7,705 research outputs found

    Effects of Land Management Strategies on the Dispersal Pattern of a Beneficial Arthropod

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    Several arthropods are known to be highly beneficial to agricultural production. Consequently it is of great relevance to study the importance of land management and land composition for the conservation of beneficial aphid-predator arthropod species in agricultural areas. Therefore our study focusing on the beneficial arthropod Bembidion lampros had two main purposes: I) identifying the physical barriers to the species’ dispersal in the agricultural landscape, and II) assessing the effect of different land management strategies (i.e. use of pesticides and intensiveness) on the dispersal patterns. The study was conducted using genetic analysis (microsatellite markers) applied to samples from two agricultural areas (in Denmark) with different agricultural intensity. Land management effects on dispersal patterns were investigated with particular focus on: physical barriers, use of pesticide and intensity of cultivation. The results showed that Bembidion lampros disperse preferably through hedges rather than fields, which act as physical barriers to gene flow. Moreover the results support the hypothesis that organic fields act as reservoirs for the re-colonization of conventional fields, but only when cultivation intensity is low. These results show the importance of non-cultivated areas and of low intensity organic managed areas within the agricultural landscape as corridors for dispersal (also for a species typically found within fields). Hence, the hypothesis that pesticide use cannot be used as the sole predictor of agriculture’s effect on wild species is supported as land structure and agricultural intensity can be just as important

    Dissecting the 3D structure of elliptical galaxies with gravitational lensing and stellar kinematics

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    The combination of strong gravitational lensing and stellar kinematics provides a powerful and robust method to investigate the mass and dynamical structure of early-type galaxies. We demonstrate this approach by analysing two massive ellipticals from the XLENS Survey for which both high-resolution HST imaging and X-Shooter spectroscopic observations are available. We adopt a flexible axisymmetric two-component mass model for the lens galaxies, consisting of a generalised NFW dark halo and a realistic self-gravitating stellar mass distribution. For both systems, we put constraints on the dark halo inner structure and flattening, and we find that they are dominated by the luminous component within one effective radius. By comparing the tight inferences on the stellar mass from the combined lensing and dynamics analysis with the values obtained from stellar population studies, we conclude that both galaxies are characterised by a Salpeter-like stellar initial mass function.Comment: Proceedings of the IAU Symposium 309, Contributed Talk, Vienna, July 2014; 4 pages, 2 figure

    The non-universality of the low-mass end of the IMF is robust against the choice of SSP model

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    We perform a direct comparison of two state-of-the art single stellar population (SSP) models that have been used to demonstrate the non-universality of the low-mass end of the Initial Mass Function (IMF) slope. The two public versions of the SSP models are restricted to either solar abundance patterns or solar metallicity, too restrictive if one aims to disentangle elemental enhancements, metallicity changes and IMF variations in massive early-type galaxies (ETGs) with star formation histories different from the solar neighborhood. We define response functions (to metallicity and \alpha-abundance) to extend the parameter space of each set of models. We compare these extended models with a sample of Sloan Digital Sky Survey (SDSS) ETGs spectra with varying velocity dispersions. We measure equivalent widths of optical IMF-sensitive stellar features to examine the effect of the underlying model assumptions and ingredients, such as stellar libraries or isochrones, on the inference of the IMF slope down to ~0.1 solar masses. We demonstrate that the steepening of the low-mass end of the Initial Mass Function (IMF) based on a non-degenerate set of spectroscopic optical indicators is robust against the choice of the stellar population model. Although the models agree in a relative sense (i.e. both imply more bottom-heavy IMFs for more massive systems), we find non-negligible differences on the absolute values of the IMF slope inferred at each velocity dispersion by using the two different models. In particular, we find large inconsistency in the quantitative predictions of IMF slope variations and abundance patterns when sodium lines are used. We investigate the possible reasons for these inconsistencies.Comment: 16 pages, 9 figures, 2 tables, accepted for publication on Ap

    Intralabyrinthine Vestibular Schwannoma Responsive to Intratympanic Gentamicin Treatment

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    Intralabyrinthine schwannoma (ILS) is a rare benign tumor that affects the ends of cochlear and vestibular nerves. In a majority of the cases, it occurs with unilateral progressive sensorineural hearing loss. Less frequent symptoms include tinnitus, imbalance, vertigo, or fullness. The advent of magnetic resonance imaging allows early diagnosis and enables an appropriate therapeutic protocol. This report describes a case of intravestibular schwannoma, with fluctuating hearing loss and intractable vertigo, treated with intratympanic gentamicin. The patient was a 28-year-old woman with intractable vertigo and fluctuating left-side hearing loss caused by left intravestibular schwannoma. Because surgery was temporarily rejected by the patient, a single dose of intratympanic gentamicin was administered. Following this, the patient showed a significant improvement in the symptoms. However, moderate to flat sensorineural hearing loss was also observed. Intratympanic gentamicin infiltration is a valid therapeutic option for patients with ILS, affected by intractable vertigo, when the patient refuses surgery

    Transient hypercortisolism and symptomatic hyperthyroidism associated to primary hyperparathyroidism in an elderly patient: case report and literature review.

