Generation and reactivity of N,N-dimethylaminobenzotriazolylcarbene a new nucleophilic carbene

N,N-Dimethylaminobenzotriazolylcarbene ( 5 ) reacted with phenyl isocyanate in a [1+2+2] cycloaddition and then with nucleophiles to generate various hydantoins 10 in a one-pot procedure. It was also found that this novel carbene reacted with trans-dibenzoylethylene ( 11 ) in a [1+4] cycloaddition, generating 2-dimethylamino-3-benzoyl-5-phenylfuran ( 13 ) and 2-phenyl-3-[benzotriazol-1-yl]-4-benzoylfuran ( 14 ) whose structures were confirmed by ¹H-¹³C long range correlations as well as the structure of furan 14 being confirmed by X-ray crystallography.     

Effect of physical aging on nucleation of amorphous indomethacin

Differential scanning calorimetry has been used to study glassy indomethacin aged at 0 and -10 degrees C for periods of time up to 109 and 210 days, respectively. The results demonstrate the emergence of a small melting peak of the alpha-polymorph after aging for 69 days at 0 degrees C and for 147 days at -10 degrees C (i.e., approximately 55 degrees C below the glass-transition temperature) that provides evidence of nucleation occurring in the temperature region of the beta-relaxation. The evolution of an endothermic recovery peak temperature features a plateau at longer annealing times that suggests that the glass has made significant progress toward reaching the supercooled liquid state. It has been found that the melting peaks become detectable after the recovery peak has reached the plateau. The results highlight the importance of studying physical aging in the temperature region of the beta-relaxation as a means of evaluating the physical stability of amorphous pharmaceutical materials.     

Approximating the Partition Function of Morse Oscillators

A simple method is proposed leading to reasonable approximations of the partition function of Morse oscillators in terms of elementary functions.     

Making decisions in the absence of clear facts

Bennis and O’Toole [Bennis, W.G., O’Toole, J., 2005. How business schools lost their way. Harvard Business Review 83, 96–104] have recently argued that decision makers need guidance in ‘making decisions in the absence of clear facts’. As such, decision makers must be able to resourcefully use whatever limited information is available and advantageously portray its implications. Based on recently published theory which directly addresses this requirement, this paper demonstrates, through a practical example, how decision makers can make systemic decisions in situations characterized by extremely limited information and, furthermore, what form such decisions can take. Evidence is provided, therefore, that operational research can effectively address what appears to be a gap in management training.     

Novel ring-cleaving reaction of 4-nitro-1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane with nucleophiles

When 4-nitro-AF4 is treated with nucleophiles such as alkoxides and cyanide, a novel ring opening, cyclophane destroying reaction is observed whereby, via an S_NAr mechanism, the nucleophile attacks the bridgehead aryl carbon vicinal to the nitro group with subsequent aryl-CF₂ bond cleavage.     

Temperature induced rotation in a [4.4]cyclophane

The synthesis, the X-ray, NMR and molecular modeling structure determination of a new orthopara[4.4]cyclophane are reported. The similarity of the π(CO)-π(Ar) driven conformational equilibrium of this compound to the work of an amusement ride machinery is also revealed.     

The next generation of C2-symmetric ligands: A di-N-heterocyclic carbene (NHC) ligand and the synthesis and X-ray characterization of mono- and dinuclear rhodium(I) and iridium(I) complexes

A new C₂-symmetric chelating di-N-heterocyclic carbene (NHC) ligand is reported. The stable free di-carbene (+/−)[DEAM-BY] (3) forms upon treating the imidazolium salt (+/−)[DEAM-BI][OTf]₂ (2) with potassium bis-trimethylsilylamide (where DEAM-BY = trans-9,10-dihydro-9,10-ethanoanthracene-11,12-bis(1-benzyl)imidaz-2-ylidene and DEAM-BI = trans-9,10-dihydro-9,10-ethanoanthracene-11,12-bis(1-benzyl)imidazolium). Metalation reactions of 2 with [Rh(COD)Cl]₂ and [Ir(COD)Cl]₂ are carried out under mild conditions to produce either mono- or bimetallic complexes. Each compound is characterized by NMR spectroscopy, combustion analysis, and single-crystal X-ray crystallography.     

Anharmonic stabilization of the high-pressure simple cubic phase of calcium

The phonon spectrum of the high-pressure simple cubic phase of calcium, in the harmonic approximation, shows imaginary branches that make it mechanically unstable. In this Letter, the phonon spectrum is recalculated by using density-functional theory ab initio methods fully including anharmonic effects up to fourth order at 50 GPa. Considering that the perturbation theory cannot be employed with imaginary harmonic frequencies, a variational procedure based on the Gibbs-Bogoliubov inequality is used to estimate the renormalized phonon frequencies. The results show that strong quantum anharmonic effects make the imaginary phonons become positive even at zero temperature so that the simple cubic phase becomes mechanically stable, as experiments suggest. Moreover, our calculations find a superconducting T(c) in agreement with experiments and predict an anomalous behavior of the specific heat.     

Impact of geometry on the TM photonic band gaps of photonic crystals and quasicrystals

Here we demonstrate a novel quantitative procedure to pursue statistical studies on the geometric properties of photonic crystals and photonic quasicrystals (PQCs) which consist of separate dielectric particles. The geometric properties are quantified and correlated to the size of the photonic band gap (PBG) for wide permittivity range using three characteristic parameters: shape anisotropy, size distribution, and feature-feature distribution. Our concept brings statistical analysis to the photonic crystal research and offers the possibility to predict the PBG from a morphological analysis.     

Simulation of ion beam extraction and focusing system

The characteristics of ion beam extraction and focused to a volume as small as possible were investigated with the aid of computer code SIMION 3D version 7. This has been used to evaluate the extraction characteristics (accel-decel system) to generate an ion beam with low beam emittance and high brightness. The simulation process can provide a good study for optimizing the extraction and focusing system of the ion beam without any losses and transported to the required target. Also, a study of a simulation model for the extraction system of the ion source was used to describe the possible plasma boundary curvatures during the ion extraction that may be affected by the change in an extraction potential with a constant plasma density meniscus.