当前脉冲星领域一个重要的研究热点是磁星.本文在朱翠等(Zhu C,Gao Z F,Li X D,Wang N,Yuan J P,Peng Q H 2016 Mod.Phys.Lett.311650070)工作的基础上,重新研究了磁星超强磁场下(B>>B_(cr),B_(cr)是电子的.量子临界磁场)电子朗...当前脉冲星领域一个重要的研究热点是磁星.本文在朱翠等(Zhu C,Gao Z F,Li X D,Wang N,Yuan J P,Peng Q H 2016 Mod.Phys.Lett.311650070)工作的基础上,重新研究了磁星超强磁场下(B>>B_(cr),B_(cr)是电子的.量子临界磁场)电子朗道能级的稳定性及其对电子压强的影响.首先,对弱磁场极限下(B<<B_(cr))中子星内部电子压强进行必要的回顾;然后,通过引入电子朗道能级稳定性系数g_(v)和Dirac-δ函数,推导出在超强磁场下修正的相对论电子压强P_(e)的表达式,给出表达式适用条件:物质密度P≥10^(7)g·cm^(-3).和B_(cr)≤B<10^(17)G(1 G=10^(-4)T).超强磁场通过修正相对论电子的相空间,提高了电子数密度n_(e),而n_(e)的增加意味着Pe的增加.利用修正的电子压强表达式,讨论了超强磁场下费米子自旋极化现象、电子磁化现象以及超强磁场对物态方程的修正.最后,本文的结果与其他类似工作进行对比,并对未来的工作进行展望.本文的研究将为磁星以及强磁化白矮星的物态方程和热演化的探索提供极有价值的参考,将为普通射电脉冲星等离子磁层数值模拟、高磁场脉冲星辐射机制等相关研究提供有用的信息.展开更多
随着计算机数字技术的高速发展,甚长基线干涉仪测量(Very Long Baseline Interferometry,VLBI)所需的关键观测终端设备基带转换器(Base Band Converter,BBC)已从模拟系统(Analog BBC,ABBC)发展为数字系统(Digital BBC,DBBC)。相对于模...随着计算机数字技术的高速发展,甚长基线干涉仪测量(Very Long Baseline Interferometry,VLBI)所需的关键观测终端设备基带转换器(Base Band Converter,BBC)已从模拟系统(Analog BBC,ABBC)发展为数字系统(Digital BBC,DBBC)。相对于模拟系统,数字系统具有很高的灵活性,并能成倍提高VLBI观测带宽,进而能满足各种高灵敏度的观测需求。考虑到这些技术优势,以及新疆天文台南山站在国内和国际VLBI网中的重要作用,南山站2016年对VLBI终端系统进行了升级,引进了一套意大利Hat-Lab公司研发的DBBC2终端。介绍了DBBC2系统的主要构成模块和工作原理以及系统的组装、连接、配置、校准和调试方法。在对系统硬件和软件进行全面的检测和测试后,与国内和国际的主要台站开展了联合观测,并多次成功获得相关干涉条纹。这一系列的成功观测表明,南山DBBC2系统已成功安装,并具有很高的可靠性。应用新的DBBC2系统,南山站可参与2/4 Gbps的记录速率的宽带VLBI观测,极其有助于天文学家对宇宙中更暗弱的射电源开展毫角秒分辨率的成图观测。展开更多
Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 ne...Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 neutron Cooper pair is only about 0.048 MeV,the outgoing high-energy neutrons（E k（n） 60 MeV） created by the EC can easily destroy the 3 P 2 neutron Cooper pairs through the interaction of nuclear force.In the anisotropic neutron superfluid,each 3 P 2 neutron Cooper pair has magnetic energy 2μ n B in the applied magnetic field B,where μ n = 0.966 × 10 23 erg.G 1 is the absolute value of the neutron abnormal magnetic moment.While being destroyed by the high-energy EC neutrons,the magnetic moments of the 3 P 2 Cooper pairs are no longer arranged in the paramagnetic direction,and the magnetic energy is released.This released energy can be transformed into thermal energy.Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction,and then it is radiated in the form of thermal photons from the surface.After highly efficient modulation within the star＇s magnetosphere,the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of magnetars.By introducing related parameters,we calculate the theoretical luminosities of magnetars.The calculation results agree well with the observed parameters of magnetars.展开更多
In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are consider...In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are considered. We find that hydrogen bonding becomes a key element in inducing the anomalous switching of ssDNA monolayers. This finding accords well with the experimental observations. Based on our theoretical model, we predict that the anomalous switching induced by water vapor will be applicable to a wide range of hydrogen bonds polymers, and ssDNA-water hydrogen bonds and water-water hydrogen bonds hybridization will lead to the hydrogen-bond network formation of 3D ssDNA monolayers.展开更多
