Current developments in elastic and acoustic metamaterials science.

The concept of metamaterial recently emerged as a new frontier of scientific research, encompassing physics, materials science and engineering. In a broad sense, a metamaterial indicates an engineered material with exotic properties not found in nature, obtained by appropriate architecture either at macro-scale or at micro-/nano-scales. The architecture of metamaterials can be tailored to open unforeseen opportunities for mechanical and acoustic applications, as demonstrated by an impressive and increasing number of studies. Building on this knowledge, this theme issue aims to gather cutting-edge theoretical, computational and experimental studies on elastic and acoustic metamaterials, with the purpose of offering a wide perspective on recent achievements and future challenges. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Elastic metasurfaces for Scholte-Stoneley wave control.

In this work, we investigate the dynamics of Scholte-Stoneley waves (SSWs) travelling along elastic metasurfaces, e.g. thin resonant structures embedding mechanical oscillators, placed at the interface between solid and fluid. To this purpose, an analytical dispersion law, valid in the long-wavelength regime, is derived and used to reveal the hybridization of SSWs with the collective resonance of the mechanical oscillators and the conversion of SSWs into leaky modes within the fluid. The analytical predictions are validated through numerical simulations that include both dispersive and harmonic analysis. Our findings disclose the capabilities of elastic metasurfaces in filtering, trapping and converting SSWs along fluid-solid interfaces, thus supporting the design of novel devices for solid-fluid interaction across various engineering applications, including microfluidics. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Guiding near-source elastic waves in a semi-infinite medium.

In this work, we propose elastic metamaterials with phase discontinuities to steer the propagation of near-source bulk waves in a semi-infinite elastic medium. Our design exploits an array of embedded subwavelength resonators with tailored masses to attain a complete phase shift spanning [Formula: see text]. This phase control allows for diverse wave functionalities, such as directional refraction and energy focusing. Through the use of dispersion diagrams and the generalized Snell's law, along with a multiple scattering formulation, we analytically demonstrate the effectiveness of our design in achieving the desired wavefront manipulation. The proposed design has the potential to advance the field of guiding elastic waves using metamaterials and find practical applications in areas such as isolating ground-borne vibrations in densely urbanized regions and energy harvesting. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

Current developments in elastic and acoustic metamaterials science.

The concept of metamaterial recently emerged as a new frontier of scientific research, encompassing physics, materials science and engineering. In a broad sense, a metamaterial indicates an engineered material with exotic properties not found in nature, obtained by appropriate architecture either at macro-scale or at micro-/nano-scales. The architecture of metamaterials can be tailored to open unforeseen opportunities for mechanical and acoustic applications, as demonstrated by an impressive and increasing number of studies. Building on this knowledge, this theme issue aims to gather cutting-edge theoretical, computational and experimental studies on elastic and acoustic metamaterials, with the purpose of offering a wide perspective on recent achievements and future challenges.This article is part of the theme issue, 'Current developments in elastic and acoustic metamaterials science (Part 2)'.

Mechanical Hemolytic Anemia Associated With Mitral Valve Repair: A Case Report With Literature Review.

Hemolytic anemia could be caused by several conditions, depending on intrinsic or extrinsic defects of the erythrocyte. The latter group includes mechanical intravascular hemolysis, generally related to malfunctioning prosthetic heart valves or, rarely, heart valves repair. We describe a case of a child with Down syndrome, who developed hemolytic anemia after mitral valve repair. We observed that this condition is a rare complication in pediatrics, with only 7 cases reported in literature. Mechanical hemolysis should always be considered in the differential diagnosis of a new-onset hemolytic anemia, especially in patients with valvular heart disease, undergoing cardiac surgery.

Sequencing radium 223 and other life-prolonging agents in castration-resistant prostate cancer patients.

Background: Radium 223 (RA223) is currently administered as part of a therapeutic sequence with the other life-prolonging agents (LPAs) for metastatic castration-resistant prostate cancer (mCRPC). Patients & methods: We retrospectively reviewed the clinical records of patients who had received at least three LPAs including RA223. Results: Median overall survival (OS) from the start of first-line treatment was 39.8 months, with the patients who completed all six planned courses of RA223 having a longer OS than those who did not (53.2 vs 29.5 months; p < 0.0001). Conclusions: Our study confirms the activity of RA223 regardless of the treatment line in which it is administered and suggests that patient selection plays a central role in maximizing this activity.

