On the square of a uniserial module (Logic, Language, Algebraic system and Related Areas in Computer Science)

A module M is said to be lifting if, for any submodule N of M, there exists a direct summand X of M contained in N such that NX is small in MX. A module M is said to satisfy the finite internal exchange property if, for any direct summand X of M and any finite direct sum decomposition M = ⊕^ni=1 Mi, there exists M´i ⊆ Mi (i = 1, 2, ... , n) such that M = X⊕(⊕^ni=1 M´i). In this paper, we solve negatively the open problem "does any lifting module satisfy the finite internal exchange property?" by considering the square of a certain lifting module

Possibility of Concentration of Non-volatile Species near the Surface of Comet 67P/Churyumov-Gerasimenko

The cometary materials are thought to be the reservoir of primitive materials in the Solar System. The recent detection of glycine and CH$_3$NH$_2$ by the ROSINA mass spectrometer in the coma of 67P/Churyumov-Gerasimenko suggests that amino acids and their precursors may have been formed in an early evolutionary phase of the Solar System. We investigate the evolution of cometary interior considering the evaporation process of water followed by the concentration of non-volatile species. We develop a Simplified Cometary Concentration Model (SCCM) to simulate the evaporation and concentration processes on the cometary surface.We use 67P/Churyumov-Gerasimenko as the benchmark of SCCM. We investigate the depth of the layer where non-volatile species concentrate after the numerous passages of perihelion after the formation of the Solar System. As a result, the SCCM explains the observed production rates of water and CH$_3$NH$_2$ at 100 comet years. SCCM results suggest that the non-volatile species would concentrate at depths between 0 and 100cm of comet surface within 10 comet years. Our results also suggest that the non-volatile species would concentrate several meters beneath the surface before it hit the early Earth. This specific mass of non-volatile species may provide unique chemical condition to the volcanic hot spring pools.Comment: accepted to A&

Proliferation Potentials of Human Intracranial Neoplasms Assessed with Ki-67 (MIB-1) Labeling Index and Argyrophilic Nucleolar Organizer Regions

To evaluate the accuracy of the Ki-67 labeling index (LI) as an index of brain tumor proliferation, specimens of 303 intracranial neoplasms were examined for tumor proliferation potentials as assessed by MIB-1 (Ki-67 antigen) immunostaining and/or counting the argyrophilic nucleolar organizer regions (Ag-NORs). The Ki-67 LIs were higher in the histologically high grade tumors, i.e., the metastatic carcinomas, malignant lymphomas, glioblastomas, medulloblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas, anaplastic ependymomas, and anaplastic meningiomas compared to the histologically low grade tumors, i.e., the pilocytic astrocytomas, grade II astrocytomas, oligodendrogliomas, ependymomas, meningiomas other than those of the anaplastic variety, and pituitary adenomas. The number of Ag-NORs was not correlated with the tumor grade, and was inconsistent with the growth potential in some tumors. Moreover, in the consecutive sections of 87 tumors stained for both Ki-67 and Ag-NORs, the number of Ag-NORs did not correlate with the tumor Ki-67 LI in a regression analysis (r = 0.139). The patients with a high grade astrocytoma (anaplastic astrocytoma and glioblastoma) and a tumor Ki-67 LI > 10 had significantly shorter survival periods than those of the patients with a Ki-67 LI < 10 (p = 0.029). Our results thus suggest that Ki-67 is a potential marker of tumor growth activity and that the Ki-67 LI may be of use as an indicator of the prognosis of patients with brain tumor. The number of Ag-NORs may not always reflect the growth potential of some tumors

A new numerical method for constructing quasi-equilibrium sequences of irrotational binary neutron stars in general relativity

We propose a new numerical method to compute quasi-equilibrium sequences of general relativistic irrotational binary neutron star systems. It is a good approximation to assume that (1) the binary star system is irrotational, i.e. the vorticity of the flow field inside component stars vanishes everywhere (irrotational flow), and (2) the binary star system is in quasi-equilibrium, for an inspiraling binary neutron star system just before the coalescence as a result of gravitational wave emission. We can introduce the velocity potential for such an irrotational flow field, which satisfies an elliptic partial differential equation (PDE) with a Neumann type boundary condition at the stellar surface. For a treatment of general relativistic gravity, we use the Wilson--Mathews formulation, which assumes conformal flatness for spatial components of metric. In this formulation, the basic equations are expressed by a system of elliptic PDEs. We have developed a method to solve these PDEs with appropriate boundary conditions. The method is based on the established prescription for computing equilibrium states of rapidly rotating axisymmetric neutron stars or Newtonian binary systems. We have checked the reliability of our new code by comparing our results with those of other computations available. We have also performed several convergence tests. By using this code, we have obtained quasi-equilibrium sequences of irrotational binary star systems with strong gravity as models for final states of real evolution of binary neutron star systems just before coalescence. Analysis of our quasi-equilibrium sequences of binary star systems shows that the systems may not suffer from dynamical instability of the orbital motion and that the maximum density does not increase as the binary separation decreases.Comment: 20 pages, 18 figures, more results of convergence tests are added, revised version accepted for publication in PR

