A Novel Technique to Reconstruct the Z mass in WZ/ZZ Events with Lepton(s), Missing Transverse Energy and Three Jets at CDFII

Observing WZ/ZZ production at the Tevatron in a final state with a lepton, missing transverse energy and jets is extremely difficult because of the low signal rate and the huge background. In an attempt to increase the acceptance we study the sample where three high-energy jets are reconstructed, where about 1/3 of the diboson signal events are expected to end. Rather than choosing the two E$_{T}$-leading jets to detect a Z signal, we make use of the information carried by all jets. To qualify the potential of our method, we estimate the probability of observing an inclusive diboson signal at the three standard deviations level (P$_{3\sigma}$) to be about four times larger than when using the two leading jets only. Aiming at applying the method to the search for the exclusive WZ/ZZ$\rightarrow \ell \nu q\bar{q}$ channel in the three jets sample, we analyzed separately the sample with at least one $b$-tagged jet and the sample with no tags. In WZ/ZZ$\rightarrow \ell \nu b\bar{b}$ search, we observe a modest improvement in sensitivity over the option of building the Z-mass from the two leading jets in E$_T$ . Studies for improving the method further are on-going.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 3 pages, 8 figur

Credit rationing and the financial structure of Italian small and medium enterprises

Our aim is to analyze the effect of public subsidies on the development path of Italian small and medium enterprises (SMEs). Public subsidies to SMEs have been often used with the aim of favoring economic growth in less developed regions. The main theoretical arguments justifying this intervention are related to the idea that public subsidies can solve lack-ofcapital problems deriving from asymmetric information. According to Stiglitz and Weiss (1981), public subsidies to rationed firms can reduce the informational gap, leading subsidized firms to reduce their financial constraints and to increase their investment levels. Results obtained modelling leverage, performance and investment behaviour in a panel of around 1,900 enterprises over the years 1989 to 1994 seem to confirm the working hypotheses. However, they can not be considered as conclusive and further research is needed in this context.Public subsidies, credit rationing, asymmetric information, Markov regression models

A simplified exactly solvable model for beta-amyloid aggregation

We propose an exactly solvable simplified statistical mechanical model for the thermodynamics of beta-amyloid aggregation, generalizing a well-studied model for protein folding. The monomer concentration is explicitly taken into account as well as a non trivial dependence on the microscopic degrees of freedom of the single peptide chain, both in the alpha-helix folded isolated state and in the fibrillar one. The phase diagram of the model is studied and compared to the outcome of fibril formation experiments which is qualitatively reproduced.Comment: 4 pages, 2 figure

Exploring the correlation between the folding rates of proteins and the entanglement of their native states

The folding of a protein towards its native state is a rather complicated process. However there are empirical evidences that the folding time correlates with the contact order, a simple measure of the spatial organisation of the native state of the protein. Contact order is related to the average length of the main chain loops formed by amino acids which are in contact. Here we argue that folding kinetics can be influenced also by the entanglement that loops may undergo within the overall three dimensional protein structure. In order to explore such possibility, we introduce a novel descriptor, which we call "maximum intrachain contact entanglement". Specifically, we measure the maximum Gaussian entanglement between any looped portion of a protein and any other non-overlapping subchain of the same protein, which is easily computed by discretized line integrals on the coordinates of the $C_{\alpha}$ atoms. By analyzing experimental data sets of two-state and multistate folders, we show that also the new index is a good predictor of the folding rate. Moreover, being only partially correlated with previous methods, it can be integrated with them to yield more accurate predictions.Comment: 8 figures. v2: new titl

Linking in domain-swapped protein dimers

The presence of knots has been observed in a small fraction of single-domain proteins and related to their thermodynamic and kinetic properties. The exchanging of identical structural elements, typical of domain-swapped proteins, make such dimers suitable candidates to validate the possibility that mutual entanglement between chains may play a similar role for protein complexes. We suggest that such entanglement is captured by the linking number. This represents, for two closed curves, the number of times that each curve winds around the other. We show that closing the curves is not necessary, as a novel parameter $G'$, termed Gaussian entanglement, is strongly correlated with the linking number. Based on $110$ non redundant domain-swapped dimers, our analysis evidences a high fraction of chains with a significant intertwining, that is with $|G'| > 1$. We report that Nature promotes configurations with negative mutual entanglement and surprisingly, it seems to suppress intertwining in long protein dimers. Supported by numerical simulations of dimer dissociation, our results provide a novel topology-based classification of protein-swapped dimers together with some preliminary evidence of its impact on their physical and biological properties.Comment: v2: some new paragraphs and new abstrac

