Superconducting atomic contacts inductively coupled to a microwave resonator

We describe and characterize a microwave setup to probe the Andreev levels of a superconducting atomic contact. The contact is part of a superconducting loop inductively coupled to a superconducting coplanar resonator. By monitoring the resonator reflection coefficient close to its resonance frequency as a function of both flux through the loop and frequency of a second tone we perform spectroscopy of the transition between two Andreev levels of highly transmitting channels of the contact. The results indicate how to perform coherent manipulation of these states.Comment: 14 pages, 10 figures, to appear in special issue on break-junctions in JOPC

Comparison of complexed species of Eu in alumina-bound and free polyacrylic acid: A spectroscopic study

International audienceThe speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAAads) was studied at pH 5 in 0.1 M NaClO4. Structural parameters were obtained from 7F0 → 5D0 excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu LIII-edge extended X-ray absorption fine structure (EXAFS) spectra. The coordination mode was also investigated by infrared spectroscopy. To elucidate the nature of the complexed species, Eu–acetate complexes were used as references. The spectroscopic techniques show that two carboxylate groups with 2–3 (EuPAA) and 4–5 (EuPAAads) water molecules are coordinated to Eu in the first coordination sphere. For EuPAAads, the coordination between carboxylate groups and Eu appears to be bidendate. A similar coordination is probable for EuPAA but the EXAFS data indicate a slightly distorted coordination. The results show that the degree of freedom of carboxylate groups is not the same for free or adsorbed PAA. For PAA, the degree of freedom is constrained by the flexibility of the methylene chain. When PAA is adsorbed on alumina, the polymer chains cannot any more be treated as independent chains. One may rather assume formation of aggregates that form an organic layer at the mineral surface presenting a complex arrangement of carboxylate groups

Student perspectives on the relationship between a curve and its tangent in the transition from Euclidean Geometry to Analysis

The tangent line is a central concept in many mathematics and science courses. In this paper we describe a model of students’ thinking – concept images as well as ability in symbolic manipulation – about the tangent line of a curve as it has developed through students’ experiences in Euclidean Geometry and Analysis courses. Data was collected through a questionnaire administered to 196 Year 12 students. Through Latent Class Analysis, the participants were classified in three hierarchical groups representing the transition from a Geometrical Global perspective on the tangent line to an Analytical Local perspective. In the light of this classification, and through qualitative explanations of the students’ responses, we describe students’ thinking about tangents in terms of seven factors. We confirm the model constituted by these seven factors through Confirmatory Factor Analysis

Diversité Des Loranthaceae Et Leur Impact Sur Vitellaria Paradoxa C.F.Gaertn.: Un Fruitier À Grande Valeur Socio-Économique Au Nord-Bénin

Shea butter: Vitellaria paradoxa C. F. Gaertn (Sapotaceae) is a fruit tree in the Sudano-Sahelian region where it is a major economic source. Unfortunately, in Benin, the species has been revealed in recent decades, the target of parasitic vascular plants of Loranthaceae family that threaten its conservation. The present study, carried out in northern Benin, evaluated the impact of these parasitic plants on the shea of two phytogeographical zones. The botanical inventory identified three species of Loranthaceae in fields and protected areas. The rate of infestation and parasite density were assessed and their variation on shea was assessed. The results show that shea is parasitized by three species of Loranthaceae in varying proportions: Agelanthus dodoneifolius (DC.) Polh. and Wiens (191.75 tufts / ha), Tapinanthus globiferus (A. Rich.) Van Tieghem (70.57 tufts / ha) and T. Ophiodes (Sprague) (2 tufts / ha). The impact of Loranthaceae on shea productivity varies significantly between fields and protected areas with infestation rates of 87% versus 42% and average densities per shea foot of 14.76 tufts versus 3.62 tufts. These results are data to be taken into account in the control programs against Loranthaceae which parasitize shea

Diversité, impacts et usages des Loranthaceae parasites de Cola nitida (Vent.) Schott. & Endl. au Sud-Bénin

