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Thermal emission is typically associated with a blackbody at a temperature above absolute zero, which exchanges energy with its environment in the form of radiation. Blackbody thermal emission is largely incoherent both spatially and temporally. Using principles in nanophotonics, thermal emission with characteristics that differ considerably from those of a blackbody has been demonstrated. In particular, by leveraging intrinsic properties of emerging materials or via nanostructuring at the wavelength or sub-wavelength scale, one can gain control over the directionality, temporal coherence, and other more exotic properties of thermal radiation. Typically, however, these are fixed at the time of fabrication. Gaining dynamic control of thermal emission requires exploiting external mechanisms that actively modulate radiative properties. Numerous applications can benefit from such thermal emission control, for example, in solar energy harvesting, thermo-photovoltaic energy conversion, radiative cooling, sensing, spectroscopy, imaging, and thermal camouflage. In this Tutorial, we introduce thermal emission in two domains: the far-field and the near-field, and we outline experimental approaches for probing thermal radiation in both ranges. We discuss ways for tailoring the spatial and temporal coherence of thermal emission and present available mechanisms to actively tune these characteristics. [ABSTRACT FROM AUTHOR]

Background: Balance, i.e., the ability not to fall, is often poor in neurological patients and this impairment increases their risk of falling. The Mini-Balance Evaluation System Test (Mini-BESTest), a rating scale, the Timed Up and Go (TUG) test, and gait measures are commonly used to quantify balance. This study assesses the criterion validity of these measures as balance measures. Methods: The probability of being a faller within nine months was used as the balance criterion. The Mini-BESTest, TUG (instrumented with inertial sensors), and walking test were administered before and after inpatient rehabilitation. Multiple and LASSO logistic regressions were used for the analysis. The diagnostic accuracy of the model was assessed with the area under the curve (AUC) of the receiver operating characteristic curve. Mobility measure validity was compared with the Akaike Information Criterion (AIC). Results: Two hundred and fourteen neurological patients (stroke, peripheral neuropathy, or parkinsonism) were recruited. In total, 82 patients fell at least once in the nine-month follow-up. The Mini-BESTest (AUC = 0.69; 95%CI: 0.62--0.76), the duration of the TUG turning phase (AUC = 0.69; 0.62-0.76), and other TUG measures were significant faller predictors in regression models. However, only the turning duration (AIC = 274.0) and Mini-BESTest (AIC = 276.1) substantially improved the prediction of a baseline model, which only included fall risk factors from the medical history (AIC = 281.7). The LASSO procedure selected gender, disease chronicity, urinary incontinence, the Mini-BESTest, and turning duration as optimal faller predictors. Conclusion: The TUG turning duration and the Mini-BESTest predict the chance of being a faller. Their criterion validity as balance measures in neurological patients is substantial. [ABSTRACT FROM AUTHOR]

The efficient selective and directional coupling of light to waveguiding circuitry at the nanoscale is one of the key challenges in nanophotonics, as it constitutes a prerequisite for many applications, including information processing, routing, and quantum technologies. Various exotic nanostructures and nanoparticle arrangements have been designed to achieve directional coupling with compact on-chip integration remaining one of the foremost hurdles to realizing many real-world devices. At the same time, selective coupling to one of several neighboring waveguides is much more difficult to achieve and control. To address this challenge, we demonstrate a subwavelength selective coupler integrated in a waveguide network, with selectivity controlled by wavelength, polarization, and angle of incidence. We utilize a Janus source, which is composed of a superposition of electric and magnetic dipoles, supported by a silicon nanocylinder. By placing the nanocylinder between identical single mode silicon waveguides, we successfully achieve selective coupling with a high contrast ratio between the waveguides. The operating wavelength of the Janus dipolar source can be easily tailored, and the coupling efficiency is also shown to be conveniently boosted by the addition of multiple nanocylinders. Our compact approach provides a direct path toward on-chip highly directional nanoscale sources for a plethora of applications, including information routing, metrology, and quantum technologies. [ABSTRACT FROM AUTHOR]

