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Background: Deposition of misfolded α‐synuclein (α‐Syn) aggregates in the human brain is one of the major hallmarks of synucleinopathies. Positron Emission Tomography imaging (PET) of α‐synuclein in Parkinson's disease (PD) patients is highly desirable but remains elusive. An extensive PET radioligand discovery campaign was undertaken. Here, we present the in‐vitro and preclinical in‐vivo characterization of [3H]‐ and [11C]Compound S, representing an example of a promising PET radioligand for α‐Syn. Method: Competition binding studies and autoradiographic studies were performed in cortexes of PD patients, healthy control, and Alzheimer's disease (AD) patients brain tissue, and mid‐brain region of the aged A30P mouse using [3H]S. Brain PET experiments using [11C]S were carried out in a healthy non‐human primate (NHP) and the aged homozygote A30P mice. Result: Compound S is a sub‐nanomolar affinity ligand to human and A30P mouse α‐Syn (Kd = 0.15 nM and 0.5 nM resp.). Lower affinity was observed in AD and healthy control brain tissues. [3H]S showed displaceable binding in PD brain cortex and A30P mid‐brain and brainstem, and little binding in AD and healthy control. In the NHP, [11C]S crosses the brain‐blood barrier and the uptake phase of [11C]S is followed by a washout. [11C]S PET studies in A30P mice showed higher uptake in the mid brain and brainstem regions, with standard uptake value ratios in those regions higher than 2.0. Conclusion: Compound S is potent for α‐Syn in vitro, and PET imaging in the A30P mice showed an elevated signal in regions known to accumulate α‐Syn. This dataset suggests that the Compound S has promise towards imaging α‐Syn in PD patients. [ABSTRACT FROM AUTHOR]

In this work, replacement of barium chromate (BaCrO4) in the traditional tungsten delay (W/BaCrO4/KClO4/Diatomaceous Earth (DE)) with strontium molybdate (SrMoO4) is explored both mechanistically and as an environmentally friendly alternative to currently fielded time delays. Delay performance and aging characteristics are examined at similar diameters (4.7 mm) to common delay housings. Measured maximum combustion temperatures ranged from 1507 K to 1628 K as a function of tungsten content. The measured combustion velocities ranged from 1.36 to 29.87 mm/s in 4.7 mm inner diameter aluminum housings for the alternative system. Activation energies were determined for both the traditional tungsten delay and the alternative formulation and ranged from 74.6 to 240.5 kJ/mol. The maximum measured gas production was 4.1 mL/g for all alternative formulations. Combustion products were characterized with powder X-ray diffraction and are relatively benign based upon known compound information and current regulations. Lastly, based on the data, general reaction mechanisms for pyrotechnic time delays are discussed toward design decisions of a good time delay. [ABSTRACT FROM AUTHOR]

The stoichiometric reduction of N-carbophenoxypyridinium tetraphenylborate to yield mixtures of 1,2- and 1,4-dihydropyridines is reported. The results from the density calculations indicated that the spin density of the N-carbophenoxypyridinium radical resides primarily at C4 while the positive charge in tetraphenylborate resides primarily at C2 and C6.

Pyrotechnical smoke formulations are predominantly used in the military sector for obscuring or signaling purposes. For decades, the performance was the only point of interest and no toxicity issues have been considered. Although fuels like sulfur have already been replaced in colored smoke formulations, the main ingredient still remains the dye. In the past few years certain highly toxic anthraquinone dyes, e.g. benzanthrone and vat yellow 4 have successfully been replaced by Solvent Yellow 33 (SY33). Additionally, colored smoke formulations suffer from a low efficiency and there is no published information about the yield like the amount of produced aerosol of in-use formulations. To face this issue, we designed several new blue and green smoke formulations containing 5-aminotetrazole (5-AT) as additional gas generator to increase the efficiency. Maintaining the environmental risks in an acceptable range, we applied copper(II) phthalocyanine (CuPc) for blue and a mixture of CuPc/SY33 for green formulations. A self-developed aerosol collecting setup was used to investigate the formulations. [ABSTRACT FROM AUTHOR]

