92 research outputs found
Involvement of epigenetic factors and metabolism in pluripotency maintenance in C. elegans
No full textDuring the development of multi-cellular organisms, cells undergo differentiation into
distinct cell types. Acquisition of different fates is a consequence of intermingled
multiple external stimuli (non cell autonomous) and internal events (cell autonomous).
The external stimuli include metabolism (in the sense of feeding) and contacts with
neighbouring cells which impact the cell context and modify its life history. This leads
to changes in chromatin organization and the accessibility of target genes to
transcription factors. Cell fate acquisition or differentiation is often a one-way path:
differentiated cells do not change fate. Recently however, the setup of the induction
of pluripotent stem cells (iPSCs) showed that differentiated cells can be
reprogrammed, based on the expression of specific transcription factors. IPSCs
formation correlates with heterochromatin loss.
In C. elegans, the absence of MES-2, the enzymatic core of the Polycomb complex
responsible for histone 3 lysine 27 (H3K27) methylation in heterochromatin, leads to
increased cell fate plasticity during embryonic development, measured as the
capacity to convert embryos into specific tissues by the ectopic expression of cell-fate
specifying transcription factors (cell fate challenge). Here we describe a controlled
cell fate challenge system using single copy transgenes, tractable in both embryonic
and larval stages. In embryos, similar results were obtained as for previous multicopy
arrays, with an extension of the plasticity window in the absence of H3K27
methylation. When muscle differentiation was induced in the first larval stage, worms
lacking H3K27me arrested their development, while an increased number of cells
expressing the muscle marker. Numerous non terminally differentiated lineages were
perturbed, including the V, M and P ones, mostly with unscheduled cell division.
Furthermore, ectopic muscle induction led to the division of bona fide muscle cells.
These organismal and cellular phenotypes could be rescued by knock-down of
multiple components of the Notch pathway, a cell-cell signalling pathway implicated
in asymmetric fate decisions. Interestingly, another regulator of plasticity appears to
be food availability, as starved animals are resistant to cell fate challenge. I showed
that the presence of food leads to visible reorganization of chromatin, potentially
rendering target sites accessible to the specifying transcription factors. The
presence/absence of food appear to be sensed and transduced by the insulin/insulinlike
pathway, as a daf-2 reduction of function mutation ablates the starvation-induced
cell fate challenge resistance. Although I cannot exclude the involvement of other
pathways, this work provides evidence for the function of external stimuli on cell
plasticity determination
Azienda agraria guerrieri: la forza della tradizione, il coraggio del cambiamento
No full textAzienda agraria guerrieri: la forza della tradizione, il coraggio del cambiament
ROAD SAFETY ANALYSIS USING ITALIAN GUIDELINES
No full textSafe road design is about providing a road environment which ensures vehicle speeds will be within the human tolerances
for serious injury and death wherever conflict points exist. International researchers have thus suggested a variety of approaches to
analyze the road traffic safety level as some procedures based on the valuation of the accident rates and accident frequency. The
research described in this paper aims to illustrate a network safety approach as suggested by Italian Guidelines in order to identify
homogeneous roadway segments where the crash rate (crash frequency over traffic exposure) is higher or lower than on statistically
significant thresholds referred to the whole analyzed road path. Three different road safety thresholds are suggested: a) low when the
crash rate is of less than lower limit, b) moderate when the crash rate falls between upper and lower limits, c) severe when the crash
rate is greater than the upper limit. It’s suggested an additional careful study on the road segments with high crash rate making a
comparison between existing and potential infrastructural-geometric-environmental failures to determine potential countermeasures.
The study presented here involved a rural road in Southern Italy located on flat/rolling area with a vertical grade of less than 6%,
without spiral transition curves between geometric tangent and circular elements, which is provided with controlled access or rather
road interchanges and 11 km almost of slow lane for both travel directions. The data set used for this study includes crashes from
2003 through 2010; in particular 301 crashes were observed with 444 injuries and 41 deaths over the total length of the 71.92 km.
Analysis showed that homogeneous road segments with high crash rates occurred in 16% of cases, while with medium crash rates in
38% of cases and low crash rates in 46% of cases
Safety Data Analysis: Case Study of State Highway "Tirrena Inferiore"
No full textThe road safety has become a priority field worldwide and one of the major factors describing the transport system’s state with its positive and negative changes. Many studies on driver speed behaviour are found in the scientific literature, and researchers have addressed roadway alignment consistency for travel safety in context with real operating speeds. This paper illustrates an experimental analysis conducted on the State Highway “Tirrenia Inferiore” in Southern Italy without spiral transition curves between geometric tangent and circular elements on the horizontal alignment, to check a new prediction consistency model. Two consistency measures were developed and compared with the results available in scientific literature: the first was the relative area bounded by the speed profile and the average weighted speed; the second was the standard deviation of operating speeds in each design element along the entire road investigated. Combining these two previous measures and following an extensive sensitivity analysis, a consistency model was developed and thresholds for good, acceptable and poor road consistency can be proposed. The consistency prediction model was related to numbers of crashes occurred from 2003 to 2010. It was found that as design consistency increased, number of crashes decrease significantly. Consistency model can be use for this purpose during the geometric design process or during the evaluation process for two-lane rural highways
Come le foglie
No full textFrancesca Favaro Vuoi ribellarti contro le foglie che il vento disperde? Trattienile se puoi. Hanno tanta grazia, e tanta eleganza, e non sai dove vanno a finire. (Giuseppe Giacosa, Come le foglie, Atto III, scena X) Due guerrieri si fronteggiano, sotto le mura di Ilio. Il loro sarà uno degli aristocratici duelli – singole, fulgide prove di coraggio – da cui sono intervallate più vaste battaglie. Si accingono allo scontro e l’uno, il greco Diomede, domanda all’altro, il Troiano, quale sia la ..
Elogio della poesia. Versi e saggi di Olga Sedakova. Traduzione e commento di Francesca Chessa
No full textI saggi, discorsi e versi di Olga Sedakova, selezionati in questo volume, offrono uno spaccato della Russia nel periodo sovietico tra il 1980 e il 1990. In questi scritti emerge sempre la poetessa che ne attende la fine e ne avverte prossimo il crollo. “Per Olga Sedakova, e con lei i poeti e gli artisti del disgelo chrušceviano, alla fine degli anni Sessanta essere contemporanei significò essere inattuali: esclusi dai circuiti ufficiali fin quasi alla perestrojka, esiliati nel loro proprio paese, scoprivano di avere insospettati compagni d’esilio nei grandi lirici russi del secolo d’argento e di essere contemporanei della tradizione lirica europea.” (Adalberto Mainardi). Il volume contiene un saggio autobiografico, una introduzione al suo Elogio della poesia. Inoltre tra i cicli poetici preferiti, il Viaggio in Cina e alcuni Saggi su Dante. Nella lettura di tre Canti dell’Inferno (c. XII-XIII-XIV), secondo Olga Sedakova, Dante ci presenta allegoricamente il sistema politico del suo tempo perché fosse possibile riconoscere i tiranni del nostro tempo, e di ogni tempo, prefigurati dai terribili assassini di quel cerchio. Ha scritto di lei la slavista americana Stephanie Sandler: “Esiste un poeta al mondo che in qualsiasi lingua raggiunga un equilibrio così perfetto tra la conoscenza profonda della tradizione e il coraggio nell'invenzione di una parola nuova? Olga Sedakova, in questo, non ha pari.”. Olga Sedakova (1949): oltre che poetessa moscovita, è docente alla Facoltà di Filosofia dell'Università Statale di Mosca “Lomonosov”, e membro dell’Accademia delle Scienze di Mosca. Attualmente in Italia collabora con l’Università Cattolica di Milano, con la Biblioteca Ambrosiana e con la Fondazione Russia Cristiana. Dal 2007, è Visiting professor nell’Università degli Studi di Sassari, a più riprese. Comunque, come premiatissima poetessa e come docente di grande erudizione, si ricollega alla eredità ed alla tradizione del pensiero russo, soprattutto quello del XX secolo in una sintesi letteraria e filosofica di vasto respiro.In Praise of Poetry, the autobiographical title essay here, is a wonderful introduction to Olga Sedakova the Russian poet, writer and witness to the decline, fall and aftermath of the Soviet period. Journey to a distant and enduringly noble place with her poem Chinese Journey. Experience the Power of Happiness. Accept a wonderful companion as you read Dante's Inferno XII-XIII-XIV. Visit Venice in memory of Brodsky. See an Elegy turn into a Requiem. Feel fortunate to have such a poet among us
Likelihood-type methods for comparing clustering solutions
No full textSelecting an optimal clustering solution is a longstanding problem. In
model-based clustering this amounts to choose the architecture of the model mixture
distribution. Decisions to be made pertain to: cluster prototype distribution; number of
mixture components; (optionally) restrictions on the clusters’ geometry. Classical pro-
posals address this issue via penalized model selection criteria based on the observed
likelihood function. In this study, we compare these techniques with the less explored
cross-validation alternative, which is rather popular for many other data-driven opti-
mized methods. We analyze both classical methods such as BIC, AIC, AIC3 and ICL,
and several cross-validation schemes where the risk is defined in terms of minus the
log-likelihood function. Selection methods are compared by using the Iris dataset
Molecular Cloning And Testicular Expression Of VIP In Different Phases Of The Reproductive Cycle Of The Wall Lizard Podarcis sicula
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