Higher Te Values Research Articles

Ionized gas kinematics and chemical abundances of low-mass star-forming galaxies at z ∼ 3

Context. Feedback from massive stars plays a crucial role in regulating the growth of young star-forming galaxies (SFGs) and in shaping their interstellar medium (ISM). This feedback contributes to the removal and mixing of metals via galactic outflows and to the clearance of neutral gas, which facilitates the escape of ionizing photons. Aims. Our goal is to study the impact of stellar feedback on the chemical abundances of the ISM in a sample of SFGs with strong emission lines at z ∼ 3. Methods. We selected 35 low-mass SFGs (7.9 < log(M⋆/M⊙) < 10.3) from deep spectroscopic surveys based on their CIII]λ1908 emission. We used new follow-up near-infrared (NIR) observations to examine their rest-optical emission lines and to identify ionized outflow signatures through broad emission line wings detected after Gaussian modeling of [OIII]λλ4959,5007 profiles. We characterized the gas-phase metallicity and carbon-to-oxygen (C/O) abundance of the galaxies using a Te-based method via the OIII]λ1666/[OIII]λ5007 ratio and photoionization models. Results. We find line ratios and rest-frame equivalent widths (EWs) characteristic of high-ionization conditions powered by massive stars. Our sample displays a mean rest-frame EW([OIII]λ5007) of ∼560 Å, while about 15% of the SFGs show EW([OIII]λλ4959,5007) > 1000 Å and EW(CIII]) > 5 Å, closely resembling those now seen in epoch of reionization (EoR) galaxies with the James Webb Space Telescope. We find high Te values, which imply low gas-phase metallicities 12+log(O/H) ∼ 7.5–8.5 (mean of 17% solar) and C/O abundances from 23% to 128% solar, with no apparent increasing trend with metallicity. Our sample follows the mass-metallicity relation at z ∼ 3, with some galaxies showing lower gas-phase metallicities. This results in significant deviations from the fundamental metallicity relation. From our [OIII]λλ4959,5007 line profile modeling, we find that 65% of our sample shows an outflow component, which is found both blue- or redshifted relative to the ionized gas systemic velocity, and the mean maximum velocities are vmax ∼ 280 km s−1. We find a weak correlation between vmax and the star formation rate surface density (ΣSFR) of vmax = (2.41 ± 0.03) × ΣSFR(0.06 ± 0.03). Moreover, we find that the mass-loading factor μ of our galaxy sample is typically lower than in more massive galaxies from the literature, but it is higher than in typical local dwarf galaxies. In the stellar mass range covered by our sample, we find that μ increases with ΣSFR. This suggests that for a given stellar mass, denser starbursts in low-mass galaxies produce stronger outflows. Our results complement the picture drawn by similar studies at lower redshift, suggesting that the removal of ionized gas in low-mass SFGs driven by stellar feedback is regulated by their stellar mass and by the strength and concentration of their star formation, that is, ΣSFR.

Spatial variations of effective elastic thickness of Eastern Arabia: Implications for lithospheric weakening in the Oman-UAE mountain belt

