Browse Articles

RF communication between dual band implantable and on body antennas for biotelemetry application

Abstract This paper investigates two antennas for implantable communication, which are a wide-band, low-profile transmitting antenna with a circular polarization (CP) merit immersed in a lossy medium and a corresponding wide-band, low-profile receiving antenna with a linear polarization (LP) merit placed on human tissue. The first antenna is implantable inside a human body for sensing, monitoring, and transmitting various vital signs, while the second antenna acts as a nearby receiving end. These antennas work in the 2.4-2.4835 GHz and 5.725-5.875 GHz industrial, scientific, and medical (ISM) bands. The main features of the designed transmitting antenna are its simplicity, the wide-band characteristics, which preserve the detuning effect caused by environmental heterogeneity, and the CP property at both operational ISM bands. Moreover, for introducing an electrically small antenna footprint with proper performance, the implantable antenna is designed with an entire size of 25.4 (5 $$\times$$ 5 $$\times$$ 1.016) $$\hbox {mm}^3$$ . This antenna is designed and dissected in a homogeneous skin model (HSM) as well as a three-layer phantom. On the other hand, the wide-band receiving antenna is designed on flexible material for patients’ comfort with a compact size of 134.6 ( $$20\times 26.5\times 0.254$$ ) $$\hbox {mm}^3$$ . In addition, the implantable antenna performance is evaluated in a chicken slab as well as a saline solution, while the on-body antenna is placed on the chicken slab to measure its reflection coefficient. The measured impedance BWs of the implantable antenna are 13.04 % and 33.2 % in the chicken slab while 19.5% and 25.2 % in the saline solution at the two ISM bands, respectively. While, the measured impedance BWs of the on-body antenna are 24% and 50.4 % at two operating ISM frequencies. Finally, the measured transmission coefficient between the two antennas is evaluated.

Tunable mode-locked laser in the 2.0–2.6 <b> <i>μ</i> </b>m range with GHz-level spectral width and sub-nanosecond pulse duration

Mode-locked lasers with narrow spectral bandwidths and high power spectral density are valuable for various applications that require selective and efficient light–matter interactions. However, mode-locked lasers in the mid-infrared (MIR) region so far face significant challenges in both narrowing the spectral width and expanding the tunable range. In this work, we demonstrate a Fourier transform-limited pulsed laser with ultra-narrow bandwidth by utilizing the frequency-modulated (FM) mode-locking technique in a Cr:ZnS laser. The proposed laser achieves a spectral width of ∼2 GHz (∼40 pm) and a pulse duration of ∼200 ps within a wide tunable range from 1966 to 2572 nm. By incorporating an etalon into the cavity, the spectral width is further narrowed to ∼500 MHz (∼8 pm), and the pulse duration is extended to ∼1 ns. We also find unique detuning characteristics of the FM mode-locked laser in that the narrowband mode-locked state is maintained over a large detuning frequency of ∼20 kHz, while its operating wavelength varies linearly with detuning. This property indicates a significantly better resistance to cavity length fluctuations compared to other active mode-locking schemes as well as a promising way to achieve precise wavelength fine-tuning through electronic control. The demonstrated laser, featuring an ultra-narrow spectral width at a desired mid-infrared wavelength, offers a powerful tool for high-resolution and high-sensitivity spectroscopy and coherent control of molecular vibrations.

Single-cell landscape of dynamic changes in CD8+ T cells, CD4+ T cells and exhausted T cells in hepatocellular carcinoma

High-Q silicon two-dimensional photonic crystal slot nanocavities with asymmetric low-index claddings

