We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured pr...We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).展开更多
To assess groundwater nitrate contamination and its human health risks,489 unconfined groundwater samples were collected and analyzed from Zhangjiakou,northern China.The spatial distribution of principle hydrogeochemi...To assess groundwater nitrate contamination and its human health risks,489 unconfined groundwater samples were collected and analyzed from Zhangjiakou,northern China.The spatial distribution of principle hydrogeochemical results showed that the average concentrations of ions in descend order was HCO3-,SO42-,Na+,Ca2+,Cl-,NO3-,Mg2+and K+,among which the NO3-concentrations were between 0.25 and 536.73 mg/L with an average of 29.72 mg/L.In total,167 out of 489 samples(34%)exceeded the recommended concentration of 20 mg/L in Quality Standard for Groundwater of China.The high NO3-concentration groundwater mainly located in the northern part and near the boundary of the two geomorphic units.As revealed by statistical analysis,the groundwater chemistry was more significantly affected by anthropogenic sources than by the geogenic sources.Moreover,human health risks of groundwater nitrate through oral and dermal exposure pathways were assessed by model,the results showed that about 60%,50%,32%and 26%of the area exceeded the acceptable level(total health index>1)for infants,children,adult males and females,respectively.The health risks for different groups of people varied significantly,ranked:infants>children>adult males>adult females,suggesting that younger people are more susceptible to nitrate contamination,while females are more resistant to nitrate contamination than males.To ensure the drinking water safety in Zhangjiakou and its downstream areas,proper management and treatment of groundwater will be necessary to avoid the health risks associated with nitrate contamination.展开更多
基金supported by the National Key Research and Development Program of China(2022YFF0503304,2020YFC2201600,2018YFA0404504 and 2018YFA0404601)the Ministry of Science and Technology of China(2020SKA0110402,2020SKA0110401 and 2020SKA0110100)+4 种基金the National Natural Science Foundation of China(11890691,12205388 and 12220101003)the CAS Project for Young Scientists in Basic Research(YSBR-061,YSBR-092)the China Manned Space Project with No.CMS-CSST-2021(A02,A03 and B01)the Major Key Project of PCLthe 111 project(B20019)。
文摘We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).
基金supported by the National Key R and D Program of China(No.2018YFE0204100)the China Postdoctoral Science Foundation(No.2020M680698)+1 种基金the Survey of backup groundwater sources in Zhangjiakou region(No.2013995431)。
文摘To assess groundwater nitrate contamination and its human health risks,489 unconfined groundwater samples were collected and analyzed from Zhangjiakou,northern China.The spatial distribution of principle hydrogeochemical results showed that the average concentrations of ions in descend order was HCO3-,SO42-,Na+,Ca2+,Cl-,NO3-,Mg2+and K+,among which the NO3-concentrations were between 0.25 and 536.73 mg/L with an average of 29.72 mg/L.In total,167 out of 489 samples(34%)exceeded the recommended concentration of 20 mg/L in Quality Standard for Groundwater of China.The high NO3-concentration groundwater mainly located in the northern part and near the boundary of the two geomorphic units.As revealed by statistical analysis,the groundwater chemistry was more significantly affected by anthropogenic sources than by the geogenic sources.Moreover,human health risks of groundwater nitrate through oral and dermal exposure pathways were assessed by model,the results showed that about 60%,50%,32%and 26%of the area exceeded the acceptable level(total health index>1)for infants,children,adult males and females,respectively.The health risks for different groups of people varied significantly,ranked:infants>children>adult males>adult females,suggesting that younger people are more susceptible to nitrate contamination,while females are more resistant to nitrate contamination than males.To ensure the drinking water safety in Zhangjiakou and its downstream areas,proper management and treatment of groundwater will be necessary to avoid the health risks associated with nitrate contamination.