The continental lithosphere of the Arabian Plate has evolved through a long and complex tectonic history and comprises major geological features such as an ophiolite complex, Cenozoic basalt extrusion, and Proterozoic basement outcrops. In eastern Arabia, an NW-SE to N-S oriented orogenic belt is present in Oman and the United Arab Emirates (UAE). The mountain belt formed due to the Late Cretaceous obduction of the Semail ophiolite, where a thick slab of oceanic crust and upper mantle was emplaced on the rifted Arabian continental margin. However, the mechanical strength of the lithosphere over the entire region is poorly known. In this study, we employ Bouguer gravity anomaly and topographic data, along with data on crustal properties obtained from teleseismic analyses, to assess the spatial variations in the effective elastic thickness (Te) of the eastern Arabian Plate. The joint inversion of coherence and admittance yielded Te values ranging from 10 to 50 km and an initial subsurface-to-surface load ratio (F) of 0.1 to 0.8. Te values in the southern part of eastern Arabia are low (< 20 km), while the northeastern regions of Saudi Arabia, the UAE, and Qatar exhibit intermediate to high Te values ranging from 30 to 45 km. The Oman-UAE mountain belt is associated with an intermediate Te of 30 km in the northern segment and a low Te of 20 km in the southern segment. The reduction in Te observed along the strike of the mountain belt suggests weakening of the lithosphere during the obduction of the Semail ophiolite. Te correlates well with both the seismic thickness of the lithosphere (Ts) and the decrease in shear-wave velocity at a depth of 150 km. The seismogenic thickness in eastern Arabia, however, is about 15 km, which is significantly less than Te and shows that both the crust and upper mantle contribute to the strength of the continental lithosphere. The Ts/Te ratio ranges from 1 to 9, with a maximum peak at 3–5, which is similar to the results observed for the oceanic lithosphere.

The coherence function and lithospheric elastic thickness of the Zagros fold and thrust belt

SUMMARY This study derives the spatial variation of the elastic thickness (Te) and its implications for understanding the structure, geodynamic and seismicity of the lithosphere for the Zagros fold and thrust belt region of the Arabia–Eurasia collision zone. Te is calculated using the coherence function in the fan wavelet domain based on recent terrestrial Bouguer gravity and topography data as input signals. Utilizing the load deconvolution method and Brent's method of 1-D minimization, the final Te for the survey region is estimated for each grid node of the studied area. To illustrate the mass distribution in the studied area, the subsurface loading fraction (F) is calculated simultaneously with Te in the inversion. The crust thickness and density from three different global crustal models are tested and the results obtained for these input models do not yield substantially different Te patterns. The final results are in accord with the global Te models as well as previous rheological, geodynamical and flexural studies, however, this study establishes much more detailed regional information. The calculations yield a mean value of Te of 61 km for the Zagros, with a mean estimated error of about 5 km. The high-Te values (&amp;gt;70 km) are observed in the southeast of the studied area (some parts of the Sanandaj–Sirjan zone, Urumieh–Dokhtar magmatic arc and most of the Central Iranian blocks); while over most of the northwest of the studied area, the value of Te is about 58 km. The Te results are consistent with the lithospheric structure of the study area and also support the idea of the crust–mantle decoupling. Further, there is a positive and negative correlation between the surface wave velocity and surface heat flow, respectively. The mean value estimated for the internal loading friction (F) of 0.4 means in most of the studied areas we may consider that the surface loading is dominant, or at least the ratio of the surface and subsurface loading can be assumed equal. Based on earthquake distribution in the period 1900–2020, seismicity is more likely to occur in areas with a relatively low value of Te.

Lithospheric flexural isostasy background of the 2017 Ms7.0 Jiuzhaigou earthquake and its implications for material extrusion in the northeastern Bayan Har block

We applied a 2-dimensional, non-spectral technique to investigate the spatial variations of the lithospheric effective elastic thickness (Te) in the eastern Bayan Har block and its adjacent areas. A program was designed to calculate the Moho flexure induced by topography loading, as well as the Bouguer gravity anomalies caused by that Moho flexure. The Te values were determined by minimizing the RMS differences between the observed and calculated Bouguer gravity anomalies. The results suggested that Te varies significantly from eastern Tibet to the Sichuan Basin. The eastern Bayan Har block and northern Sichuan-Yunnan block have low Te values (0 < Te < 20 km), indicating an easily deformable lithosphere. The Sichuan Basin has high Te values (40 km < Te < 100 km) acts as a rigid block that resists the eastward extrusion of plateau materials. The moderate Te values (30 km < Te < 40 km) found under the Longmen Shan fault belt indicate that the lithosphere of the Sichuan Basin plays an important role in supporting the Longmen Shan topography. The extremely low Te (Te < 10 km) observed in the seismogenic zone of the Ms7.0 Jiuzhaigou earthquake indicated that the topography is compensated locally, which is significantly different from the Longmen Shan topography. A banded region of relatively low Te values (< 40 km) stretching from the northeastern Bayan Har block to the southwestern Ordos block sketches out an escape channel for plateau materials, and challenges the existing of crustal flow on the north side of the Sichuan Basin.

