Universal convex covering problems under translation and discrete rotations

We consider the smallest-area universal covering of planar objects of perimeter 2 (or equivalently closed curves of length 2) allowing translation and discrete rotations. In particular, we show that the solution is an equilateral triangle of height 1 when translation and discrete rotation of $\pi$ are allowed. Our proof is purely geometric and elementary. We also give convex coverings of closed curves of length 2 under translation and discrete rotations of multiples of $\pi/2$ and $2\pi/3$. We show a minimality of the covering for discrete rotation of multiples of $\pi/2$, which is an equilateral triangle of height smaller than 1, and conjecture that the covering is the smallest-area convex covering. Finally, we give the smallest-area convex coverings of all unit segments under translation and discrete rotations $2\pi/k$ for all integers $k\ge 3$

Prevalence and risk factors of Helicobacter pylori infection in Korea: Nationwide multicenter study over 13 years

Background : The aim of this study was to evaluate the time trend of seropositivity of Helicobacter pylori (H. pylori) over the period of 13 years in an asymptomatic Korean population, and investigate associated risk factors. Methods : This cross-sectional nationwide multicentre study surveyed anti-H. pylori IgG antibodies in 19,272 health check-up subjects (aged [greater than and equal to]16 years) in 2011. Risk factors for H. pylori infection were investigated using logistic regression. Seropositivity in asymptomatic subjects without H. pylori eradication was compared between the years 1998 and 2005. Birth cohort effects were also evaluated. Results : After exclusion of subjects with a history of H. pylori eradication therapy (n = 3,712, 19.3%) and gastric symptoms (n = 4,764, 24.7%), the seroprevalence of H. pylori infection was 54.4% in 10,796 subjects. This was significantly lower than the seroprevalence of 59.6% in 2005 and that of 66.9% in 1998, and this decrease of seropositivity of H. pylori became widespread across all ages and in most areas of the country. This decreasing trend could be explained by cohort analysis. All younger birth cohorts had a lower seroprevalence of H. pylori than older birth cohorts at the same age. Decreased seroprevalence within the same birth cohorts also accounted for this phenomenon. Clinical risk factors of H. pylori infection were higher cholesterol level ([greater than and equal to] 240 mg/dl) (OR = 1.33; 95% CI = 1.14-1.54), male gender, older age, low income, and residence in a rural area. Conclusions : A decreasing trend of H. pylori seroprevalence due to a birth cohort effect requires further studies on its related human host factors as well as socio-economic and hygienic factors. In addition, the relationship between H. pylori infection and high cholesterol level needs more investigation regarding underlying pathogenesis.This work was supported by the National Research Foundation of Korea (NRF) grant for the Global Core Research Center (GCRC) funded by the Korea government (MSIP) (No. 2011-0030001)Peer Reviewe

Bond operator theory of doped antiferromagnets: from Mott insulators with bond-centered charge order, to superconductors with nodal fermions

The ground states and excitations of two-dimensional insulating and doped Mott insulators are described by a bond operator formalism. While the method represents the degrees of freedom of an arbitrary antiferromagnet exactly, it is especially suited to systems in which there is a natural pairing of sites into bonds, as in states with spontaneous or explicit spin-Peierls order (or bond-centered charge order). In the undoped insulator, as discussed previously, we obtain both paramagnetic and magnetically-ordered states. We describe the evolution of superconducting order in the ground state with increasing doping--at low doping, the superconductivity is weak, can co-exist with magnetic order, and there are no gapless spin 1/2 fermionic excitations; at high doping, the magnetic order is absent and we obtain a BCS d-wave superconductor with gapless spin 1/2, nodal fermions. We present the critical theory describing the onset of these nodal fermionic excitations. We discuss the evolution of the spin spectrum, and obtain regimes where a spin 1 exciton contributes a sharp resonance in the dynamic spin susceptiblity. We also discuss the experimental consequences of low-energy, dynamically fluctuating, spin-Peierls order in an isotropic CuO_2 plane--we compute consequences for the damping and dispersion of an optical phonon involving primarily the O ions, and compare the results with recent neutron scattering measurements of phonon spectra.Comment: 16 pages + 14 pages of appendices, 18 figures; (v3) expanded discussion of theory and experimental implications; (v4) Removed some introductory review discussion and moved it to cond-mat/010823

Agent-based approach for generation of a money-centered star network

The history of trade is a progression from a pure barter system. A medium of exchange emerges autonomously in the market, a position currently occupied by money. We investigate an agent-based computational economics model consisting of interacting agents considering distinguishable properties of commodities which represent salability. We also analyze the properties of the commodity network using a spanning tree. We find that the "storage fee" is more crucial than "demand" in determining which commodity is used as a medium of exchange. (C) 2008 Elsevier B.V. All rights reserved.X1155sciescopu

