Spin-orbit induced mixed-spin ground state in RRNiO3_3 perovskites probed by XAS: new insight into the metal to insulator transition

We report on a Ni L$_{2,3}$ edges x-ray absorption spectroscopy (XAS) study in $R$NiO$_3$ perovskites. These compounds exhibit a metal to insulator ($MI$) transition as temperature decreases. The L$_{3}$ edge presents a clear splitting in the insulating state, associated to a less hybridized ground state. Using charge transfer multiplet calculations, we establish the importance of the crystal field and 3d spin-orbit coupling to create a mixed-spin ground state. We explain the $MI$ transition in $R$NiO$_3$ perovskites in terms of modifications in the Ni$^{3+}$ crystal field splitting that induces a spin transition from an essentially low-spin (LS) to a mixed-spin state.Comment: 4 pages, 4 figures, accepted as PRB - Rapid Comm. Dez. 200

Short-range charge-order in RRNiO3_{3} perovskites (RR=Pr,Nd,Eu) probed by X-ray absorption spectroscopy

The short-range organization around Ni atoms in orthorhombic $R$NiO$_{3}$ ($R$=Pr,Nd,Eu) perovskites has been studied over a wide temperature range by Ni K-edge x-ray absorption spectroscopy. Our results demonstrate that two different Ni sites, with different average Ni-O bond lengths, coexist in those orthorhombic compounds and that important modifications in the Ni nearest neighbors environment take place across the metal-insulator transition. We report evidences for the existence of short-range charge-order in the insulating state, as found in the monoclinic compounds. Moreover, our results suggest that the two different Ni sites coexists even in the metallic state. The coexistence of two different Ni sites, independently on the $R$ ion, provides a common ground to describe these compounds and shed new light in the understanding of the phonon-assisted conduction mechanism and unusual antiferromagnetism present in all $R$NiO$_{3}$ compounds.Comment: 4 pages, 3 figures, accepted PRB - Brief Report Dec.200

Thyroglossal duct carcinoma

We report a 56-year-old Malay woman with a tumour that involved the skin and caused hyoid bone erosion. There was no clinical or radiological evidence of regional lymph node involvement. A modified radical neck dissection with preservation of the accessory nerve and internal jugular vein was performed, followed by an "extended" Sistrunk operation. The surgical defect was reconstructed with a pectoralis major myocutaneous flap. Our literature review showed that this is the first reported thyroglossal duct carcinoma which involved the skin and required a pedicle flap reconstruction

Elevated frequency of abnormalities in barn swallows from Chernobyl

Ever since the Chernobyl accident in 1986, that contaminated vast areas in surrounding countries with radiation, abnormalities and birth defects have been reported in human populations. Recently, several studies suggested that the elevated frequency of such abnormalities can be attributed to poverty and stress in affected human populations. Here, we present long-term results for a free-living population of barn swallows, Hirundo rustica, demonstrating the presence of 11 morphological abnormalities in populations around Chernobyl, but much less frequently in an uncontaminated Ukrainian control population and three more distant control populations. The presence of these abnormalities in barn swallows is associated with reduced viability. These findings demonstrate a link between morphological abnormalities and radiation in an animal population that cannot be attributed to poverty and stress. The most parsimonious hypothesis for abnormalities in animal and human populations alike is that the effects are caused by the same underlying cause, viz. radiation derived from the Chernobyl accident

Observation of insulator-metal transition in EuNiO3_{3} under high pressure

The charge transfer antiferromagnetic (T$_{N}$ =220 K) insulator EuNiO$_{3}$ undergoes, at ambient pressure, a temperature-induced metal insulator MI transition at T$_{MI}$=463 K. We have investigated the effect of pressure (up to p~20 GPa) on the electronic, magnetic and structural properties of EuNiO$_{3}$ using electrical resistance measurements, {151}^Eu nuclear resonance scattering of synchrotron radiation and x-ray diffraction, respectively. With increasing pressure we find at p$_{c}$ =5.8 GPa a transition from the insulating state to a metallic state, while the orthorhombic structure remains unchanged up to 20 GPa. The results are explained in terms of a gradual increase of the electronic bandwidth with increasing pressure, which results in a closing of the charge transfer gap. It is further shown that the pressure-induced metallic state exhibits magnetic order with a lowervalue of T$_{N}$ (T$_{N}$ ~120 K at 9.4 GPa) which disappears between 9.4 and 14.4 GPa.Comment: 10 pages, 3 figure

