CamEPrints
Not a member yet
689 research outputs found
Sort by
Translation of Leaderless mRNAs and Structure of cspD mRNA in E. coli
No full textPart I: Translation of leaderless mRNA in E. coli\ud
Spedalieri G., Köhrer C., RajBhandary U.L.\ud
Leaderless mRNAs are present in all three domains of life.\ud
They do not have a 5’ untranslated region (5’UTR), they start directly with the initiation codon, AUG in most cases. In Escherichia coli these mRNAs are very rare and show inefficient translation. In contrast, leaderless mRNAs are quite prevalent in archaea, where they are translated as efficiently as the “leadered” mRNAs containing the typical Shine-Dalgarno sequence.\ud
In leaderless translation initiation 70S ribosomes are thought to be used without a typical pre-initiation complex involving a 30S ribosomal subunit. In this study, the goal is to answer two fundamental questions: (i) Is AUG strictly required as initiation codon? (ii) Is the formylmethionyl-tRNAfMet (fMet-tRNAfMet) required as initiator tRNA? Is the amino acid “methionine” important?\ud
Using a chloramphenicol acetyltransferase reporter system for studying in vivo translation of leaderless mRNAs in E. coli, we have found that the initiation codon AUG is not absolutely required and the amino acid “methionine” plays a fundamental role.\ud
\ud
Part II: Structural and functional characterization of\ud
cspD mRNA in Escherichia coli\ud
Gaetana Spedalieri, Anna Brandi and Anna Maria Giuliodori\ud
\ud
Expression of cspD, a gene belonging to the csp family of\ud
Escherichia coli, is exclusively induced at 37°C during\ud
stationary-phase or upon glucose starvation and does not increase during cold-shock. To shed light on the mechanisms responsible for the regulation of cspD expression, I have elucidated by enzymatic and chemical probing the secondary structure of cspD mRNA as a function of temperature. The structure, which was also validated by mutagenesis, demonstrates that cspD mRNA does not undergo any temperature-dependent structural rearrangement.\ud
Functional analyses suggest that the presence of a helix\ud
occluding the initiation codon might be partly responsible for the scarce translation of cspD mRNA and that RNase III is likely involved in the regulation of cspD gene expression. Overall, these data suggest that induction of cspD, like that of many other csp gene of E. coli, is controlled also at a posttranscriptional level
Study of growth rate of alkali feldspar in Phlegraean Fields trachytes
No full textThe aim of the work presented in this paper is to acquire experimental knowledge of the growth kinetics of alkali feldspar in Phlegraean Fields trachytic melts, with\ud
emphasis on magmas erupted in the Monte Nuovo event of 1538, to constrain system time scales of magmatic processes. Data on alkali feldspar crystallization kinetics in trachytic melts are totally absent from the available scientific literature.\ud
Starting from a trachytic composition coming from Phlegrean Fields, cooling and decompression experiments were performed at different condition of T and P and with\ud
different duration (crystallization time): experimental pressure varies between 30 and 200 MPa, temperature between 750 and 860°C, time between 7200 and 57600 seconds and\ud
fO2 = NNO + 0.8 (Di Matteo et al., 2004). For every series of decompression experiment with constant ∆T, we always performed an experiment where there was no decompression, to allow a comparison between the growth rate in decompressed experiments with the growth rate in the constant PH2O conditions.\ud
To obtain the dimensions of alkali feldspar crystals backscattered images were collected with the Scanning Electron Microscope (SEM) and were used to measure the\ud
length and the width of the crystals with Photoshop 7.0. A reasonable approximation for growth rate is to average the half-length of the ten longest alkali feldspar crystals in any experiment, as employed by Fenn (1977), Hammer & Rutherford (2002) and Couch (2002). The ratio between half-length and crystallization time (that is the duration of the\ud
experiment) is used to calculate the growth rate G.\ud
The crystal growth rate varies for cooling experiments from 3,6x10-8 to 3,9x10-7 cm/s, while for decompression experiments it varies from 1.4x10-8 to 1.6x10-7 cm/s. In\ud
