Near-UV photodissociation dynamics of CH2I2

The near-UV photodissociation dynamics of CH2I2 has been investigated using a combination of velocitymap (slice) ion imaging and ab initio calculations characterizing the excited states. Ground state I(2 P3/2) and spin-orbit excited I*(2 P1/2) atoms were probed using 2+1 resonance-enhanced multiphoton ionization (REMPI) or with single-photon VUV ionization. Two-color ion images were recorded at pump wavelengths of 355 nm, 266 nm and 248 nm, and one-color ion images at the REMPI wavelengths of ~304 nm and ~280 nm. Analysis of the ion images shows that, regardless of iodine spin-orbit state, ~20% of the available energy is partitioned into translation ET at all excitation wavelengths indicating that the CH2I co-fragment is formed highly internally excited. The translational energy distributions comprise a slow, “statistical” component that peaks near zero and faster components that peak away from zero. The slow component makes an increasingly large contribution to the distribution as the excitation wavelength is decreased. The C–I bond dissociation energy of D0 = 2.155±0.008 eV is obtained from the trend in the ET release of the faster components with increasing excitation energy. The I and I* ion images are anisotropic, indicating prompt dissociation, and are characterized by β parameters that become increasingly positive with increasing ET. The decrease in β at lower translational energies can be attributed to deviation from axial recoil. MRCI calculations including spin-orbit coupling have been performed to identify the overlapping features in the absorption spectrum and characterize onedimensional cuts through the electronically excited potential energy surfaces. The excited states are of significantly mixed singlet and triplet character. At longer wavelengths, excitation directly accesses repulsive states primarily of B1 symmetry, consistent with the observed !β∀, while shorter wavelengths accesses bound states, also of B1 symmetry that are crossed by repulsive states

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement.

An enantioselective aza-Piancatelli rearrangement has been developed using a chiral Brønsted acid based on pentacarboxycyclopentadiene (PCCP). This reaction provides rapid access to valuable chiral 4-amino-2-cyclopentenone building blocks from readily available starting material and is operationally simple

Embodied uncertainty: living with complexity and natural hazards

In this paper, we examine the concept of embodied uncertainty by exploring multiple dimensions of uncertainty in the context of risks associated with extreme natural hazards. We highlight a need for greater recognition, particularly by disaster management and response agencies, of uncertainty as a subjective experience for those living at risk. Embodied uncertainty is distinguished from objective uncertainty by the nature of its internalisation at the individual level, where it is subjective, felt and directly experienced. This approach provides a conceptual pathway that sharpens knowledge of the processes that shape how individuals and communities interpret and contextualise risk. The ways in which individual characteristics, social identities and lived experiences shape interpretations of risk are explored by considering embodied uncertainty in four contexts: social identities and trauma, the co-production of knowledge, institutional structures and policy and long-term lived experiences. We conclude by outlining the opportunities that this approach presents, and provide recommendations for further research on how the concept of embodied uncertainty can aid decision-making and the management of risks in the context of extreme natural hazards

Reversible Actuation via Photoisomerization-Induced Melting of a Semicrystalline Poly(Azobenzene)

Photoisomerization of azobenzene in polymer matrices is a powerful method to convert photon energy into mechanical work. While most previous studies have focused on incorporating azobenzene within amorphous or liquid crystalline materials, the limited extents of molecular ordering and correspondingly modest enthalpy changes upon switching in such systems has limited the achievable energy densities. In this work, we introduce a semicrystalline main-chain poly(azobenzene), where photoisomerization is capable of reversibly triggering melting and recrystallization under essentially isothermal conditions. These materials can be drawn into aligned fibers, yielding optically driven two-way shape memory actuators capable of reversible bending

