Cs adsorption on Si(001) surface: ab initio study

First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Cs adsorption on the Si(001) surface for 0.5 and 1 ML coverages. We found that the saturation coverage corresponds to 1 ML adsorption with two Cs atoms occupying the double layer model sites. While the 0.5 ML covered surface is of metallic nature, we found that 1 ML of Cs adsorption corresponds to saturation coverage and leads to a semiconducting surface. The results for the electronic behavior and surface work function suggest that adsorption of Cs takes place via polarized covalent bonding.Comment: 8 pages, 7 figure

Para to Ortho transition of metallic dimers on Si(001)

Extensive electronic structure calculations are performed to obtain the stable geometries of metals like Al, Ga and In on the Si(001) surface at 0.5 ML and 1 ML coverages. Our results coupled with previous theoretical findings explain the recent experimental data in a comprehensive fashion. At low coverages, as shown by previous works, `Para' dimers give the lowest energy structure. With increasing coverage beyond 0.5 ML, `Ortho' dimers become part of low energy configurations leading toward a `Para' to `Ortho' transition at 1 ML coverage. For In mixed staggered dimers (`Ortho' and `Para') give the lowest energy configuration. For Ga, mixed dimers are non-staggered, while for Al `Para' to `Ortho' transition of dimers is complete. Thus at intermediate coverages between 0.5 and 1 ML, the `Ortho' and `Para' dimers may coexist on the surface. Consequently, this may be an explanation of the fact that the experimental observations can be successfully interpreted using either orientation. A supported zigzag structure at 0.5 ML, which resembles ${\rm (CH)_x}$, does not undergo a dimerization transition, and hence stays semi-metallic. Also, unlike ${\rm (CH)_x}$ the soliton formation is ruled out for this structure.Comment: 8 pages, 6 figure

In situ growth regime characterization of cubic GaN using reflection high energy electron diffraction

Cubic GaN layers were grown by plasma-assisted molecular beam epitaxy on 3C-SiC (001)substrates. In situ reflection high energy electron diffraction was used to quantitatively determine the Ga coverage of the GaN surface during growth. Using the intensity of the electron beam as a probe,optimum growth conditions of c-GaN were found when a 1 ML Ga coverage is formed at the surface. 1 micrometer thick c-GaN layers had a minimum surface roughness of 2.5 nm when a Ga coverage of 1 ML was established during growth. These samples revealed also a minimum full width at half maximum of the (002)rocking curve.Comment: 3pages with 4 figure

A study of Mg adsorption on Si(001) surface from first principles

First-principles calculations using density functional theory based on norm-conserving pseudopotentials have been performed to investigate the Mg adsorption on the Si(001) surface for 1/4, 1/2 and 1 monolayer coverages. For both 1/4 and 1/2 ML coverages it has been found that the most favorable site for the Mg adsorption is the cave site between two dimer rows consistent with the recent experiments. For the 1 ML coverage we have found that the most preferable configuration is when both Mg atoms on 2x1 reconstruction occupy the two shallow sites. We have found that the minimum energy configurations for 1/4 ML coverage is a 2x2 reconstruction while for the 1/2 and 1 ML coverages they are 2x1.Comment: 7 pages, 4 figure

A Simple, Quick, and Precise Procedure for the Determination of Water in Organic Solvents

A procedure for the UV/VIS-spectroscopic determination of water by the use of a solvatochromic pyridiniumphenolate betaine is given. The water content of organic solvents is calculated by a two parameter equation from λmax of the dye. A typical, detection limit is of the order of 1 mg in 1 ml solvent for routine spectrometers. The parameters for the determination of water are given for a number of commonly used solvents

