New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity ...values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.
Nanophotonics and metamaterials have revolutionized the way we think about optical space (ɛ,μ), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the ...volumes, and to manipulate optical signals with extremely small footprints and energy requirements. Significant efforts are now devoted to finding suitable materials and strategies for the dynamic control of the optical properties. Transparent conductive oxides exhibit large ultrafast nonlinearities under both interband and intraband excitations. Here we show that combining these two effects in aluminium-doped zinc oxide via a two-colour laser field discloses new material functionalities. Owing to the independence of the two nonlinearities, the ultrafast temporal dynamics of the material permittivity can be designed by acting on the amplitude and delay of the two fields. We demonstrate the potential applications of this novel degree of freedom by dynamically addressing the modulation bandwidth and optical spectral tuning of a probe optical pulse.
Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We ...experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.
In the face of global population growth and the uneven distribution of water supply, a better knowledge of the spatial and temporal distribution of surface water resources is critical. Remote sensing ...provides a synoptic view of ongoing processes, which addresses the intricate nature of water surfaces and allows an assessment of the pressures placed on aquatic ecosystems. However, the main challenge in identifying water surfaces from remotely sensed data is the high variability of spectral signatures, both in space and time. In the last 10years only a few operational methods have been proposed to map or monitor surface water at continental or global scale, and each of them show limitations. The objectives of this study are to develop, demonstrate and validate the adequacy of a generic multi-temporal and multi-spectral image analysis method to detect water surfaces automatically, and to monitor them in near real-time at the African continental scale as a first step towards global scale coverage. The proposed approach, based on a transformation of the RGB color space into HSV, provides dynamic information at the continental scale. Two different validations were done at the continental scale over Africa: i) The algorithm validation checked the ability of the proposed algorithm to perform as effectively as human interpretation of the image: it showed an accuracy of 96.6% and no commission errors. ii) The product validation was carried out by using an independent dataset derived from high resolution imagery: the continental permanent water surface product showed an accuracy of 91.5% and few commission errors. Potential applications of the proposed method have been identified and discussed. The methodology that has been developed is generic: it can be applied to sensors with similar bands with good reliability, and minimal effort. Moreover, this experiment at the African continental scale showed that the methodology is efficient for a large range of environmental conditions. Additional preliminary tests over other continents indicate that the proposed methodology could also be applied at the global scale without too many difficulties.
•An innovative water body detection method using a colorimetric analysis was developed.•It allows characterization of their spatial and temporal dynamics from MIR, NIR and Red.•It is easily adaptable to other sensors with same spectral channels.•It provides highly reliable detection over a wide range of environmental conditions.
Time-varying metasurfaces are emerging as a powerful instrument for the dynamical control of the electromagnetic properties of a propagating wave. Here we demonstrate an efficient time-varying ...metasurface based on plasmonic nano-antennas strongly coupled to an epsilon-near-zero (ENZ) deeply subwavelength film. The plasmonic resonance of the metal resonators strongly interacts with the optical ENZ modes, providing a Rabi level spitting of ∼30%. Optical pumping at frequency ω induces a nonlinear polarization oscillating at 2ω responsible for an efficient generation of a phase conjugate and a negative refracted beam with a conversion efficiency that is more than 4 orders of magnitude greater compared to the bare ENZ film. The introduction of a strongly coupled plasmonic system therefore provides a simple and effective route towards the implementation of ENZ physics at the nanoscale.
To assess admission rates to seven General Hospital Psychiatric Wards (GHPWs) located in the Lombardy Region in the 40 days after the start of Coronavirus disease 2019 (COVID-19) epidemic, compared ...to similar periods of 2020 and 2019.
Anonymized data from the regional psychiatric care register have been obtained and analyzed. The seven GHPWs care for approximately 1.4 million inhabitants and have a total of 119 beds.
In the 40-day period (February 21-March 31, 2020) after the start of the COVID-19 epidemic in Italy, compared to a similar 40-day period prior to February 21, and compared to two 40-day periods of 2019, there has been a marked reduction in psychiatric admission rates. The reduction was explained by voluntary admissions, while there was not a noticeable reduction for involuntary admissions. The reduction was visible for all diagnostic groups, except for a group of 'Other' diagnoses, which includes anxiety disorders, neurocognitive disorders, etc.
Large-scale pandemics can modify voluntary admission rates to psychiatric facilities in the early phases following pandemic onset. We suggest that the reduction in admission rates may be due to fear of hospitals, seen as possible sites of contagion, as well as to a change in thresholds of behavioral problems acting as a trigger for admission requests from family relatives or referrals from treating clinicians. It is unclear from the study whether the reduction in admissions was contributed to most by the current pandemic or the lockdown imposed due to the pandemic.
