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61.
Ethyl pyridazine-3-carboxylate is used to synthesize previously unknown pyridazine derivatives. 相似文献
62.
A comparison is given between the dipole moments found experimentally for 1, 2, 4-triazole and its derivatives and those computed vectorially. In 1, 2, 4-triazoles unsubstituted on nitrogen, the hydrogen is attached at N1 in the majority of cases. The 1, 2, 4-triazoles undergo acylation on N1. Under the influence of a strong electron acceptor (a p-nitrophenyl substituent), the electron cloud of the triazole ring is highly polarized.For communication III see [1]. 相似文献
63.
5-Nitro-2-furylglyoxylic acid is prepared from 5-nitro-2-furacylpyridinium bromide via 4-dimethylaminophenylirnino (5-nitro-2-furoyl) acetonitrile, and also by the action of N -bromosuccinimide on 5-nitro-2-furylglyoxal. The following derivatives are prepared: semicarbazone, thiosemicarbazone, guanylhydrazonef 2, 4-dinitrophenylhydrazone, 4-dimethylaminoanilide and 3- (5-nitro-2-furyl) quinoxalin-2-ol.For Part IX see [1]. 相似文献
64.
A. R. Vieira Brigitte Hiller M. C. Nemes Marcos Sampaio 《International Journal of Theoretical Physics》2013,52(10):3494-3503
Arbitrary regularization dependent parameters in Quantum Field Theory are usually fixed on symmetry or phenomenology grounds. We verify that the quadratically divergent behavior responsible for the lack of naturalness in the Standard Model (SM) is intrinsically arbitrary and regularization dependent. While quadratic divergences are welcome for instance in effective models of low energy QCD, they pose a problem in the SM treated as an effective theory in the Higgs sector. Being the very existence of quadratic divergences a matter of debate, a plausible scenario is to search for a symmetry requirement that could fix the arbitrary coefficient of the leading quadratic behavior to the Higgs boson mass to zero. We show that this is possible employing consistency of scale symmetry breaking by quantum corrections. Besides eliminating a fine-tuning problem and restoring validity of perturbation theory, this requirement allows to construct bounds for the Higgs boson mass in terms of $\delta m^{2}/m^{2}_{H}$ (where m H is the renormalized Higgs mass and δm 2 is the 1-loop Higgs mass correction). Whereas $\delta m^{2}/m^{2}_{H}<1$ (perturbative regime) in this scenario allows the Higgs boson mass around the current accepted value, the inclusion of the quadratic divergence demands $\delta m^{2}/m^{2}_{H}$ arbitrarily large to reach that experimental value. 相似文献
65.
Neuroimaging methodology predominantly relies on the blood oxygenation level dependent (BOLD) signal. While the BOLD signal is a valid measure of neuronal activity, variances in fluctuations of the BOLD signal are not only due to fluctuations in neural activity. Thus, a remaining problem in neuroimaging analyses is developing methods that ensure specific inferences about neural activity that are not confounded by unrelated sources of noise in the BOLD signal. Here, we develop and test a new algorithm for performing semiblind (i.e., no knowledge of stimulus timings) deconvolution of the BOLD signal that treats the neural event as an observable, but intermediate, probabilistic representation of the system's state. We test and compare this new algorithm against three other recent deconvolution algorithms under varied levels of autocorrelated and Gaussian noise, hemodynamic response function (HRF) misspecification and observation sampling rate. Further, we compare the algorithms' performance using two models to simulate BOLD data: a convolution of neural events with a known (or misspecified) HRF versus a biophysically accurate balloon model of hemodynamics. We also examine the algorithms' performance on real task data. The results demonstrated good performance of all algorithms, though the new algorithm generally outperformed the others (3.0% improvement) under simulated resting-state experimental conditions exhibiting multiple, realistic confounding factors (as well as 10.3% improvement on a real Stroop task). The simulations also demonstrate that the greatest negative influence on deconvolution accuracy is observation sampling rate. Practical and theoretical implications of these results for improving inferences about neural activity from fMRI BOLD signal are discussed. 相似文献
66.
Dr. Josh Abbenseth Dr. Florian Wätjen Dr. Markus Finger Prof. Dr. Sven Schneider 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23780-23784
The utilization of monomeric, lower phosphorous oxides and oxoanions, such as metaphosphite (PO2−), which is the heavier homologue of the common nitrite anion but previously only observed in the gas phase and by matrix isolation, requires new synthetic strategies. Herein, a series of rhenium(I–III) complexes with PO2− as ligand is reported. Synthetic access was enabled by selective oxygenation of a terminal phosphide complex. Spectroscopic and computational examination revealed slightly stronger σ-donor and comparable π-acceptor properties of PO2− compared to homologous NO2−, which is one of the archetypal ligands in coordination chemistry. 相似文献
67.
Dr. Chi Chung Lee Dr. Jarett Wilcoxen Caleb J. Hiller Prof. Dr. R. David Britt Prof. Dr. Yilin Hu 《Angewandte Chemie (International ed. in English)》2018,57(13):3411-3414
Binding and activation of CO by nitrogenase is a topic of interest because CO is isoelectronic to N2, the physiological substrate of this enzyme. The catalytic relevance of one‐ and multi‐CO‐bound states (the lo‐CO and hi‐CO states) of V‐nitrogenase to C−C coupling and N2 reduction was examined. Enzymatic and spectroscopic studies demonstrate that the multiple CO moieties in the hi‐CO state cannot be coupled as they are, suggesting that C−C coupling requires further activation and/or reduction of the bound CO entity. Moreover, these studies reveal an interesting correlation between decreased activity of N2 reduction and increased population of the lo‐CO state, pointing to the catalytic relevance of the belt Fe atoms that are bridged by the single CO moiety in the lo‐CO state. Together, these results provide a useful framework for gaining insights into the nitrogenase‐catalyzed reaction via further exploration of the utility of the lo‐CO conformation of V‐nitrogenase. 相似文献
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70.
Pálfy and Pudlák (Algebra Universalis 11, 22–27, 1980) posed the question: is every finite lattice isomorphic to an interval sublattice of the lattice of subgroups of a finite group? in this paper we will look at examples of lattices that can be realized as subloop lattices but not as subgroup lattices. This is a first step in answering a new question: is every finite lattice isomorphic to an interval sublattice of the subloop lattice of a finite loop? 相似文献