Linear ketenimines. Variable structures of C,C-dicyanoketenimines and C,C-bis-sulfonylketenimines

C,C-Dicyanoketenimines 10a-c were generated by flash vacuum thermolysis of ketene NS-acetals 9a-c or by thermal or photochemical decomposition of alpha-azido-,beta-cyanocinnamonitrile 11. In the latter reaction, 3,3-dicyano-2-phenyl-1-azirine 12 is also formed. IR spectroscopy of the keteniminines isolated in Ar matrixes or as neat films, NMR spectroscopy of 10c, and theoretical calculations (B3LYP/6-31G*) demonstrate that these ketenimines have variable geometry, being essentially linear along the CCN-R framework in polar media (neat films and solution), but in the gas phase or Ar matrix they are bent, as is usual for ketenimines. Experiments and calculations agree that a single CN substituent as in 13 is not enough to enforce linearity, and sulfonyl groups are less effective that cyano groups in causing linearity. C,C-Bis(methylsulfonyl)ketenimines 4-5 and a C-cyano-C-(methylsulfonyl)ketenimine 15 are not linear. The compound p-O2NC6H4N=C= C(COOMe)2 previously reported in the literature is probably somewhat linearized along the CCNR moiety. A computational survey (B3LYP/6-31G*) of the inversion barrier at nitrogen indicates that electronegative C-substituents dramatically lower the barrier; this is also true of N-acyl substituents. Increasing polarity causes lower barriers. Although N-alkylbis(methylsulfonyl)ketenimines are not calculated to be linear, the barriers are so low that crystal lattice forces can induce planarity in N-methylbis(methylsulfonyl)ketenimine 3.

Nondeterministic gates for photonic single-rail quantum logic

We discuss techniques for producing, manipulating, and measuring qubits encoded optically as vacuum- and single-photon states. We show that a universal set of nondeterministic gates can be constructed using linear optics and photon counting. We investigate the efficacy of a test gate given realistic detector efficiencies.

The effect of water, brine and ethanol flotation on the quality and shelf life of macadamia kernels 2. Kernel pieces

Raw macadamia kernel pieces were immersed in water (specific gravity 1.00 g/cm(3)), brine (SG 1.02 g/cm(3)) or ethanol solution (SG 0.97 g/cm(3)) for 30 or 60 s, then re-dried to below 1.5% moisture (wet basis) and stored under vacuum for 0, 4 and 12 months. Flotation in water had no effect on the quality or shelf life of the kernel pieces over 12 months storage, as measured by sensory evaluation of the kernels and chemical analysis of the kernel oil. Immersion in a salt solution caused unacceptable changes in quality during storage, increasing as storage time increased. Flotation in dilute ethanol also caused unacceptable quality changes during storage. Therefore, only flotation of macadamia kernel pieces in water can be recommended for commercial operations. Microbiological concerns with such a process still need to be addressed.

Evaluation of various pre-treatments for the dehydration of banana and selection of suitable drying models

The thin-layer drying behaviour of bananas in a beat pump dehumidifier dryer was examined. Four pre-treatments (blanching, chilling, freezing and combined blanching and freezing) were applied to the bananas, which were dried at 50 degreesC with an air velocity of 3.1 m s(-1) and with the relative humidity of the inlet air of 10-35%. Three drying models, the simple model, the two-term exponential model and the Page model were examined. All models were evaluated using three statistical measures, correlation coefficient, root means square error, and mean absolute percent error. Moisture diffusivity was calculated based on the diffusion equation for an infinite cylindrical shape using the slope method. The rate of drying was higher for the pre-treatments involving freezing. The sample which was blanched only did not show any improvement in drying rate. In fact, a longer drying time resulted due to water absorption during blanching. There was no change in the rate for the chilled sample compared with the control. While all models closely fitted the drying data, the simple model showed greatest deviation from the experimental results. The two-term exponential model was found to be the best model for describing the drying curves of bananas because its parameters represent better the physical characteristics of the drying process. Moisture diffusivities of bananas were in the range 4.3-13.2 x 10(-10) m(2)s(-1). (C) 2002 Published by Elsevier Science Ltd.

The effect of water, brine and ethanol flotation on the quality and shelf life of macadamia kernels - 1. Whole kernels

Whole macadamia kernels were immersed in water (specific gravity 1.00 g/cm(3)), brine (SG 1.02 g/cm(3)) and ethanol solution (SG 0.97 g/cm(3)) for 30 or 60 s, re-dried to 1.0-1.5% moisture (wet basis) and stored under vacuum for 0, 4 and 12 months. Immersion in water had no effect on the quality or shelf life of kernels, as measured by sensory evaluation and analysis of the kernel oil. Immersion in brine and ethanol solutions changed the flavour of kernels, but had no effect on shelf life or kernel oil stability over 12 months storage. Water flotation to separate kernels based on differences in oil content is therefore feasible, but microbiological concerns need to be investigated.

N-aminopyrroledione-hydrazonoketene-pyrazolium oxide-pyrazolone rearrangements and pyrazolone tautomerism

Flash vacuum thermolysis (FVT) of 1-(dimethylamino)pyrrole-2,3-diones 5 causes extrusion of CO with formation of transient hydrazonoketenes 7. The transient ketenes 7 are observable in the form of weak bands at 2130 (7a) or 2115 cm(-1) (7b) in the Ar matrix IR spectra resulting from either FVT or photolysis of either 5 or 1,1- dimethylpyrazolium-5- oxides 8, and these absorptions are in excellent agreement with B3LYP/6-31G* frequency calculations. Under FVT conditions the ketenes 7 cyclize to pyrazolium oxides 8, which undergo 1,4-migration of a methyl group to yield 1,4-dimethyl-3-phenylpyrazole-5(4H)-one 9a and 1,4,4-trimethyl-3-phenylpyrazole-5(4H)-one 9b. All three tautomers of 9a have been characterized, viz. the CH form 9a (most stable form in the gas phase, the solid state and solvents of low polarity), the OH form 9a' (metastable solid at room temperature) and the NH form 9a (stable in aprotic dipolar solvents). The isomeric 1,4-dimethyl-5-phenylpyrazole-3(2H)-one 12 tautomerizes to the 3-hydroxypyrazole 12'. The crystal structure of the hydrochloride 14 of 9a'/9a is reported, representing the first structurally characterised example of a protonated 5-hydroxypyrazole.

Methoxy(2-pyridyl)ketene

Matrix photolysis of 3-methoxycarbonyl-1,2,3-triazolo[1,5-a]pyridine (12) affords s-E-2-pyridylketene (4), but flash vacuum thermolysis of 12 gives methoxy(2-pyridyl)ketene (15), predominantly in the s-Z-conformation. Matrix photolysis of 15 affords 2-acetylpyridine. Copyright (C) 2003 John Wiley Sons, Ltd.

Synthesis and complexation properties of some novel lariat-crown ethers

Several new lariat-crown ethers bearing either bridged bisdioxine or tetraoxaadamantane units as chiral substituents are prepared by reacting the corresponding amino-crown ether derivatives with the dimeric alpha-oxoketene, the latter obtained by flash vacuum pyrolysis of a furan-2,3-dione precursor. Complexation properties towards differently charged metal ions are investigated by H-1 NMR titration to obtain complexation constants (K-c-values for potassium/ sodium rhodanides: 480-1100 mol dm(-3)), as well as extraction experiments to explore the metal ion transportation abilities of the new lariat crown derivatives. In particular, a significantly increased ability to transport metal ions from water into chloroform was found with spherical tetraoxaadamantyl derivatives when compared with the free amino-benzocrown ethers.

The effect of pretreatments on the drying rate and quality of dried bananas

The effects that four pretreatments (blanching, chilling, freezing, and combined blanching and freezing), used prior to drying, had on the drying rate and quality of bananas were investigated. An untreated sample was used as a control. The bananas were dried at 50 degreesC in a heat pump dehumidifier dryer, using an air velocity of 3.1 m s(-1), until a final moisture content of approximately 25% dry weight basis was attained. While the initial drying rate was highest for the blanched treatment, the two pretreatments involving freezing resulted in the shortest drying times. The blanched sample was most preferred in terms of colour while the frozen samples exhibited extensive browning. The texture and flavour was significantly (P < 0.05) reduced in all samples that involved blanching and/or freezing.

Induction in the timed interval calculus

The Timed Interval Calculus, a timed-trace formalism based on set theory, is introduced. It is extended with an induction law and a unit for concatenation, which facilitates the proof of properties over trace histories. The effectiveness of the extended Timed Interval Calculus is demonstrated via a benchmark case study, the mine pump. Specifically, a safety property relating to the operation of a mine shaft is proved, based on an implementation of the mine pump and assumptions about the environment of the mine. (C) 2002 Elsevier Science B.V. All rights reserved.

New structure formation on gamma-irradiation of poly(chlorotrifluoroethylene)

The radiation chemistry of PCTFE at different temperatures has been studied. The polymer was irradiated under vacuum to absorbed doses of up to 1500 kGy. Three irradiation temperatures were chosen. These included ambient temperature, a temperature well above the T, and a temperature above the crystalline melting temperature. These were 298, 423 and 493 K, respectively. The formation of new structures was identified by solid-state FTIR and F-19 NMR. No branching was observed below the melting temperature, but branches were observed above the melting temperature. G-values for chain-end formation were 1.5 and 2.4 at room temperature and 423 K, respectively and the G-value for the formation of double bonds was found to be < 0.1. For the irradiations at 493 K, the G-values for the formation of chain ends, double bonds and branching points were 3.6, 0.2 and 0.5, respectively. The presence of long-chain branches within the polymer structure could not be proven for radiolysis at 493 K, but scission predominates and network formation does not occur upon irradiation. DSC studies of the polymers irradiated at ambient temperature were consistent with chain scission leading to an increase in the percentage crystallinity, as observed for other fluoropolymers. (C) 2003 Elsevier Science Ltd. All rights reserved.

Quantum theory of the far-off-resonance continuous-wave Raman laser: Heisenberg-Langevin approach

We present the quantum theory of the far-off-resonance continuous-wave Raman laser using the Heisenberg-Langevin approach. We show that the simplified quantum Langevin equations for this system are mathematically identical to those of the nondegenerate optical parametric oscillator in the time domain with the following associations: pump pump, Stokes signal, and Raman coherence idler. We derive analytical results for both the steady-state behavior and the time-dependent noise spectra, using standard linearization procedures. In the semiclassical limit, these results match with previous purely semiclassical treatments, which yield excellent agreement with experimental observations. The analytical time-dependent results predict perfect photon statistics conversion from the pump to the Stokes and nonclassical behavior under certain operational conditions.

A study of the radiation chemistry of poly(chlorotrifluoroethylene) by ESR spectroscopy

The ESR spectra of poly(chlorotrifluoroethylene) were recorded following gamma-radiolysis under vacuum at room temperature and 77 K. The very broad spectrum at 77 K revealed little fine structure with which to identity the radicals formed upon irradiation, but subsequent photobleaching and annealing studies, together with radiolytic studies at higher temperatures, afforded scope for making radical assignments. Both main-chain radicals and a range of chain-end radicals have been identified. The G-values for radical formation were 1.55, 0.36 and 0.32 at 77 K, 273 K and room temperature, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.