Symplectic analysis of time-frequency spaces

We present a different symplectic point of view in the definition of weighted modulation spaces and weighted Wiener amalgam spaces. All the classical time-frequency representations, such as the short-time Fourier transform (STFT), the τ-Wigner distributions and the ambiguity function, can be written as metaplectic Wigner distributions \mu(A)(f\otimes\bar g), where \mu(A) is the metaplectic operator and A is the associated symplectic matrix. Namely, time-frequency representations can be represented as images of metaplectic operators, which become the real protagonists of time-frequency analysis. In [13], the authors suggest that any metaplectic Wigner distribution that satisfies the so-called shift-invertibility condition can replace the STFT in the definition of modulation spaces. In this work, we prove that shift-invertibility alone is not sufficient, but it has to be complemented by an upper-triangularity condition for this characterization to hold, whereas a lower-triangularity property comes into play for Wiener amalgam spaces. The shift-invertibility property is necessary: Rihaczek and conjugate Rihaczek distributions are not shift-invertible and they fail the characterization of the above spaces. We also exhibit examples of shift-invertible distributions without upper-triangularity condition which do not define modulation spaces. Finally, we provide new families of time-frequency representations that characterize modulation spaces, with the purpose of replacing the time-frequency shifts with other atoms that allow to decompose signals differently, with possible new outcomes in applications

Quasi-Banach algebras and Wiener properties for pseudodifferential and generalized metaplectic operators

We generalize the results for Banach algebras of pseudodifferential operators obtained by Gr\"ochenig and Rzeszotnik in [24] to quasi-algebras of Fourier integral operators. Namely, we introduce quasi-Banach algebras of symbol classes for Fourier integral operators that we call generalized metaplectic operators, including pseudodifferential operators. This terminology stems from the pioneering work on Wiener algebras of Fourier integral operators [11], which we generalize to our framework. This theory finds applications in the study of evolution equations such as the Cauchy problem for the Schr\"odinger equation with bounded perturbations, cf. [7].Comment: 26 page

Metaplectic Gabor Frames and Symplectic Analysis of Time-Frequency Spaces

We introduce new frames, called \textit{metaplectic Gabor frames}, as natural generalizations of Gabor frames in the framework of metaplectic Wigner distributions. Namely, we develop the theory of metaplectic atoms in a full-general setting and prove an inversion formula for metaplectic Wigner distributions on $\mathbb{R}^d$. Its discretization provides metaplectic Gabor frames. Next, we deepen the understanding of the so-called shift-invertible metaplectic Wigner distributions, showing that they can be represented, up to chirps, as rescaled short-time Fourier transforms. As an application, we derive a new characterization of modulation and Wiener amalgam spaces. Thus, these metaplectic distributions (and related frames) provide meaningful definitions of local frequencies and can be used to measure effectively the local frequency content of signals

Biochemical Alterations in Semen of Varicocele Patients: A Review of the Literature

Oxidative stress is a mechanism underlying different kinds of infertility in human males. However, different results can be observed in relation to the method used for its evaluation. Varicocele patients show a number of biochemical abnormalities, including an altered distribution of coenzyme Q between seminal plasma and sperm cells and also an apparent defect in the utilization of antioxidants. Moreover, an influence of systemic hormones on seminal antioxidant system was observed too. Finally, the effects of surgical treatment on oxidativestress indexes and the possible usefulness of some medical therapies, like coenzyme Q supplementation, are discussed. In conclusion, published data show a role of oxidative stress in varicocele-related male infertility, but at present we do not know the precise molecular mechanisms underlying these phenomena

Beyond ‘BRICS’: ten theses on South–South cooperation in the twenty-first century

Grounded in a review of past and present academic South–South cooperation literatures, this article advances ten theses that problematise empirical, theoretical, conceptual and methodological issues essential to discussions of South–South cooperation in the 21st century. This endeavour is motivated by the perceived undermining, especially in the contemporary Anglophone academic South–South cooperation literature, of the emancipatory potential historically associated with South–South cooperation. By drawing on the interventionist South–South cooperation agendas of ‘left’-leaning Latin America-Caribbean governments, the article seeks to establish a dialogue between social science theories and less ‘visible’ analyses from academic (semi)peripheries. The ten theses culminate in an exploration of the potential of South–South cooperation to promote ‘alternative’ development

Factors associated with unhealthy behaviours and health outcomes: a cross-sectional study among tuscan adolescents (Italy)

BackgroundWe aimed to determine the extent to which three core variables (school environment, peer group and family affluence) were associated with unhealthy behaviours and health outcomes among Tuscan adolescents. The unhealthy behaviours considered were smoking, alcohol consumption, sedentary lifestyle and irregular breakfast consumption; health outcomes were classified as self-reported health, multiple health complaints and life satisfaction. School environment was measured in terms of liking school, school pressure, academic achievement and classmate support; peer groups were evaluated in terms of the number of peers and frequency of peer contact. Family affluence was measured on a socioeconomic scale.MethodsData were taken from the Tuscan 2009/10 survey of ¿Health Behaviour in School-aged Children¿, a WHO cross-national survey. A binary logistic multiple regression (95% confidence intervals) was implemented.ResultsThe total sample comprised 3291 school students: 1135 11-year-olds, 1255 13-year-olds and 901 15-year-olds. Peer group and school environment were associated with unhealthy behaviours such as smoking, alcohol consumption and sedentary lifestyle. Family affluence proved to have less impact on unhealthy behaviours, except in the case of adolescents living in low-income families. Poor health outcomes were directly related to a negative school environment. Regarding the influence of family affluence, the results showed higher odds of life dissatisfaction and poor self-reported health status in medium-income families, while low-income families had higher odds only with regard to life dissatisfaction. A consistent pattern of gender differences was found in terms of both unhealthy behaviours and health outcomes.ConclusionsUnhealthy behaviours are strongly related to the school environment and peer group. A negative school environment proved to have the strongest relation with poor health outcomes

Oxidative Stress and Low-Grade Inflammation in Polycystic Ovary Syndrome: Controversies and New Insights

The pathophysiology of Polycystic Ovary Syndrome (PCOS) is quite complex and different mechanisms could contribute to hyperandrogenism and anovulation, which are the main features of the syndrome. Obesity and insulin-resistance are claimed as the principal factors contributing to the clinical presentation; in normal weight PCOS either, increased visceral adipose tissue has been described. However, their role is still debated, as debated are the biochemical markers linked to obesity per se. Oxidative stress (OS) and low-grade inflammation (LGI) have recently been a matter of researcher attention; they can influence each other in a reciprocal vicious cycle. In this review, we summarize the main mechanism of radical generation and the link with LGI. Furthermore, we discuss papers in favor or against the role of obesity as the first pathogenetic factor, and show how OS itself, on the contrary, can induce obesity and insulin resistance; in particular, the role of GH-IGF-1 axis is highlighted. Finally, the possible consequences on vitamin D synthesis and activation on the immune system are briefly discussed. This review intends to underline the key role of oxidative stress and low-grade inflammation in the physiopathology of PCOS, they can cause or worsen obesity, insulin-resistance, vitamin D deficiency, and immune dyscrasia, suggesting an inverse interaction to what is usually considered