Search Results (1,745)

A square patch metasurface is designed, simulated, fabricated, and experimentally tested to investigate polarization characteristics quantitatively. The metasurface consists of one layer unit cell in the form of a square patch with one via and a lumped resistor, which is used for harvesting RF (radio frequency) energy. FR4 dielectric is used as a substrate supported by a metal ground plane. Polarization-dependent properties with specific surface current patterns and voltage dip are obtained when simulating under normal incidence of a plane wave. This characteristic results from changes in surface current conditions when the polarization angle is varied. A voltage dip appears at a specific polarization angle when the surface current pattern is symmetrical. This condition occurs when the position of the lumped resistor from the center of the patch is perpendicular to the linearly polarized incident electric field. A couple of 10 × 10 arrays with different resistor positions are fabricated and tested. The experimental results are in good agreement with the simulated results. The proposed design demonstrates a symmetric unit cell structure with one via and a resistor that exhibits polarization-dependent behavior for linear polarization. An asymmetric patch design is explored through both simulation and measurement to mitigate polarization dependence by suppressing the dip behavior, albeit at the expense of reduced absorption efficiency. This study provides a complete polarization analysis for both symmetric and asymmetric patch metasurfaces with a single via and a single lumped resistor, and introduces a predictive relation between the position of the resistor relative to the center of the patch and the resulting voltage dip behavior. Full article

Background/Objectives: Brainstem ischemic strokes comprise 10% of ischemic strokes and are challenging to diagnose due to small lesion size and complex presentations. Diffusion-weighted imaging (DWI) is crucial for detecting ischemia, yet it can miss small lesions, especially when only axial slices are employed. This study investigated whether ischemic lesions visible in a single imaging plane correspond to smaller volumes and whether coronal DWI enhances detection compared to axial DWI alone. Methods: This retrospective single-center study examined 134 patients with brainstem ischemic strokes between December 2018 and November 2023. All patients underwent axial and coronal DWI. Clinical data, NIH Stroke Scale (NIHSS) scores, and modified Rankin Scale (mRS) scores were recorded. Diffusion-restricted lesion volumes were calculated using multiple models (planimetric, ellipsoid, and spherical), and lesion visibility per imaging plane was analyzed. Results: Brainstem ischemic strokes were detected in 85.8% of patients. Coronal DWI alone identified 6% of lesions that were undetectable on axial DWI; meanwhile, axial DWI alone identified 6.7%. Combining both improved overall sensitivity to 86.6%. Ischemic lesions visible in only one plane were significantly smaller across all volume models. Higher NIHSS scores were strongly correlated with larger diffusion-restricted lesion volumes. Coronal DWI correlated better with clinical severity than axial DWI, especially in the midbrain and medulla. Conclusions: Coronal DWI significantly improves the detection of small brainstem infarcts and should be incorporated into routine stroke imaging protocols. Infarcts visible in only one plane are typically smaller, yet still clinically relevant. Combined imaging enhances diagnostic accuracy and supports early and precise intervention in posterior circulation strokes. Full article

Constructing heterojunctions can combine the superior performance of different two-dimensional (2D) materials and eliminate the drawbacks of a single material, and modulating heterojunctions can enhance the capability and extend the application field. Here, we investigate the physical properties of the heterojunctions formed by the contact of different atom planes of Janus MoSSe (JMoSSe) and graphene (Gr), and regulate the Schottky barrier of the Gr/JMoSSe heterojunction by the number of layers and the electric field. Due to the difference in atomic electronegativity and surface work function (WF), the Gr/JSMoSe heterojunction formed by the contact of S atoms with Gr exhibits an n-type Schottky barrier, whereas the Gr/JSeMoS heterojunction formed by the contact of the Se atoms with Gr reveals a p-type Schottky barrier. Increasing the number of layers of JMoSSe allows the Gr/JMoSSe heterojunction to achieve the transition from Schottky contact to Ohmic contact. Moreover, under the control of an external electric field, the Gr/JMoSSe heterojunction can realize the transition among n-type Schottky barrier, p-type Schottky barrier, and Ohmic contact. The physical mechanism of the layer number and electric field modulation effect is analyzed in detail by the change in the interface electron charge transfer. Our results will contribute to the design and application of nanoelectronics and optoelectronic devices based on Gr/JMoSSe heterojunctions in the future. Full article