Multiaddressable Photochromic Architectures: From Molecules to Materials

Multiaddressable architectures comprising light‐responsive photochromic molecules and different stimuli‐responsive components are appealing platforms for intelligent materials because of not only the potential diversity of components and corresponding properties, but also the functions resulting from their synergistic interactions. A variety of multiaddressable photochromic architectures are being designed to meet the demands of applications in different areas ranging from molecular machines to smart materials. This review highlights exciting recent advances in the field of multiaddressable systems that employ photoswitching molecules, specifically with regard to photo‐/chemical‐addressable, photo‐/pH‐addressable, photo‐/thermal‐addressable, photo‐/redox‐addressable, and multi‐photoaddressable architectures. Design concepts, crosstalk between different components, and photoswitch integration in these multiaddressable systems are discussed

Evitando la exploración de puertos a través de DEP: un sistema dedicado

La seguridad en redes es un tópico que ha captado la atención en la mayoría de las investigaciones y desarrollos relacionados a redes. Tener redes seguras significa definir políticas de seguridad y tener herramientas capaces de detectar y prevenir distintos ataques. Existen numerosos puntos a considerar a la hora de hacer una red segura. Uno de ellos son las vulnerabilidades provistas por el software. Las vulnerabilidades son la puerta de acceso para los distintos ataques. El sistema operativo LINUX, la familia de protocolos de comunicación TCP/IP y el software de aplicación poseen varias. Los puntos de ataque de TCP/IP son producto de sus características jerárquicas y la amplia familia de protocolos. Si bien existen muchos ataques, la exploración de puertos es uno de los más comunes. La presente propuesta tiene como objetivo mostrar una herramienta: Sistema para la Detección de Exploración de Puertos(DEP), la cual permite detectar actividades de exploración ´on de puertos en la computadora local y evitar el acceso de extraños, no sólo en el momento sino también en el futuro.VI Workshop de Procesamiento Distribuido y Paralelo (WPDP)Red de Universidades con Carreras en Informática (RedUNCI

Evitando la exploración de puertos a través de DEP: un sistema dedicado

La seguridad en redes es un tópico que ha captado la atención en la mayoría de las investigaciones y desarrollos relacionados a redes. Tener redes seguras significa definir políticas de seguridad y tener herramientas capaces de detectar y prevenir distintos ataques. Existen numerosos puntos a considerar a la hora de hacer una red segura. Uno de ellos son las vulnerabilidades provistas por el software. Las vulnerabilidades son la puerta de acceso para los distintos ataques. El sistema operativo LINUX, la familia de protocolos de comunicación TCP/IP y el software de aplicación poseen varias. Los puntos de ataque de TCP/IP son producto de sus características jerárquicas y la amplia familia de protocolos. Si bien existen muchos ataques, la exploración de puertos es uno de los más comunes. La presente propuesta tiene como objetivo mostrar una herramienta: Sistema para la Detección de Exploración de Puertos(DEP), la cual permite detectar actividades de exploración ´on de puertos en la computadora local y evitar el acceso de extraños, no sólo en el momento sino también en el futuro.VI Workshop de Procesamiento Distribuido y Paralelo (WPDP)Red de Universidades con Carreras en Informática (RedUNCI

Building Squares with Optimal State Complexity in Restricted Active Self-Assembly

Tile Automata is a recently defined model of self-assembly that borrows many concepts from cellular automata to create active self-assembling systems where changes may be occurring within an assembly without requiring attachment. This model has been shown to be powerful, but many fundamental questions have yet to be explored. Here, we study the state complexity of assembling n × n squares in seeded Tile Automata systems where growth starts from a seed and tiles may attach one at a time, similar to the abstract Tile Assembly Model. We provide optimal bounds for three classes of seeded Tile Automata systems (all without detachment), which vary in the amount of complexity allowed in the transition rules. We show that, in general, seeded Tile Automata systems require Θ(log^{1/4} n) states. For Single-Transition systems, where only one state may change in a transition rule, we show a bound of Θ(log^{1/3} n), and for deterministic systems, where each pair of states may only have one associated transition rule, a bound of Θ(({log n}/{log log n})^{1/2})