Advancing Plastic Recycling: Challenges and Opportunities in the Integration of 3D Printing and Distributed Recycling for a Circular Economy.

The concept of the circular economy has emerged as a promising solution to address the mounting concerns surrounding plastic waste and the urgent need for sustainable resource management. While conventional centralized recycling remains a common practice for plastic waste, centralized facilities may prove inadequate in handling the ever-increasing volumes of plastic waste generated globally. Consequently, exploring alternative recycling methods, such as distributed recycling by additive manufacturing, becomes paramount. This innovative approach encompasses actively involving communities in recycling practices and promotes a circular economy. This comprehensive review paper aims to explore the critical aspects necessary to realize the potential of distributed recycling by additive manufacturing. In this paper, our focus lies on proposing schemes that leverage existing literature to harness the potential of distributed recycling by additive manufacturing as an effective approach to plastic waste management. We explore the intricacies of the recycling process, optimize 3D printing parameters, address potential challenges, and evaluate the mechanical properties of recycled materials. Our investigation draws heavily from the literature of the last five years, as we conduct a thorough critical assessment of DRAM implementation and its influence on the properties of 3D printing structures. Through comprehensive analysis, we reveal the potential of recycled materials in delivering functional components, with insights into their performance, strengths, and weaknesses. This review serves as a comprehensive guide for those interested in embracing distributed recycling by additive manufacturing as a transformative approach to plastic recycling. By fostering community engagement, optimizing 3D printing processes, and incorporating suitable additives, it is possible to collectively contribute to a more sustainable future while combatting the plastic waste crisis. As progress is made, it becomes essential to further delve into the complexities of material behavior, recycling techniques, and the long-term durability of recycled 3D printed components. By addressing these challenges head-on, it is feasible to refine and advance distributed recycling by additive manufacturing as a viable pathway to minimize plastic waste, fostering a circular economy and cultivating a cleaner planet for generations to come.

Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas.

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress-strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

Hemodynamic changes associated with common EEG patterns in critically ill patients: Pilot results from continuous EEG-fNIRS study.

Functional near-infrared spectroscopy (fNIRS) is currently the only non-invasive method allowing for continuous long-term assessment of cerebral hemodynamic. We evaluate the feasibility of using continueous electroencephalgraphy (cEEG)-fNIRS to study the cortical hemodynamic associated with status epilepticus (SE), burst suppression (BS) and periodic discharges (PDs). Eleven adult comatose patients admitted to the neuroICU for SE were recruited, and cEEG-fNIRS monitoring was performed to measure concentration changes in oxygenated (HbO) and deoxygenated hemoglobin (HbR). Seizures were associated with a large increase HbO and a decrease in HbR whose durations were positively correlated with the seizures' length. Similar observations were made for hemodynamic changes associated with bursts, showing overall increases in HbO and decreases in HbR relative to the suppression periods. PDs were seen to induce widespread HbO increases and HbR decreases. These results suggest that normal neurovascular coupling is partially retained with the hemodynamic response to the detected EEG patterns in these patients. However, the shape and distribution of the response were highly variable. This work highlighted the feasibility of conducting long-term cEEG-fNIRS to monitor hemodynamic changes over a large cortical area in critically ill patients, opening new routes for better understanding and management of abnormal EEG patterns in neuroICU.

Cortical thinning is associated with brain pulsatility in older adults: An MRI and NIRS study.

Aging is accompanied by global brain atrophy occurring unequally across the brain. Cortical thinning is seen with aging with a larger loss in the frontal and temporal subregions. We explored the link between regional cortical thickness and regional cerebral pulsatility. Sixty healthy individuals were divided into two age groups, young (aged 19-31) and older (aged 65-75) adults. Each participant underwent a near-infrared spectroscopy (NIRS) scan to index regional brain pulsatility from cerebral pulse-transit-time-to-the peak-of-the-pulse (PTTp), an anatomical magnetic resonance imaging (MRI) and a phase-contrast MRI (PC-MRI) scan to measure arterial and cerebrospinal fluid (CSF) pulsatility. In older adults, the greatest association between cerebral pulsatility and cortical thickness was found in superior and middle temporal and superior, middle and inferior frontal areas, which are the regions perfused first by the internal carotid arteries. This association dropped in the postcentral and superior parietal regions. These findings suggest higher brain pulsatility as a potential risk factor contributing to cortical thinning for some brain regions more than others.

Longitudinal Impact of Physical Activity on Brain Pulsatility Index and Cognition in Older Adults with Cardiovascular Risk Factors: A NIRS Study.

Recent studies have shown that optical indices of cerebral pulsatility, including cerebral pulse amplitude, are linked to cerebrovascular health. A chronically higher cerebral pulsatility is associated with cognitive decline. Although it is widely known that regular physical activity improves cognitive functions, little is known about the association between physical activity and the optical index of cerebral pulsatility. This study assessed the impact of 12 months of regular physical activity on the changes in the optical index of cerebral pulsatility and explored its association with cognition. A total of 19 older adults (aged 59-79 years) with cardiovascular risk factors (CVRF) completed the study. Low-intensity, short-duration walking as a brief cardiovascular challenge was used to study the impact of regular physical activity on post-walking changes in cerebral pulsatility index. The participants walked on a gym track while a near-infrared spectroscopy (NIRS) device recorded hemodynamics data from the frontal and motor cortex subregions. Our data indicated that 12 months of physical activity was associated with lower global cerebral pulse amplitude, which was associated with higher cognitive scores in executive functions. Further, the global cerebral pulsatility index was reduced after short-duration walking, and this reduction was greater after 12 months of regular physical activity compared with the baseline. This may be an indication of improvement in cerebrovascular response to the cardiovascular challenge after regular physical activity. This study suggests that 12 months of physical activity may support cognitive functions through improving cerebral pulsatility in older adults with CVRF.

