An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields

Combustion stabilization and enhancement of the flammability limits are mandatory objectives to improve nowadays combustion chambers. At this purpose, the use of an electric field in the flame region provides a solution which is, at the same time, easy to implement and effective to modify the flame structure. The present work describes an efficient flamelet progress-variable approach developed to model the fluid dynamics of flames immersed in an electric field. The main feature of this model is that it can use complex ionization mechanisms without increasing the computational cost of the simulation. The model is based on the assumption that the combustion process is not directly influenced by the electric field and has been tested using two chemi-ionization mechanisms of different complexity in order to examine its behavior with and without the presence of heavy anions in the mixture. Using a one- and two-dimensional numerical test cases, the present approach has been able to reproduce all the major aspects encountered when a flame is subject to an imposed electric field and the main effects of the different chemical mechanisms. Moreover, the proposed model is shown to produce a large reduction in the computational cost, being able to shorten the time needed to perform a simulation up to 40 times.Comment: 26 pages, 13 figures, paper accepted for publication on Computers and Fluid

Inverse Renormalization Group in Quantum Field Theory

We propose inverse renormalization group transformations within the context of quantum field theory that produce the appropriate critical fixed point structure, give rise to inverse flows in parameter space, and evade the critical slowing down effect in calculations pertinent to criticality. Given configurations of the two-dimensional φ4 scalar field theory on sizes as small as V=82, we apply the inverse transformations to produce rescaled systems of size up to V′=5122 which we utilize to extract two critical exponents. We conclude by discussing how the approach is generally applicable to any method that successfully produces configurations from a statistical ensemble and how it can give novel insights into the structure of the renormalization group

Peri-implant marginal bone changes and soft tissue conditions around single implants with laser-microgrooved collar placed in regenerated extraction sockets and in native bone: 2-year results of RCT

The aim of present study was to compare peri-implant marginal bone changes and soft tissues conditions around single implants placed in alveolar sockets regenerated with porcine xenograft and collagen membrane or non-regenerated native bone. Forty patients who required single tooth extraction and single implant placement in premolar/molar area, were enrolled in this study. Subjects were randomly assigned to the control group (S; extraction sockets spontaneously healed) or to the test group (R; extraction sockets grafted with porcine-derived bone and covered with collagen membrane). Six months after extractions, single tapered implants with laser-microgrooved collars were inserted. For each implant, radiographic MBL and clinical parameters were evaluated during 2 years of function. At the 24-month follow-up, a survival rate of 100% was reported for all implants. For the S group, the mean marginal bone loss (MBL) was 0.118 ± 0.07 mm while for the R group the mean MBL was 0.131± 0.03 mm. No statistically significant differences were reported among groups (P >0.05). Between the two groups, no statistically significant differences were found also for plaque index, bleeding on probing, probing depth and gingival recession. At the 24-month follow-up, results showed that implants with laser-microgrooved collar surface placed in regenerated extraction sockets and in native bone did not performed differently with respect to implant survival, MBL and peri-implant soft tissue parameters

An Algorithmic Approach to Quantum Field Theory

The lattice formulation provides a way to regularize, define and compute the Path Integral in a Quantum Field Theory. In this paper we review the theoretical foundations and the most basic algorithms required to implement a typical lattice computation, including the Metropolis, the Gibbs sampling, the Minimal Residual, and the Stabilized Biconjugate inverters. The main emphasis is on gauge theories with fermions such as QCD. We also provide examples of typical results from lattice QCD computations for quantities of phenomenological interest.Comment: 44 pages, to be published in IJMP

Sarcopenia: age-related skeletal muscle changes from determinants to physical disability.

Human aging is characterized by skeletal muscle wasting, a debilitating condition which sets the susceptibility for diseases that directly affect the quality of life and often limit life span. Sarcopenia, i.e. the reduction of muscle mass and/or function, is the consequence of a reduction of protein synthesis and an increase in muscle protein degradation. In addition, the capacity for muscle regeneration is severely impaired in aging and this can lead to disability, particularly in patients with other concomitant diseases or organ impairment. Immobility and lack of exercise, increased levels of proinflammatory cytokines, increased production of oxygen free radicals or impaired detoxification, low anabolic hormone output, malnutrition and reduced neurological drive have been advocated as being responsible for sarcopenia. It is intriguing to notice that multiple pathways converge on skeletal muscle dysfunction, but the factors involved sometimes diverge to different pathways, thus intersecting at critical points. It is reasonable to argue that the activity of these nodes results from the net balance of regulating mechanisms, as in the case of the GH/IGF-1 axis, the testosterone and Cortisol functions, the pro- and anti-inflammatory cytokines and receptors. Both genetic and epigenetic mechanisms operate in regulating the final phenotype, the extent of muscle atrophy and reduction in strength and force generation. It is widely accepted that intervention on lifestyle habits represents an affordable and practical way to modify on a large scale some detrimental outcomes of aging, and particularly sarcopenia. The identification of the molecular chain able to reverse sarcopenia is a major goal of studies on human aging

