460 research outputs found
Energy relaxation and triplet formation
We combined femtosecond (fs) VIS pump–IR probe spectroscopy with fs VIS
pump–supercontinuum probe spectroscopy to characterize the photoreaction of
the hexacoordinated Al(tpfc-Br8)(py)2 in a comprehensive way. Upon fs
excitation at ∼400 nm in the Soret band, the excitation energy relaxes with a
time constant of (250 ± 80) fs to the S2 and S1 electronic excited states.
This is evident from the rise time of the stimulated emission signal in the
visible spectral range. On the same time scale, narrowing of broad infrared
signals in the C=C stretching region around 1500 cm−1 is observed. Energy
redistribution processes are visible in the vibrational and electronic
dynamics with time constants between ∼2 ps and ∼20 ps. Triplet formation is
detected with a time constant of (95 ± 3) ps. This is tracked by the complete
loss of stimulated emission. Electronic transition of the emerging triplet
absorption band overlaps considerably with the singlet excited
stateabsorption. In contrast, two well separated vibrational marker bands for
triplet formation were identified at 1477 cm−1 and at 1508 cm−1. These marker
bands allow a precise identification of triplet dynamics in corrole systems
The Vibrational Spectrum of the hydrated Alanine-Leucine Peptide in the Amide region from IR experiments and First Principles Calculation
We have combined infrared (IR) experiments with molecular dynamics (MD)
simulations in solution at finite temperature to analyse the vibrational signature
of the small floppy peptide Alanine-Leucine. IR spectra computed from first-
principles MD simulations exhibit no distinct differences between conformational
clusters of alpha-helix/beta-sheet-like folds with different orientations of the bulky leucine
side chain. All computed spectra show two prominent bands, in good agreement
with the experiment, that are assigned to the stretch vibrations of the carbonyl
and carboxyl group, respectively. Variations in band widths and exact maxima
are likely due to small fluctuations in the backbone torsion angles
Efficient chaining of seeds in ordered trees
We consider here the problem of chaining seeds in ordered trees. Seeds are
mappings between two trees Q and T and a chain is a subset of non overlapping
seeds that is consistent with respect to postfix order and ancestrality. This
problem is a natural extension of a similar problem for sequences, and has
applications in computational biology, such as mining a database of RNA
secondary structures. For the chaining problem with a set of m constant size
seeds, we describe an algorithm with complexity O(m2 log(m)) in time and O(m2)
in space
Domain-wall depinning assisted by pure spin currents
We study the depinning of domain walls by pure diffusive spin currents in a
nonlocal spin valve structure based on two ferromagnetic permalloy elements
with copper as the nonmagnetic spin conduit. The injected spin current is
absorbed by the second permalloy structure with a domain wall and from the
dependence of the wall depinning field on the spin current density we find an
efficiency of 6*10^{-14}T/(A/m^2), which is more than an order of magnitude
larger than for conventional current induced domain wall motion. Theoretically
we reproduce this high efficiency, which arises from the surface torques
exerted by the absorbed spin current that lead to efficient depinning.Comment: 11 pages, 3 figures, accepted for publication in Phys. Rev. Let
First records of Hyalomma rufipes and Ixodes neitzi (Acari: Ixodidae) found on large carnivores in South Africa
Ixodid ticks (Acari: Ixodidae) are important disease vectors for large carnivores, but the composition of the tick communities that parasitize carnivores is poorly understood. We collected ticks from leopards (Panthera pardus) and brown hyenas (Hyaena brunnea) in the Soutpansberg Mountains, South Africa, to determine which species feed on these carnivores. We identified a total of eight tick species belonging to six genera, and recorded Ixodes neitzi and Hyalomma rufipes on P. pardus for the first time
Gene variant effects across sodium channelopathies predict function and guide precision therapy
Pathogenic variants in the voltage-gated sodium channel gene family (SCNs) lead to early onset epilepsies, neurodevelopmental disorders, skeletal muscle channelopathies, peripheral neuropathies and cardiac arrhythmias. Disease-associated variants have diverse functional effects ranging from complete loss-of-function to marked gain-of-function. Therapeutic strategy is likely to depend on functional effect. Experimental studies offer important insights into channel function, but are resource intensive and only performed in a minority of cases. Given the evolutionarily conserved nature of the sodium channel genes we investigated whether similarities in biophysical properties between different voltage-gated sodium channels can predict function and inform precision treatment across sodium channelopathies. We performed a systematic literature search identifying functionally assessed variants in any of the nine voltage-gated sodium channel genes until 28 April 2021. We included missense variants that had been electrophysiologically characterised in mammalian cells in whole-cell patch-clamp recordings. We performed an alignment of linear protein sequences of all sodium channel genes and correlated variants by their overall functional effect on biophysical properties. Of 951 identified records, 437 sodium channel-variants met our inclusion criteria and were reviewed for functional properties. Of these, 141 variants were epilepsy-associated (SCN1/2/3/8A), 79 had a neuromuscular phenotype (SCN4/9/10/11A), 149 were associated with a cardiac phenotype (SCN5/10A) and 68 (16%) were considered benign. We detected 38 missense variant pairs with an identical disease-associated variant in a different sodium channel gene. 35 out of 38 of those pairs resulted in similar functional consequences indicating up to 92% biophysical agreement between corresponding sodium channel variants (odds ratio = 11.3; 95% CI = 2.8 to 66.9; P < 0.001). Pathogenic missense variants were clustered in specific functional domains, whereas population variants were significantly more frequent across non conserved domains (odds ratio = 18.6; 95% CI = 10.9 to 34.4; P < 0.001). Pore-loop regions were frequently associated with loss-of-function (LoF) variants, whereas inactivation sites were associated with gain-of-function (GoF; odds ratio = 42.1, 95% CI = 14.5 to 122.4; P < 0.001), whilst variants occurring in voltage-sensing regions comprised a range of gain- and loss-of-function effects. Our findings suggest that biophysical characterisation of variants in one SCN-gene can predict channel function across different SCN-genes where experimental data are not available. The collected data represent the first GoF versus LoF topological map of SCN proteins indicating shared patterns of biophysical effects aiding variant analysis and guiding precision therapy. We integrated our findings into a free online webtool to facilitate functional sodium channel gene variant interpretation (http://SCN-viewer.broadinstitute.org)
Relationship between nonadiabaticity and damping in permalloy studied by current induced spin structure transformations
By direct imaging we determine spin structure changes in Permalloy wires and disks due to spin transfer torque as well as the critical current densities for different domain wall types. Periodic domain wall transformations from transverse to vortex walls and vice versa are observed, and the transformation mechanism occurs by vortex core displacement perpendicular to the wire. The results imply that the nonadiabaticity parameter β does not equal the damping α, in agreement with recent theoretical predictions. The vortex core motion perpendicular to the current is further studied in disks revealing that the displacement in opposite directions can be attributed to different polarities of the vortex core
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