Interferometric cavity ring-down technique for ultra-high Q-factor microresonators

Microresonators (MRs) are key components in integrated optics. As a result, the estimation of their energy storage capacity as measured by the quality factor (Q) is crucial. However, in MR with high/ultra-high Q, the surface-wall roughness dominates the intrinsic Q and generates a coupling between counter-propagating modes. This splits the usual sharp single resonance and makes difficult the use of classical methods to assess Q. Here, we theoretically show that an interferometric excitation can be exploited in a Cavity Ring-Down (CRD) method to measure the ultimate Q of a MR. In fact, under suitable conditions, the resonant doublet merges into a single Lorentzian and the time dynamics of the MR assumes the usual behavior of a single-mode resonator unaffected by backscattering. This allows obtaining a typical exponential decay in the charging and discharging time of the MR, and thus, estimating its ultimate Q by measuring the photon lifetime.Comment: 5 pages and 2 figure

Field-Induced Nonlinearities in Silicon Waveguides Embedded in Lateral p-n Junctions

Silicon waveguides embedded in lateral p-n junctions show field-induced optical nonlinearities. By properly polarizing the junction, these can be used to achieve electro-optic modulation through the Direct Current Kerr effect. In addition, these enable second-order nonlinear processes such as the electric-field-induced second harmonic generation (EFISHG). In this work, we study in detail electro-optic effects in integrated silicon microresonators and demonstrate experimentally a field-induced resonance wavelength shift. This process is due to both the DC Kerr effect and the plasma-dispersion effect. By means of finite element method simulations, these effects are properly modeled and their contributions are accurately disentangled. The strength of the equivalent second-order nonlinear coefficient that would have provided the same electro-optic effect is about 16 pm/V. This result is comparable with that of materials possessing an intrinsic second order nonlinearity, and is one order of magnitude stronger than the most recent measurements of strain-induced Pockels effect in silicon

Photonic neural networks based on integrated silicon microresonators

The recent progress of artificial intelligence (AI) has boosted the computational possibilities in fields where standard computers are not able to perform. The AI paradigm is to emulate human intelligence and therefore breaks the familiar architecture on which digital computers are based. In particular, neuromorphic computing, artificial neural networks (ANN) and deep learning models mimic how the brain computes. Large networks of interconnected neurons whose synapsis are individually strengthened or weakened during the learning phase find many applications. With this respect, photonics is a suitable platform to implement ANN hardware thanks to its speed, low power dissipation and multi-wavelength opportunities. One photonic device candidate to perform as an optical neuron is the optical microring resonator. Indeed microring resonators show both a nonlinear response and a capability of optical energy storage, which can be interpreted as a fading memory. Moreover, by using silicon photonics, the photonic integrated circuits can be fabricated in volume and with integrated electronics on board. For these reasons, here, we describe the physics of silicon microring resonators and of arrays of microring resonators for application in neuromorphic computing. We describe different types of ANNs from feed-forward networks to photonics extreme learning machines and reservoir computing. In addition, we discuss also hybrid systems where silicon microresonators are coupled to other active materials. this review aims to introduce the basics and to discuss the most recent developments in the field.Comment: 35 pages, 23 figure

Struktura dna, veličina čestica sedimenta i makrobentoska zajednica u eksploatiranim i ne-eksploatiranim područjima srednjeg Jadrana (Italija)

