Canonic Structure Research Articles

Can Cluster Structure Affect Kinetic Method Measurements? The Curious Case of Glutamic Acid's Gas-Phase Acidity

The gas-phase acidities of aspartic, glutamic, and 2-aminoadipic acid have been determined by the kinetic method in a triple-quadrupole instrument. Although aspartic acid behaves in the conventional way and gives a DeltaH(acid) value of 1340 kJ mol(-1), glutamic and 2-aminoadipic acids give kinetic method plots with two distinct slopes. This leads to DeltaH(acid) values of 1350 and 1366 kJ mol(-1) for glutamic acid, and 1355 and 1369 kJ mol(-1) for 2-aminoadipic acid. The value for aspartic acid and the low collision energy value for glutamic acid are consistent with recent measurements by Poutsma and co-workers in a quadrupole ion trap. The experiments are supported by calculations at the G3(MP2) and OLYP/aug-cc-pVTZ levels. Computational studies of model clusters of the amino acids with trifluoroacetate suggest there are distinct preferences. Glutamic and 2-aminoadipic acid prefer clusters where the amino acid adopts a zwitterion-like structure whereas aspartic acid prefers to adopt a conventional (canonic) structure in its clusters. This result along with the computed stabilities of zwitterion-like conformations of the deprotonated amino acids leads to the following explanation for the presence of two slopes in the kinetic method plots. At low collision energies, the deprotonated amino acid dissociates from the cluster, with rearrangement if necessary, to give its preferred conformation, but at high collision energies, the deprotonated amino acid directly dissociates in the conformation preferred in the cluster. For glutamic and 2-aminoadipic acids, this is a zwitterion-like structure that is about 20 kJ mol(-1) less stable than the global minimum.

Canonic inference and commutative orthogonal block structure

It is shown how to define the canonic formulation for orthogonal models associated to commutative Jordan algebras. This canonic formulation is then used to carry out inference. The case of models with commutative orthogonal block structures is stressed out.

Application of the Array Scanning Method to 1D-periodic Microstrip Lines

The Array Scanning Method (ASM) is employed to analyze the excitation of 1D- periodic microstrip lines by a nonperiodic source. It should be noted that the nonperiodic nature of the source precludes the direct application of Floquet's theorem. However, a combination of the ASM with the Method of Moments allows for the computation of the current density launched on the line. Some results are presented showing the current excited by a delta-gap voltage source at frequencies corresponding to passband as well as to stopband regimes of the periodic microstrip line. DOI: 10.2529/PIERS060906151926 Planar printed structures with periodicity along one or two dimensions (1D- or 2D-periodic structures, respectively) are of great interest in their application to the design of passive microwave circuit components such as fllters, EBG's, and leaky-wave antennas with scanning capabilities. Most of the previous studies devoted to these structures have been restricted to the computation of the propagation characteristics of their modal solutions (Bloch waves or Floquet modes) to flnd, for example, the difierent frequency passbands and stopbands and the radiative regimes. This work proposes an e-cient approach to deal with the excitation of 1D-periodic microstrip lines by a single nonperiodic source. The presence of a nonperiodic source breaks the periodicity of the problem, thus causing the usual techniques based on the direct application of Floquet's theorem not to be applicable. This fact notably increases the degree of di-culty of the problem under consideration with respect to the modal analysis of the periodic structure that is being excited. As it will be explained, the formulation presented here to overcome this di-culty relies on the fact that the current excited by the nonperiodic source can be expressed as a continuous superposition of Floquet-periodic functions that are solutions to auxiliary Floquet-periodic problems. For simplicity, a simple canonic structure will be considered, which consists of a uniform microstrip line periodically loaded with gaps (or, equivalently, an inflnite 1D array of rectangular metallic patches) and excited by a delta-gap voltage source. In order to solve the above-mentioned auxiliary problems, the method of moments is employed. Our goal is the computation of the current excited on a periodic microstrip line when it is excited by a delta-gap voltage source. Speciflcally, the structure under study (see Fig. 1) is an

One-bit processing for digital control

The paper presents a new methodology and architecture for digital control. Control laws can be efficiently implemented with one-bit signals at both the input and output. ΔΣ modulation is used to shape either analogue or multi-bit digital signals into 1-bit format. The 1-bit signals can be applied directly to physical systems, i.e. pulse-density modulation. A modified canonic controller structure is developed, in which there are no multipliers. Some problems arising from sampling and quantisation are discussed. As an example, a practical 1-bit processing architecture for DC motor control is presented.

