Publications

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

No abstract is provided for this article.

Groundwater contamination by chlorinated hydrocarbons, such as tetrachloroethene (PCE) or trichloroethene (TCE), is a major concern throughout the United States. A developing strategy for the remediation of PCE and TCE contaminated aquifers is anaerobic biodegradation. From a TCE contaminated groundwater site, microorganisms were enriched with the ability to anaerobically convert PCE and TCE completely to ethene. Kinetic studies performed with this culture showed that degradation of PCE, TCE, and vinyl chloride (VC) was first order with respect to substrate concentration up to their solubility. It was also shown that, although VC inhibited TCE degradation, a finite degradation rate could be achieved in the presence of high VC concentrations.\n PCE and TCE form dense-nonaqueous-phase liquids (DNAPLs) which can provide a persistent groundwater contamination source. Under saturating PCE and TCE conditions, these chlorinated ethenes were rapidly converted to ethene with little or no accumulation of VC. These results suggest that anaerobic remediation can potentially be used in the remediation of PCE and TCE DNAPLs.

The silane tetrakis(4-cyanophenyl)silane (1) was prepared by the reaction of 4-lithiobenzonitrile with silicon tetrachloride at −100 °C. This tetrahedral molecular building block crystallizes with AgOTf (OTf = O3SCF3) from benzene and dichloromethane to give [Ag2Si(p-C6H4CN)4][OTf]2·2C6H6 (2). The extended solid structure of 2 is composed of interpenetrating "double layers" which are 3-connected via trigonal planar Ag and tetrahedral Si centers. The individual nets contain six-membered rings which are folded in one corner along a Si···Si vector to give an envelope conformation. Overall, the structure is heavily cross-linked via −CN−Ag(1)−NC−, −Ag(1)−Ag(2)−NC−, and −CN−Ag(2)(μ-O3SCF3)2Ag(2)−NC− linkages. Compound 1 also crystallizes with AgPF6, to give {Ag3[Si(p-C6H4CN)4]2}[PF6]3·1.6THF·0.5C6H6·CH2Cl2 (3). This coordination network also contains 3-connected nets, with six-membered rings in the chair conformation. These nets are interwoven to form the 3-dimensional structure. Compounds 2 and 3 are air-sensitive, and their structures are readily broken up by dissolution in acetone. The network of 2 appears to lose crystallinity when exposed to heat and vacuum (by PXRD) but nonetheless retains some properties as a molecular sieve.

Bulk amorphous alloys, such as the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (at%) alloy, have received much interest of late. This study seeks to investigate mechanical properties of this amorphous metal, including fracture and fatigue behavior in the presence of air and sodium chloride solution. For the fully amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 (at%) alloy, plane-strain fracture toughness (K Ic) values of 18 to 68 MPa√m have been measured, the significant sample-to-sample variability being associated with the presence of residual stresses following processing and a dependence on loading rate. Upon partial or complete crystallization, the alloy becomes severely embrittled, with K Ic dropping to ∼1 MPa√m. Moreover, in NaCl solution, static load testing reveals a threshold value for cracking, K ISCC, as low as ∼0.8 MPa√m. Results from fatigue testing in air and sodium chloride, as well as fatigue testing under potential control, suggest that quite distinct mechanisms of fatigue-crack propagation are active in air and NaCl solution. Specifically, in air, fatigue-crack propagation behavior is similar to that observed in polycrystalline metals and is associated with alternating blunting and re-sharpening of the crack tip, as evidenced by the presence of fatigue striations. In NaCl solution, conversely, the high crack-growth rates likely depend on an anodic process, which results in a brittle mode of failure.

A unified study of the applications of Volterra functional series to nonlinear-system analysis is presented with special emphasis on frequency-domain results which either have not been published before, or where rigour had been lacking. In particular, an in-depth analysis of the harmonic and intermodulation frequency components due to each Volterra kernel of a given order will be presented and explicit formulas which complement those already published will be given. The effects of manipulating various kernels, which need not be symmetric, on the overall response, as well as on the composite kernels will be investigated. These results are then applied to the analysis of dynamical systems described by a system of nonlinear state equations and a read-out map

