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In this work, an actively tunable terahertz metamaterial (TTM) is proposed to realize variable optical attenuation and sensing applications. The unit cell of TTM is composed of H-shaped resonator (HSR) and C-shaped resonator (CSR). The resonant frequency can be tuned from 0.60 THz to 0.82 THz and show an analog electromagnetically induced transparency (EIT) phenomenon. By adjusting the geometry parameters of HSR and CSR, the enhanced quality (Q) factor is obtained from 2 to 14. Moreover, the CSR can be rotated from 0° to 90° to show the potential in the variable optical attenuator (VOA) application. The resonant intensity at 0.60 THz can be gradually decreased and then disappeared eventually when the CSR rotated from 0° to 90° in TE mode. While the resonant intensity at 0.60 THz can be gradually increased and then reach maximum value from 0° to 90° in TM mode. To demonstrate the proposed TTM can be used for the environmental sensing application, the TTM is exposed on the ambient environment with different refractive indexes from 1.0 to 2.2. The maximum sensitivity is 67 GHz. This work offers a novel approach for the THz metamaterial using for the VOA, optical switching, and sensing applications.

An infrared (IR) tunable perfect meta-absorber (TPM) is presented, which is configured of metal-insulator-metal (MIM) structure. The unit cell of the TPM device is composed of two opposite T-shaped and two rod-shaped Au resonators on the reflective mirror layer. The optimized feature size of TPM can achieve perfect absorption and the resonant wavelength can be tuned from blue-shift first and then red-shift by increasing the gap size between two T-shaped resonators continuously. The tuning process of red shift is linear. By changing the distance between two rod-shaped resonators, the TPM device exhibits red shift linearly. Moreover, TPM device shows polarization-dependent characteristic that the main absorption resonance can be attenuated from 100% to 0% by changing polarization angle from 0° to 90° of incident IR light. The resonance of TPM device has an excellent linear relationship with the ambient refractive index, and the sensitivity and maximum figure of merit (FOM) are calculated as 1249 nm/RIU and 21 RIU−1, respectively. These results prove that the design of the proposed TPM device is very suitable for the use of IR sensing, polarization switching, and refractive index sensing applications.

This study presents and demonstrates a design of a micro-electro-mechanical system (MEMS) reconfigurable terahertz (THz) metamaterial absorber (TMA) that shows tunable free spectra range with a maximum value as 166 GHz in transverse magnetic mode and switchable resonance from 1.24 THz to 1.53 THz. The unit structure of TMA consists of two movable rectangular resonators aside and an x-shaped resonator at the center comprising two c-shaped resonators connected upside down. The material configuration of TMA is typical of the metal–insulator-metal sandwich configuration. That is a bottom Au layer preventing the penetration of the THz wave, a dielectric SiO2 layer to accommodate and absorb the incident wave, and a patterned Au structure array to select the resonant frequency. The electromagnetic response of TMA could be flexibly modulated when the structure is reconfigured by changing the gaps between x-shaped resonators and rectangular resonators based on the MEMS platform. Meanwhile, owing to the asymmetry of resonant structure, the electromagnetic response of TMA could be tuned from single-, dual-, triple- quad-resonances by varying the polarization state of incidence. Furthermore, the sensitivity of TMA is explored and demonstrated with remarkable linearity under a variation of the surrounding environment refractive index from 1.0 to 2.0. The feasibility of TMA is validated as the experimental absorption spectra are well meet the simulation results. The above results indicate the proposed TMA possesses great potential applications in multiple resonance switches, polarization switches, and highly efficient environmental sensors.

