Proton-Stabilized Photochemically Reversible E/Z Isomerization of Spiropyrans

Spiropyrans undergo C-spiro-O bond breaking to their ring-open protonated E-merocyanine form upon protonation and irradiation via an intermediate protonated Z-merocyanine isomer. We show that the extent of acid-induced ring opening is controlled by matching both the concentration and strength of the acid used and with strong acids full ring opening to the Z-merocyanine isomer occurs spontaneously allowing its characterization by H-1 NMR spectroscopy as well as UV/vis spectroscopy, and reversible switching between Z/E-isomerization by irradiation with UV and visible light. Under sufficiently acidic conditions, both E- and Z-isomers are thermally stable. Judicious choice of acid such that its pK(a) lies between that of the E- and Z-merocyanine forms enables thermally stable switching between spiropyran and E-merocyanine forms and hence pH gating between thermally irreversible and reversible photochromic switching

Marcapasso de Dupla-Câmara e Desfibrilador Mono-Câmara

A convivência entre marcapassos e desfibriladores está em vias de desaparecimento, mas ainda se impoe em alguns casos particulares. Este trabalho faz o balanço entre as compatibilidades e as incompatibilidades dos modelos recentes. O presente relato de caso refere-se a um paciente no qual o desfibrilador foi escolhido e posicionado atrás do grande peitoral esquerdo, de modo a separá-lo de um marcapasso de dupla-câmara implantado anteriormente. A programaçao de ambos, que eram da mesma marca, pôde ser efetuada pelo mesmo programador, mediante subterfúgios. Nenhuma interferência sobreveio entre os dois aparelhos, sendo necessário apenas corrigir algumas incompatibilidades na programaçao do marcapasso, passíveis de comprometer o funcionamento do desfibrilador

Onecut-dependent Nkx6.2 transcription factor expression is required for proper formation and activity of spinal locomotor circuits.

In the developing spinal cord, Onecut transcription factors control the diversification of motor neurons into distinct neuronal subsets by ensuring the maintenance of Isl1 expression during differentiation. However, other genes downstream of the Onecut proteins and involved in motor neuron diversification have remained unidentified. In the present study, we generated conditional mutant embryos carrying specific inactivation of Onecut genes in the developing motor neurons, performed RNA-sequencing to identify factors downstream of Onecut proteins in this neuron population, and employed additional transgenic mouse models to assess the role of one specific Onecut-downstream target, the transcription factor Nkx6.2. Nkx6.2 expression was up-regulated in Onecut-deficient motor neurons, but strongly downregulated in Onecut-deficient V2a interneurons, indicating an opposite regulation of Nkx6.2 by Onecut factors in distinct spinal neuron populations. Nkx6.2-null embryos, neonates and adult mice exhibited alterations of locomotor pattern and spinal locomotor network activity, likely resulting from defective survival of a subset of limb-innervating motor neurons and abnormal migration of V2a interneurons. Taken together, our results indicate that Nkx6.2 regulates the development of spinal neuronal populations and the formation of the spinal locomotor circuits downstream of the Onecut transcription factors

Marcapasso de Dupla-Câmara e Desfibrilador Mono-Câmara

A convivência entre marcapassos e desfibriladores está em vias de desaparecimento, mas ainda se impoe em alguns casos particulares. Este trabalho faz o balanço entre as compatibilidades e as incompatibilidades dos modelos recentes. O presente relato de caso refere-se a um paciente no qual o desfibrilador foi escolhido e posicionado atrás do grande peitoral esquerdo, de modo a separá-lo de um marcapasso de dupla-câmara implantado anteriormente. A programaçao de ambos, que eram da mesma marca, pôde ser efetuada pelo mesmo programador, mediante subterfúgios. Nenhuma interferência sobreveio entre os dois aparelhos, sendo necessário apenas corrigir algumas incompatibilidades na programaçao do marcapasso, passíveis de comprometer o funcionamento do desfibrilador

N,N′-Disubstituted Indigos as Readily Available Red-Light Photoswitches with Tunable Thermal Half-Lives

