Using rapid scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude

X band rapid scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid scan and continuous wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid scan EPR results in signal to noise improvements by factors between 10 and 50. Rapid scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and continuous wave EPR spectrometer for rapid scan EP

Radical Activation of N–H and O–H Bonds at Bismuth(II)

The development of unconventional strategies for the activation of ammonia (NH3) and water (H2O) is of capital importance for the advancement of sustainable chemical strategies. Herein we provide the synthesis and characterization of a radical equilibrium complex based on bismuth featuring an extremely weak Bi–O bond, which permits the in situ generation of reactive Bi(II) species. The ensuing organobismuth(II) engages with various amines and alcohols and exerts an unprecedented effect onto the X–H bond, leading to low BDFEX–H. As a result, radical activation of various N–H and O–H bonds─including ammonia and water─occurs in seconds at room temperature, delivering well-defined Bi(III)-amido and -alkoxy complexes. Moreover, we demonstrate that the resulting Bi(III)–N complexes engage in a unique reactivity pattern with the triad of H+, H–, and H• sources, thus providing alternative pathways for main group chemistry

Community structure and ethnic preferences in school friendship networks

Recently developed concepts and techniques of analyzing complex systems provide new insight into the structure of social networks. Uncovering recurrent preferences and organizational principles in such networks is a key issue to characterize them. We investigate school friendship networks from the Add Health database. Applying threshold analysis, we find that the friendship networks do not form a single connected component through mutual strong nominations within a school, while under weaker conditions such interconnectedness is present. We extract the networks of overlapping communities at the schools (c-networks) and find that they are scale free and disassortative in contrast to the direct friendship networks, which have an exponential degree distribution and are assortative. Based on the network analysis we study the ethnic preferences in friendship selection. The clique percolation method we use reveals that when in minority, the students tend to build more densely interconnected groups of friends. We also find an asymmetry in the behavior of black minorities in a white majority as compared to that of white minorities in a black majority.Comment: submitted to Physica

A Two Coordinate Iron II Imido Complex with NHC Ligation Synthesis, Characterization, and Its Diversified Reactivity of Nitrene Transfer and C H Bond Activation

Iron terminal imido species are typically implicated as reaction intermediates in iron catalyzed transformations. While a large body of work has been devoted to mid and high valent iron imidos, to date the chemistry of iron II imidos has remained largely unexplored due to the difficulty in accessing them. Herein, we present a study on the two coordinate iron II imido complex [ IPr Fe NArTrip ] 3; IPr 1,3 bis 2 amp; 8242;,6 amp; 8242; diisopropylphenyl imidazol 2 ylidene; ArTrip 2,6 bis 2 amp; 8242;,4 amp; 8242;,6 amp; 8242; triisopropylphenyl phenyl prepared from the reaction of an iron 0 complex with the bulky azide ArTripN3. Spectroscopic investigations in combination with DFT calculations established a high spin S 2 ground spin state for 3, consistent with its long Fe N multiple bond of 1.715 2 revealed by X ray diffraction analysis. Complex 3 exhibits unusual activity of nitrene transfer and C H bond activation in comparison to the reported iron imido complexes. Specifically, the reactions of 3 with CH2 amp; 9552;CHArCF3, an electron deficient alkene, and CO, a strong amp; 960; acid, readily afford nitrene transfer products, ArCF3CH amp; 9552;CHNHArTrip and ArTripNCO, respectively, yet no similar reaction occurs when 3 is treated with electron rich alkenes and PMe3. Moreover, 3 is inert toward the weak C sp3 H bonds in 1,4 cyclohexadiene, THF, and toluene, whereas it can cleave the stronger C sp H bond in p trifluoromethylphenylacetylene to form an iron II amido alkynyl complex. Interestingly, intramolecular C sp3 H bond functionalization was observed by adding p Tol 2CN2 to 3. The unique reactivity of 3 is attributed to its low coordinate nature and the high negative charge population on the imido N atom, which render its iron imido unit nucleophilic in natur

Experimental assignment of long range magnetic communication through Pd amp; Pt metallophilic contacts

