On partial shadowing of complete pseudo-orbits

In recent years many new definitions of shadowing, using a notion of ergodic (or average) pseudo-orbit were introduced. While, under the assumption of chain mixing, average pseudo-orbit usually can be equivalently replaced by pseudo-orbit in these definitions of shadowing, it is not completely clear when these shadowing properties (i.e. approximation of a pseudo-orbit by a real orbit on a sufficiently large set of indices) can or cannot occur. In this paper we analyze necessary and sufficient conditions for shadowing over a set with positive density (or syndetic). While we do not provide full characterization, a few relations to standard notions from topological dynamics are obtained.     

Join of two graphs admits a nowhere-zero 3-flow

Let G be a graph, and λ the smallest integer for which G has a nowherezero λ-flow, i.e., an integer λ for which G admits a nowhere-zero λ-flow, but it does not admit a (λ ? 1)-flow. We denote the minimum flow number of G by Λ(G). In this paper we show that if G and H are two arbitrary graphs and G has no isolated vertex, then Λ(G ∨ H) ? 3 except two cases: (i) One of the graphs G and H is K ₂ and the other is 1-regular. (ii) H = K ₁ and G is a graph with at least one isolated vertex or a component whose every block is an odd cycle. Among other results, we prove that for every two graphs G and H with at least 4 vertices, Λ(G ∨ H) ? 3.     

Incidence angle dependence on structural and optical properties of UHV deposited copper nano layers

Copper nano-layers with different incident angles as vertical, 20 and 30 degrees, same 73.3 nm thicknesses, and same deposition rate, were deposited on glass substrates, at 373K temperature, under UHV conditions. Their nano-structures were determined by AFM and XRD methods. Their optical properties were measured by spectrophotometry in the spectral range of 300–1100 nm. Kramers–Kronig relations were used for the analysis of the reflectivity curves of Cu films to obtain the optical constants of the nano layers. Different incident angles show important effects on both structural and optical properties. The effective medium approximation was employed to establish the relation between structure zone model (SZM) and EMA predictions. By increasing incidence angle the separation of metallic grains increases, hence the volume fraction of voids increases. That is in agreement with AFM analysis. The predictions of Drude free-electron theory are compared with experimental results for dielectric functions of these nano layers. There is a good agreement between our optical results and Hangman's optical results for a bulk standard Cu sample.     

Design and fabrication of emissive biased limiter and its effect on tokamak plasma

In this paper, an emissive-biased limiter (EBL) was designed and fabricated then the magneto hydrodynamic activity was investigated based on Mirnov oscillations and hard X-ray spectroscopy through the tokamak plasma biasing. The EBL is positioned at r/a=0.92, and the biased voltage, which is varied from?250 to 250 V, applied between the head of the emissive limiter and vacuum chamber. Furthermore, the effects of the biased limiter for both negative and positive applied voltages are measured, and the results are compared with cold-biased limiter. As the results of IR-T1 tokamak suggest, in emissive negative polarity, the duration of plasma current is increased, compared with no bias, cold positive and emissive positive polarities. The amplitude of Mirnov fluctuations in emissive negative polarity is larger and more regular, compared with emissive positive polarity. The amplitude of the hard X-ray fluctuation in emissive negative polarity is very low compared with cold negative, cold positive and emissive positive polarities which leads to minimum energy loss.     

Rapid and Direct Spectrofluorometric and Chemometrics Methods for the Simultaneous Determination of Two Dansyl Derivatives

ABSTRACT

In this study the simultaneous molecular spectrofluorometric determination of ultratrace amounts of two dansyl chloride derivatives, DMNPS (5-(dimethylamino)naphthalene-1-sulfonyl 4-phenylsemicarbazide) and DMNPH (2-(5-(dimethylamino)naphthalen-1-ylsulfonyl)-N-phenylhydrazinecarbothioamide), was accomplished using a genetic algorithm joint partial least squares (GA-PLS) technique that leads to very low detection limits (lower than 10^?6 mol/L) The linear dynamic ranges of the compounds were 1–6 µ mol L^?1 and 1–7 µ mol L^?1 for DMNPS and DMNPH, respectively. Quantification was performed using the emission wavelength range from 360 to 600 nm with an optimum calibration sample number of 25 and prediction sample number of 7. The technique was proved to be beneficial.     