Objectives
Despite recent pharmacological progress, memory impairment is still frequently reported in people living with HIV. We aimed to conduct a systematic literature review investigating the ...presence of impairment of (sub)components of memory function in patients prescribed highly active antiretroviral therapy (ART).
Methods
We adopted a cognitive neuropsychological model of memory function as the theoretical framework, distinguishing between a short‐term working memory component and a long‐term component of memory, along with their specific (sub)components. We systematically searched for the presence of impairment of each (sub)component in the selected papers. Careful consideration was given to study design and methods and control of covariates.
Results
Only the central executive component of working memory has been consistently reported to be impaired in HIV infection. The other two (sub)components, namely the phonological loop and the visuospatial sketchpad, were unimpaired. Discordant results have been obtained as to verbal and visual episodic memory, as some authors reported an association with HIV infection, whereas others did not. There is little evidence for semantic memory deficit in HIV infection, while there are suggestions that the neural substrate of implicit memory may be damaged by the effects of HIV infection and inflammation. Most studies in this area have been conducted in small samples and with poor control for covariates. Thus, conclusions regarding the association of memory dysfunction with HIV infection are hampered by methodological issues such as selection bias and unmeasured confounding.
Conclusions
The task remains for future research to ascertain the impact of HIV infection on memory function.
Brazil is one of the three major fruit producers in the world. Native and/or exotic Brazilian fruits have great nutritional and economic potential. Eggfruit, blackberry, Brazilian guava, atemoya, ...bacuri, sweetsop, starfruit, feijoa, cactus pear, fruit of wolf, breadfruit, jaboticaba, jackfruit, rose apple, lychee, mangaba and marolo are already present in the Brazilian diet, but they are not yet industrialized and are minor agricultural products. These fruits are produced and used in the manufacture of handicraft products such as jellies and sweets that are available in free markets, but production is small-scale and without safe operational procedures. These fruits are seasonal with large postharvest losses. Thus, it is necessary to initiate competitive agribusinesses in the producing regions for these fruits to enhance local economies. This review summarizes the major nutritional and bioactive compounds found in these fruits, the technological aspects of their cultivation, and future prospects for introducing consumption of these fruits and their respective products to Brazilian and/or foreign markets.
► A wide variety of native and/or exotic fruits are consumed in Brazil. ► Fresh fruit consumption may assist in rapid recovery from dehydration. ► Non-digestible carbohydrates, such as fibers, are very common in these fruits. ► Only cactus pear and lychee are classified as low-fiber fruits.
Introduction
Depression is a severe mental disorder with an estimated 3.8% of the population affected, representing a leading cause of disability worldwide. Being linked to reduced quality of life ...and individual functioning, medical morbidity and mortality, depression has a huge social and economic impact. A wide range of potentially modifiable factors for depression has been identified. Among these, social factors (e.g. support/engagement) appear to play a major role in the emergence and severity of depression.
Objectives
We aimed at providing a quantitative synthesis of the consistency and magnitude of the association between measures of social connection and depression. Social connection included both quantitative (i.e. existence/absence of social relationships) and functional (i.e. support provided) measures of social relationships, as well as measures focusing on social inequalities related to participation in community spaces/activities (i.e. social discrimination).
Methods
We searched PubMed, PsycINFO, Cochrane Library and EMBASE. The strength of the association between exposure factors (social measures) and depression was extracted and equivalent odds ratios were computed to compare the strength of the effect sizes among meta-analyses. The quality of each review was assessed using AMSTAR-2.
Results
As a result of the selection process 47 studies were included in the umbrella review. Social support was found to have a protective role on depression, with an observed moderate/strong effect in peripartum population and a weaker effect in clinical populations (e.g. AIDS/HIV patients). A moderate association between stigma/discrimination and depression emerged in clinical populations (e.g. epilepsy, mental illness, post-stroke), while a weaker effect was found in (ethnic) minorities. There are still few studies quantitatively investigating the link between depression and other social measures (e.g. community connectedness).
Conclusions
Our findings align with the literature on social connection and mental health, confirming the role of social determinants in the emergence and severity of depression, particularly in the case of vulnerable populations. Social factors emerge as important modifiable targets in the context of depression prevention. Efforts to counteract disconnection at the societal and individual levels and to reduce stigma should be central to an effective depression prevention agenda.
Disclosure of Interest
None Declared
Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered ...metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.
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