The static and predictable characteristics of cyber systems give attackers an asymmetric advantage in gathering useful information and launching attacks.To reverse this asymmetric advantage,a new defense idea,called M...The static and predictable characteristics of cyber systems give attackers an asymmetric advantage in gathering useful information and launching attacks.To reverse this asymmetric advantage,a new defense idea,called Moving Target Defense(MTD),has been proposed to provide additional selectable measures to complement traditional defense.However,MTD is unable to defeat the sophisticated attacker with fingerprint tracking ability.To overcome this limitation,we go one step beyond and show that the combination of MTD and Deception-based Cyber Defense(DCD)can achieve higher performance than either of them.In particular,we first introduce and formalize a novel attacker model named Scan and Foothold Attack(SFA)based on cyber kill chain.Afterwards,we develop probabilistic models for SFA defenses to provide a deeper analysis of the theoretical effect under different defense strategies.These models quantify attack success probability and the probability that the attacker will be deceived under various conditions,such as the size of address space,and the number of hosts,attack analysis time.Finally,the experimental results show that the actual defense effect of each strategy almost perfectly follows its probabilistic model.Also,the defense strategy of combining address mutation and fingerprint camouflage can achieve a better defense effect than the single address mutation.展开更多
Hydroxyurea has been used to synchronize cultured cells to S-phase and used to treat patients with sicklecell anemia. Recently, we found that hydroxyurea can induce the apoptosis of HEL (human erythroleukemia) cells.T...Hydroxyurea has been used to synchronize cultured cells to S-phase and used to treat patients with sicklecell anemia. Recently, we found that hydroxyurea can induce the apoptosis of HEL (human erythroleukemia) cells.The induced HEL cells showed ultrastructurally chromatin condensation with regular crescents at the nuclear edges and apoptotic bodies. However, the cells of K562, another human erythroleukemia cell line, did not show such morphological changes. Under fluoroscope, the HEL cells after induction often displayed a clear reduction in nuclear diameter and nuclear chromatin cleavage and condensation and the presence of nuclear ring and apoptotic bodies. Analysis with flow cytometry showed that the percentage of apoptotic cells is about 30-40% after HEL cells were induced by hydroxyurea for 3 days. DNA ladder can be observed by electrophoretic analysis.展开更多
The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highreso...The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated. An extended beads-on-astring (width of ～ 15-20nm, height of ～ 2-3nm for eachindividual nucleosome) can be consistently observed. Furthermore, superbeads (width of ～ 40nm, height of ～ 7nm)are demonstrated. Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained eitherby using AFM or by using electron microscopy. In addition, tightly coiled chromatin fibers (～ 50-60nm and ～90-110nm) can be revealed. Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning thefolding pattern of interphase chromatin fibers.展开更多
On January 15,2022,a 26 years old female(Case A)went to a sampling site for coronavirus disease 2019(COVID-19)testing due to excessive fatigue and fever for two days.This patient preliminarily tested positive for seve...On January 15,2022,a 26 years old female(Case A)went to a sampling site for coronavirus disease 2019(COVID-19)testing due to excessive fatigue and fever for two days.This patient preliminarily tested positive for severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)using a quantitative real-time reverse transcription polymerase chain reaction(qRT-PCR)method.展开更多
cAMP response element binding protein (CREB) is a transcription factor in nucleus. The activating CREB can specifically bind to the cAMP response element (CRE). The present result showed that erythropoietin (EPO) coul...cAMP response element binding protein (CREB) is a transcription factor in nucleus. The activating CREB can specifically bind to the cAMP response element (CRE). The present result showed that erythropoietin (EPO) could induce the phosphorylation of CREB on Serine133 (Pser133), as detected by western blot analysis. in addition, the EPO-dependent activation of CREB binding to CRE element was demonstrated by electrophoretic mobility shift assay. However, the binding of CREB to CRE element could be inhibited by anti-CREB-Pser133 antibody. The data obtained suggested that the EPO-mediated CREB phosphorylation might be critical to both the binding of CREB to the CRE element and the activation of the CREB transcription factor.展开更多
