ALBERT

Description: Paracrine regulation in mesenchymal stem cells: the role of Rap1 Cell Death and Disease 6, e1932 (October 2015). doi:10.1038/cddis.2015.285 Authors: Y Zhang, Z Zhang, F Gao, H-F Tse, V Tergaonkar & Q Lian

Description: The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap Eg changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 1010 can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 1010%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices. Scientific Reports 4 doi: 10.1038/srep07587

Description: This paper presents a design methodology of multisine signals, so that they can be used as phase references or standards convenient for modulated measurements. To achieve an extendable measurement bandwidth, the spectrum of each multisine is designed with three successive segments, where the left (lower-frequency) and right (higher-frequency) ending ones have the same phase spectra. In this way several multisines, one by one overlapped at the ending segments, can jointly serve as an integrated phase reference/standard signal, which in theory has an arbitrarily extendable bandwidth. By the example of “Schroeder” phase relationship, the proposed method is experimentally verified for wideband modulated measurements, where the designed multisines are used as the phase references and standards, respectively, of a nonlinear vector network analyzer test bed. In this work, a phase measurement error less than ±1 deg. is experimentally confirmed for 1601-tone measurements with 160 MHz modulation bandwidth around 2 GHz.

Description: 〈sec〉〈st〉Synopsis〈/st〉〈p〉〈textbox textbox-type="graphic"〉〈p〉〈inline-fig〉〈/inline-fig〉〈/p〉〈/textbox〉〈/p〉 〈p〉Combining genetic mouse models and global expression profiling, the transcription factor YinYang1 (YY1) is shown to exert binary roles in muscle stem cells to switch energy metabolism and allow for expansion during muscle development and injury response.〈/p〉 〈p〉 〈l type="unord"〉〈li〉〈p〉Conditional deletion of YY1 in Pax7-expressing muscle progenitor cells causes defective muscle development and early postnatal death.〈/p〉〈/li〉 〈li〉〈p〉Inducible ablation of YY1 in adult muscle impairs acute injury induced muscle regeneration and aggravates chronic stress in muscular dystrophy mice.〈/p〉〈/li〉 〈li〉〈p〉YY1 deletion effects are cell-autonomous and reduce muscle stem cell activation and proliferation.〈/p〉〈/li〉 〈li〉〈p〉YY1 represses expression of mitochondrial genes in stem cells.〈/p〉〈/li〉 〈li〉〈p〉YY1 activates glycolytic genes during stem cell activation via increasing Hif1α protein stability.〈/p〉〈/li〉〈/l〉 〈/p〉〈/sec〉

Description: 〈p〉Skeletal muscle satellite cells (SCs) are adult muscle stem cells responsible for muscle regeneration after acute or chronic injuries. The lineage progression of quiescent SC toward activation, proliferation, and differentiation during the regeneration is orchestrated by cascades of transcription factors (TFs). Here, we elucidate the function of TF Yin Yang1 (YY1) in muscle regeneration. Muscle-specific deletion of YY1 in embryonic muscle progenitors leads to severe deformity of diaphragm muscle formation, thus neonatal death. Inducible deletion of YY1 in SC almost completely blocks the acute damage-induced muscle repair and exacerbates the chronic injury-induced dystrophic phenotype. Examination of SC revealed that YY1 loss results in cell-autonomous defect in activation and proliferation. Mechanistic search revealed that YY1 binds and represses mitochondrial gene expression. Simultaneously, it also stabilizes Hif1α protein and activates Hif1α-mediated glycolytic genes to facilitate a metabolic reprogramming toward glycolysis which is needed for SC proliferation. Altogether, our findings have identified YY1 as a key regulator of SC metabolic reprogramming through its dual roles in modulating both mitochondrial and glycolytic pathways.〈/p〉

Description: Central Asia is currently a semiarid-arid region, dominated by the Westerlies. It is important to understand mechanisms of climate and precipitation changes here, as water availability in the region is crucial today and in the future. High-resolution, absolutely-dated oxygen isotope (δ18O) records of stalagmites from Kesang Cave characterize a dynamic precipitation history over most of the past 500,000 years. This record demonstrates, for the first time, that climate change in the region exhibits a processional rhythm with abrupt inceptions of low δ18O speleothem growth at times of high Northern Hemisphere summer insolation followed by gradual δ18O increases that track decreases of insolation. These observations and interpretations contrast with the interpretation of nearby, but higher elevation ice core records. The absolutely-dated cave δ18O shifts can be used to correlate the regional climate variability by providing chronological marks. Combined with other paleoclimate records, the Kesang observations suggest that possible incursions of Asian summer monsoon rainfall or related moisture into the Kesang site and/or adjacent areas during the high insolation times may play an important role in changing orbital-scale hydrology of the region. Based on our record, arid climate will prevail in this region for the next several millennia, providing that anthropogenic effects do not supersede natural processes.

