Unusual surface and edge morphologies, sp2 to sp3 hybridized transformation and electronic damage after Ar+ ion irradiation of few-layer graphene surfaces

Roughness and defects induced on few-layer graphene (FLG) irradiated by Ar+ ions at different energies were investigated using X-ray photoemission spectroscopy (XPS) and atomic force microscopy techniques. The results provide direct experimental evidence of ripple formation, sp2 to sp3 hybridized carbon transformation, electronic damage, Ar+ implantation, unusual defects and edge reconstructions in FLG, which depend on the irradiation energy. In addition, shadowing effects similar to those found in oblique-angle growth of thin films were seen. Reliable quantification of the transition from the sp2-bonding to sp3-hybridized state as a result of Ar+ ion irradiation is achieved from the deconvolution of the XPS C (1s) peak. Although the ion irradiation effect is demonstrated through the shape of the derivative of the Auger transition C KVV spectra, we show that the D parameter values obtained from these spectra which are normally used in the literature fail to account for the sp2 to sp3 hybridization transition. In contrast to what is known, it is revealed that using ion irradiation at large FLG sample tilt angles can lead to edge reconstructions. Furthermore, FLG irradiation by low energy of 0.25 keV can be a plausible way of peeling graphene layers without the need of Joule heating reported previously

Fish germplasm resources and exploited fisheries of the rivers of kerala and bionomics of ‘red canarese barb’, hypselobarbus thomassi (day 1874)

Cochin University of Science & Technology

Preparation and Study of Optical Properties of CdS, CdS-TiO2 and CdS-Au Nanocomposites for Photonic Applications

