Security devices based on liquid crystals doped with a colour dye

Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices. Employing liquid crystal and dichroic colorants, we have developed devices that show, with the aid of a polarizer, multiple images on each side of the device. Rubbed polyimide is used as alignment layer on each substrate of the LC cell. By rubbing the polyimide in different directions in each substrate it is possible to create any kind of symbols, drawings or motifs with a greyscale; the more complex the created device is, the more difficult is to fake it. To identify the motifs it is necessary to use polarized light. Depending on whether the polarizer is located in front of the LC cell or behind it, different motifs from one or the other substrate are shown. The effect arises from the dopant colour dye added to the liquid crystal, the induced orientation and the twist structure. In practice, a grazing reflection on a dielectric surface is polarized enough to see the effect. Any LC flat panel display can obviously be used as backlight as well

Cymantrene–Triazole "Click" Products: Structural Characterization and Electrochemical Properties

We report the first known examples of triazole-derivatized cymantrene complexes (η5-[4-substituted triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I), obtained via a “click” chemical synthesis, bearing a phenyl, 3-aminophenyl, or 4-aminophenyl moiety at the 4-position of the triazole ring. Structural characterization data using multinuclear NMR, UV–vis, ATR-IR, and mass spectrometric methods are provided, as well as crystallographic data for (η5-[4-phenyltriazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I) and (η5-[4-(3-aminophenyl)triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I). Cyclic voltammetric characterization of the redox behavior of each of the three cymantrene–triazole complexes is presented together with digital simulations, in situ infrared spectroelectrochemistry, and DFT calculations to extract the associated kinetic and thermodynamic parameters. The trypanocidal activity of each cymantrene–triazole complex is also examined, and these complexes are found to be more active than cymantrene alone

Optically Induced Reorientation in Nematic Cylindrical Structures

Cyclindrical structures of nematics give rise to several opto-optical effects related to molecular reorientation. One of these effects is the formation of diffraction ring patterns similar to the ones observed in planar cells, but differing in shape. Another effect has been observed, namely a quasi-chaotic motion of rings with a very large angular spread; this motion can be obtained using a cw laser and high power densities. The phenomenon could be attributed to thermal motion, however, there are some features that cannot be explained by a purely thermal effect, e.g., a wavelength dependence of the threshold and the frequencies of the ring motion

First report in Venezuela of Colletotrichum gloeosporioides (Coeolomycete) and its teleomorph Glomerella cingulata on Eucalyptus urophylla Blake and its hybrid Urograndis.

CONTENIDO Editorial. Propuesta de evaluación, acreditación e integración de la educación superior agrícola y ambiental venezolana. Propose of evaluation, accreditation and integration of the venezuelan higher education agricole and environmental. Suárez, Arlene; Rodríguez Mezerhane, Arlene y González Lanza, Rafael Artículos Primer reporte de Colletotrichum gloeosporioides (Coeolomycete) y su estado teleomórfico Glomerella cingulata sobre Eucalyptus urophylla Blake y su híbrido Urograndis en Venezuela. First report in Venezuela of Colletotrichum gloeosporioides (Coeolomycete) and its teleomorph Glomerella cingulata on Eucalyptus urophylla Blake and its hybrid Urograndis. Ely Bali, Francisca; Holmquist, Otón y Mohali C. Sari Evaluación del proceso de deforestación en tres cuencas del piedemonte lacustrino de la cordillera de Los Andes. Evaluation of the deforestation process in three watersheds of lacustrine piedmonts in the Andes mountains. Pozzobon B., Ennio N.; Hernández B., Edgar A. y Dugarte Castillo, Iván D. Evaluación financiera del primero y segundo ciclo de corta en el compartimiento 1 del lote boscoso El Dorado, Tumeremo, estado Bolívar - Venezuela. Financial evaluation of the first and second harvest in the compartment 1 of the El Dorado - Tumeremo forest lot, Bolivar State - Venezuela. Noguera L., Oscar E.; Andrade, Víctor y Carrero G., Omar E. Efecto del estrés hídrico sobre el rendimiento de tres variedades de tomate (Lycopersicon esculentum, Mill.). Drought stress effect on the yield of three varieties of tomato (Lycopersicon esculentum, Mill.). Mukandama, J. P.; González, María C. y Montilla, Eugenio Composición florística del municipio Boconó, estado Trujillo - Venezuela. Aportes preliminares para su reconocimiento y valoración. Composition floristica of municipality Boconó, Trujillo State - Venezuela. Preliminary contribution for its recognition and valorization. Dubuc de Isea, Lourdes Estudio preliminar de las propiedades mecánicas de la especie Azadirachta indica (Neem), proveniente del estado Falcón - Venezuela. Preliminary study of the mechanical properties of the species Azadirachta indica (Neem), coming from the Facon State-Venezuela. Reyes C., Elio C.; Valero, Styles W. y Garay J., Dario A. Variaciones de la composición florística en subtipos de bosque de la selva de Bajío en la Reserva Forestal Caparo, Llanos occidentales de Venezuela. Viariations on the floristic composition of forest subtypes of the selva de Bajio in the Forest Reserve Caparo, western plains of Venezuela. Kochaniewicz, Grzegorz y Plonczak Ratschiller, Miguel Andrés Selección de modelos para predecir distribuciones diamétricas en plantaciones de teca a partir de variables del Rodal con la función Weibull. Selection of models for prediction diameter distribution of teak plantations from spot variables with Weibull function. Quevedo R., Ana Mercedes; Jerez R., Mauricio y Moret, Ana Yajaira Importancia de la aplicación de las técnicas de decisión multicriterio (MCDM), en la industria forestal mecánica de Venezuela. Importance of the application of the techniques of decision multicriterio (MCDM), in the industry forest mechanics of Venezuela. Aragonés Beltrán, Pablo; García Melón, Mónica; Contreras Miranda, Wilver y Owen de Contreras, Mary E. La ecología industrial, el ecodiseño y los procesos mas limpios en la industria del mueble con madera en Venezuela. The industrial ecology, the ecodiseno and the processes clean in the industry of the piece of furniture with wood in Venezuela. Contreras Miranda, Wilver; Owen de Contreras, Mary E. y Capuz Rizo, Salvador Anatomía foliar y xilemática de Ochoterenaea colombiana Barkley. Leaf and wood anatomy of Ochoterenaea colombiana Barkley. Araque, Osmari Z. y Gámez A., Luis E. Plantaciones forestales e industrias asociadas en Venezuela. Aspectos socio-económicos. Forest plantations and associated industries in Venezuela. Socio-economic aspects. González, Ronalds; Plonczak Ratschiller, Miguel Andrés y Stock, Jürgen Evaluación de métodos de interpolación en la construcción de un modelo digital de elevación con fines hidrológicos: aplicación en una cuenca andina de montaña. Evaluation of interpolation methods in the construction of a digital model of elevation with hydrological ends: application in an Andean watershed of mountain. Pacheco A., Carlos E. y Barrios R., Alex G. Tesis Determinación de las fuentes actuales y potenciales de erosión en la cuenca media y alta del río Mucujepe, estado Mérida-Venezuela. Determination of present and potential sources of erosion in the middle and upper watersheds of the Mucujepe river, Merida State - Venezuela. Linares, Yamilet Modelado de distribuciones diamétricas en plantaciones de Teca en el área experimental Caparo, Barinas - Venezuela. Modeling diameter distributions for Teak plantations in the Caparo experimental station, Barinas State - Venezuela. Quevedo R., Ana [email protected]@[email protected] analíticosemestra