134 research outputs found
2-[((E)-2-{2-[(E)-2-Hydroxybenzylidene]hydrazinecarbonyl}hydrazinylidene)methyl]phenol
The molecule of the title compound, C15H14N4O3, is completed by the application of crystallographic twofold symmetry, with the carbonyl group lying on the rotation axis. The molecule is close to planar: the greatest deviation of a torsion angle from 0° is 7.3 (2)° about the bond linking the phenol ring to the rest of the molecule. An intramolecular O—H⋯N(imine) hydrogen bond is formed in each half of the molecule. The carbonyl O atom is anti with respect to the amine H atoms and this allows for the formation of N—H⋯O(hydroxyl) hydrogen bonds in the crystal, which results in supramolecular layers lying parallel to (100)
N′-[(2Z)-4-Oxo-4-phenylbut-2-en-2-yl]pyridine-4-carbohydrazide
There are significant twists in the title compound, C16H15N3O2, as seen in the dihedral angle between the benzene and adjacent but-2-enal group [29.26 (4)°] and between the pyridine ring and amide group [24.79 (6)°]. A twist is also evident around the hydrazine bond [the C—N—N—C torsion angle is −138.25 (13)°]. The conformation about the ethene bond is Z. An intramolecular N—H⋯O hydrogen bond involving the benzoyl O atom and leading to an S(6) motif is formed. Significant delocalization of π-electron density is found in this part of the molecule. In the crystal, helical supramolecular chains aligned along the b axis and mediated by N—H⋯O hydrogen bonds are formed
Noise induced rupture process: Phase boundary and scaling of waiting time distribution
A bundle of fibers has been considered here as a model for composite
materials, where breaking of the fibers occur due to a combined influence of
applied load (stress) and external noise. Through numerical simulation and a
mean-field calculation we show that there exists a robust phase boundary
between continuous (no waiting time) and intermittent fracturing regimes. In
the intermittent regime, throughout the entire rupture process avalanches of
different sizes are produced and there is a waiting time between two
consecutive avalanches. The statistics of waiting times follows a Gamma
distribution and the avalanche distribution shows power law scaling, similar to
what have been observed in case of earthquake events and bursts in fracture
experiments. We propose a prediction scheme that can tell when the system is
expected to reach the continuous fracturing point from the intermittent phase.Comment: 6 pages, 8 figure
N′-[(E)-2-Hydroxy-5-iodobenzylidene]furan-2-carbohydrazide monohydrate
The organic molecule of the title monohydrate, C12H9IN2O3·H2O, features a disordered furyl ring with the major component [site occupancy = 0.575 (18)] having the carbonyl O and furyl O atoms syn, and the other conformation having these atoms anti. The molecule is slightly twisted with the dihedral angle between the benzene and furyl rings being 10.3 (6)° (major component). An intramolecular O—H⋯N(imine) hydrogen bond is formed. In the crystal, the water molecule accepts a hydrogen bond from an amine H atom, and forms two O—H⋯O(carbonyl) hydrogen bonds, thereby linking three different carbohydrazide molecules. The result is a supramolecular layer parallel to (001). The closest contacts between layers are of the type I⋯I, at a distance of 3.6986 (6) Å
Concomitant yield optimization of tannase and gallic acid by Bacillus licheniformis KBR6 through submerged fermentation : an industrial approach
The present study is concerned with the evaluation of tannase and gallic acid production effi cacy of Bacillus licheniformis KBR6 under diff erent environmental conditions through submerged fermentation. Results have shown that diff erent environmental conditions and mineral sources have diff erential infl uences on tannase and gallic acid production. Highest tannase and gallic acid yield was observed at incubation period of 18 h and 22 h, respectively. At tannic acid concentration of 15 g/l, maximum cell mass (0.75 g/l), cell yield coeffi cient (0.08 g/g), specifi c growth rate (37.5 mg/g/h), tannase yield (16.3 U/g) and specifi c tannase production rate (0.80 U/g/h) were observed, however, at higher tannic acid concentration a decrease in tannase yield and production rate were observed, but gallic acid production increased with increasing tannic acid concentration. Additional carbohydrate sources like glucose, fructose, and lactose showed positive infl uence on enzyme yield. Among the studied nitrogen sources urea and NH4Cl, and of the phosphate sources KH2PO4 showed favourable eff ects on cell growth and simultaneous enzyme and gallic acid production. Temperature of 35 °C was found to be optimum for tannase and gallic acid production. Of all the studied metal ions Ca2+, Mg2+ and Na+ showed positive eff ect whereas, Co2+, Ag2+, Pb2+, Hg2+ showed inhibitory eff ects
Fluid Induced Particle Size Segregation in Sheared Granular Assemblies
We perform a two-dimensional molecular-dynamics study of a model for sheared
bidisperse granular systems under conditions of simple shear and Poiseuille
flow. We propose a mechanism for particle-size segregation based on the
observation that segregation occurs if the viscous length scale introduced by a
liquid in the system is smaller than of the order of the particle size. We show
that the ratio of shear rate to viscosity must be small if one wants to find
size segregation. In this case the particles in the system arrange themselves
in bands of big and small particles oriented along the direction of the flow.
Similarly, in Poiseuille flow we find the formation of particle bands. Here, in
addition, the variety of time scales in the flow leads to an aggregation of
particles in the zones of low shear rate and can suppress size segregation in
these regions. The results have been verified against simulations using a full
Navier-Stokes description for the liquid.Comment: 11 pages, REVTEX format, ps figures compressed uuencoded separately
or by e-mail from [email protected]. A postscript version of the
paper will be available from
http://www.ica1.uni-stuttgart.de/local/WWW/papers/papers.htm
Mean field and Monte Carlo studies of the magnetization-reversal transition in the Ising model
Detailed mean field and Monte Carlo studies of the dynamic
magnetization-reversal transition in the Ising model in its ordered phase under
a competing external magnetic field of finite duration have been presented
here. Approximate analytical treatment of the mean field equations of motion
shows the existence of diverging length and time scales across this dynamic
transition phase boundary. These are also supported by numerical solutions of
the complete mean field equations of motion and the Monte Carlo study of the
system evolving under Glauber dynamics in both two and three dimensions.
Classical nucleation theory predicts different mechanisms of domain growth in
two regimes marked by the strength of the external field, and the nature of the
Monte Carlo phase boundary can be comprehended satisfactorily using the theory.
The order of the transition changes from a continuous to a discontinuous one as
one crosses over from coalescence regime (stronger field) to nucleation regime
(weaker field). Finite size scaling theory can be applied in the coalescence
regime, where the best fit estimates of the critical exponents are obtained for
two and three dimensions.Comment: 16 pages latex, 13 ps figures, typos corrected, references adde
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