Cola nitida est une espèce fruitière à usages multiples qui, malheureusement, est souvent la cible des plantes parasites de la famille des Loranthaceae. L’objectif de la présente étude est de recenser les espèces de Loranthaceae parasites de C. nitida, d’évaluer leur impact sur ce fruitier et d’inventorier les usages thérapeutiques faits de ces plantes parasites au Sud du Bénin. Pour y parvenir, des inventaires floristique et forestier puis des enquêtes ethnobotaniques ont été réalisés. Au total, 15 plantations et 50 jardins de case abritant C. nitida ont été explorés dans 12 villages à travers lesquels 87 personnes utilisant les Loranthaceae ont été questionnées. Les résultats révèlent que sur les 552 pieds de C. nitida explorés, 6 espèces de Loranthaceae qui sont : Globimetula braunii, G. cupulata, Phragmanthera capitata, Tapinanthus bangwensis, T. belvisii et T. globiferus ont été recensées. Le taux d’infestation est de 53%. Sur le plan ethnobotanique, les Loranthaceae de C. nitida interviennent dans le traitement de 3 affections que sont : la stérilité, les fausses couches (40% chacune) et les troubles menstruels (20%). Cette étude permet de proposer l’utilisation à grande échelle des Loranthaceae comme approche de gestion durable de ces hémiparasites.© 2015 International Formulae Group. All rights reserved.Mots clés: Gui africain, biodiversité, densité parasitaire, gestion durable, BéninEnglish Title: Diversity, impacts and uses of Loranthaceae growing on Cola nitida (Vent.) Schott. & Endl. in Southern BeninEnglish AbstractCola nitida is a kind of fruit presenting international multiple uses. However, this fruit is often the target of parasitic plants of Loranthaceae family. The aim of the present work is to know the diversity and  impact of Loranthaceae on C. nitida tree and the different uses made of these parasites. A total of 552 feet of C. nitida have been explored within 15 plantations and 50 home gardens spread in 12 villages through which 87 people using Loranthaceae have been questioned. The results show that C. nitida is parasitized by 6 species of Loranthaceae (Globimetula braunii, G. cupulata, Phragmanthera capitata, Tapinanthus bangwensis, T. belvisii and T. globiferus). Infestation rate of C. nitida is 53%. On ethnobotanical level, Loranthaceae growing on C. nitida contribute to the treatment of three diseases which are barrenness, miscarriage (40% each) and menstrual disorders (20%). Pending the development of effective struggle methods against Loranthaceae growing on C. nitida, the widespread use of these parasites can contribute to maintain them in acceptable damage threshold and also generate incomes for people.© 2015 International Formulae Group. All rights reserved.Keywords: African mistletoes, biodiversity, parasite density, sustainable management, Beni

Neural field theory of adaptive effects on auditory evoked responses and mismatch negativity in multifrequency stimulus sequences

Physiologically based neural field theory (NFT) of the corticothalamic system, including adaptation, is used to calculate the responses evoked by trains of auditory stimuli that differ in frequency. In oddball paradigms, fully distinguishable frequencies lead to different standard (common stimulus) and deviant (rare stimulus) responses; the signal obtained by subtracting the standard response from the deviant is termed the mismatch negativity (MMN). In this analysis, deviant responses are found to correspond to unadapted cortex, whereas the part of auditory cortex that processes the standard stimuli adapts over several stimulus presentations until the final standard response form is achieved. No higher-order memory processes are invoked. In multifrequency experiments, the deviant response approaches the standard one as the deviant frequency approaches that of the standard and analytic criteria for this effect to be obtained. It is shown that these criteria can also be used to understand adaptation in random tone sequences. A method of probing MMNs and adaptation in random tone sequences is suggested to makes more use of such data

On the Spatial Coherence of Magnetic Ejecta: Measurements of Coronal Mass Ejections by Multiple Spacecraft Longitudinally Separated by 0.01 AU

