Crystal and magnetic structures of R2Ni2In compounds (R = Tb and Ho)

Crystal and magnetic structures of R2Ni2In (R = Tb and Ho) have been studied using powder neutron diffraction at low temperatures. The compounds crystallize as orthorhombic crystal structures of the Mn2AlB2 type. At low temperatures, the magnetic moments localized solely on the rare earth atoms form antiferromagnetic structures. The Tb magnetic moments, equal to 8.8 (4) μB and parallel to the c axis, form a collinear magnetic structure described by the propagation vector k = [½ , ½ , ½]. This magnetic structure is stable up to the Néel temperature TN = 40 K. For Ho2Ni2In a complex, temperature-dependent magnetic structure is detected. In the temperature range 6.1-8.6 K, an incommensurate sinusoidal magnetic structure, described by the propagation vector k1 = [0.24, 1, 0.52] is observed, while in the temperature interval 2.2-2.5 K a square-modulated magnetic structure, related to k2 = [0.17,{{5} \over {6}},{{1} \over {2}}] (the component along the a axis slightly differs from the commensurate value) and its third harmonics 3k2 = [0.50,{{5} \over {2}},{{3} \over {2}}] is found. At 3.1-3.7 K as well as below 2 K, a coexistence of both detected magnetic structures is observed. The Ho magnetic moments remain parallel to the c axis in both the sine- and square-modulated magnetic structures. The low-temperature heat capacity data confirm a first-order transition near 3 K.

Real-Space Infrared Spectroscopy of Ferroelectric Domain Walls in Multiferroic h-(Lu,Sc)FeO3

We employ synchrotron-based near-field infrared spectroscopy to image the phononic properties of ferroelectric domain walls in hexagonal (h) Lu_0.6Sc_0.4FeO₃, and we compare our findings with a detailed symmetry analysis, lattice dynamics calculations, and prior models of domain-wall structure. Rather than metallic and atomically thin as observed in the rare-earth manganites, ferroelectric walls in h-Lu_0.6Sc_0.4FeO₃ are broad and semiconducting, a finding that we attribute to the presence of an A-site substitution-induced intermediate phase that reduces strain and renders the interior of the domain wall nonpolar. Mixed Lu/Sc occupation on the A site also provides compositional heterogeneity over micron-sized length scales, and we leverage the fact that Lu and Sc cluster in different ratios to demonstrate that the spectral characteristics at the wall are robust even in different compositional regimes. This work opens the door to broadband imaging of physical and chemical heterogeneity in ferroics and represents an important step toward revealing the rich properties of these flexible defect states.

Design research with the use of visual and symmetry analysis in indigenous woven textiles

Since ca the 1990s, there have been developments in the weaving process for making tin chok fabrics in the Long district, Phrae province, northern Thailand, with the aim of reducing the production time and increasing the production capacity with respect to poverty alleviation and cultural revitalization. In this article, the symmetry patterns in tin chok fabrics in a collection of 17 vintage (traditional) skirts held in the Komol Antique Textile Museum, in the Long district, are examined to determine how to distinguish tin chok fabrics woven by the integrated method from those woven by the traditional method. The research includes visual and symmetry analysis, literature review, fieldwork, and the creation of a pattern booklet. This research reveals that the hem, which is one of the four parts (supplementary part one, the main part, supplementary part two and the hem) of the detachable tin chok, is key to distinguishing the fabrics made by the two methods. The four parts of tin chok made by the integrated method will always have a common vertical axis of symmetry, whereas the vertical axes of symmetry of the hem of a fabric made by the traditional method may not be aligned with the motifs in the other three parts. The frieze groups of the individual parts of the 17 vintage (traditional) skirts are decoded and possible corresponding patterns for weaving by the integrated method are generated.

Quantifying Social Interventions for Combating COVID-19 via a Symmetry-Based Model

The COVID-19 pandemic has revealed new features in terms of substantial changes in rates of infection, cure, and death as a result of social interventions, which significantly challenges traditional SEIR-type models. In this paper we developed a symmetry-based model for quantifying social interventions for combating COVID-19. We found that three key order parameters, separating degree (S) for susceptible populations, healing degree (H) for mild cases, and rescuing degree (R) for severe cases, all display logistic dynamics, establishing a novel dynamic model named SHR. Furthermore, we discovered two evolutionary patterns of healing degree with a universal power law in 23 areas in the first wave. Remarkably, the model yielded a quantitative evaluation of the dynamic back-to-zero policy in the third wave in Beijing using 12 datasets of different sizes. In conclusion, the SHR model constitutes a rational basis by which we can understand this complex epidemic and policymakers can carry out sustainable anti-epidemic measures to minimize its impact.