X-ray-Induced Changes in Wettability

We observed that hard X-ray irradiation modifies the wettability of a variety of inorganic materials. The smooth surfaces of all tested inorganic materials (ZnO, p-Si, Al2O3, SrTiO3, TiN, ZnS, CuO, Ag2O, and Cr2O3) change during it-radiation to a state of superhydrophilic wettability, and such changes are explained by the accumulation of positive surface charges by photoelectron emission. The initial wettability state is re-established within several minutes of storage in deionized water

Mitochondria-Targeting Ceria Nanoparticles as Antioxidants for Alzheimeŕs Disease

Mitochondrial oxidative stress is a key pathologic factor in neurodegenerative diseases, including Alzheimeŕs disease. Abnormal generation of reactive oxygen species (ROS), resulting from mitochondrial dysfunction, can lead to neuronal cell death. Ceria (CeO2) nanoparticles are known to function as strong and recyclable ROS scavengers by shuttling between Ce3+ and Ce4+ oxidation states. Consequently, targeting ceria nanoparticles selectively to mitochondria might be a promising therapeutic approach for neurodegenerative diseases. Here, we report the design and synthesis of triphenylphosphonium-conjugated ceria nanoparticles that localize to mitochondria and suppress neuronal death in a 5XFAD transgenic Alzheimeŕs disease mouse model. The triphenylphosphonium-conjugated ceria nanoparticles mitigate reactive gliosis and morphological mitochondria damage observed in these mice. Altogether, our data indicate that the triphenylphosphonium-conjugated ceria nanoparticles are a potential therapeutic candidate for mitochondrial oxidative stress in Alzheimeŕs disease. © 2016 American Chemical Society159621sciescopu

Performance of the QPLEX™ Alz plus assay, a novel multiplex kit for screening cerebral amyloid deposition

Background Alzheimers disease (AD) is an irreversible neurodegenerative disease characterized by the hallmark finding of cerebral amyloid deposition. Many researchers have tried to predict the existence of cerebral amyloid deposition by using easily accessible blood plasma samples, but the effectiveness of such strategies remains controversial. Methods We developed a new multiplex kit, the QPLEX™ Alz plus assay kit, which uses proteomics-based blood biomarkers to prescreen for cerebral amyloid deposition. A total of 300 participants who underwent Pittsburgh compound B (PiB)-positron emission tomography (PET) which allows imaging of cerebral amyloid deposition were included in this study. We compared the levels of QPLEX™ biomarkers between patients who were classified as PiB-negative or PiB-positive, regardless of their cognitive function. Logistic regression analysis followed by receiver operating characteristic (ROC) curve analysis was performed. The kit accuracy was tested using a randomized sample selection method. Results The results obtained using our assay kit reached 89.1% area under curve (AUC) with 80.0% sensitivity and 83.0% specificity. Further validation of the QPLEX™ Alz plus assay kit using a randomized sample selection method showed an average accuracy of 81.5%. Conclusions Our QPLEX™ Alz plus assay kit provides preliminary evidence that it can be used as blood marker to predict cerebral amyloid deposition but independent validation is needed.This work was supported by grants from the National Research Foundation (NRF) of Korea (NRF2019R1I1A1A01063525 to S-H.Han), from the Korea Health Technology R&D Project through Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI18C0630 and HI19C1132 to I. Mook-Jung), from the NRF (2018R1A5A2025964 to I. Mook-Jung, 2014M3C7A1046042 to D.Y.Lee), and from KHIDI (HI18C0630 and HI19C0149 to D.Y.Lee)

UBR2 mediates transcriptional silencing during spermatogenesis via histone ubiquitination

Ubiquitination of histones provides an important mechanism regulating chromatin remodeling and gene expression. Recent studies have revealed ubiquitin ligases involved in histone ubiquitination, yet the responsible enzymes and the function of histone ubiquitination in spermatogenesis remain unclear. We have previously shown that mice lacking the ubiquitin ligase UBR2, one of the recognition E3 components of the N-end rule proteolytic pathway, are infertile associated with meiotic arrest at prophase I. We here show that UBR2 localizes to meiotic chromatin regions, including unsynapsed axial elements linked to chromatin inactivation, and mediates transcriptional silencing via the ubiquitination of histone H2A. UBR2 interacts with the ubiquitin conjugating enzyme HR6B and its substrate H2A and promotes the HR6B–H2A interaction and the HR6B-to-H2A transfer of ubiquitin. UBR2 and ubiquitinated H2A (uH2A) spatiotemporally mark meiotic chromatin regions subject to transcriptional silencing, and UBR2-deficient spermatocytes fail to induce the ubiquitination of H2A during meiosis. UBR2-deficient spermatocytes are profoundly impaired in chromosome-wide transcriptional silencing of genes linked to unsynapsed axes of the X and Y chromosomes. Our findings suggest that insufficiency in UBR2-dependent histone ubiquitination triggers a pachytene checkpoint system, providing a new insight into chromatin remodeling and gene expression regulation