Proline affects the size of the root meristematic zone in Arabidopsis

We reported previously that root elongation in Arabidopsis is promoted by exogenous proline, raising the possibility that this amino acid may modulate root growth. To evaluate this hypothesis we used a combination of genetic, pharmacological and molecular analyses, and showed that proline specifically affects root growth by modulating the size of the root meristem. The effects of proline on meristem size are parallel to, and independent from, hormonal pathways, and do not involve the expression of genes controlling cell differentiation at the transition zone. On the contrary, proline appears to control cell division in early stages of postembryonic root development, as shown by the expression of the G2/M-specific CYCLINB1;1 (CYCB1;1) gene. The overall data suggest that proline can modulate the size of root meristematic zone in Arabidopsis likely controlling cell division and, in turn, the ratio between cell division and cell differentiation

Proline synthesis in developing microspores is required for pollen development and fertility

Background: In many plants, the amino acid proline is strongly accumulated in pollen and disruption of proline synthesis caused abortion of microspore development in Arabidopsis. So far, it was unclear whether local biosynthesis or transport of proline determines the success of fertile pollen development. Results: We analyzed the expression pattern of the proline biosynthetic genes PYRROLINE-5-CARBOXYLATE SYNTHETASE 1 & 2 (P5CS1 & 2) in Arabidopsis anthers and both isoforms were strongly expressed in developing microspores and pollen grains but only inconsistently in surrounding sporophytic tissues. We introduced in a p5cs1/p5cs1 p5cs2/P5CS2 mutant background an additional copy of P5CS2 under the control of the Cauliflower Mosaic Virus (CaMV) 35S promoter, the tapetum-specific LIPID TRANSFER PROTEIN 12 (Ltp12) promoter or the pollen-specific At5g17340 promoter to determine in which site proline biosynthesis can restore the fertility of proline-deficient microspores. The specificity of these promoters was confirmed by β-glucuronidase (GUS) analysis, and by direct proline measurement in pollen grains and stage-9/10 anthers. Expression of P5CS2 under control of the At5g17340 promoter fully rescued proline content and normal morphology and fertility of mutant pollen. In contrast, expression of P5CS2 driven by either the Ltp12 or CaMV35S promoter caused only partial restoration of pollen development with little effect on pollen fertility. Conclusions: Overall, our results indicate that proline transport is not able to fulfill the demand of the cells of the male germ line. Pollen development and fertility depend on local proline biosynthesis during late stages of microspore development and in mature pollen grains

Re: Caiulo VA, Gargani L, Caiulo S, Fisicaro A, Moramarco F, Latini G, Picano E. Lung ultrasound in bronchiolitis: comparison with chest X-ray. Eur J Pediatr. 2011;170: 1427–33

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Proline and ROS: A Unified Mechanism in Plant Development and Stress Response?

The proteinogenic amino acid proline plays crucial roles in both plant devel- opment and stress responses, far exceeding its role in protein synthesis. However, the molecular mechanisms and the relative importance of these additional functions of proline remain under study. It is well documented that both stress responses and developmen- tal processes are associated with proline accumulation. Under stress conditions, proline is believed to confer stress tolerance, while under physiological conditions, it assists in developmental processes, particularly during the reproductive phase. Due to proline’s properties as a compatible osmolyte and potential reactive oxygen species (ROS) scavenger, most of its beneficial effects have historically been attributed to the physicochemical con- sequences of its accumulation in plants. However, emerging evidence points to proline metabolism as the primary driver of these beneficial effects. Recent reports have shown that proline metabolism, in addition to supporting reproductive development, can modulate root meristem size by controlling ROS accumulation and distribution in the root meristem. The dynamic interplay between proline and ROS highlights a sophisticated regulatory network essential for plant resilience and survival. This fine-tuning mechanism, enabled by the pro-oxidant and antioxidant properties of compartmentalized proline metabolism, can modulate redox balance and ROS homeostasis, potentially explaining many of the multiple roles attributed to proline. This review uniquely integrates recent findings on the dual role of proline in both ROS scavenging and signaling, provides an updated overview of the most recent research published to date, and proposes a unified mechanism that could account for many of the multiple roles assigned to proline in plant development and stress defense. By focusing on the interplay between proline and ROS, we aim to provide a comprehensive understanding of this proposed mechanism and highlight the potential applications in improving crop resilience to environmental stress. Additionally, we address current gaps in understanding and suggest future research directions to further elucidate the complex roles of proline in plant biology

