1,721,026 research outputs found
Variational approach to the soft-Coulomb potential in low-dimensional quantum systems
Full text linkThe variational method is used to obtain the ground-and first-excited states for the soft-Coulomb central potential, 1/root r(2) + d(2), characterized by a bias distance d, taken into account as a fixed parameter. Applications are presented for spatially indirect excitons, i.e., photo-generated electronhole (e-h) bound pairs, where the two charges are kept separated in two different regions of a heterostructure. We consider one-or two-dimensional systems, namely, quantum wires or wells, respectively, and compare the results with numerical calculations obtained by finite-difference diagonalization of the Hamiltonian. An explicit example is given for GaAs-based heterostructures. (C) 2017 American Association of Physics Teachers
How and to What Degree Does Physical Structure Differ Between Natural and Artificial Habitats? A Multi-Scale Assessment in Marine Intertidal Systems
Full text linkMarine infrastructures are increasing, generating a variety of impacts and introducing artificial habitats which have low ecological value and support assemblages that differ significantly from those on natural rocky coasts. While in the past there was little ecological consideration as to how artificial structures were built, now the trend is to look for “greener” designs inspired by or mimicking nature. These greening efforts have had a strong focus on enhancing physical habitat structure to support more diverse assemblages, driven by the untested assumption that artificial habitats lack the physical structure proper to natural habitats. We tested this assumption by comparing five descriptors of physical structure (inclination; exposure; roughness; abundance, and diversity of surface morphological microelements) across a combination of natural and artificial habitats of regular and irregular morphologies (seawalls = artificial regular; cliffs = natural regular; breakwaters = artificial, irregular; and boulder fields = natural irregular) in the North Adriatic Sea. Most structural descriptors were similar between artificial and natural habitats. Only inclination was consistently steeper in the artificial than in the natural habitats. Other minor differences in roughness or in the abundance of some surface microelements were related to the general morphology (regular or irregular) of the habitat rather than to its artificial or natural identity. The outcomes challenge the widespread assumption that artificial habitats lack the physical structure proper to natural habitats and stimulate renewed consideration about other structural and non-structural elements that could enhance the performance and sustainability of artificial marine structures, such as construction material, environmental setting or maintenance. They also encourage a wider reflection about what makes an artificial building surface “greener”: structural complexity is an important ecological parameter, and its deliberate increase will lead to responses in the biota, however, this may not necessarily match “more natural” conditions
Effects of different culture conditions and leptin on GH mRNA expression and GH secretion by pig pituitary cells.
No full textGrowth hormone (GH) is enhanced in malnutrition; physiological increments in GH secretion seem to play an important role in regulating metabolism during fasting. Leptin has also been shown to play a role, amongst others, in modulating the somatotropic axis. In this study, we investigated how the composition of culture media could influence basal and leptin-stimulated GH secretion and expression in pig pituitary cells. Pituitary cells from 8-month-old sows were incubated for 48 h in presence and absence of 10% fetal calf serum, either in DMEM/Ham's F12, in arginine-free DMEM/Ham's F-12, or in DMEM/Ham's F12 Salts. Cells were then treated for 24 h with GHRH or recombinant human leptin (rhLep) individually or in association with GHRH; cell proliferation, nitric oxide (NO) production and GH expression and secretion were determined. The absence of nutritional factors induced a decrease in cell proliferation, but stimulated both GH secretion and expression. Furthermore, rhLep significantly increased GH expression and secretion irrespective of culture conditions. NO production was only significantly enhanced by leptin under DMEM/Ham's F12 culture conditions. These observations lead us to hypothesize that the adaptive capabilities of pituitary cells may overcome the negative effects of undernutrition; in this context, leptin does not seem to depend on NO pathways in modulating GH secretion
Effects of gonadal steroids on tonic luteinizing hormone (LH) release and luteinizing hormone-releasing hormone-induced LH release from bovine pituitary cells cultured in vitro
No full textThe objective of this study was to investigate the direct effect of estradiol-17β (E2) and progesterone (P4) on LH release by pituitary cells of midluteal phase cows in vitro. Pituitaries were collected at the slaughterhouse; cells were dissociated with collagenase and hyaluronidase and maintained in a static culture system in Medium 199 (M199). Various concentrations of E2 (0.1-100 nM) and P4 (0.1 and 10 nM) were used to stimulate the cells for 2, 4, 6, 15, 24, 48, or 72 h. In addition, the synergistic action of E2 and P4 was investigated by exposure of the cells to a combination of the two hormones. At the end of each incubation, the cells were challenged with LHRH (1 nM) for 2 h. The medium was collected for LH analysis at the end of each incubation period and after the LHRH challenge; furthermore, intracellular LH content was quantified at the end of each experiment. The results indicate a positive action of E2 on basal release of LH beginning after 15 h of exposure (p < 0.01). LHRH-induced LH release was modulated by E2 in a time-dependent manner with an effect at first inhibitory, then stimulatory, and finally inhibitory again (p < 0.04). P4 alone did not affect LH release, but it negatively influenced LHRH- induced LH release. P4 also exerted a positive action on intracellular LH after 6 h of incubation. A substantial inhibitory effect (p < 0.001) on both tonic LH release and LHRH-induced LH release was observed in cells exposed for 16 h to P4 after a priming with E2 for 4 h. These data clearly demonstrate that both ovarian steroids are effective in influencing LH secretion by acting directly at the pituitary level
Transport coefficients from equilibrium molecular dynamics
Full text linkThe determination of transport coefficients through the time-honored Green-Kubo theory of linear response and equilibrium molecular dynamics requires significantly longer simulation times than those of equilibrium properties while being further hindered by the lack of well-established data-analysis techniques to evaluate the statistical accuracy of the results. Leveraging recent advances in the spectral analysis of the current time series associated with molecular trajectories, we introduce a new method to estimate the full (diagonal as well as off-diagonal) Onsager matrix of transport coefficients from a single statistical model. This approach, based on the knowledge of the statistical distribution of the Onsager-matrix samples in the frequency domain, unifies the evaluation of diagonal (conductivities and viscosities) and off-diagonal (e.g., thermoelectric) transport coefficients within a comprehensive framework, significantly improving the reliability of transport coefficient estimation for materials ranging from molten salts to solid-state electrolytes. We validate the accuracy of this method against existing approaches using benchmark data on molten cesium fluoride and liquid water and conclude our presentation with the computation of various transport coefficients of the Li3PS4 solid-state electrolyte. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Effetti dell’insulina sulla produzione basale di progesterone e sulla risposta al testosterone in cellule della granulosa suine.
No full textCorrigendum to “Presence and function of kisspeptin/KISS1R system in swine ovarian follicles” (Theriogenology (2018) 115 (1–8), (S0093691X1830147X), (10.1016/j.theriogenology.2018.04.006))
No full textThe authors regret the following changes to the author group G. Basinia, F. Grassellia, S. Bussolatia, R. Ciccimarraa, M. Maranesib, A. Bufalarib, C. Dall'Agliob, F. Parilloc,#, M. Zeranib,c,*. a Dipartimento di Scienze Mediche Veterinarie, Università di Parma, 43126 Parma, Italy. b Dipartimento di Medicina Veterinaria, Università di Perugia, 06126 Perugia Italy. c Scuola di Bioscienze e Medicina Veterinaria, Università di Camerino, 62024 Matelica Italy. # Deceased. * Corresponding author: tel.: +39 0755857642; fax +39 0755857654. E-mail address: [email protected] (M. Zerani). And to the acknowledgements and figures
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