3,430 research outputs found
Star formation associated with neutral hydrogen in the outskirts of early-type galaxies
About 20 percent of all nearby early-type galaxies ( M) outside the Virgo cluster are surrounded by a disc
or ring of low-column-density neutral hydrogen (HI) gas with typical radii of
tens of kpc, much larger than the stellar body. In order to understand the
impact of these gas reservoirs on the host galaxies, we analyse the
distribution of star formation out to large radii as a function of HI
properties using GALEX UV and SDSS optical images. Our sample consists of 18
HI-rich galaxies as well as 55 control galaxies where no HI has been detected.
In half of the HI-rich galaxies the radial UV profile changes slope at the
position of the HI radial profile peak. To study the stellar populations, we
calculate the FUV-NUV and UV-optical colours in two apertures, 1-3 and 3-10
R . We find that HI -rich galaxies are on average 0.5 and 0.8 mag bluer
than the HI-poor ones, respectively. This indicates that a significant fraction
of the UV emission traces recent star formation and is associated with the HI
gas. Using FUV emission as a proxy for star formation, we estimate the
integrated star formation rate in the outer regions (R > 1R) to be on
average M yr for the HI-rich galaxies. This
rate is too low to build a substantial stellar disc and, therefore, change the
morphology of the host. We find that the star formation efficiency and the gas
depletion time are similar to those at the outskirts of spirals.Comment: 27 pages (13 without appendices). 9 figures, 5 tables, 2 appendix
tables and 12 appendix figures. Accepted for publication in MNRA
Effect Of Variation In Liquefied Petroleum Gas (LPG) Proportions In Spark Ignition Engine Emissions.
This paper presents an experimental investigation of a Liquefied Petroleum Gas (LPG) fueled four-stroke spark ignition engine. The primary objective of the study was to determine and quantify the exhaust emissions from the engine
Star formation in the outer regions of the early type galaxy NGC 4203
NGC 4203 is a nearby early-type galaxy surrounded by a very large,
low-column-density HI disc. In this paper we study the star formation
efficiency in the gas disc of NGC 4203 by using the UV, deep optical imaging
and infrared data. We confirm that the HI disc consists of two distinct
components: an inner star forming ring with radius from 1 to 3
R, and an outer disc. The outer HI disc is 9 times more massive than
the inner HI ring. At the location of the inner HI ring we detect spiral-like
structure both in the deep image and in the 8 m -IRAC
image, extending in radius up to 3 R. These two gas components
have a different star formation efficiency likely due to the different
metallicity and dust content. The inner component has a star formation
efficiency very similar to the inner regions of late-type galaxies. Although
the outer component has a very low star formation efficiency, it is similar to
that of the outer regions of spiral galaxies and dwarfs. We suggest that these
differences can be explained with different gas origins for the two components
such as stellar mass loss for the inner HI ring and accretion from the inter
galactic medium (IGM) for the outer HI disc. The low level star formation
efficiency in the outer HI disc is not enough to change the morphology of NGC
4203, making the depletion time of the HI gas much too long.Comment: Accepted for publication in MNRAS. 12 pages, 7 figure
Colour-singlet clustering of partons and recombination model for hadronization of quark-gluon plasma
colour-singlet restriction, along with flavour and spin symmetry,
on thermal partonic ensemble is shown to recombine the partons with internal
colour structure into colour-singlet multi-quark clusters which can be
identified with various hadronic modes at a given temperature. This provides a
possible basis for recombination model for hadronization of quark-gluon plasma.
This also leads to a natural explanation for the ratio of (anti)protons to
pions and the quark number scaling of the elliptic flow coefficient in
relativistic heavy-ion collisions.Comment: 5 pages; version accepted as a Rapid Communication in Phys. Rev.
The Emotion Regulation Training to Improve Quality of Life in Patients with Hypertension
Background : Quality of life is an indicator of health. Quality of life is used to evaluate the physical and psychosocial effects of an illness suffered by a person, including a person\u27s knowledge and perception of the illness. In order to achieve optimal quality of life, patients with hypertension were reported frequent use defense mechanisms to repress emotions or regulate emotions. Objective : The aim of this study was to investigate the effect of emotion regulation training to improve the quality of life among patients with hypertension. The hypothesis of this study stated that there was an influence of emotion regulation training to quality of life among patients with hypertension. Methods : The quality of life was measured by using quality of life scale based on aspect from WHOQOL-BREF (1998). An experimental method used was a pre and post-test control group design. Data were analysed by using Mann Whitney U. Results : The researchers found that there was no difference in the level of quality of life between the experimental group and the control group were not given training. However, the results of this study indicate that the quality of life scores in the experimental group increased during follow-up (p=0,002 (p<0,05). This suggest that quality of life among experimental group has increased compared to the control group, and consequently it accepted the hypothesis. Conclusion : Emotion regulation strategies can helped a person to cope the life stress that can be associated with psychological distress and quality of life
Potential algebra approach to position dependent mass Schroedinger equation
It is shown that for a class of position dependent mass Schroedinger equation
the shape invariance condition is equivalent to a potential symmetry algebra.
