Confinement effects on product selectivity in the pyrolysis of phenethyl phenyl ether in mesoporous silica

Pyrolysis of phenethyl phenyl ether confined in mesoporous silicas by covalent grafting results in significantly increased product selectivity compared with fluid phases.     

Phonon mediated photodetector

Quantum-wells and quantum dots and related semiconductor nanostructures have been widely investigated for infrared devices. Here we propose a new general approach to make use of polar optical phonons in quantum-wells for infrared (IR) and terahertz (THz) detection. As the first example, we show the coupling of phonon and intersubband transition leading to Fano resonance in photocurrent spectra. We investigate the phenomenon experimentally in specially designed GaAs/AlGaAs quantum-well infrared photodetectors. Finally, we discuss the future research and potentials.     

Structural and spectroscopic characterization of copper(II) complexes of a new bisamide functionalized imidazole tripod and evidence for the formation of a mononuclear end-on Cu-OOH species

A new polyimidazole tripod N,N-bis((1-methyl-4-pivalamidoimidazol-2-yl)methyl)-N'-((1-methylimidazol-2-yl)methyl)amine (L2) has been synthesized and shown to form intramolecular hydrogen bonds with different axial ligands bonded to Cu(II) in the solid state. The same hydrogen-bonding property of L2 appears responsible for the stabilization of a Cu(II)-OOH species in solution. The crystal structures of L2 and three of its Cu(II) complexes are reported. The [Cu(L2)X]ClO4 complexes, 4-6 (X- = Cl-, OH-, or N3-) have distorted trigonal bipyramidal geometries in the solid state and have been characterized further by UV-vis absorption, electron paramagnetic resonance (EPR) spectroscopy, and cyclic voltammetry. The reaction of [Cu(L2)OH](ClO4) (5) with H2O2 and tert-butyl hydroperoxide in methanol generates [Cu(L2)OOH](ClO4) (7) and [Cu(L2)OO(t)Bu](ClO4) (8) which have been characterized by different spectroscopic methods. The compound [Cu(L2)OO(t)Bu]+ displays a band at 395 nm (epsilon = 950 M(-1) cm(-1)) assigned to an alkylperoxo pi*(sigma) --> Cu ligand-to-metal charge transfer (LMCT) transition, while [Cu(L2)OOH]+ displays a peroxo pi*(sigma) --> Cu charge-transfer transition at 365 nm with epsilon = 1300 M(-1) cm(-1), a mass ion at m/z 593.4, and nu(O-O) stretch (resonance Raman) at 854 cm(-1) that shifts to lower energy by 46 cm(-1) upon 18O substitution.     

Electron paramagnetic resonance and thermoluminescence study of Ag ions in Li2B4O7 crystals

Electron paramagnetic resonance (EPR) is used to investigate the effects of ionizing radiation on Ag-doped lithium tetraborate (Li₂B₄O₇) crystals. Two similar, yet distinct, trapped-hole centers (Ag²⁺ ions substituting for Li⁺ ions) are produced by 60 kV x rays. One Ag²⁺ ion, labeled Center A, has no nearby defects and the other Ag²⁺ ion, labeled Center B, has a neighboring impurity which is most likely a Ag⁺ ion substituting for a Li⁺ ion. The production and thermal decay properties of the two Ag²⁺ ions are described and their g matrices and ¹⁰⁷Ag and ¹⁰⁹Ag hyperfine matrices are obtained from the EPR angular dependences. The principal values of the g matrices are similar for the two centers, but the hyperfine principal values differ significantly (Center B has smaller values than Center A). There are also differences in the directions of the principal axes for the two centers. Together, these results imply (1) that the unpaired spin is less localized for Center B and (2) that the ground-state positions of the neighboring oxygen ions are different for Centers A and B. This explains why the peaks of the Ag²⁺ charge-transfer photoluminescence bands associated with Centers A and B occur at different wavelengths (502 and 725 nm, respectively). An isochronal pulsed thermal anneal shows that these radiation-induced Ag²⁺ ions serve as the recombination site for the intense thermoluminescence peak observed near 152 °C.     