Topographic slope is a key parameter for characterizing landscape geomorphology. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) offers high-resolution along-track slopes based on the ground profiles generated by dense signal photons. However, the across-track slopes are typically derived using the ground photon geolocations from the weak-beam and strong-beam pair, limiting the retrieval accuracy and losing valid results over rugged terrains. The goal of this study is to propose a new method to derive the across-track slope merely using single-track photon data of a strong beam based on the theoretical formula of the received signal pulse width. Based on the ICESat-2 photon data over the Walker Lake area, the specific purposes are to (1) extract the along-track slope and surface roughness from the signal photon data on the ground; (2) generate an elevation frequency histogram (EFH) and calculate its root mean square (RMS) width; and (3) derive the across-track slope from the RMS width of the EFH and evaluate the retrieval accuracy against the across-track slope from the ICESat-2 product and plane fitting method. The results show that the mean absolute error (MAE) obtained by our method is 11.45°, which is comparable to the ICESat-2 method (11.61°) and the plane fitting method (12.51°). Our method produces the least invalid data proportion of ~2.5%, significantly outperforming both the plane fitting method (10.29%) and the ICESat-2 method (32.32%). Specifically, when the reference across-track slope exceeds 30°, our method can consistently yield the optimal across-track slopes, where the absolute median, inter quartile range, and whisker range of the across-track slope residuals have reductions greater than 4.44°, 1.31°, and 0.10°, respectively. Overall, our method is well-suited for the across-track slope estimation over rugged terrains and can provide higher-precision, higher-resolution, and more valid across-track slopes. Full article

The single-crystal diamond (SCD), owing to its extreme physical and chemical properties, serves as an ideal substrate for quantum sensing and high-frequency devices. However, crystal anisotropy imposes significant challenges on fabricating high-quality micro-nano structures, directly impacting device performance. This work investigates the effects of femtosecond laser processing on the SCD under two distinct crystallographic orientations via single-pulse ablation. The results reveal that ablation craters along the <100> orientation exhibit an elliptical shape with the major axis parallel to the laser polarization, whereas those along the <110> orientation form near-circular craters with the major axis at a 45° angle to the polarization. The single-pulse ablation threshold of the SCD along <110> is 9.56 J/cm², representing a 7.8% decrease compared to 10.32 J/cm² for <100>. The graphitization threshold shows a more pronounced reduction, dropping from 4.79 J/cm² to 3.31 J/cm² (31% decrease), accompanied by enhanced sp² carbon order evidenced by the significantly intensified G-band in the Raman spectra. In addition, a phase transition layer of amorphous carbon at the nanoscale in the surface layer (thickness of ~40 nm) and a narrow lattice spacing of 0.36 nm are observed under TEM, corresponding to the interlayer (002) plane of graphite. These observations are attributed to the orientation-dependent energy deposition efficiency. Based on these findings, an optimized crystallographic orientation selection strategy for femtosecond laser processing is proposed to improve the quality of functional micro-nano structures in the SCD. Full article

We propose a single-phase chiral elastic metamaterial capable of simultaneously exhibiting negative effective mass density and negative bulk modulus in the ultrasonic frequency range. The unit cell consists of a regular hexagonal frame connected to a central circular mass through six obliquely oriented, slender aluminum beams. The design avoids the manufacturing complexity of multi-phase systems by relying solely on geometric topology and chirality to induce dipolar and rotational resonances. Dispersion analysis and effective parameter retrieval confirm a double-negative frequency region from 30.9 kHz to 34 kHz. Finite element simulations further demonstrate negative refraction behavior when the metamaterial is immersed in water and subjected to 32 kHz and 32.7 kHz incident plane wave. Equifrequency curves (EFCs) analysis shows excellent agreement with simulated refraction angles, validating the material’s double-negative performance. This study provides a robust, manufacturable platform for elastic wave manipulation using a single-phase metallic metamaterial design. Full article

