Ab initio determination of melting and sound velocity of neon up to the deep interior of the Earth.

The thermophysical properties and elemental abundances of the noble gases in terrestrial materials can provide unique insights into the Earth's evolution and mantle dynamics. Here, we perform extensive ab initio molecular dynamics simulations to determine the melting temperature and sound velocity of neon up to 370 GPa and 7500 K to constrain its physical state and storage capacity, together with to reveal its implications for the deep interior of the Earth. It is found that solid neon can exist stably under the lower mantle and inner core conditions, and the abnormal melting of neon is not observed under the entire temperature (T) and pressure (P) region inside the Earth owing to its peculiar electronic structure, which is substantially distinct from other heavier noble gases. An inspection of the reduction for sound velocity along the Earth's geotherm evidences that neon can be used as a light element to account for the low-velocity anomaly and density deficit in the deep Earth. A comparison of the pair distribution functions and mean square displacements of MgSiO3-Ne and Fe-Ne alloys further reveals that MgSiO3 has a larger neon storage capacity than the liquid iron under the deep Earth condition, indicating that the lower mantle may be a natural deep noble gas storage reservoir. Our results provide valuable information for studying the fundamental behavior and phase transition of neon in a higher T-P regime, and further enhance our understanding for the interior structure and evolution processes inside the Earth.

Induction of cerebral beta-amyloidosis: intracerebral versus systemic Abeta inoculation.

Despite the importance of the aberrant polymerization of Abeta in the early pathogenic cascade of Alzheimer's disease, little is known about the induction of Abeta aggregation in vivo. Here we show that induction of cerebral beta-amyloidosis can be achieved in many different brain areas of APP23 transgenic mice through the injection of dilute Abeta-containing brain extracts. Once the amyloidogenic process has been exogenously induced, the nature of the induced Abeta-deposition is determined by the brain region of the host. Because these observations are reminiscent of a prion-like mechanism, we then investigated whether cerebral beta-amyloidosis also can be induced by peripheral and systemic inoculations or by the intracerebral implantation of stainless steel wires previously coated with minute amounts of Abeta-containing brain extract. Results reveal that oral, intravenous, intraocular, and intranasal inoculations yielded no detectable induction of cerebral beta-amyloidosis in APP23 transgenic mice. In contrast, transmission of cerebral beta-amyloidosis through the Abeta-contaminated steel wires was demonstrated. Notably, plasma sterilization, but not boiling of the wires before implantation, prevented the induction of beta-amyloidosis. Our results suggest that minute amounts of Abeta-containing brain material in direct contact with the CNS can induce cerebral beta-amyloidosis, but that systemic cellular mechanisms of prion uptake and transport to the CNS may not apply to Abeta.

[Study on the ignition mechanism of aluminum nanoparticle by fast spectroscopy].

The ignition delay times and special spectral intensity of aluminum nanopowders reacting with propylene oxide were investigated by fast spectrum system triggered by synchronous shock light singles, and the ignition mechanism was presented from those data. X-ray diffraction (XRD) spectrum indicated that aluminum nanoparticle produced by plasma method has been oxidized for its high activity, X-ray photoelectron spectroscopy (XPS) of sample revealed that there is 3 nm oxide layer on its surface. XPS of the products showed that the oxide layer thickness will increase with the increasing shock wave strength. AlO (464.8 nm) ignition times investigated by monochromator revealed that aluminum nanoparticle will be equably distributed in propylene oxide vapor for increasing shock wave strength to increase its heating surface and heating rate, and shock wave will easily crack the 3 nm oxide layer on aluminum nanoparticle present chance for core active aluminum to react with oxygen atom and containing-oxygen molecule in the reaction system to ignite.

[Spectrum studies of ignition characteristic in quick reaction of benzene].

A new optical spectroscopy system consisting of a monochromator, photomultiplier tubes (PMT), piezoelectric pressure sensor and digital phosphor oscilloscope was established to study spectrum and ignition delay time of benzene in quick reaction in a high temperature shock tube. A new method of determining ignition delay time of energetic materials behind incident shock wave is proposed. Several important products, such as H, C2 and CH, were determined in sequence of emergence time. The reaction mechanism of formation of carbon was introduced when benzene was driven under shock compression. The results indicate that in spite of the variety of Mach number, atom H always emerged first, indicating that the pyrolysis of benzene started with C-H bond instead of C-C bond. The results show that applying spectrum techniques can preferably study the ignition characteristic of benzene in quick reaction. Measuring ignition delay time by means of a prior emerged intermediate product (atom H) is more accurate than that with white color technique widely used home and abroad, and furthermore, can obviously reduce the times of experiment.