Photonic crystal nanocavities with high quality (Q) factors find extensive application in silicon (Si)-integrated photonics owing to their highly selective wavelength filtering, optical buffering, and enhanced nonlinear optical effects in the telecommunication band. High-Q Si photonic nanocavities with asymmetric claddings offer mechanical stability, high functionalities from heterogeneous materials, and vertical integration of optoelectronic devices. However, achieving a high Q factor in an asymmetric structure remains challenging because of the TE–TM coupling loss in the Si slab. To suppress the TE–TM coupling, we designed a high-Q two-dimensional (2D) Si photonic crystal slot cavity by significantly reducing the electric field components in the slab, leveraging a large dielectric discontinuity between Si and the low-index slot. We fabricated 2D Si photonic crystal slot nanocavities with asymmetric claddings consisting of a lower cladding of thermal oxide (nlc = nBOX = 1.45) and an upper cladding of infiltrated spin-on glass (nuc = nSOG = 1.3). The Q factor of this slot cavity is as high as 6.32 × 105, which is the highest Q value ever recorded among nanocavities with asymmetric claddings. Our results are useful for heterogeneous integration of Si photonic crystal nanocavities with various functionalities such as active and nonlinear optical materials, which are unattainable in conventional Si photonics.

Impact of incorporating wheat straw together with basal nitrogen ratio on panicle formation and grain yield in rice

Facile synthesis of vanadium oxide thin films by atomic layer deposition and post-annealing

We report the facile synthesis of vanadium oxide (VOx) thin films on sapphire substrates by atomic layer deposition (ALD) and post-annealing. Amorphous VOx thin films are grown by ALD employing tetrakis[ethylmethylamino]vanadium and ozone as precursors. Subsequent post-annealing of the as-grown VOx thin films at 500 °C in atmospheres of air, 1 Pa O2, and vacuum (10−4 Pa) could, respectively, result in the crystallization of V2O5, VO2, and V2O3 phases, as verified by x-ray diffraction and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) reveals that the valence states of vanadium in the annealed thin films exhibit dramatic changes with the variation of annealing atmosphere toward the targeted phases. The VO2 thin film exhibits a sharp metal–insulator transition (MIT) near 340 K with a resistivity change exceeding three orders of magnitude. The V2O3 thin film features a characteristic MIT with obvious thermal hysteresis between the cooling and warming processes, whereas the V2O5 thin film is highly insulating. The spectral weight near the Fermi level revealed by the XPS in the valence band region coincides with the changes of VOx phases and consequent transport properties due to post-annealing. Our results demonstrate that the combination of ALD and post-annealing provides a facile method for the synthesis of multivalent VOx thin films for practical applications.

Complex congenital heart and lung defects as a cause of hydrops fetalis in French bulldogs –micro-CT with contrast study

Optical anisotropy in WS2/ReS2 heterostructure with one-dimensional moiré pattern

Two-dimensional (2D) materials with low symmetry have garnered considerable attention due to their anisotropic electrical and optical properties, demonstrating great potential in various fields. Recently, 2D anisotropic/isotropic heterostructures have shown promise in breaking isotropic symmetry and inducing anisotropic responses through precise control of interfacial structures, such as moiré patterns. However, detailed experimental investigations into the correlation between anisotropic behaviors and anisotropic moiré patterns remain scarce. Here, we report optical anisotropy in WS2 by stacking a WS2/ReS2 heterostructure. Through measurements of polarized photoluminescence spectra, we observe that the intralayer excitons (both localized-state exciton LX and neutral exciton XA) of WS2 in the heterostructure exhibit pronounced anisotropy, which remains robust at both room temperature and a low temperature of ∼10 K. Furthermore, the angles between the linear polarization directions and the orientation of the corresponding one-dimensional moiré patterns remain approximately constant values (∼60° for LX and ∼45° for XA), demonstrating a clear correlation between anisotropic exciton emission and the anisotropic moiré patterns. Our work offers valuable insights into achieving artificial optical anisotropy using anisotropic/isotropic heterostructures, paving the way for enhanced performance in anisotropic sensing devices.