The lithospheric effective elastic thickness and its tectonic implications in the Ordos Block and adjacent areas

The Ordos Block, located at the western edge of the North China Block, is a stable rigid block. It is characterized by inactive tectonic activity and rare earthquakes, while the south‐west margin of this block and adjacent areas present the opposite features. There is still considerable ambiguity with regard to the lithospheric mechanical strength in these areas. The effective elastic thickness (Te), widely used for comprehending the mechanism of cratonic deformation and lithospheric dynamics, is a proxy of the lithospheric strength. This study provided detailed two‐dimensional lithospheric Te spatial variations in the Ordos and adjacent areas by using coherence analysis of the topography and Bouguer anomaly. The result showed that the higher Te values in the Ordos Block varied from 80 to 100 km and implied that it is capable of strong rigidity. The lower Te values were distributed over the Qinling Block (20–45 km), the Qilian Block and Haiyuan arcuate tectonic region (20–40 km), as well as the Baryan‐Har Block (15–30 km). By comparing the Te values with the geophysical results, we believe that the higher Te value in the Ordos Block was supported not only by the crust, but also by the upper mantle. In contrast, the mechanical strength of the south‐west margin, especially the Baryan‐Har Block and western Qinling Block, was mainly borne by the brittle upper crust, but the tectonic activity and brittle failure likely resulted in a lower Te. Furthermore, we found that a large number of shallow earthquakes were located above low‐velocity and low‐resistivity layers, most of which probably occurred in the brittle upper crust with small mechanical strength.

Estimating the effective elastic thickness of the Arctic lithosphere using the wavelet coherence method: Tectonic implications

Currently, knowledge of structure and tectonic evolution of the Arctic lithosphere remains limited. The effective elastic thickness of the lithosphere (Te) is a parameter that describes the lithospheric integrated strength and reflects its thermal and rheological properties, which helps to reveal intraplate tectonic process. In this study, we present a high-resolution Te model in the Arctic region (north of 67°N), which is highly heterogeneous and strongly correlated with various regional tectonic elements. To verify the recovered Te, its pattern is compared to those obtained in previous studies that used different methods and to available heat flow measurements and seismic velocity model and shows good agreement. High Te values are found in the Greenland shield, North American craton and Siberian craton, which are compatible with results from previous studies of high seismic velocity and low heat flow, suggesting that cold, thick lithosphere remains tectonically undisturbed. Low Te values occur in the Amerasia Basin, Baffin Bay, Eurasia Basin and North Atlantic Ocean where young oceanic lithosphere is created. Moreover, the areas affected by regional volcanism in the Siberian Traps and HALIP are dominated by reductions in Te, which we attribute to thermal rejuvenation triggered by the intrusion of magma. Weak lithosphere also dominates in tectonically active orogens as well, including the Alaska-Chukotka, Novaya Zemlya and Caledonides, and is related to the stress released during collisional deformation. We find that a few deep sedimentary basins are characterized by intermediate Te, which implies mechanical support of the surface sediment loads in a non-isostatic state. Our new Te model provides potentially significant insights into various tectonic and geodynamic problems of the Arctic lithosphere.

