The Induction of Colitis and Ileitis in Mice Is Associated with Marked Increases in Intestinal Concentrations of Stimulants of TLRs 2, 4, and 5

Peer reviewedPublisher PD

Evaluating the scale, growth, and origins of right-wing echo chambers on YouTube

Although it is understudied relative to other social media platforms, YouTube is arguably the largest and most engaging online media consumption platform in the world. Recently, YouTube's outsize influence has sparked concerns that its recommendation algorithm systematically directs users to radical right-wing content. Here we investigate these concerns with large scale longitudinal data of individuals' browsing behavior spanning January 2016 through December 2019. Consistent with previous work, we find that political news content accounts for a relatively small fraction (11%) of consumption on YouTube, and is dominated by mainstream and largely centrist sources. However, we also find evidence for a small but growing "echo chamber" of far-right content consumption. Users in this community show higher engagement and greater "stickiness" than users who consume any other category of content. Moreover, YouTube accounts for an increasing fraction of these users' overall online news consumption. Finally, while the size, intensity, and growth of this echo chamber present real concerns, we find no evidence that they are caused by YouTube recommendations. Rather, consumption of radical content on YouTube appears to reflect broader patterns of news consumption across the web. Our results emphasize the importance of measuring consumption directly rather than inferring it from recommendations.Comment: 29 pages, 21 figures, 15 table

Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O$_2$ and N$_2$, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O$_2$ doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first principles density functional theory calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C$_2$$>$O), carbonyl (C$_2$$>$C$=$O), and ketene (C$=$C$=$O), as ordered by abundance. Upon oxidation of nearly all the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60\% greater than for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O$_2$ does not contribute to the measured XPS O~1s spectra

Ploidy Reductions in Murine Fusion-Derived Hepatocytes

We previously showed that fusion between hepatocytes lacking a crucial liver enzyme, fumarylacetoacetate hydrolase (FAH), and wild-type blood cells resulted in hepatocyte reprogramming. FAH expression was restored in hybrid hepatocytes and, upon in vivo expansion, ameliorated the effects of FAH deficiency. Here, we show that fusion-derived polyploid hepatocytes can undergo ploidy reductions to generate daughter cells with one-half chromosomal content. Fusion hybrids are, by definition, at least tetraploid. We demonstrate reduction to diploid chromosome content by multiple methods. First, cytogenetic analysis of fusion-derived hepatocytes reveals a population of diploid cells. Secondly, we demonstrate marker segregation using ß-galactosidase and the Y-chromosome. Approximately 2–5% of fusion-derived FAH-positive nodules were negative for one or more markers, as expected during ploidy reduction. Next, using a reporter system in which ß-galactosidase is expressed exclusively in fusion-derived hepatocytes, we identify a subpopulation of diploid cells expressing ß-galactosidase and FAH. Finally, we track marker segregation specifically in fusion-derived hepatocytes with diploid DNA content. Hemizygous markers were lost by ≥50% of Fah-positive cells. Since fusion-derived hepatocytes are minimally tetraploid, the existence of diploid hepatocytes demonstrates that fusion-derived cells can undergo ploidy reduction. Moreover, the high degree of marker loss in diploid daughter cells suggests that chromosomes/markers are lost in a non-random fashion. Thus, we propose that ploidy reductions lead to the generation of genetically diverse daughter cells with about 50% reduction in nuclear content. The generation of such daughter cells increases liver diversity, which may increase the likelihood of oncogenesis

Age Estimates for Globular Clusters in NGC 1399

We present high signal-to-noise Keck spectra for 10 globular clusters associated with the giant Fornax elliptical NGC 1399, and compare measured line indices with current stellar population models. Our data convincingly demonstrate, for the first time, that at least some of the clusters in a giant elliptical galaxy have super-solar abundance ratios, similar to the host galaxy. From Hbeta line-strengths the majority of clusters have ages of ~11 Gyrs (within 2sigma), which is similar to the luminosity-weighted stellar age of NGC 1399. Two of the clusters (which also reveal enhanced abundance ratios) show significantly higher Hbeta values than the others. It remains unclear whether this is due to young (~2 Gyr) ages, or extremely old (> 15 Gyr) ages with a warm blue horizontal branch. However a conflict with current cosmological parameters is avoided if the young age is favored. Either alternative indicates a complicated age distribution among the metal-rich clusters and sets interesting constraints on their chemical enrichment at late epochs.Comment: 5 pages, Latex, 3 figures, 1 table, accepted for publication in ApJ

