bluuebunny/crossref_metadata_2025 huggingface dataset:
Triarylmethyl Cation Catalysis: A Tunable Lewis Acid Organo­catalyst for the Synthesis of Bisindolylmethanes
Authors: Boekell Nicholas , Cerone Dana , Boucher Maria , Quach Phong , Tentchou Nganyak Wilfried , Reavis Christine , Okoh Ifeanyi , Reid Jordan , Berg Hayley , Chang Briana , Brindle Cheyenne
Published: August 2017

Triarylmethyl cations serve as tunable organocatalysts for the synthesis of bisindolylmethanes. The catalyst structure can be modified to increase or decrease reactivity as needed to match the requirements of the substrate. High yields are achieved for a variety of substrates by using these green catalysts. Catalyst tuning allows for the use of less reactive electrophiles by increasing the reactivity of the catalyst. Acid-sensitive products can be isolated under these mild reaction conditions.
Trapping of Hexadehydro-Diels–Alder Benzynes with Exocyclic, Conjugated Enals as a Route to Fused Spirocyclic Benzopyran Motifs
Authors: Wang Tao , Oswood Christian , Hoye Thomas
Published: August 2017

Exocyclic, conjugated enals react with benzynes generated by heating various triyne-containing substrates to produce spirocyclic benzopyran derivatives. These products are consistent with a mechanistic sequence that involves initial net [2+2] cycloaddition of the benzyne and aldehyde followed by 4π-electrocyclic ring opening and 6π ring closing.
Reactions of Arynes Involving Transition-Metal Catalysis
Authors: Jiang Xuefeng , Feng Minghao
Published: August 2017

Arynes are important building blocks for introducing aromatic rings into molecules and they are frequently utilized in syntheses. Historically, arynes were generated under harsh conditions and this limited their use. Arynes can now be generated under milder conditions, e.g. from 2-(trimethylsilyl)phenyl triflate, and utilized in transition-metal­ catalyzed reactions such as [2+2+2] reactions, insertion into σ-bonds, cascade cyclizations and C–H activation reactions. This short review focuses on transition-metal-catalyzed reactions relevant to aryne intermediates generated from 2-(trimethylsilyl)phenyl triflates and other aryne precursors.

1 Introduction

2 [2+2+2] Reactions

3 Aryne Insertion into a σ-Bond

4 Cascade Cyclizations

5 C–H Activation

6 Multicomponent Reactions (MCRs)

7 Conclusion
Syntheses of Dimeric Securinega Alkaloids
Authors: Han Sunkyu , Jeon Sangbin , Park Joonoh
Published: August 2017

The isolation of flueggenines A and B by Yue and co-workers in 2006 has triggered a burst of isolation reports of dimeric and oligomeric securinega alkaloid natural products. The compelling molecular structures of these compounds with various modes of connection between monomeric securinega units have posed intriguing challenges to the synthetic organic community. Herein, we have categorized high-order securinega alkaloids based on their biosynthetic mode of dimerization or oligomerization. We then have compiled all reported syntheses of dimeric securinega alkaloids based on our classification.

1 Introduction

2 Categorization of High-Order Securinega Alkaloid Natural Products

3 Syntheses of Type I Dimeric Securinega Alkaloids

4 Syntheses of Type II Dimeric Securinega Alkaloids

5 Synthesis of Type III Dimeric Securinega Alkaloid

6 Conclusion
Transition-Metal-Free Reactions Between Boronic Acids and N-Sulfonylhydrazones or Diazo Compounds: Reductive Coupling Processes and Beyond
Authors: Valdés Carlos , Paraja Miguel , Plaza Manuel
Published: August 2017

The metal-free reaction between diazo compounds and boronic acids has been established in recent years as a powerful C(sp3)–C bond-forming reaction. This account covers the recent advances in this area. First, the various synthetic applications of reactions with N-sulfonylhydrazones as a convenient source of diazo compounds is discussed. These transformations can be regarded as reductive couplings of carbonyl compounds. Also covered is the incorporation of other mild sources of diazo compounds in these reactions: diazotization of amines and oxidation of hydrazones. Finally, the development of sequential and cascade processes is presented.

1 Introduction

2 Early Work: Reactions Between Alkylboranes and Diazo Compounds or N-Sulfonylhydrazones

2.1 Reactions Between Alkylboranes and Diazo Compounds

2.2 Reactions Between Alkylboranes and N-Sulfonylhydrazones

3 Reactions of N-Sulfonylhydrazones and Diazo Compounds with Aryl and Alkylboronic Acids

3.1 Reactions of Arylboroxines with Diazo Compounds

3.2 Reductive Couplings of N-Sulfonylhydrazones with Aryl- and Alkylboronic Acids

3.3 Three-Component Reactions Between α-Halotosylhydrazones, Boronic Acids and Indoles

4 Reactions of N-Tosylhydrazones with Alkenylboronic Acids

5 Synthesis of Allenes by Reactions with Alkynyl N-Nosylhydrazones

6 Reactions with Diazo Compounds Generated by Diazotization of Primary Amines

7 Reactions with Diazo Compounds Generated by Oxidation of ­Hydrazones

8 Reactions with Trimethylsilyldiazomethane

9 Cascade Cyclization Reactions with γ- and δ-Cyano-N-tosylhydrazones

10 Summary and Outlook
Enantioselective Palladium-Catalyzed Decarboxylative Allylation of β-Keto Esters Assisted by a Thiourea
Authors: Chung Lung , Zhang Xumu , Qian Hua , Gu Guoxian , Zhou Qinghai , Lu Jiaxiang
Published: August 2017

