Separation and gravimetric determination of rare earths with N-m-Tolyl-m-nitrobenzohydroxamic acid

N-m-Tolyl-m-nitrobenzohydroxamic acid is used as a reagent for separation and gravimetric determination of Ce(3+), La(3+), Pr(3+), Nd(3+), Sm(3+) and Gd(3+). By proper control of pH and use of masking agents these metal ions can be separated from several others and determined gravimetrically. The complexes can be weighed as (C(14)H(11)N(2)O(4))(3)M after drying.     

Selective alkylation of (hetero)aromatic amines with alcohols catalyzed by a ruthenium pincer complex

A readily available pincer ruthenium(II) complex catalyzes the selective monoalkylation of (hetero)aromatic amines with a wide range of primary alcohols (including pyridine-, furan-, and thiophene-substituted alcohols) with high efficiency when used in low catalyst loadings (1 mol %). Tertiary amine formation via polyalkylation does not occur, making this ruthenium system an excellent catalyst for the synthesis of sec-amines.     

Fixed-J level densities beyond spin cut-off approximation

It is well known that the expression for fixed-J level densityI _?(E, J)=?I(E) $\frac{\partial }{{\partial M}}$ I(M|E)| _M=J+1/2 reduces to familiar Bethe’s formula provided the conditionalM-distributionI(M|E) is approximated by a Gaussian form, so called spin cut-off approximation (M is thez-component of total angular momentumJ andE is the excitation energy). After a detailed analysis, we find that the Bethe’s formula which overestimatesI?(E, J) at highJ values, in particular near the yrast line, can be significantly improved by including a few higher-order moment terms in a suitable expansion forI(M|E) with the lowest-order term to be a Gaussian, e.g., Edgeworth expansions. We also find that, except at very low excitation energies, reasonable values (close to exact) of the moments ofI(M|E) can easily be obtained when multiple Laplace-back transform of the partition function for grand canonical ensemble is evaluated within the saddle point approximation. Furthermore, we study the effects of shell structure as well as residual interaction on the excitation energy dependence of these moments.     

Electronic structure of defects in amorphous silicon

The effects of a variety of defect centres such as T⁰₃, T⁰₂, T⁰₁ and their interacting units on the electronic structure of the amorphous silicon has been studied in a cluster Bethe lattice method. The gap states arising from these defects may explain a number of experimental observations.     

Use of chromium ferrocyanide membrane electrode in the potentiometric titration of ferrocyanide with metal ions

Membranes based on the inorganic ion-exchanger chromium ferrocyanide have been prepared, which exhibit linear response to ferrocyanide over the concentration range 10(-1)-10(-4)M. Although the electrode is not very specific for ferrocyanide, it can be used for potentiometric titration of metal ions with ferrocyanide ion or vice versa. Hg(2+), Th(6+), UO(2+)(2), Pb(2+), Cu(2+) and Zn(2+) have been determined in this way.     

Computational study of buoyancy effects in a laminar starting jet

Vortical structures formed in evolving jets are important in applications such as fuel injection in diesel engines and fuel leaks. When the jet fluid is different from the ambient fluid, the buoyancy can play an important role in determining the jet flow structure, and hence, the entrainment and fluid mixing processes. In the present study, a jet of helium injected in air is investigated, with emphasis placed on delineating the buoyancy effects on vector–scalar fields during the starting phase. We utilize a computational model, previously validated to predict the flow field of low-density gas jets. The model incorporates finite volume approach to solve the transport equation of helium mass fraction coupled with conservation equations of mixture mass and momentum. Computations were performed for a laminar jet to characterize the advancing jet front, and to capture the formation and propagation of vortex rings and the related pinch-off process. Results show significant effects of buoyancy on jet advancement, as well as on vorticity and helium concentration in the core of the vortex rings.     

Role of Buoyancy on Instabilities and Structure of Transitional Gas Jet Diffusion Flames

Transitional jet diffusion flames provide the link between dynamics of laminar and turbulent flames. In this study, instabilities and their interaction with the flow structure are explored in a transitional jet diffusion flame, with focus on isolating buoyancy effects. Experiments are conducted in hydrogen flames with fuel jet Reynolds number of up to 2,200 and average jet velocity of up to 54 m/s. Since the fuel jet is laminar at the injector exit, the transition from laminar to turbulent flame occurs by the hydrodynamic instabilities in the shear layer of fuel jet. The instabilities and the flow structures are visualized and quantified by the rainbow schlieren deflectometry technique coupled with a high-speed imaging system. The schlieren images acquired at 2,000 frames per second allowed exposure time of 23 μs with spatial resolution of 0.4 mm. Results identify a hitherto unknown secondary instability in the flame surface, provide explanation for the observed intermittency in the breakpoint length, show coherent vortical structures downstream of the flame breakpoint, and illustrate gradual breakdown of coherent structures into small-scale random structures in the far field turbulent region.