Continuous SiC fiber-reinforced SiC matrix composites (SiC/SiC), as structural heat protection integrated materials, are often used in parts for large-area heat protection and sharp leading edges, and there are a variety of low-velocity impact events in their service. In this paper, a drop hammer impact test was conducted using narrow strip samples to simulate the low-velocity impact damage process of sharp-edged components. During the test, different impact energies and impact times were set to focus on investigating the low-velocity impact damage characteristics of 2.5D SiC/SiC composites. To further analyze the damage mechanism, computed tomography (CT) was used to observe the crack propagation paths and distribution states of the composites before and after impact, while scanning electron microscopy (SEM) was employed to characterize the differences in the micro-morphology of their fracture surfaces. The results show that the in-plane impact behavior of a 2.5D needled SiC/SiC composite strip samples differs from the conventional three-stage pattern. In addition to the three stages observed in the energy–time curve—namely in the quasi-linear elastic region, the severe load drop region, and the rebound stage after peak impact energy—a plateau stage appears when the impact energy is 1 J. During the impact process, interlayer load transfer is achieved through the connection of needled fibers, which continuously provide significant structural support, with obvious fiber pull-out and debonding phenomena. When the samples are subjected to two impacts, damage accumulation occurs inside the material. Under conditions with the same total energy, multiple impacts cause more severe damage to the material compared to a single impact. Full article

Objective: To assess the long-term effects of Dienogest on clinical complaints and nodule sizes in women affected by recto-sigmoid deep endometriosis (DE). Methods: This was a single-center longitudinal prospective observational study comprising a consecutive series of women affected by recto-sigmoid DE, who underwent medical treatment with Dienogest (2 mg daily continuous). All women underwent clinical visits and transvaginal sonography (TVS) with bowel preparation prior to starting therapy and at 3–6-month intervals for at least 12 months. Clinical complaints such as dysmenorrhea, dyspareunia and dyschezia were assessed using a visual analog scale (VAS). The DE recto-sigmoid lesion was measured in the three orthogonal planes. The lesion’s volume was estimated using the prolate ellipsoid formula. The maximum diameter and lesion volume were used for analysis. Patients’ complaints and lesion sizes before starting the treatment and at final follow-up were compared. Results: From January 2017 to July 2020, 125 patients were consecutively recruited (mean age: 37 years, ranging from 20 to 50 years). The median follow-up period was 47.8 months (range: 12–74 months). We did not observe a significant correlation between the severity of the symptoms and the lesion size prior to starting therapy. Clinical complaints improved significantly during treatment (88% of women were symptomatic at initial visit, versus 53% at final follow-up, p < 0.001). The median lesion volume significantly decreased (median initial volume vs. final volume: 1.1 mL vs. 0.9 mL, p = 0.017). However, the median maximum lesion diameter did not change significantly (26.0 mm vs. 25.0 mm, p = 0.779). Conclusions: Long-term Dienogest therapy significantly relieves clinical symptoms related to recto-sigmoid DE. This is accompanied by a significant reduction in the lesion volume but not the maximum lesion diameter. Full article

Continuous low thrust is widely used in orbit transfer maneuvers. If the unknown maneuvers are not correctly compensated, the orbiting accuracy will be seriously affected. We propose a rapid method for pre-identifying thrust acceleration based on single-arc orbit determination in order to determine the orbit of non-cooperative continuous low-thrust maneuvering spacecraft. The single-arc orbit determination results of two ground-based radar observations with a certain time interval are used to inversely determine the direction and magnitude of acceleration of the spacecraft under continuous thrust based on their relationship with satellite orbit parameters. The solution error is relatively small when using this method, even over a short period of time when data are sparse. The results can then be applied to the orbital adjustment of a satellite. The results show that when the satellite climbs with maximum tangential acceleration, the interval between the two radar observations is greater than 7 h, and the proposed method can rapidly pre-identify tangential thrust acceleration with a solution error of less than 5%. When the satellite adjusts the orbital plane with the maximum normal acceleration, the average relative measurement error of the normal acceleration is about 20% when the time interval between two observations is 24 h. The longer the observation interval and the greater the thrust acceleration, the smaller the relative error. The calculation results can be used as the initial value for precision orbit determination of continuous low-thrust maneuvering spacecraft. Full article

