724 research outputs found
Fluids in cosmology
We review the role of fluids in cosmology by first introducing them in
General Relativity and then by applying them to a FRW Universe's model. We
describe how relativistic and non-relativistic components evolve in the
background dynamics. We also introduce scalar fields to show that they are able
to yield an inflationary dynamics at very early times (inflation) and late
times (quintessence). Then, we proceed to study the thermodynamical properties
of the fluids and, lastly, its perturbed kinematics. We make emphasis in the
constrictions of parameters by recent cosmological probes.Comment: 34 pages, 4 figures, version accepted as invited review to the book
"Computational and Experimental Fluid Mechanics with Applications to Physics,
Engineering and the Environment". Version 2: typos corrected and references
expande
Promoter hypomethylation of the LINE-1 retrotransposable elements activates sense/antisense transcription and marks the progression of chronic myeloid leukemia
Aberrant genome-wide hypomethylation is thought to be
related to tumorigenesis by promoting genomic instability.
Since DNA methylation is considered an important mechanism
for the silencingof retroelements, hypomethylation
in human tumors may lead to their reactivation. However,
the role of DNA hypomethylation in chronic myeloid
leukemia (CML) remains to be elucidated. In this study,
the methylation status of the LINE-1 (L1) retrotransposon
promoter was analysed in CML samples from the chronicphase
(CP, n¼140) and the blast crisis (BC, n¼47). L1
hypomethylation was significantly more frequent in BC
(74.5%) than in CP (38%) (Po0.0001). Furthermore,
L1 hypomethylation led to activation of both ORF1 sense
transcription (Po0.0001) and c-MET gene antisense
transcription (Po0.0001), and was significantly associated
with high levels of BCR–ABL (P¼0.02) and
DNMT3b4 (P¼0.001) transcripts. Interestingly, in
CP-CML, extensive L1 hypomethylation was associated
with poorer prognosis in terms of cytogenetic response
to interferon (P¼0.004) or imatinib (P¼0.034) and
progression-free survival (P¼0.005). The above results
strongly suggest that activation of both sense and
antisense transcriptions by aberrant promoter hypomethylation
of the L1 elements plays a role in the progression
and clinical behavior of the CML
Epigenetic regulation of human cancer/testis antigen gene, HAGE, in chronic myeloid leukemia
Cancer testis antigens (CTA) provide attractive targets for cancer-specific immunotherapy.
Although CTA genes are expressed in some normal tissues, such as the testis,
this immunologically protected site lacks MHC I expression and as such, does not
present self antigens to T cells. To date, CTA genes have been shown to be expressed
in a range of solid tumors via demethylation of their promoter CpG islands, but rarely
in chronic myeloid leukemia (CML) or other hematologic malignancies
Using perturbation methods and Laplace–Padé approximation to solve nonlinear problems
WOS: 000328081500009In this paper, the perturbation method and Pade transformation are used to provide an approximate solution of elliptic integrals of the second kind and of complete integrals of the first kind. Besides, we used the obtained results to calculate an analytic expression for the period of a simple pendulum. The method has an acceptable accuracy for high values of the initial amplitude, compared to the relative error < 1.7% for initial angles theta <= 70 degree
Fossil evidence for spin alignment of SDSS galaxies in filaments
We search for and find fossil evidence that the distribution of the spin axes
of galaxies in cosmic web filaments relative to their host filaments are not
randomly distributed. This would indicate that the action of large scale tidal
torques effected the alignments of galaxies located in cosmic filaments. To
this end, we constructed a catalogue of clean filaments containing edge-on
galaxies. We started by applying the Multiscale Morphology Filter (MMF)
technique to the galaxies in a redshift-distortion corrected version of the
Sloan Digital Sky Survey DR5. From that sample we extracted those 426 filaments
that contained edge-on galaxies (b/a < 0.2). These filaments were then visually
classified relative to a variety of quality criteria. Statistical analysis
using "feature measures" indicates that the distribution of orientations of
these edge-on galaxies relative to their parent filament deviate significantly
from what would be expected on the basis of a random distribution of
orientations. The interpretation of this result may not be immediately
apparent, but it is easy to identify a population of 14 objects whose spin axes
are aligned perpendicular to the spine of the parent filament (\cos \theta <
0.2). The candidate objects are found in relatively less dense filaments. This
might be expected since galaxies in such locations suffer less interaction with
surrounding galaxies, and consequently better preserve their tidally induced
orientations relative to the parent filament. The technique of searching for
fossil evidence of alignment yields relatively few candidate objects, but it
does not suffer from the dilution effects inherent in correlation analysis of
large samples.Comment: 20 pages, 19 figures, slightly revised and upgraded version, accepted
for publication by MNRAS. For high-res version see
http://www.astro.rug.nl/~weygaert/SpinAlignJones.rev.pd
Analytical Solutions for Systems of Singular Partial Differential-Algebraic Equations
This paper proposes power series method (PSM) in order to find solutions for singular partial differential-algebraic equations (SPDAEs). We will solve three examples to show that PSM method can be used to search for analytical solutions of SPDAEs. What is more, we will see that, in some cases, Padé posttreatment, besides enlarging the domain of convergence, may be employed in order to get the exact solution from the truncated series solutions of PSM
Analytical Solutions for Systems of Singular Partial Differential-Algebraic Equations
This paper proposes power series method (PSM) in order to find solutions for singular partial differential-algebraic equations (SPDAEs). We will solve three examples to show that PSM method can be used to search for analytical solutions of SPDAEs. What is more, we will see that, in some cases, Padé posttreatment, besides enlarging the domain of convergence, may be employed in order to get the exact solution from the truncated series solutions of PSM
HPM Approximations for Trajectories: From a Golf Ball Path to Mercury’s Orbit
In this work, we propose the approximated analytical solutions for two highly nonlinear problems using the homotopy perturbation method (HPM). We obtained approximations for a golf ball trajectory model and a Mercury orbit’s model. In addition, to enlarge the domain of convergence of the first case study, we apply the Laplace-Padé resummation method to the HPM series solution. For both case studies, we were able to obtain approximations in good agreement with numerical methods, depicting the basic nature of the trajectories of the phenomena
New Insights into the Evolution of Metazoan Tyrosinase Gene Family
Tyrosinases, widely distributed among animals, plants and fungi, are involved in the biosynthesis of melanin, a pigment that has been exploited, in the course of evolution, to serve different functions. We conducted a deep evolutionary analysis of tyrosinase family amongst metazoa, thanks to the availability of new sequenced genomes, assessing that tyrosinases (tyr) represent a distinctive feature of all the organisms included in our study and, interestingly, they show an independent expansion in most of the analyzed phyla. Tyrosinase-related proteins (tyrp), which derive from tyr but show distinct key residues in the catalytic domain, constitute an invention of chordate lineage. In addition we here reported a detailed study of the expression territories of the ascidian Ciona intestinalis tyr and tyrps. Furthermore, we put efforts in the identification of the regulatory sequences responsible for their expression in pigment cell lineage. Collectively, the results reported here enlarge our knowledge about the tyrosinase gene family as valuable resource for understanding the genetic components involved in pigment cells evolution and development
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
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