Study of the cap structure of (3,3), (4,4) and (5,5)-SWCNTs: application of the sphere-in-contact model

We have applied the sphere-in-contact model supported by hybrid Density Functional Theory (DFT) calculations to elucidate the cap geometry of the sub-nanometer in dimension (3,3), (4,4) and (5,5) single-wall carbon-nanotubes (SWCNTs). Our approach predicts certain cap-geometries that do not comprise of the commonly known for their stability combination of pentagonal and hexagonal carbon rings but also tetragonal, trigonal and all-pentagonal structures. Based on hybrid-DFT calcula-tions carbon atoms in these new cap geometries have similar stability to carbon found in other fullerene-like capped zig-zag and arm-chair nanotubes (i.e., (5,5), (6,6), (9,0) and (10,0)) that are known to be stable and synthetically accessible. We find that the cap structure of the (3,3)-CNTs is a pointy carbon geometry comprised of six pentagonal rings with a single carbon atom at the tip apex. In this tip geome-try the carbon atom at the tip apex does not have the usual sp2 or sp3 geometry but an unusual trigonal pyramidal configuration. DFT calculations of the molecular orbitals and density-of-states of the tip show that this tip structure apart from being stable can be used in scanning probe microscopies such as STM for very high resolution imaging

Study of the antibacterial activity of total extract and Petroleum ether, chloroform, ethyl acetate and aqueous fractions of aerial parts of heliotropium bacciferum against staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, E.coli, Salmonella enteritidis

Heliotropium bacciferum is One of the plants belonging to the family Boraginaceae , which is Restricted distribution in the south of Iran. It is used for Hypotension, fever, stomach ulcers in traditional medicine. In this study, the antibacterial effects of extracts and fractions of chloroform, ethyl acetate and aqueous, aerial parts of Heliotropium bacciferum Forssk was evaluated against five bacterial strains. The methanol extract were prepared using the percolation method. Fractions of chloroform, Petroleum ether, ethyl acetate, methanol and aqueous respectively by Liquid - Liquid fractionation of the total extract were prepared. The antibacterial activity against two Gram positive bacteria, three Gram negative bacterial using Minimum inhibitory concentration in microplate and well plate method. Results showed that H. bacciferum extracts exhibited a significant activity against strains Staphylococcus aureus, Bacillus cereus,Pseudomonas aeruginosa, E.coli, Salmonella enteritidis. MIC and well plate is between 7.6-125 μg/ml. The results of this study indicate that extracts of the plant H.bacciferum has a antimicrobial effect against strains are listed And among the extracts, aqueous part is that most antibacterial effect of the other fraction and then methanolic extract has the greatest effect

Size-dependent bond dissociation enthalpies in single-walled carbon nanotubes

We report the bond dissociation enthalpy (BDE) and the local electronic properties of Single-Walled Carbon Nanotubes (SWCNT) using density functional theory. Our analysis shows that there is a strong size-dependence of the BDE of these SWCNTs, which is inversely proportional to the radius-squared (1/r2) and the length (1/l) of SWCNT. We derive quantitative relationships from which the BDE can be calculated as a function of size and radius of the SWCNT. We find that the BDE of SWCNT outside the size-dependent region is about 480 kJ mol−1, which can be used for thermochemical calculations

TOWARDS A MODEL OF TECHNOLOGY USAGE AND DIGITAL MATURITY IN CHILDREN: A GROUNDED-THEORY APPROACH

Increased use of digital technologies by children has raised some concerns about how digital technologies may be influencing multiple aspects of children’ lives. The purpose of this study is to investigate on how children use digital technologies, aiming at identifying factors that indicate how mature children are in the use of digital technologies. We conducted a qualitative study by collecting data from five children focus groups in Spain, with a total of 20 participants. We generated 10 factors that indicate digital maturity, namely digital literacy and technology awareness, perceived benefits and risks, types and patters of technology usage, managing tensions, adult interaction and mediation, regulation of emotional responses, needs satisfaction, and digital civic behaviour. The article also develops a high-level model showing interrelations between socio-technical environment, technology usage and experiences, and reactions to technology usag

Glass-Transition Properties from Hard Spheres to Charged Point Particles

The glass transition is investigated in three dimensions for single and double Yukawa potentials for the full range of control parameters. For vanishing screening parameter, the limit of the one-component plasma is obtained; for large screening parameters and high coupling strengths, the glass-transition properties crossover to the hard-sphere system. Between the two limits, the entire transition diagram can be described by analytical functions. Different from other potentials, the glass-transition and melting lines for Yukawa potentials are found to follow shifted but otherwise identical curves in control-parameter space.Comment: 6 pages, 5 figure

SU(1,1) symmetry of multimode squeezed states

We show that a class of multimode optical transformations that employ linear optics plus two-mode squeezing can be expressed as SU(1,1) operators. These operations are relevant to state-of-the-art continuous variable quantum information experiments including quantum state sharing, quantum teleportation, and multipartite entangled states. Using this SU(1,1) description of these transformations, we obtain a new basis for such transformations that lies in a useful representation of this group and lies outside the often-used restriction to Gaussian states. We analyze this basis, show its application to a class of transformations, and discuss its extension to more general quantum optical networks

The effects of global financial crisis on information asymmetry and stock price of firms accepted in stock exchange in Iran

The global economy has always been encountering different economic crises which have affected financial variables. The global financial crisis started in the United States by the boom in house prices and reached its highest amount when some of the banks encountered bankruptcy in financial markets and then it permeated into Stock Exchanges. Although Iran incurred the least damages at the start of the global crisis due to its status in financial issues, the economic relationships between Iran and foreign countries through exports can lead to the transmission of the dangerous outcomes of the global economic crisis into the country. The goal of the present research is to study the effects of the global financial crisis on information asymmetry and stock prices of 133 companies accepted in Stock Exchanges in Iran after the use of sifting method for the years between 2004 and 2011. The research method is a descriptive one and the variables were tested by using a statistical technique. The findings of the research show that there is a meaningful difference between stock prices and information asymmetry before and after the global economic crisis on firms in different industries in Iran

Design of a Temperature-Compensated Induction Extensometer

By proper choice of materials, dimensions and circuit parameters, it is possible to design a linear displacement transducer, or extensometer, to have zero net thermal drift over any given temperature range. The chief limitation is the inability of wires and insulation to withstand very high temperatures. An extensometer has been designed and tested which could theoretically measure displacements up to 150 mm with a maximum error of ±0.15 mm caused by thermal effects over the temperature range from 0° to 1000°C. Experimental limitations prevented testing at temperatures higher than 500°C, but measured and theoretical results were in good agreement over that range. The principles involved in the temperature compensation will be discussed

The effects of global financial crisis on information asymmetry and stock price of firms accepted in stock exchange in Iran

The global economy has always been encountering different economic crises which have affected financial variables. The global financial crisis started in the United States by the boom in house prices and reached its highest amount when some of the banks encountered bankruptcy in financial markets and then it permeated into Stock Exchanges. Although Iran incurred the least damages at the start of the global crisis due to its status in financial issues, the economic relationships between Iran and foreign countries through exports can lead to the transmission of the dangerous outcomes of the global economic crisis into the country. The goal of the present research is to study the effects of the global financial crisis on information asymmetry and stock prices of 133 companies accepted in Stock Exchanges in Iran after the use of sifting method for the years between 2004 and 2011. The research method is a descriptive one and the variables were tested by using a statistical technique. The findings of the research show that there is a meaningful difference between stock prices and information asymmetry before and after the global economic crisis on firms in different industries in Iran