The transport of intensity equation enables quantitative phase imaging from only two axially displaced intensity images, facilitating the characterization of low-contrast samples like cells and microorganisms. However, the rapid selection of the correct defocused planes, crucial for real-time phase imaging of dynamic events, remains challenging. Additionally, the different images are normally acquired sequentially, further limiting phase-reconstruction speed. Here, we report on a system that addresses these issues and enables user-tuned defocusing with snapshot phase retrieval. Our approach is based on combining multi-color pulsed illumination with acousto-optic defocusing for microsecond-scale chromatic aberration control. By illuminating each plane with a different color and using a color camera, the information to reconstruct a phase map can be gathered in a single acquisition. We detail the fundamentals of our method, characterize its performance, and demonstrate live phase imaging of a freely moving microorganism at speeds of 150 phase reconstructions per second, limited only by the camera’s frame rate. Full article

Background: The Da Silva Cone procedure for Ebstein anomaly has dramatically improved tricuspid valve competence and clinical outcomes. However, preoperative left ventricular (LV) dysfunction and immediate postoperative right ventricular (RV) systolic dysfunction are frequently observed. While excellent valve outcomes are well established, recovery of biventricular function following the Cone remains less defined. This study aimed to evaluate longitudinal changes in RV and LV function postoperatively and over a minimum of six months post-Cone operation. Methods: A single center retrospective review of 134 patients who underwent Cone repair for Ebstein’s anomaly from 2016 to 2024 was performed. Echocardiograms were analyzed at three time points: preoperative (Time 1), hospital discharge (Time 2), and ≥6 months postoperative (Time 3). RV parameters included fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tricuspid S′. LV parameters included left ventricular ejection fraction (LVEF), end-diastolic volume indexed to body surface area (LVEDVi), left ventricular stroke volume (LVSVi), and mitral E/E′. Subgroup analyses examined outcomes by prior Glenn, Starnes procedure, and degree of RV dilation. Paired two sample t-tests were used to compare serial measures. Results: Median age at surgery was 7.8 years (IQR: 2.3–17.7). All patients had discharge echocardiograms; 70 had follow-up studies at ≥6 months. RV function declined postoperatively with reductions in FAC (35% to 21%), TAPSE (2.0 to 0.8 cm), and S′ (13 to 5 cm/s), all p < 0.001. By Time 3, these measures improved (FAC to 29%, TAPSE to 1.3 cm, S′ to 7 cm/s) but did not fully return to baseline. LVEDVi and LVSVi increased significantly by Time 3 (LVEDVi: 47 to 54 mL/m²; LVSVi: 30 to 34 mL/m²; p < 0.001), while LVEF remained unchanged. Patients with prior Glenn or Starnes had greater Time 1 LV volumes and lower RV function, but by Time 3, most differences resolved. Moderate–severe preoperative RV dilation was associated with worse RV function at Time 2 and normalized by Time 3. Conclusions: The Da Silva Cone procedure leads to early postoperative RV dysfunction with partial recovery over the mid-term follow-up. Concurrently, LV filling and stroke volume improve, reflecting favorable interventricular interaction. These findings support echocardiographic surveillance to guide functional recovery post-Cone and inform patient counseling. Full article

The monolithic integration of III-V semiconductors with silicon (Si) is a critical step toward advancing optoelectronic and photonic devices. In this work, we present GaAs nanoheteroepitaxy (NHE) on Si nanotips using gas-source molecular beam epitaxy (GS-MBE). We discuss the selective growth of fully relaxed GaAs nanoislands on complementary metal oxide semiconductor (CMOS)-compatible Si(001) nanotip wafers. Nanotip wafers were fabricated using a state-of-the-art 0.13 μm SiGe Bipolar CMOS pilot line on 200 mm wafers. Our investigation focuses on understanding the influence of the growth conditions on the morphology, crystalline structure, and defect formation of the GaAs islands. The morphological, structural, and optical properties of the GaAs islands were characterized using scanning electron microscopy, high-resolution X-ray diffraction, and photoluminescence spectroscopy. For samples with less deposition, the GaAs islands exhibit a monomodal size distribution, with an average effective diameter ranging between 100 and 280 nm. These islands display four distinct facet orientations corresponding to the {001} planes. As the deposition increases, larger islands with multiple crystallographic facets emerge, accompanied by a transition from a monomodal to a bimodal growth mode. Single twinning is observed in all samples. However, with increasing deposition, not only a bimodal size distribution occurs, but also the volume fraction of the twinned material increases significantly. These findings shed light on the growth dynamics of nanoheteroepitaxial GaAs and contribute to ongoing efforts toward CMOS-compatible Si-based nanophotonic technologies. Full article