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    Abstract Background: Primary hyperparathyroidism (PHPT) is often found on routine blood tests, at a relatively asymptomatic stage. However many studies suggest different systemic effects related to PHPT, which could be enhanced by an abnormal cortisol release due to chronic stress of hyperparathyroidism. Being PHPT frequently found in the 6th to 7th decade of life, a careful and multifaceted approach should be taken. Case presentation: We report the case of an elderly patient with symptomatic PHPT and incidental pulmonary embolism. He was treated with hydration, zoledronic acid, cinacalcet and high-dose unfractionated heparin. Parathyroid surgery was successfully performed, but patient's conditions suddenly worsened because of a transient thyrotoxicosis, probably induced by a previous exposure to iodine load and/or thyroid surgical manipulation. A short-term treatment with beta-blockers was introduced for symptomatic relief. The patient also presented a transient hypercortisolism with elevated ACTH, likely due to stress related not only to aging and hospitalization but also to PHPT, resolved only four months after parathyroid surgery. Conclusion: Chronic hyperparathyroidism has been linked with increased all-cause mortality. A functional chronic hypercortisolism could be established, enhancing PHPT related disorders. Only parathyroid surgery has been demonstrated to cure PHPT and complications related, showing similar outcome between older and younger patients. However, the management of post-operative period should be more careful in fragile patients. In particular, the early diagnosis and treatment of a transient post-operative thyrotoxicosis could improve recovery. Due to the increase in prevalence and the evidence of many related complications even in asymptomatic PHPT, expert opinion-based guidelines for surgical treatment of PHPT should be developed especially for elderly patients

    Observations Outside the Light-Cone: Algorithms for Non-Equilibrium and Thermal States

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    We apply algorithms based on Lieb-Robinson bounds to simulate time-dependent and thermal quantities in quantum systems. For time-dependent systems, we modify a previous mapping to quantum circuits to significantly reduce the computer resources required. This modification is based on a principle of "observing" the system outside the light-cone. We apply this method to study spin relaxation in systems started out of equilibrium with initial conditions that give rise to very rapid entanglement growth. We also show that it is possible to approximate time evolution under a local Hamiltonian by a quantum circuit whose light-cone naturally matches the Lieb-Robinson velocity. Asymptotically, these modified methods allow a doubling of the system size that one can obtain compared to direct simulation. We then consider a different problem of thermal properties of disordered spin chains and use quantum belief propagation to average over different configurations. We test this algorithm on one dimensional systems with mixed ferromagnetic and anti-ferromagnetic bonds, where we can compare to quantum Monte Carlo, and then we apply it to the study of disordered, frustrated spin systems.Comment: 19 pages, 12 figure

    Berry phase for a spin 1/2 in a classical fluctuating field

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    The effect of fluctuations in the classical control parameters on the Berry phase of a spin 1/2 interacting with a adiabatically cyclically varying magnetic field is analyzed. It is explicitly shown that in the adiabatic limit dephasing is due to fluctuations of the dynamical phase.Comment: 4 pages, 1 figure, published versio

    Regulating the Regulators: The Post-Translational Code of Class I HDAC1 and HDAC2

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    Class I histone deacetylases (HDACs) are cellular enzymes expressed in many tissues and play crucial roles in differentiation, proliferation, and cancer. HDAC1 and HDAC2 in particular are highly homologous proteins that show redundant or specific roles in different cell types or in response to different stimuli and signaling pathways. The molecular details of this dual regulation are largely unknown. HDAC1 and HDAC2 are not only protein modifiers, but are in turn regulated by post-translational modifications (PTMs): phosphorylation, acetylation, ubiquitination, SUMOylation, nitrosylation, and carbonylation. Some of these PTMs occur and crosstalk specifically on HDAC1 or HDAC2, creating a rational “code” for a differential, context-related regulation. The global comprehension of this PTM code is central for dissecting the role of single HDAC1 and HDAC2 in physiology and pathology

    Detection of gravitational waves from the QCD phase transition with pulsar timing arrays

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    If the cosmological QCD phase transition is strongly first order and lasts sufficiently long, it generates a background of gravitational waves which may be detected via pulsar timing experiments. We estimate the amplitude and the spectral shape of such a background and we discuss its detectability prospects.Comment: 7 pages, 5 figs. Version accepted by PR

    Entanglement production by quantum error correction in the presence of correlated environment

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    We analyze the effect of a quantum error correcting code on the entanglement of encoded logical qubits in the presence of a dephasing interaction with a correlated environment. Such correlated reservoir introduces entanglement between physical qubits. We show that for short times the quantum error correction interprets such entanglement as errors and suppresses it. However for longer time, although quantum error correction is no longer able to correct errors, it enhances the rate of entanglement production due to the interaction with the environment.Comment: 7 pages, 3 figures, published versio
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