Record breaking magnetic exchange interactions have previously been reported for 3d metal dimers of the form [M Pt SAc 4 pyNO2 ]2 M Ni or Co that are linked in the solid state via metallophilic Pt amp; 8943;Pt bridges. This contrasts the terminally capped monomers [M Pt SAc 4 py 2], for which neither metallophilic bridges nor magnetic exchange interactions are found. Computational modeling has shown that the magnetic exchange interaction is facilitated by the pseudo closed shell d8 amp; 8943;d8 metallophilic interaction between the filled Pt2 5dz2 orbitals. We present here inelastic neutron scattering experiments on these complexes, wherein the dimers present an oscillatory momentum transfer dependence of the magnetic transitions. This allows for the unequivocal experimental assignment of the distance between the coupled ions, which matches exactly the coupling pathway via the metallophilic bridges. Furthermore, we have synthesized and magnetically characterized the isostructural palladium analogues. The magnetic coupling across the Pd amp; 8943;Pd bridge is found through SQUID magnetometry and FD FT THz EPR spectroscopy to be much weaker than via the Pt amp; 8943;Pt bridge. The weaker coupling is traced to the larger radial extent of the 5dz2 orbitals compared to that of the 4dz2 orbitals. The existence of a palladium metallophilic interaction is evaluated computationally from potential surface cuts along the metal stretching direction. Similar behavior is found for the Pd amp; 8943;Pd and Pt amp; 8943;Pt systems with clear minima along this coordinate and provide estimates for the force constant for this distortion. The estimated M amp; 8943;M stretching frequencies are found to match experimental observed, polarized bands in single crystal Raman spectra close to 45 cm amp; 8722;1. This substantiates the existence of energetically relevant Pd amp; 8943;Pd metallophilic interactions. The unique properties of both Pt2 and Pd2 constitutes an orthogonal reactivity, which can be utilized for steering both the direction and strength of magnetic interaction

Protocol for a phase 1 homeopathic drug proving trial

<p>Abstract</p> <p>Background</p> <p>This study protocol adapts the traditional homeopathic drug proving methodology to a modern clinical trial design.</p> <p>Method</p> <p>Multi-centre, randomised, double-blind, placebo-controlled phase 1 trial with 30 healthy volunteers. The study consists of a seven day run-in period, a five day intervention period and a 16 day post-intervention observation period. Subjects, investigators and the statisticians are blinded from the allocation to the study arm and from the identity of the homeopathic drug. The intervention is a highly diluted homeopathic drug (potency C12 = 10²⁴), Dose: 5 globules taken 5 times per day over a maximum period of 5 days. The placebo consists of an optically identical carrier substance (sucrose globules). Subjects document the symptoms they experience in a semi-structured online diary. The primary outcome parameter is the number of specific symptoms that characterise the intervention compared to the placebo after a period of three weeks. Secondary outcome parameters are qualitative differences in profiles of characteristic and proving symptoms and the total number of all proving symptoms. The number of symptoms will be quantitatively analysed on an intention-to-treat basis using ANCOVA with the subject's expectation and baseline values as covariates. Content analysis according to Mayring is adapted to suit the homeopathic qualitative analysis procedure.</p> <p>Discussion</p> <p>Homeopathic drug proving trials using the terminology of clinical trials according GCP and fulfilling current requirements for research under the current drug regulations is feasible. However, within the current regulations, homeopathic drug proving trials are classified as phase 1 trials, although their aim is not to explore the safety and pharmacological dynamics of the drug, but rather to find clinical indications according to the theory of homeopathy. To avoid bias, it is necessary that neither the subjects nor the investigators know the identity of the drug. This requires a modification to the informed consent process and blinded study materials. Because it is impossible to distinguish between adverse events and proving symptoms, both must be documented together.</p> <p>Trial registration</p> <p>ClinicalTrials.gov identifier: NCT01061229.</p

Promoting More Physical Activity and Less Sedentary Behaviour During the COVID-19 Situation – SportStudisMoveYou (SSMY): A Randomized Controlled Trial

Objective: To determine the effect of an innovative, online-based intervention, addressing the possible decline of physical activity (PA) and increase of sedentary behavior (SB) during COVID-19 stay at home restrictions in Switzerland. Methods: This study investigated the effect of a two-week, social cognitive theory based, online-video moderate to vigorous (MV)PA or SB intervention on MVPA and SB behaviour and intention via a 3 group by 2 time point parallel randomized controlled trial during the COVID-19 pandemic. Adults (≥18 yo) were recruited over the internet between April 10th and April 19th 2020 (n = 129; 75.2% female; mean age = 29.0 [SD 11.8] years). Both intervention groups received five videos targeting either SB for the SB group or MVPA for the MVPA group and were compared to an attention control group (fruit and vegetable consumption). It was hypothesized that MVPA time and intention would increase for the MVPA group and the SB group would outperform control on SB behaviour and intention indicators. Results: No significant interactions were found for the MVPA group (n = 41) versus control (n = 40). Only one significant interaction was measured for the SB group (n = 48; intention of active breaks F = (2,114) = 5.84, p = 0.004, ηp2 = 0.09). Although mostly non-significant and small effects, the MVPA group showed results pointing in the hypothesized direction on all PA indicators and the SB on all SB indicators, respectively. Conclusion: Considering this study’s limitations (e.g. small intervention dose), video-based online PA and SB interventions seem promising and feasible. This approach is appropriate for COVID-19 and other stay at home situations