Determination of technetium-99 in environmental material with rhenium as a yield monitor

The ability of the close analogue element rhenium to act as a satisfactory non-isotopic yield monitor for the analysis of⁹⁹Tc in environmental materials is explored and its performance critically evaluated in a new radioanalytical method designed specifically for use with rhenium as both carrier and yield monitor. The advantages and limitations of rhenium for this purpose are compared with isotopic tracers such as^99mTc,^97mTc and^95mTc. When employed in a well designed analytical scheme, rhenium, which has received only limited consideration in the past, is shown to be a cheap, reliable alternative to isotopic tracers.     

Cycloproparenes: Approaches to cyclopropa[c]furan

Treatment of 6,6-dichloro-3-oxabicyclo[3.1.0]-hexane (7) with potassiumt-butoxide generates the ring-strained cyclopropene8 as a reactive intermediate. With 1,3-diphenylisobenzofuran compound8 is trapped as a 51 mixture of theexo- andendo-adducts11a and11b, respectively. With furan only the ring expanded vinylcarbene12 is intercepted and spirocycle13a is formed. Carbene12 is also captured by cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, and diphenylethyne to give22–25 respectively. A likely side product in these reactions is the pyran14.On leave from Petrolite Corporation, St. Louis, MO, USA.Taken in part from a lecture delivered at the International Chemical Congress of Pacific Basin Chemical Societies, Honolulu, December 1989 (Pacifichem '89); Abstract ORGN 016. A preliminary report was communicated (see ref. [13]).     

Redox Stability Controls the Cellular Uptake and Activity of Ruthenium-Based Inhibitors of the Mitochondrial Calcium Uniporter (MCU)

The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca²⁺ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca²⁺. The best-known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. Here, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X-ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities.     

Prospects for measurement‐based quantum computing with solid state spins

This article aims to review the developments, both theoretical and experimental, that have in the past decade laid the ground for a new approach to solid state quantum computing. Measurement‐based quantum computing (MBQC) requires neither direct interaction between qubits nor even what would be considered controlled generation of entanglement. Rather it can be achieved using entanglement that is generated probabilistically by the collapse of quantum states upon measurement. Single electronic spins in solids make suitable qubits for such an approach, offering long coherence times and well defined routes to optical measurement. We will review the theoretical basis of MBQC and experimental data for two frontrunner candidate qubits – nitrogen‐vacancy (NV) centres in diamond and semiconductor quantum dots – and discuss the prospects and challenges that lie ahead in realising MBQC in the solid state.     

Triggered Functional Dynamics of AsLOV2 by Time-Resolved Electron Paramagnetic Resonance at High Magnetic Fields

We present time-resolved Gd−Gd electron paramagnetic resonance (TiGGER) at 240 GHz for tracking inter-residue distances during a protein's mechanical cycle in the solution state. TiGGER makes use of Gd-sTPATCN spin labels, whose favorable qualities include a spin-7/2 EPR-active center, short linker, narrow intrinsic linewidth, and virtually no anisotropy at high fields (8.6 T) when compared to nitroxide spin labels. Using TiGGER, we determined that upon light activation, the C-terminus and N-terminus of AsLOV2 separate in less than 1 s and relax back to equilibrium with a time constant of approximately 60 s. TiGGER revealed that the light-activated long-range mechanical motion is slowed in the Q513A variant of AsLOV2 and is correlated to the similarly slowed relaxation of the optically excited chromophore as described in recent literature. TiGGER has the potential to valuably complement existing methods for the study of triggered functional dynamics in proteins.     

Coherent state transfer between an electron and nuclear spin in (15)N@C(60)

Electron spin qubits in molecular systems offer high reproducibility and the ability to self-assemble into larger architectures. However, interactions between neighboring qubits are "always on," and although the electron spin coherence times can be several hundred microseconds, these are still much shorter than typical times for nuclear spins. Here we implement an electron-nuclear hybrid scheme which uses coherent transfer between electron and nuclear spin degrees of freedom in order to both effectively turn on or off interqubit coupling mediated by dipolar interactions and benefit from the long nuclear spin decoherence times (T(2n)). We transfer qubit states between the electron and (15)N nuclear spin in (15)N@C(60) with a two-way process fidelity of 88%, using a series of tuned microwave and radio frequency pulses and measure a nuclear spin coherence lifetime of over 100 ms.     

Evaluating a novel gasoline surrogate containing isopentane using a rapid compression machine and an engine

Simple surrogate formulations for gasoline are useful for modelling purposes and for comparing experimental results using a carefully designed fuel. Simple three-component surrogates based on primary reference fuels (PRF) and Toluene (TPRF) are frequently used to match the antiknock properties of actual gasoline fuels through the RON and MON. However, using PRF or TPRFs to test or to calibrate gasoline engines is still challenging, with the main difficulty being the capabilities of PRF fuels to match the physical properties of the road fuel such density, volatility (DVPE) and the distillation curve. To overcome such issues, an alternative to TPRF is presented in this work with a focus on premium fuel (RON98 EN228). This alternative consists of replacing some or all of isooctane by isopentane. In the event of total replacement, a three-component “THIP” (Toluene, Heptane, IsoPentane) surrogate fuel is produced. The physical and combustion properties of isopentane makes it easier to create surrogates that can match the DVPE, RON, MON and distillation characteristics of a real fuel. Furthermore, the use of isopentane allows the definition of a wider range of surrogate fuel compositions that can replicate the RON and MON of a given fuel. Surrogate formulations were developed at Shell Global Solutions that matched the RON, MON and selected physical properties of a reference premium gasoline (RPG). A Rapid Compression Machine (RCM) in PCFC was used to demonstrate that those surrogates can reproduce the essential autoignition characteristics of the selected RPG. Two mechanisms were used to predict RCM data and showed reasonable agreement, opening some perspective for further investigations. Finally, an engine test performed at Ferrari test facilities demonstrated that simple surrogates containing isopentane can be used to closely match the knock-limited combustion phasing of an RPG. In this paper, it is demonstrated such surrogates have advantages compared to TPRFs in being able to match the properties of a real fuel and that the surrogate approach is consistent with RCM data and engine results.