The effective elastic thickness of the lithosphere in the Amerasia Basin, Arctic Ocean

AbstractAs a proxy for the lithospheric strength at the time of loading, the effective elastic thickness of the lithosphere (Te) can aid in understanding the structure and evolution of the lithosphere. Here, we obtain spatial variations in Te of Amerasia Basin and surrounding regions using the fan‐shaped Morlet wavelet method. Our results show that variations in Te generally agree well with tectonic provinces in the region. The eastern part of Makarov Basin has the same lithospheric strength as Alpha and Mendeleev ridges, which may be attributed to the influence of the High Arctic large igneous province. N‐S and E‐W Te variations in Podvodnikov Basin may reflect two phases of its formation. Western and eastern parts of south Canada Basin have prominent low and high Te values, respectively. This study provides the reliable Te results of central Arctic and improves our understanding of the evolution of the Arctic.

Effective elastic thickness of Zealandia and its implications for lithospheric deformation

Zealandia was once located at the active Gondwana margin and experienced complicated tectonic evolution from continental breakup to subduction and oblique slipping along the plate boundary. Here, we investigate the lithospheric thermal and rheological properties via spatial variations in effective elastic thickness (Te). Using the topography, sediment thickness and gravity data, the fan wavelet coherence method is employed to recover Te values. The effects of dynamic topography and gravity in the subduction zone on the estimated Te are considered and removed. The final results reveal that the Te variation pattern generally coincides well with the tectonic regimes. Relatively high Te values up to 22 km are observed in North Island and the southernmost part of South Island, while central and northern South Island are dominated by smaller Te values (~15 km) similar to those of the surrounding submerged plateaus. We interpret the relatively high Te values as indicating the combined lithospheric strength due to the contacting plates in the subduction zone. To the north along the Tonga-Kermadec subduction zone, the lithosphere surprisingly exhibits anomalously high Te values, ranging from 22 to 36 km, which contradicts the geological evidence of normal faults developed in the incoming Pacific Plate and the magmatism in the overlying Australian Plate that generally contribute to low lithospheric strength. We speculate that the high-Te zone is related to the large bathymetry and gravity anomalies in the bending plate and controlled by non-isostatic factors. Finally, we find widespread low Te values covering the entire arcs and oceanic basins in northern Zealandia, which may indicate that regional lithospheric thinning associated with delamination weakened the integrated strength of the lithosphere.

Crustal architecture and isostatic compensation of the Comorin Ridge, central Indian Ocean: Implications for the breakup of east Gondwana

The Comorin Ridge, located off the southwest margin of Sri Lanka is an important geological feature with significant relevance to understand the breakup of eastern Gondwanaland. Earlier geophysical studies over this ridge provided several contrasting views due to which its origin and nature of emplacement could not be established very well. In this study, an integrated interpretation of bathymetry, gravity, geoid, and ship-borne magnetic data is carried out to bring out a well-constrained evolution model for the ridge. Results of 3-D gravity inversion of Crustal Bouguer anomalies and joint gravity-magnetic modeling indicate that the southern part of the ridge is underlain by 7–12 km thick crust intruded with volcanic rocks and the presence of 13–18 km of anomalously thicker crust below the northern part of the ridge. Further, crustal models, spatial variations in Geoid-Topography Ratio (GTR), and the effective elastic thickness (Te) value obtained in this study suggest a two-stage emplacement model for the evolution of the ridge. The observed lower Te values (7–8 km) in the southern part (0.5°N–3.5°N) and its proximity to the C34ny spreading anomaly suggest its emplacement on the oceanic lithosphere due to Marion plume activity along a fracture zone during ~88–84 Ma. On the other hand, relatively higher Te values (12.5–15 km) in the northern part (3.5°N–6.5°N) with absence seafloor-spreading magnetic anomalies suggests that it could be a marginal basement high formed at the continent-ocean boundary (COB) during the second phase of rifting between India and Sri Lanka (~94 Ma).

