7,445 research outputs found
What do gas-rich galaxies actually tell us about modified Newtonian dynamics?
It has recently been claimed that measurements of the baryonic Tully-Fisher
relation (BTFR), a power-law relationship between the observed baryonic masses
and outer rotation velocities of galaxies, support the predictions of modified
Newtonian dynamics for the slope and scatter in the relation, while challenging
the cold dark matter (CDM) paradigm. We investigate these claims, and find
that: 1) the scatter in the data used to determine the BTFR is in conflict with
observational uncertainties on the data; 2) these data do not make strong
distinctions regarding the best-fit BTFR parameters; 3) the literature contains
a wide variety of measurements of the BTFR, many of which are discrepant with
the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross
oversimplification of the complex galaxy-scale physics involved. We conclude
that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio
Modularity and community detection in bipartite networks
The modularity of a network quantifies the extent, relative to a null model
network, to which vertices cluster into community groups. We define a null
model appropriate for bipartite networks, and use it to define a bipartite
modularity. The bipartite modularity is presented in terms of a modularity
matrix B; some key properties of the eigenspectrum of B are identified and used
to describe an algorithm for identifying modules in bipartite networks. The
algorithm is based on the idea that the modules in the two parts of the network
are dependent, with each part mutually being used to induce the vertices for
the other part into the modules. We apply the algorithm to real-world network
data, showing that the algorithm successfully identifies the modular structure
of bipartite networks.Comment: RevTex 4, 11 pages, 3 figures, 1 table; modest extensions to conten
HLA gene expression is altered in whole blood and placenta from women who later developed preeclampsia
Preeclampsia is a multi-system disease that significantly contributes to maternal and fetal morbidity and mortality. In this study, we used a non-biased microarray approach to identify dysregulated genes in maternal whole blood samples which may be associated with the development of preeclampsia. Whole blood samples were obtained at 28 weeks of gestation from 5 women who later developed preeclampsia (cases) and 10 matched women with normotensive pregnancies (controls). Placenta samples were obtained from an independent cohort of 19 women with preeclampsia matched with 19 women with normotensive pregnancies. We studied gene expression profiles using Illumina microarray in blood and validated changes in gene expression in whole blood and placenta tissue by qPCR. We found a transcriptional profile differentiating cases from controls; 236 genes were significantly dysregulated in blood from women who developed preeclampsia. Functional annotation of microarray results indicated that most of the genes found to be dysregulated were involved in inflammatory pathways. Whilst general trends were preserved, only HLA-A was validated in whole blood samples from cases using qPCR (2.30 ± 0.9 fold change) whereas in placental tissue HLA-DRB1 expression was found to be significantly increased in samples from women with preeclampsia (5.88 ± 2.24 fold change). We have identified that HLA-A is up-regulated in the circulation of women who went on to develop preeclampsia. In placenta of women with preeclampsia we identified that HLA-DRB1 is up-regulated. Our data provide further evidence for involvement of the HLA gene family in the pathogenesis of preeclampsia
Maternal plasma DHA levels increase prior to 29 days post-LH surge in women undergoing frozen embryo transfer: a prospective, observational study of human pregnancy
Context:
Docosahexaenoic acid (DHA) is an important fatty acid required for neurological development but its importance during early fetal neurological organogenesis is unknown.
Objective:
To assess plasma fatty acid changes in early pregnancy in women undergoing natural cycle-frozen embryo transfer as a means of achieving accurately-timed periconceptual sampling.
Design:
Women undergoing frozen embryo transfer were recruited and serial fasting blood samples were taken pre-luteinising hormone (LH) surge, and at days 18, 29 and 45 post-LH surge and fatty acids were analysed using gas chromatography.
Setting:
Assisted Conception Unit, Glasgow Royal Infirmary, Scotland
Main outcome measures:
Plasma fatty acid concentrations, influence of twin pregnancies on DHA plasma concentration.
Results:
In pregnant women, there was a rapid, early increase in the maternal rate of change of plasma DHA concentration observed by 29 days post-LH surge (mean±SD, from 0.1±1.3 to 1.6±2.9 nmol DHA per mL plasma per day). This early pressure to increase plasma DHA concentration was further emphasised in twin pregnancies where the increase in DHA concentration over 45 days was two-fold higher than in singleton pregnancies (mean±SD increase, 74±39 nmol/mL versus 36±40 nmol/mL). An index of delta-6 desaturase activity increased 30% and positively correlated with the rate of change of DHA concentration between day 18 and 29-post LH surge (R-squared adjusted = 41%, P=0.0002). DHA was the only fatty acid with a continual accelerated increase in plasma concentration and a positive incremental area under the curve (mean±SD, 632±911 nmol/mL x day) over the first 45 days of gestation.
