10,607 research outputs found
Deglacial Tropical Atlantic Subsurface Warming Links Ocean Circulation Variability to the West African Monsoon
Multiple lines of evidence show that cold stadials in the North Atlantic were accompanied by both reductions in Atlantic Meridional Overturning Circulation (AMOC) and collapses of the West African Monsoon (WAM). Although records of terrestrial change identify abrupt WAM variability across the deglaciation, few studies show how ocean temperatures evolved across the deglaciation. To identify the mechanism linking AMOC to the WAM, we generated a new record of subsurface temperature variability over the last 21 kyr based on Mg/Ca ratios in a sub-thermocline dwelling planktonic foraminifera in an Eastern Equatorial Atlantic (EEA) sediment core from the Niger Delta. Our subsurface temperature record shows abrupt subsurface warming during both the Younger Dryas (YD) and Heinrich Event 1. We also conducted a new transient coupled ocean-atmosphere model simulation across the YD that better resolves the western boundary current dynamics and find a strong negative correlation between AMOC strength and EEA subsurface temperatures caused by changes in ocean circulation and rainfall responses that are consistent with the observed WAM change. Our combined proxy and modeling results provide the first evidence that an oceanic teleconnection between AMOC strength and subsurface temperature in the EEA impacted the intensity of the WAM on millennial time scales
Magnetic Reconnection: Sweet-Parker Versus Petschek
The two theories for magnetic reconnection, one of Sweet and Parker, and the
other of Petschek, are reconciled by exhibiting an extra condition in that of
Petschek which reduces his theory to that of Sweet and Parker, provided that
the resistivity is constant in space. On the other hand, if the resistivity is
enhanced by instabilities, then the reconnection rate of both theories is
increased substantially, but Petschek's rate can be faster. A different formula
from the usual one is presented for enhanced Petschek reconnection.Comment: 13 pages, 5 figures, 1 appendix (MR2000 proceedings
Mathematical models of magnetospheric convection and its coupling to the ionosphere
Mathematical models of magnetospheric convection and its coupling to ionospher
Effect of non-condensable gas on the startup of a loop heat pipe
It is essential to address the startup issues prior to the wide application of loop heat pipes (LHPs) in both space and terrestrial surroundings. As non-condensable gas (NCG) is an important factor affecting the startup behavior, its effects on the startup performance of an ammonia-stainless steel LHP with and without preconditioning were experimentally investigated in this work. Nitrogen with controlled amounts was used to simulate the NCG, and the temperature overshoot, liquid superheat and startup time were employed as the evaluation criteria. Four situations relating to initial liquid/vapor distribution in the evaporator were examined: (1) both evaporator core and vapor grooves are filled with liquid, (2) vapor exists in vapor grooves and the evaporator core is filled by liquid, (3) vapor grooves are filled by liquid and vapor exists in the evaporator core, and (4) vapor exists in both evaporator core and vapor grooves. Experimental results showed that with NCG presence in the LHP, the startup could only proceed in situation 1 with preconditioning, while it could proceed in situations 1, 3 or 4 without preconditioning. For the startup in situation 1, a larger NCG inventory led to much degraded startup performance, and a higher startup heat load could benefit the startup. For the startup in situation 3, the most difficult startup situation, NCG resulted in a very high temperature overshoot, which may even exceed the maximum allowable value. For the startup in situation 4, the existence of NCG in the vapor grooves could facilitate the evaporation there, leading to a very desirable startup
Comparison of Quarterly and Yearly Calibration Data for Propensity Score Adjusted Web Survey Estimates
While web surveys have become increasingly popular as a method of data collection, there is
concern that estimates obtained from web surveys may not reflect the target population of interest.
Web survey estimates can be calibrated to existing national surveys using a propensity score
adjustment, although requirements for the size and collection timeline of the reference data set
have not been investigated. We evaluate health outcomes estimates from the National Center for
Health Statistics’ Research and Development web survey. In our study, the 2016 National Health
Interview Survey as well as its quarterly subsets are considered as reference datasets for the web
data. It is demonstrated that the calibrated health estimates overall vary little when using the
quarterly or yearly data, suggesting that there is flexibility in selecting the reference dataset. This
finding has many practical implications for constructing reference data, including the reduced cost
and burden of a smaller sample size and a more flexible timeline
Nanostructured luminescently labeled nucleic acids
Important and emerging trends at the interface of luminescence, nucleic acids and nanotechnology
are: (i) the conventional luminescence labeling of nucleic acid nanostructures (e.g. DNA tetrahedron);
(ii) the labeling of bulk nucleic acids (e.g. single‐stranded DNA, double‐stranded DNA) with
nanostructured luminescent labels (e.g. copper nanoclusters); and (iii) the labeling of nucleic acid
nanostructures (e.g. origami DNA) with nanostructured luminescent labels (e.g. silver
nanoclusters). This review surveys recent advances in these three different approaches to the
generation of nanostructured luminescently labeled nucleic acids, and includes both direct and
indirect labeling methods
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Inhibition of chemotherapy resistant breast cancer stem cells by a ROR1 specific antibody.