NMR Spectral Data of Benzofurans and Bithiophenes from Hairy Root Cultures of Tagetes Patula Andthe Molecular Structure of Isoeuparin

In the course of our biosynthetic studies of constituents of hairy root cultures of Tagetes patula, we isolated four bithiophenes,[5-(3-buten-1-yny1)]-2,2′-bithiophenes(BBT),5-(4-acetoxy-1-butyny1)-2,2′-bithiophenes (BBTOAc),5-(4-hydroxy-1-butyny1)-2,2′bithiophenes (BBTOH) and 5-(3,4-diacetoxy-1-butyny1)-2,2′-bithiophenes [BBT(OAc)2]. In addition, stigmasterol, α-farnesene, three known benzofurans, of which only one was previouly isolated from T.patula, as well as a new benzofuran were obtained. The structures of the componds were determined by spectral analysis and comparison with published data. The molecular structure of the benzofuran isoeuparin was established by single crystal x-ray diffraction.     

Extending the dynamic range of an energy harvester using nonlinear damping

This paper introduces the use of nonlinear damping for extending the dynamic range of vibration energy harvesters. A cubic nonlinear damper is initially considered and the average harvested power and the throw are obtained for different sinusoidal base excitation amplitudes and frequencies, both numerically and analytically. It is demonstrated that when excited at resonance, at an amplitude below its maximum operational limit, the harvested power using a nonlinear damper can be significantly larger than that of a linear energy harvester, therefore expanding its dynamic range. A potential approach to implementing cubic nonlinearity using a shunted electromagnetic device is also presented.     

Ylide stabilized carbenes: a computational study

High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕ_S–T), broader band gap (ΔΕ_HOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd.     

2,2,9,9‐Tetramethylcyclonona‐3,5,7‐trienylidene vs. its heterocyclic analogues: A quest for stable carbenes at DFT

Replacement of α‐methylenes with BH, AlH, CMe₂, SiH₂, NH, NMe, N^tButyl, NPh, PH, O, and S in non‐planar cyclonona‐3,5,7‐trienylidene (CH₂) alters its status from an unstable transition state to rather stable minima, at B3LYP/6‐311++G**//B3LYP/6‐31 + G* levels of theory. All species appear with singlet closed shell (S_cs) global minima, except for SiH₂ and CH₂ which exhibit triplet electronic ground states. The order of stability based on singlet–triplet energy gap (ΔE_s–t / kcalmol^?1) is: CMe₂ (45.8) > NH (35.8) > NMe (32.3) > O (31.5) > N^tButyl (27.7) ≥ NPh (27.5) ≥ BH (27.4) > S (21.9) > PH (17.0) > CH₂ (?4.4) > SiH₂ (?12.5). In contrast to many reports on N‐heterocyclic carbenes, here alkyl groups appear to exert a higher stabilizing effect than heteroatoms, making CMe₂ the most stable. In addition bulky NMe, N^tButyl, and NPh appear more nucleophilic than their synthesized imidazol‐2‐ylidene congeners. Excluding SiH₂, isodesmic reactions reveal that all substituents stabilize singlet state considerably more than the corresponding triplet. Finally, this work is hoped to pave the path for future matrix isolations and IR studies of these rather stable cyclic non‐planar carbenes. Copyright © 2013 John Wiley & Sons, Ltd.     

A molecular dynamics study on the role of attractive and repulsive forces in excess heat capacity at constant volume of dense fluids

The curves of experimental heat capacity against density show a minimum around and below the critical temperature (Tc), but at higher temperatures, this minimum is not observed. In this study, the role of attractive and repulsive forces on excess heat capacity of Lennard–Jones (LJ) dense fluids has been investigated using a molecular dynamics simulation technique. LJ potential is divided into attractive and repulsive parts. From the molecular dynamics calculations, potential energy and heat capacities have been obtained for Argon at temperatures of 100–500?K. The repulsive forces play the main role in causing the heat capacities at temperatures greater than critical point. Around and below the critical temperature, the role of repulsion is dominant at high densities, but attraction has the main role at low densities, consequently at middle densities, a minimum is formed.