Land Use Land Cover Change of Qotto-Asanao Micro Watershed

The dependency of farming community on the natural resource base aggravates its degradation and deterioration. To reverse and mitigate such natural resource degradation integrated watershed management has been implemented as one of the best strategies. Integrated watershed management is an action oriented development intervention in which farming communities are actively participated in all process starting from its planning to implementation. In southern Ethiopia, a micro-watershed known as Qotto-Asano was identified and integrated watershed management has been implemented since 2011. The land use and land cover change of the micro watershed was detected using Geographical Information System (GIS) and remote sensing techniques. The major land cover categories statistically compared in to two periods, i.e., before the intervention (1986 to 2010) and during the intervention (2011 to 2015) were cultivated land, forest, shrub, grass land, wet land and area allocated for built up. As a result of watershed intervention between the period 2011 and 2015, both positive and negative changes had occurred in the micro watershed. Positive land cover pattern was observed in forest (0.73%), grass land (0.35%) and cultivated land (1.12%) while shrub (-2.42%) and bare land (0.86%) showed negative increment.  In conclusion, integrated watershed management should be given due emphasis by development practitioners as a remedy action to maintain and conserve the natural resource base. Keywords: Integrated watershed management, Land use/land cover, Geographical Information System

Low temperature synthesis of multiwalled carbon nanotubes and incorporation into an organic solar cell

Abstract: Metal nanoparticle (MNP) catalysts used for the synthesis of multiwalled carbon nanotubes (MWCNTs) consisted of single metals (Fe, Ni or Co) and bimetallic mixture (CoFe, NiFe or NiCo). MWCNTs were successfully synthesised at 200 _C in 10 min using liquefied petroleum gas as carbon source with non-equilibrium plasma enhanced chemical vapour deposition (PECVD) method. The nanostructures and the morphology of the MNPs and the MWCNTs film were characterised using relevant microscopic and spectroscopic methods. The synthesised MWCNTs were used as part of the electrode material in organic solar cell (OSC) set-up. Poly (3,4- ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) was used as an electron transporter and poly-3-hexyl thiophene (P3HT) as an electron donor. The performance of OSC devices was tested using standard electrical measurements and solar simulator operating at 100 mW/cm2. The measured power conversion efficiencies was found to be dependent on the metal catalyst used during synthesis. Among all the catalysts employed in this investigation, the best device performance was found from the synthesis of MWCNTs using Fe as a catalyst followed by Co and then Ni, respectively

Organic Solar Cells with Boron- or Nitrogen-Doped Carbon Nanotubes in the P3HT : PCBM Photoactive Layer

Either boron- or nitrogen-doped carbon nanotubes (B- or N-CNTs) were incorporated in bulk heterojunction organic solar cells photoactive layer composed of poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The physical and chemical properties were investigated using different spectroscopic techniques. The cell performance was followed from their current-voltage (J-V) characteristics. Recombination dynamics of the photo-generated free charge carriers were investigated using micro- to milliseconds transient absorption spectroscopy (TAS). Transmission electron microscopy (TEM) images revealed the presence of cone structures and bamboo compartments in B-CNTs and N-CNTs, respectively. X-ray photoelectron spectroscopy (XPS) revealed very little boron was substituted in the carbon network and presence of pyrrolic, pyridinic, and quaternary species of nitrogen in N-CNTs. J-V characteristics were found to be similar for the devices with B- and N-CNTs even though boron- and nitrogen-doped CNTs are known to have different properties, that is, p-type and n-type, respectively. TAS results showed that all devices had long lived free charge carriers but the devices with B- or N-CNTs had low power conservation efficiency and voltage

Surface Segregation of Cyclic Chains in Binary Melts of Thin Polymer Films: The Influence of Constituent Concentration

We carry out extensive molecular dynamics simulations of thin films of bead-spring models of binary mixtures composed of cyclic and linear polymer chains. We study the equilibrium behavior of the polymer chains for two very different chain lengths, which resemble short (10-mers) and long (100-mers) chains, at different concentrations of the binary mixture. We clearly show how the concentration variable affects the enrichment of either of the two polymer species at the interface, and also how the chain length influences this process

Bulk Heterojunction Solar Cell with Nitrogen-Doped Carbon Nanotubes in the Active Layer: Effect of Nanocomposite Synthesis Technique on Photovoltaic Properties

