1,721,073 research outputs found
The multifaceted aspects of stress
No full textThe effects of stress depend on the nature and duration of the exposure, with the triggering of
molecular mechanisms that allow individuals to react to the stressful context. In particular, while
acute stress induces the activation of circuits to ensure normal homeostasis and mediates
adaptive responses, chronic stress exposure has detrimental and long-lasting effects on brain
unctions. Indeed, chronic stressful life events act as precipitating factors for many psychiatric
conditions, including major depressive disorders. In this context, it is worthy of mention that there
are differences in individual susceptibility, with some people displaying vulnerability to stressful
events and others being resilient to the same adversities. Moreover, exposure to chronic adverse
situations may leave permanent ‘scars’ in the individual, which confer enhanced vulnerability forrelapse since it is possible that not all the systems impaired by chronic stress are restored during
the remission.
On these bases, it is fundamental to better understand the behavioral outcomes of stressful
events as well as the molecular changes that may sustain them for the discovery of novel
therapeutic targets and approaches to treat stress-related disorders and to promote resilience
Femtomagnetism in graphene induced by core level excitation of organic adsorbates
No full textWe predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core
level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is no more magnetic. [1]
[1] A. Ravikumar, A. Baby, H. Lin, G. P. Brivio, and G. Fratesi, Scientific Reports 6, Article number: 24603
(2016) doi:10.1038/srep2460
Principi e metodi di Telerilevamento
No full textNel panorama italiano mancava un'opera dedicata al Telerilevamento totalmente frutto del lavoro di ricerca italiano. Gli autori, studiosi di fama nazionale ed internazionale, prendendo spunto dal trentennale della messa in orbita del primo satellite per l'osservazione della Terra, il Landsat-I, hanno ritenuto opportuno proporre quest'opera di alto valore scientifico. Si tratta di un volume in cui la disciplina del Telerilevamento è descritta con estremo rigore, avendo l'ambizione di fornire un punto di riferimento durevole nel tempo; l'attenzione è rivolta agli aspetti teorici e metodologici della disciplina per evitare, nel continuo susseguirsi di nuove proposte tecnologiche, sia come strumenti di acquisizione che di elaborazione delle informazioni, una sua rapida obsolescenza. Il testo quindi costituisce un'opera di base nella cultura tecnico-scientifica italiana, adatto sia all'ambiente universitario sia ai tecnici operanti nel settore
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Substrate induced ultrafast electron injection dynamics at organic-graphene interfaces
No full textElectron core-level spectroscopies can effectively be used to investigate electron transfer rates at organic/inorganic interfaces occurring within few femtoseconds. The core-level excitation at an adsorbed molecule strongly perturbs the system and calls for a proper theoretical description. On the other hand it induces novel phenomena such as backward electron transfer (substrate-to-molecule) as we measure by X-ray resonant photoemission and calculate by a theoretical framework based on density-functional theory (DFT) [1]. The rates can be controlled by varying molecular properties like the adsorption angle [2], as well as by tailoring the substrate like we show here for molecules on graphene.
N1s core excitation induces ultrafast electron transfer (τ=4fs) for bipyridine molecules on epitaxial graphene/Ni(111), which is characterized by a strong hybridization between C and metal states. We demonstrate that this interface can be decoupled by the addition of a second layer of graphene, so that the one in contact with the molecule is less hybridized with Ni underneath. In that case, transfer rates decrease by about one order of magnitude in the experiments and in the simulations, whereas no transfer is in principle expected for molecules on freestanding graphene within the current description.
[1] G. Fratesi, C. Motta, M. I. Trioni, G. P. Brivio, and D. Sánchez-Portal, J. Phys. Chem. C 118 (2014) 8775
[2] D. Cvetko, G. Fratesi, G. Kladnik, A. Cossaro, G.P. Brivio, L. Venkataraman, and A. Morgante, Phys. Chem. Chem. Phys. 18 (2016) 2214
Alterations in local protein synthesis are associated with cognitive impairment in chronically stressed rats
No full textDepression is a complex and heterogeneous disorder that represents a major cause of disability in the world.
With this respect, cognitive deterioration is a major problem that can interfere with all areas of a person’s life, including work, school and their relationships.
