583 research outputs found
Fission and corrosion products behavior in primary circuits of LMFBR\u27s. Proceedings of an International Atomic Energy Agency Specialist\u27s Meeting, International Working Group on Fast Reactors, Karlsruhe, Federal Republic of Germany, May 5-8, 1987
An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data, volume 1
There are no author-identified significant results in this report
Thermal Diffusivities of Functionalized Pentacene Semiconductors
We have measured the interlayer and in-plane (needle axis) thermal
diffusivities of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn). The
needle axis value is comparable to the phonon thermal conductivities of
quasi-one dimensional organic metals with excellent pi-orbital overlap, and its
value suggests that a significant fraction of heat is carried by optical
phonons. Furthermore, the interlayer (c-axis) thermal diffusivity is at least
an order of magnitude larger, and this unusual anisotropy implies very strong
dispersion of optical modes in the interlayer direction, presumably due to
interactions between the silyl-containing side groups. Similar values for both
in-plane and interlayer diffusivities have been observed for several other
functionalized pentacene semiconductors with related structures.Comment: 9 pages, including 4 figures; submitted to Applied Physics Letter
The Influence of Regiochemistry on the Performance of Organic Mixed Ionic and Electronic Conductors
The Influence of Regiochemistry on the Performance of Organic Mixed Ionic and Electronic Conductors
Pipeline network features and leak detection by cross-correlation analysis of reflected waves
This paper describes progress on a new technique to detect pipeline features and leaks using signal processing of a pressure wave measurement. Previous work (by the present authors) has shown that the analysis of pressure wave reflections in fluid pipe networks can be used to identify specific pipeline features such as open ends, closed ends, valves, junctions, and certain types of bends. It was demonstrated that by using an extension of cross-correlation analysis, the identification of features can be achieved using fewer sensors than are traditionally employed. The key to the effectiveness of the technique lies in the artificial generation of pressure waves using a solenoid valve, rather than relying upon natural sources of fluid excitation. This paper uses an enhanced signal processing technique to improve the detection of leaks. It is shown experimentally that features and leaks can be detected around a sharp bend and up to seven reflections from features/ leaks can be detected, by which time the wave has traveled over 95 m. The testing determined the position of a leak to within an accuracy of 5%, even when the location of the reflection from a leak is itself dispersed over a certain distance and, therefore, does not cause an exact reflection of the wave
Conversion between Triplet Pair States Is Controlled by Molecular Coupling in Pentadithiophene Thin Films
In singlet fission (SF) the initially formed correlated triplet pair state, 1(TT), may evolve toward independent triplet excitons or higher spin states of the (TT) species. The latter result is often considered undesirable from a light harvesting perspective but may be attractive for quantum information sciences (QIS) applications, as the final exciton pair can be spin-entangled and magnetically active with relatively long room temperature decoherence times. In this study we use ultrafast transient absorption (TA) and time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy to monitor SF and triplet pair evolution in a series of alkyl silyl-functionalized pentadithiophene (PDT) thin films designed with systematically varying pairwise and long-range molecular interactions between PDT chromophores. The lifetime of the (TT) species varies from 40 ns to 1.5 μs, the latter of which is associated with extremely weak intermolecular coupling, sharp optical spectroscopic features, and complex TR-EPR spectra that are composed of a mixture of triplet and quintet-like features. On the other hand, more tightly coupled films produce broader transient optical spectra but simpler TR-EPR spectra consistent with significant population in 5(TT)0. These distinctions are rationalized through the role of exciton diffusion and predictions of TT state mixing with low exchange coupling J versus pure spin substate population with larger J. The connection between population evolution using electronic and spin spectroscopies enables assignments that provide a more detailed picture of triplet pair evolution than previously presented and provides critical guidance for designing molecular QIS systems based on light-induced spin coherence
Reproduction triggers adaptive increases in body size in female mole-rats
In social mole-rats, breeding females are larger and more elongated than non-breeding female helpers. This status-related morphological divergence is thought to arise from modifications of skeletal growth following the death or removal of the previous breeder and the transition of their successors from a non-breeding to a breeding role. However, it is not clear what changes in growth are involved, whether they are stimulated by the relaxation of reproductive suppression or by changes in breeding status, or whether they are associated with fecundity increases. Here, we show that, in captive Damaraland mole-rats (Fukomys damarensis), where breeding was experimentally controlled in age-matched siblings, individuals changed in size and shape through a lengthening of the lumbar vertebrae when they began breeding. This skeletal remodelling results from changes in breeding status because (i) females removed from a group setting and placed solitarily showed no increases in growth and (ii) females dispersing from natural groups that have not yet bred do not differ in size and shape from helpers in established groups. Growth patterns consequently resemble other social vertebrates where contrasts in size and shape follow the acquisition of the breeding role. Our results also suggest that the increases in female body size provide fecundity benefits. Similar forms of socially responsive growth might be more prevalent in vertebrates than is currently recognized, but the extent to which this is the case, and the implications for the structuring of mammalian dominance hierarchies, are as yet poorly understood.The Kalahari Mole-rat Project is supported by a European Research Council Grant awarded to T.C.-B. (no. 294494); J.T. was funded by a Natural Environment Research Council Doctoral Training Program; parts of the fieldwork were funded by a British Ecological Society Grant awarded to Markus Zöttl (no. 5301/6343).http://rspb.royalsocietypublishing.org2019-06-13hj2018Mammal Research InstituteZoology and Entomolog
Variation in growth of Damaraland mole-rats is explained by competition rather than by functional specialization for different tasks
In some eusocial insect societies, adaptation to the division of labour results in multimodal size
variation among workers. It has been suggested that variation in size and growth among nonbreeders
in naked and Damaraland mole-rats may similarly reflect functional divergence associated
with different cooperative tasks. However, it is unclear whether individual growth rates are
multimodally distributed (as would be expected if variation in growth is associated with
specialisation for different tasks) or whether variation in growth is unimodally distributed, and is
related to differences in the social and physical environment (as would be predicted if there are
individual differences in growth but no discrete differences in developmental pathways). Here we
show that growth trajectories of non-breeding Damaraland mole-rats vary widely, and that their
distribution is unimodal, contrary to the suggestion that variation in growth is the result of
differentiation into discrete castes. Though there is no evidence of discrete variation in growth,
social factors appear to exert important effects on growth rates and age-specific size, which are both
reduced in large social groups.This study was funded by an European Research Council grant to THCB (294494).http://rsbl.royalsocietypublishing2017-12-31hb2017Zoology and Entomolog
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