Determine the galaxy bias factors on large scales using bispectrum method

We study whether the bias factors of galaxies can be unbiasedly recovered from their power spectra and bispectra. We use a set of numerical N-body simulations and construct large mock galaxy catalogs based upon the semi-analytical model of Croton et al. (2006). We measure the reduced bispectra for galaxies of different luminosity, and determine the linear and first nonlinear bias factors from their bispectra. We find that on large scales down to that of the wavenumber k=0.1h/Mpc, the bias factors b1 and b2 are nearly constant, and b1 obtained with the bispectrum method agrees very well with the expected value. The nonlinear bias factor b2 is negative, except for the most luminous galaxies with M<-23 which have a positive b2. The behavior of b2 of galaxies is consistent with the b2 mass dependence of their host halos. We show that it is essential to have an accurate estimation of the dark matter bispectrum in order to have an unbiased measurement of b1 and b2. We also test the analytical approach of incorporating halo occupation distribution to model the galaxy power spectrum and bispectrum. The halo model predictions do not fit the simulation results well on the precision requirement of current cosmological studies.Comment: 9 pages, 8 figures, accepted for publication in Ap

The anti-sepsis activity of the components of Huanglian Jiedu Decoction with high lipid A-binding affinity

Huanglian Jiedu Decoction (HJD), one of the classic recipes for relieving toxicity and fever, is a common method for treating sepsis in China. However, the effective components of HJD have not yet been identified. This experiment was carried out to elucidate the effective components of HJD against sepsis. Thus, seven fractions from HJD were tested using a biosensor to test their affinity for lipid A. The components obtained that had high lipid A-binding fractions were further separated, and their affinities to lipid A were assessed with the aid of a biosensor. The levels of LPS in the blood were measured, and pathology experiments were conducted. The LPS levels and mRNA expression analysis of TNF-α and IL-6 of the cell supernatant and animal tissue were evaluated to investigate the molecular mechanisms. Palmatine showed the highest affinity to lipid A and was evaluated by in vitro and in vivo experiments. The results of the in vitro and in vivo experiments indicated that the levels of LPS, TNF-α and IL-6 of the palmatine group were significantly lower than those of the sepsis model group (p \u3c 0.01). The group treated with palmatine showed strong neutralizing LPS activity in vivo. The palmatine group exhibited stronger protective activity on vital organs compared to the LPS-induced animal model. This verifies that HJD is a viable treatment option for sepsis given that there are multiple components in HJD that neutralize LPS, decrease the release of IL-6 and TNF-α induced by LPS, and protect vital organs

A determination of dark matter bispectrum with a large set of N-body simulations

We use a set of numerical N-body simulations to study the large-scale behavior of the reduced bispectrum of dark matter and compare the results with the second-order perturbation theory and the halo models for different halo mass functions. We find that the second-order perturbation theory (PT2) agrees with the simulations fairly well on large scales of k<0.05 h/Mpc, but it shows a signature of deviation as the scale goes down. Even on the largest scale where the bispectrum can be measured reasonably well in our simulations, the inconsistency between PT2 and the simulations appears for the colinear triangle shapes. For the halo model, we find that it can only serve as a qualitative method to help study the behavior of Q on large scales and also on relatively small scales. The failure of second-order perturbation theory will also affect the precise determination of the halo models, since they are connected through the 3-halo term in the halo model. The 2-halo term has too much contribution on the large scales, which is the main reason for the halo model to overpredict the bispectrum on the large scales. Since neither of the models can provide a satisfying description for the bispectrum on scales of about 0.1h/Mpc for the requirement of precision cosmology, we release the reduced bispectrum of dark matter on a large range of scales for future analytical modeling of the bispectrum.Comment: 10 pages, 7 figures, accepted for publication in Ap

Open Collaborative Mechanical / Product Design - User as Developer A New Design Methodology for Internet Era Business Innovations and Entrepreneurship

In product design and development projects, the most important part is identifying user needs. Traditional methods such as surveys, focus group studies and interviews are expensive and sometime inaccurate in identifying those needs. Inspired by the open source software development, along with the research that has been done on the lead user method, the method of using collective customer wisdom to modify old products or even develop new products has become an emerging new design method and is starting to get popularity and success. However, the effectiveness of such method comparing to the traditional face to face close development method is a question that keeping established businesses from apply such method. At the same time, failures of early attempts to use such methods also cast doubts about the quality of this method. We set up two experiments to compare this method and the traditional face to face method, and found out that the effectiveness of both methods were about the same. Problems of implementing such method also emerged from the experiment, possible solutions are discussed, and future studies are also identified. Comparing this method to the open source software design, there is one stage of the development that is unique for mechanical products. The prototyping and manufacturing of mechanical products involved cost and quality control issues that don\u27t exist in software development. We conducted an experiment of applying a collaborative open design approach to test the possibility and necessity of applying such design method during prototype fabrication. Our results showed that open collaborative design is necessary to identify true customer needs. A product prototyping and manufacturing method is also proposed for real world practice. The open collaborative design method is new and is not easily adopted by established businesses, as they are often reluctant to implement new approaches. Entrepreneurs can usually take advantage of this situation and establish their share of the market, even possibly driving out the established businesses later on. We argue that the open collaborative design method is one such technology. Future research and practice is proposed and discussed

Green state joining of silicon carbide using polymer precursors

Green state joining of structural ceramics has shown its potential for forming large, complex components. In this work, methods of green state joining of silicon carbide using polymer precursors are explored. Pastes containing either polycarbosilane (PCS) or Allylhydridopolycarbosilane (AHPCS) are used in the joining process. It has been demonstrated that joints formed under external pressure using PCS containing pastes are indistinguishable from the matrix. The Flexural strength of joined samples having a theoretical density (TD) of 94% is measured to be 312 MPa, which is comparable to that of the control sample with similar density. Unfortunately, applied pressure is necessary for achieving thin, defect-free joints, which might limit wider application of the method. In order to eliminate applied pressure in the joining process, a method of joining SiC using AHPCS containing pastes is investigated. It is discovered that, using AHPCS containing pastes with appropriate SiC addition, crack-free joints can be obtained without applied pressure. Optimum SiC loading in the paste was determined to be in the range of 25 to 35vol%. Joints formed by AHPCS+(SiC+5wt%B) paste are essentially indistinguishable from the matrix and have an average strength of 323 MPa, comparable to that of the control sample. For better control over the quality of the joints, x-ray tomography has been used to investigate the density variations in SiC joints. The results indicate that the green density of the joints, formed by PCS containing pastes, increases from 54% to 66%TD as the applied pressure increases from ambient to 138 MPa. Also, a minimum density difference between the matrix and joint in the green state is achieved when the PCS content in the pastes is around 50vol%. Furthermore, regions with higher densities are observed at the joint/matrix interfaces, suggesting that the polymer precursor infiltrates into the matrix during the joining process using AHPCS containing pastes. In this work, a method for producing SiC whisker in situ in monolithic mixture of AHPCS and SiC is also explored