Moho depth and equivalent elastic thickness of the lithosphere over the Vema Channel: A new evidence of an aborted ridge

We investigate the Vema Channel in terms of spatial variations of the elastic thickness (Te) in the frame of the thin plate flexure model using the convolutive method. The modeling of the Moho in terms of the thin plate flexure model is done by a least squares approximation of the Moho obtained from gravity inversion. The flexure is calculated by the convolution of the crustal load with the point-load flexure response curves. The RMS difference between the gravity and flexure Moho surfaces is minimized by varying the Te by inverse modeling. The result is a solution of the flexed crust that is in best agreement with the long-wavelength component of the gravity field.The flexure Moho depths vary between 12 and 18 km and agree well with those obtained from gravity inversion. The spatial variations of Te range from 2 to 30 km and have a good correlation with the geological interpretation for an aborted ridge near Vema Channel, called in this paper as the Vema Aborted Ridge (VAR). The occurring of seamounts appears to be correlated to a weak and deformed region. Attempts of crustal breakup are marked by high Te values (30 km) while lower values (3–12 km) are found for the suggested aborted ridge. The VAR is on Isochron of 93 Ma and shows symmetrical older along both sides of its axis. Asymmetric magnetic anomalies are found over the ridge and may be related to upper-extended continental crust broken by the Vema.

Effective elastic thickness in the Central Andes. Correlation to orogenic deformation styles and lower crust high-gravity anomaly

Global studies have assessed the importance of elastic thickness (Te) on orogenic evolution, showing that the style and nature of upper crustal shortening are influenced by the inherited lithospheric strength. Thus, pioneer works have identified that the upper crustal deformation style in the easternmost sector of the Central Andes in South America are related to the elastic thickness (Te). There, the thick-skinned and pure-shear style of Santa Bárbara system was initially related to the existence of low Te values. In contrast, the thin-skinned and simple-shear style of deformation in the Subandean system involves high Te values. However, more recent Te studies in the Central Andes present conflicting results which lead to question this straightforward relation. Results from these studies show a strong dependence on the applied methodology hampering the general understanding of the lithospheric thermo-mechanical state of the Central Andes. To contribute to this issue, we perform a high-resolution Te map, using forward modeling by solving flexural equation of infinite plate model in two dimensions. To achieve this, the crust-mantle interface was calculated using a high-resolution gravity anomaly dataset which combines satellite and terrestrial data, and an average density contrast. Additionally, the gravity anomaly and the foreland basin depth in the Central Andes were best predicted by considering that lower crustal rocks fill the space deflected downward in the plate model. The obtained Te values show an inverse correlation with previous heat flow studies, and a strong spatial correlation with the styles and mechanisms of deformation in the easternmost sector of the Central Andes. In the Santa Bárbara system Te values less than 10 km predominate, whereas in the Subandean system high Te values were observed. Such high values correlate with the orogenic curvature and with an shallower gravity Moho zone, which breaks the regional trend of the Central Andes. This shallower gravity Moho is linked to a high-gravity anomaly located in the east part of the Eastern Cordillera and Subandean system. These results are also correlated with a high-velocity zone in the upper mantle previously found by receiver functions studies. This correlation could indicate changes in the properties of the lower crustal rocks that justify the shallower gravity Moho zone and explain in part the highest Te values.

Variations of the effective elastic thickness over the Ross Sea and Transantarctic Mountains and implications for their structure and tectonics

