Preliminary Study of Novel Bio-Crypto Key Generation Using Clustering-Based Binarization of ECG Features.

In modern society, the popularity of wearable devices has highlighted the need for data security. Bio-crypto keys (bio-keys), especially in the context of wearable devices, are gaining attention as a next-generation security method. Despite the theoretical advantages of bio-keys, implementing such systems poses practical challenges due to their need for flexibility and convenience. Electrocardiograms (ECGs) have emerged as a potential solution to these issues but face hurdles due to intra-individual variability. This study aims to evaluate the possibility of a stable, flexible, and convenient-to-use bio-key using ECGs. We propose an approach that minimizes biosignal variability using normalization, clustering-based binarization, and the fuzzy extractor, enabling the generation of personalized seeds and offering ease of use. The proposed method achieved a maximum entropy of 0.99 and an authentication accuracy of 95%. This study evaluated various parameter combinations for generating effective bio-keys for personal authentication and proposed the optimal combination. Our research holds potential for security technologies applicable to wearable devices and healthcare systems.

ECG Authentication Based on Non-Linear Normalization under Various Physiological Conditions.

The development and use of wearable devices require high levels of security and have sparked interest in biometric authentication research. Among the available approaches, electrocardiogram (ECG) technology is attracting attention because of its strengths in spoofing. However, morphological changes of ECG, which are affected by physical and psychological factors, can make authentication difficult. In this paper, we propose authentication using non-linear normalization of ECG beats that is robust to changes in ECG waveforms according to heart rate fluctuations in various daily activities. We performed a non-linear normalization method through the analysis of ECG alongside heart rate, evaluating similarities and authenticating the performance of our new method compared to existing methods. Compared with beats before normalization, the average similarity of the proposed method increased 23.7% in the resting state and 43% in the non-resting state. After learning in the resting state, authentication performance reached 99.05% accuracy for the resting state and 88.14% for the non-resting state. The proposed method can be applicable to an ECG-based authentication system under various physiological conditions.

Multifunctional Self-Combustion Additives Strategy to Fabricate Highly Responsive Hybrid Perovskite Photodetectors.

To resolve the inherent trade-off issue between responsivity and detectivity in FA0.9Cs0.1PbI3 perovskite photodetectors, this paper proposes a novel strategy using multifunctional self-combustion additives (urea and ammonium nitrate). During the early stages of crystallization, urea allows for the formation of a strong Lewis complex-derived low-dimensional intermediate phase; this suppresses the formation of perovskite nuclei, while ammonium ions assist the preferred grain growth along the [110] direction. During the high-temperature annealing steps, a self-combusting exothermic reaction occurs between urea as a fuel and NH4NO3 as an oxidizer, through which a locally supplied heat facilitates the removal of residual urea and byproducts. These multifunctional roles of self-combustible additives facilitate the production of high-quality, enlarged grain-structured perovskite films with improved optoelectronic properties, as confirmed by various analyses, including impedance spectroscopy and intensity-modulated photocurrent spectroscopy. The resulting FA0.9Cs0.1PbI3-based photodiode-type photodetectors exhibit outstanding performance, such as a high responsivity (0.762 A W-1) and specific detectivity (over 5.08 × 1013 Jones) at a very low external reverse bias (-0.5 V). Our findings clearly suggest that the multifunctional self-combustion additives strategy could help realize the full potential of FA1-xCsxPbI3 as a photodiode-type photodetector.

Energy Level-Graded Al-Doped ZnO Protection Layers for Copper Nanowire-Based Window Electrodes for Efficient Flexible Perovskite Solar Cells.