Enantioselective intramolecular decarboxylative allylation of β-keto esters catalyzed by a palladium bis(phosphine)-thiourea complex is reported. This procedure is not only effective for β-keto esters, but also effective for β-keto amides. An intermolecular variant of the asymmetric decarboxylative allylation is also established. DFT calculations indicate that an outer-sphere mechanism is viable for the decarboxylative allylation of β-keto esters.
A Solvent-Free Reaction for Silyl Enol Ethers Synthesis
Authors: Lanari Daniela , Morozzi Chiara , Rosati Ornelio , Curini Massimo
Published: August 2017

Silyl enol ethers are extremely useful nucleophilic intermediates for chemical transformations because they are synthetically versatile substrates for a wide range of C–C bond-forming reactions. Here, we present a new, mild, and solvent-free procedure for the synthesis of silyl enol ethers that employs a catalytic amount of solid-supported base and an equimolar amount of N,O-(bistrimethylsilyl)acetamide as a silylating agent.
Electron energy dissipation model of gate dielectric progressive breakdown in n- and p-channel field effect transistors
Authors: Lombardo S. , Wu E. Y. , Stathis J. H.
Published: August 2017

We report the data and a model showing that the energy loss experienced by the carriers flowing through breakdown spots is the primary cause of progressive breakdown spot growth. The experiments are performed in gate dielectrics of metal-oxide-semiconductor (MOS) devices subjected to accelerated high electric field constant voltage stress under inversion conditions. The model is analytical and contains few free parameters of clear physical meaning. This is compared to a large set of data on breakdown transients at various oxide thicknesses, stress voltages, and temperatures, both in cases of n-channel and p-channel transistors and polycrystalline Si/oxynitride/Si and metal gate/high k dielectric/Si gate stacks. The basic idea is that the breakdown transient is due to the growth of one or more filaments in the dielectric promoted by electromigration driven by the energy lost by the electrons traveling through the breakdown spots. Both cases of polycrystalline Si/oxynitride/Si and metal gate/high-k dielectric/Si MOS structures are investigated. The best fit values of the model to the data, reported and discussed in the paper, consistently describe a large set of data. The case of simultaneous growth of multiple progressive breakdown spots in the same device is also discussed in detail.
Bond dissociation energies of TiSi, ZrSi, HfSi, VSi, NbSi, and TaSi
Authors: Sevy Andrew , Sorensen Jason J. , Persinger Thomas D. , Franchina Jordan A. , Johnson Eric L. , Morse Michael D.
Published: August 2017

Predissociation thresholds have been observed in the resonant two-photon ionization spectra of TiSi, ZrSi, HfSi, VSi, NbSi, and TaSi. It is argued that because of the high density of electronic states at the ground separated atom limit in these molecules, the predissociation threshold in each case corresponds to the thermochemical bond dissociation energy. The resulting bond dissociation energies are D0(TiSi) = 2.201(3) eV, D0(ZrSi) = 2.950(3) eV, D0(HfSi) = 2.871(3) eV, D0(VSi) = 2.234(3) eV, D0(NbSi) = 3.080(3) eV, and D0(TaSi) = 2.999(3) eV. The enthalpies of formation were also calculated as Δf,0KH°(TiSi(g)) = 705(19) kJ mol−1, Δf,0KH°(ZrSi(g)) = 770(12) kJ mol−1, Δf,0KH°(HfSi(g)) = 787(10) kJ mol−1, Δf,0KH°(VSi(g)) = 743(11) kJ mol−1, Δf,0KH°(NbSi(g)) = 879(11) kJ mol−1, and Δf,0KH°(TaSi(g)) = 938(8) kJ mol−1. Using thermochemical cycles, ionization energies of IE(TiSi) = 6.49(17) eV and IE(VSi) = 6.61(15) eV and bond dissociation energies of the ZrSi− and NbSi− anions, D0(Zr–Si−) ≤ 3.149(15) eV, D0(Zr−–Si) ≤ 4.108(20) eV, D0(Nb–Si−) ≤ 3.525(31) eV, and D0(Nb−–Si) ≤ 4.017(39) eV, have also been obtained. Calculations on the possible low-lying electronic states of each species are also reported.
Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist
Authors: Charaev I. , Silbernagel T. , Bachowsky B. , Kuzmin A. , Doerner S. , Ilin K. , Semenov A. , Roditchev D. , Vodolazov D. Yu. , Siegel M.
Published: August 2017

