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Data Storage (data + storage)
Kinds of Data Storage Selected AbstractsDesigning Polymers to Enable Nanoscale Thermomechanical Data StorageADVANCED FUNCTIONAL MATERIALS, Issue 8 2010B. Gotsmann Abstract Nanomechanics has been slow in entering nanotechnology because of extreme conditions resulting from scaling. This is an issue in particular for polymers, although widely used in macroscale applications. Highly repetitive nanoscale deformation cycling in combination with excellent shape retention and thermal stability is demonstrated. While generic principles described are pertinent to a range of applications, this demonstration is made on the example of polymer media in high-density data storage. The information, represented as indents, is written and erased using a heated tip. A high-performance polymer with a flexible aryletherketone backbone is designed with phenylethynyl crosslink chemistry. After optimization of crosslink density and topology, unprecedented performance is achieved in all relevant metrics. Demonstrations of endurance and retention are performed at 1 Tb in,2 density, showing 108 write cycles using the same tip, 103 erase cycles and 3,×,105 read cycles of the media, and extrapolated to 10 years of retention at 85,°C. [source] Exploiting Chemical Switching in a Diels,Alder Polymer for Nanoscale Probe Lithography and Data Storage,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006B. Gotsmann Abstract Reversibly crosslinked polymer films have properties that are beneficial to scanned-probe data storage and lithographic applications that use thermomechanical nanoindentation as a write or expose mechanism. The novel polymer under study contains linkages based on thermally reversible Diels,Alder crosslinking. Thermomechanical properties on the nanometer scale are analyzed by indentation experiments on polymer thin films using heated tips. The underlying indentation mechanism is studied at varying tip temperatures and indentation times, revealing Arrhenius kinetics. This is in contrast to the Williams,Landau,Ferry kinetics usually observed for polymer systems. The discrepancy is explained by the reversible crosslinking incorporated into the structure of the polymer that allows switching between two different states: a rigid, highly crosslinked, low-temperature state, and a deformable, fragmented, high-temperature state. An individual indentation volume of less than 10,20,L (10,000,molecule pairs) is estimated. These kinetics experiments demonstrate that a chemical reaction of only a few thousand molecules can be transduced into a mechanically measurable action. The ability to cycle between two sets of properties in these materials opens up new perspectives in lithography and data storage. Examples of data storage with densities up to 1,Tb,in.,2 and maskless lithography with resolution below 20,nm are demonstrated at writing times of 10,,s per bit/pixel. [source] Superior-Performance Polymeric Composite Materials for High-Density Optical Data Storage,ADVANCED MATERIALS, Issue 5 2009Riccardo Castagna High-resolution holographic gratings are obtained using a combination of a multifunctional acrylate (DPHP/HA), a low-molecular-weight glass-forming liquid epoxy-aromatic resin (TPMTGE), and a UV-photoinitiator (Irgacure 819). Their optical properties (sensitivity, transparency, and optical shrinkage) are promising for high-density optical data storage applications. [source] High-Performance, Nondiffusive Crosslinked Polymers for Holographic Data Storage,ADVANCED MATERIALS, Issue 20 2008Anzar Khan High-performance crosslinked polymeric materials for 3D data storage are described. Their performance is based on photoisomerization of Dewar benzene derivatives, and they exhibit remarkable information storage properties including excellent photosensitivity, high data-storage capacity, good dimensional stability, and significant shelf- and archival-lifetimes. [source] A Novel Thermally Stable Spironaphthoxazine and Its Application in Rewritable High Density Optical Data Storage,ADVANCED MATERIALS, Issue 2 2005W. Yuan A novel spironaphthoxazine SOFC molecule with a stable ring-opened photomerocyanine form by incorporating a ferrocene moiety to the parent spironaphthoxazine has been synthesized. Two-dimensional luminescence images obtained by confocal microscope employing fluorescence as read-out method (see Figure) and three-dimensional high-density recording using two-photon technology of SOFC-poly(methyl methacrylate) films are demonstrated. [source] Initialization Strategies in Simulation-Based SFE Eigenvalue AnalysisCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2005Song Du Poor initializations often result in slow convergence, and in certain instances may lead to an incorrect or irrelevant answer. The problem of selecting an appropriate starting vector becomes even more complicated when the structure involved is characterized by properties that are random in nature. Here, a good initialization for one sample could be poor for another sample. Thus, the proper eigenvector initialization for