Microwave Near-Field Imaging of Two-Dimensional Semiconductors

Optimizing new generations of two-dimensional devices based on van der Waals materials will require techniques capable of measuring variations in electronic properties in situ and with nanometer spatial resolution. We perform scanning microwave microscopy (SMM) imaging of single layers of MoS_2 and n- and p-doped WSe_2. By controlling the sample charge carrier concentration through the applied tip bias, we are able to reversibly control and optimize the SMM contrast to image variations in electronic structure and the localized effects of surface contaminants. By further performing tip bias-dependent point spectroscopy together with finite element simulations, we distinguish the effects of the quantum capacitance and determine the local dominant charge carrier species and dopant concentration. These results underscore the capability of SMM for the study of 2D materials to image, identify, and study electronic defects

Microwave Near-Field Imaging of Two-Dimensional Semiconductors

Optimizing new generations of two-dimensional devices based on van der Waals materials will require techniques capable of measuring variations in electronic properties in situ and with nanometer spatial resolution. We perform scanning microwave microscopy (SMM) imaging of single layers of MoS_2 and n- and p-doped WSe_2. By controlling the sample charge carrier concentration through the applied tip bias, we are able to reversibly control and optimize the SMM contrast to image variations in electronic structure and the localized effects of surface contaminants. By further performing tip bias-dependent point spectroscopy together with finite element simulations, we distinguish the effects of the quantum capacitance and determine the local dominant charge carrier species and dopant concentration. These results underscore the capability of SMM for the study of 2D materials to image, identify, and study electronic defects

The interplay of type I and type II interferons in murine autoimmune cholangitis as a basis for sex-biased autoimmunity

We have reported on a murine model of autoimmune cholangitis, generated by altering the AU-rich element (ARE) by deletion of the interferon gamma (IFN-γ) 3\u27 untranslated region (coined ARE-Del−/−), that has striking similarities to human primary biliary cholangitis (PBC) with female predominance. Previously, we suggested that the sex bias of autoimmune cholangitis was secondary to intense and sustained type I and II IFN signaling. Based on this thesis, and to define the mechanisms that lead to portal inflammation, we specifically addressed the hypothesis that type I IFNs are the driver of this disease. To accomplish these goals, we crossed ARE-Del−/− mice with IFN type I receptor alpha chain (Ifnar1) knockout mice. We report herein that loss of type I IFN receptor signaling in the double construct of ARE-Del−/− Ifnar1−/− mice dramatically reduces liver pathology and abrogated sex bias. More importantly, female ARE-Del−/− mice have an increased number of germinal center (GC) B cells as well as abnormal follicular formation, sites which have been implicated in loss of tolerance. Deletion of type I IFN signaling in ARE-Del−/− Ifnar1−/− mice corrects these GC abnormalities, including abnormal follicular structure. Conclusion: Our data implicate type I IFN signaling as a necessary component of the sex bias of this murine model of autoimmune cholangitis. Importantly these data suggest that drugs that target the type I IFN signaling pathway would have potential benefit in the earlier stages of PBC. (Hepatology 2018;67:1408-1419)

The burden of respiratory infections among older adults in long-term care:a systematic review