We performed comparative experimental investigation of superconducting NbN nanowires which were prepared by means of positive- and negative electron-beam lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist. We show that nanowires with a thickness 4.9 nm and widths less than 100 nm demonstrate at 4.2 K higher critical temperature and higher density of critical and retrapping currents when they are prepared by negative lithography. Also the ratio of the experimental critical current to the depairing critical current is larger for nanowires prepared by negative lithography. We associate the observed enhancement of superconducting properties with the difference in the degree of damage that nanowire edges sustain in the lithographic process. A whole range of advantages which is offered by the negative lithography with positive PMMA resist ensures high potential of this technology for improving the performance metrics of superconducting nanowire singe-photon detectors.
Electric field control of ferromagnetism at room temperature in GaCrN (p-i-n) device structures
Authors: El-Masry N. A. , Zavada J. M. , Reynolds J. G. , Reynolds C. L. , Liu Z. , Bedair S. M.
Published: August 2017

We have demonstrated a room temperature dilute magnetic semiconductor based on GaCrN epitaxial layers grown by metalorganic chemical vapor deposition. Saturation magnetization Ms increased when the GaCrN film is incorporated into a (p-GaN/i-GaCrN/n-GaN) device structure, due to the proximity of mediated holes present in the p-GaN layer. Zero field cooling and field cooling were measured to ascertain the absence of superparamagnetic behavior in the films. A (p-GaN/i-GaCrN/n-GaN) device structure with room temperature ferromagnetic (FM) properties that can be controlled by an external applied voltage has been fabricated. In this work, we show that the applied voltage controls the ferromagnetic properties, by biasing the (p-i-n) structure. With forward bias, ferromagnetism in the GaCrN layer was increased nearly 4 fold of the original value. Such an enhancement is due to carrier injection of holes into the Cr deep level present in the i-GaCrN layer. A “memory effect” for the FM behavior of the (p-i-n) GaCrN device structure persisted for 42 h after the voltage bias was turned off. These measurements also support that the observed ferromagnetism in the GaCrN film is not due to superparamagnetic clusters but instead is a hole-mediated phenomenon.
Gabor analysis as contraction of wavelets analysis
Authors: Subag Eyal M. , Baruch Ehud Moshe , Birman Joseph L. , Mann Ady
Published: August 2017

We use the method of group contractions to relate wavelet analysis and Gabor analysis. Wavelet analysis is associated with unitary irreducible representations of the affine group while the Gabor analysis is associated with unitary irreducible representations of the Heisenberg group. We obtain unitary irreducible representations of the Heisenberg group as contractions of representations of the extended affine group. Furthermore, we use these contractions to relate the two analyses, namely, we contract coherent states, resolutions of the identity, and tight frames. In order to obtain the standard Gabor frame, we construct a family of time localized wavelet frames that contract to that Gabor frame. Starting from a standard wavelet frame, we construct a family of frequency localized wavelet frames that contract to a nonstandard Gabor frame. In particular, we deform Gabor frames to wavelet frames.
Terahertz absorption of lysozyme in solution
Authors: Martin Daniel R. , Matyushov Dmitry V.
Published: August 2017

Absorption of radiation by solution is described by its frequency-dependent dielectric function and can be viewed as a specific application of the dielectric theory of solutions. For ideal solutions, the dielectric boundary-value problem separates the polar response into the polarization of the void in the liquid, created by the solute, and the response of the solute dipole. In the case of a protein as a solute, protein nuclear dynamics do not project on significant fluctuations of the dipole moment in the terahertz domain of frequencies and the protein dipole can be viewed as dynamically frozen. Absorption of radiation then reflects the interfacial polarization. Here we apply an analytical theory and computer simulations to absorption of radiation by an ideal solution of lysozyme. Comparison with the experiment shows that Maxwell electrostatics fails to describe the polarization of the protein-water interface and the “Lorentz void,” which does not anticipate polarization of the interface by the external field (no surface charges), better represents the data. An analytical theory for the slope of the solution absorption against the volume fraction of the solute is formulated in terms of the cavity field response function. It is calculated from molecular dynamics simulations in good agreement with the experiment. The protein hydration shell emerges as a separate sub-ensemble, which, collectively, is not described by the standard electrostatics of dielectrics.
The isobaric heat capacity of liquid water at low temperatures and high pressures
Authors: Troncoso Jacobo
Published: August 2017

Isobaric heat capacity for water shows a rather strong anomalous behavior, especially at low temperature. However, almost all experimental studies supporting this statement have been carried out at low pressure; very few experimental data were reported above 100 MPa. In order to explore the behavior of this magnitude for water up to 500 MPa, a new heat flux calorimeter was developed. With the aim of testing the experimental methodology and comparing with water results, isobaric heat capacity was also measured for methanol and hexane. Good agreement with indirect heat capacity estimations from the literature was obtained for the three liquids. Experimental results show large anomalies in water heat capacity. This is especially true as regards its temperature dependence, qualitatively different from that observed for other liquids. Heat capacity versus temperature curves show minima for most studied isobars, whose location decreases with the pressure up to around 100 MPa but increases at higher pressures.
Novel tilt-curvature coupling in lipid membranes
Authors: Terzi M. Mert , Deserno Markus
Published: August 2017

