Tracing cell lineages in health and disease: experimental and human studies

PhDThis study aimed to investigate stem cell biology in the normal and diseased pancreas and liver employing robust methods for tracking stem cells and their progeny in both pre-clinical and human scenario. Bone marrow (BM) plasticity had been demonstrated in diseased organ remodelling. By detection of the Y chromosome in female mice receiving a sexmismatch BM transplantation, BM-derived cells were present in murine pancreas with cerulein-induced pancreatitis. BM-derived myofibroblasts functionally contributed to around 8% of the total population of myofibroblasts, the cells with a key fibrogenic role. Fibrocytes are circulating pro-fibrogenic cells; a decrease of BM-derived fibrocytes in blood and detection of these cells in areas of collagen deposition indicated they migrated to inflamed pancreas and played a role in extracellular matrix formation. IL-10 is an anti-inflammatory cytokine mainly secreted by BM; a lack of IL-10 increased the fibrosis, the inflammation and the numbers of BM-derived myofibroblasts suggesting a potential role of IL-10 in chronic pancreatitis. Mitochondrial DNA (mtDNA) mutations permit lineage tracing within human tissues. Cells having identical mtDNA mutations within a cytochrome c oxidase (CCO)- deficient area must be related having originated from a common founder cell, presumably a stem cell. I have demonstrated that regenerative nodules in cirrhotic liver are invariably clonal populations, and that these nodules often originate from progenitor cells from the abutting ductular reactions. An attempt to build a phylogenetic tree based on the accumulation of mutations in normal liver reinforced the belief that hepatic stem cells are located within the portal tract area and that their cell progeny migrate centrifugally from the portal tract region. The same techniques were applied to the pancreas, but many areas of CCO deficiency could be ascribed to autolysis, while the 3 discovery of identical mtDNA base changes within and outwith CCO-deficient patches suggested these were genetic polymorphisms, previously unreported

A scenario of heavy but visible baryonic dark matter

We consider a model in which dark matter is a composite baryon of a dark sector governed by $SU(3)$ gauge theory, with vector-like quarks also charged under $U(1)_Y$. The model provides simple answer to the dark matter stability problem: it is a result of the accidental dark baryon number conservation. And with an analogy to QCD, all physical quantities of the dark matter can be calculated by rescaling the QCD experimental results. According to the thermal freeze-out mechanism the mass of the dark matter is predicted to be $\mathcal{O}(100)$~TeV in order to achieve a correct relic abundance. Such heavy dark matter is in general hard for detection due to small dark matter number density in the universe. However, dark baryon number in our model is not necessarily strictly preserved thanks to operators suppressed by the Planck scale, and such decay operator results in a decay lifetime marginal to the current detection bound. We show our model with $\mathcal{O}(10^{27})~s$ dark matter decay life time can explain the AMS-02 anti-proton data, if it is experimentally interpreted as an access, although some theoretical uncertainty may weaken its significance. We also investigate other phenomena of this model such as the extragalactic gamma ray and neutrino signatures.Comment: 14 pages, 43 figures, published in JHE

THE PROBLEM OF TAXING FARMERS IN CHINA

Replaced with revised version of paper 08/25/03.Agricultural Finance, H22, O53,

Estimate black hole masses of AGNs using ultraviolet emission line properties

Based on the measured sizes of broad line region of the reverberation-mapping AGN sample, two new empirical relations are introduced to estimate the central black hole masses of radio-loud high-redshift ($z > 0.5$) AGNs. First, using the archival $IUE/HST$ spectroscopy data at UV band for the reverberation-mapping objects, we obtained two new empirical relations between the BLR size and \Mg/\C emission line luminosity. Secondly, using the newly determined black hole masses of the reverberation-mapping sample for calibration, two new relationships for determination of black hole mass with the full width of half maximum and the luminosity of \Mg/\C line are also found. We then apply the relations to estimate the black hole masses of AGNs in Large Bright Quasar Surveyq and a sample of radio-loud quasars. For the objects with small radio-loudness, the black hole mass estimated using the R_{\rm BLR} - L_{\eMg/\eC} relation is consistent with that from the $R_{BLR} - L_{3000\AA/1350 \AA}$ relation. But for radio-loud AGNs, the mass estimated from the R_{BLR} - L_{\eMg/\eC} relation is systematically lower than that from the continuum luminosity $L_{3000\AA/1350\AA}$. Because jets could have significant contributions to the UV/optical continuum luminosity of radio-loud AGNs, we emphasized again that for radio-loud AGNs, the emission line luminosity may be a better tracer of the ionizing luminosity than the continuum luminosity, so that the relations between the BLR size and UV emission line luminosity should be used to estimate the black hole masses of high redshift radio-loud AGNs.Comment: 19 pages, 10 figure

