The dynamics of stellar disks in live dark-matter halos

Recent developments in computer hardware and software enable researchers to simulate the self-gravitating evolution of galaxies at a resolution comparable to the actual number of stars. Here we present the results of a series of such simulations. We performed $N$-body simulations of disk galaxies with between 100 and 500 million particles over a wide range of initial conditions. Our calculations include a live bulge, disk, and dark matter halo, each of which is represented by self-gravitating particles in the $N$-body code. The simulations are performed using the gravitational $N$-body tree-code Bonsai running on the Piz Daint supercomputer. We find that the time scale over which the bar forms increases exponentially with decreasing disk-mass fraction and that the bar formation epoch exceeds a Hubble time when the disk-mass fraction is $\sim0.35$. These results can be explained with the swing-amplification theory. The condition for the formation of $m=2$ spirals is consistent with that for the formation of the bar, which is also an $m=2$ phenomenon. We further argue that the non-barred grand-design spiral galaxies are transitional, and that they evolve to barred galaxies on a dynamical timescale. We also confirm that the disk-mass fraction and shear rate are important parameters for the morphology of disk galaxies. The former affects the number of spiral arms and the bar formation epoch, and the latter determines the pitch angle of the spiral arms.Comment: 23 pages; 29 figures. Accepted by MNRA

Fundamental roles of reactive oxygen species and protective mechanisms in the female reproductive system

Controlled oxidation, such as disulfide bond formation in sperm nuclei and during ovulation, plays a fundamental role in mammalian reproduction. Excess oxidation, however, causes oxidative stress, resulting in the dysfunction of the reproductive process. Antioxidation reactions that reduce the levels of reactive oxygen species are of prime importance in reproductive systems in maintaining the quality of gametes and support reproduction. While anti-oxidative enzymes, such as superoxide dismutase and peroxidase, play a central role in eliminating oxidative stress, reduction-oxidation (redox) systems, comprised of mainly glutathione and thioredoxin, function to reduce the levels of oxidized molecules. Aldo-keto reductase, using NADPH as an electron donor, detoxifies carbonyl compounds resulting from the oxidation of lipids and proteins. Thus, many antioxidative and redox enzyme genes are expressed and aggressively protect gametes and embryos in reproductive systems

Unveiling the roles of the glutathione redox system in vivo by analyzing genetically modified mice

Redox status affects various cellular activities, such as proliferation, differentiation, and death. Recent studies suggest pivotal roles of reactive oxygen species not only in pathogenesis under oxidative insult but also in intracellular signal transduction. Glutathione is present in several millimolar concentrations in the cytoplasm and has multiple roles in the regulation of cellular homeostasis. Two enzymes, γ-glutamylcysteine synthetase and glutathione synthetase, constitute the de novo synthesis machinery, while glutathione reductase is involved in the recycling of oxidized glutathione. Multidrug resistant proteins and some other transporters are responsible for exporting oxidized glutathione, glutathione conjugates, and S-nitrosoglutathione. In addition to antioxidation, glutathione is more positively involved in cellular activity via its sulfhydryl moiety of a molecule. Animals in which genes responsible for glutathione metabolism are genetically modified can be used as beneficial and reliable models to elucidate roles of glutathione in vivo. This review article overviews recent progress in works related to genetically modified rodents and advances in the elucidation of glutathione-mediated reactions

Rabbit cardiac and slow-twitch muscle express the same phospholamban gene

AbstractThe nucleotide sequences of cDNAs encoding phospholamban were found to be virtually identical when the cDNA clones were isolated from rabbit slow-twitch (soleus) and rabbit cardiac muscle libraries. These findings demonstrate that both types of muscle express the same phospholamban gene. The deduced amino acid sequences of rabbit and dog phospholamban were identical except for a change from Asp (dog) to Glu (rabbit) at position 2. The nucleotide sequences of the 5′- and the very long 3′-untranslated regions of rabbit and dog phospholamban cDNAs also exhibited a high percentage of identity

Growing Local arm inferred by the breathing motion

Theoretical models of spiral arms suggest that the spiral arms provoke a vertical bulk motion in disc stars. By analysing the breathing motion, a coherent asymmetric vertical motion around the mid-plane of the Milky Way disc, with Gaia DR3, we found that a compressing breathing motion presents along the Local arm. On the other hand, with an N-body simulation of an isolated Milky Way-like disc galaxy, we found that the transient and dynamic spiral arms induce compressing breathing motions when the arms are in the growth phase, while the expanding breathing motion appears in the disruption phase. The observed clear alignment of the compressing breathing motion with the Local arm is similar to what is seen in the growth phase of the simulated spiral arms. Hence, we suggest that the Local arm’s compressing breathing motion can be explained by the Local arm being in the growth phase of a transient and dynamic spiral arm. We also identified the tentative signatures of the expanding breathing motion associated with the Perseus arm and also the Outer arm coinciding with the compressing breathing motion. This may infer that the Perseus and Outer arms are in the disruption and growth phases, respectively

A Method for Direct Measurement of the First-Order Mass Moments of Human Body Segments

We propose a simple and direct method for measuring the first-order mass moment of a human body segment. With the proposed method, the first-order mass moment of the body segment can be directly measured by using only one precision scale and one digital camera. In the dummy mass experiment, the relative standard uncertainty of a single set of measurements of the first-order mass moment is estimated to be 1.7%. The measured value will be useful as a reference for evaluating the uncertainty of the body segment inertial parameters (BSPs) estimated using an indirect method

Endoplasmic reticulum thiol oxidase deficiency leads to ascorbic acid depletion and noncanonical scurvy in mice

none5sì: Endoplasmic reticulum (ER) thiol oxidases initiate a disulfide relay to oxidatively fold secreted proteins. We found that combined loss-of-function mutations in genes encoding the ER thiol oxidases ERO1α, ERO1β, and PRDX4 compromised the extracellular matrix in mice and interfered with the intracellular maturation of procollagen. These severe abnormalities were associated with an unexpectedly modest delay in disulfide bond formation in secreted proteins but a profound, 5-fold lower procollagen 4-hydroxyproline content and enhanced cysteinyl sulfenic acid modification of ER proteins. Tissue ascorbic acid content was lower in mutant mice, and ascorbic acid supplementation improved procollagen maturation and lowered sulfenic acid content in vivo. In vitro, the presence of a sulfenic acid donor accelerated the oxidative inactivation of ascorbate by an H(2)O(2)-generating system. Compromised ER disulfide relay thus exposes protein thiols to competing oxidation to sulfenic acid, resulting in depletion of ascorbic acid, impaired procollagen proline 4-hydroxylation, and a noncanonical form of scurvy.openZito, Ester; Hansen, Henning Gram; Yeo, Giles S H; Fujii, Junichi; Ron, DavidZito, Ester; Hansen, Henning Gram; Yeo, Giles S H; Fujii, Junichi; Ron, Davi

Adsorption of benzene derivatives on allophane

The adsorption properties of benzene derivatives from water on allophane, extracted from soil, have been investigated by UV and FTIR spectroscopic measurements. Allophane adsorbs benzoic acid, phthalic acid, benzaldehyde, ethyl benzoate, and diethyl phthalate. Benzoic acid, phthalic acid, and benzaldehyde formed carboxylate anions on the positive sites of the hydrated alumina surface of allophane. In the case of adsorption from an acidic solution (pH 2), a small amount of a neutral species of benzoic acid was detected on the allophane. Ethyl benzoate and diethyl phthalate were adsorbed by an interaction between their carbonyl groups and the hydroxyl groups of the allophane. It was confirmed that allophane has an adsorption ability for the benzene derivatives that are not only ionic but also polar molecules. Allophane was found to be available as an absorbent for use in water purification by a simple procedure.ArticleAPPLIED CLAY SCIENCE. 43(2):160-163 (2009)journal articl

Clues to growth and disruption of two neighbouring spiral arms of the Milky Way

Studying the nature of spiral arms is essential for understanding the formation of the intricate disc structure of the Milky Way. The European Space Agency's Gaia mission has provided revolutionary observational data that have uncovered detailed kinematical features of stars in the Milky Way. However, so far the nature of spiral arms continues to remain a mystery. Here we present that the stellar kinematics traced by the classical Cepheids around the Perseus and Outer spiral arms in the Milky Way shows strikingly different kinematical properties from each other: the radial and azimuthal velocities of Cepheids with respect to the Galactic centre show positive and negative correlations in the Perseus and Outer arms, respectively. We also found that the dynamic spiral arms commonly seen in an N-body/hydrodynamics simulation of a Milky Way-like galaxy can naturally explain the observed kinematic trends. Furthermore, a comparison with such a simulation suggests that the Perseus arm is being disrupted while the Outer arm is growing. Our findings suggest that two neighbouring spiral arms in distinct evolutionary phases - growing and disrupting phases - coexist in the Milky Way.Comment: 8 pages, 7 figures; Submitted to MNRA