A new acknowledgment-type slotted-ALOHA code division multiple access （ACK-ALOHA-CDMA） channel which can be used in the inbound channels of very small aperture terminal（VSAT） networks is proposed in order to simpl...A new acknowledgment-type slotted-ALOHA code division multiple access （ACK-ALOHA-CDMA） channel which can be used in the inbound channels of very small aperture terminal（VSAT） networks is proposed in order to simplify the synchronization equipment of networks in the slotted-ALOHA- CDMA systems. By dividing all VSAT stations into M subsystems and sending out periodic inquiry signals from the Hub station to the VSAT station, the channel model is established. By the means of deriving multi-access interference（MAI） and packet detecting probability, steady-state throughput is calculated. By applying diffusion process theory to the analysis of the stability of the ACK-ALOHA-CDMA channel, the drift parameter a（r）, the diffusion parameter b（r） and the steady transition probability density p （r） are investigated. Simulation results indicate that significant performance improvement and high-bandwidth efficiency can be gained and one or two steady equilibrium points can be obtained by using this channel. Consequently, the ACK- ALOHA-CDMA channel is very suitable for cutting down on the expense of satellite VSAT systems and distributed packet radio networks.展开更多
Cathepsin D （CTSD） is a lysosomal acidic endoproteinase that plays an important role in immune response, In this study, we obtained sweetfish （Plecoglossus altivelis） CTSD （PaCTSD） via de-novo transcriptome sequ...Cathepsin D （CTSD） is a lysosomal acidic endoproteinase that plays an important role in immune response, In this study, we obtained sweetfish （Plecoglossus altivelis） CTSD （PaCTSD） via de-novo transcriptome sequencing of sweetfish macrophages. The full length cDNA sequence of PaCTSD was 1955 bp encoding a propeptide of 397 amino acids. The deduced protein had a calculated molecular weight of 43.17x 103. Multiple alignment with other known CTSD amino acid sequences revealed amino acid conservation through the teleosts. Phylogenetic tree analysis showed that PaCTSD grouped tightly with other fish CTSD, and was close to that of Atlantic salmon and rainbow trout. Subsequently, PaCTSD was prokaryotically expressed and refolded by the urea gradient method on a nickel-nitrilotriacetic acid column. Enzyme activity analysis showed that PaCTSD exhibited pH-dependent proteolytic activity. Quantitative real-time PCR showed that PaCTSD mRNA was expressed in all detected tissues in healthy sweetfish. The highest expression was observed in the spleen and white blood cells, followed by liver, head-kidney, kidney, intestine, gill, and muscle. After Listonella anguillarum infection, PaCTSD transcripts were up-regulated significantly in liver, spleen, white blood cells, and head-kidney of sweetfish. In summary, PaCTSD has proteolytic activity and is closely involved in the immune response of sweetfish.展开更多
Magnetic resonance imaging(MRI) has been extensively used in clinical diagnosis and currently over 30% MRI runs are performed in the presence of contrast agents. However, commercially available contrast agents origina...Magnetic resonance imaging(MRI) has been extensively used in clinical diagnosis and currently over 30% MRI runs are performed in the presence of contrast agents. However, commercially available contrast agents originated from small molecules typically exhibit relatively low relaxivities and insufficient circulation time. Therefore, there is a long pursuit to develop new contrast agents with high relaxivities to discriminate pathological tissues from normal ones. Compared with small molecule MRI contrast agents, the incorporation of small molecule contrast agents into macromolecular scaffolds allows for constructing macromolecular MRI contrast agents, remarkably elevating the relaxivities due in part to increased rotational correlation time(τR). Moreover, if the macromolecular scaffolds are responsive to external stimuli, the MRI signals could be selectively switched on at the desired sites(e.g., pathological tissues), further intensifying the imaging contrast. In this feature article, we outline the recent achievements in the fabrication of stimuli-responsive macromolecular MRI contrast agents. Specifically, macromolecular contrast agents being responsive to acidic p H, redox potentials, and other stimuli including photoirradiation, pathogens, and salt concentration are discussed. These smart contrast agents could affect either longitudinal(T1) or transverse(T2) relaxation times of water protons or other nuclei(e.g.,19 F), exhibiting enhanced signals in pathological tissues yet suppressed signals in normal ones and displaying promising potentials in in vitro and in vivo MRI applications.展开更多
基金The Key Laboratory Foundation of Geographical Information Science of Jiangsu Province (No.JK20050304)the Key Laboratory Foundation of Virtual Geographical Environments of Ministry of Education(No.NS206005)
文摘A new acknowledgment-type slotted-ALOHA code division multiple access （ACK-ALOHA-CDMA） channel which can be used in the inbound channels of very small aperture terminal（VSAT） networks is proposed in order to simplify the synchronization equipment of networks in the slotted-ALOHA- CDMA systems. By dividing all VSAT stations into M subsystems and sending out periodic inquiry signals from the Hub station to the VSAT station, the channel model is established. By the means of deriving multi-access interference（MAI） and packet detecting probability, steady-state throughput is calculated. By applying diffusion process theory to the analysis of the stability of the ACK-ALOHA-CDMA channel, the drift parameter a（r）, the diffusion parameter b（r） and the steady transition probability density p （r） are investigated. Simulation results indicate that significant performance improvement and high-bandwidth efficiency can be gained and one or two steady equilibrium points can be obtained by using this channel. Consequently, the ACK- ALOHA-CDMA channel is very suitable for cutting down on the expense of satellite VSAT systems and distributed packet radio networks.
