政府干预、所有权性质与股价崩盘风险

中国股市因为受到政府行为的重大影响而常常被认为是“政策市”。本文研究了政府干预和公司所有权性质及其交互作用对中国上市公司股价崩盘风险的影响。研究发现，地区政府干预水平越高，地方国企的股价崩盘风险越大，但没有证据表明地区政府干预水平对非国有控股公司和央企的股价崩盘风险有显著影响；平均来看，国有控股公司（尤其是央企）的股价崩盘风险低于非国有控股公司，地区政府干预水平的增加会弱化国有控股公司（尤其是地方国企）股价崩盘风险低于非国有控股公司的趋势。这些结果表明，政府干预和公司所有权性质及其交互作用对于股价崩盘风险具有重要影响。本文既丰富了股价崩盘风险影响因素的研究，也丰富了政府干预经济后果的研究，还丰富了所有权经济后果的研究；本文的研究结论对于监管者、地方政府和投资者也具有重要的参考价值。

Achieving a sub-10 nm nanopore array in silicon by metal-assisted chemical etching and machine learning

Solid-state nanopores with controllable pore size and morphology have huge application potential.However,it has been very challenging to process sub-10 nm silicon nanopore arrays with high efficiency and high quality at low cost.In this study,a method combining metal-assisted chemical etching and machine learning is proposed to fabricate sub-10 nm nanopore arrays on silicon wafers with various dopant types and concentrations.Through a SVM algorithm,the relationship between the nanopore structures and the fabrication conditions,including the etching solution,etching time,dopant type,and concentration,was modeled and experimentally verified.Based on this,a processing parameter window for generating regular nanopore arrays on silicon wafers with variable doping types and concentrations was obtained.The proposed machine-learning-assisted etching method will provide a feasible and economical way to process high-quality silicon nanopores,nanostructures,and devices.

Late Jurassic-Early Cretaceous tectonic switching in Liaodong Peninsula of the North China Craton and the implications for gold mineralisation

Constraining the processes of deformation during tectonic switching from compression to extension is difficult because of the scarcity or absence of associated sedimentary and magmatic rocks and weak metamorphism.The east margin of the eastern North China Craton experienced Early to Middle Jurassic compression and Early Cretaceous extension.However,the period of tectonic quiescence lasting~13 million years(between 153 and 140 Ma)during which this transition occurred is poorly understood.This paper reports the identification of small-scale N-S-trending thrust and sinistral strike-slip faults(TSS)and NWtrending thrust and dextral strike-slip faults(TDS)in the Tongyuanpu-Aiyang region,which is part of the northern Liaodong Peninsula.Calculation of the tectonic stress field using striations,fault planes and kinematics reveals a NW-SE-oriented maximum principal axis(σ1),and sub-horizontalσ2 andσ3.Assemblages of N-S-trending TSS and NW-trending TDS were arranged with right stepping and resulted in local uplift and erosion at the junctions between fault terminations,which partitioned the Early and Middle Jurassic basins into residual smaller volcanic-sedimentary basins.These basins were unconformably overlain by small Early Cretaceous volcanic-sedimentary basins,such as those at Tongyuanpu and Fangjiaweizi.Magmatic ages and the timing of basin formation constrain the initiation of tectonic switching to 156–153 Ma,and its termination to 140–139 Ma.We suggest that R-R’Riedel shears controlled the formation of the N-S-trending TSS and NW-trending TDS.The R-R’shears were produced by continued sinistral strike-slip and northward growth along the Bohai Bay segment of the Tan-Lu fault zone during the Late Jurassic to early Early Cretaceous,simultaneous with a gradual weakening in the tectonic stress field during a switch in the direction of subduction of the Palaeo-Pacific plate from NW-ward to NNW-ward.This tectonic switching might have promoted the dissolution of gold and migration of gold-bearing fluids.