Feasibility of remote robot empowered teleultrasound scanning for radioactive patients

Pressure-tuned biexciton emission in CH3NH3PbBr3 perovskite quantum dots

Pressure-induced evolution of the bandgap, structural phase transitions, and changes in exciton effects can significantly modulate the luminescent properties of lead halide perovskites (LHPs) quantum dots (QDs). Previous studies have indicated that CH3NH3PbBr3 (MAPbBr3) QDs, as a typical low-dimensional LHP material, and their photoluminescence (PL) at ambient conditions are mainly attributed to the radiative recombination of the initially generated excitons upon light absorption and the excitons involving surface states, while the existence of biexciton radiative recombination remains unclear. In this work, we confirm the existence of biexciton radiative recombination in MAPbBr3 QDs at ambient conditions through experimental measurements of excitation-intensity-dependent PL and time-resolved PL (TRPL) spectra at ambient conditions as well as temperature-dependent PL spectra (80–260 K) at ambient pressure. We also establish that the PL of MAPbBr3 QDs primarily originates from the combined effects of three excitons radiative recombination physical processes: biexcitons, initially generated excitons upon light absorption, and excitons involving surface states. Furthermore, through in situ high-pressure PL, absorption, and TRPL spectroscopy measurements, we reveal that the recombination lifetimes and the relative contributions of these three excitons in MAPbBr3 QDs are all subject to alteration in response to the pressure-induced bandgap evolution and the structural phase transitions, thereby modulating their PL emission characteristics.

Studying the impact of chitosan salicylaldehyde/schiff base/CuFe2O4 in PC3 cells via theoretical studies and inhibition of PI3K/AKT/mTOR signalling

Abstract In this elucidation, the nucleophilic attack of salicyladehyde with chitosan, which was obtained from the shrimp shell, afforded the cellulose aldehyde (Schiff base), and then the dispersion of CuFe2O4 on the surface of cellulose aldehyde gave the novel nanomaterial of bimetallic oxide, which was confirmed through spectral analysis such as FT-IR, NMR, SEM, and XRD analysis. Moreover, the anti-proliferative effect of chitosan, chitosan salicylaldehyde, and chitosan salicylaldehyde/CuFe2O4 was evaluated in PC3 human prostate cancer cells and HSF normal human skin fibroblasts. After 48 h, PC3 cell proliferation was significantly inhibited by chitosan salicylaldehyde/CuFe2O4 and chitosan salicylaldehyde (IC50 = 35.3 and 45.55 µg/ml, respectively) without any effects on normal HSF cells. The mRNA expression levels of PI3K, AKT, mTOR, and CCND1 were examined in PC3-treated cells by using QRT-PCR, and the results demonstrated that, by down-regulating the expression levels of these genes, chitosan salicylaldehyde/CuFe2O4 significantly affected prostate cancer cell proliferation, progression, and autophagy more than chitosan salicylaldehyde. Furthermore, the docking stimulation of the chitosan derivatives with different proteins showed the presence of CuFe2O4 particles effect on the interaction inside their pockets and increased the activities, and it’s related to biological evaluation. Additionally, the theoretical investigation of these chitosan derivatives and the determination of their physical descriptors showed the activity of bimetallic oxide and the presence of electrostatic hydrogen bond interaction. Finally, these findings may suggest that chitosan salicylaldehyde/CuFe2O4 has a promising anticancer impact against prostate cancer.

Superionic conduit of alkaline earth metals confined by two-dimensional boron–carbon layers

Superionic conductors feature fast super-ion diffusion in the solid-state framework, making them ideal materials for safe, high-performing electrolytes. It is, therefore, in hot pursuit of seeking solid-state electrolyte materials with high energy density and flexible operation conditions. Here, we verified a class of two-dimensional superionic conduction in A(BC)2, in which A are alkaline earth metals such as Be, Mg, and Ca, and boron–carbon (BC) form graphene-like layers. Our first-principles molecular dynamics simulation, boosted by high-accuracy machine-leaning potentials, shows that alkaline metal becomes super-ions under high-temperature conditions, moving freely between BC layers. Differences in superionic conduit lead to the diffusion in Be(BC)2 driven by the vacancy mechanism. In contrast, the diffusion in Mg(BC)2 and Ca(BC)2 is jointly driven by both the vacancy and cooperative mechanisms. We demonstrate that the superionic transition temperature is controlled by the deficiency of mobile super-ions, tuning from 1300 to 1600 K, with up to 2.5% cation defects. With superior thermal stability, these two-dimensional compounds are promising electrolyte materials with ultrahigh heat resistivity capable of operating under high-temperature environments such as deep drills and aerospace devices.

