Activation of MHD reconnection on ideal timescales

Magnetic reconnection in laboratory, space and astrophysical plasmas is often invoked to explain explosive energy release and particle acceleration. However, the timescales involved in classical models within the macroscopic MHD regime are far too slow to match the observations. Here we revisit the tearing instability by performing visco-resistive two-dimensional numerical simulations of the evolution of thin current sheets, for a variety of initial configurations and of values of the Lunquist number $S$, up to $10^7$. Results confirm that when the critical aspect ratio of $S^{1/3}$ is reached in the reconnecting current sheets, the instability proceeds on ideal (Alfv\'enic) macroscopic timescales, as required to explain observations. Moreover, the same scaling is seen to apply also to the local, secondary reconnection events triggered during the nonlinear phase of the tearing instability, thus accelerating the cascading process to increasingly smaller spatial and temporal scales. The process appears to be robust, as the predicted scaling is measured both in inviscid simulations and when using a Prandtl number $P=1$ in the viscous regime.Comment: Accepted for publication in Plasma Physics and Controlled Fusio

From growth goals to proactive organizational resilience: first evidence in women-led and non-women-led Italian wineries

In a fast-changing world, characterized by evenly unexpected challenges and shocks, being resilient is a crucial aspect for every organization. Drawing from the goal setting theory and the double standards of competence perspective, this study aims at understanding the antecedents of organizational proactive resilience. More precisely, it looks at the impact of quantitative and qualitative organizational growth goals on proactive resilience, distinguishing between women-led and non-women-led firms. Based on a unique sample of 167 Italian wineries (67 women-led and 100 non-women-led), this paper tests this theoretical model using path analysis techniques. The wine sector is a particularly interesting context to study the phenomenon due to its exposure to natural disasters, new consumers' behaviours that are requiring firms to continuously innovate and differentiate in a traditionally low-tech sector, but also changes happening at wineries' management level. In fact, the sector has been traditionally male dominated, but women are increasingly taking the lead. The findings indicate that growth goals differently contribute to proactive organizational resilience, but their effects vary in women- and non-women-led businesses. Specifically, these results suggest that in women-led wineries, proactive organizational resilience depends on quantitative growth goals while in non-women-led wineries businesses this depends on qualitative growth goals

Majorana: from atomic and molecular, to nuclear physics

In the centennial of Ettore Majorana's birth (1906-1938?), we re-examine some aspects of his fundamental scientific production in atomic and molecular physics, including a not well known short communication. There, Majorana critically discusses Fermi's solution of the celebrated Thomas-Fermi equation for electron screening in atoms and positive ions. We argue that some of Majorana's seminal contributions in molecular physics already prelude to the idea of exchange interactions (or Heisenberg-Majorana forces) in his later workson theoretical nuclear physics. In all his papers, he tended to emphasize the symmetries at the basis of a physical problem, as well as the limitations, rather than the advantages, of the approximations of the method employed.Comment: to appear in Found. Phy

Exploring the attitude towards the adoption of a sustainable diet: a cross-country comparison

Purpose: Understanding the determinants that influence consumers' attitude to adopt sustainable diets represents an important area of research to promote sustainable food consumption. The aim of this study is to investigate how (1) the individual openness to new foods (ONFs), (2) the involvement in food trends (IFTs) and (3) the social media use (SMU) can potentially impact the attitude towards the adoption of a sustainable diet (ATSD). Design/methodology/approach: The authors conducted a structured survey in eight countries: Italy, Germany, Poland, USA, Brazil, Japan, Korea and China. The final sample of 5,501 individuals was analysed applying a structural equation model. Findings: The main results show that attitude towards the ATSD is influenced differently by the antecedents investigated in each country. In particular, the ONF positively influences the ATSD only in Italy, USA and Germany. IFT positively influences the ATSD only in Italy, Poland and USA, while negatively in Germany. SMU has a positive influence on the ATSD only in Japan, USA and Germany, while a negative one in Brazil and Korea. Originality/value: This study presents a cross-country comparison about the antecedents of attitude towards the ATSD, thus providing evidence for the need of ad hoc marketing strategies by companies and policies by institutions at single country level

The virtuous cycle of stakeholder engagement in developing a sustainability culture: Salcheto winery

