1,842 research outputs found
On the Lack of Correlation Between [OIII]/[OII] and Lyman-Continuum Escape Fraction
We present the first results of our pilot study of 8 photometrically selected
Lyman continuum (LyC) emitting galaxy candidates from the COSMOS field and
focus on their optical emission line ratios. Observations were performed in the
H and K bands using the Multi-Object Spectrometer for Infra-Red Exploration
(MOSFIRE) instrument at the Keck Observatory, targeting the [OII], H,
and [OIII] emission lines. We find that photometrically selected LyC emitting
galaxy candidates have high ionization parameters, based on their high
[OIII]/[OII] ratios (O32), with an average ratio for our sample of 2.50.2.
Preliminary results of our companion Low Resolution Imaging Spectrometer (LRIS)
observations, targeting LyC and Ly, show that those galaxies with the
largest O32 are typically found to also be Ly emitters. High O32
galaxies are also found to have tentative non-zero LyC escape fractions
() based on band photometric detections. These results are
consistent with samples of highly ionized galaxies, including confirmed LyC
emitting galaxies from the literature. We also perform a detailed comparison
between the observed emission line ratios and simulated line ratios from
density bounded H regions modeled using the photoionization
code MAPPINGS V. Estimates of for our sample fall in the range
from 0.0-0.23 and suggest possible tension with published correlations between
O32 and , adding weight to dichotomy of arguments in the
literature. We highlight the possible effects of clumpy geometry and mergers
that may account for such tension.Comment: 21 pages, 11 figures, 3 tables, accepted for publication in MNRA
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Combining quantitative and qualitative survey work. Methodological framework, practical issues, and case studies
This document is an output of the DFID funded research project R7033 "Methodological Framework for Integrating Qualitative and Quantitative Approaches for Socio-Economic Survey Work". The project's main objective was to improve survey methodologies used in the natural resources sector, leading in turn to improved quality of information required for decision-making at the various stages of natural resources programmes and projects. The project, which was jointly implemented by the Natural Resources Institute and the Statistical Services Centre, attempted to bridge the gap between informal I qualitative methods on the one hand and formal I quantitative ones on the other. The document is presented in the form of a manual, allowing the user to read each of its parts and sections independently of each other. Nevertheless, cross references indicate links to other parts of the document where appropriate. Part I provides a methodological framework, which will also be available as a Best-Practice Guideline published by the Natural Resources Systems Programme of DFID. Part 11, which contains six theme papers, looks into a number of practical issues encountered when combining quantitative and qualitative survey techniques. And finally, in Part III case studies are used to demonstrate how the two approaches can be integrated in survey work and experiments related to the natural resources sector. The framework document, theme papers and case studies have been produced between 1998 and 2000
The long non-coding {RNA} {H19} suppresses carcinogenesis and chemoresistance in hepatocellular carcinoma
The long non-coding RNA (lncRNA) H19 represents a maternally expressed and epigenetically regulated imprinted gene product and is discussed to have either tumor-promoting or tumor-suppressive actions. Recently, H19 was shown to be regulated under inflammatory conditions. Therefore, aim of this study was to determine the function of H19 in hepatocellular carcinoma (HCC), an inflammation-associated type of tumor. In four different human HCC patient cohorts H19 was distinctly downregulated in tumor tissue compared to normal or non-tumorous adjacent tissue. We therefore determined the action of H19 in three different human hepatoma cell lines (HepG2, Plc/Prf5, and Huh7). Clonogenicity and proliferation assays showed that H19 overexpression could suppress tumor cell survival and proliferation after treatment with either sorafenib or doxorubicin, suggesting chemosensitizing actions of H19. Since HCC displays a highly chemoresistant tumor entity, cell lines resistant to doxorubicin or sorafenib were established. In all six chemoresistant cell lines H19 expression was significantly downregulated. The promoter methylation of the H19 gene was significantly different in chemoresistant cell lines compared to their sensitive counterparts. Chemoresistant cells were sensitized after H19 overexpression by either increasing the cytotoxic action of doxorubicin or decreasing cell proliferation upon sorafenib treatment. An H19 knockout mouse model (H19Δ3) showed increased tumor development and tumor cell proliferation after treatment with the carcinogen diethylnitrosamine (DEN) independent of the reciprocally imprinted insulin-like growth factor 2 (IGF2). In conclusion, H19 suppresses hepatocarcinogenesis, hepatoma cell growth, and HCC chemoresistance. Thus, mimicking H19 action might be a potential target to overcome chemoresistance in future HCC therapy
Evidence for CP Violation in B0 -> D+D- Decays
We report measurements of the branching fraction and CP violation parameters
in B0 -> D+D- decays. The results are based on a data sample that contains 535
