A convenient route to carbocyclic analogs of nucleosides: (±) aristeromycin

Stereocontrolled elaboration of cyclopentadiene-azomethine adducts $\text{1}$⁶ and $\text{2}$⁷ led to a short total synthesis of (±) aristeromycin. In the course of this work a novel zinc reduction ($\text{6}$/$\text{7}$+$\text{9}$) was observed. Also, ozonolysis of the $\text{gem}$-dihalo olefin $\text{10}$ in methanol directly gave the methyl ester $\text{12}$.     

Rake utilisation problem

The ‘Rake Utilisation Problem’ has been discussed in this paper. The rake, which consists of approximately 15 rail compartments (bogies) is currently moving on origin to destination basis. A plan, based on the hypercube [1] structure, has been developed to find optimal routes for these rakes and thereby utilise them in the best possible manner. A rake can be put to further transit nodes on different links provided it satisfies the two constraints: (i) Standardisation, (ii) Railway Time Table Schedule. Significant savings can be achieved by the implementation of the above plan.     

Structures of clausenin and clausenidin two new pyranocoumarins from the roots of clausena heptaphylla Wt. & Arn.

From the roots of Clausena heptaphylla, Wt. & Arn., two pyranocoumarins have been isolated. On the basis of spectral and degradative evidence they have been constituted as I and IV respectively.¹     

Bound-free transitions and the dissociation limit

Following a sequential two-photon excitation, fluorescence is observed from several selectively excited single rotational-vibrational energy levels of theE ³ π0 _g ⁺ state of molecular iodine. The re-emittedE →B fluorescence spectrum from each of the populated rovibrational level of theE state consists of a series of sharp lines terminating on the various discrete ro-vibrational levels of theB state and a few broad lines due to transitions taking place on to the continuum of theB state. The point of transition from sharp lines to broad features in the fluorescence spectrum has been utilized to determine theB state dissociation limit. This method of obtaining the dissociation limit of the molecular electronic states appears to be quite simple and straightforward.     

Electronic Transition Moment Variation in the C2Π–X2Σ+ System of Boron Monoxide

The extensive band system belonging to the C²Π_r–X²Σ⁺ transition of boron monoxide (BO) molecule lying in the vacuum ultraviolet region (150–230 nm) has been recorded in emission in a hollow cathode glow. A few new bands involving high v′ levels of C state have been observed. The Franck–Condon factors and r‐centroids were computed for the C–X system. By correlating the measured intensities to theory, the (relative) variation of the C–X electronic transition moment with internuclear separation was examined.     

Transient and steady-state behavior of auto-igniting propane and dimethyl ether fuel jets in high-temperature vitiated coflows

In the current study, the auto-ignition dynamics of cold fuel jets issuing into a high-temperature, vitiated environments is investigated. Due to the short time scale of these events, high-speed measurements are used to resolve the coupled spatio-temporal behavior. The present study uses high-speed (20-kHz) OH* chemiluminescence imaging to identify the location and timing of the formation of the initial ignition kernels, providing visualization of the ignition dynamics and a detailed statistical evaluation of ignition heights and ignition delay times across a broad parameter space which includes variations in fuel type, dilution levels, coflow temperature, and coflow oxidizer content. The auto-ignition location and ignition delay times show a strong sensitivity to coflow temperature with increased sensitivities at lower coflow temperatures. Comparisons between kernel formation location for the transient jet and the fluctuating flame base of the subsequent, steady-state flame is presented, highlighting the role of flame propagation on flame stabilization. Results indicate that at lower temperatures the flame stabilization mechanism is dominated by auto-ignition, but at higher coflow temperatures, flame propagation plays a key role. The effects of variations in the hot, coflow oxidizer content on ignition properties were found to be noticeable, but still significantly less than variations in the temperature.     

Fourier transform spectral study of BΣ-XΣ system of AlO

The spectrum of B²Σ⁺-X²Σ⁺ system of AlO has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.05 cm⁻¹. Nineteen bands of the Δv = 1, 0, −1, and −2 sequences of this band system have been analyzed for the rotational structure. Out of which seven bands, viz. 3-2, 4-3, 2-3, 3-4, 4-5, 5-6 and 6-7 have been analyzed for the first time. The rotational lines of these 19 bands along with 20 earlier analyzed bands, a total of 7200 lines, have been fitted in a simultaneous least squares fit. The study has resulted in determining more precise vibrational and rotational constants of the two states. Because of the high resolution employed it became necessary to invoke H₀ and H₁ coefficients, and a fifth order term to explain the anomalous spin-doubling observed in the v″ = 5, 6 and 7 levels of the X²Σ⁺ state.