The Role of Prox1 during Mouse Pancreas Organogenesis

The pancreas is a mixed (exocrine and endocrine) glandular organ that is important for food digestion and glucose homeostasis. Developmental anomalies or disorders that affect normal pancreas homeostasis may cause various life-threatening diseases such as pancreatitis, diabetes, cystic fibrosis, and pancreatic cancer. In the past two decades, an increasing number of studies have begun to unravel the molecular and cellular mechanisms regulating mammalian pancreas organogenesis. The information extracted from these studies should be valuable both, to better understand the etiology of some pancreatic diseases, and to design new therapeutic tools to cure those diseases. A recent study reported expression of the homeodomain transcription factor Prox1 in the presumptive pancreatic region of mouse embryos1. This finding raised the possibility that, similar to other tissues, proper pancreas development requires the function of Prox1. The studies of my Ph.D thesis sought to uncover the role of Prox1 during mouse pancreas organogenesis. First, the expression of Prox1 in the developing pancreas was thoroughly characterized and the pancreatic tissues of Prox1-nullizygous embryos were analyzed (Chapter 2). Second, since Prox1-nullizygous embryos die at around embryonic day (E) 14.5, we generated a (Prox1loxP/loxP novel mouse model ;Pdx1.Cre) with conditional inactivation of Prox1 in pancreatic progenitors, to investigate whether loss of Prox1 function affects late aspects of pancreas organogenesis (Chapter 3). Third, upon identifying Opn as a novel pancreatic gene, we performed an extensive analysis of its expression in the pancreas of mouse embryos and adults and characterized this organ of Opn-nullizygous mice (Chapter 4)

LHC Charge Asymmetry as Constraint on Models for the Tevatron Top Anomaly

The forward-backward asymmetry $A_{FB}^{t\bar t}$ in top quark production at the Tevatron has been observed to be anomalously large by both CDF and D0. It has been suggested that a model with a $W'$ coupling to $td$ and $ub$ might explain this anomaly, and other anomalies in $B$ mesons. Single-top-quark production in this model is large, and arguably in conflict with Tevatron measurements. However the model might still be viable if $A_{FB}^{t\bar t}$ is somewhat smaller than its current measured central value. We show that even with smaller couplings, the model can be discovered (or strongly excluded) at the LHC using the 2010 data sets. We find that a suitable charge-asymmetry measurement is a powerful tool that can be used to constrain this and other sources of anomalous single-top production, and perhaps other new high-energy charge-asymmetric processes.Comment: 25 pages, 4 figures, note adde

The Discovery of the Most Metal-Rich White Dwarf: Composition of a Tidally Disrupted Extrasolar Dwarf Planet

Cool white dwarf stars are usually found to have an outer atmosphere that is practically pure in hydrogen or helium. However, a small fraction have traces of heavy elements that must originate from the accretion of extrinsic material, most probably circumstellar matter. Upon examining thousands of Sloan Digital Sky Survey spectra, we discovered that the helium-atmosphere white dwarf SDSS J073842.56+183509.6 shows the most severe metal pollution ever seen in the outermost layers of such stars. We present here a quantitative analysis of this exciting star by combining high S/N follow-up spectroscopic and photometric observations with model atmospheres and evolutionary models. We determine the global structural properties of our target star, as well as the abundances of the most significant pollutants in its atmosphere, i.e., H, O, Na, Mg, Si, Ca, and Fe. The relative abundances of these elements imply that the source of the accreted material has a composition similar to that of Bulk Earth. We also report the signature of a circumstellar disk revealed through a large infrared excess in JHK photometry. Combined with our inferred estimate of the mass of the accreted material, this strongly suggests that we are witnessing the remains of a tidally disrupted extrasolar body that was as large as Ceres.Comment: 7 pages in emulateapj, 5 figures, accepted for publication in Ap

