The complex nature of the nuclear forces generates a broad range and diversity of observational phenomena. Heavy nuclei, though orders of magnitude less massive than neutron stars, are governed by ...the same underlying physics, which is enshrined in the nuclear equation of state. Heavy nuclei are expected to develop a neutron-rich skin where many neutrons collect near the surface. The thickness of this skin is strongly sensitive to the poorly-known density dependence of the symmetry energy near saturation density. An accurate and model-independent determination of the neutron-skin thickness of heavy nuclei would provide a significant first constraint on the density dependence of the nuclear symmetry energy. The determination of the neutron-skin thickness of heavy nuclei has far reaching consequences in many areas of physics as diverse as heavy-ion collisions, polarized electron and proton scattering off nuclei, precision tests of the standard model using atomic parity violation, and nuclear astrophysics. While a systematic and concerted experimental effort has been made to measure the neutron-skin thickness of heavy nuclei, a precise and model-independent determination remains elusive. The measurement of parity-violating asymmetries provides a clean and model-independent determination of the weak form factor of the nucleus which is dominated by the neutron distribution. However, measuring parity-violating asymmetries of the order of a part per million is both challenging and time-consuming. Alternative observables sensitive to the symmetry energy have been proposed and measured successfully in recent experimental campaigns. These data are valuable, but interpretations contain implicit model dependence that hinder the clean determination of the neutron-skin thickness. How to move forward at a time when many new facilities are being commissioned and how to strengthen the synergy with other areas of physics are primary goals of this review.
Metamaterial-based cloaks make objects different from their surrounding appear just like their surrounding. To date, cloaking has been demonstrated experimentally in many fields of research, ...including electrodynamics at microwave frequencies, optics, static electric conduction, acoustics, fluid dynamics, thermodynamics and quasi two-dimensional solid mechanics. However, cloaking in the seemingly simple case of three-dimensional solid mechanics is more demanding. Here, inspired by invisible core-shell nanoparticles in optics, we design an approximate elasto-mechanical core-shell 'unfeelability' cloak based on pentamode metamaterials. The resulting three-dimensional polymer microstructures with macroscopic overall volume are fabricated by rapid dip-in direct laser writing optical lithography. We quasi-statically deform cloak and control samples in the linear regime and map the displacement fields by autocorrelation-based analysis of recorded movies. The measured and the calculated displacement fields show very good cloaking performance. This means that one can elastically hide objects along these lines.
Large-scale linkage of international clinical datasets could lead to unique insights into disease aetiology and facilitate treatment evaluation and drug development. Hereto, multi-stakeholder ...consortia are currently designing several disease-specific translational research platforms to enable international health data sharing. Despite the recent adoption of the EU General Data Protection Regulation (GDPR), the procedures for how to govern responsible data sharing in such projects are not at all spelled out yet. In search of a first, basic outline of an ethical governance framework, we set out to explore relevant ethical principles and norms.
We performed a systematic review of literature and ethical guidelines for principles and norms pertaining to data sharing for international health research.
We observed an abundance of principles and norms with considerable convergence at the aggregate level of four overarching themes: societal benefits and value; distribution of risks, benefits and burdens; respect for individuals and groups; and public trust and engagement. However, at the level of principles and norms we identified substantial variation in the phrasing and level of detail, the number and content of norms considered necessary to protect a principle, and the contextual approaches in which principles and norms are used.
While providing some helpful leads for further work on a coherent governance framework for data sharing, the current collection of principles and norms prompts important questions about how to streamline terminology regarding de-identification and how to harmonise the identified principles and norms into a coherent governance framework that promotes data sharing while securing public trust.
► Anthropogenic marine debris (AMD) in northern-central Chile (SE Pacific) is dominated by plastics. ► Most AMD are household items. ► The types of AMD are similar between coastal waters and local ...shores, and between sandy beaches and rocky shores. ► The results indicate that most AMD has local origins, calling for local solutions.
Anthropogenic marine debris (AMD) is frequently studied on sandy beaches and occasionally in coastal waters, but links between these two environments have rarely been studied. High densities of AMD were found in coastal waters and on local shores of a large bay system in northern-central Chile. No seasonal pattern in AMD densities was found, but there was a trend of increasing densities over the entire study period. While plastics and Styrofoam were the most common types of AMD both on shores and in coastal waters, AMD composition differed slightly between the two environments. The results suggest that AMD from coastal waters are deposited on local shores, which over time accumulate all types of AMD. The types and the very low percentages of AMD with epibionts point to mostly local sources. Based on these results, it can be concluded that a reduction of AMD will require local solutions.
As part of the hypothalamic-pituitary adrenal (HPA) axis, the hypothalamus exerts pivotal influence on metabolic and endocrine homeostasis. With age, these processes are subject to considerable ...change, resulting in increased prevalence of physical disability and cardiac disorders. Yet, research on the aging human hypothalamus is lacking. To assess detailed hypothalamic microstructure in middle adulthood, 39 healthy participants (35-65 years) underwent comprehensive structural magnetic resonance imaging. In addition, we studied HPA axis dysfunction proxied by hair cortisol and waist circumference as potential risk factors for hypothalamic alterations. We provide first evidence of regionally different hypothalamic microstructure, with age effects in its anterior-superior subunit, a critical area for HPA axis regulation. Further, we report that waist circumference was related to increased free water and decreased iron content in this region. In age, hair cortisol was additionally associated with free water content, such that older participants with higher cortisol levels were more vulnerable to free water content increase than younger participants. Overall, our results suggest no general age-related decline in hypothalamic microstructure. Instead, older individuals could be more susceptible to risk factors of hypothalamic decline especially in the anterior-superior subregion, including HPA axis dysfunction, indicating the importance of endocrine and stress management in age.
