Background
Understanding and characterizing delamination in composite laminates is fundamental for analysing their structural integrity, since operational loads may promote the propagation of ...interlaminar defects. Propagation often occurs in mode II and is driven by shear stress. However, the methods used to characterise this propagation mode are affected by frictional effects between crack surfaces.
Objective
This work aims to build up an experimental method to identify the effect of friction in a 4 points End Notched Flexure test, which does not require the use of analytical or numerical models of the specimen.
Methods
This goal is achieved by performing a series of loading–unloading cycles before the delamination test, which helps to calibrate an analytical expression that estimates the energy dissipated by friction, and the analytical expression is then inserted into the formulation of the Irwin-Kies equation. Experimental validation is carried out considering tests on different materials and different friction conditions between the crack surfaces, as well as validation by means of a virtual experiment being performed for comparison with an analytical model presented in literature. The novelty of this method lies in the fact that it does not require the development of any analytical or numerical model of the specimen and consequently no calibration between models and the experiment is required.
Results
Tests on composite specimens show good results, the friction contribution estimated by the method is comparable with those presented in the literature. Moreover, the virtual experiment shows that there is a good match between the results obtained using this method and those obtained using an analytical model presented in the literature.
Conclusions
This method seems to provide satisfactory results for both real and virtual experiments, moreover, the procedure is relatively simple, making it a suitable method for the evaluation of frictional effects in the 4 point End Notched Flexure test.
Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales
. This variability seems mostly random, although some ...quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare
in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet
, plasma instabilities
or orbital motion in an accretion disc
. Here we report results of intense optical and γ-ray flux monitoring of BL Lacertae (BL Lac) during a dramatic outburst in 2020 (ref.
). BL Lac, the prototype of a subclass of blazars
, is powered by a 1.7 × 10
M
(ref.
) black hole in an elliptical galaxy (distance = 313 megaparsecs (ref.
)). Our observations show QPOs of optical flux and linear polarization, and γ-ray flux, with cycles as short as approximately 13 h during the highest state of the outburst. The QPO properties match the expectations of current-driven kink instabilities
near a recollimation shock about 5 parsecs (pc) from the black hole in the wake of an apparent superluminal feature moving down the jet. Such a kink is apparent in a microwave Very Long Baseline Array (VLBA) image.
ABSTRACT
In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in ...the BVRI bands acquired at 36 observatories around the world. In mid-2021 the source showed its historical maximum, with R = 11.14. The light curves display many episodes of intraday variability, whose amplitude increases with source brightness, in agreement with a geometrical interpretation of the long-term flux behaviour. This is also supported by the long-term spectral variability, with an almost achromatic trend with brightness. In contrast, short-term variations are found to be strongly chromatic and are ascribed to energetic processes in the jet. We also analyse the optical polarimetric behaviour, finding evidence of a strong correlation between the intrinsic fast variations in flux density and those in polarization degree, with a time delay of about 13 h. This suggests a common physical origin. The overall behaviour of the source can be interpreted as the result of two mechanisms: variability on time-scales greater than several days is likely produced by orientation effects, while either shock waves propagating in the jet, or magnetic reconnection, possibly induced by kink instabilities in the jet, can explain variability on shorter time-scales. The latter scenario could also account for the appearance of quasi-periodic oscillations, with periods from a few days to a few hours, during outbursts, when the jet is more closely aligned with our line of sight and the time-scales are shortened by relativistic effects.
Abstract Background Our study aims at disclosing epidemiology and most relevant clinical features of esophageal atresia (EA) pointing to a model of multicentre collaboration. Methods A detailed ...questionnaire was sent to all Italian Units of pediatric surgery in order to collect data of patients born with EA between January and December 2012. The results were crosschecked by matching date and place of birth of the patients with those of diagnosis-related group provided by the Italian Ministry of Health (MOH). Results A total of 146 questionnaires were returned plus a further 32 patients reported in the MOH database. Basing on a total of 178 patients with EA born in Italy in 2012, the incidence of EA was calculated in 3.33 per 10,000 live births. Antenatal diagnosis was suspected in 29.5% patients. 55.5% showed associated anomalies. The most common type of EA was Gross type C (89%). Postoperative complications occurred in 37% of type C EA and 100% of type A EA. A 9.5% mortality rate was reported. Conclusions This is the first Italian cross-sectional nationwide survey on EA. We can now develop shared guidelines and provide more reliable prognostic expectations for our patients.
Growing evidence underlines the pivotal role of infant gut colonization in the development of the immune system. The possibility to modify gut colonization through probiotic supplementation in ...childhood might prevent atopic diseases. The aim of the present systematic review and meta‐analysis was to evaluate the effect of probiotic supplementation during pregnancy and early infancy in preventing atopic diseases. PubMed, Embase and Cochrane Library were searched for randomized controlled trials evaluating the use of probiotics during pregnancy or early infancy for prevention of allergic diseases. Fixed‐effect models were used, and random‐effects models where significant heterogeneity was present. Results were expressed as risk ratio (RR) with 95% confidence interval (CI). Seventeen studies, reporting data from 4755 children (2381 in the probiotic group and 2374 in the control group), were included in the meta‐analysis. Infants treated with probiotics had a significantly lower RR for eczema compared to controls (RR 0.78 95% CI: 0.69–0.89, P = 0.0003), especially those supplemented with a mixture of probiotics (RR 0.54 95% CI: 0.43–0.68, P < 0.00001). No significant difference in terms of prevention of asthma (RR 0.99 95% CI: 0.77–1.27, P = 0.95), wheezing (RR 1.02 95% CI: 0.89–1.17, P = 0.76) or rhinoconjunctivitis (RR 0.91 95% CI: 0.67–1.23, P = 0.53) was documented. The results of the present meta‐analysis show that probiotic supplementation prevents infantile eczema, thus suggesting a new potential indication for probiotic use in pregnancy and infancy.
