ALBERT

Description: Ultrasonic interferometry measurements in conjunction with in situ X-ray techniques have been used to measure compressional and shear wave velocities and densities of MgSiO3 perovskite (Mg-Pv) and Mg0.95Fe0.042+Fe0.013+SiO3 perovskite ((Mg, Fe)-Pv) in the multianvil at pressures up to 25 GPa and temperatures to 1200 K. Data for Mg-Pv are consistent with previous studies and the (Mg, Fe)-Pv sample has almost identical shear properties to Mg-Pv. The adiabatic bulk modulus, Ks, for (Mg, Fe)-Pv, however, is found to be substantially lower than Mg-Pv, with a refined value of 236 GPa and a pressure derivative of 4.7. It is proposed that this low KS value result from a change in the elasticity of Fe-bearing perovskite at low pressures

Description: [1]  Phase relations in harzburgite have been determined between 14 and 24 GPa and 1473 and 1673 K. At 1673 K, harzburgite transformed to wadsleyite + garnet + clinopyroxene below 19 GPa and decomposed into an assemblage of ringwoodite + garnet + stishovite above 20 GPa. Certain amounts of akimotoite were produced at still higher pressures (22–23 GPa). Finally perovskite and magnesiowüstite were found to coexist with garnet at 24.2 GPa. Compositions of all the phases were analyzed and elemental partitioning coefficients were determined among co-existing phases. Combining our experimental data with available thermoelastic properties of major minerals in the earth's mantle, we modeled the velocity and density signatures of the stagnated oceanic slabs in the mantle transition zone (MTZ) under eastern China, based on kinematic slab thermal structure analysis. We examined two end-member slab models: a conventional straight slab with deformation thickening, and an undulated slab with an oscillating wavelength of 200 km. We found that an undulated (buckled) slab model yields velocity anomalies (about 1–2% for Vp) that are consistent with seismic tomography models, taking into account of low-pass filtering effects in seismic tomography studies. On the other hand, straight slab models yield velocity anomalies that are too high comparing with seismic tomography models. Our models provide important constraints on the thermal structure, mineralogy, composition, density, and velocities of slab materials in the MTZ.

Description: We use receiver functions calculated for data collected by the INDEPTH-IV seismic array to image the three-dimensional geometry of the crustal and upper mantle velocity discontinuities beneath northeastern Tibet. Our results indicate an average crustal thickness of 65 to 70 km in northern Tibet. In addition, we observe a 20 km Moho offset beneath the northern margin of the Kunlun Mountains, a 10 km Moho offset across the Jinsha River Suture and gently northward dipping Moho beneath the Qaidam Basin. A region in the central Qiangtang Terrane with higher than normal crustal Vp/Vs ratio of ∼1.83 can be the result of the Eocene magmatic event. In the Qiangtang Terrane, we observe a significant lithospheric mantle discontinuity beneath the Bangong-Nujiang Suture at 80 km depth which dips ∼10° to the north, reaching ∼120 km depth. We interpret this feature as either a piece of Lhasa Terrane or remnant oceanic slab underthrust below northern Tibet. We detect a ∼20 km depression of the 660-km discontinuity in the mantle transition zone beneath the northern Lhasa Terrane in central Tibet, which suggests this phase transition has been influenced by a dense and/or cold oceanic slab. A modest ∼10 km depression of the 410-km discontinuity located beneath the northern Qiangtang Terrane may be the result of localized warm upwelling associated with small-scale convection induced by the penetration of the sinking Indian continental lithosphere into the transition zone beneath the central Tibetan Plateau.