Nanophotonics can be regarded as a fusion of nanotechnology and photonics and it is an emerging field providing researchers opportunities in fundamental science and new technologies. In recent times many new methodsand techniques have been developed to prepare materials at nanoscale dimensions. Most of these materials exhibit unique and interesting optical properties and behavior. Many of these have been found to be very useful to develop new devices and systems such as tracers in biological systems, optical limiters, light emitters and energy harvesters. This thesis presents a summary of the work done by the author in the field by choosing a few semiconductor systems to prepare nanomaterials and nanocomposites. Results of the study of linear and nonlinear optical properties of materials thus synthesized are also presented in the various chapters of this thesis. CdS is the material chosen here and the methods and the studies of the detailed investigation are presented in this thesis related to the optical properties of CdS nanoparticles and its composites. Preparation and characterization methods and experimental techniques adopted for the investigations were illustrated in chapter 2 of this thesis. Chapter 3 discusses the preparation of CdS, TiO2 and Au nanoparticles. We observed that the fluorescence behaviour of the CdS nanoparticles, prepared by precipitation technique, depends on excitation wavelength. It was found that the peak emission wavelength can be shifted by as much as 147nm by varyingthe excitation wavelengths and the reason for this phenomenon is the selective excitation of the surface states in the nanoparticles. This provided certain amount of tunability for the emission which results from surface states.TiO2 nanoparticle colloids were prepared by hydrothermal method. The optical absorption study showed a blue shift of absorption edge, indicating quantum confinement effect. The large spectral range investigated allows observing simultaneously direct and indirect band gap optical recombination. The emission studies carried out show four peaks, which are found to be generated from excitonic as well as surface state transitions. It was found that the emission wavelengths of these colloidal nanoparticles and annealed nanoparticles showed two category of surface state emission in addition to the excitonic emission. Au nanoparticles prepared by Turkevich method showed nanoparticles of size below 5nm using plasmonic absorption calculation. It was also found that there was almost no variation in size as the concentration of precursor was changed from 0.2mM to 0.4mM.We have observed SHG from CdS nanostructured thin film prepared onglass substrate by chemical bath deposition technique. The results point out that studied sample has in-plane isotropy. The relative values of tensor components of the second-order susceptibility were determined to be 1, zzz 0.14, xxz and 0.07. zxx These values suggest that the nanocrystals are oriented along the normal direction. However, the origin of such orientation remains unknown at present. Thus CdS is a promising nonlinear optical material for photonic applications, particularly for integrated photonic devices. CdS Au nanocomposite particles were prepared by mixing CdS nanoparticles with Au colloidal nanoparticles. Optical absorption study of these nanoparticles in PVA solution suggests that absorption tail was red shifted compared to CdS nanoparticles. TEM and EDS analysis suggested that the amount of Au nanoparticles present on CdS nanoparticles is very small. Fluorescence emission is unaffected indicating the presence of low level of Au nanoparticles. CdS:Au PVA and CdS PVA nanocomposite films were fabricated and optically characterized. The results showed a red-shift for CdS:Au PVA film for absorption tail compared to CdS PVA film. Nonlinear optical analysis showed a huge nonlinear optical absorption for CdS:Au PVA nanocomposite and CdS:PVA films. Also an enhancement in nonlinear optical absorption is found for CdS:Au PVA thin film compared to the CdS PVA thin film. This enhancement is due to the combined effect of plasmonic as well as excitonic contribution at high input intensity. Samples of CdS doped with TiO2 were also prepared and the linear optical absorption spectra of these nanocompositeparticles clearly indicated the influence of TiO2 nanoparticles. TEM and EDS studies have confirmed the presence of TiO2 on CdS nanoparticles. Fluorescence studies showed that there is an increase in emission peak around 532nm for CdS nanoparticles. Nonlinear optical analysis of CdS:TiO2 PVA nanocomposite films indicated a large nonlinear optical absorption compared to that of CdS:PVA nanocomposite film. The values of nonlinear optical absorption suggests that these nanocomposite particles can be employed for optical limiting applications. CdSe-CdS and CdSe-ZnS core-shell QDs with varying shell size were characterized using UV–VIS spectroscopy. Optical absorption and TEM analysis of these QDs suggested a particle size around 5 nm. It is clearly shown that the surface coating influences the optical properties of QDs in terms of their size. Fluorescence studies reveal the presence of trap states in CdSe-CdS and CdSe- ZnS QDs. Trap states showed an increase as a shell for CdS is introduced and increasing the shell size of CdS beyond a certain value leads to a decrease in the trap state emission. There is no sizeable nonlinear optical absorption observed. In the case of CdSe- ZnS QDs, the trap state emission gets enhanced with the increase in ZnS shell thickness. The enhancement of emission from trap states transition due to the increase in thickness of ZnS shell gives a clear indication of distortion occurring in the spherical symmetry of CdSe quantum dots. Consequently the nonlinear optical absorption of CdSe-ZnS QDs gets increased and the optical limiting threshold is decreased as the shell thickness is increased in respect of CdSe QDs. In comparison with CdSe-CdS QDs, CdSe-ZnS QDs possess much better optical properties and thereby CdSe-ZnS is a strong candidate for nonlinear as well as linear optical applications.

Synthesis and Photoluminescence Properties of Novel Red Phosphors for White Light Emitting Diode Applications