BACKGROUND: Respiratory infections among older adults in long-term care facilities (LTCFs) are a major global concern, yet a rigorous systematic synthesis of the literature on the burden of respiratory infections in the LTCF setting is lacking. To address the critical need for evidence regarding the global burden of respiratory infections in LTCFs, we assessed the burden of respiratory infections in LTCFs through a systematic review of the published literature. METHODS: We identified articles published between April 1964 and March 2019 through searches of PubMed (MEDLINE), EMBASE, and the Cochrane Library. Experimental and observational studies published in English that included adults aged ≥60 residing in LTCFs who were unvaccinated (to identify the natural infection burden), and that reported measures of occurrence for influenza, respiratory syncytial virus (RSV), or pneumonia were included. Disagreements about article inclusion were discussed and articles were included based on consensus. Data on study design, population, and findings were extracted from each article. Findings were synthesized qualitatively. RESULTS: A total of 1451 articles were screened for eligibility, 345 were selected for full-text review, and 26 were included. Study population mean ages ranged from 70.8 to 90.1 years. Three (12%) studies reported influenza estimates, 7 (27%) RSV, and 16 (62%) pneumonia. Eighteen (69%) studies reported incidence estimates, 7 (27%) prevalence estimates, and 1 (4%) both. Seven (27%) studies reported outbreaks. Respiratory infection incidence estimates ranged from 1.1 to 85.2% and prevalence estimates ranging from 1.4 to 55.8%. Influenza incidences ranged from 5.9 to 85.2%. RSV incidence proportions ranged from 1.1 to 13.5%. Pneumonia prevalence proportions ranged from 1.4 to 55.8% while incidence proportions ranged from 4.8 to 41.2%. CONCLUSIONS: The reported incidence and prevalence estimates of respiratory infections among older LTCF residents varied widely between published studies. The wide range of estimates offers little useful guidance for decision-making to decrease respiratory infection burden. Large, well-designed epidemiologic studies are therefore still necessary to credibly quantify the burden of respiratory infections among older adults in LTCFs, which will ultimately help inform future surveillance and intervention efforts

Variations of Li and Mg isotope ratios in bulk chondrites and mantle xenoliths

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 75 (2011): 5247-5268, doi:10.1016/j.gca.2011.06.026.We present whole rock Li and Mg isotope analyses of 33 ultramafic xenoliths from the terrestrial mantle, which we compare with analyses of 30 (mostly chondritic) meteorites. The accuracy of our new Mg isotope ratio measurement protocol is substantiated by a combination of standard addition experiments, the absence of mass independent effects in terrestrial samples and our obtaining identical values for rock standards using 2 different separation chemistries and 3 different mass-spectrometric introduction systems. Carbonaceous, ordinary and enstatite chondrites have irresolvable mean stable Mg isotopic compositions (δ25Mg = -0.14 ± 0.06; δ26Mg = - 0.27 ± 0.12‰, 2sd), but our enstatite chondrite samples have lighter δ7Li (by up to ~3‰) than our mean carbonaceous and ordinary chondrites (3.0 ± 1.5‰, 2sd), possibly as a result of spallation in the early solar system. Measurements of equilibrated, fertile peridotites give mean values of δ7Li = 3.5 ± 0.5‰, δ25Mg = -0.10 ± 0.03‰ and δ26Mg = -0.21 ± 0.07‰. We believe these values provide a useful estimate of the primitive mantle and they are within error of our average of bulk carbonaceous and ordinary chondrites. A fuller range of fresh, terrestrial, ultramafic samples, covering a variety of geological histories, show a broad positive correlation between bulk δ7Li and δ26Mg, which vary from -3.7 to +14.5‰, and -0.36 to +0.06‰, respectively. Values of δ7Li and δ26Mg lower than our estimate of primitive mantle are strongly linked to kinetic isotope fractionation, occurring during transport of the mantle xenoliths. We suggest Mg and Li diffusion into the xenoliths is coupled to H loss from nominally anhydrous minerals following degassing. Diffusion models suggest that the co-variation of Mg and Li isotopes requires comparable diffusivities of Li and Mg in olivine. The isotopically lightest samples require ~5-10 years of diffusive ingress, which we interpret as a time since volatile loss in the host magma. Xenoliths erupted in pyroclastic flows appear to have retained their mantle isotope ratios, likely as a result of little prior degassing in these explosive events. High δ7Li, coupled with high [Li], in rapidly cooled arc peridotites may indicate that these samples represent fragments of mantle wedge that has been metasomatised by heavy, slab-derived fluids. If such material is typically stirred back into the convecting mantle, it may account for the heavy δ7Li seen in some oceanic basalts.PPvS was supported by NERC grant NER/C510983/

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Bostonia: The Boston University Alumni Magazine. Volume 16

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs