Search Results (31)

Thoracic electrical impedance tomography (EIT) provides real-time, bedside imaging of pulmonary function and has demonstrated significant clinical value in guiding treatment strategies for critically ill patients. However, the practical application of EIT remains challenging due to its susceptibility to measurement disturbances, such as electrode contact problems and patient movement. These disturbances often manifest as spike-like noise that can severely degrade EIT image quality. To address this issue, we propose a robust Principal Component Analysis (RPCA)-based approach that models EIT data as the sum of a low-rank matrix and a sparse matrix. The low-rank matrix captures the underlying physiological signals, while the sparse matrix contains spike-like noise components. In simulation studies considering different spike magnitudes, widths and channels, all the image correlation coefficients between RPCA-processed images and the ground truth exceeded 0.99, and the image error of the original fEIT image with spike-like noise was much larger than that after RPCA processing. In eight patient cases, RPCA significantly improved the image quality (image error: p < 0.001; image correlation coefficient: p < 0.001) and enhanced the clinical EIT-based indexes accuracy (p < 0.001). Therefore, we conclude that RPCA is a promising technique for reducing spike-like noise in clinical EIT data, thereby improving data quality and potentially facilitating broader clinical application of EIT. Full article

Optical microresonators supporting whispering-gallery modes (WGMs) have become a versatile platform for achieving electromagnetically induced transparency-like (EIT-like) phenomena. We theoretically and experimentally demonstrated the tunable coupled-mode induced transparency based on the surface nanoscale axial photonics (SNAP) microresonator. Single-EIT-like and double-EIT-like (DEIT-like) effects with one or more transparent windows are achieved due to dense mode families and tunable resonant frequencies. The experimental results can be well-fitted by the coupled mode theory. An automatically adjustable EIT-like effect is discovered by immersing the sensing region of the SNAP microresonator into an aqueous environment. The sharp lineshape and high slope of the transparent window allow us to achieve a liquid refractive index sensitivity of 2058.8 pm/RIU. Furthermore, we investigated a displacement sensing phenomenon by monitoring changes in the slope of the transparent window. We believe that the above results pave the way for multi-channel all-optical switching devices, multi-channel optical communications, and biochemical sensing processing. Full article

ScAlMgO₄ (SCAM), which can be used as an epitaxial substrate material of GaN in power devices, faces the challenge of achieving a high-quality surface by ultra-precision polishing due to its brittle and easily cleaved characteristics, which are closely associated with its mechanical properties. The micromechanical properties of SCAM single crystals were evaluated by nanoindentation and microscratch tests using different indenters. The elastic modulus E_IT and the indentation hardness H_IT of SCAM obtained by nanoindentation were 226 GPa and 12.1 GPa, respectively. Leaf-shaped chips and the associated step-like planes of SCAM can be found in the severely damaged regime during scratching by Berkovich and Vickers indenters with sharp edges due to the intersection of intense radial and lateral cracks. The fracture toughness (K_c = 1.12 MPa·m^1/2) of SCAM can be obtained by using a scratch-based methodology for a spherical indenter based on linear elastic fracture mechanics (LEFM) under an appropriate range of applied loads. An optimal expression for calculating the fracture toughness of easily cleaved materials, including SCAM, via the Vickers indenter-induced cracking method using a Berkovich indenter was recommended. Full article

Accommodating multiple tasks within a tiny metasurface unit cell without them interfering with each other is a significant challenge. In this paper, an electromagnetic (EM) wave modulation metasurface capable of reflection, transmission, and absorption is proposed. This multitasking capability is achieved through a cleverly designed multi-layer structure comprising an EM Wave Shield Layer (ESL), a Polarization Modulation Layer (PML), and a Bottom Plate Layer (BPL). The functionality can be arbitrarily switched by embedding control materials within the structure. Depending on external excitation conditions, the proposed metasurface can realize reflection-type co-planar polarization to cross-polarization conversion, transmission-type electromagnetically induced transparency-like (EIT-like) modes, and broadband absorption. Notably, all tasks operate approximately within the same operating frequency band, and their performance can be regulated by the intensity of external excitation. Additionally, the operating principle of the metasurface is analyzed through impedance matching, an oscillator coupling model, and surface current distribution. This metasurface design offers a strategy for integrated devices with multiple functionalities. Full article

Pulmonary monitoring is crucial for the diagnosis and management of respiratory conditions, especially after the epidemic of coronavirus disease. Electrical impedance tomography (EIT) is an alternative non-radioactive tomographic imaging tool for monitoring pulmonary conditions. This review proffers the current EIT technical principles and applications on pulmonary monitoring, which gives a comprehensive summary of EIT applied on the chest and encourages its extensive usage to clinical physicians. The technical principles involving EIT instrumentations and image reconstruction algorithms are explained in detail, and the conditional selection is recommended based on clinical application scenarios. For applications, specifically, the monitoring of ventilation/perfusion (V/Q) is one of the most developed EIT applications. The matching correlation of V/Q could indicate many pulmonary diseases, e.g., the acute respiratory distress syndrome, pneumothorax, pulmonary embolism, and pulmonary edema. Several recently emerging applications like lung transplantation are also briefly introduced as supplementary applications that have potential and are about to be developed in the future. In addition, the limitations, disadvantages, and developing trends of EIT are discussed, indicating that EIT will still be in a long-term development stage before large-scale clinical applications. Full article

Background: Electrical Impedance Tomography (EIT), combined with variable ventilation strategies and Artificial Intelligence (AI), is poised to revolutionize critical care by transitioning from reactive to predictive approaches. This integration aims to enhance patient outcomes through personalized interventions and real-time monitoring. Methods: this narrative review explores the principles and applications of EIT, variable ventilation, and AI in critical care. EIT impedance sensing creates dynamic images of internal physiology, aiding the management of conditions like Acute Respiratory Distress Syndrome (ARDS). Variable ventilation mimics natural breathing variability to improve lung function and minimize ventilator-induced lung injury. AI enhances EIT through advanced image reconstruction techniques, neural networks, and digital twin technology, offering more accurate diagnostics and tailored therapeutic interventions. Conclusions: the confluence of EIT, variable ventilation, and AI represents a significant advancement in critical care, enabling a predictive, personalized approach. EIT provides real-time insights into lung function, guiding precise ventilation adjustments and therapeutic interventions. AI integration enhances EIT diagnostic capabilities, facilitating the development of personalized treatment plans. This synergy fosters interdisciplinary collaborations and sets the stage for innovative research, ultimately improving patient outcomes and advancing the future of critical care. Full article

The measurements of microwave (μw) and radio-frequency (RF) radiation quantitative parameters may be based on the quantum–optical approach to determine the spectral characteristics of radiation transitions between the Rydberg states of atoms. Frequencies and matrix elements are calculated for dipole transitions between opposite-parity Rydberg states $n{\mathrm{L}_{ }^1}_{\mathrm{L}}$ and $n^{\prime }{\left(\mathrm{L}\pm 1\right)_{ }^1}_{\mathrm{L}\pm 1}$ (where $n^{\prime }=$ $n,n\pm 1,n\pm 2$) of the singlet series in the alkaline–earth–metal-like atoms of group IIb (Zn, Cd, Hg) and Yb. The matrix elements determine the shifts of Rydberg-state energy levels in the field of resonance μw or RF radiation, splitting the resonance of electromagnetically induced transparency (EIT) for intensely absorbed probe radiation. Numerical computations based on the single-electron quantum defect method (QDM) and the Fues’ model potential (FMP) approach with the use of the most reliable data from the current literature on quantum defect values are performed for frequencies and matrix elements of transitions between singlet Rydberg states of ¹S₀-, ¹P₁-, ¹D₂-, and ¹F₃-series in Zn, Cd, Hg, and Yb atoms. The calculated data are approximated by polynomials in the powers of the principal quantum numbers. The polynomial coefficients are determined with the use of a standard curve-fitting interpolation polynomial procedure for numerically calculated functions. These approximation expressions provide new possibilities for accurately evaluating the frequencies and matrix elements of dipole transitions between Rydberg states over a wide range of quantum numbers n >> 1, accompanied by the emission and absorption of μw and RF photons. Full article

Induced pluripotent stem cell (iPSC) technology enables differentiation of human hepatocytes or hepatocyte-like cells (iPSC-HLCs). Advances in 3D culturing platforms enable the development of more in vivo-like liver models that recapitulate the complex liver architecture and functionality better than traditional 2D monocultures. Moreover, within the liver, non-parenchymal cells (NPCs) are critically involved in the regulation and maintenance of hepatocyte metabolic function. Thus, models combining 3D culture and co-culturing of various cell types potentially create more functional in vitro liver models than 2D monocultures. Here, we report the establishment of 3D cultures of iPSC-HLCs alone and in co-culture with human umbilical vein endothelial cells (HUVECs) and adipose tissue-derived mesenchymal stem/stromal cells (hASCs). The 3D cultures were performed as spheroids or on microfluidic chips utilizing various biomaterials. Our results show that both 3D spheroid and on-chip culture enhance the expression of mature liver marker genes and proteins compared to 2D. Among the spheroid models, we saw the best functionality in iPSC-HLC monoculture spheroids. On the contrary, in the chip system, the multilineage model outperformed the monoculture chip model. Additionally, the optical projection tomography (OPT) and electrical impedance tomography (EIT) system revealed changes in spheroid size and electrical conductivity during spheroid culture, suggesting changes in cell–cell connections. Altogether, the present study demonstrates that iPSC-HLCs can successfully be cultured in 3D as spheroids and on microfluidic chips, and co-culturing iPSC-HLCs with NPCs enhances their functionality. These 3D in vitro liver systems are promising human-derived platforms usable in various liver-related studies, specifically when using patient-specific iPSCs. Full article

The analogy of electromagnetically induced transparency (EIT) in perovskite metamaterials is characterized by the numerical simulations in finite-difference time-domain (FDTD). The perovskite metamaterials consist of two cut wire resonators (CWRs) and a disk resonator (DR) on a polyimide substrate. The analysis revealed the characteristic dynamics of the electromagnetic field, the near-field couplings of CWRs and DR, and the EIT-like spectral features of perovskite metamaterials as functions of the asymmetry parameter and polarization direction. The strong coupling and destructive interference of bright and bright–dark transitions in perovskite metamaterials displayed EIT-like transparency at 653.5 GHz with a high Q-factor of approximately 1470, a sensitivity of 531 GHz/RIU and a figure of merit of around 780. In addition, perovskite metamaterials exhibited slow light with a group delay of about 106 ps and a group index of approximately 3100. These results may provide an important perspective for understanding the coupling mechanism and applications of perovskite materials in slow-light devices, THz sensors, and tunable switching in THz spectral region. Full article

We theoretically demonstrated optical phase switches in light storage-like experiments. Typical light storage (LS) and retrieval experiments consist of the probe field in the probe channel with writing and reading fields across the drive branch, as well as its recovery. The probe and first drive pulses as the standard electromagnetically induced transparency (EIT) effect of storing light are used in the proposed scheme for the atomic excitations. A train of probe pulses is used after a short storage period to induce Raman gain in the drive channel. The proposed scheme was applied to alkali-metal atoms such as ²³Na, ⁸⁷Rb, and ³⁹K vapours. Spatiotemporal phase variations for generated drive pulses were found to shape in the form of discrete phase distributions. The proposed approach in the process of obtaining phase discrete distributions for different irradiation intensities was tested. For weak fields, the discrete distributions were distinct as a result of the differences in the upper hyperfine structure (hf) and the atomic relaxations. However, for moderate fields, the discrete phase distributions are smeared by the atomic relaxations. Full article

Terahertz (THz) metamaterial (MM) biosensors are a potential method of biomolecule detection. However, there have been few reports on the detection of trace proteins. In this study, we designed a novel THz biosensor consisting of graphene, polyimide (PI), and electromagnetically induced transparency-like (EIT-like) MMs for the ultra-sensitive detection of ovalbumin (OVA). The doping analyte can influence the Fermi level and electrical conductivity of graphene, as well as the coupling of resonators in MMs. These changes are reflected in the magnitude, phase, and frequency changes in the transmission spectra. The biosensor achieved a high sensitivity function for OVA and reached a limit of detection (LoD) of 8.63 pg/mL. The results showed that by regulating the Fermi level of graphene between the valence band, Dirac point, and conduction band, the sensitivity and LoD of MM-based THz biosensors can be enhanced. Such biosensors have the potential to be used in the high-sensitivity detection of trace proteins in biomedical fields. Full article