The effective elastic thickness (Te) is a proxy for lithospheric strength, and it depends primarily on the thermal gradient and composition of the lithosphere. Accordingly, spatial variations in Te reflect changes in lithospheric properties and can be used to better understand the structure and tectonics of particular regions. In this paper, we investigate the Ross Sea and Transantarctic Mountains in terms of Te using gravity and topographic data and the fan wavelet transform technique. The results reveal that relatively high Te values dominate in the extensional basins of the Ross Sea and the hinterland of Transantarctic Mountains, whereas very low Te values occur along the Transantarctic Mountain Front and in the deep ocean basin, with the lowest Te values are found the vicinity of Ross Island and onshore in northern Victoria Land. In addition, the spatial variations in Te correlate well with lithospheric structure at the regional scale. By combining these findings with published seismic and heat flow data, we conclude that the presence of a zone of anomalously lowTe values parallel to the coast indicates that the lithosphere beneath the Transantarctic Mountain Front is extremely weak due to Cenozoic volcanism and extension. The Te values increase from the Transantarctic Mountain Front (7km) toward the center of the continent (~80km), which indicates that the continental lithosphere underlying East Antarctica belongs to the classic Gondwanan craton. The increase in Te indicates that the Transantarctic Mountain Front marks the continent-continent boundary between East Antarctica and West Antarctica. The Te values in the other extensional basins of the Ross Sea exhibit little variation and average approximately 35km. The relatively high Te values are interpreted to indicate that the lithosphere cooled and became mechanically stronger between late Cretaceous extension and Eocene-Neogene deposition.

Spatial variations in the effective elastic thickness of the lithosphere in Southeast Asia

As a proxy for long-term lithospheric strength, detailed information on lateral effective elastic thickness (Te) variations can aid in understanding the distribution pattern of surface deformation and its response to long-term forces. Here we present high-resolution maps of spatial variations of Te for the complex SE Asian region by analyzing the coherence of topography and Bouguer gravity anomaly data. We find that after considering the gravity deficit of less dense sediment, the recovered Te maps are more representative of the geology, particularly in elongated rift basins. The results show that the Te variation pattern in SE Asia, in general, agrees well with its tectonic provinces and major tectonic boundaries. The oceanic basins, the Indosinian suture zones between the Indochina and Sibumasu blocks, and the Makassar Strait are characterized by low Te, while moderate and high Te values are recovered in the Khorat plateau, West Burma, the Singapore Ridge, the Con Song Swell, Borneo, the northern Australian margin and the Molucca Sea. The Te pattern in the south Indonesian margin is complicated by the approach and collision of oceanic plateaus and seamounts with the fore-arc region. The heterogeneous strength features are consistent with the complex assemblage of different tectonic units, and significant deformation during Cenozoic tectonic events. In the Indochina Peninsula, the extruded displacement during the India-Eurasia collision might have been partitioned and absorbed by the combined mechanism of the extrusion and viscous tectonic models. As a result, the offshore displacements of the major strike-slip faults in the South China Sea are much smaller than originally assumed, thus having less effect on the development of the South China Sea than other mechanisms such as the slab pull of the proto-South China Sea. Since the displacement driven by the boundary tectonic forces has been greatly absorbed and decreased by subduction and deformation in the active margins and adjacent weak regions, the motion velocity of the interior regions is greatly lower than the boundary active margins, and they are largely free of seismicity and volcanism. Our results suggest that East Borneo might share a similar crustal basement, and represent a broad tectonic zone of the destroyed Meso-Tethys Ocean extending from West-Middle Java, through East Borneo to northern Borneo of the Sarawak and Sabah. The Indosinian zones between the Indochina and Sibumasu blocks might extend further southeastward across Billiton Island to offshore of southern Borneo, and the Singapore platform and SW Borneo might belong to the same block. The results also show that the internal load fraction F is high in the coastal area of South China, the northern margin of the South China Sea, and the coastal area of Indochina, which, in general, agrees with the distribution of a high-velocity lower crustal layer and Late Cenozoic basaltic rocks.

