Clinical characteristics and outcomes of atrial flutter in neonates.

BACKGROUND: Atrial flutter is an uncommon arrhythmia that can cause severe morbidity, including heart failure and even death in refractory cases. This study investigated the clinical characteristics, treatment, and long-term outcomes of patients with neonatal atrial flutter and its association with heart failure. METHODS: We retrospectively reviewed atrial flutter cases observed in our center between 1999 and 2021 and analyzed the clinical characteristics, treatment, and recurrence according to the presence of heart failure. RESULTS: The study comprised 15 patients with atrial flutter, with median bodyweight and gestational age of 2.7 kg, 37+4 weeks, respectively. Twelve patients were diagnosed with atrial flutter on the first day of life. The median atrial and ventricular rates were 440/min, 220/min, respectively. Four patients exhibited congestive heart failure. Episodic recurrence was noted in five patients and occurred at a higher rate in patients with congestive heart failure (p = 0.004). Antiarrhythmic drugs for maintenance treatment were administered more often in patients with heart failure (p = 0.011). Initial treatment included direct current cardioversion (n = 9), digoxin (n = 4), and observation (n = 2). Four patients treated with cardioversion experienced recurrence during the neonatal period, and none of those treated with digoxin experienced recurrence. The median follow-up duration was 7 years, during which no atrial flutter recurrence was evident. CONCLUSION: Neonates with congestive heart failure had a higher recurrence of atrial flutter. Direct current cardioversion is the most reliable treatment for neonatal atrial flutter, whereas digoxin may be a viable treatment option in refractory and recurrent cases.

SARS-CoV-2 spike protein detection using slightly tapered no-core fiber-based optical transducer.

The label-free detection of SARS-CoV-2 spike protein is demonstrated by using slightly tapered no-core fiber (ST-NCF) functionalized with ACE2. In the fabricated sensor head, abrupt changes in the mode-field diameter at the interfaces between single-mode fiber and no-core fiber excite multi-guided modes and facilitate multi-mode interference (MMI). Its slightly tapered region causes the MMI to be more sensitive to the refractive index (RI) modulation of the surrounding medium. The transmission minimum of the MMI spectrum was selected as a sensor indicator. The sensor surface was functionalized with ACE2 bioreceptors through the pretreatment process. The ACE2-immobilized ST-NCF sensor head was exposed to the samples of SARS-CoV-2 spike protein with concentrations ranging from 1 to 104 ng/mL. With increasing sample concentration, we observed that the indicator dip moved towards a longer wavelength region. The observed spectral shifts are attributed to localized RI modulations at the sensor surface, which are induced by selective bioaffinity binding between ACE2 and SARS-CoV-2 spike protein. Also, we confirmed the capability of the sensor head as an effective and simple optical probe for detecting antigen protein samples by applying saliva solution used as a measurement buffer. Moreover, we compared its detection sensitivity to SARS-CoV-2 and MERS-CoV spike protein to examine its cross-reactivity. In particular, we proved the reproducibility of the bioassay protocol adopted here by employing the ST-NCF sensor head reconstructed with ACE2. Our ST-NCF transducer is expected to be beneficially utilized as a low-cost and portable biosensing platform for the rapid detection of SARS-CoV-2 spike protein.

Continuous wavelength tuning of the first-order general comb spectrum.

Here we show the continuous wavelength tunability of a general transmittance function (GTF), besides flat-top and narrow band transmittance functions, which is mostly obtainable in the first-order fiber comb filter composed of a polarization beam splitter to form a polarization-diversified loop, four waveplates, and two birefringent fiber segments. On the basis of polarization conditions, which should be satisfied to continuously tune the GTF, waveplate orientation angles (WOAs), which gave an extra phase shift of 1-360° to a specifically chosen GTF, were found using a newly proposed WOA search scheme. Wavelength-tuned comb spectra were calculated at eight WOA sets (i.e., Sets I-VIII) selected from the above WOA sets. In the fabricated filter whose free spectral range was ~0.8 nm, its comb spectrum redshifted step by step by ~0.1 nm, resulting in a total displacement of ~0.7 nm, when the WOA set changed from Set I to VIII. The calculated and measured spectra clearly show that an arbitrary GTF can be continuously wavelength-tuned by properly choosing WOAs.

