74 research outputs found
A High-Order Conservative Semi-Lagrangian Solver for 3D Free Surface Flows with Sediment Transport on Voronoi Meshes
No full textIn this paper, we present a conservative semi-Lagrangian scheme designed for the numeri
cal solution of 3D hydrostatic free surface flows involving sediment transport on unstructured Voronoi meshes. A high-order reconstruction procedure is employed for obtaining a piecewise polynomial representation of the velocity field and sediment concentration within each control volume. This is subsequently exploited for the numerical integration of the Lagrangian trajectories needed for the discretization of the nonlinear convective and viscous terms. The presented method is fully conservative by construction, since the transported quantity or the vector field is integrated for each cell over the deformed volume obtained at the foot of the characteristics that arises from all the vertexes defining the computational element. The semi-Lagrangian approach allows the numerical scheme to be unconditionally stable for what concerns the advection part of the governing equations.
Furthermore, a semi-implicit discretization permits to relax the time step restriction due
to the acoustic impedance, hence yielding a stability condition which depends only on the
explicit discretization of the viscous terms. A decoupled approach is then employed for the hydrostatic fluid solver and the transport of suspended sediment, which is assumed to be passive. The accuracy and the robustness of the resulting conservative semi-Lagrangian scheme are assessed through a suite of test cases and compared against the analytical solution whenever is known. The new numerical scheme can reach up to fourth order of accuracy on general orthogonal meshes composed by Voronoi polygons
A Join Operator for Property Graphs
No full textIn the graph database literature the term "join" does not refer to an operator combining two graphs, but involves path traversal queries over a single graph. Current languages express binary joins through the combination of path traversal queries with graph creation operations. Such solution proves to be not efficient. In this paper we introduce a binary graph join operator and a corresponding algorithm outperforming the solution proposed by query languages for either graphs (Cypher, SPARQL) and relational databases (SQL). This is achieved by using a specific graph data structure in secondary memory showing better performance than state of the art graph libraries (Boost Graph Library, SNAP) and database systems (Sparksee
Conditional deletion of TrkB alters adult hippocampal neurogenesis and anxiety-related behavior.
No full textBrain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which has been reported to regulate neurogenesis in the dentate gyrus, but the molecular control over this process remains unclear. We demonstrated that by activating TrkB receptor tyrosine kinase, BDNF controls the size of the surviving pool of newborn neurons at the time of connectivity. The TrkB-dependent decision regarding survival in these newborn neurons takes place at approximately four to six weeks of age. Before newborn neurons start to die they exhibit a drastic reduction in dendritic complexity and spine density, which may reflect a failure of these cells to integrate appropriately. Both the failure to become integrated, and subsequent dying, leads to impaired neurogenesisdependent plasticity and increased anxiety-like behavior in mice lacking a functional TrkB receptor in newborn neurons. Thus, our data demonstrate the importance of BDNF/TrkB signaling for the survival and integration of newborn neurons in the adult hippocampus and suggest a critical function of these neurons in regulating the anxiety state of the animal
Effect of pinching on structural resilience: performance of reinforced concrete and timber structures under repeated cycles
No full textThis article attempts to define pinching of two structural joints, reinforced concrete (RC) and wood ones. In particular, the research outlines differences and analogies between pinching of an RC portal and a Light Timber Frame (LTF) wall. This is done by focusing on the concavity of pinching in their response under repeated cycles, which produces differences in the energy dissipation. The response of the two structural archetypes under pseudo-static and dynamic simulations is analysed using the Atan hysteresis model modification. The truncated incremental dynamic analysis (TIDA) of the two systems modelled as single-degree-of-freedom (SDOF) oscillators yielded the fragility curves, approximated by a lognormal cumulative distribution (CDF). The stability of RC under repeated cycles reveals its significant resilience compared to LTF structures. The examination of the fragility functions supports a discussion about the relation between the pinching concavity and the notion of structural resilience by introducing a robustness index ranging from 0 to 1. Ultimately, a parametric analysis of a fictitious structural system derived from the timber one by varying the concavity of the pinching path leads to the estimation of the robustness index as a function of the pinching concavity
QuaranTalks. Dialoghi dalla quarantena di Bologna Business School
No full textI QuaranTalks sono stati un modo per riflettere in maniera agile e fresca sui temi più importanti di un periodo inatteso che entrerà nella storia, ma soprattutto un’occasione per stare insieme, anche se lontani. Sin dall’inizio del lockdown dovuto al Covid-19 abbiamo ricevuto moltissimi messaggi da parte dei nostri Alumni, sparsi nelle imprese di tutto il mondo, nei quali ricordavano il senso di comunità che si vive a Bologna Business School e chiedevano di restare in contatto, soprattutto in quel momento.
