operate concurrently under high electric fields and elevated temperatures approaching or surpassing 150 °C. [2,4,8,[11][12][13] However, to date, the search for polymer dielectrics that provide appreciable energy densities at temperatures well above 100 °C has led to only marginal success. High temperature operation under high electric field is challenging for polymer dielectrics. For example, biaxially oriented polypropylene (BOPP), the state-of-the-art commercially available dielectric polymer used for energy storage, has a remarkable breakdown strength of ≈700 MV m −1 and ultralow loss, but can only operate continuously at temperatures up to 85 °C and for a short duration with significant derating at 105 °C. [14,15] Many heat resistant polymers have been designed and studied for high-temperature applications, but they are incapable of operating at an electric field similar to BOPP. [11,16,17] This is because their conjugated aromatic backbones that are able to withstand high temperature, built at the cost of largely reduced bandgaps, lead to high electrical conductivities and poor energy densities especially at elevated temperatures. Recent efforts for enhanced energy storage performance at high temperature via nanocomposites or coating modifications of polymer films, although encouraging, are prohibitively challenging for industrial-scale production due to requirements of (either) materials cost and (or) laborious multi-step synthesis and processing. [2,12,13,18,19] As a result, BOPP is still used today with cumbersome active cooling. The availability of flexible polymer dielectrics, capable of stable operation under ultrahigh electric field and elevated temperature is the limiting factor for high power density electrification and electronics.Due to hot carrier excitation, injection, and transport, assisted under thermal and electric extremes, polymers exhibit a nonlinear increase in electrical conduction, [20][21][22] leading to the reduction of the discharged energy density, largely increased energy loss and ultimately dielectric breakdown failure [23] . While the complexity of these processes makes the study of engineering conduction mechanism under critical electric fields far from fully understood, past studies revealed the dominant role of the bandgap in determining electrical conduction and intrinsic breakdown strength of the polymer dielectrics. [20,[24][25][26][27] However, careful evaluation of common high-temperature polymers reveals, unfortunately, an inverse Flexible dielectrics operable under simultaneous electric and thermal extremes are critical to advanced electronics for ultrahigh densities and/or harsh conditions. However, conventional high-performance polymer dielectrics generally have conjugated aromatic backbones, leading to limited bandgaps and hence high conduction loss and poor energy densities, especially at elevated temperatures. A polyoxafluoronorbornene is reported, which has a key design feature in that it is a polyolefin consisting of repeating units of fairly rigid fused bicycl...

14The Red Sea Rift, an archetype of a newly formed ocean basin, is an ideal environment in 15 which to study the controversial processes associated with continental rifting. Different models 16 have been proposed to explain how rifting in the Red Sea evolved; however, accurate constraints 17 on lithospheric structure have not been available to discriminate rifting models. We use the S-18 wave receiver function technique to produce the first images of the lithosphere-asthenosphere 19 boundary (LAB) structure along the Red Sea and throughout the Arabian Peninsula. 20Lithospheric thickness varies considerably, with thin lithosphere centered on the rift axis, 21 thickening toward the Arabian interior. Gravity data are well fit by our structural model and 22indicate that high surface topography along the rift flank is not in isostatic equilibrium, requiring 23 2 dynamic compensation for its support. While our derived structure is consistent with active 24 rifting processes, previous studies demonstrated that the Red Sea initiated as a passive rift. 25 Therefore, our results suggest a two-stage rifting history, where extension and erosion by flow in 26 the underlying asthenosphere are responsible for variations in LAB depth. LAB topography 27 guides asthenospheric flow beneath western Arabia and the Red Sea, demonstrating the 28 important role lithospheric variations play in the thermal modification of tectonic environments. 29

14

Regional seismic waveforms reveal significant differences in the structure of the Arabian Shield and the Arabian Platform. We estimate lithospheric velocity structure by modelling regional waveforms recorded by the 1995–1997 Saudi Arabian Temporary Broadband Deployment using a grid search scheme. We employ a new method whereby we narrow the waveform modelling grid search by first fitting the fundamental mode Love and Rayleigh wave group velocities. The group velocities constrain the average crustal thickness and velocities as well as the crustal velocity gradients. Because the group velocity fitting is computationally much faster than the synthetic seismogram calculation this method allows us to determine good average starting models quickly. Waveform fits of the Pn and Sn body wave arrivals constrain the mantle velocities. The resulting lithospheric structures indicate that the Arabian Platform has an average crustal thickness of 40 km, with relatively low crustal velocities (average crustal P‐ and S‐wave velocities of 6.07 and 3.50 km s−1, respectively) without a strong velocity gradient. The Moho is shallower (36 km) and crustal velocities are 6 per cent higher (with a velocity increase with depth) for the Arabian Shield. Fast crustal velocities of the Arabian Shield result from a predominantly mafic composition in the lower crust. Lower velocities in the Arabian Platform crust indicate a bulk felsic composition, consistent with orogenesis of this former active margin. P‐ and S‐wave velocities immediately below the Moho are slower in the Arabian Shield than in the Arabian Platform (7.9 and 4.30 km s−1, and 8.10 and 4.55 km s−1, respectively). This indicates that the Poisson’s ratios for the uppermost mantle of the Arabian Shield and Platform are 0.29 and 0.27, respectively. The lower mantle velocities and higher Poisson’s ratio beneath the Arabian Shield probably arise from a partially molten mantle associated with Red Sea spreading and continental volcanism, although we cannot constrain the lateral extent of a zone of partially molten mantle.

