Tuning of the blue emission from europium-doped alkaline earth chloroborate thin films activated in air

Thin films of M[SUB2]B[SUB5]O[SUB9]Cl:Eu (M = Ca, Sr, Ba) were prepared on glass substrates using spray pyrolysis. Blue cathodoluminescence due to the abnormal reduction of Eu[SUB3+] → Eu[SUB2+] was obtained by annealing films in air. The cation of the host lattice was found to affect the effectiveness of the reduction process, which could result in influencing the emission band. By selecting types and composition of alkaline cation, it was possible to tune the dominant emitting wavelength between 435 to 465 nm. Activation of the films occurred at temperatures suitable for the use of glass substrates. © 2003 American Institute of Physics.published_or_final_versio

Green, blue, and yellow cathodoluminescence of Ba[sub 2]B[sub 5]O[sub 9]Cl thin-films doped with Tb[sup 3+], Tm[sup 3+], and Mn[sup 2+]

Green, blue, and yellow cathodoluminescence (CL) have been obtained for thin-films of Ba[sub 2]B[sub 5]O[sub 9]C1 doped with Tb[sup 3+], Tm[sup 3+], and Mn[sup 2+], respectively. These phosphor films were deposited by spray pyrolysis, and then activated in air at temperatures suitable for use on glass substrates. The CL characteristic peaks of the films correspond to transitions between electronic energy levels of Tm[sup 3+], Tb[sup 3+], and Mn[sup 2+] ions. The chromaticity coordinates, dominant wavelength, and color purity were determined for each phosphor. Saturation effects were observed as the beam current density increased. The more severe current saturation of Mn-doped film may be due to a greater ground state deplection of Mn luminescent centers than that of the Tb and Tm. © 2003 American Institute of Physics.published_or_final_versio

In situ growth of blue-emitting thin films of cerium-doped barium chloride hydrate at low temperatures

Blue emission was observed from thin films of barium chloride hydrate doped with cerium. The films were deposited by spray pyrolysis of aqueous solutions with substrate temperatures between 250 and 450°C. The cathodoluminescence (CL) spectrum consists of two peaks at 443 and 485 nm due to 4f-5d transitions of cerium ion. The dependence of the emission band on deposition temperature and Ce/Ba ratio is discussed. The CL luminance and luminous efficiency at 5 kV were 120 cd/m² and 0.48 lm/W, respectively, for the films deposited at temperatures as low as 250°C. The results indicate barium chloride hydrate doped with cerium is a blue phosphor that exhibits relatively efficient luminescence after processing at low temperatures. © 2003 American Institute of Physics.published_or_final_versio

Observation of the solid-state photo-CIDNP effect in entire cells of cyanobacteria Synechocystis

Cyanobacteria are widely used as model organism of oxygenic photosynthesis due to being the simplest photosynthetic organisms containing both photosystem I and II (PSI and PSII). Photochemically induced dynamic nuclear polarization (photo-CIDNP) 13C magic-angle spinning (MAS) NMR is a powerful tool in understanding the photosynthesis machinery down to atomic level. Combined with selective isotope enrichment this technique has now opened the door to study primary charge separation in whole living cells. Here, we present the first photo-CIDNP observed in whole cells of the cyanobacterium Synechocystis

The solid-state photo-CIDNP effect

The solid-state photo-CIDNP effect is the occurrence of a non-Boltzmann nuclear spin polarization in rigid samples upon illumination. For solid-state NMR, which can detect this enhanced nuclear polarization as a strong modification of signal intensity, the effect allows for new classes of experiments. Currently, the photo- and spin-chemical machinery of various RCs is studied by photo-CIDNP MAS NMR in detail. Until now, the effect has only been observed at high magnetic fields with 13C and 15N MAS NMR and in natural photosynthetic RC preparations in which blocking of the acceptor leads to cyclic electron transfer. In terms of irreversible thermodynamics, the high-order spin structure of the initial radical pair can be considered as a transient order phenomenon emerging under non-equilibrium conditions and as a first manifestation of order in the photosynthetic process. The solid-state photo-CIDNP effect appears to be an intrinsic property of natural RCs. The conditions of its occurrence seem to be conserved in evolution. The effect may be based on the same fundamental principles as the highly optimized electron transfer. Hence, the effect may allow for guiding artificial photosynthesis

Old wine in new bottles: Exploring pragmatism as a philosophical framework for the discipline of coaching

The practice and industry of organizational coaching are now well established, but how it is understood theoretically continues to lag behind. In this paper we analyze possible reasons for this state of affairs and argue that the development of coaching as an academic discipline will benefit from adopting philosophical pragmatism as an overarching theoretical framework. This move will enable coaching academics to utilize the contributions to knowledge that different paradigms generate. Positioning pragmatism as a theory of action we argue that organizational coaching is by default a pragmatic enterprise and provide three examples of the considerable benefits to be gained by conceptualizing it this way. (1) Drawing from the pragmatists’ ideas, particularly those of John Dewey, we demonstrate how the theoretical understanding of organizational coaching can be enhanced by considering its nature as a joint inquiry. (2) Pragmatism suggests development as an ultimate purpose for organizational coaching which also helps to resolve fundamental conceptual debates. (3) In light of the complexity and diversity involved in the way that organizational coaching is practiced, pragmatism offers coaches a useful framework for developing the flexibility required for navigating the multiplicity of influences on their practice