Designing perturbative metamaterials from discrete models.

Identifying material geometries that lead to metamaterials with desired functionalities presents a challenge for the field. Discrete, or reduced-order, models provide a concise description of complex phenomena, such as negative refraction, or topological surface states; therefore, the combination of geometric building blocks to replicate discrete models presenting the desired features represents a promising approach. However, there is no reliable way to solve such an inverse problem. Here, we introduce 'perturbative metamaterials', a class of metamaterials consisting of weakly interacting unit cells. The weak interaction allows us to associate each element of the discrete model with individual geometric features of the metamaterial, thereby enabling a systematic design process. We demonstrate our approach by designing two-dimensional elastic metamaterials that realize Veselago lenses, zero-dispersion bands and topological surface phonons. While our selected examples are within the mechanical domain, the same design principle can be applied to acoustic, thermal and photonic metamaterials composed of weakly interacting unit cells.

Composite 3D-printed metastructures for low-frequency and broadband vibration absorption.

Architected materials that control elastic wave propagation are essential in vibration mitigation and sound attenuation. Phononic crystals and acoustic metamaterials use band-gap engineering to forbid certain frequencies from propagating through a material. However, existing solutions are limited in the low-frequency regimes and in their bandwidth of operation because they require impractical sizes and masses. Here, we present a class of materials (labeled elastic metastructures) that supports the formation of wide and low-frequency band gaps, while simultaneously reducing their global mass. To achieve these properties, the metastructures combine local resonances with structural modes of a periodic architected lattice. Whereas the band gaps in these metastructures are induced by Bragg scattering mechanisms, their key feature is that the band-gap size and frequency range can be controlled and broadened through local resonances, which are linked to changes in the lattice geometry. We demonstrate these principles experimentally, using advanced additive manufacturing methods, and inform our designs using finite-element simulations. This design strategy has a broad range of applications, including control of structural vibrations, noise, and shock mitigation.

Acoustic properties of porous microlattices from effective medium to scattering dominated regimes.

Microlattices are architected materials that allow for an unprecedented control of mechanical properties (e.g., stiffness, density, and Poisson's coefficient). In contrast to their quasi-static mechanical properties, the acoustic properties of microlattices remain largely unexplored. This paper analyzes the acoustic response of periodic millimeter-sized microlattices immersed in water using experiments and numerical simulations. Microlattices are fabricated using high-precision stereolithographic three-dimensional printing in a large variety of porosities and lattice topologies. This paper shows that the acoustic propagation undergoes a frequency dependent transition from a classic poroelastic behaviour that can be described by Biot's theory to a regime that is dominated by scattering effects. Biot's acoustic parameters are derived from direct simulations of the microstructure using coupled fluid and solid finite elements. The wave speeds predicted with Biot's theory agree well with the experimental measures. Within the scattering regime, the signals show a strong attenuation and dispersion, which is characterized by a cut-off frequency. The strong dispersion results in a frequency dependent group velocity. A simplified model of an elastic cylindrical scatterer allows predicting the signal attenuation and dispersion observed experimentally. The results in this paper pave the way for the creation of microlattice materials for the control of ultrasonic waves across a wide range of frequencies.

Patients' self-evaluation of symptoms, signs and compliance to therapy for heart failure surveillance: A pilot study on identification of worsening heart failure.

In patients with chronic heart failure (HF), it is unclear whether self-evaluation of HF-related symptoms and signs may contribute to the surveillance of clinical stability over time or the early identification of worsening HF.   Therefore, HF-related symptoms and signs, and compliance to therapy were investigated by a self-administrated questionnaire in patients hospitalized due to worsening HF (cases) as well in those with stable HF (controls).  The temporal interval of interest for the questionnaire focused on 2 to 7 days before the hospitalization of the control visit.  A method called "classic" extrapolated a surveillance score by 4 questions revealing HF-related symptoms or signs (higher score indicative of more symptoms or sings reported).  Alternatively, 3 additional questions enriched the "classic" questionnaire, including one on whether the health status was perceived as stable, improved or worsening.  The score from "perceived health status"  inquiry was used as "conditional factor" to computed the surveillance score as: conditional factor + [conditional factor X (the sum of the points yielded by the responses to each question on symptoms, sings and compliance to therapy)].  Among 51 patients hospitalized due to worsening HF and 104 with chronic HF (retrospective study), the area under the curve (receiver operating characteristic) discriminating worsening HF was 0.90 by the classic, and 0.96 by the conditional method (both p<0.001), yielding error rates of 2 in 10 by the classic and 1 in 10 by the conditional method.  In a pilot longitudinal study in 37 ambulatory HF patients from a different population source, predicting worsening HF by alternative questionnaires within 12 weeks from the visit yielded consistent results.  In conclusion, patients' self-monitoring symptoms, signs and compliance by a standardized questionnaire and a conditional method for generating relative a score, may be a promising method for HF stability surveillance.