High Sensitivity Polarimetric Optical Fiber Pressure Sensor Based on Tapered Polarization-Maintaining and Fiber Bragg Grating.

In this paper, we propose a high sensitivity polarimetric optical fiber pressure sensor (OFPS) using a polarization-diversity loop composed of a polarization beam splitter, polarization controllers, and a sensor head. The sensor head consists of 8-cm-long tapered panda-type polarization-maintaining fiber (PMF) and a fiber Bragg grating (FBG) directly spliced with PMF, and the sensor head is located inside a pressure chamber. A pressure-induced birefringence change due to the photoelastic effect can be greatly enhanced at the tapered section of PMF, thereby increasing the pressure sensitivity of the sensor head. The tapered PMF was fabricated using a fusion splicer, and the tapered length and center waist diameter of the tapered PMF segment were ~350 and ~56.82 µm, respectively. At the polarization-diversity loop, PMF is used as a birefringent element to create an interference spectrum due to polarization interference. A pressure-induced birefringence change of PMF results in a wavelength shift of the interference spectrum. Because the PMF birefringence also has a cross sensitivity to temperature, the FBG is utilized for the compensation of the temperature effect on it. The resonance wavelength of the FBG is sensitive to ambient temperature changes but insensitive to changes in pressure. This spectral response of the FBG can be used to compensate additional ambient temperature changes occurred at the sensor head. The pressure sensitivity of our sensor was measured as approximately -27.70 nm/MPa, and an adjusted R² value representing the sensor linearity was measured as ~0.9903 in a measurement range of 0-0.5 MPa. Our fabricated sensor exhibits the highest pressure sensitivity among previously reported polarimetric OFPS.

Pressure and Temperature Dependence of Field-Induced Oscillation in Two-Terminal Device Based on Vanadium Dioxide Thin Film.

In this paper, we investigated the pressure and temperature dependence of the frequency and amplitude of the field-induced oscillation created in a two-terminal device based on a vanadium dioxide (VO2) thin film. First, a simple oscillation circuit was constructed using a VO2-based two-terminal device, a standard resistor, and a DC power supply. Then, the frequency and amplitude variation of the field-induced oscillation was observed for pressure changes applied to the VO2 device in a pressure chamber. This variation of the oscillation characteristics was also examined for ambient temperature changes applied to the VO2 device using a plate heater. When the chamber pressure increased from 0 to 5 MPa with a step of 1 MPa at 25 °C, the oscillation frequency increased from ~592 to ~739 kHz, and the oscillation amplitude decreased from ~12.60 to ~11.40 V. Similarly, when the heater temperature increased from 25 to 50 °C (step: 5 °C) without applied pressure, the oscillation frequency increased from ~592 to ~819 kHz, and the oscillation amplitude decreased from ~12.60 to ~7.16 V. Owing to linear pressure and temperature responses of the VO2 oscillation, the pressure and temperature sensitivities of the oscillation frequency and amplitude could be obtained as four different constant coefficients from the measurement results. These coefficients can be directly utilized for simultaneously measuring pressure and temperature variation applied to the VO2 device, which can be beneficially applied to localized temperature and pressure sensing at a very small area less than 1 mm².

60 mA Bidirectional Current Gating in Vanadium-Dioxide-Based Planar Device Using CO2 Laser.

Here we show 60 mA bidirectional current gating in a two-terminal planar device based on a highly resistive vanadium dioxide (VO2) thin film by harnessing photothermally induced phase transition occurred in VO2 when irradiating the VO2 film with a CO2 laser oscillating at 10.6 µm. The VO2 thin film was grown by a pulsed laser deposition method, and the two-terminal planar device was fabricated using the VO2 film isolated with sub-millimeter dimensions. The bidirectional current gating between 0 and 60 mA was accomplished by irradiating the VO2-based device with repetitive pulses of the CO2 laser. In terms of laser modulation parameters such as the pulse width and repetition rate, their effect on the transient responses of laser-gated currents was also investigated. With a minimum energy per pulse of ~766 mJ, a stable bidirectional current gating of up to 60 mA could be successfully implemented for the repetition rates of 0.5-3.0 Hz in a VO2 device biased at ~5.4 V, showing a switching contrast between off- and on-state currents of ~11089. This maximum onstate current (60 mA) and switching contrast are the highest values among previous gating results attained in VO2 devices with a CO2 laser.

