- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Radial multipliers in solutions of the Helmholtz equations
摘要： We define radial multipliers using solutions of the Helmholtz equation, which depend on the radial coordinate, and we find the recurrence relations between them in the space of any dimension m > 1, in which the Helmholtz operator is defined. It is shown that the procedure of differentiation of these multipliers leads to a system of solutions of the Helmholtz equation, represented as products of the radial multipliers and harmonic polynomials. Theorems about the properties of radial multipliers and the structure of harmonic polynomials in the solutions of Helmholtz equation are given. These solutions constructed using radial multipliers and harmonic polynomials are proposed to be used in gradient elasticity for multi-layered domains with spherical and cylindrical boundaries, since they allow to present boundary conditions in explicit algebraic form.
关键词： Gradient elasticity,generalized Papkovich–Neuber representation,Helmholtz equation,radial multipliers,harmonic polynomials
更新于2025-09-23 15:23:52
-
Proof-of-principle demonstration of vertical-gravity-gradient measurement using a single-proof-mass double-loop atom interferometer
摘要： We demonstrate a proof-of-principle of direct Earth gravity-gradient measurement with an atom interferometer-based gravity gradiometer using a single proof mass of cold 87Rb atoms. The atomic gradiometer is implemented in the so-called double-loop configuration, hence providing a direct gravity-gradient dependent phase shift insensitive to dc acceleration and constant rotation rate. The atom interferometer (AI) can be either operated as a gravimeter or a gradiometer by simply adding an extra Raman π pulse. We demonstrate gravity-gradient measurements first using a vibration isolation platform and second without seismic isolation using the correlation between the AI signal and the vibration signal measured by an auxiliary classical accelerometer allowing one to bypass the absence of common-mode vibration noise rejection in a double-loop geometry. The simplicity of the experimental setup (a single atomic source and unique detection) and the immunity of the AI to rotation-induced contrast loss make it a possible candidate for onboard gravity-gradient measurements.
关键词： gradiometer,gravity gradient,vibration isolation,atom interferometer,correlation technique
更新于2025-09-23 15:23:52
-
The twisted solenoid RF phase gradient transmit coil for TRASE imaging
摘要： TRASE is an MRI k-space encoding method that uses radio-frequency (RF or B1) transmit phase gradient fields to achieve millimeter-level spatial resolution. Image quality is critically dependent upon the efficient generation of B1 fields with uniform magnitude and strong phase gradients. We present the design of a new family of phase gradient transmit coil based upon a solenoid twisted about a transverse axis. This design has many attractive geometric, electrical and magnetic characteristics, including the capability to spatially encode in the direction of the main static B0 field without obstructing access to the bore. Analytical, numerical simulation and experimental results are presented, including demonstration of 1-dimensional TRASE encoding without the use of PIN diode switches. Twisted solenoid coils significantly expand the capabilities of TRASE MRI.
关键词： Phase gradient,TRASE,k-space,RF coil
更新于2025-09-23 15:23:52
-
Fluorescent Ag clusters conjugated with anterior gradient-2 antigen aptamer for specific detection of cancer cells
摘要： Fluorescent probes with small size, low toxic and specific recognition are of fundamental interests as well as of practical prospects in bioimaging. Though various probes have been reported up to now, including traditional organic dye, quantum dots, rare earth-based particles, and recently emerged carbon dots, silicon dots, polymer dots and metal cluster et al., the relatively large size and lack of specify are far from satisfaction in cellular imaging. As confirmed in previous reports, the large size might influence the functions of target, where the consequent drawback of non-specific is requiring conjugate with additional ligands which brings even larger size and complex procedures. In such a context, fluorescent metal nanoclusters have rapidly attracted widely concern for their integrated advantages of small size, high stability, unique selectivity and tunable properties by simply selecting different stabilizer. In considering a wide variety of stabilizer, aptamer, as a class of ssDNA, has received particular interest because of the easy production, reduced size comparing with antibody and selectively binding ability in molecule level with specific structures. Former researches have proved that cytosine has strong interaction with Ag cations. Therefore, colorful Ag clusters (AgNCs) have been continuously prepared using different DNA sequences in a simple reductive reaction after mixing both aptamer and Ag cation. Additionally, the as synthesized AgNCs do not influence the selectivity of the aptamer itself. For example, Sun et al. reported a one-step process to synthesize silver nanoclusters by specific aptamer which can selectively image the nuclei of CCRF cells, clearly demonstrates the strength of the aptamer capsulated Ag clusters. Anterior gradient protein 2 homolog (AGR), a homolog of xenopus anterior gradient-2 (XAG-2) of Xenopus laevis, is a typical protein