Ascorbic acid microencapsulation by spray chilling: Production and characterization

This study reports on the use of spray chilling to synthesize solid lipid microparticles containing ascorbic acid and describes the characterization of the resulting microparticles. Lauric acid (LA)/oleic acid (OA) mixtures at 70/30, 80/20, and 90/10 g:g ratios served as carrier. Different carrier/core (core = aqueous ascorbic acid solution 30 g/100 g) ratios, namely 70/30, 75/25, and 80/20 (g:g), were tested. The synthesized microparticles presented high TE values, which varied from 89% to 98%; differences between experiments were not significant (p > 0.05). EE values were inversely proportional to the amount of LA in the carrier; EE ranged from 58% to 88%. The mean volume moment of particle D[4,3] of the microparticles containing LA concentrations of 70 g/100 g of lipid and 90 g/100 g of lipid ranged from 45 to 67 μm and from 18 to 24 μm, respectively. The core release profile revealed that microparticles containing intermediate concentration of LA in the carrier (80 g/100 g of lipid) retained the ascorbic acid core better. The ratio between the fatty acids used as carrier rather than the ratio between the carrier and the core affected the characteristics of the microparticles the most.

Assessment of the effect of parallel temperature gradients in the JET SOL on Te measured by divertor target Langmuir probes

Higher than expected electron temperatures (Te) are often measured by divertor Langmuir probes (LP) in high recycling and detached regimes in JET and other tokamaks. As a possible mechanism to explain this discrepancy, we investigate the effect of penetration of fast, almost collisionless electrons connecting the hot upstream scrape-off layer (SOL) region to the divertor targets in JET. We simulate the electron velocity distribution function (EVDF) near the divertor targets using a simple 1D kinetic model using parallel SOL profiles from EDGE2D-EIRENE simulations. The resulting EVDF is used to construct synthetic LP current–voltage (IV) characteristics and evaluation of Te is performed in the same way as for experimental data. Results indicate that the process does not explain the anomalously high Te values estimated from the target probe measurements if the EDGE2D-EIRENE simulated parallel profiles are a good representation of reality.

Elastic thickness of the Himalayan–Tibetan orogen estimated from the fan wavelet coherence method, and its implications for lithospheric structure

This paper is concerned with the spatial variation of the elastic thickness (Te) in the Himalayan–Tibetan orogen and its implications for the understanding of lithospheric structure and deformation. New Te maps of the Himalayan–Tibetan orogen are generated from the new combined satellite-terrestrial gravity (EIGEN6C3stat) and topography (ETOPO1) models using the fan wavelet coherence technique. The high-Te values (>60 km) are observed in the Indian shield and the Tarim basin; while the low-Te values (<40 km) are prevailing over most of the Tibetan Plateau. We also find that the Te distributions estimated using the high and low central wavenumber (i.e., |k0|) wavelets are different in southern Tibet. By combining constraints from the current seismic and thermo-rheological modeling, this difference may reflect that the strength of the lithosphere in southern Tibet mainly resides in the lithospheric mantle. Within most parts of central and northern Tibet, the Te values are relatively low (<30 km), indicating that the entire lithosphere is weak. Our analysis finds that the Te variations are probably associated with changes in lithosphere structure. We interpret the abrupt changes in Te between southern and northern Tibet to indicate the location of the underthrusting strong Indian lithosphere beneath Tibet. Our results suggest that the northern limit of the underthrusting Indian plate reaches as far north as the Hindu Kush and the southwestern margin of the Tarim basin (near 70°–80°E), and extends along the Bangong-Nujiang Suture in the central (80°–87°E). Eastward between 87°E–93°E, it may move to the Indus-Tsangpo Suture, indicating a delamination of Indian mantle lithosphere there. Further to the east, it may underthrust northward beneath the eastern Qiangtang block.

Spatial variations of effective elastic thickness of the lithosphere in Central America and surrounding regions