Some rare indigo derivatives have been known for a long time to be photochromic upon irradiation with red light, which should be advantageous for many applications. However, the absence of strategies to tune their thermal half-lives by modular molecular design as well as the lack of proper synthetic methods to prepare a variety of such molecules from the parent indigo dye have so far precluded their use. In this work, several synthetic protocols for N-functionalization have been developed, and a variety of N-alkyl and N-aryl indigo derivatives have been prepared. By installation of electron-withdrawing substituents on the N-aryl moieties, the thermal stability of the Z-isomers could be enhanced while maintaining the advantageous photoswitching properties upon irradiation with red light (660 nm LED). Both experimental data and computational results suggest that the ability to tune thermal stability without affecting the dyes' absorption maxima originates from the twisted geometry of the N-aryl groups. The new indigo photoswitches reported are expected to have a large impact on the development of optical methods and applications in both life and material sciences

Charge transfer from the carotenoid can quench chlorophyll excitation in antenna complexes of plants

The photosynthetic apparatus of higher plants can dissipate excess excitation energy during high light exposure, by deactivating excited chlorophylls through a mechanism called nonphotochemical quenching (NPQ). However, the precise molecular details of quenching and the mechanism regulating the quenching level are still not completely understood. Focusing on the major light-harvesting complex LHCII of Photosystem II, we show that a charge transfer state involving Lutein can efficiently quench chlorophyll excitation, and reduce the excitation lifetime of LHCII to the levels measured in the deeply quenched LHCII aggregates. Through a combination of molecular dynamics simulations, multiscale quantum chemical calculations, and kinetic modeling, we demonstrate that the quenching level can be finely tuned by the protein, by regulating the energy of the charge transfer state. Our results suggest that a limited conformational rearrangement of the protein scaffold could act as a molecular switch to activate or deactivate the quenching mechanism.FWN – Publicaties zonder aanstelling Universiteit Leide

Communication efficient multi-processor FFT

Computing the Fast Fourier Transform on a distributed memory architecture by a direct pipelined radix-2 algorithm, a bi-section or multi-section algorithm, all yield the same communications requirement, if communication for all FFT stages can be performed concurrently, the input data is in normal order, and the data allocation consecutive. With a cyclic data allocation, or bit-reversed input data and a consecutive allocation, multi-sectioning offers a reduced communications requirement by approximately a factor of two. For a consecutive data allocation, normal input order, a decimation-in-time FFT requires that (P/N) + d - 2 twiddle factors be stored for P elements distributed evenly over N processors, and the axis subject to transformation distributed over 2d processors. No communication of twiddle factors is required. The same storage requirements hold for a decimation-in-frequency FFT, bit-reversed input order, and consecutive data allocation. The opposite combination of FFT type and data ordering requires a factor of log2 N more storage for N processors. The peak performance for a Connection Machine system CM-200 implementation is 12.9 Gflops/s in 32-bit precision, and 10.7 Gflops/s in 64-bit precision for unordered transforms local to each processor. The corresponding execution rates for ordered transforms are 11.1 Gflops/s and 8.5 Gflops/s, respectively. For distributed one- and two-dimensional transforms the peak performance for unordered transforms exceeds 5 Gflops/s in 32-bit precision, and 3 Gflops/s in 64-bit precision. Three-dimensional transforms executes at a slightly lower rate. Distributed ordered transforms executes at a rate of about 1/2 to 2/3 of the unordered transforms.Engineering and Applied Science

Making Sense of Family Deaths in Urban Senegal: Diversities, Contexts, and Comparisons

Despite calls for cross-cultural research, Minority world perspectives still dominate death and bereavement studies, emphasizing individualized emotions and neglecting contextual diversities. In research concerned with contemporary African societies, on the other hand, death and loss are generally subsumed within concerns about AIDS or poverty, with little attention paid to the emotional and personal significance of a death. Here, we draw on interactionist sociology to present major themes from a qualitative study of family deaths in urban Senegal, theoretically framed through the duality of meanings-in-context. Such themes included family and community as support and motivation; religious beliefs and practices as frameworks for solace and (regulatory) meaning; and material circumstances as these are intrinsically bound up with emotions. Although we identify the experience of (embodied, emotional) pain as a common response across Minority and Majority worlds, we also explore significant divergencies, varying according to localized contexts and broader power dynamics