Multiferroic order parameters in rhombic antiferromagnetsRCrO3

Currently, active research is aimed at perovskite-based oxides, including rare earth orthochromites, which exhibit magnetoelectric properties owed to intrinsic magnetic interactions in external electric and magnetic fields. Due to a variety of structural instabilities and couplings in these materials, understanding the underlying magnetoelectric mechanisms is a challenge. In this paper, we explore magnetoelectric properties of the rare earth orthochromites in the framework of symmetry analysis. Our calculations show the presence inRCrO₃of electric dipole moments localized in the vicinity of Cr³⁺ions. The electric dipole moments, appearing due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase, are arranged in an antiferroelectric mode. We have demonstrated the presence of electric dipole moments in the unit cell ofRCrO_3,localized in the vicinity of Cr³⁺ions. The inversion symmetry breaks due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase, the electric dipoles become arranged in an antiferroelectric mode. We have introduced the basic distortive order parameters in consistence with the symmetry ofRCrO₃: the polar order parameters (D,Q₂,Q₃,P) and the axial order parameterΩ_band classified them according to the irreducible representations of theRCrO₃symmetry group (D_2h¹⁶). We have determined the symmetry-allowed couplings between distortive, ferroelectric and magnetic orderings and found possible exchange-coupled magnetic and ferroelectric structures. The presented analysis makes it possible to explain experimentally observed polarization reversal and the concomitant reorientation of spins in a series ofRCrO₃compounds and to predict the possible scenarios of phase transitions inRCrO₃.

Symmetry analysis of complex magnetic structure in monoclinically distorted Er3Cu4Sn4

The magnetic structure in Er₃Cu₄Sn₄ has been determined using high-resolution powder neutron diffraction, supported by symmetry analysis. At low temperatures, Er₃Cu₄Sn₄ assumes a crystal structure of the Tm₃Cu₄Sn₄ type (in the monoclinic space group C2/m). The Er atoms occupy two distinct Wyckoff sites: 2c and 4i. It has been found that the Er magnetic moments on the 2c site form a commensurate antiferromagnetic structure (k₁ = [0, 0, ½]) below 6 K. The magnetic moments reach 8.91 (8) μ_B at 1.4 K and are parallel to the b axis. The Er magnetic moments on the 4i site order below 2 K and form an incommensurate antiferromagnetic sine-modulated structure (k₂ = [1, 0.4667 (1), ½]), with magnetic moments lying in the ac plane and perpendicular to the a axis. The amplitude of modulation equals 8.7 (1) μ_B at 1.4 K.

Symmetry analysis for monitoring safety of newly marketed drugs

INTRODUCTION

A postmarketing study without a comparator group has been recognized as a problem as it provides no measure of association. Nevertheless, the design is sometimes used in company postmarketing studies particularly when the study involves the primary data collection. In this report, the "Symmetry Analysis Cohort Design" without a comparator group but with a control period is proposed.

METHODS AND RESULTS

In the proposed design, the rate ratio is estimated using the method of prescription sequence symmetry analysis with slight modification so that the rate ratio can be estimated using data on subjects who have started the drug during the study period but no data on other subjects.

DISCUSSION

The proposed design has an advantage that it can provide the measure of association. Another advantage common to all self-controlled methods is that the effect of the measured and unmeasured confounders is automatically canceled out when the effect is stable over the study period. Compared with the standard design with a comparator group, the proposed design also has weaknesses. For example, adjustment of confounding by the indication may be difficult when the indication is an acute condition. In addition, the rate ratio is not valid when the probability of the prescription of the drug is dependent on the occurrence of the outcome in the unexposed (pre-dose) period. The design may be used to evaluate the need for further studies although its real usefulness is to be determined in the future.

Cardiovascular drugs and erectile dysfunction - a symmetry analysis

AIM

Erectile dysfunction is a common problem among patients with cardiovascular diseases and the influence of cardiovascular drugs is much debated. The aim of this study was to evaluate the short term potential for different cardiovascular drugs to affect the risk of being prescribed a drug against erectile dysfunction.

METHODS

We employed a symmetry analysis design and included all Danish male individuals born before 1950 who filled their first ever prescription for a cardiovascular drug and a 5-phosphodiesterase inhibitor within a 6 month interval during 2002-2012. If the cardiovascular drug induces erectile dysfunction, this would manifest as a non-symmetrical distribution of subjects being prescribed the cardiovascular drug first vs. persons following the opposite pattern. Furthermore, we calculated the number of patients needed to treat for one additional patient to be treated for erectile dysfunction (NNTH).

RESULTS

We identified 20 072 males with a median age of 64 years (IQR 60-70) who initiated a cardiovascular drug and a 5-phosphodiesterase inhibitor within a 6 month interval. Sequence ratios showed minor asymmetry in prescription orders after adjustment for trends in prescribing. This asymmetry was most profound for thiazides (1.28, 95% CI 1.20, 1.38), calcium channel blockers (1.29, 95% CI 1.21, 1.38) and ACE inhibitors (1.29, 95% CI 1.21, 1.37), suggesting a small liability of these drugs to provoke erectile dysfunction. NNTH values were generally large, in the range of 330-6400, corresponding to small absolute effects.

CONCLUSION

Our study does not suggest that cardiovascular drugs strongly affect the risk of being prescribed a drug against erectile dysfunction on a short term basis.