基金Foundation items： The project was supported by the Program for the National Natural Science Foundation of China （31201970, 31372555）, Zhejiang Provincial Natural Science Foundation of China （LZ13C- 190001, LQ13C190002）
文摘Cathepsin D （CTSD） is a lysosomal acidic endoproteinase that plays an important role in immune response, In this study, we obtained sweetfish （Plecoglossus altivelis） CTSD （PaCTSD） via de-novo transcriptome sequencing of sweetfish macrophages. The full length cDNA sequence of PaCTSD was 1955 bp encoding a propeptide of 397 amino acids. The deduced protein had a calculated molecular weight of 43.17x 103. Multiple alignment with other known CTSD amino acid sequences revealed amino acid conservation through the teleosts. Phylogenetic tree analysis showed that PaCTSD grouped tightly with other fish CTSD, and was close to that of Atlantic salmon and rainbow trout. Subsequently, PaCTSD was prokaryotically expressed and refolded by the urea gradient method on a nickel-nitrilotriacetic acid column. Enzyme activity analysis showed that PaCTSD exhibited pH-dependent proteolytic activity. Quantitative real-time PCR showed that PaCTSD mRNA was expressed in all detected tissues in healthy sweetfish. The highest expression was observed in the spleen and white blood cells, followed by liver, head-kidney, kidney, intestine, gill, and muscle. After Listonella anguillarum infection, PaCTSD transcripts were up-regulated significantly in liver, spleen, white blood cells, and head-kidney of sweetfish. In summary, PaCTSD has proteolytic activity and is closely involved in the immune response of sweetfish.
基金supported by the National Natural Science Foundation of China (51690150, 51690154, 21674103, 51722307, 51673179)the International S&T Cooperation Program of China (ISTCP) of MOST (2016YFE0129700)+1 种基金the Natural Science Foundation of Anhui Province (1708085QB34)the Fundamental Research Funds for the Central Universities (WK3450000003, WK2060200023)
文摘Magnetic resonance imaging(MRI) has been extensively used in clinical diagnosis and currently over 30% MRI runs are performed in the presence of contrast agents. However, commercially available contrast agents originated from small molecules typically exhibit relatively low relaxivities and insufficient circulation time. Therefore, there is a long pursuit to develop new contrast agents with high relaxivities to discriminate pathological tissues from normal ones. Compared with small molecule MRI contrast agents, the incorporation of small molecule contrast agents into macromolecular scaffolds allows for constructing macromolecular MRI contrast agents, remarkably elevating the relaxivities due in part to increased rotational correlation time(τR). Moreover, if the macromolecular scaffolds are responsive to external stimuli, the MRI signals could be selectively switched on at the desired sites(e.g., pathological tissues), further intensifying the imaging contrast. In this feature article, we outline the recent achievements in the fabrication of stimuli-responsive macromolecular MRI contrast agents. Specifically, macromolecular contrast agents being responsive to acidic p H, redox potentials, and other stimuli including photoirradiation, pathogens, and salt concentration are discussed. These smart contrast agents could affect either longitudinal(T1) or transverse(T2) relaxation times of water protons or other nuclei(e.g.,19 F), exhibiting enhanced signals in pathological tissues yet suppressed signals in normal ones and displaying promising potentials in in vitro and in vivo MRI applications.