Measurements of coronal mass ejections (CMEs) by multiple spacecraft at small radial separations but larger longitudinal separations is one of the ways to learn about the three-dimensional structure of CMEs. Here, we take advantage of the orbit of the Wind spacecraft that ventured to distances of up to 0.012 astronomical units (au) from the Sun-Earth line during the years 2000 to 2002. Combined with measurements from ACE, which is in a tight halo orbit around L1, the multipoint measurements allow us to investigate how the magnetic field inside magnetic ejecta (MEs) changes on scales of 0.005 - 0.012 au. We identify 21 CMEs measured by these two spacecraft for longitudinal separations of 0.007 au or more. We find that the time-shifted correlation between 30-minute averages of the non-radial magnetic field components measured at the two spacecraft is systematically above 0.97 when the separation is 0.008 au or less, but is on average 0.89 for greater separations. Overall, these newly analyzed measurements, combined with 14 additional ones when the spacecraft separation is smaller, point towards a scale length of longitudinal magnetic coherence inside MEs of 0.25 - 0.35 au for the magnitude of the magnetic field but 0.06 - 0.12 au for the magnetic field components. This finding raises questions about the very nature of MEs. It also highlights the need for additional "mesoscale" multi-point measurements of CMEs with longitudinal separations of 0.01 - 0.2 au.Comment: Published in ApJL, 6 page

Testing models of dental development in the earliest bony vertebrates, Andreolepis and Lophosteus

Theories on the development and evolution of teeth have long been biased by the fallacy that chondrichthyans reflect the ancestral condition for jawed vertebrates. However, correctly resolving the nature of the primitive vertebrate dentition is challenged by a dearth of evidence on dental development in primitive osteichthyans. Jaw elements from the Silurian–Devonian stem-osteichthyans Lophosteus and Andreolepis have been described to bear a dentition arranged in longitudinal rows and vertical files, reminiscent of a pattern of successional development. We tested this inference, using synchrotron radiation X-ray tomographic microscopy (SRXTM) to reveal the pattern of skeletal development preserved in the sclerochronology of the mineralized tissues. The tooth-like tubercles represent focal elaborations of dentine within otherwise continuous sheets of the dermal skeleton, present in at least three stacked generations. Thus, the tubercles are not discrete modular teeth and their arrangement into rows and files is a feature of the dermal ornamentation that does not reflect a polarity of development or linear succession. These fossil remains have no bearing on the nature of the dentition in osteichthyans and, indeed, our results raise questions concerning the homologies of these bones and the phylogenetic classification of Andreolepis and Lophosteus

Using a stochastic continuous-time Markov chain model to examine alternative timing and duration of the COVID-19 lockdown in Kuwait: what can be done now?

Background Kuwait had its first COVID-19 in late February, and until October 6, 2020 it recorded 108,268 cases and 632 deaths. Despite implementing one of the strictest control measures-including a three-week complete lockdown, there was no sign of a declining epidemic curve. The objective of the current analyses is to determine, hypothetically, the optimal timing and duration of a full lockdown in Kuwait that would result in controlling new infections and lead to a substantial reduction in case hospitalizations. Methods The analysis was conducted using a stochastic Continuous-Time Markov Chain (CTMC), eight state model that depicts the disease transmission and spread of SARS-CoV 2. Transmission of infection occurs between individuals through social contacts at home, in schools, at work, and during other communal activities. Results The model shows that a lockdown 10 days before the epidemic peak for 90 days is optimal but a more realistic duration of 45 days can achieve about a 45% reduction in both new infections and case hospitalizations. Conclusions In the view of the forthcoming waves of the COVID19 pandemic anticipated in Kuwait using a correctly-timed and sufficiently long lockdown represents a workable management strategy that encompasses the most stringent form of social distancing with the ability to significantly reduce transmissions and hospitalizations

Coherent manipulation of Andreev states in superconducting atomic contacts

Coherent control of quantum states has been demonstrated in a variety of superconducting devices. In all these devices, the variables that are manipulated are collective electromagnetic degrees of freedom: charge, superconducting phase, or flux. Here, we demonstrate the coherent manipulation of a quantum system based on Andreev bound states, which are microscopic quasiparticle states inherent to superconducting weak links. Using a circuit quantum electrodynamics setup we perform single-shot readout of this "Andreev qubit". We determine its excited state lifetime and coherence time to be in the microsecond range. Quantum jumps and parity switchings are observed in continuous measurements. In addition to possible quantum information applications, such Andreev qubits are a testbed for the physics of single elementary excitations in superconductors.Comment: Supplementary Materials at the end of the fil