3D Model Atmospheres for Extremely Low-Mass White Dwarfs

We present an extended grid of mean three-dimensional (3D) spectra for low-mass, pure-hydrogen atmosphere DA white dwarfs (WDs). We use CO5BOLD radiation-hydrodynamics 3D simulations covering Teff = 6000-11,500 K and logg = 5-6.5 (cgs units) to derive analytical functions to convert spectroscopically determined 1D temperatures and surface gravities to 3D atmospheric parameters. Along with the previously published 3D models, the 1D to 3D corrections are now available for essentially all known convective DA WDs (i.e., logg = 5-9). For low-mass WDs, the correction in temperature is relatively small (a few per cent at the most), but the surface gravities measured from the 3D models are lower by as much as 0.35 dex. We revisit the spectroscopic analysis of the extremely low-mass (ELM) WDs, and demonstrate that the 3D models largely resolve the discrepancies seen in the radius and mass measurements for relatively cool ELM WDs in eclipsing double WD and WD + milli-second pulsar binary systems. We also use the 3D corrections to revise the boundaries of the ZZ Ceti instability strip, including the recently found ELM pulsators.Comment: 11 pages, 8 figures, accepted for publication in the Astrophysical Journa

Pulsed Beam Tests at the SANAEM RFQ Beamline

A proton beamline consisting of an inductively coupled plasma (ICP) source, two solenoid magnets, two steerer magnets and a radio frequency quadrupole (RFQ) is developed at the Turkish Atomic Energy Authority's (TAEA) Saraykoy Nuclear Research and Training Center (SNRTC-SANAEM) in Ankara. In Q4 of 2016, the RFQ was installed in the beamline. The high power tests of the RF power supply and the RF transmission line were done successfully. The high power RF conditioning of the RFQ was performed recently. The 13.56 MHz ICP source was tested in two different conditions, CW and pulsed. The characterization of the proton beam was done with ACCTs, Faraday cups and a pepper-pot emittance meter. Beam transverse emittance was measured in between the two solenoids of the LEBT. The measured beam is then reconstructed at the entrance of the RFQ by using computer simulations to determine the optimum solenoid currents for acceptance matching of the beam. This paper will introduce the pulsed beam test results at the SANAEM RFQ beamline. In addition, the high power RF conditioning of the RFQ will be discussed.Comment: 6 pages, 6 figures. Proceedings of the International Particle Accelerator Conference 2017 (IPAC'17), May 14-19, 2017, TUPAB015, p. 134

Evaluation of in vitro antifungal activity of potassium bicarbonate on Rhizoctonia solani AG 4 HG-I, Sclerotinia sclerotiorum and Trichoderma sp.

The effect of increased concentrations of potassium bicarbonate (KHCO3) as a possible alternative to synthetic fungicides for controlling Rhizoctonia solani AG 4 HG-I and Sclerotinia sclerotiorum was evaluated in vitro, in this study. In addition, the effect of potassium bicarbonate on Trichoderma sp., a natural antagonist on R. solani AG 4 HG-I and S. sclerotiorum was determined. Potassium bicarbonate substantially inhibited (P<0.05) the growth of the three fungal strains. Mycelial growth of R. solani AG 4 HG-I significantly decreased as the concentration of bicarbonate increased, especially at concentrations greater than 200 mM. Similarly, mycelial growth of both S. sclerotiorum and Trichoderma sp. dramatically reduced in increasing concentrations of KHCO3. Mycelial growth of either fungi was completely inhibited when exposed to 100 mM bicarbonate. In addition, KHCO3 concentrations higher than 10 mM caused significant (P<0.05) reduction of the sclerotium formation of S. sclerotiorum. Also, sclerotium germination and de novo sclerotium formation were significantly inhibited as the concentrations of KHCO3 increased. As a result, it was concluded that potassium bicarbonate was an alternative chemical agent for  controlling R. solani AG 4 HG-I and S. sclerotiorum. Also, KHCO3 was found to have negative effects on Trichoderma sp.Key words: Antifungal effect, KHCO3, soil borne pathogens, sclerotium germination

Current frameworks for reference ET and crop coefficient calculation

Estimation of evapotranspiration is under continual development and evolution, with significant developments and standardizations made during the past three decades for both reference ET (ETref) and for crop coefficients (Kc). These standardizations provide consistency and reproducibility in estimating ETref and a consistent basis for determining and expressing Kc curves, especially at the local scale. The application of the dual Kc procedure is growing, and has strong potential for improving accuracy of ET estimates as compared to the single Kc approach. This article describes current structures for estimating crop coefficients including the standardized FAO-56 dual Kc approach, with example applications. Emphasis is placed on estimation of parameters and special cases to be considered. Newer bases for establishing Kcb curves include thermal units and vegetation indices