Breast cancers enduring treatment with chemotherapy may be enriched for cancer stem cells or tumor-initiating cells, which have an enhanced capacity for self-renewal, tumor initiation, and/or metastasis. Breast cancer cells that express the type I tyrosine kinaselike orphan receptor ROR1 also may have such features. Here we find that the expression of ROR1 increased in breast cancer cells following treatment with chemotherapy, which also enhanced expression of genes induced by the activation of Rho-GTPases, Hippo-YAP/TAZ, or B lymphoma Mo-MLV insertion region 1 homolog (BMI1). Expression of ROR1 also enhanced the capacity of breast cancer cells to invade Matrigel, form spheroids, engraft in Rag2-/-[Formula: see text] mice, or survive treatment with paclitaxel. Treatment of mice bearing breast cancer patient-derived xenografts (PDXs) with the humanized anti-ROR1 monoclonal antibody cirmtuzumab repressed expression of genes associated with breast cancer stemness, reduced activation of Rho-GTPases, Hippo-YAP/TAZ, or BMI1, and impaired the capacity of breast cancer PDXs to metastasize or reengraft Rag2-/-[Formula: see text] mice. Finally, treatment of PDX-bearing mice with cirmtuzumab and paclitaxel was more effective than treatment with either alone in eradicating breast cancer PDXs. These results indicate that targeting ROR1 may improve the response to chemotherapy of patients with breast cancer
Somatostatin receptor 5 and cannabinoid receptor 1 activation inhibit secretion of glucose-dependent insulinotropic polypeptide from intestinal K cells in rodents.
AIMS/HYPOTHESIS: Glucose-dependent insulinotropic polypeptide (GIP) is an enteroendocrine hormone that promotes storage of glucose and fat. Its secretion from intestinal K cells is triggered by nutrient ingestion and is modulated by intracellular cAMP. In view of the proadipogenic actions of GIP, this study aimed to identify pathways in K cells that lower cAMP levels and GIP secretion. METHODS: Murine K cells purified by flow cytometry were analysed for expression of G(αi)-coupled receptors by transcriptomic microarrays. Somatostatin and cannabinoid receptor expression was confirmed by quantitative RT-PCR. Hormone secretion in vitro was measured in GLUTag and primary murine intestinal cultures. cAMP was monitored in GLUTag cells using the genetically encoded sensor Epac2-camps. In vivo tolerance tests were performed in cannulated rats. RESULTS: Purified murine K cells expressed high mRNA levels for somatostatin receptors (Sstrs) Sstr2, Sstr3 and Sstr5, and cannabinoid receptor type 1 (Cnr1, CB1). Somatostatin inhibited GIP and glucagon-like peptide-1 (GLP-1) secretion from primary small intestinal cultures, in part through SSTR5, and reduced cAMP generation in GLUTag cells. Although the CB1 agonist methanandamide (mAEA) inhibited GIP secretion, no significant effect was observed on GLP-1 secretion from primary cultures. In cannulated rats, treatment with mAEA prior to an oral glucose tolerance test suppressed plasma GIP but not GLP-1 levels, whereas the CB1 antagonist AM251 elevated basal GIP concentrations. CONCLUSIONS/INTERPRETATION: GIP release is inhibited by somatostatin and CB1 agonists. The differential effects of CB1 ligands on GIP and GLP-1 release may provide a new tool to dissociate secretion of these incretin hormones and lower GIP but not GLP-1 levels in vivo
Bis(1,10-phenanthroline-κ2 N,N′)bis(thiocyanato-κN)cadmium
The title compound, [Cd(NCS)2(C12H8N2)2], has been obtained from the decomposition reaction of dithiooxamide in a dimethylformamide solution containing 1,10-phenanthroline (phen) and Cd(NO3)2·4H2O. Its crystal structure is formed by monuclear CdII entities in which the metal atom is sited on a twofold rotation axis. The CdII atom is six-coordinated in the form of a distorted octahedron by two chelating phenanthroline molecules and two thiocyanate anions coordinated through their N atoms. In the crystal, C—H⋯N hydrogen bonds are established between the phenanthroline and thiocyanate ligands of neighbouring complexes
Genomic analysis identifies unique signatures predictive of brain, lung, and liver relapse
The ability to predict metastatic potential could be of great clinical importance, however, it is uncertain if predicting metastasis to specific vital organs is feasible. As a first step in evaluating metastatic predictions, we analyzed multiple primary tumors and metastasis pairs and determined that >90% of 298 gene expression signatures were found to be similarly expressed between matched pairs of tumors and metastases; therefore, primary tumors may be a good predictor of metastatic propensity. Next, using a dataset of >1,000 human breast tumor gene expression microarrays we determined that HER2-enriched subtype tumors aggressively spread to the liver, while basal-like and claudin-low subtypes colonize the brain and lung. Correspondingly, brain and lung metastasis signatures, along with embryonic stem cell, tumor initiating cell, and hypoxia signatures, were also strongly expressed in the basal-like and claudin-low tumors. Interestingly, low “Differentiation Scores,” or high expression of the aforementioned signatures, further predicted for brain and lung metastases. In total, these data identify that depending upon the organ of relapse, a combination of gene expression signatures most accurately predicts metastatic behavior
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