The determination of magnetic structures using low temperature nuclear orientation:166mHo-Ho

It is demonstrated that the low temperature nuclear orientation technique can be used to determine the axes of quantization in a multiaxial ordered ensemble of nuclear spins. Expressions for the anisotropic -ray intensity from particular geometries are derived for the case in which each subsystem has its own axial symmetry. The determination of the atomic magnetic structure in antiferromagnets is discussed and the results of recent experiments on helically ordered^166mHo-Ho are presented. In these experiments, the angular variation of the intensities of some of the more intense -rays were measured and compared to theory. A value of 80.4(1)°, not including systematic errors, was obtained for the semi-cone angle of the helix formed by the atomic magnets.     

Simulation of vector semibinary homogeneous random fields and modeling of broken clouds

A vector-valued homogeneous random field is said to be semibinary if its single-point marginal distribution is a sum of a singular distribution and a continuous one. In this paper, we present methods of numerical simulation of semibinary fields on the basis of the correlation structure and the marginal distribution. As an example we construct a combined model of cloud top height and optical thickness using satellite observations.     

Asymptotic representation of the weights in the Gauss quadrature formula

Translated from Matematicheskie Zametki, Vol. 47, No. 4, pp. 63–68, April, 1990.     

γ-Ray emission from oriented nuclei in a multiaxis nuclear spin system: 166mHo165Ho

A new method is proposed to measure multiaxis nuclear spin structures using γ-ray emission from oriented radioactive nuclei. This method, which depends only on angular momentum theory, is presented for helical spin structures. The atomic magnetic structure can also be obtained when the nuclear magnetism is produced by hyperfine interaction. Measurements on ^166mHo in a single crystal of ¹⁶⁵Ho metal show that the spin axes form a single cone with a half-angle of 80.4±0.4°.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.