Towards a comprehensive taxonomy for characterizing robots

Every day a new robot is developed with advanced characteristics and technical qualities. The increasingly rapid growth of robots and their characteristics demands bridging between the application requirements and the robot specifications. This process requires a supporting conceptual structure that can capture as many robot qualities as possible. Presenting robot characteristics through the proposed conceptual structure would enable designers to optimize robot capabilities against application requirements. It would also help application developers to select the most appropriate robot. Without a formal structure, an accurate linking between the robot domain and the application domain is not possible. This paper presents a novel theoretical representation that can capture robot features and capabilities and express them as descriptive dimensions to be used to develop a capability profile. The profile is intended to unify robot description and presentation. The proposed structure is reinforced with several layers, sections, categorizations and levels to allow a detailed explanation of robot characteristics. It is hoped that the proposed structure will influence the design, development, and testing of robots for specific applications. At the same time, it would help in highlighting the corresponding outlines in robot application requirements

Edith Stein's Thomism

After her baptism at the age of 32, Stein engaged with Aquinas on several levels. Initially she compared his thought with that of Husserl, then proceeded to translate several of his works, and attempted to explore some of his fundamental concepts (potency and act) phenomenologically. She arrived finally in Finite and Eternal Being at a philosophical position inspired by his synthesis of Christian faith and philosophical tradition without abandoning her phenomenological starting point and method. Whether one would want to call this position Thomist depends on what one understands Thomism to be

EFEK EKSTRAK DAUN KELOR (Moringa oleifera) PADA PERTUMBUHAN BAKTERI (Edwardsiella tarda) YANG MENGINFEKSI IKAN LELE SANGKURIANG (Clarias Gariepinus) SECARA IN VITRO

Tujuan penelitian ini untuk mengetahui Konsentrasi Minimum Ekstrak Daun Kelor (Moringa oleifera) Terhadap Pertumbuhan Bakteri Edwardsiella tarda Yang Menginfeksi Ikan Lele Sangkuriang (Clarias gariepinus) Secara In Vitro. Perlakuan penelitian konsentrasi minimum ekstrak daun kelor (Moringa oleifera) terhadap pertumbuhan bakteri Edwardsiella tarda yang menginfeksi ikan lele Sangkuriang (Clarias gariepinus) secara In Vitro adalah sebagai berikut: kontrol Positif 1 ml DMSO 10% (1 ml suspensi kuman), kontrol Negatif= 1 ml ekstrak daun kelordengan konsentrasi 100% + 1 ml DMSO 10%, perlakuan A. Konsentrasi 50 % (1 ml ekstrak daun kelor 100% + 1 ml DMSO 10% + 1 ml suspensi kuman), perlakuan B. Konsentrasi 40% (0.8 ml ekstrak daun kelor 100% +1.2 ml DMSO 10%  + 1 ml suspensi kuman), perlakuan C. Konsentrasi 30% (0.6 ml ekstrak daun kelor 100% + 1.4 ml DMSO 10%  + 1 ml suspensi kuman), perlakuan D. Konsentrasi 20% (0.4 ml ekstrak daun kelor 100% + 1.6 ml DMSO 10%  + 1 ml suspensi kuman) Hasil penelitian Konsentrasi Minimum Ekstrak Daun Kelor (Moringa oleifera) Terhadap Pertumbuhan Bakteri  Edwardsiella tarda yang Menginfeksi Ikan Lele Sangkuriang (Clarias Gariepinus)  Secara In Vitro dapat disimpulkan sebagai berikut: pemberian ekstrak daun kelor (Moringa oleifera) dapat menghambat pertumbuhan bakteri Edwardsiella tarda yang di ambil dari ikan lele sangkuriang (Clarias Gariepinus),  konsentrasi ekstrak dau kelor (Moringa oleifera) 20 %, 30%, 40% dan 50% dapat menghambat bakteri Edwardsiella tarda., pada konsentrasi ekstrak dau kelor (Moringa oleifera) 10% bakteri Edwardsiella tarda  masih tumbuh dengan baik.Kata Kunci: Edwardsiella tarda, Moringa oleifera, Clarias gariepinu