Origin of geochemical heterogeneity in the mantle : constraints from volcanism associated with Hawaiian and Kerguelen mantle plumes

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007.Includes bibliographical references.Lavas derived from long-lived mantle plumes provide important information of mantle compositions and the processes that created the geochemical heterogeneity within the mantle. Kerguelen and Hawaii are two long-lived mantle plumes and lavas associated with them have very different geochemical characteristics. In this thesis I studied the geochemical compositions of the lavas associated with Kerguelen plume (Mt. Capitole in Kerguelen Archipelago) and Hawaiian plume (Mauna Kea, East Molokai and West Molokai volcanoes) to understand what processes contributed to the geochemical variations observed in Kerguelen and Hawaiian lavas and the geochemical structure of the mantle beneath them. Mt. Capitole is in the central part of the Kerguelen Archipelago and is attributed to Cenozoic volcanism arising from the Kerguelen hotspot. Based on the study of Mt. Capitole and previous isotopic data for the Kerguelen Plateau, Kerguelen Archipelago and Heard Island, I propose that two stages of mixing can explain the significant Sr, Nd, Hf and Pb isotopic heterogeneity. The first mixing process, best shown by the submarine lavas from Northern Kerguelen Plateau, is between a depleted component (i.e., relatively low 87Sr/86Sr with high 143Nd/144Nd and 176Hf/177Hf), probably related to Southeast Indian Ocean mid-ocean ridge basalt, but possibly intrinsic to the Kerguelen plume, and an enriched Kerguelen plume component. From -34 Ma to 0.7060) and low 143Nd/144Nd ( 1.5 Ma), the oldest volcano on the Kea-trend, maintains the Kea-like geochemical characteristics. As East Molokai and other Kea-trend volcanoes (Mauna Kea, Kohala, Haleakala and West Maui) migrate away from the hotspot and evolve from the shield to postshield stage, isotopic ratios of 87Sr/86Sr decrease and 143Nd/144Nd and 176Hf/177Hf increase in postshield lavas; however, all Kea postshield lavas have similar ratios of Sr, Nd, Hf and Pb showing that the periphery of the hotspot sampled by Kea-trend postshield lavas had long-term geochemical homogeneity (>1.5 My). The temporal changes in Sr, Nd and Hf isotope ratios are attributed to incorporation of a depleted component that dominantly sampled by rejuvenated stage lavas. This depleted component has Kea-trend Pb isotopic characteristics, relatively low 208Pb/204pb at a given 206Pb/204Pb, and it is probably not related to oceanic lithosphere or the source of mid-ocean ridge basalt. The Loa-Kea spatial geochemical differences end at West Molokai shield (- 1.9 Ma) which is the oldest Loa-trend volcano on the double parallel chains. West Molokai shield includes lavas with Loa- and Kea-like geochemical characteristics; a mixed Loa- Kea source is required. In contrast, West Molokai postshield lavas are exclusively Kea-like. This change in source geochemistry can be explained by the observed change in strike of the Pacific plate near Molokai Island so that as West Molokai volcano moved away from a mixed Loa-Kea source it sampled only the Kea side of a bilaterally zoned plume (Abouchami et al., Nature, v434, 2005).by Guangping Xu.Ph.D

Letter to the editor: From Min Gong et al: "Risk for infections during treatment with denosumab for osteoporosis: a systematic review and meta-analysis"

To the editor: We read with great interest the systematic review by Diker-Cohen et al (1) about the risk of infection under the treatment of denosumab for osteoporosis. This is a well-conducted systematic review that provided us with valuable information about the safety of denosumab. We would like to point out some concerns about the analytic methods used in the systematic review. We noticed that the main outcome of this systematic review was the serious adverse events of infections (SAEIs), and the authors reported the results measured by risk ratio (RR) and risk difference (RD). The authors claimed that they used RD with the Mantel-Haenszel method to deal with studies with no events in both arms. We totally agree with this. However, for RR, they failed to use a valid method to deal with studies with no events; instead, they discarded such studies in the meta-analysis. This is problematic as such studies generally indicate no difference for treatment effects for balanced trials, and discarding them is expected to result in an overestimate of the effects (2). In their systematic review of SAEI outcome, 9 out of 34 studies had no events in both arms, and 5 of them had balanced sample size in treatment and control arms.Scopu

Galaxy Morphology Classification Using Multi-Scale Convolution Capsule Network

The classification of galaxy morphology is a hot issue in astronomical research. Although significant progress has been made in the last decade in classifying galaxy morphology using deep learning technology, there are still some deficiencies in spatial feature representation and classification accuracy. In this study, we present a multi-scale convolutional capsule network (MSCCN) model for the classification of galaxy morphology. First, this model improves the convolutional layers through using a multi-branch structure to extract multi-scale hidden features of galaxy images. In order to further explore the hidden information in the features, the multi-scale features are encapsulated and fed into the capsule layer. Second, we use a sigmoid function to replace the softmax function in dynamic routing, which can enhance the robustness of MSCCN. Finally, the classification model achieving 97% accuracy, 96% precision, 98% recall, and 97% F1-score under macroscopic averaging. In addition, a more comprehensive model evaluation were accomplished in this study. We visualized the morphological features for the part of sample set, which using the t-distributed stochastic neighbor embedding (t-SNE) algorithm. The results shows that the model has the better generalization ability and robustness, it can be effectively used in the galaxy morphological classification

The flavor-changing rare top decays t→cVVt\to c V V in topcolor-assisted technicolor theory

In the framework of topcolor-assisted technicolor (TC2) theory, we calculate the contributions of the scalars(the neutral top-pion $\pi_{t}^{0}$ and the top-Higgs $h_{t}^{0}$) to the flavor-changing rare top decays $t\to c V V$(V= W, g, $\gamma$ or Z). Our results show that $h_{t}^{0}$ can enhance the standard model $B_{r}^{SM}(t\longrightarrow cWW)$ by several orders of magnitude for most of the parameter space. The peak of the branching ratio resonance emerges when the top-Higgs mass is between $2m_{W}$ and $m_{t}$. The branching ratio $B_{r}(t\to c W W)$ can reach $10^{-3}$ in the narrow range.Comment: Latex file, 11pages, 2 eps figure

RESET Current Reduction for Phase Change Memory Based on Standard 0.13-μm CMOS Technology

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Curing hemophilia A by NHEJ-mediated ectopic F8 insertion in the mouse

BACKGROUND: Hemophilia A, a bleeding disorder resulting from F8 mutations, can only be cured by gene therapy. A promising strategy is CRISPR-Cas9-mediated precise insertion of F8 in hepatocytes at highly expressed gene loci, such as albumin (Alb). Unfortunately, the precise in vivo integration efficiency of a long insert is very low (~ 0.1%). RESULTS: We report that the use of a double-cut donor leads to a 10- to 20-fold increase in liver editing efficiency, thereby completely reconstituting serum F8 activity in a mouse model of hemophilia A after hydrodynamic injection of Cas9-sgAlb and B domain-deleted (BDD) F8 donor plasmids. We find that the integration of a double-cut donor at the Alb locus in mouse liver is mainly through non-homologous end joining (NHEJ)-mediated knock-in. We then target BDDF8 to multiple sites on introns 11 and 13 and find that NHEJ-mediated insertion of BDDF8 restores hemostasis. Finally, using 3 AAV8 vectors to deliver genome editing components, including Cas9, sgRNA, and BDDF8 donor, we observe the same therapeutic effects. A follow-up of 100 mice over 1 year shows no adverse effects. CONCLUSIONS: These findings lay the foundation for curing hemophilia A by NHEJ knock-in of BDDF8 at Alb introns after AAV-mediated delivery of editing components

Regulation of RIPK1 activation by TAK1-mediated phosphorylation dictates apoptosis and necroptosis

Stimulation of TNFR1 by TNFα can promote three distinct alternative mechanisms of cell death: necroptosis, RIPK1-independent and -dependent apoptosis. How cells decide which way to die is unclear. Here, we report that TNFα-induced phosphorylation of RIPK1 in the intermediate domain by TAK1 plays a key role in regulating this critical decision. Using phospho-Ser321 as a marker, we show that the transient phosphorylation of RIPK1 intermediate domain induced by TNFα leads to RIPK1-independent apoptosis when NF-κB activation is inhibited by cycloheximide. On the other hand, blocking Ser321 phosphorylation promotes RIPK1 activation and its interaction with FADD to mediate RIPK1-dependent apoptosis (RDA). Finally, sustained phosphorylation of RIPK1 intermediate domain at multiple sites by TAK1 promotes its interaction with RIPK3 and necroptosis. Thus, absent, transient and sustained levels of TAK1-mediated RIPK1 phosphorylation may represent distinct states in TNF-RSC to dictate the activation of three alternative cell death mechanisms, RDA, RIPK1-independent apoptosis and necroptosis