Endoscopic Treatment and Prevention of Acute Variceal Hemorrhage

Gastroesophageal varices occur in more than half of patients with cirrhosis and the incidence increases as liver function worsens. Although the mortality rate for acute variceal bleeding has decreased with the development of variceal endoscopic hemostasis and administration of vasoactive drugs and prophylactic antibiotics, it still reaches 20%. Therefore, surveillance of variceal occurrence and the prevention of their bleeding is very important in patients with cirrhosis. In patients with liver cirrhosis accompanied by portal hypertension, esophagogastroduodenoscopy should be performed to diagnose varices and stratify their bleeding risk. The interval of endoscopic surveillance is adjusted according to variceal condition and cirrhosis severity. If varices are diagnosed, primary prophylaxis (e.g., non-selective beta-blockers or endoscopic prophylaxis) is required to prevent variceal bleeding. Appropriate treatment, including timely endoscopic hemostasis, should be performed in patients with acute variceal bleeding, and secondary prophylaxis is required to prevent rebleeding. Endoscopic variceal ligation is the recommended endoscopic treatment for acute esophageal variceal bleeding; endoscopic variceal obstruction is usually recommended in patients with gastric varices. To prevent bleeding, endoscopic surveillance should be performed at regular intervals until the varices have been eradicated, and endoscopic followup should be performed periodically even after their disappearance. In this review, we investigate the role of endoscopy in the treatment and management of gastroesophageal varices

The discovery of blue-cored dwarf early-type galaxies in isolated environments

The presence of blue-cored dwarf early-type galaxies (dE(bc)s) in high-density environments supports the scenario of the transformation of infalling late-type galaxies into quiescent dwarf early-type galaxies by environmental effects. While low-density environments lacking environmental processes could not be relevant to the formation of dE(bc)s, we discovered a large sample of rare dE(bc)s in isolated environments at z < 0.01 using the NASA-Sloan Atlas catalog. Thirty-two isolated dE(bc)s were identified by visual inspection of the Sloan Digital Sky Survey images and g - r color profiles. We found that (1) isolated dE(bc)s exhibit similar structural parameters to dE(bc)s in the Virgo cluster; (2) based on the ultraviolet-r color-magnitude relation, color gradients, and optical emission lines of dE(bc)s, isolated dE(bc)s show more vigorous, centrally concentrated SF compared to their counterparts in the Virgo cluster; (3) at a given stellar mass, isolated dE(bc)s tend to have a larger fraction of gas mass than their Virgo counterparts. We discuss a scenario of episodic SF sustained by gas accretion, suggested by Sanchez Almeida et al., in which the star-bursting blue compact dwarf galaxy (BCD)-quiescent BCD (QBCD) cycle can be repeated during the Hubble time. We suggest that, in this cadence, isolated dE(bc)s might be QBCDs at pre- or post-BCD stages. Our results imply that dE(bc)s comprise a mixture of objects with two types of origins, nature or nurture, depending on their environment.Comment: 8 pages, 5 figures, accepted for publication in Astrophysical Journa

MINLP formulations for continuous piecewise linear function fitting

We consider a nonconvex mixed-integer nonlinear programming (MINLP) model proposed by Goldberg et al. (Comput Optim Appl 58:523–541, 2014. https://doi.org/10.1007/s10589-014-9647-y) for piecewise linear function fitting. We show that this MINLP model is incomplete and can result in a piecewise linear curve that is not the graph of a function, because it misses a set of necessary constraints. We provide two counterexamples to illustrate this effect, and propose three alternative models that correct this behavior. We investigate the theoretical relationship between these models and evaluate their computational performance

The properties of early-type galaxies in the Ursa Major cluster

Using SDSS-DR7 and NASA/IPAC Extragalactic Database spectroscopic data, we identify 166 galaxies as members of the Ursa Major cluster with Mr < -13.5 mag. We morphological classify all galaxies by means of carefully inspecting g-, r-, i-band colour and monochromatic images. We show that the Ursa Major cluster is dominated by late-type galaxies, but also contains a significant number of early- type galaxies, particularly in the dwarf regime. We present further evidence for the existence of several subgroups in the cluster, consistent with previous findings. The early-type fraction is found to correlate with the mass of the subgroup. We also investigate environmental effects by comparing the properties of the Ursa Major early-type dwarf galaxies to those of the Virgo cluster. In contrast to the Virgo, the red sequence of the Ursa Major cluster is only sparsely populated in the optical and ultraviolet colour-magnitude relations. It also shows a statistically significant gap between -18 < Mr < -17 mag, i.e. the Ursa Major cluster lacks early-type dwarf galaxies at the bright end of their luminosity function. We discover that the majority of early-type dwarf galaxies in the Ursa Major cluster have blue cores with hints of recent or ongoing star formation. We suggest that gravitational tidal interactions can trigger central blue star forming regions in early-type dwarfs. After that, star formation would only fade completely when the galaxies experience ram pressure stripping or harassment, both of which are nearly absent in the Ursa Major cluster.Comment: 19 pages, 18 figures, 2 tables, Accepted for publication in MNRA