Large-order NSPT for lattice gauge theories with fermions:the plaquette in massless QCD

Numerical Stochastic Perturbation Theory (NSPT) allows for perturbative computations in quantum field theory. We present an implementation of NSPT that yields results for high orders in the perturbative expansion of lattice gauge theories coupled to fermions. The zero-momentum mode is removed by imposing twisted boundary conditions; in turn, twisted boundary conditions require us to introduce a smell degree of freedom in order to include fermions in the fundamental representation. As a first application, we compute the critical mass of two flavours of Wilson fermions up to order $O(\beta^{-7})$ in a ${\mathrm{SU}}(3)$ gauge theory. We also implement, for the first time, staggered fermions in NSPT. The residual chiral symmetry of staggered fermions protects the theory from an additive mass renormalisation. We compute the perturbative expansion of the plaquette with two flavours of massless staggered fermions up to order $O(\beta^{-35})$ in a ${\mathrm{SU}}(3)$ gauge theory, and investigate the renormalon behaviour of such series. We are able to subtract the power divergence in the Operator Product Expansion (OPE) for the plaquette and estimate the gluon condensate in massless QCD. Our results confirm that NSPT provides a viable way to probe systematically the asymptotic behaviour of perturbative series in QCD and, eventually, gauge theories with fermions in higher representations.Comment: 49 pages, 28 figures. Revised version, to be published in EPJC. Some references added, typos corrected, and improved discussion on finite-volume effect

Perturbative expansions from Monte Carlo simulations at weak coupling: Wilson loops and the static-quark self-energy

Perturbative coefficients for Wilson loops and the static-quark self-energy are extracted from Monte Carlo simulations at weak coupling. The lattice volumes and couplings are chosen to ensure that the lattice momenta are all perturbative. Twisted boundary conditions are used to eliminate the effects of lattice zero modes and to suppress nonperturbative finite-volume effects due to Z(3) phases. Simulations of the Wilson gluon action are done with both periodic and twisted boundary conditions, and over a wide range of lattice volumes (from $3^4$ to $16^4$) and couplings (from $\beta \approx 9$ to $\beta \approx 60$). A high precision comparison is made between the simulation data and results from finite-volume lattice perturbation theory. The Monte Carlo results are shown to be in excellent agreement with perturbation theory through second order. New results for third-order coefficients for a number of Wilson loops and the static-quark self-energy are reported.Comment: 36 pages, 15 figures, REVTEX documen

Effects of dark chocolate in a population of Normal Weight Obese women: a pilot study.

BACKGROUND: Normal weight obese (NWO) syndrome is defined as an excessive body fat associated with a normal body mass index and characterized by a higher risk for cardiovascular morbidity and mortality. Recent studies have demonstrated that dark chocolate (DC) has beneficial effects in the prevention of cardiovascular diseases (CVD) due to its anti-inflammatory and antioxidant properties. AIM: The aim of the present study was to investigate the effects of DC consumption on lipid profile, inflammatory markers, biochemical parameters, and blood pressure, in NWO women. MATERIALS AND METHODS: 15 women affected by NWO syndrome, aged 20-40 years, were included in the study. After a DC-free washout period, subjects received DC (100 g/die) containing 70% cocoa for 7-days. Body composition by Dual energy-X-ray absorptiometry (DXA) was performed at baseline. Blood pressure, anthropometric measurements, biochemical parameters and plasma levels of some cytokines were measured before and after DC consumption. RESULTS: After DC consumption, we observed a significant increase in the HDL cholesterol level (Delta% = +10.41±13,53; p ≤ 0.05), a significant decrease of total cholesterol/HDL cholesterol ratio (Delta %= -11.45±7.03; p ≤ 0.05), LDL/HDL cholesterol ratio (Delta % = -11.70±8.91; p ≤ 0.05), and interleukin-1 receptor antagonist (IL-1Ra) (Delta % = -32.99±3.84; p ≤ 0.05). In addition, a reduction in abdomen circumference was observed. We also found a positive correlation between changes in atherogenic indices, and IL-1Ra, abdomen reduction. CONCLUSIONS: Our findings suggest that regular consumption of DC could be useful in maintaining a good atherogenic profile, due to the favourable effects on HDL cholesterol, lipoprotein ratios and inflammation markers