On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane’s reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters. In the present paper, we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. This term arises because, as one moves along the membrane, the curvature-induced change of transverse distances contributes to the area strain—an effect that was believed to be small but nevertheless ends up contributing at the same (quadratic) order as all other terms in their Hamiltonian. We illustrate the consequences of this amendment by deriving the monolayer and bilayer Euler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations. A particularly curious aspect of our new term is that its associated coupling constant is the second moment of the lipid monolayer’s lateral stress profile—which within this framework is equal to the monolayer Gaussian curvature modulus, κ¯m. On the one hand, this implies that many theoretical predictions now contain a parameter that is poorly known (because the Gauss-Bonnet theorem limits access to the integrated Gaussian curvature); on the other hand, the appearance of κ¯m outside of its Gaussian curvature provenance opens opportunities for measuring it by more conventional means, for instance by monitoring a membrane’s undulation spectrum at short scales.
Electronic spectrum of the protonated diacetylene cation (H2C4H+)
Authors: Catani Katherine J. , Muller Giel , Jusko Pavol , Theulé Patrice , Bieske Evan J. , Jouvet Christophe
Published: August 2017

The B̃1A1←X̃1A1 electronic band system of the protonated diacetylene cation (H2C4H+) is measured over the 230–295 nm range by photodissociating H2C4H+ ions stored in a cryogenic ion trap and by photodissociating H2C4H+ tagged with Ar and N2 in a tandem mass spectrometer. The B̃1A1←X̃1A1 band system has an origin at 34 941 cm−1 for H2C4H+, 34 934 cm−1 for H2C4H+–Ar, and 34 920 cm−1 for H2C4H+–N2. The spectra of H2C4H+, H2C4H+–Ar, and H2C4H+–N2 display similar vibronic structure, which is assigned using ab initio calculations to progressions in two symmetric a1 C–C stretch vibrational modes (ν6 and ν4), with band spacings of 860 and 1481 cm−1, respectively.
Symmetry consideration in zero loop-area Sagnac interferometry at oblique incidence for detecting magneto-optic Kerr effects
Authors: Zhu X. D.
Published: August 2017

I present a detailed account of a zero loop-area Sagnac interferometer operated at oblique incidence for detecting magneto-optic Kerr effects arising from a magnetized sample. In particular, I describe the symmetry consideration and various optical arrangements available to such an interferometer that enables measurements of magneto-optic effects due to both in-plane and out-of-plane magnetization of the sample with optimizable signal-to-noise ratios.
A temperature compensation methodology for piezoelectric based sensor devices
Authors: Wang Dong F. , Lou Xueqiao , Bao Aijian , Yang Xu , Zhao Ji
Published: August 2017

A temperature compensation methodology comprising a negative temperature coefficient thermistor with the temperature characteristics of a piezoelectric material is proposed to improve the measurement accuracy of piezoelectric sensing based devices. The piezoelectric disk is characterized by using a disk-shaped structure and is also used to verify the effectiveness of the proposed compensation method. The measured output voltage shows a nearly linear relationship with respect to the applied pressure by introducing the proposed temperature compensation method in a temperature range of 25–65 °C. As a result, the maximum measurement accuracy is observed to be improved by 40%, and the higher the temperature, the more effective the method. The effective temperature range of the proposed method is theoretically analyzed by introducing the constant coefficient of the thermistor (B), the resistance of initial temperature (R0), and the paralleled resistance (Rx). The proposed methodology can not only eliminate the influence of piezoelectric temperature dependent characteristics on the sensing accuracy but also decrease the power consumption of piezoelectric sensing based devices by the simplified sensing structure.
Study of virtual cathodes formation during beam-wave interaction in the reltron oscillator
Authors: Mahto Manpuran , Jain P. K.
Published: August 2017

In the present work, a high power microwave oscillator—reltron has been analyzed to investigate the virtual cathode formation mechanism during the beam-wave interaction. In reltron, a side coupled modulation cavity is used as its RF interaction structure containing three metal grids along the longitudinal direction. The space charge current responsible for the virtual cathode and its steady state electric field distribution has been analyzed. Space charge and beam impedance conditions for efficient device operation have been demonstrated. It has been shown that during the beam-wave interaction in the device, first a virtual cathode forms in the post-acceleration gap, and then the second virtual cathode develops between the first and second grids of the modulation cavity. These two virtual cathodes co-exist and cause the formation of a third virtual cathode between the second and third grids. At this instant, only the third virtual cathode remains, and for sustained device oscillation, this process repeats periodically in the device. The present study would be useful in understanding the beam-wave interaction mechanism as well as the design and development of efficient reltron devices.
Ti segregation in regulating the stress and microstructure evolution in W-Ti nanocrystalline films
Authors: Kaub Tyler , Thompson Gregory B.
Published: August 2017

