1,319 research outputs found
A Study and Analysis on the Physical Shading Effect of Water Quality Control in Constructed Wetlands
Experimental study on a new type floating breakwater
In the article, a new type floating breakwater is proposed based on comparing the performance of different kinds of floating breakwater that include pontoon type breakwater, scrap tire breakwater, mat float type breakwater etc. The outstanding feature of the new type breakwater is that damping at bottom of breakwater can increase wave energy dissipation and decrease coefficient of wave transmission and reflection. The relative width and relative submergence depth (the ratio of width to wave length W/L and submergence depth to wave length D/L) on the performance of the breakwater are discussed based on a series of physical model test in flume. The relationship between critical transmission coefficient (Ct=0.5) and relative width is given by experiment. In the actual design and application process, the various parameters are not independent, so the relationship between transmission coefficient and different parameters is analyzed in this paper
Hadronic B Decays to Charmed Baryons
We study exclusive B decays to final states containing a charmed baryon
within the pole model framework. Since the strong coupling for is larger than that for , the two-body charmful decay
has a rate larger than
as the former proceeds via the pole while the latter via the
pole. By the same token, the three-body decay receives less baryon-pole contribution than
. However, because the important charmed-meson
pole diagrams contribute constructively to the former and destructively to the
latter, has a rate slightly larger than
. It is found that one quarter of the rate comes from the resonant contributions. We discuss
the decays and
and stress that they are not color suppressed even though they can only proceed
via an internal W emission.Comment: 25 pages, 6 figure
Wolfenstein Parametrization at Higher Order: Seeming Discrepancies and Their Resolution
In different Wolfenstein parametrizations derived from different exact
parametrizations of the Cabibbo-Kobayashi-Maskawa matrix, we explicitly study
seeming discrepancies between the matrix elements at the higher order of the
expansion parameter . A systematic way of resolving the seeming
discrepancies is proposed. We find that most of the discrepancies can be
naturally resolved by a proper redefinition of the numerically small (of order
) parameters. Our approach is further applied to the cases for the
Wolfenstein-{\it like} parametrizations, such as the Qin-Ma parametrization.Comment: 5 pages, two paragraphs added to explain the motivation for
considering various Wolfenstein-like parametrizations; version to appear in
PL
Remarks on the Qin-Ma Parametrization of Quark Mixing Matrix
Recently, Qin and Ma (QM) have advocated a new Wolfenstein-like
parametrization of the quark mixing matrix based on the triminimal expansion of
the Cabibbo-Kobayashi-Maskawa (CKM) parametrization. The CP-odd phase in the QM
parametrization is around just as that in the CKM parametrization.
We point out that the QM parametrization can be readily obtained from the
Wolfenstein parametrization after appropriate phase redefinition for quark
fields and that the phase in both QM and CKM parametrizations is
related to the unitarity angles , and , namely,
or . We show that both QM and Wolfenstein
parametrizations can be deduced from the CKM and Chau-Keung-Maiani ones. By
deriving the QM parametrization from the Fritzsch-Xing (FX) parametrization of
the quark mixing matrix, we find that the phase of the FX form is in the
vicinity of and hence . We discuss the
seeming discrepancy between the Wolfenstein and QM parametrizations at the high
order of .Comment: 8 pages, a shortened version accepted by PL
Identification of differentially expressed genes induced by Bamboo mosaic virus infection in Nicotiana benthamiana by cDNA-amplified fragment length polymorphism
Background: The genes of plants can be up- or down-regulated during viral infection to influence the replication of viruses. Identification of these differentially expressed genes could shed light on the defense systems employed by plants and the mechanisms involved in the adaption of viruses to plant cells. Differential gene expression in Nicotiana benthamiana plants in response to infection with Bamboo mosaic virus (BaMV) was revealed using cDNA-amplified fragment length polymorphism (AFLP). Results: Following inoculation with BaMV, N. benthamiana displayed differential gene expression in response to the infection. Isolation, cloning, and sequencing analysis using cDNA-AFLP furnished 90 cDNA fragments with eight pairs of selective primers. Fifteen randomly selected genes were used for a combined virus-induced gene silencing (VIGS) knockdown experiment, using BaMV infection to investigate the roles played by these genes during viral infection, specifically addressing the means by which these genes influence the accumulation of BaMV protein. Nine of the 15 genes showed either a positive or a negative influence on the accumulation of BaMV protein. Six knockdown plants showed an increase in the accumulation of