Transferable group contributions for a variety of chemical phenomena and compounds

An approximate method for calculating molecular electrostatic potential (MEP) maps and atomic point charge models for large molecules in a reduced computational time is proposed and tested for two widely used basis sets (STO-3G and 6–31G*). The method avoids the molecular orbital calculation of the whole system by expressing its first order electronic density matrix in terms of transferable localized orbitals (TLO), previously determined on model molecules, via a localization process followed by the cutting of the tails, and stored in two databases (one for each basis set). For systems with a canonic electronic structure TLO are made of a single vector, involving either two nuclei (to describe the covalent bond between those atoms) or one nucleus (to describe lone pairs and inner shells). Conversely, delocalized π systems require many-center TLO, formed by a suitable number of vectors. Density functions of large chemical compounds can thus be built up automatically from a code that recognizes which fragments are contained in the system of interest, extracts them from the chosen database, reorders the atoms consistently with the pertinent TLO and places them in the correct position and orientation on the relevant atoms. A great number of chemical groups were parameterized and the efficiency of the method was evaluated on different systems, including aliphatic hydrocarbons. Numerical calculations on several molecules revealed that this approximation brought no significant loss of accuracy with respect to the corresponding Hartree-Fock (HF) values for the examined properties. Although the method is specifically designed to produce approximate wavefunctions, the point charge models obtained by fitting the corresponding MEP represent a viable alternative when ab initio HF calculations are not affordable, and can be used in connection with any popular force field.

Towards a Theory of Timbre for Music Analysis

In this article, I explore ways of facilitating discourse about the timbral structures of musical pieces. I address three areas of timbral study: (1) dimensions, (2) auditory streaming and pitch, and (3) change rate and attentional focus. In (1) I draw upon psychoacoustical approaches to timbre, suggesting that dimensions may be divided into “analytical” and “holistic” types. In (2), I draw upon Parncutt'S pitch salience algorithm (1992) and Huron'S perceptual voice-leading Principles (2001) for stream salience estimations; and in (3), I offer notational and analytical preference rules for a theoretical model of timbral change. In order to illustrate the usefulness of modes of inquiry (2) and (3), the article includes sample analyses, principally of bars 1–11 of Schoenberg'S Opus 16, No. 3 ( Farben). Although listeners generally have difficulty perceiving the canonic structure of Farben, application of Parncutt'S algorithm reveals that if Schoenberg had intended the moving canonic voices to be perceptually salient, his choice of pitches for the five-voice chords was well judged. I suggest that the divergence between listeners' perceptions and the Parncutt results may be attributed to various factors highlighted in Huron'S voice-leading Principles, and to the timbral change rate. A theory of timbre must draw upon analytical techniques that are adaptable to many different contexts. The eclectic tool-set that I have offered here is based on perception. Application of the proposed perceptual tools provides insight into specific hearings and, perhaps more importantly, may enable listeners to hear in new ways.

Solution Structure of the Ras Binding Domain of the Protein Kinase Byr2 from Schizosaccharomyces pombe

Background: After activation, small GTPases such as Ras transfer the incoming signal to effectors by specifically interacting with the binding domain of these proteins. Structural details of the binding domain of different effectors determine which pathway is predominantly activated. Byr2 from fission yeast is a functional homolog of Raf, which is the direct downstream target of Ras in mammalians that initiates a protein kinase cascade. The amino acid sequence of Byr2's Ras binding domain is only weakly related to that of Raf, and Byr2's three-dimensional structure is unknown. Results: We have solved the 3D structure of the Ras binding domain of Byr2 (Byr2RBD) from Schizosaccharomyces pombe in solution. The structure consists of three α helices and a mixed five-stranded β pleated sheet arranged in the topology ββαββαβα with the first seven canonic secondary structure elements forming a ubiquitin superfold. 15N- 1H-TROSY-HSQC spectroscopy of the complex of Byr2RBD with Ras•Mg 2+•GppNHp reveals that the first and second β strands and the first α helix of Byr2 are mainly involved in the protein-protein interaction as observed in other Ras binding domains. Although the putative interaction site of H-Ras from human and Ras1 from S. pombe are identical in sequence, binding to Byr2 leads to small but significant differences in the NMR spectra, indicating a slightly different binding mode. Conclusions: The ubiquitin superfold appears to be the general structural motif for Ras binding domains even in cases with vanishing sequence identity. However, details of the 3D structure and the interacting interface are different, thereby determining the specifity of the recognition of Ras and Ras-related proteins.