METALWORKING AT MAYAPAN, YUCATAN, MEXICO: DISCOVERIES FROM THE R-183 GROUP

This article presents a compositional analysis of metal artifacts from the Postclassic period (a.d. 1100–1450) city of Mayapan, Yucatan, Mexico. We document metallurgical production at R-183, an elite residential group and one of the most significant archaeological contexts associated with metalworking at Mayapan. Salvage excavations in 1998 recovered a small cache containing 282 copper bells, two miniature ceramic vessels filled with metal, and production debris including loose casting sprues and miscast bells. Metallographic analysis of a small copper bell and wire fragments from the cache reveals lost-wax casting production techniques. X-ray fluorescence spectrometry (XRF) of metal artifacts provides insight into the range of metals used by the R-183 metalworkers, which included copper- lead, copper-tin, and copper-arsenic alloys, and how these alloys compare to assemblages recovered from other contexts at the city. Our findings strongly suggest the use of remelting and casting techniques, likely utilizing remelted metals of both West and central Mexican origin, together with the use of imported goods made from a range of copper alloys

Extraction of decision rules using genetic algorithms and simulated annealing for prediction of severity of traffic accidents by motorcyclists

The objective of this study is to analysis of accident of motorcyclists on Bogotá roads in Colombia. For detection of conditions related to crashes and their severity, the proposed model develops the strategies to enhance road safety. In this context, data mining and machine learning techniques are used to investigate 34,232 accidents by motorcyclists during January 2013 to February 2018. Both the Genetic algorithm and simulated annealing are applied in conjunction with mining rules (support, confidence, lift, and comprehensibility) as per objectives of the problem. The application of a hybrid algorithm allows for the creation and definition of optimal hierarchical decision rules for the prediction of the severity of motorcycle traffic accidents. The proposed method yields good results in the metrics of recall (90.07%), precision (89.87%), and accuracy (90.06%) on the data set. The results increase the prediction by 20–21% in comparisons with the following methods: Decision Trees (CART, ID3, and C4.5), Support Vector Machines (SVMs), K-Nearest Neighbor (KNN), Naive Bayes, Neural Networks, Random Forest, and Random Tree. The proposed method defines 11 rules for the prediction of accidents with material damage, 24 rules with injuries, and 12 rules with fatalities. The variables with the most recurrence in the definition of rules are time, weather and road conditions, and the number of victims involved in the accidents. Finally, the interactions of the conditions and characteristics presented in motorcycle accidents are analyzed which contribute to the definition of countermeasures for road safety. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature

Formulation and constraints on decaying dark matter with finite mass daughter particles

Decaying dark matter cosmological models have been proposed to remedy the overproduction problem at small scales in the standard cold dark matter paradigm. We consider a decaying dark matter model in which one CDM mother particle decays into two daughter particles, with arbitrary masses. A complete set of Boltzmann equations of dark matter particles is derived which is necessary to calculate the evolutions of their energy densities and their density perturbations. By comparing the expansion history of the universe in this model and the free-streaming scale of daughter particles with astronomical observational data, we give constraints on the lifetime of the mother particle, $\Gamma^{-1}$, and the mass ratio between the daughter and the mother particles $m_{\rm D}/m_{\rm M}$. From the distance to the last scattering surface of the cosmic microwave background, we obtain $\Gamma^{-1}>$ 30 Gyr in the massless limit of daughter particles and, on the other hand, we obtain $m_{\rm D} >$ 0.97$m_{\rm M}$ in the limit $\Gamma^{-1}\to 0$. The free-streaming constraint tightens the bound on the mass ratio as $(\Gamma^{-1}/10^{-2}{\rm Gyr}) \lesssim ((1-m_{\rm D1}/m_{\rm M})/10^{-2})^{-3/2}$ for $\Gamma^{-1} < H^{-1}(z=3)$.Comment: 20 pages, 7 figure

Associations of sickness absence for pain in the low back, neck and shoulders with wider propensity to pain

Objectives: To explore the association of sickness absence ascribed to pain at specific anatomical sites with wider propensity to musculoskeletal pain.Methods: As part of the CUPID (Cultural and Psychosocial Influences on Disability) study, potential risk factors for sickness absence from musculoskeletal pain were determined for 11 922 participants from 45 occupational groups in 18 countries. After approximately 14 months, 9119 (78%) provided follow-up information about sickness in the past month because of musculoskeletal pain, including 8610 who were still in the same job. Associations with absence for pain at specific anatomical sites were assessed by logistic regression and summarised by ORs with 95% CIs.Results: 861 participants (10%) reported absence from work because of musculoskeletal pain during the month before follow-up. After allowance for potential confounders, risk of absence ascribed entirely to low back pain (n=235) increased with the number of anatomical sites other than low back that had been reported as painful in the year before baseline (ORs 1.6 to 1.7 for ≥4 vs 0 painful sites). Similarly, associations with wider propensity to pain were observed for absence attributed entirely to pain in the neck (ORs up to 2.0) and shoulders (ORs up to 3.4).Conclusions: Sickness absence for pain at specific anatomical sites is importantly associated with wider propensity to pain, the determinants of which extend beyond established risk factors such as somatising tendency and low mood. Better understanding of why some individuals are generally more prone to musculoskeletal pain might point to useful opportunities for prevention