Right ventricle involvement in patients with breast cancer treated with chemotherapy.

BACKGROUND: Anthracyclines can cause left ventricular (LV) dysfunction. There is little data about right ventricular (RV) damage during chemotherapy. AIM: This study aimed to investigate the toxic effects of chemotherapy, analyzing its impact on right ventricular function. MATERIAL AND METHODS: A prospective study was conducted, enrolling 83 female patients (55 ± 11 years old) affected by breast cancer treated with anthracyclines. Cardiological evaluation, HFA risk score assessment and comprehensive echocardiogram, including speckle tracking analysis and 3D analysis, were performed before starting chemotherapy (T0) and at 3 (T1), 6 (T2) and 12 months (T3) after beginning treatment. RV function was assessed with tricuspid annular plane excursion (TAPSE), S' wave of the tricuspid annulus, fractional area change (FAC), RV global longitudinal strain (RV-GLS), free wall strain (RV-FWLS) and RV 3D ejection fraction (RV-3DEF). Subclinical LV CTRCD was defined as a reduction of GLS > 15% compared to baseline. Subclinical RV cardiotoxicity was defined as the co-presence of a relative decrease of 10% from baseline in RV-3DEF and a relative reduction of 15% from baseline RV-FWLS. RESULTS: After chemotherapy, we found a significant reduction in 2D-LVEF (p = < 0.001) and 3D-LVEF (p = < 0.001), in LV-GLS and RVLS (p = < 0.001), in FAC and TAPSE, also RV-3DEF reduced significantly (p = 0.002). 39% of patients developed LV subclinical CTRCD; 28% of patients developed RV subclinical cardiotoxicity. LV and RV changes occurred concomitantly, and no RV echocardiographic parameters were found to predict the development of LV CTRCD and vice-versa. CONCLUSION: After anthracyclines-based chemotherapy, LV and RV subclinical damage occurs, and it can be detected early by speckle-tracking and 3D echocardiography.

Transcranial direct current stimulation preconditioning modulates the effect of high-frequency repetitive transcranial magnetic stimulation in the human motor cortex.

Experimental studies emphasize the importance of homeostatic plasticity as a mean of stabilizing the properties of neural circuits. In the present work we combined two techniques able to produce short-term (5-Hz repetitive transcranial magnetic stimulation, rTMS) and long-term (transcranial direct current stimulation, tDCS) effects on corticospinal excitability to evaluate whether and how the effects of 5-Hz rTMS can be tuned by tDCS preconditioning. Twelve healthy subjects participated in the study. Brief trains of 5-Hz rTMS were applied to the primary motor cortex at an intensity of 120% of the resting motor threshold, with recording of the electromyograph traces evoked by each stimulus of the train from the contralateral abductor pollicis brevis muscle. This interventional protocol was preconditioned by 15 min of anodal or cathodal tDCS delivered at 1.5 mA intensity. Our results showed that motor-evoked potentials (MEPs) increased significantly in size during trains of 5-Hz rTMS in the absence of tDCS preconditioning. After facilitatory preconditioning with anodal tDCS, 5-Hz rTMS failed to produce progressive MEP facilitation. Conversely, when 5-Hz rTMS was preceded by inhibitory cathodal tDCS, MEP facilitation was not abolished. These findings may give insight into the mechanisms of homeostatic plasticity in the human cerebral cortex, suggesting also more suitable applications of tDCS in a clinical setting.

Experiences and Needs of Patients, Caregivers and Nurses during the COVID-19 Pandemic: Study Protocol for a Mixed-Methods Multicentre Study.

