446 research outputs found

    Non-renormalizability of noncommutative SU(2) gauge theory

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    We analyze the divergent part of the one-loop effective action for the noncommutative SU(2) gauge theory coupled to the fermions in the fundamental representation. We show that the divergencies in the 2-point and the 3-point functions in the θ\theta-linear order can be renormalized, while the divergence in the 4-point fermionic function cannot.Comment: 15 pages, results presented at ESI 2d dilaton gravity worksho

    Renormalization group scale-setting from the action - a road to modified gravity theories

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    The renormalization group (RG) corrected gravitational action in Einstein-Hilbert and other truncations is considered. The running scale of the renormalization group is treated as a scalar field at the level of the action and determined in a scale-setting procedure recently introduced by Koch and Ramirez for the Einstein-Hilbert truncation. The scale-setting procedure is elaborated for other truncations of the gravitational action and applied to several phenomenologically interesting cases. It is shown how the logarithmic dependence of the Newton's coupling on the RG scale leads to exponentially suppressed effective cosmological constant and how the scale-setting in particular RG corrected gravitational theories yields the effective f(R)f(R) modified gravity theories with negative powers of the Ricci scalar RR. The scale-setting at the level of the action at the non-gaussian fixed point in Einstein-Hilbert and more general truncations is shown to lead to universal effective action quadratic in Ricci tensor.Comment: v1: 15 pages; v2: shortened to 10 pages, main results unchanged, published in Class. Quant. Gra

    Varenicline and evaluated outcomes in smoking cessation programmes

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    The morbidity and mortality rates attributed to smoking are substantial and cigarette smoke remains the first preventable cause of premature death worldwide. Despite the knowledge of the adverse consequences of smoking, many smokers struggle to quit. Cigarette smoking is the primary cause of chronic obstructive pulmonary disease, and smoking cessation represents the most effective way of stopping its progression. Varenicline is one of the first-line smoking cessation aids recommended in many Clinical Practice Guidelines and its efficacy and safety have been demonstrated in several clinical trials. Varenicline has a unique mechanism of action and clinical trials support its use as an effective and generally well-tolerated therapy. This article reviews the clinical pharmacological trials on smoking cessation published in recent years on varenicline, with particular attention to the outcomes used in the studies. MedLine, the Cochrane database and Embase were evaluated. Almost all the trials have, as a primary endpoint, the abstinence from cigarettes at 9-12 weeks of treatment. Only one study considers lung function spirometric changes as a secondary endpoint. No study has evaluated lung function. This marker could be very important as a way of evaluating, objectively, an improvement in lung function, which correlates also with subjective parameters, as dyspnea and fatigue

    Varenicline and evaluated outcomes in smoking cessation programmes.

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    The morbidity and mortality rates attributed to smoking are substantial and cigarette smoke remains the first preventable cause of premature death worldwide. Despite the knowledge of the adverse consequences of smoking, many smokers struggle to quit. Cigarette smoking is the primary cause of chronic obstructive pulmonary disease, and smoking cessation represents the most effective way of stopping its progression. Varenicline is one of the first-line smoking cessation aids recommended in many Clinical Practice Guidelines and its efficacy and safety have been demonstrated in several clinical trials. Varenicline has a unique mechanism of action and clinical trials support its use as an effective and generally well-tolerated therapy. This article reviews the clinical pharmacological trials on smoking cessation published in recent years on varenicline, with particular attention to the outcomes used in the studies. MedLine, the Cochrane database and Embase were evaluated. Almost all the trials have, as a primary endpoint, the abstinence from cigarettes at 9-12 weeks of treatment. Only one study considers lung function spirometric changes as a secondary endpoint. No study has evaluated lung function. This marker could be very important as a way of evaluating, objectively, an improvement in lung function, which correlates also with subjective parameters, as dyspnea and fatigue

    Influence of attention alternation on movement-related cortical potentials in healthy individuals and stroke patients.

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    OBJECTIVE: In this study, we analyzed the influence of artificially imposed attention variations using the auditory oddball paradigm on the cortical activity associated to motor preparation/execution. METHODS: EEG signals from Cz and its surrounding channels were recorded during three sets of ankle dorsiflexion movements. Each set was interspersed with either a complex or a simple auditory oddball task for healthy participants and a complex auditory oddball task for stroke patients. RESULTS: The amplitude of the movement-related cortical potentials (MRCPs) decreased with the complex oddball paradigm, while MRCP variability increased. Both oddball paradigms increased the detection latency significantly (p<0.05) and the complex paradigm decreased the true positive rate (TPR) (p=0.04). In patients, the negativity of the MRCP decreased while pre-phase variability increased, and the detection latency and accuracy deteriorated with attention diversion. CONCLUSION: Attention diversion has a significant influence on MRCP features and detection parameters, although these changes were counteracted by the application of the laplacian method. SIGNIFICANCE: Brain-computer interfaces for neuromodulation that use the MRCP as the control signal are robust to changes in attention. However, attention must be monitored since it plays a key role in plasticity induction. Here we demonstrate that this can be achieved using the single channel Cz

    Helmet CPAP treatment in patients with COVID-19 pneumonia: a multicenter, cohort study

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    Helmet CPAP treatment fails in up to 44% of patients with moderate-to-severe hypoxemic acute respiratory failure due to COVID-19 pneumoni

    Magnetism in Cr-doped ZnS: Density-functional theory studies

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    We investigated the magnetism and aggregation trends in cubic Zn1-xCrxS using the density-functional theory calculations.We demonstrate that all studied configurations show ground state half-metallic ferromagnetism (HMF); and Cr impurities are energetically favorable to planar cluster into delta-doping structures. The single-layer delta-doping structures of Zn0.75Cr0.25S and Zn0.875Cr0.125S show ferromagnetic stabilization energies (\Delta E_AF) of 0.551 and 0.561 eV/Cr-Cr pair, respectively. The half-layer delta-doping structure of Zn0.875Cr0.125S and double-layer delta-doping structure of Zn0.75Cr0.25S show \Delta E_AF of 0.394 and 0.166 eV/Cr-Cr pair, respectively. Furthermore, our studies indicate that the cubic ZnS/CrS heterostructure, one extreme situation of the delta-doping structure, also shows ground state HMF. The origin of HMF is discussed using a simple crystal field model. Finally, we anticipate the potential spintronics application of Zn1-xCrxS.Comment: 13 pages, 4 figure
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