Ultrasonic pretreatment of corn slurry for saccharification: A comparison of batch and continuous systems

The effects of ultrasound on corn slurry saccharification yield and particle size distribution was studied in both batch and continuous-flow ultrasonic systems operating at a frequency of 20 kHz. Ground corn slurry (28% w/v) was prepared and sonicated in batches at various amplitudes (192–320 μm_{peak-to-peak (p–p)}) for 20 or 40 s using a catenoidal horn. Continuous flow experiments were conducted by pumping corn slurry at various flow rates (10–28 l/min) through an ultrasonic reactor at constant amplitude of 12 μm_p–p. The reactor was equipped with a donut shaped horn. After ultrasonic treatment, commercial alpha- and gluco-amylases (STARGEN^TM 001) were added to the samples, and liquefaction and saccharification proceeded for 3 h. The sonicated samples were found to yield 2–3 times more reducing sugars than unsonicated controls. Although the continuous flow treatments released less reducing sugar compared to the batch systems, the continuous flow process was more energy efficient. The reduction of particle size due to sonication was approximately proportional to the dissipated ultrasonic energy regardless of the type of system used. Scanning electron microscopy (SEM) images were also used to observe the disruption of corn particles after sonication. Overall, the study suggests that both batch and continuous ultrasonication enhanced saccharification yields and reduced the particle size of corn slurry. However, due to the large volume involve in full scale processes, an ultrasonic continuous system is recommended.     

Critical Behavior of Two Interacting Linear Polymer Chains in a Good Solvent

A model of two interacting (chemically different) linear polymer chains is solved exactly using the real-space renormalization group transformation on a family of Sierpinski gasket type fractals and on a truncated 4-simplex lattice. The members of the family of the Sierpinski gasket-type fractals are characterized by an integer scale factorb which runs from 2 to ∞. The Hausdorff dimensiond _F of these fractals tends to 2 from below asb → ∞. We calculate the contact exponenty for the transition from the State of segregation to a State in which the two chains are entangled forb = 2-5. Using arguments based on the finite-size scaling theory, we show that forb→∞, y = 2 - v(b) d _F, wherev is the end-toend distance exponent of a chain. For a truncated 4-simplex lattice it is shown that the system of two chains either remains in a State in which these chains are intermingled in such a way that they cannot be told apart, in the sense that the chemical difference between the polymer chains completely drop out of the thermodynamics of the system, or in a State in which they are either zipped or entangled. We show the region of existence of these different phases separated by tricritical lines. The value of the contact exponenty is calculated at the tricritical points.     

Dielectric properties of lanthanum-doped CaCu3Ti4O12 synthesized by semi-wet route

Effect of La³⁺ doping at Ca²⁺ site in CaCu₃Ti₄O₁₂ has been examined. Compositions with x=0.10, 0.20 and 0.30 were synthesized in the system Ca_(1−3x/2)La_xCu₃Ti₄O₁₂ by semi-wet method. Powder X-ray diffraction confirmed the formation of monophasic compounds. The structure remains cubic similar to CaCu₃Ti₄O₁₂. Lattice parameter increases slightly with increasing La³⁺ concentration. Microstructure has been studied using scanning electron microscopy (SEM). Average grain size is in the range 2-4 μm for various compositions. Energy-dispersive spectrometer (EDS) studies confirm the stoichiometry of the synthesized materials. Dielectric constant, dielectric loss and conductivity of the samples decrease with increasing lanthanum concentrations.     

An improved model for computing the reflectivity of a AlAs/GaAs based distributed bragg reflector and vertical cavity surface emitting laser

In this paper, reflectivity of a Distributed Bragg Reflector (DBR) has been computed by considering the effects of changes of wavelength on the changes of the refractive index of the materials of DBR layers. The intrinsic losses of the materials have been included in the computation of the reflectivity of the DBR. It has been found that the effect of change of the wavelength on the refractive index of the DBR materials reduces the Full Width Half Maxima (FWHM) of the stop band significantly which is expected to improve the laser characteristics. If the FWHM is reduced, the thickness of the active layer of a VCSEL can also be reduced which will further reduce the threshold current of the device. It has been found that the intrinsic losses of the materials have a significant effect on the reflectivity of a DBR. It has also been found that peak reflectivity of a 20 pair AlAs/GaAs DBR reduces by 0.2% after including the intrinsic losses (with a value of the intrinsic losses α = 10 cm^?1).     

Working group report: Quantum chromodynamics sub-group

This is the report of the QCD working sub-group at the Tenth Workshop on High Energy Physics Phenomenology (WHEPP-X).      

Effect of illumination on the space charge limited current in organic bulk heterojunction diodes

Current–voltage (J–V) characteristics of organic bulk heterojunction diodes based on an interpenetrating network of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C₆₁-butyric acid methyl esters (PCBM) have been studied in the dark and under halogen lamp illumination. The diodes contained 1:1 and 1:0.6 weight ratios of P3HT and PCBM. For both diodes the currents measured in dark (J _d , commonly known as the dark current) in forward bias are found to agree with the space charge limited current (SCLC). The illuminated current consists of a current due to applied voltage (J _da ) and the light generated current (J _L ). J _da  extracted from the illuminated current agrees well with Shockley’s diffusion and recombination current. This observation shows that illumination changes the SCLC into Shockley’s diffusion and recombination current. The forward current under illumination has been observed to be greater than the dark current, which is contrary to the photo–voltaic (PV) theory. This result is well explained by the change of SCLC into Shockley’s diffusion and recombination current. Former address of S.C. Jain: IMEC, Kapeldreef 75, 3001 Leuven, Belgium.