Polymeric pseudo-crown ether for cation recognition via cation template-assisted cyclopolymerization.

Cyclopolymerization is a chain polymerization of bifunctional monomers via alternating processes of intramolecular cyclization and intermolecular addition, to give soluble linear polymers consisting of in-chain cyclic structures. Though cyclopolymers comprising in-chain multiple large rings potentially show unique functionality, they generally require the elaborate design of bifunctional monomers. Here we report cation template-assisted cyclopolymerization of poly(ethylene glycol) dimethacrylates as an efficient strategy directly yielding polymeric pseudo-crown ethers with large in-chain cavities (up to 30-membered rings) for selective molecular recognition. The key is to select a size-fit metal cation for the spacer unit of the divinyl monomers to form a pseudo-cyclic conformation, where the two vinyl groups are suitably positioned for intramolecular cyclization. The marriage of supramolecular chemistry and polymer chemistry affords efficient, one-pot chemical transformation from common chemical reagents with simple templates to functional cyclopolymers

Nap1 regulates proper CENP-B binding to nucleosomes

CENP-B is a widely conserved centromeric satellite DNA-binding protein, which specifically binds to a 17-bp DNA sequence known as the CENP-B box. CENP-B functions positively in the de novo assembly of centromeric nucleosomes, containing the centromere-specific histone H3 variant, CENP-A. At the same time, CENP-B also prevents undesired assembly of the CENP-A nucleosome through heterochromatin formation on satellite DNA integrated into ectopic sites. Therefore, improper CENP-B binding to chromosomes could be harmful. However, no CENP-B eviction mechanism has yet been reported. In the present study, we found that human Nap1, an acidic histone chaperone, inhibited the non-specific binding of CENP-B to nucleosomes and apparently stimulated CENP-B binding to its cognate CENP-B box DNA in nucleosomes. In human cells, the CENP-B eviction activity of Nap1 was confirmed in model experiments, in which the CENP-B binding to a human artificial chromosome or an ectopic chromosome locus bearing CENP-B boxes was significantly decreased when Nap1 was tethered near the CENP-B box sequence. In contrast, another acidic histone chaperone, sNASP, did not promote CENP-B eviction in vitro and in vivo and did not stimulate specific CENP-B binding to CENP-A nucleosomes in vitro. We therefore propose a novel mechanism of CENP-B regulation by Nap1

Finding a Connection Chain for Tracing Intruders

Abstract. Intruders usually log in through a chain of multiple computer systems to hide their origins before breaking into their targets, which makes tracing difficult. In this paper we present a method to find the connection chain of an intruder for tracing back to the origin. We focus on telnet and rlogin as interactive applications intruders use to log in through hosts. The method involves setting up packet monitors at as many traffic points as possible on the Internet to record the activities of intruders at the packet level. When a host is compromised and used as a step-through host to access another host, we compare the packet logs of the intruder at that host to logs we have recorded all over the Internet to find the closest match. We define the ‘deviation ’ for one packet stream on a connection from another, and implement a system to compute deviations. If a deviation is small, the two connections must be in the same connection chain. We present some experimental results showing that the deviation for two unrelated packet streams is large enough to be distinguished from the deviation for packet streams on connections in the same chain.

Ultra-highly efficient SOT-writing in MTJs with strain-induced magnetic anisotropy

In order to break through limits of conventional MRAMs, MTJs with strain-induced magnetic anisotropy were intensively tested as SOT-MRAM cells. Small critical switching-current of 10–25 μA and switching-voltage of about 0.055 V, and almost no retention energy dependence of them were predicted and confirmed by experiments. Finally, high write efficiency of 1750 kBT/V (4.1 kBT/μA) and high write-power efficiency of 100 [kBT/(μA·V)] were obtained

Phase Behavior of a Carbon Dioxide/Methyl Trimethoxy Silane/Polystyrene Ternary System

Recently, polymeric foams filled with a silica aerogel have been developed. The phase behavior of CO2/silicon alkoxide binary systems and CO2/silicon alkoxide/polymer ternary systems is an important factor that affects the design of novel processes. The phase behavior of a carbon dioxide (CO2)/methyl trimethoxy silane (MTMS)/polystyrene (PS) ternary system was measured using a synthetic method involving the observation of the bubble and cloud point. The phase boundaries were measured at temperatures ranging from 313.2 to 393.2 K and CO2 weight fractions between 0.01 and 0.08. The CO2/MTMS/PS system showed a similar CO2 mass fraction dependence of the phase behavior to that observed for the CO2/tetramethyl orthosilicate (TMOS)/PS system. When the phase boundaries of these systems were compared, the vapor-liquid (VL) and vapor-liquid-liquid (VLL) lines were found to be nearly identical, while the liquid-liquid (LL) lines were different. These results indicate that the affinity between the silicon alkoxide and polymer greatly influences the liquid-liquid phase separation