Utilization of Agro-Residual Ligno-Cellulosic Substances by Using Solid State Fermentation: A Review

Agro-residual wastes contain many usable substrates of high value such as carbohydrates and fi bers. Direct disposal of these wastes as burning or landfill will cause serious environmental problems. Thus, designing new methods for exploitation and treatment of these wastes to produce useful products with great economic advantages are substantial. Solid state fermentation (SSF) has become an attractive method in recent years due to its features of using these wastes directly as raw materials or substrates. Thus, SSF is considered as an environmentally-friendly technique for waste treatment. This paper reviews the exploitation of the agro-residual wastes through SSF technology

InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography

Close-packed micro-lenses with dimensions of the order of wavelength have been integrated onto the indium-tin-oxide (ITO) layer of GaN light-emitting diodes employing nanosphere lithography. The ITO lens arrays are transferred from a self-assembled silica nanosphere array by dry etching, leaving the semiconductor layer damage-free. An enhancement of up to 63.5% on optical output power from the lensed light-emitting diode (LED) has been observed. Lens-patterned LEDs are also found to exhibit reduced emission divergence. Three-dimensional finite-difference time-domain simulations performed for light extraction and emission characteristics are found to be consistent with the observed results. © 2012 American Institute of Physics.published_or_final_versio

Floquet theory of neutrino oscillations in the earth

We review the Floquet theory of linear differential equations with periodic coefficients and discuss its applications to neutrino oscillations in matter of periodically varying density. In particular, we consider parametric resonance in neutrino oscillations which can occur in such media, and discuss implications for oscillations of neutrinos traversing the earth and passing through the earth's core.Comment: LaTeX, 28 pages, 8 eps figures. Contribution to the special issue of Yad. Fiz. dedicated to the memory of A.B. Migda

Formation of incipient soot particles from polycyclic aromatic hydrocarbons: A ReaxFF molecular dynamics study

In this study, we present the results from a series of ReaxFF molecular dynamics (MD) simulations to uncover the underlying mechanisms behind the nucleation and growth of incipient soot particles from polycyclic aromatic hydrocarbons (PAHs). PAHs, namely, naphthalene, anthracene, pyrene, coronene, ovalene and circumcoronene, are selected for ReaxFF MD simulations over a range of temperatures from 400 to 2500 K. Distinctive mechanisms of incipient soot formation are identified with respect to PAH mass and temperature. At low temperatures (e.g., 400 K), all types of the above PAHs can nucleate into incipient soot particles in stacked structures due to physical interactions. With the increase of temperature, the possibility of physical nucleation decreases for each PAH. At moderate temperatures (e.g., 1600 K), it becomes difficult for these PAH monomers, except circumcoronene grows into incipient soot particles. When the temperature increases to 2500 K, all the PAHs become chemically active, which not only leads to the formation of incipient soot particles but also takes the graphitization with the increase of the carbon-to-hydrogen (C/H) ratios in the particles. In addition to the formation of fullerene-like soot particles, stacked particles connected by ‘carbon bridges’ are also observed for large PAHs like coronene, ovalene and circumcoronene

Investigation of methane oxidation by palladium-based catalyst via ReaxFF Molecular Dynamics simulation

Catalytic oxidations of methane over palladium-based nanoparticles, with and without oxygen coating, are investigated using ReaxFF Molecular Dynamics simulations. The simulation results show the complete dynamic process of the above catalytic reactions at the atomic level and help to reveal the underlying mechanisms both qualitatively and quantitatively. It is found that oxygen molecules are significantly easier to be adsorbed on both bare and oxygen-coated Pd surfaces compared with CH4. The presence of adsorbed O2 molecules on the surface blocks the active sites for CH4 adsorption on the oxygen-coated Pd surfaces. By comparing the adsorptive dissociation of CH4 over Pd nanoparticles with different levels of oxygen coverage, we find that it is much easier for the adsorptive dissociation of CH4 on oxygen-coated Pd nanoparticles than that on bare Pd nanoparticles at low temperatures. In contrast to the rapid dissociation of CH4 after adsorption, the dissociation of O2 requires much higher temperature than adsorption. Moreover, the CH4 dissociation rate increases with the rising temperature and is sensitive to the level of oxygen coverage on the surface. In addition, the activation energies for the adsorptive dissociation of CH4 are determined by fixed-temperature simulations from 400 to 1000 K through the changes of CH4 concentration and are found to be 3.27 and 2.28 kcal mol−1 on 0.3 and 0.7 ML oxygen-coated Pd nanoparticles, respectively, which are consistent with density functional theory calculations and experiments

Statistical optimization of media components to enhance citric acid production from paddy straw using solid state fermentation

A sequential optimization based on experimental design method was employed to optimize the concentration of media components for improvement of citric acid production from paddy straw by solid state fermentation using Aspergillus niger. The optimization procedure for the media components (NH4NO3, KH2PO4, MgSO4, CuSO4, ZnSO4, FeSO4 and MnSO4) was carried out using the Plaket-Burman Design (PBD) for the screening and Central Composite Design (CCD) for the optimization. The result obtained from (PBD) indicates NH4NO3, KH2PO4 and MgSO4 were the most significant components that affect the citric acid production. The maximum yield obtained by (CCD) was 39.5 g citric acid/kg of paddy straw. The statistical analysis showed that the optimum media concentration was 0.03 g/L for NH4NO3, 2.08 g/L for KH2PO4 and 0.015 g/L for MgSO4, which gives the maximum predicted yield of citric acid (51.1 g citric acid/Kg paddy straw)

Design Aspects of Bioreactors for Solid-state Fermentation: A Review

Solid-state fermentation has gained renewed attention, not only from researchers but also from industries, due to several advantages over submerged fermentations. This is partly because solid-state fermentation has lower energy requirements, higher yields, produces less wastewater with less risk of bacterial contamination, and partly because of environmental concerns regarding the disposal of solid wastes. This paper reviews different types of bioreactors that have been used for various purposes and the recent process developments in solid-state fermentation

Passive phloem loading and long-distance transport in a synthetic tree-on-a-chip

Vascular plants rely on differences of osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as M\"unch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power long-distance transport. Whereas most herbaceous plants use active mechanisms to increase phloem concentration above that of the photosynthetic cells, in most tree species, for which transport distances are largest, loading seems to occur via passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the nonlinear dynamics that arise during export and determine the ability of passive loading to drive long-distance transport. We first demonstrate that in our device, phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of M\"unch transport, where phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with the hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive long-distance transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies