182 research outputs found
On the investigations of galaxy redshift periodicity
In this article we present a historical review of study of the redshift
periodicity of galaxies, starting from the first works performed in the
seventies of the twentieth century until the present day. We discuss the
observational data and methods used, showing in which cases the discretization
of redshifts was observed. We conclude that galaxy redshift periodisation is an
effect which can really exist. We also discussed the redshift discretization in
two different structures: the Local Group of galaxies and the Hercules
Supercluster. Contrary to the previous studies we consider all galaxies which
can be regarded as a structure member disregarding the accuracy of velocity
measurements. We applied the power spectrum analysis using the Hann function
for weighting, together with the jackknife error estimator. In both the
structures we found weak effects of redshift periodisation.Comment: 10 pages, 4 figures, to be published in Part. and Nucl. Lett. 200
Humanistic Criminology: Roots from Peter Kropotkin
Kropotkin\u27s extensive writings on criminological issues have been almost totally neglected. Through critical historical and macro-structural analyses Kropotkin assessed institutional arrangements disclosing how they were or were not meeting human needs. Our exploration focuses on Kropotkin\u27s theoretical contributions, his feelings-based criminology and his extremely insightful dualistic conceptualization of human nature . His contributions to penology, and his assessment of social arrangements which would meet the complex and ever-changing needs of humankind are briefly examined. Kropotkin\u27s analytic framework provides an insightful and provocative base from which to synthesize criminological thought and research and from which to take action to alter social arrangements which do not meet human needs
Oscillating universes as eigensolutions of cosmological Schr\"odinger equation
We propose a cosmological model which could explain, in a very natural way,
the apparently periodic structures of the universe, as revealed in a series of
recent observations. Our point of view is to reduce the cosmological
Friedman--Einstein dynamical system to a sort of Schr\"odinger equation whose
bound eigensolutions are oscillating functions. Taking into account the
cosmological expansion, the large scale periodic structure could be easily
recovered considering the amplitudes and the correlation lengths of the galaxy
clusters.Comment: 12 pages, Latex, submitted to Int. Jou. of Theor. Phy
The Metallicity of Intergalactic Gas in Cosmic Voids
We have used the Hubble/STIS and FUSE archives of ultraviolet spectra of
bright AGN to identify intergalactic Lya absorbers in nearby (z < 0.1) voids.
From a parent sample of 651 Lya absorbers, we identified 61 void absorbers
located more than 1.4/h_70 Mpc from the nearest L* or brighter galaxy.
Searching for metal absorption in high-quality (S/N > 10) spectra at the
location of three diagnostic metal lines (O VI 1032, C IV 1548, Si III 1206),
we detected no metal lines in any individual absorber, or in any group of
absorbers using pixel co-addition techniques. The best limits on metal-line
absorption in voids were set using four strong Lya absorbers with N(H I) >
10^{14} cm^-2, with 3-sigma equivalent-width limits ranging from 8 mA (O VI),
7-15 mA (C IV), and 4-10 mA (Si III). Photoionization modeling yields
metallicity limits Z < 10^{-1.8+/-0.4} Z_sun, from non-detections of C IV and O
VI, some 6 times lower than those seen in Lya and OVI absorbers at z < 0.1.
Although the void Lya absorbers could be pristine material, considerably deeper
spectra are required to rule out a universal metallicity floor produced by
bursts of early star formation, with no subsequent star formation in the voids.
The most consistent conclusion derived from these low-z results, and similar
searches at z = 3-5, is that galaxy filaments have increased their mean IGM
metallicity by factors of 30-100 since z = 3.Comment: Accepted for ApJ, 8 pages including Fig 1a,
Kinematics and binaries in young stellar aggregates. II. NGC 6913 = M29
Between 1996 and 2003 we have obtained 226 high resolution spectra of 16
stars in the field of the young open cluster NGC 6913, to the aim of
constraining its main properties and study its internal kinematics. Twelve of
the program stars turned out to be members, one of them probably unbound. Nine
are binaries (one eclipsing and another double lined) and for seven of them the
observations allowed to derive the orbital elements. All but two of the nine
discovered binaries are cluster members. In spite of the young age (a few Myr),
the cluster already shows signs that could be interpreted as evidence of
dynamical relaxation and mass segregation. However, they may be also the result
of an unconventional formation scenario. The dynamical (virial) mass as
estimated from the radial velocity dispersion is larger than the cluster
luminous mass, which may be explained by a combination of the optically thick
interstellar cloud that occults part of the cluster, the unbound state or
undetected very wide binary orbit of some of the members that inflate the
velocity dispersion and a high inclination for the axis of a possible cluster
angular momentum. All discovered binaries are hard enough to survive average
close encounters within the cluster and do not yet show sign of relaxation of
the orbital elements to values typical of field binaries.Comment: Astron.Astrophys. submitted, 8 figures, 7 tables, 12 pages. Figures 1
and 6 degraded in quality with respect to originals to save file dimension
Human GLB1 knockout cerebral organoids: A model system for testing AAV9-mediated GLB1 gene therapy for reducing GM1 ganglioside storage in GM1 gangliosidosis
GM1 gangliosidosis is an autosomal recessive neurodegenerative disorder caused by the deficiency of lysosomal gangliosidebeta-galactosidase (beta-gal) and resulting in accumulation of GM1 ganglioside. The disease spectrum ranges from infantile to late onset and is uniformly fatal, with no effective therapy currently available. Although animal models have been useful for understanding disease pathogenesis and exploring therapeutic targets, no relevant human central nervous system (CNS) model system has been available to study its early pathogenic events or test therapies. To develop a model of human GM1 gangliosidosis in the CNS, we employed CRISPR/Cas9 genome editing to target GLB1 exons 2 and 6, common sites for mutations in patients, to create isogenic induced pluripotent stem (iPS) cell lines with lysosomal beta-gal deficiency. We screened for clones with \u3c 5% of parental cell line beta-gal enzyme activity and confirmed GLB1 knockout clones using DNA sequencing. We then generated GLB1 knockout cerebral organoids from one of these GLB1 knockout iPS cell clones. Analysis of GLB1 knockout organoids in culture revealed progressive accumulation of GM1 ganglioside. GLB1 knockout organoids microinjected with AAV9-GLB1 vector showed a significant increase in beta-gal activity and a significant reduction in GM1 ganglioside content compared with AAV9-GFP-injected organoids, demonstrating the efficacy of an AAV9 gene therapy-based approach in GM1 gangliosidosis. This proof-of-concept in a human cerebral organoid model completes the pre-clinical studies to advance to clinical trials using the AAV9-GLB1 vector
Ca II Triplet Spectroscopy of Giants in SMC Star Clusters: Abundances, Velocities and the Age-Metallicity Relation
We have obtained spectra at the Ca II triplet of individual red giants in
seven SMC star clusters whose ages range from ~4 to 12 Gyr. The spectra have
been used to determine mean abundances for six of the star clusters to a
typical precision of 0.12 dex. When combined with existing data for other
objects, the resulting SMC age-metallicity relation is generally consistent
with that for a simple model of chemical evolution, scaled to the present-day
SMC mean abundance and gas mass fraction. Two of the clusters (Lindsay 113 and
NGC 339), however, have abundances that ~0.5 dex lower than that expected from
the mean age-metallicity relation. It is suggested that the formation of these
clusters, which have ages of ~5 Gyr, may have involved the infall of uneriched
gas, perhaps from the Magellanic Stream. The spectra also yield radial
velocities for the seven clusters. The resulting velocity dispersion is 16 +/-
4 km/sec, consistent with those of the SMC planetary nebula and carbon star
populations.Comment: 28 pages including 4 figure
Cerebral organoids derived from Sandhoff disease-induced pluripotent stem cells exhibit impaired neurodifferentiation
Sandhoff disease, one of the GM2 gangliosidoses, is a lysosomal storage disorder characterized by the absence of beta-hexosaminidase A and B activity and the concomitant lysosomal accumulation of its substrate, GM2 ganglioside. It features catastrophic neurodegeneration and death in early childhood. How the lysosomal accumulation of ganglioside might affect the early development of the nervous system is not understood. Recently, cerebral organoids derived from induced pluripotent stem (iPS) cells have illuminated early developmental events altered by disease processes. To develop an early neurodevelopmental model of Sandhoff disease, we first generated iPS cells from the fibroblasts of an infantile Sandhoff disease patient, then corrected one of the mutant HEXB alleles in those iPS cells using CRISPR/Cas9 genome-editing technology, thereby creating isogenic controls. Next, we used the parental Sandhoff disease iPS cells and isogenic HEXB-corrected iPS cell clones to generate cerebral organoids that modeled the first trimester of neurodevelopment. The Sandhoff disease organoids, but not the HEXB-corrected organoids, accumulated GM2 ganglioside and exhibited increased size and cellular proliferation compared with the HEXB-corrected organoids. Whole-transcriptome analysis demonstrated that development was impaired in the Sandhoff disease organoids, suggesting that alterations in neuronal differentiation may occur during early development in the GM2 gangliosidoses
The Interpretation of Photoelectric Colors for Stars of Types B-F
The accumulation of photoelectric data on the Johnson-Morgan system of B - V and U - B colors makes a preliminary theoretical reconnaissance desirable The colors were predicted for atmospheres of a wide range of effective temperatures and electron pressures. The effects of the Balmer jump on the response in the U band and of the Balmer lines in the B band were included, using averages taken over spectral type and luminosity classes. Table 2 gives the predicted fluxes as compared to a black body, the corrected B - V and U - B colors, and the color temperatures The zero point is based on Code's spectral scans of two stars. The results are most useful for differential effects over small ranges of 0 and P_e; the general temperature and pressure scale derived colorimetrically seems reasonable. The large effect of lines in certain white dwarfs explains some features of the observed colors
Gravitational structure formation in scale relativity
In the framework of the theory of scale relativity, we suggest a solution to
the cosmological problem of the formation and evolution of gravitational
structures on many scales. This approach is based on the giving up of the
hypothesis of differentiability of space-time coordinates. As a consequence of
this generalization, space-time is not only curved, but also fractal. In
analogy with Einstein's general relativistic methods, we describe the effects
of space fractality on motion by the construction of a covariant derivative.
The principle of equivalence allows us to write the equation of dynamics as a
geodesics equation that takes the form of the equation of free Galilean motion.
Then, after a change of variables, this equation can be integrated in terms of
a gravitational Schrodinger equation that involves a new fundamental
gravitational coupling constant, alpha_{g} = w_{0}/c. Its solutions give
probability densities that quantitatively describe precise morphologies in the
position space and in the velocity space. Finally the theoretical predictions
are successfully checked by a comparison with observational data: we find that
matter is self-organized in accordance with the solutions of the gravitational
Schrodinger equation on the basis of the universal constant w_{0}=144.7 +- 0.7
km/s (and its multiples and sub-multiples), from the scale of our Earth and the
Solar System to large scale structures of the UniverseComment: 34 pages, 42 figures. Higher quality figures adde
- …