Description: We present a high-resolution record of lacustrine sedimentation spanning ca. 30 000 to 9000 cal. a BP from Onepoto maar, northern North Island, New Zealand. The multi-proxy record of environmental change is constrained by tephrochronology and accelerator mass spectrometric 14 C ages and provides evidence for episodes of rapid environmental change during the Last Glacial Coldest Period (LGCP) and Last Glacial–Interglacial Transition (LGIT) from northern New Zealand. The multi-proxy palaeoenvironmental record from Onepoto indicates that the LGCP was cold, dry and windy in the Auckland region, with vegetation dominated by herb and grass in a beech forest mosaic between ca. 28 500 and 18 000 cal. a BP. The LGCP was accompanied by more frequent fires and influx of clastic sediment indicating increased erosion during the LGCP, with a mid-LGCP interstadial identified between ca. 25 000 and 23 000 cal. a BP. Rapid climate amelioration at ca. 18 000 cal. a BP was accompanied by increased terrestrial biomass exemplified by the expansion of lowland podocarp forest, especially Dacrydium cupressinum . Increasing biomass production is reversed briefly by LGIT perturbations which are apparent in many of the proxies that span ca. 14 000–10 500 cal. a BP, suggesting generally increased wetness and higher in situ aquatic plant productivity with reduced terrestrial organic matter and terrigenous detrital influx. Furthermore, conditions at that time were probably warmer and frosts rare based on the increasing importance of Ascarina . The subsequent early Holocene is characterised by podocarp conifer forest and moist mild conditions. Postglacial sea-level rise breached the crater rim and deposited 36 m of estuarine mud after ca. 9000 cal. a BP. Copyright © 2011 John Wiley & Sons, Ltd.

Description: Dissolved inorganic carbon isotope (δ 13 C DIC ) is an important tool to reveal the carbon cycle in lake systems. However, there are only few studies focusing on the spatial variation of δ 13 C DIC of closed lakes. Here we analyze the characteristics of δ 13 C DIC of 24 sampled lakes (mainly closed lakes) across the Qiangtang Plateau (QTP) and identify the driving factors for its spatial variation. The δ 13 C DIC value of these observed lakes varies in the range of -15.0‰ 3.2‰, with an average value of -1.2‰. The δ 13 C DIC value in closed lakes is close to the atmospheric isotopic equilibrium value, much higher than that in rivers and freshwater lakes reported before. The high δ 13 C DIC value of closed lakes is mainly attributed to the significant contribution of carbonate weathering in the catchment and the evasion of dissolved CO 2 induced by the strong evaporation of lake water. The δ 13 C DIC value of closed lakes has a logarithmic correlation with water chemistry (TDS, DIC and pCO 2 ), also suggesting that the evapo-concentration of lake water can influence the δ 13 C DIC value. The δ 13 C DIC value shows two opposite logarithmic correlations with lake size depending on the δ 13 C DIC range. This study suggests that the δ 13 C in carbonates in lacustrine sediments can be taken as an indicator of lake volume variation in closed lakes on QTP. Copyright © 2011 John Wiley & Sons, Ltd.

Description: Angiotensin II (Ang II), a biologically active peptide of the renin–angiotensin system (RAS), plays an important role in promoting cell migration via Angiotensin II type 1 receptor (AT1R). In this study, we examined the mechanisms by which Ang II affected cell migration in AT1R-positive MDA-MB-231 human breast cancer cells. Ang II increased cell migration and expression of matrix metalloproteinase (MMP)-2,-9 in a dose-dependent manner. Ang II-mediated cell migration was reduced by specific blocking of MMP-2 and MMP-9, as well as with pretreatment with inhibitors of AT1R, phosphatidylinositol 3-kinase (PI3K), Akt, and NF-κB. Similarly, Ang II-mediated expression of MMP-2,-9 was downregulated by pretreatment with inhibitors of AT1R and PI3K. In addition, Ang II treatment significantly induced phosphorylation of PI3K, Akt, and resulted in increased NF-κB activity. These findings suggest that Ang II activates the AT1R/PI3K/Akt pathway, which further activates IKKα/β and NF-κB, resulting in enhanced expression of MMP-2,-9 and migration in human breast cancer cells. Therefore, targeting Ang II/AT1R/PI3K/Akt/NF-κB signaling could be a novel anti-metastatic therapy for breast cancer. J. Cell. Physiol. © 2014 Wiley Periodicals, Inc.