x 10^6 BBbar pairs collected at the Upsilon(4S) resonance, with the Belle
detector at the KEKB asymmetric-energy e+e- collider. We obtain [1.97 +- 0.20
(stat) +- 0.20 (syst)] x 10^(-4) for the branching fraction of B0 -> D+D-. The
measured values of the CP violation parameters are: S = -1.13 +- 0.37 +- 0.09,
A = 0.91 +- 0.23 +- 0.06, where the first error is statistical and the second
is systematic. We find evidence of CP violation in B0 -> D+D- at the 4.1 sigma
confidence level. While the value of S is consistent with expectations from
other measurements, the value of the parameter A favors large direct CP
violation at the 3.2 sigma confidence level, in contradiction to Standard Model
expectations.Comment: 12 pages, 3 figures, submitted to PR
Study of the Baryon-Antibaryon Low-Mass Enhancements in Charmless Three-body Baryonic B Decays
The angular distributions of the baryon-antibaryon low-mass enhancements seen
in the charmless three-body baryonic B decays B+ -> p pbar K+, B0 -> p pbar Ks,
and B0 -> p Lambdabar pi- are reported. A quark fragmentation interpretation is
supported, while the gluonic resonance picture is disfavored. Searches for the
Theta+ and Theta++ pentaquarks in the relevant decay modes and possible
glueball states G with 2.2 GeV/c2 < M-ppbar < 2.4 GeV/c2 in the ppbar systems
give null results. We set upper limits on the products of branching fractions,
B(B0 -> Theta+ p)\times B(Theta+ -> p Ks) Theta++
pbar) \times B(Theta++ -> p K+) G K+) \times
B(G -> p pbar) < 4.1 \times 10^{-7} at the 90% confidence level. The analysis
is based on a 140 fb^{-1} data sample recorded on the Upsilon(4S) resonance
with the Belle detector at the KEKB asymmetric-energy e+e- collider.Comment: 14 pages, 13 figure files, update of hep-ex/0409010 for journal
submisssio
Measurements of Branching Fractions and Polarization in B > K^* rho Decays
We present results of a study of the charmless vector-vector decays B^0 ->
K^{*0} rho^0 and B^+ ->K^{*0} rho^+. The results are based on a 140 fb^{-1}
data sample collected by the Belle detector at the KEKB asymmetric e^+e^-
collider. We obtain the branching fraction B(B^+ -> K^{*0} rho^+)=(6.6 +-
2.2(stat.) +- 0.8 (syst.)) x 10^{-6}, and set upper limits on the branching
fractions B(B^0 -> K^{*0} rho^0) f_0(980)
K^{*0})<5.2 x 10^{-6}. We also perform a helicity analysis of the rho and K^*
vector mesons in the decay B^+ -> K^{*0} rho^+, and obtain the longitudinal
polarization fraction R_0(B^+ -> K^{*0} rho^+)=0.50 +-
0.19(stat.)+0.05-0.07}(syst.).Comment: 11 pages, 4 figures, submitted to ICHEP04, Beijing, Chin
Observation of a near-threshold omega-J/psi mass enhancement in exclusive B-->K omega J/psi decays
We report the observation of a near-threshold enhancement in the omega-J/psi
invariant mass distribution for exclusive B-->K omega J/psi decays. The results
are obtained from a 253 fb-1 data sample that contains 275 million BB-bar meson
pairs that were collected near the Upsilon(4S) resonance with the Belle
detector at the KEKB asymmetric energy e+e- collider. The statistical
significance of the omega-J/psi mass enhancement is estimated to be greater
than 8 sigma.Comment: 12 pages, 4 figures, submitted to Physical Review Letter
Measurement of Time-Dependent CP-Violating Asymmetries in Decay
We present a measurement of CP-violation parameters in the B0 -> KsKsKs decay
based on a sample of 275 x 10^6 BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider.
One neutral B meson is fully reconstructed in the decay B0 -> KsKsKs, and the
flavor of the accompanying B meson is identified from its decay products.
CP-violation parameters are obtained from the asymmetry in the distributions of
the proper-time interval between the two B decays: S = +1.26 +/- 0.68(stat) +/-
0.20(syst) and A = +0.54 +/- 0.34(stat) +/- 0.09(syst).Comment: 10 pages, 2 figures 10 pages, 2 figure
Measurement of D0 -> pilnu (Klnu) Form Factors and Absolute Branching Fractions
Using a 282 1/fb data sample collected by the Belle experiment at the KEKB
e+e- collider, we study D0 decays to K-l+nu and pi-l+nu final states. The D0
flavor and momentum are tagged through a full reconstruction of the recoiling
charm meson and additional mesons from fragmentation. The reconstruction method
provides very good resolution in neutrino momentum and in q^2 = (p_l+p_nu)^2.
Normalizing to the total number of D0 tags, we measure the absolute branching
fractions to be B(D0 -> Klnu) =(3.45 +- 0.07stat +- 0.20syst)% and B(D0 ->
pilnu) = (0.255 +- 0.019stat +- 0.016syst)% and the semi-leptonic form factors
(within the modified pole model) f+^K(0) = 0.695 +- 0.007stat +- 0.022syst and
f+^pi(0) = 0.624 +- 0.020stat +- 0.030syst.Comment: 9 pages, 2 figures, submitted to Phys. Rev. Let
Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar
We present the first evidence of the decay B- --> tau- nu_tau-bar using 414
fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at
the KEKB asymmetric-energy e+e- collider. Events are tagged by fully
reconstructing one of the B mesons in hadronic modes. We detect the signal with
a significance of 3.5 standard deviations including systematics, and measure
the branching fraction to be Br(B- --> tau- nu_tau-bar) = (1.79
+0.56-0.49(stat) +0.46-0.51(syst))*10^-4. This implies that f_B = 0.229
+0.036-0.031(stat) +0.034-0.037(syst) GeV and is the first direct measurement
of this quantity.Comment: 6 pages, 3 figures, to appear in Physical Review Letter
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