bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global Ionospheric Current System Associated With Penetration Electric Field and New Mechanism for the Generation of Dayside Westward Electric Field at Low Latitudes During Northward IMF
Authors: Huang Chao‐Song 
Published: April 2019

AbstractIt is well known that penetration and shielding electric fields are related to the southward and northward turnings of the interplanetary magnetic field (IMF). The shielding electric field is assumed to be caused by the region‐2 field‐aligned currents. We have analyzed observations of equatorial ionospheric plasma drifts measured by the Jicamarca incoherent scatter radar and global ground magnetic perturbations in an event when the IMF fluctuates between southward and northward. The vertical plasma drifts/zonal electric fields in the dayside equatorial ionosphere are well correlated with the IMF reorientations, indicating that the disturbance electric fields in the equatorial ionosphere are caused by the IMF. Magnetometer data are used to reconstruct the global ionospheric currents and convection. The DP 2 current system consists of a large vortex in the afternoon‐evening sector and a much smaller vortex in the dawn sector, and the ionospheric currents associated with the dayside penetration electric field extend into the postmidnight sector. The downward plasma drift and southward magnetic perturbations at equatorial latitudes during northward IMF are correlated with the reverse convection in the polar cap, indicating that the polar electric field associated with the reverse convection is an important source of the westward electric field in the dayside equatorial region. A new mechanism is proposed to explain the generation of westward electric field in the dayside equatorial ionosphere during northward IMF.
On the Nature of the Intraseasonal Variability of Nighttime Ionospheric Irregularities Over Taiwan
Authors: Joshi L. M. , Tsai L. C. , Su S. Y. , Caton Ronald G. , Groves K. M. , Lu C. H. 
Published: April 2019

AbstractThe nature of intraseasonal (within a season) variability of the nighttime ionospheric irregularities has been studied utilizing the observation of the recently installed VHF scintillation receiver from Pingtung, Taiwan. Investigation is based on observations made in 2015 (high‐moderate solar epoch) and 2017 (low solar epoch). Detailed investigation has revealed coexistence of planetary‐scale variability (3–7 days), 10‐ to 16‐day variability, and > 25‐day variability in 2015. Interestingly, the Lomb‐Scargle frequency domain analysis indicated the variability of larger timescales to display somewhat greater amplitudes. The virtual height of the F layer, h'F, over Sanya, also indicated intraseasonal periodicities similar to S4 periodicities observed at Pingtung. Observations have also revealed that, equatorial plasma bubbles (EPBs) over Pingtung tended to occur on contiguous nights as compared to isolated occurrence, and > 60% of the EPB nights were part of two or more (up to 6) nights of contiguous occurrence. Spectral analysis revealed a quasi‐27‐day variability in the ap and AE geomagnetic indices presumably associated with the solar rotation period. The time period of geomagnetic variability corresponded with the period of dominant S4 variability, indicating that the effect of geomagnetic activity on the low‐latitude ionosphere can be periodic in nature. In 2017 (low solar flux), even with a very low occurrence of ionospheric irregularities, planetary‐scale variability was observed. The dominant period of S4 variability in the autumnal equinox was highly correlated with the periodic geomagnetic activity. Results indicate that a deeper understanding of the periodic intraseasonal variability can be imperative for extended range forecast/prediction of ionospheric irregularities.
A Numerical Model Analysis of the Mean and Seasonal Nitrogen Budget on the Northeast U.S. Shelf
Authors: Zhang Shuwen , Stock Charles A. , Curchitser Enrique N. , Dussin Raphael 
Published: April 2019