A new antisense tRNA construct for the genetic treatment of human immunodeficiency virus type 1 infection

Different strategies proposed in the literature to attempt gene therapy of AIDS are based mainly on the intracellular production of RNA and protein therapeutics. This report describes the construction and the anti-human immunodeficiency virus type 1 (HIV-1) activity of a new type of antisense tRNA directed against a nucleotide region in the first coding exon of HIV-1 tat (nucleotides 5924 to 5943; Los Alamos data bank) which is conserved among many HIV-1 clones. The anti-tat antisense sequence was inserted into a tRNA(Pro) backbone by replacement of the anticodon loop, without altering the tRNA canonic tetraloop structure. The antisense tRNA was able to interact effectively with its target in vitro. Jurkat cells that constitutively expressed the anti-tat tRNA following retroviral vector transduction exhibited significant resistance to HIV-1 de novo infection. Resistance seemed to correlate with the level of antisense expression. This is the first time that such a tRNA antisense strategy has been shown to be effective as a genetic treatment of HIV-1 infection in tissue culture. The construct design proposed in this report has some intrinsic advantages: the transcript is driven by a polymerase III promoter, the short length of the RNA minimizes effects of intramolecular base pairing that may impair target recognition, and the antisense RNA has the stability and intracellular fate of a native tRNA molecule.

Voice Leading as a Spatial Function in the Music of Ligeti

Technically speaking I have always approached musical texture through part-writing. Both Atmospheres and Lontano have a dense canonic structure. But you cannot actually hear the polyphony, the canon. You hear a kind of impenetrable texture, something like a very densely woven cobweb. I have retained melodic lines in the process of composition, they are governed by rules as strict as Palestrina's or those of the Flemish school, but the rules of this polyphony are worked out by me. The polyphonic structure does not come through, you cannot hear it; it remains hidden in a microscopic, underwater world, to us inaudible. I call it micropolyphony (such a beautiful word!).'

Spatial modifications of Gaussian beams diffracted by reflection gratings

By using an angular spectral representation, we show that the fields of Gaussian beams scattered by reflection gratings differ markedly from those predicted by geometrical considerations. We find that, in general, each diffracted beam exhibits a lateral displacement, a focal shift, and an angular deflection; in addition, the size of the beam width is enlarged or reduced. The beam changes are largest if the incidence angle is phase matched to a leaky wave that may be supported by the grating. This phase condition is identical to that for which Wood’s anomalies of the resonant variety occur if plane waves, instead of bounded beams, are incident. By evaluating the spatial modifications of beams diffracted at a canonic grating structure consisting of a sinusoidal reactance plane, we show that the magnitudes of the beam effects can be considerably large. We also examine the special case of blazed diffracted orders and find that their corresponding beams are not extinguished completely but appear with reduced intensity and strong profile distortion.

Two-element type normal n-ports

A new classification of RLC reciprocal n-ports in normal and non-normal systems is proposed. The normal systems exhibit the most natural generalization of the scalar RLC one-ports; they admit canonic synthesis representations. Let R, L and C be open loop parameters of an RLC reciprocal n-port with m = n dynamically linearly independent loops. For a normal system R, L and C must commute pairwise. Alternatively, the Hermitian components of Z(s) shall commute. There exists a complete set of common orthonormal eigenvectors for R, L and C. With respect to this coordinate system the normal n-port admits a canonic structure. A normal n-port can be canonically synthesized by a unit R, L and C and an adequate supply of ideal transformers. Such decoupling is not realizable for non-normal n-ports.

