The performance of semiconductor devices is fundamentally governed by charge-carrier dynamics within the active materials1–6. Although advances have been made towards understanding these dynamics ...under steady-state conditions, the importance of non-equilibrium phenomena and their effect on device performances remains elusive7,8. In fact, the ballistic propagation of carriers is generally considered to not contribute to the mechanism of photovoltaics (PVs) and light-emitting diodes, as scattering rapidly disrupts such processes after carrier generation via photon absorption or electric injection9. Here we characterize the spatiotemporal dynamics of carriers immediately after photon absorption in methylammonium lead iodide perovskite films using femtosecond transient absorption microscopy (fs-TAM) with a 10 fs temporal resolution and 10 nm spatial precision. We found that non-equilibrium carriers propagate ballistically over 150 nm within 20 fs of photon absorption. Our results suggest that in a typical perovskite PV device operating under standard conditions, a large fraction of carriers can reach the charge collection layers ballistically. The ballistic transport distance appears to be limited by energetic disorder within the materials, probably due to disorder-induced scattering. This provides a direct route towards optimization of the ballistic transport distance via improvements in materials and by minimizing the energetic disorder. Our observations reveal an unexplored regime of carrier transport in perovskites, which could have important consequences for device performance.Charge-carrier dynamics are fundamental to the operation and performance of semiconductor devices. In methylammonium lead iodide perovskites, carriers in the non-equilibrium regime after excitation propagate ballistically over 150 nm within 20 fs.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Aims
To determine the need for care robots among nurses and to suggest how robotic care should be prioritized in integrated nursing care services.
Background
Korea is expected to be a super‐aged ...society by 2030. To solve care issues with elderly inpatient caused by informal caregivers, the government introduced “integrated nursing care services”; these are comprehensive care systems staffed by professionally trained nurses. To assist them, a care robot development project has been launched.
Design
The study applied a cross‐sectional survey.
Methods
In 2016, we conducted a multicentre survey involving 302 Registered Nurses in five hospitals including three tertiary and two secondary hospitals in Korea. The questionnaire consisted of general characteristics of nurses and their views on and extents of agreement about issues associated with robotic care.
Results
Trial centre nurses and those with ≥10 years of experience reported positively on the prospects for robotic care. The top‐three desired primary roles for care robots were “measuring/monitoring”, “mobility/activity” and “safety care”. “Reduction in workload”, especially in terms of “other nursing services” which were categorized as nonvalue‐added nursing activities, was the most valued feature. The nurses approved of the aid by care robots but were concerned about device malfunction and interruption of rapport with patients.
Conclusion
Care robots are expected to be effective in integrated nursing care services, particularly in “measuring/monitoring”. Such robots should decrease nurses’ workload and minimize nonvalue‐added nursing activities efficiently. No matter how excellent care robots are, they must cooperate with and be controlled by nurses.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK, VSZLJ
We discovered that impulse-radio ultra-wideband (IR-UWB) radar could recognize cardiac motions in a non-contact fashion. Therefore, we measured the heart rate (HR) and rhythms using an IR-UWB radar ...sensor and evaluated the validity and reliability of the measurements in comparison to electrocardiography. The heart beats were measured in 6 healthy volunteers (18 samples) with normal sinus rhythm (NSR) and 16 patients (36 samples) with atrial fibrillation (AF) using both an IR-UWB radar sensor and electrocardiography simultaneously. The participants hold their breath for 20 seconds during the data acquisition. In subjects with NSR, there was excellent agreement of HR (intraclass correlation coefficient ICC 0.856), average R-R interval (ICC 0.997) and individual R-R intervals between the two methods (ICC 0.803). In subjects with AF, HR (ICC 0.871) and average R-R interval (ICC 0.925) from the radar sensor also agreed well with those from electrocardiography, though there was a small disagreement in the individual R-R intervals between the two methods (ICC 0.697). The rhythms computed by the signal-processing algorithm showed good agreement between the two methods (Cohen's Kappa 0.922). The IR-UWB radar sensor is precise and accurate for assessing HR and rhythms in a non-contact fashion.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
There have been many efforts to enhance the performance and the stability of Li-ion battery. It is crucial to develop a new material as well as to understand the mechanism of microstructure formation ...of the electrode in order to enhance the performance of the battery. In this study, the effect of sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) on the microstructure formation as well as on the rheological properties in the aqueous anode slurries is investigated. The graphite particles aggregate with each other due to their hydrophobicity and form a gel structure in an aqueous slurry. Both CMC and SBR induce the dispersion of the graphite particles by adsorbing onto the graphite surface. In the graphite/CMC/SBR slurry, the SBR can affect the dispersion of the graphite particles at low CMC concentration, while the microstructure is not changed regardless of added SBR at high CMC concentration because the SBR cannot adsorb on the graphite surface due to the presence of CMC. The microstructure of the slurry is also confirmed by the cryo-SEM images. Understanding the role of the binders on the microstructure formation will be helpful for the effective design of the battery slurries.