The periodate salts NaIO4 and KIO4 are critically evaluated as potential replacements for KClO4 in pyrotechnic compositions. Key differences between the physical and chemical properties of the periodate and perchlorate oxidizers are presented. The thermochemical characteristics of binary flash/incendiary compositions containing Al, MgAl, or Mg as the fuel and periodate or perchlorate salts as oxidizers were studied using the FactSage 6.4 software package. The computational results are compared to existing experimental data. The tendency of NaIO4 to form gaseous Na, an emitter of yellow light, in such reactions promotes high luminous efficiencies. Due to a lack of literature addressing the stability and aging characteristics of periodate-containing formulations, it is recommended that further research should be undertaken to evaluate potential chemical incompatibilities. Other concerns, including the availability and toxicological properties of the periodates, are also discussed. [ABSTRACT FROM AUTHOR]

Transition-metal hydride radical cations (TMHRCs) are involved in a variety of chemical and biochemical reactions, making a more thorough understanding of their properties essential for explaining observed reactivity and for the eventual development of new applications. Generally, these species may be treated as the ones formed by one-electron oxidation of diamagnetic analogues that are neutral or cationic. Despite the importance of TMHRCs, the generally sensitive nature of these complexes has hindered their development. However, over the last four decades, many more TMHRCs have been synthesized, characterized, isolated, or hypothesized as reaction intermediates. This comprehensive review focuses on experimental studies of TMHRCs reported through the year 2014, with an emphasis on isolated and observed species. The methods used for the generation or synthesis of TMHRCs are surveyed, followed by a discussion about the stability of these complexes. The fundamental properties of TMHRCs, especially those pertaining to the Mâ€"H bond, are described, followed by a detailed treatment of decomposition pathways. Finally, reactions involving TMHRCs as intermediates are described. [ABSTRACT FROM AUTHOR]

Replacement reactive systems for the tungsten delay composition (W/BaCrO4/KClO4/diatomaceous earth) are needed due to recent concerns over the toxicity of hexavalent chromium and perchlorates. Systems based on condensed phase reactions, that are typically used in combustion synthesis (e.g., Ti/C or Ni/Al) are of interest as replacements due to their wide range of combustion velocities and potentially low environmental impact. In this work, the combustion characteristics of the Ti/C-3Ni/Al reactive system were examined in microchannels with inner diameters ranging from 3.0-6.0 mm (i.e., similar to that of a common delay housing). It was found that this reactive system could be tailored to overcome the heat losses associated with small diameter microchannels by changing the relative amounts of Ti/C and 3Ni/Al. At 40 wt.-% Ti/C content, the failure diameter was found to be between 3.0 and 4.0 mm, while at 30 wt.-% Ti/C the failure diameter was between 4.8 and 6.0 mm. Measured combustion temperatures in metal microchannels were approximately 1700 K while those of unconfined pellets were around 100 K greater. Increasing Ti/C content resulted in faster combustion velocities while decreasing microchannel diameter resulted in slower combustion velocities. At these small sizes the effects of adding a thermal barrier (specifically Grafoil™) to minimize radial heat losses to the microchannel were shown to be minimal with respect to combustion velocity. The Ti/C-3Ni/Al system was shown to be a suitable delay fuze composition with tunable combustion velocities ranging from 2.1-38.1 mm s−1 in aluminum microchannels with diameters ranging from 4.0-6.0 mm. [ABSTRACT FROM AUTHOR]

The article discusses the technical and public relations competition between the U.S. and Soviet space programs between 1981 and 1986. It discusses the anti-communism of then-U.S. president Ronald Reagan, space exploration in the context of the Cold War, and the significance of the U.S. National Aeronautics and Space Administration (NASA) project known as the Space Transportation System (STS). The article also discusses the development of a Soviet space shuttle and propaganda efforts in the periodicals "America Illustrated" and "Soviet Life."

Gassy pyrotechnic delays composed of tungsten, antimony(III) oxide, potassium periodate, and various lubricants have been developed for use in the US Army hand-held signal. The new compositions were developed to replace the current formulation, which contains potassium perchlorate and barium chromate, chemicals that are facing increasing scrutiny due to environmental regulation. The hand-held signal delay housing was used to demonstrate the burning rate tunability of the new compositions. The addition of 1-5 % of waxy lubricants (stearic acid or calcium stearate) was found to have a profound effect on burning rate. The effect of tungsten content and the Sb2O3/KIO4 ratio on burning rate was also probed. A wide range of inverse burning rates (2 to 15 s cm−1) were demonstrated, which encompasses the 7 to 8.5 s cm−1 range required by the hand-held signal. The W/KIO4 reaction produces I2, which was observed by visible spectroscopy in the vapor above a sample of combustion residue. [ABSTRACT FROM AUTHOR]