A NEW TOP MASS MEASUREMENT IN THE DILEPTON CHANNEL

In questa tesi si descrive un nuovo metodo per la misura della massa del quark top con l'esperimento CDF al collisionatore Tevatron di Fermilab (Batavia, Il, USA). Il quark top viene prodotto in coppie top-antitop nelle collisioni di protoni e antiprotoni all'energia di 1.96\ TeV nel centro di massa. Tali coppie seguono tre possibili canali di decadimento: "all-hadronic", "lepton+jets" e "dilepton", dando luogo a configurazioni diverse e a diverse osservabili nello stato finale. In questa analisi è stato usato il canale dileptonico t+tbar -> (W+ + b)+(W- + bbar) -> (l+ + nu + b)+(l- + nubar + bbar) per la misura della massa del quark top. Questo canale, in cui i bosoni W decadono entrambi leptonicamente, ha il pregio di un buon rapporto segnale/fondo, al prezzo di una cinematica non completamente determinata dalla misura, data la presenza di due neutrini nello stato finale, e di una bassa statistica. La misura della massa in questo canale è tuttavia importante per assicurare, mediante la consistenza con le misure negli altri canali, che nel campione non vi sono contributi da processi diversi di quello ipotizzato. Il metodo da noi usato per ricostruire la massa del top quark è una versione del cosiddetto Template Mass Method (TMT), in cui si sfrutta il paragone fra distribuzioni di osservabili sensibili alla massa del top in eventi simulati e nei dati. Questa misura è un risultato ufficiale di CDF: essa si colloca ai primi posti in questo canale per quanto riguarda la sensibilità ottenuta. I miglioramenti inseriti nel nostro metodo di analisi sulla scorta dell'esperienza passata, oltre che, naturalmente, l'aumentata statistica che si è resa disponibile nel tempo hanno reso possibile il raggiungimento di tale traguardo. Il nostro metodo di analisi, chiamato "PHI method", fissa il valore degli angoli azimutali dei due neutrini, ricostruisce evento per evento la massa invariante scegliendo quella corrispondente alla ricostruzione che meglio si adatta ad un evento top-antitop. Dopodichè reitera la procedura variando le due variabili fissate e fa una media opportunamente pesata di tutte le masse invarianti restituite. Una volta ottenute le masse evento per evento si procede col "likelihood fit" finale: la distribuzione in tale massa proveniente dai dati viene confrontata con quelle costruite a partire da eventi simulati per il segnale e fondi ("templates"), dal momento che ogni singolo evento selezionato dai dati può essere un evento top-antitop dileptonico o un evento di fondo. Il risultato di questo paragone restituisce in uscita il nostro miglior estimatore della massa del top. Il fit viene fatto usando la likelihood, una funzione di distribuzione costruita sommando i templates di fondo, pesati in base alle frequenze aspettate, e il template di segnale, dipendente dalla massa del top. Il metodo ha successo perchè questa distribuzione risulta comunque fortemente dipendente dalla vera massa del quark top. Rispetto alle precedenti misure della massa con il metodo dei templates in questo canale abbiamo apportato i seguenti miglioramenti: 1) Utilizzo della selezione lepton+track ("LTRK"), che è meno vincolante rispetto alla selezione che richiede l'identificazione di due leptoni ("DIL") e dà un incremento significativo della statistica utilizzabile, al prezzo di una modesta diminuzione del rapporto segnale/fondo. 2) Utilizzo nella ricostruzione degli eventi di distribuzioni Breit-Wigner relativistiche e larghezza di decadimento del top dipendente dalla sua massa come previsto dal Modello Standard. Il risultato è una sensibile riduzione dell'errore statistico da cui l'estimatore della massa del top è affetto. 3) Costruzione tramite accurate simulazioni delle funzioni di trasferimento che, a partire dall'impulso del getto misurato, ricostruiscono l'impulso del partone da cui esso proviene. 4) Una diversa procedura per la stima del fondo dovuto a eventi mal misurati ("fakes"). Tale contributo è stato stimato direttamente usando i dati, mentre in passato veniva fatto partendo da eventi di produzione di "W+jets" simulati in QCD. In questa tesi il contributo personale del candidato è stato in primo luogo la selezione degli eventi lepton+track, su cui si basa tutto l'impianto suddetto, la stima dei fondi, in particolar modo quelli relativi ai "fakes", che ne costituiscono la maggiore fonte, e la valutazione di alcuni contributi all' errore sistematico sull'estimatore della massa del top. Un intenso lavoro in stretta collaborazione col dr. Igor Suslov è stato fatto per testare, raffinare e concludere la misura. I piani per il futuro prevedono che il codice di selezione entri a far parte degli archivi ufficiali di analisi a disposizione della Collaborazione. Attualmente (dicembre 2007) è iniziata la procedura interna preliminare alla pubblicazione del risultato. Dopo la pubblicazione il risultato ottenuto sarà utilizzato nella stima combinata della massa del top al Tevatron