8,031 research outputs found
Differentiation of Lactobacillus-probiotic strains by visual comparison of random amplified polymorphic DNA (RAPD) profiles
In the present study, distinctive RAPD fingerprints were generated for 12 Lactobacillus-probiotic strains from 5 Lactobacillus species (L. brevis, L. reuteri, L. gallinarium, L. salivarius and L. panis) after optimization of the RAPD parameters such as MgCl2, Taq polymerase, primer concentration and type of primer. The strains were differentiated under the same PCR protocol but different concentration of primer OPM-05 (50 pmole to differentiate the 5 L. brevis strains and 75 pmole to differentiate 2 strains of L. gallinarium, 3 strains of L. reuteri, a strain of L. panis and L. salivarius). The RAPD fingerprints generated could be differentiated by visual comparison of the profiles, without being analysed by relevant software. This allows specific, rapid, immediate and convenient identification of the Lactobacillus strains
Fourth Order Algorithms for Solving the Multivariable Langevin Equation and the Kramers Equation
We develop a fourth order simulation algorithm for solving the stochastic
Langevin equation. The method consists of identifying solvable operators in the
Fokker-Planck equation, factorizing the evolution operator for small time steps
to fourth order and implementing the factorization process numerically. A key
contribution of this work is to show how certain double commutators in the
factorization process can be simulated in practice. The method is general,
applicable to the multivariable case, and systematic, with known procedures for
doing fourth order factorizations. The fourth order convergence of the
resulting algorithm allowed very large time steps to be used. In simulating the
Brownian dynamics of 121 Yukawa particles in two dimensions, the converged
result of a first order algorithm can be obtained by using time steps 50 times
as large. To further demostrate the versatility of our method, we derive two
new classes of fourth order algorithms for solving the simpler Kramers equation
without requiring the derivative of the force. The convergence of many fourth
order algorithms for solving this equation are compared.Comment: 19 pages, 2 figure
CO2 Reforming of CH4 over Ni/SBA-15: Influence of Ni Loading on the Metalsupport Interaction and Catalytic Activity
The influence of Ni loading on the properties of Ni/SBA-15 and CO2 reforming of CH4 were studied. XRD, BET and TGA results indicated that the increasing Ni loading (3–10 wt%) decreased the crystallinity, surface area and physically adsorbed water content of the catalysts. FTIR, TEM and H2-TPR analysis confirmed the formation of Ni–O–Si by the substitution of surface silanol groups with Ni species and the maximum substitution of surface silanol groups with Ni were achieved at 5 wt%, while further increased in Ni loading stimulate the agglomeration of Ni particles. The activity of catalysts followed the order of 5Ni/SBA-15 > 3Ni/SBA-15 ≈ 10Ni/SBA-15 > SBA-15, with the conversion of CH4 and CO2 over 5Ni/SBA-15 was about 89% and 88% respectively, and CO2/CH4 ratio of 1.02. The superior catalytic performance of 5Ni/SBA-15 towards CO2 reforming of CH4 probably was related with the formation of metal-support interaction, Ni–O–Si, which enhanced the stabilization of the active Ni species on SBA-15 support and altered the properties of catalyst towards an excellent catalytic performance. The analysis of spent catalysts found that the presence of Ni–O–Si minimizes the growth of encapsulating graphite carbon and thus enhanced the stability of catalyst. This study provides new perspectives on the Ni-based catalyst, particularly on the influence of Ni on the metal-support interaction and catalytic performance of Ni/SBA-15 towards CO2 reforming of CH4
Fractional-Period Excitations in Continuum Periodic Systems
We investigate the generation of fractional-period states in continuum
periodic systems. As an example, we consider a Bose-Einstein condensate
confined in an optical-lattice potential. We show that when the potential is
turned on non-adiabatically, the system explores a number of transient states
whose periodicity is a fraction of that of the lattice. We illustrate the
origin of fractional-period states analytically by treating them as resonant
states of a parametrically forced Duffing oscillator and discuss their
transient nature and potential observability.Comment: 10 pages, 6 figures (some with multiple parts); revised version:
minor clarifications of a couple points, to appear in Physical Review
Kinetic Model and Simulation Analysis for Propane Dehydrogenation in an Industrial Moving Bed Reactor
A kinetic model for propane dehydrogenation in an industrial moving bed reactor is developed based on the reported reaction scheme. The kinetic parameters and activity constant are fine tuned with several sets of balanced plant data. Plant data at different operating conditions is applied to validate the model and the results show a good agreement between the model predictions and plant observations in terms of the amount of main product, propylene produced. The simulation analysis of key variables such as inlet temperature of each reactor (T