Keck Spectroscopy of Candidate Proto-globular Clusters in NGC 1275

Keck spectroscopy of 5 proto-globular cluster candidates in NGC 1275 has been combined with HST WFPC2 photometry to explore the nature and origin of these objects and discriminate between merger and cooling flow scenarios for globular cluster formation. The objects we have studied are not HII regions, but rather star clusters, yet their integrated spectral properties do not resemble young or intermediate age Magellanic Cloud clusters or Milky Way open clusters. The clusters' Balmer absorption appears to be too strong to be consistent with any of the standard Bruzual & Charlot evolutionary models at any metallicity. If these models are adopted, an IMF which is skewed to high masses provides a better fit to the data. A truncated IMF with a mass range of 2-3 Mo reproduces the observed Balmer equivalent widths and colors at about 450 Myr. Formation in a continuous cooling flow appears to be ruled out since the age of the clusters is much larger than the cooling time, the spatial scale of the clusters is much smaller than the cooling flow radius, and the deduced star formation rate in the cooling flow favors a steep rather than a flat IMF. A merger would have to produce clusters only in the central few kpc, presumably from gas in the merging galaxies which was channeled rapidly to the center. Widespread shocks in merging galaxies cannot have produced these clusters. If these objects are confirmed to have a relatively flat, or truncated, IMF it is unclear whether or not they will evolve into objects we would regard as bona fide globular clusters.Comment: 30 pages (AAS two column style, including 9 tables and 7 figures) to appear in the AJ (August issue), also available at http://www.ucolick.org/~mkissler/Sages/sages.html (with a full resolution Fig.1) Revised Version: previous posted version was an uncorrect ealier iteration, parts of the text, tables and figures changed. The overall conclusions remain unchange

Mixed metal-organic framework mixed-matrix membranes : insights into simultaneous moisture-triggered and catalytic delivery of nitric oxide using cryo-scanning electron microscopy

Funding: This work was supported by the European Research Council grant ADOR (Advanced Grant 787073). The authors acknowledge the EPSRC Light Element Analysis Facility Grant (EP/T019298/1) and the EPSRC Strategic Equipment Resource Grant (EP/R023751/1).The fundamental chemical and structural diversity of metal–organic frameworks (MOFs) is vast, but there is a lack of industrial adoption of these extremely versatile compounds. To bridge the gap between basic research and industry, MOF powders must be formulated into more application-relevant shapes and/or composites. Successful incorporation of varying ratios of two different MOFs, CPO-27-Ni and CuBTTri, in a thin polymer film represents an important step toward the development of mixed MOF mixed-matrix membranes. To gain insight into the distribution of the two different MOFs in the polymer, we report their investigation by Cryo-scanning electron microscopy (Cryo-SEM) tomography, which minimizes surface charging and electron beam-induced damage. Because the MOFs are based on two different metal ions, Ni and Cu, the elemental maps of the MOF composite cross sections clearly identify the size and location of each MOF in the reconstructed 3D model. The tomography run was about six times faster than conventional focused ion beam (FIB)-SEM and the first insights to image segmentation combined with machine learning could be achieved. To verify that the MOF composites combined the benefits of rapid moisture-triggered release of nitric oxide (NO) from CPO-27-Ni with the continuous catalytic generation of NO from CuBTTri, we characterized their ability to deliver NO individually and simultaneously. These MOF composites show great promise to achieve optimal dual NO delivery in real-world medical applications.Publisher PDFPeer reviewe

Heavy Meson Electromagnetic Mass Differences from QCD

We compute the electromagnetic mass differences of mesons containing a single heavy quark in terms of measurable data using QCD-based arguments in heavy-quark effective theory. We derive an unsubtracted dispersion relation that shows that the mass differences are calculable in terms of the properties of the lowest-lying physical intermediate states. We then consider the problem in the large-$N$ limit, where $N$ is the number of QCD colors. In this limit, we can write a kind of double-dispersion relation for the amplitude required to determine the electromagnetic mass difference. We use this to derive analogs of the Weinberg sum rules for heavy meson matrix elements valid to leading order in $1/N$ and to $O(1/m_Q)$ in the heavy quark expansion. In order to obtain our final result, we assume that the electromagnetic mass differences and sum rules are dominated by the lowest-lying states in analogy with the situation for the $\pi^+$--$\pi^0$ mass difference. Despite the fact that some of the matrix elements appearing in our final result have not yet been accurately measured, we can obtain useful numerical estimates: for example, we obtain (M_{B^+} - M_{B^0})^{EM} \simeq +1.8 \MeV. We argue that our results are accurate to about $30\%$.Comment: 20 pages, plain TeX, 1 uuencoded postscript figur

