1,401 research outputs found

    Lagrangian description of Heisenberg and Landau-von Neumann equations of motion

    Full text link
    An explicit Lagrangian description is given for the Heisenberg equation on the algebra of operators of a quantum system, and for the Landau-von Neumann equation on the manifold of quantum states which are isospectral with respect to a fixed reference quantum state.Comment: 13 page

    Transparency, Expectations Anchoring and Inflation Target

    Get PDF
    In various speeches, former Fed Chairman Ben Bernanke contrasted the proposal of setting a higher inflation target by claiming that it could unanchor inflation expectations. A standard New Keynesian framework with learning supports this claim both asymptotically, because a higher inflation target shrinks the E-stability region when a central bank follows a Taylor rule, and in the transition phase, because a higher inflation target slows down the speed of convergence of expectations. Transparency helps anchoring expectations. However, the importance of being transparent diminishes with the level of the inflation target. Finally, the higher the inflation target, the more policy should respond to inflation and the less to output to guarantee E-stability. Hence, a policy that increases both the inflation target and the monetary policy response to output would be \u201creckless\u201d

    Experimental Evidence and Clinical Implications of Pituitary Adenoma Stem Cells

    Get PDF
    Pituitary adenomas, accounting for 15% of diagnosed intracranial neoplasms, are usually benign and pharmacologically and surgically treatable; however, the critical location, mass effects and hormone hypersecretion sustain their significant morbidity. Approximately 35% of pituitary tumors show a less benign course since they are highly proliferative and invasive, poorly resectable, and likely recurring. The latest WHO classification of pituitary tumors includes pituitary transcription factor assessment to determine adenohypophysis cell lineages and accurate designation of adenomas, nevertheless little is known about molecular and cellular pathways which contribute to pituitary tumorigenesis. In malignant tumors the identification of cancer stem cells radically changed the concepts of both tumorigenesis and pharmacological approaches. Cancer stem cells are defined as a subset of undifferentiated transformed cells from which the bulk of cancer cells populating a tumor mass is generated. These cells are able to self-renew, promoting tumor progression and recurrence of malignant tumors, also conferring cytotoxic drug resistance. On the other hand, the existence of stem cells within benign tumors is still debated. The presence of adult stem cells in human and murine pituitaries where they sustain the high plasticity of hormone-producing cells, allowed the hypothesis that putative tumor stem cells might exist in pituitary adenomas, reinforcing the concept that the cancer stem cell model could also be applied to pituitary tumorigenesis. In the last few years, the isolation and phenotypic characterization of putative pituitary adenoma stem-like cells was performed using a wide and heterogeneous variety of experimental models and techniques, although the role of these cells in adenoma initiation and progression is still not completely definite. The assessment of possible pituitary adenoma-initiating cell population would be of extreme relevance to better understand pituitary tumor biology and to identify novel potential diagnostic markers and pharmacological targets. In this review, we summarize the most updated studies focused on the definition of pituitary adenoma stem cell phenotype and functional features, highlighting the biological processes and intracellular pathways potentially involved in driving tumor growth, relapse, and therapy resistance

    The Geometry of the solution space of first order Hamiltonian field theories III: Palatini's formulation of General Relativity

    Full text link
    We complete the program started in two companion papers of defining a Poisson bracket structure on the space of solutions of the equations of motion of first order Hamiltonian field theories. The case of General Relativity is addressed by looking at it as a particular non-Abelian gauge theory in a suitable low-energy limit and via a technique related to the coisotropic embedding theorem

    The Geometry of the solution space of first order Hamiltonian field theories I: from particle dynamics to free Electrodynamics

    Full text link
    We analyse the problem of defining a Poisson bracket structure on the space of solutions of the equations of motions of first order Hamiltonian field theories. The cases of Hamiltonian mechanical point systems (as a (0 + 1)-dimensional field) and more general field theories without gauge symmetries are addressed by showing the existence of a symplectic (and, thus, a Poisson) structure on the space of solutions. Also the easiest case of gauge theory, namely free electrodynamics, is considered: within this problem, a pre-symplectic tensor on the space of solutions is introduced, and a Poisson structure is induced in terms of a flat connection on a suitable bundle associated to the theory

    Emerging Role of Cellular Prion Protein in the Maintenance and Expansion of Glioma Stem Cells