Flexible perovskite solar cells (PSCs) have attracted significant interest as promising candidates for portable and wearable devices. Copper nanowires (CuNWs) are promising candidates for transparent conductive electrodes for flexible PSCs because of their excellent conductivity, flexibility, and cost-effectiveness. However, because of the thermal/chemical instability of CuNWs, they require a protective layer for application in PSCs. Previous PSCs with CuNW-based electrodes generally exhibited poor performances compared with their indium tin oxide-based counterparts because of the neglect of the interfacial energetics between the electron transport layer (ETL) and CuNWs. Herein, an Al-doped ZnO (AZO) protective layer fabricated using atomic layer deposition is introduced. The AZO/CuNW-based composite electrode exhibits improved thermal/chemical stability and favorable band alignment between the ETL and CuNWs, based on the Al dopant concentration tuning. As a result, the Al content gradient AZO (g-AZO), composed of three successively deposited AZO layers, leads to highly efficient flexible PSCs with a power conversion efficiency (PCE) of 14.18%, whereas the PCE of PSCs with a non-g-AZO layer is 12.34%. This improvement can be attributed to the efficient electron extraction and reduced charge recombination. Furthermore, flexible PSCs based on g-AZO-based composite electrodes retain their initial PCE, even after 600 bending cycles, demonstrating excellent mechanical stability.

Strain-Mediated Phase Stabilization: A New Strategy for Ultrastable α-CsPbI3 Perovskite by Nanoconfined Growth.

All-inorganic cesium lead triiodide (CsPbI3 ) perovskite is considered a promising solution-processable semiconductor for highly stable optoelectronic and photovoltaic applications. However, despite its excellent optoelectronic properties, the phase instability of CsPbI3 poses a critical hurdle for practical application. In this study, a novel stain-mediated phase stabilization strategy is demonstrated to significantly enhance the phase stability of cubic α-phase CsPbI3 . Careful control of the degree of spatial confinement induced by anodized aluminum oxide (AAO) templates with varying pore sizes leads to effective manipulation of the phase stability of α-CsPbI3 . The Williamson-Hall method in conjunction with density functional theory calculations clearly confirms that the strain imposed on the perovskite lattice when confined in vertically aligned nanopores can alter the formation energy of the system, stabilizing α-CsPbI3 at room temperature. Finally, the CsPbI3 grown inside nanoporous AAO templates exhibits exceptional phase stability over three months under ambient conditions, in which the resulting light-emitting diode reveals a natural red color emission with very narrow bandwidth (full width at half maximum of 33 nm) at 702 nm. The universally applicable template-based stabilization strategy can give in-depth insights on the strain-mediated phase transition mechanism in all-inorganic perovskites.

Cervical lymphadenopathy from PRP treatment with microneedling therapy.

BACKGROUND: Platelet-rich plasma is highly enriched plasma that contains a large concentration of platelets that secrete various growth factors and is used in a wide variety of surgical and cosmetic procedures, including hair regrowth and skin rejuvenation. METHODS: Microneedling therapy is being combined with platelet-rich plasma to potentiate patient's cosmetic effects. While microneedling therapy and platelet-rich plasma therapy have been around for years and are growing in popularity internationally, there are limited data regarding complications when they are used in conjunction. RESULTS: We present a case in which a patient presented with acute, painful lymphadenopathy shortly after undergoing the combination treatment of a microneedling pen with platelet-rich plasma therapy. CONCLUSION: Individuals should know of the potential adverse effect of microneedling pen therapy used in conjunction with platelet-rich plasma therapy, and it should be included in patient consent forms and doctor-patient education.

Time-Resolved Observations of Photo-Generated Charge-Carrier Dynamics in Sb2Se3 Photocathodes for Photoelectrochemical Water Splitting.

Solar-energy conversion by photoelectrochemical (PEC) devices is driven by the separation and transfer of photogenerated charge carriers. Thus, understanding carrier dynamics in a PEC device is essential to realizing efficient solar-energy conversion. Here, we investigate time-resolved carrier dynamics in emerging low-cost Sb2Se3 nanostructure photocathodes for PEC water splitting. Using terahertz spectroscopy, we observed an initial mobility loss within tens of picoseconds due to carrier localization and attributed the origin of carrier localization to the rich surface of Sb2Se3 nanostructures. In addition, a possible recombination at the interface between Sb2Se3 and the back contact is elucidated by time-resolved photoluminescence analysis. We also demonstrated the dual role of the RuO x co-catalyst in reducing surface recombination and enhancing charge transfer in full devices using intensity-modulated spectroscopy. The relatively low onset potential of the Sb2Se3 photocathode is attributed to the sluggish charge transfer at a low applied bias rather than to fast surface recombination. We believe that our insights on carrier dynamics would be an important step toward achieving highly efficient Sb2Se3 photocathodes.