[Study on micro-behaviours shock ignition for epoxypropane using spectrum techniques].

The micro-behaviours of shock ignition of epoxypropane were studied by OMA (optical multii channal system) and monochromator techniques. The radicals O, CH2O, C2, CH, CH3O, CO2 and H2O were observed by OMA spectrometer. The delay time and critical condition of shock ignition were determined using three monochromators and gauge. The emergence of intermediate product of O for epoxypropane after shock ignition is always the earliest.

The Priority position paper: Protecting Europe's food chain from prions.

Bovine spongiform encephalopathy (BSE) created a global European crisis in the 1980s and 90s, with very serious health and economic implications. Classical BSE now appears to be under control, to a great extent as a result of a global research effort that identified the sources of prions in meat and bone meal (MBM) and developed new animal-testing tools that guided policy. Priority ( www.prionpriority.eu ) was a European Union (EU) Framework Program 7 (FP7)-funded project through which 21 European research institutions and small and medium enterprises (SMEs) joined efforts between 2009 and 2014, to conduct coordinated basic and applied research on prions and prion diseases. At the end of the project, the Priority consortium drafted a position paper ( www.prionpriority.eu/Priority position paper) with its main conclusions. In the present opinion paper, we summarize these conclusions. With respect to the issue of re-introducing ruminant protein into the feed-chain, our opinion is that sustaining an absolute ban on feeding ruminant protein to ruminants is essential. In particular, the spread and impact of non-classical forms of scrapie and BSE in ruminants is not fully understood and the risks cannot be estimated. Atypical prion agents will probably continue to represent the dominant form of prion diseases in the near future in Europe. Atypical L-type BSE has clear zoonotic potential, as demonstrated in experimental models. Similarly, there are now data indicating that the atypical scrapie agent can cross various species barriers. More epidemiological data from large cohorts are necessary to reach any conclusion on the impact of its transmissibility on public health. Re-evaluations of safety precautions may become necessary depending on the outcome of these studies. Intensified searching for molecular determinants of the species barrier is recommended, since this barrier is key for important policy areas and risk assessment. Understanding the structural basis for strains and the basis for adaptation of a strain to a new host will require continued fundamental research, also needed to understand mechanisms of prion transmission, replication and how they cause nervous system dysfunction and death. Early detection of prion infection, ideally at a preclinical stage, also remains crucial for development of effective treatment strategies.

Infectivity of prion protein bound to stainless steel wires: a model for testing decontamination procedures for transmissible spongiform encephalopathies.

OBJECTIVES: To establish an animal model to study transmissible spongiform encephalopathy using hamsters and steel wires contaminated with infectious brain materials as transfer vehicles, and, based on this model, to test decontamination procedures against the infectious prion proteins on the steel wires as a near real situation bioassay. DESIGN: Infectious brain materials were given to healthy hamsters intracerebrally either as a suspension or as dried materials on the surface of steel wires. The animals were observed for 18 months. During this period, animals showing definitive clinical signs were euthanized. Decontamination studies were performed by reprocessing contaminated steel wires with different disinfection agents and procedures before implantation. RESULTS: Pathological prion proteins were able to bind to the steel wires and caused disease after the contaminated wires were implanted in the brains of hamsters. When the contaminated wires were treated with different reprocessing procedures before implantation, infectivity was reduced, which was manifested directly by prolonged survival time of the test animals. These results show that this model can be used as a bioassay to validate reprocessing procedures for surgical instruments. CONCLUSIONS: At the time of submission of this article, only the group of hamsters incubated with wires reprocessed with an alkaline detergent, followed by sterilization with a modified cycle in a hydrogen peroxide gas plasma sterilizer (4 injections), showed no clinical signs of disease and remained alive. Two animals from the group receiving sodium hydroxide followed by autoclaving (at 134 degrees C for 18 minutes) died. Furthermore, the tested enzymatic cleaning agent seemed to have no positive effect.