By employing molecular theory, we systematically investigate the shift of solubility of poly（N-isopropylacrylamide）（PNIPAM） brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water...By employing molecular theory, we systematically investigate the shift of solubility of poly（N-isopropylacrylamide）（PNIPAM） brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydrogen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series： Na Cl＆gt;Na Br＆gt;Na I. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.展开更多
Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA（ss DNA）tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DN...Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA（ss DNA）tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows： i） when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii）for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii） when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high.展开更多
In this work, we investigate the effects of thiocyanate anions on the switching and the structure of poly(Nisopropylacrylamide)(PNIPAM) brushes using a molecular theory. Our model takes into consideration the PNIPAM–...In this work, we investigate the effects of thiocyanate anions on the switching and the structure of poly(Nisopropylacrylamide)(PNIPAM) brushes using a molecular theory. Our model takes into consideration the PNIPAM–anion bonds, the electrostatic effects and their explicit coupling to the PNIPAM conformations. It is found that at low thiocyanate anion concentration, as the anion concentration of thiocyanate increases, thiocyanate anions are more associated with PNIPAM chains through the PNIPAM–anion bonds, which contributes to stronger electrostatic repulsion and leads to an increase of lower critical solution temperature(LCST). By analyzing the average volume fractions of PNIPAM brushes,it is found that the PNIPAM brush presents a plateau structure. Our results show that the thiocyanate anions promote phase segregation due to the PNIPAM–anion bonds and the electrostatic effect. According to our model, the reduction of LCST can be explained as follows: at high thiocyanate anion concentration, with the increase of thiocyanate concentration, more ion bindings occurring between thiocyanate anions and PNIPAM chains will result in the increase of the hydrophobicity of PNIPAM chains;when the increase of electrostatic repulsion is insufficient to overcome the hydrophobic interaction of PNIPAM chains, it will lead to the reduction of brush height and LCST at high thiocyanate anion concentration. Our theoretical results are consistent with the experimental observations, and provide a fundamental understanding of the effects of thiocyanate on the LCST of PNIPAM brushes.展开更多
文摘当前脉冲星领域一个重要的研究热点是磁星.本文在朱翠等(Zhu C,Gao Z F,Li X D,Wang N,Yuan J P,Peng Q H 2016 Mod.Phys.Lett.311650070)工作的基础上,重新研究了磁星超强磁场下(B>>B_(cr),B_(cr)是电子的.量子临界磁场)电子朗道能级的稳定性及其对电子压强的影响.首先,对弱磁场极限下(B<<B_(cr))中子星内部电子压强进行必要的回顾;然后,通过引入电子朗道能级稳定性系数g_(v)和Dirac-δ函数,推导出在超强磁场下修正的相对论电子压强P_(e)的表达式,给出表达式适用条件:物质密度P≥10^(7)g·cm^(-3).和B_(cr)≤B<10^(17)G(1 G=10^(-4)T).超强磁场通过修正相对论电子的相空间,提高了电子数密度n_(e),而n_(e)的增加意味着Pe的增加.利用修正的电子压强表达式,讨论了超强磁场下费米子自旋极化现象、电子磁化现象以及超强磁场对物态方程的修正.最后,本文的结果与其他类似工作进行对比,并对未来的工作进行展望.本文的研究将为磁星以及强磁化白矮星的物态方程和热演化的探索提供极有价值的参考,将为普通射电脉冲星等离子磁层数值模拟、高磁场脉冲星辐射机制等相关研究提供有用的信息.
