Conditional access system (CAS) is a key technical component in digital TV broadcasting through which TV op-erators manage the appropriate rights of different subscribers in order to protect their commercial benefits....Conditional access system (CAS) is a key technical component in digital TV broadcasting through which TV op-erators manage the appropriate rights of different subscribers in order to protect their commercial benefits. The normal digital TV receiver can only receive and decode the pay TV programs scrambled by one specific CAS. In this paper, the authors proposed a smartcard conditional access interface (SCAI) scheme in order to make the digital TV receiver be a common receiving platform independent of any specific CAS employed at the broadcasting head-end. As a result, it only needs to include a common condi-tional access software package (CCAP) without any requirement of hardware modification in the receiver. Comparison between the two mentioned DVB-CI-based schemes showed that the cost of such kind receiver is greatly reduced. The main design points of the proposed scheme and its reference implementation’s architecture are presented in this paper. This scheme is also one of the candidate national standards for Chinese digital TV broadcasting industry.展开更多
Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized ma...Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized management and transmission latency of the cloud makes it difficult to support real-time processing and distributed access structures.As a result,fog computing and the Internet of Things(IoT)have emerged as crucial applications.Fog-assisted proxy re-encryption is a commonly adopted technique for sharing cloud ciphertexts.It allows a semitrusted proxy to transforma data owner’s ciphertext into another re-encrypted ciphertext intended for a data requester,without compromising any information about the original ciphertext.Yet,the user revocation and cloud ciphertext renewal problems still lack effective and secure mechanisms.Motivated by it,we propose a revocable conditional proxy re-encryption scheme offering ciphertext evolution(R-CPRE-CE).In particular,a periodically updated time key is used to revoke the user’s access privileges while an access condition prevents a malicious proxy from reencrypting unauthorized ciphertext.We also demonstrate that our scheme is provably secure under the notion of indistinguishability against adaptively chosen identity and chosen ciphertext attacks in the random oracle model.Performance analysis shows that our scheme reduces the computation time for a complete data access cycle from an initial query to the final decryption by approximately 47.05%compared to related schemes.展开更多
After securing a market for their dried red chilli peppers in China,elated farmers in Uganda are expanding the spicy crop cultivation to thousands of acres.China’s increasing appetite for international cuisine and sp...After securing a market for their dried red chilli peppers in China,elated farmers in Uganda are expanding the spicy crop cultivation to thousands of acres.China’s increasing appetite for international cuisine and spices has created a most welcome demand for high-quality chillies.And given Uganda’s unique climate and soil conditions that allow for diverse chilli varieties,the East African country has a competitive edge.This has led to Uganda and China now having trade agreements in place,facilitating exports.展开更多
Emergency medical services (EMS) are a vital element of the public healthcare system in China,^([1])providing an opportunity to respond to critical medical conditions and save people’s lives.^([2])The accessibility o...Emergency medical services (EMS) are a vital element of the public healthcare system in China,^([1])providing an opportunity to respond to critical medical conditions and save people’s lives.^([2])The accessibility of EMS has received considerable attention in health and transport geography studies.^([3])One of the optimal gauges for evaluating the accessibility of EMS is the response time,which is defined as the time from receiving an emergency call to the arrival of an ambulance.^([4])Beijing has already reduced the response time to approximately12 min,and the next goal is to ensure that the response time across Beijing does not exceed 12 min (the information comes from the Beijing Emergency Medical Center).展开更多
Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previou...Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previous study revealed that the FtsZ in S.mutans(SmFtsZ) has higher self-assembly and GTPase activity under acidic stress,which may be responsible for acid resistance and ca riogenesis of S.mutans.However,the functional structure mechanism of SmFtsZ under low pH conditions is still unclear.Here,we further reported the crystal structure of S.mutans FtsZ,revealing a unique lateral interface.Through protein polymerization and GTPase activity assay,we experimentally demonstrated that the mutation of Arg68 on this lateral interface significantly reduced the functional activity of FtsZ in an acidic environment.The phenotype assay and rat caries model further showed that the mutation of Arg68 effectively inhibited the acid resistance of S.mutans and the occurrence and progress of dental caries in vivo.By employing a molecular dynamics simulation analysis,we conclude that the mutation of Arg68 disrupts the conformation change necessary for SmFtsZ polymerization under acidic conditions.Our study proposes a novel mechanism to maintain FtsZ function in bacteria and could be a potential target for antimicrobial drugs to inhibit the growth of S.mutans in acidic environments.展开更多
Two 1-methyl-1H-benzo[d]imidazole derivatives, C_（18）H_（14）CuN_4O_4·C_4H_8O_2（1） and C_9H_9N_3O（2）, have been synthesized and characterized by NMR, MS, FT-IR, elementary analysis and X-ray single-crystal ...Two 1-methyl-1H-benzo[d]imidazole derivatives, C_（18）H_（14）CuN_4O_4·C_4H_8O_2（1） and C_9H_9N_3O（2）, have been synthesized and characterized by NMR, MS, FT-IR, elementary analysis and X-ray single-crystal diffraction. Compound 1 crystallizes in monoclinic, space group P2_1/n with a = 9.6888（3）, b = 7.3772（2）, c = 14.3277（4）A, β = 95.819（3）°, V = 1018.81（5） A3, M_r = 501.98, Z = 2, D_c = 1.636 g/cm^3, F（000） = 518, μ = 1.123 mm^（-1）, MoKα radiation（λ = 0.71073 A）, the final R = 0.0325 and wR = 0.0859 for 1821 observed reflections with I 〉 2σ（I）. Compound 2 crystallizes in monoclinic, space group C2/c with a = 14.2908（14）, b = 14.4268（13）, c = 8.4802（6） A, β = 108.513（9）o, V = 1657.9（3） A3, M_r = 175.19, Z = 8, D_c = 1.404 g/cm^3, F（000） = 736, μ = 0.097 mm^（-1）, Mo Kα radiation（λ = 0.71073 A）, the final R = 0.0563 and wR = 0.1531 for 1231 observed reflections with I 〉 2σ（I）. Intermolecular（N-H···N, N-H···O） and intramolecular（N-H···N, C-H···O） hydrogen bonds, as well as C-H···π and π-π stacking interactions, help to stabilize the crystal structure of compound 2.展开更多
基金Project (No. 200442) supported by the Electronics DevelopmentFoundation for the Key Industrialization Project of the Ministry of0Information Industry, China
文摘Conditional access system (CAS) is a key technical component in digital TV broadcasting through which TV op-erators manage the appropriate rights of different subscribers in order to protect their commercial benefits. The normal digital TV receiver can only receive and decode the pay TV programs scrambled by one specific CAS. In this paper, the authors proposed a smartcard conditional access interface (SCAI) scheme in order to make the digital TV receiver be a common receiving platform independent of any specific CAS employed at the broadcasting head-end. As a result, it only needs to include a common condi-tional access software package (CCAP) without any requirement of hardware modification in the receiver. Comparison between the two mentioned DVB-CI-based schemes showed that the cost of such kind receiver is greatly reduced. The main design points of the proposed scheme and its reference implementation’s architecture are presented in this paper. This scheme is also one of the candidate national standards for Chinese digital TV broadcasting industry.
基金supported in part by the National Science and Technology Council of Republic of China under the contract numbers NSTC 114-2221-E-019-055-MY2NSTC 114-2221-E-019-069.
文摘Cloud data sharing is an important issue in modern times.To maintain the privacy and confidentiality of data stored in the cloud,encryption is an inevitable process before uploading the data.However,the centralized management and transmission latency of the cloud makes it difficult to support real-time processing and distributed access structures.As a result,fog computing and the Internet of Things(IoT)have emerged as crucial applications.Fog-assisted proxy re-encryption is a commonly adopted technique for sharing cloud ciphertexts.It allows a semitrusted proxy to transforma data owner’s ciphertext into another re-encrypted ciphertext intended for a data requester,without compromising any information about the original ciphertext.Yet,the user revocation and cloud ciphertext renewal problems still lack effective and secure mechanisms.Motivated by it,we propose a revocable conditional proxy re-encryption scheme offering ciphertext evolution(R-CPRE-CE).In particular,a periodically updated time key is used to revoke the user’s access privileges while an access condition prevents a malicious proxy from reencrypting unauthorized ciphertext.We also demonstrate that our scheme is provably secure under the notion of indistinguishability against adaptively chosen identity and chosen ciphertext attacks in the random oracle model.Performance analysis shows that our scheme reduces the computation time for a complete data access cycle from an initial query to the final decryption by approximately 47.05%compared to related schemes.
