scholarly journals Magnetic Aromaticity of Cycloporphyrin Nanorings

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 991-1004
Author(s):  
Alessandro Landi ◽  
Francesco Ferdinando Summa ◽  
Guglielmo Monaco

The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson’s classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current.

2021 ◽  
Vol 103 (3) ◽  
Author(s):  
Ovidiu Cristinel Stoica

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Antje Torge ◽  
Rainer Haeckel ◽  
Mustafa Özcürümez ◽  
Alexander Krebs ◽  
Ralf Junker

Abstract It has been observed that the estimation of reference intervals of leukocytes in whole venous blood leads to higher upper reference limits (uRLs) with indirect methods than has been reported in the literature determined by direct approaches. This phenomenon was reinvestigated with a newer, more advanced indirect method, and could be confirmed. Furthermore, a diurnal variation was observed with lower values during the morning and higher values in the late afternoon and at night. This observation can explain why indirect approaches using samples collected during 24 h lead to higher uRLs than direct methods applied on samples collected presumably in the morning.


1984 ◽  
Vol 32 (6) ◽  
pp. 593-607 ◽  
Author(s):  
C E Farnum ◽  
N J Wilsman

A postembedment method for the localization of lectin-binding glycoconjugates was developed using Epon-embedded growth plate cartilage from Yucatan miniature swine. By testing a variety of etching, blocking, and incubation procedures, a standard protocol was developed for 1 micron thick sections that allowed visualization of both intracellular and extracellular glycoconjugates with affinity for wheat germ agglutinin and concanavalin A. Both fluorescent and peroxidase techniques were used, and comparisons were made between direct methods and indirect methods using the biotin-avidin bridging system. Differential extracellular lectin binding allowed visualization of interterritorial , territorial, and pericellular matrices. Double labeling experiments showed the precision with which intracellular binding could be localized to specific cytoplasmic compartments, with resolution of binding to the Golgi apparatus, endoplasmic reticulum, and nuclear membrane at the light microscopic level. This method allows the localization of both intracellular and extracellular lectin-binding glycoconjugates using fixation and embedment procedures that are compatible with simultaneous ultrastructural analysis. As such it should have applicability both to the morphological analysis of growth plate organization during normal endochondral ossification, as well as to the diagnostic pathology of matrix abnormalities in disease states of growing cartilage.


2021 ◽  
pp. 2140005
Author(s):  
S. M. M. Rasouli ◽  
S. Jalalzadeh ◽  
P. V. Moniz

We start by presenting a brief summary of fractional quantum mechanics, as means to convey a motivation towards fractional quantum cosmology. Subsequently, such application is made concrete with the assistance of a case study. Specifically, we investigate and then discuss a model of stiff matter in a spatially flat homogeneous and isotropic universe. A new quantum cosmological solution, where fractional calculus implications are explicit, is presented and then contrasted with the corresponding standard quantum cosmology setting.


<em>Abstract.</em>—In this paper, we provide an introduction to water quality benefit estimation for noneconomists. Net water quality benefits are typically measured using the concept of consumer surplus, which is estimated using a number of economic valuation methodologies. These are divided into direct and indirect methods. Direct methods involve questioning survey respondents to determine their consumer surplus. Indirect methods use data from consumer market behavior to estimate economic values. When limited time or funding preclude costly data collection and the development of new consumer surplus estimates, the method of benefit transfer is used to tailor preexisting consumer surplus estimates to fit new policy situations. We provide an example of benefit transfer by estimating the value of water quality improvements for the Cape Fear River in North Carolina. Benefit transfer methods are used with three valuation approaches to estimate the benefits of water quality improvement.


2019 ◽  
Vol 17 (08) ◽  
pp. 1941011
Author(s):  
Catalina Curceanu ◽  
Raffaele Del Grande ◽  
Matthias Laubenstein ◽  
Kristian Piscicchia

Collapse models consist in dynamical reformulations of the standard quantum mechanics aiming to solve the measurement problem. The standard Schrödinger dynamics is modified with the introduction of nonlinear and stochastic terms, which induce the wave function collapse in space. Collapse models predict slight deviations from the standard quantum mechanics predictions, in particular the emission of a “spontaneous radiation”, which we explored to set the most stringent limits on the collapse models parameters in a broad range. To this end, the X-ray emission data collected by the IGEX collaboration are analyzed and compared with the spectrum of the spontaneous photon emission process predicted by the theories. The results of the data analyses, and the ongoing experimental efforts will be presented.


2011 ◽  
Vol 133 (7) ◽  
Author(s):  
L. P. Wang ◽  
S. Basu ◽  
Z. M. Zhang

The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the “indirect” and “direct” methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff’s law. On the other hand, a few studies have used a combination of Maxwell’s equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating the far-field thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry–Pérot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method.


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