1,723,072 research outputs found
The Evolution of Extracellular Hemoglobins of Annelids, Vestimentiferans, and Pogonophorans.
No full textThe evolution of extracellular hemoglobins of annelids, vestimentiferans, and pogonophorans was investigated by applying cladistic and distance-based approaches to reconstruct the phylogenetic relationships of this group of respiratory pigments. We performed this study using the aligned sequences of globin and linker chains that are the constituents of these complex molecules. Three novel globin and two novel linker chains of Sabella spallanzanii described in an accompanying paper (Pallavicini, A., Negrisolo, E., Barbato, R., Dewilde, S., Ghiretti-Magaldi, A., Moens, L., and Lanfranchi, G. (2001) J. Biol. Chem. 276, 26384--26390) were also included. Our results allowed us to test previous hypotheses on the evolutionary pathways of these proteins and to formulate a new most parsimonious model of molecular evolution. According to this novel model, the genes coding for the polypeptides forming these composite molecules were already present in the common ancestor of annelids, vestimentiferans, and pogonophorans
The predicted metallicity distribution of stars in dwarf spheroidal galaxies
No full textWe predict the metallicity distribution of stars and the ageÐmetallicity relation for six dwarfspheroidal (dSph) galaxies of the Local Group by means of a chemical evolution model thatis able to reproduce several observed abundance ratios, and the present-day total mass andgas content of these galaxies. The model adopts up-to-date nucleosynthesis and takes into
account the role played by supernovae of different types (II, Ia) allowing us to follow indetail the evolution of several chemical elements (H, D, He, C, N, O, Mg, Si, S, Ca and
Fe). Each galaxy model is specified by the prescriptions of the star formation rate and by
the galactic wind effciency chosen to reproduce the main features of these galaxies. These
quantities are constrained by the star formation histories of the galaxies as inferred by the
observed colourÐmagnitude diagrams (CMD). The main conclusions are: (i) Þve of the six
dSph galaxies are characterized by very low star formation efÞciencies ( 0.005Ð0.5 Gyr1)
with only Sagittarius having a higher one ( 1.0 Ð5.0 Gyr1); (ii) the wind rate is proportional
to the star formation rate and the wind efÞciency is high for all galaxies, in the range i
6Ð15; (iii) a high wind efÞciency is required in order to reproduce the abundance ratios and
the present-day gas mass of the galaxies; (iv) the predicted ageÐmetallicity relation implies
that the stars of the dSphs reach solar metallicities in a time-scale of the order of 2Ð6 Gyr,
depending on the particular galaxy; (v) the metallicity distributions of stars in dSphs exhibit
a peak around [Fe/H] 1.8 to 1.5 dex, with the exception of Sagittarius, which shows a
peak around [Fe/H] 0.8 dex; (iv) the predicted metallicity distributions of stars suggest
that the majority of stars in dSphs are formed in a range of metallicity in agreement with the
one of the observed stars
Pressor responses to hyperventilation in normotensive and hypertensive elderly subjects.
No full textBackground: Recently we showed that the hyperventilation test induces different blood pressure (BP) responses both in healthy subjects and patients with essential hypertension. Aim: We evaluated whether pressor responses to hyperventilation change with aging in normotensive and hypertensive subjects and whether they are related to the daytime pressor profile. Methods: Forty-three elderly normotensive subjects and 94 elderly hypertensive patients (45 with essential hypertension and 49 with secondary hypertension) underwent five minutes of forced hyperventilation and daily ambulatory BP monitoring. Results: Hyperventilation did not significantly change BP in normotensive subjects and secondary hypertensive patients, whereas it decreased (p<0.01) BP in essential hypertensive patients. Hierarchical cluster analysis based on BP responses to hyperventilation disclosed three groups of subjects in each studied population: group 1 exhibited a reduction (p<0.05) in BP (prevalent in essential hypertensives, 76 %), group 2 no change (prevalent in normotensives, 70 %, and in secondary hypertensives, 76 %), and group 3 an increase (p<0.05). Pressor daytime profiles of hypertensive patients showed significant differences according to pressor responses to hyperventilation. In group 1 patients the peak ambulatory SBP correlated (p<0.01) to the pre-hyperventilation SBP, whereas in group 3 it correlated (p<0.01) to the hyperventilation peak SBP. Group 2 did not show major daily BP fluctuations. Conclusions: 1) Aging decreases reactivity to the effects of respiratory alkalosis in elderly normotensive subjects; 2) hyperventilation induces significant pressor changes overall in essential hypertension; 3) the significant pressor responses to hyperventilation reflect the daytime pressor profiles predicting the highest daily fluctuations of BP values
Chemical evolution models for local group dwarf spheroidal galaxies: the evolution of Fe-peak elements
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A device for the skin-contact thermal resistance measurement
No full textThe skin-contact thermal resistance is a parameter that allows evaluating, in steady condition, the heat flow at the interface between the skin and a rigid surface at a known temperature. At the current state of the art, it is evaluated with empirical equations and is known to be dependent on the contact pressure, on the surface characteristics, and on the skin conductivity. The need to measure skin and contact thermal resistance with low uncertainty led to the realization of the device described in this paper. The instrumentbased on the principle of the thermoflowmeterhas been designed with the goal of minimizing the measurement uncertainty with contact temperatures ranging between 12 C° and 27° and contact areas from 50 to 314 mm2. The device allows varying and controlling the interface pressure and temperature that, according to existing literature studies, are likely to influence the skin thermal properties. The different temperatures needed for the evaluation of the thermal resistance are measured with individually calibrated thermocouples. The metrological characterization of the flowmeter was performed under vacuum, and the effect of convective heat exchanges in normal operation was modeled and compensated. Measurement repeatability and reproducibility were assessed by measuring the thermal resistance of plastic materials in operational conditions. Preliminary tests showed that the skin-contact thermal resistances measured in different conditions are compatible with the theoretically evaluated ones, with improvement in uncertainty due to direct measurement. © 2006 IEEE
Deindustralizzazione: un problema complesso
No full textCon il termine “deindustrializzazione” si fa usualmente riferimento ad un complesso di processi di natura economica, produttiva, urbanistica e territoriale relativi alla riduzione o all’annullamento delle attività industriali in una società o in una parte di essa. Gli equilibri economici, nella modernità post-industriale, cambiano, portando «Stati Uniti ed Europa Occidentale iniziano a conoscere l’emorragia di decine di milioni di posti di lavoro, il collasso della partecipazione sindacale, la minaccia di sparizione di un intero progetto sociale e di un sistema di vita» (Garruccio, 2016, p.37-38).
Per far fronte al processo di trasformazione post-industriale che vede protagonista il panorama alpino, l’Unione Europea ha predisposto, come vedremo, una serie di accordi di cooperazione transnazionale tra i sette stati alpini. Progetti come trAILs hanno l’obiettivo di analizzare gli effetti della deindustrializzazione in aree distanti dai grandi centri urbani – qui segnatamente montani e, ancor più alpini – così da mettere in luce le difficoltà e le esigenze di una periferia (a tratti) abbandonata a sé stessa, così come le comunità che la popolano. Per la sua complessità intrinseca, il processo di significazione della montagna deve necessariamente passare attraverso il filtro dell’immaginario collettivo di coloro che, nel corso delle varie epoche, si sono affacciati ad essa (Salgaro, 2003): i pendii montani diventano prima luogo di scontro per la ridefinizione dei confini territoriali e il controllo delle risorse; poi, con il processo di industrializzazione e la progressiva perdita di peso del settore primario (in termini di valore aggiunto al Pil) diventano aree per l’insediamento di attività industriali di base, estrattive o energetiche, assecondando i processi economici globali , o aree prede dello spopolamento. In altre parole, qual è l’immaginario nel quale le comunità alpine si identificano? Qual è il “futuro possibile” che, oggi, anima queste collettività
The Rise of a New Discipline to Manage Metropolitan Urban Systems
No full textToday’s cities are facing a moment of both maximum growth and maximum vulnerability at the same time as increasing inequality and climate change. At this pace, many cities will become metropolises by the end of the century. Governance mechanisms need to be created that ensure integral solutions
for the quality of life of future generations. However, decision-makers are organized in a sectoral way and territories are subdivided into multiple jurisdictions and levels of government. In order to migrate toward good metropolitan governance, it is necessary to train a new generation of leaders in
understanding metropolitan issues and create a sense of belonging for people in a metropolis. A new metropolitan discipline able to synthesize the knowledge required to operate in this environment is imperative
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