Background: An extended interval between the two primary doses may reduce the risk of myocarditis/pericarditis after COVID-19 mRNA vaccination. Taiwan has implemented a two-dose regimen with a 12-week interval for adolescents. Here we present nationwide data of myocarditis/pericarditis following COVID-19 vaccinations. Methods: Data on adverse events of myocarditis/pericarditis were from the Taiwan Vaccine Adverse Events Reporting System between March 22, 2021, and February 9, 2022. The reporting rates according to sex, age, and vaccine type were calculated. We investigated the rates among young individuals under different two-dose intervals and among those who received two doses of different vaccines. Results: Among 204 cases who met the case definition of myocarditis/pericarditis, 75 cases occurred after the first dose and 129 after the second. The rate of myocarditis/pericarditis after COVID-19 vaccination varied across sex and age groups and was highest after the second dose in males aged 12–17 years (126.79 cases per million vaccinees) for the BNT162b2 vaccine and in males aged 18–24 years (93.84 cases per million vaccinees) for the mRNA-1273 vaccine. The data did not suggest an association between longer between-dose interval and lower rate of myocarditis/pericarditis among males and females aged 18–24 or 25–29 years who received two doses of the BNT162b2 or mRNA-1273 vaccine. Rates of myocarditis/pericarditis in males and females aged 18–49 years after receiving ChAdOx1-S - mRNA-1273 vaccination was significantly higher than after ChAdOx1-S - ChAdOx1-S vaccination. Conclusions: Myocarditis and pericarditis are rare following mRNA vaccination, with higher risk occurring in young males after the second dose.

As ultrathin optical elements with subwavelength structures densely arranged, planar lens or called metalens can effectively focus incident wave. Due to the compact design and wide operating frequency of metalens, it becomes promising in applications like information encryption, imaging, and wireless communication fields. However, the fabrication of large-aperture metalens is still time-consuming and costly while the focusing performances are commonly tuned by introducing active materials requiring extra stimuli, such as laser and electrical pulses. In this study, five designs of metalenses with synthetic rectangular aperture are proposed and demonstrated with excellent focusing performances. By reconfiguring the synthetic aperture, focusing properties like focusing lengths, full width at half maximum values, and modulation transfer function can be tuned with great flexibility. With a polarization-dependent phase-shifting structure, the proposed metalens shows different focusing performances with incident wave under transverse magnetic field and transverse electric field modes. By utilizing spatial multiplexing, terahertz variable foci metalenses based on a stretchable single-, dual- and quad-axis synthetic rectangular optical sparse aperture are investigated to achieve tunable multifocal performances. These designs provide a novel strategy that can reconfigure the synthetic aperture with stretchable substrate to make metalens with multifunction and active tunability, which show promising applications in imaging, information encryption, and space telescope areas.

Background: The global rise in nosocomial infections associated with gram-negative bacteria and the spread of multi-drug resistant Acinetobacter baumannii (MDR-AB) pose public health concerns. This study investigates the inhibitory effects and possible inhibitory mechanism of Pseudomonas aeruginosa (PA) on selected clinical strains of A. baumannii (AB) isolated from Taiwanese patients. Methods: Four and eight clinical strains of AB and PA, respectively, were randomly selected from the bacterial collection of Feng-Yuan Hospital, Taiwan. Antimicrobial-susceptibility was performed on the AB strains. Inhibition potential of the PA strains against AB was assessed by measuring the inhibition zones. In vitro analysis using phenazine-1-carboxamide (PCN) was conducted to assess the possible inhibitory mechanism of PA, which was later confirmed in the clinical isolates by liquid chromatography-mass spectrometry. Results: All the clinical AB strains showed resistance to the eleven antibiotics and were classified as MDR-AB. The nine PA strains exert either a high (PA3596, PA3681, PA3772, and ATCC27853) or a low (PA3613, PA3625, PA3712, PA3715, and PA3744) degree of inhibition against AB strains. 0.25 mg/ml PCN had a clearer inhibition zone than 0.05 mg/ml PCN, suggesting a dose-dependent inhibition of PCN on the AB strains. The four PA strains that demonstrated a high degree of inhibition had a relatively high amount of PCN. Conclusion: Selected strains of PA exert inhibitory actions on MDR-AB with PCN being a possible inhibitory agent. This finding raises the possibility of developing effective therapeutic antibiotics and disinfectant from specific components of PA for the treatment and control of Acinetobacter-associated infections in hospital settings.