基金supported by the National Key Research and Development Program of China(No.2016YFB0800601)the Key Program of NSFC-Tongyong Union Foundation(No.U1636209)+1 种基金the National Natural Science Foundation of China(61602358)the Key Research and Development Programs of Shaanxi(No.2019ZDLGY13-04,No.2019ZDLGY13-07)。
文摘The static and predictable characteristics of cyber systems give attackers an asymmetric advantage in gathering useful information and launching attacks.To reverse this asymmetric advantage,a new defense idea,called Moving Target Defense(MTD),has been proposed to provide additional selectable measures to complement traditional defense.However,MTD is unable to defeat the sophisticated attacker with fingerprint tracking ability.To overcome this limitation,we go one step beyond and show that the combination of MTD and Deception-based Cyber Defense(DCD)can achieve higher performance than either of them.In particular,we first introduce and formalize a novel attacker model named Scan and Foothold Attack(SFA)based on cyber kill chain.Afterwards,we develop probabilistic models for SFA defenses to provide a deeper analysis of the theoretical effect under different defense strategies.These models quantify attack success probability and the probability that the attacker will be deceived under various conditions,such as the size of address space,and the number of hosts,attack analysis time.Finally,the experimental results show that the actual defense effect of each strategy almost perfectly follows its probabilistic model.Also,the defense strategy of combining address mutation and fingerprint camouflage can achieve a better defense effect than the single address mutation.
文摘Hydroxyurea has been used to synchronize cultured cells to S-phase and used to treat patients with sicklecell anemia. Recently, we found that hydroxyurea can induce the apoptosis of HEL (human erythroleukemia) cells.The induced HEL cells showed ultrastructurally chromatin condensation with regular crescents at the nuclear edges and apoptotic bodies. However, the cells of K562, another human erythroleukemia cell line, did not show such morphological changes. Under fluoroscope, the HEL cells after induction often displayed a clear reduction in nuclear diameter and nuclear chromatin cleavage and condensation and the presence of nuclear ring and apoptotic bodies. Analysis with flow cytometry showed that the percentage of apoptotic cells is about 30-40% after HEL cells were induced by hydroxyurea for 3 days. DNA ladder can be observed by electrophoretic analysis.
文摘The organization of the higher order structure of chromatin in chicken erythrocytes has been examined withtapping-mode scanning force microscopy under conditionsclose to their native environment. Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated. An extended beads-on-astring (width of ～ 15-20nm, height of ～ 2-3nm for eachindividual nucleosome) can be consistently observed. Furthermore, superbeads (width of ～ 40nm, height of ～ 7nm)are demonstrated. Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained eitherby using AFM or by using electron microscopy. In addition, tightly coiled chromatin fibers (～ 50-60nm and ～90-110nm) can be revealed. Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning thefolding pattern of interphase chromatin fibers.
基金Funded by The Capital Health Development and Research of Special(2021-1G-3012)Beijing Science and Technology Planning Project(Z201100005420010)and(Z211100002521019)Beijing Talent Project(2020A050,2020A051).
文摘On January 15,2022,a 26 years old female(Case A)went to a sampling site for coronavirus disease 2019(COVID-19)testing due to excessive fatigue and fever for two days.This patient preliminarily tested positive for severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)using a quantitative real-time reverse transcription polymerase chain reaction(qRT-PCR)method.
文摘cAMP response element binding protein (CREB) is a transcription factor in nucleus. The activating CREB can specifically bind to the cAMP response element (CRE). The present result showed that erythropoietin (EPO) could induce the phosphorylation of CREB on Serine133 (Pser133), as detected by western blot analysis. in addition, the EPO-dependent activation of CREB binding to CRE element was demonstrated by electrophoretic mobility shift assay. However, the binding of CREB to CRE element could be inhibited by anti-CREB-Pser133 antibody. The data obtained suggested that the EPO-mediated CREB phosphorylation might be critical to both the binding of CREB to the CRE element and the activation of the CREB transcription factor.