both cases G is higher in experiments with lower duration, while it trends to decrease with increasing experimental duration.\ud
From the comparison between cooling and decompression growth rates we can see that the former are slightly lower than the latter. This is because the amount of dissolved\ud
water in the melt depends on the experimental starting pressure. In decompression experiments pressure is lowered and consequently the amount of dissolved water in the\ud
melt lowers as well, implying a lower mobility of cations and consequently a lower crystal growth rate.\ud
The estimate of alkali feldspar growth rate together with the study of the CSD (Crystal Size Distribution) is useful to determine residence and ascent times (t = -1/ Gs,\ud
where s is the slope of the CSD) of trachytic phlegraean magmas to forecast eruptive dynamics of volcanic events that can involve the area. The values of G presented here are the same (10-8 cm/s) or differ at the most of an order of magnitude (10-7 cm/s) from the growth rates used by Piochi et al., (2005) for Monte Nuovo, so the ascent time that will be calculated will be similar or lower than those estimated by Piochi et al., (2005)
Catalogo bibliografico web di Ateneo: estensione delle funzionalita'
Get PDFIl lavoro illustrato in questa tesi riguarda il progetto formativo da me sviluppato durante lo svolgimento di uno stage presso l’Area Biblioteche dell’Universita' degli\ud
Studi di Camerino.\ud
Il catalogo bibliografico web di Ateneo, modulo del software Aleph, ver. 18.1, e' uno strumento flessibile ed adattabile alle esigenze dell’utenza a cui viene proposto, il suo compito e' quello di gestire a livello informatico i servizi di una biblioteca.\ud
Il sistema ALEPH (Automated Library Expandable Program), sviluppato alla fine degli anni ’70, vanta oggi centinaia di installazioni in biblioteche e consorzi di tutto il\ud
mondo. I moduli in cui il software si articola (Catalogazione/Copie, Acquisizione/Periodici, Circolazione, ILL) consentono agli operatori di gestire i vari flussi e le attivita' della biblioteca, mentre l’OPAC WEB, il componente che interessa il nostro progetto, offre all’utente diversificati strumenti di ricerca e servizi\ud
personalizzati.\ud
Lo scopo del progetto e' quello di estendere i servizi bibliografici offerti dalle biblioteche Unicam agli utenti, permettendone una personalizzazione.\ud
Il primo servizio che ho aggiunto riguarda la possibilita' di generare statistiche di utilizzo del catalogo web. Questa funzione consente la verifica di numerosi parametri\ud
tra cui il numero di accessi giornalieri, le pagine piu' visualizzate, le fasce orarie di maggior utilizzo, le zone geografiche da cui si accede al catalogo. Questo servizio e'\ud
disponibile per tutti coloro che usano il catalogo, ma risulta particolarmente utile al personale della biblioteca, in quanto consente loro di valutare l’utilizzo del sistema.\ud
Per poter inserire questa funzione e' stato innanzitutto necessario trovare un software in grado di generare statistiche sugli accessi ad un sito web che fosse adatto al nostro scopo e nello stesso tempo compatibile con l’architettura del sistema; successivamente e' stato installato e configurato con Apache, il server su cui risiede il sistema Aleph.\ud
Uno dei principali scopi del progetto e' quello di ampliare le possibilita' di ricerca del catalogo web di ateneo, cosicche' chi lo utilizza non sia limitato nelle ricerche alle sole risorse bibliografiche Unicam, ma possa accedere anche ad altri cataloghi, nazionali ed internazionali. Per aggiungere questa funzione abbiamo sfruttato lo\ud
standard internazionale Z39.50, un protocollo, supportato da Aleph, per la comunicazione tra sistemi informatici che risulta particolarmente utile ed efficace nell’integrazione e nel dialogo tra basi di dati per l’interrogazione e lo scambio di dati bibliografici. Una volta studiato il funzionamento dello standard Z39.50 abbiamo configurato il catalogo Unicam in modo da renderlo accessibile dall’esterno\ud