In this study, two kinds of nanostructured metasurfaces are presented and compared to exhibit ultrahigh color purity and selectivity in the visible wavelength range. The proposed nanostructured metasurfaces are composed of all-dielectric materials, which are Si3N4 fabricated on quartz substrates to form one-dimensional (1D) and two-dimensional (2D) nanogratings (NGs). These nanostructured metasurfaces exhibit over 98 % reflection intensity with ultra-narrow bandwidths less than 20 nm to perform vivid red, green, and blue colors, implying the potentials in high-saturation display. Among nanostructured metasurfaces, 2D-NGs allow a wider range of incident angle than 1D-NGs and show polarization-independent characteristic owing to the symmetric arrangement in nanoscale in the incident plane. Furthermore, the numerical simulation results prove that 1D-NGs and 2D-NGs exhibit single- and dual-resonance when exposed on the ambient environment with different refractive indexes. Such excellent optical performances verify their potentials not only in high-resolution display but also in chemical sensing applications.

Summary: We propose and demonstrate a metamaterial design by integrating a microelectromechanical system (MEMS) electrothermal actuator (ETA) platform and a cross-shaped metamaterial (CSM) to perform opto-logic function characteristics. Reconfigurable and stretchable mechanisms of CSM are achieved by driving different DC bias voltages on ETA to improve the limitations induced by the conventional use of the flexible substrate. The optical responses of CSM are tunable by the electrical signals inputs. By driving a DC bias voltage of 0.20 V, a tuning range of CSM is 0.54 THz is obtained and it and provides perfect zero-transmission characteristics. In addition, the “XNOR” logic gate function of CSM is realized at 1.20 THz, which plays a key role in the all opto-logic network communication system. The proposed MEMS-based CSM exhibits potential applications in logical operation, signal modulation, optical switching, THz imaging, and so on.

We propose a stretchable metalens on polydimethylsiloxane (PDMS) substrate. By stretching the stretchable metalens device along x- and y-axis directions, it exhibits highly tunable focal length and achromatic characteristics. The focal length of stretchable metalens keeps as stable and shows a good relationship to the change of the period of stretchable metalens. When the incident wavelengths are 480 nm, 530 nm, 580 nm, and 660 nm, the focal lengths of stretchable metalens can be tuned in a quite linear range by stretching the period of stretchable metalens from 450 nm to 800 nm. The tuning range of focal length is over 200% for these four incident wavelengths. All the full width at half maximum (FWHM) values for different incident wavelengths are small than 2.5 µm. It means the proposed stretchable metalens possesses the stable beam shape of focus length in the whole visible spectrum. The stretchable metalens provides an effective approach in stretchable device applications and new directions for the future designs in metalens applications, such as the next generation of 3D stereo imaging and holographic projection.

We present a design of MEMS-based tunable terahertz (THz) metamaterial (TTM) with polarization-dependent sensing characteristic. The MEMS-based TTM device is reconfiguration by using two electrostatic comb-drive actuators, which exhibits tunable dual-band resonances in both transverse electric (TE) mode and transverse magnetic (TM) modes. The tuning ranges of free spectra ranges are 42 GHz and 82 GHz for TE and TM modes, respectively by increasing the gap between the left and right semicircle-shaped ring resonators. The electromagnetic responses of the proposed MEMS-based TTM device can be switched between dual-resonance and triple-resonance by changing the distance between the left and right semicircle-shaped ring resonators along y-axis direction. These results indicate MEMS-based TTM device shows polarization-sensitive and switching characteristics. MEMS-based TTM device is particularly sensitive to the environmental refraction index, and there is a linear relationship between the shift of resonant frequency and the change of refraction index. The sensitivity is 0.186 THz/RIU while the maximum figure of merit and quality factor reach 208 and 248, respectively at the first TE resonance. These outstanding and unique results of MEMS-based TTM device provide an effective approach for the design of highly linear and sensitive gas and environmental applications.