Alberto Forchielli - Stefano Domenicali - Alec Ross - Luciano Floridi - Francesco Stellacci, Gaetano Manfredi - Lucia Annunziata - Lorenzo Cherubini - Enrico Letta - Sergio Dompé - Mauro Porcini - Alon Wolf - Vincenzo Novari - Guido Barilla - Giampiero Maioli - Domenico De Masi - Brunello Cucinelli - Nicola Bertinelli - Alex Zanardi - Romano Prodi - Pier Luigi Celli - Giuseppe Cucchi - Stefano Bonaccini - Michele Antoniazzi - Francesco Micheli - Lorenzo Bonaccorsi - Salvatore Rossi - Paolo Scaroni - Vincenzo Paglia - Alessandro Chiesi - Carlo Bonanni - Emma Marcegaglia - Matteo Zuppi - Gabriel Sanchez Zinny - Gabriele Gravina - Michele Colajanni - Anna Ascani - Sabino Cassese - Fabiola Giannotti - Francesco Boccia - Eric Schmid
Bone defects in Shwachman-diamond Syndrome: cellular oe systemic impairment?
No full textBONE DEFECTS IN SHWACHMAN-DIAMOND SYNDROME: CELLULAR OR SYSTEMIC IMPAIRMENT?
Frattini A1, 2*, Villa I3, Valli R1, Montalbano G1, De Paoli E1, Bergami E4, Zecca M4, Pasquali F1, Maserati E1
1Human and Medical Genetics, Department of Clinical and Experimental Medicine, University of Insubria, Varese, Italy; 2 Institute of Genetic and Biomedical Research (IRGB), National Research Council (CNR), Milan, Italy; 3Bone Metabolism Unit, San Raffaele Scientific Institute, Milan, Italy, 4Oncoematologia Pediatrica, IRCCS Policlinico San Matteo, Pavia, Italy
Bone defects in Shwachman-Diamond syndrome (SDS) are characterized by abnormal development of growth plate and delay of secondary center of ossification that lead to a number of variable skeletal signs and early-onset low turnover osteoporosis.
The few amount of published data has not yet clarified if the SDS bone defect is systemic or cell-autonomous. The goal of our project is to investigate the physiopathology of SDS bone defects, by clarifying if they are due to a systemic imbalance of hormones and cytokines that regulate cartilage and bone formation or to an imbalance of adipogenesis versus osteoblastogenesis, as reported in the conditional sbds mouse model.
We obtained serum samples from blood of four Italian SDS patients, 3 male and 1 female (age 4-43 years) with a wide range of different skeletal manifestations. The importance of the GH/IGF1/PTH axis in skeletal growth is well known, whereas vitamin D plays an essential role in development and maintenance of a healthy mineralized skeleton. To define the possible role of a systemic defect we evaluated seric levels of Growth Hormone (GH), Insulin-Growth Factor 1 (IGF-1), Parathyroid Hormone (PTH), alkaline phosphatase (ALP), and Vitamin D.