Biomechanical characterization of a chronic type a dissected human aorta.

Aortic dissection is one of the most lethal cardiovascular diseases. A chronic Type A (Stanford) dissected aorta was retrieved for research from a 73-year-old male donor without diagnosed genetic disease. The aorta presented a dissection over the full length, and it reached a diameter of 7.7 cm in its ascending portion. The descending thoracic aorta underwent layer-specific quasi-static and dynamic mechanical characterizations after layer separation. Mechanical tests showed a physiological (healthy) behavior of the intima and some mechanical anomalies of the media and the adventitia. In particular, the static stiffness of both these layers at smaller strains was three times smaller than any one measured for twelve healthy aortas. When the viscoelastic properties were tested, adventitia presented a larger relative increase of the dynamic stiffness at 3 Hz with respect to most of the healthy aortas. The loss factor of the adventitia, which is associated with dissipation, was at the lower limit of those measured for healthy aortas. It seems reasonable to attribute these anomalies of the mechanical properties exhibited by the media and the adventitia to the severe remodeling secondary to the chronic nature of the dissection. However, it cannot be excluded that some of the mechanical anomalies were present before remodeling.

Can magnesium reduce central neurodegeneration in Alzheimer's disease? Basic evidences and research needs.

Magnesium (Mg) is a crucial divalent cation with more than 300 cellular functions. This ion shows therapeutic properties in several neurological diseases. Although there are numerous basic evidences showing that Mg can inhibit pathological processes involved in neuroglial degeneration, this low-cost option is not well-considered in clinical research and practice for now. Nevertheless, none of the expensive drugs currently recommended by the classic guidelines (in addition to physiological rehabilitation) had shown exceptional effectiveness. Herein, focusing on Alzheimer's disease (AD), we analyze the therapeutic pathways that support the use of Mg for neurogenesis and neuroprotection. According to experimental findings reviewed, Mg shows interesting abilities to facilitate toxin clearance, reduce neuroinflammation, inhibit the pathologic processing of amyloid protein precursor (APP) as well as the abnormal tau protein phosphorylation, and to reverse the deregulation of N-methyl-D-aspartate receptors. Currently, some crucial details of the mechanisms involved in these proved effects remain elusive and clinical background is poor. Therefore, further studies are required to enable a better overview on pharmacodynamic targets of Mg and thus, to find optimal pharmacologic strategies for clinical use of this ion.

fNIRS improves seizure detection in multimodal EEG-fNIRS recordings.

In the context of epilepsy monitoring, electroencephalography (EEG) remains the modality of choice. Functional near-infrared spectroscopy (fNIRS) is a relatively innovative modality that cannot only characterize hemodynamic profiles of seizures but also allow for long-term recordings. We employ deep learning methods to investigate the benefits of integrating fNIRS measures for seizure detection. We designed a deep recurrent neural network with long short-term memory units and subsequently validated it using the CHBMIT scalp EEG database-a compendium of 896 h of surface EEG seizure recordings. After validating our network using EEG, fNIRS, and multimodal data comprising a corpus of 89 seizures from 40 refractory epileptic patients was used as model input to evaluate the integration of fNIRS measures. Following heuristic hyperparameter optimization, multimodal EEG-fNIRS data provide superior performance metrics (sensitivity and specificity of 89.7% and 95.5%, respectively) in a seizure detection task, with low generalization errors and loss. False detection rates are generally low, with 11.8% and 5.6% for EEG and multimodal data, respectively. Employing multimodal neuroimaging, particularly EEG-fNIRS, in epileptic patients, can enhance seizure detection performance. Furthermore, the neural network model proposed and characterized herein offers a promising framework for future multimodal investigations in seizure detection and prediction.

Multichannel wearable fNIRS-EEG system for long-term clinical monitoring.

Continuous brain imaging techniques can be beneficial for the monitoring of neurological pathologies (such as epilepsy or stroke) and neuroimaging protocols involving movement. Among existing ones, functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) have the advantage of being noninvasive, nonobstructive, inexpensive, yield portable solutions, and offer complementary monitoring of electrical and local hemodynamic activities. This article presents a novel system with 128 fNIRS channels and 32 EEG channels with the potential to cover a larger fraction of the adult superficial cortex than earlier works, is integrated with 32 EEG channels, is light and battery-powered to improve portability, and can transmit data wirelessly to an interface for real-time display of electrical and hemodynamic activities. A novel fNIRS-EEG stretchable cap, two analog channels for auxiliary data (e.g., electrocardiogram), eight digital triggers for event-related protocols and an internal accelerometer for movement artifacts removal contribute to improve data acquisition quality. The system can run continuously for 24 h. Following instrumentation validation and reliability on a solid phantom, performance was evaluated on (1) 12 healthy participants during either a visual (checkerboard) task at rest or while pedalling on a stationary bicycle or a cognitive (language) task and (2) 4 patients admitted either to the epilepsy (n = 3) or stroke (n = 1) units. Data analysis confirmed expected hemodynamic variations during validation recordings and useful clinical information during in-hospital testing. To the best of our knowledge, this is the first demonstration of a wearable wireless multichannel fNIRS-EEG monitoring system in patients with neurological conditions. Hum Brain Mapp 39:7-23, 2018. © 2017 Wiley Periodicals, Inc.