that secret by gland cancer cell. Since being discovered as a pro-oncogenic protein that weakens p53 gene activity in 2004. Clinical studies have shown that AGR is highly expressed in pancreatic, breast, and prostate cancer cells, etc. The molecular function and clinical relevance of AGR with variety cancers have thus been increasingly investigated. Specifically, it is a functional protein that plays a key role in variety of biological systems, including the development of vertebrate tissue and the inflammatory tissue injury response. Overall, Tian's results demonstrated that AGR overexpression could predict poor overall survival (OS) and poor time to tumor progression (TTP) of all solid tumor patients. Therefore, fluorescence recognizing of AGR is important for detecting gland cancer cells. At present, a number of reports related with AGR have been reported, but few on specific recognition probes. Through a series of screening, Wu et al. discovered AGR's corresponding aptamer “C14B1”. Few years later, Hu et al. successfully achieved the direct detection of AGR in vitro. However, in the cell imaging field, there is scarcely report on AGR detection. Therefore, synthesis of fluorescent AgNCs conjugating with aptamer to target AGR could provide a novel method for recognizing human gland cancer cell with a high selectivity, efficiency, and low cytotoxicity. In this paper, modified AGR aptamer (MA) were used as template to synthesize AgNCs. Specifically, MA's sequence is 5′-CGG GTG GGA GTT GTG GGG GGG GGT GGG AGG GTT TTTTT CCC CCC CCC CCC-3′ (50 bases). This sequence consists of two functional parts, AGR-apt sequence for recognition AGR in breast cancer (MCF-7) cells, where 12 cytosine base sequence (12C) for effectively preparing fluorescent AgNCs. According to Li's research, a T5 loop (-TTTTT-) could enhance the fluorescence intensity and avoid the influence of space hindrance. It was incorporated between the 3′ end of the apt and 12C sequence. Eventually, according to optimized reaction conditions, MA stabilized silver nanocluster (MA@AgNCs) with a small size, suitable stability, good selectivity was prepared. The fluorescence excitation peak and emission peak of MA@AgNCs were located at 510 nm and 565 nm respectively with a quantum yield as high as 87.43%. Moreover, MA@AgNCs shows descent specific recognition of MCF-7 cells, suggesting the prepared MA@AgNCs have the ability to selective target gland cancer cell and potentially utilized for clinical diagnosis and treatment.
关键词： Bio-probe,Cell imaging,Anterior gradient-2 antigen,Silver nanoclusters,Aptamer
更新于2025-09-23 15:23:52
-
Graded-Index Fluoropolymer Antireflection Coatings for Invisible Plastic Optics
摘要： Plastic optics are used in an ever-expanding range of applications and yet a durable, high performance antireflection (AR) coating remains elusive for this material class. Here, we introduce a sacrificial porogen approach to produce ultralow refractive index nanoporous fluoropolymer AR coatings via thermal co-evaporation of Teflon AF and the small molecule N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (NPD). Using this approach, we demonstrate a five-layer, step-graded AR coating that reduces the solar spectrum-averaged (400 < λ < 2000 nm) reflectance of acrylic plastic to <0.5% for incidence angles up to 40° and withstands over three months of outdoor rooftop exposure with minimal degradation. A trilayer coating optimized for the visible range yields luminous reflectivity down to ~0.1%, effectively rendering double-side coated acrylic plastic invisible under room lighting conditions. Strong adhesion to most optical plastics, an outstanding combination of mechanical, chemical, and environmental durability, and compatibility with commercial vacuum coating systems should enable this AR technology to find widespread practical use.
关键词： gradient-index,polymer optics,sacrificial porogen,antireflection,nanoporous
更新于2025-09-23 15:23:52
-
Nonlinear Diffraction in Asymmetric Dielectric Metasurfaces
摘要： Metasurfaces provide new and promising mechanisms to control and manipulate light at the nanoscale. While most metasurfaces are designed to operate in the linear regime, it was recently shown that such metasurfaces may also generate nonlinear signal, by manipulating the higher order susceptibility terms. As such, metasurfaces can generate additional harmonics, without the need for light propagation, as typically occur in nonlinear crystals. While such demonstrations typically rely on the nonlinear properties of metals, we hereby report the design, fabrication and experimental characterization of a resonant dielectric metasurface made of amorphous silicon to create and manipulate second harmonic light and control its diffraction patterns. As shown in the paper, the second harmonic generation of light follows selection rules which rely on the asymmetry of the meta-atom. Given the fact that silicon crystals are centrosymmetric, the generation of second harmonic signal in amorphous silicon is intriguing. In fact, second harmonic signal is generated mostly from the surface of the meta atom. It is the use of nanostructures that increases the surface to volume ratio and enables second harmonic generation. Additionally, the meta atom is designed to exploit its spectral resonances in the principal and the second harmonic frequencies for providing electromagnetic field enhancement which assist in boosting up the generation of second harmonic signal.