Background/Objective: Laser therapy has gained attention in dental practice to minimize bleeding and enhance blood clot formation. This study aimed to explore the utilization and to compare the clinical efficacy of laser-mediated hemostasis for older patients receiving routine dental treatment. Methods: A prospective observational study was conducted across research networks between October 2023 and August 2024, involving 60 patients aged 50 years and older (average = 63.35 years) at risk of postoperative bleeding following dental treatments. Additionally, laser therapy for hemostasis was selected and provided among calibrated operators. A single researcher performed data collection. Before statistical analysis, data verification and clinical assessment were conducted by the operators and researcher. A clinical cut-off for hemostasis was set at 5 min. Two diode laser machines were used namely, an 810 nm and dual wavelengths of 635 nm and 980 nm. Results: There were 94 extraction sockets, 28 procedures of scaling and root planing and 18 procedures of minor oral surgery. Combining laser ablating sulcular fiber and photobiomodulation initiating blood clot formation was a preferable hemostatic technique for extraction socket, while photobiomodulation alone was a preferred technique for soft tissue hemostasis (p < 0.001). All operators confirmed that 97.86 percent of bleeding events achieved more rapid hemostasis. 61.43 percent of bleeding events clinically achieved hemostasis within 5 min by using laser-mediated hemostasis alone (p = 0.092). Full recovery of the extraction socket was significantly observed during the 2- to 4-week follow-up period (p = 0.005). No clinical complications were reported. Conclusions: Laser-mediated hemostasis effectively reduced hemostatic duration, prevented postoperative bleeding and promoted wound healing in older patients undergoing routine dental treatment. Full article

This paper presents a compact four-port multiple-input multiple-output (MIMO) antenna for Internet-of-Things (IoT) devices. As electronic IoT devices become smaller, MIMO antennas should also be compact for ease of integration and multi-port operation for a high channel capacity. Instead of using a single-polarized radiator, which increases the antenna size when scaling to a multi-port MIMO array, a dual-polarized radiator is utilized. This helps to achieve multi-port operation with compact size features. To reduce the mutual coupling between the MIMO elements, an I-shaped defected ground structure is inserted into the ground plane. The measured results indicate that the final four-port MIMO antenna with overall dimensions of 0.92 $\lambda$× 0.73 $\lambda$× 0.03 $\lambda$ at 5.5 GHz can achieve an operating bandwidth of about 2.2% with isolation better than 20 dB and a gain higher than 6.0 dBi. Additionally, the proposed method is also applicable to a large-scale MIMO array. Full article

Background/Objectives: The aim of this case series is to evaluate the outcomes and safety of video-assisted mastectomy, illustrating the harmonious collaboration of oncologic and plastic surgery. This novel minimally invasive technique allows immediate prosthetic reconstruction and represents a cost-effective alternative to robotic breast surgery. Methods: Video-assisted, single-port nipple-sparing mastectomies were performed in patients with small to medium-sized breasts, followed by immediate direct-to-implant reconstruction with either prepectoral or dual plane implant placement. The patients’ electronic medical records were analyzed, including demographic characteristics, operative times and histopathology reports. Results: A total of 18 patients underwent successful video-assisted mastectomy, without conversion to traditional open procedure. Fifteen of the operations were risk-reducing mastectomies. Twelve patients had complementary procedures performed concurrently on the previously operated contralateral breast (delayed reconstruction/expander-to-implant exchange). Moreover, three patients benefited from additional minimally invasive techniques during the same surgery (prophylactic laparoscopic hysterectomy). Immediate breast reconstruction with polyurethane or microtextured breast implants up to 450 cc was performed, with satisfactory aesthetic outcomes and no cancer recurrences at 6 to 12 months postoperative follow-up. Early complications included transient hypercapnia, areolar congestion and cellulitis. No skin necrosis or implant-related complications were reported. The most frequently encountered late issues were contour irregularities. Conclusions: Video-assisted mastectomy facilitates the safe removal of proven pathologic or healthy breast tissue with minimal damage to the breast’s skin envelope, facilitating single-stage breast reconstruction. Full article