uncertainty analysis involving Monte Carlo simulations is essential for efficient random eigenvalue analysis. Most simulation procedures to date have been sequential in nature, that is, a random vector to describe the structural system is simulated, a FE analysis is conducted, the response quantities are identified by post-processing, and the process is repeated until the standard error in the response of interest is within desired limits. A different approach is to generate all the sample (random) structures prior to performing any FE analysis, sequentially rank order them according to some appropriate measure of distance between the realizations, and perform the FE analyses in similar rank order, using the results from the previous analysis as the initialization for the current analysis. The sample structures may also be ordered into a tree-type data structure, where each node represents a random sample, the traverse of the tree starts from the root of the tree until every node in the tree is visited exactly once. This approach differs from the sequential ordering approach in that it uses the solution of the "closest" node to initialize the iterative solver. The computational efficiencies that result from such orderings (at a modest expense of additional data storage) are demonstrated through a stability analysis of a system with closely spaced buckling loads and the modal analysis of a simply supported beam. [source] Photochromic Properties of Perhydro- and Perfluorodithienylcyclopentene Molecular SwitchesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2003Jaap J. D. de Jong Abstract Various substituted phenylthienyl perhydro- and perfluorocyclopentenes have been synthesized in order to compare their spectroscopic and photochromic properties. The difference in the electron densities of the central cyclopentene moieties in the perhydrocyclopentene and perfluorocyclopentene molecular switches has only a small effect on the absorption maxima of the electronic spectra, but causes some subtle changes in substituent and solvatochromic effects. The photochromic behaviour is remarkably similar, and both type of switches combine excellent quantum yields (0.6) with high degrees of photoconversion (> 0.85). The main difference is the lower photochemical and thermal stability of the perhydrocyclopentene molecular switches. It is concluded that in most studies the perhydrocyclopentenes are an excellent alternative for the perfluorocyclopentenes, while the perfluorocyclopentenes might be better suited for applications such as data storage, which depend critically on fatigue resistance and thermal stability. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Designing Polymers to Enable Nanoscale Thermomechanical Data StorageADVANCED FUNCTIONAL MATERIALS, Issue 8 2010B. Gotsmann Abstract Nanomechanics has been slow in entering nanotechnology because of extreme conditions resulting from scaling. This is an issue in particular for polymers, although widely used in macroscale applications. Highly repetitive nanoscale deformation cycling in combination with excellent shape retention and thermal stability is demonstrated. While generic principles described are pertinent to a range of applications, this demonstration is made on the example of polymer media in high-density data storage. The information, represented as indents, is written and erased using a heated tip. A high-performance polymer with a flexible aryletherketone backbone is designed with phenylethynyl crosslink chemistry. After optimization of crosslink density and topology, unprecedented performance is achieved in all relevant metrics. Demonstrations of endurance and retention are performed at 1 Tb in,2 density, showing 108 write cycles using the same tip, 103 erase cycles and 3,×,105 read cycles of the media, and extrapolated to 10 years of retention at 85,°C. [source] Improving the ON/OFF Ratio and Reversibility of Recording by Rational Structural Arrangement of Donor,Acceptor MoleculesADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Ying Ma Abstract Organic molecules with donor,acceptor (D,A) structure are an important type of material for nanoelectronics and molecular electronics. The influence of the electron donor and acceptor units on the electrical function of materials is a worthy topic for the development of high-performance data storage. In this work, the effect of different D,A structures (namely D,,,A,,,D and A,,,D,,,A) on the electronic switching properties of triphenylamine-based molecules is investigated. Devices based on D,,,A,,,D molecules exhibit excellent write,read,erase characteristics with a high ON/OFF ratio of up to 106, while that based on A,,,D,,,A molecules exhibit irreversible switching behavior with an ON/OFF ratio of about (3.2,×,101),(1,×,103). Moreover, long retention time of the high conductance state and low threshold voltage are observed for the D,A switching materials. Accordingly, stable and reliable nanoscale data storage is achieved on the thin films of the D,A molecules by scanning tunneling microscopy. The influence of the arrangement of the D and A within