attraverso il protocollo Z39.50. Successivamente e' stato necessario effettuare determinate configurazioni affinche' fosse possibile accedere dal catalogo Unicam alle risorse bibliografiche di altri enti o universita'. Infine abbiamo integrato all’interfaccia web OPAC del catalogo di ateneo la possibilita' di effettuare una ricerca attraverso Z39.50 sfruttando le configurazioni precedentemente realizzate.\ud
Al fine di reperire ulteriori informazioni su un record bibliografico, cioe' sul risultato di una ricerca, abbiamo aggiunto una funzione che sfrutta la tecnologia di Google\ud
Libri, un database di risorse bibliografiche digitalizzate. In seguito all’aggiunta di questa funzione, quando un utente effettua una ricerca sul catalogo web di ateneo, ha\ud
immediato accesso alle informazioni disponibili sul database Google relative al target della sua ricerca, quali ad esempio l’anteprima del libro, l’intero libro\ud
digitalizzato se non protetto da copyright, l’indice del libro.\ud
Per inserire questa funzione nel catalogo web di ateneo abbiamo dovuto innanzitutto integrare il servizio Google libri alle pagine del web OPAC, in modo tale che fosse\ud
compatibile con i record di ricerca presenti in Aleph. A tal scopo abbiamo dovuto creare un apposito script che permettesse la comunicazione tra Aleph ed il servizio\ud
Google libri.\ud
Sempre nell’ottica di ampliare le possibilità di utilizzo del catalogo web di ateneo abbiamo aggiunto un’ulteriore funzione che consenta di collegare i record presenti in\ud
catalogo a servizi di condivisione di informazioni bibliografiche come Delicious, Reddit, StumbleUpon etc etc. Questa funzione permette agli utenti di condividere i\ud
risultati delle proprie ricerche attraverso l’utilizzo dei diffusi servizi di social bookmarking. L’integrazione di questo servizio e' stata necessaria in quanto l’utilizzo\ud
dei sistemi di social network è cresciuto esponenzialmente negli ultimi anni, quindi con questa operazione abbiamo rinnovato le possibilità di condivisione dei record\ud
bibliografici del catalogo di ateneo
Se questa vi sembra una valutazione: il merito nel sistema universitario nazionale, le classifiche estive e le considerazioni dell’Università di Macerata sull’applicazione dell’art. 2 della Legge n. 1 del 2009.
No full textIl merito nel sistema universitario nazionale, le classifiche estive e le considerazioni dell’Università di Macerata sull’applicazione dell’art. 2 della Legge n. 1 del 2009
Cesium and rubidium salts of Keggin-type heteropolyacids as stable meso-microporous matrix for anode catalyst for H2/O2 Proton Exchange Membrane Fuel Cell, Direct Methanol Fuel Cell and Direct Ethanol Fuel Cell\ud
No full text\ud
In various applications, fuel cells are widely recognized as very attractive devices to obtain directly electric energy from the electrochemical combustion of chemical products. Low temperature fuel cells, which generally utilize proton electrolyte membranes, seem to be also of utility for a large of power applications.\ud
However, the final choice of the fuel is still difficult and depends greatly on the field of application. Utilization of pure hydrogen or hydrogen-rich gases, rather than alcohols, as fuels in Polymer Electrolyte Membrane Fuel Cell (PEMFC) leads to higher electric efficiencies. Due to the problems related to the hydrogen storage, the hydrogen-oxygen PEMFC is the best choice for stationary applications. Direct alcohols (methanol and ethanol) fuel cells based on solid polymer electrolytes are widely proposed for portable and mobile applications due to relatively low prices of the methanol and ethanol fuels\ud
and easiness of storage. The major impediment in the development of fuel cells operating on hydrogen, methanol, and ethanol is deactivation of the anode electrocatalyst by trace level of CO. Thus, the most active Pt electrocatalyst for the oxidation of hydrogen and alcohols (e.g. methanol, and ethanol) is deactivated by strong adsorption of carbon monoxide, and leads to decreased performance of fuel cell.\ud
Therefore, a new inexpensive, stable electrocatalyst must be developed, which is tolerant to high levels of CO (particularly, for direct alcohol fuel cell) or that could\ud
preferably utilize CO.\ud