The COVID-19 pandemic is a major public health problem with millions of confirmed cases and deaths described. Nurses are among the health care professionals most involved at the front line, caring for those affected by COVID-19. Patients and families have been subjected to a high emotional burden of fear, anxiety, and uncertainty. The COVID-19 pandemic has had a significant impact on the approach to patients, the organisation of care, and communication with patients and their families, all requiring considerable adaptation on the part of nurses and health care professionals. The overall aim of this research was to find out the needs of patients with COVID-19, the nursing interventions provided and their outcomes, and to explore the experiences of the nurses, patients, and caregivers. A mixed method study will be performed with a convergent design. The study was divided into three phases. Quantitative methods involved nurses and patients affected by COVID-19 with a questionnaire. Qualitative methods involved nurses, patients, and caregivers with interviews and finally a quantitative analysis of the nursing documentation of the interviewed patients. We hope that this study will help us to understand and identify the main nursing and support needs expressed by patients and their families at different stages of their illness.

Impaired glutamatergic neurotransmission in migraine with aura? Evidence by an input-output curves transcranial magnetic stimulation study.

OBJECTIVE: An imbalance between activity of inhibitory and facilitatory intracortical circuits could play a central role in migraine etiology. We used input-output curves to achieve further information about intracortical excitability of motor cortex in migraine with aura. METHODS: Input-output curves were measured in the right abductor pollicis brevis muscle at rest in 12 patients suffering from migraine with aura and 8 healthy subjects. Stimuli were delivered at intensity ranging from 100% to 160% of resting motor threshold with 10-second inter-stimulus intervals. Seven patients were studied before and during treatment with levetiracetam. RESULTS: Results showed a greater motor-evoked potential amplitude in response to increasing intensity of stimuli in patients compared to controls (P < .02). This increased facilitatory effect was abolished by levetiracetam (P < .005). CONCLUSIONS: Our findings support the hypothesis of an interictal cortical hyper-responsivity in migraine patients that appears to be normalized by levetiracetam. This effect could support the potential therapeutic role of levetiracetam in migraine with aura prevention.

Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) during capsaicin-induced pain: modulatory effects on motor cortex excitability.

Evidence by functional imaging studies suggests the role of left DLPFC in the inhibitory control of nociceptive transmission system. Pain exerts an inhibitory modulation on motor cortex, reducing MEP amplitude, while the effect of pain on motor intracortical excitability has not been studied so far. In the present study, we explored in healthy subjects the effect of capsaicin-induced pain and the modulatory influences of left DLPFC stimulation on motor corticospinal and intracortical excitability. Capsaicin was applied on the dorsal surface of the right hand, and measures of motor corticospinal excitability (test-MEP) and short intracortical inhibition (SICI) and facilitation (ICF) were obtained by paired-pulse TMS on left motor cortex. Evaluations were made before and at different times after capsaicin application in two separate sessions: without and with high-frequency rTMS of left DLPF cortex, delivered 10 min. after capsaicin application. We performed also two control experiments to explore: 1: the effects of Left DLPFC rTMS on capsaicin-induced pain; 2: the modulatory influence of left DLPFC rTMS on motor cortex without capsaicin application. Capsaicin-induced pain significantly reduced test MEP amplitude and decreased SICI leaving ICF unchanged. Left DLPFC rTMS, together with the analgesic effect, was able to revert the effects of capsaicin-induced pain on motor cortex restoring normal MEP and SICI levels. These data support the notion that that tonic pain exerts modulatory influence on motor intracortical excitability; the activation of left DLPFC by hf rTMS could have analgesic effects, reverting also the motor cortex excitability changes induced by pain stimulation.

Leprosy: report of a case with severe peripheral neuropathy.

Leprosy (Hansen's disease) is a chronic granulomatous infectious disease, caused by Mycobacterium leprae, with cutaneous and neurological manifestations. Leprosy is very rare in Europe but some cases are reported, especially among people coming from endemic areas. Here, we report a case of Hansen's disease and emphasize the importance of a prompt diagnosis and treatment also in non-endemic areas.

Reduced cerebellar inhibition in migraine with aura: a TMS study.