Stakeholder engagement in sustainability represents a powerful driver for value creation. Drawing from stakeholder theory, this paper explores how a firm with a proactive sustainable behaviour engages stakeholders in developing innovation and creating value. A longitudinal, single case study of the Salcheto winery was carried out. Since the late 1990s, Salcheto has been at the forefront of wine eco-innovation and it has played a key role in the development of Montepulciano (Tuscany, Italy) as one of the first sustainable wine clusters worldwide. The development of a sustainable wine culture is one of the firm's various innovations. In doing so, the firm has had to face three challenges - identity creation, legitimization and enhancement - and has engaged its stakeholders through three specific mechanisms (adoption and development; co-creation and diffusion; exploitation and contamination). This virtuous cycle of stakeholder engagement has resulted in value creation at a firm, stakeholder and local level

Thermal stability and aggregation of sulfolobus solfataricus b-glycosidase are dependent upon the N-e-methylation of specific lysyl residues: critical role of in vivo post-translational modifications.

Methylation in vivo is a post-translational modification observed in several organisms belonging to eucarya, bacteria, and archaea. Although important implications of this modification have been demonstrated in several eucaryotes, its biological role in hyperthermophilic archaea is far from being understood. The aim of this work is to clarify some effects of methylation on the properties of β-glycosidase from Sulfolobus solfataricus, by a structural comparison between the native, methylated protein and its unmethylated counterpart, recombinantly expressed in Escherichia coli. Analysis by Fourier transform infrared spectroscopy indicated similar secondary structure contents for the two forms of the protein. However, the study of temperature perturbation by Fourier transform infrared spectroscopy and turbidimetry evidenced denaturation and aggregation events more pronounced in recombinant than in native β-glycosidase. Red Nile fluorescence analysis revealed significant differences of surface hydrophobicity between the two forms of the protein. Unlike the native enzyme, which dissociated into SDS-resistant dimers upon exposure to the detergent, the recombinant enzyme partially dissociated into monomers. By electrospray mapping, the methylation sites of the native protein were identified. A computational analysis of β-glycosidase three-dimensional structure and comparisons with other proteins from S. solfataricus revealed analogies in the localization of methylation sites in terms of secondary structural elements and overall topology. These observations suggest a role for the methylation of lysyl residues, located in selected domains, in the thermal stabilization of β-glycosidase from S. solfataricu

Modulation of different clusterin isoforms in human colon tumorigenesis

Clusterin is a ubiquitous secretory heterodimeric disulfide-linked glycoprotein, which is implicated in several physiological processes, including immune regulation, cell adhesion and morphological transformation, lipid transportation, tissue remodelling, membrane recycling and cell-cell interactions. A large number of studies have focused their interest on clusterin gene products as mediators of cell cycle progression and cell death induction, although data on the different isoforms and their role in the different cell processes are still obscure. Recently, an increased clusterin expression in breast cancer has been reported. In order to elucidate the role of clusterin in tumor progression and whether one of its isoforms is preferentially expressed in tumorigenesis, we examined its presence throughout the different steps of human colon carcinoma, one of the best-characterized models of human tumor progression. The immunohistochemical observation of 30 bioptic and surgical colon specimens demonstrated a cell compartment clusterin translocation from the nucleus to the cytoplasm directly related to tumor progression. In fact, a nuclear localization found in healthy colonic mucosa is consistent with the involvement of the proapoptotic nuclear form in the regulation of cell cycle progression and in cell death induction. The progression towards high-grade and metastatic carcinoma leads to cytoplasmic clusterin distribution. Protein extracts from freshly isolated cells of the same patients confirm in high-grade carcinomas with metastatic nodes the complete loss of the proapoptotic nuclear form and a cytoplasmic overexpression of the highly glycosylated form. Data obtained from in vitro experiments confirm that this form is released in the extracellular space and corresponded to the fully glycosylated one. These data suggest that the controversial data on clusterin function in tumors may be related to the pattern shift of its isoform production. As the secreted form of clusterin is correlated to cell matrix formation, cell membrane remodeling and cell-cell adhesion, the overexpression of this form in highly aggressive tumors and metastatic nodes could be a potential new prognostic and predictive marker for colon carcinoma aggressiveness