AbstractThe supply of nitrogen is a primary limiting factor for the productivity of the Northeast United States (NEUS) continental shelf. In this study, a 12‐year (1996–2007) retrospective physical‐biogeochemical simulation over the Northwest Atlantic was used to analyze the mean and seasonal NEUS shelf nitrogen budget, including the connections between shelf subregions: the Gulf of Maine/Georges Bank (GoM/GB), and the Mid‐Atlantic Bight (MAB). The model captures the primary mean and seasonal patterns of shelf circulation, nitrate, and plankton dynamics. Results confirm aspects of previous nitrogen budget analyses, including the dominance of offshore nitrogen influxes into the GoM/GB and the prominent role of riverine influxes and sedimentary denitrification in the MAB. However, detailed spatiotemporal analysis of nitrogen fluxes highlights the importance of dispersed inflows of shallow to intermediate depth waters (0–75 m), which can at times exceed the deep nitrogen influx emphasized in previous studies. A seasonal analysis shows a pronounced shift from the net import of nitrogen to the GoM/GB region during late fall and winter, to the net export of nitrogen from the region in the spring and early summer. The MAB, in contrast, consistently exports nitrogen to offshore waters. The prominence of the 0‐75m nitrogen supply has implications for the roles of Labrador Slope Water and Atlantic Temperate Slope Water on the NEUS ecosystems, as Atlantic Temperate Slope Water has greater nitrate concentrations than Labrador Slope Water at depth but often less at the surface. Results suggest the need for further study of shallow to intermediate depth inflows beyond those from the Scotian Shelf, particularly during the fall/winter of net nitrogen inflow.
Farmer and Farmland Owner Views on Spatial Targeting for Soil Conservation and Water Quality
Authors: Zimmerman E. K. , Tyndall J. C. , Schulte L. A. , Larsen G. L. D. 
Published: April 2019

AbstractThe U.S. Corn Belt is highly productive with respect to grain and livestock commodities but often neglects to deliver other benefits such as soil stability, nutrient retention, and clean water. New precision technologies and conservation planning frameworks offer opportunities to adapt the current agricultural system to meet environmental goals along with production by strategically placing best management practices (BMPs) to target and address specific in‐field resource concerns. To understand farmers' and farmland owners' willingness to participate in such targeting schemes, we conducted in‐depth interviews with 18 farmers and farmland owners whose fields were targeted for soil and nutrient loss in two watersheds in central Iowa. We examined their current application of BMPs and opportunities and constraints to further adoption. We found that farmers and farmland owners often recognized the importance of producing a diverse suite of on‐ and off‐farm environmental benefits but lacked the context, information, certainty, and strong incentives to manage for them. Interviewees were generally receptive to using technologies to target BMPs to areas with resource concerns but expressed concerns about applications on their own land. They specifically perceived challenges related to cost, management complexity, coordination with government programs, and loss of autonomy. For broad acceptance, a spatially targeted conservation approach would need to be paired with expanded partnerships, trusted technical service, and adaptation incentives to reduce farm‐level economic trade‐offs.
S-nitrosylation of the Peroxiredoxin-2 promotes S-nitrosoglutathione-mediated lung cancer cells apoptosis via AMPK-SIRT1 pathway
Authors: Zhang Yihan , Sun Changning , Xiao Guokai , Shan Hui , Tang Luyao , Yi Yujiao , Yu Wengong , Gu Yuchao 
Published: April 2019

AbstractProtein S-nitrosylation, the redox-based posttranslational modification of a cysteine thiol by the attachment of a nitric oxide (NO) group, is responsible for a variety of signaling effects. Dysregulation of S-nitrosylation may be directly linked to cancer apoptotic resistance and cancer therapy outcomes, emphasizing the importance of S-nitrosylation in cancer. Peroxiredoxin-2 (Prdx2), an antioxidant enzyme, plays an important role in the protection of cancer cells from oxidative radical damage caused by hydrogen dioxide (H2O2), which is a potential target for cancer therapy. Our studies showed that, as an endogenous NO carrier, S-nitrosoglutathione (GSNO) induced apoptosis in lung cancer cells via nitrosylating Prdx2. The nitrosylation of Prdx2 at Cys51 and Cys172 sites disrupted the formation of Prdx2 dimer and repressed the Prdx2 antioxidant activity, causing the accumulation of endogenous H2O2. H2O2 activated AMPK, which then phosphorylated SIRT1 and inhibited its deacetylation activity toward p53 in A549 cells or FOXO1 in NCI-H1299 cells. Taken together, our results elucidate the roles and mechanisms of Prdx2 S-nitrosylation at Cys51 and Cys172 sites in lung cancer cells apoptosis and this finding provides an effective lung cancer treatment strategy for managing aberrant Prdx2 activity in lung cancers.
Blockade of miR-142-3p promotes anti-apoptotic and suppressive function by inducing KDM6A-mediated H3K27me3 demethylation in induced regulatory T cells
Authors: Gao Ji , Gu Jian , Pan Xiongxiong , Gan Xiaojie , Ju Zheng , Zhang Shaopeng , Xia Yongxiang , Lu Ling , Wang Xuehao 
Published: April 2019