Several series of Eu3+ based red emitting phosphor materials were synthesized using solid state reaction route and their properties were characterized. The present studies primarily investigated the photoluminescence properties of Eu3+ in a family of closely related host structure with a general formula Ln3MO7. The results presented in the previous chapters throws light to a basic understanding of the structure, phase formation and the photoluminescence properties of these compounds and their co-relations. The variation in the Eu3+ luminescence properties with different M cations was studied in Gd3-xMO7 (M = Nb, Sb, Ta) system.More ordering in the host lattice and more uniform distribution of Eu3+ ions resulting in the increased emission properties were observed in tantalate system.Influence of various lanthanide ion (Lu, Y, Gd, La) substitutions on the Eu3+ photoluminescence properties in Ln3MO7 host structures was also studied. The difference in emission profiles with different Ln ions demonstrated the influence of long range ordering, coordination of cations and ligand polarizability in the emission probabilities, intensity and quantum efficiency of these phosphor materials. Better luminescence of almost equally competing intensities from all the 4f transitions of Eu3+ was noticed for La3TaO7 system. Photoluminescence properties were further improved in La3TaO7 : Eu3+ phosphors by the incorporation of Ba2+ ions in La3+ site. New red phosphor materials Gd2-xGaTaO7 : xEu3+ exhibiting intense red emissions under UV excitation were prepared. Optimum doping level of Eu3+ in these different host lattices were experimentally determined. Some of the prepared samples exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. In the present studies, Eu3+ acts as a structural probe determining the coordination and symmetry of the atoms in the host lattice. Results from the photoluminescence studies combined with the powder XRD and Raman spectroscopy investigations helped in the determination of the correct crystal structures and phase formation of the prepared compounds. Thus the controversy regarding the space groups of these compounds could be solved to a great extent. The variation in the space groups with different cation substitutions were discussed. There was only limited understanding regarding the various influential parameters of the photoluminescence properties of phosphor materials. From the given studies, the dependence of photoluminescence properties on the crystal structure and ordering of the host lattice, site symmetries, polarizability of the ions, distortions around the activator ion, uniformity in the activator distribution, concentration of the activator ion etc. were explained. Although the presented work does not directly evidence any application, the materials developed in the studies can be used for lighting applications together with other components for LED lighting. All the prepared samples were well excitable under near UV radiation. La3TaO7 : 0.15Eu3+ phosphor with high efficiency and intense orange red emissions can be used as a potential red component for the realization of white light with better color rendering properties. Gd2GaTaO7 : Eu3+, Bi2+ red phosphors give good color purity matching to NTSC standards of red. Some of these compounds exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. However thermal stability and electrical output using these compounds should be studied further before applications. Based on the studies in the closely related Ln3MO7 structures, some ideas on selecting better host lattice for improved luminescence properties could be drawn. Analyzing the CTB position and the number of emission splits, a general understanding on the doping sites can be obtained. These results could be helpful for phosphor designs in other host systems also, for enhanced emission intensity and efficiency.

Effects of red brick production on land use, household income, and greenhouse gas emissions in Khartoum, Sudan

In Khartoum (Sudan) a particular factor shaping urban land use is the rapid expansion of red brick making (BM) for the construction of houses which occurs on the most fertile agricultural Gerif soils along the Nile banks. The objectives of this study were to assess the profitability of BM, to explore the income distribution among farmers and kiln owners, to measure the dry matter (DM), nitrogen (N), phosphorus (P), potassium (K) and organic carbon (C_org) in cow dung used for BM, and to estimate the greenhouse gas (GHG) emissions from burned biomass fuel (cow dung and fuel wood). About 49 kiln owners were interviewed in 2009 using a semi-structured questionnaire that allowed to record socio-economic and variable cost data for budget calculations, and determination of Gini coefficients. Samples of cow dung were collected directly from the kilns and analyzed for their nutrients concentrations. To estimate GHG emissions a modified approach of the Intergovernmental Panel on Climate Change (IPCC) was used. The land rental value from red brick kilns was estimated at 5-fold the rental value from agriculture and the land rent to total cost ratio was 29% for urban farms compared to 6% for BM. The Gini coefficients indicated that income distribution among kiln owners was more equal than among urban farmers. Using IPCC default values the 475, 381, and 36 t DM of loose dung, compacted dung, and fuel wood used for BM emit annually 688, 548, and 60 t of GHGs, respectively.

Trabajando y compartiendo en red : elaboraci??n del informe individualizado para los ciclos formativos

Se presenta experiencia educativa que propone la creaci??n de una red virtual entre centros que compartan los mismos ciclos formativos. Se realiza en el IES Aynadamar en Granada. Los objetivos son: contactar con los posibles interesados y establecer las comunicaciones necesarias; organizar la red; facilitar el acceso a todos los interesados en participar; organizar el foro de debate y sus contenidos; organizar el banco de recursos; programar las medidas necesarias para la dinamizaci??n de la red.

En red ando.