Description: The bi-spectral method retrieves cloud optical thickness ( τ ) and cloud droplet effective radius ( r e ) simultaneously from a pair of cloud reflectance observations, one in a visible or near infrared (VIS/NIR) band and the other in a shortwave-infrared (SWIR) band. A cloudy pixel is usually assumed to be horizontally homogeneous in the retrieval. Ignoring sub-pixel variations of cloud reflectances can lead to a significant bias in the retrieved τ and r e . In the literature, the retrievals of τ and r e are often assumed to be independent and considered separately when investigating the impact of sub-pixel cloud reflectance variations on the bi-spectral method. As a result, the impact on τ is contributed only by the sub-pixel variation of VIS/NIR band reflectance and the impact on r e only by the sub-pixel variation of SWIR band reflectance. In our new framework, we use the Taylor expansion of a two-variable function to understand and quantify the impacts of sub-pixel variances of VIS/NIR and SWIR cloud reflectances and their covariance on the τ and r e retrievals. This framework takes into account the fact that the retrievals are determined by both VIS/NIR and SWIR band observations in a mutually dependent way. In comparison with previous studies, it provides a more comprehensive understanding of how sub-pixel cloud reflectance variations impact the τ and r e retrievals based on the bi-spectral method. In particular, our framework provides a mathematical explanation of how the sub-pixel variation in VIS/NIR band influences the r e retrieval and why it can sometimes outweigh the influence of variations in the SWIR band and dominate the error in r e retrievals, leading to a potential contribution of positive bias to the r e retrieval. We test our framework using synthetic cloud fields from a large-eddy simulation and real observations from MODIS. The predicted results based on our framework agree very well with the numerical simulations. Our framework can be used to estimate the retrieval uncertainty from sub-pixel reflectance variations in operational satellite cloud products and to help understand the differences in τ and r e retrievals between two instruments.

Description: High-pressure (HP) metagreywacke from the Namche Barwa complex, Eastern Himalayan Syntaxis (EHS), consists of garnet, biotite, plagioclase, quartz, rutile and ilmenite with or without K-feldspar, sillimanite, cordierite, spinel and orthopyroxene. Two types of metagreywacke are recognized: medium-temperature (MT) and high-temperature (HT) types. Garnet in the MT metagreywacke shows significant growth zoning and contains lower MgO than the weakly zoned garnet in the HT metagreywacke. Petrographic observations and phase equilibria modelling for four representative samples indicate that both types of metagreywacke experienced clockwise P–T paths subdivided into three stages: stage I is the pre-peak prograde to pressure peak ( P max ) stage characterized by progressive increase in P–T conditions. The P max conditions are estimated using the garnet composition with maximum CaO, being 12.5–13.5 kbar and 685–725 °C for the MT metagreywacke, and 15–16 kbar and 825–835 °C for the HT one. Stage II is the post- P max decompression with heating or near-isothermal to T max stage and the T max conditions, constrained using the garnet compositions with maximum MgO, are 11 kbar and 760 °C for the MT metagreywacke, and ~12 kbar and 830–845 °C for the HT one. The modelled mineral assemblages at T max are garnet + biotite + K-feldspar + rutile + plagioclase ± ilmenite in the presence of melt for both types of metagreywacke, consistent with the petrographic observations. Stage III is the post- T max retrograde metamorphism, characterized by decompression and cooling. The modelling suggests that the melts with high Na/K ratios (1.7–5.2) have been produced during stages I and II, which could be responsible for the formation of sodium-rich leucogranites. This study and previous results indicate that the Higher Himalayan Crystallines (HHC) in the Eastern Himalayan Syntaxis consist of MT–HP and HT–HP metamorphic units separated by a speculated tectonic contact. Petrological and structural discontinuities within the EHS cannot be easily interpreted with ‘tectonic aneurysm’ model. This article is protected by copyright. All rights reserved.

Description: Wentilactone B induces G2/M phase arrest and apoptosis via the Ras/Raf/MAPK signaling pathway in human hepatoma SMMC-7721 cells Cell Death and Disease 4, e657 (June 2013). doi:10.1038/cddis.2013.182 Authors: Z Zhang, L Miao, C Lv, H Sun, S Wei, B Wang, C Huang & B Jiao

Description: 〈sec〉〈st〉Synopsis〈/st〉〈p〉〈textbox textbox-type="graphic"〉〈p〉〈inline-fig〉〈/inline-fig〉〈/p〉〈/textbox〉〈/p〉 〈p〉An interaction between mitochondrial outer membrane protein FUNDC1 and chaperone HSC70 promotes degradation or aggregation of unfolded cytosolic proteins on the mitochondria, thereby maintaining cellular proteostasis but reducing mitochondrial fitness.〈/p〉 〈p〉 〈l type="unord"〉〈li〉〈p〉Upon proteostatic stress, FUNDC1 interacts with HSC70 to promote the mitochondrial translocation of proteasomal clients, which are subsequently degraded by LONP1.〈/p〉〈/li〉 〈li〉〈p〉Mitochondrial translocation of proteasomal clients promotes the formation of mitochondrion-associated protein aggregates (MAPAs).〈/p〉〈/li〉 〈li〉〈p〉MAPAs are distinct from aggresomes and contain ubiquitinated proteins, P62 and mitochondrial proteins.〈/p〉〈/li〉 〈li〉〈p〉FUNDC1 mediates the autophagic degradation of MAPAs, linking mitophagy and aggrephagy.〈/p〉〈/li〉 〈li〉〈p〉FUNDC1/HSC70-mediated mitochondrial translocation of proteasomal clients prior to MAPA formation contributes to cell senescence.〈/p〉〈/li〉〈/l〉 〈/p〉〈/sec〉