On these bases, it is important to characterize cognitive dysfunctions within the context of a depressive phenotype in order to identify the underlying systems, which may represent an important target for drug intervention. To this aim, adult male Wistar rats were exposed to chronic mild stress (CMS), a well-established model of depression, for 7 weeks before being tested in the novel object recognition (NOR). The animals were then sacrificed immediately after the end of the test session for the molecular analyses.
The behavioral analysis shown that both the anhedonic and the resilient animals developed impairments in the cognitive performance as indicated by the reduction of the discrimination index in the NOR test.
At molecular level, we first investigated the activity-regulated genes (Arc) and the neural PAS domain 4 (Npas4) in the dorsal hippocampus and we found that their expression was markedly increased after the NOR, in control as well as in CMS rats. Among the mechanisms involved in the stress response but also in memory and cognitive functions, we decided to focus on the de-novo protein synthesis at synaptic levels.
We investigated the role of NMDA/mTOR activation as fundamental regulators of the initiation as well as of the elongation step.
We found that in the crude membrane fraction, the phosphorylation of the NMDA subunit GluN2B at the serine 1303 was significantly increased in control rats exposed to NOR, but not in CMS rats. Accordingly, pmTOR (Ser2448), a downstream target of the NMDA receptor, was similarly upregulated after the test in normal animals, but not in those exposed to the chronic stress.
Next, we measured one of the element involved in the protein synthesis, namely eukaryotic elongation factor 2 (eEF2) and we found an increase in the ratio of the peEF2/eEF2 after the NOR in control animals but not in those exposed to the CMS paradigm, suggesting a shift from the general translation to the translation of specific mRNA containing the upstream open reading frame (uORF).
We believe that the different modulation of these molecular players may contribute to the cognitive impairment observed in CMS rats. On these bases, pharmacological intervention able to correct these alterations might ameliorate functions that are deteriorated in patients with major depression and stress-related disorders
Alterations in local protein synthesis are associated with cognitive impairment in chronically stressed rats
No full textDepression is a complex and heterogeneous disorder that represents a major cause of disability in the world.
With this respect, cognitive deterioration is a major problem that can interfere with all areas of a person’s life, including work, school and their relationships.
On these bases, it is important to characterize cognitive dysfunctions within the context of a depressive phenotype in order to identify the underlying systems, which may represent an important target for drug intervention. To this aim, adult male Wistar rats were exposed to chronic mild stress (CMS), a well-established model of depression, for 7 weeks before being tested in the novel object recognition (NOR). The animals were then sacrificed immediately after the end of the test session for the molecular analyses.
The behavioral analysis shown that both the anhedonic and the resilient animals developed impairments in the cognitive performance as indicated by the reduction of the discrimination index in the NOR test.
At molecular level, we first investigated the activity-regulated genes (Arc) and the neural PAS domain 4 (Npas4) in the dorsal hippocampus and we found that their expression was markedly increased after the NOR, in control as well as in CMS rats. Among the mechanisms involved in the stress response but also in memory and cognitive functions, we decided to focus on the de-novo protein synthesis at synaptic levels.
We investigated the role of NMDA/mTOR activation as fundamental regulators of the initiation as well as of the elongation step.
We found that in the crude membrane fraction, the phosphorylation of the NMDA subunit GluN2B at the serine 1303 was significantly increased in control rats exposed to NOR, but not in CMS rats. Accordingly, pmTOR (Ser2448), a downstream target of the NMDA receptor, was similarly upregulated after the test in normal animals, but not in those exposed to the chronic stress.
Next, we measured one of the element involved in the protein synthesis, namely eukaryotic elongation factor 2 (eEF2) and we found an increase in the ratio of the peEF2/eEF2 after the NOR in control animals but not in those exposed to the CMS paradigm, suggesting a shift from the general translation to the translation of specific mRNA containing the upstream open reading frame (uORF).
We believe that the different modulation of these molecular players may contribute to the cognitive impairment observed in CMS rats. On these bases, pharmacological intervention able to correct these alterations might ameliorate functions that are deteriorated in patients with major depression and stress-related disorders
Non Parametric Statistical Tests for the Analysis of Multiple-sensor Time Series of Remotely Sensed Data
No full text- …
