The design of a source to simulate the gamma-ray spectrum emitted by a radioisotope thermoelectric generator

A simulated source was designed to duplicate the gamma spectrum of a uniform cylindrical 2200-watt Pu02 radioisotope thermoelectric generator containing 81% Pu-238 and 1.2 ppm Pu-236. Gamma rays from the decay of Pu-238, Am-241, Pu-239, and the 0-18(alpha,n)Ne-21 reaction were catalogued in broad energy groups. Two 46- and one 22-mc Th-228 sources provided simulation at various times in the life of the fuel capsule up to 18 years, which covers the time span of an outer planet mission. Emission from Th-228 represents the overwhelming contribution of the gamma spectrum after the first few years. The sources, in the form of 13-inch rods, were placed in a concentric hole in a cylinder of depleted uranium, which provided shielding equivalent to the self-shielding of the fuel capsule. The thickness of the U-238 cylinder (0.55cm) was determined by Monte Carlo calculations to insure that the spectrum emerging from the simulated source matched that of the fuel capsule

Task constraints of large-sided soccer games : effects of manipulating rewarding rules

The aim of the study was to examine how rewarding rules affects team tactical behaviour, players’ technical, physical and physiological performance in large-sided football games. An elite youth team (age: 14.0±0.2 years) performed 8 vs. 8 large-sided games under three experimental conditions: i) rewarding passing rule (PASS); ii) rewarding compact defending rule (COM); iii) control condition (CNT), using a Latin squared design. Positional data were used to compute effective play-space, team width, length, length-width ratio and approximate entropy, and capture distance covered and average speed displacement. Heart rate values were recorded using short-range radio telemetry. All bouts were filmed, and technical variables based on the TSAP were assessed. Magnitude-based inference and precision estimation was employed. Results showed mainly trivial and small differences between conditions for almost all variables. Received balls (RB) was the single variable that very likely increased with a moderate effect for COM compared to CNT. The small overall effects might indicate that rewarding rules effectiveness depends on i) creating affordances for the desired behaviour instead of trying to directly reward the behaviour; ii) its accordance with team identity; iii) its suitability to players’ skill level iv) combining rules with other coaching tools v) the timescale of exposure

Activities of the RTG Radiation Test Laboratory Progress report, 1 Jul. - 31 Dec. 1969

Safety, gamma ray spectrum, and data analysis of SNAP fuel capsule

Reactive oxygen species in iridium-based OER catalysts

Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous IrIII/IV oxyhydroxides (IrOx) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO2, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive species is not solely a property of the metal but is intimately tied to the electronic structure of oxygen. We use a combination of synchrotron-based X-ray photoemission and absorption spectroscopies, ab initio calculations, and microcalorimetry to show that holes in the O 2p states in amorphous IrOx give rise to a weakly bound oxygen that is extremely susceptible to nucleophilic attack, reacting stoichiometrically with CO already at room temperature. As such, we expect this species to play the critical role of the electrophilic oxygen involved in O–O bond formation in the electrocatalytic OER on IrOx. We propose that the dynamic nature of the Ir framework in amorphous IrOx imparts the flexibility in Ir oxidation state required for the formation of this active electrophilic oxygen

In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

Water splitting performed in acidic media relies on the exceptional performance of iridium-based materials to catalyze the oxygen evolution reaction (OER). In the present work, we use in situ X-ray photoemission and absorption spectroscopy to resolve the long-standing debate about surface species present in iridium-based catalysts during the OER. We find that the surface of an initially metallic iridium model electrode converts into a mixed-valent, conductive iridium oxide matrix during the OER, which contains OII− and electrophilic OI− species. We observe a positive correlation between the OI− concentration and the evolved oxygen, suggesting that these electrophilic oxygen sites may be involved in catalyzing the OER. We can understand this observation by analogy with photosystem II; their electrophilicity renders the OI− species active in O-O bond formation, i.e. the likely potential- and rate-determining step of the OER. The ability of amorphous iridium oxyhydroxides to easily host such reactive, electrophilic species can explain their superior performance when compared to plain iridium metal or crystalline rutile-type IrO2

Formation of unexpectedly active Ni–Fe oxygen evolution electrocatalysts by physically mixing Ni and Fe oxyhydroxides

We present an unusual, yet facile, strategy towards formation of physically mixed Ni–Fe(OxHy) oxygen evolution electrocatalysts. We use in situ X-ray absorption and UV-vis spectroscopy, and high-resolution imaging to demonstrate that physical contact between two inferior Ni(OH)2 and Fe(OOH) catalysts self-assemble into atomically intermixed Ni–Fe catalysts with unexpectedly high activity

Bibliophilia in Ottoman Aleppo: Muḥammad al-Taqawī and his Medical Library

Recent research has shown that book collecting by private individuals and institutions was a widespread phenomenon in Bilād al-Shām. At least from the Ayyubid period onwards, countless volumes were produced, changed hands in the book market, and lay around in libraries. To this day, Damascus occupies a central position in our knowledge about libraries and book culture in general, while other cities and regions lag behind. In this article, the inventory of an Aleppine book collector is used to take a glimpse at the book culture of Aleppo in the first decades of the seventeenth century. Although most probably not reflecting the sum total of his library, the inventory still allows to ascertain the specific taste of its compiler, an otherwise unknown Aleppine bibliophile. The inventory also provides evidence for the early distribution of Arabic print and pushes the door open for investigating the role of local agents in the early days of attempts by Orientalists to acquire Arabic manuscripts for European libraries

A bet-hedging strategy for denitrifying bacteria curtails their release of N2O

publishedVersio

Basal lamina formation at the site of spinal cord transection

The pia-glial basal lamina (BL) at the site of spinal cord injury could be an important physical impediment to central nervous system regeneration. We used an epithelial BL-specific immunohistochemical stain to determine the location of the pia-glial BL after spinal cord transection. Small segments of BL were found at the margin of the lesion 5 days after transection. After 10 days, longer and more numerous segments were seen. At 20 days, the entire transected end of the spinal cord was capped by a layer of BL.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50298/1/410080204_ftp.pd