Deamidation accelerates amyloid formation and alters amylin fiber structure

Deamidation of asparagine and glutamine is the most common nonenzymatic, post-translational modification. Deamidation can influence the structure, stability, folding, and aggregation of proteins and has been proposed to play a role in amyloid formation. However there are no structural studies of the consequences of deamidation on amyloid fibers, in large part because of the difficulty of studying these materials using conventional methods. Here we examine the effects of deamidation on the kinetics of amyloid formation by amylin, the causative agent of type 2 diabetes. We find that deamidation accelerates amyloid formation and the deamidated material is able to seed amyloid formation by unmodified amylin. Using site-specific isotope labeling and two-dimensional infrared (2D IR) spectroscopy, we show that fibers formed by samples that contain deamidated polypeptide contain reduced amounts of β-sheet. Deamidation leads to disruption of the N-terminal β-sheet between Ala-8 and Ala-13, but β-sheet is still retained near Leu-16. The C-terminal sheet is disrupted near Leu-27. Analysis of potential sites of deamidation together with structural models of amylin fibers reveals that deamidation in the N-terminal β-sheet region may be the cause for the disruption of the fiber structure at both the N- and C-terminal β-sheet. Thus, deamidation is a post-translational modification that creates fibers that have an altered structure but can still act as a template for amylin aggregation. Deamidation is very difficult to detect with standard methods used to follow amyloid formation, but isotope-labeled IR spectroscopy provides a means for monitoring sample degradation and investigating the structural consequences of deamidation.     

Trusted Threat Intelligence Sharing in Practice and Performance Benchmarking through the Hyperledger Fabric Platform

Historically, threat information sharing has relied on manual modelling and centralised network systems, which can be inefficient, insecure, and prone to errors. Alternatively, private blockchains are now widely used to address these issues and improve overall organisational security. An organisation’s vulnerabilities to attacks might change over time. It is utterly important to find a balance among a current threat, the potential countermeasures, their consequences and costs, and the estimation of the overall risk that this provides to the organisation. For enhancing organisational security and automation, applying threat intelligence technology is critical for detecting, classifying, analysing, and sharing new cyberattack tactics. Trusted partner organisations can then share newly identified threats to improve their defensive capabilities against unknown attacks. On this basis, organisations can help reduce the risk of a cyberattack by providing access to past and current cybersecurity events through blockchain smart contracts and the Interplanetary File System (IPFS). The suggested combination of technologies can make organisational systems more reliable and secure, improving system automation and data quality. This paper outlines a privacy-preserving mechanism for threat information sharing in a trusted way. It proposes a reliable and secure architecture for data automation, quality, and traceability based on the Hyperledger Fabric private-permissioned distributed ledger technology and the MITRE ATT&CK threat intelligence framework. This methodology can also be applied to combat intellectual property theft and industrial espionage.     

探测到来自地幔的中微子

地球内部长寿命的放射性同位素的不断衰变对地球加热并发射出中微子。用大型探测器可以观测这些中微子。Borexino 合作组最近报道了一组新的关于这种“地球中微子”的数据,并指出,其中至少一些源自地幔。这项工作可以使研究人员更好地理解放射性衰变如何帮助驱动内部的地球物理过程,包括地幔中岩石的缓慢迁移。
中微子与物质的相互作用极其微弱。当中微子穿过1 光年厚的铅墙时,只有一半的中微子被阻止,所以,探测中微子是很具挑战性的。但是Borexino 和另一个国际合作组KamLAND 使用大型探测器曾以很高的置信度探测到地球中微子。研究人员希望通过更多的数据获得关于放射性同位素在地球内部的分布,以及它们释放给地下不同区域的热量分布的进一步信息。