Sensitivity of second-order two-pair digital filters

The paper provides a detailed analysis of the coefficient quantization error on the amplitude response for a general second-order section. Seven classes of two-pair structures and the canonic direct form structure are used to realize the section. The amplitude response sensitivity of the second-order Bections obtained for sixth-order low-pass digital filters with variable bandwidth for the four types of classic approximation is computed. Finally, in order to minimize the deterioration due to coefficient quantization in the amplitude-frequency respense of a digital filter, it is proposed that the realization of the digital filter should be by cascade connection of second-order sections chosen by using the above results. This deterioration is then evaluated by computer simulation.

L'acquisition du langage repensée : les recherches inter-langues (II)

Summary : Recent work in two domains of language acquisition — the processing of simple sentences and lexical structuration — is discussed in the light of methodological problems encountered in cross-linguistic studies. The main result of a large number of studies focusing on the development of comprehension strategies used by children of diverse native languages (English, Italian, French, Turkish, Hebrew, Chinese, etc.) has led to the refection of the notion of a universal of word order on which acquisition would be based. Children seem to be equally equipped to handle inflected languages as well as languages where word order plays an important role. While Slobin and Bever (1982) interpret these results by referring to the construction of a canonic structure sentence related to the notion of a prototype for a given language, Bates and MacWhinney (1982c) present a model based on eue validity : the order in which eues (order, case marking, inflections, semantic characteristics) useful for sentence comprehension appear in child language depends largely on the relative validity of these eues in a given language. The lexico-syntactic structuration of certain domains that are parti-cularly interesting for studying form/function relations which are very varied is centered upon the acquisition of locative and temporal expressions and upon the psycholinguistic resuit of the lexical differentiation of certain connectives (contrastive and adversative). Key-words : Developmental psycholinguistics, language acquisition, cross-linguistic studies.

Basic stress analysis of hyperbolic regimes in plastic media

AbstractNonlinear problems of two-dimensional deformation or stress in solid continua are considered where the in-plane components of stress are self-equilibrated and subject to a scalar constraint. In applications the latter is often a yield condition for plastic media. Such field equations are frequently hyperbolic, with a pair of characteristic curves through any point. The primary aim is to express the integrable differential relations along the curves in their simplest form, by an optimal choice of coordinates and variables. Special cases of this problem are now classical, but the general case has received little attention and the universal canonic structure of the relations has escaped notice.

Routh-approximant time-domain reduced-order models for single-input single-output systems

The problem of deriving reduced-order models of a higher-dimensional system from its state-space description is considered under the constraint that the model-reduction procedure should not involve the evaluation of system eigenvalues, should not involve any optimisation algorithm and should yield a stable lower-order model for a stable system. The Routh-approximant modelling procedure in the frequency domain has the above characteristics. This paper presents a time-domain adaptation of the Routh-approximant frequency-domain modelling procedure to achieve the above objectives for s.i.s.o. systems. The lower-order time-domain model matrices are derived by a suitable truncation of the original system matrices in their γ-δ canonic structure. The aggregation matrix relating the system and model state vectors is also derived. A numerical example is included to illustrate the procedure.

Analysis and synthesis of a class of nonlinear systems

A unified approach for the analysis and synthesis of a class of nonlinear systems is discussed. The analytical approach is based on the Volterra series representation of the input/output relationship of nonlinear systems. A canonic structure is presented for a class of nonlinear systems. The necessary and sufficient condition for the realizability of a given nonlinear system in terms of the canonic structure is presented. This synthesis procedure is based on a simple algorithm for separating a multivariable polynomial using the zeroes of a single variable polynomial. The synthesis procedure is also shown to yield computationally simpler models for a class of nonlinear systems.

Conjugated systems obtained by reaction of cyclic amides with dehydrogenation and dehydration agents—III: Mesoionic compounds; anhydro dihydroxides of 1,4-disubstituted-3,5-bis(arylthio)-2,6-dihydroxy-pyrazinium

Derivatives of anhydro-3,5-bis(phenylthio)2,6-dihydroxy-1,4-diphenyl pyrazinium dihydroxide (IIa) with H atoms at the para positions of the phenyl rings systematically substituted with a NO 2 group, Br and a OMe group (IIb-j), and derivatives of the same compound with phenyl groups systematically substituted with Me groups at positions 1 and 4 (IVk-m) have been prepared. The IR, NMR and electronic spectra of these compounds are in agreement with the assumed prevailing participation of the canonic structure of the aromatic type VIII α in their real structure.