Petroglyphs, engraved throughout the Holocene into rock varnish coatings on sandstone, were investigated in the Ha’il region of northwestern Saudi Arabia, at Jabal Yatib, Jubbah, and Shuwaymis. The rock art has been created by removing the black varnish coating and thereby exposing the light sandstone underneath. With time, the varnish, a natural manganese (Mn)-rich coating, grows back. To study the rate of regrowth, we made 234 measurements by portable X-ray fluorescence (pXRF) on intact varnish and engraved petroglyphs. Since many petroglyphs can be assigned to a specific time period, a relationship between their ages and the Mn surface densities (DMn) of the regrown material could be derived. This relationship was improved by normalizing the DMn in the petroglyphs with the DMn of adjacent intact varnish. In turn, we used this relationship to assign a chronologic context to petroglyphs of unknown ages. Following the removal of the varnish by the artist and prior to the beginning of Mn oxyhydroxide regrowth, a thin Fe-rich film forms on the underlying rock. This initial Fe oxyhydroxide deposit may act as catalyst for subsequent fast Mn oxidation. After a few decades of relatively rapid growth, the regrowth of the Mn-rich varnish slows down to about 0.017 µg cm–2 a–1 Mn, corresponding to about 0.012% a–1 Mn of the intact varnish density, or about 1.2 nm a–1, presumably due to a change of the catalytic process. Our results suggest that petroglyphs were engraved almost continuously since the pre-Neolithic period, and that rock varnish growth seems to proceed roughly linear, without detectable influences of the regional Holocene climatic changes.

Abstract. We determined crustal and lithospheric mantle velocity structure beneath the Arabian Shield through the modeling of receiver function stacks obtained from teleseismic P waves recorded by the 9 station temporary broadband array in

[1] We present a multiple step procedure for joint modeling of surface wave group velocity dispersion curves and teleseismic receiver functions for lithospheric velocity structure. The method relies on an initial grid search for a simple crustal structure, followed by a formal iterative inversion, an additional grid search for shear wave velocity in the mantle, and finally, forward modeling of transverse isotropy to resolve LoveRayleigh surface wave dispersion discrepancy. It considers longer-period surface wave group velocity (SWGV) dispersion, allowing for the resolution of deeper structure compared to previous joint inversions. The grid search for simple crustal structure is facilitated using a library of precomputed receiver functions and SWGV dispersion curves. The iterative inversion improves fit to the data by increasing the number of layers in the crust when necessary. In order to fit the SWGV for periods greater than about 50 s, we perform a grid search over mantle velocities including the mantle lid and low-velocity zone, keeping the crustal structure fixed to the values from the previous step. In some cases a clear Love-Rayleigh discrepancy prevents a simultaneous fit of the group velocities with an isotropic model. The Love-Rayleigh discrepancy can be resolved by allowing shear wave transverse isotropy with a vertical symmetry axis (v SH À v SV differences) in the uppermost mantle. The method is applied to 10 stations in the Arabian Peninsula sampling various tectonic environments including active continental rifting and stable regions. The resulting shear velocity models confirm rapid crustal thinning of the Arabian Shield toward the Red Sea; however, we do not find strong evidence for crustal thickening toward the Arabian Platform. Our results suggest that the mantle lithosphere thickness varies regionally but that the mantle shear velocities beneath the Arabian Shield and Red Sea coast are generally anomalously low. Furthermore, our results indicate the presence of strong polarization anisotropy (up to about 10%) in the lithospheric upper mantle, in the vicinity of, as well as farther away from, the Red Sea. Our modeling yields v SV > v SH in the southwestern part of the Arabian Peninsula, consistent with vertical flow, and v SH > v SV in the northwestern part of the Arabian Peninsula and the continental interior, consistent with horizontal flow, indicating that the mantle flow pattern is not uniform along the axis of the Red Sea.Citation: Tkalčić, H., M. E. Pasyanos, A. J. Rodgers, R. Gök, W. R. Walter, and A. Al-Amri (2006), A multistep approach for joint modeling of surface wave dispersion and teleseismic receiver functions: Implications for lithospheric structure of the Arabian Peninsula,

No abstract