Note on strongly Lie nilpotent rings

This note contains a few introductory results on strongly Lie nilpotent rings and, in particular, an analogue of a well known theorem of P. Hall on nilpotent groups

The size criteria in minimally invasive video-assisted thyroidectomy

BACKGROUND: Thyroid size is a very important criteria of MIVAT exclusion because the working space provided by the technique is limited. The aim of this work has been to verify the suitability of MIVAT and its applicability in clinical practice, not only in patients with a thyroid volume up to 25 ml but also in patients with a thyroid volume included from 25 to 50 ml. METHODS: From January 2003 to February 2006, 33 patients have been selected for MIVAT. A completely gasless procedure was carried out through a central 20 to 35 mm skin incision performed "high" between the cricoid and jugular notch. RESULTS: The patients were separated in 2 groups. The first group (less than 25 ml) included 23 patients, the second group (from 25 to 50 ml) included 10 patients. The skin incision performed was from 20 to 25 mm (mean 23.61 mm ± 1.83) long in the first group and from 25 to 35 mm (mean 27.8 mm ± 2.20) long in the second one; this difference is significant (t test p < 0.001). CONCLUSION: Our study suggest that the MIVAT using for thyroids bigger than 25 ml and up to 50 ml in volume is feasible and safe. This way allows more patients, excluded before, to take the advantages of minimally invasive approach

Role of the flat-designed surface in improving the cyclic fatigue resistance of endodontic NiTi rotary instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel-titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon-Mann-Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p &lt; 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments

Fatigue resistance of new and used nickel-titanium rotary instruments: a comparative study

Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones

The minimally invasive open video-assisted approach in surgical thyroid diseases

BACKGROUND: The targets of minimally invasive surgery (MIVA) could be summarised by: achievement of the same results as those obtained with traditional surgery, less trauma, better post-operative course, early discharge from hospital and improved cosmetic results. The minimally invasive techniques in thyroid surgery can be described as either endoscopic "pure" approach (completely closed approach with or without CO(2 )insufflation), or "open approach" with central neck mini-incision or "open video-assisted approach". Traditionally, open thyroidectomy requires a 6 to 8 cm, or bigger, transverse wound on the lower neck. The minimally invasive approach wound is much shorter (1.5 cm for small nodules, up to 2–3 cm for the largest ones, in respect of the exclusion criteria) upon the suprasternal notch. Patients also experience much less pain after MIVA surgery than after conventional thyroidectomy. This is due to less dissection and destruction of tissues. Pathologies treated are mainly nodular goiter; the only kind of thyroid cancer which may be approached with endoscopic surgery is a small differentiated carcinoma without lymph node involvement. The patients were considered eligible for MIVA hemithyroidectomy and thyroidectomy on the basis of some criteria, such as gland volume and the kind of disease. In our experience we have chosen the minimally invasive open video-assisted approach of Miccoli et al. (2002). The aim of this work was to verify the suitability of the technique and the applicability in clinical practice. METHODS: A completely gasless procedure was carried out through a 15–30 mm central incision about 20 mm above the sternal notch. Dissection was mainly performed under endoscopic vision using conventional endoscopic instruments. The video aided group included 11 patients. All patients were women with a average age of 54. RESULTS: We performed thyroidectomy in 8 cases and hemithyroidectomy in 3 cases. The operative average time has been 170 minutes. CONCLUSION: Nowadays this minimally invasive surgery, in selected patients, clearly demonstrates excellent results regarding patient cure rate and comfort, with shorter hospital stay, reduced postoperative pain and most attractive cosmetic results

Set-theoretic solutions of the Yang–Baxter equation associated to weak braces

We investigate a new algebraic structure which always gives rise to a set-theoretic solution of the Yang–Baxter equation. Specifically, a weak (left) brace is a non-empty set S endowed with two binary operations + and ∘ such that both (S, +) and (S, ∘) are inverse semigroups and a∘(b+c)=(a∘b)-a+(a∘c)anda∘a-=-a+ahold, for all a, b, c∈ S, where - a and a- are the inverses of a with respect to + and ∘ , respectively. In particular, such structures include that of skew braces and form a subclass of inverse semi-braces. Any solution r associated to an arbitrary weak brace S has a behavior close to bijectivity, namely r is a completely regular element in the full transformation semigroup on S× S. In addition, we provide some methods to construct weak braces

Numerical Calculation of Crack Parameters for Propagation Assessment in a Complex Component with Residual Stresses

AbstractFatigue is an actual issue, especially in the structural assessment of highly critical components where failure may provoke the loss of the whole system they belong to. This is especially true in a damage tolerant scenario. In this case the use of a component is permitted even after damage has occurred, but extensive knowledge of the damage status and the effect of the damage on the reliability of the component is required. An experimental approach to damage tolerance is often very complex both for the damage creation and for the subsequent step of fatigue tests. A reliable and efficient methodology for fatigue simulation and crack propagation is therefore of interest both from a theoretical and an industrial point of view. The aim of the paper is to investigate crack parameters in a transmission shaft subjected to ballistic impact damage; cracks can nucleate from the point of damage and propagate due the application of service loads Starting from the outcome of a FEM simulation of a ballistic impact, different strategies for numerical crack propagation under service loads are presented and assessed. Specifically the damage under investigation is composed of two holes separated by a septum. Experiments reveal that the crack that nucleates from one of the two holes is strongly influenced by residual stresses. The complexity and the variety of the phenomena involved (complex damage, presence of residual stresses, shape of the component) make the numerical simulation of the phenomenon not trivial and give grounds for a thorough investigation of different modelling approaches

A systematic review of a polyvagal perspective on embodied contemplative practices as promoters of cardiorespiratory coupling and traumatic stress recovery for ptsd and ocd: Research methodologies and state of the art

Baseline respiratory sinus arrhythmia (RSA) has been proposed as a transdiagnostic biomarker of stress vulnerability across psychopathologies, and a reliable association between PTSD, OCD and lower resting RSA was found. Contemplative practices have been linked to the activation of the vagus as well as to an increased RSA that, according to the polyvagal theory, reflects the activation of the ventral vagal complex (VVC) and may promote PTSD and OCD recovery. PubMed and Scopus databases were selected to conduct a search following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 guidelines, and A MeaSurement Tool to Assess systematic Reviews-2 (AMSTAR-2) was used to appraise the methodological quality for this systematic review. Six articles met the inclusion criteria (one cross-sectional study, one study with pre-post measurements, two cohort studies and two RCT studies). Mindfulness-related interventions promoted parasympathetic activity, an increased vagal tone and improvements in PTSD and OCD symptoms. According to the polyvagal theory, mindfulness-related and compassion-related meditations would be conceptualized as neural exercises expanding the capacity of the ventral vagal complex to regulate the present state and to promote resilience. Clinical and methodological issues are discussed

I bi-ideali nei semigruppi regolari e negli ortogruppi

Abstract