There are currently two state-of-the-art methods which increase CO tolerance of the fuel cell anode. One method is to use a Pt-alloy catalyst (e. g. PtRu, PtSn, PtMo,PtW). The other method is to use the zeolite as matrix, and limit the preferential formation of CO clusters on platinum by the steric constraints imposed by the zeolites framework, followed by facile oxidation to CO2 by interaction with the surface or bridged hydroxyls of the zeolites. Furthermore, the porous nature of the zeolite support material provides relatively improved gas permeability and minimizes the disadvantage associated with restricted gas diffusion in the electrode. The ideal support would also an enhanced electrochemically active surface area by dispersion of the metal catalyst.\ud
Keggin-type heteropolyacids show appreciable acid catalytic properties that are of practical importance as illustrated in numerous recent reviews. The fact that heteropolyanions undergo spontaneous adsorption (from aqueous solution) on\ud
various substrates provides a simple tool for modification of electrode surfaces. Among other important issues related to electrocatalysis are their ability to undergo fast reversible multi-electron transfers and super-acid properties resulting in the increased availability and mobility of protons at the electrocatalytic interfaces.\ud
Consequently, polyacids were considered for fuel cell research. With respect to the oxygen reduction, the adsorbed heteropolyacid (particularly H3PW12O40) nanostructures do not seem to block access of reactant molecules to catalytic Pt. Further, their presence at the interface shifts formation of the inhibiting Pt-oxo (PtOH or PtO) species towards more positive potentials thus increasing the potential range where catalytic metallic (Pt0) sites exist. It is reasonable to expect that, by analogy to the activating role of WO3 and partially reduced hydrogen tungsten oxide bronzes during elect oxidation of\ud
methanol, the related heteropolyblue tungstates should also enhance reactivity of Pt during oxidation of organic fuels. Stanis and co-workers reported that the addition of adsorbed HPAs can improve the performance of Pt anodes in a fuel cell under CO-poisoned conditions. Also Farell et al. postulated that HPAs can act as cocatalysts with platinum for methanol electrooxidation.\ud
Among limitations in practical applications of heteropolyacids is their very good solubility in aqueous solutions including acids as well as their ability to undergo desorption during long-term operation. Thus it is necessary to stabilize heteropolyacid layers at electrocatalytic interfaces without loosing their activating properties. An interesting alternative arises from the possibility of formation of acidic salts of\ud
heteropolytungstates or molybdates by partial exchange of protons with large cations (such as Cs+, Rb+, NH4+ or K+) in the parent heteropolyacid. Consequently, a watersoluble\ud
polyacid of low surface area (<5 m2g-1) is transferred into a water-insoluble acid salt precipitate characterized by the surface area exceeding 100 m2g-1. Contrary to\ud
zeolites exchanged with alkali metals, heteropolyacid salts remain strong acidity.\ud
The resulting materials have occurred to be efficient solid shape-selective acid catalysts for a variety of organic liquid-phase reactions that include hydrogenations and\ud
oxidations. The pore size and acidity of heteropolyacid salt can be controlled by the cation content. For example, when the Cs content, x, is initially increased in CsxH3-\ud
xPW12O40 from 0 to 2, the number of surface protons decreases but, later, it significantly increases when x changes from 2 to 3 to show the highest surface acidity at x = 2.5.\ud
In the present work, we consider the salts of Keggin-type heteropolyacids containing 2.5 moles of Cs+ and Rb+ cations in 1 mole of the heteropoly salt. The system with such Cs or Rb-content is micro-mesoporous, and it is characterized by very good stability and, while being insoluble in water, it exhibits high acidity (proton availability and mobility).\ud
The aim of this work is to study the applicability of the Cs and Rb salts of Keggin type heteropolyacids as a stable meso-microporous matrix for anode catalyst for H2/O2 Proton Exchange Membrane Fuel Cell, Direct Methanol Fuel Cell and Direct Ethanol Fuel Cell.\ud