文摘随着计算机数字技术的高速发展,甚长基线干涉仪测量(Very Long Baseline Interferometry,VLBI)所需的关键观测终端设备基带转换器(Base Band Converter,BBC)已从模拟系统(Analog BBC,ABBC)发展为数字系统(Digital BBC,DBBC)。相对于模拟系统,数字系统具有很高的灵活性,并能成倍提高VLBI观测带宽,进而能满足各种高灵敏度的观测需求。考虑到这些技术优势,以及新疆天文台南山站在国内和国际VLBI网中的重要作用,南山站2016年对VLBI终端系统进行了升级,引进了一套意大利Hat-Lab公司研发的DBBC2终端。介绍了DBBC2系统的主要构成模块和工作原理以及系统的组装、连接、配置、校准和调试方法。在对系统硬件和软件进行全面的检测和测试后,与国内和国际的主要台站开展了联合观测,并多次成功获得相关干涉条纹。这一系列的成功观测表明,南山DBBC2系统已成功安装,并具有很高的可靠性。应用新的DBBC2系统,南山站可参与2/4 Gbps的记录速率的宽带VLBI观测,极其有助于天文学家对宇宙中更暗弱的射电源开展毫角秒分辨率的成图观测。
基金Project supported by the National Natural Science Foundation of China(Grant No.10773005)the National Basic Research Program of China(Grant No.2009CB824800)+1 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX 2 -YW-T09)the Key Directional Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China(Grant Nos.10173020,10673021,10778631 and 10903019)
文摘Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 neutron Cooper pair is only about 0.048 MeV,the outgoing high-energy neutrons（E k（n） 60 MeV） created by the EC can easily destroy the 3 P 2 neutron Cooper pairs through the interaction of nuclear force.In the anisotropic neutron superfluid,each 3 P 2 neutron Cooper pair has magnetic energy 2μ n B in the applied magnetic field B,where μ n = 0.966 × 10 23 erg.G 1 is the absolute value of the neutron abnormal magnetic moment.While being destroyed by the high-energy EC neutrons,the magnetic moments of the 3 P 2 Cooper pairs are no longer arranged in the paramagnetic direction,and the magnetic energy is released.This released energy can be transformed into thermal energy.Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction,and then it is radiated in the form of thermal photons from the surface.After highly efficient modulation within the star＇s magnetosphere,the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of magnetars.By introducing related parameters,we calculate the theoretical luminosities of magnetars.The calculation results agree well with the observed parameters of magnetars.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21264016,11464047,and 21364016)the National Basic Research Program of China(Grant No.2012CB821500)the Natural Science Foundation of Xinjiang Uygur Autonomous Region,China(Grant No.2013211A053)
文摘In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are considered. We find that hydrogen bonding becomes a key element in inducing the anomalous switching of ssDNA monolayers. This finding accords well with the experimental observations. Based on our theoretical model, we predict that the anomalous switching induced by water vapor will be applicable to a wide range of hydrogen bonds polymers, and ssDNA-water hydrogen bonds and water-water hydrogen bonds hybridization will lead to the hydrogen-bond network formation of 3D ssDNA monolayers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21264016,11464047,and 21364016)the Joint Funds of Xinjiang Natural Science Foundation,China(Grant No.2015211C298)
文摘By employing molecular theory, we systematically investigate the shift of solubility of poly（N-isopropylacrylamide）（PNIPAM） brushes in sodium halide solutions. After considering PNIPAM–water hydrogen bonds, water–anion hydrogen bonds, and PNIPAM–anion bonds and their explicit coupling to the PNIPAM conformations, we find that increasing temperature lowers the solubility of PNIPAM, and results in a collapse of the layer at high enough temperatures. The combination of the three types of bonds would yield a decrease in the solubility of PNIPAM following the Hofmeister series： Na Cl＆gt;Na Br＆gt;Na I. PNIPAM–water hydrogen bonds are affected by water–anion hydrogen bonds and PNIPAM–anion bonds. The coupling of polymer conformations and the competition among the three types of bonds are essential for describing correctly a decrease in the solubility of PNIPAM brushes, which is determined by the free energy associated with the formation of the three types of bonds. Our results agree well with the experimental observations, and would be very important for understanding the shift of the lower critical solution temperature of PNIPAM brushes following the Hofmeister series.
基金Project supported by the Joint Funds of Xinjiang Natural Science Foundation,China(Grant No.2015211C298)
文摘Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA（ss DNA）tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows： i） when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii）for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii） when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high.
基金Project supported by the Joint Funds of Xinjiang Natural Science Foundation(Grant No.2019D01C333)the National Natural Science Foundation of China(Grant Nos.11847610 and 21764015)the National Basic Research Program of China(Grant No.2015CB857100)
文摘In this work, we investigate the effects of thiocyanate anions on the switching and the structure of poly(Nisopropylacrylamide)(PNIPAM) brushes using a molecular theory. Our model takes into consideration the PNIPAM–anion bonds, the electrostatic effects and their explicit coupling to the PNIPAM conformations. It is found that at low thiocyanate anion concentration, as the anion concentration of thiocyanate increases, thiocyanate anions are more associated with PNIPAM chains through the PNIPAM–anion bonds, which contributes to stronger electrostatic repulsion and leads to an increase of lower critical solution temperature(LCST). By analyzing the average volume fractions of PNIPAM brushes,it is found that the PNIPAM brush presents a plateau structure. Our results show that the thiocyanate anions promote phase segregation due to the PNIPAM–anion bonds and the electrostatic effect. According to our model, the reduction of LCST can be explained as follows: at high thiocyanate anion concentration, with the increase of thiocyanate concentration, more ion bindings occurring between thiocyanate anions and PNIPAM chains will result in the increase of the hydrophobicity of PNIPAM chains;when the increase of electrostatic repulsion is insufficient to overcome the hydrophobic interaction of PNIPAM chains, it will lead to the reduction of brush height and LCST at high thiocyanate anion concentration. Our theoretical results are consistent with the experimental observations, and provide a fundamental understanding of the effects of thiocyanate on the LCST of PNIPAM brushes.