the molecular backbone disclosed in this study will be of significance for improving the electronic switching properties (ON/OFF current ratio and reversibility) of new molecular systems, so as to achieve more efficient data storage through appropriate design strategies. [source] Surface Plasmonics: Plasmonic Crystals: A Platform to Catalog Resonances from Ultraviolet to Near-Infrared Wavelengths in a Plasmonic Library (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Mater. Research in the field of surface plasmonics is finding application in many areas; for example, in data storage, nano-electronics, and biosensing. In their feature article on page 529, H. Gao et al. describe recent progress in manipulating surface plasmons from the ultraviolet to near-infrared wavelengths using nanostructured plasmonic crystals (shown in the cover image), and build a comprehensive library of plasmonic resonances, bringing together for the first time the resonance characteristics of key plasmonic materials. [source] Low-Distortion Holographic Data Storage Media Using Free-Radical Ring-Opening PolymerizationADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Kyongsik Choi Abstract Holographic data storage, due to its potential to increase capacity beyond one terabyte per disk, is tipped to be one of the next generation optical data storage technologies. Polymer-based systems are leading candidates due to their high dynamic range, high sensitivities, and flexible and easy production, and yet polymerization-shrinkage-induced distortion is a major hurdle for its reliable use. In this paper, a new free radical polymerization holographic recording medium, based on low shrink cyclic allylic sulfides (LS-CASs) ring-opening monomers, is proposed and demonstrated. The percentage of volume shrinkage is measured to be 0.02%, with refractive index (RI) contrast of (1.01,±,0.5),×,10,3. The measured volume shrinkage is, to the authors' best knowledge, the best reported so far in the literature. Other parameters such as sensitivity, dynamic range, and dark reaction properties are also measured, where the values can be optimized with high RI functional groups without sacrificing the low shrinkage. [source] High-Density Periodically Ordered Magnetic Cobalt Ferrite Nanodot Arrays by Template-Assisted Pulsed Laser DepositionADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Xingsen Gao Abstract A novel nanopatterning method using pulsed laser deposition through an ultrathin anodic aluminium oxide (AAO) membrane mask is proposed to synthesize well-ordered nanodot arrays of magnetic CoFe2O4 that feature a wide range of applications like sensors, drug delivery, and data storage. This technique allows the adjustment of the array dimension from ,35 to ,300,nm in diameter and ,65 to ,500,nm in inter-dot distance. The dot density can be as high as 0.21 Terabit in.,2. The microstructure of the nanodots is characterized by SEM, TEM, and XRD and their magnetic properties are confirmed by well-defined magnetic force microscopy contrasts and by hysteresis loops recorded by a superconducting quantum interference device. Moreover, the high stability of the AAO mask enables the epitaxial growth of nanodots at a temperature as high as 550,°C. The epitaxial dots demonstrate unique complex magnetic domains such as bubble and stripe domains, which are switchable by external magnetic fields. This patterning method creates opportunities for studying novel physics in oxide nanomagnets and may find applications in spintronic devices. [source] Low-Temperature-Grown Transition Metal Oxide Based Storage Materials and Oxide Transistors for High-Density Non-volatile MemoryADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Myoung-Jae Lee Abstract An effective stacked memory concept utilizing all-oxide-based device components for future high-density nonvolatile stacked structure data storage is developed. GaInZnO (GIZO) thin-film transistors, grown at room temperature, are integrated with one-diode (CuO/InZnO),one-resistor (NiO) (1D,1R) structure oxide storage node elements, fabricated at room temperature. The low growth temperatures and fabrication methods introduced in this paper allow the demonstration of a stackable memory array as well as integrated device characteristics. Benefits provided by low-temperature processes are demonstrated by fabrication of working devices over glass substrates. Here, the device characteristics of each individual component as well as the characteristics of a combined select transistor with a 1D,1R cell are reported. X-ray photoelectron spectroscopy analysis of a NiO resistance layer deposited by sputter and atomic layer deposition confirms the importance of metallic Ni content in NiO for bi-stable resistance switching. The GIZO transistor shows a field-effect mobility of 30,cm2,V,1,s,1, a Vth of +1.2,V, and a drain current on/off ratio of up to 108, while the CuO/InZnO heterojunction oxide diode has forward current densities of 2,×,104,A,cm,2. Both of these materials show the performance of state-of-the-art oxide devices. [source] Multifunctional Mesostructured Silica