Sang Hyun Park’s research while affiliated with Hanyang University Medical Center and other places

Membranes of complex oxides like perovskite SrTiO3 extend the multi-functional promise of oxide electronics into the nanoscale regime of two-dimensional materials. Here we demonstrate that free-standing oxide membranes supply a reconfigurable platform for nano-photonics based on propagating surface phonon polaritons. We apply infrared near-field imaging and -spectroscopy enabled by a tunable ultrafast laser to study pristine nano-thick SrTiO3 membranes prepared by hybrid molecular beam epitaxy. As predicted by coupled mode theory, we find that strong coupling of interfacial polaritons realizes symmetric and antisymmetric hybridized modes with simultaneously tunable negative and positive group velocities. By resolving reflection of these propagating modes from membrane edges, defects, and substrate structures, we quantify their dispersion with position-resolved nano-spectroscopy. Remarkably, we find polariton negative dispersion is both robust and tunable through choice of membrane dielectric environment and thickness and propose a novel design for in-plane Veselago lensing harnessing this control. Our work lays the foundation for tunable transformation optics at the nanoscale using polaritons in a wide range of freestanding complex oxide membranes.

Background As the elderly population continues to grow, the demand for antiaging products is increasing concurrently. On our face, wrinkles begin to form first around the eyes, where the skin is the thinnest. Previous studies have suggested that irradiating the skin with light-emitting diode (LED)/infrared emitting diode (IRED) light at 600 to 660 nm/800 to 860 nm, stimulates the cells of the dermis and epidermal tissue and is effective in wrinkle improvement and antiaging. Therefore, we aimed to evaluate the efficacy and safety of low-level light therapy masks. Materials and methods A randomized, sham device-controlled, double-blind clinical trial was conducted at 2 institutions. Sixty Asian descent individuals between the ages of 30 and 65 years who showed type II to V skin type on the Fitzpatrick scale were included. Among participants with a score of 2 to 4 on the crow’s feet grading scale (CFGS) at rest (without expression), those who sought temporary improvement in both crow’s feet were selected. The participants were categorized into 2 groups: the experimental group, which used a device with a combination of 630 nm LED (max 10 mW/cm ³ ) and 850 nm IRED (max 10 mW/cm ³ ), and the control group, which used the sham device. Efficacy evaluation included various evaluations, including the CFGS as rated by independent raters, CFGS scores assigned by investigators, and the Global Aesthetic Improvement Scale evaluation by both investigators and the participants. Results After using the LED mask for 16 weeks, the CFGS score of the independent raters and investigators showed significant differences at 8, 12, and 16 weeks. In addition, considering the success criteria of this study, a comparison of independent raters showed an improvement rate of ≥69.2% (full analysis set [FAS]: 86.2%, per-protocol set [PPS]: 89.3%) and a difference of ≥49.2% from the control group (FAS: 69.5%, PPS: 72.6%). The change in scores from the baseline showed significant differences between the test group and the control groups at 8, 12, and 16 weeks for both independent raters and investigators. Conclusion LED and IRED phototherapies at 630 nm and 850 nm, respectively, are effective, safe, well-tolerated, and painless treatment for skin rejuvenation.

We analyze a plasmonic model on a honeycomb lattice of metallic nanodisks that hosts nodal lines protected by local symmetries. Using both continuum and tight-binding models, we show that a combination of a synthetic time-reversal symmetry, inversion symmetry, and particle-hole symmetry enforce the existence of nodal lines enclosing the $\mathrm{K}$ and $\mathrm{K}'$ points. The nodal lines are not directly gapped even when these symmetries are weakly broken. The existence of the nodal lines is verified using full-wave electromagnetic simulations. We also show that the degeneracies at nodal lines can be relieved by introducing a Kekul\'e distortion that acts to mix the nodal lines near the $\mathrm{K},\mathrm{K}'$ points. Our findings open pathways for designing novel plasmonic and photonic devices without reliance on complex symmetry engineering, presenting a convenient platform for studying nodal structures in two-dimensional systems.