AbstractIn vitro induced human regulatory T cells (iTregs) have in vivo therapeutic utility. MicroRNAs (miRNAs) are a family of approximately 22-nucleotide non-coding RNAs that are processed from longer precursors by the RNases Drosha and Dicer. miRNAs regulate post-transcriptional protein expression through messenger RNA destabilization or translational silencing; miR-142-3p regulates natural Treg function through autophagy. We hypothesized that this miRNA may also have an iTreg regulation function. Antagomir-mediated knockdown of miR-142-3p improved Foxp3 (forkhead box P3) expression, regulatory function, cytokine expression, and apoptosis of iTregs in vitro, with or without inflammatory cytokine stimulation. miR-142-3p knockdown increased autophagy-related protein 16-1-mediated autophagy. Target prediction and luciferase assay results indicated that miR-142-3p binds directly to lysine demethylase 6A (KDM6A), which resulted in demethylation of H3K27me3 and in turn upregulated expression of the anti-apoptotic protein Bcl-2. Based on these results, we propose a novel strategy that uses knockdown of miR-142-3p to enhance anti-apoptotic ability and function of iTregs by increasing KDM6A and Bcl-2 expression. This approach might be used as a treatment to control established chronic immune-mediated autoimmune and inflammatory diseases.
Exosomes from adipose-derived mesenchymal stem cells prevent cardiomyocyte apoptosis induced by oxidative stress
Authors: Liu Zhi , Xu Yueqiao , Wan Yungao , Gao Jing , Chu Yanyan , Li Jing 
Published: April 2019

AbstractExosomes from bone marrow stem cells or cardiac progenitor cells can reduce apoptosis in myocardial cells after ischemia and reperfusion injury. However, there is little known about the effects of exosomes from adipose-derived stem cells (ADSCs), which are more abundant and have a lower risk of side effects. The aim of this study was to characterize exosomes from ADSCs and evaluate their cardioprotective actions against ischemia reperfusion injury. The exosomes were isolated from ADSCs and analyzed by protein marker expression, transmission electron microscopy, and nanoparticle tracking analysis. The ADSC-exosomes were then used for ex vivo investigation of the cardioprotective effects on cardiomyocytes after exposure to oxidative stress. Exosomes from ADSCs exhibited a diameter of 150 nm and expressed the marker proteins, CD9 and CD29. ADSC-exosomes had no effect on proliferation of untreated cardiomyocytes. In contrast, ADSC-derived exosomes reduced apoptosis in myocardial cells subjected to oxidative stress. This study confirms that exosomes originating from ADSCs can protect cardiomyocytes from oxidative stress.
Staged developmental mapping and X chromosome transcriptional dynamics during mouse spermatogenesis
Authors: Ernst Christina , Eling Nils , Martinez-Jimenez Celia P. , Marioni John C. , Odom Duncan T. 
Published: April 2019

AbstractMale gametes are generated through a specialised differentiation pathway involving a series of developmental transitions that are poorly characterised at the molecular level. Here, we use droplet-based single-cell RNA-Sequencing to profile spermatogenesis in adult animals and at multiple stages during juvenile development. By exploiting the first wave of spermatogenesis, we both precisely stage germ cell development and enrich for rare somatic cell-types and spermatogonia. To capture the full complexity of spermatogenesis including cells that have low transcriptional activity, we apply a statistical tool that identifies previously uncharacterised populations of leptotene and zygotene spermatocytes. Focusing on post-meiotic events, we characterise the temporal dynamics of X chromosome re-activation and profile the associated chromatin state using CUT&RUN. This identifies a set of genes strongly repressed by H3K9me3 in spermatocytes, which then undergo extensive chromatin remodelling post-meiosis, thus acquiring an active chromatin state and spermatid-specific expression.
Enzyme-responsive progelator cyclic peptides for minimally invasive delivery to the heart post-myocardial infarction
Authors: Carlini Andrea S. , Gaetani Roberto , Braden Rebecca L. , Luo Colin , Christman Karen L. , Gianneschi Nathan C. 
Published: April 2019