Comparative transcriptomic characterization of aluminum, sodium chloride, cadmium and copper rhizotoxicities in Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>Rhizotoxic ions in problem soils inhibit nutrient and water acquisition by roots, which in turn leads to reduced crop yields. Previous studies on the effects of rhizotoxic ions on root growth and physiological functions suggested that some mechanisms were common to all rhizotoxins, while others were more specific. To understand this complex system, we performed comparative transcriptomic analysis with various rhizotoxic ions, followed by bioinformatics analysis, in the model plant <it>Arabidopsis thaliana</it>.</p> <p>Results</p> <p>Roots of <it>Arabidopsis </it>were treated with the major rhizotoxic stressors, aluminum (Al) ions, cadmium (Cd) ions, copper (Cu) ions and sodium (NaCl) chloride, and the gene expression responses were analyzed by DNA array technology. The top 2.5% of genes whose expression was most increased by each stressor were compared with identify common and specific gene expression responses induced by these stressors. A number of genes encoding glutathione-S-transferases, peroxidases, Ca-binding proteins and a trehalose-synthesizing enzyme were induced by all stressors. In contrast, gene ontological categorization identified sets of genes uniquely induced by each stressor, with distinct patterns of biological processes and molecular function. These contained known resistance genes for each stressor, such as <it>AtALMT1 </it>(encoding Al-activated malate transporter) in the Al-specific group and <it>DREB </it>(encoding dehydration responsive element binding protein) in the NaCl-specific group. These gene groups are likely to reflect the common and differential cellular responses and the induction of defense systems in response to each ion. We also identified co-expressed gene groups specific to rhizotoxic ions, which might aid further detailed investigation of the response mechanisms.</p> <p>Conclusion</p> <p>In order to understand the complex responses of roots to rhizotoxic ions, we performed comparative transcriptomic analysis followed by bioinformatics characterization. Our analyses revealed that both general and specific genes were induced in <it>Arabidopsis </it>roots exposed to various rhizotoxic ions. Several defense systems, such as the production of reactive oxygen species and disturbance of Ca homeostasis, were triggered by all stressors, while specific defense genes were also induced by individual stressors. Similar studies in different plant species could help to clarify the resistance mechanisms at the molecular level to provide information that can be utilized for marker-assisted selection.</p

Comparative transcriptomic characterization of aluminum, sodium chloride, cadmium and copper rhizotoxicities in Arabidopsis thaliana

Abstract Background Rhizotoxic ions in problem soils inhibit nutrient and water acquisition by roots, which in turn leads to reduced crop yields. Previous studies on the effects of rhizotoxic ions on root growth and physiological functions suggested that some mechanisms were common to all rhizotoxins, while others were more specific. To understand this complex system, we performed comparative transcriptomic analysis with various rhizotoxic ions, followed by bioinformatics analysis, in the model plant Arabidopsis thaliana. Results Roots of Arabidopsis were treated with the major rhizotoxic stressors, aluminum (Al) ions, cadmium (Cd) ions, copper (Cu) ions and sodium (NaCl) chloride, and the gene expression responses were analyzed by DNA array technology. The top 2.5% of genes whose expression was most increased by each stressor were compared with identify common and specific gene expression responses induced by these stressors. A number of genes encoding glutathione-S-transferases, peroxidases, Ca-binding proteins and a trehalose-synthesizing enzyme were induced by all stressors. In contrast, gene ontological categorization identified sets of genes uniquely induced by each stressor, with distinct patterns of biological processes and molecular function. These contained known resistance genes for each stressor, such as AtALMT1 (encoding Al-activated malate transporter) in the Al-specific group and DREB (encoding dehydration responsive element binding protein) in the NaCl-specific group. These gene groups are likely to reflect the common and differential cellular responses and the induction of defense systems in response to each ion. We also identified co-expressed gene groups specific to rhizotoxic ions, which might aid further detailed investigation of the response mechanisms. Conclusion In order to understand the complex responses of roots to rhizotoxic ions, we performed comparative transcriptomic analysis followed by bioinformatics characterization. Our analyses revealed that both general and specific genes were induced in Arabidopsis roots exposed to various rhizotoxic ions. Several defense systems, such as the production of reactive oxygen species and disturbance of Ca homeostasis, were triggered by all stressors, while specific defense genes were also induced by individual stressors. Similar studies in different plant species could help to clarify the resistance mechanisms at the molecular level to provide information that can be utilized for marker-assisted selection.</p

Opposing role of condensin hinge against replication protein A in mitosis and interphase through promoting DNA annealing

Condensin is required for chromosome dynamics and diverse DNA metabolism. How condensin works, however, is not well understood. Condensin contains two structural maintenance of chromosomes (SMC) subunits with the terminal globular domains connected to coiled-coil that is interrupted by the central hinge. Heterotrimeric non-SMC subunits regulate SMC. We identified a novel fission yeast SMC hinge mutant, cut14-Y1, which displayed defects in DNA damage repair and chromosome segregation. It contains an amino acid substitution at a conserved hinge residue of Cut14/SMC2, resulting in diminished DNA binding and annealing. A replication protein A mutant, ssb1-418, greatly alleviated the repair and mitotic defects of cut14-Y1. Ssb1 protein formed nucleolar foci in cut14-Y1 cells, but the number of foci was diminished in cut14-Y1 ssb1-418 double mutants. Consistent with the above results, Ssb1 protein bound to single-strand DNA was removed by condensin or the SMC dimer through DNA reannealing in vitro. Similarly, RNA hybridized to DNA may be removed by the SMC dimer. Thus, condensin may wind up DNA strands to unload chromosomal components after DNA repair and prior to mitosis. We show that 16 suppressor mutations of cut14-Y1 were all mapped within the hinge domain, which surrounded the original L543 mutation site