Polarization-Controlled Switching of Dual-Wavelength Lines with Orthogonal Polarization in Erbium-Doped Fiber Ring Laser.

By incorporating an inline switching filter, which is comprised of a polarization-diversified loop (PDL), two fiber Bragg gratings (FBGs) with different resonances, and three quarter-wave plates (QWPs), we propose a dual-wavelength-switchable erbium-doped fiber (EDF) ring laser that can select and switch between two lasing lines with orthogonal polarization. The proposed laser is composed of EDF, a 980 nm laser diode, a wavelength-division-multiplexing coupler, a rotatable linear polarizer, an optical isolator, a 3 dB optical coupler, and the inline switching filter. At a special combination of the orientation angles of the three QWPs, the inline filter can offer a different transmittance according to input polarization, e.g., reflection spectra of one and the other of the two FBGs for linear horizontally and vertically polarized input light, respectively. At this special combination of the QWPs, one of two different resonances of the two FBGs can be selected by varying laser cavity polarization through the adjustment of the orientation angle of the rotatable linear polarizer. Consequently, switching operation between two laser lines with orthogonal polarization at the two FBG resonance wavelengths could be obtained by properly controlling cavity polarization. The polarization extinction ratio of each lasing line was measured as more than 19.9 dB.

Laser-Regulated 60 mA Current Switching in VO2-Based Two-Terminal Device Using 976 nm Laser Diode.

By incorporating a high-power 976 nm laser diode (LD), we demonstrated laser-regulated current switching in a two-terminal planar device based on a vanadium dioxide (VO2) thin film. The VO2 thin film was grown by pulsed laser deposition method and etched to sub-millimeter dimension for the fabrication of a two-terminal device. The reversible current switching was implemented by controlling the on/off state of the LD, which illuminates the VO2-based device. The transient responses of the device currents were analyzed when the device was excited with laser pulses of various repetition rates of up to 5.0 Hz with a pulse width fixed as 75 ms. A switching contrast between off- and on-state currents was calculated as ~9530, and average rising and falling times were measured as ~31 and ~21 ms, respectively.

Broadband efficient modulation of light transmission with high contrast using reconfigurable VO2 diffraction grating.

Ultra-compact dynamically reconfigurable modulation of optical transmission has been widely studied by using subwavelength-spaced resonant metasurface structures containing reconfigurable optical materials. However, it has been difficult to achieve high transmissivity, large modulation depth, and broad bandwidth simultaneously with the conventional resonance-based metasurface schemes. Here, we propose a reconfigurable phase-transition diffractive grating, made of thick VO2 ridge waveguides, for achieving the above-mentioned three goals simultaneously in the near-infrared range. Based on the large dielectric-to-plasmonic transition characteristic of VO2 in the near-infrared range, diffraction directivity of dual-VO2 ridge waveguide is designed to be tuned by thermally driven phase transition of VO2 for transverse electrically polarized illumination. Then, the diffractive VO2 ridge waveguide grating composed of the periodically arranged dual VO2 ridge waveguides is designed with on-state efficiency around 0.3 and minimum modulation depth about 0.35 over a broad bandwidth of 550 nm (1100-1650 nm). The working principle and excellent modulation performance are thoroughly verified through numerical and experimental studies.

Coating Chitosan Thin Shells: A Facile Technique to Improve Dispersion Stability of Magnetoliposomes.