Microspheres from an Ultrasonic Aerosol Spray,ADVANCED FUNCTIONAL MATERIALS, Issue 19 2008Li Li Abstract Multifunctional mesostructured silica microspheres are prepared using ultrasonic aerosol spray in conjunction with solvent evaporation-induced assembly. Rare earth ion,phenanthroline complexes, magnetite particles, photoacid generators, and pH-sensitive dyes are chosen as luminescent, magnetic, and photosensitive components. The incorporation of these functional components into mesostructured silica microspheres can be readily realized by dispersing them in the precursor solution of the aerosol spray process. Luminescent microspheres that can emit at multiple wavelengths when excited at a single wavelength are produced by the addition of multiple rare earth complexes into the precursor solution. The addition of magnetite particles leads to the production of magnetic luminescent microspheres. Photoacid generators and pH-sensitive dyes are further employed to produce magnetic photosensitive microspheres that can release acid and change color upon UV light illumination. Such multifunctional microspheres could have exciting potential for many optical and biotechnological applications, such as multiplexed labeling, diagnosis, simultaneous imaging and therapy, cell capture and separation, targeted delivery, and optical data storage. [source] Exploiting Chemical Switching in a Diels,Alder Polymer for Nanoscale Probe Lithography and Data Storage,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2006B. Gotsmann Abstract Reversibly crosslinked polymer films have properties that are beneficial to scanned-probe data storage and lithographic applications that use thermomechanical nanoindentation as a write or expose mechanism. The novel polymer under study contains linkages based on thermally reversible Diels,Alder crosslinking. Thermomechanical properties on the nanometer scale are analyzed by indentation experiments on polymer thin films using heated tips. The underlying indentation mechanism is studied at varying tip temperatures and indentation times, revealing Arrhenius kinetics. This is in contrast to the Williams,Landau,Ferry kinetics usually observed for polymer systems. The discrepancy is explained by the reversible crosslinking incorporated into the structure of the polymer that allows switching between two different states: a rigid, highly crosslinked, low-temperature state, and a deformable, fragmented, high-temperature state. An individual indentation volume of less than 10,20,L (10,000,molecule pairs) is estimated. These kinetics experiments demonstrate that a chemical reaction of only a few thousand molecules can be transduced into a mechanically measurable action. The ability to cycle between two sets of properties in these materials opens up new perspectives in lithography and data storage. Examples of data storage with densities up to 1,Tb,in.,2 and maskless lithography with resolution below 20,nm are demonstrated at writing times of 10,,s per bit/pixel. [source] Magnonics: Spin Waves on the NanoscaleADVANCED MATERIALS, Issue 28 2009Sebastian Neusser Abstract Magnetic nanostructures have long been in the focus of intense research in the magnetic storage industry. For data storage the nonvolatility of magnetic states is of utmost relevance. As information technology generates the need for higher and higher data-transfer rates, research efforts have moved to understand magnetization dynamics. Here, spin waves and their particle-like analog, magnons, are increasingly attracting interest. High-quality nanopatterned magnetic media now offer new ways to transmit and process information without moving electrical charges. This new functionality is enabled by spin waves. They are confined by novel functioning principles, which render them especially suitable to operate at the nanoscale. Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light. Combined with nonvolatility, multifunctional metamaterials might be formed. We report recent advances in this rapidly increasing research field called magnonics. [source] High-Performance, Nondiffusive Crosslinked Polymers for Holographic Data Storage,ADVANCED MATERIALS, Issue 20 2008Anzar Khan High-performance crosslinked polymeric materials for 3D data storage are described. Their performance is based on photoisomerization of Dewar benzene derivatives, and they exhibit remarkable information storage properties including excellent photosensitivity, high data-storage capacity, good dimensional stability, and significant shelf- and archival-lifetimes. [source] How to run an effective journal club: a systematic reviewJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 5 2008Y. Deenadayalan BPT IMMP BEHM (MBA) Abstract Background, Health-based journal clubs have been in place for over 100 years. Participants meet regularly to critique research articles, to improve their understanding of research design, statistics and critical appraisal. However, there is no standard process of conducting an effective journal club. We conducted a systematic literature review to identify core processes of a successful health