This study proposed a novel global minimum search method for predicting the most stable biomolecule complex, which combines the strengths of three global minimum search methods (stochastic tunnelling, basin hopping, and discrete molecular dynamics) to efficiently improve the spatial domain search ability of the stochastic tunnelling–basin hopping (STUN–BH) method from our previous study. The epithelial cell adhesion molecule (EpCAM, PDB code: 4MZV) was used as a benchmark target molecule for the EpCAM aptamer EpA (AptEpA). For the most stable AptEpA/EpCAM complex predicted by our new method, the AptEpA was attached to the entangling loop fragments of the two EpCAM molecules with the most AptEpA residues. After the AptEpA/EpCAM complex had equilibrated with the water environment through a molecular dynamics simulation at 300 K for 10 ns, stable hydrogen bonds formed between the bases of AptEpA and EpCAM residues of the secondary structures, which included the alpha helix and beta sheet becoming less stable in the water environment. Those hydrogen bonds formed between the bases of AptEpA and EpCAM loop fragment residues remained stable in the water environment.

We present two types of tunable terahertz metamaterial (TTM) resonator. They are denoted as TTM-1 and TTM-2 for TTM resonators composed of a moveable metal frame carrying with inner disc and inner ring on Si substrates, respectively. The electromagnetic responses of TTM resonators are caused by the inductance-capacitance coupling effect between the incident THz wave into TTM structure. There is a Fano-resonance with a reflection intensity of 99% excited by electromagnetic wave within TTM-1 at 2.62 THz. By actively moving the metal frame in a specific direction, it enables a modulation of resonant frequency. The tuning ranges of TTM-1 and TTM-2 are 0.19 THz and 0.79 THz, respectively. Furthermore, TTM devices have the ability of anti-inference by moving metal frame transversely. It means TTM devices exhibit stable characteristic used in dynamic motion. Such designs of TTM configurations provide a high-efficiency THz resonator in the THz-waves applications such as filtering, switching, polarizing, sensing, and imaging fields.

A design of electrostatically tunable metamaterial is proposed in the terahertz (THz) frequency range using electric split-ring resonators (eSRR), which shows polarization-dependent and switching characteristics. The eSRR is composed of anchored rectangular split-ring resonators and a movable middle I-shaped metal bar. By exploiting electrostatic force to change the gap within eSRR and the distance of middle I-shaped metal bar, the electromagnetic characteristics of eSRR can be controlled. The electromagnetic response of eSRR shows a single-resonance in transverse electric (TE) mode and keeps as quite stable. In transverse magnetic (TM) mode, the electromagnetic response of eSRR shows dual- and triple-resonance. Such eSRR design is able to be used in lots of applications, such as polarizers, actively tunable filters, frequency-selective detectors, tunable high-efficiency sensors, and multi-functional switches in the THz optoelectronic devices.

We present a design of programmable terahertz (THz) metamaterial (PTM) with multiple logic characteristics. The proposed PTM device is composed of a cut-wire resonator (CWR) sandwiched two face-to-face split-ring resonators (SRRs). By moving CWR along z-axis direction to change vertical distance between CWR and substrate, the programmable coding digits could be switched from four digits to five digits by alternating the polarization of incident THz wave. The electromagnetic responses of PTM device are stable in TE mode and can be tuned by moving vertical distance of CWR in TM mode. These results indicate the potential possibilities of PTM to be used as a stable polarization switch and an effective programmable metamaterial in the THz frequency range.

We present two types of tunable terahertz (THz) metamaterials (TTM-1 and TTM-2) to explore their extraordinary optical properties. The proposed TTMs are composed of Au layers with 300 nm in thickness on Si substrates. The designs of TTMs exhibit superior properties in adjustability for high-efficiency THz switching characteristic. By changing the geometrical dimensions of TTMs, the corresponding electromagnetic responses could be tuned and switched between single-band and dual-band resonances. TTM-1 exhibits three switching windows with higher switching ratios by embedding different materials into the cavity underneath the complementary metamaterial. TTM-2 can be tuned to have two resonances and then merge into one resonance by increasing the height between the inner and outer rings. The transmission intensity of TTM-2 can be tuned from 0 to 0.7 at 0.57 THz by changing the sizes of inner and outer rings. TTM-2 exhibits tunable filter, single-/dual-band switch, tunable free spectrum range, and tunable bandwidth characteristics by varying the radius of the inner and outer rings. This study paves a way to the possibility of tunable high-efficiency switch, filter, polarizer, and other THz applications.