•The effect of binders on the microstructure in anode slurry is investigated.•The microstructure is analyzed by viscoelastic properties and cryo-SEM imgaes.•CMC and SBR influence the microstructure formation of the slurry in different ways.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Current cardiorespiratory monitoring equipment can cause injuries and infections in neonates with fragile skin. Impulse-radio ultra-wideband (IR-UWB) radar was recently demonstrated to be an ...effective contactless vital sign monitor in adults. The purpose of this study was to assess heart rates (HRs) and respiratory rates (RRs) in the neonatal intensive care unit (NICU) using IR-UWB radar and to evaluate its accuracy and reliability compared to conventional electrocardiography (ECG)/impedance pneumography (IPG).
The HR and RR were recorded in 34 neonates between 3 and 72 days of age during minimal movement (51 measurements in total) using IR-UWB radar (HRRd, RRRd) and ECG/IPG (HRECG, RRIPG) simultaneously. The radar signals were processed in real time using algorithms for neonates. Radar and ECG/IPG measurements were compared using concordance correlation coefficients (CCCs) and Bland-Altman plots.
From the 34 neonates, 12,530 HR samples and 3,504 RR samples were measured. Both the HR and RR measured using the two methods were highly concordant when the neonates had minimal movements (CCC = 0.95 between the RRRd and RRIPG, CCC = 0.97 between the HRRd and HRECG). In the Bland-Altman plot, the mean biases were 0.17 breaths/min (95% limit of agreement LOA -7.0-7.3) between the RRRd and RRIPG and -0.23 bpm (95% LOA -5.3-4.8) between the HRRd and HRECG. Moreover, the agreement for the HR and RR measurements between the two modalities was consistently high regardless of neonate weight.
A cardiorespiratory monitor using IR-UWB radar may provide accurate non-contact HR and RR estimates without wires and electrodes for neonates in the NICU.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Contamination by per- and polyfluoroalkyl substances (PFASs) is of great concern in global environments. Due to strong regulation of legacy PFASs, emerging PFASs including alternatives and precursors ...have been introduced to the industrial market. In this study, legacy and emerging PFASs were measured in seawater, sediment, and bivalves collected along the Korean coast to investigate the occurrence, distribution, contamination sources, and bioaccumulation potential of PFASs. Wide concentration ranges of legacy PFASs were detected in multiple environmental samples, indicating widespread contamination. C8-based PFASs (e.g., PFOA and PFOS) were still major contaminants in all of the environmental samples. Some precursors, such as 8:2 fluorotelomer sulfonate (8:2 FTS) and N-ethyl-perfluorooctane sulfonamidoacetic acid (N-EtFOSAA), and perfluoro-2-propoxypropanoic potassium 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F–53B), an alternative to PFOS, were detected in sediment or bivalve samples, implying a shift in consumption patterns from legacy to emerging PFASs. The highest concentrations of PFASs in environmental samples were found at the locations near industrial complexes, such as those for the semi-conductor, paper mill, automobile, and metal-plating industry. This result indicates that PFAS contamination is associated with intensive industrial activities in the coastal environment. Matrix-dependent contamination and profiles of PFASs were observed. Seawater was dominated by short-chained PFASs as a prompt reflection of regulation, while the sediment and bivalves were dominated by long-chained PFASs. Carbon-chain length was a major factor governing environmental behavior and bioaccumulation of PFASs. This was the first nation-wide survey on legacy and emerging PFASs in the coastal environment of Korea.