Magnetoliposomes (ML) have been emerging as a novel multifunctional nanoparticle with a wide range of biomedical and therapeutic applications over the past decade. Although the ML system has shown excellent performances, the stability and lipid peroxidation of liposomal components are still remaining as key issues and need to be solved for intensive applications. Changing zeta potential of nanoparticles' surface can be seen as a potential way to achieve the stable dispersion. In this work, we have employed the positive charged, abundant and cheap chitosan to coat ML in order to change the zeta potential of the ML system and examined the stability of chitosan@magnetoliposomes (CML) in long-term storage. The combining of pH-sensitive chitosan with temperature-sensitive phospholipid formed a novel pH- and temperature-sensitive nanoparticles which can be promisingly used as controllable drug release applications. These novel CML with chitosan thin shells showed excellent stability in long-term storage; meanwhile, the bare ML sample showed aggregations and forming micrometer-size particles. The CML system can achieve a drug encapsulation efficiency of nearly 50% and an enhanced drug release behavior under pH 5 at 45 °C.

Bidirectional current triggering in planar devices based on serially connected VO2 thin films using 965 nm laser diode.

By incorporating a 965 nm laser diode, the bidirectional current triggering of up to 30 mA was demonstrated in a two-terminal planar device based on serially connected vanadium dioxide (VO2) thin films grown by pulsed laser deposition. The bidirectional current triggering was realized by using the focused beams of laser pulses through the photo-thermally induced phase transition of VO2. The transient responses of laser-triggered currents were also investigated when laser pulses excited the device at a variety of pulse widths and repetition rates of up to 4.0 Hz. A switching contrast between off- and on-state currents was obtained as ~8333, and rising and falling times were measured as ~39 and ~29 ms, respectively, for 50 ms laser pulses.

Effect of multiple-sweeping on ablation performance during ex vivo laser nephrectomy.

BACKGROUND AND OBJECTIVE: Fiber-assisted laser surgery has been employed as a minimally invasive method in various medical fields. In spite of multiple sweeping on tissue during laser treatments, the rate of tissue removal gradually decreases and eventually leads to longer irradiation times as well as deeper thermal injury. The objective of the current study was to quantitatively investigate the effect of multiple fiber sweeps on ablation performance during ex vivo 532-nm laser nephrectomy. MATERIALS AND METHODS: Porcine kidney tissue was used to evaluate variations in tissue ablation and coagulative necrosis after pre- and multiple-sweeping with a 532 nm wavelength at various fiber speeds (2, 4, and 6 mm/second). The distance between a fiber tip and tissue surface was initially set at 1.5 mm, and no further distance change was performed. Double-integrating spheres in conjunction with an adding-doubling method were employed to measure variations in optical properties of the tested tissue. The extent of ablation and coagulation was quantified to identify the role of multiple-sweeping at various fiber conditions. RESULTS: Optical property measurements showed a 30% decrease in light absorption but a more than threefold increase in light scattering after irreversible thermal denaturation. Pre-sweeping yielded insignificant effects on tissue coagulation due to almost consistent coagulation depths with numbers of pre-sweeps. Ablation depths increased with more numbers of fiber sweeps and slower fiber speeds whereas coagulation depths thickened primarily with the slower speeds. Multiple-sweeping induced saturation in ablation volume with the increasing numbers of multiple-sweeps irrespective of the fiber speed. CONCLUSION: A combination of coagulation barriers, spatial distribution of power, and temporal interplay of optical energy could attribute to continuously lessen the amount of the ablated tissue with the multiple sweeps. Optical power modulation with varying fiber conditions (speed and distance) will be examined to optimize surgical parameters and to sustain the equivalent ablation performance of the first sweep with the multiple sweeping for laser nephrectomy. Lasers Surg. Med. 48:616-623, 2016. © 2016 Wiley Periodicals, Inc.

20 mA bidirectional laser triggering in planar devices based on vanadium dioxide thin films using CO(2) laser.