Description: Polycrystalline samples of San Carlos olivine were deformed at high-pressure (2.8–7.8 GPa), high-temperature (1153 to 1670 K), and strain rates between 7.10−6 and 3.10−5 s−1, using the D-DIA apparatus. Stress and strain were measured in situ using monochromatic X-rays diffraction and imaging, respectively. Based on the evolution of lattice strains with total bulk strain and texture development, we identified three deformation regimes, one at confining pressures below 3–4 GPa, one above 4 GPa, both below 1600 K, and one involving growth of diffracting domains associated with mechanical softening above ∼1600 K. The softening is interpreted as enhanced grain boundary migration and recovery. Below 1600 K, elasto-plastic self-consistent analysis suggests that below 3–4 GPa, deformation in olivine occurs with large contribution from the so-called “a-slip” system [100](010). Above ∼4 GPa, the contribution of the a-slip decreases relative to that of the “c-slip” [001](010). This conclusion is further supported by texture refinements. Thus for polycrystalline olivine, the evolution in slip systems found by previous studies may be progressive, starting from as low as 3–4 GPa and up to 8 GPa. During such a gradual change, activation volumes measured on polycrystalline olivine cannot be linked to a particular slip system straightforwardly. The quest for “the” activation volume of olivine at high pressure should cease at the expense of detailed work on the flow mechanisms implied. Such evolution in slip systems should also affect the interpretation of seismic anisotropy data in terms of upper mantle flow between 120 and 300 km depth.

Description: The multi-anvil high-pressure technique is an important tool in high-pressure mineralogy and petrology, as well as in chemical synthesis, allowing the treatment of large (millimeter-size) samples of minerals, rocks, and other materials at pressures of a few GPa to over 25 GPa and simultaneous uniform temperatures up to 2500 °C and higher. A series of cell assemblies specially designed and implemented for interlaboratory use are described here. In terms of the size of the pressure medium and the anvil truncation size, the five sizes of assemblies developed here are an 8/3, 10/5, 14/8, 18/12, and 25/15 assembly. As of this writing, these assemblies are in widespread use at many laboratories. The details of design, construction, and materials developed or used for the assemblies are presented here.

Description: Questions Above-ground, below-ground and individual mass–density relationships for perennial herbs were examined along a natural precipitation gradient in northern Tibet. We asked: (1) how do the self-thinning exponents respond to variation in precipitation; and (2) what mechanisms drive the observed population self-thinning? Location The alpine grassland of northern Tibet. Methods Forty-seven fenced sites along a precipitation gradient were established and surveyed in 2011 and 2012. Data (geographic coordinates, elevation, and vegetation information) were collected for Stipa purpurea populations at each site. Population self-thinning exponents were estimated using reduced major axis regression. Results The self-thinning exponents for below-ground (−1.27, −0.47) and individual biomass (−1.26, −0.46) increased with increasing mean annual precipitation, but those for above-ground biomass decreased with precipitation (0.18, −0.25). Soil resources (moisture and nutrients) are a more important constraining factor for below-ground components than light is for above-ground components. Root competition for below-ground resources dominated in S .  purpurea population self-thinning. The driving force of density regulation changed from above-ground competition to below-ground competition with increased drought stress. Our results indicate that an increased root/shoot ratio was linked to enhanced below-ground competition and weakened above-ground competition. Our study further confirmed the hypothesis that plant populations in different environments exhibit different biomass allocation patterns, which, in turn, leads to different biomass–density relationships. Conclusions Our study revealed the mechanisms of population self-thinning for perennial herbs in the extreme environment of northern Tibet, where below-ground processes play a critical role in regulating population self-thinning. Our study also advances understanding of the interactions between above- and below-ground processes, providing baseline knowledge useful for local grassland management. Above–ground, below–ground and individual mass–density relationships for Stipa purpurea populations were examined along a natural precipitation gradient in Northern Tibet. Our study revealed the mechanisms of population self–thinning for perennial herbs in the extreme environment of Northern Tibet, where below–ground process plays a critical role in regulating population self–thinning.

Description: [1]  The mass balance in the Inner Tibet Plateau (ITP) derived from satellite gravimetry (GRACE) showed a positive rate that was attributed to the glacier mass gain, whereas glaciers in the region, from other field-based studies, showed an overall mass loss. In this study, we examine lake's water level and mass changes in the Tibetan Plateau (TP) and suggest that the increased mass measured by GRACE was predominately due to the increased water mass in lakes. For the 200 lakes in the TP with 4 to 7 years of ICESat data available, the mean lake level and total mass change rates were +0.14 m/year and +4.95 Gt/year, respectively. Compared those in the TP, 118 lakes in the ITP showed higher change rates (+0.20 m/year and +4.28 Gt/year), accounting for 59% area and 86% mass increase of the 200 lakes. The lake's mass increase rate in the ITP explains the 61% increased mass (~7 Gt/year) derived from GRACE [ Jacob et al ., 2012], while it only accounts for 53% of the total lake area in the ITP.