Liquid phase hydrogenation and hydrodenitrogenation of aromatic nitrogen-containing environmental pollutants

Carcinogenic aromatic nitro-compounds are hydrogenated at 80–140 °C in the presence of a silica sol–gel entrapped combined palladium-[Rh(cod)Cl]₂ catalyst to give hydroaromatic amines and nitrogen-free hydrocarbons. The process involves initial transformation of the nitro to an amino function. Further hydrogenation causes denitrogenation and saturation of the aromatic moieties. Using 1-aminonaphthalene as a model substrate reveals simultaneous formation of 1- and 5-aminotetralin. While the former amine is readily converted into tetralin and 1-aminodecalins, the 5-aminotetralin gives, in a slow process, only the aminodecalins. The latter compounds are slowly denitrogenated to decalins. The catalytic hydrogenation of the aromatic compounds is accompanied by NH₃ elimination by which secondary amines are formed in a reversible fashion. The entrapped catalyst is leach-proof and recyclable. However, its catalytic activity in the different steps changes during the recycling. The high activity of the combined catalyst results from synergism between the two different metal nuclei.     

Findings about the BMMPP for modeling dependent and simultaneous data in reliability and queueing systems

The batch Markov‐modulated Poisson process (BMMPP) is a subclass of the versatile batch Markovian arrival process (BMAP), which has been widely used for the modeling of dependent and correlated simultaneous events (as arrivals, failures, or risk events). Both theoretical and applied aspects are examined in this paper. On one hand, the identifiability of the stationary BMMPP_m(K ) is proven, where K is the maximum batch size and m is the number of states of the underlying Markov chain. This is a powerful result for inferential issues. On the other hand, some novelties related to the correlation and autocorrelation structures are provided.     

Synthesis of threitol ceramide and [14C]threitol ceramide,non-glycosidic analogues of the potent CD1d antigen α-galactosyl ceramide

The synthesis of threitol ceramide, which is a non-glycosidic analogue of the potent CD1d antigen α-galactosyl ceramide, is described. The synthesis of a ¹⁴C-labelled threitol ceramide analogue is also presented. This radiolabelled analogue will allow the intracellular trafficking pattern/itinerary of this iNKT-CD1d cell agonist to be studied.     

beta-turn mimetic: synthesis of cyclic thioenamino peptides

[reaction: see text] Following the discovery of callynormine A, a marine metabolite of a new class, the cyclic endiamino peptides, and the synthesis of compounds of this group, we have now prepared an analogue group of compounds, i.e., cyclic thioenamine peptides. The latter peptides contain the alpha-amino-beta-thioacrylamide functionality, a potential new type of beta-turn mimic. The superiority of the SH group over the NH(2) group in the reaction with enol-tosylates was demonstrated.     

Cutoff solitons in axially uniform systems

The optical response of axially uniform nonlinear photonic bandgap fibers is studied theoretically. We observe gap-soliton-like generation and associated bistability, similar to what is typically found in periodically modulated nonlinear structures. This response stems from the nature of the guided-mode dispersion relations, which involve a frequency cutoff at zero wave vector. In such systems, solutions with zero group velocities and minimal coupling to radiation modes come in naturally. We term such solitons "cutoff solitons"; they provide an interesting alternative to gap solitons in periodically index-modulated fibers for in-fiber all-optical signal processing.     

Synthesis of 9-substituted tetrahydrodiazepinopurines: studies toward the total synthesis of asmarines

A methodology for the preparation of asmarine analogues has been developed. The asmarines are cytotoxic marine alkaloids with a unique tetrahydro[1,4]diazepino[1,2,3-g,h]purine (THDAP) structure. Three cyclization methods were applied for the preparation of the 9,9-disubstituted 10-hydroxy-THDAP system, namely, aminomercurization, iodocyclization, and acid-catalyzed cyclization. The DMPM group of the NOH functionality and cyanoethyl group of the N-9 atom were found to be the most suitable protecting groups. The structures of all compounds were mainly determined from NMR measurements including (15)N chemical shifts obtained from (15)NH HMBC spectra. The end products are at least about 1 order of magnitude less active than the natural product asmarine B.     

Hydroxide ion initiated reactions under phase transfer catalysis conditions—IV : Effect of catalyst structure

The nature of the quat-anion interactions in a PTC/OH^? system was probed by examining the reactivity and selectivity of a CA/O-ambident anion towards an alkylating agent in the presence of various quats. It is suggested that the accessibility of the positive N center of the qual for association with the anion is the major factor in determining the behavior of PTC/OH^? reactions proceeding through the Makosza mechanism.     

Quantitative NMR spectrometry of phase-transfer catalysts: Part 1. Determination of Extraction Constants and Water of Hydration

Proton magneticf resonance spectrometry was applied for evaluation of the distribution ratios and apparent extraction constants of tetraalkylammonium and tetraalkylphosphonium salts in two liquid-phase systems. Triethylbenzyl- and tetrabutylammonium chloride in dichloromethane and chlorobenzene, respectively, were shown to be salted out in the presence of aqueous sodium hydroxide solutions. ¹H-n.m.r. spectrometry was also used to determine the degree of hydration of quaternary onium salts in two-phase systems. The results were compatible with those obtained by the Karl Fischer method.     

Three-dimensional relativistic-covariant poisson brackets

Using the algebraic properties of Poisson brackets, we extend the three-dimensional brackets (for a single free particle) to conform to the demands of special relativity. This yields, in an essentially unique way, the manifestly covariant extension [x ,p _v]=+p p _v/m ² c ². Position and time then become fully dynamical variables expressible in terms of the canonical conjugateq _i andp _i and the time parameter asx _i =q _i +p _i(q ·p)/m ²c² andt = +E(q ·p)/m ²c⁴. In the quantized version, the length associated with a particle of massm is shown to be an integral multiple of the Compton wavelength _C =/mc.