Studies performed in Italy for assessing the effects of fishing activities have been largely confined to the Adriatic Sea. They mostly investigated effects of experimentally induced impacts. The objective of this study was to compare a commercial fishing ground with an area in which no fishing was conducted. The two areas were less than 2 km apart and close to a gas platform in the central Adriatic. Seabed morphology, sediment grain size, and macrobenthic community composition were investigated. There were clear physical effects on the seabed morphology, mostly as a consequence of the trawling passage. Strong and unequivocal signs of disturbance were not detected from the grain size analysis but there was a major spatial variability of sediment distribution. There were signs of stress in the macrobenthic community, i.e., reduction of complexity and diversity, increased variability of distributional patterns, and fewer large longlived species in the fished area.Talijanske studije za utvrđivanje utjecaja ribolovnih aktivnosti bile su uglavnom usmjerene na Jadransko more istražujući učinke pretežito tijekom eksperimentalnih potega. Cilj ove studije je usporedba područja izložena gospodarskom ribolovu i područja koja se gospodarski ne iskorištavaju. Dva istraživana područja su smještena 2 km od plinske platforme u srednjem Jadranu. Istraživani su: struktura morskog dna, veličina i struktura sedimenta, te makrobentoske zajednice. Jasno je uočljiv fizički učinak na strukturu morskog dna, uglavnom kao posljedica prolaska koća. Nisu utvrđeni jaki i jasni znakovi poremećaja u veličini čestica sedimenta, ali je utvrđena značajna prostorna varijabilnost u distribuciji sedimenta. U eksploatiranom području nađeni su znakovi stresa u makrobentoskoj zajednici tj. poremećaj u kompleksnosti i raznolikosti, povećane varijabilnosti u raspostranjenosti i manji broj velikih i dugoživućih vrsta

Prospettive di cura per soggetti con “gravi disturbi di personalità” autori di reato: un percorso terapeutico-riabilitativo in una “struttura protetta” convenzionata

The authors describe the therapeutic-rehabilitative program supported by the National Health Service that a young man suffering from serious personality disorders, “narcissistic” and “borderline”, took part in at a protected residential psychiatric facility (Centro di Riabilitazione ‘Villa San Pietro’, Arco, TN, Italy). The young man had attempted suicide 4 times, once very seriously, and had repeatedly committed a serious crime that resulted in his being sentenced to 4 years in prison on a plea bargain. Following an initial period spent in prison, he was ordered by the Court to be sent to a Rehabilitation Community where he was under house arrest as recommended by the Head of the Department of Mental Health in the province where the man resided. The first part of this paper gives a detailed description of the young man's personal and clinical background, which represents the basis for a thorough comprehension of the guidelines and dynamics of the therapeutic-rehabilitative program designed for him. He followed the program for two years, which is amply illustrated in the second part of this report. The specific and non-specific therapeutic instruments used or applied in the program are described. The non-specific instruments refer to the particular structural and organizational features of the Villa San Pietro Clinic: high level of protection and security as well as a large number of patients. The specific instruments concern a specialized rehabilitative methodology which rotates around three psychotherapists, each with a well-defined role in working with the patient. There is only slight mention of psychiatric drugs and integrated rehabilitative activities, such as vocational training, expression and socialization activities, as these are frequently available in most psychiatric Rehabilitation Centres. We have described in detail, however, the psychotherapeutic techniques of the cognitive-behavioral type, which were particularly important in the therapy program planned for this individual. The peculiar aspect of the therapeutic path followed by our patient in the Rehabilitation Center was the fact that the man continually took part in the treatment in all its aspects. In regards to this, we point out the importance of having a house arrest during the first months of recovery and until a full therapeutic alliance had been achieved. This was a circumstance that allowed the young man to come voluntarily to the clinic to participate in the rehabilitative program until its positive conclusion, even after the unexpected judicial decision to grant him a pardon. This pardon, however, created a dramatic conflict for the patient, which he was able to overcome on his own in a short time, by using his acquired strategies for coping (described in detail). Some  months after discharge patient shows a good recovery and stable clinical conditions. He’s constantly attending the Mental Health State Centre and he’s steadily followed by a psychologist undergoing regular psychiatric valuations. He’s now living at home with his parents actually following pharmacologic therapy with no relational or behavioural problems. Still is in progress a closely planned program of progressive coming back to work.Viene descritto il percorso terapeutico-riabilitativo, in una struttura psichiatrica protetta convenzionata [Centro di Riabilitazione “Villa San Pietro” di Arco (TN)], di un giovane uomo, affetto da un grave di disturbo di personalità di tipo misto, narcisistico e borderline, con quattro pregressi tentativi di suicidio – uno dei quali gravissimo -, autore di un grave reato con condanna patteggiata a quattro anni, inviato agli arresti domiciliari in Comunità, dopo un periodo iniziale di detenzione in carcere; l’invio è avvenuto su disposizione dell’Autorità Giudiziaria in seguito alla proposta formulata dal Dipartimento di Psichiatria del territorio di residenza del paziente.La descrizione approfondita dell’anamnesi personale e clinica del paziente, che costituisce la prima parte di questo lavoro, rappresenta il presupposto fondamentale per comprendere appieno le linee guida e le dinamiche del percorso terapeutico-riabilitativo, protrattosi per due anni e illustrato estesamente nella seconda parte del lavoro. Si descrivono gli strumenti terapeutici specifici ed aspecifici utilizzati nel trattamento. Gli strumenti aspecifici risultano connessi alle particolari caratteristiche strutturali e organizzative di Villa San Pietro: forte contenimento ed elevato numero di pazienti. Gli strumenti specifici riguardano una metodica riabilitativa specializzata imperniata sull’intervento integrato di tre psicoterapeuti, ciascuno con un ruolo ben definito nel setting di lavoro col paziente. Sono solo accennati gli interventi psicofarmacologici e le attività riabilitative strutturate di tipo occupazionale, espressivo e risocializzante, in quanto strumenti di lavoro presenti comunemente nella maggioranza delle comunità riabilitative psichiatriche. Vengono invece descritte dettagliatamente le tecniche di intervento psicoterapeutico di tipo cognitivo-comportamentale per l’importanza che hanno rivestito nel percorso riabilitativo. S’individua l’aspetto chiave del percorso in Comunità nell’adesione continuativa al trattamento: a tal proposito si sottolinea l’importanza della presenza degli arresti domiciliari durante i primi mesi di ricovero, fino al pieno sviluppo di una valida alleanza terapeutica, che ha permesso la prosecuzione volontaria del ricovero e del percorso riabilitativo fino al loro felice completamento, anche dopo un improvviso ed imprevisto provvedimento giudiziario di indulto. Tale indulto ha infatti determinato l’insorgere di una traumatica conflittualità nel paziente, per fortuna risoltasi, in breve tempo, con opportune strategie di coping, illustrate nel dettaglio. A distanza di qualche mese dalle dimissioni il paziente mantiene un quadro clinico soddisfacente e stabilizzato. Frequenta regolarmente il Centro di Salute Mentale, ove è seguito da una psicologa e dove si sottopone a regolari controlli psichiatrici. Mostra una buona compliance farmacologia e vive a casa dei genitori, senza manifestare conflittualità relazionali o disturbi comportamentali. È inoltre in corso un progetto articolato di graduale reinserimento lavorativo