As a proxy for long-term lithospheric strength, the effective elastic thickness (Te) can be used to understand the relationship between lithospheric rheology and geodynamic evolution of complex tectonic settings. Here we present, for the first time, high-resolution maps of spatial variations of Te in Central America and surrounding regions from the analysis of the coherence between topography and Bouguer gravity anomaly using multitaper and wavelet methods. Regardless of the technical differences between the two methods, there is a good overall agreement in the spatial variations of Te recovered from both methods. Although absolute Te values can vary in both maps, the qualitative Te structure and location of the main Te gradients are very similar. The pattern of the Te variations in Central America and surrounding regions agrees well with the tectonic provinces in the region, and it is closely related to major tectonic boundaries, where the Middle American and Lesser Antilles subduction zones are characterized by a band of high Te on the downgoing slab seaward of the trenches. These high Te values are related to internal loads (and in the case of the southernmost tip of the Lesser Antilles subduction zone also associated with a large amount of sediments) and should be interpreted with caution. Finally, there is a relatively good correlation, despite some uncertainties, between surface heat flow and our Te results for the study area. These results suggest that although this area is geologically complex, the thermal state of the lithosphere has profound influence on its strength, such that Te is strongly governed by thermal structure.

Crustal structure and tectonic setting of the south central Andes from gravimetric analysis

Based on terrestrial gravity data, in this paper we prepared a map of Bouguer anomalies, which was filtered to separate shallow and deep gravity sources. Based on a density model and gravimetric inversion techniques, the discontinuous crust-mantle boundary and the top of crystalline basement were modeled. Subsequently, the equivalent elastic thickness (Te) was evaluated, considering information from the crust-mantle discontinuity and topographic load, finding high Te values in the eastern Andean foothills and west of the Velasco range. These results are consistent with the positive isostatic and residual Bouguer anomaly values, which suggest the presence of high-density rocks in the mid-to upper crust. In addition, petrographic and geochemical analysis conducted in surface outcrops suggest a mantle origin.

MR thermometry in the human prostate gland at 3.0T for transurethral ultrasound therapy

To investigate the spatial, temporal, and temperature resolution of a segmented gradient echo echo-planar imaging (EPI) technique as applied to proton resonance frequency (PRF) shift thermometry at 3 T in the human prostate gland, and to determine appropriate sequence parameters for magnetic resonance imaging (MRI)-controlled transurethral ultrasound thermal therapy. Eleven healthy volunteers (age range 23-58) were scanned at 3 T with a 16-channel torso coil to study the behavior of a gradient echo EPI thermometry sequence. The temperature stability and geometric distortion were assessed for 11 different parameter sets. In a further five volunteers, the prostate T2* was measured. For all scan parameters investigated, the temperature standard deviation within the prostate was less than 1°C, while the distortion was less than 1 mm. Temperature stability was best with higher TE values (up to 25 msec), larger voxel sizes and lower EPI factors, but this had to be balanced against requirements for good spatial and temporal resolution. Prostate T2* values ranged from 30-50 msec. A good balance between temperature stability and temporal/spatial resolution is obtained with TE = 15 msec, voxel size = 1.14 mm, and EPI factor = 9, resulting in a dynamic scan time of 7.2 seconds for the nine slices.

A new assessment of the elastic thickness (Te) structure of the Indian shield, and its implications

&lt;p&gt;The elastic thickness (Te) of continents is a matter of much debate. Recent studies have shown that a number of factors control the continental Te, including age, heat flow, and lithospheric thickness. Here, we estimate the Te structure of the whole Indian shield using an improved isotropic fan wavelet land ocean deconvolution methodology, and we compare these results with the global published Te estimates in the Archean, Proterozoic and younger geological provinces. Our study reveals low (0-45 km/0-35 km), intermediate (45-70 km) and high (70-100 km) Te values in the Archean/Quaternary, the Proterozoic, and the Tertiary provinces, respectively, of the Indian shield. This is in contrast with global estimates of Te in similar geological provinces. In the absence of any correlation of Te with any controlling parameters, we propose that the mantle properties, rather than the tectonic history, are responsible for influences on the Te values within the Indian shield. The global positioning system horizontal velocity vectors yielded a locking depth of ca. 20 ±4 km, and the aseismic creep beyond correlates well with the high strength of ca. 70 km to 100 km in the central Himalayan foreland.&lt;/p&gt;