Our preliminary results showed quite normal levels in all our patients; one patient had low level of vitamin D. The limited number of patients analyzed does not allow to draw definite conclusions, but we may speculate that either the SDS bone defect is not systemic or that the systemic impairment may be limited during the infancy affecting the development of cartilage but is not significant in the adult.
On the other hand, the bone defect may be due to an imbalance in differentiation of adipocytes vs osteoblasts (cell-autonomous defect): this study is in progress by the differentiation of mesenchymal stem cells obtained from bone marrow of SDS patients
TrkB signaling directs the incorporation of newly generated periglomerular cells in the adult olfactory bulb.
No full textIn the adult rodent brain, the olfactory bulb (OB) is continuously supplied with new neurons which survival critically depends on their successful integration into pre-existing networks. Yet, the extracellular signals that determine the selection which neurons will be ultimately incorporated into these circuits are largely unknown. Here, we show that immature neurons express the catalytic form of the brain-derived neurotrophic factor receptor TrkB [full-length TrkB (TrkB-FL)] only after their arrival in the OB, at the time when inte-gration commences. To unravel the role of TrkB signaling in newborn neurons, we conditionally ablated TrkB-FL in mice via Cre expression in adult neural stem and progenitor cells. TrkB-deficient neurons displayed a marked impairment in dendritic arborization and spine growth. By selectively manipulating the signaling pathways initiated by TrkB in vivo, we identified the transducers Shc/PI3K to be required for dendritic growth, whereas the activation of phospholipase C-was found to be responsible for spine formation. Further-more, long-term genetic fate mapping revealed that TrkB deletion severely compromised the survival of new dopaminergic neurons, leading to a substantial reduction in the overall number of adult-generated periglomerular cells (PGCs), but not of granule cells (GCs). Surprisingly, this loss of dopaminergic PGCs was mirrored by a corresponding increase in the number of calretinin PGCs, suggesting that distinct subsets of adult-born PGCs may respond differentially to common extracellular signals. Thus, our results identify TrkB signaling to be essential for balancing the incorporation of defined classes of adult-born PGCs and not GCs, reflecting their different mode of integration in the OB. © 2013 the authors
Polarized Expression of p75NTR Specifies Axons during Development and Adult Neurogenesis
No full textSummaryNewly generated neurons initiate polarizing signals that specify a single axon and multiple dendrites, a process critical for patterning neuronal circuits in vivo. Here, we report that the pan-neurotrophin receptor p75NTR is a polarity regulator that localizes asymmetrically in differentiating neurons in response to neurotrophins and is required for specification of the future axon. In cultured hippocampal neurons, local exposure to neurotrophins causes early accumulation of p75NTR into one undifferentiated neurite to specify axon fate. Moreover, knockout or knockdown of p75NTR results in failure to initiate an axon in newborn neurons upon cell-cycle exit in vitro and in the developing cortex, as well as during adult hippocampal neurogenesis in vivo. Hence, p75NTR governs neuronal polarity, determining pattern and assembly of neuronal circuits in adult hippocampus and cortical development.Video Abstrac
Relationship between Azithromycin and Cardiovascular Outcomes in Unvaccinated Patients With COVID-19 and Preexisting Cardiovascular Disease (vol 12, e028939, 2023)
No full textIn the article by Maria Bergami et al, “Relationship Between Azithromycin and Cardiovascular Outcomes in Unvaccinated Patients With COVID-19 and Preexisting Cardiovascular Disease,” which published online July 14, 2023 (J Am Heart Assoc. 2023;12:e028939. DOI: 10.1161/JAHA.122.028939) and appeared in the July 18, 2023 issue of the journal, a correction was needed. The incorrect academic degree was provided for author Natalia Fabin. The author’s degree has been corrected as follows: Natalia Fabin, MD. The authors regret the error. The correction has been made to the current online version of the article, which is available here: https://www. ahajournals.org/doi/10.1161/JAHA.122.028939
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