Purpose Widely used breast cancer risk-prediction tools are based on data from Western countries, but risk factors may differ for Asian women. Hence, we aimed to develop a risk assessment tool for breast cancer in Asian women using a nationwide, population-based mammographic screening cohort. Materials and Methods Women aged ≥40 years who underwent breast cancer screening and general health examination in 2009 were included. Age, body mass index (BMI), breast density, lifestyle and reproductive factors, and comorbidities were used to develop 5-year breast cancer risk-prediction models for premenopausal (n=771,856) and postmenopausal (n=1,108,047) women at baseline. The best-fit risk prediction model was constructed using backward stepwise selection in a Cox proportional hazards model and was transformed into a risk score nomogram. The performance was assessed by discrimination and calibration. Results In premenopausal women, high BMI, low parity, short breastfeeding period, early age at menarche, high breast density, a history of benign breast masses, and family history of breast cancer contributed to the risk prediction of breast cancer. In postmenopausal women, age, diabetes mellitus, dyslipidemia, late-onset menopause, and hormone replacement therapy use were additional risk predictors of breast cancer. Our risk-prediction model showed a concordant statistic of 0.58 (0.57–0.59) for premenopausal women and 0.64 (0.63–0.65) for postmenopausal women. The calibration plot demonstrated good correlations for both models. Conclusion Our breast cancer risk-prediction model demonstrated performance comparable to that of Western countries, especially among postmenopausal women. This provides a foundation for implementing risk-based screening recommendations in Asian women.

Reducing the risk of urethral strictures after transurethral surgery for patients with bladder cancer requires effective strategies. We compared the clinical outcomes of a novel drug-injectable urethral catheter set (NIUS) with hyaluronic acid (HA) with those of the conventional intraurethral HA injection method. This six-center, prospective, randomized, single-blind trial included 192 male patients aged ≥ 20 years scheduled to undergo transurethral surgery. The primary outcome was patient-reported satisfaction. Secondary outcomes were patient-reported pain intensity, clinician-reported convenience, and urethral strictures. Cystourethroscopy was performed under direct visualization. Outcomes of the experimental (NIUS with HA) and control (HA) groups were compared using the chi-square test and t-test. The post-transurethral surgery rate was significantly higher in the experimental group than in the control group (p < 0.001). Overall, 40% and 21.7% of patients in the experimental and control groups, respectively, were very satisfied (p < 0.001). The experimental group had lower postoperative pain intensity scores (p < 0.001), higher clinician-reported convenience scores (p < 0.001), and fewer urethral strictures within 3 months postoperatively (p < 0.001) than the control group. The NIUS with HA after transurethral surgery significantly enhanced patient satisfaction, reduced pain, improved clinician convenience, and was associated with a reduction in grade 1 urethral strictures. Thus, NIUS with HA enhances post-surgery outcomes through improved patient satisfaction and reduced urethral strictures. Trial registration: Cris.nih.go.kr (KCT0007010).

Federated learning (FL) methods for multi-organ segmentation in CT scans are gaining popularity, but generally require numerous rounds of parameter exchange between a central server and clients. This repetitive sharing of parameters between server and clients may not be practical due to the varying network infrastructures of clients and the large transmission of data. Further increasing repetitive sharing results from data heterogeneity among clients, i.e ., clients may differ with respect to the type of data they share. For example, they might provide label maps of different organs ( i.e . partial labels) as segmentations of all organs shown in the CT are not part of their clinical protocol. To this end, we propose an efficient communication approach for FL with partial labels. Specifically, parameters of local models are transmitted once to a central server and the global model is trained via knowledge distillation (KD) of the local models. While one can make use of unlabeled public data as inputs for KD, the model accuracy is often limited due to distribution shifts between local and public datasets. Herein, we propose to generate synthetic images from clients’ models as additional inputs to mitigate data shifts between public and local data. In addition, our proposed method offers flexibility for additional finetuning through several rounds of communication using existing FL algorithms, leading to enhanced performance. Extensive evaluation on public datasets in few communication FL scenario reveals that our approach substantially improves over state-of-the-art methods.