Nonlinear resonant tunneling diode (RTD) circuits for microwave A/D conversion

Short-duration electrical pulses play important roles in ultrafast time-domain metrology: they are used to sample rapidly varying signals or as probe signals in ranging radars, time-domain reflectometry and in communication. In this work, we design a nonlinear transmission, which is loaded with resonant tunneling diode to be suitable for microwave A/D conversion. A resonant tunneling diode (RTD) has a negative differential resistance that means when the voltage increases the current decreases. The equivalent circuit of monostable line is given. The simulation is performed by using OrCad program. Results show that a spike is produced and after a charging time constant, another switching occurs. Hence – similar to a relaxation oscillator – the spiking period is determined by the amplitude and frequency of the input current. The transmission line itself ensures the generation and propagation of identical spikes, such as solitons formed after few diodes.     

Packing and covering with linear programming: A survey

This paper considers the polyhedral results and the min–max results on packing and covering problems of the decade. Since the strong perfect graph theorem (published in 2006), the main such results are available for the packing problem, however there are still important polyhedral questions that remain open. For the covering problem, the main questions are still open, although there has been important progress. We survey some of the main results with emphasis on those where linear programming and graph theory come together. They mainly concern the covering of cycles or dicycles in graphs or signed graphs, either with vertices or edges; this includes the multicut and integral multiflow problems.     

A New Practical Preparation of bis(Trimethylsilyl) Peroxide

Bis(trimethylsilyl) peroxide can be readily obtained by reaction of trimethylchlorosilane with the hexamethylenetetramine-hydrogene peroxide complex.     

Novel dialkyl vinyl ether phosphonate monomers: Their synthesis and alternated radical copolymerizations with electron‐accepting monomers

Three new vinyl ether monomers containing phosphonate moieties were synthesized from transetherification reaction. We showed that the yield was dependent on the spacer length between the vinyl oxy group and the phosphonate moieties: when the spacer is a single methylene side reaction may occur, leading to the formation of acetal compounds. Free‐radical copolymerizations of phosphonate‐containing vinyl ether monomers with maleic anhydride were carried out, leading to alternated copolymers of rather low molecular weights (from 1000 to 7000 g/mol). Both gel permeation chromatography and ³¹P NMR analyses enhanced possible intramolecular transfer reactions occurring from the phosphonate moieties. Kinetic investigation showed that the electron‐withdrawing character of the phosphonate moieties tends to decrease the rate of copolymerization. Nevertheless, almost complete monomers conversion was reached after 30 min of reaction with dimethyl vinyloxyethylphosphonate (VEC₂PMe). Then, radical copolymerization of VEC₂PMe with a series of electron‐accepting monomers, that is, dibutyl maleate, dibutylitaconate, itaconic anhydride, butyl maleimide, and methyl maleimide, led to a series of alternated copolymers. From kinetic investigation, we showed that the higher the electron‐accepting effect, the faster the vinyl ether consumption and the higher the molecular weights. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Charge transport and contact resistance in coplanar devices based on colloidal polyaniline dispersion

The charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N‐vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three‐dimensional variable‐range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge‐transport interlayer in organic solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1710–1716     

Bounds on the Dimension of Trivariate Spline Spaces: A Homological Approach

We consider the vector space of globally differentiable piecewise polynomial functions defined on a three-dimensional polyhedral domain partitioned into tetrahedra. We prove new lower and upper bounds on the dimension of this space by applying homological techniques. We give an insight of different ways of approaching this problem by exploring its connections with the Hilbert series of ideals generated by powers of linear forms, fat points, the so-called Fröberg–Iarrobino conjecture, and the weak Lefschetz property.     

Quantification of β‐aminopropionitrile,an inhibitor of lysyl oxidase activity,in plasma and tumor of mice by liquid chromatography tandem mass spectrometry