关键词： Metasurfaces,Nonlinear optics,Dielectric metasurfaces,Phase gradient metasurfaces
更新于2025-09-23 15:23:52
-
[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - Multi-Scale Gradient Domain Underwater Image Enhancement
摘要： Underwater images often suffer from low visibility, due to the attenuation and scattering of the propagated light, which are caused by the dense and non-uniform medium. Based on the observation that degradation of underwater images occurs both in contrast and color, this paper aims at compensating the contrast and color saturation of the image respectively. To achieve this, we first white balance the degraded image to remove the color casts while producing a natural appearance of the underwater image. Then propose a multi-scale gradient domain contrast enhancement strategy to increase the visibility, and compensate the attenuation of color saturation according to the estimated transmission. Both qualitative and quantitative results demonstrate the effectiveness of the proposed method. Our method yields accurate results with significantly enhanced contrast and superior color, even better than other state-of-the-art methods.
关键词： Underwater image,Gradient Domain,Contrast enhancement,Edge-preserving image decomposition,Color correction
更新于2025-09-23 15:22:29
-
Fabrication and electromagnetic wave absorption property of quartz ceramics with a gradient distribution of BaTiO3
摘要： Quartz ceramics with a uniform/gradient distribution of BaTiO3 (U/G–SO–BTO) are fabricated by cold pressing a powder blend with BTO followed by sintering and using a combined technique of spreading the powder blends with gradually increased BTO layer–by–layer and sintering. The electromagnetic wave absorption properties of these two ceramics are studied in detail. For U–SO–BTO samples, the primary electromagnetic re?ection is strong due to the aggravated impedance mismatch at their surfaces. The electromagnetic wave re?ectivity of U–SO–BTO could only reach ?7.0 dB when the sample thickness is 6 mm and the BTO content is 8.0 wt%, and it decreases slightly to ?8.1 dB when the sample thickness is increased to 10.0 mm and the BTO content is decreased to 5.0 wt% simultaneously. For G–SO–BTO samples, electromagnetic waves could enter with little re?ection due to the weak surface impedance mismatch, and the electromagnetic waves entering these samples could propagate forward while being absorbed gradually with little re?ection because of the weak impedance mismatch at the interfaces. The G–SO–BTO samples are promising excellent electromagnetic absorbing materials because their electromagnetic wave re?ectivity could reach a level lower than ?12.0 dB and could decrease further from –12.2 to ?13.1 dB as the layer thickness increases from 1.0 to 2.0 mm.
关键词： Impedance mismatch,Electromagnetic wave absorption,Quartz ceramics,Electromagnetic re?ection,Gradient distribution,BaTiO3
更新于2025-09-23 15:22:29
-
Automatic Pathological Lung Segmentation in Low-dose CT Image using Eigenspace Sparse Shape Composition
摘要： Segmentation of lungs with severe pathology is a nontrivial problem in clinical application. Due to complex structures, pathological changes, individual differences and low image quality, accurate lung segmentation in clinical 3D CT images is still a challenging task. To overcome these problems, a novel dictionary-based approach is introduced to automatically segment pathological lungs in 3D low-dose CT images. Sparse shape composition is integrated with eigenvector space shape prior model, called eigenspace sparse shape composition, to reduce local shape reconstruction error caused by weak and misleading appearance prior information. To initialize the shape model, a landmark recognition method based on discriminative appearance dictionary is introduced to handle lesions and local details. Furthermore, a new vertex search strategy based on gradient vector flow field is also proposed to drive shape deformation to target boundary. The proposed algorithm is tested on 78 3D low-dose CT images with lung tumors. Compared to state-of-the-art methods, the proposed approach can robustly and accurately detect pathological lung surface.
关键词： gradient vector flow,Pathological lung segmentation,discriminative appearance dictionary,eigenspace sparse shape composition
更新于2025-09-23 15:22:29
-
Microfluidic Long-Term Gradient Generator with Axon Separation Prototyped by 185 nm Diffused Light Photolithography of SU-8 Photoresist
摘要： We have developed a cast micro?uidic chip for concentration gradient generation that contains a thin (~5 μm2 cross-sectional area) microchannel. The diffusion of diffused 185 nm ultraviolet (UV) light from an inexpensive low-pressure mercury lamp exposed a layer of the SU-8 photoresist from the backside and successfully patterned durable 2 μm-high microchannel mold features with smooth bell-shaped sidewalls. The thin channel had appropriate ?ow resistance and simultaneously satis?ed both the rapid introduction of test substance and long-term maintenance of gradients. The average height and width at the half height of the channel, de?ned by a 2 μm-wide line mask pattern, were 2.00 ± 0.19 μm, and 2.14 ± 0.89 μm, respectively. We were able to maintain the concentration gradient of Alexa Fluor 488 ?uorescent dye inside or at the exit of the thin microchannel in an H-shaped micro?uidic con?guration for at least 48 h. We also demonstrated the cultivation of chick embryo dorsal root ganglion neuronal cells for 96 h, and the directional elongation of axons under a nerve growth factor concentration gradient.
关键词： prototyping,axon elongation,micro?uidic gradient generator,SU-8,microchannel
更新于2025-09-23 15:22:29