Penalized Regressions: The Bridge versus the Lasso

Abstract

Bridge regression, a special family of penalized regressions of a penalty function Σ|β_j|^γ with γ ≤ 1, considered. A general approach to solve for the bridge estimator is developed. A new algorithm for the lasso (γ = 1) is obtained by studying the structure of the bridge estimators. The shrinkage parameter γ and the tuning parameter λ are selected via generalized cross-validation (GCV). Comparison between the bridge model (γ ≤ 1) and several other shrinkage models, namely the ordinary least squares regression (λ = 0), the lasso (γ = 1) and ridge regression (γ = 2), is made through a simulation study. It is shown that the bridge regression performs well compared to the lasso and ridge regression. These methods are demonstrated through an analysis of a prostate cancer data. Some computational advantages and limitations are discussed.     

A Novel Electrochemical Aptasensor for Carcinoembryonic Antigen Detection Based on Target‐induced Bridge Assembly

The present study describes a novel electrochemical aptasensor for detection of carcinoembryonic antigen (CEA), a key cancer biomarker. The sensing strategy relied on the CEA‐induced bridge assembly, as a physical barrier, on the surface of gold electrode, resulting in a significant increase of the sensor sensitivity. Under optimal conditions, the aptasensing platform showed a wide linear range (3 pg/mL to 40 ng/mL) and a low detection limit (0.9 pg/mL). Some possible interfering materials were also assessed and the results indicated that the designed aptasensor had good specificity toward CEA. The quantitation of CEA in the spiked human serum samples confirmed the reliability and applicability of the electrochemical aptasensor. So, the developed sensing method has a potential application in the clinical diagnosis.     

Radical-Bridged Heterometallic Single-Molecule Magnets Incorporating Four Lanthanoceniums

The syntheses and magnetic properties of organometallic heterometallic compounds [K(THF)₆]{Co^I[(μ₃-HAN)RE₂Cp*₄]₂} ( 1-RE ) and [K(Crypt)]₂{Co^I[(μ₃-HAN)RE₂Cp*₄]₂} ( 2-RE ) containing hexaazatrinaphthylene radicals (HAN⋅³⁻) and four rare earth (RE) ions are reported. 1-RE shows isolable species with ligand-based mixed valency as revealed by cyclic voltammetry (CV) thus leading to the isolation of 2-RE via one-electron chemical reduction. Strong electronic communication in mixed-valency supports stronger overall ferromagnetic behaviors in 2-RE than 1-RE containing Gd and Dy ions. Ac magnetic susceptibility data reveal 1-Dy and 2-Dy both exhibit slow magnetic relaxation. Importantly, larger coercive field was observed in the hysteresis of 2-Dy at 2.0 K, indicating the enhanced SMM behavior compared with 1-Dy . Ligand-based mixed-valency strategy has been used for the first time to improve the magnetic coupling in lanthanide (Ln) SMMs, thus opening up new ways to construct strongly coupled Ln-SMMs.     

A new [Ni4] distorted cubane assembly on four solvent derived μ3-OMe corners: Solvent dependent formation and cleavage of exogenous bridges

A new Ni₄ distorted cubane complex [Ni₄(μ₃-OMe)₄Q₄(MeOH)₄] (1) (where Q⁻ is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)₂ · 4H₂O in refluxing MeOH via solvent derived μ₃-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni₄(OMe)₄] cubane is covered by four Q⁻ and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH₂(CH₂)₂OH), an amine substituted ethanol, producing monomeric [NiQ₂(Hgl)₂] · 2H₂O (2 · 2H₂O) instead and is able to cleave 1 to yield 2 · 2H₂O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J₁ = −1.8(1) cm⁻¹, J₂ = 3.9(1) cm⁻¹ and g = 2.24.     

Luminescent molecular hybrid system derived from 2-furancarboxylic acid and silylated monomer coordinated to rare earth ions

In this study, silica-based organic-inorganic hybrids were prepared by the sol-gel method. Tetraethoxysilane (abbreviated as TEOS) and a kind of monomer (abbreviated as FA-APES) derived from modified 2-furancarboxylic acid (abbreviated as FA) with (3-aminopropyl)triethoxysilane (abbreviated as APES) were used as the inorganic and organic fragments, respectively. Coordination reaction between lanthanides (europium and terbium ions) and CO group of the monomer happened simultaneously. And after days of aging process the resultant materials showed characteristic luminescence of lanthanides. The enhancement of luminescence can be seen by the comparison with simply doped lanthanide hybrid systems. And it can be explained by the coordination ability of the organic counterpart. IR, NMR, UV-vis absorption, low-temperature phosphorescence spectroscopy and fluorescence spectroscopy were applied to characterize and the above spectroscopic data revealed that the triplet state energy of organic ligand matches with the emissive energy level of lanthanides (especially of Tb³⁺).     

两亲性接枝共聚物在选择性溶剂中自组装行为的模拟研究

利用粗粒化分子动力学(CGMD)方法研究了两亲性接枝共聚物在不同选择性溶剂中的自组装行为. 分析了主链刚性及链长对自组装结构的影响. 研究结果表明, 当溶剂对主链为良溶剂而对支链为不良溶剂时, 两亲性接枝共聚物随主链刚性的增加自组装形成花状胶束、 花桥状胶束及桥状胶束, 并且组分比例对自组装结构影响很大; 随着链长的增加, 柔性链出现单花状胶束到多花状胶束的转化. 当溶剂对主链为不良溶剂而对支链为良溶剂时, 可得到近球形或椭球形核壳状胶束及束状结构; 不同链长时, 柔性接枝共聚物链均只能得到近球形的单核壳状胶束.     

Characterization of 3-bridge links with infinitely many 3-bridge spheres

In an earlier paper, the author constructed an infinite family of 3-bridge links each of which admits infinitely many 3-bridge spheres up to isotopy. In this paper, we prove that if a prime, unsplittable link L in S³ admits infinitely many 3-bridge spheres up to isotopy then L belongs to the family.     

高温超导SMES磁体的失超检测研究

失超保护是保证磁体安全运行的重要措施,而失超检测是失超保护正常动作的前提。由于SMES磁体运行工况的特殊性,现有失超检测方法在失超信号提取上遇到电磁噪声干扰严重的问题。文中针对高温超导SMES的运行工况,对电桥检测法进行了改进,通过对电桥信号的滤波设计解决电磁噪声干扰,设计了一套适用于高温超导SMES磁体在交变电流情况下的失超检测系统,同时进行了高温超导磁体的失超检测实验。实验结果表明,此系统能快速、准确地检测失超信号,并输出保护动作信号。     

A State-dependent Division Scheme for the Potential of Simple Fluids

Abstract

A new division scheme for the pair potential into long-range and short-range parts is presented, which takes account of the dependence on the density and makes possible the extraction of the bridge function B(r) in the core region. The calculation of the correlation functions is carried out with the hybridized mean spherical approximation (HMSA). As attested by the comparison with the simulation results, HMSA used with this potential separation is suitable to produce accurate bridge function and pair correlation function for the Lennard-Jones fluid.