Objective: To test with the Rasch analysis the psychometric properties of the Falls Efficacy Scale International, a questionnaire for measuring concern about falling. Design: Longitudinal observational study, before–after rehabilitation. Setting: Inpatient rehabilitation. Subjects: A total of 251 neurological patients with balance impairment. Interventions: Physiotherapy and occupational therapy aimed at reducing the risk of falling. Main measures: Participants (median age, first–third quartile: 74.0, 65.5–80.5 years; stroke and polyneuropathy: 43% and 21% of the sample, respectively) received a balance assessment (Falls Efficacy Scale International included) pre- and post-rehabilitation. Rasch analysis was used to evaluate the Falls Efficacy Scale International. Differential item functioning, which assesses the measures' stability in different conditions (e.g. before vs. after treatment) and in different groups of individuals, was tested for several variables. Results: Patients suffered a moderate balance impairment (Mini-BESTest median score; first–third quartile: 15; 11–19), mild–moderate concern about falling (Falls Efficacy Scale International: 28; 21–37) and motor disability (Functional Independence Measure, motor domain: 70.0; 57.0–76.5). Falls Efficacy Scale International items fitted the Rasch model (range of infit and outfit mean square statistics: 0.8–1.32 and 0.71–1.45, respectively) and the questionnaire's reliability was satisfactory (0.87). No differential item functioning was found for treatment, gender, age and balance impairment. Differential item functioning was found for diagnosis and disability severity, but it is shown that it is not such as to bias measures. Conclusions: Falls Efficacy Scale International ordinal scores can be turned into interval measures, i.e. measures of the type of temperature. Being differential item functioning-free for treatment, these measures can be safely used to compare concern about falling before and after rehabilitation, such as when interested in assessing the rehabilitation effectiveness. [ABSTRACT FROM AUTHOR]

Post-stroke locomotion is usually characterized by asymmetrical gait patterns, compensatory movements of trunk and nonparetic limb, altered motor coordination, and wide inter-stride variability. This pilot study was designed to test a twofold hypothesis: post-stroke survivors can exploit the redundancy of the segmental angles to stabilize the 3D footpath trajectory during the swing phase, in accordance with the Uncontrolled Manifold (UCM) theory; an intense rehabilitative treatment improves both motor performance and outcomes of the UCM analysis. Ten stroke survivors underwent two evaluation sessions, before and after a conventional multidisciplinary intensive rehabilitation program, encompassing clinical tests and gait analysis, both overground and on treadmill. In addition, the UCM analysis was implemented to investigate whether variance of segmental angles is structured to minimize the inter-stride variability of the 3D footpath during the swing phase of treadmill locomotion. Both clinical and spatio-temporal parameters improved after the treatment, even if the statistical significance was reached for a limited set of them. The UCM analysis suggested that post-stroke survivors exploit the redundancy of lower limbs segmental angles mainly during the late swing, without significant differences between affected and unaffected sides. Thereafter, the main significant effects of the rehabilitative treatment consisted in strengthening the synergistic organization of the redundant segmental angles involving a more accurate control of the 3D footpath. Concluding, the UCM theory can be a promising tool to appraise the effects of a specific rehabilitative protocol on motor coordination in post-stroke survivors. [ABSTRACT FROM AUTHOR]

Background: The timed up and go (TUG) test is widely used for assessing treatments effectiveness on elderly mobility. Although the TUG test consists of different tasks (e.g. walking and turning), the total TUG duration (TTD) is usually the only outcome measure, with TTD shortening indicating the patient's improvement.Research Question: Does TTD shortening reflect the improvement of each TUG tasks or does it reflect the improvement of only some of them?Methods: This retrospective study recruited 120 elderly patients (mean, SD: 76.9, 6.6 years) admitted to inpatient rehabilitation because of an acute or chronic neurological disease (acute patients, AP; chronic patients, CP). TTD and TUG tasks duration was measured on admission and discharge (five trials/session) by means of the instrumental TUG test (ITUG). Likelihood ratios (LRs) were used for inferring TUG tasks improvement from TTD improvement. TTD and TUG tasks have improved if at least four measurements on discharge were shorter than the shortest measurement on admission.Results: TTD improvement per se is not enough to claim that all the TUG tasks have improved (LR+AP = 1.32; LR+CP = 1.85). Conversely, if TTD has not improved, not even a single TUG task has improved (LR-AP = 0.13; LR-CP = 0.19). If TTD has improved, there is at least one TUG task that actually improved (LR+AP = 3.17; LR+CP = 9.54). The improvement of all TUG tasks can be only inferred in the (unusual) event of a large TTD shortening (AP: >39%, LR+AP = 6.26; CP: >30%, LR+CP = 9.0).Significance: In most cases, TTD improvement is not associated with the improvement of all TUG tasks. Moreover, when TTD has improved there is at least a TUG task that has improved, but that remains unknown. To actually understand how treatments ameliorate patients' mobility, ITUG with TUG task duration measurement should be preferred to TTD. [ABSTRACT FROM AUTHOR]