All-Solution-Processed Thermally and Chemically Stable Copper-Nickel Core-Shell Nanowire-Based Composite Window Electrodes for Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have recently attracted tremendous attention because of their excellent efficiency and the advantage of a low-cost fabrication process. As a transparent electrode for PSCs, the application of copper nanowire (CuNW)-network was limited because of its thermal/chemical instability, despite its advantages in terms of high optical/electrical properties and low-cost production. Here, the copper-nickel core-shell nanowire (Cu@Ni NW)-based composite electrode is proposed as a bottom window electrode for PSCs, without the involvement of a high-cost precious metal and vacuum process. The dense and uniform Ni protective shell for CuNWs is attainable by simple electroless plating, and the resulting Cu@Ni NWs exhibit outstanding chemical stability as well as thermal stability compared with bare CuNWs. When the Ni layer with the optimal thickness is introduced, the Cu@Ni NW electrode shows a high transmittance of 80.5% AVT at 400-800 nm, and a sheet resistance of 49.3 ± 5 Ω sq-1. Using the highly stable Cu@Ni NWs, the composite electrode structure is fabricated with sol-gel-derived Al-doped zinc oxide (AZO) over-layer for better charge collection and additional protection against iodine ions from the perovskite. The PSCs fabricated with AZO/Cu@Ni NW-based composite electrode demonstrate a power conversion efficiency (PCE) of 12.2% and excellent long-term stability maintaining 91% of initial PCE after being stored for 500 h at room temperature. Experimental results demonstrate the potential of highly stable Cu@Ni NW-based electrodes as the cost-effective alternative transparent electrode, which can facilitate the commercialization of PSCs.

Facile Sol-Gel-Derived Craterlike Dual-Functioning TiO2 Electron Transport Layer for High-Efficiency Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) are considered promising materials for low-cost solar energy harvesting technology. An electron transport layer (ETL), which facilitates the extraction of photogenerated electrons and their transport to the electrodes, is a key component in planar PSCs. In this study, a new strategy to concurrently manipulate the electrical and optical properties of ETLs to improve the performance of PSCs is demonstrated. A careful control over the Ti alkoxide-based sol-gel chemistry leads to a craterlike porous/blocking bilayer TiO2 ETL with relatively uniform surface pores of 220 nm diameter. Additionally, the phase separation promoter added to the precursor solution enables nitrogen doping in the TiO2 lattice, thus generating oxygen vacancies. The craterlike surface morphology allows for better light transmission because of reduced reflection, and the electrically conductive craterlike bilayer ETL enhances charge extraction and transport. Through these synergetic improvements in both optical and electrical properties, the power conversion efficiency of craterlike bilayer TiO2 ETL-based PSCs could be increased from 13.7 to 16.0% as compared to conventional dense TiO2-based PSCs.

Investigating Recombination and Charge Carrier Dynamics in a One-Dimensional Nanopillared Perovskite Absorber.

Organometal halide perovskite materials have become an exciting research topic as manifested by intense development of thin film solar cells. Although high-performance solar-cell-based planar and mesoscopic configurations have been reported, one-dimensional (1-D) nanostructured perovskite solar cells are rarely investigated despite their expected promising optoelectrical properties, such as enhanced charge transport/extraction. Herein, we have analyzed the 1-D nanostructure effects of organometal halide perovskite (CH3NH3PbI3- xCl x) on recombination and charge carrier dynamics by utilizing a nanoporous anodized alumina oxide scaffold to fabricate a vertically aligned 1-D nanopillared array with controllable diameters. It was observed that the 1-D perovskite exhibits faster charge transport/extraction characteristics, lower defect density, and lower bulk resistance than the planar counterpart. As the aspect ratio increases in the 1-D structures, in addition, the charge transport/extraction rate is enhanced and the resistance further decreases. However, when the aspect ratio reaches 6.67 (diameter ∼30 nm), the recombination rate is aggravated due to high interface-to-volume ratio-induced defect generation. To obtain the full benefits of 1-D perovskite nanostructuring, our study provides a design rule to choose the appropriate aspect ratio of 1-D perovskite structures for improved photovoltaic and other optoelectrical applications.