Art and Psychological Well-Being: Linking the Brain to the Aesthetic Emotion

Empirical studies suggest that art improves health and well-being among individuals. However, how aesthetic appreciation affects our cognitive and emotional states to promote physical and psychological well-being is still unclear. In this review, we consider the idea that the positive emotional output elicited from the aesthetic experience affects mood, and indirectly promotes health and well-being. First, we examine evidence that arts promoting well-being involve art museums, healthcare settings, and education. Second, we review some neuroimaging studies addressing aesthetic experience and emotional processing. In particular, we leveraged advances in neuroaesthetics to explore different hypotheses about the determinants of aesthetic pleasure during art reception, in the attempt to clarify how experiencing art promotes well-being. Finally, we propose research on aesthetic experience and psychophysiological measures of stress, with the goal of promoting a focused use of art as a tool for improving well-being and health

Transmembrane Peptides as Sensors of the Membrane Physical State

Cell membranes are commonly considered fundamental structures having multiple roles such as confinement, storage of lipids, sustain and control of membrane proteins. In spite of their importance, many aspects remain unclear. The number of lipid types is orders of magnitude larger than the number of amino acids, and this compositional complexity is not clearly embedded in any membrane model. A diffused hypothesis is that the large lipid palette permits to recruit and organize specific proteins controlling the formation of specialized lipid domains and the lateral pressure profile of the bilayer. Unfortunately, a satisfactory knowledge of lipid abundance remains utopian because of the technical difficulties in isolating definite membrane regions. More importantly, a theoretical framework where to fit the lipidomic data is still missing. In this work, we wish to utilize the amino acid sequence and frequency of the membrane proteins as bioinformatics sensors of cell bilayers. The use of an alignment-free method to find a correlation between the sequences of transmembrane portion of membrane proteins with the membrane physical state (MPS) suggested a new approach for the discovery of antimicrobial peptides