Alkylation of tricarbonylcyclohexadienyliron salts (1) with lithium alkyls

The salts $\text{1}$ (Y=H, OMe, Me) react with RLi(R=Me, n-Bu, i-Pr, t-Bu) in CH₂Cl₂ at low temperature to give $\text{2}$ and $\text{3}$ in excellent yields. Nucleophilic addition at the 1-position of $\text{1}$ (Y=OMe) has been observed for the first time.     

An organophotocatalytic late-stage N–CH3 oxidation of trialkylamines to N-formamides with O2 in continuous flow

We report an organophotocatalytic, N–CH₃-selective oxidation of trialkylamines in continuous flow. Based on the 9,10-dicyanoanthracene (DCA) core, a new catalyst (DCAS) was designed with solubilizing groups for flow processing. This allowed O₂ to be harnessed as a sustainable oxidant for late-stage photocatalytic N–CH₃ oxidations of complex natural products and active pharmaceutical ingredients bearing functional groups not tolerated by previous methods. The organophotocatalytic gas–liquid flow process affords cleaner reactions than in batch mode, in short residence times of 13.5 min and productivities of up to 0.65 g per day. Spectroscopic and computational mechanistic studies showed that catalyst derivatization not only enhanced solubility of the new catalyst compared to poorly-soluble DCA, but profoundly diverted the photocatalytic mechanism from singlet electron transfer (SET) reductive quenching with amines toward energy transfer (E_nT) with O₂.

An N–CH₃-selective trialkylamine oxidation to N-formamides is reported in continuous flow using gaseous O₂. A novel, enhanced-solubility dicyanoanthracene organophotocatalyst switched the photochemical mechanism from electron to energy transfer.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Equivalent step-index profile for graded W-fibres: application to TE01 mode cut-off

Snyder's equivalent step-index method is extended to the case of graded profiles with a depressed cladding. This method is then used to determine the limit of monomode operation. Comparison with the results obtained by an exact numerical technique is made for a large variety of simulated profiles, including those with ripples in the cladding. Conclusions are drawn concerning the sensitivity of various profile-shapes to such ripple structure. The method is applied also to measured profiles, reconstructed by a well-known tomographic procedure. In this latter case a comparison is made with experimentally determined values.On leave from CNET, Lannion, France.     

Optically active tricarbonyl(cyclohexadienyl)iron(1+) salts: Synthetic equivalents to spatially directed organic cations

Optically active tricarbonyl (cyclohexdienyl)iron(1+) salts I, II and III are examples of olefin complexes with moleoular asymmetry due to coordination uith a transition metal. Their reactions serve to direct the eventual specific formation of a new chiral centre of known absolute configuration. The absolute configuration of the 2-methoxy-5-methyl salt I is defined its application to the asymmetric synthesis of λ-disubstituted cyclohexenones is described.     

On a problem of Chowla

The equation $\text{Σ}\text{f(n)}\text{n}\text{= 0}$ is studied for periodic algebraically-valued functions f and, in particular, a well known problem of Chowla in this context is resolved. The work depends on an application of a theorem of the first author concerning linear forms in the logarithms of algebraic numbers.     

A millimetre wavelength absorption in soda lime silica glass

Dispersive Fourier transform determinations of the optical constants of soda lime silica glass below 20 cm^-1 at 293 K have allowed the presence of a broad, discrete absorption feature centred on 9 cm^-1 to be inferred. The feature is tentatively linked to a similar feature previously seen in the spectrum of fused silica.     

The fluorescence of diphenyl- and retinol-polyenes

The unusual fluorescence properties of the polyenes are listed. The fluorescence lifetimes and/or quantum yields of the first four all-trans diphenylpolyenes have been determined in seven solvents between ?50 and 50°C. A model is proposed to account for the unusual fluorescence behaviour in terms of a low-lying ¹Ag state, coupled to ¹B_u, and which shifts to lower energies on intramolecular rotation.     

Development of a Cerebral Autoregulation Model for Use With Clinical Blood Flow Measurements

Cerebral autoregulation is the mechanism which controls blood flow to the brain despite variations in blood pressure. Although important this mechanism is currently not well understood, with autoregulatory failure difficult to diagnose. In this paper we develop a simple model based upon those measurements available in the clinical setting. The model can replicate previous results and is used to investigate a variety of hypothetical autoregulatory responses. Furthermore the model has been extended by including the autoregulatory vessels themselves to explain the observed influence of increased carbon dioxide levels in the blood. A focus on only those measurements which may be realistically obtained in human patients avoids the need for estimating many unknown parameters or the modelling of complex and poorly understood physiological process necessary in previous, more complicated, models.