Evolution of cosmological perturbations in an RG-driven inflationary scenario

A gauge-invariant, linear cosmological perturbation theory of an almost homogeneous and isotropic universe with dynamically evolving Newton constant G and cosmological constant $\Lambda$ is presented. The equations governing the evolution of the comoving fractional spatial gradients of the matter density, G and $\Lambda$ are thus obtained. Explicit solutions are discussed in cosmologies, featuring an accelerated expansion, where both G and $\Lambda$ vary according to renormalization group equations in the vicinity of an ultraviolet fixed point. Finally, a similar analysis is carried out in the late universe regime described by the part of the renormalization group trajectory close to the gaussian fixed point.Comment: 18 pages; improved discussion and references added; fitted to match published versio

The efficacy of Radiofrequency Ablation in the treatment of benign thyroid nodules and recurrent well-differentiated thyroid carcinomas.

Purpose: The aim of our study was to evaluate, in our experience, the effectiveness of the Radiofrequency Ablation (RFA)in the treatment of benign thyroid nodules and thyroid malignancies. Materials and methods: The study included 23 patients, 15 with nodular goiter (NG) with contraindication or refusing surgery and 8 with inoperable recurrent well-differentiated thyroid cancers (RTC). RFA was performed in a single session under ultrasound guidance, under local anesthesia and mild sedation using 18- or 19-gauge internally cooled, single tipped electrode with 7- and 10-mm active tips. The pre- and post-treatment evaluations included: contrast-enhanced ultrasound (CEUS) and unenhanced Computed Tomography (CT) study for the NGs, completed with contrast media in patients with RTCs. Of each lesion the initial volume (V), the vascularity and the proportion of solid component were assessed; for NGs we also evaluated thyroid function, local symptoms (according to a score of 0-10 severity) and a cosmetic score defined by the radiologist according to a 1-4 scale (not palpable, palpable but not visible, visible only during swallowing and visible in any position). The follow-up in 21/23 patients ranged between 6 and 18 months; 2/8 patients with RTCs did not undergo 6-months follow-up, respectively for systemic progression of disease and onset of severe comorbidity. Volume Reduction Rate was assessed during the follow-up and therapeutic success was defined as a> 50% VRR. Residual vital tissue was also assessed by using CEUS or post-contrastographic CT examinations. Complications were also evaluated. For NGs we also tried whether there was a correlation between VRR at 6 months follow-up and some parameters such as age, gender, mean energy per millilitre of pre-treatment nodule volume, nodule initial volume, initial nodule solidity and initial nodule vascularity. Results: Mean V of lesions before treatment was 29.5 ± 24.7 mL for NGs (range: 5.5-90ml), and 4.7 ± 3.5 ml (range: 0.8 to 8.8 ml) for RTCs. The mean VRR at 6, 12 and 18 months were respectively 74.3%, 79.8% and 82.3% for NGs. At last follow-up, the therapeutic success rate of NGs was 100% (15/15). The overall recurrence rate was 0% (0/15). We found that volume, residual vital tissue, cosmetic score and symptom score of NGs were significantly lower at last follow-up than before treatment (P <0.0005 for all comparison). Initial nodule volume, vascularity and energy delivered per millilitre of pre-treatment nodule volume demonstrated to be significantly related to 6-months VRR (P < 0.0001 for all analysis). The VRR of RTCs was 68.4%, 66.4% and 64.4% during the follow-up at 6, 12 and 18 months. At last follow-up, the therapeutic success rate for RTCs was 83% (5/6) with overall regrowth and/or recurrence rate of 0% (0/6). In no case of NGs dysphonia was observed; 3/6 patients with paratracheal RCT, closely adjacent to the danger triangle of the recurrent laryngeal nerve, have reported dysphonia (permanent in 2 cases and transient in 1 patient). Conclusions: RFA demonstrated in our experience to be an effective and safe interventional technique and may represent a viable alternative to surgery in selected patients

Inflation in asymptotically safe f(R) theory

We discuss the existence of inflationary solutions in a class of renormalization group improved polynomial f(R) theories, which have been studied recently in the context of the asymptotic safety scenario for quantum gravity. These theories seem to possess a nontrivial ultraviolet fixed point, where the dimensionful couplings scale according to their canonical dimensionality. Assuming that the cutoff is proportional to the Hubble parameter, we obtain modified Friedmann equations which admit both power law and exponential solutions. We establish that for sufficiently high order polynomial the solutions are reliable, in the sense that considering still higher order polynomials is very unlikely to change the solution.Comment: Presented at 14th Conference on Recent Developments in Gravity: NEB 14, Ioannina, Greece, 8-11 Jun 201

