Characterization and Comparison of the Tissue-Related Modules in Human and Mouse

Background: Due to the advances of high throughput technology and data-collection approaches, we are now in an unprecedented position to understand the evolution of organisms. Great efforts have characterized many individual genes responsible for the interspecies divergence, yet little is known about the genome-wide divergence at a higher level. Modules, serving as the building blocks and operational units of biological systems, provide more information than individual genes. Hence, the comparative analysis between species at the module level would shed more light on the mechanisms underlying the evolution of organisms than the traditional comparative genomics approaches. Results: We systematically identified the tissue-related modules using the iterative signature algorithm (ISA), and we detected 52 and 65 modules in the human and mouse genomes, respectively. The gene expression patterns indicate that all of these predicted modules have a high possibility of serving as real biological modules. In addition, we defined a novel quantity, "total constraint intensity,'' a proxy of multiple constraints (of co-regulated genes and tissues where the co-regulation occurs) on the evolution of genes in module context. We demonstrate that the evolutionary rate of a gene is negatively correlated with its total constraint intensity. Furthermore, there are modules coding the same essential biological processes, while their gene contents have diverged extensively between human and mouse. Conclusions: Our results suggest that unlike the composition of module, which exhibits a great difference between human and mouse, the functional organization of the corresponding modules may evolve in a more conservative manner. Most importantly, our findings imply that similar biological processes can be carried out by different sets of genes from human and mouse, therefore, the functional data of individual genes from mouse may not apply to human in certain occasions.

Technology development of photovoltaic concentrator system

The developments of standard, projects and technology of PV concentrator system was briefly reported. A detailed description of photovoltaic concentrator system was given, which included technology and recent development of optical components, receivers and balance of system (BOS). The heat sink of passive cooling and active cooling was given. A brief discussion promise of this technology was included. Finally, main technological problems were presented.

Voltage sensing buck converter-based technique for maximum photovoltaic solar energy delivery

A voltage sensing buck converter-based technique for maximum solar power delivery to a load is presented. While retaining the features and advantages of the incremental conductance algorithm, this technique is more desirable because of single sensor use. The technique operates by maximising power at the buck converter output instead of the input.

Dye-sensitized solar cells based on a single layer deposition of TiO 2 from a new formulation paste and their photovoltaic performance

A new strategy for enhancing the efficiency and reducing the production cost of TiO 2 solar cells by design of a new formulated TiO 2 paste with tailored crystal structure and morphology is reported. The conventional three- or four-fold layer deposition process was eliminated and replaced by a single layer deposition of TiO 2 compound. Different TiO 2 pastes with various crystal structures, morphologies and crystallite sizes were prepared by an aqueous particulate sol-gel process. Based on simultaneous differential thermal (SDT) analysis the minimum annealing temperature to obtain organic-free TiO 2 paste was determined at 400°C, being one of the lowest crystallization temperatures of TiO 2 photoanode electrodes for solar cell application. Photovoltaic measurements showed that TiO 2 solar cell with pure anatase crystal structure had higher power conversion efficiency (PCE) than that made of pure rutile-TiO 2. However, the PCE of solar cells depends on the anatase to rutile weight ratio, reaching a maximum at a specific value due to the synergic effect between anatase and rutile TiO 2 nanoparticles. Moreover, it was found that the PCE of solar cells made of crystalline TiO 2 powders was much higher, increasing in the range 32-84% depending on anatase to rutile weight ratio, than that of prepared by amorphous powders. TiO 2 solar cell with the morphology of mixtures of nanoparticles and microparticles had higher PCE than the solar cell with the same phase composition containing TiO 2 nanoparticles due to the role of TiO 2 microparticles as light scattering particles. The presented strategy would open up new insight into fabrication and structural design of low-cost TiO 2 solar cells with high power conversion efficiency. © 2012 Elsevier Ltd.

Photovoltaic measurements in carbon nanotube - Amorphous silicon core/shell nanowire

Carbon nanotube is one of the promising materials for exploring new concepts in solar energy conversion and photon detection. Here, we report the first experimental realization of a single core/shell nanowire photovoltaic device (2-4μm) based on carbon nanotube and amorphous silicon. Specifically, a multi-walled carbon nanotube (MWNTs) was utilized as the metallic core, on which n-type and intrinsic amorphous silicon layers were coated. A Schottky junction was formed by sputtering a transparent conducting indium-tin-oxide layer to wrap the outer shell of the device. The single coaxial nanowire device showed typical diode ratifying properties with turn-on voltage around 1V and a rectification ratio of 104 when biased at ±2V. Under illumination, it gave an open circuit voltage of ∼0.26V. Our study has shown a simple and useful platform for gaining insight into nanowire charge transport and collection properties. Fundamental studies of such nanowire device are important for improving the efficiency of future nanowire solar cells or photo detectors. © 2012 IEEE.

Non-destructive optical characterization of phase separation in bulk heterojunction organic photovoltaic cells

The dithiophene donor-acceptor copolymers that are bridged either with carbon (C-PCPDTBT) or silicon atoms (Si-PCPDTBT) belong to a promising family of materials for use in photoactive layers for organic photovoltaic cells (OPVs). In this work, we implement the non-destructive Spectroscopic Ellipsometry technique in the near infrared to the far ultraviolet spectral region in combination with advanced theoretical modeling to investigate the vertical distribution of the C-PCPDTBT and Si-PCPDTBT polymer and fullerene ([6,6]-phenyl C71-butyric acid methyl ester - PC70BM) phases in the blend, as well as the effect of the polymer-to-fullerene ratio on the distribution mechanism. It was found that the C-PCPDTBT:PC70BM blends have donor-enriched top regions and acceptor-enriched bottom regions, whereas the donor and acceptor phases are more homogeneously intermixed in the Si-PCPDTBT:PC70BM blends. We suggest that the chemical incompatibility of the two phases as expressed by the difference in their surface energy, may be a key element in promoting the segregation of the lower surface phase to the top region of the photoactive layer. We found that the increase of the photoactive layer thickness reduces the polymer enrichment at the cathode, producing a more homogeneous phase distribution of donor and acceptor in the bulk that leads to the increase of the OPV efficiency. © 2014 Elsevier B.V.