AbstractInjectable biopolymer hydrogels have gained attention for use as scaffolds to promote cardiac function and prevent negative left ventricular (LV) remodeling post-myocardial infarction (MI). However, most hydrogels tested in preclinical studies are not candidates for minimally invasive catheter delivery due to excess material viscosity, rapid gelation times, and/or concerns regarding hemocompatibility and potential for embolism. We describe a platform technology for progelator materials formulated as sterically constrained cyclic peptides which flow freely for low resistance injection, and rapidly assemble into hydrogels when linearized by disease-associated enzymes. Their utility in vivo is demonstrated by their ability to flow through a syringe and gel at the site of MI in rat models. Additionally, synthetic functionalization enables these materials to flow through a cardiac injection catheter without clogging, without compromising hemocompatibility or cytotoxicity. These studies set the stage for the development of structurally dynamic biomaterials for therapeutic hydrogel delivery to the MI.
Effect of molecular architecture on ring polymer dynamics in semidilute linear polymer solutions
Authors: Zhou Yuecheng , Hsiao Kai-Wen , Regan Kathryn E. , Kong Dejie , McKenna Gregory B. , Robertson-Anderson Rae M. , Schroeder Charles M. 
Published: April 2019

AbstractUnderstanding the dynamics of ring polymers is a particularly challenging yet interesting problem in soft materials. Despite recent progress, a complete understanding of the nonequilibrium behavior of ring polymers has not yet been achieved. In this work, we directly observe the flow dynamics of DNA-based rings in semidilute linear polymer solutions using single molecule techniques. Our results reveal strikingly large conformational fluctuations of rings in extensional flow long after the initial transient stretching process has terminated, which is observed even at extremely low concentrations (0.025 c*) of linear polymers in the background solution. The magnitudes and characteristic timescales of ring conformational fluctuations are determined as functions of flow strength and polymer concentration. Our results suggest that ring conformational fluctuations arise due to transient threading of linear polymers through open ring chains stretching in flow.
Visualizing conformation transitions of the Lipid II flippase MurJ
Authors: Kuk Alvin C. Y. , Hao Aili , Guan Ziqiang , Lee Seok-Yong 
Published: April 2019

AbstractThe biosynthesis of many polysaccharides, including bacterial peptidoglycan and eukaryotic N-linked glycans, requires transport of lipid-linked oligosaccharide (LLO) precursors across the membrane by specialized flippases. MurJ is the flippase for the lipid-linked peptidoglycan precursor Lipid II, a key player in bacterial cell wall synthesis, and a target of recently discovered antibacterials. However, the flipping mechanism of LLOs including Lipid II remains poorly understood due to a dearth of structural information. Here we report crystal structures of MurJ captured in inward-closed, inward-open, inward-occluded and outward-facing conformations. Together with mutagenesis studies, we elucidate the conformational transitions in MurJ that mediate lipid flipping, identify the key ion for function, and provide a framework for the development of inhibitors.
Measuring topology from dynamics by obtaining the Chern number from a linking number
Authors: Tarnowski Matthias , Ünal F. Nur , Fläschner Nick , Rem Benno S. , Eckardt André , Sengstock Klaus , Weitenberg Christof 
Published: April 2019

AbstractInteger-valued topological indices, characterizing nonlocal properties of quantum states of matter, are known to directly predict robust physical properties of equilibrium systems. The Chern number, e.g., determines the quantized Hall conductivity of an insulator. Using non-interacting fermionic atoms in a periodically driven optical lattice, here we demonstrate experimentally that the Chern number determines also the far-from-equilibrium dynamics of a quantum system. Extending a respective proposal to Floquet systems, we measure the linking number that characterizes the trajectories of momentum-space vortices emerging after a strong quench. We observe that it directly corresponds to the ground-state Chern number. This one-to-one relation between a dynamical and a static topological index allows us to experimentally map out the phase diagram of our system. Furthermore, we measure the instantaneous Chern number and show that it remains zero under the unitary dynamics.
Scalable dissolution-dynamic nuclear polarization with rapid transfer of a polarized solid
Authors: Kouřil Karel , Kouřilová Hana , Bartram Samuel , Levitt Malcolm H. , Meier Benno 
Published: April 2019

