5,262 research outputs found

    An updated checklist of Recent ostracods (Crustacea: Ostracoda) from inland waters of Sicily and adjacent small islands with notes on their distribution and ecology

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    Because of its position in the middle of the Mediterranea Sea and a complex geological history that has promoted repeated waves of biological colonization, Sicily (Southern Italy) is of particular interest from a biogeographical perspective. A number of previous investigations, dating back as far as the end of the 19th century, have contributed to gather information about the occurrence of Recent non-marine ostracods in Sicily, making this region one of the most intensively studied areas of the Central Mediterranean. Published data on ostracod distributions have been integrated through an extensive field survey on mainland Sicily and surrounding small islands and archipelagos. Altogether, 271 ostracod samples and 11 sediment samples from dry water bodies were analysed from 218 sites visited between 2002 and 2017. Sampling sites were selected to encompass all the most common types of freshwater aquatic habitats, both natural and artificial, present in the area. Thirty-nine ostracods were identified at species level and 12 at supraspecific level. The present study reports four species (Cypria subsalsa, Eucypris mareotica, Physocypria kerkyrensis, Vestalenula boteai) and one genus (Vestalenula) as new for both peninsular Italy and adjacent islands, and three species (Candonopsis novaezelandiae, Ilyocypris inermis, Neglecandona neglecta) and two genera (Candonopsis and Physocypria) as new for Sicily. The updated checklist of the study area now includes at least 46 nominal species and other taxa identified at supraspecific level, belonging to 28 genera in 8 families (Candonidae, Cyprididae, Cytherideidae, Darwinulidae, Hemicytheridae, Ilyocyprididae, Limnocytheridae and Notodromadidae). The present investigation represents a significant addition to the knowledge of the ostracod diversity and distribution in the Sicilian area and in Italy as a whole. It also provides a sound baseline data for further comparative faunal studies aimed at investigating the affinities and origins of the central Mediterranean inland-water ostracod faunas, and to analyse their biogeographic patterns

    Distribution of Recent ostracods in inland waters of Sicily (Southern Italy)

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    From 2003 to 2005, freshwater ostracods were sampled in 67 water bodies of mainland Sicily (Provinces of Agrigento, Caltanisetta, Catania, Enna, Palermo, Messina, Ragusa, Siracusa and Trapani) located from sea level up to 1300 m a.s.l. This survey took into account streams, springs, wells, but especially temporary and ephemeral habitats (e.g., flooded meadows, temporary ponds). The aim of this research was to give the first comprehensive picture of the regional ostracod fauna and establish relationships between the distribution of ostracod species and some habitat features. Altogether, 21 ostracod taxa belonging to five families (Candonidae, Ilyocyprididae, Cyprididae, Notodromadidae, and Limnocytheridae) were identified. A maximum of four species was found in a single sample. The most frequent species was Heterocypris incongruens, followed by Eucypris virens. The following ten taxa have been found only once: Candona lindneri, Ilyocypris decipiens, Notodromas persica, Trajancypris clavata, Herpetocypris brevicaudata, Heterocypris salina, Cypridopsis cf. elongata, Cypridopsis vidua, Potamocypris cf. villosa, and Limnocythere inopinata. The faunal assemblage of Sicily is compared with the known ostracod distribution in some Mediterranean areas

    Amazon piperaceae with potential insecticide use.

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    The Amazon rainf orest is a potential source of essential oils, such as thosef ound in the family Piperaceae, to which the species known as long pepper and pepper jack belong . The genus Piper comprises around 700 species, among the 140-300 species that are part of the rainf orestfl ora of the Amazon region. The literature describes the composition of its essential oils, with various biological activities such as larvicide, antimicrobial, and antioxidant activities, among others. The use of essential oils as af uture alternative to insecticides is af ield that is growing, and this chapter presents a literature review of studiesf ocusing on Amazonian Piperaceae essential oils that have potential insecticide use. The species Piper aduncum L., P. callosum, P. divaricatum, P. hispidinervum, P. hostimannianum, P. humaytanum, P. marginatum, P. nigrum L., and P. tuberculatum, have shown excellent results in studies to evaluate their potential as plants with biological activities that can be used to control pests that cause damage to agricultural crops, or to human health. The essential oil of P. aduncum is the one that has been most widely studied f or its potential as an insecticide, showingeff ectiveness in the control of various species of agricultural pests in Brazil e.g ., Cerotomatingomarianus Bechyné, Tenebrio molitor L., Solenopsis saevissima. The Reports in the literature on the essential oils of Piperaceae demonstrate their ability to inhibit or delay insect maturation, reducing reproductive capacity, and causing death by starvation or direct toxicity. The main constituents present in the composition of the essential oils are phenylpropanoids, farnesene, and a-bisabolol. The wide biological diversity, largely unexplored, especially in tropical regions like the Amazon rainf orest, holdsgreat potentialf or research into new products that could replace conventional insecticides, or be used as part of synergisticf ormulations in the eff orts to control insect resistance to these products

    Solution of the infinite range t-J model

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    The t-J model with constant t and J between any pair of sites is studied by exploiting the symmetry of the Hamiltonian with respect to site permutations. For a given number of electrons and a given total spin the exchange term simply yields an additive constant. Therefore the real problem is to diagonalize the "t- model", or equivalently the infinite U Hubbard Hamiltonian. Using extensively the properties of the permutation group, we are able to find explicitly both the energy eigenvalues and eigenstates, labeled according to spin quantum numbers and Young diagrams. As a corollary we also obtain the degenerate ground states of the finite UU Hubbard model with infinite range hopping -t>0.Comment: 15 pages, 2 figure

