Effetti delle basse temperature su Arabidopsis thaliana

Le piante sono continuamente sottoposte ad innumerevoli stress biotici ed abiotici, cioè a tutti quei fattori esterni quali altri organismi viventi e condizioni ambientali avverse che possono influire negativamente sulla loro crescita e sul loro sviluppo. In quanto organismi sessili, le piante non hanno la possibilità di muoversi per evitare questi fattori potenzialmente dannosi e di conseguenza sono state costrette ad adottare nel corso dell’evoluzione una serie di accorgimenti che garantissero la loro sopravvivenza; questi adattamenti comprendono meccanismi di resistenza o di tolleranza ai fattori stressanti che si possono riassumere nell’attivazione di specifiche vie di trasduzione del segnale, nell’espressione di specifici geni e nelle modifiche a livello strutturale. Uno di questi meccanismi di difesa è rappresentato dall’acclimatazione, fenomeno che permette il graduale adattamento dei singoli organismi in seguito all’esposizione a bassi livelli di stress; l’acclimatazione può quindi permettere la sopravvivenza della pianta in condizioni che altrimenti sarebbero letali o il mantenimento della produttività in situazioni che possono essere dannose per i raccolti. Numerosi studi dimostrano che lo stress da congelamento rappresenta una delle condizioni avverse più pericolose a causa dei danni che induce a livello cellulare; le risposte adottate dalla pianta in seguito all’acclimatazione comprendono modifiche nella concentrazione osmotica di diversi soluti, nel contenuto d’acqua delle cellule, nella struttura dei lipidi di membrana e nei livelli dei regolatori di crescita, oltre all’accumulo di proteine con funzione protettiva. Nella presente tesi vengono descritti a livello proteomico gli effetti che temperature di congelamento (fino a -12°C) inducono su Arabidopsis thaliana: in particolare viene effettuato un confronto attraverso il software PDQuest tra i pattern proteici ottenuti tramite elettroforesi bidimensionale (2D-PAGE) di piante non acclimatate al freddo ed acclimatate previa esposizione a 4°C per sette giorni e poi sottoposte a stress da congelamento. I risultati ottenuti hanno permesso l’individuazione di spot proteici differenzialmente espressi nei profili elettroforetici delle varie tesi utilizzate, cioè piante di 13, 20 e 27 giorni trattate a -10°C per 12 ore (da analisi preliminari le piante 20d sono risultate le più resistenti allo stress, soprattutto previa acclimatazione). Gli spot di interesse sono stati successivamente analizzati tramite spettrometria di massa per identificare le proteine corrispondenti e stabilire la loro funzione

The Fashion Content Of Vogue\u27s September Issues Under Editor-In-Chiefs Grace Mirabella And Anna Wintour

The study examines the two editor-in-chiefs of Vogue magazine in recent history, Grace Mirabella and Anna Wintour, and the fashion content of the September issues of the magazine under their editorships. Fifteen September issues from each editor-in-chief were analyzed to understand how the September issue had evolved as well as the development of fashion content in the magazine. The personal influences of Grace Mirabella and Anna Wintour respectively were found in the fashion content of the September issues. Vogue issues analyzed from Mirabella\u27s editorship shoa concentration of fashion content on the functionality of clothing with a focus on American designers. The Vogue issues analyzed from Wintour\u27s editorship had a fashion content concentrating on the combination of European and American designers, and a mixture of high and low-end fashion. This analysis shothe lack of celebrity in Vogue from Mirabella\u27s editorship and the predominant feature of celebrity during Wintour\u27s editorship. The findings of this study reveal that the personal taste and style of the respective editor-in-chiefs of Vogue influences and directs the fashion content of the magazine

The Importance of Contextualized, Facet-Level Personality Measures

A problem that has arisen in the field of personality psychology is that while personality traits are related to outcome variables, the predictive validity of these associations is low to medium (Rosenthal, 1994; Rosnow & Rosenthal, 1989). One of the reasons for this is because personality has traditionally been defined as something generalizable across situations and time. This generalizability across situations and time is called the invariance of personality (Mischel, 2004). We argue that personality is stable at a different level of analysis, and that level of analysis is the specific context, but not stable across different situations. The current study looked at a fully contextualized personality measure and compared it to a non-contextualized measure of the same personality trait/facets to assess whether incremental validity can be gained by targeting specific situations. Results show that despite the presence of nuisance factors for both general and academic conscientiousness that the contextualized measure showed incremental validity

High operating temperature in V-based superconducting quantum interference proximity transistors