journal club. Method, We searched a range of library databases using established keywords. All research designs were initially considered to establish the body of evidence. Experimental or comparative papers were then critically appraised for methodological quality and information was extracted on effective journal club processes. Results, We identified 101 articles, of which 21 comprised the body of evidence. Of these, 12 described journal club effectiveness. Methodological quality was moderate. The papers described many processes of effective journal clubs. Over 80% papers reported that journal club intervention was effective in improving knowledge and critical appraisal skills. Few papers reported on the psychometric properties of their outcome instruments. No paper reported on the translation of evidence from journal club into clinical practice. Conclusion, Characteristics of successful journal clubs included regular and anticipated meetings, mandatory attendance, clear long- and short-term purpose, appropriate meeting timing and incentives, a trained journal club leader to choose papers and lead discussion, circulating papers prior to the meeting, using the internet for wider dissemination and data storage, using established critical appraisal processes and summarizing journal club findings. [source] UV-photodimerization in uracil-substituted dendrimers for high density data storageJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2007Brian Lohse Abstract Two series of uracil-functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2-bis(hydroxymethylpropionic acid) bis-MPA backbones were prepared and their photoinduced (2,+2,) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th generation were synthesized and investigated as potential materials for high capacity optical data storage with their dimerization efficiency compared to uracil as a reference compound. This allows the impact of increasing the generation number of the dendrimers, both the number of chromophores, as well as the different steric environments, on the performance of each series of dendrimers to be investigated. The (uracil)12 -[G-2]-bis-MPA and (uracil)8 -[G-1]-PAMAM were observed to have high dimerization efficiency in solution with different behavior being observed for the PAMAM and bis-MPA dendrimers. The dendrimers with the best dimerization efficiency in solution were then examined in the solid state as thin films cast on quartz plates, and their film qualities along with their photodimerization performance studied. High quality films with a transmission response of up to 70% in 55 s. when irradiated at 257 nm with an intensity of 70 mW/cm2 could be obtained suggesting future use as recording media for optical data storage. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4401,4412, 2007 [source] Oil-immersion or solid-immersion power enhancement of very-small-aperture lasersLASER PHYSICS LETTERS, Issue 6 2006Q. Gan Abstract An analysis of the enhancement of light transmission through a sub-wavelength aperture by oil- or solid-immersion is presented in this letter. An output power enhancement phenomenon related to the oil-immersion or solid-immersion mechanism is realized experimentally and reported for a very-smallaperture laser, which is in agreement with simulation analysis. This phenomenon could be useful for future optical data storage, microscopy and lithography. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Synthesis and Photoresponsive Properties of Optically Active Methacrylic Polymers Bearing Side-Chain Azocarbazole MoietiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2009Luigi Angiolini Abstract The synthesis of a novel optically active methacrylic monomer containing in the side chain the (S)-3-hydroxy- N -phenyl pyrrolidine ring linked to a 4-cyanophenylazocarbazole moiety [(S)- MCAPP - C] and of the analogous achiral monomer (MCAPE-C) is described. Both the monomers have been radically polymerized to produce the corresponding homopolymers as well as the copolymer at 50% molar composition. The photoinduction of birefringence has been assessed on thin films of the polymeric materials in order to evaluate their behavior as materials for optical data storage. Surface relief gratings (SRG) can also be inscribed over the material. The results are interpreted in terms of different cooperative performance and conformational stiffness of the chromophoric co-units in the polymeric derivatives. [source] Numerical simulation of particle trajectory and atmospheric dispersion of airborne releasesMETEOROLOGICAL APPLICATIONS, Issue 3 2009S. Shoaib Raza Abstract Numerical simulation of particle trajectory and atmospheric dispersion has been performed for an airborne accidental release from a nuclear power plant site. A Long-range Particle transport and Dispersion Model (LPDM) based on a Lagrangian approach is developed and tested in this work. The Lagrangian transport/dispersion model is directly coupled with an atmospheric prediction model, RAMS (Regional Atmospheric Modeling System), to provide necessary meteorological fields in a three-dimensional domain. An