Renormalisation group improvement of scalar field inflation

We study quantum corrections to Friedmann-Robertson-Walker cosmology with a scalar field under the assumption that the dynamics are subject to renormalisation group improvement. We use the Bianchi identity to relate the renormalisation group scale to the scale factor and obtain the improved cosmological evolution equations. We study the solutions of these equations in the renormalisation group fixed point regime, obtaining the time-dependence of the scalar field strength and the Hubble parameter in specific models with monomial and trinomial quartic scalar field potentials. We find that power-law inflation can be achieved in the renormalisation group fixed point regime with the trinomial potential, but not with the monomial one. We study the transition to the quasi-classical regime, where the quantum corrections to the couplings become small, and find classical dynamics as an attractor solution for late times. We show that the solution found in the renormalisation group fixed point regime is also a cosmological fixed point in the autonomous phase space. We derive the power spectrum of cosmological perturbations and find that the scalar power spectrum is exactly scale-invariant and bounded up to arbitrarily small times, while the tensor perturbations are tilted as appropriate for the background power-law inflation. We specify conditions for the renormalisation group fixed point values of the couplings under which the amplitudes of the cosmological perturbations remain small.Comment: 17 pages; 2 figure

Renormalisation group improvement of the early universe dynamics

Selected applications of the Functional Renormalisation Group Equation technique to the early universe dynamics

Dependency cases referred to a children's agency for protective services.

Thesis (M.S.)--Boston Universit

Sparks fade with distance: The effect of electric field distribution on global motion perception using different tES techniques

Previous evidence has shown that high-frequency transcranial random noise stimulation (hf-tRNS) reduces motion coherence thresholds when applied with a cephalic montage (i.e., return electrode over Cz). Extracephalic montages, which avoid stimulating regions under the return electrode, have also been used to modulate behavioral performance. In this study, we investigated the effects of different transcranial electrical stimulation (tES) protocols on visual motion discrimination, placing the return electrode on the ipsilateral arm. We assessed the impact of electrode positioning using hf-tRNS, anodal, cathodal transcranial direct current stimulation (tDCS), and Sham stimulation over hMT+, a brain region involved in global motion perception. Motion direction discrimination was measured using random dot kinematograms (RDKs). Given the increased distance between the stimulation and return electrodes in this montage, we expected a smaller reduction in motion discrimination thresholds compared to our previous study. Our results suggest that increasing interelectrode distance alters current flow characteristics - such as current distribution and focality - within the cortical areas under the target electrode, producing different effects. Additionally, no significant effects were observed with the other tES protocols tested. Our findings suggest that change in the interelectrode distance influences current flow characteristics, such as current distribution and focality, within the cortical areas under the target electrode, resulting in differential neuromodulatory effects. These results highlight the importance of stimulation configuration on performance, particularly a potential electric field shift due to the change in the interelectrode distance. Given the widespread application of brain stimulation techniques in clinical and cognitive research, our results can guide future studies carefully considering this further aspect of stimulation montage configurations

Artichoke biorefinery: From food to advanced technological applications

A sequential extraction process has been designed for valorizing globe artichoke plant residues and waste (heads, leaves, stalks, and roots left in the field) by means of green extraction techniques according to a biorefinery approach. We investigated two cascading extractions based on microwave-assisted extractions (MAE) and green solvents (water and ethanol) that have been optimized for varying temperature, solvent and extraction time. In the first step, phenols were extracted with yields that ranged between 6.94 mg g−1 dw (in leaves) and 3.28 mg g−1 dw (in roots), and a phenols productivity of 175.74 kg Ha−1. In the second step, inulin was extracted with impressive yields (42% dw), higher than other conventional inulin sources, corresponding to an inulin productivity of 4883.58 kg Ha−1. The remaining residues were found to be valuable feedstocks both for bioenergy production and green manure (back to the field), closing the loop according to the Circular Economy paradigm

Visual Perceptual Learning of Form–Motion Integration: Exploring the Involved Mechanisms with Transfer Effects and the Equivalent Noise Approach

Background: Visual perceptual learning plays a crucial role in shaping our understanding of how the human brain integrates visual cues to construct coherent perceptual experiences. The visual system is continually challenged to integrate a multitude of visual cues, including form and motion, to create a unified representation of the surrounding visual scene. This process involves both the processing of local signals and their integration into a coherent global percept. Over the past several decades, researchers have explored the mechanisms underlying this integration, focusing on concepts such as internal noise and sampling efficiency, which pertain to local and global processing, respectively. Objectives and Methods: In this study, we investigated the influence of visual perceptual learning on non-directional motion processing using dynamic Glass patterns (GPs) and modified Random-Dot Kinematograms (mRDKs). We also explored the mechanisms of learning transfer to different stimuli and tasks. Specifically, we aimed to assess whether visual perceptual learning based on illusory directional motion, triggered by form and motion cues (dynamic GPs), transfers to stimuli that elicit comparable illusory motion, such as mRDKs. Additionally, we examined whether training on form and motion coherence thresholds improves internal noise filtering and sampling efficiency. Results: Our results revealed significant learning effects on the trained task, enhancing the perception of dynamic GPs. Furthermore, there was a substantial learning transfer to the non-trained stimulus (mRDKs) and partial transfer to a different task. The data also showed differences in coherence thresholds between dynamic GPs and mRDKs, with GPs showing lower coherence thresholds than mRDKs. Finally, an interaction between visual stimulus type and session for sampling efficiency revealed that the effect of training session on participants’ performance varied depending on the type of visual stimulus, with dynamic GPs being influenced differently than mRDKs. Conclusion: These findings highlight the complexity of perceptual learning and suggest that the transfer of learning effects may be influenced by the specific characteristics of both the training stimuli and tasks, providing valuable insights for future research in visual processing