SUMMARY Activations were performed by means of natrium‐evipan (Bayer). Small doses (0.10–0.20 g) of evipan were administered intravenously. The drug was injected slowly, concomitantly with continuous recording of the EEG. In all the cases solutions of 0.05 g evipan/ml normal saline or distilled water were injected. The rate of administration was, on the average, 1 ml solution every 10 sec. Evipan‐induced EEG activation was achieved following standard bipolar recordings with 3 min of hyperventilation. Eighty‐three patients and 4 normal controls underwent evipan EEG activation. The patients were studied in the following groups: 41 with epileptic seizures ascertained clinically; 14 with non‐epileptic paroxysmal manifestations (8 with seizures indefinite in clinical aspect, 3 with syncopal seizures, 1 with migrainous attacks and 2 with paroxysmal vertigo (Menière)); 21 neurotic cases; 7 focal cerebral lesions (2 tumors and 5 cerebrovascular accidents). The bioelectric changes produced by administration of small doses of evipan were not accompanied by disagreeable subjective sensations nor by sleep. The main duration of an activation is 20 min at the maximum. After this time interval the patient can leave the laboratory room without any risk whatsoever. The results obtained show that evipan constantly induces bioelectric changes such as: diffuse synchronization or resynchronization of the background activity, increase in tracing amplitude and appearance of focal anomalies or diffuse, lesional or irritative anomalies. The latter were particularly conspicuous in patients clinically showing epileptic seizures. It is worth noting that the increase in amplitude occurring in epileptics with evipan exceeds 2–3 times the amplitude of the initial EEG tracings. The increase is very early in epileptics following very small doses of evipan and lasts longer than with the other categories of patients. This high voltage amplitude of bioelectric tracings was interpreted as a functional reorganization phenomenon, diffuse or restricted to particular epileptogenic circuits and systems of the brain. The amplitude increase was regarded as pathognomonic for epilepsy, as it only occurred in patients with clinical epilepsy and was constantly associated with comitial, diffuse or focal anomalies. On the basis of data obtained, the amplitude increase was estimated as an electro‐encephalographic equivalent of the convulsive predisposition of the brain. In a great number of cases evipan activation induces electroencephalographically a delimitation of lesional or epileptogenic foci. The setting off of foci is accounted for by the absence of bioelectric resynchronization induced by evipan at the level of the damaged cerebral areas. RÉSUMÉ Des activations ont été effectuées avec l'Évipan sodique (Bayer) en solution de 0.05 g/ml dans du sérum physiologique. De petites doses du produit (0.10 à 0.20 g) ont été utilisées en injection intra‐veineuse lente (1 ml de solution en 10 secondes) pendant un enregistrement continu de l'E.E.G. Quatre‐vingt trois malades et 4 témoins normaux ont étéétudiés dont on avait préalablement enregistré l'E.E.G. standard comportant une épreuve de l'hyperpnée de 3 minutes. Les malades se groupaient de la façon suivante: 41 épileptiques; 14 sujets souffrant de crises non épileptiques (crises de nature indéterminée, 8 cas; syncopes, 3 cas; migraine, 1 cas; vertiges paroxystiques, 2 cas); 21 névrotiques; 7 sujets souffrant de lésions cérébrales en foyer (tumeur, 2 cas; foyer vasculaire, 5 cas). L'activation de ces sujets par l'Evipan sodique s'est effectuée en 20 minutes au maximum et ne s'est accompagnée d'aucune sensation subjective désagréable. Cette activation s'exprime par une synchronisation ou une resynchronisation diffuse de l'activité fondamentale de l'E.E.G., phénomène qui est particulièrement précoce, important et durable chez les épileptiques dont l'amplitude des tracés est doublée ou même triplée. Chez les sujets souffrant de crises épileptiques focalisées et chez ceux porteurs d'une lésion focalisée non épileptogène, l'activation fait apparaître des anomalies E.E.G. focales de type irritatif ou non irritatif ou augmente l'amplitude dc telles anomalies lorsqu'elles préexistaient. Pareilles modifications des tracés sont interprétées par les auteurs comme la manifestation d'un phénomène de réorganisation fonctionnelle, diffuse ou localisée, de certains circuits et systèmes épileptogènes du cerveau; elles sont considérées comme pathognomoniques de l'épilepsie et représenteraient un équivalent électroencépha‐lographique de la prédisposition convulsivante du cerveau.

Abstract Studies on the development of palladium, nickel, and rhodium catalysts for the hydroamination of dienes and vinylarenes are described. Enantioselective catalysts based on palladium have been developed for the addition of arylamines to dienes and for Markovnikov addition of arylamines to vinylarenes. In addition, nickel catalysts for the addition of aliphatic amines to dienes have been developed, and rhodium catalysts for the first transition metal-catalyzed aminations of vinylarenes that generate terminal amines as the major product are described. Mechanistic data on the hydroamination of vinylarenes with palladium and rhodium is also provided.

Abstract : During the past 3 years, we have exploited the memristor's enabling potentials for designing intelligent machines with learning and adaptive capabilities. We have conducted an in-depth study of the nonlinear dynamics of several ion-channels which underpins the biological basis of life itself, where voltage-gated ion channels, with their complex biochemical synaptic dynamics, are memristors. We have discovered that the Hodgkin-Huxley axon is made of memristors, in addition to conventional circuit elements. In particular, we have proved that the potassium voltage-gated ion channel is a first-order voltage-controlled memristor, and that the sodium voltage-gated ion channel is a second-order voltage-controlled memristor. We have derived the DC V-I curves of the potassium and sodium ion channels, as well as that of the Hodgkin-Huxley Axon. The most significant result of our 3-year research is our derivation of the memristor-based Hodgkin-Huxley Axon circuit model, which along with our principle of local activity and its gem, the edge of chaos, allow us to resolve 3 fundamental unsolved problems from Neurobiology, including the precise nonlinear dynamical mechanism which gives rise to the action potential.