The experimental part is divided into four chapters (from 6 to 9). In the Chapter 6, we present characterization of cesium, rubidium and ammonium salts of Keggin types heteropolyacids by infrared spectroscopy (IR), scanning electron microscopy (SEM), and cyclic voltammetry (CV) measurements.\ud
In Chapter 7, we illustrate incorporation and activation of Pt centers in the conductive high surface-area zeolite-type robust, Cs2.5H0.5PW12O40 matrices through application of mixing and electrochemical methods. To evaluate electrocatalytic activity towards the hydrogen oxidation of the investigated electrode material, we have performed the diagnostic rotating disc electrode voltammetric measurements. In a case of the catalytic layer prepared by corrosion of Pt counter electrode (electrochemical\ud
method), CO-stripping and HRTEM measurements have been performed to comment the electrochemically active area of catalyst, dimensions of Pt particles and platinum\ud
loading.\ud
In Chapter 8, we report on the performance of electrocatalysts (prepared by mixing method) towards methanol oxidation in acidic media. The Cs and Rb salts of\ud
H3PW12O40, H3PMo12O40, H4SiW12O40, H4SiMo12O40 were used as zeolite matrix for Pt40%/Vulcan XC-72 carbon nanoparticles (Pt/C). The techniques of cyclic voltammetry, staircase voltammetry, chronoamperometry, electrochemical impedance\ud
spectroscopy, CO stripping voltammetry were applied to compare the Pt-base electrocatalyst activity and stability to methanol oxidation.\ud
In Chapter 9, the system composed of Pt40%/Vulcan XC-72 carbon modified with Cs2.5-HPAs matrix (prepared by mixing method) has been examined with respect to ethanol electrooxidation by several different electrochemical techniques. Comparison has been made to commercial Pt/C.\u
Transient dynamics of vegetation in upper timberline of fagus sylvatica L. forests in the Monti Sibillini national park
No full textThe research wants to supply useful elements of knowledge to the management of plant communities in zones of transition at the upper limit of beech woods in the Monti Sibillini National Park. In this area there are historical and scientific evidences that attest the weight of the pressure of domestic wild breeding (sheep, caws, horses), in the definition of present edge of the forest. Such limit, today, is certainly more downwards with respect to the natural capacity of beech wood that would arrive until 1840 - 1850 m. s. l. m. The pastural activity that in the last centuries has modeling present landscape, in the last 60 years had a strong reorganization: that determined a new natural expansion of the forests. The phenomenon is rapid and great to the lowest heights, whereas seems very slow, or even worthless in delicate environments of the highest limit of the forest. This is the reason for that it becomes interesting to study this special aspect of the phenomenon. To understand and to expect the dynamics in these areas of transition, besides the study of the climatic change (analysis that asks for big engagement of time, of money and of personnel), it has to be also considered the impact of the decreased human disturbance on the natural forest populations. In last years, many authors prefer this second hypothesis to explain new expansion happened over woodlands, attributing instead to the climatic change an effect to await it in the long period. It has to report that in reference to the forest vegetation it says “short period” also for temporal ranks of 100 – 300 years. Some scholars, besides, affirm that this logic of short period is especially useful for observations of middle-small space dimension, that is to say to regional scale, or of landscape, or local. The present work just examines a regional and landscape scale, to arrive then to more detailed local analysis, sometimes even micro research stations. \ud
Particularly, this study would want to characterize itself for the following aspects: \ud
a) the affected territory: \ud
It is the extreme and peculiar environmental context of the highest part of the Monti Sibillini. These areas are the sole, in the Umbro-marchigiana portion of Apennine, that for their altitude are higher of the area of potential vegetation of beech. There are a lot of tops above 2000 m. that overtop an important calcareous plateau. In the area in examination, besides, is almost completely absent the shrubby layer above the forest, that in other Apennine zones is retained necessary for lift of beech;\ud