Se presenta memoria final de proyecto educativo que propone la introducción de las nuevas tecnologías en las aulas como elemento motivador. Se realiza en el CEIP Andrés Bernáldez en Los Palacios y Villafranca, Sevilla. Los objetivos son: elevar el nivel de motivación y gusto por el aprendizaje de nuestro alumnado; incorporar el uso de las nuevas tecnologías al currículum y práctica cotidiana de nuestro centro; formarnos en aquellas tareas específicas que nos ayuden a desarrollar los objetivos anteriores; difundir el proyecto a nivel de la web del centro y a nivel documental.

En la red aprendo.

Propiciar en el alumnado del tercer ciclo de E. Primaria un aumento del conocimiento de los recurso tecnológicos, aportando materiales que desarrollan el currículo y que permiten, además, generar conocimiento mediante la búsqueda guiada en la red de forma que el acceso a la información sea más rápido, preciso y eficiente.

RED-EBARRIOS.

Se pretende dar alfabetización en TIC a toda la comunidad educativa, alumnado, profesorado y padres así como la implantación progresiva de las Nuevas Tecnologías en el Aula y el uso de Internet como herramienta didáctica. Se impulsan los apoyos desde Infantil a sexto de E. Primaria en el Aula de Informática para incorporar el uso del ordenador como herramienta de trabajo.

Instalación y administración de una red inalámbrica y un servidor de internet.

El proyecto ha consistido en la instalación y administración de una red inalámbrica y la instalación y administración de un servidor de servicios de internet. Entre los servicios suministrados han estado: un servidor web, al que se podrá acceder desde dentro y fuera del centro a través de una dirección IP pública; un servidor de correo para proporcionar correo electrónico al alumnado del centro, con un dominio propio; y un servidor ftp para que cualquier alumno o alumna pueda descargarse los recursos que deposite el profesorado de sus respectivas materias-áreas-módulos. En cuanto a la administración de la red inalámbrica, para proteger el acceso de usuarios no registrados o no autorizados a la misma se preveerán mecanismos de acceso restringidos a ciertas tarjetas y-o a ciertos usuarios.

Amigo Sancho, cabalgamos por la red.

Se presenta memoria final de proyecto educativo que pretende aunar el uso de las TIC de forma significativa con el fomento de la lectura, la comunicación y la educación en valores que propugna la obra de 'El Quijote', utilizando la edición de un periódico realizado por el alumnado con ayuda de internet, cámara digital, ordenador y escáner. Se realiza en el CEIP Reyes Católicos de Vera, Almería. Los objetivos son: familiarizar al alumnado con las TIC; desarrollar habilidades que propicien la alfabetización funcional; posibilitar el incremento de la motivación, el disfrute y el interés en las experiencias de aprendizaje a través de internet; favorecer la oportunidad de intercambios lingüísticos orales, escritos y gráficos en un marco significativo; aprender a escuchar, opinar, debatir, compartir, dialogar y llegar a acuerdos; aprender a asumir responsabilidades; favorecer el trabajo el equipo; brindar la oportunidad para que se establezcan situaciones comunicativas diversas; mejorar la autoestima; crear un ambiente idóneo para investigar y realizar tareas; conocer el funcionamiento y la elaboración de un periódico; implicar a las familias así como a personas de diferentes profesiones en esta tarea investigativa; trabajar al menos durante dos cursos consecutivos bajo este enfoque. Los materiales obtenidos han sido: Cds con los periódicos editados; un ejemplar de cada periódico; libro del quijote interpretado por el alumnado de tercero; disquete con las traducciones al inglés; Don Quijote bilingüe.

Instalación y puesta en funcionamiento de una red inalámbrica en el centro educativo.

