Minimum energy paths for conformational changes of viral capsids

In this work we study how a viral capsid can change conformation using techniques of Large Deviations Theory for stochastic differential equations. The viral capsid is a model of a complex system in which many units - the proteins forming the capsomers - interact by weak forces to form a structure with exceptional mechanical resistance. The destabilization of such a structure is interesting both per se, since it is related either to infection or maturation processes, and because it yields insights into the stability of complex structures in which the constitutive elements interact by weak attractive forces. We focus here on a simplified model of a dodecahederal viral capsid, and assume that the capsomers are rigid plaquettes with one degree of freedom each. We compute the most probable transition path from the closed capsid to the final configuration using minimum energy paths, and discuss the stability of intermediate states.Comment: 27 pages, 4 figures. New version, to appear in Physical Review

New group theoretical methods for applications in virology and quasicrystals

Non-crystallographic symmetries are ubiquitous in physics, chemistry and biology. Prominent examples are quasicrystals, alloys with long-range order but no translational periodicity in their atomic organisation, and viruses, micro-organisms consisting of a protein shell, the capsid, that in most cases displays icosahedral symmetry. Group theory plays a crucial role in understanding their structures and their physical and geometrical properties. In this thesis new group theoretical methods are introduced, to characterise virus organisation and model structural transitions of icosahedral quasicrystals. It is shown that these problems can be described via the embedding of non-crystallographic groups into the point group of higher dimensional lattices. Indeed, the analysis of orbits of such embeddings, akin to the construction of quasicrystals via the cut-and-project method, provides a rigorous mathematical construction of finite nested point sets with non-crystallographic symmetry at each distinct radial level. In the case of icosahedral symmetry, it is shown that the point arrays thus obtained can be used to provide constraints on the geometry of viral capsids, encoding information on the organisation of the capsid proteins and the genomic material collectively. Moreover, structural transitions of icosahedral quasicrystals can be analysed in a group theoretical framework through continuous rotations in the higher dimensional space connecting distinct copies of the embedded icosahedral group, sharing a common maximal subgroup. These rotations induce in projection continuous transformations between aperiodic point sets that preserve the symmetry described by the common subgroup. Theoretical methods as well as applications are discussed, with emphasis on the computational and geometric aspect of group theory

A group theoretical approach to structural transitions of icosahedral quasicrystals and point arrays

In this paper we describe a group theoretical approach to the study of structural transitions of icosahedral quasicrystals and point arrays. We apply the concept of Schur rotations, originally proposed by Kramer, to the case of aperiodic structures with icosahedral symmetry; these rotations induce a rotation of the physical and orthogonal spaces invariant under the icosahedral group, and hence, via the cut-and-project method, a continuous transformation of the corresponding model sets. We prove that this approach allows for a characterisation of such transitions in a purely group theoretical framework, and provide explicit computations and specific examples. Moreover, we prove that this approach can be used in the case of finite point sets with icosahedral symmetry, which have a wide range of applications in carbon chemistry (fullerenes) and biology (viral capsids).Peer reviewe

Quality of colonoscopy in an organised colorectal cancer screening programme with immunochemical faecal occult blood test. The EQuIPE study (Evaluating Quality Indicators of the Performance of Endoscopy)

OBJECTIVES: To assess variation in the main colonoscopy quality indicators in organised colorectal cancer (CRC) screening programmes based on faecal immunochemical test (FIT). DESIGN: Data from a case-series of colonoscopies of FIT-positive subjects were provided by 44 Italian CRC screening programmes. Data on screening history, endoscopic procedure and histology results, and additional information on the endoscopy centre and the endoscopists were collected. The adenoma detection rate (ADR) and caecal intubation rate (CIR) were assessed for the whole population and the individual endoscopists. To explore variation in the quality indicators, multilevel analyses were performed according to patient/centre/endoscopist characteristics. RESULTS: We analysed 75 569 (mean age: 61.3 years; men: 57%) colonoscopies for positive FIT performed by 479 endoscopists in 79 centres. ADR ranged from 13.5% to 75% among endoscopists (mean: 44.8%). ADR was associated with gastroenterology specialty (OR: 0.87 for others, 95% CI 0.76 to 0.96) and, at the endoscopy centre level, with the routine use of sedation (OR: 0.80 if occasional (600 colonoscopies; 95% CI 1.11 to 2.04) and, at the endoscopy centre level, screening-dedicated sessions (OR: 2.18; 95% CI 1.24 to 3.83) and higher rates of sedation (OR: 0.47 if occasional; 95% CI 0.24 to 0.92). CONCLUSIONS: The quality of colonoscopy was affected by patient-related, endoscopist-related and centre-related characteristics. Policies addressing organisational issues should improve the quality of colonoscopy in our programme and similar programmes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions

Revisional Surgery After One Anastomosis/Minigastric Bypass: an Italian Multi-institutional Survey

Background: Efficacy and safety of OAGB/MGB (one anastomosis/mini gastric bypass) have been well documented both as primary and as revisional procedures. However, even after OAGB/MGB, revisional surgery is unavoidable in patients with surgical complications or insufficient weight loss. Methods: A questionnaire asking for the total number and demographics of primary and revisional OAGB/MGBs performed between January 2006 and July 2020 was e-mailed to all S.I.C. OB centres of excellence (annual caseload > 100; 5-year follow-up > 50%). Each bariatric centre was asked to provide gender, age, preoperative body mass index (BMI) and obesity-related comorbidities, previous history of abdominal or bariatric surgery, indication for surgical revision of OAGB/MGB, type of revisional procedure, pre- and post-revisional BMI, peri- and post-operative complications, last follow-up (FU). Results: Twenty-three bariatric centres (54.8%) responded to our survey reporting a total number of 8676 primary OAGB/MGBS and a follow-up of 62.42 ± 52.22 months. A total of 181 (2.08%) patients underwent revisional surgery: 82 (0.94%) were suffering from intractable DGER (duodeno-gastric-esophageal reflux), 42 (0.48%) were reoperated for weight regain, 16 (0.18%) had excessive weight loss and malnutrition, 12 (0.13%) had a marginal ulcer perforation, 10 (0.11%) had a gastro-gastric fistula, 20 (0.23%) had other causes of revision. Roux-en-Y gastric bypass (RYGB) was the most performed revisional procedure (109; 54%), followed by bilio-pancreatic limb elongation (19; 9.4%) and normal anatomy restoration (19; 9.4%). Conclusions: Our findings demonstrate that there is acceptable revisional rate after OAGB/MGB and conversion to RYGB represents the most frequent choice

Colorectal cancer after bariatric surgery (Cric-Abs 2020): Sicob (Italian society of obesity surgery) endorsed national survey

Background The published colorectal cancer (CRC) outcomes after bariatric surgery (BS) are conflicting, with some anecdotal studies reporting increased risks. The present nationwide survey CRIC-ABS 2020 (Colo-Rectal Cancer Incidence-After Bariatric Surgery-2020), endorsed by the Italian Society of Obesity Surgery (SICOB), aims to report its incidence in Italy after BS, comparing the two commonest laparoscopic procedures-Sleeve Gastrectomy (SG) and Roux-en-Y gastric bypass (GBP). Methods Two online questionnaires-first having 11 questions on SG/GBP frequency with a follow-up of 5-10 years, and the second containing 15 questions on CRC incidence and management, were administered to 53 referral bariatric, high volume centers. A standardized incidence ratio (SIR-a ratio of the observed number of cases to the expected number) with 95% confidence intervals (CI) was calculated along with CRC incidence risk computation for baseline characteristics. Results Data for 20,571 patients from 34 (63%) centers between 2010 and 2015 were collected, of which 14,431 had SG (70%) and 6140 GBP (30%). 22 patients (0.10%, mean age = 53 +/- 12 years, 13 males), SG: 12 and GBP: 10, developed CRC after 4.3 +/- 2.3 years. Overall incidence was higher among males for both groups (SG: 0.15% vs 0.05%; GBP: 0.35% vs 0.09%) and the GBP cohort having slightly older patients. The right colon was most affected (n = 13) and SIR categorized/sex had fewer values < 1, except for GBP males (SIR = 1.07). Conclusion Low CRC incidence after BS at 10 years (0.10%), and no difference between procedures was seen, suggesting that BS does not trigger the neoplasm development

L’evoluzione degli insegnamenti di Ragioneria

This chapter aims at analysing how the teachings in accounting evolved from the foundation of the School of Commerce in Venice in 1868 for the first century of its activity. As teachings in accounting we consider the courses dealing with recognition methods and accounting principles both applying in private and public entities, but also the courses dealing with business practice where accounting played a relevant role (such as the case of the course entitled ‘Banco modello’). During this period the number, name and contents of teachings in accounting changed as consequence of the influence of the scientific thought of two great Maestri of Italian accounting: Fabio Besta and Gino Zappa, both teachers in Venice