Here we report the fabrication and characterization of fully superconducting quantum interference proximity transistors (SQUIPTs) based on the implementation of vanadium (V) in the superconducting loop. At low temperature, the devices show high flux-to-voltage (up to 0.52$\ \textrm{mV}/\Phi_0$) and flux-to-current (above 12$\ \textrm{nA}/\Phi_0$) transfer functions, with the best estimated flux sensitivity $\sim$2.6$\ \mu\Phi_0/\sqrt{\textrm{Hz}}$ reached under fixed voltage bias, where $\Phi_0$ is the flux quantum. The interferometers operate up to $T_\textrm{bath}\simeq$ 2 $\textrm{K}$, with an improvement of 70$\%$ of the maximal operating temperature with respect to early SQUIPTs design. The main features of the V-based SQUIPT are described within a simplified theoretical model. Our results open the way to the realization of SQUIPTs that take advantage of the use of higher-gap superconductors for ultra-sensitive nanoscale applications that operate at temperatures well above 1 K.Comment: Published version with Supplementary Informatio

Preliminary demonstration of a persistent Josephson phase-slip memory cell with topological protection

Superconducting computing promises enhanced computational power in both classical and quantum approaches. Yet, scalable and fast superconducting memories are not implemented. Here, we propose a fully superconducting memory cell based on the hysteretic phase-slip transition existing in long aluminum nanowire Josephson junctions. Embraced by a superconducting ring, the memory cell codifies the logic state in the direction of the circulating persistent current, as commonly defined in flux-based superconducting memories. But, unlike the latter, the hysteresis here is a consequence of the phase-slip occurring in the long weak link and associated to the topological transition of its superconducting gap. This disentangles our memory scheme from the large-inductance constraint, thus enabling its miniaturization. Moreover, the strong activation energy for phase-slip nucleation provides a robust topological protection against stochastic phase-slips and magnetic-flux noise. These properties make the Josephson phase-slip memory a promising solution for advanced superconducting classical logic architectures or flux qubits

Thermal superconducting quantum interference proximity transistor

Superconductors are known to be excellent thermal insulators at low temperature owing to the presence of the energy gap in their density of states (DOS). In this context, the superconducting \textit{proximity effect} allows to tune the local DOS of a metallic wire by controlling the phase bias ($\varphi$) imposed across it. As a result, the wire thermal conductance can be tuned over several orders of magnitude by phase manipulation. Despite strong implications in nanoscale heat management, experimental proofs of phase-driven control of thermal transport in superconducting proximitized nanostructures are still very limited. Here, we report the experimental demonstration of efficient heat current control by phase tuning the superconducting proximity effect. This is achieved by exploiting the magnetic flux-driven manipulation of the DOS of a quasi one-dimensional aluminum nanowire forming a weal-link embedded in a superconducting ring. Our thermal superconducting quantum interference transistor (T-SQUIPT) shows temperature modulations up to $\sim 16$ mK yielding a temperature-to-flux transfer function as large as $\sim 60$ mK/$\Phi_0$. Yet, phase-slip transitions occurring in the nanowire Josephson junction induce a hysteretic dependence of its local DOS on the direction of the applied magnetic field. Thus, we also prove the operation of the T-SQUIPT as a phase-tunable \textit{thermal memory}, where the information is encoded in the temperature of the metallic mesoscopic island. Besides their relevance in quantum physics, our results are pivotal for the design of innovative coherent caloritronics devices such as heat valves and temperature amplifiers suitable for thermal logic architectures.Comment: 8 pages, 4 figure

Fully superconducting josephson bolometers for gigahertz astronomy

The origin and the evolution of the universe are concealed in the evanescent diffuse extragalactic background radiation (DEBRA). To reveal these signals, the development of innovative ultra-sensitive bolometers operating in the gigahertz band is required. Here, we review the design and experimental realization of two bias-current-tunable sensors based on one dimensional fully superconducting Josephson junctions: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). In particular, we cover the theoretical basis of the sensors operation, the device fabrication, their experimental electronic and thermal characterization and the deduced detection performance. Indeed, the nano-TES promises a state-of-the-art noise equivalent power (NEP) of about 5 × 10−20 W/√Hz, while the JES active region is expected to show an unprecedented NEP of the order of 10−25 W/√Hz. Therefore, the nano-TES and JES are strong candidates to push radio astronomy to the next level

InAs nanowire superconducting tunnel junctions: spectroscopy, thermometry and nanorefrigeration

We demonstrate an original method -- based on controlled oxidation -- to create high-quality tunnel junctions between superconducting Al reservoirs and InAs semiconductor nanowires. We show clean tunnel characteristics with a current suppression by over $4$ orders of magnitude for a junction bias well below the Al gap $\Delta_0 \approx 200\,\mu {\rm eV}$. The experimental data are in close agreement with the BCS theoretical expectations of a superconducting tunnel junction. The studied devices combine small-scale tunnel contacts working as thermometers as well as larger electrodes that provide a proof-of-principle active {\em cooling} of the electron distribution in the nanowire. A peak refrigeration of about $\delta T = 10\,{\rm mK}$ is achieved at a bath temperature $T_{bath}\approx250-350\,{\rm mK}$ in our prototype devices. This method opens important perspectives for the investigation of thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.Comment: 6 pages, 4 color figure