) and hydrogen to total hydrocarbon ratio (H2/THC) affecting process performance is performed to identify the operating condition to maximize the production of propylene. Within the range of operating conditions applied in the present studies, the operating condition to maximize the propylene production at the same weighted average
inlet temperature (WAIT) is ΔT
= -2, ΔT
inrx1
= +1, ΔT
inrx2
inrx
= +1 , ΔT
inrx4
inrx3
= +2 and ΔH2/THC= -0.02. Under this condition, the surplus propylene produced is 7.07 tons/day as compared with base case
On the construction of high-order force gradient algorithms for integration of motion in classical and quantum systems
A consequent approach is proposed to construct symplectic force-gradient
algorithms of arbitrarily high orders in the time step for precise integration
of motion in classical and quantum mechanics simulations. Within this approach
the basic algorithms are first derived up to the eighth order by direct
decompositions of exponential propagators and further collected using an
advanced composition scheme to obtain the algorithms of higher orders. Contrary
to the scheme by Chin and Kidwell [Phys. Rev. E 62, 8746 (2000)], where
high-order algorithms are introduced by standard iterations of a force-gradient
integrator of order four, the present method allows to reduce the total number
of expensive force and its gradient evaluations to a minimum. At the same time,
the precision of the integration increases significantly, especially with
increasing the order of the generated schemes. The algorithms are tested in
molecular dynamics and celestial mechanics simulations. It is shown, in
particular, that the efficiency of the new fourth-order-based algorithms is
better approximately in factors 5 to 1000 for orders 4 to 12, respectively. The
results corresponding to sixth- and eighth-order-based composition schemes are
also presented up to the sixteenth order. For orders 14 and 16, such highly
precise schemes, at considerably smaller computational costs, allow to reduce
unphysical deviations in the total energy up in 100 000 times with respect to
those of the standard fourth-order-based iteration approach.Comment: 23 pages, 2 figures; submitted to Phys. Rev.
Complete genome sequence of lignin-degrading streptomyces sp. S6 isolated from oil palm plantation in Malaysia
Streptomyces spp. are bacteria that are responsible for the degradation of aromatic compounds and produce secondary metabolites. Here, we present a complete genome sequence of Streptomyces sp. strain S6, which was isolated from an oil palm plantation, with a 7.8-Mbp liner chromosome, a GC content of 72%, and 4,266 coding sequences
Inversion Symmetry and Critical Exponents of Dissipating Waves in the Sandpile Model
Statistics of waves of topplings in the Sandpile model is analysed both
analytically and numerically. It is shown that the probability distribution of
dissipating waves of topplings that touch the boundary of the system obeys
power-law with critical exponent 5/8. This exponent is not indeendent and is
related to the well-known exponent of the probability distribution of last
waves of topplings by exact inversion symmetry s -> 1/s.Comment: 5 REVTeX pages, 6 figure
Short time evolved wave functions for solving quantum many-body problems
The exact ground state of a strongly interacting quantum many-body system can
be obtained by evolving a trial state with finite overlap with the ground state
to infinite imaginary time. In this work, we use a newly discovered fourth
order positive factorization scheme which requires knowing both the potential
and its gradients. We show that the resultaing fourth order wave function
alone, without further iterations, gives an excellent description of strongly
interacting quantum systems such as liquid 4He, comparable to the best
variational results in the literature.Comment: 5 pages, 3 figures, 1 tabl
Exact partition functions of the Ising model on MxN planar lattices with periodic-aperiodic boundary conditions
The Grassmann path integral approach is used to calculate exact partition
functions of the Ising model on MxN square (sq), plane triangular (pt) and
honeycomb (hc) lattices with periodic-periodic (pp), periodic-antiperiodic
(pa), antiperiodic-periodic (ap) and antiperiodic-antiperiodic (aa) boundary
conditions. The partition functions are used to calculate and plot the specific
heat, , as a function of the temperature, . We find that
for the NxN sq lattice, for pa and ap boundary conditions are different
from those for aa boundary conditions, but for the NxN pt and hc lattices,
for ap, pa, and aa boundary conditions have the same values. Our exact
partition functions might also be useful for understanding the effects of
lattice structures and boundary conditions on critical finite-size corrections
of the Ising model.Comment: 17 pages, 13 Postscript figures, uses iopams.sty, submitted to J.
Phys. A: Math. Ge
- …