Subtle clinical cerebellar alterations have been found in migraine. Moreover, abnormalities in visual and motor cortex excitability consistent with a lack of inhibitory efficiency have been described in migraine, and it is known that cerebellum exerts an inhibitory control on cerebral cortex. Here, we investigated if impairment of cerebellar activity on motor cortex, i.e. reduced inhibitory control, can be found in migraine. Ten migraineurs with aura and seven healthy controls underwent a transcranial magnetic stimulation (TMS) protocol to investigate the cerebellar inhibitory drive on motor cortex: a conditioning pulse on right cerebellar cortex was delivered 5, 7, 10, 15 ms before a test stimulus (TS) on contralateral motor cortex. The cerebellar conditioning stimulus inhibits the size of the motor-evoked potential (MEP) produced by the TS alone by approximately 30-50%. Amplitude of MEP to TS alone showed no significant difference between patients and controls. Cerebellar conditioning TMS showed a significant deficit of cerebellar inhibition in migraine patients as compared to controls at all interstimulus intervals (5-15 ms) tested. Cerebellar inhibition is reduced in migraineurs. This could account, at least in part, for the reduced inhibitory efficiency previously showed in cerebral cortex of these patients.

Cortical inhibition and habituation to evoked potentials: relevance for pathophysiology of migraine.

Dysfunction of neuronal cortical excitability has been supposed to play an important role in etiopathogenesis of migraine. Neurophysiological techniques like evoked potentials (EP) and in the last years non-invasive brain stimulation techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation gave important contribution to understanding of such issue highlighting possible mechanisms of cortical dysfunctions in migraine. EP studies showed impaired habituation to repeated sensorial stimulation and this abnormality was confirmed across all sensorial modalities, making defective habituation a neurophysiological hallmark of the disease. TMS was employed to test more directly cortical excitability in visual cortex and then also in motor cortex. Contradictory results have been reported pointing towards hyperexcitability or on the contrary to reduced preactivation of sensory cortex in migraine. Other experimental evidence speaks in favour of impairment of inhibitory circuits and analogies have been proposed between migraine and conditions of sensory deafferentation in which down-regulation of GABA circuits is considered the more relevant pathophysiological mechanism. Whatever the mechanism involved, it has been found that repeated sessions of high-frequency rTMS trains that have been shown to up-regulate inhibitory circuits could persistently normalize habituation in migraine. This could give interesting insight into pathophysiology establishing a link between cortical inhibition and habituation and opening also new treatment strategies in migraine.

A case of atypical sporadic hemiplegic migraine associated with PFO and hypoplasia of vertebro-basilar system.

We describe the case of a patient with atypical hemiplegic migraine and associated basilar symptoms, where a large patent foramen ovale (PFO) and hypoplasia of basilar artery were found. The longer period of 4-year remission of the headache attacks was coincident with the percutaneous PFO closure. When 5 years after, hemiplegic migraine attacks relapsed, with more relevant basilar symptoms, a mild re-opening of PFO was found. The atypical presentation of attacks with basilar symptoms and prolonged hemiplegia does not strictly fit the diagnostic criteria of ICHD-II.

Motor intracortical inhibition in PD: L-DOPA modulation of high-frequency rTMS effects.

Dopaminergic drugs and deep brain stimulation restore cortical inhibition in Parkinson disease (PD) patients. High-frequency rTMS was also found to increase cortical inhibition in PD but its therapeutic effect is still controversial. Here we hypothesize that, if dopaminergic drugs reverse to normal cortical excitability in M1, the effect of high-frequency (hf)-rTMS in PD patients could depend on whether they are in a medicated or unmedicated state. The present study aims to explore the lasting effects of sub-threshold hf rTMS trains over M1 on cortical inhibition in patients with "on" and without "off" L-DOPA treatment. Fourteen PD patients were examined twice while "on" and "off" medication. In both conditions, a paired-pulse paradigm was used to evaluate short intracortical inhibition (SICI) and long intracortical inhibition (LICI) that were evaluated before and after hf rTMS trains applied on the motor cortex. The results were compared with those obtained from normal controls. In baseline condition, SICI and LICI were significantly reduced in "off" compared to "on" patients and controls. hf-rTMS over the motor cortex significantly increased SICI and LICI in "off" medication PD patients. Magnetic stimulation proved to be ineffective when the same patients were in "on" state. The results showed that hf-rTMS affected intracortical inhibition (ICI) only in unmedicated patients. By restoring cortical inhibitory circuits dopaminergic drugs, normalize the excitability changes in M1 subsequent to motor rTMS. Whether patients are in a medicated or an unmedicated state would therefore appear to be critical for rTMS effects in PD patients. If a positive correlation exists between increased cortical inhibition and clinical improvement, hf-rTMS during the "off" state could be regarded as a potential add-on treatment to reduce the need of L-dopa and thus delay the adverse effects of its chronic use.