AbstractIn dissolution-dynamic nuclear polarization, nuclear spins are hyperpolarized at cryogenic temperatures using radicals and microwave irradiation. The hyperpolarized solid is dissolved with hot solvent and the solution is transferred to a secondary magnet where strongly enhanced magnetic resonance signals are observed. Here we present a method for transferring the hyperpolarized solid. A bullet containing the frozen, hyperpolarized sample is ejected using pressurized helium gas, and shot into a receiving structure in the secondary magnet, where the bullet is retained and the polarized solid is dissolved rapidly. The transfer takes approximately 70 ms. A solenoid, wound along the entire transfer path ensures adiabatic transfer and limits radical-induced low-field relaxation. The method is fast and scalable towards small volumes suitable for high-resolution nuclear magnetic resonance spectroscopy while maintaining high concentrations of the target molecule. Polarization levels of approximately 30% have been observed for 1-13C-labelled pyruvic acid in solution.
Origin and differentiation trajectories of fibroblastic reticular cells in the splenic white pulp
Authors: Cheng Hung-Wei , Onder Lucas , Novkovic Mario , Soneson Charlotte , Lütge Mechthild , Pikor Natalia , Scandella Elke , Robinson Mark D. , Miyazaki Jun-ichi , Tersteegen Anne , Sorg Ursula , Pfeffer Klaus , Rülicke Thomas , Hehlgans Thomas , Ludewig Burkhard 
Published: April 2019

AbstractThe splenic white pulp is underpinned by poorly characterized stromal cells that demarcate distinct immune cell microenvironments. Here we establish fibroblastic reticular cell (FRC)-specific fate-mapping in mice to define their embryonic origin and differentiation trajectories. Our data show that all reticular cell subsets descend from multipotent progenitors emerging at embryonic day 19.5 from periarterial progenitors. Commitment of FRC progenitors is concluded during the first week of postnatal life through occupation of niches along developing central arterioles. Single cell transcriptomic analysis facilitated deconvolution of FRC differentiation trajectories and indicated that perivascular reticular cells function both as adult lymphoid organizer cells and mural cell progenitors. The lymphotoxin-β receptor-independent sustenance of postnatal progenitor stemness unveils that systemic immune surveillance in the splenic white pulp is governed through subset specification of reticular cells from a multipotent periarterial progenitor cell. In sum, the finding that discrete signaling events in perivascular niches determine the differentiation trajectories of reticular cell networks explains the development of distinct microenvironmental niches in secondary and tertiary lymphoid tissues that are crucial for the induction and regulation of innate and adaptive immune processes.
Characterising side chains in large proteins by protonless 13C-detected NMR spectroscopy
Authors: Pritchard Ruth B. , Hansen D. Flemming 
Published: April 2019

AbstractSide chains cover protein surfaces and are fundamental to processes as diverse as substrate recognition, protein folding and enzyme catalysis. However, characterisation of side-chain motions has so far been restricted to small proteins and methyl-bearing side chains. Here we present a class of methods, based on 13C-detected NMR spectroscopy, to more generally quantify motions and interactions of side chains in medium-to-large proteins. A single, uniformly isotopically labelled sample is sufficient to characterise the side chains of six different amino acid types. Side-chain conformational dynamics on the millisecond time-scale can be quantified by incorporating chemical exchange saturation transfer (CEST) into the presented methods, whilst long-range 13C-13C scalar couplings reporting on nanosecond to millisecond motions can be quantified in proteins as large as 80 kDa. The presented class of methods promises characterisation of side-chain behaviour at a level that has so far been reserved for the protein backbone.
PDGFRα+ stromal adipocyte progenitors transition into epithelial cells during lobulo-alveologenesis in the murine mammary gland
Authors: Joshi Purna A. , Waterhouse Paul D. , Kasaian Katayoon , Fang Hui , Gulyaeva Olga , Sul Hei Sook , Boutros Paul C. , Khokha Rama 
Published: April 2019

AbstractThe mammary gland experiences substantial remodeling and regeneration during development and reproductive life, facilitated by stem cells and progenitors that act in concert with physiological stimuli. While studies have focused on deciphering regenerative cells within the parenchymal epithelium, cell lineages in the stroma that may directly contribute to epithelial biology is unknown. Here we identify, in mouse, the transition of a PDGFRα+ mesenchymal cell population into mammary epithelial progenitors. In addition to being adipocyte progenitors, PDGFRα+ cells make a de novo contribution to luminal and basal epithelia during mammary morphogenesis. In the adult, this mesenchymal lineage primarily generates luminal progenitors within lobuloalveoli during sex hormone exposure or pregnancy. We identify cell migration as a key molecular event that is activated in mesenchymal progenitors in response to epithelium-derived chemoattractant. These findings demonstrate a stromal reservoir of epithelial progenitors and provide insight into cell origins and plasticity during mammary tissue growth.