BaMV, suggesting that they played a role in the resistance to viral infection, while three plants showed a reduction in coat protein, indicating a positive influence on the accumulation of BaMV in plants. An interesting observation was that eight of the nine plants showing an increase in BaMV coat protein were associated with cell rescue, defense, death, aging, signal transduction, and energy production. Conclusions: This study reports an efficient and straightforward method for the identification of host genes involved in viral infection. We succeeded in establishing a cDNA-AFLP system to help track changes in gene expression patterns in N. benthamiana plants when infected with BaMV. The combination of both DNA-AFLP and VIGS methodologies made it possible to screen a large number of genes and identify those associated with infections of plant viruses. In this report, 9 of the 15 analyzed genes exhibited either a positive or a negative influence on the accumulation of BaMV in N. benthamiana plants
Implications of Recent Measurements of Hadronic Charmless B Decays
Implications of recent CLEO measurements of hadronic charmless B decays are
discussed. (i) Employing the Bauer-Stech-Wirbel (BSW) model for form factors as
a benchmark, the data indicate that the form factor
is smaller than that predicted by the BSW model, whereas the
data of imply that the form factors are greater than the BSW model's values. (ii) The tree-dominated
modes imply that the effective
number of colors N_c(LL) for (V-A)(V-A) operators is preferred to be smaller,
while the current limit on shows that N_c(LR)>3. The data of and clearly indicate that . (iii) In
order to understand the observed suppression of and
non-suppression of modes, both being governed by the form factor
, the unitarity angle is preferred to be greater than
. By contrast, the new measurement of no
longer strongly favors . (iv) The observed pattern K^-\pi^+\sim
\ov K^0\pi^-\sim {2\over 3}K^-\pi^0 is consistent with the theoretical
expectation: The constructive interference between electroweak and QCD penguin
diagrams in the mode explains why {\cal B}(B^-\to K^-\pi^0)>{1\over
2}{\cal B}(\ov B^0\to K^-\pi^+). (v) The observation \nc(LL)<3<\nc(LR) and
our preference for \nc(LL)\sim 2 and \nc(LR)\sim 6 are justified by a
recent perturbative QCD calculation of hadronic rare B decays in the heavy
quark limit.Comment: 21 pages; CLEO measurements of several charmless B decay modes are
updated. Discussion of the unitarity angle gamma in the \rho\pi mode is
revise
Efficient rooting for establishment of papaya plantlets by micropropagation
A low cost micropropagation protocol to produce high quality root systems which are easy and economical to acclimatize is essential for large-scale micropropagation of papaya (Carica papaya L.). In this study, individual shoots (> 0.5 cm) with 2 similar to 3 leaves from in vitro papaya multiple shoots were cultured on MS agar medium containing 2.5 mu M IBA under dark conditions for 1 week for root induction. They were then transferred to agar or vermiculite media, containing half strength MS medium, under aerated or non-aerated conditions, for root development. Rooting percentage of shoots cultured for 2 weeks in aerated vermiculite was 94.5%, compared with 90.0% in non-aerated vermiculite, 71.1% in aerated agar, and 62.2% in non-aerated agar. Shoots with roots were acclimated in vermiculite under 100% RH for 1 week and then under ambient conditions for 2 weeks in a temperature-controlled growth chamber (28 degrees C). The survival rates of the plantlets were 94.5% from aerated vermiculite, 87.8% from non-aerated vermiculite, 42.2% from aerated agar, and 35.6% from non-aerated agar. Thus, root induction in low-concentration IBA agar medium followed by root development in vermiculite containing half strength MS medium under aerated conditions results in efficient rooting of in vitro papaya shoots
B -> J/psi K^* Decays in QCD Factorization
The hadronic decay B -> J K^* is analyzed within the framework of QCD
factorization. The spin amplitudes A_0, A_\parallel and A_\perp in the
transversity basis and their relative phases are studied using various
different form-factor models for B-K^* transition. The effective parameters
a_2^h for helicity h=0,+,- states receive different nonfactorizable
contributions and hence they are helicity dependent, contrary to naive
factorization where a_2^h are universal and polarization independent. QCD
factorization breaks down even at the twist-2 level for transverse hard
spectator interactions. Although a nontrivial strong phase for the A_\parallel
amplitude can be achieved by adjusting the phase of an infrared divergent
contribution, the present QCD factorization calculation cannot say anything
definite about the phase phi_\parallel. Unlike B -> J/psi K decays, the
longitudinal parameter a_2^0 for B -> J/psi K^* does not receive twist-3
corrections and is not large enough to account for the observed branching ratio
and the fraction of longitudinal polarization. Possible enhancement mechanisms
for a_2^0 are discussed.Comment: 21 pages, 1 figure, a table and a reference added, some typos
correcte
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