237 research outputs found
Analytical theory of coherent synchrotron radiation wakefield of short bunches shielded by conducting parallel plates
We develop a general model of coherent synchrotron radiation (CSR) impedance
with shielding provided by two parallel conducting plates. This model allows us
to easily reproduce all previously known analytical CSR wakes and to expand the
analysis to the situations not explored before. It reduces calculations of the
impedance to taking integrals along the trajectory of the beam. New analytical
results are derived for the radiation impedance with shielding for the
following orbits: a kink, a bending magnet, a wiggler of finite length, and an
infinitely long wiggler. All our formulas are benchmarked agains numerical
simulations with the CSRZ computer code
Generalized Panofsky-Wenzel theorem in curvilinear coordinate systems applicable to non-ultrarelativistic beams
This note gives an introduction to the theories of impedances and wakes in
particle accelerators. The standard formulation assumes that the beam is
traveling along a straight orbit with constant velocity .
On this note, we show the possibility of extending the formulation for beams
traveling along a curved orbit but assuming to be constant.Comment: 22 pages, 1 figure. arXiv admin note: text overlap with
arXiv:2101.0436
General formulation of impedance in Frenet-Serret coordinate system
In accelerator physics, the concept of impedance is popularly used to
describe the interactions of charged particles inside a bunch or between
bunches in a train. Standard formulations of impedance assume that the driving
charge has a constant velocity in the direction of the
Cartesian coordinate system. For the case of driving charge moving along a
curved orbit, impedance can be formulated in the Frenet-Serret coordinate
system, but there seems to be a lack of systematic formulations. This note
presents an effort in this direction.Comment: 11 page
Potential-well bunch lengthening in electron storage rings
The cubic equation derived by B. Zotter has been popularly used for electron
storage rings to describe the scaling law of potential-well bunch lengthening.
This equation has also often been used to calculate the effective impedance
when the bunch lengthening is measured or simulated. This paper discusses the
validity of Zotter's equation and presents an alternative but self-consistent
equation for potential-well bunch lengthening. Its applications to predicting
bunch lengthening and extracting effective impedance from bunch length
measurements are also addressed.Comment: 6 pages, 4 figures, submitted to 20th Annual Meeting of Particle
Accelerator Society of Japan (PASJ2023). arXiv admin note: text overlap with
arXiv:2307.0128
Singlino-dominated dark matter in general NMSSM
The general Next-to-Minimal Supersymmetric Standard Model (NMSSM) describes
the singlino-dominated dark-matter (DM) property by four independent
parameters: singlet-doublet Higgs coupling coefficient , Higgsino mass
, DM mass , and singlet Higgs self-coupling
coefficient . The first three parameters strongly influence the
DM-nucleon scattering rate, while usually affects the scattering only
slightly. This characteristic implies that singlet-dominated particles may form
a secluded DM sector. Under such a theoretical structure, the DM achieves the
correct abundance by annihilating into a pair of singlet-dominated Higgs bosons
by adjusting 's value. Its scattering with nucleons is suppressed when
is small. This speculation is verified by sophisticated
scanning of the theory's parameter space with various experiment constraints
considered. In addition, the Bayesian evidence of the general NMSSM and that of
-NMSSM is computed. It is found that, at the cost of introducing one
additional parameter, the former is approximately times the
latter. This result corresponds to Jeffrey's scale of 8.05 and implies that the
considered experiments strongly prefer the general NMSSM to the -NMSSM.Comment: 29 pages, 9 figure
Impacts of Intensified Agriculture Developments on Marsh Wetlands
A spatiotemporal analysis on the changes in the marsh landscape in the Honghe National Nature Reserve, a Ramsar reserve, and the surrounding farms in the core area of the Sanjiang Plain during the past 30 years was conducted by integrating field survey work with remote sensing techniques. The results indicated that intensified agricultural development had transformed a unique natural marsh landscape into an agricultural landscape during the past 30 years. Ninety percent of the natural marsh wetlands have been lost, and the areas of the other natural landscapes have decreased very rapidly. Most dry farmland had been replaced by paddy fields during the progressive change of the natural landscape to a farm landscape. Attempts of current Chinese institutions in preserving natural wetlands have achieved limited success. Few marsh wetlands have remained healthy, even after the establishment of the nature reserve. Their ecological qualities have been declining in response to the increasing threats to the remaining wetland habitats. Irrigation projects play a key role in such threats. Therefore, the sustainability of the natural wetland ecosystems is being threatened by increased regional agricultural development which reduced the number of wetland ecotypes and damaged the ecological quality
Gossip Consensus Algorithm Based on Time-Varying Influence Factors and Weakly Connected Graph for Opinion Evolution in Social Networks
We provide a new gossip algorithm to investigate the problem of opinion consensus with the time-varying influence factors and weakly connected graph among multiple agents. What is more, we discuss not only the effect of the time-varying factors and the randomized topological structure but also the spread of misinformation and communication constrains described by probabilistic quantized communication in the social network. Under the underlying weakly connected graph, we first denote that all opinion states converge to a stochastic consensus almost surely; that is, our algorithm indeed achieves the consensus with probability one. Furthermore, our results show that the mean of all the opinion states converges to the average of the initial states when time-varying influence factors satisfy some conditions. Finally, we give a result about the square mean error between the dynamic opinion states and the benchmark without quantized communication
Strand antagonism in RNAi: an explanation of differences in potency between intracellularly expressed siRNA and shRNA
Strategies to regulate gene function frequently use small interfering RNAs (siRNAs) that can be made from their shRNA precursors via Dicer. However, when the duplex components of these siRNA effectors are expressed from their respective coding genes, the RNA interference (RNAi) activity is much reduced. Here, we explored the mechanisms of action of shRNA and siRNA and found the expressed siRNA, in contrast to short hairpin RNA (shRNA), exhibits strong strand antagonism, with the sense RNA negatively and unexpectedly regulating RNAi. Therefore, we altered the relative levels of strands of siRNA duplexes during their expression, increasing the level of the antisense component, reducing the level of the sense component, or both and, in this way we were able to enhance the potency of the siRNA. Such vector-delivered siRNA attacked its target effectively. These findings provide new insight into RNAi and, in particular, they demonstrate that strand antagonism is responsible for making siRNA far less potent than shRNA
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