Se presenta memoria final de proyecto educativo que pretende la implantación de un nodo inalámbrico de una cobertura aproximada de 2 km omnidireccionales con el fin de dar acceso a la red del centro desde los hogares a toda la comunidad educativa. Con ello, se permitirá acceder a información relativa al centro y consulta a internet con carácter gratuito utilizando para ello tecnología wireless de última generación. Se realiza en el IES Inca Garcilaso de Montilla, Córdoba. Los objetivos son: acceder a la información del centro mediante una conexión inalámbrica; permitir a toda la comunidad educativa una conexión inalámbrica desde casa a internet, totalmente gratuita, utilizando la infraestructura de red del IES; promover la utilización de las nuevas tecnologías y el acceso a la sociedad de la información; fomentar el uso de sofware libre entre la comunidad educativa; apoyar el proceso de enseñanza-aprendizaje utilizando las nuevas tecnologías. El proceso consta de varias fases: instalación y configuración de un nodo 'WLAN' en el centro; instalación y configuración de un servidor de contenidos con sofware libre; formación al profesorado en la utilización de la red inalámbrica y la plataforma elearning; difusión del proyecto entre la comunidad educativa; formación y asesoramiento al alumnado para la utilización y conexión a la red inalámbrica del centro, y el acceso a los contenidos depositados en el servidor; puesta en funcionamiento de la red. Los resultados concretos han sido: creación de una red ciudadana libre de uso generalizado por la comunidad educativa, con acceso inalámbrico; utilización de la red inalámbrica para acceder a información del centro y a internet; utilización del alumnado de las nuevas tecnologías como herramienta de ayuda para su formación; utilización generalizada de las nuevas tecnologías en la práctica docente; creación de una plataforma que ayude al intercambio de ideas y proyectos entre profesorado y alumnado; promover la utilización del software libre.

Guia d'equipaments d'educació ambiental i ús públic de la Xarxa de Parcs Naturals de la Diputació de Barcelona.'Guía de equipamientos de educación ambiental y uso público de la red de Parques Naturales de la Diputación de Barcenona'.

Título tomado de la cubierta

Generalization over contrast and mirror reversal, but not figure-ground reversal, in an "edge-based

Baylis & Driver (Nature Neuroscience, 2001) have recently presented data on the response of neurons in macaque inferotemporal cortex (IT) to various stimulus transformations. They report that neurons can generalize over contrast and mirror reversal, but not over figure-ground reversal. This finding is taken to demonstrate that ``the selectivity of IT neurons is not determined simply by the distinctive contours in a display, contrary to simple edge-based models of shape recognition'', citing our recently presented model of object recognition in cortex (Riesenhuber & Poggio, Nature Neuroscience, 1999). In this memo, I show that the main effects of the experiment can be obtained by performing the appropriate simulations in our simple feedforward model. This suggests for IT cell tuning that the possible contributions of explicit edge assignment processes postulated in (Baylis & Driver, 2001) might be smaller than expected.

El ocio activo como oferta en la red española de ciudades educadoras.

a) Comprobar cual es la oferta de ocio activo que se dá desde los entes municipales para las edades escolares (de 0 a 18 años); b) Saber en que espacios de la ciudad se realizan estas actividades y c) Determinar la temporalidad de la realización de estas actividades. De entre las ciudades españolas pertenecientes a la Asociación Internacional de Ciudades Educadoras, se escogieron aquellas que recogían experiencias que iban dirigidas a las edades de 0 y 18 años, pretendiendo abarcar toda la infancia y adolescencia, escogiendo aquellas que contemplaban la práctica de actividad física. Los datos recogidos se obtienen de diferentes fuentes siendo la principal la base de datos de la Red Española de Ciudades Educadoras. La conclusión general que puede extraerse de este estudio es que los espacios urbanos son el principal elemento de educación de la ciudadanía en hábitos de promoción de salud y fomento de las prácticas de actividad física. La educación en estos hábitos, dirigidas a las edades de 0 a 18 años, sobrepasa los límites de la escuela. La oferta se dirige a todas las edades incidiendo particularmente en las edades de la Educación Secundaria, a partir de los 13 años. Los centros educativos acogen parte de las experiencias, sin embargo, es de notar la ausencia de la actividad a lo largo del periodo vacacional. La organización de la vida académica y la gestión de los centros dificulta la posibilidad de un uso no escolar de los mismos. Por otro lado, la población de 0 a 6 años recibe una escasa atención, recayendo el cuidado de estos niños/as sobre las familias dejando con ello de educar a una parte importante de la ciudadanía en el valor del ocio constructivo. Por último destacar la actual tendencia a considerar a la ciudad como agente educativo.