385 research outputs found
Cosmological Constraints on the Sign-Changeable Interactions
Recently, Cai and Su [Phys. Rev. D {\bf 81}, 103514 (2010)] found that the
sign of interaction in the dark sector changed in the approximate redshift
range of 0.45\,\lsim\, z\,\lsim\, 0.9, by using a model-independent method to
deal with the observational data. In fact, this result raises a remarkable
problem, since most of the familiar interactions cannot change their signs in
the whole cosmic history. Motivated by the work of Cai and Su, we have proposed
a new type of interaction in a previous work [H. Wei, Nucl. Phys. B {\bf 845},
381 (2011)]. The key ingredient is the deceleration parameter in the
interaction , and hence the interaction can change its sign when our
universe changes from deceleration () to acceleration (). In the
present work, we consider the cosmological constraints on this new type of
sign-changeable interactions, by using the latest observational data. We find
that the cosmological constraints on the model parameters are fairly tight. In
particular, the key parameter can be constrained to a narrow range.Comment: 15 pages, 1 table, 8 figures, revtex4; v2: published versio
PENENTUAN MASSA FOTOKATALIS DAN SUHU OPTIMUM PADA PROSES FOTODEGRADASI ZAT WARNA RHODAMIN B MENGGUNAKAN FOTOKATALIS TiO2(DETERMINATION OF OPTIMUM TEMPERATURE AND PHOTOCATALYST MASS OF RHODAMINE B PHOTODEGRADATION PROCESS BY TiO2 PHOTOCATALYST)
Abstrak Telah dilakukan penelitian tentang penentuan massa fotokatalis dan suhu optimum pada proses fotodegradasi zat warna Rhodamin B menggunakan fotokatalis TiO2. Massa fotokatalis dan suhu optimum pada proses fotodegradasi zat warna Rhodamin B ditentukan dengan variasi massa 0 mg sampai 100 mg dan variasi suhu 30 oC sampai 60 oC. Fotodegradasi dilakukan dalam reaktor tertutup yang dilengkapi dengan lampu UV. Konsentrasi zat warna yang tersisa setelah fotodegradasi diukur dengan spektrofotometer UV-Vis. Kondisi maksimum pengukuran adalah pada panjang gelombang 553,40 nm. Hasil penelitian menunjukkan bahwa massa fotokatalis optimum pada proses fotodegradasi zat warna Rhodamin B sebesar 70 mg dan suhu optimum pada 50 oC. Kata kunci: massa fotokatalis, suhu larutan, Rhodamin B, TiO2. Abstract The determination of optimum temperature and photocatalyst mass of Rhodamine B photodegradation process was studied using TiO2 as catalyst. Optimum temperature and photocatalyst mass of Rhodamine B photodegradation process was determined by variation of mass 0 mg to 100 mg and variation of temperature at 30 oC to 60 oC. Photodegradation carried out in a closed reactor completed with UV lamp. The remaining of Rhodamine B concentration after photodegradation was measured by UV-Vis spectrophotometer. Maximum condition of measurement was at wavelength of 553,40 nm. The result showed that optimum photocatalyst mass of Rhodamine B photodegradation process was 70 mg and optimum temperature was 50 oC. Key Words: photocatalyst mass, solution’s temperature, Rhodamine B, TiO
Horava-Lifshitz Dark Energy
We formulate Horava-Lifshitz cosmology with an additional scalar field that
leads to an effective dark energy sector. We find that, due to the inherited
features from the gravitational background, Horava-Lifshitz dark energy
naturally presents very interesting behaviors, possessing a varying
equation-of-state parameter, exhibiting phantom behavior and allowing for a
realization of the phantom divide crossing. In addition, Horava-Lifshitz dark
energy guarantees for a bounce at small scale factors and it may trigger the
turnaround at large scale factors, leading naturally to cyclic cosmology.Comment: 17 pages, no figures, version published at EJP
Steamed panax notoginseng and its saponins inhibit the migration and induce the apoptosis of neutrophils in a zebrafish tail-fin amputation model
Panax notoginseng (PN) is a Chinese medicinal herb that is traditionally used to treat inflammation and immune-related diseases. Its major active constituents are saponins, the types and levels of which can be changed in the process of steaming. These differences in saponins are causally relevant to the differences in the therapeutic efficacies of raw and steamed PN. In this study, we have prepared the extracts of steamed PN (SPNE) with 70% ethanol and investigated their immunomodulatory effect using a zebrafish tail-fin amputation model. A fingerprint-effect relationship analysis was performed to uncover active constituents of SPNE samples related to the inhibitory effect on neutrophil number. The results showed that SPNE significantly inhibited the neutrophil number at the amputation site of zebrafish larvae. And SPNE extracts steamed at higher temperatures and for longer time periods showed a stronger inhibitory effect. Ginsenosides Rh-1, Rk(3), Rh-4, 20(S)-Rg(3), and 20(R)-Rg(3), of which the levels were increased along with the duration of steaming, were found to be the major active constituents contributing to the neutrophil-inhibiting effect of SPNE. By additionally investigating the number of neutrophils in the entire tail of zebrafish larvae and performing TUNEL assays, we found that the decreased number of neutrophils at the amputation site was due to both the inhibition of their migration and apoptosis-inducing effects of the ginsenosides in SPNE on neutrophils. Among them, Rh-1 and 20(R)-Rg(3) did not affect the number of neutrophils at the entire tail, suggesting that they only inhibit the migration of neutrophils. In contrast, ginsenosides Rk(3), Rh-4, 20(S)-Rg(3), and SPNE did not only inhibit the migration of neutrophils but also promoted neutrophilic cell death. In conclusion, this study sheds light on how SPNE, in particular the ginsenosides it contains, plays a role in immune modulation.Animal science
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
Running coupling: Does the coupling between dark energy and dark matter change sign during the cosmological evolution?
In this paper we put forward a running coupling scenario for describing the
interaction between dark energy and dark matter. The dark sector interaction in
our scenario is free of the assumption that the interaction term is
proportional to the Hubble expansion rate and the energy densities of dark
sectors. We only use a time-variable coupling (with the scale factor
of the universe) to characterize the interaction . We propose a
parametrization form for the running coupling in which the
early-time coupling is given by a constant , while today the coupling is
given by another constant, . For investigating the feature of the running
coupling, we employ three dark energy models, namely, the cosmological constant
model (), the constant model (), and the time-dependent
model (). We constrain the models with the current
observational data, including the type Ia supernova, the baryon acoustic
oscillation, the cosmic microwave background, the Hubble expansion rate, and
the X-ray gas mass fraction data. The fitting results indicate that a
time-varying vacuum scenario is favored, in which the coupling crosses
the noninteracting line () during the cosmological evolution and the sign
changes from negative to positive. The crossing of the noninteracting line
happens at around , and the crossing behavior is favored at about
1 confidence level. Our work implies that we should pay more attention
to the time-varying vacuum model and seriously consider the phenomenological
construction of a sign-changeable or oscillatory interaction between dark
sectors.Comment: 8 pages, 5 figures; refs added; to appear in EPJ
Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar
The branching ratios and Angular distributions for J/psi decays to Lambda
Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
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