Innovative goods authentication strategies are of fundamental importance considering the increasing counterfeiting levels. Such a task has been effectively addressed with the so-called physical ...unclonable functions (PUFs), being physical properties of a system that characterize it univocally. PUFs are commonly implemented by exploiting naturally occurring non-idealities in clean-room fabrication processes. The broad availability of classic paradigm PUFs, however, makes them vulnerable. Here, we propose a hybrid plasmonic/photonic multilayered structure working as a three-level strong PUF. Our approach leverages on the combination of a functional nanostructured surface, a resonant response, and a unique chromatic signature all together in one single device. The structure consists of a resonant cavity, where the top mirror is replaced with a layer of plasmonic Ag nanoislands. The naturally random spatial distribution of clusters and nanoparticles formed by this deposition technique constitutes the manufacturer-resistant nanoscale morphological fingerprint of the proposed PUF. The presence of Ag nanoislands allows us to tailor the interplay between the photonic and plasmonic modes to achieve two additional security levels. The first one is constituted by the chromatic response and broad iridescence of our structures, while the second by their rich spectral response, accessible even through a common smartphone light-emitting diode. We demonstrate that the proposed architectures could also be used as an irreversible and quantitative temperature exposure label. The proposed PUFs are inexpensive, chip-to-wafer-size scalable, and can be deposited over a variety of substrates. They also hold a great promise as an encryption framework envisioning morpho-cryptography applications.
Critical periods of developmental plasticity contribute to the refinement of neural connections that broadly shape brain development. These windows of plasticity are thought to be important for the ...maturation of perception, language, and cognition. Synaptic properties in cortical regions that underlie critical periods influence the onset and duration of windows, although it remains unclear how mechanisms that shape synapse development alter critical-period properties. In this study, we demonstrate that inactivation of a single copy of syngap1, which causes a surprisingly common form of sporadic, non-syndromic intellectual disability with autism in humans, induced widespread early functional maturation of excitatory connections in the mouse neocortex. This accelerated functional maturation was observed across distinct areas and layers of neocortex and directly influenced the duration of a critical-period synaptic plasticity associated with experience-dependent refinement of cortical maps. These studies support the idea that genetic control over synapse maturation influences the duration of critical-period plasticity windows. These data also suggest that critical-period duration links synapse maturation rates to the development of intellectual ability.
Mutations that cause intellectual disability (ID) and autism spectrum disorder (ASD) are commonly found in genes that encode for synaptic proteins. However, it remains unclear how mutations that ...disrupt synapse function impact intellectual ability. In the SYNGAP1 mouse model of ID/ASD, we found that dendritic spine synapses develop prematurely during the early postnatal period. Premature spine maturation dramatically enhanced excitability in the developing hippocampus, which corresponded with the emergence of behavioral abnormalities. Inducing SYNGAP1 mutations after critical developmental windows closed had minimal impact on spine synapse function, whereas repairing these pathogenic mutations in adulthood did not improve behavior and cognition. These data demonstrate that SynGAP protein acts as a critical developmental repressor of neural excitability that promotes the development of life-long cognitive abilities. We propose that the pace of dendritic spine synapse maturation in early life is a critical determinant of normal intellectual development.
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► Pathogenic SYNGAP1 mutations promote early maturation of hippocampal spine synapses ► Mutations lead to neonatal hyperactivity of the hippocampal trisynaptic circuit ► Mutations have greatest impact during the first 3 weeks of development ► Reversal of mutations in adults does not improve behavior and cognition
A monogenic mouse model connects premature development of hippocampal dendritic spine synapses to life-long disruptions in cognition and memory. These findings indicate that the pace of synapse maturation in early life is a critical determinant of normal intellectual development.
Introduction
Perinatal period is characterized by a broad range of physical, psychological and relational changes. Maternal perinatal depression (PD) is defined as an episode of major depression with ...the onset from pregnancy to the first year after delivery. Depressive symptoms influence the earlier mother-child interaction and impact on child cognitive, affective and behavioral development.
Objectives
Purpose of our study was to evaluate the consequences of PD on sleep-wake patterns in the early stages of infant development. We aim to investigate the presence of poor sleep in infants/ toddlers and also to identify differences in sleep ecology variables.
Methods
We enrolled, from December 2019 to September 2020, a clinical sample of children born from women with PD (N=19, m.a.=13,7, SD= 7,6) and a healthy control group (N=21, m.a.=15,5, SD=5,43). Infant sleep data were obtained from the Brief Infant Sleep Questionnaire (BISQ). Poor sleepers were defined by the following criteria: >3 night wakings, nocturnal wakefulness >1 hr or total sleep duration <9 hr. Maternal depression was assessed with clinical and psychometric evaluation. T-test was used for comparison between the two samples.
Results
Statistical analysis indicates that there were not significant differences between the two groups concerning night wakings (p= .678), nocturnal wakefulness (p= .815), total sleep duration (p= .209) and nocturnal sleep onset time (p= .475).
Conclusions
Our findings suggest that PD is not a risk-factor in the onset of infant sleep problems. Probably negative parentig, affective disengagement, delegation in maternal care and sedative effects of pharmacotherapy may affect mother’s perception of her infant’s sleep.
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