14,143 research outputs found
Competing order and nature of the pairing state in the iron pnictides
We show that the competition between magnetism and superconductivity can be
used to determine the pairing state in the iron arsenides. To this end we
demonstrate that the itinerant antiferromagnetic phase (AFM) and the
unconventional sign-changing superconducting state (SC) are near the
borderline of microscopic coexistence and macroscopic phase separation,
explaining the experimentally observed competition of both ordered states. In
contrast, conventional pairing is not able to coexist with magnetism.
Expanding the microscopic free energy of the system with competing orders
around the multicritical point, we find that static magnetism plays the role of
an intrinsic interband Josephson coupling, making the phase diagram sensitive
to the symmetry of the Cooper pair wavefunction. We relate this result to the
quasiparticle excitation spectrum and to the emergent SO symmetry of
systems with particle-hole symmetry. Our results rely on the assumption that
the same electrons that form the ordered moment contribute to the
superconducting condensate and that the system is close to particle-hole
symmetry. We also compare the suppression of SC in different regions of the
FeAs phase diagram, showing that while in the underdoped side it is due to the
competition with AFM, in the overdoped side it is related to the disappearance
of pockets from the Fermi surface.Comment: 24 pages, 13 figures; revised versio
Comparison of 30 THz impulsive burst time development to microwaves, H-alpha, EUV, and GOES soft X-rays
The recent discovery of impulsive solar burst emission in the 30 THz band is
raising new interpretation challenges. One event associated with a GOES M2
class flare has been observed simultaneously in microwaves, H-alpha, EUV, and
soft X-ray bands. Although these new observations confirm some features found
in the two prior known events, they exhibit time profile structure
discrepancies between 30 THz, microwaves, and hard X-rays (as inferred from the
Neupert effect). These results suggest a more complex relationship between 30
THz emission and radiation produced at other wavelength ranges. The multiple
frequency emissions in the impulsive phase are likely to be produced at a
common flaring site lower in the chromosphere. The 30 THz burst emission may be
either part of a nonthermal radiation mechanism or due to the rapid thermal
response to a beam of high-energy particles bombarding the dense solar
atmosphere.Comment: accepted to Astronomy and Astrophysic
Phase diagrams in kappa-carrageenan/locust bean gum systems
Gelation (Tgel) and melting (Tm) temperatures of kappa-carrageenan gels and 4:1 kappa-carrageenan/locust bean gum mixed gels, at different total potassium concentrations (CT), were determined by means of rheological (dynamic and viscosimetric) measurements. The log CT was linearly related to Tgel−1 and Tm−1. Differences found between both systems are discussed
Clinicians’ perceptions of Norwegian women’s experiences of infertility diseases
Background: Norway has one of the best health systems in the world. However, it has a low birth rate, which decreased by 21.2% between 2009 and 2018, and one of the highest rates of infertility prevalence. The aim of this study is to understand how Norwegian doctors perceive female infertility diseases, namely those that are more difficult to diagnose and to treat, and that are more common in their practice. Method: Descriptive qualitative study was conducted with gynecologists and general practitioners. The sample resulted from the establishment of five criteria and on the doctors’ acceptance to participate in this study. Our sample comprised thirteen highly qualified and experienced doctors. Qualitative content analysis was the method chosen to analyze the collected data. Results: Clinical diseases (polycystic ovary syndrome, endometriosis and vulvodynia) and consequences of these diseases were the pinpointed themes. These led to a set of sub-themes: the main symptoms and the treatment of the diseases, from the perspective of both women and doctors (stigmatization, disturbances in women’s daily life, diagnostic delay, and governmental support). Conclusions: The three most relevant disorders mentioned were polycystic ovary syndrome, endometriosis and vulvodynia. These diseases cause several impacts on the lives of women, because they feel stigmatized and limited in their daily life and sexuality, and the diagnosis of these diseases takes too much time. Governments should better redistribute the financing of women’s health and allocate resources to specialized centers.info:eu-repo/semantics/publishedVersio
Nano-hydroxyapatite in oral care cosmetics: characterization and cytotoxicity assessment
Nano-hydroxyapatite has been used as an oral care ingredient, being incorporated in several products for the treatment of dental hypersensitivity and enamel remineralisation. Despite its promising results, regulatory and safety concerns have been discussed and questioned by the European Scientific Committee on Consumer Safety (SCCS) regarding the usage of hydroxyapatite nanoparticles in oral care products. In this work, a commercially available nano-hydroxyapatite was characterized and its cytocompatibility towards human gingival fibroblasts was evaluated, as well as its irritation potential using the in vitro HET-CAM assay. All the conditions chosen in this study tried to simulate the tooth brushing procedure and the hydroxyapatite nanoparticles levels normally incorporated in oral care products. The commercial hydroxyapatite nanoparticles used in this study exhibited a rod-like morphology and the expected chemical and phase composition. The set of in vitro cytotoxicity parameters accessed showed that these nanoparticles are highly cytocompatible towards human gingival fibroblasts. Additionally, these nanoparticles did not possess any irritation potential on HET-CAM assay. This study clarifies the issues raised by SCCS and it concludes that this specific nano-hydroxyapatite is cytocompatible, as these nanoparticles did not alter the normal behaviour of the cells. Therefore, they are safe to be used in oral care products.The authors acknowledge the support of the Biointerfaces and Nanotechnology i3S Scientific Platform, as well as LuÃs Teixeira and Marta Ferro from University of Aveiro for the characterization of the HA-NP with TEM. Financial support from the European Union (FEDER funds POCI/01/0145/FEDER/007265) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/QUI/50006/2019 is acknowledged
A symplectic realization of the Volterra lattice
We examine the multiple Hamiltonian structure and construct a symplectic
realization of the Volterra model. We rediscover the hierarchy of invariants,
Poisson brackets and master symmetries via the use of a recursion operator. The
rational Volterra bracket is obtained using a negative recursion operator.Comment: 8 page
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