Robust variable selection for nonlinear models with diverging number of parameters

We focus on the problem of simultaneous variable selection and estimation for nonlinear models based on modal regression (MR), when the number of coefficients diverges with sample size. With appropriate selection of the tuning parameters, the resulting estimator is shown to be consistent and to enjoy the oracle properties

Robust variable selection in partially varying coefficient single-index model

By combining basis function approximations and smoothly clipped absolute deviation (SCAD) penalty, this paper proposes a robust variable selection procedure for a partially varying coefficient single-index model based on modal regression. The proposed procedure simultaneously selects significant variables in the parametric components and the nonparametric components. With appropriate selection of the tuning parameters, we establish the theoretical properties of our procedure, including consistency in variable selection and the oracle property in estimation. Furthermore, we also discuss the bandwidth selection and propose a modified expectation-maximization (EM)-type algorithm for the proposed estimation procedure. The finite sample properties of the proposed estimators are illustrated by some simulation examples.The research of Zhu is partially supported by National Natural Science Foundation of China (NNSFC) under Grants 71171075, 71221001 and 71031004. The research of Yu is supported by NNSFC under Grant 11261048

Cloning and characterization of peptidylprolyl isomerase B in the silkworm, Bombyx mori

Peptidylprolyl isomerases (PPIases) play essential roles in protein folding and are implicated in immune response and cell cycle control. Our previous proteomic analysis indicated that Bombyx mori PPIases may be involved in anti- Bombyx mori nucleopolyhedrovirus (BmNPV) response. To help investigate this mechanism, we cloned a B. mori PPIase gene PPIB and characterized it by bioinformatic and experimental analysis. We found that the B. mori PPIB gene contains 4 exons and its cDNA is about of618 bp, encoding a protein of 205 amino acid residues (21474.41 Da) with an isoelectric point of 8.05. PPIB contains conserved and unique cyclophilin domain and belongs to cyclophilin superfamily. Its transcription could be detected by PCR in all the B. mori tissue samples, which is consistent withnormal PPIase expression pattern and their essential roles. It is localized in cytoplasm revealed by fluorescence microscopy. We also successfully expressed this protein in E. coli and characterized it by SDS-PAGE and Mass Spectrometry. The cloned DNA sequence was submitted to GenBank (EU583493)

Response of grasslands conversion to croplands on soil organic carbon in Bashang area of Northern China

This study investigated the effects of two types of grasslands conversion to croplands on soil organic carbon (SOC) in Bashang area where it is a typical agro-pastoral ecotone of Northern China using a pare-site method. The results showed that the SOC contents and densities decreased with increasing soil depth. The soil bulk density and SOC content significantly decreased in the upper horizon after the grasslands was converted into croplands. The SOC densities were approximately 2.3 - 2.7 and 4.2 - 9.1 kg C m-2 in the upper horizons of site 1 and site 2, respectively, with significant differences between grasslands and croplands. The SOC densities up to 60 cm depth were much higher in site 2 (intrazonalgrassland-cropland) than in site 1 (zonal grassland-cropland), reaching approximately 13.24 - 22.49 and 5.36 - 6.49 kg C m-2, respectively. The conversion of grasslands to croplands induced a moderate loss ofSOC, with a range of - 4 to 55% for the 0 - 60 cm depth over about 20-year period. To conserve the present status, potential conversion should be banned in both zonal and intrazonal grassland, the zonalgrassland should be enforced “turning cropland to grassland” policy, and the intrazonal grassland be reasonably used

Phonon arithmetic in a trapped ion system

Single-quantum level operations are important tools to manipulate a quantum state. Annihilation or creation of single particles translates a quantum state to another by adding or subtracting a particle, depending on how many are already in the given state. The operations are probabilistic and the success rate has yet been low in their experimental realization. Here we experimentally demonstrate (near) deterministic addition and subtraction of a bosonic particle, in particular a phonon of ionic motion in a harmonic potential. We realize the operations by coupling phonons to an auxiliary two-level system and applying transitionless adiabatic passage. We show handy repetition of the operations on various initial states and demonstrate by the reconstruction of the density matrices that the operations preserve coherences. We observe the transformation of a classical state to a highly non-classical one and a Gaussian state to a non-Gaussian one by applying a sequence of operations deterministically

Antiferromagnetic fluctuations in the normal state of LiFeAs

We present a detailed study of 75As NMR Knight shift and spin-lattice relaxation rate in the normal state of stoichiometric polycrystalline LiFeAs. Our analysis of the Korringa relation suggests that LiFeAs exhibits strong antiferromagnetic fluctuations, if transferred hyperfine coupling is a dominant interaction between 75As nuclei and Fe electronic spins, whereas for an on-site hyperfine coupling scenario, these are weaker, but still present to account for our experimental observations. Density-functional calculations of electric field gradient correctly reproduce the experimental values for both 75As and 7Li sites.Comment: 5 pages, 3 figures, thoroughly revised version with refined experimental data, accepted for publication as a Rapid Communication in Physical Review B

STM and RHEED study of the Si(001)-c(8x8) surface

The Si(001) surface deoxidized by short annealing at T~925C in the ultrahigh vacuum molecular beam epitaxy chamber has been in situ investigated by high resolution scanning tunnelling microscopy (STM) and reflected high energy electron diffraction (RHEED). RHEED patterns corresponding to (2x1) and (4x4) structures were observed during sample treatment. The (4x4) reconstruction arose at T<600C after annealing. The reconstruction was observed to be reversible: the (4x4) structure turned into the (2x1) one at T>600C, the (4x4) structure appeared again at recurring cooling. The c(8x8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8x8) structure decreased as the sample cooling rate was reduced. The (2x1) structure was observed on the surface free of the c(8x8) one. The c(8x8) structure has been evidenced to manifest itself as the (4x4) one in the RHEED patterns. A model of the c(8x8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.Comment: 26 pages, 12 figure