Our research aims to assess the performance of a new generation of consumer activity trackers (Fitbit Charge 4.sup.TM : FBC) to measure sleep variables and sleep stage classifications in patients ...with chronic insomnia, compared to polysomnography (PSG) and a widely used actigraph (Actiwatch Spectrum Pro: AWS). We recruited 37 participants, all diagnosed with chronic insomnia disorder, for one night of sleep monitoring in a sleep laboratory using PSG, AWS, and FBC. Epoch-by-epoch analysis along with Bland-Altman plots was used to evaluate FBC and AWS against PSG for sleep-wake detection and sleep variables: total sleep time (TST), sleep efficiency (SE), waking after sleep onset (WASO), and sleep onset latency (SOL). FBC sleep stage classification of light sleep (LS), deep sleep (DS), and rapid eye movement (REM) was also compared to that of PSG. When compared with PSG, FBC notably underestimated DS (-41.4, p < 0.0001) and SE (-4.9%, p = 0.0016), while remarkably overestimating LS (37.7, p = 0.0012). However, the TST, WASO, and SOL assessed by FBC presented no significant difference from that assessed by PSG. Compared with PSG, AWS and FBC showed great accuracy (86.9% vs. 86.5%) and sensitivity (detecting sleep; 92.6% vs. 89.9%), but comparatively poor specificity (detecting wake; 35.7% vs. 62.2%). Both devices showed better accuracy in assessing sleep than wakefulness, with the same sensitivity but statistically different specificity. FBC supplied equivalent parameters estimation as AWS in detecting sleep variables except for SE. This research shows that FBC cannot replace PSG thoroughly in the quantification of sleep variables and classification of sleep stages in Chinese patients with chronic insomnia; however, the user-friendly and low-cost wearables do show some comparable functions. Whether FBC can serve as a substitute for actigraphy and PSG in patients with chronic insomnia needs further investigation.
The problem of attenuation correction (AC) for quantitative positron emission tomography (PET) had been considered solved to a large extent after the commercial availability of devices combining PET ...with computed tomography (CT) in 2001; single photon emission computed tomography (SPECT) has seen a similar development. However, stimulated in particular by technical advances toward clinical systems combining PET and magnetic resonance imaging (MRI), research interest in alternative approaches for PET AC has grown substantially in the last years. In this comprehensive literature review, the authors first present theoretical results with relevance to simultaneous reconstruction of attenuation and activity. The authors then look back at the early history of this research area especially in PET; since this history is closely interwoven with that of similar approaches in SPECT, these will also be covered. We then review algorithmic advances in PET, including analytic and iterative algorithms. The analytic approaches are either based on the Helgason–Ludwig data consistency conditions of the Radon transform, or generalizations of John’s partial differential equation; with respect to iterative methods, we discuss maximum likelihood reconstruction of attenuation and activity (MLAA), the maximum likelihood attenuation correction factors (MLACF) algorithm, and their offspring. The description of methods is followed by a structured account of applications for simultaneous reconstruction techniques: this discussion covers organ-specific applications, applications specific to PET/MRI, applications using supplemental transmission information, and motion-aware applications. After briefly summarizing SPECT applications, we consider recent developments using emission data other than unscattered photons. In summary, developments using time-of-flight (TOF) PET emission data for AC have shown promising advances and open a wide range of applications. These techniques may both remedy deficiencies of purely MRI-based AC approaches in PET/MRI and improve standalone PET imaging.
This paper investigates the performance limits of cognitive-uplink fixed satellite service (FSS) and terrestrial fixed service (FS) operating in the range 27.5-29.5 GHz for Ka-band. In light of ...standard recommendations from the International Telecommunications Union and a rain-fading channel model, we analyze the interference level at the FS receiver by considering statistical properties of the channel, propagation losses, and antenna patterns. By employing the interference constraint criterion at the FS, an analytical expression for the capacity of the cognitive-uplink FSS is derived, which is useful in understanding the limits in performance and the potential application of the considered coexistence scenario. Simulations are carried out to verify the theoretical derivations and highlight the impact of key parameters on the performance limits.
•316L stainless steel samples with various grain sizes were successfully fabricated.•The fracture morphologies were systematically analyzed.•The dimple size increased with the increase of average ...grain size.•The grain size effects on dimple size and the strength/ductility were uncovered.
The aim of this work is to understand the relationship among average grain size, dimple size and tensile properties of 316L stainless steel via directly experimental results. We have successfully prepared samples with the average grain size from a few microns to tens of microns through cold rolling and annealing processes. Uniaxial tensile tests were performed to confirm the Hall-Petch relationship between the grain size and yield strength. In order to uncover the grain size dependence of ductility, the fracture morphologies in details were observed. It revealed that the dimple size is positively related to the value of D1/2 (D is the average diameter of grain size). A larger grain size was believed to result in a larger dimple so as to achieve a higher ductility (uniform elongation).
Despite the rapid development in the past years, performances of the perovskite solar cell are still limited by the photovoltage and fill factor that are mainly determined by the charge-carrier ...dynamics. In this review, the charge-carrier dynamics of the cell in a wide time span are summarized and discussed to provide a comprehensive understanding of the optoelectronic processes of the perovskite material and devices. Generally, free carriers are generated rapidly and dominate the following transport and recombination processes that mainly occur within a microsecond time scale. The relatively slow defect and ion dynamics and their characteristic time have also been presented. A physics stability regarding this cell is proposed based on understanding the ion dynamics, and the significance of regulating ion and electron dynamics is highlighted. We finally emphasize that elucidation of the band-edge energy structure and charge nature of the perovskite is still an open question.
