Abstract:
:Compressional waves that sample the lowermost mantle west of Central America show a rapid change in travel times of up to 4 s over a sampling distance of 300 km and a change in waveforms. The differential travel times of the PKP waves (which traverse Earth's core) correlate remarkably well with predictions for S-wave tomography. Our modeling suggests a sharp transition in the lowermost mantle from a broad slow region to a broad fast region with a narrow zone of slowest anomaly next to the boundary beneath the Cocos Plate and the Caribbean Plate. The structure may be the result of ponding of ancient subducted Farallon slabs situated near the edge of a thermal and chemical upwelling.
journal_name
Proc Natl Acad Sci U S Aauthors
Sun X,Song X,Zheng S,Helmberger DVdoi
10.1073/pnas.0609143103subject
Has Abstractpub_date
2007-01-02 00:00:00pages
26-30issue
1eissn
0027-8424issn
1091-6490pii
0609143103journal_volume
104pub_type
杂志文章abstract::Eukaryotic cells irradiated with high doses of UV exhibit cell-cycle responses referred to as G(1)/S, intraS, and G(2)/M checkpoints. After a moderate UV dose that approximates sunlight exposure and is lethal to fission yeast checkpoint mutants, we found unexpectedly that these cell-cycle responses do not occur. Inste...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0607343103
更新日期:2006-10-24 00:00:00
abstract::In addition to their well-recognized hepatotropism, all hepatitis B viruses (HBVs) display marked species specificity, growing poorly or not at all in species other than those closely related to their natural hosts. We have examined the molecular basis for this narrow host range, using duck HBV (DHBV) and heron HBV (H...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.14.6259
更新日期:1995-07-03 00:00:00
abstract::The exquisite selectivity and catalytic activity of enzymes have been shaped by the effects of positive and negative selection pressure during the course of evolution. In contrast, enzyme variants engineered by using in vitro screening techniques to accept novel substrates typically display a higher degree of catalyti...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0500063102
更新日期:2005-05-10 00:00:00
abstract::Spontaneous reciprocal mitotic recombination in the yeast Saccharomyces cerevisiae, associated with heteroallelic recombination, occurs almost exclusively at the two-strand stage and involves recombination of unduplicated chromosomes (i.e., during G1) or the unduplicated regions of chromosomes during the S phase of mi...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.75.9.4436
更新日期:1978-09-01 00:00:00
abstract::To test for direct and indirect effects of a top predator on three lower trophic levels, we conducted two multiyear predator addition experiments in a tropical wet forest. Periodic additions of a top predator (predatory clerid beetle) to a wet forest understory shrub caused a reduction in the predatory beetle's prey (...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.96.9.5072
更新日期:1999-04-27 00:00:00
abstract::We describe a 98-base-pair region (-38 to +60) in the long terminal repeat of the Drosophila gypsy retrotransposon that is sufficient for accurate normal-level transcription. We find that, unlike most RNA polymerase II (pol II) promoters, the gypsy promoter includes downstream sequences that are required for full acti...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.88.1.102
更新日期:1991-01-01 00:00:00
abstract::Specific binding properties of the tritium-labeled delta opiate receptor agonist [3H][2-D-penicillamine, 5-D-penicillamine]enkephalin [( 3H][D-Pen2, D-Pen5]enkephalin) were characterized in the rat brain and in a mouse neuroblastoma-rat glioma hybrid cell line (NG 108-15). Saturation isotherms of [3H][D-Pen2, D-Pen5]e...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.82.8.2543
更新日期:1985-04-01 00:00:00
abstract::Although the transport sector is responsible for a large and growing share of global emissions affecting climate, its overall contribution has not been quantified. We provide a comprehensive analysis of radiative forcing from the road transport, shipping, aviation, and rail subsectors, using both past- and forward-loo...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0702958104
更新日期:2008-01-15 00:00:00
abstract::In the United States, the iconic groundfish fishery for Gulf of Maine cod has endured several dramatic reductions in annual catch limits and been federally declared an economic disaster. Using a repeated cross-sectional survey of fishing captains to assess potential social impacts of the fishery failure, we found that...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1913914116
更新日期:2019-11-12 00:00:00
abstract::The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.94.4.1258
更新日期:1997-02-18 00:00:00
abstract::Genetic data in the mouse have shown that endothelin 3 (ET3) and its receptor B (ETRB) are essential for the development of two neural crest (NC) derivatives, the melanocytes and the enteric nervous system. We report here the effects of ET3 in vitro on the differentiation of quail trunk NC cells (NCC) in mass and clon...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.24.14214
更新日期:1998-11-24 00:00:00
abstract::Fossil glycoproteins of the soluble organic matrix are present in an 80-million-year-old mollusk shell from the Late Cretaceous Period. Discrete molecular weight components, as determined by gel electrophoresis, are preserved. The fossil organic matrix was compared with the organic matrix of a living representative sp...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 历史文章,杂志文章
doi:10.1073/pnas.73.8.2541
更新日期:1976-08-01 00:00:00
abstract::Ca channel currents were studied in freshly dispersed bovine adrenal glomerulosa cells to better understand the control of aldosterone secretion by extracellular K concentration (Ko) and angiotensin II (AII). The whole-cell variation of the patch voltage clamp technique was used. Two types of Ca channels were found. O...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.7.2412
更新日期:1988-04-01 00:00:00
abstract::Bone morphogenetic protein 4 (BMP-4) induces ventral mesoderm but represses dorsal mesoderm formation in Xenopus embryos. We show that BMP-4 inhibits two signaling pathways regulating dorsal mesoderm formation, the induction of dorsal mesoderm (Spemann organizer) and the dorsalization of ventral mesoderm. Ectopic expr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.26.12141
更新日期:1995-12-19 00:00:00