Balance impairment is a hallmark of Parkinson's disease with dramatic effects for patients (e.g. falls). Its assessment is thus of paramount importance. The aim of this work is to assess which measures from the instrumented Timed Up and Go test (recorded with inertial sensors) are valid balance measures in Parkinson's disease and evaluate their responsiveness to rehabilitation. The Mini-BESTest (a criterion-standard balance measure) and the instrumented Timed Up and Go test (with inertial sensors secured to the trunk) were administered to 20 Parkinson's disease patients before and after inpatient rehabilitation (median [IQR]; 76.5 [8.25] years; 5 females; Hoehn and Yahr stage: 2.5 [0.5]). 81 parameters from the instrumented Timed Up and Go test were evaluated. Multiple factor analysis (a variant of principal component analysis for repeated measurements) and effect sizes were used to assess validity and responsiveness, respectively. Only the first component of the multiple factor analysis correlated with the Mini-BESTest, and 21 measures from the instrumented Timed Up and Go test had large loadings on this component. However, only three of these 21 measures also directly correlated with the Mini-BESTest (trunk angular velocities from sit-to-walk and turning; r = 0.46 to 0.50, P = 0.021 to 0.038). Sit-to-walk angular velocity showed greater responsiveness than the Mini-BESTest, while turning showed slightly less. Angular velocities from the turning and sit-to-walk phases of the Timed Up and Go test are valid balance measures in Parkinson's disease and are also responsive to rehabilitation. • Balance impairment is a serious problem in Parkinson's disease and its assessment is important. • The Mini-BESTest is a criterion-standard measure of balance in Parkinson's disease. • We tested if the Timed Up and Go test with trunk posture monitoring using inertial sensors provides proper balance measures. • Angular velocities from the sit-to-walk and turning phases correlate with the Mini-BESTest scale. • Sit-to-walk and turning angular velocities are also responsive to rehabilitation. [ABSTRACT FROM AUTHOR]

The design of far‐field radiation diagrams from combined electric and magnetic dipolar sources has recently found applications in nanophotonic metasurfaces that realize tailored reflection and refraction. Such dipolar sources also exhibit important near‐field evanescent coupling properties with applications in polarimetry and quantum optics. Here, a rigorous theoretical framework is introduced for engineering the angular spectra encompassing both far‐ and near‐fields of electric and magnetic sources and a unified description of both free space and guided mode directional radiation is developed. The approach uses the full parametric space of six complex‐valued components of magnetic and electric dipoles in order to engineer constructive or destructive near‐field interference. Such dipolar sources can be realized with dielectric or plasmonic nanoparticles. It is shown how a single dipolar source can be designed to achieve the selective coupling to multiple waveguide modes and far‐field simultaneously with a desired amplitude, phase, and direction. [ABSTRACT FROM AUTHOR]

Unidirectional evanescent-wave coupling from circularly polarized dipole sources is one of the most striking types of evidence of spin-orbit interactions of light and an inherent property of circularly polarized dipoles. Polarization handedness self-determines propagation direction of guided modes. In this paper, we compare two different approaches currently used to describe this phenomenon: the first requires the evaluation of the coupling amplitude between dipole and waveguide modes, while the second is based on the calculation of the angular spectrum of the dipole. We present an analytical expression of the angular spectrum of dipole radiation, unifying the description for both electric and magnetic dipoles. The symmetries unraveled by the implemented formalism show the existence of specific terms in the dipole spectrum which can be recognized as being directly responsible for directional evanescent-wave coupling. This provides a versatile tool for both a comprehensive understanding of the phenomenon and a fully controllable engineering of directionality of guided modes. [ABSTRACT FROM AUTHOR]

The Timed Up and Go (TUG) test is a common mobility measure in rehabilitation. With the instrumental TUG test (ITUG; i.e. the TUG measured by inertial measurement units, IMUs), several movement measures are newly available. However, the clinical meaning of these new measures is not totally clear. Aim of the current work is to evaluate the validity of different ITUG parameters as a measure of balance. Neurological patients (n = 122; 52 females; 89 older than 65 years) completed the TUG test with IMUs secured to their back. IMUs signals were used to split the TUG test in five phases (sit-to-stand, walk1, turn1, walk2 and turn-and-sit) and twelve movement parameters were obtained. Experienced clinicians administered the Mini-BESTest (MB) scale, a sound balance measure. The partial least square regression (PLSR) was used to explore the association between the ITUG variables and the MB measure. A PLSR model with twelve ITUG variables had satisfactory fit parameters (RMSEP: 11%; R2: 0.41, 95% CI: 0.28-0.54; regression line: 1, 95% CI: 0.78-1.22). Three ITUG variables (i.e. turn1 vertical angular velocity, turn1 duration and turn2 vertical angular velocity) were found to be the most important predictors of the MB measure. A PLSR model with the turning variables only had fit parameters comparable to that of the twelve variables model. Turning parameters from the TUG test are good predictors of the MB scale. The mean angular velocity during turning and the duration of the turning phase are thus proposed as a valid, ratio-level measures of balance in neurological patients. [ABSTRACT FROM AUTHOR]

