31,575 research outputs found
Open clusters: their kinematics and metellicities
We review our work on Galactic open clusters in recent years, and introduce
our proposed large program for the LOCS (LAMOST Open Cluster Survey). First,
based on the most complete open clusters sample with metallicity, age and
distance data as well as kinematic information, some preliminary statistical
analysis regarding the spatial and metallicity distributions is presented. In
particular, a radial abundance gradient of - 0.058 0.006 dex kpc
was derived, and by dividing clusters into age groups we show that the disk
abundance gradient was steeper in the past. Secondly, proper motions,
membership probabilities, and velocity dispersions of stars in the regions of
two very young open clusters are derived. Both clusters show clear evidence of
mass segregation, which provides support for the ``primordial'' mass
segregation scenarios. Based on the great advantages of the forthcoming LAMOST
facility, we have proposed a detailed open cluster survey with LAMOST (the
LOCS). The aim, feasibility, and the present development of the LOCS are
briefly summarized.Comment: 7 pages, 4 figures, submitted to Proceeding of IAU Symposium No.248:
"A Giant Step:from Milli- to Micro-arcsecond Astrometry
Two-component model for the chemical evolution of the Galactic disk
In the present paper, we introduce a two-component model of the Galactic disk
to investigate its chemical evolution. The formation of the thick and thin
disks occur in two main accretion episodes with both infall rates to be
Gaussian. Both the pre-thin and post-thin scenarios for the formation of the
Galactic disk are considered. The best-fitting is obtained through
-test between the models and the new observed metallicity distribution
function of G dwarfs in the solar neighbourhood (Hou et al 1998). Our results
show that post-thin disk scenario for the formation of the Galactic disk should
be preferred. Still, other comparison between model predictions and
observations are given.Comment: 23 pages, 7 figure
Antioxidant and Antitumor Activity of Indonesian Herbal Ingredients
The present study was to aimed to evaluated and compare in vitro antioxidant activities of 2 Indonesian herbal ingredients (A and B), determined total phenol content., cytotoxic and apoptosis induction activities on HL-60 cells. These data were providing some useful information for people healthy dietary and the new potential application of natural antioxidant containing food materials in functional foods and also as new cancer therapeutics promising candidates. The parameters were total antioxidant activity, amount of total cytotoxic effect on the growth of human promyelocytic leukemia cells (HL-60). Statistical comparison was perform with Student's t-test at p<0.05. The correlation coefficient (r2) between the parameters tested was established by regression analysis. The scavenging effect of extracts herbal on DPPH radicals increased from 0.3-1.5 mg/ml, where is sample A 14.33% to 64.29% and sample B 9.09% to 57.53% was obtained. High content of total phenol compounds were in sample A (21.72 mg GAE/g), lower amounts were in sample B (17.53 mg GAE/g). Apoptosis of HL-60 cells from the morphological changes side (chromatin condensation). Chromatin condensation, a specific and distinct feature of apoptotic cells, was found in the majority of treated cells. The results indicated that the cell death receptor pathway was involved in the apoptosis induced by Indonesian herbal extracts
Which Constituent Quark Model Is Better?
A comparative study has been done by calculating the effective baryon-baryon
interactions of the 64 lowest channels consisting of octet and decuplet baryons
with three constituent quark models: the extended quark gluon exchange model,
the Goldstone boson exchange model and the quark gluon meson exchange hybrid
model. We find that these three models give similar results for 44 channels.
Further tests of these models are discussed.Comment: 6pp., 3 figs., Asia-Pacific Few-Body Conf. II (Shanghai, Aug.25-30
2002), to appear in MPLA; references adde
Eigenvalues of Ruijsenaars-Schneider models associated with root system in Bethe ansatz formalism
Ruijsenaars-Schneider models associated with root system with a
discrete coupling constant are studied. The eigenvalues of the Hamiltonian are
givein in terms of the Bethe ansatz formulas. Taking the "non-relativistic"
limit, we obtain the spectrum of the corresponding Calogero-Moser systems in
the third formulas of Felder et al [20].Comment: Latex file, 25 page
FHL2 regulates hematopoietic stem cell functions under stress conditions.
FHL2, a member of the four and one half LIM domain protein family, is a critical transcriptional modulator. Here, we identify FHL2 as a critical regulator of hematopoietic stem cells (HSCs) that is essential for maintaining HSC self-renewal under regenerative stress. We find that Fhl2 loss has limited effects on hematopoiesis under homeostatic conditions. In contrast, Fhl2-null chimeric mice reconstituted with Fhl2-null bone marrow cells developed abnormal hematopoiesis with significantly reduced numbers of HSCs, hematopoietic progenitor cells (HPCs), red blood cells and platelets as well as hemoglobin levels. In addition, HSCs displayed a significantly reduced self-renewal capacity and were skewed toward myeloid lineage differentiation. We find that Fhl2 loss reduces both HSC quiescence and survival in response to regenerative stress, probably as a consequence of Fhl2-loss-mediated downregulation of cyclin-dependent kinase-inhibitors, including p21(Cip) and p27(Kip1). Interestingly, FHL2 is regulated under the control of a tissue-specific promoter in hematopoietic cells and it is downregulated by DNA hypermethylation in the leukemia cell line and primary leukemia cells. Furthermore, we find that downregulation of FHL2 frequently occurs in myelodysplastic syndrome and acute myeloid leukemia patients, raising a possibility that FHL2 downregulation has a role in the pathogenesis of myeloid malignancies
Analytical solutions of the lattice Boltzmann BGK model
Analytical solutions of the two dimensional triangular and square lattice
Boltzmann BGK models have been obtained for the plain Poiseuille flow and the
plain Couette flow. The analytical solutions are written in terms of the
characteristic velocity of the flow, the single relaxation time and the
lattice spacing. The analytic solutions are the exact representation of these
two flows without any approximation.Comment: 10 pages, no postscript figure provide
The shape of disorder broadened Landau subbands in graphene
Density of states (DOS) of graphene under a high uniform magnetic field and
white-noise random potential is numerically calculated. The disorder broadened
zero-energy Landau band has a Gaussian shape whose width is proportional to the
random potential variance and the square root of magnetic field. Wegner-type
calculation is used to justify the results
Singlet Charge Quark hiding the Top: Tevatron and LEP Implications
If and quarks are strongly mixed with a weak singlet charge
quark, could be suppressed via the mode,
thereby the top quark could still hide below , whereas the heavy quark
signal observed at the Tevatron is due to the dominantly singlet quark .
This may occur without affecting the small value. Demanding GeV and m_t \ltap M_W, we find that cannot be too
suppressed. The heavy quark decays via , and bosons. The latter
can lead to -tagged jet events, while the strong -- mixing is
reflected in sizable fraction. decay occurs at tree
level and may be at the order, leading to the signature of , all isolated and with large , at order.Comment: 10 pages + 3 Figures (not included), ReVTeX, NTUTH-94-1
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