abstract::Cell-mediated immunity is critical for host resistance to tuberculosis. T lymphocytes recognizing antigens presented by the major histocompatibility complex (MHC) class I and class II molecules have been found to be necessary for control of mycobacterial infection. Mice genetically deficient in the generation of MHC c...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.96.26.15190
更新日期:1999-12-21 00:00:00
abstract::The proapoptotic activity of the "BH3-only" molecule BAD can be differentially regulated by survival factor signaling. Bad-deficient mice lacking both BAD long and BAD short proteins proved viable, and most cell types appeared to develop normally. BAD did not exclusively account for cell death after withdrawal of surv...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1533446100
更新日期:2003-08-05 00:00:00
abstract::By analogy with receptor-mediated endocytosis, clathrin-coated membrane segments at locations other than at the plasma membrane have been implicated in intracellular membrane transport/sorting. The crucial role of the Golgi apparatus in these processes prompted us to study the distribution at this level of clathrin-im...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.82.16.5385
更新日期:1985-08-01 00:00:00
abstract::Antigen-specific activation of T lymphocytes, via stimulation of the T-cell antigen receptor (TCR) complex, is marked by a rapid and sustained increase in the concentration of cytoplasmic free Ca2+ ([Ca2+]i). It has been suggested that the second messenger inositol 1,4,5-trisphosphate (IP3) produced after TCR stimulat...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.13.6007
更新日期:1995-06-20 00:00:00
abstract::Real-life decisions are often repeated. Whether considering taking a job in a new city, or doing something mundane like checking if the stove is off, decisions are frequently revisited even if no new information is available. This mode of behavior takes a particularly pathological form in obsessive-compulsive disorder...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.2014271117
更新日期:2021-01-05 00:00:00
abstract::Diabetic peripheral neuropathy (DPN) is the most common complication in both type 1 and type 2 diabetes. Here we studied some phenotypic features of a well-established animal model of type 2 diabetes, the leptin receptor-deficient db(-)/db(-) mouse, and also the effect of long-term (6 mo) treatment with coenzyme Q10 (...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1220794110
更新日期:2013-01-08 00:00:00
abstract::The importance of receptor binding in the potent immunogenicity of Escherichia coli heat-labile enterotoxin B subunit (EtxB) was tested by comparing its immunogical properties with those of a receptor binding mutant, EtxB(G33D). Subcutaneous immunization of EtxB(G33D) resulted in 160-fold reduction in antibody titer c...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.1.226
更新日期:1996-01-09 00:00:00
abstract::The thyroid hormone and retinoid X receptors form a heterodimer with each other and mediate thyroid hormone (T3)-dependent transcription. Retinoid X receptor, in addition, forms a homodimer and mediates 9-cis-retinoic acid-dependent transcription. Here, recombinant thyroid hormone receptor and recombinant retinoid X r...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.91.5.1647
更新日期:1994-03-01 00:00:00
abstract::Fluorescence photobleaching recovery and immunofluorescence methods have been used to study the lateral mobility and topographical distribution of a major cell surface glycoprotein (CSP). Both endogenous CSP and fluorescent-labeled exogenous CSP bind to the cell surface in a fibrillar pattern and are immobile on the e...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.74.7.2909
更新日期:1977-07-01 00:00:00
abstract::We introduced radioactive precursors directly into identified neurons of Aplysia californica. [(3)H]-Choline and L-[(3)H]tryptophan were injected with pressure into nerve cell bodies to study synthesis of acetylcholine and serotonin. We confirmed the cholinergic nature of R2, L10, and L11, identified neurons of the ab...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.70.12.3371
更新日期:1973-12-01 00:00:00
abstract::Estimation of evolutionary distances has always been a major issue in the study of molecular evolution because evolutionary distances are required for estimating the rate of evolution in a gene, the divergence dates between genes or organisms, and the relationships among genes or organisms. Other closely related issue...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.11.5899
更新日期:1998-05-26 00:00:00
abstract::A mutant subline of V79 Chinese hamster cells resistant to antimycin A (ANT) was obtained by treatment with ethyl methanesulfonate followed by serial selection in ANT-containing medium. Clonal derivatives of the resistant line are less susceptible than parent cells to growth inhibition by ANT in mass populations and s...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.75.11.5604
更新日期:1978-11-01 00:00:00
abstract::V79 Chinese hamster fibroblasts are widely used for mutagenicity testing but have the serious limitation that they do not express cytochromes P-450, which are needed for the activation of many promutagens to mutagenic metabolites. A full-length cDNA clone encoding the monooxygenase cytochrome P-450IIB1 under control o...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.16.5769
更新日期:1988-08-01 00:00:00
abstract::Bathorhodopsin-rhodopsin difference spectra of native 11-cis-rhodopsin and regenerated 9-cis-rhodopsin were measured at room temperature with a double-beam laser spectrophotometer after excitation at 532 nm. A detailed analysis of data obtained at 85 psec after excitation suggests that the bathorhodopsins generated fr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.80.7.1887
更新日期:1983-04-01 00:00:00
abstract::The 5' flanking sequences and the intron of the mouse Hoxa-7 gene were searched for regulatory elements that can function in Drosophila. Only the intron is able to activate a lacZ fusion gene in various tissues of Drosophila embryos. This enhancer function requires a cluster of three homeodomain binding sites (HB1-ele...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.24.13884
更新日期:1996-11-26 00:00:00
abstract::REPRESSOR OF SILENCING 1 (ROS1) is a DNA demethylation enzyme that was previously identified during a genetic screen for the silencing of both RD29A-LUC and 35S-NPTII transgenes on a T-DNA construct. Here we performed a genetic screen to identify additional mutants in which the 35S-NPTII transgene is silenced. We iden...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1208557109
更新日期:2012-07-10 00:00:00