Design of Ultra-compact Graphene-based Superscatterers

The energy-momentum dispersion relation is a fundamental property of plasmonic systems. In this paper, we show that the method of dispersion engineering can be used for the design of ultra-compact graphene-based superscatterers. Based on the Bohr model, the dispersion relation of the equivalent planar waveguide is engineered to enhance the scattering cross section of a dielectric cylinder. Bohr conditions with different orders are fulfilled in multiple dispersion curves at the same resonant frequency. Thus the resonance peaks from the first and second order scattering terms are overlapped in the deepsubwavelength scale by delicately tuning the gap thickness between two graphene layers. Using this ultra-compact graphene-based superscatterer, the scattering cross section of the dielectric cylinder can be enhanced by five orders of magnitude.Comment: This paper has been accepted by IEEE Journal of Selected topics in Quantum Electronic

The Effects of Corequisite Remediation: Evidence From a Statewide Reform in Tennessee

Corequisite remediation, which mainstreams students deemed academically underprepared into college-level courses with additional learning support, is rapidly being adopted by colleges across the nation. This paper provides the first causal evidence on a system-wide corequisite reform, using data from all 13 community colleges affiliated with the Tennessee Board of Regents. Using regression discontinuity and difference-in-regression-discontinuity designs, the authors estimated the causal effects of placement into corequisite remediation compared with placement into traditional prerequisite remediation and direct placement into college-level courses. For students on the margin of the college readiness threshold, those placed into corequisite remediation were 15 percentage points more likely to pass gateway math and 13 percentage points more likely to pass gateway English within one year of enrollment than similar students placed into prerequisite remediation. Compared with their counterparts placed directly into college-level courses, students placed into corequisite remediation had similar gateway course completion rates and were about 8 percentage points more likely to enroll in and pass a subsequent college-level math course after completing gateway math. The positive effects of corequisite remediation compared with prerequisite remediation in math were largely driven by efforts to guide students to take math courses aligned with the requirements for their program rather than placing most students into the algebra–calculus track by default, as has been the standard practice. The authors found no significant impacts of placement into corequisite remediation on enrollment persistence, transfer to a four-year college, or degree completion. This suggests that corequisite reforms, though effective in helping students pass college-level math and English, are not sufficient to improve college completion rates overall

Design and finite element mode analysis of noncircular gear

The noncircular gear transmission is an important branch of the gear transmission, it is characterized by its compact structure, good dynamic equilibration and other advantages, and can be used in the automobile, engineering machine, ship, machine tool, aviation and spaceflight field etc. Studying on the dynamics feature of noncircular gear transmission can improve the ability to carry loads of, reduce the vibration and noise of, increase the life of the noncircular gear transmission machine, provides guidance for the design of the noncircular gear, and has significant theories and practical meanings. In this paper, the gear transmission technique is used to studied the design method of the noncircular gear, which contains distribution of teeth on the pitch curve, designs of the tooth tip curve and the tooth root curve, design of the tooth profile curve, the gear system dynamics principle is introduced to establish dynamics model for the noncircular gear; basic theory of finite element and mode analysis method are applied, finite element model for the noncircular gear is established, natural vibration characteristic of the noncircular gear is studied. And the oval gear is taken as an example, the mathematics software MathCAD, the 3D modeling software UG and the finite element software ABAQUS are used to realize precise 3D model of the oval gear. The finite element method is used, the natural vibration characteristic of the oval gear is studied, the main vibration types and natural frequencies of the oval gear and that of the equivalent cylindrical gears are analyzed and compared, the conclusions received reflect the dynamics performance of the oval gear, and solid foundation is laid for dynamics research and engineering application of the oval gear transmission

Innovators and Imitators in Product-Market Competition and Accounting Reporting

In this study, we examine firms’ investments in explorative initiatives and their choices of capitalization method in a product-market competition setting. Since the capitalization of exploration expenditures may contain information on whether a firm’s exploration investment is successful, financial reports may reveal important information to competitors, and thus may have real consequences in product-market competition. In our paper, we identify two driving forces that induce firms to choose different capitalization methods: an information-spillover effect and a preempting effect. We also find that enforcing an accounting method that requires firms to capitalize expenditures of only successful explorations may increase or decrease innovation investments. Our study sheds light on the impact that the recognition of exploratory success has on firms’ exploration investments