This paper explores the effect of Ti's segregation and corresponding effect on the intrinsic thin film growth stress and microstructural evolution in a series of W1-x(Ti)x alloys where x is varied from 0 to 20 at. %. We report that the addition of the Ti solute reduces the compressive W growth stress, with further reductions achieved through in-situ annealing during growth. Upon examination of the microstructure, Ti did not appear to have a dramatic effect in altering the film's grain size and distribution, but it did increase the fraction of low angle grain boundaries. We confirmed that the A15 to bcc W phase transformation, which occurs in the early stages of W growth, diminished with increasing Ti content. This has been explained with respect to Ti's preference for gettering residual oxygen, a known stabilizer for the A15 phase. Collectively, this work demonstrates the impact of solute segregation in the control of residual stresses, specific grain boundary formations, and phase transformation control in growing thin films.
Exchange bias mechanism at the ferromagnetic/antiferromagnetic interface with rotatable antiferromagnetic spins: A Monte Carlo study
Authors: Hu Yong , Wang Yuying , Chi Xiaodan , Li Xuesi , Du An , Shi Feng
Published: August 2017

We perform modified Monte Carlo simulations on a ferromagnetic/antiferromagnetic bilayer structure with adjustable antiferromagnetic anisotropy and degree of exchange coupling. Generally, both the antiferromagnetic anisotropy and the degree of exchange coupling at the ferromagnetic/antiferromagnetic interface are difficult to be directly detected experimentally. However, they may play crucial roles in establishing the exchange bias properties through determining whether the antiferromagnetic spins at the interface are rotatable or pinned. Therefore, we precisely calculated the numbers of rotatable and pinned antiferromagnetic spins at the interface and analyzed their contribution to exchange bias and coercivity in the specified ranges of antiferromagnetic anisotropy and degree of exchange coupling. The simulation results may help to clarify the experimental controversies concerning the occurrence of exchange bias effect prior to the detection of pinned uncompensated antiferromagnetic spins. They can also be used to properly interpret the dependence of exchange bias on several-nanometer antiferromagnetic layer thicknesses.
Physics of erupting solar flux ropes: Coronal mass ejections (CMEs)—Recent advances in theory and observation
Authors: Chen James
Published: August 2017

Solar eruptions, observed as flares and coronal mass ejections (CMEs), are the most energetic visible plasma phenomena in the solar system. CMEs are the central component of solar eruptions and are detected as coherent magnetized plasma structures expanding in the solar wind (SW). If they reach the Earth, their magnetic fields can drive strong disturbances in the ionosphere, causing deleterious effects on terrestrial technological systems. The scientific and practical importance of CMEs has led to numerous satellite missions observing the Sun and SW. This has culminated in the ability to continuously observe CMEs expanding from the Sun to 1 AU, where the magnetic fields and plasma parameters of the evolved structures (“ejecta”) can be measured in situ. Until recently, the physical mechanisms responsible for eruptions were major unanswered questions in solar and by extension stellar physics. New observations of CME dynamics and associated eruptive phenomena are now providing more stringent constraints on models, and quantitative theory-data comparisons are helping to establish the correct mechanism of solar eruptions, particularly the driving force of CMEs and the evolution of their magnetic fields in three dimensions. Recent work has demonstrated that theoretical results can simultaneously replicate the observed CME position-time data, temporal profiles of associated solar flare soft X-ray emissions, and the magnetic field and plasma parameters of CME ejecta measured at 1 AU. Thus, a new theoretical framework with testable predictions is emerging to model eruptions and the coupling of CME ejecta to geomagnetic disturbances. The key physics in CME dynamics is the Lorentz hoop force acting on toroidal “flux ropes,” scalable from tokamaks and similar laboratory plasma structures. The present paper reviews the latest advances in observational and theoretical understanding of CMEs with the emphasis on quantitative comparisons of theory and observation.
Ultra-low frequency shock dynamics in degenerate relativistic plasmas
Authors: Islam S. , Sultana S. , Mamun A. A.
Published: August 2017

A degenerate relativistic three-component plasma model is proposed for ultra-low frequency shock dynamics. A reductive perturbation technique is adopted, leading to Burgers' nonlinear partial differential equation. The properties of the shock waves are analyzed via the stationary shock wave solution for different plasma configuration parameters. The role of different intrinsic plasma parameters, especially the relativistic effects on the linear wave properties and also on the shock dynamics, is briefly discussed.
Note: Iodine dissociation with a pulsed arc discharge
Authors: Saghafifar H. , Goodarzi M. S.
Published: August 2017

A new method is presented to dissociate iodine molecules in gas discharge. A high repetition rate spark gap is designed and used to trigger the circuit. Absorption spectroscopy is applied to measure the dissociation fraction of iodine molecules. It is found that more than 35% of iodine molecules are dissociated. The effect of switching frequency on the dissociation coefficient is investigated by changing the frequency of the rotating spark gap. Pulsed and equivalent direct current circuits are compared, and it is found that in the constant current glow discharge the dissociation fraction is near to the zero and negligible.
New Products
Authors: Mandelis Andreas
Published: August 2017

In order to supplement manufacturers’ information, this Department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials which supersede earlier data or suggest new research applications.
Correlation between local structure and glass forming ability enhanced by similar element substitution in (La-Ce)-Co-Al bulk metallic glasses
Authors: Li Xuan , Zhang Tao
Published: August 2017

Similar element substitution is an effective strategy to develop bulk metallic glasses (BMGs) with high glass forming ability (GFA). However, the relationship between the local structure and the GFA enhancement has not been clarified when similar element is introduced. In this paper, the local structures of the ternary La65Co25Al10 and pseudo-ternary (La0.7Ce0.3)65Co25Al10 BMGs were studied by ab-initio molecular dynamics. Partial pair correlation function, bond angle distribution, coordination number, solute-solute avoidance, Voronoi polyhedron, and free volume were used to characterize the local structure. After partial substitution of Ce for La, the (La0.7Ce0.3)65Co25Al10 BMG exhibited higher degree of solute-solute avoidance, more icosahedral-like Voronoi polyhedrons, and less free volume, which may be the structural origin of the higher GFA induced by similar element substitution.
Structure and properties of barium tin boro-phosphate glass systems with very low photoelastic constant
Authors: Itadani M. , Tricot G. , Doumert B. , Takebe H. , Saitoh A.
Published: August 2017

Glasses in the BaO–SnO–P2O5–B2O3 system were prepared and evaluated in order to formulate preform glasses suitable for the fabrication of fiber cores with a very low photoelastic constant. A first glass system (I: xBaO–(60–x)SnO–40P2O5) was designed with a constant P2O5 content and various BaO contents (0–40 mol. %). Introduction of 3 mol. % of B2O3 to enhance the glass stability leads to the second glass system (II: x′BaO–(57–x′)SnO–40P2O5–3B2O3) with 33–38 mol. % BaO. The structure of both systems was investigated by 1D/2D magic-angle spinning nuclear magnetic resonance, Raman, and Fourier transform infrared spectroscopic techniques. 31P NMR showed the presence of Q2 and Q1 units in the first system and correlation 11B/31P NMR indicated that boron enters into the network as B(OP)4 structural units. The photoelastic constant was determined and the stability of the best formulations as well as their refractive index dispersion was established. The drawing temperature and isothermal heating time (without crystal precipitation) parameters were also accurately measured by using experimental time-temperature-transition. Considering that the refractive indices of the core and the cladding materials must match, detailed core and cladding compositions for a fiber enabling single-mode waveguide transmission were proposed.
Portable double-sided pulsed laser heating system for time-resolved geoscience and materials science applications
Authors: Aprilis G. , Strohm C. , Kupenko I. , Linhardt S. , Laskin A. , Vasiukov D. M. , Cerantola V. , Koemets E. G. , McCammon C. , Kurnosov A. , Chumakov A. I. , Rüffer R. , Dubrovinskaia N. , Dubrovinsky L.
Published: August 2017

A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique. The system can be easily coupled with equipment at synchrotron facilities, particularly for nuclear resonance spectroscopy experiments. Examples of applications include investigations of high-pressure high-temperature behavior of iron oxides, both in house and at the European Synchrotron Radiation Facility using the synchrotron Mössbauer source and nuclear inelastic scattering.
Characterization technique for inhomogeneous 4H-SiC Schottky contacts: A practical model for high temperature behavior
Authors: Brezeanu G. , Pristavu G. , Draghici F. , Badila M. , Pascu R.
Published: August 2017

In this paper, a characterization technique for 4H-SiC Schottky diodes with varying levels of metal-semiconductor contact inhomogeneity is proposed. A macro-model, suitable for high-temperature evaluation of SiC Schottky contacts, with discrete barrier height non-uniformity, is introduced in order to determine the temperature interval and bias domain where electrical behavior of the devices can be described by the thermionic emission theory (has a quasi-ideal performance). A minimal set of parameters, the effective barrier height and peff, the non-uniformity factor, is associated. Model-extracted parameters are discussed in comparison with literature-reported results based on existing inhomogeneity approaches, in terms of complexity and physical relevance. Special consideration was given to models based on a Gaussian distribution of barrier heights on the contact surface. The proposed methodology is validated by electrical characterization of nickel silicide Schottky contacts on silicon carbide (4H–SiC), where a discrete barrier distribution can be considered. The same method is applied to inhomogeneous Pt/4H–SiC contacts. The forward characteristics measured at different temperatures are accurately reproduced using this inhomogeneous barrier model. A quasi-ideal behavior is identified for intervals spanning 200 °C for all measured Schottky samples, with Ni and Pt contact metals. A predictable exponential current-voltage variation over at least 2 orders of magnitude is also proven, with a stable barrier height and effective area for temperatures up to 400 °C. This application-oriented characterization technique is confirmed by using model parameters to fit a SiC-Schottky high temperature sensor's response.
A reconfigurable silicon-on-insulator diode with tunable electrostatic doping
Authors: Cristoloveanu Sorin , Lee Kyung Hwa , Bawedin Maryline
Published: August 2017

P-N diodes can be emulated in ultrathin, fully depleted Silicon-On-Insulator films by appropriately biasing the front and back gates. Adjacent electron and hole populations form a virtual P-N junction. Systematic current-voltage I-V characteristics are presented revealing similarities and major differences with those of conventional P-N diodes with ion-implanted doping. The lateral electric field from the anode combines with the gate-induced vertical field and leads to unusual two-dimensional effects. A distinct merit of the virtual diode is the possibility to adjust the concentrations of electrostatic doping via the gates. The reverse current, forward current, and depletion depth become gate-controlled. Our experiments show that by modifying the type, N or P, of electrostatic doping, the virtual diode can be reconfigured in 8 other devices: semi-virtual diodes, PIN diodes, tunneling field-effect transistors or band-modulation FET.
Pair 2-electron reduced density matrix theory using localized orbitals
Authors: Head-Marsden Kade , Mazziotti David A.
Published: August 2017

Full configuration interaction (FCI) restricted to a pairing space yields size-extensive correlation energies but its cost scales exponentially with molecular size. Restricting the variational two-electron reduced-density-matrix (2-RDM) method to represent the same pairing space yields an accurate lower bound to the pair FCI energy at a mean-field-like computational scaling of O(r3) where r is the number of orbitals. In this paper, we show that localized molecular orbitals can be employed to generate an efficient, approximately size-extensive pair 2-RDM method. The use of localized orbitals eliminates the substantial cost of optimizing iteratively the orbitals defining the pairing space without compromising accuracy. In contrast to the localized orbitals, the use of canonical Hartree-Fock molecular orbitals is shown to be both inaccurate and non-size-extensive. The pair 2-RDM has the flexibility to describe the spectra of one-electron RDM occupation numbers from all quantum states that are invariant to time-reversal symmetry. Applications are made to hydrogen chains and their dissociation, n-acene from naphthalene through octacene, and cadmium telluride 2-, 3-, and 4-unit polymers. For the hydrogen chains, the pair 2-RDM method recovers the majority of the energy obtained from similar calculations that iteratively optimize the orbitals. The localized-orbital pair 2-RDM method with its mean-field-like computational scaling and its ability to describe multi-reference correlation has important applications to a range of strongly correlated phenomena in chemistry and physics.
Monoenergetic ion beam acceleration from transversely confined near-critical plasmas by intense laser pulses
Authors: Zhang W. L. , Qiao B. , Shen X. F. , Chang H. X. , Zhang H. , Zhou C. T. , He X. T.
Published: August 2017

An advanced target for production of high-energy monoenergetic ion beams by intense laser pulses is proposed, in which the near-critical plasma is transversely confined between the high-Z dense wires. It is found that the ion acceleration is significantly enhanced due to the strong magnetic dipole vortex formed at the rear of the target, where large electron current density gradients from the wires to the vacuum exist. The magnetic dipole vortex helps to realize the contraction of ion momentum phase spaces and reduction of the beam divergence so that monenergetic, highly directed, and collimated ion beams can be obtained. Two-dimensional particle-in-cell simulations have shown that monoenergetic proton beams with a peak energy of 105 MeV and particle number about 2.2 × 1011 are produced by using the advanced target at a laser intensity of 2.7 × 1020 W/cm2 and a pulse duration of 0.65 ps.
Life-cycle analysis of photovoltaic systems in Hong Kong
Authors: Lou Siwei , Li Danny H. W. , Chan Wilco W. , Lam Joseph C.
Published: August 2017

This paper studied the payback period of grid-connected photovoltaic (PV) panels by the net present value method. The PV performance data were acquired by on-site measurements of two rooftop projects in subtropical Hong Kong. The sensitivity of various variables to the payback period was evaluated by the Extended Fourier Amplitude Sensitivity Test. The monetary payback periods were evaluated at different values of the most relevant variables and compared with the embodied energy and greenhouse gas payback periods. The PV panels of the two projects produced 122–143 kWh/m2 electricity per year in Hong Kong, which saved 139–163 HKD electricity tariff per square meter per year. The sensitivity analysis showed that the monetary payback period was sensitive to the initial cost and tariff increase rate uncertainties. The PV monetary payback period varied from 13.4 to 16.8 years at different tariff increase rates and investment costs, based on the current carbon trading benefit. The monetary payback period was much greater than the embodied energy and greenhouse gas payback periods, which were 10.8–12.7 years and 5.3–6.2 years, respectively. Implications of the payback period differences were discussed.
High-resolution charge carrier mobility mapping of heterogeneous organic semiconductors
Authors: Button Steven W. , Mativetsky Jeffrey M.
Published: August 2017

Organic electronic device performance is contingent on charge transport across a heterogeneous landscape of structural features. Methods are therefore needed to unravel the effects of local structure on overall electrical performance. Using conductive atomic force microscopy, we construct high-resolution out-of-plane hole mobility maps from arrays of 5000 to 16 000 current-voltage curves. To demonstrate the efficacy of this non-invasive approach for quantifying and mapping local differences in electrical performance due to structural heterogeneities, we investigate two thin film test systems, one bearing a heterogeneous crystal structure [solvent vapor annealed 5,11-Bis(triethylsilylethynyl)anthradithiophene (TES-ADT)—a small molecule organic semiconductor] and one bearing a heterogeneous chemical composition [p-DTS(FBTTh2)2:PC71BM—a high-performance organic photovoltaic active layer]. TES-ADT shows nearly an order of magnitude difference in hole mobility between semicrystalline and crystalline areas, along with a distinct boundary between the two regions, while p-DTS(FBTTh2)2:PC71BM exhibits subtle local variations in hole mobility and a nanoscale domain structure with features below 10 nm in size. We also demonstrate mapping of the built-in potential, which plays a significant role in organic light emitting diode and organic solar cell operation.
Design and hardware validation of modified P&O algorithm by fuzzy logic approach based on model predictive control for MPPT of PV systems
Authors: Talbi Billel , Krim Fateh , Rekioua Toufik , Laib Abdelbaset , Feroura Hamza
Published: August 2017