    Comment on ``BCS to Bose-Einstein crossover phase diagram at zero temperature for a d_{x^2-y^2} order parameter superconductor: Dependence on the tight-binding structure''

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    The work by Soares et al. [Phys. Rev. B 65, 174506 (2002)] investigates the BCS-BE crossover for d-wave pairing in the 2-dimensional attractive Hubbard model. Contrary to their claims, we found that a non-pairing region does not exist in the density vs coupling phase diagram. The gap parameter at T=0, as obtained by solving analytically as well as numerically the BCS equations, is in fact finite for any non-zero density and coupling, even in the weak-coupling regime.Comment: 7 pages, 1 figur

    Existence of Saturated Ferromagnetic and Spiral States in 1D Lieb-Ferrimagnetic Models away from Half-Filling

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    In order to study conditions for the appearance of ferromagnetism in a wide filling region, we investigate numerically three types of one-dimensional Lieb-ferrimagnetic Hubbard models: a periodic diamond (PD) chain, a periodic alternately-attached leg (PAAL) chain and an open diamond (OD) chain. All of these models have a flat band (or equivalently, degenerate single-electron eigenvalues). The PD and OD chains commonly have a local-loop structure. Nagaoka's theorem holds only in the PD chain. At half-filling, it have been rigorously proven that all of these models are ferrimagnet. Away from half-filling, however, quite different magnetic properties are found. In the fillings 1/3< rho_e <1/2, the ground state of the PD chain for a infinitely-large U is the extended ferromagnetic state, that is, the saturated ferromagnetic state or the spiral state for odd or even number of electrons, respectively. In the PAAL chain, on the other hand, there is no magnetic order. Thus, the flat band is found to be not a sufficient condition of the extended ferromagnetic state. We find, moreover, that the saturated ferromagnetism appears in the OD chain, although the Nagaoka theorem does not hold on this chain. This indicates that the local-loop structure plays an important role on the appearance of the extended ferromagnetic state.Comment: 4 pages, 4 figures, 2 tables. to be published in J. Phys. Soc. Jpn. Vol. 68 No.

    Homogeneous Fermion Superfluid with Unequal Spin Populations

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    For decades, the conventional view is that an s-wave BCS superfluid can not support uniform spin polarization due to a gap Δ\Delta in the quasiparticle excitation spectrum. We show that this is an artifact of the dismissal of quasiparticle interactions VqpV_{qp}^{} in the conventional approach at the outset. Such interactions can cause triplet fluctuations in the ground state and hence non-zero spin polarization at "magnetic field" h<Δh<\Delta. The resulting ground state is a pairing state of quasiparticles on the ``BCS vacuum". For sufficiently large VqpV_{qp}, the spin polarization of at unitarity has the simple form mμ1/2m\propto \mu^{1/2}. Our study is motivated by the recent experiments at Rice which found evidence of a homogenous superfluid state with uniform spin polarization.Comment: 4 pages, 3 figure

    A comparison of validated methods used to assess impaired awareness of hypoglycaemia in type 1 diabetes: an observational study

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    Introduction Clarke, Gold and Pedersen are validated methods to assess awareness of hypoglycaemia. Identifying impaired awareness of hypoglycaemia (IAH) is critical for supporting people with structured education and diabetes technologies, to reduce harm of hypoglycaemia. This study compares the Clarke score, Gold score and Pedersen methods and their correlations with features of hypoglycaemia unawareness and patient characteristics, to evaluate the accuracy of the methods in identifying IAH. Methods This retrospective, observational questionnaire-based study collected routine clinical data from 100 people with type 1 diabetes. The questionnaire included the three validated scoring methods, frequency of severe and nocturnal hypoglycaemia, knowledge and worry of hypoglycaemia and hypoglycaemia symptom scores using the Edinburgh Hypoglycaemia Scale. Data were analysed for IAH prevalence and the associations with features of IAH. The concordance of Clarke, Gold and Pedersen methods was evaluated using Spearman’s correlation coefficient. Results The prevalence of IAH in this cohort identified by Clarke, Gold and Pedersen methods was 18%, 19% and 61% respectively. The mean autonomic symptom score in people with IAH was significantly reduced using the Clarke method (P = 0.0002) but not on Gold (P = 0.12) and Pedersen methods (P = 0.79). For people with IAH assessed using the Clarke method, scores for night-time worry regarding hypoglycaemia (P = 0.04) and self-reported frequency of nocturnal hypoglycaemia (P = 0.001) were increased. Spearman’s correlation coefficients between Pedersen and Clarke and Pedersen and Gold were Rs = 0.555 (P < 0.001) and Rs = 0.645 (P < 0.001) respectively. A moderate association was observed between Clarke and Gold Rs = 0.5669 (P < 0.001). Conclusion Whilst Clarke and Gold methods determined a similar prevalence of IAH, people identified with IAH assessed by the Clarke method had a significant association with the features and characteristics of IAH, including reduced autonomic symptoms. This study suggests that performing more than one score is important for a reliable risk assessment of IAH

    Signatures of Superfluidity in Dilute Fermi Gases near a Feshbach Resonance

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    We present a brief account of the most salient properties of vortices in dilute atomic Fermi superfluids near a Feshbach resonance.Comment: 6 pages, 1 figure, and jltp.cls. Several typos and a couple of inaccuracies have been correcte
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