Enhanced compatibility between a copper nanowire-based transparent electrode and a hybrid perovskite absorber by poly(ethylenimine).

Copper nanowires (CuNWs) have been applied to hybrid perovskite solar cells (PSCs) as a window electrode. By sandwiching the CuNW network between aluminum-doped zinc oxide and adopting a poly(ethylenimine) buffer layer, the compatibility between the CuNWs and the perovskite layer could be dramatically improved. PSCs containing the CuNW-based composite electrode exhibited an average power conversion efficiency of 8.65%.

Retarding Crystallization during Facile Single Coating of NaCl-Incorporated Precursor Solution for Efficient Large-Area Uniform Perovskite Solar Cells.

We demonstrated crystallization retardation of CH3NH3PbI3 thin film during single coating of precursor solution by simple addition of NaCl. NaCl was codissolved into a precursor mixture solution containing PbI2 and methylammonium iodide (MAI). Dissolved NaCl interacted with the PbI2 in solution and produced a stable intermediate phase, which was converted to a full-coverage uniform perovskite absorber layer via reaction with MAI during a single spin-coating. The resulting planar-structure perovskite solar cell made from NaCl-supplemented precursor solution showed a 48% improvement in power conversion efficiency (PCE) (maximum value 15.16%) over the device fabricated without the additive. Our NaCl-supplemented single coating represents an easy approach to effectively obtain highly reproducible uniform performance at an overall position in 5 cm × 5 cm sized cells (divided into 20 subcells with an active area of 0.06 cm2) with average PCEs of 12.00 ± 0.48%.

Fully solution-processed transparent electrodes based on silver nanowire composites for perovskite solar cells.

We report all-solution-processed transparent conductive electrodes based on Ag nanowire (AgNW)-embedded metal oxide composite films for application in organometal halide perovskite solar cells. To address the thermal instability of Ag nanowires, we used combustive sol-gel derived thin films to construct ZnO/ITO/AgNW/ITO composite structures. The resulting composite configuration effectively prevented the AgNWs from undergoing undesirable side-reactions with halogen ions present in the perovskite precursor solutions that significantly deteriorate the optoelectrical properties of Ag nanowires in transparent conductive films. AgNW-based composite electrodes had a transmittance of ∼80% at 550 nm and sheet resistance of 18 Ω sq(-1). Perovskite solar cells fabricated using a fully solution-processed transparent conductive electrode, Au/spiro-OMeTAD/CH3NH3PbI3 + m-Al2O3/ZnO/ITO/AgNW/ITO, exhibited a power conversion efficiency of 8.44% (comparable to that of the FTO/glass-based counterpart at 10.81%) and were stable for 30 days in ambient air. Our results demonstrate the feasibility of using AgNWs as a transparent bottom electrode in perovskite solar cells produced by a fully printable process.

Clinical utility of chimerism status assessed by lineage-specific short tandem repeat analysis: experience from four cases of allogeneic stem cell transplantation.

Chimerism testing permits early prediction and documentation of successful engraftment, and also facilitates detection of impending graft rejection. In this study, we serially monitored chimerism status by short tandem repeat-based PCR in nucleated cells (NC), T cells and natural killer (NK) cells after myeloablative allogeneic stem cell transplantation (SCT). Four patients with myeloid malignancies showed discrepant chimerism results among those three fractions. Three patients had mixed chimerism (MC) of donor/host T cells at a time point around the onset of chronic graft-versus-host disease (GVHD). In two patients with disease relapse, MC of NK cells preceded a morphological relapse or NK cells showed a higher percentage of patient cells compared to NC. Therefore, our study shows that chimerism analysis in lineage-specific cells might be useful in predicting clinical outcome after allogeneic SCT in certain patients.