ELDOR-detected NMR at Q-Band

In recent years, electron–electron double resonance detected nuclear magnetic resonance (EDNMR) has gained considerable attention as a pulsed electron paramagnetic resonance technique to probe hyperfine interactions. Most experiments published so far were performed at W-band frequencies or higher, as at lower frequencies detection of weakly coupled low-γ nuclei is hampered by the presence of a central blind spot, which occurs at zero frequency. In this article we show that EDNMR measurements and a meaningful data analysis is indeed possible at intermediate microwave frequencies (Q-band, 34 GHz), once experimental parameters have been optimized. With highly selective detection pulses and Gaussian shaped electron–electron double resonance (ELDOR) pulses it is possible to detect low-γ nuclei coupled to paramagnetic Mn²⁺. Weakly coupled ¹⁴N resonances, which are separated from the zero frequency by only 2.8 MHz, were readily detected. In systems where different spin active nuclei are coupled to the electron spin, particular care has to be taken when using higher powered ELDOR pulses, as combination frequencies from the two nuclei (?m _S = ±1, ?m _I,1 = ±1, ?m _I,2 = ±1) can lead to severe line broadening and complicated EDNMR spectra. We also compare the EDNMR spectra of ¹³C-labeled Mn–DOTA to ¹³C-Mims electron–nuclear double resonance to get a better insight into the similarities and differences in the results of the two techniques for ¹³C hyperfine coupling.     

Effects of aversive odour presentation on inhibitory control in the Stroop colour-word interference task

Background  

Due to the unique neural projections of the olfactory system, odours have the ability to directly influence affective processes. Furthermore, it has been shown that emotional states can influence various non-emotional cognitive tasks, such as memory and planning. However, the link between emotional and cognitive processes is still not fully understood. The present study used the olfactory pathway to induce a negative emotional state in humans to investigate its effect on inhibitory control performance in a standard, single-trial manual Stroop colour-word interference task. An unpleasant (H₂S) and an emotionally neutral (Eugenol) odorant were presented in two separate experimental runs, both in blocks alternating with ambient air, to 25 healthy volunteers, while they performed the cognitive task.     

Synthesis of the isotopically labeled JAK1/3 inhibitor [D7]-R545 and its oxidative metabolite [D7]-R935: Protecting group-directed regioselective bromination to access 3,4,5-substituted anilines

An extensive medicinal chemistry campaign and subsequent SAR studies led to the discovery of the highly potent and selective JAK1/3 inhibitor R545. To support advanced pre-clinical DMPK studies of R545, the isotopically labeled versions of the drug and its metabolite R935 were required. Herein, we describe the development of synthetic routes to deuterium-labeled [D₇]-R545 and its oxidative metabolite [D₇]-R935. Deuterium atoms were introduced at several sites in the target molecules by employing a convergent synthesis strategy. The desired regiochemistry at the right-hand side of [D₇]-R935 was established via a newly discovered protecting group-directed bromination. The described synthetic approach gave rise to the desired deuterium-labeled target compounds and sufficient quantities were synthesized to enable pre-clinical DMPK studies.     

Simple multiwavelength time-division multiplexed light source for sensing applications

We present a novel multiwavelength, time-division multiplexed laser design that continuously cycles through N spectrally narrow wavelengths, spending a specified, fixed time on each one. The design is based on a matched compressor/stretcher and a custom waveform generator applying modulation preferably to the gain medium. The realization discussed here utilizes a pulsed semiconductor optical amplifier in an all-fiber cavity containing fiber Bragg gratings. The laser cycles through 19 wavelengths in a 44 nm wide spectral band (1333-1377 nm) every 15 micros. The source contains no moving parts, offers high repetition rates, narrow spectral linewidths, and custom spectral profiling of the output.     

Synthese und Koordinationschemie von Diisocyanmethan

Synthesis and Coordination Chemistry of Disocyanomethane Disocyanomethane ( 1 ) was synthesized starting from bis(formylamido)methane by the Ugi method. 1 decomposes vigourously above its melting point (−15 °C) into a brown insoluble solid. The isocyanide can be stabilized by coordination to a transition metal complex fragment. The complexes (CO)₅Cr(CN‐CH₂‐NC) ( 2 ), (CO)₅Cr(CN‐CH₂‐NC)Cr(CO)₅ ( 3 ), CpMn(CO)₂(CN‐CH₂‐NC) ( 4 ), CpMn(CO)₂(CN‐CH₂‐NC)(CO)₂MnCp ( 5 ), CpMn(CO)₂‐(CN‐CH₂‐NC)Cr(CO)₅ ( 6 ), CpMn(CO)₂(CN‐CH₂‐NC)Cu(pz*)₃BH ( 7 ) and (CO)₅Cr(CN‐CH₂‐NC)Cu(pz*)₃BH ( 8 ) (pz* = 3, 5‐dimethylpyrazolyl) were synthesized and characterized spectroscopically. The structures of bis(formylamido)methane, monoclinic, P2₁/c, a = 9.189(5), b = 6.881(3), c = 7.616(2)Å, β = 91.24(4)°, R₁ = 0.0475, wR₂ = 0.1748, and the diisocyanomethane complexes 2 , monoclinic, C2/c, a = 24.996(7), b = 5.882(2), c = 20.572(6)Å, β = 134.62(2)°, R₁ = 0.0582, wR₂ = 0.1357, 4 , monoclinic, P2₁/a, a = 12.143(4), b = 5.848(2), c = 14.301(5)Å, β = 97.77(3)°, R₁ = 0.0355, wR₂ = 0.0972, 6 monoclinic, P2₁/c, a = 11.537(7), b = 12.248(5), c = 12.54(2)Å, β = 102.75(8), R₁ = 0.1333, wR₂ = 0.3024 and 7 , triclinic, P1¯, a = 9.8841(9), b = 9.9517(9), c = 16.2479(15)Å, α = 104.790(2), β = 90.530(2), γ = 98.213(2)°, R₁ = 0.0416, wR₂ = 0.1198 were determined by single crystal X‐ray diffraction.     

Kolloide: Die Welt der vernachlässigten Dimensionen

Aquatic colloids are abundant in all natural aquatic systems. Aquatic colloids consist of clay minerals, micro‐organisms, humic substances, and anthropogenic colloids like soot and platinum (from catalysts in motor vehicles). Colloids may enhance contaminant transport due to sorption of hydrophobic organic compounds. They can have negative effects on water quality, especially micro‐organisms like pathogens or viruses. Colloids also can cause pore blocking and subsequent head loss in groundwater production wells. However, colloids can be useful in groundwater remediation or waster water treatment (e.g. tensides, flocculation, catalysts). The origin of colloids is due to weathering, degradation of organic compounds, dissolution or precipitation as well as hydrochemical or hydraulic gradients. Colloid stability is dominated by surface properties. New analytical tools like field flow fractionation, laser induced breakdown detection and scanning x‐ray microscopy will provide new insight into the behaviour of aquatic colloids.     

Optimal greedy policies for stochastic control models

We introduce the notion of a greedy policy for general stochastic control models. Sufficient conditions for the optimality of the greedy policy for finite and infinite horizon are given. Moreover, we derive error bounds if the greedy policy is not optimal. The main results are illustrated by Bayesian information models, discounted Bayesian search problems, stochastic scheduling problems, single-server queueing networks and deterministic dynamic programs.