Nonnegative (s, t)-potent matrices

This paper contains a study of matrices satisfying A^s = A^t for different positive integers s and t. Representations, similar to Flor's well-known characterization of a nonnegative idempotent matrix, are obtained for nonnegative matrices of this type.     

Carbocyclic synthesis via boranes: stereochemical implications of boron annulation

Boron annulation, hydroboration-carbonylation, of substituted 1,5,9-decatrienes was utilized to prepare the cadinane sesquiterpene system. Stereochemical aspects of the triene hydroboration process and the carbonylation reaction have been analyzed through glc separation of boronate esters. Structural assignments for these esters and their oxidation (H₂O₂/NaOH) products were made through high field ¹H-NMR and other physical and spectral considerations.     

Some properties of Q-matrices

This paper deals with the class of Q-matrices, that is, the real n × n matrices M such that for every q ∈ $\text{R}$^n×1, the linear complementarity problem

$\text{Iw ? Mz = q}$

,

$\text{w ? 0, z ? 0, and w}{}^{\mathrm{T}}\text{z = 0}$

, has a solution. In general, the results are of two types. First, sufficient conditions are given on a matrix M so that M ∈ Q. Second, conditions are given so that M ? Q.     

The Synthesis,Photophysical Characterization,and X‐Ray Structure Analysis of Two Polymorphs of 4,4′‐Diacetylstilbene

A palladium(II) acetate‐catalyzed synthesis of 1 that utilizes the novel triazene 1‐{4‐[(E)‐morpholin‐4‐yldiazenyl]phenyl}ethanone as a synthon is described. The room temperature absorption spectra of 1 in various solvents exhibited a π→π* transition in the range of 330–350 nm. Compound 1 was observed to be luminescent, with room‐temperature solution and solid‐state emission spectra that exhibited maxima in the range 400–500 nm. All room‐temperature absorption and emission spectra exhibited some degree of vibrational structure. The emission spectrum of 1 at 77 K in propanenitrile glass was broad and featureless with a maximum at 447 nm. Compound 1 crystallized as a yellow and colorless polymorph. X‐Ray structure analyses of both of these polymorphs and 1‐{4‐[(E)‐morpholin‐4‐yldiazenyl]phenyl}ethanone are presented.     

A geometric and analytic approach to the process of melt vitrification. I. Thermodynamic treatment

By using simple geometric concepts, general thermodynamic dependences governing the process of vitrification are derived. The thermodynamic driving forces of crystallization, ΔG_f,c(T), and stabilization, ΔG_st(T), melts and glasses are considered in the entire temperature interval from temperatures below the glass transition temperature, T_g, to temperatures high above the melting point, T_m. It is show that at large deviations from T_g the temperature dependence of the driving force for stabilization, ΔG_st(T), is non-symmetric and expressions derived by a Taylor expansion become a poor approximation. By using an appropriate thermodynamic model, a more general expression for ΔG_st(T) is obtained and the thermodynamic basis for the existence of superheated glasses is established. The thermodynamic instability of glasses below and above T_g, i.e., of supercooled and superheated glasses is discussed.     

Thermochemistry of the high and ambient temperature lithium vanadium bronze phases LixV2O5

The enthalpies of formation of a series of high and low temperature phases in the ternary oxide system Li_xV₂O₅ have been determined by solution calorimetry. Samples of the former, α-Li_0.04V₂O₅, β-Li_0.30V₂O₅, β'-Li_0.48V₂O₅ and γ-LiV₂O₅, were prepared by solid state reaction at 650°C. The ambient temperature materials Li_0.1V₂O₅(I), Li_0.45V₂O₅(II) and Li_1.03V₂O₅(III) were prepared by n-butyl lithiation in hexane. The thermochemistries of the two classes of material were examined and related to structural features and to the observed behaviour of V₂O₅ as a battery cathode material in lithium cells.     

An example of a nonregular semimonotoneQ-matrix

In their paper, Aganagic and Cottle gave necessary and sufficient conditions for aP ₀-matrix to be aQ-matrix. In his paper, Pang showed that the same characterization holds for anL-matrix.In this paper, we show that a similar characterization for anE ₀-matrix (semimonotone orL ₁-matrix) is not possible. This is done by providing a counterexample to the inclusionE ₀ Q R ₀, thus answering in the negative a question first posed by Pang.     

Updates on softwood-to-ethanol process development

Softwoods are generally considered to be one of the most difficult lignocellulosic feedstocks to hydrolyze to sugars for fermentation, primarily owing to the nature and amount of lignin. If the inhibitory effect of lignin can be significantly reduced, softwoods may become a more useful feedstock for the bioconversion processes. Moreover, strategies developed to reduce problems with softwood lignin may also provide a means to enhance the processing of other lignocellulosic substrates. The Forest Products Biotechnology Group at the University of British Columbia has been developing softwood-to-ethanol processes with SO₂-catalyzed steam explosion and ethanol organosolv pretreatments. Lignin from the steam explosion process has relatively low reactivity and, consequently, low product value, compared with the highvalue coproduct that can be obtained through organosolv. The technical and economic challenges of both processes are presented, together with suggestions for future process development.     

Nonnegative Drazin inverses

A characterization of nonnegative matrices which have a nonnegative Drazin inverse is given. A necessary and sufficient condition for a real matrix to have a nonnegative Drazin inverse is also presented.