Through-the-Wall Imaging Using Differential SAR Dehmollaian, M.; Thiel, M.; Sarabandi, K.
IEEE transactions on geoscience and remote sensing,
05/2009, Letnik:
47, Številka:
5
Journal Article
Recenzirano
An algorithm for imaging of targets behind walls is proposed to reduce the wall reflection and enhance the signal-to-clutter ratio. The image formation is based on differential ...synthetic-aperture-radar image formation employing a continuous-wave radar system. In this approach, instead of using individual backscattered signals, the image is formed by employing the difference signals obtained by subtracting two successive signals along the track. This way, specular reflections are totally eliminated without the need for the knowledge of the wall parameters. This also affects the point target response which is corrected by an integration process. By using backscattered fields from small trihedral corner reflectors behind a poured concrete wall, measured over a frequency band of 1-2.5 GHz, the proposed method is demonstrated.
•Anthropogenic litter was surveyed at riversides and on beaches near river mouths.•Litter composition and abundance patterns were compared between the two environments.•Rivers transport litter to ...beaches and wind and water currents determine its deposition.•Litter composition is characteristic of each river and attributable to human influences.•Strongly persistent, buoyant items make up the main share of riverine and beach litter.
Composition and abundance of persistent buoyant litter (plastics, polystyrene and manufactured wood) were investigated at riversides and on adjacent coastal beaches of four rivers flowing into the SE Pacific Ocean. Persistent buoyant litter made up the main share of litter at riversides (36–82%) and on coastal beaches near the river mouths (67–86%). The characteristic litter composition of each river is attributable to human influences along its course. Riverine litter items were deposited to both sides of the river mouths on coastal beaches, and their abundance generally declined with distance from the river mouth. However, maximum litter accumulations were often found on beaches north of the river mouth, suggesting a long-term influence of the prevailing equatorward low-level jet along the Chilean coast. The results confirm that riverine transport has an important impact on litter abundances on coastal beaches.
Interstitial fluid (ISF) refers to the fluid between the parenchymal cells and along the perivascular spaces (PVS). ISF plays a crucial role in delivering nutrients and clearing waste products from ...the brain. This narrative review focuses on the use of MRI techniques to measure various ISF characteristics in humans. The complementary value of contrast‐enhanced and noncontrast‐enhanced techniques is highlighted. While contrast‐enhanced MRI methods allow measurement of ISF transport and flow, they lack quantitative assessment of ISF properties. Noninvasive MRI techniques, including multi‐b‐value diffusion imaging, free‐water‐imaging, T2‐decay imaging, and DTI along the PVS, offer promising alternatives to derive ISF measures, such as ISF volume and diffusivity. The emerging role of these MRI techniques in investigating ISF alterations in neurodegenerative diseases (eg, Alzheimer's disease and Parkinson's disease) and cerebrovascular diseases (eg, cerebral small vessel disease and stroke) is discussed. This review also emphasizes current challenges of ISF imaging, such as the microscopic scale at which ISF has to be measured, and discusses potential focus points for future research to overcome these challenges, for example, the use of high‐resolution imaging techniques. Noninvasive MRI methods for measuring ISF characteristics hold significant potential and may have a high clinical impact in understanding the pathophysiology of neurodegenerative and cerebrovascular disorders, as well as in evaluating the efficacy of ISF‐targeted therapies in clinical trials.
Level of Evidence
3
Technical Efficacy
Stage 2
Perivascular spaces (PVS) and blood–brain barrier (BBB) disruption are two key features of cerebral small vessel disease (cSVD) and neurodegenerative diseases that have been linked to cognitive ...impairment and are involved in the cerebral waste clearance system. Magnetic resonance imaging (MRI) offers the possibility to study these pathophysiological processes noninvasively in vivo. This educational review provides an overview of the MRI techniques used to assess PVS functionality and BBB disruption. MRI‐visible PVS can be scored on structural images by either (subjectively) counting or (automatically) delineating the PVS. We highlight emerging (diffusion) techniques to measure proxies of perivascular fluid and its movement, which may provide a more comprehensive understanding of the role of PVS in diseases. For the measurement of BBB disruption, we explain the most commonly used MRI technique, dynamic contrast‐enhanced (DCE) MRI, as well as a more recently developed technique based on arterial spin labeling (ASL). DCE MRI and ASL are thought to measure complementary characteristics of the BBB. Furthermore, we describe clinical studies that have utilized these MRI techniques in cSVD and neurodegenerative diseases, particularly Alzheimer's disease (AD). These studies demonstrate the role of PVS and BBB dysfunction in these diseases and provide insight into the large overlap, but also into the differences between cSVD and AD. Overall, MRI techniques may provide valuable insights into the pathophysiological mechanisms underlying these diseases and have the potential to be used as markers for disease progression and treatment response.
Level of Evidence
3
Technical Efficacy
Stage 2
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