    Get PDF
    Cellular prion protein (PrPC) is a membrane-anchored glycoprotein representing the physiological counterpart of PrP scrapie (PrPSc), which plays a pathogenetic role in prion diseases. Relatively little information is however available about physiological role of PrPC. Although PrPC ablation in mice does not induce lethal phenotypes, impairment of neuronal and bone marrow plasticity was reported in embryos and adult animals. In neurons, PrPC stimulates neurite growth, prevents oxidative stress-dependent cell death, and favors antiapoptotic signaling. However, PrPC activity is not restricted to post-mitotic neurons, but promotes cell proliferation and migration during embryogenesis and tissue regeneration in adult. PrPC acts as scaold to stabilize the binding between dierent membrane receptors, growth factors, and basement proteins, contributing to tumorigenesis. Indeed, ablation of PrPC expression reduces cancer cell proliferation and migration and restores cell sensitivity to chemotherapy. Conversely, PrPC overexpression in cancer stem cells (CSCs) from dierent tumors, including gliomas\u2014the most malignant brain tumors\u2014is predictive for poor prognosis, and correlates with relapses. The mechanisms of the PrPC role in tumorigenesis and its molecular partners in this activity are the topic of the present review, with a particular focus on PrPC contribution to glioma CSCs multipotency, invasiveness, and tumorigenicity

    Intraoperative sonography for nonpalpable breast lesions: Additional indications for a consolidate technique.

    Get PDF
    This prospective study evaluated the intraoperative ultrasound scan (IUSS) for nonpalpable breast lesions' detection. A total of 108 consecutive female patients underwent surgery using IUSS: Frozen sections demonstrated clear margins in 95.5% of neoplastic patients. Only four (4.5%) patients underwent local re-excision in the same operation. IUSS demonstrated to be quick, accurate, useful, effective, and safe for the intraoperative management of neoplastic nonpalpable breast lesions when performed by a surgeon who has undergone US training, particularly for people in whom alternative approaches can show some limitations due to contraindications or because of scheduling constraints, costs, and patient discomfort

    Neurodegeneration in Alzheimer Disease: Role of Amyloid Precursor Protein and Presenilin 1 Intracellular Signaling

    Get PDF
    Alzheimer disease (AD) is a heterogeneous neurodegenerative disorder characterized by (1) progressive loss of synapses and neurons, (2) intracellular neurofibrillary tangles, composed of hyperphosphorylated Tau protein, and (3) amyloid plaques. Genetically, AD is linked to mutations in few proteins amyloid precursor protein (APP) and presenilin 1 and 2 (PS1 and PS2). The molecular mechanisms underlying neurodegeneration in AD as well as the physiological function of APP are not yet known. A recent theory has proposed that APP and PS1 modulate intracellular signals to induce cell-cycle abnormalities responsible for neuronal death and possibly amyloid deposition. This hypothesis is supported by the presence of a complex network of proteins, clearly involved in the regulation of signal transduction mechanisms that interact with both APP and PS1. In this review we discuss the significance of novel finding related to cell-signaling events modulated by APP and PS1 in the development of neurodegeneration

    Soil bacterial community response to differences in agricultural management along with seasonal changes in a Mediterranean region

    Get PDF
    Land-use change is considered likely to be one of main drivers of biodiversity changes in grassland ecosystems. To gain insight into the impact of land use on the underlying soil bacterial communities, we aimed at determining the effects of agricultural management, along with seasonal variations, on soil bacterial community in a Mediterranean ecosystem where different land-use and plant cover types led to the creation of a soil and vegetation gradient. A set of soils subjected to different anthropogenic impact in a typical Mediterranean landscape, dominated by Quercus suber L., was examined in spring and autumn: a natural cork-oak forest, a pasture, a managed meadow, and two vineyards (ploughed and grass covered). Land uses affected the chemical and structural composition of the most stabilised fractions of soil organic matter and reduced soil C stocks and labile organic matter at both sampling season. A significant effect of land uses on bacterial community structure as well as an interaction effect between land uses and season was revealed by the EP index. Cluster analysis of culture-dependent DGGE patterns showed a different seasonal distribution of soil bacterial populations with subgroups associated to different land uses, in agreement with culture-independent T-RFLP results. Soils subjected to low human inputs (cork-oak forest and pasture) showed a more stable bacterial community than those with high human input (vineyards and managed meadow). Phylogenetic analysis revealed the predominance of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes phyla with differences in class composition across the site, suggesting that the microbial composition changes in response to land uses. Taken altogether, our data suggest that soil bacterial communities were seasonally distinct and exhibited compositional shifts that tracked with changes in land use and soil management. These findings may contribute to future searches for bacterial bio-indicators of soil health and sustainable productivity. X Maite Sampedro Pellicer, Affiliation: ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) Casaccia Research Center, Technical Unit for Sustainable Development and Innovation of Agro-Industrial System, Rome, Italy X Maria Cristiana Papaleo, Affiliation: Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Florence, Italy X Alessio Mengoni, Affiliation: Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Florence, Italy X Luigi Ledda, Affiliation: Dipartimento di Agraria, University of Sassari, Sassari, Italy X Renato Fani, Affiliation: Laboratory of Microbial and Molecular Evolution, Department of Biology, University of Florence, Florence, Italy X Anna Benedetti, Affiliation: Consiglio per la Ricerca e la Sperimentazione in Agricoltura - Research Centre for the Soil-Plant System, Rome, Italy X Claudia Dalmastr
    corecore