We present terahertz (THz) metamaterial with multi-configurations, which are composed of H-shaped, II-shaped, and IHI-shaped configurations, respectively. By changing the geometrical dimension of H-shaped metamaterial, the electromagnetic response exhibits switch and bandwidth modulation characteristics between 0.20 THz and 0.30 THz. For II-shaped metamaterial, the electromagnetic response shows the single-resonance and dual-resonance switching and tunable free spectrum range (FSR) characteristics. The superimposed structures of H- and II-shaped metamaterials to form IHI-shaped metamaterial, which exhibits the combinations of H- and II-shaped metamaterials characterizations. The resonances could be switched at 0.25 THz, 0.55 THz, and 0.95 THz depending on the metamaterial pattern. To increase the flexibility of proposed device, there are composed of dual-layer IHI-shaped metamaterial on Si substrate. The FSR could be tuned from 0.16 THz to 0.05 THz by changing the height of top IHI-shaped metamaterial. These optical properties of IHI-shaped metamaterial open an avenue to be used in widespread applications with high portability, flexibility, and compatibility. Keywords: Metamaterial, Terahertz, Resonator, Modulator, Multi-functionality

We present four designs of actively switchable terahertz metamaterials (ASTMs) to explore their extraordinary optical characteristics. They are denoted as ASTM_1, ASTM_2, ASTM_3, and ASTM_4, respectively. ASTM_1 and ASTM_2 are composed of asymmetrically single-layer L-shaped metamaterial and asymmetrically dual-layer L-shaped metamaterial with rotated 0° on Si substrate, respectively. ASTM_3 and ASTM_4 are composed of asymmetrically dual-layer L-shaped metamaterial with rotated 90° and asymmetrically connected L-shaped metamaterial on Si substrate, respectively. ASTM_1 shows three resonances at 0.19 THz, 0.33 THz, and 0.49 THz. The tuning range of first resonance is 0.06 THz by changing the gap between the L-shaped metamaterial. While ASTM_2 shows three resonances at 0.15 THz, 0.28 THz, and 0.42 THz. The tuning range of first resonance is 0.05 THz by changing the height between top and bottom L-shaped metamaterials. By changing the gap and height of L-shaped metamaterials, ASTM_3 and ASTM_4 exhibit the optical switching characteristic. The transmission spectra of four ASTMs show the polarization-independent characteristic. Such optical properties of ASTM designs provide the possibilities of THz metamaterial to be used in active switching optoelectronics applications, such as sensors, logic devices, programmable devices, and so on. Keywords: Metamaterial, Terahertz, Modulator, Resonator, Switch

We propose two designs of plasmonic metamaterial mid-infrared (MIR) sensors, which are composed of metallic nanograting on SiO2 layer with a bottom mirror to form metal–insulator-metal (MIM) configurations. These MIM configurations are denoted as MIM-S and MIM-D to represent MIM composed of single metal nanograting and double metal nanogratings, respectively. The electromagnetic responses of MIM-S and MIM-D are investigated and compared with and without embedded a SiO2 layer between top nanograting and bottom mirror layer. By changing the height of insulator layer, the absorption spectra of MIM-S can be tuned with a linearly wavelength tuning range of 2.4 μm. Furthermore, MIM-D exhibits not only tunable resonance by changing the gap between top and bottom nanogratings, but also switch characteristics by changing the horizontal shift of top nanograting. For the environment sensor application, MIM-S and MIM-D exhibit the sensitive/insensitive to refraction index and tunable FSR characteristics by changing ambient refraction index. Such results provide the MIM devices can be used as multifunctional sensors. This study proposes an implementation strategy of actively tunable filter, switch, and high-sensitive refraction index sensor in the MIR wavelength range. Keywords: Plasmonic metamaterial, Metal-insulator-metal structure, Infrared sensor, Nanograting

