MODELING THE ANTENNA INPUT IMPEDANCE BY THE METHOD OF MOMENTS

The paper presents a comparison of excitation source models when modeling antennas by the method of moments. By using a set of adjacent edges when specifying the impact, it is possible to obtain correct results when the computational grid of the antenna model is more frequent. This is shown on the example of a symmetric electric vibrator.

Vibration characteristics analysis and structure optimization of air-pressure subsoiler

Aiming at the problems of strong vibration, inconsistent subsoiling depth and high failure rate of air-pressure subsoiler, air-pressure subsoiler vibration characteristics was studied. In order to decrease the vibration, For the first time, the vibration characteristics of air-pressure subsoiler were obtained by modal analysis and vibration test. The vibration characteristics of the whole air-blown subsoiler are analyzed Through time domain analysis, it is found that the vibration acceleration of four deep loosening shovel is inconsistent. When the diesel engine is started, it is easy to cause inconsistent subsoiler depth. Then, by analyzing the vibration characteristics of the whole air-pressure subsoiler, it can be known that the external excitation source of the air-blown subsoiler is close to its own natural frequency. In order to avoid resonance caused by the vibration frequency of the external excitation source being close to the natural frequency of the air-pressure subsoiler, and to reduce the inconsistency of the subsoil depth, we optimize the design of air-pressure subsoiler. Instead of diesel engines, the steering gear box is connected with tractor power output shaft to provide power. The modal simulation of the optimized air-pressure subsoiler shows that the first-order natural frequency is obviously improved and the external excitation frequency is successfully avoided. It not only avoids resonance, reduces the damage of resonance components, but improves the service life of the subsoiler, greatly improves the structural reliability of the air-pressure subsoiler, at the same time, removes the main external excitation source, which greatly reduces the vibration in actual production and the inconsistency of subsoiling, which is of great significance in actual production. It provides a reference for the research of vibration characteristics, resonance avoidance and structure optimization of agricultural equipment.

Characterization of red fluorescent reporters for dual-color in vivo three-photon microscopy

Three-photon (3P) microscopy significantly increases the depth and resolution of in vivo imaging due to decreased scattering and nonlinear optical sectioning. Past studies used separate 1300 and 1700 nm excitation sources to excite green and red fluorescent proteins. Recently work shows that a single 1300 nm excitation source allows for dual color 3P imaging with increased signal-to-background and decreased average power. Future use of single excitation 3P microscopes would reduce the need for additional custom optical elements and decrease cost. However, there is a lack of experimental data characterizing the excitation properties of specific fluorophore combinations in the near-infrared range. Here, we assess the dual-color imaging potential of tdTomato or mScarlet in combination with EGFP when excited by a single excitation source tuned from 1225-1360 nm in the living mouse brain. We find that tdTomato and mScarlet, expressed in oligodendrocytes and neurons respectively, have exceptional signal-to-background in the 1300-1360 nm range in deep cortex, consistent with enhanced 3P cross sections. These results suggest that a single excitation source is advantageous for multiple applications of dual-color structural and functional brain imaging highlighting the importance of empirical characterization of individual fluorophores in the near-infrared region.

Dual Detection High-Speed Capillary Electrophoresis for Simultaneous Serum Protein Analysis and Immunoassays

Serum protein electrophoresis (SPE) and immunoassays are important tools used clinically to diagnose disease. SPE separates serum proteins into bands whose shape and amplitude can alert clinicians to a range of disorders. This is usually followed by more specific immunoassays to quantify important antigens and confirm a diagnosis. Here we develop a high-speed capillary electrophoresis (HSCE) platform capable of both SPE measurements and quantifying immunoassays, simultaneously. The HSCE uses a 10 cm long total length separation capillary (50 μm i.d., 80 μm o.d.) with an 8 cm length-to-detector for rapid analysis times. This is important for throughput in clinical settings and for quantifying immunoassays, where antigen-antibody complexes continually dissociate once injected into the non-equilibrium conditions of the separation capillary. A single laser excitation source is focused into the detection zone of the capillary to measure both refractive index (SPE) and fluorescence signals (immunoassays), simultaneously. Light scattered back towards the excitation source measures refractive index changes using back-scatter interferometry (BSI), while fluorescence is collected from below the capillary with a high numerical aperture objective. To validate the dual detection HSCE approach, SPE and immunoassays are measured from human serum samples pre-incubated with fluorescein and an anti-fluorescein monoclonal antibody. We show that the BSI signal measures characteristic SPE profiles for human serum separated in 100 mM boric acid (pH 10), 100 mM arginine (pH 11), and 20 mM CHES (pH 10). For the immunoassay, the fluorescence electropherograms reveal that CHES provides the optimal buffer for measuring the immunocomplex and separating it from the free antigen. Immunoassays in CHES yield a LOD of 23 nM and a LOQ of 70 nM for the detection of fluorescein. Elevated pH is used in SPE to ensure all proteins are charged and to reduce protein adsorption to the capillary walls. The high pH, however, also reduces antibody affinity. Preliminary studies carried out in 50 mM barbital at pH 8 show improved stability of the immunocomplex and better separation for immunoassay quantification, but loss of resolution in the SPE. Further optimization will open new capabilities for measuring orthogonal diagnostic signals in seconds with HSCE.

Terahertz Raman Measurements Using a Spatial Heterodyne Raman Spectrometer

We propose a method of measuring the terahertz (THz) Raman spectra of a material. As Raman spectroscopy is a measurement of the relative frequency spectrum relative to the frequency of the excitation source, it is not necessary to use an expensive THz source and THz detector. Instead, an ultraviolet, visible, or infrared excitation source and corresponding detector can be used. A combination of prisms and gratings is used to widen the field of view at high resolution. The resolution of the system is 4.945 cm−1 (0.149 THz), and the spectral range is 2531.84 cm−1 (75.963 THz). We measured the THz Raman spectra of solid powder, aqueous solutions, and mixtures, and studied the effects of environment, container material, and time of measurement on the spectra. The results show that the system is not significantly affected by interference from the water environment and has good stability and repeatability. This method can be applied in many fields such as material detection and environmental protection.