Background: In the last few years, new noninvasive strategies have emerged as rehabilitative treatments for patients with stroke. Action observation treatment (AOT) is a rehabilitation approach based on the properties of the mirror neuron system with a positive impact on modifying cortical activation patterns and improving the upper limb kinematics. AOT involves the dynamic process of observing purposeful actions with the intention of imitating and then practicing those actions. In recent years, several clinical studies suggested the effectiveness of AOT in patients with stroke to improve motor recovery and autonomy in activities of daily living. However, a deeper knowledge of the behavior of the sensorimotor cortex during AOT seems to be essential., Objective: The aim of this clinical trial, conducted in 2 neurorehabilitation centers and in patients' homes, is to investigate the effectiveness of AOT in patients with stroke, confirming the translational power of a tailored treatment. Particular emphasis will be placed on the predictive value of neurophysiological biomarkers. In addition, the feasibility and impact of a home-based AOT program will be investigated., Methods: A 3-arm, assessor-blinded, randomized controlled trial will be performed by enrolling patients with stroke in the chronic stage. A total of 60 participants will be randomly allocated to receive 15 sessions of AOT with different protocols (AOT at the hospital, AOT at home, and sham AOT), 3 sessions per week. The primary outcome will be assessed using the Fugl-Meyer Assessment-Upper Extremity scores. Secondary outcomes will be clinical, biomechanical, and neurophysiological assessment., Results: The study protocol is part of a project (project code GR-2016-02361678) approved and funded by the Italian Ministry of Health. The study began with the recruitment phase in January 2022, and enrollment was expected to end in October 2022. Recruitment is now closed (December 2022). The results of this study are expected to be published in spring 2023. Upon completion of the analyses, we will examine the preliminary effectiveness of the intervention and neurophysiological outcomes., Conclusions: This study will be used to evaluate the effectiveness of 2 different AOT scenarios (ie, AOT at the hospital and AOT at home) in patients with chronic stroke and to assess the predictive value of neurophysiological biomarkers. Specifically, we will attempt to induce the functional modification of the cortical components by exploiting the features of the mirror neuron system, demonstrating relevant clinical, kinematic, and neurophysiological changes after AOT. With our study, we also want to provide, for the first time in Italy, the AOT home-based program while assessing its feasibility and impact., Trial Registration: ClinicalTrials.gov NCT04047134; https://clinicaltrials.gov/ct2/show/NCT04047134., International Registered Report Identifier (irrid): DERR1-10.2196/42094., (©Peppino Tropea, Francesco Infarinato, Irma Sterpi, Marco Ottaviani, Paola Antoniotti, Paola Romano, Michela Picardi, Michela Goffredo, Riccardo Re, Sanaz Pournajaf, Agnese Seregni, Antonio Caronni, Marco Franceschini, Massimo Corbo. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 20.04.2023.)

Study of photonic spin-orbital interactions, which involves control of the propagation and spatial distributions of light via its polarization, is not only important at the fundamental level but also has significant implications for functional photonic applications that require active tuning of directional light propagation. Many of the experimental demonstrations have been attributed to the spin-momentum locking characteristic of evanescent waves. In this Letter, we show another property of evanescent waves: the polarization-dependent direction of the imaginary part of the Poynting vector, i.e., reactive power. Based on this property, we propose a simple and robust way to tune the directional far-field scattering from nanoparticles near a surface under evanescent wave illumination by controlling its polarization and direction of the incident light.

Unidirectional scattering from circularly polarized dipoles has been demonstrated in near-field optics, where the quantum spin-Hall effect of light translates into spin-momentum locking. By considering the whole electromagnetic field, instead of its spin component alone, near-field directionality can be achieved beyond spin-momentum locking. This unveils the existence of the Janus dipole, with side-dependent topologically protected coupling to waveguides, and reveals the near-field directionality of Huygens dipoles, generalizing Kerker's condition. Circular dipoles, together with Huygens and Janus sources, form the complete set of all possible directional dipolar sources in the far- and near-field. This allows the designing of directional emission, scattering, and waveguiding, fundamental for quantum optical technology, integrated nanophotonics, and new metasurface designs.