advantage of this direct coupling is that the meteorological data generated by RAMS can be used directly for trajectory calculations without storage, thus reducing the CPU time consumed in the data storage and retrieval. This effort was done to be able to use this directly coupled modelling system for real-time predictions in case of an accidental release from a potential site. The simulated Lagrangian trajectories were compared with those obtained using observed hourly weather data obtained from an on-site meteorological tower. The results indicated that this one-way coupling between LPDM-RAMS provided almost identical trajectories when compared with those obtained using LPDM alone driven by hourly observed wind data. The comparison demonstrated the reliability of the RAMS meteorological predictions for the site under consideration. The comparison also indicated that LPDM (run in a stand alone mode), with hourly-observed wind data, could also be used for trajectory calculations over flat terrain. The model was developed on a parallel processing computer (SGI workstation, ORIGIN 2000 computer with eight processors) for use in real-time forecast mode. The computational time was about one-third of the simulation time, while using four processors. The model options need to be explored to reduce the computational time further and test its performance for real-time atmospheric dispersion applications. Copyright © 2009 Royal Meteorological Society [source] Magnetoimpedance (MI) in amorphous wires: new materials and applicationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009Larissa V. Panina Abstract The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for applications in smart sensory systems (self-sensing composites) operating at microwave frequencies owing to still very large MI ratios of 50,100% in Co-rich amorphous wires at GHz frequencies. Here we introduce two types of MI wire composites: 2D-arrays and mixtures of wire pieces. In such materials the effective permittivity has strong dispersion in a frequency band determined by a plasma frequency or a dipole resonance, respectively. If MI wires are used as constituent elements, this dispersion may be very sensitive to the magnetic properties of wires since the wire impedance determines the relaxation parameter of the effective permittivity. For example, increasing the wire impedance by establishing the magnetisation along the axis with an external magnetic field broadens the resonance band, decreases the reflection amplitude and may open a bandpass. Depending on the magnetic anisotropy in wires, tuning can be realized with both magnetic field and stress. It is foreseen that MI-wire composite materials could be suitable for large scale applications, in particular, for free space filters in secure wireless systems and for microwave nondestructive testing and control in civil engineering. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of solvent, film thickness, and hydrogen bonding on surface-relief gratingsPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Woo-Hyuk Jung This work focuses on the development of a new type of surface-relief grating (SRG) using more effective materials than a typical epoxy-based azopolymer for the recording layer of optical data storage. Thus, aniline-based azopolymers were synthesized by reaction of N,N -diglycidylaniline with aniline (An) followed by diazocoupling with 4-aminobenzonitrile or 4-nitroaniline. Such azopolymers when spin-cast from THF/dioxane showed better diffraction efficiency than those cast from THF alone due to residual dioxane creating a large free volume in the solid state. A second diazocoupling reaction of the diazopolymers initially obtained produced polymers with bis(diazobenzene) substituents which exhibited a higher saturation level of the diffraction efficiency for a thicker than for a thinner film. Azopolymers in which the diazo substituents incorporated hydroxyl groups ortho to the diazo unit were obtained via the reaction of the diglycidyl ether of bisphenol-A with aniline or 3-hydroxyaniline followed by coupling with diazotised hydroxynitroaminobenzene. These hydroxy groups, presumably as a result of their H-bonding to the diazo-N, effectively prevented the photoisomerization of the chromophores, so that the polymers showed no SRG at a normal laser intensity of 100 mW/cm2. Polyurethane-based azopolymers, synthesized with toluene-2,4-diisocyanate and disperse orange 17 containing no hydroxyl groups in the main chains, showed better diffraction efficiency than the other azopolymers with nitro group substituents. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] ,So that we might have roses in December': The functions of autobiographical memoryAPPLIED COGNITIVE PSYCHOLOGY, Issue 8 2009John F. Kihlstrom Autobiographical memory is not merely declarative and episodic in nature. It also entails explicit self-reference, chronological organization and causal relations. It entails conscious recollection, in terms of remembering, knowing, feeling or believing. Its functions may be agentic or nonagentic, but all are assigned, not intrinsic, and thus are observer-relative features of reality. Questions about function risk committing the adaptationist fallacy. Intrapersonally, autobiographical memory is a critical component in the mental representation of self. Interpersonally, autobiographical memory provides a basis for establishing and maintaining social relationships. Autobiographical memory is an individual right, and it may also be an ethical obligation. The popularity of memoir as a literary genre indicates that it is also a means of making money. In a future world of artificial minds with infinite capacity for data storage, there still will be no substitute for the human capacity to remember what really matters and forget what does not. Copyright © 2009 John Wiley & Sons, Ltd. [source] Life, information, entropy, and time: Vehicles for semantic inheritanceCOMPLEXITY, Issue 1 2007Antony R. Crofts Abstract Attempts to understand how information content can be included in an accounting of the energy flux of the biosphere have led to the conclusion that, in information transmission, one component, the semantic content, or "the meaning of the message," adds no thermodynamic burden over and above costs arising from coding, transmission and translation. In biology, semantic content has two major roles. For all life forms, the message of the genotype encoded in DNA specifies the phenotype, and hence the organism that is tested against the real world through the mechanisms of Darwinian evolution. For human beings, communication through language and similar abstractions provides an additional supra-phenotypic vehicle for semantic inheritance, which supports the cultural heritages around which civilizations revolve. The following three postulates provide the basis for discussion of a number of themes that demonstrate some important consequences. (i) Information transmission through either pathway has thermodynamic components associated with data storage and transmission. (ii) The semantic content adds no additional thermodynamic cost. (iii) For all semantic exchange, meaning is accessible only through translation and interpretation, and has a value only in context. (1) For both pathways of semantic inheritance, translational and copying machineries are imperfect. As a consequence both pathways are subject to mutation and to evolutionary pressure by selection. Recognition of semantic content as a common component allows an understanding of the relationship between genes and memes, and a reformulation of Universal Darwinism. (2) The emergent properties of life are dependent on a processing of semantic content. The translational steps allow amplification in complexity through combinatorial possibilities in space and time. Amplification depends on the increased potential for complexity opened by 3D interaction specificity of proteins, and on the selection of useful variants by evolution. The initial interpretational steps include protein synthesis, molecular recognition, and catalytic potential that facilitate structural and functional roles. Combinatorial possibilities are extended through interactions of increasing complexity in the temporal dimension. (3) All living things show a behavior that indicates awareness of time, or chronognosis. The ,4 billion years of biological evolution have given rise to forms with increasing sophistication in sensory adaptation. This has been linked to the development of an increasing chronognostic range, and an associated increase in combinatorial complexity. (4) Development of a modern human phenotype and the ability to communicate through language, led to the development of archival storage, and invention of the basic skills, institutions and mechanisms that allowed the evolution of modern civilizations. Combinatorial amplification at the supra-phenotypical level arose from the invention of syntax, grammar, numbers, and the subsequent developments of abstraction in writing, algorithms, etc. The translational machineries of the human mind, the "mutation" of ideas therein, and the "conversations" of our social intercourse, have allowed a limited set of symbolic descriptors to evolve into an exponentially expanding semantic heritage. (5) The three postulates above open interesting epistemological questions. An understanding of topics such dualism, the élan vital, the status of hypothesis in science, memetics, the nature of consciousness, the role of semantic processing in the survival of societies, and Popper's three worlds, require recognition of an insubstantial component. By recognizing a necessary linkage between semantic content and a physical machinery, we can bring these perennial problems into the framework of a realistic philosophy. It is suggested, following Popper, that the ,4 billion years of evolution of the biosphere represents an exploration of the nature of reality at the physicochemical level, which, together with the conscious extension of this exploration through science and culture, provides a firm epistemological underpinning for such a philosophy. © 2007 Wiley Periodicals, Inc. Complexity, 2007 [source] | ||||||||||||||||||||||||||||