By utilizing a CO2 laser centered at ~10.6 µm as an optical stimulus, we demonstrated bidirectional laser triggering in a two-terminal planar device based on a highly resistive vanadium dioxide (VO2) thin film. The break-over voltage of the VO2-based device was measured as large as ~294.8 V, which resulted from the high resistivity of insulating VO2 grains comprising the thin film and the large electrode separation of the device. The bidirectional current switching of up to 20 mA was achieved by harnessing the dramatic resistance variation of the device photo-thermally induced by the laser illumination. The transient responses of laser-triggered currents were also analyzed when laser pulses excited the device at a variety of pulse widths and repetition rates. In the transient responses, a maximum switching contrast between off- and on-state currents was measured as ~7067 with an off-state current of ~2.83 µA, and rising and falling times were measured as ~30 and ~16 ms, respectively, for 100 ms laser pulses.

Bidirectional laser triggering of planar device based on vanadium dioxide thin film.

By incorporating a 1550 nm laser diode, bidirectional laser triggering was investigated in a two-terminal planar device based on vanadium dioxide (VO2) thin film grown by sol-gel method. A specific bias voltage range enabling the bidirectional laser triggering was experimentally found from the current-voltage characteristics of the VO2-based device, which was measured in a current-controlled mode. At a bias voltage selected within the range, 10 mA bidirectional triggering was implemented with a maximum amplitude switching ratio of ~68.2, and the transient responses of light-triggered currents were also analyzed.

Customizable Nichrome Wire Heaters for Molecular Diagnostic Applications.

Accurate sample heating is vital for nucleic acid extraction and amplification, requiring a sophisticated thermal cycling process in nucleic acid detection. Traditional molecular detection systems with heating capability are bulky, expensive, and primarily designed for lab settings. Consequently, their use is limited where lab systems are unavailable. This study introduces a technique for performing the heating process required in molecular diagnostics applicable for point-of-care testing (POCT), by presenting a method for crafting customized heaters using freely patterned nichrome (NiCr) wire. This technique, fabricating heaters by arranging protrusions on a carbon black-polydimethylsiloxane (PDMS) cast and patterning NiCr wire, utilizes cost-effective materials and is not constrained by shape, thereby enabling customized fabrication in both two-dimensional (2D) and three-dimensional (3D). To illustrate its versatility and practicality, a 2D heater with three temperature zones was developed for a portable device capable of automatic thermocycling for polymerase chain reaction (PCR) to detect Escherichia coli (E. coli) O157:H7 pathogen DNA. Furthermore, the detection of the same pathogen was demonstrated using a customized 3D heater surrounding a microtube for loop-mediated isothermal amplification (LAMP). Successful DNA amplification using the proposed heater suggests that the heating technique introduced in this study can be effectively applied to POCT.

A frontal projection-type three-dimensional display.

In a typical auto-stereoscopic three-dimensional display, the parallax barrier or lenticular lens is located in front of the display device. However, in a projection-type auto-stereoscopic display, such optical components make it difficult to display elemental images on the screen or to reconstruct a three-dimensional image, even though a projection-type display has many advantages. Therefore, it is necessary to use a rear projection technique in a projection-type auto-stereoscopic display, despite the fact that this is an inefficient use of space. We propose here a frontal projection-type auto-stereoscopic display by using a polarizer and a quarter-wave retarding film. Since the proposed method uses a frontal projection scheme and passive polarizing components, it has the advantage of being both space saving and cost effective. This is the first report that describes a frontal projection-type auto-stereoscopic display based on a parallax barrier and integral imaging by using a projector. Experimental results that support the proposed method are provided.

Pulsed magneto-motive optical coherence tomography for remote cellular imaging.

We developed pulsed magneto-motive optical coherence tomography (PMM-OCT) to reduce environmental temperature in the measurement volume and to expand the effective magnetic field distance from a pulse source. The proposed PMM-OCT system consisted of a spectral-domain OCT system and a customarily designed electrical pulse generator. The enhanced magnetic field allowed the proposed system to be able to image magnetically labeled cells in a distance as far as 30 mm away from the pulse generator. As an easy and sensitive approach, our PMM-OCT may be beneficially applied to a molecular-level imaging systems.

Postoperative Complications of Esophageal Atresia and Role of Endoscopic Balloon Dilatation in Anastomotic Strictures.

