH and H groups resulting in a quite unique type of H-bonded molecular water with its oxygen forming a hydronium ion like structure OH3+-OH. This water structure is different from the water dimeric structures found as yet on oxide and metal surfaces for partially dissociated (H2O-OH-H) overlayers

Prediction models for short children born small for gestational age (SGA) covering the total growth phase. Analyses based on data from KIGS (Pfizer International Growth Database)

<p>Abstract</p> <p>Background</p> <p>Mathematical models can be developed to predict growth in short children treated with growth hormone (GH). These models can serve to optimize and individualize treatment in terms of height outcomes and costs. The aims of this study were to compile existing prediction models for short children born SGA (SGA), to develop new models and to validate the algorithms.</p> <p>Methods</p> <p>Existing models to predict height velocity (HV) for the first two and the fourth prepubertal years and during total pubertal growth (TPG) on GH were applied to SGA children from the KIGS (Pfizer International Growth Database) - 1^styear: N = 2340; 2^ndyear: N = 1358; 4^thyear: N = 182; TPG: N = 59. A new prediction model was developed for the 3^rdprepubertal year based upon 317 children by means of the all-possible regression approach, using Mallow's C(p) criterion.</p> <p>Results</p> <p>The comparison between the observed and predicted height velocity showed no significant difference when the existing prediction models were applied to new cohorts. A model for predicting HV during the 3^rdyear explained 33% of the variability with an error SD of 1.0 cm/year. The predictors were (in order of importance): HV previous year; chronological age; weight SDS; mid-parent height SDS and GH dose.</p> <p>Conclusions</p> <p>Models to predict growth to GH from prepubertal years to adult height are available for short children born SGA. The models utilize easily accessible predictors and are accurate. The overall explained variability in SGA is relatively low, due to the heterogeneity of the disorder. The models can be used to provide patients with a realistic expectation of treatment, and may help to identify compliance problems or other underlying causes of treatment failure.</p

The Auxological and Biochemical Continuum of Short Children Born Small for Gestational Age (SGA) or with Normal Birth Size (Idiopathic Short Stature)

Objective. Retrospective single-centre analysis of growth characteristics in 182 healthy short children born small for gestational age (SGA) or appropriate for gestational age (idiopathic short stature, ISS). Methods. Birth size references from the USA and Sweden were compared, and for the classification as SGA or ISS the Swedish reference was chosen. Height, target height (TH), bone age (BA), predicted adult height (PAH), IGF-I and IGFBP-3 values were compared between SGA and ISS. Results. In the combined group, birth weight and length showed a symmetric Gaussian distribution. The American reference overestimates the percentage of short birth length and underestimates that of low birth weight. In childhood, SGA children were shorter than ISS (−3.1 versus −2.6 SDS, P < .001), also in comparison to TH (−2.6 versus −1.9 SDS, P < .001). TH, height SDS change over time, BA delay, and PAH were similar. IGF-I and IGFBP-3 were lower in ISS (P = .03 and .09). Conclusions. SGA children represent the left tail of the Gaussian distribution of birth size in short children. The distinction between SGA and ISS depends on birth size reference. Childhood height of SGA is lower than of ISS, but the other auxological features are similar

Использование IoT-технологий в защите окружающей среды

Большинство дискуссий вокруг феномена Интернета вещей (IoT) обычно сводится к тем потенциальным преимуществам для бизнеса и к тем удобствам для пользователей, которые обеспечивают интеллектуальные устройства и объекты, окружающие нас ежедневно. Однако, каким образом Интернет вещей и индустриальный Интернет вещей (M2M - machine-to-machine), то есть беспроводная передача данных и информации между устройствами и объектами, будет способствовать устойчивому развитию и защите окружающей среды.Most of the discussions around the phenomenon of the Internet of Things (IoT) usually boils down to those potential benefits for the business and to those amenities for users that provide intelligent devices and objects that surround us daily. However, how the Internet of things and the industrial Internet of things (M2M - machine-to-machine), that is, the wireless transmission of data and information between devices and objects, can have a beneficial effect on our lives and will contribute to sustainable development and the protection of the environment on the planet

Development of the heat and mass transfer model for the study of the temperature traces water droplets in a flame

The heat and mass transfer model is developed with using Ansys Fluent. The typical temperature of gases in the trace of water droplets is determined (initial temperature of gases 1170 К). Several types for the location of water droplets are studied: two successive water droplets; two parallel water droplets; five water droplets in checkerboard order. The hypothesis about gas temperature reduction in the trace of a moving liquid is confirmed

Interaction of ethylbenzene and styrene with iron oxide model catalyst films at low coverages: a NEXAFS study

The adsorption of ethylbenzene and styrene on well ordered epitaxial iron oxide model catalyst films with different stoichiometries was investigated using near edge X-ray absorption fine structure spectroscopy (NEXAFS). On the iron-terminated Fe3O4(111) and a?Fe2O3(0001) surfaces a chemisorption of ethylbenzene and styrene is observed which initially occurs on the iron sites via the p-electron system of the phenyl ring. This forces the molecules into an almost flat lying configuration (h6 like ring adsorption geometry). In the case of ethylbenzene this adsorption complex is supposed to lead to an activation of the C-H bonds thus facilitating the dehydrogenation to styrene. The tilt angle of the aromatic ring systems increase to about 40° when approaching monolayer saturation. In contrast, the interaction with the oxygen-terminated FeO(111) surface is weak and of the physisorption type. The adsorbate-adsorbate interaction dominates and causes a tilted adsorption of the molecules from the beginning

Atomic and Electronic Structures of Unreconstructed Polar MgO(111) Thin Film on Ag(111)

Atomic and electronic structures of a polar surface of MgO formed on Ag(111) was investigated by using reflection high energy electron diffraction (RHEED), Auger electron spectroscopy, electron energy loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS). A rather flat unreconstructed polar MgO(111) 1$\times$1 surface could be grown by alternate adsorption of Mg and O$_{2}$ on Ag(111). The stability of the MgO(111) surface was discussed in terms of interaction between Ag and Mg atoms at the interface, and charge state of the surface atoms. EELS of this surface did not show a band gap region, and finite density of states appeared at the Fermi level in UPS. These results suggest that a polar MgO(111) surface was not an insulating surface but a semiconducting or metallic surface.Comment: 6 figures, to be published in Phys. Rev.