Melting phase relations in the eclogite-carbonate system were studied at 6 GPa and 900–1500 °C. Starting mixtures were prepared by blending natural bimineral eclogite group A (Ecl) with eutectic Na-Ca-Mg-Fe (N2) and K-Ca-Mg-Fe (K4) carbonate mixtures (systems Ecl-N2 and Ecl-K4). In the Ecl-N2 system, the subsolidus assemblage is represented by garnet, omphacite, eitelite, and a minor amount of Na₂Ca₄(CO₃)₅. In the Ecl-K4 system, the subsolidus assemblage includes garnet, clinopyroxene, K₂Mg(CO₃)₂, and magnesite. The solidus of both systems is located at 950 °C and is controlled by the following melting reaction: Ca₃Al₂Si₃O₁₂ (Grt) + 2(Na or K)₂Mg(CO₃)₂ (Eit) = Ca₂MgSi₃O₁₂ (Grt) + [2(Na or K)₂CO₃∙CaCO₃∙MgCO₃] (L). The silica content (in wt%) in the melt increases with temperature from < 1 at 950 °C to 3–7 at 1300 °C, and 7–12 at 1500 °C. Thus, no gradual transition from carbonate to kimberlite-like (20–32 wt% SiO₂) carbonate-silicate melt occurs even as temperature increases to mantle adiabat. This supports the hypothesis that the high silica content of kimberlite is the result of decarbonation at low pressure. As temperature increases from 950 to 1500 °C, the melt Ca# ranges from 58–60 to 42–46. The infiltration of such a melt into the peridotite mantle should lower its Ca# and causes refertilization from harzburgite to lherzolite and wehrlitization. Full article

This study discusses the case of a 200 m² container garden set up in a polluted and neglected area of the School of Management and Economics of the University of Turin. ‘L’Orto della SME’ is self-managed, and it has become a hub for a variety of stakeholders, within and outside the university. The project is part of the framework Proposal for Citizen Engagement, promoted by EIT Food Cross-KIC, which contributes to the New European Bauhaus (NEB). The paper looks at how such projects contribute to create social cohesion around sustainability issues of circularity and waste management. The case presents several autoethnographic elements, like tales and stakeholders’ voices, stemming from the direct involvement of the authors in developing the project. The article presents how a stakeholder network was created and how internal and external stakeholders were involved in co-creation activities, such as (multi-stakeholder) workshops and focus groups. Our findings show that NEB principles can be effectively applied to initiatives like the container garden to tackle issues of social inclusion, equality and sustainable production and consumption. This is further emphasized by the empowerment and agency gained by diverse stakeholders to approach sustainability matters. Full article

In this paper, a slot microring with an asymmetric grating structure is proposed. Through the coupling between the grating and the slot microring, a high free spectral range or EIT-like effects with a high quality factor can be achieved in the same device. The grating is designed as an asymmetric structure to realize the modulation of the optical signal and the control of the resonance peak by changing the grid number, and the effect of different grating periods on the output spectrum is explored. The results show that changing the grating on slot sidewalls can increase or decrease the number of resonant peaks. By selecting a specific period of the gratings on both sides of the slot, the distance between adjacent resonance peaks can be increased to achieve modulation of the free spectral range. In this paper, depending on the grating period, we obtain a quality factor of 5016 and an FSR of 137 nm, or a quality factor of 10,730 and an FSR of 92 nm. The refractive index sensing simulation is carried out for one of the periods, which can achieve a sensitivity of 370 nm/RIU. Therefore, the proposed new structure has certain advantages in different sensing applications. Full article

Metamaterial analogues of electromagnetically induced transparency (EIT) enable a unique avenue to endow a coupled resonator system with quantum interference behavior, exhibiting remarkable properties in slow-wave and highly sensitive sensing. In particular, tunable and ultracompact-chip-integrated EIT-like effects reveal fantastic application prospects in plasmonic circuits and networks. Here, we demonstrate an electrically tuned on-chip EIT analogue by means of dynamic EIT modules side-coupled to ultrathin corrugated metallic strips supporting spoof surface plasmon polaritons (SSPPs). By embedding PIN diodes into the subradiant mode, on-to-off control of the destructive coupling between the radiative and subradiant modes results in dynamic chip-scale EIT-like behavior under the change of the bias voltage, allowing for an electrically tunable group delay of the surface waves. The physical mechanism of the active modulation is elucidated with the coupled mode theory. In addition, the cascaded capacity performed by installing multiple EIT modules with an interval of equivalent wavelength are also characterized on a planar plasmonic waveguide. The proposed system will pave a versatile route toward dynamic control in chip-scale functional devices. Full article