Purpose: Esophageal atresia (EA) with or without tracheoesophageal fistula (TEF) is a congenital anomaly that can cause frequent digestive and nutritional problems, even after repair. The most common complication is anastomotic stricture, for which reoperation or balloon dilatation is performed. This study aimed to evaluate the postoperative complications of EA and the role of endoscopic balloon dilatation (EBD) in cases of anastomotic stricture. Methods: We retrospectively analyzed patients diagnosed with EA with or without TEF between January 2000 and February 2021. Patients' baseline characteristics, associated anomalies, and postoperative complications were reviewed. Results: Among 26 patients, 14 (53.8%) were male, 12 (46.2%) had coexisting anomalies, and the median follow-up was 6.1 years (range, 1.2-15.7 years). In univariate analysis, prematurity, low birth weight, and long-gap EA were associated with postoperative complications in 12 (46.2%) patients. Among the 10 (38.5%) patients with anastomotic stricture, nine (90.0%) required EBD. Regarding the first EBD, it was performed at a median of 3.3 months (range, 1.2-7.6 months) post-repair, while the average patient weight was 4.6 kg. The mean diameter ranged from 3.3 to 9.1 mm without major complications. In univariate analysis, long-gap EA alone was significantly associated with EBD. Conclusion: Approximately half of the patients experienced complications after EA repair. In particular, patients with a long-gap EA had a significantly increased risk of complications, such as anastomotic strictures. EBD can be safely used, even in infants.

Passband-Flattened Frequency-Tunable Optical Fiber Multiwavelength Filter with Composite Combination of Waveplates.

We propose a passband-flattened frequency-tunable optical multiwavelength filter with a composite combination of waveplates, which is realized by harnessing a polarization-diversified loop structure. The proposed filter comprises a polarization beam splitter (PBS), two polarization-maintaining fiber (PMF) segments of equal length, an ordered waveplate combination (OWC) of a half-wave plate (HWP) and a quarter-wave plate (QWP) before the first PMF segment, and an OWC of a QWP and an HWP before the second PMF segment. The second PMF segment is butt-coupled to one port of the PBS so that its slow axis is oriented at 22.5° for the horizontal axis of the PBS. Based on the filter transmittance derived through the Jones calculus, we found the orientation angle (OA) sets of the four waveplates, which could induce an extra phase shift Φ from 0° to 360° in the passband-flattened transmittance function. From the transmission spectra calculated at the eight selected OA sets, which caused Φ to increase from 0° to 315° by steps of 45°, it was confirmed that the passband-flattened multiwavelength spectrum can be continuously tuned by properly controlling the OAs. This indicates continuous wavelength tunability based on composite OWCs. Then, this theoretical prediction was verified by experimental demonstration.

Fiber-optic label-free biosensor for SARS-CoV-2 spike protein detection using biofunctionalized long-period fiber grating.

With COVID-19 widespread worldwide, people are still struggling to develop faster and more accurate diagnostic methods. Here we demonstrated the label-free detection of SARS-CoV-2 spike protein by employing a SARS-CoV-2 spike antibody-conjugated phase-shifted long-period fiber grating (PS-LPFG) inscribed with a CO2 laser. At a specific cladding mode, the wavelength separation (λD) between the two split dips of a PS-LPFG varies with the external refractive index, although it is virtually insensitive to ambient temperature variations. To detect SARS-CoV-2 spike protein, SARS-CoV-2 spike antibodies were immobilized on the fiber surface of the fabricated PS-LPFG functionalized through chemical modification. When exposed to SARS-CoV-2 spike protein with different concentrations, the antibody-immobilized PS-LPFG exhibited the variation of λD according to the protein concentration, which was caused by bioaffinity binding-induced local changes in the refractive index at its surface. In particular, we also confirmed the potential of our sensor for clinical application by detecting SARS-CoV-2 spike protein in virus transport medium. Moreover, our sensor could distinguish SARS-CoV-2 spike protein from those of MERS-CoV and offer efficient properties such as reusability and storage stability. Hence, we have successfully fabricated a promising optical transducer for the detection of SARS-CoV-2 spike protein, which can be unperturbed by external temperature disturbances.