Are there ethnic and religious variations in uptake of bowel cancer screening?:A retrospective cohort study among 1.7 million people in Scotland

This work was supported by the Chief Scientist’s Office (grant number CZH/4/878), Cancer Research UK (grant number C3743/A16594), and supplementary funding from NHS Health Scotland. ISD and National Records of Scotland both made ‘in-house’ contributions to the work.Objective Cancer screening should be equitably accessed by all populations. Uptake of colorectal cancer screening was examined using the Scottish Health and Ethnicity Linkage Study that links the Scottish Census 2001 to health data by individual-level self-reported ethnicity and religion. Setting Data on 1.7 million individuals in two rounds of the Scottish Bowel Cancer Screening Programme (2007–2013) were linked to the 2001 Census using the Scottish Community Health Index number. Main outcome measure Uptake of colorectal cancer screening, reported as age-adjusted risk ratios (RRs) by ethnic group and religion were calculated for men and women with 95% CI. Results In the first, incidence screening round, compared with white Scottish men, Other White British (RR 109.6, 95% CI 108.8 to 110.3) and Chinese (107.2, 95% CI 102.8 to 111.8) men had higher uptake. In contrast, men of all South Asian groups had lower uptake (Indian RR 80.5, 95% CI 76.1 to 85.1; Pakistani RR 65.9, 95% CI 62.7 to 69.3; Bangladeshi RR 76.6, 95% CI 63.9 to 91.9; Other South Asian RR 88.6, 95% CI 81.8 to 96.1). Comparable patterns were seen among women in all ethnic groups, for example, Pakistani (RR 55.5, 95% CI 52.5 to 58.8). Variation in uptake was also observed by religion, with lower rates among Hindu (RR (95%CI): 78.4 (71.8 to 85.6)), Muslim (69.5 (66.7 to 72.3)) and Sikh (73.4 (67.1 to 80.3)) men compared with the reference population (Church of Scotland), with similar variation among women: lower rates were also seen among those who reported being Jewish, Roman Catholic or with no religion. Conclusions There are important variations in uptake of bowel cancer screening by ethnic group and religion in Scotland, for both sexes, that require further research and targeted interventions.Publisher PDFPeer reviewe

Imaging of the protoelliptical NGC 1700 and its globular cluster system

An excellent candidate for a young elliptical, or `protoelliptical' galaxy is NGC 1700. Here we present new B, V and I band imaging using the Keck telescope and reanalyse existing V and I band images from the Hubble Space Telescope. After subtracting a model of the galaxy from the Keck images NGC 1700 reveals two symmetric tidal tail-like structures. If this interpretation is correct, it suggests a past merger event involving two spiral galaxies. These tails are largely responsible for the `boxiness' of the galaxy isophotes observed at a radius of about 13 kpc. We also show that the B-I colour distribution of the globular cluster system is bimodal. The mean colour of the blue population is consistent with those of old Galactic globular clusters. Relative to this old, metal poor population, we find that the red population is younger and more metal rich. This young population has a similar age and metallicity as that inferred for the central stars, suggesting that they are both associated with an episode of star formation triggered by the merger that may have formed the galaxy. Although possessing large errors, we find that the majority of the age estimates of NGC 1700 are reasonably consistent and we adopt a `best estimate' for the age of 3.0 +/-1.0 Gyr. This relatively young age places NGC 1700 within the age range where there is a notable lack of obvious candidates for protoellipticals. The total globular cluster specific frequency is rather low for a typical elliptical, even after taking into account fading of the galaxy over the next 10 Gyr. We speculate that NGC 1700 will eventually form a relatively `globular cluster poor' elliptical galaxy.Comment: 15 pages, 15 figures, accepted for publication in MNRA