Background: It is generally understood that cancer patients are at an increased risk for osteoporosis. Additionally, recent studies have suggested a shared pathophysiological mechanism between the development of cancer and osteoporosis. The purpose of this investigation was to investigate whether low bone mineral density is associated with cancer risk. Methods: We enrolled 8780 subjects who underwent dual-energy X-ray absorptiometry (DXA) and cancer screening from January 1, 2008–December 31, 2012 from a cohort selected from Chang Gung Health Care Center in Taiwan. The study end point was a definite pathological diagnosis of cancer or admission for cancer treatment. Results: During a mean follow-up of 6.6 ± 1.5 years, 110 incident cases of cancer occurred. The overall incidence of cancer was significantly higher in those patients with a low BMD (1.3%) than in those with a normal BMD (1.0%). Multivariate Cox regression analysis showed that older age, smoking, and low BMD (hazard ratio: 1.5; 95% confidence interval: 1.0–2.3) were significant independent risk factors for cancer. Conclusion: Our investigation suggested that subjects with a low BMD may have a higher long-term risk of cancer compared with subjects with a normal BMD. Keywords: Bone mineral density, Cancer

An ultra-narrowband terahertz (THz) perfect absorber with metal-insulator-metal (PA-MIM) microstructures is presented. MIM microstructures is composed of Al disk on SiO2/Al/Si substrate. This MIM configuration will induce dipole-image interaction and cause an electromagnetic confinement between MIM microstructures to eliminate the reflection. Therefore, the design of MIM can absorb most of THz wave to realize the THz PA. The absorption intensity of proposed device could be reached 99% with an ultra-high Q-factor of 143. By modifying the gap between top and bottom Al disks of MIM, the electromagnetic response can be tuned from single-band to dual-band resonance. These resonances can be actively controlled the corresponding absorption intensities to possess tunability in application of THz switch and THz variable optical attenuator (VOA). This tunable ultra-narrowband THz PA-MIM paves a way to be an important role in THz applications, such as sensors, detectors, solar cells, coherent thermal emitters and so on. Keywords: Metamaterial, THz filter, THz resonator, Ultra-narrowband

We present the electromagnetic coupling effects in four types of electric split-ring resonators (eSRRs). These four designs of eSRRs are based on SRR tailored with single-, dual-, triple-, and quad-split, respectively. The near-field electromagnetic coupling responses indicate the resonance caused from the inductive-capacitive (LC) resonance between eSRRs. According to the patterns of eSRR are symmetrical or asymmetrical configurations, these eSRRs exhibit polarization-dependence, polarization-independence, resonant frequency shifting, resonant intensity modulation, and resonant switching characteristics, respectively. To increase the flexibility and applicability of eSRRs, two patterned eSRR layers are designed on elastic substrate for the enhancement of the resonant tunability. The designs of eSRRs open an avenue to a new direction for future optical applications, which offer significant promise in flexible electronics applications. This work provides future tunable THz designs based on flexible actuation mechanism to deform the geometrical dimensions between eSRRs microstructures. Keywords: Metamaterial, Terahertz, Resonator, Modulator, Multi-functionality

Objective: To explore the expression and function of nucleotide-binding oligomerization domain (NOD) proteins NOD1 and NOD2 and provide guidance for prophylaxis and treatment of neonatal infection., Methods: Peripheral blood samples were collected from preterm infants, term infants and, healthy adult volunteers. A portion of collected blood was used to examine the expression of NOD1 and NOD2 by real-time PCR. The remaining blood was stimulated in vitro with NOD2 agonist L-Ala-D-Glu-meso (Tri-DAP) or NOD1 agonist muramyl dipeptide (MurNAc-L-Ala-D-isoGln; MDP) for 4 h. Consequently, the levels of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) were quantified by enzyme-linked immunosorbent assay (ELISA)., Results: NOD1 expression was found to be decreased in preterm and term newborns compared with adults. NOD2 was significantly lower in preterm infants alone in comparison with adults. After treated by Tri-DAP or MDP, the levels of IL-6 and TNF-α in peripheral blood were significantly lower in preterm and term newborns when comparing to adults., Conclusion: NOD1 and NOD2 expression and induced release of pro-inflammatory mediators were impaired in infants, contributing to the high susceptibility of infants to infection. Our results insisted on developing a new immunological approach for prophylaxis and treatment of neonatal infection., (Copyright © 2018. Published by Elsevier B.V.)