Predicting the hub interactome of COVID-19 and oral squamous cell carcinoma: uncovering ALDH-mediated Wnt/β-catenin pathway activation via salivary inflammatory proteins

Regulation of intermolecular interaction energies for improving polarization-sensitive photodetection

In this study, we systematically modified the polymer structure by incorporating non-conjugated units and substituting atoms in the fused-ring core, resulting in significant alterations to intermolecular interaction energies of −974.1, −1076.4, and −1115.1 kJ/mol between the polymer:chloroform and polymer:ethylene glycol. These modifications greatly enhance the orientation of the all-polymer backbone and the intrinsic polarization-sensitive performance of the device, demonstrating exceptional capabilities in polarized light detection and imaging. The optimal device exhibits an ultra-fast response speed of 10.6 μs, a wide frequency response of 17.78 kHz, and a large linear dynamic range of 132.3 dB with good imaging ability, indicating potential benefits for a diverse array of extreme applications. This work illustrates how the strategy of incorporating non-conjugated units and modifying the core atoms can contribute to continuous improvements in molecular orientation and polarized light detection.

Enhancing epigenetic aging clocks in cetaceans: accurate age estimations in small endangered delphinids, killer whales, pilot whales, belugas, humpbacks, and bowhead whales

Abstract This study presents refined epigenetic clocks for cetaceans, building on previous research that estimated ages in several species from bottlenose dolphins to bowhead and humpback whales using cytosine methylation levels. We combined publicly available data (generated on the HorvathMammalMethylChip40 platform) from skin (n = 805) and blood (n = 286) samples across 13 cetacean species, aged 0 to 139 years. By combining methylation data from different sources, we enhanced our sample size, thereby strengthening the statistical validity of our clocks. We used elastic net regression with leave one sample out (LOO) and leave one species out (LOSO) cross validation to produce highly accurate blood only (Median Absolute Error [MAE] = 1.64 years, r = 0.96), skin only (MAE = 2.32 years, r = 0.94) and blood and skin multi-tissue (MAE = 2.24 years, r = 0.94) clocks. In addition, the LOSO blood and skin (MAE = 5.6 years, repeated measures r = 0.83), skin only (MAE = 6.22 years, repeated measures r = 0.81), and blood only (MAE = 4.11 years, repeated measures r = 0.95) clock analysis demonstrated relatively high correlation toward cetacean species not included within this current data set and provide evidence for a broader application of this model. Our results introduce a multi-species, two-tissue clock for broader applicability across cetaceans, alongside single-tissue multi-species clocks for blood and skin, which allow for more detailed aging analysis depending on the availability of samples. In addition, we developed species-specific clocks for enhanced precision, resulting in four blood-specific clocks and eight skin-specific clocks for individual species; all improving upon existing accuracy estimates for previously published species-specific clocks. By pooling methylation data from various studies, we increased our sample size, significantly enhancing the statistical power for building accurate clocks. These new epigenetic age estimators for cetaceans provide more accurate tools for aiding in conservation efforts of endangered cetaceans.

Buried Au nanoparticles-assisted enhancement of local electric field toward improved resistance switching in Au/ZnO/Si structures

In this work, we reported the fabrication of improved Au/ZnO/Si resistance switching (RS) devices achieved by introducing buried cone-like Au nanoparticles (NPs). The Au NPs were facilely obtained by thermally annealing a thin Au film grown on a Si substrate, which did not influence the subsequent growth of ZnO thin films. Electric measurements verified typical RS behaviors in the Au/ZnO/Si devices, which are related to the recovery and rupture of conductive filaments due to electric field-driven oxygen vacancy migration. Notably, COMSOL-based electrostatic field simulations on Au/ZnO/Au structures have shown that an enhanced local electric field with 4.5 times enhancement was produced at the tip of Au NPs, which facilitated the oxygen vacancies migration around the tip of Au NPs. Accordingly, controlled formation and rupture of conductive filaments are proposed in the Au/ZnO/Au NPs/Si devices, which greatly improved the RS window, stability, and endurance. The results shown in this work may pave the way for the fabrication of high-performance oxide-based RS devices in the future.