Conclusions:
An increase in maternal plasma DHA concentration is initiated in human pregnancy prior to neural tube closure which occurs at 28 days' gestation
Differential expression of microRNA-206 and its target genes in pre-eclampsia
Objectives: Pre-eclampsia is a multi-system disease that significantly contributes to maternal and fetal morbidity and mortality. In this study, we used a non-biased microarray approach to identify novel circulating miRNAs in maternal plasma that may be associated with pre-eclampsia.
Methods: Plasma samples were obtained at 16 and 28 weeks of gestation from 18 women who later developed pre-eclampsia (cases) and 18 matched women with normotensive pregnancies (controls). We studied miRNA expression profiles in plasma and subsequently confirmed miRNA and target gene expression in placenta samples. Placental samples were obtained from an independent cohort of 19 women with pre-eclampsia matched with 19 women with normotensive pregnancies.
Results: From the microarray, we identified 1 miRNA that was significantly differentially expressed between cases and controls at 16 weeks of gestation and 6 miRNAs that were significantly differentially expressed at 28 weeks. Following qPCR validation only one, miR-206, was found to be significantly increased in 28 week samples in women who later developed pre-eclampsia (1.4 fold change ± 0.2). The trend for increase in miR-206 expression was mirrored within placental tissue from women with pre-eclampsia. In parallel, IGF-1, a target gene of miR-206, was also found to be down-regulated (0.41 ± 0.04) in placental tissue from women with pre-eclampsia. miR-206 expression was also detectable in myometrium tissue and trophoblast cell lines.
Conclusions: Our pilot study has identified miRNA-206 as a novel factor up-regulated in pre-eclampsia within the maternal circulation and in placental tissue
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Stable isotope metabolomics of pulmonary artery smooth muscle and endothelial cells in pulmonary hypertension and with TGF-beta treatment.
Altered metabolism in pulmonary artery smooth muscle cells (PASMCs) and endothelial cells (PAECs) contributes to the pathology of pulmonary hypertension (PH), but changes in substrate uptake and how substrates are utilized have not been fully characterized. We hypothesized stable isotope metabolomics would identify increased glucose, glutamine and fatty acid uptake and utilization in human PASMCs and PAECs from PH versus control specimens, and that TGF-β treatment would phenocopy these metabolic changes. We used 13C-labeled glucose, glutamine or a long-chain fatty acid mixture added to cell culture media, and mass spectrometry-based metabolomics to detect and quantify 13C-labeled metabolites. We found PH PASMCs had increased glucose uptake and utilization by glycolysis and the pentose shunt, but no changes in glutamine or fatty acid uptake or utilization. Diseased PAECs had increased proximate glycolysis pathway intermediates, less pentose shunt flux, increased anaplerosis from glutamine, and decreased fatty acid β-oxidation. TGF-β treatment increased glycolysis in PASMCs, but did not recapitulate the PAEC disease phenotype. In TGF-β-treated PASMCs, glucose, glutamine and fatty acids all contributed carbons to the TCA cycle. In conclusion, PASMCs and PAECs collected from PH subjects have significant changes in metabolite uptake and utilization, partially recapitulated by TGF-β treatment
Law, politics and the governance of English and Scottish joint-stock companies 1600-1850
This article examines the impact of law on corporate governance by means of a case study of joint-stock enterprise in England and Scotland before 1850. Based on a dataset of over 450 company constitutions together with qualitative information on governance practice, it finds little evidence to support the hypothesis that common-law regimes such as England were more supportive of economic growth than civil-law jurisdictions such as Scotland: indeed, levels of shareholder protection were slightly stronger in the civil-law zone. Other factors, such as local political institutions, played a bigger role in shaping organisational forms and business practice
Designing multiplayer games to facilitate emergent social behaviours online
This paper discusses an exploratory case study of the design of games that facilitate spontaneous social interaction and group behaviours among distributed individuals, based largely on symbolic presence 'state' changes. We present the principles guiding the design of our game environment: presence as a symbolic phenomenon, the importance of good visualization and the potential for spontaneous self-organization among groups of people. Our game environment, comprising a family of multiplayer 'bumper-car' style games, is described, followed by a discussion of lessons learned from observing users of the environment. Finally, we reconsider and extend our design principles in light of our observations
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