Control of linear systems according to the minimal variance criterion--A new approach to the disturbance problem

The problem of minimizing the ensemble average of a performance index in the presence of control noise has received substantial attention in the literature. This work considers a generalization of viewpoint, in which the index variance is minimized while its expectation is constrained. Necessary and sufficient relations are derived for linear, time-invariant systems and disturbances having rational spectra. The open-loop, optimal-feedback solution is specified by its characteristic equation and boundary conditions for Gaussian noises and plants with distinct eigenvalues. The canonic structure of a noise-free plant incorporating covariance data from the disturbance process is shown to have fundamental significance in the optimal solution. Several examples are presented.

A Property of "Grassmann's Law" in Indic

IN INDIC, original voiced aspirates (IE bh dh gh g (to) h) are dissimilated into unaspirated voiced stops (Skt b d j g) if the next syllable begins with an aspirate, appearing in its ordinary shape (Skt bh dh h gh). Something similar happens in Greek: before an aspirate (Gk ph th Ich, from IE bh, etc.) in the following syllable, an old aspirate goes to the corresponding plain p, t, or k. The two IE subfamilies affected are precisely those in which aspiration functions as a distinctive feature.' Whatever the relation between the two processes may be,2 and whatever may account for the differences between them, the existence of such differences is clear enough. The principal one lies in the outcome itself. In Indic (where both voiced and voiceless aspirates occur) the dissimilation product of, say, dh remains voiced and hence coincides with the old d. In Greek, on the other hand, where all voiced aspirates are phonetically devoiced and where there are no other aspirates, the result is t.3 Thus, Gk. tei'ch(os) 'wall' corresponds to Skt deh(O) 'rampart,' both representing IE dh-'h. This was H. Grassmann's finding.4 It accounts for a good many cases, some in which reduplication is involved (Gk ti-the-si: Skt dd-dh&-ti 'puts') and others in which the inducing and the induced consonant are the final and the initial consonant, respectively, of a root. This seemed sufficient. Questions of phonemic compatibility and canonic morph structure were not raised in a systematic fashion in Grassmann's time. Meanwhile certain severe and highly symmetrical mutual restrictions upon the cooccurrence of consonants in IE roots have become known. The particular restriction which interests us here is that which prohibits voiceless stops from appearing together with aspirates. The type bhewt pewdh does not anciently exist; neither, incidentally, does bewd, i. e. a combination of two plain voiced stops. It is conversely implied that pewt pewd bewt bewdh bhewd bhewdh occur freely.5 This would seem to impart to the Greek variety of Grassmann's law a status quite different from that of its counterpart in India. If IE bhewdh yields Gk peuth (Hom. pe'thomai 'inquire'), this kind of change cannot ever lead to homonymy with another inherited root, since pewdh is excluded as a source. In other words, the dissimilation is here not a step in a merger process but only in a reassignment of phones in a neutralized area. Precisely for this reason, occasional Greek forms like thuphlos for tuphlos 'blind' have little importance. They should certainly not be taken as manifestations of a serious assimilatory trend capriciously counteracting the fundamental dissimilation.7 The fact is rather that aspiration functions in Greek very largely as a property of the (discontinuous) consonant sequence as a whole, its precise location in one segment or another remaining for some time non-distinctive.8 The Indic picture appears at first in a different light. We are given to understand that for a Skt bodh there are indeed two possible sources, namely bhewdh (bodhati 'awakens,' cognate with Gk pezithomai) and tbewdh-a specific item the lack of which is thought to be only a lexical accident. If, however, a search is made for a more appropriate case, none will turn up. No homonyms have arisen. This is perhaps not for want of a basis in the ancestor, since a count in Pokorny 9 (where of course the good is thoroughly mixed with the bad) yields about 38 'roots' of the type gerbh (that is,