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Compared with the Shockley-Queisser limit, the emerging perovskite solar cell still has short boards in terms of photovoltage and fill factor that are mainly determined by the charge-carrier dynamics. Here, the charge-carrier dynamics of the cell in a wide time span are summarized and discussed to provide a comprehensive understanding of the optoelectronic processes. We hope that this review will be able to help further understand the essential properties of the perovskite materials and devices, provide inspiration for solving the crucial issues of the cell, and have value for other photoelectric applications.
Under practical working conditions, carrier cooling can be realized within picoseconds, thus making it possible to establish a universal framework to describe the carrier transport and recombination behaviors within microseconds. The response of trap states is found mainly in a millisecond-time scale, while ion transport has a characteristic time in the scale of seconds. The ion dynamics is proposed to be a giant threat to the physics stability of the cell by influencing the interface atomic bonding, doping, and defect properties. For the cell, controls of the electron dynamics are effective routes to approaching the theoretical limit, while regulating the ion dynamics to improve the device stability is the key to commercialization.
The latest discoveries and controversies on the material and charge natures and their physics mechanisms, such as hot carrier cooling, second-order recombination dynamics, indirect bandgap scenario, and excitonic features, indicate that our understanding of the photon-electron-lattice interactions within the perovskite is still in the nascent stage. More investigations of these physics properties are desired, not only for fundamental understanding but also for extending the applications of the perovskite material.
Charge-carrier dynamics play a critical role in determining the photoelectric conversion performance of perovskite solar cells toward the Shockley-Queisser limit. These dynamics in a wide time span are summarized and discussed here to provide clear insight into the fundamental physics processes of the cell. The critical dynamics parameters are derived from the literature and presented. In particular, the defect and ion dynamics are discussed to elucidate the slow charge response and stability issue of the cell.
Exosomes are cell-derived nanovesicles that transfer molecular cargo from donor to recipient cells and mediate intercellular communication. Advancement in elucidating the biological capabilities and ...functionalities of exosomes has revealed the striking roles of exosomes as conveyors of bioactive molecules across the biological barriers. Tumor-derived exosomes hold great promise to serve as a liquid biopsy tool for cancer diagnosis and prognosis, as large quantities of exosomes are excreted by tumor cells continuously into the circulation, carrying the molecular cargo (DNA, RNA, proteins) reflective of the genetic and signaling alterations in tumor cells. Two inherent characteristics of exosomes offer important opportunities for drug delivery: their superb transcellular permeability and biocompatibility. Exosomes are uniquely capable of encapsulating a variety of payloads and deliver them to the target tissues. This review discusses the potential of tumor-derived exosomes in cancer liquid biopsies as well as the underlying mechanisms. Furthermore, the recent progress of developing exosomes as highly versatile and efficient drug carriers is also summarized.
Solid-state thermoelectric technology, interconverting heat to electrical energy, offers a promising solution for relaxing global energy problems. A high dimensionless figure of merit ZT is desirable ...for high-efficiency thermoelectric power generation. To date, thermoelectric materials research has focused on increasing the material's ZT. Here we first fabricated phase-separated Sn1-xPbxSe materials by hydrothermal synthesis. We demonstrate that the simultaneous optimization of the power factor and significant reduction in thermal conductivity can be achieved in the phase-separated Sn1-xPbxSe material. The introduction of the PbSe phase contributes to improvement of the electrical conductivity and power factor of the SnSe phase. Meanwhile, nanoscale precipitates and mesoscale grains define all-scale hierarchical architectures to scattering phonons, leading to low lattice thermal conductivity. These two favorable factors lead to remarkably high thermoelectric performance with ZT ∼ 1.7 at 873 K in polycrystalline SnSe + 1% PbSe along the pressing direction, which is a record-high ZT for SnSe polycrystals. These findings highlight the prospects of realizing highly effective solid-state thermoelectric devices.
Assessment of muscle function is an essential indicator for estimating elderly health, evaluating motor function, and instructing rehabilitation training, which also sets urgent requirements for ...mechanical sensors with superior quantification, accuracy, and reliability. To overcome the rigidity and vulnerability of traditional metallic electrodes, we synthesize an ionic hydrogel with large deformation tolerance and fast self-healing ability. And we propose a stretchable, self-healing, and skin-mounted (Triple S) active sensor (TSAS) based on the principles of electrostatic induction and electrostatic coupling. The skin modulus-matched TSAS provides outstanding sensing properties: maximum output voltage of 78.44 V, minimal detection limit of 0.2 mN, fast response time of 1.03 ms, high signal-to-noise ratio and excellent long-term service stability. In training of arm muscle, the functional signals of biceps and triceps brachii muscles as well as the joint dexterity of bending angle can be acquired simultaneously through TSAS. The signal can also be sent wirelessly to a terminal for analysis. With the characteristics of high sensitivity, reliability, convenience, and low-cost, TSAS shows its potential to be the next-generation procedure for real-time assessment of muscle function and rehabilitation training.
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