文摘After securing a market for their dried red chilli peppers in China,elated farmers in Uganda are expanding the spicy crop cultivation to thousands of acres.China’s increasing appetite for international cuisine and spices has created a most welcome demand for high-quality chillies.And given Uganda’s unique climate and soil conditions that allow for diverse chilli varieties,the East African country has a competitive edge.This has led to Uganda and China now having trade agreements in place,facilitating exports.
基金supported by National Key Research & Development Program of China (2022YFC3006201)。
文摘Emergency medical services (EMS) are a vital element of the public healthcare system in China,^([1])providing an opportunity to respond to critical medical conditions and save people’s lives.^([2])The accessibility of EMS has received considerable attention in health and transport geography studies.^([3])One of the optimal gauges for evaluating the accessibility of EMS is the response time,which is defined as the time from receiving an emergency call to the arrival of an ambulance.^([4])Beijing has already reduced the response time to approximately12 min,and the next goal is to ensure that the response time across Beijing does not exceed 12 min (the information comes from the Beijing Emergency Medical Center).
基金supported by the Beijing Natural Science Foundation:7222220National Natural Science Foundation of China (82001039)+2 种基金Research Foundation of Peking University School and Hospital of Stomatology:PKUSS20230117The Fundamental Research Funds for the Central UniversitiesYoung Elite Scientist Sponsorship Program by CAST (No.2019QNRC001 to Y.L.L)。
文摘Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previous study revealed that the FtsZ in S.mutans(SmFtsZ) has higher self-assembly and GTPase activity under acidic stress,which may be responsible for acid resistance and ca riogenesis of S.mutans.However,the functional structure mechanism of SmFtsZ under low pH conditions is still unclear.Here,we further reported the crystal structure of S.mutans FtsZ,revealing a unique lateral interface.Through protein polymerization and GTPase activity assay,we experimentally demonstrated that the mutation of Arg68 on this lateral interface significantly reduced the functional activity of FtsZ in an acidic environment.The phenotype assay and rat caries model further showed that the mutation of Arg68 effectively inhibited the acid resistance of S.mutans and the occurrence and progress of dental caries in vivo.By employing a molecular dynamics simulation analysis,we conclude that the mutation of Arg68 disrupts the conformation change necessary for SmFtsZ polymerization under acidic conditions.Our study proposes a novel mechanism to maintain FtsZ function in bacteria and could be a potential target for antimicrobial drugs to inhibit the growth of S.mutans in acidic environments.
基金Supported by the National Natural Science Foundation of China(No.31370373 and 21102084)Natural Science Foundation of Hubei Province(No.2012FKC14401)
文摘Two 1-methyl-1H-benzo[d]imidazole derivatives, C_（18）H_（14）CuN_4O_4·C_4H_8O_2（1） and C_9H_9N_3O（2）, have been synthesized and characterized by NMR, MS, FT-IR, elementary analysis and X-ray single-crystal diffraction. Compound 1 crystallizes in monoclinic, space group P2_1/n with a = 9.6888（3）, b = 7.3772（2）, c = 14.3277（4）A, β = 95.819（3）°, V = 1018.81（5） A3, M_r = 501.98, Z = 2, D_c = 1.636 g/cm^3, F（000） = 518, μ = 1.123 mm^（-1）, MoKα radiation（λ = 0.71073 A）, the final R = 0.0325 and wR = 0.0859 for 1821 observed reflections with I 〉 2σ（I）. Compound 2 crystallizes in monoclinic, space group C2/c with a = 14.2908（14）, b = 14.4268（13）, c = 8.4802（6） A, β = 108.513（9）o, V = 1657.9（3） A3, M_r = 175.19, Z = 8, D_c = 1.404 g/cm^3, F（000） = 736, μ = 0.097 mm^（-1）, Mo Kα radiation（λ = 0.71073 A）, the final R = 0.0563 and wR = 0.1531 for 1231 observed reflections with I 〉 2σ（I）. Intermolecular（N-H···N, N-H···O） and intramolecular（N-H···N, C-H···O） hydrogen bonds, as well as C-H···π and π-π stacking interactions, help to stabilize the crystal structure of compound 2.