Evaluating experimentally the viability of employing hybrid nanofluids as an operating fluid in a shell-and-tube heat exchanger

Abstract The use of hybrid nanofluids (HNF) in heat transfer applications has become the subject of studies during recent periods. Its ability to transfer heat is superior to single nanofluids, and this has been proven in many research. Shell and tube heat exchanger is one of the most common types and are therefore always under research to improve their performance. This study is a practical study that examines the effectiveness of HNF in their use as operating fluids in shell-and-tube heat exchangers instead of traditional operating fluids. A laboratory heat exchanger was used to complete this study. A group of HNF (MWCNTs- Al2O3/water) was synthesized at different concentration rates ranging from 0.4 to 2%. Tests were conducted for Reynolds values in the range from 2500 to 12,560. By measuring the variables in the tests and calculating some factors the results showed that, in comparison between the use of HNF and distilled water, it was found that there is an increase in the value of the Nusselt number for the HNF over the distilled water in a range of 10- 28.5%. The effectiveness increased when using the HNF by up to 22.7% compared to distilled water. Through experiments, an equation was deduced to calculate the value of the Nusselt number. There is good agreement between the results of this research and previous literature.

Heat transfer characteristics of a flat plate pulsating heat pipe with microstructures for unidirectional thermal-to-mechanical energy conversion

The phase change of a liquid into vapor results in a sharp volume expansion, generating a powerful driving force, which is fundamental for the operation of pulsating heat pipes (PHPs). However, the performance of PHPs is hindered by instability arising from the lack of directional control over the expansion process. In this work, we propose a PHP incorporating thermal-to-mechanical energy conversion (TMC) microstructures, which direct the TMC by controlling the expansion in desired directions, thereby more efficiently utilizing the driving force. Two designs for enhancement of TMC, i.e., one featuring a vapor actuator microstructure (VA-PHP) and another with diameter-variant channels (DVC-PHP), were fabricated and experimentally investigated under low inclination angles and horizontal orientations (0°, 1°, 5°, and 9°). The experimental results indicated that the incorporation of the TMC microstructures into the PHPs facilitated more efficient startup, enhanced unidirectional circulation, and reduced the dependence on the inclination angle. Notably, while the conventional PHP failed to operate at small inclination angles, the VA-PHP achieved stable operation at 1°, and the DVC-PHP further maintained stable operation even at 0°. The robust performance of the proposed PHPs at low inclination angles demonstrates the potential of TMC microstructures to overcome orientation-dependent limitations, thereby delivering a practical solution for improving the effectiveness of PHPs.

Author Correction: Spatially modulated structural colour in bird feathers

Efficient room-temperature spin-amplified luminescence of an InAs quantum dot tunnel coupled with a thin GaNAs spin filter

Dilute nitride GaNAs has attracted much attention for spin generation owing to its defect-engineered spin filtering at room temperature. Strong, circularly polarized luminescence reflecting the spin-polarized electron states generated by a GaNAs spin filter is needed to realize practical opto-spintronics applications. This study examined the impacts of the GaNAs thickness on the room-temperature spin-polarized luminescence properties of tunnel-coupled InAs quantum dots (QDs) through polarization- and time-resolved photoluminescence in combination with a rate equation analysis. Reducing the GaNAs thickness from 20 to 5 nm increased the QD luminescence intensity by over an order of magnitude at low excitation powers. This increased luminescence was attributed to decreased electron capture in the deep-level defect states of GaNAs, which resulted from fewer defects in thinner GaNAs layers. Furthermore, the reduction in GaNAs thickness decreased the excitation power needed to maximize electron spin polarization of QDs while maintaining a near-maximum value. This efficient spin-amplified luminescence of QDs was achieved through spin-selective capture of QD electrons by defect states under low excitation spin densities. These results demonstrate that using a thin GaNAs spin filter can result in strong QD luminescence and high circular polarization at room temperature and low excitation spin densities. The findings give valuable implications for the development of spin-functional optical devices utilizing a GaNAs spin filter.