Nanocomposites of poly(3-hexylthiophene) (P3HT) and nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized by two methods; specifically, direct solution mixing and in situ polymerization. The nanocomposites were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray dispersive spectroscopy, UV-Vis spectrophotometry, photoluminescence spectrophotometry (PL), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis, and dispersive surface energy analysis. The nanocomposites were used in the active layer of a bulk heterojunction organic solar cell with the composition ITO/PEDOT:PSS/P3HT:N-CNTS:PCBM/LiF/Al. TEM and SEM analysis showed that the polymer successfully wrapped the N-CNTs. FTIR results indicated good π-π interaction within the nanocomposite synthesized by in situ polymerization as opposed to samples made by direct solution mixing. Dispersive surface energies of the N-CNTs and nanocomposites supported the fact that polymer covered the N-CNTs well. J-V analysis show that good devices were formed from the two nanocomposites, however, the in situ polymerization nanocomposite showed better photovoltaic characteristics

Scientific Foundations of Audiology: Perspectives from Physics, Biology, Modeling, and Medicine

With advancements across various scientific and medical fields, professionals in audiology are in a unique position to integrate cutting-edge technology with real-world situations. Scientific Foundations of Audiology provides a strong basis and philosophical framework for understanding various domains of hearing science in the context of contemporary developments in genetics, gene expression, bioengineering, neuroimaging, neurochemistry, cochlear and mid-brain implants, associated speech processing and understanding, molecular biology, physics, modeling, medicine, and clinical practice. Key features of this text include: - Highly technical information presented in a cohesive and understandable manner (i.e., concepts without complex equations) - Discussion of integrating newly developed technology within the clinical practice of audiology - State-of-the-art contributions from a stellar array of international, world-class experts Scientific Foundations of Audiology is geared toward doctoral students in audiology, physics, and engineering; residents in otolaryngology, neurology, neurosurgery, and pediatrics; and those intermediaries between innovation and clinical reality

Organic solar cells with boron- or nitrogen-doped carbon nanotubes in the P3HT : PCBM photoactive layer

Either boron- or nitrogen-doped carbon nanotubes (B- or N-CNTs) were incorporated in bulk heterojunction organic solar cells photoactive layer composed of poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The physical and chemical properties were investigated using different spectroscopic techniques. The cell performance was followed from their current-voltage (-) characteristics. Recombination dynamics of the photo-generated free charge carriers were investigated using micro- to milliseconds transient absorption spectroscopy (TAS). Transmission electron microscopy (TEM) images revealed the presence of cone structures and bamboo compartments in B-CNTs and N-CNTs, respectively. X-ray photoelectron spectroscopy (XPS) revealed very little boron was substituted in the carbon network and presence of pyrrolic, pyridinic, and quaternary species of nitrogen in N-CNTs. - characteristics were found to be similar for the devices with B- and N-CNTs even though boron- and nitrogen-doped CNTs are known to have different properties, that is, p-type and n-type, respectively. TAS results showed that all devices had long lived free charge carriers but the devices with B- or N-CNTs had low power conservation efficiency and voltage201

Aqueous Processed All-Polymer Solar Cells with High Open-Circuit Voltage Based on Low-Cost Thiophene-Quinoxaline Polymers

Eco-friendly solution processing and the low-cost synthesis of photoactive materials are important requirements for the commercialization of organic solar cells (OSCs). Although varieties of aqueous-soluble acceptors have been developed, the availability of aqueous-processable polymer donors remains quite limited. In particular, the generally shallow highest occupied molecular orbital (HOMO) energy levels of existing polymer donors limit further increases in the power conversion efficiency (PCE). Here, we design and synthesize two water/alcohol-processable polymer donors, poly[(thiophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-T)) and poly[(selenophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-Se)) with oligo(ethylene glycol) (OEG) side chains, having deep HOMO energy levels (∼−5.4 eV). The synthesis of the polymers is achieved in a few synthetic and purification steps at reduced cost. The theoretical calculations uncover that the dielectric environmental variations are responsible for the observed band gap lowering in OEG-based polymers compared to their alkylated counterparts. Notably, the aqueous-processed all-polymer solar cells (aq-APSCs) based on P(Qx8O-T) and poly[(N,N′-bis(3-(2-(2-(2-methoxyethoxy)-ethoxy)ethoxy)-2-((2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-methyl)propyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-(2,5-thiophene)] (P(NDIDEG-T)) active layer exhibit a PCE of 2.27% and high open-circuit voltage (VOC) approaching 0.8 V, which are among the highest values for aq-APSCs reported to date. This study provides important clues for the design of low-cost, aqueous-processable polymer donors and the fabrication of aqueous-processable OSCs with high VOC