Maximum power point tracking (MPPT) techniques play an essential role in efficiency improvement of photovoltaic systems. The present paper deals with the development of an enhanced MPPT algorithm in order to achieve maximum power point for any climatic conditions. The method under study is composed of two advanced approaches: a modified perturb and observe (MPO) algorithm based on a fuzzy logic controller for ensuring an optimal output of photovoltaic current and a model predictive current controller. The MPO algorithm is implemented with minimum rules to reduce the computational burden. The proposed MPPT is discussed, verified, and compared through simulations under the MATLAB/Simulink™ environment, which presents a high dynamic performance under various conditions. Furthermore, a hardware validation using a dSPACE DS 1104 board is built in order to test and to assess, in real-time, the proposed MPPT.
Integrated dielectrophoretic and surface plasmonic platform for million-fold improvement in the detection of fluorescent events
Authors: Velmanickam Logeeshan , Fondakowski Michael , Lima Ivan T. , Nawarathna Dharmakeerthi
Published: August 2017

We present an integrated dielectrophoretic (DEP) and surface plasmonic technique to quantify ∼1 pM of fluorescent molecules in low conductivity buffers. We have established a DEP force on target molecules to bring those molecules and place them on the nanometallic structures (hotspots) for quantification through surface plasmonic effects. Our results show that the DEP is capable of placing the fluorescent molecules on the hotspots, which are depicted as a significant reduction in the fluorescence lifetime of those molecules. To efficiently integrate the DEP and plasmonic effects, we have designed and utilized pearl-shaped interdigitated electrodes (PIDEs) in experiments. These electrodes generate 2–3 times higher DEP force than traditional interdigitated electrodes. Therefore, high-throughput assays can be developed. The nanometallic structures were strategically fabricated in the periphery of PIDEs for smooth integration of DEP and plasmonic detection. With the introduction of DEP, about 106-fold improvement was achieved over existing plasmonic-based detection. Therefore, this simple addition to the existing surface plasmonic-based detection will enable the disease related protein detection.
Probing material conductivity in two-terminal devices by resistance difference
Authors: Lu Yang , Chen I-Wei
Published: August 2017

It is generally impossible in two-terminal devices to separate the resistance of the device material from the parasitic resistance of terminals, interfaces, and serial loads, yet such information is needed to understand device physics. Here, we present an exact resistance-difference analysis, for a library of similarly configured two-terminal devices with self-similar material responses to external perturbations (electric current, temperature, and magnetic field), to obtain the relative conductivity change Δσ/σ in the device material using device-resistance data only. An outstanding example is nanometallic Mo/Si3N4:Pt/Pt resistance memory, in which electrons in Si3N4:Pt—the device material—display entirely different physics from those in the Pt and Mo electrodes. Our method unraveled their individual Δσ/σ, which for Si3N4:Pt exhibits self-similarity over different resistance states and film thicknesses.
Thermal bistability through coupled photonic resonances
Authors: Khandekar Chinmay , Rodriguez Alejandro W.
Published: August 2017

We present a scheme for achieving thermal bistability based on the selective coupling of three optical resonances. This approach requires one of the resonant frequencies to be temperature dependent, which can occur in materials exhibiting strong thermo-optic effects. For illustration, we explore thermal bistability in two different passive systems, involving either a periodic array of Si ring resonators or parallel GaAs thin films separated by vacuum and exchanging heat in the near field. Such a scheme could prove to be useful for thermal devices operating with transition times on the order of hundreds of milliseconds.
Latest Permian (Changhsingian) to Early Triassic (Induan-Olenekian) of the Mt Goodwin Sub-group at Blacktip gas field, southeastern Bonaparte Basin, Australia
Authors: Gorter John , Nicoll Robert , Caudullo Andrea , Purcell Robyn , Kostas Kon
Published: August 2017

Gas was discovered in intra-Mt Goodwin Sub-group sandstones (Ascalon Formation) of the southeastern Bonaparte Basin in Blacktip–1 in 2001 from a zone characterised by a discrete seismic amplitude anomaly. This integrated study uses wireline logs, cores, cuttings, palynology, micropaleontology and geochemical analyses to determine the depositional environment of the Mt Goodwin Sub-group reservoirs and the source rock potential of this large, latest Permian (Changhsingian) to Early Triassic (Induan Olenekian) section of the Bonaparte Basin in northern Australia. Specific outcomes include a better understanding of the Early Triassic reservoir sandstone depositional environment and recognition of marker horizons on electric logs and seismic profiles, resulting in a more consistent regional interpretive framework for the uppermost Permian (Changhsingian) and Early Triassic (Induan Olenekian), in the Bonaparte Basin.