b) the object of study: \ud
The regeneration of beech wood towards its higher limits (above 1600 m.), in spite of difficult environmental conditions and delicate ecological features of this species. \ud
General summary of carried out activity \ud
Scientific reference hypothesis is based on the check of eventual tendencies to change in higher limit of beech wood happened in short period ("short" according to forest parameters …). This type of approach ascribes eventual shift of forests from decreased human pressure. Instead, in case such gone back it is not observed, we investigate the motive that can clash the expansion of the forest to the high. \ud
The study was turned by means of the following actions: \ud
a) Bibliographic inquiry on the relating arguments to the study;\ud
b) Diachronic inquiry to identify happened changes during the period 1980 – 2008; \ud
c) Determination and analysis of 12 stations of study retained necessary to represent in appropriate way the regeneration "to the high" of the beech woods inside Monti Sibillini National Park; \ud
d) Check of the "qualitative" aspects of the woodland neighbors to the higher edge. This observation is directed to the check of potential sources of sexual propagation of the beech in the areas now except for exploitation from domestic grazing. \ud
e) Execution of different types of relief in every choice area, to note ecological data, environmental data, plant diversity data; \ud
f) Elaboration of samples taken in the field; \ud
g) Evaluation of the disturbance brought from wild ungulates and of domestic livestock; \ud
h) Analysis of the results. \ud
Expected results\ud
a) Creation of a functional model useful to carrying out foreseeing tools of potential dynamics of expansion of the beech woods towards their natural highest limit; \ud
b) Formulation of hypothesis on the mechanisms and the criticality of forest expansion towards high; \ud
c) First check of the abovementioned hypothesis, and definition of an experimental protocol for the continuation of the research. \ud
d) Creation of a cartography with the relevant precise identification of sample areas, necessary for eventual following checks on the evolution of upper margin of the beech-woods. \u
A Whole War Inside One Small Body: War in Children’s Literature
No full textSeparation – from your family, your home, your country; a journey – to escape, to return, or an inward journey of healing, self discovery and self construction: these are recurrent themes in the four novels about children and war that are examined in this study of works by critically acclaimed authors Rachel Anderson, Bernard Ashley, Peter Dickinson and Robert Westall. These stories have different wars as their contexts, in different countries and historical periods: Vietnam, the Gulf, civil conflicts in African countries and London gang warfare, but while varying in their approaches, the novels share a richness of setting, characterisation and narrative structure, and a powerful capacity to involve readers emotionally and intellectually. Causes are explained or suggested, but it is essentially upon the far-reaching effects of war in time and place, on ordinary people, the civilian population and children, especially, that the authors turn their attention
Università degli Studi di Macerata. Bilancio sociale dell'esercizio 2008.
No full textGestione, attività, impegni, risultati, obiettivi e criticità nel campo della didattica e della ricerca, nei rapporti con il territorio e con il contesto internazionale: l’Università di Macerata si racconta nel Bilancio sociale 2009, uno strumento ancora poco diffuso tra gli atenei italiani. Il Bilancio sociale è uno strumento volontario di rendicontazione che consente alle imprese private e alle Pubbliche Amministrazioni di realizzare una strategia di comunicazione diffusa e trasparente. Si tratta di un documento in grado di fornire, ai diversi soggetti interessati, informazioni sugli effetti sociali e ambientali che derivano dalle scelte fatte