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•Legacy and emerging PFASs were measured for multiple environmental matrices in Korea.•C8-based PFASs were still major contaminants in the coastal environment.•Predominant compounds of PFASs were different depending on multiple matrices.•Some precursors and F–53B, an alternative to PFOS, were detected in sediment or bivalves.•Carbon-chain length was a major factor for behavior and bioaccumulation of PFASs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We used real-time fluorescence microscopy to investigate the migration of latex particles in drying battery slurries. The time evolution of the fluorescence signals revealed that the migration of the ...latex particles was suppressed above the entanglement concentration of carboxymethyl cellulose (CMC), while it was significantly enhanced when CMC fully covered the surfaces of the graphite particles. In particular, a two-step migration was observed when the graphite particles flocculated by depletion attraction at high CMC/graphite mass ratios. The transient states of the nonadsorbing CMC and graphite particles in a medium were discussed, and the uses of this novel measurement technique to monitor the complex drying processes of films were demonstrated.
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IJS, KILJ, NUK, PNG, UL, UM
There has been the possibility for respiration and carotid pulsation to be simultaneously monitored from a distance using impulse-radio ultra-wideband (IR-UWB) radar. Therefore, we investigated the ...validity of simultaneous respiratory rates (RR), pulse rates (PR) and R-R interval measurement using IR-UWB radar. We included 19 patients with a normal sinus rhythm (NSR) and 14 patients with persistent atrial fibrillation (PeAF). The RR, PR, R-R interval and rhythm were obtained simultaneously from the right carotid artery area in a supine position and under normal breathing conditions using IR-UWB radar. There was excellent agreement between the RR obtained by IR-UWB radar and that manually counted by a physician (intraclass correlation coefficient ICC 0.852). In the NSR group, there was excellent agreement between the PR (ICC 0.985), average R-R interval (ICC 0.999), and individual R-R interval (ICC 0.910) measured by IR-UWB radar and electrocardiography. In the PeAF group, PR (ICC 0.930), average R-R interval (ICC 0.957) and individual R-R interval (ICC 0.701) also agreed well between the two methods. These results demonstrate that IR-UWB radar can simultaneously monitor respiration, carotid pulse and heart rhythm with high precision and may thus be utilized as a noncontact continuous vital sign monitoring in clinical practice.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
While full-night polysomnography is the gold standard for the diagnosis of obstructive sleep apnea, its limitations include a high cost and first-night effects. This study developed an algorithm for ...the detection of respiratory events based on impulse-radio ultra-wideband radar and verified its feasibility for the diagnosis of obstructive sleep apnea. A total of 94 subjects were enrolled in this study (23 controls and 24, 14, and 33 with mild, moderate, and severe obstructive sleep apnea, respectively). Abnormal breathing detected by impulse-radio ultra-wideband radar was defined as a drop in the peak radar signal by ≥30% from that in the pre-event baseline. We compared the abnormal breathing index obtained from impulse-radio ultra-wideband radar and apnea-hypopnea index (AHI) measured from polysomnography. There was an excellent agreement between the Abnormal Breathing Index and AHI (intraclass correlation coefficient = 0.927). The overall agreements of the impulse-radio ultra-wideband radar were 0.93 for Model 1 (AHI ≥ 5), 0.91 for Model 2 (AHI ≥ 15), and 1 for Model 3 (AHI ≥ 30). Impulse-radio ultra-wideband radar accurately detected respiratory events (apneas and hypopneas) during sleep without subject contact. Therefore, impulse-radio ultra-wideband radar may be used as a screening tool for obstructive sleep apnea.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Legacy and novel flame retardants (FRs) such as polybrominated diphenyl ethers (PBDEs), novel BFRs, and organophosphate flame retardants (OPFRs) were measured in water and sediment collected from ...highly industrialized bays of Korea. Predominant compounds in sediment were BDE 209, DBDPE, and BTBPE for BFRs, and TCPP and TBOEP for OPFRs, respectively. Higher alternative FR concentrations were observed compared to those reported for previous studies. The highest BFR concentrations were found in locations close to industrial complexes, while the OPFR concentrations were highest in locations close to domestic regions and a wastewater treatment plant. Different contamination sources were observed for BFRs and OPFRs. The ratio of DBDPE/BDE 209 in sediment ranged from 0.84 to 28, indicating a shift in consumption of BFRs. A significant decline in PBDEs suggests the effectiveness of domestic and global regulations. Despite this, sedimentary PBDE concentrations may pose adverse health risks to benthic organisms and humans.
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•Industrialized bays were severely contaminated with legacy and novel flame retardants.•High ratio of DBDPE/BDE 209 in sediment indicates a shift to deca-BDE alternatives.•Contamination sources were different for brominated and phosphate flame retardants.•Significantly declining trend of PBDEs was attributed to domestic and global regulations.•Sedimentary PBDEs may pose potential health risks to benthic organisms and humans.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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