Lysyl oxidase enzymes are reported to be involved in patho‐physiological process such as tumorigenesis. β‐Aminopropionitrile (BAPN) is an irreversible inhibitor of lysyl oxidase activity, suggesting a potentially useful therapeutic of interest in oncology. This paper describes the first assay concerning the quantification of BAPN by mass spectrometry. A high‐performance liquid chromatography tandem mass spectrometry (LC‐MS/MS) assay was developed for the quantification of BAPN in plasma and tumor of mice. This method combines dansyl chloride (Dns) derivatization and extraction using a solid‐phase extraction Oasis^© Max column. Deuterated BAPN was used as internal standard (IS). Separation was achieved using an C₁₈ column HypersylGold, (ThermoElectron), 3.0 µm (100 × 2.1 mm i.d.). Gradient elution with water containing 0.1% acetic acid (A) and acetonitrile containing 0.1% acetic acid (B) was applied. Detection was performed with an electrospray ionization interface operating in negative ion mode. Selected reaction monitoring was used with ion transitions m/z 302 → 249 for BAPN–Dns and m/z 306 → 250 for the IS. The method was fully validated in plasma and was linear and sensitive in the range of 10–500 ng/mL. The lower limit of quantification in plasma was 2.5 ng/mL. This validated assay was successfully applied to a kinetic study of BAPN in mouse plasma and demonstrates that BAPN reaches the tumoral tissue. Copyright © 2014 John Wiley & Sons, Ltd.     

Role of reactive species in processing materials at laboratory temperature by spray plasma devices

Processing the aerosol of metal salts in non-equilibrium plasma represents a promising technique that combines the advantages of spray pyrolysis with the high reactivity of plasmas at nearlaboratory temperature in order to produce mixed-oxides and perovskite materials. The aim of this paper is to describe the principles of this new technique and to present the various applications and latest developments. This technique’s capacity to deposit various mixed metal oxides with precise stoichiometry is demonstrated. It is shown that oxidant plasma species play a key role in the chemical transformation of starting materials into oxides at laboratory temperature, while the configuration of the reactor determines the morphology and texture of the deposited layers. Two different reactor configurations are presented. The porous layers of La _x Sr_1−x MnO₃ as the cathode for fuel cells were synthesised in a wave shock reactor configuration, while nanostructured ZnO-Al layers to form a transparent conductive cathode for photovoltaic cells were deposited in the spray plasma reactor of the latest generation for this technique. The experimental results emphasise the role of plasma species in the rate of chemical reactions and in the chemical composition of the deposited layers.     

An Investigation of 1:1 Adducts of Gallium Trihalides with Triarylphosphines by Solid‐State 69/71Ga and 31P NMR Spectroscopy

Several 1:1 adducts of gallium trihalides with triarylphosphines, X₃Ga(PR₃) (X=Cl, Br, and I; PR₃=triarylphosphine ligand), were investigated by using solid‐state ^69/71Ga and ³¹P NMR spectroscopy at different magnetic‐field strengths. The ^69/71Ga nuclear quadrupolar coupling parameters, as well as the gallium and phosphorus magnetic shielding tensors, were determined. The magnitude of the ⁷¹Ga quadrupolar coupling constants (C_Q(⁷¹Ga)) range from approximately 0.9 to 11.0 MHz . The spans of the gallium magnetic shielding tensors for these complexes, δ₁₁?δ₃₃, range from approximately 30 to 380 ppm; those determined for phosphorus range from 10 to 40 ppm. For any given phosphine ligand, the gallium nuclei are most shielded for X=I and least shielded for X=Cl, a trend previously observed for In^III–phosphine complexes. This experimental trend, attributed to spin‐orbit effects of the halogen ligands, is reproduced by DFT calculations. The signs of C_Q(^69/71Ga) for some of the adducts were determined from the analysis of the ³¹P NMR spectra acquired with magic angle spinning (MAS). The ¹J(^69/71Ga,³¹P) and ΔJ(^69/71Ga, ³¹P) values, as well as their signs, were also determined; values of ¹J(⁷¹Ga,³¹P) range from approximately 380 to 1590 Hz. Values of ¹J(^69/71Ga,³¹P) and ΔJ(^69/71Ga,³¹P) calculated by using DFT have comparable magnitudes and generally reproduce experimental trends. Both the Fermi‐contact and spin‐dipolar Fermi‐contact mechanisms make important contributions to the ¹J(^69/71Ga,³¹P) tensors. The ³¹P NMR spectra of several adducts in solution, obtained as a function of temperature, are contrasted with those obtained in the solid state. Finally, to complement the analysis of NMR spectra for these adducts, single‐crystal X‐ray diffraction data for Br₃Ga[P(p‐Anis)₃] and I₃Ga[P(p‐Anis)₃] were obtained.