Explicit realization of such algebras have been obtained for some shape
invariant potentials
Can Van Hove singularities be observed in relativistic heavy-ion collisions ?
Based on general arguments the in-medium quark propagator in a quark-gluon
plasma leads to a quark dispersion relation consisting of two branches, of
which one exhibits a minimum at some finite momentum. This results in a
vanishing group velocity for collective quark modes. Important quantities such
as the production rate of low mass lepton pairs and mesonic correlators depend
inversely on this group velocity. Therefore these quantities, which follow from
self energy diagrams containing a quark loop, are strongly affected by Van Hove
singularities (peaks and gaps). If these sharp structures could be observed in
relativistic heavy-ion collisions it would reveal the physical picture of the
QGP as a gas of quasiparticles.Comment: 12 pages including nine figures and style files, invited talk given
at the ICPAQGP-2001, November 26-30, 2001, Jaipur, Indi
Thymoquinone overcomes chemoresistance and enhances the anticancer effects of bortezomib through abrogation of NF-κB regulated gene products in multiple myeloma xenograft mouse model
Multiple myeloma (MM) is a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow. With the advent of novel targeted agents, the median survival rate has increased to 5 -7 years. However, majority of patients with myeloma suffer relapse or develop chemoresistance to existing therapeutic agents. Thus, there is a need to develop novel alternative therapies for the treatment of MM. Thus in the present study, we investigated whether thymoquinone (TQ), a bioactive constituent of black seed oil, could suppress the proliferation and induce chemosensitization in human myeloma cells and xenograft mouse model. Our results show that TQ inhibited the proliferation of MM cells irrespective of their sensitivity to doxorubicin, melphalan or bortezomib. Interestingly, TQ treatment also resulted in a significant inhibition in the proliferation of CD138+ cells isolated from MM patient samples in a concentration dependent manner. TQ also potentiated the apoptotic effects of bortezomib in various MM cell lines through the activation of caspase-3, resulting in the cleavage of PARP. TQ treatment also inhibited chemotaxis and invasion induced by CXCL12 in MM cells. Furthermore, in a xenograft mouse model, TQ potentiated the antitumor effects of bortezomib (p < 0.05, vehicle versus bortezomib + TQ; p < 0.05, bortezomib versus bortezomib + TQ), and this correlated with modulation of various markers for survival and angiogenesis, such as Ki-67, vascular endothelial growth factor (VEGF), Bcl-2 and p65 expression. Overall, our results demonstrate that TQ can enhance the anticancer activity of bortezomib in vitro and in vivo and may have a substantial potential in the treatment of MM
Recursive residuals for linear mixed models
This paper presents and extends the concept of recursive residuals and their estimation to an important class of statistical models, Linear Mixed Models (LMM). Recurrence formulae are developed and recursive residuals are defined. Recursive computable expressions are also developed for the model’s likelihood, together with its derivative and information matrix. The theoretical framework for developing recursive residuals and their estimation for LMM varies with the estimation method used, such as the fitting-of-constants or the Best Linear Unbiased Predictor method. These methods are illustrated through application to an LMM example drawn from a published study. Model fit is assessed through a graphical display of the developed recursive residuals and their Cumulative Sums
Comparative study of selected indoor concentration from selective laser sintering process using virgin and recycled polyamide nylon (pa12)
Additive manufacturing (AM) stands out as one of the promising technologies that
have huge potential towards manufacturing industry. The study on additive manufacturing
impact on the environment and occupational exposure are attracting growing attention recently.
However, most of the researcher focus on desktop and fused deposition modelling type and less
attention given to the industrial type of AM. Usually, during the selective laser sintering process,
recycle powder will be used again to reduce cost and waste. This article compares the PM 2.5,
carbon dioxide (CO2) and total volatile organic compound (TVOC) concentration between virgin
and recycles powder using polyamide-nylon (PA12) towards indoor concentration. Four phases
of sampling involve during air sampling accordingly to the Industry Code of Practice on Indoor
Air Quality 2010 by DOSH Malaysia. It was found that PM 2.5 and CO2
concentration are mainly
generated during the pre-printing process. The recycle powder tended to appear higher compared
to virgin powder in terms of PM 2.5, and CO2. The peak value of PM 2.5 is 1452 μg/m3 and CO2
is 1218 ppm are obtained during the pre-printing process during 8 hours of sampling. TVOC
concentration from recycling powder is slightly higher during the post- printing phase where
confirm the influence of the powder cake and PA12 temperature from the printing process. In
summary, this work proves that elective laser sintering (SLS) machine operators are exposed to
a significant amount of exposure during the SLS printing process. Mitigation strategies and
personal protective equipment are suggested to reduce occupational exposure
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